Beryn Frank

Will central nervous systems in the adult mammal regenerate after bypassing a lesion? A study in the mouse and chick visual systems

Abstract We determined whether or not optic axons in the adult mammalian retina would regenerate well if allowed to bypass a lesion scar. In one series we produced microlesions with fine needles in the ganglion cell fiber layer of adult mouse retinas and later examined the retinas as silver-stained flat mounts to observe the behavior of optic axons that bypassed the lesion. Such axons continued to grow abortively, i.e., grew randomly and for only short distances, whether growing within a sector of Wallerian (anterograde) degeneration or in the neighboring zone of intact optic axon bundles. In a second series we produced optic nerve crushes in adult mice and observed the behavior of optic axons growing retrograde into the retina. These fibers similarly grew abortively whether in a zone of intact fiber bundles or when a retinal lesion was produced with the crush, in the sector of Wallerian degeneration. Retinal lesions in newly hatched chicks produced a comparable picture of abortive (short-distance) growth, but the optic and centrifugal fibers had a greater tendency to remain oriented within the ganglion cell fiber layer than did mouse axons. This improved orientation may be the consequence of the greater number of optic fibers in the chick retina and hence the greater opportunity for nonspecific contact guidance. The results indicate that blockage (by a lesion scar or myelin debris) and hypoxia are not the key causes of regenerative failure, as regeneration failed even when those factors were minimal.

A characteristic vesiculobullous eruption in patients with chronic lymphocytic leukemia

We report ten cases of a characteristic vesiculobullous eruption in patients with chronic lymphocytic leukemia. Clinically, six lesions were thought to represent insect bites. All ten patients had bone marrow examinations that confirmed the diagnosis of chronic lymphocytic leukemia. In six of ten patients serum protein and immunoelectrophoresis were performed. Six patients had immunoglobulin disturbances: one polyclonal IgG and IgM gammopathy, two monoclonal IgM gammopathies, two decreased levels of IgA, and one hypogammaglobulinemia. Direct and indirect immunofluorescence procedures were performed on two patients and results were negative. Immunoperoxidase procedures for IgG stained nonspecifically along torn/separated areas of the basement membrane in five patients. No immunohistochemistry was performed on the remaining three patients. The etiology and pathogenesis of these lesions are unknown. We favor the concept that they represent an unusual reaction to an arthropod bite, secondary to the underlying lymphoproliferative disorder. A second, and less likely theory, is that these lesions represent an unusual clinical presentation of bullous pemphigoid in patients with chronic lymphocytic leukemia.

Mast cells in sun-exposed and non-sun-exposed skin. An autopsy study.

One hundred ten skin biopsies were taken from 55 consecutive autopsies to evaluate the number and location of mast cells in the dermis. For each autopsy, one biopsy was taken from the V of the neck (sun-exposed area) and the other from the upper thigh (non–sun-exposed area). Normal-appearing skin was biopsied. There were 28 men and 27 women ranging in age from 16 to 94 years. Fifty-three patients were Caucasian and two were Negro. Mast cells were counted in 10 random high-power fields in the papillary dermis only. The average number of mast cells per high-power field (x 400) in sun-exposed skin for both men and women was 8.19 (65/mm2 or 13,000/mm3) with one standard deviation of 4.08, while that of non–sun-exposed skin was 7.52 (60/mm2 or 11,900/mm3) with one standard deviation of 3.62. The difference between the number of mast cells in sun-exposed and non–sun-exposed skin was not statistically significant. In addition, no statistically significant differences were observed for the average number of mast cells per high-power field in regard to sex or the presence of malignancies.

Axon end-bulb swellings and rapid retrograde degeneration after retinal lesions in young animals

After making a lesion of the retina, anterograde (Wallerian) and retrograde degeneration of optic axons occurred more rapidly in newborn mice than in adults. Axon sprouting occurred only in adult mice, perhaps because retrograde degeneration may have been too rapid and severe for sprouting to occur in newborns. Retinal lesions in mice of any age produced end-bulb swellings initially on both sides of the lesion. In all animals, dense packing of lysosomes and other organelles occurred in end-bulbs on the side of Wallerian degeneration but did not occur in end-bulbs on the retrograde side, where accumulation of smooth endoplasmic reticulum was the most characteristic change. Retrograde end-bulbs appeared much like growth cones, which sprouted in adults, but degenerated in younger animals. Continuing daily enlargement of end-bulb swellings was noted on the Wallerian side of lesions in adults, but not in newborns. Such enlargement is believed to have resulted from retrograde axoplasmic transport and suggests that such transport may be greater in adults than in newborns.

Pyridine-Silver Methods for the Study of Optic Axons in Retinal Whole Mounts

The optic fibers in the retinas of diverse species may be selectively stained and viewed en bloc in the embryonic and adult states. Treat the eye as follows: 1) 50% pyridine for at least 16 hr, 2) distilled water 3--4 hr, 3) 20% H2O2 until the eye is a light brown, 4) 95% ethanol overnight, 5) 1.5% AgNO3 for 2--6 days at 37 C, 6) in water, remove the vitreous, then direct 0.25% pyrogallic acid in 1.25% formalin against the retina for 2--5 secs until the optic fibers are reduced to a coffee-copper color (1--4 minutes), 7) dissect the retina and mount flat on a glass slide, 8) cover with glycerin, apply a coverslip, and fix in place with nail polish. Variants for particular species are given. The technique offers an advantage over Golgi and methylene blue methods which tend to stain only a small percentage of fibers and frequently do not work at the earliest stages of development.

Retina as a model system in paraplegia research: Pharmacologic studies

Abstract The retina may be a useful model system for the rapid testing of potentially neuroregenerative agents. We tested 24 different pharmacologic agents for their ability to promote regeneration of severed optic axons in the adult mouse retina. In this initial series of 738 mice, these agents were ineffective in reducing scar formation, stimulating axonal elongation, improving axonal guidance or retarding retrograde degeneration.