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Page 175 of 547-
The filum terminale of the frog spinal cord. Light and electron microscopic observations.
The filum terminale, or terminal portion of the spinal cord, was studied in normal adult frogs (Rana pipiens) bu means of light and electron microscopy. Astroglial cells are the predominant elements in this region. The rostral portion of the filum terminale consists mainly of (1) a peripheral dense ring of myelinated and some unmyelinated nerve fibers, and processes of astrobytes terminating at the subpial space; (2) an intermediate zone, in which astrocytes are the main cellular elements in addition to a few degenerated neurons; and (3) a central region where the central canal is lined by dark and light ependymal cells. In the caudal portion of the filum terminale, the amount of neuropil is greatly reduced. This region os formed mainly by astrocytic glial cells and very few neuronal elements. The central canal in the caudal portion is located ventrally and contains a lining consisting almost exclusively of dark ependymal cells.
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The effects of adrenalectomy and cortisol treatment on cell types, other than corticotrophs, in the anterior pituitary of the mouse.
This investigation was designed to characterize changes due to adrenalectomy and cortisol treatment in cell types, other than corticotrophs, in the anterior pituitary of the mouse. Cortisol injections resulted in a reduced number of mammotrophs and an increased number of somatotrophs. By 5 days post-adrenalectomy an increase in the number of mammotrophs and a decrease in the number of somatotrophs was observed. No changes were noted in the number of gonadotrophs or thyrotrophs due to either adrenalectomy or cortisol treatment.
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Myeloid bodies associated with lipid droplets in pinealocytes of blind, blind-bulbectomized, blind-underfed or blind cold-exposed rats.
The ultrastructure of pinealocytes was studied in rats subjected to manipulations known as enhancers of pineal actions: blindness (B), blindness + olfactory bulbectomy (BObx), blindness + underfeeding (BU), blindness + cold exposure (BC). A large number of myeloid bodies (MBs) were found especially in the light pinealocytes of BObx, BU and BC rats but not in intact controls. These MBs were, in most cases, associated with lipid droplets. The presence of a large number of MBs in rats in which pineal-dependent gonadal impairment has been demonstrated, strongly supports the hypothesis that MBs play a role in pineal photoneuroendocrine activity.
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Ultrastructural changes in neurons of the anterior subdivision of the rat hypothalamic ventromedial nucleus following repeated immobilization stress.
The fine structure of neuronal somata of the anterior subdivision of the hypothalamic ventromedial nucleus (VMN) was studied in repeatedly immobilized rats. After the 40th immobilization daily for 150 min a small population of neuronal somata containing endoplasmic reticulum formations classified as lamellar bodies and whorls were identified in the area investigated. These neuronal somata differed from the neighbouring perikarya of VMN also in several other ultrastructural features. They showed an extraordinarily dilated cisternae of the rough endoplasmic reticulum and of the Golgi complexes, moderately swollen mitochondria and a large number of free ribosomes evenly distributed in the cytoplasm.
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Ultrastructural effects of perfomic acid oxidation of epoxy-embedded tissue with and without early uranyl staining.
Epoxy-embedded blocks of glutaradehyde and OSO4 fixed adenohypophyseal tissue were immersed in performic acid, rinsed and sectioned for electron microscopy. Sections exhibited a general image intensity equivalent to control sections but their stainability with both uranyl acetate and lead citrate stains was increased. It was concluded that osmium was not removed by performic acid oxidation. Membranes of endoplasmic reticulum and the Golgi apparatus were not visible, and other components (acidophil granules, in particular) were markedly distored in shape after oxidation. Such changes, however, were not evident in specimens previously exposed to uranyl acetate during ethanol dehydration.
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Coordinated neural progenitor adaptations contribute to primate neocortical downscaling.
Most primates have a large, highly folded (gyrencephalic) neocortex, a feature present in the primate common ancestor. In contrast, several New World monkey species display a comparatively small and largely smooth, unfolded (lissencephalic) neocortex. One prominent example is the common marmoset, an increasingly popular model in neuroscience. This phenotype likely reflects an evolutionary reduction from the ancestral primate condition, implying modifications in neurodevelopmental programs. One essential basis for neocortical development is the activity and behavior of neural progenitor cells (NPCs). Here, we identify coordinated adaptations in NPC biology that bias neurodevelopmental trajectories toward neocortical downscaling. By combining marmoset and human cerebral organoids with analyses of fetal marmoset neocortical tissue and previously published histological data, we uncover multiple adaptations in apical and basal progenitors that converge on reduced progenitor capacity, alter early progenitor dynamics, and likely constrain neuronal output, thereby limiting the size and folding of the marmoset neocortex.
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Investigation on the pars tuberalis of the hypophysis of Psammodromus algirus L. (Sauria). An electron microscopy study.
The anatomic-microscopic and cytological aspects of the lateral lobes of adenohypophysis of Psammodromus algirus have been studied. Along the whole of its extension, the 'pars tuberalis' appears to be separated from the hypothalamic region by a space of 1600 A with a winding course filled with fibrillar matrix. The main inclusions of 'pars tuberalis' cells are glycogen granules histochemically characterized by the Thiery's method. A correlation between the electron and light microscopy observations on the lateral lobes of Psammodromus algirus is attempted.
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Ultrastructural changes in neurons and neuroglia of the avian telencephalon (hyperstriatum accessorium) following tri-ortho-cresyl-phosphate intoxication.
Ultrastructural reactions of neurons of the avian forebrain following tri-ortho-cresyl-phosphate (TOCP) poisoning are described. The neurons show a marked increase in the rough endoplasmic reticulum (RER), with RER specializations such as lamellar bodies and subsurface cisternae, as well as a proliferation of the Golgi complex and neurofilaments. In addition, an increase in the number of dense bodies and mitochondrial osmiophilia is noted. Similar changes can also be observed in the neuroglia. These alterations appear 10-13 days after TOCP ingestion.
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[Features of the development of the dendrites of differentiating pyriform cerebellar cortex neurons in mammals and man].
Pecularities of development of the differentiating piriform neuron cerebellum cortex dendrite system in the mammals and in man were studied with light and electron microscopy. Three consequent stages are involved in the process: the formation of a dilated portion of apical (supranuclear) cytoplasm with an increased amount of organelles; the formation of a temporary apical cytoplasmic mitre (cone); the development of the dendrite system occurring on the background of reduction of this temporary cytoplasmic formation. In the course of differentiation, a distinct change of the dendrite cytoplasm contents from reticular to tubular ones takes place.
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The pituitary cleft of the rat: an electron microscopic study.
The epithelium of the pituitary cleft and its colloid have been studied at the ultrastructural level in normal, adrenalectomized, castrated, dehydrated and lactating adult rats. Both control and experimental animals showed cells in different stages of degradation inside the cleft and mixed with the colloid. These exfoliated cells seems to have originated from the cleft's epithelium of the adjacent granular cells. In adrenalectomized and castrated rats the rostral epithelium of the cleft had large intercellular spaces that in some instances appeared to open directly into the cleft. Occasionally, the adenohypophysial canaliculi of the adrenalectomized rats were also seen connecting with the cleft. In lactating and castrated animals dark cells appeared more frequently in the rostral and caudal epithelium of the cleft. The results obtained suggest that the colloids is originated at least in part by involuted pituitary cells. There is also evidence that the follicular cavities of the Pars distalis and the cleft are continuous structures.