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Integrated population dynamics models use a variety of data types, and all the data used impact modeled processes and estimated dynamics. Paired age-length data treated as conditional age-at-length (CAAL) data are increasingly being used as a data component in stock assessment models. The original intent of the use of CAAL data was to directly estimate the length-at-age process, including the associated variability in length-at-age. However, we show that introduction of CAAL data that are not representative of the age-structure of the population can cause bias and imprecision in estimates of not only growth, but also dynamics and management quantities. Estimation of an appropriate age-based observations-modeled process may improve model performance. We also show that even the use of representative CAAL data in a model with misspecified age-based systems-modeled processes (natural mortality and time-varying growth) can lead to bias and imprecision in growth, dynamics, and management quantities. In these cases, estimation of an age-based observations-modeled process magnified the bias and imprecision. Greater consideration of this type of data is needed.

Integrated analysis has increasingly been the preferred approach for conducting stock assessments and providing the basis for management advice for fish and invertebrate stocks around the world. Many decisions are required when developing integrated stock assessments. For example, the analyst needs to decide whether the model fits the data, if the optimization was successful, if estimates are consistent retrospectively, and if the model is suitable to predict future stock responses to fishing. This study provides practical guidelines for implementing selected diagnostic tools that can assist analysts in identifying problems with model specifications and alternatives that can be explored to minimize or eliminate such problems. Emphasis is placed on reviewing the implementation and interpretation of contemporary model diagnostic tools. We first describe each diagnostic approach and its utility. We then proceed by providing a “cookbook recipe” on how to implement each of the diagnostics, together with an interpretation of the results, using two worked examples of integrated stock assessments with Stock Synthesis. Further, we provide a conceptual flow chart that lays out a generic process of model development and selection using the presented model diagnostics. Based on this, we propose the following four properties as objective criteria for evaluating the plausibility of a model: (1) model convergence, (2) fit to the data, (3) model consistency, and (4) prediction skill. It would greatly benefit the stock assessment community if the next generation of stock assessment models could include the diagnostic tests presented in this study as a set of open source tools.

Stock assessment analysts are exploring an increasingly diverse and complex range of models while also facing higher expectations for consistency, documentation, and transparency in reports and management advice, all within a tight timeline. Meeting these goals requires increased efficiency at all steps in the assessment process from data processing, through model development and selection, to report writing and review. Here, we describe one widely used tool that has proven successful in increasing the efficiency of the assessment process: the r4ss package, which supports the use of the Stock Synthesis modeling framework. What began 15 years ago as a tool to provide simple model diagnostics, including plots showing data and model results, has grown into a large collection of R functions to support many aspects of the assessment process. We provide an overview of the r4ss features and illustrate its utility with examples from recent applications. Finally, we discuss lessons learned from the ongoing development of r4ss that can be applied to similar efforts associated with the next generation of stock assessment packages.

Theoretical considerations and applied examples suggest that stock assessments are highly sensitive to the weighting of different data sources whenever data sources conflict regarding parameter estimates. Previous iterative reweighting approaches to weighting compositional data are generally ad hoc, do not propagate uncertainty about data-weighting when calculating uncertainty intervals, and often are not re-adjusted when conducting sensitivity or retrospective analyses. We therefore incorporate the Dirichlet-multinomial distribution into Stock Synthesis, and propose it as a model-based method for estimating effective sample size. This distribution incorporates one additional parameter per fleet (with the option of mirroring its value among fleets), and we show that this parameter governs the ratio of nominal (“input”) and effective (“output”) sample size. We demonstrate this approach using data for Pacific hake, where the Dirichlet-multinomial distribution and an iterative reweighting approach previously developed by McAllister and Ianelli (1997) give similar results. We also use simulation testing to explore the estimation properties of this new estimator, and show that it provides approximately unbiased estimates of variance inflation when compositional samples capture clusters of individuals with similar ages/lengths. We conclude by recommending further research to develop computationally efficient estimators of effective sample size that are based on alternative, a priori consideration of sampling theory and population biology.

Objectives The present study tested whether self-reported school and leisure-time physical activity have a reciprocal relationship with Physical Education (PE)-based motivational regulations described by self-determination theory. Participants were 635 11- and 12-year-old school children from the United Kingdom. Design & Method A cross-lagged longitudinal design over two time points was employed. Study hypotheses were analyzed using latent factor reciprocal effects models. Results Following temporal invariance tests, data revealed positive relationships between both types of physical activity and subsequent changes in autonomous motivation, but not the oft-stated reverse relationship. No relationships were observed involving introjected regulation. Theoretically aligned relationships between external regulation and changes in physical activity were observed, but no reverse relationships. Both types of physical activity behavior were negatively associated with changes in amotivation in PE, but surprisingly, amotivation in PE positively predicted changes in leisure-time physical activity. Conclusions In general, physical activity participation may help children internalize reasons for partaking in PE and foster self-determination. However, the widespread theory that self-determined PE motives can develop school and leisure-time physical activity participation was not compellingly demonstrated.

Few studies have attempted to identify distinct psychological correlates of different forms of classroom disengagement. Drawing from basic psychological needs theory (Deci & Ryan, 2000), this study investigated two divergent mechanisms predicting active and passive classroom disengagement. Pupils (N= 647; age = 11–14 years) and their respective teachers completed a questionnaire measuring the study variables. Using structural equation modelling, pupils’ perceptions of teacher psychological control positively predicted pupils’ autonomy and competence frustration in class. Pupils’ competence frustration indirectly and positively associated with teacher-rated passive disengagement (e.g. daydreaming in class), via reduced feelings of vitality. Pupils’ autonomy frustration demonstrated positive associations with both active disengagement (e.g. talking and making noise) and passive disengagement but neither relationship was explained by feelings of vitality. These distinct mechanisms may have implications for educators, identifying potential causes of different forms of pupil disengagement and the importance of avoiding psychological control in classrooms.

Fishery catch projection models play a central role in fishery management, yet are underrepresented in the literature. A wide range of statistical approaches are employed for the task, including multiple regression models, autoregressive methods, different classes of generalized linear models, mixed model approaches and many others. However, the applicability of these statistical approaches can be limited in specific cases of complex fisheries. We developed a new catch projection model for quota-based fisheries on the West Coast of the U.S. to forecast annual catch and landings for a variety of groundfish species in the Northeast Pacific Ocean. The model projects total and landed catch of each species by individual vessel and for the entire fishing fleet, using a combination of weighted mean vessel attainment rates and historical catch rates, and generates uncertainty intervals. It demonstrated an ability to produce highly accurate predictions at both fleet (R 2 = 0.9847) and vessel levels (R 2 = 0.8447). The model framework contains much built-in versatility, is generalizable enough to serve a variety of quota based applications, and the approach can be tailored to other fisheries around the world. With the proliferation of quota based management of commercial fisheries, tools such as this one are increasingly useful for sustainable management of fishery resources.

