Additive genetic and environmental variation interact to shape the dynamics of seasonal migration in a wild bird population

Dissecting joint micro-evolutionary and plastic responses to environmental perturbations requires quantifying interacting components of genetic and environmental variation underlying expression of key traits. This ambition is particularly challenging for phenotypically discrete traits where multiscale decompositions are required to reveal nonlinear transformations of underlying genetic and environmental variation into phenotypic variation, and when effects must be estimated from incomplete field observations. We devised a joint multistate capture-recapture and quantitative genetic animal model, and fitted this model to full-annual-cycle resighting data from partially-migratory European shags (${Gulosus~{}aristotelis}$) to estimate key components of genetic, environmental and phenotypic variance in the ecologically critical discrete trait of seasonal migration versus residence. We demonstrate non-negligible additive genetic variance in latent liability for migration, resulting in detectable micro-evolutionary responses following two episodes of strong survival selection. Further, liability-scale additive genetic effects interacted with substantial permanent individual and temporary environmental effects to generate complex nonadditive effects on expressed phenotypes, causing substantial intrinsic gene-by-environment interaction variance on the phenotypic scale. Our analyses therefore reveal how temporal dynamics of partial seasonal migration arise from combinations of instantaneous micro-evolution and within-individual phenotypic consistency, and highlight how intrinsic phenotypic plasticity could expose genetic variation underlying discrete traits to complex forms of selection.

Consequences of cross-season demographic correlations for population viability

Demographic correlations are pervasive in wildlife populations and can represent important secondary drivers of population growth. Empirical evidence suggests that correlations are in general positive for long-lived species, but little is known about the degree of variation among spatially segregated populations of the same species in relation to environmental conditions. We assessed the relative importance of two cross-season correlations in survival and productivity, for three Atlantic puffin (Fratercula arctica) populations with contrasting population trajectories and non-overlapping year-round distributions. The two correlations reflected either a relationship between adult survival prior to breeding on productivity, or a relationship between productivity and adult survival the subsequent year. Demographic rates and their correlations were estimated with an integrated population model, and their respective contributions to variation in population growth were calculated using a transient-life table response experiment. For all three populations, demographic correlations were positive at both time lags, although their strength differed. Given the different year-round distributions of these populations, this variation in the strength population-level demographic correlations points to environmental conditions as an important driver of demographic variation through life-history constraints. Consequently, the contributions of variances and correlations in demographic rates to population growth rates differed among puffin populations, which has implications for-particularly small-populations' viability under environmental change as positive correlations tend to reduce the stochastic population growth rate.

Quantifying the impacts of predation by Great Black-backed Gulls Larus marinus on an Atlantic Puffin Fratercula arctica population: Implications for conservation management and impact assessments

The management of predator-prey conflicts can be a key aspect of species conservation. For management approaches to be effective, a robust understanding of the predator-prey relationship is needed, particularly when both predator and prey are species of conservation concern. On the Isle of May, Firth of Forth, Scotland, numbers of breeding Great Black-backed Gulls Larus marinus, a generalist predator, have been increasing since the 1980s, which has led to increasing numbers of sympatrically breeding Atlantic Puffins Fratercula arctica being predated during the breeding season. This may have consequences for species management on the Isle of May and impact assessments of offshore windfarms in the wider Firth of Forth area. We used population viability analysis to quantify under what predation pressure the Atlantic Puffin population may decline and become locally extinct over a three-generation period. The predation level empirically estimated in 2017 (1120 Puffins per year) was not sufficient to drive a decline in the Puffin population. Rather, an increase to approximately 3000 Puffins per year would be required to cause a population decline, and >4000 to drive the population to quasi-extinction within 66 years. We discuss the likelihood of such a scenario being reached on the Isle of May, and we recommend that where predator-prey conflicts occur, predation-driven mortality should be regularly quantified to inform conservation management and population viability analyses associated with impact assessments.

Increased parental effort fails to buffer the cascading effects of warmer seas on common guillemot demographic rates

Climate warming can reduce food resources for animal populations. In species exhibiting parental care, parental effort is a 'barometer' of changes in environmental conditions. A key issue is the extent to which variation in parental effort can buffer demographic rates against environmental change. Seabirds breed in large, dense colonies and globally are major predators of small fish that are often sensitive to ocean warming. We explored the causes and consequences of annual variation in parental effort as indicated by standardised checks of the proportions of chicks attended by both, one or neither parent, in a population of common guillemots Uria aalge over four decades during which there was marked variation in marine climate and chick diet. We predicted that, for parental effort to be an effective buffer, there would be a link between environmental conditions and parental effort, but not between parental effort and demographic rates. Environmental conditions influenced multiple aspects of the prey delivered by parents to their chicks with prey species, length and energy density all influenced by spring sea surface temperature (sSST) in the current and/or previous year. Overall, the mean annual daily energy intake of chicks declined significantly when sSST in the current year was higher. In accordance with our first prediction, we found that parental effort increased with sSST in the current and previous year. However, the increase was insufficient to maintain chick daily energy intake. In contrast to our second prediction, we found that increased parental effort had major demographic consequences such that growth rate and fledging success of chicks, and body mass and overwinter survival of breeding adults all decreased significantly. Common guillemot parents were unable to compensate effectively for temperature-mediated variation in feeding conditions through behavioural flexibility, resulting in immediate consequences for breeding population size because of lower adult survival and potentially longer-term impacts on recruitment because of lower productivity. These findings highlight that a critical issue for species' responses to future climate change will be the extent to which behavioural buffering can offer resilience to deteriorating environmental conditions.

