Glutamic acid decarboxylase in different areas of the developing chick central nervous system.

The temporal course of the development of GAD activity in GABAergic neurons was studied in the chick retina, optic lobe and cerebellum. The developmental pattern of GAD activity was similar in the three areas studied, showing typical sigmoideal curves, which reached a maximal value at the 3rd post-hatching day. Kinetic studies during development revealed that Km remained unchanged while Vmax increased 3-fold in the retina (48.99 +/- 0.84 nmol/hr/mg protein), almost 4-fold in the optic lobe (162.77 +/- 4.32 nmol/hr/mg protein) and 3.5 fold in the cerebellum (69.30 +/- 1.26 nmol/hr/mg protein). The developmental pattern of GAD activity in homogenates of the three areas studied from dark-reared and light-reared chicks with respect to normal light-dark cycle animals showed no significant differences. These results indicate that the increase in GAD activity during development are not due to a change in the affinity for its substrate but rather to changes in the concentration of the enzyme. The developmental pattern of GAD activity in the chick visual system was not affected by environmental conditions suggesting that the developmental profile is light-independent.

Light and dark adaptation influences GABA receptor sites in the chick retina.

The aim of the present study was to investigate the effect of environmental conditions such as light-and-dark-adaptation on the plasticity of GABA receptor sites in the chick retina. In chicks exposed to light for 5 hr (light-adapted), specific [3H]GABA binding was increased by 35% in comparison to the binding found in chicks maintained in darkness (dark-adapted). Conversely, in the retina of chicks exposed to darkness for 5 hr, specific [3H]GABA binding was decreased by 28% with respect to that found in chicks kept in the light. Scatchard analysis of the binding data revealed that the affinity of GABA for its receptor binding site was higher in the retinas of light-adapted chicks than in those of dark-adapted chicks (Kd values of 19.20 +/- 1.23 and 27.20 +/- 1.47 nM, respectively). On the contrary, the maximal number of binding sites (Bmax) remained unchanged in light- and dark-adapted chicks (5.2 +/- 0.10 and 5.3 +/- 0.15 pmol/mg protein, respectively). These results suggest the involvement of GABA receptors in the regulation of visual function.

The effect of acute ethanol administration on GABA receptor binding in cerebellum and hypothalamus.

The effect of the intraperitoneal administration of ethanol on [3H]GABA binding and glutamic acid decarboxylase (GAD) in cerebellum and hypothalamus was investigated. Acute ethanol administration produced an increase in the binding capacity of the high affinity GABA binding sites and a decrease in the binding capacity of low affinity sites. A decrease in the binding capacity of the high affinity GABA binding sites and an increase in the binding capacity of the low affinity sites were observed in the hypothalamus. No apparent changes were detected in the binding affinities for the two types of GABA receptor sites in both brain areas following ethanol treatment. Ethanol enhanced GAD activity in the cerebellum and reduced GAD activity in the hypothalamus. Changes in GABA binding may be involved in some of the neuropharmacological effects of ethanol.

Experimental orchitis induced in rats by passive transfer of an antiserum to seminiferous tubule basement membrane.

A multifocal damage of the testis was obtained when rats were injected intravenously or under the tunica albuginea of the testis with a rabbit antiseminiferous tubule basement membrane serum. The damage was characterized by foci of perivascular and peritubular infiltrates of mononuclear round cells, infolding, thickening, and rupture of the seminiferous tubular wall and different degrees of injury of the germinal epithelium such as, cell disorganization, cell sloughing, and atrophy. Delamination and thickening of seminiferous tubule basement membrane and vacuolization of the Sertoli cell cytoplasm was often observed by electron microscopy. A linear deposit of rabbit gamma-globulin was detected by immunohistochemical techniques along the basement membranes of the seminiferous tubules and vessels. Testicular damage was not detected in rats injected with normal rabbit serum, used as control. In the kidneys of rats injected intravenously with the immune serum, a deposit of rabbit gamma-globulin was detected along glomerular basement membrane. Focal areas of mononuclear cell infiltrates, hypercellularity of glomeruli and thickening of glomerular capillary walls and Bowman's capsule were also observed.

Partial chemical and immunological characterization of pepsin-solubilized collagen from the tunica albuginea of rat testis.

A pepsin-solubilized collagen was isolated from the tunica albuginea of rat testis. Intrinsic viscosity, amino acid and carbohydrate composition were similar to data reported for other soluble collagens. An antiserlm to the pepsin-solubilized collagen was obtained and by indirect immunofluorescence an antigen-antibody reaction was observed in the collagen fibers of the tunica albuginea and in the intertubular collagen fibers of rat testis. By serological and immunofluorescence techniques, cross-reactions with other collagens indicates a lack of organ specificity. A strong cross-reaction between this antiserum and basement membranes from different organs of the rat was also found.