This allows evaluators to better develop and refine mid-level programme theories. However, this is only one phase in the process of developing and evaluating complex interventions. We describe and exemplify how social scientists can integrate realist principles across all phases of the Medical Research Council framework. Intervention development, modelling, and feasibility and pilot studies need to theorise the contextual conditions necessary for intervention mechanisms to be activated. Where interventions are scaled up and translated into routine practice, realist principles also have much to offer in facilitating knowledge about longer-term sustainability, benefits and harms. Integrating a realist approach across all phases of complex intervention science is vital for considering the feasibility and likely effects of interventions for different localities and population subgroups.The integration of realist evaluation principles within randomised controlled trials  enables evaluations of complex interventions to answer questions about  The original UK Medical Research Council (MRC) framework for evaluating complex interventions recommended sequential phases of development, feasibility testing and evaluation, culminating in the estimation of an effect size via a randomised controlled trial (RCT), prior to wider implementation . This emactualised to produce particular social outcomes  whenever randomisation is practicable . FinallyThis article outlines how realist evaluation principles have much to offer public health intervention science, not only for trials of effectiveness but also across all phases of public health intervention science, from intervention development, feasibility and pilot studies to post-evaluation scale-up studies. For example, as the number and range of feasibility and pilot studies proliferates , a realiSome of the authors of the revised MRC guidance have subsequently argued that approaches such as complex systems science and realist evaluation may become routine within public health evaluation methods once sufficient empirical examples are available to guide practice . This arWithin the revised MRC guidance, there is relatively little attention paid to the developmental phase of the complex intervention cycle ,b. OtherMore recently, theoretically orientated tools have been developed, such as the ‘Behaviour Change Wheel’  and the Addressing these existing gaps in the literature and via engagement with a realist lens, we recommend further development and use of the following three methods to support intervention development and modelling: mixed-methods evidence synthesis; formative mixed-method, multi-case-study research; and, pragmatic formative process evaluation. These methods would support the development of more three-dimensional (3-D) logic models, which focus not only on complex the pathways from (1) inputs to (2) outcomes but also the (3) contextual dimensions that activate or mitigate causal processes. Intervention logic models (referred to as implementation models by Blueprints Youth Programmes resource developed in the USA (http://www.blueprintsprograms.com/) and the UK Investing in Children database (http://investinginchildren.eu/), which accredit lists of ‘effective’ interventions without consideration of which contexts such interventions might be suitable.The process of designing more theoretically driven interventions and specifying potential CMO configurations has been hindered by the dominant paradigm within evidence syntheses: systematic reviews still typically focus on synthesising only quantitative studies answering questions about ‘what works’ at the expense of understanding how, in what context and for whom . These eMixed-methods reviews have similarities with mixed-methods primary research, thus there are many ways in which the products of different syntheses methods can be combined to overcome the limitations with traditional systematic review methods. ‘Realist reviews’ have been suggested as an alternative (or adjunct) to address the lack of focus on CMO configurations in current evidence syntheses . HoweverFirst, reviews can synthesise information on theories of change and evidence on intervention processes to develop hypotheses about the mechanisms via which interventions are intended to work, as well as how implementation and effectiveness might be affected by the characteristics of different populations and places. For example, two recent mixed-methods reviews – one examining how the school environment and school–environment interventions influence health, and one examining the effects of community-based positive youth development (PYD) interventions – have synthesised intervention theories and the findings from process evaluation reports as well as estimates of intervention effects to hypothesise how school environment and PYD interventions can improve health, for whom and in what contexts , 2016. ASecond, reviews can use meta-regression or qualitative comparative analysis (QCA)  to examiAs well as mixed-methods systematic reviews to identify the relevant theoretical and evidence base, before new interventions are piloted it is often useful to undertake formative, mixed-method case-study research to understand their socio-ecological context, explore potential intervention delivery and hypothesise mechanisms of action. Such formative case studies can employ purposive sampling to provide contextual diversity, informed by initial theories, and generate insights regarding how these contexts might interact with intervention mechanisms to influence outcomes for different groups.One example of this design is a current formative study to develop and model a new intervention to be delivered in further education (FE) colleges to promote safe sex and relationships among 16–19-year-olds. Six FE colleges in England and Wales were purposively sampled according to type and size of institution. A phased approach to data collection and analysis supports the consideration of CMO. First, focus groups and interviews have been used to explore the views of students, teachers, managers and sexual health service providers on how interventions deliverable within FE colleges might work to improve relationships and sexual health. Second, informed by these data, a larger cross-section of students and staff were surveyed to develop theories about how these mechanisms might interact with context to play out differently in different settings and/or with different groups of students  and/or baseline sexual risk). Finally, findings from these elements will be brought together to refine a 3-D intervention logic model which incorporates consideration of CMO configurations.The design and development of a new film-based intervention targeting teenage men to prevent unintended pregnancy has also involved formative, mixed-methods research in a range of settings . To deveThe development of new interventions and modelling of theories of change can also be enhanced by pragmatic process evaluations of interventions already in routine practice . AlthougThese evaluations allow for the examination of mechanisms not only of intended benefits but also unanticipated consequences, including unintended harms. For example, a pragmatic formative process evaluation of a school-based social and emotional learning intervention identified a number of iatrogenic effects as a consequence of the stigmatising referral processes and negatively labelling young people . ThroughOur suggestion is not that resources should be used to retrospectively theorise all existing interventions on an exhaustive basis. However, once existing interventions are deemed to warrant outcome and process evaluation they should be first subjected to pragmatic formative process evaluation to help develop the intervention logic model, model realist CMO hypotheses and, if necessary, refine delivery methods prior to larger-scale evaluation and scale-up. Without a clear theory of change, subsequent evaluations employing a realist perspective will be of more limited value. One example of where an existing but under-theorised intervention was subjected to pragmatic process evaluation was the Welsh National Exercise Referral Scheme (NERS) . TheoretFeasibility and pilot studies should also apply a realist approach to explore implementation and potential mechanisms of action in a range of contexts prior to larger effectiveness trials. Following the development of MRC guidance on complex interventions , the volThe dominance of such binary assessments is now reflected in the widespread use of binary ‘progression criteria’, including by funders, to determine whether a subsequent, larger evaluation is warranted e.g. . FeasibiFirst, purposive sampling criteria should be used in pilot RCTs to ensure there is sufficient diversity in aspects of context that have been pre-hypothesised to affect feasibility, acceptability and causal mechanisms. It is essential to assess these in a range of contexts, but this rarely happens in practice. One example is a pilot cluster RCT of whole-school restorative approach to prevent bullying and aggression in secondary schools . This stSecond, like subsequent realist RCTs  may foster mechanisms similar to the intervention in some contexts, which is rarely considered by trialists at present. For example, a meta-analysis of studies examining adherence to HIV care concluded that between-study variation in intervention effectiveness could be explained as much by differences in behaviour change elements in the usual care arms of the included studies as by variation in interventions . More fuRealist approaches can also be applied where interventions are scaled up after successful trials. Evaluations of scale-ups can examine long-term benefits and harms and how these vary by context. These studies can occur over a wider range of settings, populations and time periods and