Hugo R. Seibel

Evidence for Multiple Serotonergic Influences on LH Release in Ovariectomized Rats and for Modulation of Their Relative Effectiveness by Estrogen

Both opiates and serotonin (5HT) are known to inhibit LH release in ovariectomized rats, and estrogen has been shown to reverse certain serotonergic effects. Therefore studies were undertaken to compare the effects of morphine and the serotonin agonist 5-methoxy-N,N-dimethyltryptamine (5MEODMT) on LH release in ovariectomized rats with and without estrogen priming. Serial blood samples were collected via jugular cannulae before and 5, 15, 30 and 60 min after intravenous administration of morphine, 5MEODMT or both to rats receiving no pretreatment, or a serotonin receptor antagonist (methysergide, METH; or ketanserin, KET) 60 min earlier. In the absence of estrogen, morphine inhibited LH release, and the response was delayed by METH or abolished by KET, suggesting mediation by serotonin2 (5HT2) receptors. 5MEODMT alone failed to alter the release of LH significantly, but apparently activated both stimulatory and inhibitory serotonergic systems. Blockade of 5HT2 receptors with KET enabled an inhibitory system to prevail. No significant changes in LH concentrations were observed following combined administration of morphine and 5MEODMT. Similarly, in estrogen-primed rats morphine appeared to activate both inhibitory (5HT2) and stimulatory (5HT1) systems, resulting in no net change unless the inhibitory system had been antagonized by KET. Administration of 5MEODMT alone or in combination with morphine resulted in a strong stimulatory effect which appeared to be mediated by 5HT1 receptors. These results suggest the existence of a multiplicity of serotonergic influences on the release of LH in the rat, not only in terms of particular species of 5HT receptors, but also in neuronal connectivity.(ABSTRACT TRUNCATED AT 250 WORDS)

A Light and Electron Microscopic Study of the Pineal Body of the Nutria (Myocastor Coypus)

Light and electron microscopic studies of the nutria (Myocastor coypus) pineal gland revealed pinealocytes interspersed among glial, vascular, and neuronal elements. Each pinealocyte possessed a single process that terminated within the parenchyma near the perivascular region. The eccentrically located nucleus in these cells contained euchromatic chromatin, a prominent nucleolus, and a highly infolded nuclear envelope. The cytoplasm was rich in mitochondria, Golgi complexes, and glycogen particles. The smooth endoplasmic reticulum (SER) was better developed thant he rough endoplasmic reticulum (RER) and polyribosomes were not abundant. Long profiles of subsurface cisterns constituted prominent cytoplasmic features, and these were most conspicuous in the regions of soma-somatic apposition. The bulbous endings of the pinealocyte processes were filled with clear, round, secretory vesicles. Dense-cored vesicles were rarely observed. Glia reminiscent of protoplasmic astrocytes displayed cytoplasmic processes that enveloped blood vessels, invested the pineal periphery, and intervened among the pinealocytes. They thus seemed to form a barrier between the meningeal capsule and vascular space on the one hand and the parenchyma on the other.

Recurrent glomerulonephritis in human renal homografts

Recurrent glomerulonephritis in kidneys transplanted to glomerulonephritic recipients is becoming more obvious. It has been suggested that the disease process which caused the original disease in the recipient is also operative in the transplanted tissue. This study compared the ultrastructure and immunofluorescence of the native kidneys of four patients with their respective sequential, transplant biopsies. In each case, subepithelial humps and IgG, characteristic of a complex type of nephritis, were observed in both the original diseased kidneys and in the transplants. This would indicate that the immunopathologic process which caused the original glomerulonephritis and led to transplantation is also operative in the transplanted tissue.

Heterogeneity of Renal Mitochondria of the Rat

Summary Mitochondria were isolated from renal cortex, red medulla, white medulla and whole kidney of the rat. Electron micrographs showed very few mitochondria in the white medullary region of kidney compared to the other areas. Mitochondria in red medulla were somewhat larger and more spherical than those in cortex. Relative degrees of control of mitochondrial respiration by Pi acceptor (RCR) were: red medulla > whole kidney > cortex >> white medulla. Use of the lipophilic probe tetrabutylammonium bromide indicated that the inner membrane NADH dehydrogenase receptor site(s) were more lipophilic in red medullary mitochondria than in cortical mitochondria. Variation in energy gradients due to mitochondrial heterogeneity in the respective renal tissues could not be completely correlated with previously reported gradients in renal protein and RNA biosynthesis.

Effect of biogenic amines on the endocrine axis and esterase activity of hamster testes.

Summary Pinealectomy reverses the loss of testis and seminal vesicle weights of blinded hamsters. Treatment with moderate doses of serotonin and melatonin does not cause further decrease in reproductive organ weights, or appreciably affect adrenal and pituitary gland weights of blinded hamsters. The seminiferous tubules of blinded hamsters exhibit primarily spermatogonia containing lipid aggregations and numerous lysosomal bodies. Blinded hamsters have significantly higher levels of testicular esterase activity than do control, pinealectomized, and blinded and pinealectomized hamsters. This suggests that the higher esterase activity results from greater lysosomal activity.