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Biomedical subjects

A Torvik

Publications and source records attributed to A Torvik.

At least 73 records · Page 4Linked to original sources
PubMed1978

Transitory block of the arachnoid granulations following subarachnoid haemorrhage. A postmortem study.

The arachnoid granulations of the superior sagittal sinus were examined for blockage by erythrocytes in 43 cases of subarachnoid haemorrhage. Ten cases had survived for more than two weeks after the haemorrhage. Among 33 cases with acute haemorrhage, 17 had evidence of blocking of the granulations. The severity of the block varied from complete clogging of nearly all granulations to slight filling of a few of them. Cases with some days' survival showed evidence of phagocytosis of the entrapped erythrocytes by macrophages. Several of the cases with old haemorrhage had groups of haemosiderin macrophages in the granulations but none showed fibrosis (except for one single villus). It is concluded that clogging of the arachnoid granulations may contribute to the raised intracranial pressure in some cases of acute subarachnoid haemorrhage. However, the observations do not support the hypothesis that the haemorrhage may lead to fibrosis or scarring of the granulations with chronic impairment of the cerebrospinal fluid resorption and subsequent hydrocephalus.

Acute Disease↗
PubMed1977

The pathology of experimental obstructive hydrocephalus. Electron microscopic observations.

Obstructive hydrocephlus was produced in 10-14 day-old rabbits by injection of kaolin into the cisterna magna and the ependyma and subependymal tissue was studied by electron microscopy. Generally, the study confirmed recent light microscopic observations on similar models (Torvik et al., 1976). In contrast to most previous reports, it was found that the ependyma adapted remarkably well to ventricular dilatation. No true ependymal defects occurred even in extensive hydrocephalus except at the sites of the ventricular synechiae which sometimes ruptured. The specialized ependymal junctions remained intact but outside the junctions the intercellular clefts were widened, particularly along the lateral wall of the lateral ventricle. The density of the microvilli and cilia decreased, probably because of the increase in the surface area of the ependyma. Dense bundles of filaments developed in the ependymal cells of the hydrocephalic animals. The extracellular space of the subependymal white matter appeared increased but there was no evidence of destruction of fibres or cells. Thus, the reduction of the cerebral mantle thickness was probably mainly caused by pre-sure atrophy.

Animals↗
PubMed1977

A case of chronic demyelinating polyneuropathy resembling the Guillain-Barré syndrome.

A case of demyelinating polyneuropathy is reported which was clinically and pathologically indistinguishable from the Guillain-Barré syndrome, with the exception that the symptoms progressed steadily for 7 months. Pathologically, the peripheral nerves and intraspinal roots showed selective demyelination with axonal sparing and patchy mononuclear inflammation. The posterior columns of the spinal cord also showed selective demyelination with axonal sparing. The simultaneous destruction of central and peripheral myelin is discussed in relation to the immune theory for the Guillain-Barré syndrome. Numerous anterior horn cells showed severe chromatolysis although there was little axon loss. It is suggested that chromatolysis may occur after severe and longstanding demyelination.

Demyelinating Diseases↗
PubMed1977

The spinal cord central canal in kaolin-induced hydrocephalus.

In order to study the cause of the great individual variations in kaolin-induced hydrocephalus, the lower brain stem and upper spinal cord were examined histologically in a series of young rabbits that had received injections of kaolin into the cisterna magna. Animals with complete occlusion of the outlets from the fourth ventricle into the subarachnoid space showed only a moderate ventricular dilatation, while cases with marked hydrocephalus also plugs of kaolin in the caudal part of the fourth ventricle. The intraventricular kaolin was adherent to the roof of the fourth ventricle by strands of connective tissue and it is suggested that the plugs served as valves that initially occluded the opening of the central canal and were then lifted away as the ventricle dilated and the roof moved posteriorly. The animals with marked hydrocephalus also had extensive dilatation of the central canal with cleft formation in the posterior columns. The observations support the concept that in hydrocephalus the central canal may serve as an alternative resorption route for the cerebrospinal fluid through communication with the spinal subarachnoid space.

Animals↗
PubMed1976

The origin of reactive cells in retrograde and Wallerian degeneration. Experiments with intravenous injection of 3H-DFP-labeled macrophages.

