The use of intravenous lipid emulsions (ILEs) as antidote in local anaesthetic systemic toxicity has gained widespread support following convincing data from animal models, and successful case reports in humans. Proposed beneficial mechanisms of action for ILEs include intravascular sequestration of intoxicant and subsequent enhanced redistribution to biologically inert tissues, augmentation of fatty acid utilisation for ATP synthesis in the context of metabolic poisoning, and direct cardiotonic and ion channel effects. The evidence base for use of ILEs in acute drug intoxication is evolving. The present evidence supports use of ILEs only in local anaesthetic systemic toxicity and in lipophilic cardiotoxin intoxication when there is an immediate threat to life, and other therapies have proven ineffective. Intravenous lipid emulsion (ILE) has a long history of use as a parenteral nutrition formulation in both adult and paediatric patients. Over the past decade, ILE also emerged as a novel treatment for iatrogenic and intentional drug poisonings. Progress from nutritional replacement to antidote has been rapid, necessitating regular review of the rationale and evidence base for administration.As early as 1998 Weinberg and colleagues reported attenuation of bupivacaine toxicity in a rat model . Still eIn 2006 Rosenblatt and colleagues  reportedLikewise in 2007, Sirianni and colleagues  publisheThe dissemination of these and other subsequent cases of clinical use of ILE has seen ILE make the transition from bench-top modelling to clinically utilised antidote without the evidence base commonly associated with introduction of newly formulated drugs. There have been many recent systematic reviews on this topic of a high standard -10. It iThere are presently four small human trials involving the use of ILE: one clinical randomised controlled trial of limited methodologic quality, one case–control study and two pharmacokinetic evaluations. While this small body of human trial work is of importance, it is not sufficient to form a view on the use of ILE in toxicology. The weight of present data is in benchtop and animal models and collated human case reports. While it is possible to evaluate such an evidence base, there are clear limits to the breadth such evidence can generalise to everyday clinical practice.In the setting of immediate threat to life where other treatments are not proving effective, it is reasonable to use an agent when there is an established rationale for use and 'all or nothing' cases such as those described above have been reported. Table Given the above rationale, this paper first outlines the available laboratory evidence on mechanism of action of ILE as antidote, and then progresses to review reported clinical experience.Knowledge of the proposed pharmacologic mechanisms of action of ILE in acute intoxication is important when considering clinical application. Despite extensive and ongoing study the precise mode of action for ILE in many poisonings remains to be fully elucidated. At present both pharmacokinetic and pharmacodynamic actions have been postulated to play a role in the action of ILE as antidote. Whilst synergy between proposed actions may exist, the relative contributions of each remain uncertain. It is quite possible that each mechanism may variably contribute to clinically observed improvement depending on unique combinations of patient factors, the mode and duration since poisoning, and the particular intoxicant.First forwarded by Weinberg in 1998 [P < 0.0016) and increased coronary sinus effluent bupivacaine concentration (P < 0.008) were recorded, in keeping with rapid tissue detoxification. Similarly, Chen and colleagues [Evidence in support of the lipid sink has been derived from both pre-clinical models and human reports. Following their study with the prototypical lipophilic local anaesthetic bupivacaine in whole rat models of cardiotoxicity , Weinberlleagues  have shoSubsequent authors investigating the effect of ILE injection in whole rats have demonstrated evidence of enhanced drug redistribution with reduced bupivacaine concentration in heart, brain, lung, kidney and splenic tissue observed following ILE treatment . The hepin vitro sequestration of lipophilic drugs in human plasma spiked with lipid emulsion, and subsequently assembled a compendium of predicted lipid extraction efficiency on the basis of the intrinsic pharmacologic parameters for over 50 commonly used drugs.Support for a lipid sink effect is not confined to lipophilic local anaesthetics, with animal models and human cases demonstrating an effect with a range of disparate intoxicants, including calcium channel blockers -27, lipoIn vivo studies using non-local anaesthetic drugs have confirmed sink effects in intact animal models and human subjects. In a rabbit model of intravenous clomipramine toxicity, increased total blood concentrations of clomipramine were seen in concert with improved blood pressure following ILE injection, consistent with sequestration of toxin into an intravascular lipid phase [P = 0.07).id phase . Litoniuid phase  similarlid phase . ILE hasid phase . In the Human pharmacokinetic data are limited to two clinical studies and sporadic case reports. Minton and colleagues  demonstrWhile attractive in its simplicity, emerging evidence suggests application of the sink theory must be approached with some caution in all but a few overdose scenarios. A pure sink effect may be important in cardiac arrest due to direct intravenous bolus administration of intoxicant - the centralised circulation meaning that rapid equilibration of heart and brain concentrations with the introduced, centrally confined lipid phase may be possible. Subsequent redistribution of intoxicant to peripheral fat depots on return of effective circulation would conceivably ensue - such a situation could be hypothesized to occur in most forms of LAST.Any pharmacokinetic effect for ILE in the non-arrested patient likely depends on both the pharmacokinetic phase and circulatory status at the time of intoxication. Increased plasma carriage for lipophilic toxins with ILE injection will increase drug transport between organ systems according to a complex interplay of tissue drug affinity, relative concentration, and perfusion. As such, net movement of intoxicant may not prove universally beneficial . For example, in one study investigating the effect of ILE on thiopental anaesthesia in rabbits, early lipid administration appeared to increase the depth, but not overall duration, of anaesthesia. This could be explained by the action of lipid emulsion as a high affinity conduit - maintaining blood concentrations able to interact with the brain during early redistribution to hydrophilic tissues, before augmenting later redistribution from rapidly perfused to lesser perfused lipophilic tissues .Perhaps most vexing is the issue of ILE administration following enteric overdose. Data suggesting that ILE injection may actually augment absorption of lipophilic toxins from the gastrointestinal lumen have emerged, with increased mortality reported when ILE was administered early in the course of oral amitriptyline and verapamil toxicity , and earThe sum of what is known on the pharmacokinetic effects of ILE as antidote seems to be that there are demonstrable effects on absorption, distribution and redistribution for lipophilic intoxicants. Early ILE use in enteric poisoning may be contraindicated because of potential for enhancing gastrointestinal absorption, albeit any such adverse effect is likely dependent on adequate intestinal perfusion, and mitigated somewhat by development of shock-like states secondary to intoxication. The clinical corollary of this would be that effects on blood concentrations following ILE administration likely depend on the timing of administration relative to both the pharmacokinetic phase and the mode of intoxication. It would also seem prudent to ensure actions necessary to mitigate gastrointestinal absorption, such as activated charcoal, were taken before or contemporaneous to lipid emulsion.in silico model for the observed effect on recovery of rats from bupivacaine-induced shock. The model of best fit included all three factors, with the direct cardiotonic effect being the most prominent factor responsible for observed improvement [While clinical and experimental effects spanning agents and organ systems favour a pharmacokinetic mechanism as important in the action of ILE, they are not a complete explanation. Recent data have emerged that suggest lipid emulsions at the doses used have direct cardiotonic effects. Experimentally, rats infused with lipid emulsion showed increased blood pressure and aortic flow rates relative to the same volume of saline. Additionally, isolated rat hearts in isovolumetric contraction were seen to contract more forcefully, with increased oxygen demand, when perfusate was augmented with lipid emulsion . Stehr arovement .It seems likely that direct cardiotonic effects play a significant role as one of the mechanisms responsible for resuscitation from drug-induced cardiotoxicity. This may be particularly so in the arrested or critically compromised circulation in order to offer immediate support before any distributive effects are likely to occur.There is evidence that metabolic pathways influenced by lipid emulsion are important in the experimental mechanism of action of ILE. Partownavid and colleagues  demonstrWhile experimental data showing reduction in myocardial bupivacaine concentration post-ILE demonstrate that pharmacokinetic mechanisms play a role in ILE resuscitation, these metabolic experiments are compelling that metabolic and cardiotonic considerations are at least a necessary, if not sufficient, mechanism of action in experimental bupivacaine toxicity. This, in concert with the data on direct cardiotonic effects, is particularly important in the clinical development of ILE as antidote, as it suggests that pharmacokinetic testing alone will tend to incompletely evaluate the potential for antidotal action of ILE. Metabolic factors may furthermore hold differential importance depending on the toxic compound.Free fatty acids, the levels of which increase with ILE, are known to have effects on both sodium and calcium ion channel function. Arachidonic, linoleic and linolenic acid all increased calcium currents through activated calcium channels in isolated guinea pig cardiac myocytes . This efMottram and colleagues  demonstrFew investigators have studied ILE in human populations. Taftachi and colleagues  reportedGil and colleagues  evaluateThe LIPAEMIC investigators reported 48 cases of use of ILE where details of intoxicant, treatment and outcome were entered into an online registry. Complete capture of all cases treated in contributing centres was unlikely based on declining reporting rates over the time of data collection, meaning that inherent positive publication bias in case reports and series may still have been acting on this dataset. Increases were seen over a short timespan in both GCS in cases where lipid was used for altered conscious state (median GCS increasing from 4 to 8 over 30 minutes) and systolic blood pressure in shocked patients (median systolic pressure increasing from 70 to 90 mmHg over 30 minutes). One serious complication (bronchospasm) and two minor adverse effects were recorded. Given the nature of data collection, these results hold significance as contributors to hypothesis generation .The ToxIC consortium reported a case series of nine uses of ILE from three tertiary referral centres . IndicatThree case series have been reported as conference abstracts. The Washington poisons centre reported five cases of use : bupivacTwo recent publications have summarised individual cases reported in the literature ,10. CaseStudies investigating ILE as antidote that report negative results in animal models have mainly used the porcine model. Swine are known to be more prone to complement-mediated allergic type reactions with liposomal formulations, and this may be important in negative