High Degree Of Individual Variation Research Articles

Optimizing and Predicting Antidepressant Efficacy in Patients with Major Depressive Disorder Using Multi-Omics Analysis and the Opade AI Prediction Tools.

According to the World Health Organization (WHO), major depressive disorder (MDD) is the fourth leading cause of disability worldwide and the second most common disease after cardiovascular events. Approximately 280 million people live with MDD, with incidence varying by age and gender (female to male ratio of approximately 2:1). Although a variety of antidepressants are available for the different forms of MDD, there is still a high degree of individual variability in response and tolerability. Given the complexity and clinical heterogeneity of these disorders, a shift from "canonical treatment" to personalized medicine with improved patient stratification is needed. OPADE is a non-profit study that researches biomarkers in MDD to tailor personalized drug treatments, integrating genetics, epigenetics, microbiome, immune response, and clinical data for analysis. A total of 350 patients between 14 and 50 years will be recruited in 6 Countries (Italy, Colombia, Spain, The Netherlands, Turkey) for 24 months. Real-time electroencephalogram (EEG) and patient cognitive assessment will be correlated with biological sample analysis. A patient empowerment tool will be deployed to ensure patient commitment and to translate patient stories into data. The resulting data will be used to train the artificial intelligence/machine learning (AI/ML) predictive tool.

Sex differences and individual variability in the captive Jamaican fruit bat (Artibeus jamaicensis) intestinal microbiome and metabolome

The intestinal microbiome plays an important role in mammalian health, disease, and immune function. In light of this function, recent studies have aimed to characterize the microbiomes of various bat species, which are noteworthy for their roles as reservoir hosts for several viruses known to be highly pathogenic in other mammals. Despite ongoing bat microbiome research, its role in immune function and disease, especially the effects of changes in the microbiome on host health, remains nebulous. Here, we describe a novel methodology to investigate the intestinal microbiome of captive Jamaican fruit bats (Artibeus jamaicensis). We observed a high degree of individual variation in addition to sex- and cohort-linked differences. The intestinal microbiome was correlated with intestinal metabolite composition, possibly contributing to differences in immune status. This work provides a basis for future infection and field studies to examine in detail the role of the intestinal microbiome in antiviral immunity.

ВЛИЯНИЕ КРАТКОСРОЧНОЙ ИЗОЛЯЦИИ В ГЕРМООБЪЕКТЕ МАЛОГО ОБЪЕМА НА СУБКЛИНИЧЕСКУЮ РЕАКТИВАЦИЮ ЛАТЕНТНЫХ ПАТОГЕНОВ ЧЕЛОВЕКА ВИРУСНОЙ И БАКТЕРИАЛЬНОЙ ПРИРОДЫ

The paper presents data of the investigations of subclinical reactivation of 7 human herpes viruses and bacteria Mycoplasmahominis, Ureaplasmaurealiticum and Chlamydiatrachomatis from 6 participants in a 14-day isolation study conducted in a small chamber with controlled environment. Purpose of analysis was to establish correlations between DNAs of latent viral and bacterial pathogens in bio-liquids of organism and indices of the natural and adaptive immune system. It was determined that short-term isolation in a small chamber may provoke reactivation of latent pathogens both of the viral and bacterial nature. The events can be triggered by changes in the immune status and appear in consequence of depressed immunological control of latent infections. Dynamics of the latent infections lytic cycle in the course of the study demonstrated a high degree of individual variability.

Individual variation within wild populations of an arid-zone lizard dictates oxidative stress levels despite exposure to sublethal pesticides

