Saccharomyces cerevisiae.We describe a statistical framework for QTL mapping using bulk segregant analysis (BSA) based on high throughput, short-read sequencing. Our proposed approach is based on a smoothed version of the standard  Quantitative or complex phenotypes are traits that are under the control of multiple genes and environmental factors. Identifying the parts of the genome that contribute to variation in complex traits (Quantitative Trait Loci or QTLs), and ultimately the genes and alleles that are mechanistically responsible for trait variation, is a primary challenge in animal and plant breeding, population studies of human health and disease, and evolutionary genetics. In this study we describe an analytical framework that allows investigators to marry a QTL mapping approach called “bulk segregant analysis” (BSA) with high-throughput genome sequencing methodologies in order to map traits quickly, efficiently, and in a relatively inexpensive manner. This framework provides a statistical basis for analyzing BSA experiments that use next-generation sequencing and will help to accelerate the identification of QTLs in both model and non-model organisms. Bulk segregant analysis BSA;  is a QTLIn bulk segregant studies based on high-throughput sequencing there are two sources of variation that affect allele frequency estimates. The first is variation due to the sampling of segregants that constitute the bulks themselves. This source of variation can be minimized by increasing both the size of the segregant population and the size of the bulk samples. The second source of variation is a consequence of the measurement technique used to estimate allele frequencies in the bulks. In the case of sequencing of pooled DNA samples, the sources of variation of this second type include, but are not limited to, library preparation, sequencing chemistry, sequencing coverage, post-sequencing alignment of reads, and base/allele calling algorithms. Here again, some of these sources of variation can be minimized by standardization of experimental protocols and analysis pipelines. However some of these sources of variation, particularly stochasticity in sequencing coverage, are an inherent property of short-read sequencing methods.In this paper, we develop explicit statistical models to describe the sources of variation that should be considered in the analysis of BSA-sequencing data. We first develop test statistics based on the classic Consider the experimental design with an Fh parent . The -vaThe counts in A natural statistic to characterize the data at each SNP is the standard aterials  for a geHowever, due to the hierarchical sampling scheme, the usual expectation that A simulation model was used to test the accuracy of approximate equations (8) and (9). We simulated genetic data for a chromosomal region of 10 cM in recombinational length. Informative markers were uniformly distributed along this chromosome with The full distribution of A substantial source of variation in A methodological issue arises when kernel smoothing is used – at the beginning or end of a data series it can produce a biased estimate because the data included in the kernel bandwidth is asymmetric. The simplest way to deal with this is to append a reflected version of the values that fall within the right half-bandwith (at the beginning of the series) and left half-bandwidth (at the end of the series), run the kernel smoother as normal, and then trim the appended values from the output.The null expectation of om  and  . The obsIn addition to the theoretical expectations discussed above, an empirical estimate of the null distribution of Recall that for a log-normal distribution: Let Let Use Hampel's rule Construct a trimmed data set Let The logic of this procedure is as follows. The median and MAD are robust estimators of location and spread respectively For the null simulations in A weighted moving average is a type of low-pass filter; the larger the window size the lower the frequncy of signals that are rejected by the filter. The choice of smoothing width, In Since recombination rates vary across genomes, a given genetic distance will correspond to a range of physical distances. In terms of the choice of smoothing width, higher recombination rates favor smaller window sizes . If regional recombination rates are known this can be incorporated into the analysis; however the use of average chromosomal or genomic recombination rates to choose a single physical size for the smoothing window should not be problematic unless recombination rates vary widely. In such cases, one can calculate Based on the arguments developed above, we propose the following analytical pipeline for the analysis of BSA-sequencing data sets. We assume that sequencing reads have been aligned to a reference genome where physical distances between polymorphic sites and (approximate) rates of recombination are known. We assume that all sites are biallelic. Following alignment of reads to a reference genome, per site counts of each allele are generated from the reads. Our recommended analysis pipeline for estimating QTLs is as follows:For each variable site, calculate At each site calculate Estimate parameters of the log-normal null-distribution (i.e. no QTL) of d 12 and  or usingUsing Use a false discovery rate approach FDR;  to accouDefine candidate QTL regions as continuous runs of significant sitesWe used simulations to conduct a simple power analysis of our proposed methodology. In this analysis we used the mean Saccharomyces cerevisiaeTo demonstrate the correspondence between theory and data we here draw on a BSA-sequencing data set generated to identify loci that contribute to variation in colony morphology in the budding yeast The yeast data consist of a low and high bulk, each composed of 288 homozygous diploid segregants drawn from an FBecause there are two sequencing runs per DNA pool, variation in allele frequency estimates between sequencing runs from the same segregant bulk should be exclusively due to stochastic aspects of the sequencing reaction and primary bioinformatics analyses . The structure of this data set is thus useful for dissecting the impact of sequencing variation on estimates of The two low samples .The use of a test based on the ion e.g. . For exaion e.g. ,  is expOur simulations suggest that for the experimental design considered here using bulk sizes as large as 15–20% of the phenotyped segregant population increases power to detect causal QTLs despite the fact that this means relatively smaller allele frequency differences between bulks. This is due to tradeoffs between bulk-size, selection intensity, and the variance of allele frequencies under the hierarchical sampling. Consider, for example, a single locus with alleles Sequencing can introduce complications such as biases toward particular nucleotide calls; however in general this should effect both segregant bulks in the same direction. Due to the averaging affect of In this paper we have focused on QTL mapping with an FOther experimental designs, such as backcrosses, will not have allele frequencies of 0.5. For these situations the null expected distributions of To create the bulked DNA pools each segregant was grown overnight in liquid medium to saturation . The gray histogram represents the observed distribution of (PDF)Click here for additional data file.Text S1Generalization of theoretical results to include segregation distortion.(PDF)Click here for additional data file.Text S2Miscellaneous information. This file includes information on: 1) estimation of the parameters of a log-normal distribution from the expected mean and variance of a variable of interest; 2) the expected shape of the (PDF)Click here for additional data file.


