Neurons in the central nervous system are separated by extracellular spaces, the distribution, composition and function of which are not unequivocally known. Earlier electron microscopic studies of chemically-fixed tissues demonstrated extracellular spaces composed of uniformly narrow, apparently empty channels constituting 3-5% of the brain volume. The results of more recent morphological and non-morphological studies support the existence of less uniform intercellular channels, varying in dimension from 100 Å to almost 1 μ, and constituting 20-25% of the brain volume. Although this space is not revealed in electron micrographs of chemicallyfixed nervous tissues, it is demonstrated readily in specimens fixed by freeze-drying or freeze-substitution (Fig. 1). The dynamic nature of those extracellular spaces, as visualized in electron micrographs of nervous tissue fixed by freeze-substitution, was demonstrated in studies of normalbrain maturation. An extracellular space of 40% became gradually smaller as development proceeded to reach the smaller extracellular space characteristic of mature animals.
Lysosomal storage disease involving the brain, spinal cord, liver, and spleen was discovered in a 6-month-old male emu ( Dromaius novaehollandiae). The diagnosis was based on light and electron microscopic studies and histochemical staining characteristics. This is the first case of lysosomal storage disease reported in a ratite.
It is well established at present that the course of pathological processes in local brain trauma depends on immunological reactivity of the organism and to a great extent on its sensitization to brain antigens.This study was undertaken to clarify the early ultrastructural changes of the nervous tissue in perifocal area of local brain wound in normal rabbits, those sensitized to brain antigens or desensitized by brain antigens after preliminary sensitization. In addition, the influence of sensitization and desensitization per se on brain tissue ultrastructure was studied. The animals were sensitized and desensitized with intravenous and intraperitoneal 20% water-salt extract of homologous brain tissue. The immunological state of the animals was checked by using the complement fixation test. The fixation of antibrain antibodies in perifocal area of the wound was studied by the direct Coons immunofluorescence method.
Bromodeoxyuridine (BrdU) immunohistochemistry is the method of choice for labeling newly generated cells in the brain. Most BrdU studies utilize paraformaldehyde-fixed brain tissue because of its compatibility with both BrdU and other immunohistochemical methods. However, stronger fixation is required for electron microscopic studies, and unfixed tissue is needed for biochemical and molecular studies. Because there are no systematic studies comparing the effects of different fixatives on BrdU immunohistochemistry in brain tissue, we compared BrdU immunohistochemical methods in brain tissue fixed with 4% paraformaldehyde, a mixed glutaraldehyde–paraformaldehyde fixative for electron microscopy, and unfixed tissue from brains perfused only with buffer and flash frozen. After optimizing immunostaining protocols, qualitative assessments of light microscopic diaminobenzidine labeling and of double-label immunofluorescence with confocal microscopy demonstrated excellent BrdU labeling in each of the three groups. Quantitative stereological assessment of the number of BrdU-labeled cells in rat dentate gyrus showed no significant difference in the number of labeled cells detected with each perfusion protocol. Additionally, we developed a protocol to visualize BrdU-labeled cells in the electron microscope with adequate preservation of fine structure in both rat and monkey brain.
Dr. Diamond has presented important in vivo evidence reaffirming the thesis of Dr. Odell that unbound bilirubin is the toxin causing kernicterus. Unfortunately, we have not yet learned how to apply this knowledge to the management of the jaundiced newborn infant. For example, we are still left with the problem of deciding which jaundiced infant needs treatment. Recent electron microscopic studies in the Gunn rat emphasize this point. At birth, in homozygous (jj) rats born to heterozygous (Jj) mothers, no staining of the tissues is present and there are no cellular abnormalities to be found in the brain. By 4 to 8 hours of life, jj animals display slight clinical jaundice and their brains, after perfusion with saline or formalin to wash out capillary blood, exhibit equivocal localized staining.
Fluorescence and electron microscopic studies of corpus striatum of the brain