The effect of hypothalamic lesions on adrenal function in intact and adenohypophysectomized cockerels

Activation of thymocyte deoxyribonucleic acid degradation by endogenous glucocorticoids

Immature lymphocytes in the thymus gland are killed by treatment with exogenous glucocorticoids. This steroid-mediated lymphocytolysis is preceded by numerous alterations in lymphocyte metabolism, including a DNA-degrading process in which the genome is cleaved at internucleosomal intervals. To date, this process has only been characterized by treating lymphocytes in vitro with glucocorticoids or by exogenous treatment of whole animals with adrenal steroids. To determine whether thymocyte DNA degradation could be activated by endogenous glucocorticoids, 4-wk-old chicks were treated with porcine adrenocorticotropic hormone (ACTH). This procedure elevated serum corticosterone levels approximately 80-fold within 2 h of hormone treatment. Following ACTH administration, thymocyte DNA was isolated and analyzed by agarose gel electrophoresis. The ACTH activated a DNA-degrading process that generated internucleosomal fragments of DNA identical in size to those observed following exogenous treatment with synthetic or naturally occurring glucocorticoids. Furthermore, this response could be inhibited by the glucocorticoid antagonist RU486 (17 beta-hydroxy-11 beta, 4-dimethylaminophenyl-17 alpha-propynl-estra-4,9,diene-3-one), indicating that adrenal steroids activate this process via the glucocorticoid receptor. These results demonstrate that lymphocyte DNA degradation does not result solely from exogenous glucocorticoid treatment; moreover, endogenous glucocorticoids can mediate this process and may thereby play an important role in thymic gland function.

Distribution of glucocorticoid receptor-like immunoreactivity in the brain, and its relation to CRF and ACTH immunoreactivity in the hypothalamus of the japanese quail, Coturnix coturnix japonica

Monoclonal antibody (MAb49) against the rat liver glucocorticoid receptor was used to evaluate glucocorticoid receptor (GR) immunoreactive structures in the brain of the japanese quail, Coturnix coturnix japonica. Using the avidin-biotin technique, the immunoreaction was present in the nerve cell nuclei in intact male birds. High density of glucocorticoid receptor-like immunoreactivity was found in the tubero-infundibular area, nucleus paraventricularis, posteromedialis and lateralis hypothalami, lateral septum and in some brainstem nuclei. Cerebellar cortex was also immunopositive. In contrast to mammals, no immunoreactive cell nuclei were found in the hippocampal region. The glucocorticoid receptors were colocalized with adrenocorticotropin (ACTH) immunoreactivity in the tubero-infundibular region, while corticotropin releasing factor (CRF) positive cells in the paraventricular nucleus did not contain glucocorticoid receptor-like immunoreactivity in their cell nuclei.

Corticosterone and aldosterone dose-dependent responses to ACTH and angiotensin II in the duck (Anas platyrhynchos)

The effects of [1-24]ACTH, [5-Val]angiotensin II, and potassium (K+) on the secretion of corticosterone and aldosterone by tissue slices from the subcapsular (SCZ) and inner (IZ) zones of the duck adrenal gland were determined using incubation and superfusion systems. Both methods demonstrated that the release of corticosterone and aldosterone from IZ and SCZ cells was dependent on the ACTH dose concentration. The IZ cells produced more corticosterone than the SCZ cells in response to stimulation with 1-1000 ng ACTH/ml. The dose response by aldosterone from the cells of the SCZ and the IZ were comparable, but the proportion of aldosterone per total amount of steroid released was greater by cells of the SCZ (11.3%), than by cells of the IZ (3.6%). Elevating the K+ concentration in the incubation medium from 4.0 to 6.5 and 11.2 mM did not directly stimulate corticosteroid release or potentiate the stimulatory effect of ACTH. Superfusion with 10(-12) to 10(-5) M AII stimulated the release of aldosterone from the SCZ cells but had no detectable effect on the IZ and failed to stimulate corticosterone release from either the SCZ or IZ cells. The results presented here demonstrate that in the bird stimulation for the release of corticosterone and aldosterone are different. Methodology for superfusion of adrenal tissue and for the direct radioimmunoassay of aldosterone and corticosterone in the superfusate are described.

Localization of corticotropin-releasing factor-containing neurons in the brain of the domestic fowl. An immunohistochemical study

The corticotropin-releasing factor (CRF)-containing neurons were investigated in the brain of the domestic fowl by means of the peroxidase-antiperoxidase technique at the light-microscopic level. The detection of CRF-immunoreactivity was facilitated by silver intensification. CRF-containing perikarya were found in the paraventricular, preoptic and mammillary nuclei of the hypothalamus and in some extrahypothalamic areas (nuclei dorsomedialis and dorsolateralis thalami, nucleus accumbens septi, lobus parolfactorius, periaqueductal gray of the mesencephalon, nucleus oculomotorius ventralis). Immunoreactive nerve fibers and terminals were demonstrated in the external zone of the median eminence and the organum vasculosum of the lamina terminalis. These results indicate that an immunologically demonstrable CRF-neurosecretory system also exists in the avian central nervous system.

Effect of acute stress on catecholamine content in the hypothalamic nuclei of Japanese quail

Concentration of noradrenaline, adrenaline and dopamine in eight hypothalamic nuclei or areas (nucleus hypothalamicus medialis anterior, n. periventricularis magnocellularis, n. hypothalamicus lateralis anterior, n. hypothalamicus medialis posterior, n. hypothalamicus lateralis posterior, eminentia medialis, n. tuberis, area hypothalamica posterior) have been determined by a sensitive radioenzymatic micromethod in male Japanese quail restrained for 30 min. In control quail the highest concentrations were found in the a. hypothalamica posterior, n. periventricularis magnocellularis and n. hypothalamicus medialis anterior; the lowest was in the n. hypothalamicus medialis posterior. After restraint, noradrenaline concentrations decreased in the n. periventricularis magnocellularis and n. hypothalamicus medialis posterior. However, the concentration of adrenaline increased in the n. tuberis under the same conditions. In stressed animals the dopamine concentration was lower than in controls in the n. periventicularis and higher in the n. tuberis.

Inhibition of adrenocortical function by intravenous administration of sodium pentobarbital in cocks

The response of awake and anesthesized cocks with sodium pentobarbital to stressful stimuli has been examined. The stressful stimuli was immersion in cold water. In the awake cocks plasma corticosterone concentration was increased about 4 fold; they started shivering shortly after immersion and recovered after cessation of the treatment. In the anesthesized ones there was no increase in plasma corticosterone concentration, they did not shiver and died shortly after immersion.