PLoS Biology, describes specifically how this works for the plexin receptor, suggesting a somewhat more complicated model in which plexin and its binding partners mediate the formation of a multiprotein array in order to activate plexin signaling.How exactly does receptor signaling work? Though receptors come in a wide variety of shapes and sizes, they share common features. Typically, some portion of the receptor sticks outside the membrane, poised to recognize proteins or small molecules that are passing by the cell, while another portion hangs inside the cell, ready to transmit a signal to internal signaling proteins. The simplest mode of receptor signaling occurs when a receptor binds to its external target and undergoes minor structural changes, changing the receptor's ability to bind to and regulate proteins inside the cell. Work from Christian Bell and colleagues, published in this issue of The intracellular portion of the plexin receptor contains a region called the GTPase activating protein (GAP) domain, which binds to signaling proteins of the Ras GTPase family. Plexin binding inactivates Ras GTPases, which initiates a signaling cascade that changes the direction of axon growth. To activate the plexin GAP domain, two other proteins must simultaneously bind to plexin: semaphorin on the extracellular side and an activated member of the RhoGTPase family on the intracellular side. Thus, the plexin receptor requires binding at both ends to function properly.A number of recent studies revealed that semaphorin binding on the extracellular side leads to the pairing of two plexin receptors. While it is known that pairing is a common mode of receptor activation, it was not clear how semaphorin- and RhoGTPase-binding activate the GAP domain. Because receptor proteins are threaded through the membrane, it is nearly impossible to study the structure of the entire protein. Instead, the researchers focused only on the intracellular region of plexin, determining the structure of this intracellular region (using human Plexin-B1) while bound to an activated member of the RhoGTPase family (Rac1*).As expected from previous studies, the researchers' data showed that activated RhoGTPase interacts with a domain on plexin called the RhoGTPase binding domain (RBD). In fact, RhoGTPase interacts exclusively with the RBD and does not make any contacts with the GAP domain—thus, ruling out the possibility that the RhoGTPase might directly affect the GAP domain and contribute to its activation.cyto). This is particularly interesting given the extracellular pairing that forms between plexin and semaphorin. The triplet revealed that activated RhoGTPase interacts with another, previously unidentified site on plexin (which the researchers refer to as site B), in addition to the RBD. The team confirmed that this site is important by showing that mutations in site B negatively impact both the binding of RhoGTPase to plexin and plexin function in the cell. Because site B is very close to the site on the GAP domain where Ras GTPases are thought to bind, it may mediate how activated RhoGTPases contribute to the activation of the GAP domain.Interestingly, the researchers also observed a novel triplet formation—each RhoGTPase molecule appeared to interact with two molecules of the intracellular portion of plexin  A Dual Binding Mode for RhoGTPases in Plexin Signalling. doi:10.1371/journal.pbio.1001134


While the study of the information technology (IT) implementation process and its outcomes has received considerable attention, the examination of pre-adoption and pre-implementation stages of configurable IT uptake appear largely under-investigated. This paper explores managerial behaviour during the periods prior the effective implementation of a clinical information system (CIS) by two Canadian university multi-hospital centers.Adopting a structurationist theoretical stance and a case study research design, the processes by which CIS managers' patterns of discourse contribute to the configuration of the new technology in their respective organizational contexts were longitudinally examined over 33 months.Although managers seemed to be aware of the risks and organizational impact of the adoption of a new clinical information system, their decisions and actions over the periods examined appeared rather to be driven by financial constraints and power struggles between different groups involved in the process. Furthermore, they largely emphasized technological aspects of the implementation, with organizational dimensions being put aside. In view of these results, the notion of 'rhetorical ambivalence' is proposed. Results are further discussed in relation to the significance of initial decisions and actions for the subsequent implementation phases of the technology being configured.Theoretical and empirically grounded, the paper contributes to the underdeveloped body of literature on information system pre-implementation processes by revealing the crucial role played by managers during the initial phases of a CIS adoption. The purpose of this investigation was to examine the initial phases of a joint clinical information system (CIS) implementation in two Canadian university and multi-hospital health centres. The adoption of new information technologies (IT) currently constitutes one of the major institutional pressures on health care delivery systems. Health care organizations display information-intensive business processes wherein health professionals strive to keep abreast of the best possible medical knowledge . At the Being behind other industries with regard to IT diffusion , the degConfigurable refers to technologies that are highly parameterizable, that is they are built up from a range of components to meet the very specific requirements of a particular organization  shared his concern that at the MHOSP1 there is no Clinical Informatics group. He feels that this group should be a department (something that is permanent) not a committee. This group should be composed of multi-disciplinary and multi-professional users. This type of department would be required before we go live with a CIS. Many participants in the group were in agreement." We consider that this issue is crucial in order to define the norms regulating the meaningful use of the CIS, and also to reinforce the local knowledge of CIS end-users vis-à-vis the global knowledge usually imposed by CIS vendors and external consultants. However, and despite the fact that most CIS committee members agreed upon this proposition, top managers cited funding constraints to postpone the issue to the implementation phase. As a result, the CIS was initially conceived as a purely technical device, the construction of its clinical meaning being postponed to subsequent phases of the CIS Project.A Selection Task Force composed of 10 clinicians  was created with the mandate of evaluating the 32 responses to the request for proposals according to four categories: technical infrastructure and interfaces, security, reports, and business proposal. Three of 32 met the minimum requirements  and maximum cost allowance. Formal demonstrations took place in January 2003. The CIS vendor was selected by CIS top managers in March 2003, an event that marked the end of the pre-adoption phase.the selection of the CIS vendor, many concerns about the financing of the CIS, in terms of both the purchase of the system and the costs of its implementation became more and more explicit, raised in particular by nursing staff around the table:Although the dominant issue during this sub-period was "Many users have great concerns about the financing of the CIS. For the proper integration and implementation of a CIS, funds must be made readily available not only to purchase CIS software but also for process re-engineering, training, equipment , extra resources, etc. The user community has yet to see a firm commitment from upper management of MHOSP1 indicating that funds will be made available for the proper implementation of the CIS." Indeed, discourses regarding cost issues also dominated this second sub-period of CIS pre-adoption. CIS is a very costly IT, so top managers selected their CIS with the best balance between minimum organizational requirements and maximum cost allowance in view. Nevertheless, a CIS implementation cost involves not only the cost of the technology itself, but also the cost of training and organizational change that its adoption implies. Focusing on technological aspects of CIS adoption, the discussion about these organizational costs was, again, postponed by top CIS managers to following phases of the project.Once the CIS selection (or pre-adoption) phase was finished, an unexpectedly long pre-implementation stage began. Contract negotiations began and the definition of the project scope was undertaken at each MHOSP. These processes were heavily tainted by the struggle to obtain a clear budgetary compromise from hospital upper management for the CIS once it was already selected.resources for the CIS led to the elaboration by CIS top managers of three different budgetary scenarios: Plan A, advance funding from the budget for a new MHOSP1 site; Plan B, a 10-year loan authorization; and Plan C, funds from the hospital foundation (Meeting #20: September 2003). At the same time, a global budget increase from CDN $15 M to $17 M per site was accepted by hospital upper management, and funding from the Rainbow Program of $3.4 M in the first year of implementation remained secured . No clear decision regarding the source of the bulk of the CIS budget was made at that time. These were the circumstances that progressively placed the CIS stakeholders in a very difficult position regarding the resources needed for successful CIS adoption. Concerning the scope of the CIS implementation project, three major phases were defined: Phase 1 included 'results reporting' and 'data warehouse'; Phase 2 consisted of piloting the project in 1 or 2 clinical programs for 'order entry' and 'clinical notes'; finally, Phase 3 concerned rapid 'order entry deployment' and a more gradual 'clinical notes deployment' . A few weeks later, clinical documentation deployment was segregated to a fourth Phase .The battle for financial end-users' involvement are strongly advocated  is providing funds to the [Rainbow Program]. However, it is a high-risk project and the CFI will benchmark its evolution, as well as the CIS Project in that regard. Since point-of-care data collection is necessary for the [Rainbow Program], the CIS needs to feed research with this detailed data. This is the essence of the [Rainbow Program]. Hence, for clinical notes, a specialized [Rainbow Program] front-end has to be integrated into the CIS. This needs to be part of the initial roll out (Phase 1) if we do not know to lose the funding from CFI." Contractual agreements with the vendor were established under the pressure of budgetary constraints. In this context, questions relative to timeline and the scope of services to be provided by the vendor were discussed. The issue of the intellectual property of the system also attracted great attention:"[CIS top manager] indicated that for the changes for research, the idea will belong to the researcher but the incarnation of these ideas into the [CIS] product will then belong to [the vendor]. [CIS top manager] indicated that lawyers have looked into this issue and that for [the vendor] this is a showstopper. They will not sign a contract if it means that MHOSP1 and MHOSP2 will get royalties from the sales of their [CIS] product to other customers." )as is, and a maximum of 30% customization would be tolerated. In this situation, the fit with the software will be achieved by changing user practices. Making such changes is always risky and complex, particularly when it involves harmonizing local practices with those of a quite different organizational culture  ends in March 2006 and the [Rainbow Program] must have something to show, such as data flow, research data study, etc. With this in mind, we could sign a reduced scope contract with [the vendor] so that we get an early start. The reduced scope would be a scaling down of the project for research only. This scaled down scope still needs to be worked out so as to clearly identify how we would proceed with the deployment to the wards and the clinics for the [Rainbow Program] only." A new phase, called