Somatic growth in fishes often varies through time. Despite this, most stock assessments either fix or estimate a time-invariant growth relationship because estimating time-varying growth parameters can be data intensive and subject to multiple sources of bias. Additionally, estimates of growth are often confounded with estimates of selectivity, particularly if selectivity is also time varying. Incorporating empirical weight-at-age (EWAA) information into assessments is a little-studied alternative that accounts for time-varying growth, but foregoes fixing or estimating growth and length–weight relationships. However, this method requires annual measures of fish weights at each age, and missing values must therefore be interpolated. We used Stock Synthesis in a simulation-testing framework to compare the effect of estimating a single time-invariant growth curve, time-varying growth curves, and incorporating EWAA information on management quantities and parameter estimates. We ran simulations across two fish life histories (hake-like and rockfish-like) and three data cases (data-rich, data-rich with a late-starting survey, and data-moderate). We found that when growth was time invariant, the EWAA approach was unbiased but had twice the median average relative error compared to a model that estimated growth from age and length data. However, for data-rich cases with time-varying growth, the EWAA method resulted in more accurate estimates of spawning stock biomass compared to the approach that estimated time-invariant and time-varying growth parameters, as evidenced by at least a five-fold reduction in range of median relative errors. The magnitude of this effect was greatest for the long-lived, slow-growing life history. For the relatively fast-growing species, estimates from the EWAA method were particularly sensitive to interpolating missing values.

Analysts conducting stock assessments using integrated, age-structured models must discretize length data into a limited number of bins (data bins). Furthermore, some modeling frameworks also allow users to specify a distinct structure for how lengths of fish are represented in the model (model bins). The effect of choices regarding the number and width of these bins on model output is unclear, and these choices are made inconsistently in assessments across regions and species. Here, we used the stock synthesis modeling framework, and the ss3sim stock assessment simulation package, to explore the effects of choices about length discretization on stock assessment performance for three fish life-history types and four data cases. We found that, with all other aspects of a model fixed, increasing the model bin width tended to increase estimates of spawning biomass, but this effect depended on the shape of length-based processes (e.g., growth, maturity, and selectivity). Thus, we suggest analysts using model bins wider than 1 cm explore the effect of this decision on derived management quantities. In the context of estimation, there generally was a predictable tradeoff between estimation accuracy and model run time, with finer model and data bins always improving estimation accuracy and model convergence, but increasing run time. In some cases, wider data bins reduced run time (by up to 50%) with little sacrifice in model estimation performance, particularly those using conditional age-at-length data. This study identifies key aspects to consider when binning length, and provides pertinent information for stock assessment best practice guidelines.

The present study longitudinally explored sports coaches' psychological well-being (positive affect and integration of coaching with one's sense of self) and ill-being (negative affect and devaluation of coaching) as predictors of their perceived autonomy supportive and controlling interpersonal styles towards individuals under their instruction. Participants were 195 sport coaches who completed questionnaire measures at three time points across an eleven-month period. Controlling for social desirability, multilevel analyses revealed that within-person increases and individual differences in positive affect and integration were positively associated with autonomy support. Conversely, within-person increases and individual differences in negative affect, but not devaluation, were associated with increased use of interpersonal control. The indicators of well-being did not predict interpersonal control and the indicators of ill-being did not predict autonomy support. In their entirety, the present findings suggest that autonomy supportive and controlling interpersonal styles have unique correlates, and affective determinants may play a particularly central role in controlling interpersonal styles. Supporting the psychological health of coaches may lead them to create an adaptive interpersonal environment for their athletes.

Objective To examine the effects of communication skills training on physiotherapists' supportive behavior during clinical practice. Design Randomized trial. Setting Hospital outpatient physiotherapy clinics. Participants Physiotherapists (N=24) and patients (N=24) with chronic low back pain. Interventions Two hospital clinics were randomly assigned to the intervention arm. Physiotherapists (n=12) received 8 hours of communication skills training focused on supporting patients' psychological needs. Physiotherapists (n=12) from 2 other hospital clinics formed a waitlist control arm. Main Outcome Measures Verbal communication between each physiotherapist and a patient was recorded on an audiotape, and independent, blinded raters used the Health Care Climate Questionnaire to assess physiotherapists' needs-supportive behavior (primary outcome). Results Independent raters' Health Care Climate Questionnaire scores favored the intervention arm (Cohen's d=2.27; P

SummaryThe SAMHD1 triphosphohydrolase inhibits HIV-1 infection of myeloid and resting T cells by depleting dNTPs. To overcome SAMHD1, HIV-2 and some SIVs encode either of two lineages of the accessory protein Vpx that bind the SAMHD1 N or C terminus and redirect the host cullin-4 ubiquitin ligase to target SAMHD1 for proteasomal degradation. We present the ternary complex of Vpx from SIV that infects mandrills (SIVmnd-2) with the cullin-4 substrate receptor, DCAF1, and N-terminal and SAM domains from mandrill SAMHD1. The structure reveals details of Vpx lineage-specific targeting of SAMHD1 N-terminal “degron” sequences. Comparison with Vpx from SIV that infects sooty mangabeys (SIVsmm) complexed with SAMHD1-DCAF1 identifies molecular determinants directing Vpx lineages to N- or C-terminal SAMHD1 sequences. Inspection of the Vpx-DCAF1 interface also reveals conservation of Vpx with the evolutionally related HIV-1/SIV accessory protein Vpr. These data suggest a unified model for how Vpx and Vpr exploit DCAF1 to promote viral replication.

