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Action of colchicine on axonal flow and pituicytes in the hypothalamopituitary system of the rat.
Changes in the hypothalamo-pituitary tract and the pituicytes of the rat were studied after intrathecal and intraperitoneal injections of colchicine. Radioautography with 35S-cysteine demonstrates that intrathecal colchicine prevents the migration of neurosecretory granules from the supraoptic and paraventricular nuclei to the posterior lobe of the pituitary. This results in accumulations of neurosecretory granules and in the formation in the axons of elongated structures resembling neurosecretory products, although they sometimes have a fibrillary content. Neurotubules appear to remain intact in these conditions. The stimulation of the posterior pituitary by dehydration, in particular after injection of the diuretic furosemide, leads to an increased activity of pituicytes. When colchicine is injected at the same time as furosemide, a considerable new formation of centrioles is observed in the pituicytes. These become associated with ciliary vesicles, and form numerous cilia of the 9 + 0 type. An increased number of centrioles is also seen in the endothelial cells of the posterior lobe of the pituitary. These apparently paradoxical results were briefly discussed in relation to the action of colchicine on neurotubules and axonal flow and to the limited data from the literature indicating a stimulation of cilia formation under the action of colchicine and other drugs.
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Ultrastructure of the pineal organ of the killifish, Fundulus heteroclitus, with special reference to the secretory function.
The pineal organ of the killifish, Fundulus heteroclitus, was investigated by electron microscopy under experimental conditions; its general and characteristic features are discussed with respect to the photosensory and secretory function. The strongly convoluted pineal epithelium is usually composed of photoreceptor, ganglion and supporting cells. In addition to the well-differentiated photosensory apparatus, the photoreceptor cell contains presumably immature dense-cored vesicles (140-220 nm in diameter) associated with a well-developed granular endoplasmic reticulum in the perinuclear region and the basal process. These dense-cored vesicles appear rather prominent in fish subjected to darkness. The ganglion cell shows the typical features of a nerve cell; granular endoplasmic reticulum, polysomes, mitochondria and Golgi apparatus are scattered in the electron-lucent cytoplasm around the spherical or oval nucleus. The dendrites of these cells divide into smaller branches and form many sensory synapses with the photoreceptor basal processes. Lipid droplets appear exclusively in the supporting cell, which also contains well-developed granular endoplasmic reticulum and Golgi apparatus. Cytoplasmic protrusions filled with compact dense-cored vesicles (90-220 nm in diameter) are found in dark-adapted fish. The origin of these cytoplasmic protrusions, however, remains unresolved. Thus, the pineal organ of the killifish contains two types of dense-cored vesicles which appear predominantly in darkness. The ultrastructural results suggest that the pineal organ of fish functions not only as a photoreceptor but also as a secretory organ.
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Response of tanycytes to aging in the median eminence of the rat.
Age-related changes in tanycytes of the median eminence were observed at both the light and electron microscopic level in male and female rats at ages 4 weeks to 14 months. The most obvious changes involved a marked progressive increase in number and size of droplets identified histochemically as neutral lipid and the development of complex degenerate bodies in the perivascular contact zone. These degenerate bodies consisted of large multiple complexes of myelin figures containing intercalated channels and pools of electron-dense material. They often occurred interspersed among large lipid droplets. The degenerate bodies (myelin figure complexes) and associated lipid droplets occupied much of the contact zone in the older animals. Evidence of axonal degeneration and tanycytic phagocytosis of deteriorating neural elements was also present. These age-related changes occurred independent of sex and were not affected by gonadectomy. This tanycyte response to aging in the median eminence is very similar to the response of neurohypophysial pituicytes to axonal degeneration, suggesting a phagocytic glial role for tanycytes.
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Pinealocyte dense-cored vesicles and synaptic ribbons: a correlative ultrastructural-biochemical investigation in rats and mice.
