A device for dark field microphotography at low magnifications

Adult albino rats received callosotomies or lesions in the paracingular cortex. Between 12 h and 3 months after injury the structure and topography of the degeneration products were studied by light- and electron-microscopy. The degeneration process was quantified by television-image analysis applied to sections prepared according to a new technique that stains reliably degenerating terminals and lysosomes (Gallyas et al. 1980). All types of cortico-cortical connections show a multiphasic degeneration process: During a precursor stage a small number of dense bodies and mitochondrial granules are stained. These and the few early degenerating axon terminals are much more diffusely distributed than the large number of terminals that degenerate during the following period. The terminal degeneration shows a biphasic time course. One maximum appears at 2-7 days post operation, which corresponds to the well known direct consequence of axotomy. The second peak at 10-20 days post operation could be caused by transneuronal reorganization of the cortical connectivity. Terminal degeneration always begins along the borders between cortical regions and areas, but it may change its laminar and columnar distribution pattern during the second phase. The degeneration products that are phagocytosed by astrocytes seem to be removed by intracellular transport to their perivascular endfeet. The degeneration process ends with fiber degeneration which, especially in laminae I and VI, may form a separate peak after 20 days or more.

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The temporo-spatial course of degeneration after cutting cortico-cortical connections in adult rats

Wolff

Eins

Holzgraefe

et al. 1981

Cell Tissue Res.

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Distribution patterns and individual variations of callosal connections in the albino rat

Záborszky

Wolff

1982

Anat Embryol

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After complete callosotomy the distribution of degeneration products was re-investigated in adult albino rats. Three to seven days post operation, coronal, horizontal and "flattened" sections were impregnated according to the new methods of Gallyas et al. (1980) which stain degenerating axons and terminals, respectively. The regional distribution patterns of callosal terminals were directly visualized with dark field illumination at low magnification. With this technique the distribution pattern of axons and terminals could be compared between different cortical regions and individuals. Callosal terminals tend to accumulate in patches or bands along the borders of cortical regions and areas. The concentration of callosal terminals was especially high at the common corners of more than two cortical areas. The callosal system shows a rather constant distribution pattern which is composed of column shaped subunits. Considerable individual variations were recognized concerning the number, position, shape, density and contiguity of the columnar units either occupied by callosal connections or empty. Although the laminar distribution of callosal terminals shows some similarities in different areas of the cortex, there is no common laminar pattern characteristic either for the whole neocortex or for any cortical region. The comparison between consecutive sections stained either for degenerating fibers or degenerating axon terminals revealed that the callosal axons do not determine directly the arrangement and packing density of callosal synapses. Whatever determines the position and amount of callosal synapses this influence seems to be exerted via translation into the columnar organization.

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A simple device for ultramicroscopic studies of motile microorganisms

Passarelli

Barsanti

Gualtieri

1990

Micron and Microscopica Acta

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A device for dark field microphotography at low magnifications

Cited by 7 publications

References 2 publications

The temporo-spatial course of degeneration after cutting cortico-cortical connections in adult rats

The temporo-spatial course of degeneration after cutting cortico-cortical connections in adult rats

Distribution patterns and individual variations of callosal connections in the albino rat

A simple device for ultramicroscopic studies of motile microorganisms

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