Hierarchical Variation in Phenotypic Flexibility across Timescales and Associated Survival Selection Shape the Dynamics of Partial Seasonal Migration

AbstractPopulation responses to environmental variation ultimately depend on within-individual and among-individual variation in labile phenotypic traits that affect fitness and resulting episodes of selection. Yet complex patterns of individual phenotypic variation arising within and between time periods, as well as associated variation in selection, have not been fully conceptualized or quantified. We highlight how structured patterns of phenotypic variation in dichotomous threshold traits can theoretically arise and experience varying forms of selection, shaping overall phenotypic dynamics. We then fit novel multistate models to 10 years of band-resighting data from European shags to quantify phenotypic variation and selection in a key threshold trait underlying spatioseasonal population dynamics: seasonal migration versus residence. First, we demonstrate substantial among-individual variation alongside substantial between-year individual repeatability in within-year phenotypic variation ("flexibility"), with weak sexual dimorphism. Second, we demonstrate that between-year individual variation in within-year phenotypes ("supraflexibility") is structured and directional, consistent with the threshold trait model. Third, we demonstrate strong survival selection on within-year phenotypes-and hence on flexibility-that varies across years and sexes, including episodes of disruptive selection representing costs of flexibility. By quantitatively combining these results, we show how supraflexibility and survival selection on migratory flexibility jointly shape population-wide phenotypic dynamics of seasonal movement.

Earlier and more frequent occupation of breeding sites during the non-breeding season increases breeding success in a colonial seabird

Competition for high‐quality breeding sites in colonial species is often intense, such that individuals may invest considerable time in site occupancy even outside the breeding season. The site defense hypothesis predicts that high‐quality sites will be occupied earlier and more frequently, consequently those sites will benefit from earlier and more successful breeding. However, few studies relate non‐breeding season occupancy to subsequent breeding performance limiting our understanding of the potential life‐history benefits of this behavior. Here, we test how site occupancy in the non‐breeding season related to site quality, breeding timing, and breeding success in a population of common guillemots Uria aalge, an abundant and well‐studied colonially breeding seabird. Using time‐lapse photography, we recorded occupancy at breeding sites from October to March over three consecutive non‐breeding seasons. We then monitored the successive breeding timing (lay date) and breeding success at each site. On average, sites were first occupied on the 27th October ± 11.7 days (mean ± SD), subsequently occupied on 46 ± 18% of survey days and for 55 ± 15% of the time when at least one site was occupied. Higher‐quality sites, sites with higher average historic breeding success, were occupied earlier, more frequently and for longer daily durations thereafter. Laying was earlier at sites that were occupied more frequently and sites occupied earlier were more successful, supporting the site defense hypothesis. A path analysis showed that the return date had a greater or equal effect on breeding success as lay date. Pair level occupancy had no effect on breeding timing or success. The clear effect of non‐breeding occupancy of breeding sites on breeding timing and success highlights the benefits of this behavior on demography in this population and the importance of access to breeding sites outside the breeding season in systems where competition for high‐quality sites is intense.

Site-dependent regulation of breeding success: evidence for the buffer effect in the common guillemot, a colonially-breeding seabird

Density-dependent regulation can offer resilience to wild populations experiencing fluctuations in environmental conditions because, at lower population sizes, the average quality of habitats or resources is predicted to increase. Site-dependent regulation is a mechanism whereby individuals breed at the highest quality, most successful, sites, leaving poorer quality, less successful sites vacant. As population size increases, higher quality sites become limiting but when populations decline, lower quality sites are vacated first, offering resilience. This process is known as the 'buffer effect'. However, few studies have tested whether such regulation operates in populations experiencing changes in size and trend. We used data from a population of common guillemots Uria aalge, a colonially breeding seabird, to investigate the relationship between site occupancy probability, site quality and population size and trend. These data were collected at five sub-colonies spanning a 38-year period (1981-2018) comprising phases of population increase, decrease and recovery. We first tested whether site quality and population size in sub-colonies explained which sites were occupied for breeding, and if this was robust to changes in sub-colony trend. We then investigated whether disproportionate use of higher quality sites drove average site quality and breeding success across sub-colony sizes and trends. Finally, we tested whether individuals consistently occupied higher quality sites during periods of decline and recovery. Higher quality sites were disproportionality used when sub-colony size was smaller, resulting in higher average site quality and breeding success at lower population sizes. This relationship was unaffected by changes in sub-colony trend. However, contrary to the predictions of the buffer effect, new sites were established at a similar rate to historically occupied sites during sub-colony decline and recovery despite being of lower quality. Our results provide support for the buffer effect conferring resilience to populations, such that average breeding success was consistently higher at lower population size during all phases of population change. However, this process was tempered by the continued establishment of new, lower quality, sites which could act to slow population recovery after periods when colony size was low.

Episodes of opposing survival and reproductive selection cause strong fluctuating selection on seasonal migration versus residence

Quantifying temporal variation in sex-specific selection on key ecologically relevant traits, and quantifying how such variation arises through synergistic or opposing components of survival and reproductive selection, is central to understanding eco-evolutionary dynamics, but rarely achieved. Seasonal migration versus residence is one key trait that directly shapes spatio-seasonal population dynamics in spatially and temporally varying environments, but temporal dynamics of sex-specific selection have not been fully quantified. We fitted multi-event capture-recapture models to year-round ring resightings and breeding success data from partially migratory European shags (Phalacrocorax aristotelis) to quantify temporal variation in annual sex-specific selection on seasonal migration versus residence arising through adult survival, reproduction and the combination of both (i.e. annual fitness). We demonstrate episodes of strong and strongly fluctuating selection through annual fitness that were broadly synchronized across females and males. These overall fluctuations arose because strong reproductive selection against migration in several years contrasted with strong survival selection against residence in years with extreme climatic events. These results indicate how substantial phenotypic and genetic variation in migration versus residence could be maintained, and highlight that biologically important fluctuations in selection may not be detected unless both survival selection and reproductive selection are appropriately quantified and combined.