studies involving ILE. Weinberg and Rubinstein  surveyedLiterature reports of vasopressor administration in concert with ILE-based resuscitation from local anaesthetic induced cardiac arrest in animal models have returned conflicting findings. In 2009, Hiller and colleagues  demonstrThe generic nature of the sink hypothesis in ILE-based resuscitation from toxin-induced cardiac arrest has led some to question potential interaction with therapeutically administered lipophilic drugs. It would seem apparent that any effect on redistribution of toxic agents might also likewise affect agents administered therapeutically. ILE has been shown to sequester amiodarone in plasma, and ameliorate its hypotensive action when given in overdose in whole pigs . The cliIn keeping with the pharmacokinetic theory of ILE’s mechanism, increased gastrointestinal absorption of lipophilic intoxicant might be predicted with ILE use as blood with increased affinity for highly soluble xenobiotics perfuses intestinal mucosa. ILE administration early in the course of enteric overdose may thereby paradoxically serve to increase gut absorption and speed development of systemic toxicity. While data in support of this are still emerging -44, signAdministration of ILE for its antidotal effect remains an ‘off-label’ indication. Much of what is known about ILE toxicity is derived from historic studies of use in parenteral nutrition situations. When administered for this indication, allergic phenomena, pancreatitis, induced bacteraemia, fat embolism, and myocardial failure are possible. Few reports of adverse events when administered in the context of life-threatening poisoning exist, with hyperamylasaemia , and aduThe sporadic and unpredictable nature of LAST renders randomised controlled study of ILE in this setting difficult to impossible. The level of evidence available - animal models and case data - is supportive of effect and not likely to be increased. Reflecting this, ILE has been incorporated into LAST practice guidelines of governing bodies for anaesthetists worldwide .Typical administration regimes recommend initial bolus injection of 1.5 ml/kg 20 % lipid emulsion followed by an infusion of 15 ml/kg/hour with accommodation for additional boluses to be given at 5 minute intervals. A recommendation not to exceed 12 ml/kg ILE has been proposed. Defining maximum length of treatment has not been explored in depth, although there is an isolated reported case where low dose lipid was used for some days .in extremus, but extending any recommendation beyond this situation would require further human study. Furthermore, the pharmacokinetic consideration for ILE potentially exacerbating toxicity early in the course of enteric overdose necessitates proceeding with caution. ILE has been suggested as reasonable by the American College of Medical Toxicology, American Heart Association, and European Resuscitation Council for patients exhibiting intractable haemodynamic instability, or overt arrest, secondary to lipophilic drug toxicity that has proven refractory to available therapies. In this instance administration of ILE in accord with guidelines for use in LAST appears reasonable. It is the opinion of the authors that, at present, ILE utilisation for the purpose of reversal of drug-induced coma cannot be recommended outside the confines of a randomised clinical trial.Recommendation of ILE use in non-local anaesthetic drug poisoning remains controversial. While the present review outlines that the level of evidence in this area is evolving, the weight of evidence remains the same as in the field of local anaesthetics. Such a level of evidence can rationally be extended to the clinical situation of the patient Human randomised trials are possible in this field and necessary to evaluate whether ILE has a more general role in treatment of intoxicated patients. Registry data aimed at capture of all instances of ILE application are also required to determine an accurate denominator of ILE use, such that clinical performance characteristics may be inferred. Similarly, safety data in humans cannot be derived unless all cases of ILE use and outcomes are collated to central registries as significant adverse events may occur rarely and require many thousands of uses to identify.in vitro [Basic science experimentation is furthermore required to delineate optimal doses and formulations of ILE for human application. Research exploring the utility of liposomal detoxification vesicles has proven informative, with engineered liposomes demonstrating ability to sequester lipophilic toxins with far greater affinity than standard ILE in vitro . Subsequin vitro .Recent advances in understanding the mechanism of ILE treatment in poisoning suggest ion channel, metabolic and cardiotonic effects are of importance along with the more frequently quoted pharmacokinetic (sink) theory. While the evidence base for ILE use in acute drug intoxication is evolving, the present evidence supports use of ILE only in LAST and in lipophilic cardiotoxin intoxication when there is an immediate threat to life, and other therapies have proven ineffective.


Chronic tinnitus (ringing of the ears) is a medically untreatable condition that reduces quality of life for millions of individuals worldwide. Most cases are associated with hearing loss that may be detected by the audiogram or by more sensitive measures. Converging evidence from animal models and studies of human tinnitus sufferers indicates that, while cochlear damage is a trigger, most cases of tinnitus are not generated by irritative processes persisting in the cochlea but by changes that take place in central auditory pathways when auditory neurons lose their input from the ear. Forms of neural plasticity underlie these neural changes, which include increased spontaneous activity and neural gain in deafferented central auditory structures, increased synchronous activity in these structures, alterations in the tonotopic organization of auditory cortex, and changes in network behavior in nonauditory brain regions detected by functional imaging of individuals with tinnitus and corroborated by animal investigations. Research on the molecular mechanisms that underlie neural changes in tinnitus is in its infancy and represents a frontier for investigation. Some of these studies were comparable with the animal ones as they focused on the auditory system, particularly the auditory cortex, with an emphasis on spontaneous activity, neural synchrony and tonotopic mapping . We therefore begin in “Hearing loss, resulting for instance from exposure to loud noise, is considered an important risk factor for developing tinnitus. Consequently, a history of recreational, occupational, and firearm noise exposure may all be associated with increased likelihood of acquiring tinnitus. The relationship between noise exposure and tinnitus, however, differs depending on the presence or absence of hearing impairment. Occupational noise exposure is more likely to correlate with significant tinnitus in participants with hearing impairment, while leisure-time noise exposure is more associated with increased occurrence of significant tinnitus in participants without audiometric (frequencies ≤8 kHz) hearing loss  compared with non-tinnitus human ears (n = 106). Tinnitus and non-tinnitus ears were carefully matched for hearing loss (thresholds ≤15 dB HL). The results show that loudness sensitivity is indeed enhanced in tinnitus subjects compared with non-tinnitus subjects, including subjects with normal audiograms. How far these results are generalizable to the 45 % of tinnitus sufferers who do not volunteer reports of increased sensitivity to environmental sounds , likely upon N-methyl-D-aspartate (NMDA) receptor activation. A significant body of pharmacological evidence indicates a role of glutamate-sensitive NMDA receptor activation during stimuli-dependent excitatory events in the cochlea”.Knipper et al.  emphasizThe evidence for an involvement of NMDA receptors in tinnitus is as strong for salicylate as for noise-induced tinnitus. A dose-dependent effect of salicylate on NMDA receptor currents in neonatal spiral ganglion neurons has been described  in the presence of decreased SFR. Most of these problems disappear if behavioral tests only reflect increased SFR in subcortical structures. However, that still questions the role of primary auditory cortex in tinnitus perception.In 2011, at an international tinnitus conference in Buffalo (NY), one of us reviewed the predictions of these tests in comparison to the findings of changes in SFR and stimulus-induced firing rates and LFP amplitude in primary auditory cortex, and summarized them in the paper resulting therefrom . The associated hyper-responsiveness to startle stimuli presented alone and the sensitization to background noise suggested that noise exposure leads to increases in the gain of auditory responsiveness.Since that conference, improvements in the startle response techniques have resulted and we review here some of the new findings. Chen et al.  examinedCorroborating findings of the effects of hearing loss on the ASR were presented by Yurosko et al. , who meaTemporary threshold shift (TTS)-causing noise exposure can result in immediate, permanent partial degeneration of the auditory nerve in mice despite complete threshold recovery and lack of hair cell damage , as well as from filling-in effects from tinnitus. We  is a factor that may contribute to reduced startle suppression by temporal gaps in background sound. Sensitization of startle responses after noise exposure or salicylate is a further factor that could modulate the extent of startle suppression induced by gaps after these procedures. However, it should be noted that several animal studies did find significant frequency specificity in the extent to which gaps in background sound suppress the startle response, with peak suppression failure coinciding with frequencies where tinnitus was expected to have occurred . However, 2–3 months later, behavioral evidence of tinnitus was evident only at a narrower frequency range (20–31 kHz) representing a presumed chronic condition. Extracellular recordings confirmed a significantly higher SFR in IC neurons in sound-exposed compared to control mice. Sun et al.  and midbrain  that are important in attention, emotion, and plasticity  that can take several forms. The most common are termed Hebbian and anti-Hebbian Feldman . HebbianArc mRNA and protein in the AC. This again suggests that tinnitus may be linked to a failure to adapt central circuits to reduced cochlear input.Singer et al.  examinedArc gene and the early growth response gene-1 (Egr-1) gene were decreased in the IC and AC. Expression of NMDA receptor subunit 2B was increased and all these changes returned to normal 14 days after treatment with salicylate ceased. This long-time administration of salicylate induced tinnitus markedly but reversibly caused neural plasticity changes in the IC and the AC. Decreased expression of Arc and Egr-1 might be involved with instability of synaptic plasticity in tinnitus. The failure to mobilize Arc in the cortex suggested that tinnitus is linked to a failure to adapt central circuits to reduced cochlear input. One has to keep in mind that application of salicylate damages spiral ganglion cells in culture  in neural changes underlying tinnitus. Corticotrophin-releasing hormone (CHR) is released in response to stress from the median eminence of the hypothalamus and acts on the pituitary, but is also expressed in the amygdala and hippocampus, which are structures important in emotion and memory. CRH binds to G-protein-coupled receptors and in the hippocampus primes changes in LTP, while in the amygdala CRH release enhances memory consolidation (see Joëls and Baram A receptor (GABAAR) currents were evoked by bath application of the subunit selective agonist, gaboxadol (0.1-10 μM), in the presence of glutamatergic blockers. Two months following tinnitus-inducing sound exposure, significant (p = 0.02) increases in tonic GABAAR currents were observed