Phase 1A, was then established and added to the contract with the vendor. However:"It is indicated that the lengthy negotiations between [the Rainbow Program] and MHOSP1/MHOSP2 was becoming a problem for [the vendor]. [...] There is more and more pressure to sign a reduced scope contract between [the vendor] and the 2 MHOSPs whether the [Rainbow Program] contract is signed or not. [...] [The Rainbow Program's representative] indicated that [the Rainbow Program] wants to participate directly in all discussions between [the vendor] and the 2 MHOSPs if things are to move forward faster." dependent position vis-à-vis the Rainbow Program  during the weeks before signing the contract with the vendor. MHOSP1 depended, on the one hand, on the Rainbow Program for funds and on the other, on the CIS vendor for global CIS knowledge. Furthermore, this dependency on external CIS stakeholders had to be added to the lack of internal mobilization of CIS end-users. Indeed, the signing of the contract between both MHOSPs and the CIS vendor took place in June 2004, before the signing of the contract with the Rainbow Program in July 2004, thanks to a bank loan that would allow CIS hospital top managers to undertake the implementation of Phase 1A, while waiting for funds for the whole CIS project.As a result, MHOSP1 was placed in a clear Compared to the power struggles at MHOSP1, quite a different scenario was found at MHOSP2. First, the CIS committee in this hospital was constituted just a few weeks before the CIS selection. Second, the absence of external actors --the Rainbow Program representatives participated only in MHOSP1 meetings-- attenuated the power struggles, because here there were fewer conflicting interests. In MHOSP2, we have broken down the period examined into three bracketed sub-periods.the impact of the CIS adoption on their business processes, as illustrated in the following excerpt:The discussions held during the first meetings of the CIS committee in MHOSP2 mainly involved monitoring the CIS selection . Along with this, members of this committee expressed, from the beginning, their concern about "There are worries regarding the CIS adoption and the current management practices of access, the single sign-on, etc. A discussion is held around current work on a number of applications. The preferred strategy is the following: the CIS utilization to integrate clinical information rather than the implementation of a single sign-on technology for a set of applications." In sum, the pre-adoption phase of the CIS was shorter and less complex in this hospital than in MHOSP2. Indeed, most of the work with regard to the CIS selection was made by the CIS top managers of this hospital in collaboration with their counterparts in MHOSP1, prior the creation of the MHOSP2 CIS planning committee.Once the CIS was selected, MHOSP2 actively participated in the process of negotiation with the vendor. In this sense, CIS budgetary uncertainty and delays due to changes at the political government level were highlighted as puzzling:"Negotiations advance slowly. Certain crucial points remain unclear, in particular the date when the French version of the system will be available. In addition, the members of the committee are worried regarding funds. This appears very problematic, particularly within the context of the current budgetary exercise at MHOSP2 and the political context tied to the change in provincial government." internal needs. Their stated purpose was to implement a CIS that will provide accurate clinical information and help improve clinical activities. Despite such concerns, a critical element emerging from the project was the need to harmonize the CIS package to at least 70% of the other sites. The organizational and political impact to do so appeared to be, at this moment, underestimated. For instance, CIS committee members' discursive practices during this sub-period showed a high concern with the possible effects of such high standardization on users' day-to-day practices and on how end-users might react to these changes. Nevertheless, no clear plan to deal with these organizational issues at an operational level was discussed. Still, such concerns sometimes appeared to be trivialized:During the CIS committee meetings at MHOSP2, it appeared clear that, although external legitimacy and image were important aspects of the CIS project, CIS top managers were much more concerned with their "[The vendor] agrees to an important reduction, which brings them to the same monetary level of their initial offer, although the scope of the project is now much more important than that included in the proposition. One of the conditions of this reduction is that 70% of the system must be identical for MHOSP2 and MHOSP1. [The CIS project director] indicates that the hospital CEO does not see any inconvenience to this constraint." .communication, apparently aware that distorted messages can be very detrimental to the future acceptance of the CIS.As noted previously, the issue of end-user involvement, and particularly that of physicians, was constantly discussed in the MHOSP2 meetings, especially once the decision to undertake Phase 1A was made. The committee decided to focus on physicians and other health professionals, members of the clinical unit pilots, in the reduced-scope CIS implementation. Top managers were also very concerned with strategies of In addition, the battle for funds continued. Although the Rainbow Program representatives never attended MHOSP2 CIS committee meetings, these negotiations had a great impact on committee discussions. Indeed, when support from upper management was obtained for funds in Phase 1A --in other words, when they reached a greater bargaining power-- MHOSP2 favoured signing the contract despite unresolved misunderstandings with the Rainbow Program:"MHOSP2 has already obtained the support from its Board of Governors in order to request the budget necessary for Phase 1A, and is seriously considering signing the contract with [the vendor] without waiting for the conclusions of the negotiations with [the Rainbow Program]. It is not clear at this moment if MHOSP1 will be able to do so. A last chance meeting will take place with [the Rainbow Program] on Friday, May 29." In contrast to functionalist social theory, which dilutes human agency under the deterministic effect of social structure, Giddens' structuration theory explicitly enhances social actors' intentionality, knowledgeability and reflexivity: human agents have reasons for acting as they do, although such purposeful behaviour involves unintended consequences regarding the recursively-related social structure, which in turn will affect future conduct. As Giddens notes, it is the examination of "the follow of intentional conduct" that allows us to foresee and explain possible future "unintended consequences" of our actions .conscious and intended decisions and actions, made by virtue of their power position and particular interests in the project, and largely justified by them in the present circumstances, i.e. institutional IT imperative and severe financial uncertainty. In doing so, CIS top managers not only have intentionally shaped the initial phases of the CIS implementation but also, according to a structurationist stance, set a frame within which future phases of the CIS implementation can be reasonably foreseen to be particularly complex.When applying these ideas in the present project, we can therefore state that CIS top managers' flow of decisions and actions during the CIS selection and pre-implementation phases have over time led to (1) financial dependency vis-à-vis external stakeholders, (2) a focus on technical issues and (3) a disregard (despite awareness) of organizational issues of the CIS adoption. All these have been to avoid making decisions on end-user involvement by recurrently postponing the discussion on this issue to subsequent phases of the CIS project (MHOSP1), or undertaking no concrete action to put user concerns into operation (MHOSP2). To do so, they have mobilized their nondecision-making power to exclude from the discussion such threatening issue in the current situation, without the risk exposure of making a formal decision in this regard [In view of the high financial uncertainty that has surrounded the initial phases of this CIS Project, its top managers have been able s regard . In effeclear emphasis on technical aspects of the CIS implementation. This has mainly been, again, because the dominant issue of budgetary constraints and the dependency on external actors were out of their control and could potentially obstruct the accomplishment of a project that is highly relevant for them. In this context, we suggest that the separation between technical and social issues may constitute a discursive strategy for concealing problems and barriers that could impede the continuity of the project during pre-implementation phases.Also, avowing the importance of the organizational side of CIS projects, CIS top managers' decisions and actions have shown a rhetorical ambivalence. Rhetoric has lately attracted much attention among organizational scholars [ambiguity that characterizes these organizational settings whose actors must struggle with [Operating in a very uncertain context, and positioned in a clear external dependency regarding financial resources, these CIS top managers have nonetheless displayed the remarkable ability to create an internal organizational space for decision and non-decision making with regard to the CIS project over time. We call this managerial discursive ability scholars . Accordischolars . This asgle with . We thermight not be without negative consequences in the following phases of the CIS Project --the CIS master implementation plan includes four consecutive phases, hospitals having initiated or being to the point of initiating Phase 2 (i.e. computerized physician order entry) at the time of writing these words. From a structurationist perspective, we consider that although we can always change the chain of events with new decisions, actions and interventions --a possibility that is foreseeable here due to very slow pace of this CIS implementation-- these changes are within a given range; they have limits. Accordingly, the adjustment between technology and clinical practices, as previously mentioned, appears to be particularly difficult in this project --the CIS uptake by end-users is rather modest to date, and it appears to be particularly scarce among nurses.It is important to note here that, with regard to financial resources, rhetorical ambivalence has proven to be successful in the mid-term as the budget for the project was finally approved by governmental authorities in fall 2009. At that time, Phase 1 of CIS implementation, i.e. visualization of results, was almost completed in both hospitals, with an increasing but still partial uptake among clinicians. However, rhetorical ambivalence Although the emphasis on technical issues is rather frequent in similar projects , it is aAlthough the study of the IT implementation process and its outcomes has received considerable attention, the examination of pre-adoption and pre-implementation stages of configurable IT uptake appears largely under-investigated. In order to fulfill this research gap, a longitudinal case study was undertaken in which the periods prior the effective implementation of a CIS by two Canadian university multi-hospital centres were explored in-depth. This investigation appears therefore innovative at a methodological level because it adopts a process-based approach and a longitudinal design. In effect, whereas prior research exists on medical patient records implementation, most of these studies are factor-oriented, i.e., they seek to explain implementation in terms of relationships between dependent and independent variables. The work follows therefore the advice of the organizers of the Symposium 'Doing Longitudinal Studies of Health Care Change: Studying Health Care Change' at the 2010 Academy of Management Annual meeting: "In-depth longitudinal case studies of health care change are needed to better understand how these processes occur and how they might be more successfully managed" .to put forward the crucial role played by top managers' initial decisions and actions, discursively enacted, in the structuration of a configurable IT. The lack of purposive