David S. Maxwell

Immunocytochemical localization of glycerol-3-phosphate dehydrogenase in rat oligodendrocytes

In this study, two indirect immunoperoxidase staining procedures were used to investigate the cellular localization of rat brain glycerol-3-phospate dehydrogenase (EC 1.1.1.8;GPDH). At the light and electron microscopic level, we found that the use of monospecific rabbit antibodies to GPDH consistently resulted in the specific staining of only one glial cell population. GPDH-positive cells in perineuronal, interfascicular and perivascular positions were identified as oligodendrocytes by classical morphological criteria. The specificity of GPDH antigen-antibody reaction was determined by qualitative and quantitative immunochemical methods and by imunocytochemical controls for immunologic and methodologic sources of nonspecific reaction product. The illustrative data from this study serve to qualitatively define GPDH as a biochemical marker for oligodendrocytes in rat central nervous tissue. In view of the fact that the synthesis of rat brain GPDH is specifically regulated by glucocorticoids, the positive results obtained in this study further warrant the interpretation that rat oligodendrocytes are target cells for glucocorticoids.

Hippocampal electrical activity I. Morphological aspects

Abstract 1. 1. The histology of the hippocampus in the rat and rabbit was studied by electron microscopy with the object of relating the geometrical configuration of hippocampal cells to hippocampal electrical activity. 2. 2. Measurements of the hippocampus of the rabbit were made by light microscopy. 3. 3. A striking feature of the hippocampus is the relationship between glial processes and synaptic endings. 4. 4. Particular attention was paid to extraneuronal spaces where extracellular currents may flow.

Ultrastructural changes in neurons of the spinal anterior horn of ageing mice with particular reference to the accumulation of lipofuscin pigment.

SummaryStructural changes in neurons in the cervical anterior horn of ageing mice have been studied. The main age-related neurocytological change observed during this study is progressive accumulation of lipofuscin. The pigment was present in some nerve cells as early as six weeks after birth. Various types of membrane-bound granules encountered in the anterior horn cells were characterized on the basis of their shape, size and fine structure into primary lysosome-like (L1) granules (dense bodies), autophagic vacuole-like (L2) granules and mature (L3) pigment granules of complex substructure and irregular configuration.L1,L3 andL3 types of granules appear to represent respectively early, intermediate and mature stages in a developmental continuum of lipofuscin pigment granules. Transitional stages suggest that matureL3 pigment granules evolve by gradual alteration of lysosome-likeL1 andL2 granules. A probable sequence of morphologic events accompanying the transformation of lysosome-like granules into mature lipofuscin pigment granules is suggested.

Hippocampal electrical activity III. Unitary events and genesis of slow waves

Abstract Evidence has been brought forward to suggest that the slow wave activity of the rabbit hippocampus is dependent on the summed activity of slow potentials (“inactivation” processes) which in turn seem to be generated by summed postsynaptic potentials. Probably the limited extraneuronal space, described in paper I, plays a role in these events and in the marked hysteresis noted in amplitude of hippocampal pyramidal spikes when plotted against interval. This effect is not limited from one spike to the immediately succeeding one.

Cytoplasmic laminar bodies in the striate cortex

A laminated cytoplasmic inclusion consisting of curved parallel arrays of thick-walled microtubules separated by a layer of granular dense material has been identified in neurons within the visual cortex of a monkey. This body appears to be a continuation of the granular endoplasmic reticulum and previously has been noted in neurons related to other levels of the visual system. The present observations would tentatively appear to support the hypothesis of Morales, Duncan, and Rehmet that these structures are specializations of the visual system, although their presence in cerebellar stellate cells indicates that this distribution is not unique.

Experimental Immunogenic Proliferative Retinopathy in Monkeys

When a small amount of bovine serum albumin (BSA) was injected into the posterior vitreous body of a sensitized monkey, an immunogenic response occurred in the major blood vessels of the optic disk. In nonsensitized monkeys, the same phenomenon appeared after repeated intravitreal injections of small amounts of BSA. Focal leaks of fluorescein from the optic disk vessels were demonstrated by fluorescein angiography. Correlative light and electron microscopy revealed infiltration of acute and chronic inflammatory cells from the vessels of the optic disk into the vitreous body. When larger amounts of BSA were injected in sensitized monkeys, in addition to optic nerve involvement, there were scattered retinal vascular hemorrhagic and exudative lesions throughout the posterior pole. Immunologic mechanisms can result in preferential optic disk involvement with formation of proliferative lesions during the healing phase of the immunogenic inflammation.

The response of the arachnoid villus to an intracisternal injection of autogenous brain tissue. An electron microscopic study in the macaque monkey.

THE PUHPOSE of this study was to examine the response of arachnoid cells within arachnoid villi to an intracisternal injection of an animal’s previously extirpated and ground brain tissue. There is not as yet universal agreement regarding the nature of the communication between the subarachnoid space and dural venous sinuses at the sites of cerebrospinal fluid (CSF) return to the blood. Several investigator+-3 have interpreted their observations as suggesting that arachnoid villi are provided with tubules or other “open” channels which allow a “bulk” flow in the resorption of CSF. However, recent light and electron microscopic observations of the villi of monkeys and dogs4J indicate that the arachnoid villus is invested completely with a nonfenestrated endothelium which serves to partition the CSF within the vilIus from the venous blood in the dural sinuses. No tubules or other open pathways are present, in our experience, in the monkey or dog arachnoid villi. Furthermore, studies on the fate of erythrocytes following subarachnoid hemorrhage and of a foreign tracer protein (horseradish peroxidase) following intracisternal injections demonstrate that arachnoid cells within arachnoid villi are able to entrap, phagocytose, and apparently degrade these endogenous and exogenous substances in enzymatic inclusions (presumably lysosomes) . Moreover, the peroxidase is prevented from

Dendritic Vacuolization in the Central Nervous System of Rats After Long-term Voluntary Consumption of Ethanol

Adult male rats were housed in a colony environment for six months, with ad lib access to anise-flavored 10% ethanol in water. Animals were then removed from the colony, and their consumption of alcohol during a period in isolated housing was measured. Individual rats were scored as high, moderate, and low consumers. Animals from each scoring category were killed for light and electron microscopic study of central nervous system tissue. High consumers frequently displayed varicose distortions of the dendritic profiles, with internal membranous vesicles. Such abnormalities were rarely found in dendrites of low-ethanol-consuming colony mates. The dendritic vacuoles often appeared empty and membrane-limited. Some vacuoles contained membranous inclusions. Dendrites which displayed electron-lucent cavities without membranous limits or contents were also found. Some invaginations of dendritic membranes were identified. The possible sequential relationship between these forms of dendritic alterations could not be determined. Some neuron cell bodies displayed vacuolar inclusions as well. Dendritic and somatic abnormalities were found in cerebral and cerebellar cortices, hippocampus, mammillary bodies, and the periaqueductal gray matter of the brain stem.