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Biomedical subjects

S Rubinstein

Publications and source records attributed to S Rubinstein.

At least 55 records · Page 3Linked to original sources
PubMed1986

Constipation and meconium ileus equivalent in patients with cystic fibrosis.

Constipation and its complications, particularly meconium ileus equivalent, may become management problems in patients with cystic fibrosis. The medical records of 168 patients with cystic fibrosis were reviewed for the prevalence of constipation and meconium ileus equivalent. Of 168 patients, 54 (32%) had experienced at least one episode of constipation which responded to oral or rectal laxative therapy. In 16 of the study group (9%) meconium ileus equivalent developed. Patients younger than 5 years of age had a lower prevalence and those older than 30 years of age had a much higher prevalence of both conditions. Those with prolonged histories of inadequately controlled steatorrhea appeared to be at higher risk for the eventual development of meconium ileus equivalent. Recurrences and complications of constipation may be avoided by instituting early and aggressive therapy.

Adolescent↗
PubMed1985

The role of calcium and Ca2+-ATPase in maintaining motility in ram spermatozoa.

Extracellular calcium at millimolar concentrations inhibits collective motility of ejaculated ram spermatozoa. In untreated cells, or when motility was made dependent upon glycolytic activity, there is very small inhibition, but when motility was made dependent upon mitochondrial respiration there is very high inhibition in motility by increasing extracellular Ca2+ concentration. Quercetin, which inhibits (Ca2+ + Mg2+)-ATPase activity in isolated plasma membranes, also inhibits motility mainly in cells that have been made dependent upon glycolytic activity, but there is also inhibition in untreated cells. When motility was made dependent upon mitochondrial activity, there is no inhibition but rather some stimulation in motility by quercetin. The inhibitory effect of quercetin is enhanced by increasing Ca2+ concentration in the medium. Quercetin also inhibits uptake of calcium into the cells, in a mechanism by which a calcium channel is involved. This inhibition is high only when the glycolysis is inhibited in the cells. The rate of glycolysis is decreased by quercetin or ouabain, but their effects on motility are quite different. Based on these data, it appears that the plasma membrane (Ca2+ + Mg2+)-ATPase or the Ca2+ pump have a functional role in the regulation of spermatozoa motility. This motility regulation is functioning through mechanisms which include glycolytic activity and maintenance of intracellular calcium concentrations.

Animals↗
PubMed1985

Suppression of defective-sporulation phenotypes by mutations in the major sigma factor gene (rpoD) of Bacillus subtilis.

Mutations (crsA47 and crsA4) in the major sigma factor gene (rpoD) of Bacillus subtilis RNA polymerase have been found to be powerful intergenic suppressors of spoOB, spoOE, spoOF, spoOK and spoIIG mutations. The crsA47 suppressor restores sporulation of spoOE, spoOF, spoOK and spoIIG mutants to levels near those of wild type bacteria and substantially improves the sporulation of a spoOB strain. The crsA mutations are shown to prevent the induction by aliphatic alcohols of SpoO phenocopies in wild type B. subtilis cells.

Bacillus subtilis↗
PubMed1984

Evidence for the presence of ATP-dependent calcium pump and ATPase activities in bull sperm head membranes.

Biochemical studies were carried out to demonstrate for the first time direct evidence for the presence of ATP-dependent calcium uptake activity in plasma membrane isolated from the head of bull spermatozoa. The purified plasma membrane vesicles contain also Na+-K+-ATPase, Mg2+-ATPase and Ca2+-ATPase activities. All the activities mentioned were followed in parallel in isolated plasma membranes from the sperm tail. These results together with others, suggest the involvement of the ATP-dependent calcium pump in regulation of intracellular calcium in the process of capacitation and acrosome reaction.

Adenosine Triphosphatases↗
PubMed1984

Effect of gossypol-acetic acid on calcium transport and ATPase activity in plasma membranes from ram and bull spermatozoa.

The effects of gossypol acetic acid on the activity of Mg-ATPase and Ca-Mg-ATPase and on calcium uptake by plasma membranes from ram and bull spermatozoa were examined. The three parameters were almost completely inhibited by 10 microM gossypol for both ram and bull sperm. In order to assess the effects of higher gossypol concentrations isolated membrane vesicles were loaded with calcium by operating the ATP-dependent calcium pump after which gossypol was added and calcium uptake followed. At 10 microM gossypol, additional calcium uptake was 85% inhibited while at 40 microM a release of the accumulated calcium was observed. The inhibitory effect of 10 microM gossypol was almost completely reversible by simple dilution of gossypol-treated membranes, whilst at 40 microM the effect was only 50% reversible. The data show a high degree of similarity between bull and ram, suggesting minimal differences between the two species as far as the structure and function of the sperm plasma membrane is concerned.

