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Biomedical subjects

D Harel

Publications and source records attributed to D Harel.

At least 37 records · Page 2Linked to original sources
PubMed1987

Direct invasion of the central nervous system by Mycoplasma pneumoniae: a report of two cases.

We studied two patients with involvement of the central nervous system (CNS) associated with Mycoplasma pneumoniae. One patient had encephalitis and acute cerebellar ataxia, whereas the second had a mixed picture of encephalitic reaction superimposed on a disseminated malignancy of unknown origin. Specific IgM antibodies to M. pneumoniae were detected in the patients' sera but not in their cerebrospinal fluid. M. pneumoniae was repeatedly isolated by cultures from throat swabs and cerebrospinal fluid samples from both patients. Our patients add to previous reports suggesting that CNS involvement may result from direct invasion of the CNS by the pathogen.

Aged↗
PubMed1986

Horseradish peroxidase as a cytochemical marker of blood-brain barrier integrity in oxygen toxicity in the central nervous system.

The ultrastructural integrity of endothelial tight junctions in cerebral microvessels of the rat exposed to hyperbaric oxygen was examined to find whether or not there are alterations of the blood-brain barrier in the initial phase of central nervous system oxygen toxicity. Rats were pre-implanted with cortical electrodes for continuous EEG and provided with two polyethylene cannulae inserted into the common carotid artery. HRP was administered to unanesthetized rats through a cannula directed into the brain, before the onset of O2 pressurization. As soon as the early electrical discharges of oxygen toxicity were recorded (20 to 30 min), the animal was killed by injection with saturated KCl into the heart. Examination of small blood vessels in both LM and EM did not support the possibility that the blood-brain barrier is altered prior to the first electrical discharge appearing in central nervous system oxygen toxicity.

Animals↗
PubMed1986

DNAMAT: an efficient graphic matrix sequence homology algorithm and its application to structural analysis.

We present a fast algorithm to produce a graphic matrix representation of sequence homology. The algorithm is based on lexicographical ordering of fragments. It preserves most of the options of a simple naive algorithm with a significant increase in speed. This algorithm was the bais for a program, called DNAMAT, that has been extensively tested during the last three years at the Weizmann Institute of Science and has proven to be very useful. In addition we suggest a way to extend our approach to analyse a series of related DNA or RNA sequences, in order to determine certain common structural features. The analysis is done by 'summing' a set of dot-matrices to produce an overall matrix that displays structural elements common to most of the sequences. We give an example of this procedure by analysing tRNA sequences.

Algorithms↗
PubMed1980

Hypopituitarism after aseptic cavernous sinus thrombosis.

A 44-year-old man developed aseptic thrombosis of the cavernous sinuses. He recovered but 3 months later presented a clinical and laboratory picture of pituitary insufficiency. After 3 years of hormonal replacement therapy, he was in good physical condition.

Adult↗
PubMed1978

Influence of a GABA transaminase inhibitor on central nervous system oxygen toxicity.

A decrease in brain GABA concentration has been implied as the cause of convulsions induced by hyperbaric oxygen (HOP). We therefore examined the influence of sodium valproate, an anticonvulsant and GABA transaminase inhibitor on HOP-induced convulsions in rats. The mean latency of occurrence of the first electrical discharge in the ECoG and the appearance of the first clinical seizure in awake chronically implanted rats was unchanged by administration of sodium valproate prior to HOP exposure. We conclude that either the sodium valproate inhibition of GABA removal is insufficient to compensate for HOP inhibition of its production, or else that GABA concentration changes are not causally related to HOP-induced seizures.

4-Aminobutyrate Transaminase↗
PubMed1975

Excitability of the cortex in normal and adrenalectomized rats during repeated exposures to high oxygen pressure.

The excitability of the cortex in adrenalectomized and normal adult male rats to High Oxygen Pressure (HOP) was studied 2, 3, 4, 6, 8, 12 and 22 d after bilateral adrenalectomy and implantation of cerebral electrodes. Continuous electroencephalographic (EEG) recordings were obtained until the appearance of the first paroxysmal electrical discharges, which was considered to be the first indicator of the toxic effects of hyperbaric oxygen. A statistically significant change in excitability of the cortex to oxygen toxicity from 2 to 22 d following adrenalectomy was shown. Comparison of the sensitivity of the normal and adrenalectomized rats to HOP 2 d after the operation showed significant resistance of adrenalectomized rats at this time. This resistance disappeared gradually, when compared with normal rats, and cortical susceptibility increased significantly 22 d after adrenalectomy. The possible disturbances responsible for the changes in excitability of the cortex to HOP in adrenalectomized rats are discussed.

Adrenalectomy↗
PubMed1975

Methohexital as an activator in epileptic patients with normal electroencephalograms.

The activation by a short-acting barbiturate, methohexital, of spike and wave discharges in epileptic patients with normal EEG tracings was evaluated. Seventy-five patients and 20 healthy control subjects were studied. Non-specific changes--desynchronization, fast sharp activity and diffuse slowing--appeared in all the tracings. Only eleven patients had positive activation after methohexital administration. The results were not encouraging and indicate that methohexital is not reliable as a diagnostic tool in problematic cases of verified or suspected epilepsy with normal EEG tracings.

Action Potentials↗