so have particular strengths in understanding how context shapes outcomes.One example of this is the evaluation of the scale-up of the Intervention with Microfinance for AIDS and Gender Equity (IMAGE), which did not explicitly use a realist approach but nonetheless embodied some of its key principles. The IMAGE intervention combined group-based lending with gender and HIV education, and facilitated community mobilisation campaigns, targeting women living in poverty in rural South Africa. Following a cluster RCT trial that suggested that this was effective in reducing rates of intimate partner violence , this inThere are few, if any, other examples of such MRC ‘implementation’ studies using realist approaches, although there are examples of ‘natural experiments’ of large-scale interventions using realist approaches e.g. . HoweverPublic health evaluators have typically under-theorised and under-researched how interventions are intended to engage with their social contexts to enact change . If evalWhile realist RCTs are becoming more common, large-scale outcome evaluations are only one phase in the process of identifying effective, sustainable interventions to improve health. It is also much more difficult to undertake realist RCTs and scale-up studies without earlier phases of development and piloting that develop and refine programme theories and CMO hypotheses. To facilitate a step-change in the quantity and quality of realist RCTs, the development of complex interventions and their theories of change, and preliminary feasibility and pilot studies, should also now adopt a realist focus on context and mechanisms of actions. Purposive sampling is particularly important to ensure a range of contexts are studied at an early stage and the role of context is therefore theorised alongside the intervention logic model. It is then possible to test hypothesised mechanisms of actions  and examine how outcomes vary by subgroup and place  within large-scale realist RCTs, as well refining and building new hypotheses within these trials via qualitative data. In some cases, it may also be possible to test moderated mediation (i.e. whether there is an effect mediated by certain mechanisms only under specific contexts), which remains rare in RCTs.Adopting such a realist approach across all phases of intervention science is vital for considering the likely effects of interventions on different social groups and addressing inequalities in health and other outcomes. For example, at the stage of developing interventions and modelling their mechanisms, it is important to theorise the processes and outcomes for different sub-populations. If more complex logic models are not developed to embrace system-focussed theory it is unlikely that new interventions will respond effectively to the most entrenched social problems and reduce inequalities . FeasibiThe major barrier to formally testing CMO configurations within individual studies are the small sample sizes that trials often use, powered to examine effects on primary outcomes but not necessarily sufficiently powered to detect differences in all secondary or intermediate (process) outcomes. Trials are rarely designed with secondary analyses according to mediators or population subgroup in mind , and cliIf RCTs that adopt realist principles become increasingly common, there is also a need for infrastructure investment to develop the procedures for conducting realist analyses (while avoiding data dredging), facilitate and coordinate new studies, and to develop guidance for developing and reporting robust intervention theory of change. First, there is potential for social science trials teams with expertise in realist methodologies to operate within existing clinical trials units to combine expertise in trial statistics and realist approaches for social interventions.Second, further investment in transdisciplinary research networks – which involve researchers from multiple disciplines, policymakers, practitioners and the public – is required to increase the quantity, quality and relevance of realist intervention science. This transdisciplinary approach limits the problems created by the separation of the research community from policy and practice, including the concentration of academics on efficacy trials that have little impact on practice . InformeThird, protocol and reporting guidelines should aim to facilitate a step-change towards the realist complex intervention science methods recommended above. For example, trial protocols should include pre-specified moderator and mediator analysis but also allow for iteration in order to refine hypotheses during a trial in light of emerging qualitative data . GuidancThese investments in a realist complex invention science infrastructure and new reporting guidelines would support the cost-effective use of evaluation research funding, and the development of policy-relevant evidence to improve health. Significantly, such an approach offers a way to fully theorise and promote progression through the phases in the MRC framework for the development and evaluation of complex interventions. In turn, greater use of realist RCTs and scale-up studies will, in the long term, support new evidence syntheses that answer a wider range of questions about what works, for whom and under what circumstances, and what carries on working once scaled up and sustained. Those developing interventions or describing their intended mechanisms of action can then draw on such reviews to think more clearly about intended mechanisms and how these interact with context to enable outcomes to manifest.


Endocrine therapy-induced hair loss (ETIHL) associated with aromatase inhibitors and tamoxifen treatment is currently mostly reported but remained an unresolved therapeutic issue in patients with breast cancer (BC) since the number of studies regarding the management is limited in literature. Herein we investigated the possible causes of this clinical problem and its relation with endocrine therapies widely used for BC survivors and made some modest practical recommendations in light of the literature review in order to provide an optimal management. On the basis of literature findings, common causes of hair loss apart from endocrine therapies should be investigated with an initial evaluation workup and then should be corrected, if observed. Treatment with topical 5-alpha reductase inhibitors and supplementation of Vitamin C and omega-3 fatty acids are likely appeared to be the most appropriate treatment agents for ETIHL without causing an adverse effect on BC prognosis. However, more prospective, randomised, placebo-controlled studied are required in order to confirm our results and also identify the clinical effects of this problem on patients with BC. Tamoxifen and Aromatase Inhibitors (AIs) currently hold an important place as endocrine therapy (ET) in adjuvant and/or metastatic setting of the patients with Hormone Receptor (i.e. Estrogen Receptor+ and/or Progesterone Receptor+) positive invasive or non-invasive breast cancer (BC)  Although it is known that chemotherapy-induced HL during adjuvant chemotherapy is a temporary clinical issue, it constitutes a great concern and cosmetic problem in patients with BC. Many patients therefore tries to overcome this period by covering their heads with a wig, however, this situation may psychologically leads to treatment rejection or discontinuation. By contrast, although patients with advanced disease treated with chemotherapy also faced with similar HL problems, cosmetic care in such patients generally remains in the background as they are primarily aware of the importance of the metastatic process along with the treatment response  with mitotane and ketoconazole which are used to disrupt the ovarian or adrenal androgenic hormones synthesis may provide this effect  in hair texture  may preclude both HL on the scalp and male pattern hair growth in other parts of the body. Genuinely, the fact that patients with deficiency of congenital 5-alpha reductase enzyme activity rarely present  could possibly be the most appropriate and potent treatment options in the treatment of ETIHL. It is also clear that systemic suppression methods of androgen synthesis may not be appropriate options due to systemic potential side effects which can not be worth to take risk for cosmetic purposes and may also lead to potential comorbidities or mortalities. Despite having no adverse effect on BC prognosis, vitamin E does not appear to be beneficial since they might provoke the male pattern HL by its possible androgenic effects.Endocrine therapy-induced HL have remained an important but less cared cosmetic problem in patients with breast cancer. When considering that one forth of the patients with breast cancer using endocrine therapy encounter with this clinical problem; rather than suggesting patients anti-HL methods, it would be more beneficial and effective to suggest them (before they start the complaining of HL problem) to be aware of that HL could be resolved. Today, there is no evidence based therapy with regard to this issue. In addition to those suggestions, before planning an initial endocrine therapy, several factors which may lead to HL including zinc and trace element deficiencies, other endocrine disorders and fungal or bacterial infections on the scalp should be primarily evaluated in patients suffering ETIHL.In conclusion, we would like to emphasise that topical 5-alpha reductase inhibitors and supplementation of vitamin C and omega 3 fatty acids in a non-toxic dose without leading to any adverse effect on the prognosis of the patients with breast cancer appear to be the most appropriate options in the management. However, more prospective, placebo-controlled studies are currently required to prove the efficacy of these treatment methods in endocrine therapy induced hair loss.


