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Biomedical subjects

M Schwartz

Publications and source records attributed to M Schwartz.

At least 811 records · Page 45Linked to original sources
PubMed1976

Alcohol dehydrogenase-negative mutants in Drosophila: defects at the structural locus?

Sixteen Adh-negative mutants (induced by ethyl methanesulfonate) were examined for the presence of inactive alcohol dehydrogenase (ADH) protein. Four techniques were utilized in an effort to detect this protein: hybrid enzyme formation, intra-cistronic complentation, sodium dodecyl sulfate electrophoresis and antibody precipitation. Eleven of the sixteen negative strains showed evidence of inactive ADH protein and are preseumably mutations in the strutural element. These results are discussed in light of some recent models of gene organization in higher organisms.

Alcohol Oxidoreductases↗
PubMed1976

Ionic pathways of secretory membrane of frog gastric mucosa in Cl--free media.

Experiments were performed to determine the return ionic pathways of the secretory membrane of frog gastric mucosa associated with the electrogenic H+ pump in Cl--free media. The replacement of a 52 mM Na2SO4 secretory solution with a 52 mM K2SO4 secretory solution led to a decrease of resistance, an increase of the H+ secretory rate, and a reversal of the PD. The replacement of 52 mM Na2SO4 with 52 mM MgSO4 led to an increase of resistance and a decrease of the H+ rate. These results provided evidence for the existence of K+ and Na+ pathways, the former having a lower resistance than the latter. Short-circuiting the mucosa in Mg2+ solutions increased the H+ rate to the value in Na+ solutions, hence ruling out the possibility that Mg2+ might interfere with the H+ pump. The fact that the Mg2+ secretory solution, without K+ or Na+, did not abolish the H+ rate suggested the presence of at least a third ionic pathway. presumably SO42-, providing that Mg2+ does not penetrate the mucosa.

Animals↗
PubMed1976

Immediate short-time effects of ethacrynic acid on frog gastric mucosa in chloride-free solutions.

The presence of ethacrynic acid in the nutrient sulphate solution produces, generally in less than 3 min, a decrease in resistance accompanied by an increase in transmucosal PD. These results strongly suggest that the dominant effect of ethacrynic acid is not on the Na+ pathway of the nutrient membrane, but without further knowledge of the resistance of other ionic pathways, it cannot be inferred whether the effect predominates on the K+ pathway as in Cl- media.

Animals↗
PubMed1976

Dental prepayment.

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Insurance, Dental↗
PubMed1976

Improvement of perfusion-flow in the isolated rat liver, under the influence of streptase.

Accumulation of radioactive material in the isolated rat liver was noted when 125I-fibrinogen was added to the perfusing medium. Owing to an enhanced production of fibrinogen and to a diminished fibrinolysis, fibrin deposits were found to occur in the capillaries of fhe isolated liver. This would cause a decrease of hepatic flow and an impairment of the nutrition of this organ which leads to subsequent necrosis. Administration of streptase removed the fibrin deposits and restored the perfusive flow in the isolated liver.

Animals↗
PubMed1975

On the significance of the retention of ligand by protein.

When a solution of binding protein and its ligand is dialyzed against a large volume of ligand-free medium the rate of exit of the ligand from the protein-containing compartment can be extremely slow, much slower than the rate observed in the absence of protein. This is what we call retention of ligand by protein. A simple calculation demonstrates that when the protein concentration is in large excess over the total ligand concentration, the exit of ligand follows quasi-first-order kinetics, the half-life being proportional to (1 + (P)/Kd), where (P) is the concentration of binding sites, and Kd the dissociation constant characteristic of the equilibrium between the ligand and the protein. Experimental verification of this relation is provided in the case of the periplasmic maltose-binding protein of Escherichia coli; The implications of the retention effect in biochemical techniques are discussed, as well as its possible significance in biological phenomena, such as bacterial chemotaxis and transport, mechanism of hormone action, or transmission of the nerve impulse.

Bacterial Proteins↗
PubMed1975

A rare case of megaloblastic anaemia caused by disturbances in the plasma cobalamin binding proteins in a patient with hepatocellular carcinoma.

A patient with hepatocellular carcinoma, megaloblastic anaemia and increased concentration of serum cobalamin is described. Plasma TC I was increased to 10,000 times the normal concentration, thus explaining the increased concentration of serum cobalamin and a false Schilling test. The increase in plasma TC I in concurrence with undetectable amounts of plasma TC II was a likely explanation for the anaemia. The electron microscopic picture of the hepatocellular carcinoma was in accordance with TC I being produced by the tumour cells.

Anemia, Macrocytic↗
PubMed1975

Control of expression of the pyr genes in Salmonella typhimurium: effects of variations in uridine and cytidine nucleotide pools.

The differential rate of synthesis of five of the pyrimidine biosynthetic enzymes coded for by pyrB-F, and the endogenous concentrations of the individual pyrimidine nucleotides were determined in specially constructed mutants of Salmonella typhimurium. In the mutants employed the different pyrimidine nucleotide pools may be manipulated individually during exponential growth. The results obtained indicate the following. (i) The expression of pyrB, pyrE, and pyrF is controlled by a uridine nucleotide in a noncoordinate manner. (ii) The expression of pyrC and pyrD is regulated predominantly by a cytidine nucleotide. Under all conditions investigated, their expression seems to be coordinated, even though the genes are not contiguous on the chromosome. (iii) The low-molecular-weight effectors involved in controlling the expression of the pyr genes are neither uridine 5'-monophosphate nor cytidine 5'-monophosphate, but rather the corresponding di- or triphosphates.

Amidohydrolases↗