Integrated assessment models frequently track population abundance at age, and hence account for fishery removals using a function representing fishery selectivity at age. However, fishery selectivity may have an unusual shape that does not match any parametric function. For this reason, previous research has developed flexible ‘non-parametric’ models for selectivity that specify a penalty on changes in selectivity as a function of age. In this study, we describe an alternative ‘semi-parametric’ approach to selectivity, which specifies a penalty on differences between estimated selectivity at age and a pre-specified parametric model whose parameters are freely estimated, while also using cross-validation to select the magnitude of penalty in both semi- and non-parametric models. We then compare parametric, semi-parametric, and non-parametric models using simulated data and evaluate the bias and precision of estimated depletion and fishing intensity. Results show that semi- and non-parametric models result in little decrease in precision relative to the parametric model when the parametric model matches the true data-generating process, but that the semi- and non-parametric models have less bias and greater precision when the parametric function is misspecified. As expected, the semi-parametric model reverts to its pre-specified parametric form when age-composition sample size is low but performs similarly to the non-parametric model when sample size is high. Overall, results indicate few disadvantages to using the non-parametric model given the range of simulation scenarios explored here, and that the semi-parametric model provides a selectivity specification that is intermediate between parametric and non-parametric forms.

Summary FAN1 is a structure-selective DNA repair nuclease with 5′ flap endonuclease activity, involved in the repair of interstrand DNA crosslinks. It is the only eukaryotic protein with a virus-type replication-repair nuclease (“VRR-Nuc”) “module” that commonly occurs as a standalone domain in many bacteria and viruses. Crystal structures of three representatives show that they structurally resemble Holliday junction resolvases (HJRs), are dimeric in solution, and are able to cleave symmetric four-way junctions. In contrast, FAN1 orthologs are monomeric and cleave 5′ flap structures in vitro, but not Holliday junctions. Modeling of the VRR-Nuc domain of FAN1 reveals that it has an insertion, which packs against the dimerization interface observed in the structures of the viral/bacterial VRR-Nuc proteins. We propose that these additional structural elements in FAN1 prevent dimerization and bias specificity toward flap structures., Graphical Abstract, Highlights • Bacterial proteins comprising solely a VRR-Nuc domain are dimeric in solution • Bacterial VRR-Nuc domains act as Holliday-junction-resolving enzymes • A conserved helical insertion in the FAN1 VRR-Nuc domain prevents dimerization • FAN1 monomers cannot cleave Holliday junctions and instead cleave 5′ flap DNA, The Fanconi anemia pathway is responsible for clearing DNA interstrand crosslinks that block DNA replication and transcription leading to genome instability. Here, Pennell et al. characterize the Fanconi-anemia-associated nuclease FAN1, comparing the structure and activity of its catalytic VRR-Nuc domain with prokaryotic examples. FAN1 is monomeric with 5′ flap specificity, whereas prokaryotic VRR-Nuc domains are dimeric Holliday-junction-resolving enzymes. FAN1 is proposed to contain a conserved helical insertion blocking dimer formation and consequently restricting substrate specificity.

Objective To examine well-being and work performance changes accompanying participation in a 16-week uncontrolled feasibility lunchtime walking trial. Method Participants were 75 (92% female; M age = 47.68) previously physically inactive non-academic employees from a large British university. Multilevel modelling analyses examined well-being and work performance trajectories from baseline to post-intervention, to four months later, controlling for group membership and trait affectivity. Results Increases in perceptions of health, subjective vitality, and work performance, and decreases in fatigue at work were observed. Changes were sustained four months after the end of the intervention. No changes were identified for enthusiasm, nervousness and relaxation at work. Conclusion Although this was a relatively small uncontrolled feasibility trial, the results suggest that participation in a walking programme may be associated with sustainable well-being benefits and improvements in perceptions of work performance.

Objectives Based on Basic Needs Theory (BNT: Deci & Ryan, 1985 ), this study examined longitudinal relationships between autonomy support from two sources, psychological need satisfaction, subjective vitality and self-reported physical activity during a walking intervention for physically inactive adults. We proposed that autonomy support provided via a walk leader and the overall programme would independently predict change in subjective vitality and physical activity from baseline to week 16 (post-intervention) and at four month follow-up. Further, we proposed that direct relationships among sources of autonomy support and outcomes would be mediated by autonomy, relatedness, and competence need satisfaction. Design A longitudinal examination. Methods Participants (N = 69; n = 63 females, n = 6 males) from a 16-week walking programme completed a multi-section questionnaire measuring the aforementioned variables at three time points, including a four month post-intervention follow-up. Results Both hypotheses were partly supported. Autonomy support from the walk leader positively predicted changes in subjective vitality from baseline to week 16 and in physical activity from baseline to follow-up. Autonomy support from the programme positively predicted changes in subjective vitality from baseline to week 16. Finally, autonomy gained from the walk leader mediated the relationship between autonomy support and subjective vitality, and between perceived autonomy support and physical activity. Conclusions Findings indicate that autonomy support from both a walk leader and wider programme can predict psychological need satisfaction, subjective vitality and physical activity. Clinicians and researchers implementing future walking interventions may increase physical activity and subjective vitality by facilitating psychological need satisfaction through autonomy support from both sources.

Objective Self-determination theory describes how an individual’s underlying motives determine self-regulatory outcomes. Building on this, we investigated whether different types of motivation predict lapse in exercise behavior, and particularly the emotional responses to lapse in the form of guilt, anxiety, and relief. Method Study 1 entailed a self-report, cross-sectional investigation using structural equation modeling to test study hypotheses (N = 343, M age: 24.30 years, 215 female). Study 2 employed a 21-day daily diary using multi-level modeling to test study hypotheses (N = 89, M age: 25.90 years, 55 female). Motivation was self-reported at the beginning of the study with all other variables self-reported daily. Results Autonomous motivation was shown to negatively associate with lapse. When lapse occurred, autonomous motivation was inconsistently associated with the tendency for individuals to feel decreased relief and guilt. In contrast, introjected regulation displayed inconsistent associations with lapse, but increased the likelihood that individuals would experience guilt and anxiety following lapse. External regulation did not reliably predict lapse and emotions across studies. Conclusions Our findings suggest autonomous motivation may protect against lapses in goal-directed behavior. Controlling forms of motivation, however, may promote less-optimal emotional processes implicated in poor self-regulation.

Objective Physical education (PE) programs aim to promote physical activity (PA) and reach most school-aged youth. However, PA levels within PE lessons are often low. In this cluster-randomized controlled trial, we examined the effects of three self-determination theory-based motivational strategies on PA and sedentary behavior, as well as their hypothesized antecedents during PE lessons. Methods Data were collected in Sydney, Australia (October–December 2011). After baseline testing, teachers (n = 16) and their classes (n = 288 students; M = 13.6 years, 50.4% male) were randomly assigned to one of four teaching strategy conditions: (1) explaining relevance; (2) providing choice; (3) complete free choice; or (4) usual practice. Teachers then delivered the assigned strategy. Primary outcomes were accelerometer-assessed PA and student motivation during lessons. Secondary outcomes included sedentary behavior, perceptions of teachers' support and psychological needs satisfaction. Results The ‘free choice’ intervention increased PA (p < .05). ‘Providing choice’ and ‘free choice’ interventions decreased sedentary behavior (p < .05). The interventions did not influence motivation, but students' autonomy increased during both choice-based interventions (p < .05). Conclusions Promoting choice can produce short-term increases in PA and decreases in sedentary behavior, as well as increased perceived autonomy during PE lessons.

