Thermogenic activity of growth hormone transgenic mice

The objective was to determine the effect of a mouse metallothionein/bovine growth hormone transgene on resting metabolic rate (RMR), cold-induced thermogenesis, and beta-agonist stimulated nonshivering thermogenesis in mice. Non-transgenic littermates were used as controls. Open-circuit indirect calorimetry was used to assess RMR and cold-induced thermogenesis in 64 mice. Air temperature in the chamber was set at 31 degrees C for RMR and was decreased to 28, 25, 21, or 17 degrees C to determine cold-induced thermogenesis. Response to the beta-agonist isoproterenol was evaluated by monitoring changes in colonic temperature of 34 mice upon injection of the drug or saline. Despite the fact that RMR tended to be lower in transgenics than in nontransgenics, at 31 degrees C transgenic mice were able to regulate colonic temperature at the same level as nontransgenics, but colonic temperature decreased in transgenics relative to nontransgenics as air temperature was reduced. For each degree decrease in air temperature between 31 and 17 degrees C, nontransgenic mice increased heat production by 1.03 +/- .10 watt/kg, whereas transgenic mice increased it by only .56 +/- .08 watt/kg, indicating that the thermogenic response of transgenics to cold was inferior. The magnitude of the maximal increase in colonic temperature after isoproterenol injection was similar for both groups, but the response was slower in transgenics. We suggest that lean body mass and substrate availability for shivering thermogenesis are reduced in transgenics relative to total body weight, and that they allow colonic temperature to decrease to conserve energy.

SEX DETERMINATION IN BEES .30. EFFECTS OF JUVENILE-HORMONE ON THE DEVELOPMENT OF TERGAL GLANDS IN MELIPONA

Worker larvae of Melipona rufiventris, M. quadrifasciata and M. compressipes were treated topically with juvenile hormone (JH) during the cocoon-spinning phase. Examination of the tergites of the queens obtained following JH application showed induced differentiation into adults with full female (queen) traits. Melipona workers had tergal glands only in tergite II, whereas natural and JH-induced queens had tergal glands in tergite II plus additional glands in at least one other of tergites Ill to VII.

Effects of central alpha-adrenergic agonists on hormone-induced 3% NaCl and water intake

Male rats received intracerebroventricular (ICV) renin (600 ng) or daily subcutaneous injections of deoxycorticosterone (5 mg) to induce 3% NaCl and water intake. Noradrenaline (NOR; 40-160 nmol) and clonidine (CLO; 5-20 nmol) injected ICV. induced 70 to 100% inhibition of the intakes. Phenylephrine (PHE; 40-160 nmol) injected ICV induced 60 to 95% inhibition of the intakes. NOR and PHE induced a stronger inhibition on the 3% NaCl intake induced by renin than on the intake induced by deoxycorticosterone (DOC), and CLO did the opposite. CLO was always more effective than PHE to induce inhibition of the intakes. The results suggest that NOR inhibits hormone (angiotensin II, aldosterone)-induced NaCl intake by acting mainly on alpha(2)-adrenergic receptors.

ENDOCRINE INTERACTION BETWEEN ZINC AND PROLACTIN - AN INTERPRETATIVE REVIEW

Zinc plays a very important role in animal and human metabolism. Nowadays, it is one of the most extensively studied trace element, since its sphere of action has been demonstrated to be very broad. From the biochemical standpoint, it controls more than 300 different enzymes, many of them involved with intermediary metabolism, DNA and RNA synthesis, gene expression, and immunocompetence. It also plays a significant role in hormonal homeostasis, since it can interact with almost all hormones. Zn2+ is closely related to the thyroid and steroid hormones, insulin, parathormone, and pituitary hormones, particularly prolactin (PRL). Zn2+ can inhibit PRL secretion within a range of physiologically and pharmacologically relevant concentrations. This property has raised the possibility of clinical applications of zinc. In this article, we review the Literature on the subject in an attempt to provide a comprehensible general view.

Non-ventilation during early incubation in combination with dexamethasone administration during late incubation: 1. Effects on physiological hormone levels, incubation duration and hatching events

This study investigated the effect of non-ventilation of the incubator during the first 10 days of incubation and its combination with dexamethasone administration at day 16 or 18 of incubation on hatching parameters and embryo and post-hatch chick juvenile physiology. A total of 2400 hatching eggs produced by Cobb broiler breeders were used for the study. Blood samples were collected at day 18 of incubation, at internal pipping stage (IP), at the end of hatch (day-old chick) and at 7-daypost-hatch for T-3, T-4 and corticosterone levels determination. From 448 to 506 h of incubation, the eggs were checked individually in the hatcher every 2 h for pipping and hatching. The results indicate that non-ventilation during the first 10-day shortened incubation duration up to IP, external pipping (EP) and hatch, had no effect on hatchability and led to higher T-3 levels at IP but lower corticosterone levels at 7-day-post-hatch. The injection of dexamethasone at days 16 and 18 of incubation affected hatching and blood parameters in both the ventilated and non-ventilated embryos differentially and the effect was dependent on the age of the embryo. Dexamethasone increased T-3 levels and T-3/T-4 ratios but the effect was greater with early non-ventilation of eggs. Dexamethasone decreased hatchability but the effect was greater when injected at day 16 and especially in ventilated embryos. The effects of incubation protocols and dexamethasone treatments during incubation were still apparent in the hatched chicks until 7 days of age. The changes in T-3, T-4 and corticosterone levels observed in response to the early incubation conditions and late dexamethasone treatments in this study suggest that incubator ventilation or non-ventilation may influence the hypothalamic-pituitary-adrenal axis (HPA) regulation of stress levels (in terms of plasma corticosterone levels) and thyroid function in the embryo with impact on incubation duration, hatching events and early post-hatch life of the chick. Our results also suggest that some stages of development are more sensitive to dexamethasone administration as effects can be influenced by early incubation protocols. (c) 2006 Elsevier B.V. All rights reserved.

