Effect of cortisol, its polymeric derivative and adenylate cyclase activators on the content of cyclic AMP in rat thymocytes

In has been shown that cortisol immobilized on polyvinylpyrrolidone (PVP-GC) affects cyclic AMP production stimulated by adenosine and isoproterenol in rat thymocytes. This effect of PVP-GC is specific for cortisol: antiglucocorticoid progesterone (at a concentration of 10(-5) M) inhibited completely the action of PVP-GC on the intracellular cAMP level. It is suggested that cortisol effect on cAMP production is one of the mechanisms of glucocorticoid hormone action in target cells.     

Superoxide perturbation of the organization of vascular endothelial cell membranes

Cultured porcine thoracic aorta endothelial cells were covalently labeled with 4-maleimido-2,2,6,6-tetramethylpiperidinooxyl. Electron paramagnetic resonance spectrometry revealed two major binding environments representing strongly and weakly immobilized species. The disorder parameter of weak/strong, determined from the respective peak amplitudes, was irreversibly elevated following incubation of endothelial cells with a superoxide-generating system, indicating increased membrane fluidity. The rate of increase in membrane disorder was dependent upon superoxide generation rates. Incorporation of the spin-label at concentrations less than 250 microM had no effect on cell viability. The cellular proteins reacting with the spin-label were predominantly membrane proteins, characterized by immunoblotting using a rabbit anti-4-maleimido-2,2,6,6-tetramethylpiperidinooxyl IgG, following sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrophorectic transfer to nitrocellulose.     

Growth-dependent expression of a cell surface glycoprotein

The expression of the hepatocellular membrane receptor for desialylated galactose-termining glycoproteins was studied during different proliferative stages of a human hepatoma cell line. Rapidly growing cells exhibited a reduced endocytotic rate of desialylated orsomucoid as compared to non-growing cells. This reduction was shown to be the consequence of a lower concentration of active cell-surface associated receptor protein in the dividing cells.     

Rat striatal dopamine and tetrahydrobiopterin content following an intrastriatal injection of manganese chloride

Injection of manganese into the rat corpus striatum causes a rapid fall in the biopterin and dopamine (DA) content ipsilateral to the lesion. Two weeks after the lesion both biopterin and DA are partially recovered. Controls, injected with saline or magnesium, do not show alterations in their DA or cofactor levels. It is proposed that the fall in DA levels results from a rapid displacement of the amine from its storage sites by manganese followed by a decrease in the rate of DA synthesis causes by the drop in cofactor levels.     

Quantification of human spermatogenesis: germ cell degeneration during spermatocytogenesis and meiosis in testes from younger and older adult men

Germ cell degeneration during spermatocytogenesis and meiosis was investigated to explain the age-related decline in daily sperm production (DSP). Numbers of Types A-dark, A-pale, and B-spermatogonia, potential daily sperm production per g parenchyma (PDSP) based on type B-spermatogonia, early primary spermatocytes, and late primary spermatocytes, and DSP per g based on early spermatids were determined in 15 men aged 20 to 48 yr (mean +/- SEM, 33 +/- 2 yr) and 15 men aged 52 to 90 yr (65 +/- 3 yr). Testes obtained within 15 h of death (largely due to trauma or heart failure) were perfused vascularly with glutaraldehyde. The number of each cell type per g parenchyma was calculated as the product of the percentage of nuclei in the parenchyma times a correction factor for section thickness and nuclear diameter divided by the volume of a single nucleus of that cell type. Paired testicular weight was lower (p less than 0.01) in older men (33 +/- 3 g) than in the younger men (49 +/- 3 g). Younger and older men had similar numbers of A-dark, A-pale, and B-spermatogonia per g parenchyma. PDSP based on late primary spermatocytes and DSP based on early spermatids were lower (p less than 0.01) in older men than in younger men. In younger men, PDSP was similar (p greater than 0.05) between B-spermatogonia and late primary spermatocytes, whereas DSP measured at the spermatid level was abruptly lower than that estimated from younger cell types. Older men showed reduction in PDSP between early and late primary spermatocytes, with further reduction occurring in DSP at the spermatid level.(ABSTRACT TRUNCATED AT 250 WORDS)