Fat mass and obesity associated protein (Fto) is a nucleic acid demethylase, with a preference for thymine or uracil, according to the recent structural data. This fact suggests that methylated single-stranded RNA, rather than DNA, may be the primary Fto substrate. Fto is abundantly expressed in all hypothalamic sites governing feeding behavior. Considering that selective modulation of Fto levels in the hypothalamus can influence food intake, we set out to investigate the effect of 48 h fasting on the Fto expression in lateral hypothalamic area, paraventricular, ventromedial and arcuate nucleus, the regulatory centres of energy homeostasis. We have demonstrated that 48 h fasting causes not only an increase in the overall hypothalamic levels of both Fto mRNA and protein, but also alters Fto intracellular distribution. This switch happens in some neurons of paraventricular and ventromedial nucleus, as well as lateral hypothalamic area, resulting in the majority of the enzyme being localized outside the cell nuclei. Interestingly, the change in the Fto intracellular localization was not observed in neurons of arcuate nucleus, suggesting that fasting did not universally affect Fto in all of the hypothalmic sites involved in energy homeostasis regulation. Both Fto mRNA and catechol-O-methyltransferaze mRNA were upregulated in the identical time-dependent manner in fasting animals. This fact, combined with the knowledge of the Fto substrate preference, may provide further insight into monoamine metabolism in the state of disturbed energy homeostasis.

SUMMARYThermal stressors such as low and high ambient temperature elicit an abundance of neuroendocrine responses including activation of the hypothalamo-pituitary-adrenal (HPA) axis and arginine vasopressin (AVP) release. The exposure to heat is a particularly interesting model for studying AVP action because this kind of stressor represents not only an unpleasant experience but also a threat to osmotic homeostasis. As AVP has long been recognized as a hormone involved in the modulation of HPA axis activity, the aim of this study was to elucidate the role of AVP in acutely heat-exposed rats using Nelivaptan, a selective vasopressin 1b receptor (V1bR) antagonist. Rats were exposed to high ambient temperature (38°C) for 60min. The circulating hormones were determined by ELISA or chemiluminescence, and intrapituitary adrenocorticotropic hormone (ACTH) and V1bR level were determined by western blot. The results obtained show that V1bR blockade negatively affected the increase in blood ACTH caused by heat exposure. This treatment alone, or in combination with Nelivaptan, decreased intrapituitary V1bR levels while circulating AVP concentration was increased under the same conditions. Furthermore, a strong correlation was observed between blood ACTH and corticosterone concentration. In conclusion, our results directly confirm the positive role of AVP in the regulation of ACTH secretion from the pituitary in animals exposed to heat. Moreover, the results suggest that AVP from the general circulation influences pituitary V1bR.

One of the useful properties of probiotic bacteria is their capacity to bind different targets, thus eliminating them through feces. It is supposed that one of these targets could be cadmium, a widespread environmental toxicant that causes various disturbances in biological systems. This study examined the protective effects of probiotic supplementation against cadmium-induced toxicity in the rat. The experiment was conducted in the course of 5 weeks. Animals were divided into four groups: (1) controls, (2) probiotics treated, (3) cadmium treated, and (4) probiotics + cadmium treated. The cadmium concentration was measured in the blood, liver, kidney, and feces, as well as the blood alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as biomarkers of the liver function. Histomorphological changes in the liver and kidney were also determined. Our results revealed that probiotics combined with cadmium increase this metal concentration in feces. As a result, blood, liver, and kidney Cd levels, as well as blood ALT and AST activities were lessened compared to the rat group treated with cadmium only. Besides, probiotics consumed simultaneously with cadmium attenuated histomorphological changes in the liver and kidney caused by cadmium. The rise in lactobacilli number in feces of rats treated simultaneously with cadmium and probiotics results in strong correlation with the increase of Cd concentration in their feces and the decrease of Cd concentration in their blood. We speculate that probiotics actively contribute to cadmium excretion through feces, probably, by its binding to their bacterial cell wall.

Abstract:The increased ambient temperature affects the function of hypothalamic-pituitary-adrenal (HPA) axis. Since the correlation among vasopressin (VP), adrenocorticotropic hormone (ACTH) and corticosterone (CORT) responses to various stressors have been long recognized, the aim of this study was to reveal the aforementioned hormones production and morphology of the pituitary gland after exposure to acute heat. Rats were exposed to high ambient temperature (38°C) for 20 or 60 minutes. The circulating hormones were determined by an ELISA test or chemiluminescence's method. The results obtained show the elevation in ACTH and CORT secretion depending on the duration of heat exposure. The VP concentration increased only after prolonged exposure to heat (60 min). The pituitary morphology was examined by routine and fluorescent immunohistochemistry as well as electron microscopy. Observed changes in the anterior and posterior pituitary well corresponded to circulating hormones, regarding the volume density of ACTH-immunopositive cells, percentage of ACTH immunopositive area v. total area and number of VP-immunopositive containing varicose fibers per total area. Acute heat exposure also induced changes in shapes of ACTH-immunopositive cells. Cells appeared stellate with numerous slender cytoplasmic processes and degranulated, which is the most obvious after 20 min. In addition, immunopositivity of endothelial and anterior pituitary cells for VP suggests its influence on ACTH secretion.

Rats have the ability to synthesize vitamin C in the liver. In the present work, we tested whether its additional intake improves antioxidative protection of the tissue. Thus, we studied the liver’s oxidative status in rats given two supplements of ascorbic acid over a four-week period of time. Our results confirmed that the additional intake of ascorbate improves the liver’s antioxidative defense in a dose-dependent manner. The explanation for the disproportion between the ratio of employed doses of vitamin C and their effects on the studied parameters probably lies in the mechanism of tissue accumulation of ascorbate and balance of its alimentary and endogenous availability

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In the hypothalamus, insulin takes on many roles involved in energy homoeostasis. Therefore, the aim of this study was to examine hypothalamic insulin expression during the initial phase of the metabolic response to fasting. Hypothalamic insulin content was assessed by both radioimmunoassay and Western blot. The relative expression of insulin mRNA was examined by qPCR. Immunofluorescence and immunohistochemistry were used to determine the distribution of insulin immunopositivity in the hypothalamus. After 6-h fasting, both glucose and insulin levels were decreased in serum but not in the cerebrospinal fluid. Our study showed for the first time that, while the concentration of circulating glucose and insulin decreased, both insulin mRNA expression and insulin content in the hypothalamic parenchyma were increased after short-term fasting. Increased insulin immunopositivity was detected specifically in the neurons of the hypothalamic periventricular nucleus and in the ependymal cells of fasting animals. These novel findings point to the complexity of mechanisms regulating insulin expression in the CNS in general and in the hypothalamus in particular.

Understanding osmolarity and tonicity is one of the more challenging endeavors undertaken by students of the natural sciences. We asked students who completed a course in animal physiology to submit an essay explaining what they found most perplexing about this subject, and what in-class activities proved most useful to them. Students had difficulty distinguishing osmolarity from tonicity and determining tonicity based on the solution’s composition. The most useful activities were questions requiring simultaneous consideration of both osmolarity and tonicity. Problems that require calculating osmotic concentration and the volumes of body fluid compartments after administration or loss of various solutions emphasize the significance of osmolarity and tonicity in the context of systemic homeostasis and clinical medicine. We hope that our approach to teaching osmolarity and tonicity will prove useful to physiology lecturers who are looking for new ways of introducing this complicated topic to their health professions students.