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Biomedical subjects

A HESS

Publications and source records attributed to A HESS.

At least 19 recordsLinked to original sources
PubMed1960

The fine structure of degenerating nerve fibers, their sheaths, and their terminations in the central nerve cord of the cockroach (Periplaneta americana).

The connectives above and below the second thoracic ganglion and nerves to and from the mesothoracic leg were severed in Periplaneta americana. Isolated ganglia and severed nerve cord were examined in the electron microscope. In the connectives, sheaths of degenerating fibers remain continuous but become thicker and more dense. There is increase in number and more haphazard disposition of the neuroglial processes which ensheath the axons. The cytoplasm contains vacuoles. Dense droplets normally intercalated between the layers of neuroglial processes ensheathing the axons are strikingly increased in number. The axoplasm with its organelles forms dense clumps. Mitochondria in axons are enlarged, the intramitochondrial matrix is more dense, and the internal folds are disorganized. In ganglia, mitochondrial changes in terminal parts of the axons appear similar to those described in the parent axons in the connective. The synaptic portions of nerve fibers appear very dense. Alterations of the sheath are minimal. Synaptic particles in the degenerating axoplasmic coagulum undergo only slight morphological changes and are still present up to 6 days after severance of their nerve fibers. It is difficult to assess whether there are any alterations in the total number of synaptic particles during degeneration.

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PubMed1958

The fine structure of nerve cells and fibers, neuroglia, and sheaths of the ganglion chain in the cockroach (Periplaneta americana).

The abdominal nerve cord of Periplaneta americana was studied utilizing light and electron microscopes. In the nerve cells, delicate granules, similar to those probably responsible for cytoplasmic basophilia, are evenly distributed in "dark" cells and clumped in "light" cells. Neuroglial cells are stained metachromatically by cresyl violet. The neuroglial cells have many processes which ramify extensively and are enmeshed to form overlapping layers. These imbricated processes ensheath the nerve cells; the inner layer of the sheath penetrates into the neuron and is responsible for the appearance of the trophospongium of Holmgren. Nerve fibers are embedded within glial cells and surrounded by extensions of the plasma membrane similar to mesaxons. Depending on their size, two or several nerve fibers may share a single glial cell. Nerve fibers near their terminations on other nerve fibers contain particles and numerous, large mitochondria. The ganglion is ensheathed by a thick feltwork of connective tissue and perilemmal cells. The abdominal connective has a thinner connective tissue sheath which is without perilemmal cells. The nerve fibers and sheaths in the connective become thinner as they pass through ganglia.

Animals↗