in MGB neurons from tinnitus compared to control animals contralateral to the exposure. Results in NT neurons were not statistically different from those of C or T neurons. Analysis of spontaneous inhibitory postsynaptic potentials revealed no differences in measured parameters, implying that net synaptic GABA transmission (phasic inhibition) in MGB was not reduced in T animals. There was no down-regulation of inhibitory transmission in the MGB in animals expressing behavioral evidence of tinnitus. In contrast, tonic GABAAR currents were elevated in MGB neurons, lending some support to the notion that cortical dynamics putatively associated with tinnitus, such as increased SRF and neural synchrony in cortical neurons affected by hearing loss  or temporal  resolution compared to physiological experiments in animals. However, human studies can manipulate the presence or absence of tinnitus and hyperacusis based on verbal reports from the participants and assess both with psychoacoustic methods. Functional imaging is also well suited to investigating brain network behavior associated with tinnitus and its correlated conditions including hyperacusis and emotional distress.Numerous animal studies reviewed in the previous section have demonstrated elevated spontaneous and sound-evoked activity in brainstem auditory pathways. In humans with and without tinnitus, Gu et al.  assessedA recent comprehensive study by Melcher and colleagues , that can identify areas of net increased or decreased metabolic activity in brain regions related to tinnitus and measure functional coupling between these regions, and electromagnetic methods, that measure changes in synchronous (phase locked) activity of neurons occurring in and between brain regions possibly related to tinnitus. Previous reviews by Lanting et al. , VannestThe cerebellum is involved in some aspects of tinnitus-related hyperactivity as several studies in humans and animals have reported, although the overall picture is not consistent. PET studies of spontaneous activity  obtained when tinnitus was suppressed by masking or lidocaine from PET images obtained during baseline scans where tinnitus was experienced. They found a larger difference in neuronal activity between unmasked and masked conditions in the tinnitus patients compared to the controls. The increased neuronal activity associated with tinnitus occurred predominantly in the right hemisphere with significant foci in the middle frontal and middle temporal gyri, in addition to lateral and mesial posterior sites. The results were consistent with the hypothesis that the sensation of tinnitus is associated with activity in cortical regions functionally linked to areas subserving attention, emotion and memory. Group analysis of PET data  and Weisz and colleagues , there are now several reports of resting-state oscillatory brain changes recorded electromagnetically in tinnitus patients compared to controls under baseline conditions. Table n = 15) but residual excitation (a post-masking increase in tinnitus) in other subjects (n = 5). In a whole-brain analysis using beamforming methods, 30 clusters of significant power changes between tinnitus high and tinnitus low were detected within subjects, which were heterogeneous in terms of their frequency ranges and in terms of the direction of power change for a given cortical area between subjects. A wide region of the brain was covered by the clusters, but the most consistent clusters showing tinnitus high/low differences (besides the auditory cortex discussed below) were in the cerebellum, anterior temporal lobe, posterior cingulate cortex, ventromedial prefrontal cortex, medial occipital lobe, and anterior cingulate cortex. More consistent changes related to tinnitus changes were found in the auditory cortex. During RI, Sedley et al. found increases in gamma band oscillations relative to a control masker during epochs in which tinnitus was increased in qualitative agreement with the results of Weisz et al. , emotion , and memory . At this time, three viewpoints can be distinguished regarding the role of nonauditory regions in the development and experience of tinnitus.The first viewpoint proposes that functional and structural changes in nonauditory regions are driven by tinnitus-related neural activity occurring in central auditory pathways that is necessary and sufficient for the experience of tinnitus. While the nonauditory changes are therefore not crucial for tinnitus perception, they are responsible for its associated consequences such as persistent activity in auditory attention networks  and of individuals with threshold shifts but no tinnitus , or injury to low threshold high spontaneous rate ANFs in the cochlear nerve , or both factors. During the course of aging, the threshold shifts up to ~40 dB at 4 kHz commencing at ~50 % of the lifespan  and are closely paralleled by OHC loss, suggesting damage to the transduction mechanism as the principal cause , neural gain is increased in subcortical auditory structures and in the auditory cortex, as expressed by increased driven neural responses in these structures and by behavioral measures. Increases in SFR are also observed after noise trauma in several central auditory nuclei, and occur in this case against a background of reduced activity in ANFs, whereas, following salicylate, changes in SFR are more variable across auditory nuclei and are associated with increased SFR in ANFs. This difference between the effects of noise trauma and salicylate on SFR could be secondary to different levels of activity in the cochlear nerve following these procedures, or to mechanisms that modulate SFR different from changes in central gain. In this regard, computational models suggest that changes in central gain may be sufficient to increase SFR in central auditory pathways, which could be the neural basis for tinnitus. However, caution is needed, because changes in SFR and central gain are inconsistently correlated in the animal data. Other neural mechanisms that may underlie tinnitus  have received less investigation in animal studies. A challenge for animal models going forward is to rule out impaired temporal processing or hyperacusis as the source of neural and behavioral changes seen in these studies, separately from tinnitus. Within the limits of this challenge, animal studies have provided evidence for the centralization of tinnitus over time, and have revealed neuroplastic mechanisms that may contribute to the development of tinnitus percepts.An advantage of human studies is that the presence or absence of tinnitus can be reported verbally and verified by psychoacoustic measurements. Electromagnetic imaging studies of human tinnitus sufferers have revealed changes in synchronous neural population activity in the auditory cortex in different frequency bands, the most consistent being increased slow wave activity  and increased gamma oscillations (>40 Hz) from the region of the auditory cortex with several reports of reduced alpha activity (8–12 Hz) as well. Increased delta may reflect deafferentation of thalamocortical projections leading to increased gamma oscillations in local networks consequent on disinhibition of cortical neurons. Reduced alpha is thought to signal desynchronization of longer-range network activity in the auditory cortex following reduced inhibition in (or the deployment of attention to) this region. These results regarding oscillatory responses are consistent with animal studies that point to aberrant neural synchrony as a possible mechanism for tinnitus. Because the findings are obtained from resting neuromagnetic baselines, their spectral (tonotopic) signatures cannot be determined, but data from cats subjected to noise trauma show increased synchronous activity confined to tonotopic frequency regions affected by hearing loss, which is also where human tinnitus percepts lie. Functional imaging of tinnitus in humans has further revealed increased activity in nonauditory brain networks known to be involved in consciousness, memory, and emotion, with the limited animal data currently available corroborating these changes when physiological measurements extend to these regions. Several functional roles have been proposed for nonauditory regions, including most notably gating access to dorsal prefrontal structures responsible for conscious perception, which could explain dynamic fluctuations of tinnitus awareness with task demands. Nonauditory mechanisms involved in tinnitus may also account for dissociations between the co-occurrence of tinnitus and threshold shift, but another possibility raised by recent animal studies and supported findings in humans points to undetected cochlear neuropathy in these cases.Animal models permit invasive experimentation that cannot be conducted in humans, and results obtained from them can guide human investigations. A good example of how the two approaches have been complementary are studies of human tinnitus patients revealing increased gain in ABRs recorded for suprathreshold sounds and steepened behavioral loudness growth functions compared to controls, both results confirming expectations based on animal data. Going in the other direction, evidence for involvement of nonauditory regions in tinnitus obtained from human functional imaging has been corroborated by recent animal experiments which have extended their observations to these regions. Animal and human studies are also converging to suggest a role for trophic mechanisms in establishing correlates of tinnitus, including structural and functional neuroplastic changes that occur in the brain following damage to the cochlea. Looking ahead, animal and human studies are likely to provide important insight into several emerging topics, including the role of auditory and nonauditory network behavior in tinnitus, contributions from neural plasticity, and factors that modulate the experience of tinnitus as well as its generation.5 neurons. fMRI does not require synchronously driven activity, whereas EEG/MEG derived data do. Spontaneous activity can only be obtained by using PET (because it is a silent technique) that reflects the metabolic demand of the neurons. The most relevant measure in animals relating to PET measures in humans is the 2-DG one, and here the recording is likely biased toward neurons whose activity is detectable . The macroscopic stimulus-driven BOLD responses and AEP/AEF measure only central gain differences between tinnitus groups and controls, and therefore may relate more to hyperacusis than to tinnitus (Gu et al. Because studies of humans and animals necessarily involve different measurement techniques, a continuing challenge will be to understand how measurements at different levels of function relate to one another, given the constraints inherent in any single method. Animal recordings related to tinnitus reflect single- or multi-unit spontaneous firing rates, spontaneous neural synchrony based on pair-wise cross-correlations, and stimulus-evoked firing rate or LFP amplitudes and the tonotopic maps constructed therefrom. In contrast, human data are always population data reflecting activity of at least 10The problem of relating measurements at different levels is highlighted by the observation that evidence linking gamma-band oscillations to spike pair correlations is not completely consistent. Cardin et al.  found thLooking ahead to future animal studies, physiological and optogenetic methods offer the prospect of investigating the fine detail of thalamocortical dynamics in tinnitus as well as the role neuromodulators and forms of plasticity that are only beginning to receive attention in the tinnitus literature. Future animal studies may also provide insight into the intracellular and molecular mechanisms that are involved in tinnitus as well as in the processing of sound by the intact brain. Research into how results from these different methods are related by their underlying mechanisms will be needed to integrate the findings and to extrapolate them to humans where different methods of study must be used.