No evidence for fitness signatures consistent with increasing trophic mismatch over 30 years in a population of European shag Phalacrocorax aristotelis

As temperatures rise, timing of reproduction is changing at different rates across trophic levels, potentially resulting in asynchrony between consumers and their resources. The match-mismatch hypothesis (MMH) suggests that trophic asynchrony will have negative impacts on average productivity of consumers. It is also thought to lead to selection on timing of breeding, as the most asynchronous individuals will show the greatest reductions in fitness. Using a 30-year individual-level dataset of breeding phenology and success from a population of European shags on the Isle of May, Scotland, we tested a series of predictions consistent with the hypothesis that fitness impacts of trophic asynchrony are increasing. These predictions quantified changes in average annual breeding success and strength of selection on timing of breeding, over time and in relation to rising sea surface temperature (SST) and diet composition. Annual average (population) breeding success was negatively correlated with average lay date yet showed no trend over time, or in relation to increasing SST or the proportion of principal prey in the diet, as would be expected if trophic mismatch was increasing. At the individual level, we found evidence for stabilising selection and directional selection for earlier breeding, although the earliest birds were not the most productive. However, selection for earlier laying did not strengthen over time, or in relation to SST or slope of the seasonal shift in diet from principal to secondary prey. We found that the optimum lay date advanced by almost 4 weeks during the study, and that the population mean lay date tracked this shift. Our results indicate that average performance correlates with absolute timing of breeding of the population, and there is selection for earlier laying at the individual level. However, we found no fitness signatures of a change in the impact of climate-induced trophic mismatch, and evidence that shags are tracking long-term shifts in optimum timing. This suggests that if asynchrony is present in this system, breeding success is not impacted. Our approach highlights the advantages of examining variation at both population and individual levels when assessing evidence for fitness impacts of trophic asynchrony.

Assessing Risk for Mortality in Trauma: The Value of Admission Hemoglobin A1c

BACKGROUND

Recent efforts have been made to identify admission characteristics of trauma patients that are associated with increased risk of mortality. Contemporary literature has established an increased risk of mortality with admission hyperglycemia. However, the effects of longstanding hyperglycemia, as surrogated by hemoglobin A1c (HbA1c), has not been studied.

METHODS

A prospective trauma database was retrospectively reviewed identifying patients with collected HbA1c at admission. Three cohorts were defined by HbA1c: normal (N), <5.7; prediabetic (PD) 5.7-6.5; and diabetic (D) >6.5. Regression models were used to evaluate the risk of increased hospital and intensive care unit (ICU) length of stay (LOS), ventilator days, and mortality. Relative risk (RR) and 95% CI are provided as measures of significance.

RESULTS

A total of 2978 patients were included in the analysis (N: n = 1895, PD: n = 744, and D: n = 339). The D cohort was more likely to be older, female, obese, suffered blunt trauma, and triaged at the highest activation acuity level (P < .0001). Mean injury severity score (ISS) was similar between groups. The D group was more likely to have longer ICU-LOS (RR 1.5; 95% CI 1.10-2.07) and ventilator days (RR 1.52; 95% CI 1.03-2.26) than the N group. Relative to the N group, the risk of mortality was 50% higher in the PD (RR 1.49; 95% CI 1.17-1.90) and in the D cohorts (RR 1.50; 95% CI 1.03-2.18).

DISCUSSION

Trauma patients with an elevated admission HbA1c have a significantly higher risk of mortality regardless of their history of diabetes. These data add to the body of literature that documents the untoward effect of hyperglycemia on the trauma patient.

Interactions between Environmental Contaminants and Gastrointestinal Parasites: Novel Insights from an Integrative Approach in a Marine Predator

Environmental contaminants and parasites are ubiquitous stressors that can affect animal physiology and derive from similar dietary sources (co-exposure). To unravel their interactions in wildlife, it is thus essential to quantify their concurring drivers. Here, the relationship between blood contaminant residues (11 trace elements and 17 perfluoroalkyl substances) and nonlethally quantified gastrointestinal parasite loads was tested while accounting for intrinsic (sex, age, and mass) and extrinsic factors (trophic ecology inferred from stable isotope analyses and biologging) in European shags Phalacrocorax aristotelis. Shags had high mercury (range 0.65-3.21 μg g^-1 wet weight, ww) and extremely high perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) residues (3.46-53 and 4.48-44 ng g^-1 ww, respectively). Males had higher concentrations of arsenic, mercury, PFOA, and PFNA than females, while the opposite was true for selenium, perfluorododecanoic acid (PFDoA), and perfluooctane sulfonic acid (PFOS). Individual parasite loads (Contracaecum rudolphii) were higher in males than in females. Females targeted pelagic-feeding prey, while males relied on both pelagic- and benthic-feeding organisms. Parasite loads were not related to trophic ecology in either sex, suggesting no substantial dietary co-exposure with contaminants. In females, parasite loads increased strongly with decreasing selenium:mercury molar ratios. Females may be more susceptible to the interactive effects of contaminants and parasites on physiology, with potential fitness consequences.

Breeding density, fine-scale tracking, and large-scale modeling reveal the regional distribution of four seabird species

Population-level estimates of species' distributions can reveal fundamental ecological processes and facilitate conservation. However, these may be difficult to obtain for mobile species, especially colonial central-place foragers (CCPFs; e.g., bats, corvids, social insects), because it is often impractical to determine the provenance of individuals observed beyond breeding sites. Moreover, some CCPFs, especially in the marine realm (e.g., pinnipeds, turtles, and seabirds) are difficult to observe because they range tens to ten thousands of kilometers from their colonies. It is hypothesized that the distribution of CCPFs depends largely on habitat availability and intraspecific competition. Modeling these effects may therefore allow distributions to be estimated from samples of individual spatial usage. Such data can be obtained for an increasing number of species using tracking technology. However, techniques for estimating population-level distributions using the telemetry data are poorly developed. This is of concern because many marine CCPFs, such as seabirds, are threatened by anthropogenic activities. Here, we aim to estimate the distribution at sea of four seabird species, foraging from approximately 5,500 breeding sites in Britain and Ireland. To do so, we GPS-tracked a sample of 230 European Shags Phalacrocorax aristotelis, 464 Black-legged Kittiwakes Rissa tridactyla, 178 Common Murres Uria aalge, and 281 Razorbills Alca torda from 13, 20, 12, and 14 colonies, respectively. Using Poisson point process habitat use models, we show that distribution at sea is dependent on (1) density-dependent competition among sympatric conspecifics (all species) and parapatric conspecifics (Kittiwakes and Murres); (2) habitat accessibility and coastal geometry, such that birds travel further from colonies with limited access to the sea; and (3) regional habitat availability. Using these models, we predict space use by birds from unobserved colonies and thereby map the distribution at sea of each species at both the colony and regional level. Space use by all four species' British breeding populations is concentrated in the coastal waters of Scotland, highlighting the need for robust conservation measures in this area. The techniques we present are applicable to any CCPF.