However, public misconceptions of stem cell potential and applications can leave patients vulnerable to the influences of profit driven entities selling unproven treatments without solid scientific basis or appropriate clinical testing or follow up. This review provides a brief history of stem cell clinical translation together with an overview of the properties, potential, and current clinical application of various stem cell types. In doing so it presents a clearer picture of the inherent risks and opportunities associated with stem cell research translation, and thus offers a framework to help realise invested expectations more quickly, safely and effectively.We are moving into a new era of stem cell research where many possibilities for treatment of degenerative, chronic and/or fatal diseases and injuries are becoming primed for clinical trial. These reports have led millions of people worldwide to hope that regenerative medicine is about to revolutionise biomedicine: either through transplantation of cells grown in the laboratory, or by finding ways to stimulate a patient’s intrinsic stem cells to repair diseased and damaged organs. While major contributions of stem cells to drug discovery, safety and efficacy testing, as well as modelling ‘diseases in a dish’ are also expected, it is the  The immense scientific, media and public interest in stem cells over the past 15 years has largely been focused on two areas: the therapeutic potential of stem cells, and ethical controversies relating to the destruction of human embryos historically required to obtain pluripotent stem cells. What is rarely fully appreciated is the significant research progress made during these years that has resulted in a large number of stem cell-based clinical trials currently, or soon to be, underway. At the Stem cells can be divided into two broad categories, tissue-specific (‘adult’) stem cells and pluripotent stem cells. Both of these stem cell types are able to make identical copies of themselves during cell division, a process termed ‘self-renewal’. Importantly, as stem cells self-renew they retain the ability to produce the more mature functional cell types of the body, such as nerve, blood, heart or cartilage cells, through processes broadly termed ‘differentiation’. Tissue-specific stem cells normally only give rise to cells of the tissue in which they are found, for example, blood stem cells only produce blood cells. In contrast, pluripotent stem cells can produce any cell type of the body. In terms of clinical applications, both tissue-specific and pluripotent stem cells can be used to generate cells for autologous (patient-sourced) and allogenic (donor-sourced) therapies.The development of clinical stem cell therapies has occurred progressively over the last 50 years, typically via the ‘medical innovations’ route Figure . CommonlThe success of HSC transplants led scientists and clinicians to research stem cell-based therapies for other tissues. In 1981 skin stem cells were first harvested from burns patients, amplified in the laboratory and then transplanted back to the patient to partially reconstitute their skin. The , as well as their differentiation and immunomodulation properties, a large number of MSC-based clinical trials are progressing based on both their potential for pharmaceutical action or cell-replacement,20. Howein vitro has hampered development of novel therapeutic approaches using these cells. Moreover, the fact that tissue-specific stem cells can each only make a limited number of mature cell types makes production of complex tissues from these cells challenging. To overcome these significant practical limitations of tissue-specific stem cells, alternative sources of stem cells with greater developmental potential have been investigated. As a result, a variety of methods have been found for producing human pluripotent stem cells that are capable of generating any cell type in the body. These include: embryonal carcinoma cells derived from teratocarcinomas[Autologous (patient-sourced) transplantation or in vivo activation of tissue-specific stem cells offers an opportunity to develop therapies without requiring immunomodulation. However, historic and continuing difficulties in purifying, maintaining and/or expanding tissue-specific stem cells rcinomas; embryonrcinomas; embryonrcinomas or somatrcinomas; and, percinomas. ImportaKey to developing any new cell therapy from tissue-specific or pluripotent stem cells is to identify, purify and in some cases expand the most appropriate stem or differentiated cell type Figure . At the A recent review of the global landscape of stem cell clinical trials shows ‘novel’ applications - trials that do not involve established stem cell therapies - have grown dramatically, particularly using tissue-specific stem cells. Stem ceIn contrast, the first clinical trial to be approved worldwide using cells derived from human pluripotent stem cells received approval from the USA Food and Drug Administration (FDA) in 2010. This Phase I trial used human embryonic stem cell-derived oligodendrocyte precursor cells to treat acute spinal cord injury. Unfortunately, despite the immense effort invested in navigating the FDA regulatory requirements to establish this ‘first in man’ trial, in 2011 it fell victim to the high costs involved. The comin vitro produced autologous cells. Six patients will have biopsies taken for induced pluripotent stem cell production, from which retinal pigment epithelial cells will be differentiated, purified and seeded onto a cell substrate for transplantation. This process will be time, labour and cost intensive, with it expected to take 10 months before the grafts are ready for transplantation. Given that human induced pluripotent stem cells were only first described in 2007[Since commencement of the Geron trial two other human embryonic stem cell-based trials have begun and others are planned. The two commenced trials are using embryonic stem cell-derived retinal pigment epithelium to treat dry, age-related macular degeneration and Stargardt’s macular dystrophy. In 2013 in 2007 it is a The complexity of many incurable conditions, together with our insufficient understanding of normal and abnormal biology, means that it will be years before many who hope to benefit from stem cell therapies will be able to participate in clinical trials. Moreover, while hundreds of registered stem cell-based clinical trials are currently underway for a wide range of conditions, the majThese unproven stem cell ‘treatments’ include the use of autologous and allogenic stem cell transplants, and are estimated to attract thousands of patients from around the world each year. Until rMore recently, there has been growth in the number of clinics selling treatments using a patient’s own cells in countries with considerable regulation such as Australia and the USA. RegularProponents of unproven commercial therapies argue that a patient should have the right to pursue treatment using their own cells and blame over-regulation for delaying clinical progress of stem cell treatments,55. EvenAlthough there is still a role for assessment of innovative medical treatment using unproven stem cell interventions - like the initial 1957 hematopoietic and 1981 skin stem cell grafts - this approach should be considered as a ‘one-off’ and not offered widely or commercially until proven safe and effective. As recommended by the ISSCR this approach should only occur when certain conditions are satisfied such as: a robust scientific rationale; peer review of the proposed approach; data collection and clinical follow-up; undertaking only to treat a small number of patients who have provided informed consent; and commitment to more formal clinical trials in a timely manner , then large numbers of patients will have been subjected to inappropriate risks associated with medical procedures at significant health, financial and emotional cost.The pace of research into tissue-specific and pluripotent stem cells continues to increase, with new advances announced regularly. In this review we see that solid foundations of basic molecular research are required, not necessarily for establishment of therapeutic concepts, but for development of therapies towards safe and effective clinical treatments. From less successful applications we see the dangers of unproven procedures and the challenges in developing therapeutic regimes with limited molecular understanding. As the appearance of stem cell-related clinical trials accelerates, failed trials and possibly unforeseen side-effects are likely to follow. At the same time there is a danger of harmful or fatal consequences resulting from the emergence of profit-driven unproven stem cell therapies that take advantage of vulnerable patients. A concerted effort is therefore required to identify pitfalls and safeguards for timely and effective clinical translation of emerging stem cell therapies. Additionally it is not yet clear which stem cell types will be best suited to treat particular diseases. Ultimately, only further empirical research will determine for each disease whether optimal treatment is provided by the extensive proliferative and differentiation potential of pluripotent stem cells, or the potential autologous nature of tissue-specific stem cells.To address these issues we need to continue to diligently manage the expectation of patients and their families and friends, as well as those of the media, governments and financiers wanting to invest in the area. This includes correcting the misunderstanding that any source of stem cells is an automatic and unquestioned panacea for all ailments.We need to accelerate access for patients to well-regulated and adequately funded clinical trials, but these trials need to be based on a detailed, mechanistic understanding of the disease process with strong supporting pre-clinical data. We must also acknowledge that it is going to take time to develop new stem cell treatments. This will help to avoid academic, social and economic pressures from eroding the integrity of, and community confidence in, the regenerative medicine field. The recent controversy surrounding the Stimulus-Triggered Activation of Pluripotency (STAP) method highlighWe need to share results from all clinical research so that further research can be undertaken to evolve or develop promising new clinical therapies. We need to provide opportunities for innovative medicine on compassionate grounds but prevent over-enthusiasts from providing unproven and potentially unsafe procedures. Enforceable frameworks need to be developed that ensure new or ‘novel’ stem cell treatments are at least first proven safe through independent, peer-reviewed Phase I and II clinical trials in order to define for the patient the severity and frequency of unwanted side-effects.We must ensure that any new therapy is provided only with informed patient consent and rigorous long-term post-treatment monitoring. We recommend that any commercially available stem cell therapies not assessed via Phase III clinical trials should be required to be designated as experimental treatments. It is only through recognising and addressing these issues that the field will safely progress at a rate closer to the expectations of patients, thus realising maximal patient benefits without simply ‘selling hope’.ESC: Embryonic stem cells; FDA: Food and drug administration; GVHD: Graft-vs-host disease; HSC: Hematopoietic stem cells; ISSCR: International society for stem cell research; IVF: In vitro fertilization; MSC: Mesenchymal stem cell.The authors declare that they have no competing interests.The manuscript was conceived by MO’C with valuable input from MM and HM. HM, MM and MO’C all contributed to writing and editing the manuscript. All authors read and approved the final manuscript.


