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Biomedical subjects

B Katz

Publications and source records attributed to B Katz.

At least 181 records · Page 10Linked to original sources
PubMed1978

The benefits of surgery for asymptomatic gallstones.

The risk of a patient developing complications of asymptomatic cholelithiasis is high enough to justify the mortality associated with prophylactic cholecystectomy. The operation effectively stops the progression of calculous biliary tract disease. If performed when the patient is young enough and healthy enough to tolerate the operation, and before the occurrence of complications which increase the mortality risk, the overall mortality and morbidity of calculous biliary tract disease could be significantly reduced.

Aged↗
PubMed1977

Paranasal aspergilloma caused by an albino variant of Aspergillus fumigatus.

An unusual case of aspergilloma in the maxillary sinus caused by an albino variant of Aspergillus fumigatus var ellipticus is presented. Removal of the fungus ball by a left Caldwell-Luc procedure resulted in complete recovery for the patient. This case is the 17th culturally proven case of paranasal aspergilloma caused by A fumigatus, the third case reported from the United States, the first case due to aspergillosis caused by an albino strain of A fumigatus.

Adult↗
PubMed1975

The effect of procaine on the action of acetylcholine at the neuromuscular junction.

1. The effect of procaine on acetylcholine-induced membrane fluctuations (ACh noise) was studied by intracellular and focal external recording from end-plates of frog sartorius muscle. 2. With intracellular recording, ACh noise (the ratio of variance to mean depolarization) was substantially reduced by procaine, suggesting a greatly decreased amplitude of the elementary potential change. 3. Spectral analysis of the ACh noise indicated a dual average time course of the underlying "shot effects", similar to the complex shape (brief spike followed by a long tail of low intensity) of the end-plate current in pro-aine-treated muscle. 4. The post-synaptic blocking action of procaine can be largely explained by the drastic shortening of the initial high-intensity phase of the end-plate conductance change. 5. The average time course of the ACh shot effects is discussed in terms of alternative hypotheses, one attributing the complex shape to each elementary event, the other involving sequential reaction steps which produce two unequal populations of ion gates of different "life-times".

Acetylcholine↗
PubMed1973

The effect of alpha-bungarotoxin on acetylcholine receptors.

Fluctuations of membrane potential ('membrane noise') during acetylcholineinduced depolarization have been studied by intracellular recording from endplates of frog muscle fibres. When acetylcholine sensitivity had been greatly reduced by an irreversible inhibitor (alpha-bungarotoxin), analysis of the membrane noise showed that neither the amplitude nor the time course of the 'elementary' potential change (due to the molecular depolarizing action of acetylcholine) were altered.

Acetylcholine↗
PubMed1973

The characteristics of 'end-plate noise' produced by different depolarizing drugs.

1. End-plate depolarization and associated ;membrane noise' due to decamethonium, acetylthiocholine and suberyldicholine have been examined and compared with the effects of acetylcholine and carbachol.2. The transient ionic channels resulting from the action of decamethonium and acetylthiocholine are of much shorter duration than those produced by acetylcholine. They are, therefore, similarly to carbachol channels, less effective in causing membrane depolarization.3. Suberyldicholine, on the other hand, produces ion channels whose duration exceeds that of acetylcholine.4. Lowering the temperature causes an increase in amplitude of the elementary potential change produced by decamethonium and acetylthiocholine.5. The relation between the characteristic features of drug-induced membrane noise and the underlying molecular reaction rates is discussed.

Acetylcholine↗
PubMed1973

The binding of acetylcholine to receptors and its removal from the synaptic cleft.

1. Acetylcholine (ACh) noise and miniature end-plate potentials were recorded with focal external micro-electrodes.2. The effect of prostigmine on the time course of the ;molecular' and ;quantal' transmitter actions was studied. Prostigmine (10(-6) g/ml.) has little or no effect on the duration of the molecular ;gating action', while it greatly prolongs the quantal conductance change.3. After inhibition of ACh hydrolysis, the removal of the transmitter from the synapse is generally too slow to be accounted for by free diffusion. It is suggested that diffusion is delayed by binding to post-synaptic receptors. This is consistent with the finding that receptor blockage by curare or alpha-bungarotoxin shortens as well as reduces quantal transmitter action.4. The correlated effects of the receptor-blocking agents, on size and time course of the miniature end-plate currents, were subjected to a simple analysis. Its result suggests that after inhibition of cholinesterase about two thrids of the quantal packet of ACh combines with post-synaptic receptors.5. During focal external recording the effect of prostigmine on the time course of miniature end-plate potentials can become exaggerated due to what appears to be a compression artifact which obstructs outward diffusion of the transmitter.

Acetylcholine↗
PubMed1972

The statistical nature of the acetycholine potential and its molecular components.

1. When a steady dose of acetylcholine (ACh) is applied to an end-plate, the resulting depolarization is accompanied by a significant increase in voltage noise.2. The characteristic properties of this ACh noise (amplitude and time course) are examined under various experimental conditions. The voltage noise is analysed on the assumption that it arises from statistical fluctuations in reaction rate, and in the frequency of the elementary current pulses (;shot effects') produced by the action of ACh molecules.3. The elementary ACh current pulse (amplitude approximately 10(-11) A), arises from a conductance change of the order of 10(-10) Omega(-1) which lasts for approximately 1 ms (at 20 degrees C), and produces a minute depolarization, of the order of 0.3 muV. It is associated with a net charge transfer of nearly 10(-14) C, equivalent to approximately 5 x 10(4) univalent ions.4. At low temperature, and during chronic denervation, the duration of the elementary current pulse increases, and the elementary voltage change becomes correspondingly larger.5. Curare has little or no effect on the characteristics of the elementary event.6. A comparative study of ACh and carbachol actions shows that carbachol produces considerably briefer, and therefore less effective, current pulses than ACh.

Acetylcholine↗
PubMed1971

The effect of prolonged depolarization on synaptic transfer in the stellate ganglion of the squid.

1. Depolarization of the giant axon terminal of the squid causes local calcium influx which gives rise to transmitter release and post-synaptic response, and which under certain experimental conditions leads to a regenerative action potential in the presynaptic terminal itself.2. There has been conflicting evidence in the literature on the question whether the calcium permeability change in the terminal is rapidly inactivated, or whether it can persist with little diminution for hundreds of milliseconds during a depolarizing voltage step.3. Results are presented which show that there is little ;calcium inactivation', even when very large depolarizing steps are imposed on the terminal and maintained for periods of 1-2 sec.4. Contrary indications are examined and found to be attributable to an increase of potassium conductance, rather than direct inactivation of calcium conductance.

Action Potentials↗