The second dorsal spine has historically been used for age determination in the spiny dogfish shark. The dorsal spines are located on the external surface of the body and are subjected to natural wear and breakage. Two methods have been developed to account for the worn portion of the spine and extrapolate the lost annuli. We compared the performance of these methods using a large data collection assembled from multiple sources, and evaluated their utility for stock assessment and management of the spiny dogfish shark Squalus suckleyi in the Northeast Pacific Ocean. Our results showed that the two methods produced very different age estimates for older fish with worn spines. Both methods raised significant questions about some aspects of the age estimates produced, and further exploration of techniques to account for worn spine annuli is needed. It is therefore important to develop alternative methods for shark age determination, including those using stained vertebrae.

100 years after Rosa Lee (1912) showed that higher mortality on faster growing fish can alter length-at-age distributions in fish populations, we present a computationally-efficient and parsimonious method for modeling size-selective mortality within a commonly-used assessment model, Stock Synthesis. Stock Synthesis allows the normal distribution of length-at-age to be partitioned into three or five overlapping platoons with slow, medium, or fast growth trajectories. The platoons are tracked separately in the model, and experience different degrees of size-selective fishing pressure and mortality, but are assumed to be unobservable except through changes in the length distribution. Simulations are used to explore this phenomenon in conjunction with dome-shaped selectivity, an alternative explanation for observing fewer than expected large fish in sampled data, but with very different implications for population productivity. For data simulated both with and without platoons, misspecification of the assumptions about growth are found to bias model results, with selectivity often incorrectly identified as the cause of fewer observations of larger fish. Trends in dome-shaped selectivity were explored as a potential diagnostic of model misspecification.

Many fisheries stock assessment models are implemented specifically for likelihood-based estimation or for Bayesian inference (via full integration of the joint posterior distributions), but not all have appropriate structure for both statistical approaches. Bias correction of recruitment deviations, in particular, must be adjusted to achieve consistency in each case. Fisheries management often uses the two types of results similarly, setting future catch quotas based on expected values or posterior medians depending on which is available given time constraints. Using two recent examples from the U.S. west coast, Pacific hake and sablefish, both implemented in Stock Synthesis, we find that likelihood-based estimates of key management quantities, such as spawning biomass, corresponded well with posterior modes, but tend to be lower (on an absolute scale) than posterior median values and that the asymptotic approximation for uncertainty intervals based on the Hessian matrix tends to overestimate the likelihood of smaller stock sizes and underestimate that of larger stock sizes. This pattern may be caused by a basic asymmetry in most fisheries data-sets: the necessity of a minimum stock size to have generated the observed catch/time-series, but little information regarding the plausibility among much larger stock sizes. Where only one type of inference is available, this asymmetry may be important for management decision-making. Even if management takes explicit account of uncertainty, in some cases adding a precautionary buffer that scales with the relative uncertainty in point estimates, the differences in catch advice may turn out to be important and the relative reductions non-linear.

Understanding the relationship between abundance of spawners and subsequent recruitment is one of the central issues in fisheries stock assessment. We developed a new, pre-recruit survival based stock–recruitment model that enables explicit modeling of survival between embryos and age 0 recruits, and allows the description of a wide range of pre-recruit survival curves. The model is especially useful for low fecundity species that produce relatively few offspring per litter and exhibit a more direct connection between spawning output and recruitment than species generating millions of eggs. The proposed model provides additional flexibility in the stock–recruitment options that may be explored in any fishery stock assessment, and it is now available within the Stock Synthesis assessment platform. In this paper, we describe the mathematical formulation of the new stock–recruitment model, explain how this model can be specified within Stock Synthesis, and use it to model the stock–recruitment relationship of the spiny dogfish shark in the Northeast Pacific Ocean. We compare the results of the application of our new stock–recruitment model, with those from traditional Beverton–Holt relationship, and illustrate why the new approach is more appropriate for this species.

We explored within-person and individual difference associations among basic psychological need satisfaction (autonomy, competence, and relatedness), attainment of acquisitive desires (wealth and popularity) and indicators of well- and ill-being. Participants were 198 undergraduates (51% male) who completed an inventory multiple times over a university semester. Analyses revealed that increased satisfaction of all the needs and desires beyond participants’ normal levels, with the exception of relatedness, were associated with greater psychological welfare. Nonetheless, individual differences in well-being were only predicted by psychological need satisfaction, and not by the attainment of acquisitive desires. Hence, the realization of acquisitive desires may elicit within-person increases in psychological welfare; however, satisfying innate needs may be a better bet for long term psychological health.

Objectives We aimed to examine social-contextual correlates of players’ developmental experiences in an elite youth soccer context. Specifically, we hypothesized that player perceptions of team cohesion and coach rapport would be positively associated with psychological need fulfillment. In turn, psychological need satisfaction was proposed to be positively related to adaptive developmental experiences in youth soccer (i.e., opportunities for leadership, emotional regulation, and goal setting), and negatively related to social exclusion. Design Cross-sectional. Method 133 male elite soccer players, aged between 11 and 18 years old, completed a self-report questionnaire assessing the variables of interest. Results Using path analysis and bootstrapping methods, we found support for the overall model fit of the hypothesized conceptual framework and specific study hypotheses. Conclusions This study utilizes strong theoretical foundations to underscore the role of the coach and team environment in facilitating positive youth outcomes, and highlights a potential mechanism that may explain these processes.

The impact of health care reform on academic medical centers will be just as great as it is on community practices. The economics of academic medical centers and training programs has been challenging, and will become even more so as funding is cut and the demand for regional integrated systems mounts. This article is one of the first to articulate these challenges and is written by authors well positioned to understand this arena.