Dense-cored vesicles (DCV) and synaptic ribbons (SR) were quantified in the pineal gland of the rat (Sprague-Dawley) and mouse (Sasco/ICR strain), and day/night differences in frequency of these organelles correlated with levels of indoles determined by high performance liquid chromatography (HPLC). There were significant day/night differences in levels of serotonin (5HT), 5-hydroxyindole acetic acid (5HIAA), N-acetyl-5HT, and melatonin in the rat gland. Melatonin and N-acetyl-5HT were not detectable in the mouse gland sampled every 4 h over the light:dark cycle. The concentrations of 5HT and 5HIAA (ng/microgram protein) were similar in light-adapted rats and mice, but these indoles did not exhibit a circadian rhythm in the mouse gland. Correlative ultrastructural/biochemical results suggest that DCV do not contain physiologically important stores of 5HT since 1) the mouse gland contains the same number of DCV as the rat during the daytime, but only one-tenth the levels of 5HT, 2) day/night 5HT levels do not vary in the mouse gland, but there is a significant nocturnal decline in DCV numbers, and 3) 5HT levels in the rat gland decline at night when DCV numbers increase. Numbers of SR were significantly elevated at night in the rat and mouse, and the frequency of this organelle was similar in both species. However, ribbon-type SR predominated in rat pinealocytes, whereas SR in the mouse were almost exclusively spherical in shape. Day/night differences in SR numbers in the mouse gland suggest that cellular mechanisms regulating the frequency of this organelle do not involve factors related to indole metabolism. Because of the lack of photoperiodic effects on indole metabolism in the mouse pineal gland, this species is a potentially important model to study the functional relationship of pinealocyte organelles to cyclical changes in pineal products other than indoles (e.g., peptide/protein factors).
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Structure and fine structure of the hypophyseal pars distalis in endigenous African species of the genus Tilapia.
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Ultrastructure of the proximal convoluted tubules during repair following hormonally induced necrosis in rat kidney.
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The hypothalamo-hypophysial system in Acipenseridae. I. Ultrastructural organization of large neurosecretory terminals (Herring bodies) and axoventricular contacts.
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Granulated vesicles in the pineal gland of the mouse.
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Laminin in the anterior pituitary gland of the rat. Laminin in the gonadotrophic cells correlates with their functional state.
The distribution pattern of laminin in the rat anterior pituitary gland under physiological and hormonally altered conditions was studied immunohistochemically. Intense immunoreactivity of the capillaries and of the basement membranes surrounding parenchymal cells was found. Five to 10% of the parenchymal cells of normal adult rat pituitary gland exhibited also intense positive cytoplasmic staining. These were identified as gonadotrophic cells on the basis of their topographic distribution and typical 700-nm light bodies. By immunoelectron microscopy it was shown that the light bodies contain laminin and tubulin. After treatment with estrogen, which is known to suppress the function of the gonadotrophic cells, virtually no cytoplasmic laminin was found. Ultrastructurally, the number of light bodies in the gonadotrophic cells diminished significantly, from approximately 3 to 8 per cell to 0 to 1 per cell in a given section. In contrast, after castration, the number of laminin positive cells increased to a number above that found in the normal adult male rat, and the number of light bodies increased two to four times. Based on these results, it appears that the presence of cytoplasmic laminin and the number of light bodies reflects the hormonal activity of the gonadotrophic cells of the rat pituitary gland.
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Impact of psychosocial stress on pineal structure of male gerbils (Meriones unguiculatus, cricetidae).
Stress responses were investigated in 5-month-old male gerbils. Breeders having no pubescent litters served as controls. The first experimental group never left their parents' cage and were thereby fought by higher-ranking males; the second and third groups were stressed for a week by four daily 1-minute encounters with trained fighters, the second group during daytime, the third during the dark period. The first and second groups developed signs of gonadal regression, the third did not. The adrenals of the first group weighed the same as those of controls; the adrenals of both other groups were increased in weight. In the adrenal medulla of all experimental groups, a large number of cells were densely packed with noradrenaline-containing vesicles. In each experimental group the pineal changes included a remarkable decrease in nuclear size of pinealocytes, an increased number of colloidal cysts, and a reduction of that portion of the plasmalemma that is lined by subsurface cisterns. All these changes are interpreted in terms of pineal activation, as are the increased number of membrane whirls found in the first group. The third group exhibited an additional decrease in the size of mitochondria and in the number of "synaptic" structures. This finding and the day-night differences in the gonadal response indicate that stress interferes with the metabolic cyclicity of the pineal gland. However, it remains indiscernible whether the pineal stress reaction signals a general activation of the gland or a change in it's temporal activity patterns.