Learning is a complex brain function operating on different time scales, from milliseconds to years, which induces enduring changes in brain dynamics. The brain also undergoes continuous “spontaneous” shifts in states, which, amongst others, are characterized by rhythmic activity of various frequencies. Besides the most obvious distinct modes of waking and sleep, wake-associated brain states comprise modulations of vigilance and attention. Recent findings show that certain brain states, particularly during sleep, are essential for learning and memory consolidation. Oscillatory activity plays a crucial role on several spatial scales, for example in plasticity at a synaptic level or in communication across brain areas. However, the underlying mechanisms and computational rules linking brain states and rhythms to learning, though relevant for our understanding of brain function and therapeutic approaches in brain disease, have not yet been elucidated. Here we review known mechanisms of how brain states mediate and modulate learning by their characteristic rhythmic signatures. To understand the critical interplay between brain states, brain rhythms, and learning processes, a wide range of experimental and theoretical work in animal models and human subjects from the single synapse to the large-scale cortical level needs to be integrated. By discussing results from experiments and theoretical approaches, we illuminate new avenues for utilizing neuronal learning mechanisms in developing tools and therapies, e.g., for stroke patients and to devise memory enhancement strategies for the elderly. Learning refers to the ability of nervous systems to adapt to changing internal and external conditions, and includes perceptual processes of information uptake (encoding) as well as the storage of information. Adaptation arises from cellular and synaptic changes, i.e., synaptic plasticity  plays an important role for the encoding of new declarative information in the wake state, and the relation between the neocortical slow oscillation (SO) and hippocampal SPW-Rs is essential for storing and consolidating this information during sleep. Therefore it is necessary to develop models of hippocampal circuitries to predict ripple-dependent alterations of cellular properties.For perceptual learning (PL), ongoing large-scale brain dynamics associated with different states of attention interplay with learning during wakefulness. The sequence of external stimuli relative to certain brain states is relevant for perceiving these stimuli. Also the amplitude, phase, coherence and nonlinear behavior of a variety of EEG frequency bands ranging from very slow to ultra-fast rhythms influence the efficiency of passive PL. PL induced by active training requires attention mechanisms in contrast to stimulation-induced perceptual improvement. Consequently, different effects of ongoing dynamics exist. In order to reveal fundamental mechanisms underlying the diverse experimental findings at the different brain scales, computational models at various space-time scales need to be employed. Only an integrative approach will allow us to address the complex issue of the role of intrinsic neuronal activities for learning in a comprehensive and meaningful manner. By means of a number of examples we will detail the diverse aspects of this integrative work.in vitro in rat hippocampus. This work illuminates the role of neuromodulators for the regulation of brain states that are relevant for learning of declarative memories. Next, we link cellular SPW-R activity observed invasively in rats to human behavior and report the latest insights concerning consolidation of episodic memory representations mediated by hippocampal and neocortical networks. Finally we deal with the question how intrinsic states and the temporal sequences of external events interact and lead to plasticity and learning. Here the focus is set on a form of implicit learning, namely PL. In PL, perceptual abilities improve through practice, training or pure exposure to stimulation. We address the question how does the brain know which input is relevant and what is the role of endogenous oscillations herein. In this context we highlight the clinical relevance of those issues—particularly for stroke rehabilitation.In the present review article, we illustrate mechanisms of explicit memory across scales reaching from sub-cellular processes to behavior. Specifically, we elucidate how theta rhythm and dendritic computations of hippocampal neurons could contribute to the encoding of space in cognitive maps. We continue on the cellular scale and review work conducted The mammalian hippocampus plays a key role in learning and memory in general and in the formation of episodic memories in particular Squire, . LesionsHippocampal cognitive maps are very flexible and adapt to represent new environments. The hippocampus is hence one of the most plastic structures in the brain. Accordingly, long-term potentiation (LTP) was first described in the hippocampus in the early 1970s  LTP protocols require a high stimulation frequency that is far beyond firing frequencies of place cells in vivo; (2) STDP protocols, which are closer to in vivo activity, and LTD protocols require a large number of repetitions of stimuli, and the time required to deliver a sufficient number of repetitions is too long; therefore in vivo-like plasticity stimuli, e.g.,  are essential in controlling both the oscillatory state and the plasticity in the hippocampal formation  does not match the time scale of plasticity models such as STDP (tens of milliseconds) and it is unclear how the temporal order of places can be stored. To explain a possible solution to these problems, we first focus on the oscillatory state of the hippocampus during the awake state and then explain a phenomenon called “phase precession”.Complex behaviors such as spatial exploration in rodents, working memory in primates, and navigation and working memory in humans are consistently associated with theta rhythms, i.e., 4–12 Hz oscillations  of spikes decreases as a function of position , dopamine or serotonin into many parts of the brain. Systemic neuromodulation implies in this context not only that agents affect locally a set of neurons. Rather they affect the way in which neuronal assemblies are temporally formed and how interactions between sets of neurons are enabled. This is achieved by a concerted modulation of excitability and release properties of GABAergic and glutamatergic synapses. Global modulation of network activity may be locally controlled by substances that are released by individual sets of neurons. These include adenosine, adenosine triphosphate  sleep-stage 2 and SWS with a peak frequency of 0.75 Hz  evolves from a dialog between neocortex and hippocampus such that the neocortical SOs drive in parallel the generation of thalamocortical spindles as well as hippocampal SPW-Rs, with the latter accompanying the reactivation of new memory information in hippocampal networks Buzsáki, . This enCentral to this concept is the assumption that memory consolidation during sleep relies on the repeated reactivation of neuronal networks previously engaged in encoding the information. Indeed, temporal patterns of neuronal reactivation have been consistently observed during SWS after hippocampus-dependent tasks in the rat hippocampus  Do neocortical SOs indeed exert a causal top-down control such that they drive memory-reactivations and associated hippocampal ripples as well as thalamo-cortical spindles? (2) Do SOs induced ripple-spindle events conversely represent a bottom-up mechanism that facilitates the hippocampo-to-neocortical transfer of memory information to neocortical sites? So far, these questions cannot be definitely answered. Nonetheless, a causative role of the SO for hippocampus-dependent memory consolidation has been suggested by findings after experimental induction of SOs through transcranial electrical stimulation  oscillations—are dynamical, complex signals with largely chaotic properties that can be described by nonlinear mathematical expressions  potential studies show that the phase of slow cortical potentials modulates higher frequency activities Rebert,  and perfCommunication between neurons is reflected by action potentials. In EEG traces of population spikes can be recorded under certain conditions  in real-time. Brain responses are continuously monitored, translated into a perceivable—e.g., visual, acoustic or tactile—signal, and back-projected to participants who, over the course of typically several training sessions, learn to consciously regulate their brain activity. An extensive body of literature starting in the 1970s focused on neurofeedback training. Such training was implemented to control various EEG measures, providing evidence of positive effects in patients with otherwise pharmacologically intractable epilepsy, attention deficit disorder, and hyperactivity  will be of particular interest for the understanding of how coactivation-induced behavioral and cortical changes mature over the course of the application and to identify crucial neurobiological states relevant for an optimal coactivation influence . This allows to specifically trigger these states, e.g., by means of neurofeedback training or other interventions such as non-invasive brain stimulation, in order to boost coactivation-induced plasticity. The overarching goal is to identify brain states specifically sensitive to plasticity-driving interventions. The identification of such spatial or temporal states may in future help to develop new treatment options for brain injury. One possible research strategy is to investigate functional/structural brain plasticity and behavioral recovery after brain injury over time. Understanding the temporal dynamics of recovery would allow to specifically assigning appropriate neurorehabilitative interventions to certain temporal states of recovery to further optimize patients’ outcome.Another novel approach to neurofeedback learning was undertaken recently . During an art festival data from over 500 people were collected. In a collective computer game participants controlled their mental states of relaxation and concentration with EEG neurofeedback. Learning related changes in the EEG power spectrum were detectable already after a short training period of about one minute. In addition baseline brain activity predicted the training outcome indicating state-dependent learning. Such quick training effects are relevant for every-day brain-computer interfaces (BCI) applications. The study indicates a novel avenue of application-oriented neuroscience fostering the understanding of brain functionality under natural conditions—rather then laboratory settings—by linking art and science.The molecular principles of synaptic plasticity are relatively well understood. Yet the principles that orchestrate plasticity to render it a meaningful cognitive instrument are less clear. The brain continuously reorganizes thereby consolidating new memories while maintaining or erasing old ones. Understanding the underlying complex principles of interactions between the intrinsic functional connectivity  and external triggers stimulating the brain is essential for our understanding of learning. Revealing those principles is important for clinical applications and also for the development of novel neuromorphic technologies, for a comprehensive account see two special issues of the BrainModes conference series (Breakspear et al., 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.