Despite a recommendation by the World Health Organization (WHO) that typhoid vaccines be considered for the control of endemic disease and outbreaks, programmatic use remains limited. Transmission models and economic evaluation may be informative in decision making about vaccine programme introductions and their role alongside other control measures. A literature search found few typhoid transmission models or economic evaluations relative to analyses of other infectious diseases of similar or lower health burden.Modelling suggests vaccines alone are unlikely to eliminate endemic disease in the short to medium term without measures to reduce transmission from asymptomatic carriage. The single identified data-fitted transmission model of typhoid vaccination suggests vaccines can reduce disease burden substantially when introduced programmatically but that indirect protection depends on the relative contribution of carriage to transmission in a given setting. This is an important source of epidemiological uncertainty, alongside the extent and nature of natural immunity.Economic evaluations suggest that typhoid vaccination can be cost-saving to health services if incidence is extremely high and cost-effective in other high-incidence situations, when compared to WHO norms. Targeting vaccination to the highest incidence age-groups is likely to improve cost-effectiveness substantially. Economic perspective and vaccine costs substantially affect estimates, with disease incidence, case-fatality rates, and vaccine efficacy over time also important determinants of cost-effectiveness and sources of uncertainty. Static economic models may under-estimate benefits of typhoid vaccination by omitting indirect protection.Typhoid fever transmission models currently require per-setting epidemiological parameterisation to inform their use in economic evaluation, which may limit their generalisability. We found no economic evaluation based on transmission dynamic modelling, and no economic evaluation of typhoid vaccination against interventions such as improvements in sanitation or hygiene. Although largely controlled in Europe and North America, typhoid remains endemic in many parts of the world, notably Asia, where it is an important cause of febrile illness in crowded, low-income settings Salmonella Typhi in their stool or urine for many years, thereby sustaining transmission Typhoid fever is an exclusively human enterically transmitted systemic disease caused by infection with the bacterium Despite a recommendation by the World Health Organization in 2008 that typhoid vaccination be considered for the control of endemic disease and outbreaks, programmatic use remains limited In the early twentieth-century, public health officials were debating the best methods of evaluating typhoid vaccine effectiveness, and whether vaccination was a distraction from improvements in sanitation and hygiene Where health budgets are limited, allocation of resources to activities which generate the best value for money maximises the population's health . To compare between and across health states, cost utility analysis (CUA) can be employed using a common metric of health, such as disability-adjusted life-year (DALY). The World Health Organization's Choosing Interventions that are Cost-Effective project (WHO-CHOICE) describes interventions as “cost-effective” if they add a DALY at a cost of less than three times Gross Domestic Product (GDP) per capita, and “highly cost-effective” if each DALY costs less than GDP per capita. These are arbitrary thresholds and meeting them does not necessarily lead to the intervention being adopted, as health decision-makers are often required to make choices between multiple interventions that fall below these thresholds. Furthermore, even highly cost-effective activities may be too expensive overall for a health service to provide within budget: a hypothetical drug adding a year of life and costing GDP per capita for each person treated would require the entire national economy to be spent giving the drug to every member of the population By building on the germ theory of disease, and mass-action principles from the physical sciences In this review, typhoid transmission dynamic models and typhoid vaccine economic evaluations are examined for their potential contributions to informing disease control, identification of gaps in knowledge and indication of directions for further research.2PubMed was searched on 23 October 2014 without date restriction using the following terms: (“Typhoid Fever”[Mesh]) AND  AND (Humans[Mesh]) NOT “Mice”[Mesh].Personal libraries were reviewed and reference lists in papers searched for modelling and economic studies that may not have been identified by the above search strategy. Results were restricted to those available in English. We obtained information about unpublished studies through the Coalition against Typhoid and International Vaccine Institute.Studies were included if they modelled typhoid transmission and/or analysed the cost-effectiveness of vaccination in endemic settings. Endemic settings were identified using recent high-quality reviews Transmission models were assessed for their model structure, data sources, parameter estimates, use of fitting methods, sensitivity analysis and the contribution of their approach to epidemiological understanding of typhoid. Economic studies were evaluated by data sources, economic evaluation approach, perspective, comparator programmes, use of sensitivity analysis and capture of indirect effects of vaccination.3Seventy-nine titles were retrieved. Ten modelling papers were selected for review based on title or abstract. One was discarded as a non-mechanistic time series study Seven titles were identified as economic evaluation and obtained for full-text review , Table 4There was minimal overlap found between transmission modelling and economic evaluation. Of the transmission dynamic models, only those by the Cvjetanović group also had cost-effectiveness components 3.1The seven typhoid models identified range from two-state analytical tools to complex individual-based simulation or multi-state compartmental models see . Only twSalmonella Typhi is considered. González-Guzmán suggests that natural partial immunity is likely to arise but simplifies to a model with vaccine immunity only, noting that sufficiently high infectious doses can overcome immunity The structures of models  are baseWhile noting leaky immunity in those naturally infected , González-Guzmán models Ty21a oral vaccine protection as all-or-none, giving each vaccinee a probability of developing immunity or not. In this model, those who develop immunity following vaccination have 100% protection against typhoid, until vaccine wanes and they return to full susceptibility, an approach also applied by Cvjetanović While vaccination programmes are predicted to reduce typhoid incidence, uncertainty around carriage prevalence, duration and contribution to the force of infection substantially affects vaccines’ projected impact Salmonella Typhi carriage can be treated with antibiotics and/or cholecystectomy for gallstone-associated infection, but there is no demonstrated role for vaccination in clearance of carriage Chronic If immunisation of the susceptible population does not bring about typhoid elimination, then measures to reduce per case or per carrier infectivity, such as improved sanitation or hand washing with soap, might be considered instead of or in conjunction with vaccination Another feature of transmission dynamic studies is that the average age of infection increases as the force of infection decreases, for example, with the introduction of vaccine 3.2Our literature search found seven papers evaluating typhoid vaccine cost effectiveness. The earliest two of which were based on values derived from expert opinion and are less informative to current policy considerations than the most recent five which were based on field studies, as outlined in In a one-year study of a very-high typhoid incidence area – Kalkaji slum, Delhi – Bahl found average costs per episode of illness were high to both the health sector and families, excluding intangible costs such as pain, with hospitalisation an important component of health service costs Cook and colleagues conducted a CUA based on field data from multiple Asian sites WTP has also been used in economic evaluation of typhoid vaccines as an alternative approach to COI in valuing private or societal benefits. Such an approach is considered to demonstrate the value individuals place on the total benefit of the vaccine, though is confounded by ability to pay, and ability to value public sector activities foregone if vaccines are supplied through the state WTP studies are also informative to vaccine uptake, with 9% of respondents in the Kolkata survey stating they would not accept a free vaccine, with data suggesting these individuals are more likely to be older, have lower income and never boil drinking water Observing that typhoid vaccines are equivalent to one-sixth of per-capita public sector health spending in India, Cook notes the potential for user fees in financing a state-administered programme 4This review found a relatively sparse literature on typhoid modelling and vaccine economic evaluations. Of seven transmission models found, only two were published in the last 25 years and use contemporary data-fitting methods. All five field-based economic evaluations we found shared multiple common authorships around the DOMI collaboration.Although the Global Burden of Disease is a much-criticised ranking, it provides some comparator infectious diseases, with measles and syphilis ranked close to typhoid and paratyphoid fever, and cholera attributed around one-third of the annual number of DALYs Considering only a health services perspective – of treating typhoid and providing vaccine – omits private costs associated with the disease and therefore underestimates the societal impact of typhoid. Various approaches have been taken to address these costs and more completely capture the benefit of vaccination, from cost of illness studies for private expenses, estimates of health utility forgone due to illness, or by determining the extent to which people value vaccination in willingness-to-pay studies. While user fees and WTP are controversial We did not find any economic evaluation comparing typhoid vaccination programmes against other potential means of typhoid control, such as measures to improve sanitation, hygiene or water supplies. It is still not possible to answer the century-old question of whether, in a given setting and within a limited budget, vaccination should be adopted over improved sanitation and hygiene, or what combinations are optimal for control under what circumstances. Such analysis would need to be based on a transmission dynamic model, with extensive epidemiological surveillance for detailed burden of illness measurement, and comprehensive costing for CUA or CBA approaches that allow other diseases to be included in the evaluation.Salmonella Typhi immunity have in determining typhoid incidence rates found an absence of suitable immuno-epidemiological data on which to fit parameters and make strong inferences, a challenge further compounded by the absence of age structure in the model The only published data-fitted transmission model of typhoid vaccination suggests that while vaccination is effective in reducing disease incidence, if other measures are not enacted to reduce the ongoing force of infection, particularly from asymptomatic carriage, short or medium-term vaccination campaigns are unlikely to result in elimination and would see disease rebound if vaccination stopped Transmission dynamic modelling and a non-mechanistic economic analysis have shown that the level of indirect protection may have an important impact on vaccine effectiveness and cost-effectiveness respectively Using a static economic model premised only on direct protection in vaccinees may be a reasonable approximation in some situations, such as if vaccine-preventable new typhoid cases (symptomatic or otherwise) make a relatively small contribution to the force of infection compared with carriers and the unimmunised. Even in such circumstances, prior assessment with mechanistic modelling of field epidemiological data would be appropriate in estimating the relative contributions of each group to transmission.While there seems limited inter-disciplinary dialogue between typhoid modellers and economists, a unifying concern is the importance of accurately determining age-based incidence rates, which can be highly variable