SummaryLentiviruses are widespread in a variety of vertebrates, often associated with chronic disease states. However, until the recent discovery of the prehistoric endogenous lentiviruses in rabbits (RELIK) and lemurs (PSIV), it was thought that lentiviruses had no capacity for germline integration and were only spread horizontally in an exogenous fashion. The existence of RELIK and PSIV refuted these ideas, revealing lentiviruses to be present in a range of mammals, capable of germline integration, and far more ancient than previously thought. Using Gag sequences reconstructed from the remnants of these prehistoric lentiviruses, we have produced chimeric lentiviruses capable of infecting nondividing cells and determined structures of capsid domains from PSIV and RELIK. We show that the structures from these diverse viruses are highly similar, containing features found in modern-day lentiviruses, including a functional cyclophilin-binding loop. Together, these data provide evidence for an ancient capsid-cyclophilin interaction preserved throughout lentiviral evolution.

Jaagsiekte sheep retrovirus is a betaretrovirus and the causative agent of pulmonary adenocarcinoma, a transmissible lung tumour of sheep. Here we report the crystal structure of the capsid amino-terminal domain and examine the self-association properties of Jaagsiekte sheep retrovirus capsid. We find that the structure is remarkably similar to the amino-terminal domain of the alpharetrovirus, avian leukosis virus, revealing a previously undetected evolutionary similarity. Examination of capsid self-association suggests a mode of assembly not driven by the strong capsid carboxy-terminal domain interactions that characterise capsid assembly in the lentiviruses. Based on these data, we propose this structure provides a model for the capsid of betaretroviruses including the HML-2 family of endogenous human betaretroviruses.

Objectives The purpose of the study was to provide an in-depth analysis of how the Physical Education (PE) teaching context influences teachers' motivational strategies towards students. Design Qualitative semi-structured interviews Methods Using Self-determination theory (Deci, E. L., & Ryan, R. M. (2000). Psychological Enquiry, 11, 227-268 ) as a guiding framework, semi-structured interviews of 22 PE teachers were examined using categorical content analysis. Results The teachers perceived that an emphasis on student assessment and the time constraints associated with PE lessons often compelled them to use teaching strategies which conflicted with their beliefs about the most appropriate ways to motivate students. The teachers' own performance evaluations and pressure to conform to other teachers' methods also influenced the teachers' motivational strategies, but these influences were often congruent with their teaching beliefs. Additionally, the teachers discussed how perceived cultural norms associated with the teacher-student relationship impacted upon their chosen motivational strategies. These cultural norms were reported by different teachers as either in line, or in conflict with their teaching beliefs. Finally, the influence of the teachers' perceptions of their students helped produce strategies that were congruent with their beliefs, but often different to empirically suggested strategies. Conclusions It is important that teacher beliefs are targeted in education programs and that the teaching context aid in facilitating adaptive motivational strategies.

Chk2/CHEK2/hCds1 is a modular serine-threonine kinase involved in transducing DNA damage signals. Phosphorylation by ataxia telangiectasia-mutated kinase (ATM) promotes Chk2 self-association, autophosphorylation, and activation. Here we use expressed protein ligation to generate a Chk2 N-terminal regulatory region encompassing a fork-head-associated (FHA) domain, a stoichiometrically phosphorylated Thr-68 motif and intervening linker. Hydrodynamic analysis reveals that Thr-68 phosphorylation stabilizes weak FHA-FHA interactions that occur in the unphosphorylated species to form a high affinity dimer. Although clearly a prerequisite for Chk2 activation in vivo, we show that dimerization modulates potential phosphodependent interactions with effector proteins and substrates through either the pThr-68 site, or the canonical FHA phosphobinding surface with which it is tightly associated. We further show that the dimer-occluded pThr-68 motif is released by intra-dimer autophosphorylation of the FHA domain at the highly conserved Ser-140 position, a major pThr contact in all FHA-phosphopeptide complex structures, revealing a mechanism of Chk2 dimer dissociation following kinase domain activation.

In addition to the ability to bind the retroviral capsid protein, the retroviral restriction factors Fv1, Trim5alpha and Trim5-CypA share the common property of containing sequences that promote self-association. Otherwise Fv1 and Trim5alpha appear unrelated. Mutational analyses showed that restriction was invariably lost when changes designed to disrupt the sequences responsible for multimerization were introduced. A novel restriction protein could be obtained by substituting sequences from the self-associating domain of Fv1 for the Trim5 sequences in Trim5-CypA. Similarly, a fusion protein containing cyclophilin A joined to arfaptin2, a protein known to form extended dimers, was also shown to restrict HIV-1. Hence, multimerization of a capsid-binding domain could be the common minimum design feature for capsid-dependent retroviral restriction factors. However, not all domains that promote multimerization can substitute for the N-terminal domains of Fv1 and Trim5alpha. Moreover, only CypA can provide a capsid-binding site with different N-terminal domains. It is suggested that the spatial relationship between the multiple target binding sites may be important for restriction.

fi s i M h t h n o i A a r Drs Taylor and Clinchy have given us a wake-up call concerning the future of Academic Medical Centers (AMC) as this nation faces the dual challenges of unsustainable costs and the immediate need for health care reform. No matter what happens to the Patient Protection and Affordable Care Act, AMCs must change their business model or risk economic disaster. AMCs can no longer follow the traditional path that has supported them in the past decade. Sufficient money will not be available within the current business model. The Road Ahead for our teaching and research institutions demands innovation, and AMCs must be the incubator of new solutions for better health care delivery in addition to their advancing our science.

Neuropeptide Y (NPY) and peptide YY (PYY) are members of the pancreatic polypeptide family which have a high degree of primary and tertiary structural homology. They function as neurotransmitters and humoral agents in central nervous system and gastrointestinal function. During the last two decades, NPY body fluid concentrations and NPY/PYY brain receptor numbers have been demonstrated to be altered during the course of Alzheimer's disease. Recent research has shown that both NPY and PYY may be involved in aluminum metabolism in animal models. A brief discussion of the structure, biological activity and possible involvement of these peptides in aluminum metabolism and Alzheimer's disease is contained herein.

Forkhead-associated (FHA) domains are a class of ubiquitous signaling modules that appear to function through interactions with phosphorylated target molecules. We have used oriented peptide library screening to determine the optimal phosphopeptide binding motifs recognized by several FHA domains, including those within a number of DNA damage checkpoint kinases, and determined the X-ray structure of Rad53p-FHA1, in complex with a phospho-threonine peptide, at 1.6 A resolution. The structure reveals a striking similarity to the MH2 domains of Smad tumor suppressor proteins and reveals a mode of peptide binding that differs from SH2, 14-3-3, or PTB domain complexes. These results have important implications for DNA damage signaling and CHK2-dependent tumor suppression, and they indicate that FHA domains play important and unsuspected roles in S/T kinase signaling mechanisms in prokaryotes and eukaryotes.

