Nitric oxide has been suggested to be involved in the regulation of fluid and nutrient homeostasis. In the present investigation, vasopressin and nitric oxide metabolite (nitrite and nitrate) levels were determined in plasma of male Wistar rats submitted to water or food deprivation for three days. Hematocrit and plasma sodium showed marked increase in dehydrated and starved rats. Potassium levels and plasma volume decreased in both treated groups. Plasma osmolality and vasopressin levels were significantly elevated in water deprived (362.8±7.1 mOsm/kg H₂O, 17.3±2.7 pg/ml, respectively, p<0.001) rats, but not in food deprived (339.9±5.0, 1.34±0.28) rats, compared to the controls (326.1±4.1, 1.47±0.32). The alterations observed in plasma vasopressin levels were related to plasma osmolality rather than plasma volume. Plasma levels of nitrite and nitrate were markedly increased in both water and food deprived rats (respectively, 2.19±0.29 mg/l and 2.22±0.17 mg/l <i>versus</i>1.33±0.19 mg/l, both p<0.01). There was a significant negative correlation between plasma nitrite and nitrate concentration and plasma volume. These results suggest that both dehydration and starvation increase plasma nitric oxide, probably by activation of nitric oxide synthases. The release of nitric oxide may participate in the regulation of the alteration in blood flow, fluid and nutrient metabolism caused by water deprivation or starvation.

Six ponies were deprived of drinking water and food and compared over 24 hours with nondeprived ponies, ponies deprived of water but with food available, and ponies deprived of food but with water available. When food was eaten during water deprivation, plasma osmolality rose 4% from 284 mOsm/kg to 295 mOsm/kg. During water and food deprivation, plasma osmolality failed to rise, even over 24 hours, and usually fell. Packed cell volume was higher when food but not water was available. Food and/or water deprivation had no significant effect on plasma protein concentration. When food was available, the ponies drank three times more water (13.1 ± 2.1 kg) than when water but not food was available (3.5 ± 1.4 kg). Blood volume changes were calculated from packed cell volume and plasma protein data, and it was found that blood volume did not change significantly with deprivation. Urine volume did not vary with deprivation, but free water clearance changed significantly, falling when food but not water was available. Under these conditions, blood volume is maintained, but the mechanisms are not clear. When deprived of both drinking water and food, ponies failed to develop the hyperosmolality expected under these conditions. Water deprivation while food is available is a more powerful challenge to water and electrolyte homeostasis than deprivation of both food and water.

Background: Perchlorate-induced natrium-iodide symporter (NIS) interference is a well-recognized thyroid disrupting mechanism. It is unclear, however, whether a chronic low-dose exposure to perchlorate delivered by food and drinks may cause thyroid dysfunction in the long term. Thus, the aim of this review was to overview and summarize literature results in order to clarify this issue. Methods: Authors searched PubMed/MEDLINE, Scopus, Web of Science, institutional websites and Google until April 2020 for relevant information about the fundamental mechanism of the thyroid NIS interference induced by orally consumed perchlorate compounds and its clinical consequences. Results: Food and drinking water should be considered relevant sources of perchlorate. Despite some controversies, cross-sectional studies demonstrated that perchlorate exposure affects thyroid hormone synthesis in infants, adolescents and adults, particularly in the case of underlying thyroid diseases and iodine insufficiency. An exaggerated exposure to perchlorate during pregnancy leads to a worse neurocognitive and behavioral development outcome in infants, regardless of maternal thyroid hormone levels. Discussion and conclusion: The effects of a chronic low-dose perchlorate exposure on thyroid homeostasis remain still unclear, leading to concerns especially for highly sensitive patients. Specific studies are needed to clarify this issue, aiming to better define strategies of detection and prevention.

The objective of this study was to evaluate the effects of a 6, 12, 18, 24, or 30h transport period on the physiology and reproductive success of breeding age gilts, simulating transport of breeding gilts from one farm to a commercial breeding herd. Fifty gilts were allocated to one of five transport (TRANS) treatment groups; transported for 6, 12, 18, 24, or 30h. Fifteen gilts were allocated to one of five control (CON) treatments; gilts remained in their home pen for 6, 12, 18, 24, or 30h. Every 6h, gilts from one TRANS treatment were removed from the trailer. Blood samples were collected from gilts and their respective controls before and after transport. Gilts were then bred after puberty. The granulocyte to lymphocyte ratio (P<0.05) and cortisol concentrations (P<0.07) were greater in TRANS compared with CON gilts after a 6 and 12h transport period. Albumin concentrations were greater (P<0.001) in transported gilts after an 18 and 30h transport period compared with CON gilts. Blood urea nitrogen, glucose, and total protein concentrations were greater (P<0.05) in transported gilts compared with controls, regardless of the transport period. Reproductive performance measures did not differ (P>0.05) among treatments regardless of the length of transport duration. These data indicate that gilts transported for a period of up to 30h experienced initial acute stress during the first 6 to 12h and changes in water homeostasis throughout the 30h journey due to dehydration, food deprivation, and transport, however reproductive measures suggest that the long-term homeostasis of the gilts in this study were not significantly compromised. Transport of breeding gilts induced acute, transient stress but did not negatively impact reproductive performance. Interestingly, gilts were more at risk of physiological perturbations when transported 6h or less than 12 to 30h.

Mammals in drylands are facing not only increasing heat loads but also reduced water and food availability as a result of climate change. Insufficient water results in suppression of evaporative cooling and therefore increases in body core temperature on hot days, while lack of food reduces the capacity to maintain body core temperature on cold nights. Both food and water shortage will narrow the prescriptive zone, the ambient temperature range over which body core temperature is held relatively constant, which will lead to increased risk of physiological malfunction and death. Behavioural modifications, such as shifting activity between night and day or seeking thermally buffered microclimates, may allow individuals to remain within the prescriptive zone, but can incur costs, such as reduced foraging or increased competition or predation, with consequences for fitness. Body size will play a major role in predicting response patterns, but identifying all the factors that will contribute to how well dryland mammals facing water and food shortagewill copewith increasing heat loads requires a better understanding of the sensitivities and responses ofmammals exposed to the direct and indirect effects of climate change. | The South African National Research Foundation (NRF), the Carnegie Corporation of New York, the Claude Leon Foundation, the Global Change System for Analysis, Research and Training (START), the Oppenheimer Memorial Trust, the Tswalu Foundation, the University of the Witwatersrand, and the Australian Research Council. | http://jeb.biologists.org | am2022 | Anatomy and Physiology | Centre for Veterinary Wildlife Studies | Paraclinical Sciences