Reproductive performance of resident and migrant males, females and pairs in a partially migratory bird

Quantifying among‐individual variation in life‐history strategies, and associated variation in reproductive performance and resulting demographic structure, is key to understanding and predicting population dynamics and life‐history evolution. Partial migration, where populations comprise a mixture of resident and seasonally migrant individuals, constitutes a dimension of life‐history variation that could be associated with substantial variation in reproductive performance. However, such variation has rarely been quantified due to the challenge of measuring reproduction and migration across a sufficient number of seasonally mobile males and females.

We used intensive winter (non‐breeding season) resightings of colour‐ringed adult European shags (Phalacrocorax aristotelis) from a known breeding colony to identify resident and migrant individuals. We tested whether two aspects of annual reproductive performance, brood hatch date and breeding success, differed between resident and migrant males, females and breeding pairs observed across three consecutive winters and breeding seasons.

The sex ratios of observed resident and migrant shags did not significantly differ from each other or from 1:1, suggesting that both sexes are partially migratory and that migration was not sex‐biased across surveyed areas.

Individual resident males and females hatched their broods 6 days earlier and fledged 0.2 more chicks per year than migrant males and females on average. Resident individuals of both sexes therefore had higher breeding success than migrants.

Hatch date and breeding success also varied with a pair's joint migratory strategy such that resident–resident pairs hatched their broods 12 days earlier than migrant–migrant pairs, and fledged 0.7 more chicks per year on average. However, there was no evidence of assortative pairing with respect to migratory strategy: observed frequencies of migrant–migrant and resident–resident pairs did not differ from those expected given random pairing.

These data demonstrate substantial variation in two key aspects of reproductive performance associated with the migratory strategies of males, females and breeding pairs within a partially migratory population. These patterns could reflect direct and/or indirect mechanisms, but imply that individual variation in migratory strategy and variation in pairing among residents and migrants could influence selection on migration and drive complex population and evolutionary dynamics.

Permissive Hypotension: Potentially Harmful in the Elderly? A National Trauma Data Bank Analysis

Permissive hypotension is a component of damage control resuscitation that aims to provide a directed, controlled resuscitation, while countering the “lethal triad.” This principle has not been specifically studied in elderly (ELD) trauma patients (≥55 years). Given the ELD population's lack of physiologic reserve and risk of inadequate perfusion with “normal” blood pressures, we hypothesized that utilized a permissive hypotension strategy in ELD trauma patients would result in worse outcomes compared with younger patients (18–54 years). A retrospective review of National Trauma Data Bank reports from 2009 and 2010, identifying critically ill patients undergoing a “damage control laparotomy,” was performed to determine the effect of age and systolic blood pressure on outcome. Logistic regression analysis, including evaluation of an interaction between age and admission blood pressure, was performed on mortality using admission demographics, physiology, injury severity, mechanism of injury, and in-hospital complications. Although there was a higher likelihood of death with greater age, lower admission systolic blood pressure, lower Glasgow Coma Score, increased injury severity score, and acute renal failure, a synergistic effect of age and blood pressure on mortality was not identified. Permissive hypotension appears to be a possible management strategy in ELD trauma patients.

Parasitism in early life: environmental conditions shape within-brood variation in responses to infection

Parasites play key ecological and evolutionary roles through the costs they impose on their host. In wild populations, the effect of parasitism is likely to vary considerably with environmental conditions, which may affect the availability of resources to hosts for defense. However, the interaction between parasitism and prevailing conditions is rarely quantified. In addition to environmental variation acting on hosts, individuals are likely to vary in their response to parasitism, and the combined effect of both may increase heterogeneity in host responses. Offspring hierarchies, established by parents in response to uncertain rearing conditions, may be an important source of variation between individuals. Here, we use experimental antiparasite treatment across 5 years of variable conditions to test how annual population productivity (a proxy for environmental conditions) and parasitism interact to affect growth and survival of different brood members in juvenile European shags (Phalacrocorax aristotelis). In control broods, last-hatched chicks had more plastic growth rates, growing faster in more productive years. Older siblings grew at a similar rate in all years. Treatment removed the effect of environment on last-hatched chicks, such that all siblings in treated broods grew at a similar rate across environmental conditions. There were no differences in nematode burden between years or siblings, suggesting that variation in responses arose from intrinsic differences between chicks. Whole-brood growth rate was not affected by treatment, indicating that within-brood differences were driven by a change in resource allocation between siblings rather than a change in overall parental provisioning. We show that gastrointestinal parasites can be a key component of offspring's developmental environment. Our results also demonstrate the value of considering prevailing conditions for our understanding of parasite effects on host life-history traits. Establishing how environmental conditions shape responses to parasitism is important as environmental variability is predicted to increase.

Genetic and biochemical differences in populations bred for extremes in maize grain methionine concentration

BACKGROUND

Methionine is an important nutrient in animal feed and several approaches have been developed to increase methionine concentration in maize (Zea mays L.) grain. One approach is through traditional breeding using recurrent selection. Using divergent selection, genetically related populations with extreme differences in grain methionine content were produced. In order to better understand the molecular mechanisms controlling grain methionine content, we examined seed proteins, transcript levels of candidate genes, and genotypes of these populations.