Adenosine Triphosphatases↗
PubMed1983

Calcium transport by bull spermatozoa plasma membranes.

Plasma membrane isolated from frozen ejaculated bull spermatozoa were found to contain calcium transport activity. Thin-section electronmicrography of these membranes revealed relatively homogeneous vesicular membranes with sizes ranging from 2000 to 6000 A in diameter. Membrane vesicles that were exposed to oxalate as a calcium-trapping agent accumulated Ca2+ in the presence of Mg2+ and ATP. One microM of the calcium-ionophore A23187, added initially, completely inhibited net Ca2+ uptake and, if added later, caused the release of Ca2+ accumulated previously. An Arrhenius plot for the rate of Ca2+ uptake revealed a break at 32--33 degrees C, and Ea of 4.4 kcal/mol above the break and 32.2 kcal/mol below. The Ca+ uptake was inhibited by low concentrations of quercetin, which is known to be an inhibitor of (Ca2+ + Mg2+)-ATPase in many systems.

Animals↗
PubMed1983

Calcium transport and Ca2+-ATPase activity in ram spermatozoa plasma membrane vesicles.

Plasma membrane vesicles, isolated from ejaculated ram sperm, were found to contain Ca2+-activated Mg2+-ATPase and Ca2+ transport activities. Membrane vesicles that were exposed to oxalate as a Ca2+-trapping agent accumulated Ca2+ in the presence of Mg2+ and ATP. The Vmax for Ca2+ uptake was 33 nmol/mg protein per h, and the Km values for Ca2+ and ATP were 2.5 microM and 45 microM, respectively. 1 microM of the Ca2+ ionophore A23187, added initially, completely inhibited net Ca2+ uptake and, if added later, caused the release of Ca2+ previously accumulated. A Ca2+-activated ATPase was present in the same membrane vesicles which had a Vmax of 1.5 mumol/mg protein per h at free Ca2+ concentration of 10 microM. This Ca2+-ATPase had Km values of 4.5 microM and 110 microM for Ca2+ and ATP, respectively. This kinetic parameter was similar to that observed for uptake of Ca2+ by the vesicles. The Ca2+-ATPase activity was insensitive to ouabain. Both Ca2+ transport and Ca2+-ATPase activity were inhibited by the flavonoid quercetin. Thus, ram spermatozoa plasma membranes have both a Ca2+ transport activity and a Ca2+-stimulated ATPase activity with similar substrate affinities and specificities and similar sensitivity to quercetin.

Animals↗
PubMed1982

Characterization of Mg2+- and Ca2+-ATPase activity in membrane vesicles from ejaculated ram seminal plasma.

The activity of divalent cation-stimulated adenosine triphosphatase (ATPase) has been studied in vesicular membranes isolated from ejaculated ram seminal plasma. This nonspecific acidic ATPase can be activated by millimolar concentration of any one of the following cations: Ca2+, Mg2+, Zn2+, or Mn2+ to give high specific activity (approximately 300 mumol/mg/hr), in absence of the other cations. Free Zn2+ inhibits activity of this ATPase. The Km for adenosonine triphosphate (ATP) ranged between 0.17 and 0.24 mM, and for the divalent cation ranged between 0.4 and 0.8 mM. When the ATPase is activated by Ca2+, two Kms for Ca2+ concentration were found: 0.8 and 0.08 mM. It is suggested that the seminal plasma membranes also contain alkaline ATPase, which is more specific for Ca2+.

Adenosine Triphosphatases↗
PubMed1981

Convenient assay for interferons.

A convenient assay for interferons based on reduction of cytopathic effect was developed. The number of manipulations and the lengths of the various incubation steps were reduced to a minimum. The assay is simple to perform and can be completed within 16 h. Moreover, it can be used with various types of cells and a variety of viruses.

Animals↗
PubMed1979

Human leukocyte interferon: production, purification to homogeneity, and initial characterization.

A method of fractionating proteins by high-performance liquid partition chromatography has been developed and used for isolation and purification to homogeneity of one of the species of human leukocyte interferon. The homogeneous interferon exhibited a sharp peak on high-performance liquid chromatography and a single narrow band on sodium dodecyl sulfate/polyacrylamide gel electrophoresis in the presence of 2-mercaptoethanol. Extraction of the gel gave a single sharp peak of antiviral activity coinciding with the protein band. The specific activity of pure interferon was found to be 2--4 X 10(8) units/mg, based on amino acid analysis. The molecular weight is 17,500--18,000.

Amino Acids↗
PubMed1978

Human leukocyte interferon purified to homogeneity.

One of the species of human interferon produced by incubation of leukocytes with Newcastle disease virus was purified to homogeneity. It exhibited one peak of activity coinciding with a single protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Humans↗