strategies for involving clinicians from the very beginning of the project and for doing a preliminary diagnostic of existing clinical practices and the impact of the new system on these practices, can be understood as consequences of the path of dependency on external funding being built and accepted by all parties. If evidence of the critical components for CIS project success exists, how do the CIS top managers justify that their organizational decisions do not take them into account? The justifications, in our study, rely on external circumstances, meaning beyond their scope of responsibility. In these circumstances, top managers have displayed a set of discursive practices to convince everyone that they are doing right with the resources they have. They are aware of some of the likely consequences of their initial decisions, and of the fact that they are setting up a path of dependency vis-à-vis external agents. Nonetheless, they put forward a discourse indicating that everything that is under their control is being well managed and that they are able to change or alleviate adverse consequences that may emerge.Our investigation makes two major theoretical contributions that, due to the exemplary quality of the cases involved, can constitute a useful tool to inform decision-making processes at the managerial level regarding early stages of the adoption of leading-edge IT in health care institutions elsewhere. The first is rhetorical ambivalence as a discursive device used by knowledgeable and reflective managers to monitor their behaviour and others' in order to initiate/sustain the adoption of a new IT in highly ambiguous institutional contexts. Rhetorical ambivalence thus enriches the existing repertoire of managerial discursive strategies --e.g. when a same person (a manager) adopts or abandons particular discursive practices according to context [Furthermore, our investigation also contributes to the current trend of organizational studies that emphasizes the importance of rhetoric in organizational life. More particularly, we propose  context -- consti context , we alsoThe authors declare that they have no competing interests.Both authors conceived the study, organized the fieldwork, attended organizational meetings, and collected documentary material. CH performed the analysis, and drafted the article. MP contributed to the interpretation of results as well as paper editing. Both authors read and approved the final manuscript.The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1472-6947/11/42/prepub


We identify and describe the key qualitative rhythmic states in various 3-cell network motifs of a multifunctional central pattern generator (CPG). Such CPGs are neural microcircuits of cells whose synergetic interactions produce multiple states with distinct phase-locked patterns of bursting activity. To study biologically plausible CPG models, we develop a suite of computational tools that reduce the problem of stability and existence of rhythmic patterns in networks to the bifurcation analysis of fixed points and invariant curves of a Poincaré return maps for phase lags between cells. We explore different functional possibilities for motifs involving symmetry breaking and heterogeneity. This is achieved by varying coupling properties of the synapses between the cells and studying the qualitative changes in the structure of the corresponding return maps. Our findings provide a systematic basis for understanding plausible biophysical mechanisms for the regulation of rhythmic patterns generated by various CPGs in the context of motor control such as gait-switching in locomotion. Our analysis does not require knowledge of the equations modeling the system and provides a powerful qualitative approach to studying detailed models of rhythmic behavior. Thus, our approach is applicable to a wide range of biological phenomena beyond motor control. A central pattern generator (CPG) is a circuit of neuronal cells whose synergetic interactions can autonomously produce rhythmic patterns of activity that determine vital motor behaviors in animals A common component of many identified CPGs is a half-center oscillator (HCO), which is composed of two bilaterally symmetric neurons reciprocally inhibiting each other to produce an alternating anti-phase bursting pattern multi-stable rhythmic patterns as “polyrhythms.” We consider the range of basic motifs comprising three biophysical neurons and their chemical synapses, and how those relate to, and can be understood from the known principles of two-cell HCOs. We will study the roles of asymmetric and unique connections, and the intrinsic properties of their associated neurons, in generating a set of coexisting synchronous patterns of bursting waveforms. The particular kinds of network structure that we study here reflect the known physiology of various CPG networks in real animals. Many anatomically and physiologically diverse CPG circuits involve a three-cell motif Tritonia swim circuit, and the Lymnaea respiratory CPGs We are interested in exploring the constituent building blocks — or “motifs” — that may make up more complex CPG circuits, and the dynamic principles behind stable patterns of bursting that may co-exist in the circuit's repertoire of available states An important open question in the experimental study of real CPGs is whether they use dedicated circuitry for each output pattern, or whether the same circuitry is multi-functional In this work, we apply a novel computational tool that reduces the problem of stability and existence of bursting rhythms in large networks to the bifurcation analysis of fixed points (abbreviated FPs) and invariant circles of Poincaré return maps. These maps are based on the analysis of phase lags between the burst initiations in the cells. The structure of the phase space of the map reflects the characteristics the state space of the corresponding CPG motif. Equipped with the maps, we are able to predict and identify the set of robust bursting outcomes of the CPG. These states are either phase-locked or periodically varying lags corresponding to FP or invariant circle attractors (respectively) of the map. Comprehensive simulations of the transient phasic relationships in the network are based on the delayed release of cells from a suppressed, hyperpolarized state. This complements the phase resetting technique and allows a thorough exploration of network oscillations with spiking cells Our results are organized as follows: first, we describe our new computational tools, which are based on 2D return maps for phase lags between oscillators. This is a non-standard method that has general utility outside of our application, and we therefore present it here as a scientific result. We then present maps for symmetric inhibitory motifs and examine how the structure of the maps depends on the duty cycle of bursting, i.e. on how close the individual neurons are to the boundaries between activity types (hyperpolarized quiescence and tonic spiking). Here, we also examine bifurcations that the map undergoes as the rotational symmetry of the reciprocally coupled 3-cell motif is broken. This is followed by a detailed analysis of bifurcations of fixed point (FP) and invariant circle attractors of the maps, which we show for several characteristic configurations of asymmetric motifs, including a CPG based on a model of the pyloric circuit of a crustacean. We conclude the inhibitory cases with the consideration of the fine structure of a map near a synchronous state. We then discuss the maps for 3-cell motifs with only excitatory synapses, which is followed by the examination of mixed inhibitory-excitatory motifs, and finally an inhibitory motif with an additional electrical synapse in the form of a gap junction.We first introduce the types of trajectories we focus on and how we measure them. The reduced leech heart interneuron can demonstrate many regular and irregular activity types, including hyper- and de-polarized quiescence, tonic spiking and bursting oscillations. We focus on periodic bursting, and rval see .When an isolated bursting cell is set close to a transition to either tonic spiking or hyperpolarized quiescence, its network dynamics become sensitive to external perturbations from its pre-synaptic cells. For example, when the post-synaptic cell is close to the tonic-spiking boundary, excitation can cause the post-synaptic cell to burst longer or even move it (temporarily) over the boundary into the tonic spiking (TS) region. In contrast, inhibition shortens the duty cycle of the post-synaptic neuron if it does not completely suppress its activity .We reduce the problem of the existence and stability of bursting rhythmic patterns to the bifurcation analysis of fixed points (FPs) and invariant curves of Poincaré return maps for phase lags between the neurons. In this study, we mostly consider relatively weakly coupled motifs, but our approach has no inherent limitation to weak coupling. Here, the weakly coupled case is a pilot study that lets us test our technique and also uncover all rhythms, both stable and unstable, that can possibly occur in the network. Detailed scrutiny of the return maps is computationally expensive: an exploration of one parameter set can take up to three hours on a state-of-the-art desktop workstation depending on the accuracy of the mesh of initial conditions and length of the transients computed.The phase relationships between the coupled cells are defined through specific events, phase lags by the delays in burst initiations relative to that of the reference cell 1, normalized over the current network period or the burst recurrent times for the reference cell, as follows:We define a sequence of phase lag trajectory, An ordered pair, on mod 1 . Typicalweak between two cells of a motif when the convergence rate to any stable FP of the return map is slow. This means that the distance between any two successive iterates of a trajectory of the return map remains smaller than some bound, e.g. We say that coupling is A priori, the initial period (recurrence time) of the motif's dynamics is unknown due to the unknown outcome of nonlinear cell interactions; furthermore, it varies over the course of the bursting transient until it converges to a fixed value on the phase locked state. Thus, we control the initial phases between the reference cell and the others releasing the latter from inhibition at various delays. To do this, we first estimate the initial phase lag with a first order approximation, We now make some technical remarks concerning computational derivations of the map, To complete a single phase lag map we choose the initial phase lags to be uniformly distributed on a grid of at least We use a consistent labeling convention to make our diagrams of the phase lag maps easy to interpret. In the first presentation of such a map  configurations of the network with nearly identical cells and connections. We demonstrate that these symmetric network motifs are multistable and hence able to produce several coexisting bursting patterns. The homogeneous case allows us to reveal the role of the duty cycle as an order parameter that determines what robust patterns are observable. We suggest a biologically plausible switching mechanism between the possible bursting patterns by application of a small hyperpolarized current that temporarily blocks a targeted cell.We begin with a weakly coupled with nt state  and 3.Using The robustness of a rhythm to perturbations is related to the size of its attractor basin. Similarly, FPs that have much larger basins than others can be thought of as “dominating” the phase plane in terms of likelihood of becoming the active state for a random initial condition or perturbation. Two triplets of saddles surround two more unstable FPs located at approximately Let us interpret the role of a stable FP, for example the red one, in terms of phase-locked bursting patterns. Since the phases are defined modulo one, the coordinates Following this notation, the stable FP (blue) at Two FPs around Next, we consider the bursting motif that has a longer duty cycle of tivities . The corTo complete the examination of the influence of duty cycle on the repertoire and robustness of bursting outcomes of the homogeneous motif, we now consider the case of the medium-length duty cycle, Similarly to patterns .In this section, we elucidate how