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Synaptic ribbon populations in the pineal gland of the rhesus monkey (Macaca mulatta).
Pinealocytes of rhesus monkeys that had been ovariectomized and given intramuscular injections of 250 micrograms estradiol-benzoate for 3 consecutive days tended to have more synaptic ribbons (SR) and exhibited a significantly greater size of ribbon fields (RF) compared to untreated animals. These data are consistent with hypotheses that pinealocyte function in primates is altered by hormonal imbalances and that the SR participates in this response. RF were positioned in various parts of the cytoplasm and along the plasma membrane. Participation of SR in direct cell-to-cell contacts was suggested by the formation of densities along the plasma membrane. It is postulated that large RF serve as storage organelles and that the formation of RF results from division of pre-existing SR in each field. Reconstructions made from serial thin sections revealed that profiles of RF comprised separate SR that were not folded and sectioned along various planes.
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[Changes in the ultrastructure of the hypothalamus during chronic morphine poisoning].
Using electron microscopy the author studied the changes in the ultrastructure of the ventromedial hypothalamic nucleus in Wistar rats with chronic morphine intoxication (induced by unchanged or build-up doses) and upon discontinuation of morphine. Chronic morphine intoxication exerted an adverse effect on the cellular protein synthesis as well as on vesicular, granular and membranous components of cells. A correlation was detected between the pathomorphological alterations and the morphine dose. The study revealed a high sensitivity to morphine of neurons, large dendrites and interneuronal links in the period of dependence formation and the greatest vulnerability of cells and their processes during abstinence, particularly under conditions of a sharp discontinuation of morphine build-up dosage. Destructive processes observed in the experiment were also attended by manifestations of the compensatory, reparative and restorative processes detected on the 7th day after morphine discontinuation.
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Stereological analysis of daily variation in the ultrastructure of the pars intermedia of the pituitary gland of the Djungarian hamster (Phodopus sungorus).
A stereological analysis has been made of the daily changes occurring in the ultrastructure of the melanotrophs of the pars intermedia of the pituitary gland of the Djungarian or Siberian hamster, Phodopus sungorus, maintained in long day photoperiods. The rough endoplasmic reticulum, Golgi apparatus and lysosomes all declined in fractional volume throughout the photophase reaching minima at mid-scotophase and rising to reach their maxima at about the time of onset of the photophase. The mitochondria reached their peak fractional volume just before the cessation of the photophase but then also declined to a minimum at mid-scotophase. No significant changes were found to occur in the fractional volumes of the nucleus or the secretory granules. These morphological findings are compared with the changes in plasma and pituitary alpha-melanocyte-stimulating hormone levels found in the rat.
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A retinal projection to the lateral hypothalamus in the rat.
This study presents evidence for a retinal projection to neurons in the lateral hypothalamic area (LHA) of the albino rat. In Golgi-Kopsch material dendrites from LHA-neurons are observed to extend through the supraoptic commissures into the optic tract. The presence of dendrites in the optic tract is confirmed by electron microscopy. Numerous axon terminals are observed forming asymmetric synaptic contacts with these dendritic profiles. Following bilateral enucleation, many of the preterminal axons and terminals in synaptic contact with dendrites in the optic tract demonstrate dark degeneration. After intraocular injection of horseradish peroxidase, there is marked labeling of preterminal axons and terminals in the optic tract. These observations indicate that LHA neurons receive a direct retinal projection from terminals making synaptic contact with dendrites of LHA-neurons extending into the optic tract.
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Ultrastructural localization of corticotropin, beta-lipotropin, and alpha- and beta-endorphin in the porcine anterior pituitary.
The peroxidase-antiperoxidase immunocytochemical technique was used to identify the ACTH/endorphin cells in the porcine pituitary at the ultrastructural level and to determine the precise subcellular localization of the pro-ACTH/endorphin fragments. The cells display different aspects: 1) large, regular shapes with numerous and large secretory granules; 2) small, irregular and angular shapes with small granules aligned along the periphery of the cell; and 3) intermediate forms. The presence of alpha- and beta-endorphin not only in the same cells but also in the same secretory granules that contain ACTH and beta-LPH clearly indicates that both the precursor or its fragments and the above-mentioned peptides are stored in the same granules and released simultaneously by the corticotropic cells. The presence of FSH in some corticotropic cells is also discussed.
