Short communication: Characterizing arterial and venous blood gases over the gas exchange surface, the chorioallantoic membrane, of embryonic American alligators (Alligator mississippiensis) at two points of development.

Assessments of arterial and venous blood gases are required to understand the function of respiratory organs in animals at different stages of development. We measured blood gases in the arteries entering and veins leaving the chorioallantoic membrane (CAM) in embryonic alligators (Alligator mississippiensis). The CAM accounts for virtually all gas exchange in these animals, and we hypothesized that the CAM vasculature would be larger in eggs incubated in hypoxia (10% O2 for 50% or 70% of incubation), which would be reflected in a lower partial pressure of CO2 (PCO2). Contrary to this hypothesis, our measurements revealed no effects of hypoxic incubation on PCO2, and seemingly no increase in vascularization of the CAM in response to incubation in 10% O2. PCO2 was lower on the venous side, but only significantly different from arterial blood at 70% of incubation. The calculated blood flow to the CAM increased with development and was lower in both groups of alligators that had been incubated in hypoxia. Future studies should include measurements of blood parameters taken from embryos held in conditions that mirror incubation O2 levels, in combination with direct measurements of CAM artery blood flow.

Discretizing continuous variables in nutrition and obesity research: a practice that needs to be cut short.

BACKGROUND/OBJECTIVES: Nutrition and obesity researchers often dichotomize or discretize continuous independent variables to conduct an analysis of variance to examine group differences. We describe consequences associated with dichotomizing and discretizing continuous variables using two cross-sectional studies related to nutrition. SUBJECTS/METHODS: Study 1 investigated the effects of health literacy and nutrition knowledge on nutrition label accuracy (n = 612). Study 2 investigated the effects of cognitive restraint and BMI on fruit and vegetable (F/V) intake (n = 586). We compare analytic approaches where continuous independent variables were either discretized/dichotomized or analyzed as continuous variables. RESULTS: In Study 1, dichotomization of health literacy and nutrition knowledge for 2 × 2 ANOVA revealed health literacy had an effect on nutrition label accuracy. Nutrition knowledge has an effect on nutrition label accuracy, but the health literacy by nutrition knowledge interaction was not significant. When analyzed using regression, the nutrition knowledge effect was significant. The simple effect of health literacy was also significant when health literacy equals zero. Finally, the quadratic effect of health literacy was negative and significant. In Study 2, dichotomization and discretization of cognitive restraint and BMI were used for three ANOVAs, which discretized BMI in three ways. For all ANOVAs, the BMI main effect for predicting fruit and vegetable intake was significant, the interaction between BMI and cognitive restraint was non-significant, and cognitive restraint was only significant when both variables were dichotomized. When analyzed using regression, the continuous mean-centered variables, and their interaction each significantly predicted F/V intake. CONCLUSIONS: Dichotomizing continuous independent variables resulted in distortions of effect sizes across studies, an inability to assess the quadratic effect of health literacy, and an inability to detect the moderating effect of BMI. We discourage researchers from dichotomizing and discretizing continuous independent variables and instead use multiple regression to examine relationships between continuous independent and dependent variables.

Hypoxic incubation at 50% of atmospheric levels shifts the cardiovascular response to acute hypoxia in American alligators, Alligator mississippiensis.

We designed a series of studies to investigate whether hypoxia (10% O2) from 20% of incubation to hatching, or from 20 to 50% of incubation, affects cardiovascular function when juvenile American alligators reached an age of 4-5 years compared to juveniles that were incubated in 21% O2. At this age, we measured blood flows in all the major arteries as well as heart rate, blood pressure, and blood gases in animals in normoxia and acute hypoxia (10% O2 and 5% O2). In all three groups, exposure to acute hypoxia of 10% O2 caused a decrease in blood O2 concentration and an increase in heart rate in 4-5-year-old animals, with limited effects on blood flow in the major outflow vessels of the heart. In response to more acute hypoxia (5% O2), where blood O2 concentration decreased even further, we measured increased heart rate and blood flow in the right aorta, subclavian artery, carotid artery, and pulmonary artery; however, blood flow in the left aorta either decreased or did not change. Embryonic exposure to hypoxia increased the threshold for eliciting an increase in heart rate indicative of a decrease in sensitivity. Alligators that had been incubated in hypoxia also had higher arterial PCO2 values in normoxia, suggesting a reduction in ventilation relative to metabolism.

Exposure to hypoxia during embryonic development affects blood flow patterns and heart rate in juvenile American alligators during digestion.

The developmental environment can alter an organism's phenotype through epigenetic mechanisms. We incubated eggs from American alligators in 10% O2 (hypoxia) to investigate the functional plasticity of blood flow patterns in response to feeding later in life. Digestion is associated with marked elevations of metabolism, and we therefore used the feeding-induced stimulation of tissue O2 demand to determine whether there are lasting effects of developmental hypoxia on the cardiovascular response to digestion later in life. In all animals studied, digestion elicited tachycardia and an elevation of blood flow in the right aorta, left aorta, and the pulmonary artery, whereas flows in the carotid and subclavian artery did not change. We found that heart rate and systemic blood flow remained elevated for a longer time period in juvenile alligators that had been incubated in hypoxia; we also found that the pulmonary blood flow was elevated at 24, 36, and 48 h. Collectively, our findings demonstrate that exposure to hypoxia during incubation has lasting effects on the hemodynamics of juvenile alligators 4 years after hatching.

No evidence for pericardial restraint in the snapping turtle (Chelydra serpentina) following pharmacologically induced bradycardia at rest or during exercise.