RESULTS

Two populations were selected for high or low methionine concentration for eight generations and 40 and 56% differences between the high and low populations in grain methionine concentration were observed. Mean values between the high and low methionine populations differed by greater than 1.5 standard deviations in some cycles of selection. Other amino acids and total protein concentration exhibited much smaller changes. In an effort to understand the molecular mechanisms that contribute to these differences, we compared transcript levels of candidate genes encoding high methionine seed storage proteins involved in sulfur assimilation or methionine biosynthesis. In combination, we also explored the genetic mechanisms at the SNP level through implementation of an association analysis. Significant differences in methionine-rich seed storage protein genes were observed in comparisons of high and low methionine populations, while transcripts of seed storage proteins lacking high levels of methionine were unchanged. Seed storage protein levels were consistent with transcript levels. Two genes involved in sulfur assimilation, Cys2 and CgS1 showed substantial differences in allele frequencies when two selected populations were compared to the starting populations. Major genes identified across cycles of selection by a high-stringency association analysis included dzs18, wx, dzs10, and zp27.

CONCLUSIONS

We hypothesize that transcriptional changes alter sink strength by altering the levels of methionine-rich seed storage proteins. To meet the altered need for sulfur, a cysteine-rich seed storage protein is altered while sulfur assimilation and methionine biosynthesis throughput is changed by selection for certain alleles of Cys2 and CgS1.

Genomic selection in plant breeding

Genomic selection (GS) is a method to predict the genetic value of selection candidates based on the genomic estimated breeding value (GEBV) predicted from high-density markers positioned throughout the genome. Unlike marker-assisted selection, the GEBV is based on all markers including both minor and major marker effects. Thus, the GEBV may capture more of the genetic variation for the particular trait under selection.

Genome-wide association study for oat (Avena sativa L.) beta-glucan concentration using germplasm of worldwide origin

Detection of quantitative trait loci (QTL) controlling complex traits followed by selection has become a common approach for selection in crop plants. The QTL are most often identified by linkage mapping using experimental F(2), backcross, advanced inbred, or doubled haploid families. An alternative approach for QTL detection are genome-wide association studies (GWAS) that use pre-existing lines such as those found in breeding programs. We explored the implementation of GWAS in oat (Avena sativa L.) to identify QTL affecting β-glucan concentration, a soluble dietary fiber with several human health benefits when consumed as a whole grain. A total of 431 lines of worldwide origin were tested over 2 years and genotyped using Diversity Array Technology (DArT) markers. A mixed model approach was used where both population structure fixed effects and pair-wise kinship random effects were included. Various mixed models that differed with respect to population structure and kinship were tested for their ability to control for false positives. As expected, given the level of population structure previously described in oat, population structure did not play a large role in controlling for false positives. Three independent markers were significantly associated with β-glucan concentration. Significant marker sequences were compared with rice and one of the three showed sequence homology to genes localized on rice chromosome seven adjacent to the CslF gene family, known to have β-glucan synthase function. Results indicate that GWAS in oat can be a successful option for QTL detection, more so with future development of higher-density markers.

The damage control sequence in the elderly: Strategy, complexities, and outcomes

Traditional management in cases of exsanguinating abdominal trauma led to poor outcomes in critically injured patients. Because prolonged operations were not well tolerated due to the severe physiologic derangements, an abbreviated laparotomy began to be used. Patients were then resuscitated in the intensive care unit and brought back to the operating room once their physiology had been normalised. This approach has been termed the damage control sequence. Elderly trauma patients are susceptible to significant injury that may mandate a damage control sequence. For myriad reasons, including pre-existing medical conditions, decreased physiologic reserve, and the emergent nature of their injuries, the application of this management approach in the elderly is fraught with challenges. The purpose of this review is to enumerate the damage control sequence, describe the complexities of its use in the elderly, and discuss associated outcomes in this challenging patient population.

Population structure and linkage disequilibrium in oat (Avena sativa L.): implications for genome-wide association studies

The level of population structure and the extent of linkage disequilibrium (LD) can have large impacts on the power, resolution, and design of genome-wide association studies (GWAS) in plants. Until recently, the topics of LD and population structure have not been explored in oat due to the lack of a high-throughput, high-density marker system. The objectives of this research were to survey the level of population structure and the extent of LD in oat germplasm and determine their implications for GWAS. In total, 1,205 lines and 402 diversity array technology (DArT) markers were used to explore population structure. Principal component analysis and model-based cluster analysis of these data indicated that, for the lines used in this study, relatively weak population structure exists. To explore LD decay, map distances of 2,225 linked DArT marker pairs were compared with LD (estimated as r²). Results showed that LD between linked markers decayed rapidly to r² = 0.2 for marker pairs with a map distance of 1.0 centi-Morgan (cM). For GWAS, we suggest a minimum of one marker every cM, but higher densities of markers should increase marker-QTL association and therefore detection power. Additionally, it was found that LD was relatively consistent across the majority of germplasm clusters. These findings suggest that GWAS in oat can include germplasm with diverse origins and backgrounds. The results from this research demonstrate the feasibility of GWAS and related analyses in oat.

High-frequency oscillatory ventilation as a rescue therapy for adult trauma patients

BACKGROUND

High-frequency oscillatory ventilation is an alternative ventilation mode that improves oxygenation in trauma patients in whom conventional ventilation strategies have been unsuccessful.

OBJECTIVE

To evaluate the effect of high-frequency oscillatory ventilation on oxygenation, survival, and parameters predictive of survival in trauma patients.

METHODS

A retrospective case series of 24 adult patients admitted to the trauma intensive care unit at a level I trauma center between November 2001 and July 2005 and treated with high-frequency oscillatory ventilation. Survivors and nonsurvivors were compared for mechanism and severity of injury, oxygenation parameters related to high-frequency oscillatory ventilation, and hospital course.

RESULTS

Of the 8577 patients admitted during the study period, acute respiratory distress syndrome developed in 103 (1%). Of those 103 patients, 24 (23%) were treated with high-frequency oscillatory ventilation. Most of the patients treated with high-frequency oscillatory ventilation had sustained blunt trauma (79%). Oxygenation parameters improved significantly with high-frequency oscillatory ventilation in all patients, regardless of survival. Of the 24 patients treated with this ventilation mode, 15 (62%) survived. Survival did not correlate with improved oxygenation parameters but with the number of failed organ systems and injury severity.

