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Biomedical subjects

W Zenker

Publications and source records attributed to W Zenker.

At least 55 records · Page 3Linked to original sources
PubMed1979

[Fiber analysis of human ventral and dorsal roots on the basis of different acetylcholinesterase activity].

Marked differences in the AChE activity of myelinated nerve fibers of ventral and dorsal roots could be established in human post mortem material. After a fixation time of 3 h and a critical incubation period of 24 h, in the mean 96% of the myelinated ventral root but only 4% of dorsal root fibers showed reaction product, detectable by the light microscope. The percentage of stained fibres varies, to some extent, in the different segments. Groups of very thin myelinated fibres within the ventral roots between the segments C-8 and L-3, showing a conspicuous high enzyme activity, are interpreted as pre-ganglionic sympathetic fibres; similar elements in the sacral ventral roots may represent parasympathetic fibres. The method of Karnovsky, applied under conditions established in this study, can be used for analysis of fibre types in a given human peripheral nerve.

Acetylcholinesterase↗
PubMed1978

Acetylcholinesterase activity in motor nerve fibres in correlation to muscle fibre types in rat.

Rat muscle nerves were examined histochemically for their activity of acetylcholinesterase (AChE). The corresponding muscles were stained for myofibrillar ATPase and for NADH diaphorase. The nerves to the extensor digitorum longus (EDL) muscle and to the medial head of the gastrocnemius (MG) muscle consist of a motor axons of high AChE activity. Both muscles are characterized by the prevalence of type II muscle fibres. On the other hand, the soleus muscle and the quandratus femoris muscle, both mainly composed of type I muscle fibres, are innervated by a motor axons of low AChE activity. Since it is well established that EDL and MG are typical fast-twitch muscles and that the soleus, and probably also the auadratus femoris, is a typical slow-twitch muscle, it is suggested that, in rat, fast muscles are innervated by motor nerve fibres of high AChE activity and slow muscles are innervated by motor axons of low AChE activity.

Acetylcholinesterase↗
PubMed1977

Somatopetal transport of horseradish peroxidase (HRP) in the peripheral and central branches of dorsal root ganglion cells.

The axonal transport of HRP in both the peripheral and central branches of dorsal root ganglion cells was studied in rats. For studying axonal transport in the peripheral branch HRP as a dry substance was applied to the peroneal nerve injured either by teasing, by cutting or crushing. After a short survival time (22 h) mainly small spinal ganglion cells of the corresponding segments were labelled, while after a prolonged survival time (70 h) mainly large cells were labelled. These labelling differences are referred to different transport rates or to differences in the process of accumulation of HRP in neurons of various sizes. No evidence could be found for HRP transport from the peripheral into the central branch. Injection of HRP into the spinal cord (survival time 22 h) or into the dorsal column nuclei (survival time 46 h) was followed by labelling of numerous spinal ganglion cell perikarya of all sizes. Reaction product was found also within the prebifurcation segment of spinal ganglion cell processes. On the basis of light microscopic exploration only somatopetal transport could be detected.

Animals↗
PubMed1976

The prebifurcation section of the axon of the rat spinal ganglion cell.

The long nonmyelinated portion of the unipolar process of spinal ganglion cells resembles in many instances the perikaryon and is characterized by the following structural pecularities: 1. The surface membrane displays numerous invaginations and evaginations, which interdigitate with folds of the investing satellite cells, resulting in a considerable increase of the area of intercellular contact. The intercellular gap frequently widens to intercellular cisternae. 2. The axolemma of the most distal part of the nonmyelinated portion is undercoated by dense material and thus resembles the "initial segment" of multipolar nerve cells. 3. The unipolar process of spinal ganglion cells shows a conspicuously high density of neurotubules. The neurotubules frequently collect into fascicles in the same manner as was described for the initial segment of multipolar nerve cells. 4. The nonmyelinated part as well as the first internodes of the myelinated part of the unipolar cell process contain a highly developed axoplasmic reticulum, many-partly huge-mitochondria, a striking number of dense bodies and clusters of ribosomes. The myelin sheath of the first internodes of the unipolar process is unusually thin in relation to their axon diameters. At successive internodes the thickness of the myelin sheath increases stepwise, the Schwann cell loops of the paranodal zones changing their appearence correspondingly. In the great number of ultrathin sections scanned in this study, not one synapse was found, neither in the unmyelinated initial segment nor in the soma.

Animals↗
PubMed1975

Effect of zinc ions on structure and distribution of neurotubules (author's transl).

Being interested in factors stabilizing neurotubules (NTs) in situ, we decided to immerse short segments of fresh rat peripheral nerves in buffered solutions containing ZnCl2 in final concentrations up to 10-2 m prior to fixation with buffered osmium or glutaraldehyde, both containing ZnCl2. Zinc treatment resulted in a remarkable structural preservation of NTs after fixation with osmium, though they are not preserved by osmium fixation alone. Cross sections of myelinated nerve fibres show NTs arranged predominantly in compact groups. Within the groups NTs are surrounded or embedded in an electron dense fine granular material. The occurrence of incomplete C-shaped NTs and NT-like densities can be seen. NTs exhibit relatively constant distances and sometimes geometric patterns of arrangement. A lot of intertubule cross bridges and NTs with arms could be observed. In longitudinal section the bridge and arm spacing is seen to be periodic along the tubule axis at about 500 A. Zinc treatment of nerves fixed in glutaraldehyde resulted in the same ultrastructural alterations described above. The resistance of zinc-stabilized NTs to degradation by osmium and the ultrastructural changes induced by zinc are discussed. The results suggest that in the presence of zinc ions osmium-labile NTs are transformed--by disassembly and reassembly--to osmium-stabile microtubules that are not identical with preexisting ones.

Animals↗