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Biomedical subjects

E T Hedley-Whyte

Publications and source records attributed to E T Hedley-Whyte.

At least 127 records · Page 7Linked to original sources
PubMed1977

Protein transport across cerebral vessels during metrazole-induced convulsions.

The effects of pentylenetetrazole-induced convulsions on cerebrovascular permeability for horseradish peroxidase were studied in locally anesthetized, artificially respired, paralyzed cats. Horseradish peroxidase circulated for 1, 2.5, 5, 10, 30, and 60 min and accumulated in medium-size, i.e., arterial or venous, blood vessel walls. Cerebral neuropil was permeated earliest in thalamic nuclei including medial and lateral geniculate nuclei. No tight junctions containing horseradish peroxidase were found. With 1.0 and 2.5 min circulation of horseradish peroxidase, arterial adventitia and basement membranes contained more peroxidase than surrounding interstitial space in contrast to veins and capillaries. Convulsions increased the number of endothelial vesicles containing horseradish peroxidase in arteries, veins, and capillaries but total number (stained plus unstained) of endothelial vesicles was increased slightly only in capillaries. We conclude that increased permeability is initially at the arterial level, although veins may also become permeable. The role of the endothelial vesicles in transit or protein in and out of the nervous system is not clear.

Animals↗
PubMed1976

Morphological evidence of alteration in myelinstructure with maturation.

The periodicity of the myelin sheath in glutaraldehyde carbohydrazide (GACH) embedded tissues from three 10-day-old and two 43-day-old mice was investigated with the electron microscope. The mean repeat period and number of repeats per fiber was measured in 31-89 fibers in the trapezoid bodies, olfactory tract and sciatic nerves. The mean period of the myelin sheaths in both the peripheral and the central nervous systems of the 10-day-old mice (15.1 +/- 0.07 nm (S.E.M.) and 13.4 +/- 0.09 nm respectively) are smaller (rho less than 0.001) than those of the adult mice (15.9 +/- 0.08 nm and 14.7 +/- 0.06 nm respectively). These differences may be related to the known differences in chemical composition of immature and mature myelin.

Age Factors↗
PubMed1976

Hypoxic-ischemic leukoencephalopathy in man.

Three cases of hypoxic-ischemic leukoencephalopathy were studied. In two patients, the neurologic disorder followed drug overdosage; in the third, the apparent precipitating event was a postoperative myocardial infarction complicated by circulatory insufficiency. All patients were deeply unresponsive, with varying reflex patterns. In all three cases, the brain showed extensive symmetrical necrotic lesions of the central white matter, with minimal damage to gray matter structures. The lesions in case 3 showed, in addition, vascular necrosis and ring hemorrhages. Common to all cases was a prolonged period of hypoxemia, hypotension, and elevated venous pressure. Acidosis occurred in two. These observations and analysis of previous reports of similar cases suggest that leukoencephalopathy tends to occur when the hypoxemia is prolonged and is associated with periods of hypotension and metabolic imbalance.

Adult↗
PubMed1975

Distribution of [1,2-3H]cholesterol in mouse brain after injection in the suckling period.

Glutaraldehyde-carbohydrazide polymer (GACH) was used to embed olfactory tracts, trapezoid body, and sciatic nerves of 9-, 10-, and 49-day old mice 2 h, 24 h, and 6 wk (respectively) after the intraperitoneal administration of [1,2-3H]cholesterol. Greater than 94% of radioactive cholesterol was retained in the GACH-infiltrated brain 24 h or more after injection. The fine structural preservation of both central and peripheral nervous tissues was excellent. Quantitative analysis of electron microscope autoradiographs demonstrated that [1,2-3H]cholesterol is limited to blood vessel walls and lumen within the central nervous system at 2 h and 6 wk postinjection, but neurons and neuropil also contain the labeled cholesterol. The thickest myelin sheaths in the adult mice appear to be uniformly labeled throughout their width. No relationship of the retained [1,2-3H]cholesterol to the node of Ranvier was found in the adult sciatic nerve.

Age Factors↗
PubMed1975

Cellular and regional localization of pentobarbital-2-14C by radioautography of selected areas of mouse brain at loss and return of withdrawal response.

Regional and cellular distribution of pentobarbital-14C in mouse brain was determined by frozen-section radioautographic methods. The mice were studied at the times of loss (WRL) and return (WRR) of withdrawal response following a single intravenous dose of either 40 or 50 mg/kg body weight. At WRL, grey matter areas had higher concentrations of pentobarbital-2-14C than white matter. At WRR grey matter concentrations were not altered, but white matter areas were now similar to the grey. At WRL pentobarbital concentration was 55 per cent higher in large pyramidal cells in the parietal cortex than in surrounding neuropil. At WRL hippocampal pyramidal cell bodies (stratum pyramidalis) and glial cells in corpus callosum had pentobarbital levels similar to that of surrounding neuropil. Levels in the neuropil of these three areas were higher at WRR than at WRL. Lipid-rich compartments had higher pentobarbital concentrations at WRR than at WRL. The results suggest that return of consciousness after pentobarbital anesthesia is associated with intracerebral redistribution of pentobarbital even while there is continuing uptake into brain. (Key words: Brain, pentobarbital uptake; hypnotics, barbiturates, pentobarbital; pharmacokinetics, pentobarbital uptake.).

Absorptiometry, Photon↗
PubMed1972

Fine structural localization of cholesterol-1,2- 3 H in degenerating and regenerating mouse sciatic nerve.

The localization of (3)H-labeled cholesterol in nerves undergoing degeneration and regeneration was studied by radioautography at the electron microscope level. Two types of experiments were carried out: (a) Cholesterol-1,2-(3)H was injected intraperitoneally into suckling mice. 5 wk later, Wallerian degeneration was induced in the middle branch of the sciatic nerve, carefully preserving the collateral branches. The animals were then sacrificed at various times after the operation. During degeneration, radioactivity was found over myelin debris and fat droplets. In early stages of regeneration, radioactivity was found in myelin debris and regenerating myelin sheaths. Afterwards, radioactivity was found predominantly over the regenerated myelin sheaths. Radioactivity was also associated with the myelin sheaths of the unaltered fibers, (b) Wallerian degeneration was induced in the middle branch of the sciatic nerves of an adult mouse, preserving the collateral branches. Cholesterol-1,2-(3)H was injected 24 and 48 hr after the operation and the animal was sacrificed 6 wk later. Radioactivity was found in the myelin sheaths of the regenerated and unaltered fibers. The results from these experiments indicate that: (a) exogenous cholesterol incorporated into peripheral nerve during myelination remains within the nerve when it undergoes degeneration. Such cholesterol is kept in the myelin debris as an exchangeable pool from which it is reutilized for the formation of the newly regenerating fibers, especially myelin. (b) exogenous cholesterol incorporated into the nerves at the time that degeneration is beginning is also used in the formation of new myelin sheaths during regeneration, (c) mature myelin maintains its ability to incorporate cholesterol.

Animals↗