within-country or between otherwise similar settings, and are central to estimates of vaccine impact and cost-effectiveness. Heterogeneity in disease rates, transmission mechanisms and health service provision may limit external validity of both typhoid modelling studies and economic evaluations.Accurate assessment of disease burden could be done with large, population-based studies to inform incidence, complications and case-fatality rates, using blood culture confirmation of cases, or altogether improved diagnostics •Salmonella Typhi carriage studies, similar to those done in Chile in the early 1980s Large, population-based, •Salmonella Typhi, natural immunity and waning of this immunity. Seroprevalence could be linked to surveillance records to estimate the proportion of infections that are clinically apparent and notified to national authorities.Serological assay development and population-based serological surveys to determine past infection to •Epidemiological time series with consistent, transparent methodology and/or cross-referencing between methods •Age-based social contact pattern surveys, which may inform short-cycle transmission Other field epidemiology and laboratory investigations could further inform typhoid transmission dynamics For models to assess vaccination against other enteric fever control measures, findings could be incorporated from interventional field studies on the role of improvements to sanitation, hygiene and water supply in changing disease incidence and transmission. Ongoing scrutiny of vaccine efficacy and duration of vaccine protection may also be informative. Estimates of efficacy of Ty21a vaccines in recent systematic reviews are less than in the data sources for early modelling, with the reviews focusing on individual RCTs rather than cluster field studies This review has a number of limitations. In the absence of licensed human vaccines, the review does not cover paratyphoid fever or non-typhoidal salmonelloses. It covers only material in the English language, limited searches to a non-systematic enquiry of a single database and does not attempt to synthesis qualitatively or quantitatively any of the studies reviewed. Comparator studies have not been sought that consider investments in water, sanitation and hygiene as alternatives to typhoid vaccination.One possible feature observed in the course of this review is a less pessimistic assessment of disease burden, perhaps reflecting true decline, as well as a more sceptical perspective on vaccine efficacy estimates, with fewer inputs based on expert opinion alone. Any such trend towards assessment of vaccine costs and benefit firmly grounded in data is beneficial to equitable, scientifically informed health-policy setting.It has been suggested that for a model to have sufficient complexity to enable robust cost-effectiveness analysis, substantial data collection may be required 5Transmission dynamics have not yet been integrated into a comprehensive cost-utility analysis of typhoid vaccination and, as such, there is no economic evaluation that would meet contemporary gold standards Literature review, ethics approval not required.CHW and WJE have had travel and expenses paid for by the Coalition against Typhoid to attend meetings on the modelling of typhoid vaccination programmes. WJE has undertaken consultancy for the Coalition against Typhoid, which was paid to a fund held the London School of Hygiene & Tropical Medicine.CHW conducted the review and interpretation, wrote the initial draft of the manuscript and revisions. WJE contributed to the interpretation, and reviewed and edited the draft manuscript.


The ability to understand and ultimately predict ecosystem response to multiple pressures is paramount to successfully implement ecosystem-based management. Thresholds shifts and nonlinear patterns in ecosystem responses can be used to determine reference points that identify levels of a pressure that may drastically alter ecosystem status, which can inform management action. However, quantifying ecosystem reference points has proven elusive due in large part to the multi-dimensional nature of both ecosystem pressures and ecosystem responses. We used ecological indicators, synthetic measures of ecosystem status and functioning, to enumerate important ecosystem attributes and to reduce the complexity of the Northeast Shelf Large Marine Ecosystem (NES LME). Random forests were used to quantify the importance of four environmental and four anthropogenic pressure variables to the value of ecological indicators, and to quantify shifts in aggregate ecological indicator response along pressure gradients. Anthropogenic pressure variables were critical defining features and were able to predict an average of 8-13%  of the variation in ecological indicator values, whereas environmental pressures were able to predict an average of 1-5 %  of ecological indicator variation. Each pressure variable predicted a different suite of ecological indicator’s variation and the shapes of ecological indicator responses along pressure gradients were generally nonlinear. Threshold shifts in ecosystem response to exploitation, the most important pressure variable, occurred when commercial landings were 20 and 60% of total surveyed biomass. Although present, threshold shifts in ecosystem response to environmental pressures were much less important, which suggests that anthropogenic pressures have significantly altered the ecosystem structure and functioning of the NES LME. Gradient response curves provide ecologically informed transformations of pressure variables to explain patterns of ecosystem structure and functioning. By concurrently identifying thresholds for a suite of ecological indicator responses to multiple pressures, we demonstrate that ecosystem reference points can be evaluated and used to support ecosystem-based management. Natural environmental variation –3 and muA specific ocean-use sector where EBM has been repeatedly explored is ecosystem-based fisheries management (EBFM). EBFM seeks to identify, among multiple pressures and responses, the suite of management options that best address the myriad tradeoffs for fisheries within an ecosystem . Fish anEcosystem thresholds occur when a small change in a pressure causes either a large response or an abrupt change in the direction of ecosystem state or function ,16–18. UGradient forest analysis  extends http://iobis.org/mapper/?resource_id=1435). These data are routinely used to monitor trends in abundance and distribution of important living marine resources for the region [Myoxocephalus octodecemspinosus), and trophic level  bottom trawl surveys (BTS) that provide information regarding the regional ecology and oceanography of the NES LME, which spans the continental shelf from Cape Hatteras to Nova Scotia , and the raw importance value Ispvt for a predictor at each split value v in each tree t. Predictor importance Isp quantifies the contribution of a predictor to the model goodness-of-fit by computing the prediction error of the model without the predictor and comparing it to the prediction error of the full model. Specifically, Isp is estimated as the increase in OOB mean square prediction error when the predictor is randomly permuted while the other variables in the model remain constant, effectively removing the predictor signal.A random forest is an aggregation of the results from an ensemble of regression trees that synthesizes output with high classification accuracy and accounts for interactions among predictor variables ,41. An is is defined asXsi is the ith observation of indicator s, The proportion of variance explained in a random forest, or the goodness-of-fit Isp, such that p for indicator s) is calculated asThe goodness-of-fit e values . Values e values .Changes in ecosystem attributes along environmental and anthropogenic gradients were identified using gradient forest methods. Random forest methods are useful for quantifying the ability for pressure variables to predict response variables and the importance of each response variable to these predictions. Gradient forests integrate individual random forests analyses over many response variables, which are used to develop flexible, non-parametric functions to quantify thresholds in indicator response to anthropogenic and environmental pressures (see diagram and further discription of these methods in ).p were generated using the gradientForest package, which distributes R2 values for all indicators among predictors in proportion to predictor importance Isp and along the gradient of values for each predictor according to the density of raw importance values Ispvt  for each indicator along a pressure gradient, which describes the cumulative shift in indicator value along each pressure gradient and provides an estimate of the importance for any given pressure value x. Cumulative ecosystem response Fp(x) for each pressure variable was estimated as mean Fsp(x) for all indicators. The cumulative ecosystem response Fp transforms ecological units reflecting changes in ecological indicator value for each pressure variable [For the NES LME, we developed data matrices for both pressure (year x pressure variable) and response  variables. Threshold estimates along gradients of each environmental and anthropogenic pressure variable  Ispvt  quantify the importance of environmental and anthropogenic pressure variables in predicting ecological indicator response, and 2) explore empirical shape and magnitude of changes in indicator response across these pressure gradients.It can be useful to think of gradient forests in a multivariate sense, similar to PCA. The importance of each pressure variable is comparable to the length of a vector on a PCA scree-plot. But the gradient forest proves to be more informative, as the cumulative response curve is an ecologically informed transformation of the pressure variables, which can be used to predict and map potential patterns of ecological composition.R2 units, and across a common set of dimensions, via PCA. Further, the translation into a common language can also facilitate comparisons between multiple ecosystems to identify patterns in ecological indicator response to multiple pressures and levels of pressures that result in ecosystem thresholds. However, multiple pressures can also have non-additive [Given our objectives, gradient forest provided a robust and concise way to quantify the importance of pressure variables on ecological indicators of ecosystem status for the NES LME. We found anthropogenic pressure variables to be more important in predicting ecological indicator values than environmental variables. Although evidence suggests that the biological and ecological processes are being influenced by environmental pressures in the NES LME ,44, the additive  effects additive .Compared to previous studies, model prediction performance on OOB sample values  for anthropogenic pressures compared to environmental pressures, and we identified levels of fishing pressure that resulted in a distinct ecosystem structure . Care anUsing the gradient forest method, we found that increased fishing pressure  resulted in rapid compositional change in ecological indicator values. Threshold responses in energy flow indicators occurred at lower levels of fishing pressure, suggesting that with increasing fishing pressure energy transfer within the NES LME is altered. As fishing pressure increases further, threshold responses in the diversity indicator occurs. Given the multiple community configurations that can produce similar diversity indices, Link  suggestsCollectively our results indicate significant ecosystem responses when landings are at 400,000 t, which represent ~30% of the maximum ever observed for this system. Similarly, significant ecosystem responses are observed at exploitation rates of 20%. Certainly environmental pressures also elicit some response, yet fishing pressure is potentially the one variable that we can control. These results suggest that when landings approach 30% of those ever observed, or more practically that when the ratio of surveyed biomass to landings approaches 20%, the NES LME will likely be approaching an ecosystem threshold. These empirical derivations warrant further testing in other ecosystems to see if these approximate levels hold, but the method proposed here provides a highly feasible means to do so. Further, delayed effects of fishing and environmental pressures should be explored in more detail . As we cS1 Data(CSV)Click here for additional data file.S1 Fig(TIF)Click here for additional data file.S2 Fig(TIF)Click here for additional data file.