The relationship between sublethal pesticide exposure and oxidative stress in an ecologically relevant field setting is relatively unknown for reptiles. Oxidative stress is a multi-faceted concept that dictates key survival and fitness parameters in any organism. Fipronil and fenitrothion are two pesticides widely used globally for agricultural pest management. Using a field-based, BACI designed experiment we investigated the impact of sublethal pesticide exposure on oxidative stress biomarkers protein carbonyl and DNA damage (8-OHdG), in an arid-zone lizard species, Pogona vitticeps. A single ecologically relevant dose of pesticide was applied via oral gavage to treatment animals. Lizard condition, activity measures, and blood biomarkers were measured at relevant sampling intervals. Cholinesterase (ChE) and acetylcholinesterase (AChE) enzymatic biomarkers were measured in response to fenitrothion, and fipronil blood residues were measured for fipronil-treated lizards. Results suggested no significant treatment effect of either pesticide on parameters measured, however, 8-OHdG levels decreased by ≥ 45% for both pesticide treatment groups and not controls. Protein carbonyl levels showed a high degree of individual variation that proved more influential than pesticide exposure. Building our understanding of the macromolecular impacts of sublethal pesticide exposure on wild lizard populations is an integral step in addressing the current gap in literature and management practices. Our study has also highlighted the complex nature of studying oxidative stress in the field and the sheer necessity of future study.

Time-dependent memory and individual variation in Arctic brown bears (Ursus arctos)

BackgroundAnimal movement modelling provides unique insight about how animals perceive their landscape and how this perception may influence space use. When coupled with data describing an animal’s environment, ecologists can fit statistical models to location data to describe how spatial memory informs movement.MethodsWe performed such an analysis on a population of brown bears (Ursus arctos) in the Canadian Arctic using a model incorporating time-dependent spatial memory patterns. Brown bear populations in the Arctic lie on the periphery of the species’ range, and as a result endure harsh environmental conditions. In this kind of environment, effective use of memory to inform movement strategies could spell the difference between survival and mortality.ResultsThe model we fit tests four alternate hypotheses (some incorporating memory; some not) against each other, and we found a high degree of individual variation in how brown bears used memory. We found that 71% (15 of 21) of the bears used complex, time-dependent spatial memory to inform their movement decisions.ConclusionsThese results, coupled with existing knowledge on individual variation in the population, highlight the diversity of foraging strategies for Arctic brown bears while also displaying the inference that can be drawn from this innovative movement model.

Comparing the Respiratory Compensation Point With Muscle Oxygen Saturation in Locomotor and Non-locomotor Muscles Using Wearable NIRS Spectroscopy During Whole-Body Exercise

The relationship between the muscle deoxygenation breakpoint (Deoxy-BP) measured with near-infrared spectroscopy (NIRS), and the respiratory compensation point (RCP) has been well established. This relationship has also been reported using wearable NIRS, however not in locomotor and non-locomotor muscles simultaneously during whole-body cycling exercise. Our aim was to measure muscle oxygen saturation (SmO2) using wearable NIRS sensors, and to compare the Deoxy-BPs at each muscle with RCP during a ramp cycling exercise test. Twenty-two trained female and male cyclists completed a ramp exercise test to task intolerance on a cycling ergometer, at a ramp rate of 1 W every 2 s (30 W/min). SmO2 was recorded at the subjects’ right vastus lateralis (VL) and right lateral deltoid. SmO2 and the Deoxy-BPs were assessed using a piecewise double-linear regression model. Ventilation (V̇E) and gas exchange were recorded, and RCP was determined from V̇E and gas exchange using a V-slope method and confirmed by two physiologists. The SmO2 profiles of both muscles and gas exchange responses are reported as V̇O2, power output (W), and time of occurrence (TO). SmO2 profiles at both muscles displayed a near-plateau or breakpoint response near the RCP. No differences were detected between the mean RCP and mean Deoxy-BP from either the locomotor or non-locomotor muscles; however, a high degree of individual variability was observed in the timing and order of occurrence of the specific breakpoints. These findings add insight into the relationships between ventilatory, locomotor, and non-locomotor muscle physiological breakpoints. While identifying a similar relationship between these breakpoints, individual variability was high; hence, caution is advised when using wearable NIRS to estimate RCP in an incremental ramp test.

Associations Between Dysmenorrhea Symptom-Based Phenotypes and Vaginal Microbiome: A Pilot Study.

