Jun Ogata

A study of rod-like structures (Hirano bodies) in 240 normal and pathological brains

SummaryA study of rod-like structures (RLS) was made in 173 pathological and in 67 normal brains. The pathological brains included cases with varied neuropathological conditions: vascular, metabolic, degenerative, infectious, traumatic, neoplastic, etc. The ages of the patients ranged from newborn to 97 years. RLS were found in 152 pathological brains (89%) and in 50 normal brains (75%). RLS were localized in all but one case, in Ammons horn, specifically in Sommers sector and in the stratum lacunosum beneath Sommers sector. There was no correlation between any group of diseases studied and appearance or number of RLS. The number of RLS in Sommers sector increased with advancing age. In the middle age, ihowever, the stratum lacunosum showed a higher number of RLS. The results of this study idicate that there is no significant relationship between RLS and any pathological condition and therefore that they represent non-specific changes, although a correlation with advancing age is probable. Although RLS appeared to be intracellular, their exact localization was not established.

DEGENERATION OF WHITE MATTER IN HYPOXIA, ACIDOSIS AND EDEMA

In contrast to its usual effect, hypoxia appears at times to induce selective injury of the white matter with sparing of the gray. The factors involved were studied in the human brain at autopsy, with seven cases serving to illustrate the mechanisms though to be operative in this and related phenomena. It is suggested that such white matter injury results from the simultaneous effect of hypoxia and edema. The edema may be due to unrelated cause, such as trauma or hypertensive disease, but it may also be due to acidosis or other consequence of hypoxia, particularly generalized hypoxia which affects the body as a whole including the circulating blood. The uniformly diffuse, generalized cerebral edema that may result in such circumstances cannot be locally severe, even when producing severe swelling of the brain as a whole, and this results in difficulties in recognition and interpretation. With gold sublimate stains, the changes in astrocytes characteristic of edema are evident in generalized hypoxic states, and at times these may be the only recognizable histologic change. The pattern of change is like that in other cases of edema, and is thought to indicate that here too, the edema is essentially extracellular.

Light and electron microscopic studies of experimental hydrocephalus

SummaryA light and electron microscopic study of the ependymal and subependymal regions of experimental hdrocephalic cats was made. Hydrocephalus was induced by injection of kaolin into the cisterna magna. Cerebrospinal fluid (CSF) turnover was measured in all experimental cats by ventricular perfusion just prior to glutaraldehyde fixation. The cats were sacrificed at 7 (acute hydrocephalus) and at 21 or more days (chronic hydrocephalus) after kaolin. The major pathological findings were: flattened and outstretched ependymal lining, detachment of ependymal cells and rarefaction of subependymal areas with increase in the extracellular space. The significant morphological alterations in acute hydrocephalus, characterized by a marked decreased rate of CSF absorption, were flattening and outstretching of ependymal cells with minimal rarefaction of subjacent tissues. In the acute animal with a measurable amount of CSF absorption, and more clearly, in the chronic animal with higher rates of CSF absorption, detachment of ependymal calls, significant rarefaction of subependymal tissues, and marked increased subependymal extracellular space were the predominant changes. It is concluded that these pathological changes provide the morphologic substrate for transventricular absorption of CSF.

Distribution of Intraventricular Horseradish Peroxidase in Normal and Hydrocephalic Cat Brains

The distribution of intraventricularly injected horseradish peroxidase (HRP) was examined in the ependymal and subependymal tissue of both normal and experimental hydrocephalic cats by light and electron microscopy. At different time intervals after the intracisternal injection of kaolin, the hydrocephalic ventricles were perfused at various intraventricular pressures with mock cerebrospinal fluid (CSF) containing HRP. The uptake and localization of HRP by periventricular brain tissue was studied with respect to transventricular absorption of cerebrospinal fluid. The results of both light and electron microscopic studies have shown that in normal, acute or chronic hydrocephalic cats perfused at either high or low pressure the distribution of HRP is similar. The enzyme was localized mainly to the intercellular spaces, between ependymal cells, glial cells, and in perivascular spaces (in and across the basement membrane of subependymal blood vessels). HRP did not penetrate endothelial tight junctions even in chronic hydrocephalic cats undergoing significant rates of transventricular absorption of CSF. It is concluded that since the distribution of HRP in brain is determined by diffusion, its use as a tracer for the bulk movement of CSF through nervous tissue is limited. It is, however, an excellent extracellular space marker in electron microscopy.

Schwann cells and regenerated peripheral myelin in multiple sclerosis: An ultrastructural study

Tissues of a multiple sclerosis plaque in the brachium conjunctivum of the pons known to contain peripheral myelin by light microscopic studies were removed from the paraffin block and processed for electron microscopic studies. The cells related to the peripheral myelin possessed the ultrastructural characteristics of Schwann cells, with basement membranes and associated collagen fibers. No continuity was seen with the peripheral nerve tissues of any cranial nerve. These Schwann cells probably arose within the central nervous tissues by selective maturation of multi potential primitive reticular cells, a phenomenon consistent with the view that Schwann cells are mesenchymal in character.

Arteriovenous Communications in the Human Brain

The existence of arteriovenous communications in human central nervous tissues is a logical inference drawn from studies on fibrocartilage emboli. Such communications were demonstrated in the human brain at autopsy by injecting particles into the internal carotid artery and identifying them in the effluence from the internal jugular vein; these measured up to 70μ in diameter and were found in every instance of the 12 cases in which the procedure was technically successful. In 3 additional cases studied after brain removal, emboli passed from the middle cerebral artery to the superior sagittal sinus. The arteriovenous communications are thought to be normally present in the human brain and spinal cord, and are likely to play a role in cerebrovascular circulation in normal and pathological states.

The Relative Weight of the Gray and White Matter of the Normal Human Brain

The relative proportion of gray and white matter of the normal human brain was determined to be approximately 60% and 40% respectively in the cerebral hemispheres and in the brain as a whole, by calculations based on the water content of these tissues. With this technique, the value for gray matter is an approximate measure of a myelin-free abstraction, rather than of the actual anatomic gray structures; e.g. structures such as the globus pallidus which contain many myelinated fibers would act as a mixture of tissues, and would not be included entirely with the gray matter. This abstraction may have pathological significance.