Ewing sarcoma of bone is classically a permeative lesion in the diaphysis of long bones in children. While they occur primarily in children and adolescents, they can be seen in young adults in their 20s, but these are typically seen in flat bones. The permeative nature of the lesion can elicit new bone formation creating a partially sclerotic appearance, cortical expansion presenting as a “Codman triangle,” or have an “onion-skin” type of aggressive periosteal reaction/periostitis. Ewing sarcoma is rarely seen without an associated soft-tissue mass and is even rarer to just have benign-appearing periostitis . We present such a case of Ewing sarcoma in a young adult confined to just the medullary metadiaphysis without cortical erosion or soft-tissue mass. To the best of our knowledge, this is the first case to be reported in the radiology literature. We present a 29-year-old postpartum female with a four-month history of right groin pain that occasionally radiated into the hip and anterior right thigh. The pain was intermittent but worsening. She decided on physical therapy but with no improvement. Her medication was limited to ibuprofen as she was still breastfeeding and the pain worsened with standing and lifting her baby. She denied history of trauma, fever, chills, night sweats, weight loss, or night pain. Plain radiographs of the right hip and femur were normal .She subsequently received an MRI of the right hip which revealed a large marrow-replacing lesion extending from the intertrochanteric region into the proximal diaphysis with surrounding edema in the bone and soft tissues . The patWith a working diagnosis of lymphoma, the fine-needle biopsy of the lesion instead revealed viable small round blue cells surrounding a central focus of necrosis  and smalThe patient underwent chemotherapy followed by surgical wide resection and prosthetic reconstruction. The resected gross specimen showed no residual viable tumor by microscopic examination .Ewing sarcoma (ES) is one entity of what is now considered to be a group termed Ewing sarcoma family tumors (ESFT), which includes peripheral primitive neuroectodermal tumors (PNETs) and Askin tumors . ES accoThe characteristic radiologic appearance of ES is a permeative osteolytic lesion involving the diaphysis or less commonly the metaphysis of a long bone but also occurs in the flat bones. The clinical course of the tumor when it is metaphyseal begins as an intramedullary lesion that causes marrow replacement and permeates through the cortical bone and extends into the adjacent soft tissues. Interestingly, the diaphyseal course also begins in the intramedullary canal but then permeates the cortex via haversian canals and vascular channels and extends into the surrounding soft tissue leaving behind the more characteristic periosteal, multilayered reactive bone formation commonly described as an “onion-skin” periosteal reaction . Our casOsseous lymphoma can be confused with Ewing sarcoma not only clinically but also pathologically. Ewing sarcomas microscopically appear as sheets of small blue round monomorphic cells with little intercellular stroma . SeveralIn summary, Ewing sarcoma is a very aggressive tumor with variable prognosis depending on stage, site, size, microscopic feature, and biologic features. Prognosis has improved thanks to modern chemotherapy advancements.


Plants growing in their natural habitats are often challenged simultaneously by multiple stress factors, both abiotic and biotic. Research has so far been limited to responses to individual stresses, and understanding of adaptation to combinatorial stress is limited, but indicative of non-additive interactions. Omics data analysis and functional characterization of individual genes has revealed a convergence of signaling pathways for abiotic and biotic stress adaptation. Taking into account that most data originate from imposition of individual stress factors, this review summarizes these findings in a physiological context, following the pathogenesis timeline and highlighting potential differential interactions occurring between abiotic and biotic stress signaling across the different cellular compartments and at the whole plant level. Potential effects of abiotic stress on resistance components such as extracellular receptor proteins, R-genes and systemic acquired resistance will be elaborated, as well as crosstalk at the levels of hormone, reactive oxygen species, and redox signaling. Breeding targets and strategies are proposed focusing on either manipulation and deployment of individual common regulators such as transcription factors or pyramiding of non- (negatively) interacting components such as R-genes with abiotic stress resistance genes. We propose that dissection of broad spectrum stress tolerance conferred by priming chemicals may provide an insight on stress cross regulation and additional candidate genes for improving crop performance under combined stress. Validation of the proposed strategies in lab and field experiments is a first step toward the goal of achieving tolerance to combinatorial stress in crops. The on-going change in climate conditions due to mostly anthropogenic causes such as the increase in COmissions  exaggeramissions  and incrmissions . Availabmissions . Therefo~omics technologies and on-going functional characterizations of individual genes, it has become apparent that environmental adaptation is under tight regulation, which is critical for plant survival  signaling , plant h2+ . Based oresponse .omics analyses derive from a mixture of different cell types and tissues, these spatially important interactions may be missed and these datasets may lead to erroneous conclusions about components shared and their significance in abiotic and biotic stress crosstalk. Moreover, as combinatorial stress potentially results in novel interactions between signaling components, extrapolation of results from studies with single stress conditions should be done with care.The nature of pathogen perception dictates that physical barriers such as the cuticle, stomata, and cell walls are also critical for timely pathogen recognition and interception . As dataHere we will elaborate on the mechanisms involved in adaptation and tolerance to combinatorial abiotic and biotic stress, with a focus on dehydration/salt stress and fungal and bacterial pathogens interaction. This review will particularly emphasize interactions that potentially arise during the pathogenesis timeline and were as yet given little attention. We will discuss molecular components with potentially critical roles in abiotic and biotic stress tolerance crosstalk, and propose breeding approaches toward effective crop improvement against combinatorial stress.Studies on the commonly occurring combination of drought and heat stress have revealed that physiological and molecular responses of plants exposed to both stresses are markedly different from their response to the individual stresses . Similar+ and Cl-). As NaCl is an antifungal agent . In line with this argument are the many examples of reduction of fungal pathogenicity by metal accumulation . Finally genetically heightened resistance to pathogens is often accompanied by a fitness cost that may generally affect the plant performance under both abiotic stress and stress-free conditions  and induce abnormal stomata opening patterns, and all of these are critical for plant tolerance to abiotic stress . Salicylnditions .Pseudomonas syringae type III effector HopAM1 that targets HSP70 , a non-protein amino acid, results in enhanced resistance to a wide range of stresses including heat, drought, and salinity stress, as well as enhanced resistance to biotrophic as well as necrotrophic fungi  of stress responses identified distinct CREs for the response to abiotic and biotic stressors . As information under combined stress is limited, and a detailed coverage of all potential interactions is not possible, our intention is to provide leads for future research that will aid to further dissect plant adaptive responses and tolerance under combined abiotic and biotic stress.As mentioned above, abiotic and biotic stress interactions can occur at multiple levels, depending on the type of the stress , the lifestyle, and infection strategy of the pathogen  as well as the pathogenesis stage. We will summarize molecular components that according to evidence mentioned above participate in stress crosstalk. We will follow the pathogenesis timeline highlighting first extracellular interactions taking place at the epidermis and the apoplast during the initial stages of pathogenesis and moving on to the interactions in the intracellular environment during pathogen colonization , a gene that is involved in cuticle biosynthesis, exhibit increased permeability of the cuticular layer which leads to increased resistance to Botrytis cinerea  mutants pmr5 and pmr6 resulted in a SA, JA, and ET independent increase in resistance to powdery mildew species  which survey the cell wall integrity and bind to MAMPs and DAMPs . Upon activation these transmembrane proteins , send signals for the elicitation of downstream defense responses. Changes of cell wall structure and adherence to the plasma membrane upon exposure to abiotic stresses may affect their functional integrity. This is emphasized by the observation that NDR1, an essential component of disease resistance mediated by CC-NB-LRR genes , is funcsyringae . Abioticsyringae , while ssyringae .Pathogen recognition activates a battery of defense responses that target the apoplastic space. These include local cell wall enforcement, secretion of antifungal compounds at the site of intended penetration and up-regulation of enzymes with fungal cell wall degrading activities . These eHvROR2 and AtPEN1), which display diminished penetration resistance to powdery mildew pathogens  and calcium-dependent protein kinases (CDPKs) regulate ROS production by NADPH-oxidases  and MAPK kinases (MAP2Ks). Hydrogen peroxide (H2O2) has been shown to mediate activation of the three major and well-studied Arabidopsis MAPKs, MAPK3, 4, and 6, through MAP3Ks and other kinases , which encodes β-1,3-glucanase involved in callose degradation, was shown to be down regulated in response to ABA, partly elucidating ABA-mediated capacitation of callose deposition. The ahg2-1 mutant in Arabidopsis accumulates both ABA and SA and has increased expression of defense related genes, which is an indication that ABA and SA do not always act antagonistically. Transcriptome analysis of the ahg2-1 mutant revealed complex interactions between ABA and SA signaling involving altered mitochondrial and RNA metabolism  is a plant response to developmental and environmental stimuli  and pathogen defense (in the form of HR) that is initiated and regulated by redox changes, like an increased oxidation ratio of GSH and ascorbate . APX appll death . APX isoll death . Considell death  it is ofS-nitrosylation and thioredoxin-mediated reduction in the control of the oligomeric and monomeric state of NPR1  accumulation results in enhanced and accelerated cell death  and defense-related genes  mutants exhibit enhanced basal expression of many SA-responsive genes  but decrChromatin structure can also be altered by the active deposition of variants of the canonical histones. Deposition of one of the these variants, H2A.Z, is linked to transcriptional activation in response to environmental stimuli , and disIt would be highly interesting to investigate how a previously imposed stress predisposes plants at the methylation and chromatin level for the encounter of a subsequent stress, (de)sensitizing subsequent responses. This type of acclimation/predisposition may even be a useful tool for preparing seeds and propagated material for stressful environments.The plant immune system consists of successive layers counteracting suppression of defense responses by pathogens through secretion of effector proteins . RecogniArabidopsis ; therefore, the outcome of the interaction will vary with the defense mechanisms employed and on the pathogens involved.In accordance with individual abiotic and biotic stressors, each abiotic stress/pathogen/host combination should be treated independently as, despite the potential universal applicability of some interactions that were characterized in opmental  as well opmental , the envBreeding for resistance to combinatorial stress is challenging. However, various novel approaches can aid in dissecting interactions between various types of stressors and identifying genetic components that can be breeding targets. The combination of different ~omics technologies has enabled the molecular dissection of plant phenotypes . They prManipulations that induce resistance to abiotic and biotic stress such as application of priming chemicals, followed by comprehensive phenotypic characterization can be used for candidate gene identification and molecular processes underlying stress cross-tolerance. Utilization of pre-existing chemical libraries for compounds that can prime abiotic and/or biotic stress tolerance and identification of their mode of action through chemical genetics approaches can both provide biotechnological targets for crop stress improvement and an opportunity to directly use the identified chemical in agricultural practice if no unintended side effects are observed . MoreoveBreeding for resistance to exposure to combined abiotic and biotic stress by incorporation of genetic components regulating the response to both stresses faces various challenges. For example, TFs can have thousands of binding sites across the genome , increasPyramiding genes that provide increased tolerance to either stress and do not (negatively) interact with each other offers an alternative route. Strong resistance mediated by R-genes, that appear to be robust to perturbations, can be pyramided with well-characterized genes conferring abiotic stress tolerance  under different abiotic stress/pathogen combinations will demonstrate their feasibility and applicability, further leading toward the goal of breeding for crops that maintain their robustness and yield performance under diverse environmental conditions.Exploitation and deployment of different strategies (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.