and what intrinsic properties of the individual bursting cells affect the multistability of the 3-cell inhibitory motif. The answer involves an interplay between the competitive dynamical properties of individual neurons and the cooperative properties of the network. More specifically, it relies on how close an isolated cell is to the boundary between bursting and hyperpolarized quiescence and how sensitive the post-synaptic cell is to the (even weakly) inhibitory current generated by the pre-synaptic cells. We investigate these ideas by introducing asymmetries into the coupling of our homogeneous network motif. We focus on several representative cases of asymmetrically coupled motifs with one or more altered synaptic strengths, and we will elaborate on their bifurcations as we vary the asymmetry.en route from the homogeneous 3-cell motif to a rotationally-symmetric one, during which all clockwise- and counter-clockwise-directed synapses are simultaneously increased and decreased, respectively. In the limiting case of a clockwise, uni-directionally coupled motif there is a single traveling wave. The question is: in what direction will the wave travel?In this subsection, we analyze bifurcations occurring We use a new bifurcation parameter, global attractor of the network . Each HCO represents a pair of cells that typically burst in anti-phase, when isolated from other cells. When a HCO is symmetrically driven, even weakly, by another bursting cell, it can produce in-phase bursting, instead of out of phase bursting In this section, we consider transformations of rhythmic outcomes in the motif containing a single HCO with stronger reciprocally inhibitory connections, for example,  see . It turnThe following bifurcation sequence involving the dominant FP differs drastically from the saddle-node bifurcations discussed earlier. Observe from the map in heteroclinic connections that bridge the saddle-node FPs on the 2D torus. The breakdown of the heteroclinic connections with the disappearance of both FPs results in the emergence of a stable invariant circle that wraps around the torus A feature of these bifurcations of the map at the critical moment is that there are two Further increase in the coupling strength between the stronger inhibitory HCO and cell 3 cannot not qualitatively change the structure of the phase lag map, while it can have only a qualitatively effect on the size of the attractor basins of the invariant circle and the remaining FP (red). So, weakening winding number. The number is a rational if the invariant curve is made of a finite number of periodic points across the torus.This is not the case when either connection between cell 3 and the HCO is made sufficiently asymmetric. Depending on the connection's direction of asymmetry, such an imbalance causes either of the two remaining saddles to come close and annihilate with the stable red FP at phase slipping phenomenon observed in voltage traces such as those shown in The occurrence of the stable invariant curve wrapping around the torus gives rise to a From the top of the One may wonder about what determines the direction of the invariant curve on the torus and hence the order of the episodes of the shown voltage waveform. Observe that the phase slip occurs in the ion) see  and 20.Let us discuss another motif configuration, shown in The direction of the stable invariant circle flowing across the 2D torus can be reversed by making cell 3 receive stronger inhibition instead of weaker inhibition relative to the other cells. An example is depicted in the phase lag map of We now elucidate the issues involved in designing inhibitory motifs with predetermined bursting outcomes and how to control them. Let us revisit the motif with a single HCO in reciprocally stronger with cell 3 than cell 2. Such a motif has two HCOs that both contain cell 1 due to the strengthened pairs of synaptic connections: The above configurations of the inhibitory motif are bistable with two coexisting FPs: dominant blue (or green) with a large attractor basin and red with a smaller basin corresponding to the less robust A common misconception concerning modeling studies of coupled cells is that fast, non-delayed inhibitory synapses always foster anti-phase dynamics over unstable in-phase bursting. While being true in general for simple relaxation oscillators, interactions of bursting cells can be incomparably more complex even in small networks including HCOs with fast inhibitory coupling To explore the dual role of inhibition, we now explore nearly synchronous bursting in all three cells of the homogeneous, medium DC motif. Because synchronous steady states are due to spike interactions, we restrict the consideration to a relatively small positive vicinity of the synchronous state, on average, over the bursting period. In the excitatory motif, whenever the advanced cell initiatives a new bursting cycle, the synaptic current raises the voltages of post-synaptic cells, thus making it follow the pre-synaptic one, at the hyperpolarized knee-point on the quiescent manifold  in two simultaneous bifurcations. As with the case of the inhibitory motif with the HCO . It is not clear either what mechanisms a single motor system can use to generate multiple rhythms, for instance: whether CPGs use dedicated circuitry for each function or whether the same circuitry can govern several behaviors. A systematic way to explore this is to create mathematical models that use biologically plausible components and classify the possible varieties of rhythmic outcomes.We performed such a study of CPG networks based on three inter-connected neurons. We systematically varied the strength and functional form of coupling between the neurons to discover how these affect the behavioral repertoire of the CPG. To do this, we created a geometric representation of the simulated CPG behavior of each possible configuration of the network, which greatly simplifies the study of the 9-dimensional system of nonlinear differential equations. We discovered several configurations that support multiple rhythms and characterized their robustness. By varying physiologically reasonable parameters in the model, we also describe mechanisms by which a biological system could be switched between its multiple stable rhythmic states.de facto proof of the robust occurrence of the corresponding rhythmic outcomes generated by such a motif. While the occurrence of some rhythms, such as In the Homogeneous Inhibitory Motifs section, we showed that a weakly coupled, homogeneous motif comprised of three bursting interneurons with reciprocally inhibitory fast synapses can produce a variable number of polyrhythms, depending on the duty cycle of the individual components. The phase lag maps are Recall that the inhibitory current shifts the post-synaptic cell closer to the boundary or can even move it over the boundary into silence while the pre-synaptic cell remains actively spiking . In termThe gap never gets closed by weak inhibition in the long duty cycle motif as the individual cells have initially remained far enough from the boundary separating the bursting and hyperpolarized quiescence. As the result, this motif can only effectively produce two possible bursting outcomes: the clockwise The intermediate case of the medium motif is far from the above extremes and benefits from a natural optimization between the coupling strength, initial phase distributions, and the spatio-temporal characteristics of unperturbed and perturbed bursting. One such characteristic is the slow passage through the ghost of the stable equilibrium state that guarantees the robust synchrony in the short duty cycle motif. As the result, the motif can produce five stable bursting rhythms: the anti-phase In the Asymmetric Inhibitory Motifs section, we described a number of generic bifurcations of the original five polyrhythms that can occur in the homogeneous, reciprocally inhibitory motif with the medium duty cycle. We revealed the basic principles of transformations of such a multi-functional network into ones with fewer rhythms or even with a single pattern bursting pattern.phase slipping bursts that have time varying phase lags.The rhythmic outcomes of the CPG do not always have to involve phase locking, as there can be a stable pattern of While each rhythm remains robust with respect to variations of the coupling connections, one can still make the network switch between them by applying an external pulse to the targeted cell that, upon release, appropriately changes the relative phases of the cells, as demonstrated in Although there are alternative ways of creating the 3-cell reciprocally inhibitory motif with predetermined outcomes, the fundamental principles are universal: the pre-synaptic cell that produces stronger inhibition gains the larger attractor basin and therefore the corresponding rhythm led by this cell becomes predominant. In particular, a sufficient increase (or decrease) of the coupling strength of a single connection can break the intrinsic rotational symmetry of the motif to remove the possibility of observing traveling wave patterns.Of special interest are the motifs with asynchronous phase-slipping patterns that have no dominating phase-locked states. Such patterns result from the synergetic interactions between all contributing cells, and is comprised of four transient episodes, but primarily marked by a continuous transition between two primary sub-rhythms: sudden death of bursting that occurs when a rhythmic leader  we can evaluate the boundaries and region of its existence and stability, which we will call a “synchronization zone.” A boundary of the region corresponds to a bifurcation, which can be either of saddle-node type, in which the FP vanishes, or of Andronov-Hopf type, through which the FP merely changes stability. In general, our insights allow us to predict both quantitative and qualitative transformations of the observed patterns as the network configurations are altered or the network states are perturbed dynamically We study CPG network motifs comprised of three cells coupled reciprocally by non-delayed, fast chemical synapses and with weak coupling strengths. The time evolution of the membrane potential, The time constants of gating variables are The steady state values, Fast, non-delayed synaptic currents in this study are modeled using the fast threshold modulation (FTM) paradigm as follows The numerical simulations and phase analysis were accomplished utilizing the freely available software PyDSTool (version 0.88) Movie S1Polyrhythmic dynamics of 3-cell CPGs: from  to  pattern. Bursting trajectory (gray) in the 3D phase space of the model, which is made of the “active” spiking (solenoid-like shaped) and the flat hyperpolarized sections. The gap between the 2D slow nullcline, not weekly]-coupled cells of the CPG: active cell(s) above (MOV)Click here for additional data file.Movie S2Polyrhythmic dynamics of 3-cell CPGs: from  to  pattern. Bursting trajectory (gray) in the 3D phase space of the model, which is made of the “active” spiking (solenoid-like shaped) and the flat hyperpolarized sections. The gap between the 2D slow nullcline, not weekly]-coupled cells of the CPG: active cell(s) above peristaltic bursting). Shown below are the corresponding voltage waveforms. This motion picture complements (MOV)Click here for additional data file.Movie S3Multistable dynamics of an asymmetric 3-cell CPG: from  pattern to sudden death. Bursting trajectory (gray) in the 3D phase space of the model, which is made of the “active” spiking (solenoid-like shaped) and the flat hyperpolarized sections. The gap between the 2D slow nullcline, not weekly]-coupled cells of the CPG: active cell(s) above (MOV)Click here for additional data file.Movie S4Multistable map and formation of five phase-locked bursting patterns. The phase lag Poincaré map for a homogeneous 3-cell CPG revealing the attraction basins of the coexisting bursting rhythms: the red, green and blue fixed points at (MOV)Click here for additional data file.Movie S5Bistable map and phase-slipping bursting pattern. The stable invariant curve “flowing” upwards in the return map corresponds to bursting patterns with periodically varying phase lags in this asymmetric CPG, as the phase point passes throughout the ghost of the vanished fixed points. This motion picture complements (MOV)Click here for additional data file.