Dysmenorrhea is highly prevalent; it places women at risk for other chronic pain conditions. There is a high degree of individual variability in menstrual pain severity, the number of painful sites, and co-occurring gastrointestinal symptoms. Distinct dysmenorrhea symptom-based phenotypes were previously identified, but the biological underpinnings of these phenotypes are less known. One underexplored contributor is the vaginal microbiome. The vaginal microbiota differs significantly among reproductive-age women and may modulate as well as amplify reproductive tract inflammation, which may contribute to dysmenorrhea symptoms. The objective of this study was to examine associations between dysmenorrhea symptom-based phenotypes and vaginal microbiome compositions on- and off-menses. We conducted a prospective, longitudinal, pilot study of 20 women (aged 15-24 years) grouped into three dysmenorrhea symptom-based phenotypes: "mild localized pain," "severe localized pain," and "severe multiple pain and gastrointestinal symptoms." Over one menstrual cycle, participants provided vaginal swabs when they were on- and off-menses. We assayed the vaginal microbiome using 16S rRNA gene sequencing. Permutational multivariate analysis of variance tests were used to compare microbiome compositions across phenotypes, with heat maps generated to visualize the relative abundance of bacterial taxa. The vaginal microbiome compositions (n = 40) were different across the three phenotypes. After separating the on-menses (n = 20) and off-menses (n = 20) specimens, the statistically significant difference was seen on-menses, but not off-menses. Compared to the "mild localized pain" phenotype, participants in the "multiple severe symptoms" phenotype had a lower lactobacilli level and a higher abundance of Prevotella, Atopobium, and Gardnerella when on-menses. We also observed trends of differences across phenotypes in vaginal microbiome change from off- to on-menses. The study provides proof-of-concept data to support larger studies on associations between dysmenorrhea symptom-based phenotypes and vaginal microbiome that might lead to new intervention targets and/or biomarkers for dysmenorrhea. This line of research has the potential to inform precision dysmenorrhea treatment that can improve women's quality of life.

Harm Avoidance and Mobility During Middle Childhood and Adolescence among Hadza Foragers

Cross-cultural sex differences in mobility and harm avoidance have been widely reported, often emphasizing fitness benefits of long-distance travel for males and high costs for females. Data emerging from adults in small-scale societies, however, are challenging the assumption that female mobility is restricted during reproduction. Such findings warrant further exploration of the ontogeny of mobility. Here, using a combination of machine-learning, mixed-effects linear regression, and GIS mapping, we analyze range size, daily distance traveled, and harm avoidance among Hadza foragers during middle childhood and adolescence. Distance traveled increased with age and, while male adolescents had the longest daily ranges, average daily distance traveled by each sex was similar. We found few age- or sex-related patterns in harm-avoidant responses and a high degree of individual variation. When queried on the same issues, children and their parents were often in alignment as to expectations pertaining to harm avoidance, and siblings tended to behave in similar ways. To the extent that sex differences in mobility did emerge, they were associated with ecological differences in physical threats associated with sex-specific foraging behaviors. Further, we found no strong association between harm avoidance and mobility. Young Hadza foragers of both sexes are highly mobile, regardless of how harm avoidant they are. Taken together, our findings indicate that the causal arrows between harm avoidance and mobility must be evaluated in ecologically specific frameworks where cultural expectations of juvenile mobility can be contextualized.

A longitudinal study of symptom botheration in Multiple Sclerosis.

BackgroundIt is well documented that ambulatory disability in MS worsens over time, but there is a dearth of information on symptom evolution in other domains commonly affected by MS. MethodsSymptoMScreen (SyMS) is a validated tool for assessing symptom severity in 12 domains commonly affected by MS. Patients who attended two specialized MS centers filled out SyMS at each visit. We included in the study patients with neurologist-diagnosed MS who completed two SyMS questionnaires separated at least 12 months. We used the first and final assessment and adjusted for time on study, baseline SyMS score, age, sex, race, MS type, disability strata, and site. Changes over time were also examined using Markov chain estimates of moving from one level of botheration to another for each domain over 1-year periods. ResultsA total of 1,014 MS patients met the inclusion criteria. Mean composite SyMS score was 1.4 (±1.16) at baseline and increased by 0.084 (±0.73) points during 21.0 (±5.5) months of followup (p<0.0001). The initial mean composite SyMS score correlated strongly with the final mean composite SyMS score (r=0.81). Individual domain SyMS scores at baseline were highest for fatigue: 2.2 (±1.7), and lowest for vision: 1.1 (±1.3) and dexterity: 1.1 (±1.4). Small but significant increases during followup were seen in dexterity, bladder, vision, and pain domains, while significant decreases were seen in anxiety and sensory domains. We observed a high degree of inter-individual variability in symptom severity with the more extreme scores tending to resolve over time. ConclusionsSymptom botheration increases modestly year-to-year, as would be expected in a slowly progressive disease that evolves over decades. Initial symptom burden strongly correlated with final symptom burden, but there was a high degree of individual variability in symptom severity.