The consolidation of memories for places and events is thought to rely, at the network level, on the replay of spatially tuned neuronal firing patterns representing discrete places and spatial trajectories. This occurs in the hippocampal-entorhinal circuit during sharp wave ripple events (SWRs) that occur during sleep or rest. Here, we review theoretical models of lingering place cell excitability and behaviorally induced synaptic plasticity within cell assemblies to explain which sequences or places are replayed. We further provide new insights into how fluctuations in cholinergic tone during different behavioral states might shape the direction of replay and how dopaminergic release in response to novelty or reward can modulate which cell assemblies are replayed. What determines which memories are retained and which are lost is an absorbing topic for scientists and nonscientists alike, yet the mechanisms underlying the persistence of some pieces of information and the forgetting of others remain to be identified. Well-established theories propose that memories are encoded during wake behavior, with information being represented in the coordinated activity of subsets of neurons forming cell assemblies Sequential replay can occur in both a forward Concordantly, a growing body of literature has linked SWRs to learning and memory. SWR incidence during SWS is increased following training on a place-reward association task By contrast, replay, particularly during awake SWRs, has also been proposed to have functional roles other than for spatial memory consolidation; for example, in temporal credit assignment to reward locations (particularly backward replay) Despite over a decade's worth of literature describing hippocampal replay during SWRs, several questions remain. How is neuronal coordination during SWRs controlled? What selects which trajectories will be replayed within a given SWR? Do these mechanisms differ for SWRs in different behavioral states, or under different neuromodulators? In this review, we provide a critique of the evidence surrounding two current theories on how replay occurs, namely by lingering place-related excitability or as a result of synaptic plasticity. Given the limitations of both models, we then outline how neuromodulatory factors are likely to influence the mechanisms underlying replay and impart selection onto which trajectories are replayed. Finally, we propose an integrated model for replay in SWRs that takes into account the behavioral state of the animal and the underlying neuromodulatory tone.per se is lingered in an order dictated by the subthreshold spatial inputs onto place cells at the current position of the animal -3 network alone, or by rapid interactions between CA3 and the dentate gyrus (DG) If synaptic plasticity is a necessary prerequisite of replay, manipulations that induce plasticity should facilitate SWR replay, while manipulations that prevent plasticity within the hippocampus should not. This prediction has received relatively little support so far, possibly due to methodological considerations, although it has been shown that sSWR-associated unit firing increases following a plasticity-inducing protocol per se, these studies suggest that NMDAR activity and, as a by product, hippocampal synaptic plasticity, are critically involved in dynamically configuring the hippocampal network into a state that can subsequently bias the SWR activity content. In line with this, while the blockade of NMDARs during learning of new goal locations impaired the sleep reactivation of new place cell representations, it unexpectedly promoted that of old representations In another study that seemingly challenges the synaptic plasticity model, mice with NMDAR1 knockout (KO) specifically in CA3 pyramidal cells and, therefore, with an absence of NMDAR-dependent long-term potentiation (LTP) at CA3 autoassociational synapses, were found to show stronger, less variable replay of CA1 place cell activity compared with control mice per se is the plasticity mechanism utilized by such a model This model is supported by evidence suggesting that reactivation in SWRs is expressed as a function of potentially plasticity-inducing experience. For example, co-activation during awake and sleep SWRs is stronger for cell pairs with overlapping place fields This latter observation casts doubt on whether this model alone can sufficiently explain all observable replay phenomena. It is difficult to reconcile a plasticity mechanism that could bind ensembles of cells together in a manner that would enable backward replay preferentially during exploratory behaviors but forward replay during sleep The hippocampus receives constant inputs related to the behavioral state of the animal, including those leading to the release of neuromodulators, which dramatically transform the functional output of neural circuitry in vitroMicrodialysis measurements of hippocampal acetylcholine levels show variation throughout the sleep–wake cycle, with acetylcholine high during rapid eye movement (REM) sleep and active wakefulness but decreasing levels during quiet wakefulness and SWS Within the hippocampus, acetylcholine exerts wide-ranging cellular and synaptic effects in vivoin vitroin vitroIn addition, muscarinic receptor activation by endogenously released acetylcholine Clearly, the impact of acetylcholine on place cell activity during exploration and SWR activity is complex and deserves further investigation by experimentation and computational modeling. Meanwhile, the available literature, outlined above, points towards a model whereby the behavioral state of the animal influences how the hippocampus engages both the lingering excitability and synaptic plasticity mechanisms to initiate replay activity, in a manner strongly shaped by the cholinergic tone . This neThe hippocampus is also innervated by dopaminergic mesencephalic neurons from the ventral tegmental area (VTA) and substantia nigra Interestingly, place cell ensembles are more reactivated in sleep SWRs following the exploration of novel locations and/or environments Therefore, it is tempting to make the conjecture that dopamine release during exposure to spatial novelty or rewarded outcomes biases the content of subsequent SWR activity for the purpose of memory to represent locations spanning the entire novel environment or the particular behaviorally salient location, respectively. Concordantly, a recent study has shown that burst stimulation of VTA dopaminergic neurons, during exposure to a novel environment (to further enhance novelty-increased VTA firing in vivo and this facilitatory effect was abolished by D1/D5R antagonists or mimicked by D1/D5R agonists It is unclear how dopamine may bias SWR activity through the lingering excitability model since the effects of dopamine on hippocampal pyramidal cell excitability are mixed, with some studies reporting a decrease in excitability, for example by hyperpolarizing the membrane potential and augmenting the spike after hyperpolarization How the brain informs the dopaminergic systems about spatial novelty or rewarded outcomes remains to be investigated. This likely involves a complex network of multiple brain circuits In conclusion, we have proposed a new conceptual framework for understanding the ordered sequential activation of prior waking activity in SWRs. This likely occurs via a combination of mutually nonexclusive mechanisms, since none of these can explain the available literature in isolation. While many questions remain , our cur


Military personnel are deployed abroad for missions ranging from humanitarian relief efforts to combat actions; delay or interruption in these activities due to disease transmission can cause operational disruptions, significant economic loss, and stressed or exceeded military medical resources. Deployed troops function in environments favorable to the rapid and efficient transmission of many viruses particularly when levels of protection are suboptimal. When immunity among deployed military populations is low, the risk of vaccine-preventable disease outbreaks increases, impacting troop readiness and achievement of mission objectives. However, targeted vaccination and the optimization of preexisting immunity among deployed populations can decrease the threat of outbreaks among deployed troops. Here we describe methods for the computational modeling of disease transmission to explore how preexisting immunity compares with vaccination at the time of deployment as a means of preventing outbreaks and protecting troops and mission objectives during extended military deployment actions. These methods are illustrated with five modeling case studies for separate diseases common in many parts of the world, to show different approaches required in varying epidemiological settings. Military personnel are deployed abroad for missions ranging from humanitarian relief efforts to combat actions. While deployed, troops have very specific goals and objectives to achieve within the time frame of their individual deployment rotations, and delay or interruption in these activities due to reasons such as illness and disease transmission can cause operational disruptions, significant economic loss, and stressed or exceeded military medical resources.Deployed troops function in environments favorable to the rapid and efficient transmission of many viruses—resulting from infection by disease-carrying forces and local populations, high-risk behavior, and inadequate medical care —particulWhen immunity among deployed military populations is low, the risk of vaccine-preventable disease outbreaks increases. This increased risk in turn has an impact on troop readiness and achievement of mission objectives. However, the threat of outbreaks can decrease through public health interventions, particularly targeted vaccination, and the optimization of preexisting immunity among the deployed population. High seroprevalence to vaccine-preventable disease and the corresponding protective threshold have the possibility of providing protection against outbreaks to deployed troops.Here we explore, through the use of computational models of disease transmission, how preexisting immunity compares with vaccination at the time of deployment as a means of preventing outbreaks and protecting troops and mission objectives during extended military deployment actions.On average, deployed