No description available.

No description available.

No description available.

Stress is a physiological state induced by disturbance or adverse environmental conditions and is modulated by the glucocorticoid hormone corticosterone (CORT) in reptiles. Stressors can have various impacts on vertebrate trait expression and may affect survival or reproduction. Little is known about the effects of chronically elevated CORT in free-ranging reptiles, or the effect of disturbance stress on venom composition in captive snakes. In chapter 1, we investigated the effects of researcher induced disturbance on CORT levels and venom composition in a group of captive Northern Pacific rattlesnakes (Crotalus oreganus). Venom protein concentration and plasma CORT levels were compared before and after two weeks of unpredictable bouts of cage vibration, and to a non-vibrated control group. CORT levels were also assessed one week into vibration treatment. We found no effect of vibration treatment on CORT levels or on venom composition, and within-snake relative protein abundance was highly repeatable, although some variation was observed. We found a strong correlation between changes in relative abundance of several proteins and CORT. These results led us to believe that while differential forms of researcher-induced disturbance may not affect venom composition, significant changes in baseline CORT, or chronic stress, may affect the venom phenotype. In the next study, we investigated the effects of chronically elevated CORT in a wild population of radio-telemetered Southern Pacific rattlesnakes (C. helleri). Snakes were implanted intra-coelomically with either crystalline CORT or sham implants. Prior to implant and for two week periods thereafter, we sampled blood, venom, defensive behavior, and body temperature (Tb). Thermal data logger implants recorded snake Tb each hour. Snakes were tracked daily for one month, and detectability, defensive behavior, movement, home range size and thermal parameters were calculated for each group during the periods between samples. Stress reactivity was assessed as change in CORT from baseline after one hour of acute confinement stress. CORT implants led to elevated baseline CORT for at least two weeks in treatment snakes, showing that our treatment was successful. Chapter 2 describes the effects of CORT treatment on venom parameters. Increased baseline CORT was associated with increased activity of venom protein phospholipase A2, indicating that CORT may have direct effects on regulating venom protein activity. Overall, venom activity was repeatable within individual snakes. Chapter 3 describes the effect of CORT on behavioral, ecological, and physiological variables. Implant treatment led to decreased average Tb in weeks two and three. We detected a trend for lower baseline CORT to predict a greater magnitude of acute stress response. Snakes with higher testosterone levels exhibited higher defensive behavior scores. Overall, there were no other effects of implant treatment. Our results suggest that rattlesnake thermoregulation is impacted by chronic stress, which could affect other aspects of their metabolism and ecology. Results of both studies suggest baseline CORT may direct both the activity and relative abundance of venom proteins in different manners, a hypothesis which deserves further investigation using proteomic tools. When responding to an acute stressor, rattlesnakes may secrete CORT until a threshold response is reached, regardless of baseline levels. Overall, rattlesnakes appear resilient to the effects of researcher-induced disturbance in the laboratory and to two weeks of chronically elevated CORT in the field, as no change was detected in many of the parameters investigated.

BACKGROUND: Proper thyroid function is critical for normal fetal growth and neurodevelopment, as well as regulation of multiple systems in adults. There is growing evidence indicating that exposure to environmental chemicals may disrupt human thyroid function. Organophosphate flame retardants (PFRs) and per- and polyfluoroalkyl substances (PFASs) are two classes of potential thyroid disrupting chemicals commonly used in consumer products. OBJECTIVES: We characterized exposures to triphenyl phosphate (TPHP), a common PFR, and PFASs in two different U.S. populations. We assessed associations between TPHP and thyroid hormones in adults, as well as individual and joint associations of prenatal PFASs with maternal and neonatal thyroid hormones. METHODS: Analyses were conducted in two Boston, Massachusetts cohort studies: the Flame Retardant Exposure Study (FlaRE) and Project Viva, a longitudinal pre-birth cohort. In FlaRE, we used linear mixed effects models to assess covariate-adjusted associations between urinary DPHP concentrations and serum thyroid hormone levels in repeated samples from male and female adults (n=51). In Project Viva, we used both linear regression and weighted quantile sum regression to assess covariate-adjusted individual and joint associations of prenatal plasma PFAS concentrations measured in early pregnancy with maternal (n=726) and neonatal (n=465) thyroid hormone levels. RESULTS: In FlaRE, higher urinary DPHP was associated with higher total thyroxine (T4) levels in female but not male participants. We saw no associations between DPHP and free T4, total triiodothyronine, or thyroid stimulating hormone (TSH). In Project Viva, we found that higher prenatal exposure to PFASs was associated with lower maternal Free T4 Index (FT4I) and lower neonatal T4 in male infants, but was not associated with maternal T4 or TSH. Combined exposure to multiple PFASs was associated with lower maternal FT4I and neonatal T4 levels, but the relative contributions varied by individual PFAS. CONCLUSIONS: Exposures to both DPHP and PFASs were associated with altered thyroid hormone levels in these populations. Observed associations of DPHP and PFASs with thyroid hormone levels varied by sex, suggesting potential differences in susceptibility or mechanism of action. Associations between PFASs and thyroid hormones also differed across chemicals, suggesting potential differences in toxicological mechanism or potency. / 2019-11-08T00:00:00Z

