Changes in luteinizing hormone secretion after estradiol treatment in prepubertal Nelore heifers

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Paracoccidioidomycosis in the region of Botucatu (state of São Paulo, Brazil). Evaluation of serum thyroxine (T4) and triiodothyronine (T3) levels and of the response to thyrotropin releasing hormone (TRH)

T4, T3 and TSH serum levels were measured in 25 patients with paracoccidioidomycosis. Thyroid T3 reserves were measured on the basis of the increase in T3 (ΔT3) 2 h after intravenous injection of 200 μg TRH, and pituitary TSH reserves were measured on the basis of TSH increase (ΔTSH) 20 min after the same injection. Twenty healthy volunteers with no history of thyroid disease were used as controls. When the two groups were compared, the following results were obtained: (a) there was no significant difference in mean T4, T3, ΔTSH between groups; (b) reduced T3 levels were detected more frequently in patients with paracoccidioidomycosis, especially among those with the acute form of the disease or with the severely disseminated chronic form. The results suggest the occurrence of a reduction in peripheral conversion of T4 to T3, but do not indicate the occurrence of hypothyroidism in any of its forms (thyroid, pituitary or hypothalamic). © 1988 Kluwer Academic Publishers.

Pressor, dipsogenic, natriuretic and kaliuretic responses to central carbachol in rats with lesion of the medial septal area

In the present study we investigated the effect of electrolytic lesion of the medial septal area (MSA) on the dipsogenic, natriuretic, kaliuretic and pressor responses elicited by intracerebroventricular (i.c.v.) injection of the cholinergic agonist carbachol. Freely moving rats with sham or MSA lesion (1-7 days and 14-18 days) and a stainless steel cannula implanted into the lateral ventricle were studied. In sham rats, i.c.v. injection of carbachol (7.5 nmol) produced an increase in water intake (10.2 ± 1.5 ml/h), mean arterial pressure (MAP) (35 ± 5 mmHg) and urinary Na+ and K+ excretion (551 ± 83 and 170 ± 17 μEq 120 min, resp.). The pressor (18 ± 3 and 14 ± 4 mmHg, resp.) and natriuretic responses (178 ± 58 and 172 ± 38 μEq 120 min) produced by i.c.v. carbachol in acute or chronic MSA-lesioned rats were reduced. No change was observed in urinary K+ excretion and a reduced water intake (5 ± 1.3 ml/h) was observed only in acute MSA-lesioned rats. These results suggest that the MSA plays an important role for the pressor and natriuretic responses induced by central cholinergic activation in rats. A small influence of this structure on water intake may also be suggested. © 1991.

Opiate activation suppresses the drinking, pressor and natriuretic responses induced by cholinergic stimulation of the medial septal area

The present study investigates the participation and interaction between cholinergic and opiate receptors of the medial septal area (MSA) in the regulation of Na+, K+ and water excretion, drinking and blood pressure regulation. Male Holtzman rats were implanted with stainless steel cannulae opening into the MSA. Na+, K+ and water excretion, water intake and blood pressure were measured after injection of carbachol (cholinergic agonist), FK-33824 (an opiate agonist) + carbachol or naloxone (an opiate antagonist) + carbachol into MSA. Carbachol (0.5 or 2.0 nmol) induced an increase in Na+ and K+ excretion, water intake and blood pressure and reduced the urinary volume. FK-33824 reduced the urinary volume and Na+ and K+ excretion. Previous injection of FK-33824 (100 ng) into the MSA blocked the increases in Na+ and K+ excretion, water intake and blood pressure induced by carbachol. Naloxone (10 μg) produced no changes in the effect of 2.0 nmol carbachol, but potentiated the natriuretic effect induced by 0.5 nmol dose of carbachol. These data show an inhibitory effect of opiate receptors on the changes in cardiovascular, fluid and electrolyte balance induced by cholinergic stimulation of the MSA in rats. © 1992.

Role of luteinizing hormone in follicle deviation based on manipulating progesterone concentrations in mares

The effects of several doses of progesterone on FSH and LH concentrations were used to study the role of the gonadotropins on deviation in growth rates of the two largest follicles during the establishment of follicle dominance. Progesterone was given to pony mares at a daily dose rate of 0 mg (controls), 30 mg (low dose), 100 mg (intermediate dose), and 300 mg (high dose). All follicles ≥ 6 mm were ablated at Day 10 (Day 0 = ovulation) to initiate a new follicular wave; prostaglandin F(2α) was given to induce luteolysis, and progesterone was given from Days 10 to 24. The low dose did not significantly alter any of the ovarian or gonadotropin end points. The high dose reduced (P < 0.05) the ablation-induced FSH concentrations on Day 11. Maximum diameter of the largest follicle (17.2 ± 0.6 mm) and the second- largest follicle (15.5 ± 0.9 mm) in the high-dose group was less (P < 0.04) than the diameter of the second-largest follicle in the controls (20.0 ± 1.0 mm) at the beginning of deviation (Day 16.7 ± 0.4). Thus, the growth of the two largest follicles was reduced by the high dose, presumably through depression of FSH, so that the follicles did not attain a diameter characteristic of deviation in the controls. The intermediate dose did not affect FSH concentrations. However, the LH concentrations increased in the control, low, and intermediate groups, but then decreased (P < 0.05) in the intermediate group to pretreatment levels. The LH decrease in the intermediate group occurred 2 days before deviation in the controls. The maximum diameter of the largest follicle was less (P < 0.0001) in the intermediate group (27.3 ± 1.8 mm) than in the controls (38.9 ± 1.5 mm), but the maximum diameter of the second-largest follicle was not different between the two groups (19.0 ± 1.1 vs. 20.3 ± 1.0 mm). Thus, the onset of deviation, as assessed by the second-largest follicle, was not delayed by the decrease in LH. Diameter of the largest follicle by Day 18 in the intermediate group (23.1 ± 1.6 mm) was less (P < 0.05) than in the controls (28.0 ± 1.0 mm). These results suggest that circulating LH was not involved in the initiation of dominance (inhibition of other follicles by the largest follicle) but was required for the continued growth of the largest follicle after or concurrently with its initial expression of dominance.