Modelling generalisation gradients as augmented Gaussian functions.

Studying generalisation of associative learning requires analysis of response gradients measured over a continuous stimulus dimension. In human studies, there is often a high degree of individual variation in the gradients, making it difficult to draw conclusions about group-level trends with traditional statistical methods. Here, we demonstrate a novel method of analysing generalisation gradients based on hierarchical Bayesian curve-fitting. This method involves fitting an augmented (asymmetrical) Gaussian function to individual gradients and estimating its parameters in a hierarchical Bayesian framework. We show how the posteriors can be used to characterise group differences in generalisation and how classic generalisation phenomena such as peak shift and area shift can be measured and inferred. Estimation of descriptive parameters can provide a detailed and informative way of analysing human generalisation gradients.

Metabolomic Response of Equine Skeletal Muscle to Acute Fatiguing Exercise and Training.

The athletic horse, despite being over 50% muscle mass, remains understudied with regard to the effects of exercise and training on skeletal muscle metabolism. To begin to address this knowledge gap, we employed an untargeted metabolomics approach to characterize the exercise-induced and fitness-related changes in the skeletal muscle of eight unconditioned Standardbred horses (four male, four female) before and after a 12-week training period. Before training, unconditioned horses showed a high degree of individual variation in the skeletal muscle metabolome, resulting in very few differences basally and at 3 and 24 h after acute fatiguing exercise. Training did not alter body composition but did improve maximal aerobic and running capacities (p < 0.05), and significantly altered the skeletal muscle metabolome (p < 0.05, q < 0.1). While sex independently influenced body composition and distance run following training (p < 0.05), sex did not affect the skeletal muscle metabolome. Exercise-induced metabolomic alterations (p < 0.05, q < 0.1) largely centered on the branched-chain amino acids (BCAA), xenobiotics, and a variety of lipid and nucleotide-related metabolites, particularly in the conditioned state. Further, training increased (p < 0.05, q < 0.1) the relative abundance of almost every identified lipid species, and this was accompanied by increased plasma BCAAs (p < 0.0005), phenylalanine (p = 0.01), and tyrosine (p < 0.02). Acute exercise in the conditioned state decreased (p < 0.05, q < 0.1) the relative abundance of almost all lipid-related species in skeletal muscle by 24 h post-exercise, whereas plasma amino acids remained unaltered. These changes occurred alongside increased muscle gene expression (p < 0.05) related to lipid uptake (Cd36) and lipid (Cpt1b) and BCAA (Bckdk) utilization. This work suggests that metabolites related to amino acid, lipid, nucleotide and xenobiotic metabolism play pivotal roles in the response of equine skeletal muscle to vigorous exercise and training. Use of these and future data sets could be used to track the impact of training and fitness on equine health and may lead to novel predictors and/or diagnostic biomarkers.

176 Characterizing the mycobiome in piglets during the weaning transition

Abstract The importance of the microbiota in the gastrointestinal (GI) tract of animals is recognized as a critical player in host health. Recently, the significance of the mycobiome has been recognized, but culture-independent studies are limited, especially in swine. Weaning is a time of stress, dietary changes, and a predisposition to infections, making it a time of interest to industry. In this study, we sought to assess and characterize the mycobiome and microbiome in the feces and GI tract of swine from birth through the critical weaning transition (days 1–35 post-birth). In addition, we investigated environmental factors that may alter microorganisms present in piglets. Fecal bacterial populations increased in diversity over the experimental timeline and demonstrated a transition from an Enterobacteriaceae-dominated population, to a Prevotellaceae and Ruminococcaceae-dominated population by days 24–35 post-birth. These later populations are capable of fiber degradation and short chain fatty acid production. In fecal fungal populations, richness and diversity peaked at weaning and declined post-weaning. There was also a dynamic shift in the mycobiome to a Saccharomycetaceae-dominated population that remained stable into adulthood. Fungal organisms contributing to this colonization were not found in environmental samples including water, colostrum, and feed. Despite fungal populations present in the feces of sows, these maternal fungi were not similar to the piglet mycobiome and thus did not indicate a maternally-derived effect. Furthermore, the microbiomes of the GI tract showed decreased richness and diversity in the upper GI compared to the lower GI, and a high degree of individual variation and litter effect throughout the organs. This study provides insights into the early colonization and establishment of fungi during the weaning transition. Future studies will investigate the effect of the mycobiome on piglet growth and health during the weaning transition, including their role in fast- versus slow-growing piglets.

