Seasonal variations in the adrenal cortex cells of the house sparrow, Passer domesticus (L.), with special reference to a possible zonation

Effects of experimentally elevated testosterone on plasma corticosterone and corticosteroid-binding globulin in dark-eyed juncos (Junco hyemalis)

An earlier study of free-living male dark-eyed juncos found an increase in plasma corticosterone (B) in response to experimental elevation of plasma testosterone (T) (E. D. Ketterson et al., 1991, Horm. Behav. 25, 489-503). To investigate whether the increase was caused by enhanced secretion of corticosterone or by a slower clearance rate, or both, we exposed 52 captive yearling male dark-eyed juncos (Junco hyemalis) to day lengths corresponding to those of spring and implanted them with one or two testosterone-filled or sham implants (10 T-I, 22 T-II, and 20 C-males). We then examined the effect of experimentally elevated testosterone on plasma corticosterone and on corticosteroid-binding globulin (CBG), as measured by the ability of steroid-stripped plasma to bind labeled corticosterone. Plasma samples were taken five times, 2 weeks before experimental prolongation of day length and approximately every 3 weeks thereafter. Treatment with testosterone increased both plasma testosterone and plasma corticosterone two to three times above control levels, and the degree of elevation was dose-dependent. Only when all treatment groups were pooled, however, were plasma testosterone and corticosterone significantly correlated. The relationship between plasma corticosterone and time required to bleed the birds was similar for all three treatment groups, suggesting that there was no effect of treatment on the stress response. Testosterone significantly increased the capacity of the plasma to bind corticosterone, presumably because it contained more CBG, when compared to the plasma of controls. However, treatment with testosterone did not affect the affinity of the plasma for corticosterone. It seems likely that exogenous testosterone elevated corticosterone by slowing the corticosterone clearance rate via an increase in CBG. It is not clear what the net effect of chronic elevation of testosterone would be on the availability of corticosterone to target tissues.

Effects of corticosterone, metapyrone, and ACTH on testicular function at different stages of the breeding cycle in migratory redheaded bunting, Emberiza bruniceps

To study the seasonal reproductive responses, corticosterone (0.2 and 2 micrograms/day), metapyrone (0.6 mg/day), and ACTH (0.25 IU/day) were administered in male redheaded bunting, Emberiza bruniceps, during different phases of the annual gonadal cycle. All of the three treatments inhibited gonadal growth during the preparatory phase, suggesting that during the early stage of annual gonadal growth, an optimum level of the hormones of pituitary-adrenal axis is essential. In the progressive and breeding phase, while corticosterone administration had no effect, metapyrone inhibited the annual gonadal development, suggesting the necessity of increasing or increased adrenal steroid hormone during this phase. In the regressive phase, while corticosterone enhanced the rate of gonadal regression, metapyrone treatment did not allow the gonad to regress. Further, ACTH administration induced full breeding condition in the regressing gonad. It is suggested that while a higher level of adrenal steroids and a low ACTH (by exogenous corticosterone) may enhance the testicular regression, moderate levels of ACTH (caused by exogenous metapyrone) did not allow regression and increased ACTH levels (by exogenous ACTH) caused full development of the regressing gonad. Thus the sensitivity of the neuroendocrine-gonadal axis not only varies in response to photoperiod, but the reproductive system also responds differently to pharmacological administration of the above three hormones and drugs during different phases of the breeding cycle.

Cytological differentiation of the interrenal tissue of the Japanese quail, Coturnix coturnix

As reported for several other avian species there are clearly distinguishable subcapsular (SCZ) and inner (IZ) zones of interrenal tissue in the Japanese quail. The SCZ contains large columnar cells (type I) with rounded nuclei, polymorphic mitochondria with shelf-like cristae, and relatively small numbers of lipid droplets. The IZ contains two and possibly three types of cells. Type II consists of large columnar cells with moderately dense cytoplasm containing large numbers of lipid droplets and many rounded mitochondria with tubular cristae. Smooth endoplasmic reticulum (SER) and Golgi apparatus are well developed; coated vesicles occur in Golgi area and at the cell surface. Type-III cells occur in IZ and especially in its more peripheral areas. They are columnar cells with strikingly clear cytoplasm (in comparison with type II) containing mitochondria with plate-like cristae and tubular SER. Type-IV cells are sparsely distributed in IZ and occur rarely in SCZ. Type IV may be a degenerating phase of type III. After adenohypophysectomy or section of portal vessels type-I cells atrophy somewhat with a decrease in lipid droplets; type-II cells, also atrophy with conspicuous increase in size and number of lipid droplets, enlargement of mitochondria, and gradual disappearance of Ser; type-III cells decrease in number whereas type-IV cells increase. After injection of ACTH, type-I cells enlarge and their mitochondria, SER and Golgi apparatus become more conspicuous; there is a decrease in lipid droplets in type-II cells and a development of SER, polysomes and Golgi apparatus; there is also a decrease in lipid droplets and a development of SER in type-III cells after injection of 2 IU ACTH and an almost complete disappearance of lipid droplets after 4 IU ACTH; type-IV cells increase in number.