The gene 5 protein of filamentous bacteriophage fd is a single-stranded DNA-binding protein that binds non-specifically to all single-stranded nucleic acid sequences, but in addition is capable of specific binding to the sequence d(GT5G4CT4C) and the RNA equivalent r(GU5G4CU4C), the latter interaction being important for translational repression. We show that this sequence preference arises from the formation of a tetraplex structure held together by a central block of G-quartets, the structure of which persists in the complex with gene 5 protein. Binding of gene 5 protein to the tetraplex leads to formation of a ∼170 kDa nucleoprotein complex consisting of four oligonucleotide strands and eight gene 5 protein dimers, with a radius of gyration of 45 A and an overall maximum dimension of 120–130 A. A model of the complex is presented that is consistent with the data obtained. It is proposed that the G-quartet may act as a nucleation site for binding gene 5 protein to adjacent single-stranded regions, suggesting a novel mechanism for translational repression.

In recent years, there has been a growing perception that limitations in gastrointestinal absorption may be detrimental to posthatch survival and subsequent performance. This perception is based on a large body of information demonstrating that genetic selection for growth in domestic poultry alters intestinal structure from that of their wild counterparts. Furthermore, recent advances in our understanding of the energetic costs of absorption suggest that biochemical as well as structural changes in intestinal function have decreased absorptive function and efficiency in both chickens and turkeys. The recent discovery that some gastrointestinal peptides enhance nutrient absorption has allowed limited, direct testing of this hypothesis. The results of preliminary studies indicate that intestinal absorption enhancement technology may have beneficial practical application. More detailed studies are needed to fully assess the economic potential of intestinal absorption enhancement in poultry.

The structure of the L1 metallo-beta-lactamase from the opportunistic pathogen Stenotrophomonas maltophilia has been determined at 1.7 A resolution by the multiwavelength anomalous dispersion (MAD) approach exploiting both the intrinsic binuclear zinc centre and incorporated selenomethionine residues. L1 is unique amongst all known beta-lactamases in that it exists as a tetramer. The protein exhibits the alphabeta/betaalpha fold found only in the metallo-beta-lactamases and displays several unique features not previously observed in these enzymes. These include a disulphide bridge and two substantially elongated loops connected to the active site of the enzyme. Two closely spaced zinc ions are bound at the active site with tetrahedral (Zn1) and trigonal bipyramidal (Zn2) co-ordination, respectively; these are bridged by a water molecule which we propose acts as the nucleophile in the hydrolytic reaction. Ligation of the second zinc ion involves both residues and geometry which have not been previously observed in the metallo-beta-lactamases. Simulated binding of the substrates ampicillin, ceftazidime and imipenem suggests that the substrate is able to bind to the enzyme in a variety of different conformations whose common features are direct interactions of the beta-lactam carbonyl oxygen and nitrogen with the zinc ions and of the beta-lactam carboxylate with Ser187. We describe a catalytic mechanism whose principal features are a nucleophilic attack of the bridging water on the beta-lactam carbonyl carbon, electrostatic stabilisation of a negatively charged tetrahedral transition state and protonation of the beta-lactam nitrogen by a second water molecule co-ordinated by Zn2. Further, we propose that direct metal:substrate interactions provide a substantial contribution to substrate binding and that this may explain the lack of specificity which is a feature of this class of enzyme.

The structural and functional organisation of Swi6, a transcriptional regulator of the budding yeast cell cycle has been analysed by a combination of biochemical, biophysical and genetic methods. Limited proteolysis indicates the presence of a approximately 15 kDa N-terminal domain which is dispensable for Swi6 activity in vivo and which is separated from the rest of the molecule by an extended linker of at least 43 residues. Within the central region, a 141 residue segment that is capable of transcriptional activation encompasses a structural domain of approximately 85 residues. In turn, this is tightly associated with an adjacent 28 kDa domain containing at least four ankyrin-repeat (ANK) motifs. A second protease sensitive region connects the ANK domain to the remaining 30 kDa C-terminal portion of Swi6 which contains a second transcriptional activator and sequences required for heteromerisation with Swi4 or Mbp1. Transactivation by the activating regions of Swi6 is antagonised when either are combined with the central ankyrin repeat motifs. Hydrodynamic measurements indicate that an N-terminal 62 kDa fragment comprising the first three domains is monomeric in solution and exhibits an unusually high frictional coefficient consistent with the extended, multi-domain structure suggested by proteolytic analysis.

Pancreatic polypeptide (PP) is a regulatory peptide that modulates gastrointestinal function. Previously we demonstrated PP receptors in the brainstem and interpeduncular nucleus, and the PP receptors in the brainstem appear to modulate gastric motility and pancreatic exocrine secretion. The purpose of this study is to extend our understanding of the distribution of PP receptors in the rat brain in order to determine the systems that are potentially modulated by PP. Rat brains were studied using 125I-PP receptor autoradiography on cryostat sections of the entire brain cut in three planes (horizontal, sagittal, and coronal). Brain regions exhibiting PP binding sites were confirmed when identified in all three planes of section. Saturable PP binding was identified in the hypothalamus (arcuate and paraventricular n), the rostral forebrain (medial preoptic area, anterior olfactory nucleus, islands of Calleja, the dorsal endopiriform n, piriform cortex, and the bed n of the stria terminalis), medial amygdaloid n; the thalamus (anteromedial thal. n; reuniens thal. n; and paraventricular thal n), the interpeduncular red nucleus, substantia nigra, parabrachial n; locus coeruleus, mesencephalic trigeminal n, dorsal motor n of the vagus, the n solitary tract, and the area postrema. We conclude that PP receptors are distributed widely throughout the rat brain. The distribution of many of these PP binding sites corresponds to brain regions regulating digestion and autonomic function. We speculate, based on the patterns of binding in the olfactory and limbic systems, that PP receptors might be involved in positive reinforcement of ingestion behavioral as well as modulation of gastrointestinal function.