military forces consist mainly of healthy, physically-fit individuals ranging in age from 18 to 45 years. Soldiers enter and leave the deployed population via inward and outbound rotation rates and casualty rates, which may vary throughout the duration of the military action. Within military populations there is a distinct structure in which social mixing can be largely within-unit, with a lower level of between-unit contacts occurring in common areas. The deployment tasks of the individual units can vary dramatically, as can their level of contact with local populations. In regions where viruses are circulating at endemic levels, this local contact can significantly affect transmission rates to troops.Depending on the mission at hand, inward-rotating soldiers are often vaccinated against common vaccine-preventable diseases. Thus these same soldiers may already have significant preexisting immunity to certain viruses when the time comes for subsequent deployments—as a result of prior vaccination during military service, childhood vaccination, or even previous infection and recovery. While epidemiological details may vary based on the virus, this preexisting immunity is generally highly protective—though in some cases protection may wane over years or decades. The presence of preexisting immunity can be determined by blood tests, and evidence of positive serology is assumed to be protective against transmission.In contrast, vaccine-derived immunity can be highly variable. Issues such as cold-chain failure can severely impact vaccine efficacy, even to the point of complete lack of protection. Under reasonable conditions, however, many vaccines (such as measles and rubella) can confer very high immunity—nearing 95%, 96%, and even 99% efficacy—though this immunity may not be as thorough as that conferred by disease recovery or implied by the existence of positive serology for the virus as evidenced by blood tests. Some vaccines require multiple doses for full protection, and lengthy lags between immunization and protection can be problematic. Vaccination in the presence of existing immunity can be both unnecessary and costly. In addition, for some vaccines, multiple dosing can result in adverse effects; however, data on current preexisting immunity is not always available to medical personnel administering vaccination in a time-frame compatible with deployment.If the potential protective benefit of relying on preexisting immunity to protect deploying troops is significant enough, it may be feasible to reduce or eliminate mandatory predeployment vaccination—thus also reducing the potential cost and risks associated with adverse events resulting from overvaccination. But how to evaluate the comparative impacts of the two types of protection?i of the deployed population via inbound rotation (bIN) and exit through outbound rotation (bOUT) or casualty (μ); upon deployment individuals enter the susceptible (S) class and proceed to the infected (I) class based on the disease transmission rate (β) which is a function of contacts with other infected soldiers within the same (i) or different (j) units, or with infected individuals within the local population . Infected soldiers enter the removed (R) class via recovery (γ) and remain there for the duration of their deployment (ρ) (which may be less than 100%) and the vaccine efficacy (VE)  (V) are required between susceptible and removed classes with rates reflecting vaccine coverage (ρ), efficacy (VE), and duration of lag or time between doses (σ). In some situations, partially-immunized individuals within these holding classes are protected against disease so long as subsequent doses are administered on time; however for other vaccines immunity is only conferred once all doses are received, and in the meantime individuals in the holding classes are still fully or partially susceptible to transmission (δS) and with lower resulting infectiousness (δI)—(such as varicella), an entire separate level of disease classes is required for vaccinated susceptible (Svi) and vaccinated infected (Ivi)  epidemiological model for the transmission of a generic direct-transmissible disease and explore the impacts on this model of the various types of immunity. For this hypothetical situation, soldiers enter unit ployment :(1)dSid reduced :(2)dSidan 100%) :(3)dSidsmission :(4)dSidd (Ivi) :(5)dSidWe evaluate all case study disease models illustrated below from the perspective of a deployed military population functioning from a long-standing base, with four types of units having varying levels of contact with local populations ranging from high to negligible daily rates of interaction depending on duty type, based on deployment conditions as described in published literature –7.Unit-specific levels of contact with local populations are dependent upon the particular tasks assigned, with some units, such as support troops, spending only the bare minimum of time off-base; in contrast, other units such as Civil Affairs and Special Forces may interact with locals on an almost-daily basis (unpublished data). For this analysis the deployed population is assumed to consist of one unit of 1,000 soldiers with a high daily probability of contact with the local population; one unit of 1,000 soldiers with a medium-to-low daily probability of contact with locals; one unit of 2,000 soldiers with low-to-no daily probability of contact with locals; and one additional unit of 1,000 soldiers, also with low daily probability of contact with the local population .For long-standing bases, troop housing is assumed to be set up by unit and social mixing is assumed to be “cliquish” (mainly within-unit), though conditions are very crowded and so complete isolation of units is impossible. Mixing within units is assumed to be very homogeneous and high-level, with each individual within the given unit having daily contact of some kind with all other individuals of that same unit.Long-standing bases are assumed to have well-established water purification and food safety systems, with a variety of on-base dining options, though frequently fresh produce is brought in from local areas and nearby countries, increasing the risk of transmission of food-borne illness. We assume the overall deployment action lasts over a period of ten years, and individual soldiers have 12-month deployment rotations. Inbound and outbound rotation rates are assumed to vary over the deployment action , allowinMeasles is a highly infectious viral disease, causing symptoms including fever and cough as well as a blotchy red rash on the face that spreads to become more generalized. Measles virus is transmitted via droplet spread or direct contact with infected individuals and is one of the most highly communicable infectious diseases . The meaLive, attenuated measles vaccine is the preferred control measure, a single dose of which results in significant antibody response in 94%–98% of susceptibles .The transmission of measles shows marked annual seasonality, in addition to periodic large epidemics roughly every two years . MeaslesEndemic measles transmission was eliminated in the Americas in 2002 ; howeverThe mathematical structure for the respiratory transmission of measles requires the addition of an exposed class to the basic SIR model, to accommodate the incubation stage for the disease. Due to single vaccine dosing and absence of lag prior to protection, vaccinated individuals move directly from the susceptible class to the removed class based upon measles coverage rate and vaccine efficacy , Table 1ped work  and was ped work  under thAt low levels of protection, computational simulations of the measles model show that the difference between preexisting immunity and deployment vaccination, in terms of mean annual measles incidence, is minor; however this difference becomes more significant as protection levels increase .Measles is known to have minimum threshold susceptible population limits, below which transmission will not occur . Model sRubella is a mild febrile viral disease, causing flu-like symptoms as well as a nonraised rash on the face that spreads to the torso and limbs, which closely represents the rash resulting from infection with measles or scarlet fever. As with measles, rubella virus is transmitted via droplet spread or direct contact with infected individuals; however rubella is significantly less infectious , 20, 21.A live, attenuated rubella virus vaccine has been available since 1969, a single dose of which results in significant antibody response in 95%–99% of susceptibles , 20, 22.Though rubella transmission shows higher prevalence in winter and spring, it is less affected by seasonality than measles and the magnitude of the seasonal peaks is smaller , 24. RubAfter a universal vaccination campaign in 2004, endemic rubella transmission was eliminated in the United States; endemic transmission has also been eliminated in all of the WHO Region of the Americas ; howeverThe mathematical structure for the transmission of rubella closely parallels that of measles, as both diseases share common characteristics in terms of their transmission and vaccination see ), thoughThe structure of the rubella transmission model was based on published models , 27 and Similar to measles, the rubella vaccine has very high efficacy (95%) with full protection conferred immediately after immunization. However, unlike measles, there is no minimum susceptible population limit for rubella. As a result, we can observe rubella transmission persisting all the way to 100% protection . At low Overall, the simulated mean annual rubella incidence is low—even for scenarios with no immunity—however rubella cases do still occur, up to approximately 150 in total during the 10-year deployment action for no protection whatsoever (results not shown). In light of the endemic nature of rubella infection in countries throughout the world, and in combination with the suboptimal level of preexisting protection against RUB among American Warfighters, it is likely that continuing high levels of vaccination coverage in the absence of elevated preexisting seropositivity is advisable, particularly in combination with efforts to reduce effective contact rates with potentially infected local populations. Even in this case, however, symptomatic and asymptomatic rubella cases will continue to occur among deployed populations, albeit at very low