CONCLUSION

Although high-frequency oscillatory ventilation improves oxygenation, severity of traumatic injury and organ failure, not respiratory parameters, are predictors of survival. High-frequency oscillatory ventilation should be considered for pulmonary rescue of severely injured patients with acute respiratory distress syndrome.

Field hypotension in patients who arrive at the hospital normotensive: a marker of severe injury or crying wolf?

INTRODUCTION

Trauma patients with hypotension in the field who arrive at a hospital with a normal blood pressure (BP) may not be recognized as significantly injured.

METHODS

Over a 5-year period, demographic, injury severity, and disposition data were retrospectively analyzed for patients > or =16 years of age with documented hypotension in the field (systolic BP < or =90 mm Hg) and normal BP (systolic BP >90 mmHg) on hospital arrival (hypotensive group). This group was compared to patients with normal BP in the field and on hospital arrival (normotensive group).

RESULTS

During the study, 2207 patients with documented BP were transported directly from the scene. Of this number 44 (2%) were assigned to the hypotensive group, 2086 (94%) were assigned to the normotensive group, and 77 (4%) patients were hypotensive on hospital arrival. The hypotensive group had a systolic BP in the field of 70 +/- 26 mmHg compared to 140 +/- 26 mmHg in the normotensive group (p < 0.0001). Arrival BP at the hospital was normal in both groups. Compared to the normotensive group, the hypotensive group had higher Injury Severity Scores (22.0 vs. 11.1, p < 0.0001), lower Glasgow Coma Scores (10.8 vs. 14.0, p < 0.0001), lower Revised Trauma Scores (65 vs. 7.4, p < 0.0O01), more emergency department deaths (7% vs. 0%, p < 0.001), longer lengths of stay in the intensive care unit (8.6 vs. 7.0 days, p < 0.0001) and hospital (14.0 vs. 7.0 days, p < 0.0001), and increased hospital mortality (18% vs. 4%, p < 0.001).

LIMITATIONS

The retrospective design and exclusion of patients without documentation of BP in the field may have resulted in selection bias.

CONCLUSION

Despite these limitations, field hypotension is a marker of significant injury in patients arriving at the hospital normotensive.

Morbidity Reduction in Critically Ill Trauma Patients Through use of a Computerized Insulin Infusion Protocol: A Preliminary Study

BACKGROUND

Recent data have demonstrated that intensive glycemic control during critical illness improves outcome. The purpose of our study was to evaluate the effect of a computerized hospital insulin protocol (CHIP) on glycemic control and outcome in critically ill trauma patients.

METHODS

Two, 6-month cohorts were compared, one 6 months prior to chip implementation (pre-CHIP) and one from the 6-month period after implementation (post-CHIP), using finger stick blood glucose values and demographic, injury severity, and outcome variables for adult patients with intensive care unit length of stay (LOS) > or =72 hours. Infectious morbidity was based upon the National Trauma Registry of the American College of Surgeons definitions. Differences between cohorts were assessed using Student's t test and Fisher's exact test for continuous and categorical variables.

RESULTS

The 129 pre- and 128 post-CHIP patients were well matched for demographics and injury severity. Significant reductions in mean finger stick blood glucose, rates of ventilator- associated pneumonia, central venous line infection, total infections, and all LOS categories were demonstrated in the post-CHIP cohort. However, mortality was significantly higher in the post-CHIP cohort.

CONCLUSION

This preliminary study demonstrates significant morbidity and LOS reductions with the use of a CHIP, but significantly increased mortality. Further prospective studies are necessary to assess the effects of intensive glycemic control on outcome after injury, particularly in sub populations who might be adversely affected.

Body Mass Index and Outcomes in Critically Injured Blunt Trauma Patients: Weighing the Impact

BACKGROUND

The influence of increased body mass index (BMI) on morbidity and mortality in critically injured trauma patients has been studied, with conflicting results. The objective of this study was to investigate the relationship between stratified BMI and outcomes in blunt injured patients.

STUDY DESIGN

Consecutive adult trauma patients from July 2001 to November 2005 with Injury Severity Score (ISS) > or = 16 and blunt mechanism were evaluated using the National Trauma Registry of the American College of Surgeons. Demographics, injury severity, hospital course, complications, and mortality were compared among standard BMI strata. Logistic regression was used to determine odds ratios (OR) with 95% confidence intervals and evaluate BMI as an independent risk factor for morbidity and mortality. Statistical significance was set at p < 0.05.

RESULTS

The study group consisted of 1,543 patients. Controlling for age, gender, Injury Severity Score, and Revised Trauma Score, and using BMI 18.5 to 24.9 kg/m(2) as the reference category, morbid obesity (BMI> or =40 kg/m(2)) was associated with acute respiratory distress syndrome (OR 3.675, 95% CI, 1.237 to 10.916), acute respiratory failure (OR 2.793, 95% CI, 1.633 to 4.778), acute renal failure (OR 13.506, 2.388 to 76.385), multisystem organ failure (OR 2.639, 95% CI, 1.085 to 6.421), pneumonia (OR 2.487, 95% CI, 1.483 to 4.302), urinary tract infection (OR 2.332, 95% CI, 1.229 to 4.427), deep venous thrombosis (OR 4.112, 95% CI, 1.253 to 13.496), and decubitus ulcer (OR 2.841, 95% CI, 1.382 to 5.841). Morbid obesity was not associated with increased mortality (OR 0.810, 95% CI, 0.353 to 1.856).

CONCLUSIONS

This is the largest study to date evaluating the relationship between BMI and outcomes in critically injured trauma patients. Increasing BMI increases morbidity while having no proved influence on mortality.

Rural trauma recidivism: a different disease

HYPOTHESIS

Unlike the well-characterized urban trauma recidivist (RC), factors associated with the rural RC remain undefined. In an attempt to devise preventative strategies, we theorized that the rural RC profile would be similar to that of urban counterparts.

DESIGN

Retrospective review.