The type IC methyltransferase M.EcoR124I consists of a specificity subunit (HsdS) and two methylation subunits (HsdM). Using chemical modifications, we have investigated the accessibility of lysine residues in the free enzyme and in the complex with its DNA recognition sequence. A total of 41 of the 109 lysine residues in the enzyme are susceptible to modification, of which 19 are located in the HsdS subunit and 11 in each of the two HsdM subunits. DNA binding results in extensive protection of lysine residues in the HsdS subunit, while those in the HsdM subunit are only protected weakly. The DNA binding activity of the methylase is abolished when a small fraction of the accessible lysine residues are modified. Peptide mapping and N-terminal sequencing has been used to locate the rapidly modified lysine residues in HsdS that are critical for DNA binding. Highly modified residues (K297, K261 and K327) are found in the C-terminal variable domain that is responsible for DNA recognition, but others (K196, K203 and K210) are found in the conserved regions that had not previously been implicated in DNA binding.

Whole cell oxidation of aryl alkyl sulfides to sulfoxides with Acinetobacter sp. NCIMB 9871 is only slightly less enantioselective than isolated enzyme transformation with the cyclohexanone monooxygenase (CHMO) from the same species. Pseudomonas sp. NCIMB 9872 oxidises the same substrates with high and mostly opposite enantioselectivity (73–100%ee). CHMO activity was detected in the black yeast NV-2 and Xanthobacter autotrophicus DSM 431 (NCIMB 10811), but contrary to an earlier report this activity could not be detected in cell free extracts of the latter. Both species oxidised methyl phenyl sulfide exclusively to the corresponding ( R )-sulfoxide (100% ee).

Background & Aims We recently showed that intracisternal injection of apolipoprotein A-IV (apo A-IV), a protein produced by the small intestine in response to fat, inhibits gastric acid secretion. The aim of this study was to investigate the mechanism of acid inhibition by central apo A-IV. Methods Gastric acid secretion was determined in pylorus-ligated conscious rats. The effect of intracisternal injection of apo A-IV on gastric acid secretion stimulated by pentagastrin, bethanechol, or intracisternal thyrotropin-releasing hormone (central vagal stimulant) was examined. The effects of vagotomy, indomethacin, and adrenergic blockers on the acid inhibition of apo A-IV were examined to investigate the role of the vagal system, prostaglandin pathways, and adrenergic system. Results Intracisternal apo A-IV significantly inhibited pentagastrin-, bethanechol-, and thyrotropin-releasing hormone-stimulated gastric acid secretion in a similar fashion. Inhibition of pentagastrin-stimulated acid secretion by apo A-IV still occurred even in vagotomized rats. Yohimbine but not indomethacin or propranolol eliminated apo A-IV-induced inhibition of acid. Conclusions Intracisternal apo A-IV inhibits gastric acid secretion through α2-adrenergic receptors. The vagal pathway and the prostaglandin system are not involved in apo A-IV-induced acid inhibition.

Various tissues were obtained from the well-characterized genetic model ( C57BL/6J- ob ob ) of non-insulin-dependent diabetes mellitus (NIDDM) and from a diet-induced model of NIDDM produced in the same genetic background (C57BL/6J). The objectives were to determine whether the previously observed changes in guanine nucleotide-binding regulatory protein (G protein) expression in adipose tissue from ob ob mice were mirrored by concomitant changes in other tissues, and whether NIDDM of a different etiology would share similar alterations in G protein expression. Plasma membranes from adipocytes, brain, heart, liver, and testes were probed with α-subunit-specific antisera, and the level of G protein expression in each model was compared with that in its lean littermate control. Adipose, heart, and liver cell membranes from ob ob mice contained significantly less α-subunit of stimulatory G protein (G s α) than those from their lean littermates. As compared with the lean littermates, heart α-subunit-2 of inhibitory G protein (G i α-2), liver G i α-3, and adipocyte G i α-1 and G i α-3 were also reduced in ob ob mice. In contrast, G i α-2 and G o α were increased over lean-control levels in brain tissue from ob ob mice, whereas G s α was unchanged. G protein expression in the testes did not differ between lean and ob ob mice. In the diet-induced model of NIDDM, G s α expression in the liver was twofold greater in obese/diabetic mice as compared with lean controls. However, G protein expression in all other tissues examined did not differ between obese/diabetic animals and lean littermates. Although the severity of overt symptoms of NIDDM is comparable between the two models, the diet-induced model does not suffer from the documented endocrine abnormalities of hypothyroidism and hyperadrenocorticism noted in the ob ob mouse. Thus, it seems likely that the G protein changes noted in the ob ob mouse are not the direct result of the obese or diabetic condition, but may be secondary to endocrine differences between the two models.

To gain insight into the signal transduction pathways utilized by the Wnt-1-responsive mammary epithelial cell line C57MG, we screened for non-src family member tyrosine kinases expressed in these cells using a polymerase chain reaction-based technique. We identified five cDNA clones encoding receptor tyrosine kinases for which the ligand is known (fibroblast growth factor receptor, platelet-derived growth factor receptor, epithelial growth factor receptor, insulin receptor, and insulin-like growth factor receptor), two putative receptor tyrosine kinases for which the ligand remains to be identified (the products of ryk and the mouse klg homolog), and a novel tyrosine kinase. We cloned cDNAs encoding both the murine and human homologs of this kinase, the sequences of which were subsequently published under the names sky (Ohashi, K., Mizuno, K., Kuma, K., Miyata, T., and Nakamura, T. (1994) Oncogene 9, 699-705) and rse (Mark, M. R., Scadden, D. T., Wang, Z., Gu, Q., Goddard, A., and Godowski, P. J. (1994) J. Biol. Chem. 269, 10720-10728). Mouse sky RNA levels are abundant in mammary tumors derived from transgenic mice that express wnt-1, fgf-3, or both oncogenes in their mammary glands. However, little or no expression of sky is detected in mammary glands from virgin animals or in preneoplastic mammary glands from wnt-1 transgenic mice. Moreover, we find that the human homolog of sky is expressed at elevated levels when normal human mammary epithelial cells are rendered tumorigenic by the introduction of two viral oncogenes. Transient transfection of the human SKY cDNA into the quail fibrosarcoma cell line QT6 reveals that SKY is an active tyrosine kinase that augments the level of cellular phosphotyrosine. Introduction of murine Sky into RatB1a fibroblasts by retrovirus-mediated gene transfer results in morphological transformation, growth in soft agar, and the formation of tumors in nude mice. These data raise the possibility that the Sky tyrosine kinase is involved in the development and/or progression of mammary tumors.