Control Stimuli in Experimental Code-Switching Research

The current study investigates whether there is variation among different types of control stimuli in code-switching (CS) research, how such stimuli can be used to accommodate heterogeneity, and how they can also be used as a baseline comparison of acceptability. A group of native Spanish–English bilinguals (n = 20) completed a written acceptability judgment task with a 7-point Likert scale. Five different types of control stimuli were included, with three types considered to be completely acceptable (complex-sentence switches, direct-object switches, and subject–predicate switches) and two types considered to be completely unacceptable (pronoun switches and present–perfect switches). Additionally, a set of present–progressive switches were included as a comparison, as their acceptability status is still actively debated. The participants as a whole exhibited the expected grammatical distinctions among the control stimuli, but with a high degree of individual variability. Pronoun switches and auxiliary verb switches were rated significantly lower than the complex-sentence switches, direct-object switches, and subject–predicate switches. These results show that control stimuli can also establish a baseline comparison of acceptability, and recommendations for inclusion in experimental CS research are provided.

Seasonal depth and temperature use, and diel movements of lake trout (Salvelinus namaycush) in a subarctic lake

We conducted a multi-year acoustic telemetry study of lake trout (Salvelinus namaycush (Walbaum, 1792)) in a small subarctic lake to investigate depth and temperature occupancy, and vertical activity across seasons (summer, fall, and winter), diel periods (day, twilight, and night), and during summer periods of 24 h light (day and twilight). Analyses using generalized additive mixed models revealed a high degree of individual variation in depth occupancy independent of the factors hour of day, season, and diel period, whereas temperature occupancy and vertical activity were explained using the three combined factors. Habitats occupied were typically 9–20 m and 6–9.5 °C in summer, 1–3 m and 2–15 °C in fall during presumed spawning, and ≤6 m and &lt;3 °C in winter. Lake trout exhibited partial diel migration where individuals displayed a variety of vertical migratory directions within and among seasons or diel period, including during periods of 24 h light. Fish were most vertically active during periods of daylight and in fall. During 24 h light, some lake trout performed crepuscular movements, whereas individual behaviour best explained modelled depth and temperature occupancy and vertical activity. The variety of vertical patterns among individuals and seasons suggests multifactor proximate causes of partial diel migration and crepuscular movements.

Cyclic outbreaks of forest insects: A two-dimensional individual-based model

An individual-based model is presented which shows that cyclic insects outbreaks in the forest (here presented as a certain type of the dynamics of total numbers of insects in the forest) can be a result of the joint action of four factors: (1) spatial structure of the system — resources, green tree biomass, used by larval insects are distributed in a two-dimensional space, (2) properties of trees — their limited resistance to feeding by insects, and regeneration ability after some time of relaxation, when they cannot sustain a local insect population, (3) insect properties — the most important of which is the ability of adult individuals to move between spatially distributed resources and to lay eggs on neighbouring trees, and (4) the type of dynamics of local insect population exploiting resources of a tree, which depends on individual variability of insects and their progeny production. Insects disperse from the original tree and occupy successive not infested trees over the forest, omitting the trees with exploited resources that need time for regeneration. The cyclic outbreak dynamics will take place when insects have opportunity to return to the places where there are trees with regenerated resources. In addition to the cyclic outbreak, we will observe permanent outbreaks (small fluctuations of insect, combined with a similar dynamics of tree biomass) or pulse outbreaks (an increase in the number of insects, followed by their extinction and leading to a temporary destruction of tree biomass). The type of the simulation output will depend on the values of the model parameters. Intermediate resistance of trees to insect feeding and their not very short regeneration time will lead to cyclic outbreaks. Additionally great number of dispersing insects will promote cyclic outbreaks. High degree of individual variability, high mortality of adult insects or small progeny production will produce favourable conditions for permanent outbreaks. Pulse outbreaks can easily occur when insect individual variability is small or progeny production is high.