SETTING

Rural, university-affiliated, level I trauma center.

PATIENTS

All trauma patients admitted between January 1, 1994, and December 30, 2002.

INTERVENTIONS

Identification and characterization of rural trauma RCs.

MAIN OUTCOME MEASURES

Trauma recidivism incidence, risk factors, and cost.

RESULTS

Of 15 370 consecutive admissions, 528 (3.4%) were RCs. Demographic comparisons to a non-RC cohort demonstrated rural RCs to be significantly older (mean +/- SD age, 55.9 +/- 24.8 vs 39.7 +/- 24.1 years), disproportionately white (65.2% [344/528] vs 56.5% [8386/14 842]), and more likely female (49.1% [259/528] vs 37.3% [5537/14 842]) (P<.001 for all). Clinical comparisons revealed significant associations between recidivism and substance abuse. The percentage of positive blood ethanol screen results (58.7% [310/528] vs 39.9% [5923/14 842]) and the mean +/- SD blood ethanol content (132.1 +/- 139.9 mg/dL [28.7 +/- 30.4 mmol/L] vs 69.5 +/- 114.4 mg/dL [15.1 +/- 24.8 mmol/L]) were higher for RCs (P<.001 for both). In addition, cocaine use was significantly higher in the RC cohort (6.4% [34/528] vs 4.1% [607/14 842]; P=.02). The total cost for all RC admissions exceeded $7 million.

CONCLUSIONS

The rural RC profile is strikingly different from urban counterparts. The common feature seems to be substance abuse. Correspondingly, prevention strategies for recidivism must be considerably different among rural and urban populations.

Alcohol withdrawal syndrome: Turning minor injuries into a major problem

BACKGROUND

Abrupt cessation of chronic drinking patterns places hospitalized patients at risk for alcohol withdrawal syndrome (AWS). The purpose of this study was to investigate the effect of AWS on length of stay, morbidity, mortality, and cost in low injury acuity trauma patients.

METHODS

A retrospective review of the National Trauma Registry of the American College of Surgeons database from July 1999 to February 2004 was performed. All patients 15 years or older admitted to our Level I trauma center with an Injury Severity Score (ISS) <16 were included. AWS patients were compared with those without AWS. Demographics, mechanism of injury (MOI), ISS, revised trauma score, Glasgow Coma score, hospital course, morbidity, requirement of additional procedures, mortality, and cost were compared. Analysis was done with chi2 test and Student's t test. A p value of < or =0.05 determined significance.

RESULTS

Of 6,431 patients, 55 (0.9%) developed AWS. AWS patients were likely men (p < 0.001); had a higher ISS (p = 0.001) and lower Glasgow Coma score (p = 0.01); had more ventilator days (p = 0.008), intensive care unit days (p < 0.0001), and hospital days (p < 0.0001); suffered more complications, including respiratory failure (p < 0.0001), pneumonia (p < 0.0001), urinary tract infection (p = 0.0005), sepsis (p < 0.0001), tracheostomy (p < 0.0001), and percutaneous endoscopic gastrostomy (p < 0.0001); and had higher cost (p < 0.0001). Mortality was similar (p = 0.38) among groups.

CONCLUSIONS

Low injury acuity patients with AWS have increased morbidity, leading to increased hospital stay and cost. To allow minor injuries to remain minor problems, the best modality to identify patients at risk and to achieve AWS prophylaxis require further investigation.

A Collaborative Systems Approach to Rural Burn Care

A collaborative systems approach was created between the regional verified burn center (BC) and the rural verified Level 1 trauma center (TC) to treat minor burns. This study assesses the feasibility of providing outpatient burn care at the TC. A retrospective review was performed from January 2000 to June 2005 of burn patients seen at the TC. Seven trauma/critical care surgeons and a dedicated burn nurse staffed the clinic twice a week. Burn surgeons from the BC provided consultation via email and telephone links and served as the regional resource. In the TC clinic, 314 injuries occurred in 311 patients. 196 patients were male with an average age of 34.5 +/- 1.1 years. The mean burn TBSA was 2.9 +/- 0.2%. Fourteen patients (4%) required skin grafts. Patients averaged 3.5 +/- 0.1 clinic visits over a mean follow-up period of 42.9 +/- 7.4 days from initial injury. There were 1252 scheduled appointments during the study period. Silver sulfadiazine or triple antibiotic ointment was applied in the majority of the cases. Thirty-one patients (9.9%) were documented to have complications, most of which were local wound infections. Long-term sequelae (scarring, chronic pain, and contractures) occurred in 13.4% of patients. Clinical success in outpatient burn care can be achieved at a non burn center with dedicated personnel. The successful collaboration between the BC and TC can unload some minor burn care from the burn center, while providing good clinical care to the local rural population.

Low-dose dopamine: a physiologically based review

BACKGROUND

In an attempt to prevent or alter the course of acute renal failure, many surgeons continue to use low-dose dopamine. This article critically reviews the physiologic reasons why low-dose dopamine is not clinically efficacious.

METHODS

A critical review of English language literature.

RESULTS

The effect of dopamine on renal blood flow remains controversial. If dopamine does increase renal blood flow, the vascular anatomy of the kidney would limit its effectiveness. Rather than improving renal function, dopamine has been shown to impair renal oxygen kinetics, inhibit feedback systems that protect the kidney from ischemia, and may worsen tubular injury. Dopamine has not been proven useful in the prevention or alteration of the course of acute renal failure as a result of heart failure, cardiac surgery, abdominal aortic surgery, sepsis, and transplantation. Dopamine has been associated with multiple complications involving the cardiovascular, pulmonary, gastrointestinal, endocrine, and immune systems.

CONCLUSIONS

Based on the anatomy and physiology of the kidney, low-dose dopamine would not be expected to improve renal failure and this has been demonstrated by the lack of efficacy in clinical trials.

Predicting the Need for Early Tracheostomy: A Multifactorial Analysis of 992 Intubated Trauma Patients

BACKGROUND

Tracheostomy has few, severe risks, while prolonged endotracheal intubation causes morbidity. The need for tracheostomy was assessed, based on early clinical parameters.

