Grayson Scott

Erythrocytes are essential for development of cerebral vasculopathy resulting from subarachnoid hemorrhage in cats.

In an effort to determine which blood elements play a critical role in the development of cerebral vasospasm, adult cats were subjected to prepontine injection of either autogenous whole blood or erythrocyte-free blood containing latex beads as a substitute morphologic marker. Seven or 10 days later the cats were anesthetized and perfused with fixative, and the basilar arteries were prepared for light and electron microscopy. Successful clot deposition was confirmed by the presence of numerous erythrocytes or latex beads within the adventitia of vessels. In agreement with previous studies, instillation of whole blood produced luminal narrowing associated with profound ultrastructural changes in all layers of the vascular wall. No significant alterations, however, occurred in arteries bathed in erythrocyte-free blood. These findings suggest first, that erythrocytes are essential for the development of the vasculopathy associated with chronic cerebral vasospasm, and second, that the role, if any, of other blood elements is not autonomous.

Isolation of synaptic complexes in a caesium chloride density gradient: electron microscopic and immunohistochemical studies.

A technique is described for the improved isolation of synaptic complexes. Homogenates of guinea pig cerebellum and cerebral cortex were subjected to centrifugation, first in a discontinuous sucrose gradient, and secondly in a continuous caesium chloride gradient. Of the six bands that were obtained, band four contained a high proportion of synaptic complexes showing both pre‐ and postsynaptic elements attached to each other; myelin and free mitochondria were not contaminants of this fraction. Fluorescein‐labelled γ‐globulin prepared against band four reacted with synaptic regions of cerebellum and cerebral cortex, but not with cervical cord.

Antigenic properties of large ganglion cells isolated from ox retina

Antisera were prepared against large ganglion cells (>28 μm diameter) that were isolated from ox retina. The cells of the retina were dispersed with a cytosieve and a nylon cloth and then isolated by centrifugation in a discontinuous sucrose density gradient. Rabbits were injected subcutaneously with the isolated cells suspended in complete Freunds adjuvant and then injected intravenously with the cells suspended in a sucrose solution. Antibodies were obtained which formed precipitin lines in Ouchterlony plates when diffused against Triton X-100 extracts of large ganglion cells and which agglutinated selectively the large ganglion cells from retinal dispersions. The specificity of the antisera for the retinal cell types was examined using immunofluorescence and immunoperoxidase methods. Immunoglobulins reacted most intensely with the large ganglion cells and their projections in the internal plexiform layer of retinal sections. An intense reaction within the external plexiform layer was also observed. Although the antisera were prepared against the large ganglion cells from ox retinas, 6 μm thick sections of ox, dog, cat, rabbit, macaque, rat and goldfish retinas reacted similarly with the immunoglobulins, indicating that the antigens were not species-specific. A much weaker reaction was observed between the antisera and the smaller ganglion cells, the amacrine cell bodies and the cone receptor cells. The immunuglobulins also reacted with the granule and Purkinje cells in the cerebellar cortex. One predominant retinal antigen was isolated by affinity chromatography; this protein or subunit had a molecular weight of 49000 daltons as determined by electrophoresis on polyacrylamide gels containing sodium dodecylsulfate.

Does cerebral vasospasm result from denervation supersensitivity

This study examined the role of denervation supersensitivity in the development of cerebral vasospasm. Adrenergic denervation of cat basilar artery was accomplished by resection of the superior cervical ganglia or by injection of 6-hydroxydopamine into the cisterna magna. In vivo dose-response characteristics were determined for normal and for denervated arteries, and no significant differences were found between topical applications of serotonin, norepinephrine, epinephrine, fresh blood, or incubated blood. In addition, analysis of cat blood incubated in vitro revealed that the levels of serotonin, norepinephrine, and epinephrine diminished over time, whereas levels of hemoglobin and methemoglobin increased up to Day 14. The results of this study indicate that adrenergic denervation is not the cause of cerebral vasospasm and that, whatever the mechanism, hemoglobin is far more likely to play a role than are the other agents.

