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Page 180 of 547-
Oligodendrocytes in the normal and chronically de-afferented lateral geniculate body of the monkey.
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[Sensory structures in the intermediate lobe of the hypophysis].
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[Electron microscope study of neurosecretory elements of the proximal neurosecretory contact region in the sturgeon].
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A cytological study of Mauthner's cells in Xenopus laevis and Rana temporaria during metamorphosis.
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Organelle motility in rat pituitary clonal cells. I. Dynamic movements of intracellular organelles.
Intracellular organelle motion within clonal pituitary tumor cells (GH3) was observed directly with a contrast enhancement, computer-video microscope system. All particles except nuclei moved in a complex fashion. Two types of particles predominated; one large and round, the other small and elongated. We classified the movements of these particles as saltation, oscillation and slow translocation. Saltation was directional movement with velocity of the order of 1 micron/sec. Oscillation was local motion occurring within 1 micron that showed no specific direction. Its velocity was similar to that of saltation. Large particles, in particular, showed the 3rd type of movement, slow translocation. The velocity appeared to be one order slower than that of saltation. We also examined the cells with fluorescent, dark-field and electron microscopies. We concluded that the large round particles were lysosomes and the small elongated ones mitochondria. The microtubule depolymerizer, vinblastine and the microfilament depolymerizer, cytochalasin D, completely inhibited all the types of organelle movement. The mechanism and significance of these organelle movements are discussed.
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[Ultrastructure of neurons and synapses of the lateral hypothalamic area in the rat].
Ultrastructural organization of the lateral hypothalamic area (LHA) has been studied in Wistar rats. Structural peculiarities of neurons and interneuronal connections in the anterior, middle and posterior parts of the LHA have been demonstrated. In the anterior and middle parts, neurons of middle size (17-22 mcm) make the most of the cellular population; large neurons (35-50 mcm) predominate in the posterior part of the LHA. Small cells are diffusely distributed in all the parts. Two types of axons are defined: axons of the I type--with round light, and some of them, with large granular synaptic vesicles; axons of the II type contain smaller and polymorphous light synaptic vesicles. The axons form axodendritic and axosomatic synapses. The former predominate in all parts of the LHA. The axons of the I type form, mainly, asymmetrical, and the axons of the II type--symmetrical contacts. Most of the synapses are formed by the axons of the I type, overwhelmed majority of the synapses are axodendritic. Differences in localization and in distribution of the axodendritic synapses in different parts of the LHA are revealed. In the anterior part of the LHA the axodendritic synapses form synaptic muffs around large and middle dendrites, and more seldom around small and spine-shaped processes of the dendrites. In the middle and posterior parts of the LHA no synaptic muffs are revealed.
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Effects of tunicamycin on the hypothalamo-neurohypophysial system of the rat.
Intracisternal injections of tunicamycin, an inhibitor of glycosylation, decreased the incorporation of [35S]cysteine into the neurophysins in the rat neurohypophysis. Histochemical and immunocytochemical studies showed that there was no concomitant decrease in the amount of secretory product in the perikarya of the hypothalamo-neurohypophysial neurones. Indeed there was an increase, although this was not associated with neurosecretory granules as judged electron-microscopically. Tunicamycin led to the formation of so-called "colloid droplets" which were immunopositive and of which the ultrastructural correlates appeared to be product-filled dilatations of the rough endoplasmic reticulum. The observations are interpreted to suggest that glycosylation plays a rôle in the packaging of secretory material in the hypothalamo-neurohypophysial system.
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An ultrastructural study of nerve and glial cells by freeze-substitution.
The ultrastructure of nerve and glial cells in the cerebral and cerebellar cortices of mice was studied after rapid freezing followed by substitution fixation. The cerebral and cerebellar cortices were frozen by bringing them into contact with a polished pure copper block cooled at a temperature of about -196 degrees C. The tissues were fixed and substituted in acetone containing 2-4% OsO4 at -78 degrees C for 2-3 days and then prepared for electron microscopy. Tissue fixed by this method displayed the following characteristics. (1) The contour of cells, processes and intracellular membrane systems was smooth. (2) The extracellular spaces were of variable widths. (3) Microtubules were well preserved and were often observed to extend into nerve terminals and to run close to presynaptic membranes. (4) The matrix of cytoplasm and mitochondria was electron dense. Dense granules, possibly binding sites of divalent cations, were often found in the mitochondrial matrix. (5) The plasma membrane of neuronal processes was thicker than that of glial processes. (6) The plasma membranes of nerve fibres and glial processes appeared asymmetrical, the inner leaflet being slightly thicker than the outer leaflet, whereas membranes of cell organelles such as smooth endoplasmic reticulum. Golgi bodies, lysosomes, multivesicular bodies, mitochondria and synaptic vesicles, were symmetrical.
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Ultrastructural study of the human neurohypophysis. I. Neurosecretory axons and their dilatations in the pars nervosa.
Neurosecretory axons and their dilatations in the pars nervosa of the human neurohypophysis were studied electron microscopically. The axons are of two different types based on their content of neurosecretory granules (NSGs): (i) NSGs of Type A are 100-300 nm, and (ii) NSGs of type B are 50-100 nm in diameter. While fibers (or axons) of type B were scarce, showing simple swellings and terminal formations, fibers of type A were ubiquitous in the human pars nervosa, exhibiting numerous dilatations with a diversity of internal structure, apparently representing the ultrastructural manifestation of intraaxonal turnover of neurohypophysial hormones. Based on the predominating aspect of their internal structure, dilatations of type A-fibers were classified into six different types, with various transitional forms: Type I is characterized by abundant NSGs; type II by prominent mitochondria; type III by abundant lysosomal bodies; type IV by an electron-lucent matrix with few organelles; type V by prominent tubuloreticular profiles; and type VI by numerous microvesicles. The functional significance of each type is discussed and a scheme of possible interrelationships between these dilatations is proposed.
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Two types of luliberin-immunoreactive perikarya in the preoptic area of the rat.
At the light microscopic level, following immunostaining with a single antiserum against luliberin (LRF), two types of hormone-producing perikarya in the preoptic area are demonstrated. The two cell types differ in their morphological features: a bipolar, smooth-contoured cell type can be differentiated from an irregularly contoured unipolar type. Intermediate forms between both cell types occurring in the same area are not observed. Electron microscopically, both cell types contain labeled granules of similar size and immunoreactivity. It is discussed whether the uneven surface of the one cell type is due to areas of synaptic contacts, and whether both cell types are integrated in different neuronal and functional circuits. Moreover, at the ultrastructural level, from the irregularly contoured LRF-producing perikarya a further positively stained cell type, probably a glial cell, can be differentiated. The specific labeling of the latter is caused by its content of immunoreactive lysosomal bodies. Differentiation between the labeled glial cells and the irregularly contoured LRF-producing perikarya is not possible at the light microscopic level.