Individual differences reveal limited mixed-category effects during a visual working memory task

Using stimuli from different categories may expand the capacity limits of working memory (WM) by spreading item representations across distinct neural populations. We explored this mixed-category benefit by correlating individuals’ behavioral performance with fMRI measures of category information during uniform- and mixed-category trials. Behaviorally, we found weak evidence for a mixed-category benefit at the group-level, although there was a high degree of individual variability. To test whether distinct neural patterns elicited superior performance in some individuals, we correlated a multivariate measure of neural category information with multiple behavioral metrics. This revealed a widespread positive relationship, intuitive for hit rate and working memory capacity, but counterintuitive for false alarm rate. Overall, these data suggest that mixed-category effects may support working memory performance, but unexpectedly, not all participants show this benefit. Only some people may be able to take advantage of representing mixed-category information in a differentiable way.

Time-varying predatory behavior is primary predictor of fine-scale movement of wildland-urban cougars

BackgroundWhile many species have suffered from the detrimental impacts of increasing human population growth, some species, such as cougars (Puma concolor), have been observed using human-modified landscapes. However, human-modified habitat can be a source of both increased risk and increased food availability, particularly for large carnivores. Assessing preferential use of the landscape is important for managing wildlife and can be particularly useful in transitional habitats, such as at the wildland-urban interface. Preferential use is often evaluated using resource selection functions (RSFs), which are focused on quantifying habitat preference using either a temporally static framework or researcher-defined temporal delineations. Many applications of RSFs do not incorporate time-varying landscape availability or temporally-varying behavior, which may mask conflict and avoidance behavior.MethodsContemporary approaches to incorporate landscape availability into the assessment of habitat selection include spatio-temporal point process models, step selection functions, and continuous-time Markov chain (CTMC) models; in contrast with the other methods, the CTMC model allows for explicit inference on animal movement in continuous-time. We used a hierarchical version of the CTMC framework to model speed and directionality of fine-scale movement by a population of cougars inhabiting the Front Range of Colorado, U.S.A., an area exhibiting rapid population growth and increased recreational use, as a function of individual variation and time-varying responses to landscape covariates.ResultsWe found evidence for individual- and daily temporal-variability in cougar response to landscape characteristics. Distance to nearest kill site emerged as the most important driver of movement at a population-level. We also detected seasonal differences in average response to elevation, heat loading, and distance to roads. Motility was also a function of amount of development, with cougars moving faster in developed areas than in undeveloped areas.ConclusionsThe time-varying framework allowed us to detect temporal variability that would be masked in a generalized linear model, and improved the within-sample predictive ability of the model. The high degree of individual variation suggests that, if agencies want to minimize human-wildlife conflict management options should be varied and flexible. However, due to the effect of recursive behavior on cougar movement, likely related to the location and timing of potential kill-sites, kill-site identification tools may be useful for identifying areas of potential conflict.