Mispatterning in the ommatidia of Apis mellifera pupae treated with a juvenile hormone analogue

To further understand the function of morphogenetic hormones in honeybee eye differentiation, the alterations in ommatidial patterning induced by pyriproxyfen, a juvenile hormone (JH) analogue, were studied by scanning and transmission electron microscopy. Prepupae of prospective honeybee workers were treated with pyriproxyfen and the effects on ommatidial differentiation were described at the end of the pupal development. The results show that the entire ommatidia, i.e., the dioptric as well as the receptor systems, were affected by the JH analogue. The wave of ommatidial differentiation, which progresses from the posterior to the anterior region of the pupal eyes, was arrested. In treated pupae, the rhabdomeres only differentiated at the apical axis of the retinula, the secondary and tertiary pigment cells did not develop their cytoplasm protrusions, and the cone cell quartet did not pattern correctly. Simultaneously, an intense vacuolization was observed in cells forming ommatidia. In a previous study we showed that pyriproxyfen exerts an inhibition on pupal ecdysteroid secretion. In this sense, the arrested ommatidial differentiation in pyriproxyfen-treated pupae could be due to a secondary effect resulting from an alteration in pupal ecdysteroid titers. J. Morphol. 249:89-99, 2001. (C) 2001 Wiley-Liss, Inc.

Clinical features and genetic analysis of four Brazilian kindreds with resistance to thyroid hormone

Objective Resistance to thyroid hormone (RTH) is a dominantly inherited syndrome of reduced tissue responsiveness to thyroid hormone usually due to mutations located in the ligand-binding domain and adjacent hinge region of the thyroid hormone receptor beta (TR beta). In the present report we describe the clinical and laboratory characteristics and the genetic analysis of patients with this rare disorder from a Brazilian population.Patients Four unrelated Brazilian families with diagnosis of RTH were studied. Age at diagnosis varied from 14 months to 29 years.Results All affected individuals were clinically euthyroid, except for one patient who presented immediately after birth with hyperthyroidism. All individuals had tachycardia and goitre, elevated concentrations of free thyroid hormones and reduced sensitivity to thyroid hormone. Direct sequencing analysis of the TR beta gene revealed four previously reported mutations: c.949G -> A, c.1313G -> A, c.1357C -> A and c.1358dupC in families A, B, C and D, respectively.Conclusion the present report shows that the frequent mutations described in the thyroid hormone receptor worldwide are also present in the Brazilian population, which is characterized by a variable ethnic background.

Hypothalamic melanin-concentrating hormone is induced by cold exposure and participates in the control of energy expenditure in rats

Short-term cold exposure of homeothermic animals leads to higher thermogenesis and food consumption accompanied by weight loss. An analysis of cDNA-macroarray was employed to identify candidate mRNA species that encode proteins involved in thermogenic adaptation to cold. A cDNA-macroarray analysis, confirmed by RT-PCR, immunoblot, and RIA, revealed that the hypothalamic expression of melanin-concentrating hormone (MCH) is enhanced by exposure of rats to cold environment. The blockade of hypothalamic MCH expression by antisense MCH oligonucleotide in cold-exposed rats promoted no changes in feeding behavior and body temperature. However, MCH blockade led to a significant drop in body weight, which was accompanied by decreased liver glycogen, increased relative body fat, increased absolute and relative interscapular brown adipose tissue mass, increased uncoupling protein 1 expression in brown adipose tissue, and increased consumption of lean body mass. Thus, increased hypothalamic MCH expression in rats exposed to cold may participate in the process that allows for efficient use of energy for heat production during thermogenic adaptation to cold.

Benefits of soy germ isoflavones in postmenopausal women with contraindication for conventional hormone replacement therapy

Objective: To evaluate the effects of isoflavones on vasomotor symptoms and blood lipids in postmenopausal women with contraindication for conventional hormone replacement therapy (HRT). Methods: This prospective, double-blind and placebo-controlled study included 50 postmenopausal women randomly divided into two groups: 25 women on soy germ isoflavones (60 mg per day, capsules) and 25 women on placebo. Inclusion criteria included: non-vegetarian, non-asian women whose last menstruation dated at least 12 months prior to the beginning of the study, With FSH > 40 mIU/ml, hot flushes and contraindication for HRT, not using tamoxifen or antibiotic and no disease of the gastrointestinal tract. For 6 months, the Kupperman menopausal index (KMI), the vaginal cytological maturation value (MV) and both hormonal and lipid profiles were assessed. The t-test and analysis of variance (ANOVA) were employed to compare the two groups. Results: In both groups, a decreased KI rate was observed. However, isoflavone was significantly superior to placebo in reducing hot flushes (44% versus 10%, respectively) (P < 0.05). After 6 months, the isoflavone group showed increased estradiol levels with unchanged FSH, LH, and vaginal cytology, and a reduction of 11.8% in LDL and an increase of 27.3% in HDL (P < 0.05). In the placebo group, just a reduction in MV was observed after 6 months (P < 0.05). Conclusions: Soy germ isoflavone exerted favorable effects on vasomotor symptoms and lipid profile, showing itself to be an interesting alternative therapy for the postmenopausal women with contraindication for conventional HRT. (C) 2003 Elsevier B.V.. All rights reserved.