Neuronal growth cones are exquisite sensory-motor machines capable of transducing features contacted in their local extracellular environment into guided process extension during development. Extensive research has shown that chemical ligands activate cell surface receptors on growth cones leading to intracellular signals that direct cytoskeletal changes. However, the environment also provides mechanical support for growth cone adhesion and traction forces that stabilize leading edge protrusions. Interestingly, recent work suggests that both the mechanical properties of the environment and mechanical forces generated within growth cones influence axon guidance. In this review we discuss novel molecular mechanisms involved in growth cone force production and detection, and speculate how these processes may be necessary for the development of proper neuronal morphogenesis. TractioFor cells to sense the mechanical properties of their environment they must express proteins that change their conformation in response to mechanical force or tension. Depending on the type of mechanosensitive (MS) protein, conformational changes may lead to modulation of enzymatic activity, accessibility of binding sites for protein-protein interactions, or regulation of ion channel gating. One site where cell mechanosensors are likely concentrated is at integrin receptor-adhesion protein complexes, which function at the interface between the cytoskeleton and ECM Figure . AdhesioSeveral enzymes within adhesion complexes appear to be MS. For example, mechanical forces applied to cells change both the localization and activity of FAK, a key non-receptor tyrosine kinase. Importantly, FAK signaling is necessary for cell behavioral responses to locally applied forces and changes in substratum rigidity , since these signals are reduced when rigidity of the substratum is decreased. In addition, the effects of MS channel blockers on axon outgrowth is lost with knockdown of TRPC1 and partially lost with knockdown of TRPV4  family. TRP channels form both homo- and heterotetrameric cation channels. Increasing evidence suggest an important role for TRP channels for environmental sensing from entire organisms to single cells. TRP channels transduce extracellular stimuli, like mechanical force, into biochemical signals through the influx of the second messenger CaMS ion channels outside the TRP channel family may also be important. Piezo (Fam38a/b) ion channels were identified as MS channels in a siRNA based screen in the mechanically excitable Neuro2D cell line  for cell binding, as has been demonstrated for a5ß1 and vascular endothelial growth factor (VEGF) receptor  neurons within varying concentrations of agarose gels in the presence of 10% fetal bovine serum (FBS). This study found that axons extend more rapidly within softer gels <20 Pa) and that the rate of outgrowth plateaus above 60 Pa , an enzyme with glycosyltransferase activity that modifies type XVIII collagen. Interestingly, the glycosyltransferase activity of LH3 functions within adaxial cells to chemically modify collagen XVIII that is deposited on the surface of the developing myotome. In this model, collagen XVIII is glycosylated by LH3 and secreted into the ECM where it becomes a suitable substratum to promote the exit of motor axons into the periphery. While it is unclear what the precise roles of collagen glycosylation are toward developing axons, there is evidence it can regulate fibrillogenesis, crosslinking, remodeling and collagen–cell interactions, all of which likely influence mechanical signaling  from flexible neural tissues to highly rigid skin, muscle and bone suggesting a role for growth cone durotaxis in vivo.  in the drosophila eye disc controls the stiffness of the tissue. Further, disruption of Lox leads to ectopic migration of glial cells suggesting tissue stiffness defines specific migration patterns (Kim et al., in vivo, but future studies will need to clarify how and when axon growth is specifically modulated by substratum elasticity. In addition, the study of mechanosignaling during axon guidance requires the development of a robust and reliable in vivo model of growth cone durotaxis.Substratum elasticity in vivo, where they will clearly differ depending on substratum association. During axon pathfinding to distal targets, growth cones will bind many different adhesive substrata, ranging from ECM proteins to cell adhesion molecules on neighboring neurons and glia. It is important to both visualize and manipulate point contact adhesions in vivo to test their roles in axon guidance.There are many outstanding questions regarding the roles of mechanical forces in the regulation of growth cone motility and axon guidance. Within cells and growth cones, it is unclear which proteins function as mechanosensors and how molecular forces are transferred onto target proteins. In particular, it is not clear how MS ion channels are gated at the plasma membrane and the molecular targets of calcium signals. Ion channel gating may occur at point contact adhesions, where myosin II contractile forces are focused at integrin-ECM contacts (Gomez et al., in vivo. While it is clear that growth cones must migrate across widely varying elastic microenvironments en route to their proper synaptic targets, it is not known whether changes in tissue elasticity influences growth cone morphology or motility. For example, motoneuron axons begin in the soft CNS, but exit by penetrating the surrounding basal lamina (Santiago-Medina et al., in vivo. However, progress has been made by examining the effects of mutations in ECM cross linking enzymes that regulate the mechanical, but not the chemical composition of the environment (Kim et al., in vivo using AFM (Franze, Determining the roles of tissue elasticity and mechanical signaling is particularly difficult  Franze, .The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Objectives: This review sought to identify, describe and assess the effectiveness of teacher-mediated interventions that aim to support child and adolescent recovery after a natural or man-made disaster. We also aimed to assess intervention applicability to rural and remote Australian school settings.Method: A systematic search of the academic literature was undertaken utilising six electronic databases  using terms that relate to: teacher-mediated and school-based interventions; children and adolescents; mental health and wellbeing; natural disasters and man-made disasters. This was supplemented by a grey literature search.Results: A total of 20 articles reporting on 18 separate interventions were identified. Nine separate interventions had been evaluated using methodologically adequate research designs, with findings suggesting at least short-term improvement in student wellbeing outcomes and academic performance.Conclusions: Although none of the identified studies reported on Australian-based interventions, international interventions could be adapted to the Australian rural and remote context using existing psychosocial programs and resources available online to Australian schools. Future research should investigate the acceptability, feasibility and effectiveness of implementing interventions modelled on the identified studies in Australian schools settings. The impact of disaster in AustraliaBetween January 2010 and January 2015, Australia experienced 31 natural disasters including cyclones, floods, storms, tornados and bushfiresFor the purpose of this article, natural disasters refer to sudden onset of significant environmental events, including bushfires, flood and cyclones. Man-made disaster refers to war or terrorist-related activities, rather than human induced environmental disasters such as oil spills or environmental degradation.Child and adolescent mental health following a disaster,,,The trauma that children and adolescents may experience as a result of disasters is widely explored,,Children who are diagnosed with PTSD often report a decrease in post-disaster quality of lifeThe rationale for school-based, teacher-mediated interventions in Australia,,It has been argued that teachers are ideally placed to deliver post-disaster mental health programs and support to their students in the school settingIn Australia, the school setting is increasingly used to deliver support programs for students who experience trauma associated with family breakdown or the loss of a loved one. The Seasons for Growth program is an example of thisObjectivesThe primary aim of this review was to identify describe, and determine the effectiveness of, school-based teacher-mediated interventions developed to support child and adolescent mental health and wellbeing following either a natural disaster or a man-made disaster. The secondary aim was to identify interventions conducted in or relevant to the Australian rural and remote schools.Search strategyThis review was conducted in accordance with the PRISMA guidelines for systematic reviews.Eligibility criteriaAll literature identified by our search as reporting on school-based, teacher-mediated interventions to support child and adolescent recovery after a disaster was included in the review. Studies were included if they clearly described that the intervention was delivered by the classroom teacher to their students or if they described an intervention for teachers, and/or reported the outcomes of these interventions on students or the teachers. Interventions facilitated by therapists/counsellors or other health professionals in partnership with teachers were excluded, as these were not considered to be relevant to the Australian rural or remote school context. All study designs were included as long as they met the above eligibility criteria. No restrictions on the start date of the search period were imposed; the end date of the search period was July 2013, which has been subsequently updated to January 2015. The search was restricted to English language and peer-reviewed journal articles. No further search restrictions were applied.Information sourcesSix electronic databases were searched: EBSCO, Medline, PsycINFO, Embase, ERIC and CINAHL. These databases were chosen due to their target audience; health, psychology and education.Search strategyEach database was searched using terms that relate to: teacher-mediated and school-based interventions; children and adolescents; mental health and wellbeing; natural disasters and man-made disasters. For example, the specific search terms used in the EBSCO database were:  AND  AND  AND .Study selectionAll identified articles were added to an Endnote library. Duplicates were removed using the Endnote “remove duplicates” function, and through manual scanning. Based on titles, articles returned in the search that were clearly not relevant were excluded. The remaining articles were assessed based on abstracts and key words, and excluded if they did not meet the inclusion criteria. If no abstract was available full text articles were retrieved and reviewed to assess relevance. If there was uncertainty regarding article inclusion, a co-author was consulted until agreement was reached.Data itemsData extraction