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Biomedical subjects

J Spacek

Publications and source records attributed to J Spacek.

At least 91 records · Page 5Linked to original sources
PubMed1982

'Free' postsynaptic-like densities in normal adult brain: their occurrence, distribution, structure and association with subsurface cisterns.

Samples of cerebral cortex (parietal and occipital) and thalamic nuclei (ventrobasal, posterolateral, dorsal lateral geniculate) from normal, adult, aldehyde perfusion fixed mice and rats were examined by electron microscopy for the presence of free postsynaptic-like densities (FPSDs). FPSDs are plaques of intracellular paramembranous electron-dense material, ultrastructurally indistinguishable from postsynaptic densities, but not aligned with a presynaptic specialization. In a systematic survey of the neuropil around 6000 neuronal perikarya, 250 FPSDs were encountered. Almost all of these were within dendritic spines and shafts and about 90% of them were apposed by a neuronal perikaryon, the remainder by a dendritic shaft. In every case a subsurface cistern (SSC) was present in the cell body or dendrite apposed to the FPSD, and was flattened along the extent of the FPSD. In none of the material were the FPSDs associated, even remotely, with degenerating elements, suggesting that they are not formed by degeneration of presynaptic boutons. The incidence of FPSD-SSC complexes was higher in thalamus than in cerebral cortex which, together with previous observations indicating their absence from normal cerebellar cortex, suggests significant regional variations in distribution. It is suggested that FPSDs might represent synaptic precursors perhaps induced to form as a response to loss (possibly age-dependent loss) of synaptic contacts on a neuron and that the SSCs are somehow involved in maintaining the FPSDs and/or preparing them for innervation by adjacent axon terminals to form new synaptic contacts.

Animals↗
PubMed1981

Reoxygenation of anoxic human tissues. An application for electron microscopy and its limits.

The reoxygenation technique originally used by Ferguson and Richardson (1978) for the revival and the ultrastructural improvement of tracheal and bronchial mucosae obtained post-mortem, has been applied to lung parenchyma, skin, liver, cerebellar cortex and skeletal muscle. The results show that the ultrastructural changes caused by post-mortem anoxia lasting 2 1/2-5 h were at least partially reversible in the alveolar epithelium and in the epidermis after 3 h reoxygenation in O2-saturated Krebs-Henseleit physiological solution at 37 degrees C. In contrast, reoxygenation was without any positive effect on anoxic changes in liver parenchyma, cerebellar cortex and skeletal muscle. The oxygen content of the immediate environment and temperature decrease are supposed to be the main protective factors influencing the reversibility of anoxia and thus affecting the results of reoxygenation. It might be expected that other superficially localized and air-exposed tissues (the nasal, paranasal, pharyngeal, laryngeal and oral mucosae, conjunctiva and cornea) could be revived or ultrastructurally improved by the reoxygenation technique.

Autopsy↗
PubMed1980

The presence and possible significance of agranular reticulum in paranodal oligodendrocyte cytoplasm and in periglomerular astrocyte processes.

Paranodal glial loops (lateral belt cytoplasm) of myelinated CNS and PNS fibres contain tubules of agranular reticulum, as well as microtubules, wound spirally around the axon. Similar agranular elements run circumferentially in the expanded rims of sheet-like astrocytic processes encapsulating thalamic synaptic glomeruli. A role for agranular reticulum in these sites in control of the ionic composition of adjacent cellular and extracellular compartments is suggested.

Animals↗
PubMed1980

Relationships between mitochondrial outer membranes and agranular reticulum in nervous tissue: ultrastructural observations and a new interpretation.

This study is concerned with extensions of the outer membranes of mitochondria in cells of nervous tissue, and with possible relationships between the extensions and the agranular reticulum. A variety of preparative techniques was applied to a large number of different central nervous tissues (CNS) and peripheral nervous tissues (PNS), using conventional thin sections, thicker sections (100 nm or more) and 3-dimensional reconstructions of serial thin sections. Extensions were commonly observed, particularly from the ends of longitudinally oriented mitochondria in axons and dendrites. Often these had the appearance of, and could be traced into apparent continuity with, adjacent elements of the agranular membrane. In addition to these apical tubular extensions, we also observed and reconstructed short lateral tubular or sac-like extensions and vesicular protrusions of the outer mitochondrial membrane. We discuss and discount the possibility that the extensions are artefacts, consider the structural and biochemical similarities between the outer mitochondrial membrane and agranular reticulum and propose that the outer mitochondrial is part of the agranular reticulum (or a specialized portion of the agranular reticulum). We suggest that the translocation of mitochondria in nerve cells, and probably in other cells as well, involves movement of the inner mitochondrial membrane and the enclosed matrix (mitoplast) within channels of agranular reticulum in continuity, or in transient continuity, with the outer mitochondrial membrane.

Animals↗
PubMed1980

Non-synaptic membrane specializations on the necks of Purkinje cell dentritic spines.

Non-synaptic membrane contacts were found on the necks of the Purkinje cell dendritic spines between the spine and astrocyte plasma membranes. They were tight- or gap-junction-like and disappeared after short periods of anoxia. No similar membrane contacts were found on the most common type of pyramidal cell dendrite spine. It is suggested that the described contacts could influence the movement of ions in the neck area.

Animals↗
PubMed1978

Melanotic neuroectodermal tumor of infancy with highly differentiated neural component. Light and electron microscopic study.

A pigmented tumor was removed from the maxillar alveolar process of a 5-month-old boy. It was examined by light and electron microscopy and a diagnosis of melanotic neuroectodermal tumor was made. In addition to connective tissue, three main cell types were identified: undifferentiated (stem) cells, melanocytes, and nerve cells with processes forming an abundant neuropil. Numerous axo-dendritic and occasional axo-somatic synapses were observed. The neural component demonstrated better differentiation in this example than in any reported so far.

Axons↗
PubMed1977

Systemic mastocytosis. Report of a case.

The case of a 20-year-old woman with systemic mastocytosis is reported. The disorder was not preceded by a clinically diagnosed local form of the disease; fibrous changes in organs, bone changes, eosinophilia and increased serotonin, heparin or histamine levels had not been observed. Clinical symptomatology was typical and the patient died one year after the first signs of the disease.

Adult↗