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Biomedical subjects

G Sachs

Publications and source records attributed to G Sachs.

At least 325 records · Page 18Linked to original sources
PubMed1978

Evaluation of the Microcult-GC kit as a screening method for the detection of Neisseria gonorrhoeae.

The Microcult-GC Kit was compared to the standard modified Thayer-Martin plate method for the isolation and presumptive identification of Neisseria gonorrhoeae. Two hundred and thirty specimens representing urethral, endocervical, rectal, and pharyngeal sites were inoculated to both media. If only genital and rectal cultures were compared, the overall agreement was 98 percent, with a false positive rate of 1/145 (0.7 percent) and a false negative rate of 2/145 (1.4 percent). However, in the pharyngeal cultures, 16 of 32 gave false positives, thus emphasizing the manufacturer's instructions to limit the kit's use to genital and rectal cultures. The kit system gives rapid presumptive results, has a long shelf life at room temperature, and needs little laboratory equipment for proper use.

Bacteriological Techniques↗
PubMed1977

Metabolism of dog gastric mucosa. Levels of glycolytic, citric acid cycle and other intermediates.

Several metabolites, including those of glycolysis, the citric acid cycle, the hexose monophosphate shunt, glutamate, aspartate, and Coenzyme A were measured in defined parietal cell-enriched freeze-dried sections of dog gastric biopsies derived from nonsecreting and secreting tissue. In addition, NH3, ribulose 5-phosphate, glycerol, and succinate were measured in perchloric acid extracts of biopsies. The onset of secretion increased the level of glycolytic intermediates including pyruvate and lactate with the most marked increase being in fructose 1,6-diphosphate levels. The level of 6-phosphogluconate and ribulose 5-phosphate also increased, in spite of a constant NADP+/NADPH ratio. The levels of all the citric acid cycle intermediates measured also rose, the most marked rise being in malate and fumarate. The levels of glycerol, acetyl-CoA, and CoA increased, but the ratio of the latter intermediates remained constant. Calculation of the ratio of the oxidized to reduced form of diphosphopyridine nucleotide indicated a fall of the ratio in the cytoplasm and a rise in the mitochondria. From these data, it is concluded that the major energy source for acid secretion is due to an increase in citric acid cycle activity and that glycolysis, and probably also fatty acid oxidation, is stimulated to provide mitochondrial substrate.

Ammonia↗
PubMed1977

Studies on isolated subcellular components of cat pancreas. I. Isolation and enzymatic characterization.

Pancreas of the cat was fractionated into its subcellular components by centrifugation through an exponential ficoll-sucrose density gradient in a zonal rotor. This enables a preparation of four fractions enriched in plasma membranes, endoplasmic reticulum, mitochondria and zymogen granules, respectively. The first fraction, enriched by 9- to 15-fold in the plasma membrane marker enzymes, hormone-stimulated adenylate cyclase, (Na+K+)-ATPase, and 5'-nucleotidase, is contaminated by membranes derived from endoplasmic reticulum but is virtually free from mitochondrial and zymogen-granule contamination. The second fraction from the zonal gradient shows only moderate enrichment of the above marker enzymes but contains a considerable quantity of plasma membrane marker enzymes and represents mostly rough endoplasmic reticulum. The third fraction contains the bulk of mitochondria and the fourth mainly zymogen granules as assessed by electron microscopy and marker enzymes for both mitochondria and zymogen granules, namely succinic dehydrogenase, trypsin and amylase. Further purification of the plasma membrane fractions by differential and sucrose step-gradient centrifugation yields plasma membranes enriched 40-fold in basal and hormone-stimulated adenylate cyclase and (Na+K+)-ATPase.

Adenosine Triphosphatases↗
PubMed1977

Reconstitution of a proton pump from gastric mucosa.

Purified vesicular fractions from hog gastric mucosa have been incorporated into phosphatidyl serine bilayers. In the presence of MgATP on one side and symmetrical Na2SO4 solutions, a short circuit current (SCC) away from that side is observed increasing exponentially with time, while the corresponding open circuit potential (OCP) is maintained constant for greater than 30 min. In K2SO4 solutions the SCC time course is essentially unchanged, but the OCP falls to almost zero after 15-20 min. In Na -- K gradient there is a similar SCC away from the K-side whose exponential rate is increased by ATP added to both sides. The time course of these events depends only on the time from the formation on the black film. These results are interpreted as showing: (1) There is an ATP-driven proton pump generating a constant potential EH in series with a time dependent conductance gHocekt. (2) There is a shunting K-conductance gKocek't. (3) In the presence of ATP k' greater than k. (4) This time dependence is due to thickness changes in the bilayer. A model relates these results to those obtained with the intact vesicles.

