Role of Sex Steroids on the Survival, Neuritic Outgrowth of Neurons, and Dopamine Neurons in Cultured Preoptic Area and Hypothalamus

Morphological sex differences in some discrete brain regions are thought to be developed by the influence of circulating androgen during the perinatal period. In order to know whether the effect of androgen is a direct one, cells derived from neonatal rat preoptic area (POA) and/or hypothalamus were cultured in a serum-free medium, and the effects on survival, process growth of neurons, and dopaminergic function were examined. When the POA cells were exposed to testosterone (T), neuronal survival was greater than the controls, and the frequency distribution of total process length and the number of process branchings were significantly deviated from the controls. Estradiol-17β (E₂) and 5α-dihydrotestosterone had less significant effects on these parameters than T. Moreover, the addition of T increased the dopamine (DA) contents of cells and medium DA in the hypothalamic culture. E₂ also greatly increased DA content of the medium. These steroids failed to alter the DA levels in the POA cell cultures. These results generally conform to the notion of previous investigators that T has direct effects on the expansion of dendritic elements of the POA and the development of sex difference in the hypothalamic DA neurons, although the effect of T after conversion to E₂ cannot be excluded.     

Growth stimulative effect of parathyroid hormone, calcitonin and N6,O2'-dibutyryl adenosine 3';5'-cyclic monophosphoric acid on chick embryonic cartilage cultivated in a chemically defined medium

PTH (0.5 unit/ml) and CT (0.5 unit/ml) strongly stimulated the in vitro growth of the chick embryo femur in terms of elongation and dry weight increase as well as an increase in the protein, hexosamine, hydroxyproline, DNA and RNA content of the femur. A synergistic effect was observed when PTH and CT were simultaneously added to the medium, suggesting that the mechanism of the growth stimulating effect of one of these hormones might be different from that of the other. The exposure of PTH to the femur caused an increase in cyclic AMP content. The direct addition of dibutyryl cyclic AMP (1 mM) to the medium mimicked the effect of PTH on the cartilage. PTH, therefore, seems to stimulate the growth of cartilage via the increase in cyclic AMP content of the femur. CT had no effect on the cyclic AMP content of the femur.     

Effects of ACTH and calcium on cyclic AMP production and steroid output by the zona glomerulosa of the adrenal cortex.

Effects of ACTH and calcium on cyclic AMP production and steroid output by the zona glomerulosa (the capsular fraction) from the rat adrenal cortex have been studied. Although high concentrations of extracellular calcium potentiated the stimulatory action of ACTH on cyclic AMP and aldosterone output, tetracaine or verapamil inhibited aldosterone output but not cyclic AMP production during ACTH-stimulation. Lanthanum reduced both aldosterone and cyclic AMP accumulation induced by ACTH. These results suggest that an extracellular calcium would be essential in stimulating the capsular steroidogenesis without involvement of the cyclic AMP system.     

Binding sites for calcium-activated neutral protease on erythrocyte membranes are not membrane phospholipids

In order to explore the binding sites for calcium-activated neutral protease (CANP) with high calcium sensitivity (muCANP) on the inner surface of human erythrocyte membranes, we analyzed the binding of muCANP to two kinds of membranes modified by treatment with phospholipase C or Triton X-100. Binding analyses were performed using an immunoblot technique. The amount of muCANP bound to phospholipase C-treated inside-out vesicles was essentially the same as that bound to untreated inside-out vesicles. It was also observed that muCANP binds to Triton X-100-treated membranes, in which most of the integral proteins and glycerophospholipids are removed while the lining proteins remain intact. In both types of modified membrane, the bound muCANP was rapdily converted to an active form by autolysis at physiological free Ca2+ concentrations. These results indicate that the binding sites for muCANP on the inner surface of erythrocyte membranes consist of components other than membrane phospholipids. In addition, it is suggested that one of the binding sites for muCANP is some lining protein.