Experimental control of the effect of extra doses of juvenile hormone on bee development: The case of the wax glands of Apis mellifera (Hymenoptera: Apidae)

Experiments on the effect of topical application of the synthetic juvenile hormone (JH-III) and of the solvent used to dissolve the hormone on the development of the wax glands of workers of Apis mellifera, were made. The results show that it was impossible to determine the effect of the juvenile hormone (JH) apart from its solvent (acetone), which also alters the developmental pattern of the gland. Most of the experiments reported in scientific literature do not consider the effect of the solvent, analyzing the results by only comparing the treatment with the hormone plus solvent to a control without any treatment. The data presented suggests that this kind of procedure compromises the evaluation of the real JH effect.

Alterations induced by juvenile hormone in glandular cells of the Apis mellifera venom gland I - Application on the larvae (Hymenoptera: Apidae)

Histological analyses were made in order to evaluate the effects of the topic application of a synthetic juvenile hormone (JH-III Sigma) on the development of the venom glands in workers of Apis mellifera. Three experimental groups were used: the first received 1 μl of a dilution of the juvenile hormone in hexane (2μg/μl); the second group received 1 μl of hexane; and the third group, the control, did not receive any kind of treatment. The application was made on larvae at the beginning of the fifth instar and the glands were collected at different developmental stages. The results showed that the application of the diluted hormone, as well as the hexane alone, accelerated gland development in relation to the control group at all developmental stages studied. These data suggest that the juvenile hormone acts on the development of the venom gland; nevertheless, this action could be amplified by the effect of the solvent used in the present work, as well as in other studies concerning this matter.

Juvenile hormone promotes changes in the expression of hypopharyngeal gland proteins of worker Apis mellifera (Hymenoptera: Apidae)

The present investigation compares the protein electrophoreses profiles of the hypopharyngeal glands of 12 and 25 day old Apis mellifera workers, some of which were experimentally treated with an analogue of juvenile hormone in the moment of the emergence while others were not treated. According to the evaluation of the presented variations by four main bands, it is concluded that the analogue juvenile hormone changes the glandular genetic expression pattern, promoting the disappearance of two from the four main bands in 25 day old workers. The effect of this hormone is discussed as an hypopharyngeal maturation inductor, in synergetic action with the bee age acting early in the glandular cycle.

Growth hormone mRNA expression in the pituitary of Bos indicus and Bos taurus x Bos indicus crossbred young bulls treated with recombinant bovine somatotropin

The effects of breed and of recombinant bovine somatotropin (rbST) treatment on growth hormone gene expression were studied in young bulls. The experiment was completely randomized in a [2 × 2]-factorial arrangement, using two levels of rbst (0 or 250 mg/animal/14 days), and two breed groups (Nelore and Simmental x Nelore crossbred). A CDNA encoding Bos indicus growth hormone was cloned and sequenced for use as a probe in Northern and dot blot analyses. Compared to the Bos taurus structural gene, the Bos indicus CDNA was found to begin 21 bases downstream from the transcription initiation site and had only two discrepancies (C to T at position 144-His and T to C at position 354-Phe), without changes in the polypeptide sequence. However, two amino acid substitutions were found for Bubalus spp., which belong to the same tribe. The rbst treatment did not change any of the characteristics evaluated (body and pituitary gland weights, growth hormone MRNA expression level). Crossbred animals had significantly higher body weight and heavier pituitaries than Nelore cattle. Pituitary weight was proportional to body weight in both breed groups. Growth hormone MRNA expression in the pituitary was similar (P>0.075) for both breed and hormonal treatment groups, but was 31.9% higher in the pure Nelore group, suggesting that growth hormone gene transcription regulation differs among these breeds.

Influence of the application of juvenile hormone on the haemolymph total proteins and electrophoretic pattern of worker larvae of Apis mellifera

The aim of the present work was to verify the influence of the juvenile hormone (JH) applied on worker larvae of Apis mellifera 2 to 5 days old over the haemolymph total protein and electrophoretic pattern. Each larvae received topical applications of 1 ml of a solution of JH in hexane (1 μg/ml) on their 2 nd, 3 rd 4 th and 5 th day after hatching and had the amount and electrophoretic pattern of proteins from the haemolymph analyzed during the remaining days of their life. As a control, haemolymph of larvae of the same age that did not receive any kind of treatment was analyzed. The results show that the application of JH on larvae 3 or more days old affect the amount and electrophoretic pattern of the proteins, with this effect lasting through the subsequent days.