Endocrine factors in the hypothalamic regulation of food intake in females: a review of the physiological roles and interactions of ghrelin, leptin, thyroid hormones, oestrogen and insulin.

Controlling energy homeostasis involves modulating the desire to eat and regulating energy expenditure. The controlling machinery includes a complex interplay of hormones secreted at various peripheral endocrine endpoints, such as the gastrointestinal tract, the adipose tissue, thyroid gland and thyroid hormone-exporting organs, the ovary and the pancreas, and, last but not least, the brain itself. The peripheral hormones that are the focus of the present review (ghrelin, leptin, thyroid hormones, oestrogen and insulin) play integrated regulatory roles in and provide feedback information on the nutritional and energetic status of the body.

Effects of energy restriction on thyroid hormone metabolism in chickens.

Energy restriction induces changes in thyroid hormone economy in the form of a complex adaptation mechanism, in order to conserve energy storage and protein reserves. In the present work, thyroid hormone serum concentrations, hepatic deiodinase enzyme activities and hepatic deiodinase mRNA expression were examined after feed restriction and fasting. We demonstrate that during energy restriction, T 3 concentration is lowered due to a decreased T 4 activation and increased T 3 inactivation.

Glycogenic induction of thyroid hormone conversion and leptin system activation in the liver of postpartum dairy cows.

In the regulation of energy metabolism, the liver plays an important role in the reinforcement of energy production. In periparturient cows the energy homeostasis turns into a negative energy balance that may shift the physiological regulation of energy balance towards pathological processes. Propylene glycol (PG), as a complementary source of energy used in the nutrition of dairy cows, alters systemic thyroid hormone economy; however, the exact mechanism through which highly glycogenic feed supplements impact liver metabolism is little known.

Comparison of 3H-thymidine incorporation and CellTiter 96 aqueous colorimetric assays in cell proliferation of bovine mononuclear cells.

A rapid colorimetric non-radioactive assay for the determination of bovine mitogen-induced lymphocyte proliferation in cell culture was evaluated using a novel tetrazolium compound (MTS) and an electron coupling reagent (PMS) provided in the CellTiter 96 kit (Promega). The results of the new method were compared with those of the 3H-thymidine incorporation assay using parallels obtained from the same lymphocyte population. The concentrations used in the cell suspension of primary cultured lymphocytes resulted in a significant signal/background ratio when cells were prepared from peripheral blood, spleen or mesenteric lymph nodes.

Impaired local deiodination of thyroxine to triiodothyronine in dogs with symmetrical truncal alopecia.

Thyroid dysfunction causes certain dermatological alterations in dogs. Insufficient delivery of thyroid hormone to the skin may originate not only from inadequate thyroid function but also from impaired local activation of thyroxine in the target organ. Thyroid parameters and deiodination were investigated in healthy dogs (group C) and in dogs with cutaneous lesions associated with hypothyroidism (group H) or with a low-T3 syndrome (group LT).