Adenosine Triphosphatases↗
PubMed1977

Use of 1-anilino-8-naphthalene-sulfonate as a probe of gastric vesicle transport.

The interaction of 1-anilino-8-naphthalene-sulfonate (ANS) with vesicles derived from hog fundic mucosa was studied in the presence of valinomycin and with the addition of ATP. Evidence was found for two classes of sites, those rapidly accessible to ANS with a KD of 7.5 micronM and those slowly accessible, but rapidly accessed in the presence of valinomycin with a KD of 2.5 micronM. ATP transiently increases the quantum yield of the latter ANS binding sites only in the presence of valinomycin, but does not alter the number of KD of those sites. The time course of this increase correlates with H+ uptake and Rb+ extrusion by those vesicles and H+ carries such as tetrachlorsalicylanilide or nigericin abolish the ATP response. With ATP addition in the presence of SC14N and valinomycin there is transient uptake of SCN-. It is concluded that ANS is acting as a probe of a structural change dependent on a potential and H+ gradient.

Anilino Naphthalenesulfonates↗
PubMed1977

Cation transport by gastric H+:K+ ATPase.

A vesicular microsomal fraction isolated from hog fundic mucosa demonstrates the capacity to take up equal amounts of RB+ and Cl-. The amount of the Rb+ uptake is sensitive to the extravesicular osmolarity, and rate of uptake is sensitive to temperature. 86Rb+ efflux is dependent upon the cation composition of the diluting solution. ATP, but not beta-gamma methylene ATP, induces a reversible efflux of 86Rb+ from loaded vesicles, and this is dependent upon a functional K+-ATPase. The ATP induced efflux is not affected by CCCP (carbonyl cyanide m-chlorophenylhydrazone) or TCS (tetrachlorosalicylanilide) nor by lipid soluble ions or valinomycin. Nigericin inhibits the efflux by 40%. Uptake of the lipid soluble ion 14C-SCN- has been demonstrated and is enhanced by ATP only in the presence of valinomycin. The results are consistent with a neutral or isopotential exchange of H+ for Rb+ mediated by K+-ATPase.

Adenosine Triphosphatases↗
PubMed1977

Characterization of gastric mucosal membranes. IX. Fractionation and purification of K+-ATPase-containing vesicles by zonal centrifugation and free-flow electrophoresis technique.

Methods are described for purification of a vesicular membrane fraction of hog gastric mucosa using differential centrifugation, density gradient separation on zonal rotors and free-flow electrophoresis. As a result a fraction is obtained enriched 40-fold in terms of K(+)-ATPase and free of any other enzyme marker other than K(+)-activated p-nitrophenyl phosphatase. The 5'-nucleotidase and basal Mg(2+)-ATPase are clearly separated from the latter enzymes. Osmotic shock, Triton X-100 treatment or K+ ionophores increased the K(+)-ATPase activity in isotonic conditions, but K(+)-p-nitrophenyl phosphatase is not affected by these treatments, nor is the ATPase activity in the presence of NH4+. The results suggest that the electrophoretic fraction contains a major population of tight vesicles, whose permeability to K+ is rate limiting for the ATPase activity but not for the p-nitrophenyl phosphatase activity. It is concluded that K+ site for the ATPase is internal whereas the K+ site for the p-nitrophenyl phosphatase is external, hence, the K+ site must be mobile across the membrane.

4-Nitrophenylphosphatase↗
PubMed1977

Proton transport by gastric membrane vesicles.

A highly purified membrane fraction was derived from hog gastric mucosa by a combination of differential and density gradient centrifugation and free flow electrophoresis. This final fraction was 35-fold enriched with respect to cation activated ouabain-insensitive ATPase. Antibody against this fraction was shown to be bound to the luminal surface of the gastric glands. The addition of ATP to this fraction or the density gradient fraction resulted in H+ uptake into an osmotically sensitive space. The apparent Km for ATP was 1.7-10(-4) M in the absence of a K+ gradient similar to that found for ATPase activity. The reaction is specific for ATP and requires cation in the sequence K+ greater than Rb+ greater than Cs+ greater than Na+ greater than Li+ and inhibited by ATPase inhibitors such as N,N'-dicylclohexyl-carbodiimide. Maximal H+ uptake occurs with an outward K+ gradient but the minimal apparent KA is found in the absence of a K+ gradient. The pH optimum for H+ uptake is between 5.8 and 6.2 which corresponds to the pH range for phosphroylation of the enzyme, but is considerably less than the pH maximum of the K+ dependent dephosphorylation. In the presence of an inward K+ gradient, protonophores such as tetrachlorsalicylanilide only partially abolish the H+ gradient but valinomycin dissipates 75% of the gradient, and nigericin abolishes the gradient. The vesicles therefore have a low K+ conductance but a measurable H+ conductance, hence a K+ gradient can produce an H+ gradient in the presence of valinomycin. The uptake and spontaneous leak of H+ are temperature sensitive with a similar transition temperature. Ultraviolet irradiation inactivates ATPase and proton transport at the same rate, approximately at twice the rate of p-nitrophenylphosphatase inactivation. It is concluded that H+ uptake by these vesicles is probably due to a dimeric (H+ + K+)-ATPase and is probably non-electrogenic.