tables were used to record characteristics of included studies. Studies were grouped as being relevant to either 1) natural disaster events or 2) man-made disaster events. Additional data extraction items and grouping/classifications applied to studies included: a) Study design;b) Disaster of interest; c) Participant characteristics; d) Intervention characteristics; e) Teaching training characteristics; and f) Results. In order to make a judgement about the effectiveness of the identified interventions, articles were then categorised based on whether the study design conformed to Effective Practice and Organisation of Care (EPOC) guidelinesRisk of biasRisk of bias was assessed for each study meeting the EPOC criteria, utilising the suggested risk of bias criteria for EPOC reviewsGrey literature searchAdditional to the database search, a series of Google searches were conducted during July 2013, and subsequently updated in January 2015 to explore resources currently available to teachers online. Google searches used simplified combinations of the electronic database search terms, with a focus on Australia; for example ‘disaster resources Australia teachers’. While the limitations of this grey literature search strategy are acknowledgedStudy selectionFigure 1 describes the process of article identification, screening, and full text article retrieval and assessment for inclusion. A total of 1652 articles were retrieved, of which 20 articles reporting on 18 separate interventions were deemed relevant to this review.Included peer-reviewed papersOf the 20 articles, nine described seven interventions following a natural disaster and 11 articles described interventions in response to man-made disasters. The 18 interventions broadly fell into one of two categories: They either a) reported on the implementation of the intervention in the classroom and its outcomes for students (n = 12), or b) reported on the process of training teachers (n= 6). None of the interventions identified were conducted in Australia. Each intervention  is outlined in Table 1.Table 1 - Identified InterventionsStudies with EPOC designsTable 1 indicates that nine of the 18 studies were deemed to meet EPOC design criteria, and Table 2 summarises the findings of these nine studies. Three studies related to natural disasters  and 6 studies related to man-made disasters .Table 2 - EPOC Design StudiesStudy characteristics,,,Of the three studies focusing on natural disasters that met EPOC research design criteria, one focused on outcomes for teachers with the study,,,Five out of the six studies focusing on man-made disasters that met EPOC research design criteria reported data on child and adolescent mental health outcomes. As seen in Table 2, all studies reported reductions in PTSD symptomology Risk of biasRisk of bias was assessed using EPOC guidelinesTable 3 - Risk of BiasResources available to Australian schoolsTable 4 details the disaster resources provided by government and non-government organisations in Australia and New Zealand that were identified through the grey literature search. The resources fall into three categories: 1) information and fact sheets for teachers; 2) lesson plans and interactive resources to be implemented in the classroom; and 3) teacher training. Some resources are disaster-specific (e.g. bushfires), while others are more general. Almost all resources focused on natural disasters. Please see Supplementary Table 1 for further detail about these resources, including URLs. The grey literature search did not return any of the included studies in this review.Table 4 - Grey LiteratureWe identified seven school-based teacher-mediated interventions that were developed to support child and adolescent mental health and wellbeing following a natural disaster, and 11 following a man-made disaster. Eight interventions were evaluated using methodologically rigorous designs, reporting significant short-term intervention effects on some student outcomes  and teacher outcomes . Although none of the identified interventions were conducted in Australia, there is potential to adapt effective international models, drawing upon nationally relevant disaster recovery resources that are freely available online.Description of the identified interventionsThe greatest disparity evident between interventions responding to natural versus man-made was commencement time. Natural disaster interventions commenced immediately to 15 months after the disaster, while interventions targeted at man-made disasters were implemented across a broader timeframe. Differences between natural and man-made disaster interventions were also evident in their reported outcomes. Natural disaster targeted interventions more often reported behavioural changes, while man-made disaster interventions reported clinical changes and behavioural changes. Behavioural changes may be most relevant to teachers if they assist school performance and do not require clinical knowledge.Interventions were categorised according to their intervention type as either classroom based or teacher training with there being slight differences between these two categories (see Table 1). Classroom based interventions involved the classroom teacher delivering class sessions lasting between 45 minutes to two hours, which occurred on a regular basis over a number of weeks. These sessions focused on building resilience and coping strategies and included play therapy, activities to develop emotional awareness, conflict resolution, drama games, and cooperative learning, the timing of the implementation of the intervention relative to disaster onset and the duration of the interventions varied. Comparatively, teacher training interventions reported on the process of training teachers in disaster preparedness and response and provided the tools and resources to use personally or in the classroom. These were most often facilitated by mental health workers. A number of studies reported using the ‘train the trainer’ technique, which was often used to reach a large number of schools and students. All teacher-training articles focused on the goal of providing the teacher with the tools and resources to support their own recovery and to implement a mental health program in their classroom without the need for external services running the ongoing program.Effectiveness of the identified interventionsOf the interventions that were evaluated using an EPOC endorsed rigorous research design, positive findings suggest that the identified interventions may be effective for improving teacher self-efficacy and student academic, mental health and wellbeing outcomes, at least in the short term. Based on heterogeneity of intervention components, outcomes measures and follow-up periods, we were unable to determine which particular interventions characteristics were associated with which outcomes. Further methodologically rigorous research assessing similar outcomes is required before conclusions can be drawn about intervention effectiveness.Relevance of the identified interventions to the Australian context,,,,,,,Despite none of the interventions being conducted in Australia, a number of the interventions reported here were based on a particular disaster-recovery strategy  after a disaster may be the most logical next steps for this area of investigation. Consultation with Aboriginal communities would also be a crucial aspect of any intervention development. Further investigation into resources available to Australian teachers, particularly the usefulness of these resources and their ability to be implemented into the classroom may also prove beneficial. A recent study has found that approximately 50% of the teachers sampled felt that they do not have enough time to meet the mental health needs of their studentsReview limitationsPublication bias may be evident as none of the included studies reported significantly negative findings. Further, due to the difficulty of implementing and evaluating interventions in a post-disaster environment there may be interventions with successful and positive outcomes that have not been reported in the peer-reviewed literature. Many non-relevant studies were also identified through the search procedures employed. A preoccupation with PTSD was evident and the authors acknowledge the need for broader strategies addressing issues above and beyond PTSD are essential. As the inclusion criteria was limited to interventions that describe teachers delivering the support program interventions may have missed that have other school staff delivering the program. It is worth noting that if the school has resources, including other staff such as chaplains or school counsellors that can be trained to deliver interventions may be an option for some schools.While our search criteria sought to capture teacher mediated class room based interventions we acknowledge that interventions may have been missed using such a strict search strategy. Interventions such as the Classroom-Based Intervention (CBI)We have defined man-made disaster as war or terrorist-related activities, rather than human induced environmental disasters such as oil spills or environmental degradation. Although no interventions were identified which specifically addressed human-induced environmental disasters, it may be possible that our selection of search terms may have inadvertently excluded any literature discussing these types of disaster interventions. Additionally, drought was not included our search terms as it is not currently considered a natural disaster in Australia under the Australian Government’s Natural Disaster Relief and Recovery ArrangementsThe grey literature search identified resources related to resilience and wellbeing from organisations such as Beyond Blue and KidsMatter. While these resources are readily available to schools, as they were not disaster recovery specific they were not reported in this review. However, as resilience building and increasing wellbeing are often the focus of disaster recovery interventions, programs such as these could be included in future research exploring resources available to teachers post-disaster.Teacher-mediated interventions may have the potential to improve child and adolescent mental health after a disaster, although findings are inconclusive. International studies provide a useful guide for the development, implementation and evaluation of teacher-mediated disaster-response mental health programs for Australian schools. Further investigation is necessary before conclusions can be drawn about the applicability of these identified international interventions to the Australian rural and remote context. In the absence of recommendations for evidence-based teacher-mediated disaster interventions, resources aimed at increasing resilience and wellbeing may be useful for teachers attempting to manage disaster recovery in their classrooms, particularly in rural and remote locations where provision of services by mental health professionals is lacking.The authors have declared that no competing interests exist.Supplementary Table 1. Disaster Resources Summary and URLPRISMA Checklist