Trisomy 16 mice: neural, morphological, and immunological studies

The occurrence of trisomy (i.e, the presence of an additional chromosome in the genome) is associated with distinct and deleterious effects on the development and cellular processes of affected individuals. Efforts are now directed toward understanding the mechanisms by which the trisomic condition causes adverse effects. Trisomy for autosome number 21, Down’s syndrome, is of particular interest because of its high frequency (1 in 700 live births), the associated mental retardation, and the observation that individuals with the condition survive to the fourth and fifth decades. The Down syndrome has been the single most extensively investigated entity involving mental retardation since it was first identified in the middle of the 19th century.’,* The discovery of the chromosomal basis of Down’s syndrome in 19593 provided the initial impetus to relate specific phenotypic effects with cellular processes that are altered by the presence of the additional genetic material. Such studies have included: ( 1 ) detailed characterizations of Down’s syndrome morphologic phen~type;~,’ (2) identification of gene dosage phenomena for genes located on chromosome 21 (e.g., superoxide dismutase I); and ( 3 ) observations of possible effects of trisomy on cell proliferation.6 An extension of this work is now possible using trisomic mice that can be generated by using males or females with appropriate Robertsonian translocation ch rom~somes .~ The trisomy for murine autosome 16 is of interest because murine chromosome 16 contains several genes that are present in human chromosome 21. The shared genes include those coding for superoxide dismutase-1 , the alpha and beta interferon receptors, and the response of cells to beta-adrenergic agonist s t im~la t ion .~ .~ Three of these genes code for cell surface receptor linked systems. As with the Down’s syndrome, gene dosage effects also occur for the gene products of these loci in the trisomic mice. A difficulty with the trisomy 16 system is that none of these mice survive beyond term with breeding schemes that have been used so far.I0 Our current investigations include an evaluation of the effects of the additional chromosome 16 on the expression of cell surface markers, (e.g., the major histo-

ULTRASTRUCTURAL AND BIOCHEMICAL COMPARISONS OF DENDRODENDRITIC SYNAPTOSOMES FROM BOVINE SUPERIOR COLLICULI AND OLFACTORY BULBS WITH AXODENDRITIC AND AXOSOMATIC SYNAPTOSOMES

Abstract– The buoyant density, ultrastructure and protein composition of dendrodendritic (DD), axodendritic (AD) and axosomatic (AS) synaptosomes were compared. DD synaptosomes prepared from either bovine superior colliculi or olfactory bulbs sedimented in 0.32 m‐sucrose at 1000 g whereas AD and AS synaptosomes from frontal and temporal lobe cortices sedimented at 10.000 g. In gradients of Renografin the DD contacts banded at a density of 1.12 whereas AD and AS banded at 1.07. The DD contacts appeared as large clusters of serial contacts, and each individual terminal had a mean surface area of 1.48 μm2; the mean area of AD and AS terminals was less than 0.35 μm2. The protein compositions of DD, AD and AS synaptosomes were quite similar, with minor exceptions. These findings suggest that different synaptosmal types evolved from common membrane constituents.

Fractionation of subcellular elements from rat central nervous tissue in a cesium chloride gradient: Biochemical and ultrastructural studies

Abstract Subcellular particles from central nervous tissue of albino rats were separated into 6 fractions in a cesium chloride density gradient. Ultrastructural studies indicated that three of the bands were composed almost exclusively of smooth membranes; one (Band 6) contained ribosomes; one (Band 5) contained a large number of dense-core particles 900–1200 A. in diameter and Band 4 contained many multivesicular bodies. Following the injection of 3H-uridine into rats of different ages, the specific activity of each of the fractions was determined. Bands 5 and 6 had a higher specific activity than the other bands. The maximum activity was at 15 days postnatum. In the 40-day-old and the adult, the specific activity of Bands 5 and 6 was less than one-fifth that of the 15-day rat. The relation of the specific activity in each fraction to the ultrastructure of the nervous tissue at different stages of development is described and discussed.