Posterior fusion of the spine to the pelvis in paediatric and adult spinal deformity is still challenging. Especially assembling of the posterior rod construct to the iliac screw is considered technically difficult. A variety of spinopelvic fixation techniques have been developed. However, extreme bending of the longitudinal rods or the use of 90-degree lateral offset connectors proved to be difficult, because the angle between the rod and the iliac screw varies from patient to patient.We adopted a new spinopelvic fixation system, in which iliac screws are side-to-side connected to the posterior thoracolumbar rod construct, independent of the angle between the rod and the iliac screw. Open angled parallel connectors are used to connect short iliac rods from the posterior rod construct to the iliac screws at both sides. The construct resembles in form and function an architectural Flying Buttress, or lateral support arches, used in Gothic cathedrals.Three different cases that illustrate the Flying Buttress construct for spinopelvic fixation are reported here with the clinical details, radiographic findings and surgical technique used.The Flying Buttress construct may offer an alternative surgical option for spinopelvic fixation in circumstances wherein coronal or sagittal balance cannot be achieved, for example in cases with significant residual pelvic obliquity, or in revision spinal surgery for failed lumbosacral fusion. Posterior fusion of the spine to the pelvis in paediatric and adult spine deformity poses many challenges to the spine surgeon. Spinopelvic fusion is indicated in neuromuscular scoliosis with a pelvic obliquity of more than 15 degrees, stabilizing adult fixed lumbosacral coronal plane curve, reduction of high grade spondylolisthesis, spinal pseudarthrosis (Charcot spine), surgical treatment of sacral tumours requiring  sacrectomy, or as a tool to extend failed lumbosacral fixation . A solidThe original surgical technique of posterior spinopelvic fixation has been developed by Allen and Ferguson in the 1980s -7. They In our experience, however, the assembly of the rod to the iliac screws itself or via a 90-degrees lateral offset connector proved to be technical difficult, because the angle between the rod and the iliac screw varies from patient to patient. We have devised a new spinopelvic fixation system, in which iliac screws are side-to-side connected to the posterior thoracolumbar rod construct, independent of the angle between the rod and the iliac screw Figure . The conTo our best knowledge, a side-to-side construct, or FB construct, for spinopelvic fixation has never been reported before in literature. The purpose of this study was to describe the new FB construct for spinopelvic fixation. Three cases that illustrate this procedure are reported here with the clinical details, radiographic findings and surgical technique used.The patient is positioned in prone position on a Wilson spinal surgery frame . A standard midline posterior approach to expose the thoracic, lumbar and sacral spine is performed. Polyaxial and/or monoaxial pedicle screws  are connected to two long rods up to L5 or the sacrum as part of the deformity correction.Using the same approach, the posterior superior iliac spine of the pelvis is exposed bilaterally subcutaneously over the long posterior spinal muscles. In this way, the sacral insertion of the erector spinae muscles is left untouched. The right and left posterior iliac crest from the posterior superior iliac spine is identified. The outer table of the ilium is exposed subperiosteal with a Cobb periosteal elevator, until the ischiatic notch can be palpated with the index finger. The ischiatic notch is used as a reference point for the screw direction. The entry point of the screw is chosen approximately 2 cm superior to the posterior superior iliac spine at the anterior side of the iliac crest. The iliac apophysis and a small amount of the iliac crest is removed with a rongeur to allow the screw head seated deeply in the posterior superior iliac spine. The blunt pedicle finder is introduced between the two tables of the ilium aiming 1 to 2 cm cranial of the ischiatic notch to the anterior superior iliac spine . A ball-A 8-year old wheelchair depending girl with spastic cerebral palsy, congenital hydrocephalus and epileptic episodes presented with a severe progressive neuromuscular thoracolumbar scoliosis and pelvic obliquity Figure . Her weiA 42-year old female was operated in 2005 for a chordoma of L5. Patient was treated with a combined posteroanterior en bloc excision of L5. Posterior pedicle screw instrumentation was performed from L3 to S1. For anterior column reconstruction a carbonfiber stackable cage filled with tricalcium phosphate granulate and allogenic bone-grafts was placed. At two-year follow-up, she developed progressive low back pain, due to pseudarthrosis of L5-S1 and subsequently failure of both S1 screws. Revision surgery was performed by additional posterior iliac screw fixation combined with sacral alar screws in a FB construct  parallel connectors, the two iliac rods are easily linked from the iliac screws to the longitudinal posterior rod construct. In this way, these parallel connectors can be easily fixed to the longitudinal rod between two already placed and tightened pedicle screws, independent of the lumbar lordosis or residual pelvic obliquity.As a consequence, the FB construct may offer an alternative surgical option for spinopelvic fixation in circumstances wherein complete correction of the scoliotic curve cannot be achieved and significant residual pelvic obliquity persists. This is most often the case in patients with a severe rigid neuromuscular scoliosis, as shown in case 1. Both iliac rods are simply placed and subsequently connected to the posterior thoracolumbar screw-rod construct of the residual scoliotic deformity in an asymmetrical FB construct.In case the placement of more than one iliac screw on each side is indicated to provide a higher construct stability, for example in unstable situations caused by total sacrectomy , assemblFinally, the FB construct offers an attractive surgical option in revision spinal surgery for failed lumbosacral fusion, as shown in case 2 and 3. In case 2, pseudarthrosis between the cage and S1 resulted in screw breakage of the S1 screws. Unfortunately, re-placement of the broken S1 screws was not possible. Therefore, two additional sacral alar screws were placed into the lateral anterior cortical bone of the sacrum. Adding iliac screws and extending the longitudinal rod fixation to the sacrum and ilium in a FB construct did achieve a rigid fixation. By using the FB construct in revision spinal surgery, no extensive surgical dissection is necessary to add the FB construct to the existing longitudinal rod construct. In addition, the use of open parallel connectors avoids the need to temporarily loosen the pedicle screw-rod fixation to connect the iliac rods. In case 3, the osteoporotic bone quality of the sacrum could not withstand the high kyphotic forces after lumbar osteotomy in ankylosing spondylitis. This resulted in breakout of the sacral screws with loss of correction as a result of unfavourable biomechanics of a great lever arm at the lumbosacral junction and severe osteoporosis of the sacral bone. Revision of the lumbar osteotomy with extension of the instrumentation to the sacrum was easily achieved by using iliac screws and open parallel connectors in a FB construct. Obviously, primary instrumentation and fixation to the pelvis in a FB construct after lumbar osteotomy in ankylosing spondylitis with severe secondary osteoporosis will prevent this complication in the future.From a biomechanical point of view, the half arched side-to-side spinopelvic fixation is a very strong construct to transfer lateral thrust forces from the spine to the iliac crest. The mechanical philosophy and form of this construct, however, is not new. The Romans invented the lateral thrust arch, and in doing so, created the origin for the FB in Gothic cathedrals. In the Gothic architecture, a FB is known as an open half arch that gives extra support to the upper part of a wall by transmitting the thrust of a vault or roof to a support that stand outside. In this way, the load placed on the top of the arch is transferred along the curve of the arch to the sides, and thus down to the foundations. The spinopelvic fixation technique presented here resembles in form and mechanical function such an architectural FB used in many Gothic cathedrals, for example the Notre Dame Cathedral in Paris, France.Although the iliac tables of the hemipelvis have proven to be a save and solid foundation for rigid spinopelvic fixation, this technique requires fixation across a normally mobile sacroiliac joint. Obviously, this is not the case in ankylosing spondylitis, where there is no motion in the complete fused sacroiliac joints (case 3). However, in all other cases, instrumentation anterior to the posterosuperior corner of S1, the lumbosacral pivot point,17, and In conclusion, the flying buttress (FB) construct may offer an alternative surgical option for spinopelvic fixation in circumstances wherein coronal or sagittal balance cannot be achieved, for example in cases with significant residual pelvic obliquity, or in revision spinal surgery for failed lumbosacral fusion. The instrumentation of a FB construct for spinopelvic fixation has the advantage of modularity and is easy to assemble. The FB construct is a solid fixation that shows mechanical similarity with lateral thrust arches of the Gothic architecture. However, biomechanical testing and long-term follow-up of the FB construct for spinopelvic fixation is needed.The authors declare that they have no competing interests.BvR set the theoretical bases and conceived the surgical procedure, performing all of the operations and coordinated the preparation of the manuscript; MvD and DvO analysed and interpreted the patient data, and were major contributors in writing the manuscript. BvO did research and helped to list references; AS helped to draft the manuscript and revised it critically. All authors read and approved the final manuscript.