In order to examine the possible haematogenous origin of phagocytes in anterograde and retrograde degeneration, rabbit peritoneal macrophages were labeled in vitro with 3H-DFP and injected intravenously into host animals. Four or five days prior to the injection, the facial nerve was avulsed and the sciatic nerve ligated in five recipients. The animals were killed 24 h after the injection of the macrophages. Labeled cells were found in that part of the sciatic nerve which was mechanically damaged and in the liver and spleen but not in areas with retrograde or Wallerian degeneration. The possible interpretation of these findings is discussed.

Animals↗
PubMed1976

Angiographic diagnosis of teleangiectases with cavernous angioma of the posterior fossa. Report of two cases.

Two cases of pontine vascular malformation with a characteristic venous angiographic appearance are reported. Both patients had a slowly progressive clinical course, normal spinal fluid, and evidence of a pontine mass. In the late venous phase, large abnormal vessels were seen to coverage towards the midline from each cerebellar hemisphere. The abnormal vessels were microscopically identified as teleangiectases in one of the cases. Both cases had pontine hematomas, originating from a cavernous angioma in one of them; in the other the exact origin of the bleeding could not be determined. It is concluded that in cases with a progressive pontine syndrome the characteristic appearance of the venous phase of angiography may indicate a bleeding pontine vascular malformation.

Adult↗
PubMed1975

On the pathology of experimental hydrocephalus.

Acute hydrocephalus was produced in newborn rabbits by injection of kaolin into the cisterna magna. The light microscopic changes which occurred in the ependyma and periventricular brain tissue were studied. Some animals also received intraventricular injection of Evans blue albumin (EBA) at various times after the kaolin injection to study the permeability of the ependyma. There was a progressive dilatation of the lateral ventricles from the second day after the kaolin injection. Marked hydrocephalus was seen after 2 weeks. The white matter of the cerebral hemispheres showed increasing reduction in volume with the degree of hydrocephalus. Neither destruction of brain tissue nor macrophage response or inflammation were seen. The ependyma adapted remarkably well to the increased intraventricular pressure by extensive flattening and stretching. No convincing breaks or ruptures were seen. There was a patchy spongy zone beneath the ependyma, probably indicating oedema of the periventricular white matter due to transventricular absorption of the cerebrospinal fluid (CSF). Denudement of the ependymal lining is not necessary for the concept of transventricular flow of CSF. No difference was seen in the penetration of EBA into the periventricular tissue between hydrocephalic and control animals. The reduction of the cerebral mantle thickness was probably caused by simple pressure atrophy. This indicates that the morphological changes may to a large extent be reversible if the hydrocephalus is properly treated within reasonable time. The role of morphological changes in the pathophysiology of hydrocephalus if briefly commented upon in relation to certain aspects of human hydrocephalus.

Animals↗
PubMed1975

The perineuronal glial reaction after axotomy.

The perineuronal glial reaction after axotomy of the facial nerve was examined in adult mice and rats and in newborn rabbits. The facial nerve was damaged in two ways: by crush lesions, which were followed by complete neuronal regeneration, and by transection (in mice) or evulsion (in rats and rabbits), which caused extensive nerve cell disintegration. After nerve lesions which caused irreversible damage the microglial cells encircled the degenerating neurons and ultimately phagocytosed them. After crush lesions there were great species variations in the glial reaction: the neurons of rats and rabbits showed considerable and reversible separation of the synaptic terminals by glial cells, while mice showed no significant synaptic separation. It is suggested that the main function of the microglial cells may be to serve as potential phagocytes for disintegrating neurons, and that the reversible glial changes around regenerating neurons possibly represent abortive glial reactions.

Age Factors↗
PubMed1975

The relationship between microglia and brain macrophages. Experimental investigations.

A series of experiments are reported which indicate that the microglia are endogenous cells which may constitute the only source of phagocytes in certain mild degenerative conditions, such as Wallerian degeneration and retrograde nerve cell disintegration. In more extensive lesions with increased vascular permeability a substantial number of the phagocytes are derived from the blood monocytes.

Animals↗