Comparison of production systems and selection criteria of Ankole cattle by breeders in Burundi, Rwanda, Tanzania and Uganda.

A survey in Burundi, Rwanda, Tanzania and Uganda was conducted in order to determine the different production systems under which Ankole cattle are currently kept. Additionally, selection criteria of livestock keepers were documented. In Burundi, Rwanda and parts of Uganda, livestock keepers are sedentary and herds are small, whereas in the other areas Ankole cattle are kept in large herds, some of them still under a (semi-)nomadic system.

Iodothyronine deiodinases and the control of plasma and tissue thyroid hormone levels in hyperthyroid tilapia (Oreochromis niloticus).

Thyroid status is one of the most potent regulators of peripheral thyroid hormone metabolism in vertebrates. Despite this, the few papers that have been published concerning the role of thyroid hormones in the regulation of thyroid function in fish often offer conflicting data. We therefore set out to investigate the effects of tetraiodothyronine (thyroxine) (T4) or tri-iodothyronine (T3) supplementation (48 p.

Hormonal profile of growing male and female diploids and triploids of the blue tilapia,Oreochromis aureus, reared in intensive culture.

Triploidy as a result of thermal shock exposure of fertilized eggs decreases the growth rate ofOreochromis aureus as compared to their diploid controls, but this is due to the higher female ratio present in triploids (86%) and the lower growth rate of females. When females and males are considered separately, the growth rate is not significantly different in diploids and triploids. Since triploidy results in a malfunctioning steroidogenesis in females (mainly testosterone (T) and 17β-estradiol (E2)), but does not affect the growth rate, it is concluded that female gonadal steroids do not influence growth unless in pharmacological concentrations.

Evidence for the kidney as an important source of 5'-monodeiodination activity and stimulation by somatostatin in Oreochromis niloticus L.

Radioimmunoassay of 3,5,3'-triiodothyronine (T3) and thyroxine (T4) in the thyroidal region of mature male Oreochromis niloticus revealed stores of T4 but negligible levels of T3, yielding a very low T3/T4 ratio (0.3%). 5'-Deiodination (5-D) of T4 into T3 was examined in liver and kidney homogenates in vitro by radioimmunoassay of T3 with T4 as substrate.

Purification of tilapia thyrotropin from a crude pituitary homogenate by immunoaffinity chromatography using a matrix of antibodies against porcine follicle-stimulating hormone.

An immunoadsorbent matrix using antibodies against porcine follicle-stimulating hormone (pFSH), a high heterothyrotropic stimulant in tilapia, was used to purify tilapia thyrotropic hormone (t-TSH) from crude pituitary extracts. A homologous bioassay monitored TSH bioactivity during the purification. Thyroid hormones (thyroxine, T4; triiodothyronine, T3; and reverse triiodothyronine, rT3) and testosterone were measured in vivo in Tilapia nilotica.

Somatostatin increases plasma T3 concentrations in Tilapia nilotica in the presence of increased plasma T4 levels.

An injection of ovine growth hormone, porcine follicle stimulating hormone, and bovine thyrotropin stimulating hormone increased in Tilapia nilotica plasma concentrations of thyroxine (T4) and reverse triiodothyronine (rT3) after 4 and 8 hr, whereas plasma concentrations of T3 were unaffected. An injection of somatostatin (SRIF) alone did not influence thyroid hormone levels. If, however, SRIF was injected together with these hormones, which raised plasma T4, or together with T4 itself, an increase in plasma concentrations of T3 could be observed, whereas the increase in rT3 was less pronounced.

Stimulation of thyroid function by several pituitary hormones results in an increase in plasma thyroxine and reverse triiodothyronine in tilapia (Tilapia nilotica).

In this study, intravenous injection of several doses of porcine follicle stimulating hormone (pFSH: 0.002, 0.01, 0.