Mast cells in normal and sectioned peripheral nerve

Summary An investigation is reported on the properties and quantitative distribution of mast cells in normal and sectioned peripheral nerve. A considerable number of mast cells has been found in the epineurial connective tissue in normal rats, as well as scattered mast cells in the endoneurium. After nerve section there was an about five-fold increase in the number of endoneurial mast cells throughout the distal part of the sciatic nerve.The mast cell granules in normal and sectioned nerve showed the same histochemical properties as mast cell granules in other tissues, i.e. strong toluidine blue metachromasia resistant to alcohol dehydration, and persistence of dye binding and metachromasia at pH below 1. Furthermore, the metachromasia is unaffected by extraction with chloroform and methanol prior to staining. The metachromatic component of the mast cell granules can be differentiated by these properties from other metachromatic structures in normal and sectioned nerve. The significance of the findings is discussed, in particular the possible relation of endoneurial mast cells to the degradation of myelin. Acknowledgements. The authors are indebted to Miss Kristina Müntzing for skilful technical assistance.     

Transport of myo-inositol into endoneurial preparations of sciatic nerve from normal and streptozotocin-diabetic rats.

myo-Inositol transport by a viable rat sciatic-nerve preparation is described. Such 'endoneurial' nerve preparations accumulated myo-inositol by an energy-dependent saturable system. Streptozotocin-diabetes reduced myo-inositol transport into sciatic nerve by approx. 40%. Elevated medium glucose concentration reduced myo-inositol transport into control nerves to a similar extent. Fructose and sorbitol did not inhibit myo-inositol transport. Inclusion of an aldose reductase inhibitor in the medium counteracted the reduced myo-inositol transport caused by elevated glucose concentration. The importance of these results to the problem of diabetic neuropathy is discussed.     

The behavior of normal peripheral nerve in Tissue culture

Summary A phase contrast and time lapse cinematographic study of normal mouse sciatic nerve cultured in vitro was made. The Rose chamber and chicken plasma clot methods were employed. The growth was characterized by three basic cell types: a spindle-shaped cell with a bulging nucleus, a racket-shaped cell with a short wide fan-shaped process and an opposite filiform process, and a kite-shaped cell with abundant ectoplasm. The spindle-shaped cells exhibited a pulsatile rhythmic activity. The rhythm of contraction varied from two to eighteen minutes. No contractile activity was observed in the case of the racket-shaped cells nor in the kite-shaped cells. The spindle-shaped cells were thought to be Schwann cells, the kite-shaped cells were considered of a fibroblastic nature, whereas no source could be found for the racket-shaped cells, although the perineurium was considered as a possible origin. The cultures were maintained up to 80 days, but at no time were phagocytes, observed. With the methods employed no transformation of cells from one type to another took place, and the Schwann cells did not transform themselves into phagocytes.This work was supported in part by grant P-405A from the American Cancer Society and by NIH grant NB-06391-02.     

Triple staining of normal and degenerating nervous tissue.

A method of counterstaining sections impregnated according to a previously reported modification of the Glees silver impregnation is described. The basis for this counterstain is the Klüver-Barrera luxol fast blue technique. The results are illustrated and the advantages and disadvantages of the procedure are discussed.     

Motor nerve terminal loss from degenerating muscle fibers

The fate of nerve terminals following elimination of postsynaptic target cells was studied in living mouse muscle. Several days after muscle fiber damage, observations of previously identified neuromuscular junctions showed that motor nerve terminal branches had rapidly disappeared from degenerating muscle fibers. Following muscle fiber regeneration, loss of terminal branches ceased and nerve terminals regrew, reestablishing some of the original sites and adding new branches. The distribution of acetylcholine receptors reorganized in the regenerated muscle so that perfect alignment was reestablished with the newly configured nerve terminals. These results argue that the maintenance of the full complement of nerve terminal branches at a neuromuscular junction is dependent on the presence of a healthy muscle fiber. Similarly, regenerating muscle is dependent on the nerve terminal for the organization and maintenance of postsynaptic receptors.     

Antioxidants in peripheral nerve

Oxidative stress and antioxidants have been related in a wide variety of ways with nervous tissue. This review attempts to gather the most relevant information related to a) the antioxidant status in non pathologic nervous tissue; b) the hypothesis and evidence for oxidative stress (considered as the disequilibrium between prooxidants and antioxidants in the cell) as the responsible mechanism of diverse neurological diseases; and c) the correlation between antioxidant alterations and neural function, in different experimental neuropathies. Decreased antioxidant availability has been observed in different neurological disorders in the central nervous system, for example, Parkinson's disease, Alzheimer's disease, epilepsy, amyotrophic lateral sclerosis, cerebral ischaemia, etc. Moreover, the experimental manipulation of the antioxidant defense has led in some cases to interesting experimental models in which electrophysiological alterations are associated with the metabolic modifications induced. In view of the electrophysiological and biochemical effects of some protein kinase C inhibitors on different neural experimental models, special attention is dedicated to the role of this kinase in peripheral nervous tissue. The nervous tissue, central as well as peripheral, has two main special features that are certainly related to its antioxidant metabolism: the lipid-enriched membrane and myelin sheaths, and cellular excitability. The former explains the importance of the glutathione (GSH)-conjugating activity towards 4-hydroxy-nonenal, a biologically active product of lipid peroxidation, present in nervous tissue and in charge of its inactivation. The impairment of the latter by oxidative damage or experimental manipulation of antioxidant metabolism is discussed. Work on different experimental neuropathies from author's laboratory has been primarily used to provide information about the involvement of free radical damage and antioxidants in peripheral nerve metabolic and functional impairment.     

Phagocytosis of degenerating myelin in transected feline optic nerve: an immunohistochemical study

The phagocytic activity of neuroglial cells in adult feline degenerating optic nerve was investigated by immunocytochemistry at both light and electron microscopy levels. Degeneration was initiated by unilateral eye enucleation and the segment distal to the transection showing true Wallerian degeneration was examined. Following enucleation, twelve adult domestic cats were examined over a period of seven to 215 days. All cases showed slow clearance of myelin debris and absence of proliferating monocytes throughout the post-enucleation period. All phagocytic cells present were neuroglial cells, and many of these cells expressed oligodendroglial antigens. These findings demonstrate the persistence of an active population of oligodendrocytes that might play an additional functional role during Wallerian degeneration of feline optic nerve.     

Phagocytosis of degenerating myelin in transected feline optic nerve: an immunohistochemical study

The phagocytic activity of neuroglial cells in adult feline degenerating optic nerve was investigated by immunocytochemistry at both light and electron microscopy levels. Degeneration was initiated by unilateral eye enucleation and the segment distal to the transection showing true Wallerian degeneration was examined. Following enucleation, twelve adult domestic cats were examined over a period of seven to 215 days. All cases showed slow clearance of myelin debris and absence of proliferating monocytes throughout the post-enucleation period. All phagocytic cells present were neuroglial cells, and many of these cells expressed oligodendroglial antigens. These findings demonstrate the persistence of an active population of oligodendrocytes that might play an additional functional role during Wallerian degeneration of feline optic nerve.