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[Characteristics of the ultrastructure of nerve cells in the cerebral cortex of old animals].
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[Ultrastructural pathology of the macro- and microglia].
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Morphology of the neural lobe of the hypophysis in rats treated with furosemide. II. Pituicytes.
Following three days of furosemide administration, the characteristics of the pituicytes in the neural lobe of the rat hypophysis were studied. The pituicytes of the animals which were treated with furosemide and had access to water during the treatment showed scarce cytoplasm organelles, conferring them with a clear appearance (light pituicytes), and a frequent finding was neurosecretory axons enclosed in their own cytoplasm. In the animals deprived of water during treatment, the pituicytes were dense (dark pituicytes) elongated, with a well-developed Golgi apparatus, numerous profiles of smooth endoplasmic reticulum and frequent annular gap junctions. It is concluded that the dehydration induced by the diuretic agent is the cause of the prevalence of the dark pituicytes.
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Neuronal regression during ageing: an ultrastructural study of the human cortex.
Neuronal regression has been ultrastructurally investigated in a neuronal sampling of the ageing human cerebral cortex. Even though the number of specimens examined is limited, there is an indication of an age-related regression involving the intraneuronal "nucleus-ribosome system". Such regressive signs are characterized by the polymorphous outline, invagination, reduced size of the nucleus, and in the nucleolar texture. Recognizable changes in the cytoplasm are, alterations in the density and distribution of free ribosomes and in the structure and organization of the rough endoplasmic reticulum cisternae. Furthermore light cytoplasmic areas, and increased number of microtubules and the gradual congestion of the perikaryon by age pigments are reliable criteria for identifying the sequence of morphologic events that occur during neuronal ageing. The above data provide some insight into the neuronal process and adding to a previous proposed model of neuronal maturation.
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Extrahypothalamic peptidergic neurosecretion. II. Neurosecretion in the subfornical organ of Rana esculenta L.
In the subfornical organ of Rana esculenta, three basic structural elements can be demonstrated by light microscopic and immunohistological techniques used for the demonstration of products of the neurosecretory system. These elements are: (i) neurones and their processes, which the constituents of the subfornical organ proper, (ii) afferent axons of the preoptic nucleus, and (iii) subependymal cells with coarse processes. The vesicular inclusions of the two former structures correspond to the neurophysin vesicles with respect to their size, structure and reactivity. The vesicles of the subependymal cells belong to the same size class, possess a somewhat granular internal structure and react atypically after the application of the ultrahistochemical technique for the identification of neurophysin vesicles. Presumably, their content is a glycoprotein with a high proportion of cystine. The peptidergic axons of the preoptic nucleus projecting to the subfornical organ form neuroneuronal synapses.
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Cytology of the arcuate nucleus in newborn male and female rats.
Five coronal levels of the arcuate nuclei in newborn male and female rats were examined with the transmission electron microscope. The nuclei from male and female neonates appear similar in all respects. All levels exhibit a significant population of round to oval cell profiles with large centrally located nuclei and scant cytoplasm which contains predominantly ribosomes, sparse mitochondria, and a few short cisternae of rough endoplasmic reticulum. These organelle-poor cell profiles resemble neuroblasts in other parts of the developing CNS. The arcuate nuclei of neonates also exhibit some cell profiles with the variety and quantity of organelles characteristic of mature neurons in the arcuate nuclei of adult rats. In addition, the neonatal arcuate nuclei show a paucity of synapses with apparent immaturity of those present, and numerous structures identified as growth cones. Definitive macroglia are not present in the arcuate nuclei of newborn rats.
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Localization of dopamine in the endocrine hypothalamus of the rat.
Microspectrofluorometry, fluorescence histochemistry and light and electron microscopic autoradiography have established the presence of sub-populations of neurons in the arcuate-periventricular region of the rat hypothalamus that sequester both radiolabeled dopamine and demonstrate formaldehyde-induced fluorescence. These characteristics are consistent with a catecholaminergic function. Selective sequestration of 3H-dopamine at the light and ultrastructural level is discussed in the context of an ultrashort loop autoregulatory mechanism for this neuronal population.
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Blood-brain barrier injury and neuroinflammation induced by SARS-CoV-2 in a lung-brain microphysiological system.
In some patients, COVID-19 can trigger neurological symptoms with unclear pathogenesis. Here we describe a microphysiological system integrating alveolus and blood-brain barrier (BBB) tissue chips that recapitulates neuropathogenesis associated with infection by SARS-CoV-2. Direct exposure of the BBB chip to SARS-CoV-2 caused mild changes to the BBB, and infusion of medium from the infected alveolus chip led to more severe injuries on the BBB chip, including endothelial dysfunction, pericyte detachment and neuroinflammation. Transcriptomic analyses indicated downregulated expression of the actin cytoskeleton in brain endothelium and upregulated expression of inflammatory genes in glial cells. We also observed early cerebral microvascular damage following lung infection with a low viral load in the brains of transgenic mice expressing human angiotensin-converting enzyme 2. Our findings suggest that systemic inflammation is probably contributing to neuropathogenesis following SARS-CoV-2 infection, and that direct viral neural invasion might not be a prerequisite for this neuropathogenesis. Lung-brain microphysiological systems should aid the further understanding of the systemic effects and neurological complications of viral infection.
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Smooth muscle in human intracerebral arterioles.
Aterioles from the human cerebral cortex have been examined by electron microscopy in several patients aged 43 to 58 years. The wall of all arterioles (ranging in size from 10-70 microns in diameter) is composed of a single layer of endothelium and from one to 5 layers of smooth muscle cells. A basal lamina supports the endothelium and encloses the smooth muscle cells. Smooth muscle cells were identified by morphological criteria that included the presence of dense bodies, abundant microfilaments and numerous pinocytotic vesicles. Some of the intracerebral arterioles were observed in a constricted state indicating functional smooth muscle cells. The presence of functional smooth muscle cells in human intracerebral arterioles indicates that these arterioles are capable of vasoconstriction which may be a possible factor in some clinical conditions.
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Fate of neurohypophysial granule membranes after secretion in the rat: generation of a new apparent organelle by freezing and thawing secretory granules.
The contents and membranes of the secretory granules in the rat neurohypophysis were labelled in vivo with [35S]cysteine and [3H]choline respectively. Density-gradient centrifugation of the labelled granules showed the membrane label to be distributed largely between two peaks: one associated with intact granules and one with the characteristics of empty granule envelopes. Stimulation of hormones release in vitro led to the movement of membrane label from the intact granule fraction to the other one, consistent with the recapture of membrane as large vesicles. Freezing and thawing the crude granule fraction, ostensibly to aid osmotic fracture, produced a single membrane component with a density intermediate between the two original fractions.