For resections in the upper or central breast, crescent mastopexy, the batwing incision, the hemibatwing incision, donut mastopexy, B-flap resection, and the central quadrantectomy are reviewed. For lesions of the lower breast, the triangle incision, inframammary incision, and reduction mastopexy are discussed. Surgeons who are interested in adding oncoplastic breast conserving therapies to their skill sets are encouraged to implement these surgical techniques where applicable and to seek out breast fellowships or enhanced training when appropriate.When a woman is diagnosed with breast cancer many aspects of her physical, emotional, and sexual wholeness are threatened. The quickly expanding field of oncoplastic breast surgery aims to enhance the physician commitment to restore the patient's image and self-assurance. By combining a multidisciplinary approach to diagnosis and treatment with oncoplastic surgery, successful results in the eyes of the patient and physician are significantly more likely to occur. As a way to aid oncoplastic teams in determining which approach is most suitable for their patient's tumor size, tumor location, body habitus, and desired cosmetic outcome we present a review of several oncoplastic surgical approaches. For resections located anywhere in the breast, the  The diagnosis of breast cancer is a life-changing experience. Not only does it bring the woman face to face with her mortality, but also surgical treatment of breast cancer is accompanied by physical changes to the breast and body that may significantly, and often permanently, alter her perception of her physical, emotional, and sexual wholeness. Since the Early Breast Cancer Trialists' Collaborative Group established the equivalency of mastectomy and breast conserving therapy in 1985, breast conserving surgery has remained the optimal surgical treatment for the breast cancer patient .–33. B-flIn designing the B-flap resection, the breast is positioned centrally on the pectoralis muscle and the areolar margin is outlined. The diameter of the areola is measured and then a disc of skin of equal diameter is drawn on the skin of the breast just inferior to the nipple-areolar complex. This disc of skin will form the new areola. For an eccentrically placed tumor, a larger circumareolar incision can be designed to encompass the skin anterior to the lesion. In this instance, the diameter of the disc of skin should be based on the diameter of the normal areola to maintain symmetry. On the other hand, use of a larger circumareolar incision allows flexibility in positioning the nipple-areolar complex to correct ptosis. Next, two curvilinear lines are drawn from the lateral and medial edges of the native areola and skin disc. As the lines pass inferior to the skin disc, both are curved inferolaterally to converge at the lateral aspect of the inframammary skin fold. B-flap resection begins with incision of the areolar margin. Dissection is continued posteriorly while maintaining a generous gross margin around the malignancy until the pectoralis muscle is encountered. After resecting the specimen, the area of skin outlined in the inferolateral breast is de-epithelialized except for the encircled disc of skin that will form the future areola. De-epithelization is easily accomplished using tenotomy scissors to excise the pigmented epithelial layer, leaving intact the white reticular “deep” dermis layer. Wound closure is initiated by incising the breast and inframammary fold along the medial edge of the de-epithelialized skin, extending this incision through the underlying glandular tissue to the chest wall. The lower outer quadrant of the breast is then dissected off the underlying chest wall to allow superior and medial rotation and advancement of the skin disc and underlying glandular tissue to the central breast. This brings the skin disc to the position of the original nipple-areolar complex and partially restores the volume of the central breast using glandular tissue from the inferior and outer quadrants. The central breast mound is further reconstituted by suturing the transposed tissue to the surgical margin using interrupted 2–0 or 3–0 absorbable sutures in multiple layers. Partial undermining of the lower inner quadrant facilitates full-thickness approximation of the lower breast gland. Layered closure of the skin is then performed by suturing the edge of the skin disk to the original areolar skin margin and approximating the epithelialized skin margins of the infero-lateral breast after burying the de-epithelialized dermis below the skin surface. Reconstruction of the nipple and tattooing of the areola may be completed at a later date.Central quadrantectomy is performed through a circumareolar incision spanning up to 50% of the areolar circumference and may be used in patients with widely ranging breast sizes , 3534, 3When the position of the malignancy enables preservation of the nipple-areolar complex, the initial markings are drawn as described above, substituting an inverted “U-” shaped incision instead of a “V-” shaped incision with placement of the apex of the inverted “U” at the new superior areolar point. When the breast wound is closed, the vertical lines will span the distance from the inferior areolar point to the inframammary fold, and the horizontal lines will form the superior skin margin of the new inframammary fold. Modifications of the standard inferior, medial, or lateral incisions have also been described for breast conservation and include adjusting the incisions to incorporate the resected area . After designing the skin incision, resection of the breast malignancy is undertaken by incising the inframammary fold, the affected skin, and the glandular margins down to the chest wall, maintaining the dissection plane at right angles to the skin surface. If nipple and areola preservation is intended, care should be taken to preserve vascular supply to the nipple-areolar complex either by avoiding undermining the nipple-areolar complex for a parenchyma pedicle or by maintaining the retained dermis along at least two-thirds of the areolar circumference. In addition, de-epithelialization of the skin between the remaining areolar margin and new superior skin margin may be used to optimize perfusion and innervation of the nipple-areolar complex. For lesions that are eccentrically located  the surgeon may chose to “cheat” the glandular resection medially or laterally to gain adequate clearance around the malignancy. After complete excision of the malignancy, dermoglandular flaps using the remaining breast tissue can also be incorporated to fill in significant defects . Wound closure is initiated by tailor-tacking the previous incisions with staples, starting with the inferior, medial, and lateral incisions. If the originally drawn circular pattern at the apex of the Wise pattern (“U” shape) is symmetric, the nipple can also be inset, burying the de-epithelialized tissue under the incision. If better symmetry of the nipple-areolar complex is required, a cookie-cutter can be used to create a new superior incision margin after closure of the inverted “T” incisions only. Any additional skin removal is performed by de-epithelialization. When the nipple-areolar complex has been resected, the skin can be closed in either a transverse or vertical pattern, depending on the type of reduction performed. Layered closure of the parenchyma, dermis, and skin ensures maintenance of the final breast shape over time. Complications of combined reduction mammaplasty and malignancy excision occur in 17% of patients . Skin anThe procedures presented herein constitute a broad overview of the most commonly performed oncoplastic breast conserving procedures for optimizing tumor resection and cosmesis. This overview provides a starting point for surgeons interested in adding oncoplasty to the surgical options that they offer to their patients. While some of the procedures can be introduced without specialized training, breast and general surgeons seeking advanced training in oncoplastic surgery should participate in a breast fellowship program or an oncoplastic surgery course. Oncoplastic surgery courses are offered by several specialty societies, including the American Society of Breast Surgeons and the American Society of Breast Diseases.