To examine variations in the quality and cost of care provided to patients with diabetes mellitus by Community Health Centers (CHCs) compared to other primary care settings.We used data from the 2005–2008 Medical Expenditure Panel Survey . We used two dependent variables: quality of care and ambulatory care expenditures. Our primary independent variable was whether the respondent received care in a Community Health Centers (CHCs) or not. We estimated logistic regression models to determine the probability of quality of care, and used generalized linear models with log link and gamma distribution to predict expenditures for CHC users compared to non-users of CHCs, conditional on patients with positive expenditures.Results showed that variations of quality between CHC users and non-CHC users were not statistically significant. Patients with diabetes mellitus who used CHCs saved payers and individuals approximately $1,656 in ambulatory care costs compared to non-users of CHCs.These findings suggest an opportunity for policymakers to control costs for diabetes mellitus patients without having a negative impact on quality of care. Studies have shown that community health centers (CHCs) provide care to patients at lower costs than other primary care settings, but researchers are still debating if CHCs achieve these cost savings by providing lower quality of care to patients compared to other primary care settings –4 While The federal government has invested considerable resources in expanding CHCs for the last several years to provide primary care and preventive services to low-income individuals, including those with chronic conditions such as diabetes mellitus . The PatCHCs may reduce the demand for more expensive forms of care, such as outpatient specialty care, emergency care or inpatient hospitalizations for diabetes mellitus patients by providing access to quality primary care services for low-income patients, who are largely uninsured or on Medicaid. Several studies found that the usage of CHCs in underserved areas has been associated with lower hospitalization rates, fewer Emergency Department (ED) visits, and shorter inpatient stays . MedicaiIt is important for policymakers and researchers to understand whether or not CHCs achieve these cost savings at the expense of quality of care provided to patients with diabetes mellitus because diabetes mellitus is a costly chronic condition that disproportionately impacts racial/ethnic minorities and low-income populations that are served by CHCs –14. LoweWe used four years of recently available data (2005–2008) from the Medical Expenditure Panel Survey (MEPS). The MEPS is a nationally representative longitudinal survey that covers the United States civilian non-institutionalized population. We combined data from three different components of the MEPS including the Household Component (HC) file, the Office-Based Medical Providers Visits (OBMP) file, and the Outpatient Visits (OPV) file see . The HC We used two dependent variables in this analysis: quality of care and ambulatory care expenditures.Consistent with the American Diabetes mellitus Association guidelines, we used three binary indicators to measure quality of care for patients with diabetes mellitus who reported receiving the following in the past year: two or more glycated hemoglobin (HbA1c) tests, foot examinations, and eye examinations . These pThese expenditures are actual payments from all sources made by insurers and individuals as out-of-pocket costs for ambulatory care services, such as office-based services and non-emergency hospital outpatient care services. They do not include over-the-counter purchases. The MEPS subsequently validates dates of visits, diagnosis codes and procedure codes with providers and insurers.Our primary independent variable was whether the respondent received care in a CHC or not. We coded CHC as 1 if the patient reported that they received more than 50% of their care from “community health centers” or “neighborhood/family health centers”. This definition of CHC does not include rural or free health clinics because the MEPS does not include information about these particular clinics. The CHC measure was constructed using the data from the event files to calculate the proportion of office-based visits and outpatient visits that respondents received in CHCs. Those individuals who reported that they received less than 50% of their care from CHCs were considered as receiving care from other primary care settings. Non-CHC users were those patients who received their primary care elsewhere  and were coded as zero.For the quality of care models, we controlled for a set of patient characteristics known to be associated with variation in quality of care including age, race/ethnicity, sex, socio-economic status, insurance status, smoking, obesity status, general health status, co-morbid cardiovascular conditions, and regional locations .For the expenditures models we used a modified version of Aday and Andersen’s behavioral health model of health services use to estimate expenditures associated with CHC users compared to non-CHC users . In otheWe estimated logistic regression models to determine the probability of receiving at least two HbA1c tests, a foot examination, or an eye examination within the past year, as indicators of quality of care. We converted the results into marginal effects from the mean for easier interpretation. Typically, a two-part model is utilized to estimate healthcare expenditures because some patients have no expenditures and a few of those who incur expenditures have very high expenses –21. HoweOn average, about 2 percent of patients with diabetes mellitus reported using a CHC. As shown in The sample characteristics were fairly distributed among patients with diabetes mellitus who were CHC users compared to their counterparts who were non-users of CHCs. However, consistent with the literature, patients with diabetes mellitus who were CHC users compared to non-users of CHCs are less likely to have a graduate education , more likely to be poor, have a higher proportion of family incomes between 101–200% of the Federal Poverty Level (FPL) , have a lower proportion of family incomes greater than 400% of the FPL , are less likely to have private insurance , more likely to be uninsured , more likely to be in fair/poor health  and less like to live in the northeastern region of the United States .Marginal effects from multivariate logistic regressions showed that patients with diabetes mellitus who used CHCs were 12 percent more likely to receive at least two HbA1c tests in the past year compared to those patients with diabetes mellitus who used other settings of ambulatory care . On the The objective of this study was to examine variations in the quality and cost of care provided to patients with diabetes mellitus by CHCs compared to other settings of primary care by using nationally representative data sets. Findings from this study advance the literature on quality of care and ambulatory costs for patients with diabetes mellitus in primary care settings by confirming that community health centers provide equivalent quality of care at lower costs to their patients. Results showed that while the quality of diabetes mellitus care between CHC users and non-users was similar, CHC users saved approximately $1,656 in ambulatory care compared to non-users of CHCs.These findings are consistent with most studies in the literature that have found that the provision of care at CHCs is associated with significant savings while demonstrating that the quality of care provided by CHCs is comparable to other settings of primary care , 6–8. OuThis study has a few limitations. Due to the cross-sectional design of the study, we are not able to infer causality. The analysis would have to consider and address in a rigorous manner important issues of sample selection, reverse causality and measurement error before drawing any causal inferences. For instance, the quality of care variables were also self-reported measures of process outcomes of diabetes mellitus care. Although we controlled for patients who reported poor/fair health or co-morbid cardiovascular conditions, it is possible that patients with severe diabetes mellitus conditions may be more likely to visit non-CHC providers more often and may be more likely to receive diabetes mellitus tests compared to those reporting excellent/good health and no co-morbid cardiovascular conditions. Use of CHCs was self-reported, and some patients may not be able to distinguish between CHCs and other types of health centers, potentially resulting in measurement bias of the CHC variable. This bias could have been reduced by identifying provider addresses in the MEPS to determine whether care was received at a CHC. However, the geocoded files in the MEPS that would allow completing such analysis are not publicly available.We also acknowledge that the quality indicators were self-reported measures of process outcomes of diabetes mellitus care. We could not control for the severity level of diabetes mellitus because we had no information on glycemic control, achievement of HbA1c targets, or incidence of diabetes mellitus-related complications among patients. Although, recent data showed that there are about 23 million users of CHCs in the United States, it is important to note that only 2% of patients with diabetes mellitus used CHCs in our sample, which limits our ability to generalize our findings to the total population of patients with diabetes mellitus that use CHCs in the United States.This study shows that while there are no statistically significant differences in the quality of diabetes mellitus care received at CHCs compared to other primary care settings, CHC users saved approximately $1,656 in ambulatory care compared to non-users of CHCs. Assessing the mechanisms through which CHCs achieve cost savings while improving the quality of care is important because the current findings may suggest an opportunity for policymakers and clinicians to control costs without compromising the quality of care of diabetes mellitus in the U.S. For instance, it would be important to understand how CHCs save money. Are these savings due to better patient information and follow-up visits, shorter waiting times or better medical treatment? Another important and relevant question is how much the savings is out-of-pocket and how much of it should be allocated to different insurers such as private insurance and Medicaid. It would require the use of larger and longitudinal data sets to run separate models of expenditures for patients with health insurance and for out of pockets expenditures to answer these questions. Sample size limitations in the number of patients with diabetes mellitus that used CHCs precluded us from estimating separate models to answer these questions. Future research should aim to address these questions, particularly in the context of the Affordability Care Act of 2010 that seeks to aims to improve health outcomes for patients with diabetes while containing costs.S1 Datahttp://dx.doi.org/10.6084/m9.figshare.1533272.figshare. (ZIP)Click here for additional data file.