Most animals elevate cardiac output during exercise through a rise in heart rate (fH), whereas stroke volume (VS) remains relatively unchanged. Cardiac pacing reveals that elevating fH alone does not alter cardiac output, which is instead largely regulated by the peripheral vasculature. In terms of myocardial oxygen demand, an increase in fH is more costly than that which would incur if VS instead were to increase. We hypothesized that fH must increase because any substantial rise in VS would be constrained by the pericardium. To investigate this hypothesis, we explored the effects of pharmacologically induced bradycardia, with ivabradine treatment, on VS at rest and during exercise in the common snapping turtle (Chelydra serpentina) with intact or opened pericardium. We first showed that, in isolated myocardial preparations, ivabradine exerted a pronounced positive inotropic effect on atrial tissue but only minor effects on ventricle. Ivabradine reduced fH in vivo, such that exercise tachycardia was attenuated. Pulmonary and systemic VS rose in response to ivabradine. The rise in pulmonary VS largely compensated for the bradycardia at rest, leaving total pulmonary flow unchanged by ivabradine, although ivabradine reduced pulmonary blood flow during swimming (exercise × ivabradine interaction, P < 0.05). Although systemic VS increased, systemic blood flow was reduced by ivabradine both at rest and during exercise, despite ivabradine's potential to increase cardiac contractility. Opening the pericardium had no effect on fH, VS, or blood flows before or after ivabradine, indicating that the pericardium does not constrain VS in turtles, even during pharmacologically induced bradycardia.

The Resistance to Change-Beliefs Scale: Validation of a New Measure of Conservative Ideology.

The motivated social cognition (MSC) model of conservative ideology posits there are two core facets of conservative political ideology-endorsement of hierarchies and resistance to change. The present research tested the validity and reliability of a scale developed to measure resistance to change. Five studies support the validity, reliability, and factor structure of the Resistance to Change-Beliefs (RC-B) scale. Scores on the RC-B scale correlated with social and cognitive motivations as well as self-identified conservatism. RC-B also predicted more conservative stances on political issues and factor analyses supported the predicted internal structure of the RC-B scale. This provides the field with a validated instrument that avoids problems inherent in previous measures, can be used to test predictions from the MSC model, and has potential applications beyond political psychology.

Embryonic developmental oxygen preconditions cardiovascular functional response to acute hypoxic exposure and maximal ß-adrenergic stimulation of anesthetized juvenile American alligators (Alligator mississippiensis).

The effects of the embryonic environment on juvenile phenotypes are widely recognized. We investigated the effect of embryonic hypoxia on the cardiovascular phenotype of 4-year-old American alligators (Alligator mississippiensis). We hypothesized that embryonic 10% O2 preconditions cardiac function, decreasing the reduction in cardiac contractility associated with acute 5% O2 exposure in juvenile alligators. Our findings indicate that dobutamine injections caused a 90% increase in systolic pressure in juveniles that were incubated in 21% and 10% O2, with the 10% O2 group responding with a greater rate of ventricular relaxation and greater left ventricle output compared with the 21% O2 group. Further, our findings indicate that juvenile alligators that experienced embryonic hypoxia have a faster rate of ventricular relaxation, greater left ventricle stroke volume and greater cardiac power following ß-adrenergic stimulation, compared with juvenile alligators that did not experience embryonic hypoxia. When juveniles were exposed to 5% O2 for 20 min, normoxic-incubated juveniles had a 50% decline in left ventricle maximal rate of pressure development and maximal pressure; however, these parameters were unaffected and decreased less in the hypoxic-incubated juveniles. These data indicate that embryonic hypoxia in crocodilians alters the cardiovascular phenotype, changing the juvenile response to acute hypoxia and ß-adrenergic stimulation.

Regulation of blood flow in the pulmonary and systemic circuits during submerged swimming in common snapping turtle (Chelydra serpentina).

Blood flow patterns and heart rate have rarely been investigated in freely swimming turtles and their regulation during swimming is unknown. In this study, we investigated the blood flow patterns and heart rate in surfacing and during graded, submerged swimming activity in common snapping turtles. We further investigated the effects of beta-adrenergic and cholinergic receptor blockade on blood flow and heart rate during these activities. Our findings illustrate that surfacing is accompanied by an increase in heart rate that is primarily due to beta-adrenergic stimulation. During swimming, this mechanism also increases heart rate while vagal withdrawal facilitates a systemic to pulmonary (left to right) shunt. The results indicate there may be important taxonomic effects on the responses of cardiac function to activity in turtle species.

Impact of Veteran Status and Timing of PTSD Diagnosis on Criminal Justice Outcomes.

Previous research has demonstrated that jurors show a bias towards treatment for veterans with post-traumatic stress disorder (PTSD). The present research examines this bias when jurors are faced with cases of potential malingering, in which the defendant's claim of PTSD is a perceived attempt to escape legal punishments. Trial vignettes, in which veteran status and PTSD diagnosis timing were manipulated, were used to explore this phenomenon. It was found that veterans who received their diagnosis after being arrested were found guilty more often, and were diverted to treatment less often, than those who were diagnosed before an arrest. This has critical implications for mental healthcare in that it is crucial to properly diagnose and treat people before they find themselves in court. Further, the negative outcomes in court demonstrate one of the severe social impacts of untreated or late-diagnosed PTSD.

Genome Sequences of Streptomyces Phages Amela and Verse.

Amela and Verse are two Streptomyces phages isolated by enrichment on Streptomyces venezuelae (ATCC 10712) from two different soil samples. Amela has a genome length of 49,452, with 75 genes. Verse has a genome length of 49,483, with 75 genes. Both belong to the BD3 subcluster of Actinobacteriophage.