Human and non-human primates rely on the ability to perceive and interpret facial expressions to guide effective social interactions. The neuropeptide oxytocin (OT) has been shown to have a critical role in the perception of social cues, and in humans to increase the number of saccades to the eye region. To develop a useful primate model for the effects of OT on information processing, we investigated the influence of OT on gaze behavior during face processing in rhesus macaques. Forty-five minutes after a single intranasal dose of either 24IU OT or saline, monkeys completed a free-viewing task during which they viewed pictures of conspecifics displaying one of three facial expressions  for 5 s. The monkey was free to explore the face on the screen while the pattern of eye movements was recorded. OT did not increase overall fixations to the face compared to saline. Rather, when monkeys freely viewed conspecific faces, OT increased fixations to the eye region relative to the mouth region. This effect of OT was particularly pronounced when face position on the screen was manipulated so that the eye region was not the first facial feature seen by the monkeys. Together these findings are consistent with prior evidence in humans that intranasal administration of OT specifically enhances visual attention to the eye region compared to other informative facial features, thus validating the use of non-human primates to mechanistically explore how OT modulates social information processing and behavior. There is increasing evidence that the neuropeptide oxytocin (OT), functioning both as a hormone and neurotransmitter, plays a significant role in social behavior across a wide variety of species   B, E, G, and S, served as subjects. All animals were acquired from primate breeding facilities in United States where they had social-group histories as well as group-housing experience until their transfer to NIH for quarantine. After that, they were pair-housed in a rhesus monkey colony room with tactile, auditory, and visual contact with one another. The colony rooms accommodate 24 rhesus monkeys, and the four primates that served as subjects in this study have been housed at NIH between 3 and 4 years prior to this experiment. All subjects therefore have had extensive social experience, thereby making them familiar with perception and interpretation of facial cues in conspecifics. All procedures were performed in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals and were approved by the Animal Care and Use Committee of the National Institute of Mental Health.Animals had surgically implanted head posts for head fixation to allow for accurate video tracking of eye movements. An Arrington ViewPoint eye tracking system recorded eye movements while monkeys examined each conspecific face. Images were displayed on a computer monitor placed 40 cm in front of the monkey and the face stimuli subtended approximately 13° of visual angle. During the testing phase, all monkeys received controlled access to water.The task was a free viewing paradigm adopted by previous fMRI studies conducted in humans  = 0.81 p = 0.37] or across sessions  or across sessions . Furthermore, we explored whether there was an effect of OT on habituation to images within a session. We did not find any significant effect of drug by number of images repetition for total number of fixations on the face region [F = 0.34 p = 0.56] or for total looking [F = 0.06 p = 0.94].Although we repeatedly presented the same set of stimuli, the total number of fixations on the face region did not significantly differ within session  or the facial expression shown  affected the relative proportion of fixations to the face, and there was no evidence of a higher order interaction involving either factor .We began by examining if OT, facial expression, and initial face position influenced how often the monkeys fixated on the presented face. Neither the drug administered . When the eye region was centered on the initial fixation point the proportion of fixations in the eye region increased, compared to when the mouth region was presented at the central fixation point . Likewise the proportion of fixations in the mouth region was larger when it was centered on the initial fixation point compared to the eye .Next we examined how often the monkeys fixated on the eyes or mouth based on the defined AOIs Figure . The monF = 12.44, p < 0.001]. When the initial fixation point was located at the mouth region, the latency of the first saccade to the eye region was significantly shorter than the latency of the first saccade to the mouth region  when the initial fixation point was located at the eye region. However, there were no significant effects of drug on the latency of the first saccade to each region. Moreover, we investigated the direction of the first saccade. When the face was mouth centered the 42% of the first saccades were directed on the eye region, whereas when the face was eye centered the 30% of the first saccades landed on the mouth region.We further investigated the latency of the first saccade into the ROI opposite the initial fixation point Figure . The iniF = 6.2, p = 0.02; Figure F = 6.5, p = 0.01; Figure t(68) = −0.2, p > 0.05] or the mouth region . However, when the mouth region was centrally presented, OT compared to saline caused a proportional increase in how often the eye region was fixated , and a parallel decrease in how often the mouth region was fixated . Thus, OT specifically enhanced scanning of the eye region when that facial feature was not centrally presented. To illustrate the effect of OT on gaze orienting behavior we plotted patterns of fixation density when the mouth region was centrally presented (Figure We compared the effects of OT on fixations to the eyes vs. the mouth, and found that OT enhanced the general tendency of the monkeys to fixate on the eyes relative to the mouth .When we carried out analyses on the proportion of time spent in each AOI, all statistics were consistent. In other words, significant effects reported on proportion of fixations were still significant, and non-significant effects were still non-significant. Additionally, proportion of time spent viewing the face, eye, or mouth region was respectively correlated with the proportion of fixations made to each region [Face region The goal of our study was to examine the effects of OT on gaze behavior in macaques during face processing. We hypothesized that OT might not generally increase social attention, but instead bias social attention uniquely toward the eye region of another monkey face. This would replicate similar findings in humans (Guastella et al., The first aim of the current study was to investigate the effects of OT on gaze orienting behavior when monkeys viewed pictures of unfamiliar conspecifics' faces. We found that OT did not increase the proportion of fixations to the face, compared to saline. This appears to contrast with a recent study that also investigated OT effects in macaques during an unconstrained viewing task (Ebitz et al., Independently from the OT manipulation, we found that the monkeys preferred to fixate on the eyes relative to the mouth. This is consistent with prior evidence that monkeys made more saccades to the eyes than any other facial feature (Nahm et al., When we examined how OT affected fixations to the eye and mouth regions we found that OT heightened attention to the eye region when monkeys' viewed conspecific faces, relative to saline. These findings concur with prior studies examining how OT influences processing of the eyes in both monkeys (Ebitz et al., The critical OT effect on the eye region of a face was confirmed and emphasized when we analyzed the proportion of fixations in the eye and mouth region as a function of drug and initial face position. In our experiment we systematically manipulated the vertical position of the presented face so that the initial gaze of the monkey was centered on either the mouth or eye region, which prevented the monkeys from covertly deploying attention to a specific facial feature. Consistent with effects seen in humans (Challinor et al., Several limitations to this study should be noted. A sample size of four monkeys may seem small compared to human studies that have investigated behavioral effects of intranasal OT, although it is consistent with typical sample sizes used in psychopharmacological studies involving non-human primates (Chang et al., Finally, behavioral effects that follow peripheral administration of OT could be driven by at least three mechanisms. First, the peripherally administered OT could enter the CNS and bind to OT receptors there. Second, the peripherally administered OT may drive elevation of CNS OT via an unknown, indirect peripheral mechanism. In this case, OT binding to peripheral OT receptors may be driving changes in central OT levels. Finally, the peripherally administered OT may lead to behavioral effects via an entirely peripheral mechanism. There are many OT receptors in several peripheral structures including kidneys and pancreas, as well as in the heart, fat cells, and adrenal glands (Gimple and Farenholtz, In summary, intranasal administered OT in rhesus monkeys did not increase overall interest in exploring conspecifics' faces compared to saline. Instead, OT increased the number of fixations made to the eye region when the animals were allowed to freely explore monkey faces. Further, when the vertical position of the presented face was shifted to control for which feature was seen first, OT specifically enhanced attention to the eye region. Together these findings are consistent with prior evidence in humans and non-human primates that intranasal administration of OT specifically enhances social attention to the eye region compared to other informative facial features. We conclude that this supports the utility of a primate model in investigating the neurobiological mechanisms involved in the perception and processing of social information, and the role OT plays in those processes.Bruno B. Averbeck designed research; Olga Dal Monte and Pamela L. Noble performed research; Olga Dal Monte and Vincent D. Costa. analyzed data; Olga Dal Monte, Pamela L. Noble, Vincent D. Costa, and Bruno B. Averbeck wrote the paper.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.