METHODS

Adult trauma patients (January 1994-August 2004), intubated for resuscitation, ventilated >24 hours, were retrospectively evaluated for demographics, physiology, brain, and pulmonary injury. Tracheostomy patients were compared with those without. Chi-square, Mann-Whitney, and multivariate logistic regression were used with statistical significance at p < 0.05.*

RESULTS

Of 992 patients, 430 (43%) underwent tracheostomy at 9.22 +/- 5.7 days. Risk factors were age (45.6* +/- 18.8 vs. 36.7 +/- 15.9, OR: 2.1 (18 years increments), ISS (30.3* +/- 12.5 vs. 22.0 +/- 10.3, OR: 2.1 (12u increments), damage control (DC) [68%*(n = 51) vs. 32%*(n = 51), OR: 3.8], craniotomy [70%*(n = 21) versus 30%(n = 9), OR: 2.6], and intracranial pressure monitor (ICP) [65.4%*(n = 87) vs. 34.6%(n = 46), OR: 2.1]. A 100% tracheostomy rate (n = 30, 3.0%) occurred with ISS (injury severity score) = 75, ISS >or=50, and age >or=55, admit/24 hour GCS (Glasgow Coma Scale) = 3 and age >or=70, AIS abdomen, chest or extremities >or=5 and age >or=60, bilateral pulmonary contusions (BPC) and >or=8 rib fractures, craniotomy and age >or=50, craniotomy with intracranial pressure (ICP) and age >or=40, or craniotomy and GCS <or=4 at 24 hour.A tracheostomy rate of >or=90% (n = 105, 10.6%) was found with ISS >or=54, ISS >or=40, and age >or=40, admit/24 hour GCS = 3 and age >or=55, paralysis and age >or=40, BPC and age >or=55.A tracheostomy rate >or=80% (n = 248, 25.0%) occurred with ISS >or=38, age >or=80, admit/24 hour GCS = 3 and age >or=45, DC and age >or=50, BPC and age >or=50, aspiration and age >or=55, craniotomy with ICP, craniotomy with GCS <or=9 at 24 hour.

CONCLUSION

Discrete risk factors predict the need for tracheostomy for trauma patients. We recommend that patients with >or=90% risk undergo early tracheostomy and that it is considered in the >or=80% risk group to potentially decreased morbidity, increased patient comfort, and optimize resource utilization.

Isolated contralateral vertebral artery injury in a stab wound to the neck

Ipsilateral vertebral artery injuries are a rare entity following trauma to the neck. We discuss the first case of an isolated right vertebral artery injury in a patient with a left stab wound. The patient required bilateral neck explorations and, due to massive bleeding, a median sternotomy in order to obtain control of the proximal segment of the right vertebral artery. We emphasize the importance for trauma surgeons to be familiar with basic but important vascular exposures. The anatomy, surgical exposure, and management of these rare injuries are discussed.

Hypoxic pulmonary vasoconstriction is impaired in rats with nitrofen-induced congenital diaphragmatic hernia

BACKGROUND

Pulmonary hypertension and persistent fetal circulation contribute to the high mortality rate associated with congenital diaphragmatic hernia (CDH). Morphological alterations of the pulmonary vasculature in infants with CDH are thought to contribute to exaggerated vasoconstrictor responses to normal vasoconstrictor stimuli. In the pulmonary circulation, hypoxia is a potent vasoconstrictor. Under pathological conditions, hypoxia-induced vasoconstriction may contribute to the development of pulmonary hypertension.

METHODS

The authors have used the nitrofen-induced model of congenital diaphragmatic hernia in rats to investigate the magnitude of the hypoxic vasoconstrictor response. Congenital diaphragmatic hernias were induced in fetal rats by feeding nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) to pregnant Sprague-Dawley rats at midgestation. Hypoxia-induced vasoconstriction was measured in isolated, perfused third-generation pulmonary arterioles from normal rats and from rats with nitrofen-induced CDH.

RESULTS

The hypoxic vasoconstrictor response was significantly blunted in the pulmonary arterioles of fetal rats with nitrofen-induced (2% +/- 1% vasoconstriction), as compared with the responses observed in normal fetal rats (15% +/- 3% vasoconstriction, P = .004).

CONCLUSION

Blunting of the hypoxic pulmonary vasoconstrictor response may contribute to ventilation-perfusion mismatching in infants with CDH.

Vascular trauma in drug abuse: patterns of injury

We have reviewed 172 occurrences of vascular injuries caused by intravascular or perivascular drug injections. Various patterns of injury are discussed including presentation. Recommendations have been made for diagnostic evaluation, surgical and medical treatment based on proposed pathophysiologic etiologies and bacteriology. Expected outcomes are presented. It is important that all physicians become familiar with the management of these injuries as the number of patients who seek treatment for complications of substance abuse continues to increase in our present day society.

Single-antibiotic use for penetrating abdominal trauma

A prospective randomized study compared the use of moxalactam disodium vs clindamycin phosphate and tobramycin sulfate for treatment of 190 patients with penetrating abdominal trauma. Twenty-seven patients were disqualified because of early death or failure to follow the protocol. The patients in each group were comparable regarding the cause and severity of injury. No significant difference was seen in the incidence of intra-abdominal infection between the moxalactam-treated group (13%) and the clindamycin- and tobramycin-treated group (9%). The intra-abdominal infection rate in patients with colon injuries (21%) was significantly increased when compared with the patients without colon injuries (6%), but the antibiotic regimen did not significantly change the infection rate. No evidence of bleeding problems from moxalactam were noted. Changes in prothrombin and partial thromboplastin times appeared to be related to shock rather than the use of moxalactam. The most severe coagulopathies occurred prior to moxalactam therapy and were seen only in those patients who had shock requiring 10 or more units of blood. Moxalactam is as effective as combination (clindamycin and tobramycin) antimicrobial therapy in patients with penetrating abdominal trauma.