Development of Thermoregulatory Capability in Weddell Seal Pups

One of the greatest metabolic costs for endotherms is the energy allocated to thermoregulation. Weddell seals (Leptonychotes weddellii) are the southernmost breeding mammals, and as such are born into one of the most challenging thermal environments on the planet. During their nursing period, Weddell seal pups must develop the capability to survive both on the ice and in the water. Pups also concurrently shift from the use of fur to a reliance on blubber for insulation. This study examined the thermal and energetic costs associated with development and thermoregulation in Weddell seal pups. Metabolic rate (MR) in air was measured longitudinally for 4 pups every 2 weeks, starting at 1 week of age through the transition to independence (7 weeks); MR in water was measured in the same pups beginning at 3 weeks. Additionally, we assessed the molt status of each pup, and estimated body composition (blubber vs. lean mass) based on an elliptical cones model. There was a high degree of individual variability in mass‐specific MR in air in 1 week old pups (5.96–10.87 ml O2 min−1 kg−1), though in general it remained stable or decreased slightly from 1–7 weeks of age. Mass‐specific MR in water declined from 3 weeks to 7 weeks of age for 2 of the 4 pups, and remained stable for 2 pups. The difference between mass‐specific MR in air and in water also decreased from 3 to 7 weeks for 2 pups and remained steady for 2 pups; but by 5 weeks of age the difference between MR in air and in water was marginal for all 4 pups. Timing of the initiation of the molt and molt duration was also variable; two pups had molted patches by 3 weeks of age, and all but 1 pup were fully molted by 7 weeks of age. All pups gained mass from 1 to 5 weeks of age at an average rate of 2.02 ± 0.09 kg day−1 and the proportion of blubber increased from 1–3 weeks (25% to 38% of body mass). Blubber proportion remained steady from 3–5 weeks (38% to 40% of body mass) because pups gained proportionally more lean mass (61% of total mass gained). By 7 weeks, 3 of the 4 pups had weaned and were losing mass. Timing of MR equivalence in air and water did not vary with molt status (amount of lanugo) or with estimated body composition. Overall, these results indicate that Weddell seal pups have developed their thermal capabilities by ~5 weeks of age to protect themselves against increased heat loss in water, independent of the amount of lanugo fur or body composition.Support or Funding InformationThis project was funded by the National Science Foundation, Office of Polar Programs (#1543539).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Modelling the factors influencing ontogenetic dietary shifts in stream-dwelling brown trout (Salmo trutta)

Biotic and abiotic variables shape ontogenetic trajectories of animals. This study modelled (i) the body length related timing of the ontogenetic switch from aquatic to surface prey and (ii) the impacts of habitat characteristics, prey availability, and fish densities on the relative contribution of surface prey to the overall diet of native brown trout (Salmo trutta). We used individual-based models of dietary data for 170 fish (length range 48–343 mm). There was a high degree of individual variation in the use of surface prey, but logistic regression suggested that the shift from aquatic to surface prey was established at a body length of 81 mm (range 36–127 mm). Results of linear mixed-effects models highlighted the importance of fish length, benthic invertebrates, brown trout density, and water current velocity to the switch to surface prey by riverine brown trout, with fish length being the most influential variable. Our study provides evidence of the importance of ontogeny (intrinsic features of individuals linked to fish length) and individual differences in feeding behaviour to understand water-column use for feeding by stream-dwelling salmonids.

Measles, mumps, and rubella antibody patterns of persistence and rate of decline following the second dose of the MMR vaccine

BackgroundAntibodies to measles, mumps, and rubella decline 3% per year on average, and have a high degree of individual variation. Yet, individual variations and differences across antigens are not well understood. To better understand potential implications on individual and population susceptibility, we reanalyzed longitudinal data to identify patterns of seropositivity and persistence. MethodsChildren vaccinated with the second dose of measles, mumps, rubella vaccine (MMR2) at 4–6 years of age were followed up to 12 years post-vaccination. The rates of antibody decline were assessed using regression models, accounting for differences between and within subjects. ResultsMost of the 302 participants were seropositive throughout follow-up (96% measles, 88% mumps, 79% rubella). The rate of antibody decline was associated with MMR2 response and baseline titer for measles and age at first dose of MMR (MMR1) for rubella. No demographic or clinical factors were associated with mumps rate of decline. One month post-MMR2, geometric mean titer (GMT) to measles was high (3892 mIU/mL), but declined on average 9.7% per year among those with the same baseline titer and <2-fold increase post-MMR2. Subjects with ≥2-fold experienced a slower decline (≤7.4%). GMT to rubella was 149 one month post-MMR2, declining 2.6% and 5.9% per year among those who received MMR1 at 12–15 months and >15 months, respectively. GMT to mumps one month post-MMR2 was 151, declining 9.2% per year. Only 14% of subjects had the same persistence trends for all antigens. ConclusionsThe rate of antibody decay varied substantially among individuals and the 3 antigen groups. A fast rate of decline coupled with high variation was observed for mumps, yet no predictors were identified. Future research should focus on better understanding waning titers to mumps and its impacts on community protection and individual susceptibility, in light of recent outbreaks in vaccinated populations.