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Biomedical subjects

J Weiss

Publications and source records attributed to J Weiss.

At least 505 records · Page 28Linked to original sources
PubMed1975

A study of the electroencephalogram during surgery with deep hypothermia and circulatory arrest in infants.

Seveteen infants (2 1/2 to 28 months old) were continuously monitored by six-channel electroencephalography (EEG) during the entire surgical procedure of open-heart repair. They were subjected to surface hypothermia supplemented by cold extracorporeal circulation (ECC) down to an average esophageal temperature of 21 degrees C., to cardiac arrest of 40 minutes average (range 19 to 62 minutes), and to ECC rewarming. Survival time of the EEG was correlated to esophageal temperature at the time of arrest. EEG reappeared an average of 26 minutes (5.30 to 50) after the strat of rewarming ECC and became strictly continuous after 44 minutes. Reappearance latency was well correlated with the duration of arrest. Potential normalization was oberved in 13 infants, but true normalization was observed in only 2 infants during the 90 to 120 minute period after ECC. By judging the EEG and by comparing this series with two previous series of moderate and deeper hypothermia in older patients, we concluded that the immediate tolerance of the brain to deep hypothermia and circulatory arrest seems no different in infants and in older patients.

Body Temperature↗
PubMed1974

Single cell layered heart: electromechanical properties of the heart of Boltenia ovifera.

The heart of Boltenia ovifera (the sea potato) is a tubular structure formed by a single layer of myocardial cells. Electron microscopic studies show that each cell contains a single myofibril located adjacent to the luminal surface of the cell. Electrical and mechanical measurement of a cannulated perfused heart demonstrate that only the luminal membrane is excitabble and elicits contraction on depolarization. Calcium and magnesium exert antagonistic effects on tension, and potassium depolarizes the myocardium and produces contractures when the luminal membrane is exposed to various concentrations of these ions. The extraluminl membrane does not respond electrically or mechanically to calcium magnesium or potassium, and its potential seems to be effectively "clamped" by the luminal membrane. Functionaly, therefore, this heart consists of a single active membrane with the adjacent contractile apparatus.

Action Potentials↗
PubMed1974

Early and discrete changes in permeability of Escherichia coli and certain other gram-negative bacteria during killing by granulocytes.

Rapid killing of Escherichia coli by intact or disrupted rabbit granulocytes or by granulocyte fractions was found to be accompanied by an equally rapid increase in permeability of the E.coli envelope. This increase in permeability was detected by determining entry of substances that normally do not cross E.coli's permeability barrier, namely actinomycin D and o-nitrophenyl-beta-D-galactopyranoside (ONPG), a substrate for cytoplasmic beta-galactosidase. Because E.coli continue to incorporate radioactively labeled precursors into bacterial RNA and protein for at least 1 h, despite rapid killing by granulocytes, entry of actinomycin D could be measured by its inhibitory effect on macromolecular synthesis. Entry was evident within minutes after exposure to granulocytes or granulocyte fractions and is independent of pH over a range of 6.5-9.0. The effect of disrupted granulocytes or partially purified fractions on susceptibility of E.coli to actinomycin D and entry of ONPG is dose dependent. That the entry of actinomycin D and ONPG was not caused by gross destruction of the envelope is indicated by two sets of observations: (a) net influx of (42)K was maintained for at least 15 min, even though efflux of potassium was immediately accelerated upon addition of bactericidal concentrations of granulocyte fractions; (b) beta-galactosidase did not leak out of E.coli under conditions that produce maximal inhibition by actinomycin D. Different species of gram-negative bacteria exhibited different susceptibilities to the bactericidal and permeability effects of granulocyte fractions. Thus, three strains of E.coli and one strain of Salmonella typhimurium were highly susceptible to both the bactericidal and the permeability enhancing effects of granulocyte fractions, whereas two strains of Serratia marcescens and one strain of Pseudomonas aeruginosa were resistant to both effects. Another strain of P. aeruginosa was rendered susceptible to actinomycin D without being killed and two strains of S. typhimurium remained insensitive to actinomycin D while being killed by granulocytes.

Animals↗