levels.Varicella is a highly contagious disease spread by direct person-to-person contact and airborne droplet transmission, characterized by mild fever and a scabbing rash, though mild or asymptomatic infections may occur. The varicella incubation period lasts two weeks , 34, andA live attenuated varicella vaccine has been licensed for use in the US since 1995, and routine childhood vaccination is recommended at one year of age with a booster at school entry , 36. VacVaricella transmission occurs worldwide, with 95% of individuals in temperate climates experiencing infection by young adulthood . Recent The mathematical structure for the transmission and vaccination of varicella requires the addition of an exposed compartment, along with an extra level of disease classes, to accommodate the leaky nature of varicella vaccine , Table 3d models  and was d models –40 assumAt lower levels of protection, computational simulations again show that the difference between preexisting immunity and deployment vaccination, in terms of mean annual varicella incidence, is minor; however, as with measles, this difference becomes more significant as protection levels increase . ProtectEven as protection levels approach 100%, varicella cases continue to occur and we can see that there are no distinct protective thresholds for the cessation of its transmission within deployed populations. In light of the aggressive varicella attack rate among susceptible individuals, it is likely that continuing high levels of vaccination coverage in the absence of elevated preexisting seropositivity is advisable, perhaps in combination with efforts to reduce effective contact rates with potentially infected local populations.Unlike measles, rubella, and varicella, transmission of hepatitis A is assumed to be dual-mode: via direct- or close-contact between susceptible and infected individuals, and via indirect environmental exposure through the consumption of contaminated food and/or water. Hepatitis A has an incubation period lasting from two to seven weeks , 41, 42,Inactivated hepatitis A vaccine has an efficacy of 99% , 45, 47;Hepatitis A transmission is generally low in developed countries with good sanitation and hygienic conditions; however transmission can be very high in developing countries with poor conditions, and the majority of children in these regions have been infected with hepatitis A before the age of 10, mostly asymptomatically . In the The mathematical structure for the transmission and vaccination of hepatitis A requires the inclusion of a separate input corresponding to the environmental reservoir for hepatitis A, along with an additional vaccinated class, to accommodate the lag period between vaccination and full protection and the potential for continued transmission during this period , Table 4d models , 50 and d models –53 assumAs in the previous case studies, computational simulations again show that the difference between preexisting immunity and deployment vaccination, in terms of mean annual hepatitis A incidence, becomes more significant as protection levels increase, with preexisting protection having a greater impact than deployment vaccination .In spite of high vaccine efficacy (99%), there is a 30-day lag after vaccination before full protection is imparted on immunized soldiers—and within this lag period transmission of hepatitis A resulting from effective contact with infected individuals or contaminated food is still possible. This long delay dramatically reduces the effectiveness of vaccination at the beginning of deployment.For hepatitis A, again model simulations indicate that there is no protective threshold which prevents disease transmission. Even 100% vaccination coverage prevents only 85%–90% of simulated hepatitis A incidence (results not shown), due to the lengthy time-lag between vaccination and full protection. Sensitivity analyses (results not shown) indicate that exposure to contaminated food sources is a higher risk factor for hepatitis-A transmission than contact with infected individuals; thus any efforts to reduce this exposure could significantly decrease disease incidence among deployed troops. Also, although vaccination provides less protection against hepatitis A transmission among deployed populations than does preexisting seropositivity, it is likely that immunizing troops with hepatitis A vaccine at least 30 days prior to deployment may improve this protection by eliminating  the possibility of exposure to contamination during the efficacy lag period.Hepatitis B is the most serious type of viral hepatitis, causing potentially life-threatening liver infection, chronic liver disease, and risk of death due to cirrhosis of the liver and liver cancer. Hepatitis B is transmitted by direct contact with blood or other bodily fluids of infected individuals, similar to human immunodeficiency virus (HIV), though with dramatically greater infectivity. Unlike HIV, the hepatitis B virus can survive outside the body for at least 7 days. During this time, the virus can still cause infection if it enters the body of a person who is not protected by the vaccine or immunity resulting from recovery from prior infection. Hepatitis B is not spread by contaminated food or water and cannot be spread by casual contact.50%–90% of patients with acute hepatitis B infection experience subclinical illness that may remain undetected; the remaining acute patients develop symptoms that can include fever, fatigue, anorexia, nausea, body aches, jaundice, and (rarely) acute liver failure , which cA vaccine against hepatitis B has been available since 1982, which is 95-96% effective in preventing infection while conferring long-term (possibly lifelong) immunity –59. The Prevalence and incidence rates of hepatitis B vary with location as well as cultural behaviors, though seasonal patterns of transmission are absent . In WestThe mathematical structure for the transmission of hepatitis B requires that the infected class be split into acute and chronic compartments to accommodate the separate epidemiological characteristics. The model also requires the addition of three distinct holding compartments representing the separate doses required for immunity, starting with dose 1 at the time of deployment , Table 5d models . Local Hd models , as welld models .As with the previous case studies, computational simulations again show that the difference between preexisting immunity and deployment vaccination, in terms of mean annual hepatitis B incidence, becomes more significant as protection levels increase, with preexisting protection having a greater impact than deployment vaccination .For hepatitis B, simulations show that no distinct protective thresholds exist for the cessation of transmission within deployed populations for either type of immunity. Though three doses of vaccine are required for lasting immunity, partially immunized individuals are assumed to be protected at the full vaccine efficacy so long as subsequent doses are administered on schedule; thus the difference between the two types of immunity is most likely a result of the 4% of vaccinated individuals failing to receive protection due to imperfect vaccine efficacy .Protection associated with preexisting hepatitis B seropositivity resulting from previous vaccination or recovery from infection is assumed to be immediate, life-long, and complete, whereas vaccine-derived immunity is both incomplete and lengthy to acquire, with a vaccine efficacy of only 96% and a total of six months to complete the entire three-dose vaccine course. In light of the persistent level of chronic carriers worldwide, and in combination with the only moderate level of preexisting protection against hepatitis B currently among American Warfighters, it is likely that continuing high levels of vaccination coverage in the absence of elevated preexisting seropositivity is advisable, particularly in combination with efforts to reduce effective contact rates with potentially infected local populations. Even in this case, however, hepatitis B cases could continue to occur among deployed populations, particularly if partially immunized individuals do not experience full protection between doses.All models are abstractions of reality and as such involve necessary simplifications in order to produce a numerical model which can be simulated. Deterministic models, in particular—as in the case studies above—can obscure transmission dynamics at extremely low incidence levels implying that protective thresholds may possibly occur at lower levels of preexisting immunity or deployment vaccination. Also the case study population structure assumes homogeneity within subgroups, which can be inappropriate for populations structured with a high degree of segregation between groups, particularly in terms of implementing highly focused outbreak responses. However, depending on deployed conditions, this may not be an issue for the case study populations as within-unit mixing is assumed to occur within relatively confined areas and may closely approximate homogeneity. Finally, parameter values implemented during analyses were derived from a variety of data sources, some of which may not be representative of populations directly compatible with deployed US military populations. Sensitivity and uncertainty analyses performed during the case studies (results not shown) have explored these issues for the specific diseases and settings described above.There has also been some indication that detection of preexisting seropositivity to a virus may not be equivalent to full protection against transmission . ReductHowever the exploration of the protective threshold, even in the presence of model limitations, can still provide valuable insight into the best way in which to protect deploying troops from transmission of vaccine-preventable disease. Building upon these results, we can now incorporate additional aspects unique to this setting—such as the risk of adverse events resulting from the administration of multiple vaccine doses, delay in implementation of full vaccine course, or reduced vaccine efficacy due to harsh field conditions—along with cost calculations to further expand the comparison between preexisting immunity and vaccination at the time of deployment as a means of preventing outbreaks and protecting troops and mission objectives during extended military deployment actions.