Type 1 diabetes mellitus (T1D) is an autoimmune disease that results in deficient production of insulin from pancreatic beta cells. In addition to glycemic control irregularities, T1D can have profound effects on other metabolic processes in the body. Of these, bone, muscle, and adipose tissue metabolism are of interest in the fields of bone density and fracture risk. When combined with a diagnosis of T1D, the lifetime risk of fracture is up to four times higher; however, the relative risk of fracture highest in adulthood. This is of concern as fractures later in life have been shown to have adverse consequences on overall health. Understanding how fat mass and lean mass affect fracture risk in participants with and without T1D has the potential to provide support for accurately predicting and managing this fracture risk. In this cross-sectional analysis of adolescent girls ages 9 -18 with and without T1D, both groups were well matched in most areas, and significant differences between the two groups were seen at body mass index (BMI), BMI Z-score, lean mass index (LMI), LMI Z-score, hemoglobin A1c (HbA1c), and parathyroid hormone (PTH). The calculated predicted force of fall and measured failure load at the distal radius were used to investigate the load-to-strength ratio (LSR). The LSR has the potential to be beneficial in directly assessing fracture risk. From the analysis, it is possible to propose more in-depth studies of the hypothesized positive and negative effects of fat mass and lean mass, respectively on fracture risks.

No description available.

No description available.

The early developmental environment has a profound influence on an individual's life history trajectory and parents have tremendous influence over this environment. Despite the wealth of research demonstrating that incubation temperature affects a suite of traits important to fitness in reptiles, we are only now discovering that nest temperatures are a defining component of the avian developmental environment. Aspects of the nest environment may be an important and overlooked maternal effect in birds as nearly all birds physically incubate their eggs, thus providing a clear link between parental behavior and the developmental environment of the avian embryo. My research used an interdisciplinary approach, uniting concepts from life history theory, bioenergetics. immunology, and physiological ecology to investigate the importance of incubation temperature to avian phenotype. I found that incubation temperature affects a suite of traits important for future development, survival and reproduction in a species of birds. Using a population of wood ducks (Aix sponsa) that has been the subject of long term studies I investigated the effects of incubation temperature on embryonic developmental patterns and energy expenditure, and body size and condition, stress endocrinology, thermoregulatory performance, and immunocompetence in hatchling wood ducks. In all experiments freshly laid wood duck eggs were collected from nest boxes located in SC, transported to Virginia Tech and incubated at one of three temperatures (35.0, 35.9, 37.0Ë C) that fell within the range of naturally-incubated wood duck nest temperatures. I found that less than 1Ë C differences in incubation temperature affected duckling growth and body condition, stress endocrinology, immune responses, and energy expended to thermoregulate. Many of these effects persisted days to weeks after hatching. In most cases, ducklings that hatched from eggs incubated at lowest temperature performed poorer than ducklings that hatched from eggs incubated at the higher temperatures. Incubation temperature also affected wood duck embryonic developmental trajectories and energy expended during incubation with embryos from the low incubation temperature expended more energy and developing slower than ducklings incubated at the higher temperatures. Embryonic energy expenditure could contribute to effects observed on hatchling phenotype. Because I demonstrate that incubation temperature affects hatchling phenotypic quality, the variability upon which natural selection acts, my findings have implications for avian ecology, life history evolution and conservation. / Ph. D.

BACKGROUND: Postoperative hypoparathyroidism due to damage to the parathyroid glands during a thyroidectomy is a well-known surgical complication. The current gold standard intraoperative method for identifying parathyroid glands is surgical judgment; other methods are limited in both their sensitivity and convenience. There is a clear need for an objective diagnostic tool that is effective in its identification of the parathyroid glands and of their viability. We hypothesized that an intraoperative tool using Elastic Scattering Spectroscopy (ESS) has the potential to differentiate optical signatures of the parathyroid gland from surrounding tissues in real-time. METHODS: ESS optical signatures were collected intraoperatively from perfused parathyroid, thyroid, fat, muscle, and nerve tissue during thyroidectomy. The ESS data was collected using a portable, handheld, noninvasive, "cold" fiber optic probe able to detect spectra in a non-ionizing, broadband spectrum of light (320 to 920 nm). Five measurements were collected at each tissue site over a total of 1.2 seconds. Visual analysis of tissue was analyzed and compared to pathology, and spectral measurements attained with ESS. RESULTS: No complications resulted from the use of the ESS probe. Of the 10 parathyroid glands evaluated to be at risk in the study, the optical probe utilizing ESS was able to detect unique spectral features associated with the parathyroid gland. All 10 parathyroid glands are optically differentiable from surrounding tissues with ESS. CONCLUSIONS: Utilizing spectroscopy in the form of a hand-held probe is feasible for intraoperative differentiation between tissue types. Preliminary results of this spectral technique warrant further investigation. If successful, implementation of a portable ESS probe to identify the parathyroid tissue during endocrine surgical procedures could reduce surgical complications and improve patient safety.