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Ultrastructural study of the human neurohypophysis. II. Cellular elements of neural parenchyma, the pituicytes.
The pars nervosa of the neurohypophysis from 12 patients undergoing hypophysectomy for palliative treatment of advanced carcinoma was studied electron microscopically. Special attention was given to the cellular elements, the pituicytes. Five different classes of pituicytes, with various transitional forms, were elucidated based on their ultrastructural characteristics: (1) The most common type, referred to as "major pituicytes", is reminiscent of astrocytes. (2) "Dark pituicytes" are thought to represent different functional stages of the "major pituicytes". (3) "Ependymal pituicytes" are believed to provide ultrastructural evidence that human pituicytes are phylogenetically derived from ependymal cells. (4) "Oncocytic pituicytes" were observed in all cases and are of unknown significane. (5) The ultrastructural features of "granular pituicytes" suggest the existence of an active uptake and catabolism of extracellular material by pituicytes, probably through "ultraphagocytosis" or "endocytosis". These five classes of pituicytes are considered to represent different functional forms of one cell line that originates phylogenetically from the ependyma.
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Fine structure of the lateral areas of the rhombencephalic tela of the bullfrog, Rana catesbeiana.
The lateral areas of the rhombencephalic tela of the bullfrog contain long, irregular islands of ependymal cells that are similar in fine structure to the epithelium of the rhombencephalic choroid plexus. These cells are characterized by apical microvilli, numerous mitochondria and pinocytotic vesicles, and basal infoldings of the plasma membrane. Dorsally a basal limina and varying amounts of collagen occur. The pia mater associated with this ependyma includes two cell types. Fibroblast-like, loosely arranged cells without organized junctions line the subarchnoid space. The most abundant cells of the pia in this area, however, contain numerous intermediate filaments and frequent desmosomes. Caveolae lie along their plasma membranes. Closely organized sheets of similar filament-containing cells are also seen in the arachnoid mater of this animal. These findings demonstrate ependymal cells in the lateral areas of the rhombencephalic tela of the bullfrog that have the essential features of choroid plexus epithelium, with ultrastructural characteristics that suggest transport function. They are, however, usually separated from neighboring, non-fenestrated vessels by several layers of leptomeningeal cells joined by desmosomes. The relationship between structure and function of these cells is enigmatic.
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Effect of melatonin implants on gonadal weights and pineal gland fine structure of the golden hamster.
Weekly subcutaneous implants of melatonin in a beeswax pellet prevented the testicular regression which normally occurs in hamsters exposed to short photoperiod for 8 weeks. Normal (14L:10D) hamster testes were indistinguishable from the testes of melatonin-treated (1L:23D) hamsters. The exogenous melatonin had varied effects on the fine structure of the golden hamster pineal gland. Pineal ocyte nuclear characteristics of melatonin-treated hamsters (smaller average diameter, less polymorphism, and more heterochromatin) as well as apparent reductions in the amounts of hypertrophic SER and lipid moieties seemed to indicate that melatonin caused inhibition of pineal gland activity, and in this respect counteracted the effects of short photoperiod. However, an apparent increase in the number of large mitochondria, membrane whorls and dense-cored secretory vesicles in pinealocytes of melatonin-treated hamsters suggests enhanced pineal gland activity.
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Ultrastructure of neurosecretory cells at different stages of differentiation in the preoptic nucleus of immature sterlet.
Ultrastructure of neurosecretory cells of the preoptic nucleus in immature sterlet (Acipenser ruthenus L.) was studies for the first time. The dorsal zone of the preoptic nucleus houses light, dark, and pycnomorphic neurosecretory cells, which contain varying numbers of elementary secretory granules measuring 1995 plus or minus 32 A in diameter. Light cells containing numerous secretory granules with a diameter of 1707 plus or minus 27 A are predominant in the middle zone. Pycnomorphic cells are absent in this zone. The ventral zone contains only poorly differentiated cells with solitary elementary granules measuring 1100-1300 A in diameter. The neurosecretory cells also differ with respect to the number and structural characteristics of their organoids. Thus, neurosecretory cells in the preoptic nucleus are found in different morphofunctional states, a circumstance that reflects the sequence of their development in ontogenesis and different phases of the secretory cycle.
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[Intranuclear bundles of tubules in the vascular organ of the lamina terminalis].