Background/Aims: Fat feeding increases not only serum but also cerebrospinal fluid concentration of apolipoprotein (apo) A-IV, a protein produced mainly by the small intestine in the rat. We hypothesized that apo A-IV may have a central effect on gastric secretion. Methods: Gastric juice was collected by the pylorus ligation method. Rats underwent pylorus ligation and received intracistemal injection of apo A-IV under brief isoflurane anesthesia. Two hours after the injection, gastric juice was collected and gastric acid output determined. Results: Intracistemal injection of 0.5 μg apo A-IV had no effect on gastric secretion. However, gastric acid secretion was significantly inhibited by intracistemal injection of 1 ug apo A-IV. Furthermore, intracistemal administration of higher doses of apo A-IV (2.0 and 4.0 μg) resulted in greater inhibition of gastric acid secretion in a dose-dependent manner. On the contrary, 4 μg of apo A-I intracisternally injected failed to inhibit gastric acid secretion. Intraperitoneal administration of 15 μg of apo A-IV did not alter gastric secretion. Conclusions: These results suggest that apo A-IV may act in the brain to inhibit gastric acid secretion. Apo A-IV might be a central enterogastrone, which is a gastric inhibitor produced by the small intestine in response to fat feeding.

Gastrointestinal functions are precisely regulated by hormonal and neural negative feedback loops. In addition to the classic hormonal and vago-vagal reflex mechanisms, these studies indicate that there are direct actions of gut hormones on the dorsal vagal complex. The current data demonstrate that pancreatic polypeptide is released into the circulation by vagal-cholinergic dependent mechanisms. It travels to the brainstem in the circulation, transverses the blood-brain barrier through "leaky" regions of this barrier in the area postrema and nucleus of the tractus solitarius and binds to specific receptors in the dorsal vagal complex. By binding to these sites, pancreatic polypeptide can directly inhibit vagal input to the pancreas and other gastrointestinal organs. These observations provide an anatomic basis to explain why pancreatic polypeptide is a more potent inhibitor of the action of central stimulants of pancreatic secretion than it is of the response to peripheral secretagogues. They also establish a novel mechanism by which gut peptides can influence brain function directly.

A rise in intracellular calcium is the predominant signal that leads to the activation of the contractile machinery in gastrointestinal smooth muscle. The primary sources of activating calcium are illustrated in Fig. 2. Voltage- and peptide-mediated release of intracellular calcium contribute to activation of some gastrointestinal smooth muscles. However, the primary source of activating calcium appears to be an influx of calcium across the plasma membrane. The degree of modulation of electrical activity by peptides varies depending upon the region of the gastrointestinal tract studied. Second messenger systems are undoubtly involved in the transduction pathway for receptor-mediated changes in ion channel activity in gastrointestinal smooth muscle. However, in comparison to other excitable cell types, little is known about the coupling mechanisms whereby peptide-receptor binding alters ion channel activity in gastrointestinal smooth muscle. This represents one of the challenging areas to be studied in the field of gastrointestinal smooth muscle. One disease in which a better appreciation of the regulation of ion channel activity could lead to therapeutic benefit is irritable bowel syndrome. A coupling of smooth muscle electrical activity to hypermotility in irritable bowel syndrome has been reported. CCK increases the level of spike activity which triggers hypermotility [40]. It would follow that inhibition of calcium influx should reduce spiking and, therefore, hypermotility. In fact, the calcium channel blockers nifedipine and nicardipine have been shown to decrease colonic motility in irritable bowel syndrome patients [62-64]. As our understanding of gastrointestinal smooth muscle ion channels expands, development of a gastrointestinal selective calcium channel blocker may be possible. This class of agents would be effective in the treatment of irritable bowel syndrome and potentially other peptide-related spastic smooth muscle disorders.

We report here the identification on rat liver plasma membranes and microsomes of proteins that bind pancreatic polypeptide (PP) with high affinity and specificity (plasma membranes: KD = 4.6 nM, Bmax = 3.28 pmol/mg protein; microsomes: KD = 3.45 nM, Bmax = 18.7 pmol/mg protein). These binding proteins appeared coupled to a G-protein, since 0.1 mM guanosine 5'-O-(3-thiotriphosphate) decreased the affinity by half. When 125I-labeled PP-binding protein complexes covalently cross-linked with disuccinimido suberate were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, two radioactive bands with M(r) values of 52,000 and 38,000 were demonstrated. Both bands were inhibited by unlabeled PP with an IC50 of approximately 5 nM (but not by neuropeptide Y or peptide YY). After the cross-linked complexes were solubilized from liver microsomes with 0.2% Triton X-100 and gel-filtered, they did not interact with the lectins wheat germ agglutinin, Ulex europaeus agglutinin, Ricinus communis agglutinin, and soy bean agglutinin. That these binding proteins may not be glycosylated was further supported by the failure of either peptide N-glycosidase F and endo-beta-N-acetylglucosaminidase F to alter the size of the PP-binding protein complexes on gel electrophoresis. These PP-binding proteins may serve as receptors and mediate a hepatic effect of PP.

We have cloned the genes coding for the two subunits (HsdM and HsdS) of the type-I DNA methyltransferase (MTase), M· Eco R124, into the specially constructed expression vector, pJ119. These subunits have been synthesized together as an intact MTase. We have also cloned the individual subunit-encoding genes under the control of the T7 gene 10 promoter or the lac UV5 promoter. High levels of expression have been obtained in all cases. While HsdM was found to be soluble, HsdS was insoluble. However, in the presence of the co-produced HsdM subunit, HsdS was found in the soluble fraction as part of an active MTase. We have partially purified the cloned multi-subunit enzyme and shown that it is capable of DNA methylation both in vivo and in vitro.

The effects of substance P, cholecystokinin and neuropeptide Y were examined on rabbit distal colonic motility. All three agents produced increased contractile activity but the mechanisms responsible differed depending on the agent tested. In the intact animal, peptide effects were measured under basal conditions and following exposure to atropine, tetrodotoxin and the alpha-adrenergic antagonist phentolamine. Administration of all three peptides resulted in a stimulation of colonic motility. Phentolamine did not significantly effect substance P-, cholecystokinin- or neuropeptide Y-induced activity. By contrast, the in vivo activity induced by cholecystokinin and neuropeptide Y, but not substance P, was nearly eliminated by tetrodotoxin. Only the neuropeptide Y response was partially atropine sensitive. In isolated colonic strips, cholecystokinin-induced activity, but not that produced by neuropeptide Y or substance P, was blocked by tetrodotoxin. Atropine did not significantly inhibit any of the hormone-induced contractions.