Adenosine Triphosphatases↗
PubMed1977

Isolation and purification of normal and malignant colonic plasma membranes.

Plasma membrane fractions from normal colon cells and a transplantable colon adenocarcinoma were isolated and purified by differential and zonal density centrifugation. Enrichment of normal and adenocarcinoma plasma membranes was found in zonal fractions I and II (ZI and ZII) following centrifugation in an 18--50% sucrose gradient. The distribution of various marker enzymes in normal colon preparations suggested an apical origin for the membranes obtained in zonal fraction I while zonal fraction II appeared to contain basal-lateral membrane fragments. Enzymatic analysis of the plasma membrane derived from the colon tumor indicated that these fractions possess a more uniform distribution of Na-K+ ATPase perhaps reflecting a dedifferentiated state. The plasma membrane fractions isolated should prove useful for investigation of transport and other properties of vesicles derived from malignant and normal colon cells.

Adenocarcinoma↗
PubMed1977

Separation of proximal tubule cells from suspensions of rat kidney cells by free-flow electrophoresis.

Suspensions of rat kidney cells obtained by disaggregation of the kidney with 0.25% trypsin were separated by electrophoresis. Previously, we found a correlation between cells with histochemically demonstrable alkaline phosphatase (HDAP) and cells with brush borders which established that HDAP is a useful marker for rat proximal tubule cells (Kreisberg et al., '77). The starting suspension of cells for electrophoresis consisted of 38.4 +/- 5.7% nucleated cells with HDAP, 39.8 +/- 5.7% nucleated cells without HDAP, and 20.8 +/- 9.2% red blood cells. After electrophoresis, the purest fraction contained 85.8 +/- 3.5% nucleated cells with HDAP, 8.4 +/- 2.2% nucleated cells lacking HDAP, and 5.8 +/- 2.8% red blood cells; 91.9 +/- 2.4% of the nucleated cells in the purest fractions had HDAP.

Alkaline Phosphatase↗
PubMed1977

Ion pumps in the renal tubule.

Biochemical studies of renal tissue have so far not shown the presence of any active pump mechanism other than Na-K-ATPase. In this review of possible transport mechanisms for the ions Na, K, H, Cl, and HCO3, it is suggested that transport of these ions can be coupled to ATPase by conductance (uniport) processes or by ion gradients by co-transport (symport) or countertransport (antiport) systems. These may be neutral or electrogenic. Accordingly, the function of any region of the tubule will be determined by the porter(s) present in the apical or basal-lateral membrane, and by the Na-K-ATPase located almost exclusively in the basal-lateral membrane. Future research in this area will probably define these porters in vesicles isolated from specific cell types of the kidney.

Adenosine Triphosphatases↗
PubMed1977

Properties of gastric antrum. III. Selectivity and modification of shunt conductance.

The permselectivity of the paracellular pathway of amphibian (Necturus and bullfrog) antrum was investigated with respect to intracationic selectivity and the K+ and Cl- permeability ratio as a function of mucosal pH. The intracationic selectivity sequence was Rb+ greater than K+ greater than Cs+ greater than Na+ greater than Li+. Both antra showed weak cationic selectivity at pH 7.4, and at pH 4.4 for bullfrog and pH 3.0 for Necturus, the ratio Pk+/P Cl- was unity. At lower mucosal pH the tissues were anion selective. Treatment of the tissue with a water-soluble carbodiimide enhanced anion selectivity at higher pH; carbenoxolone, a weak acid, resulted in maintained cation selectivity at lower pH. These data suggest that carboxyl groups play a role in determining shunt selectivity; the increase in anion selectivity below pH 2.0 suggests that phosphate or sulfate groups could also be involved.

Amphibians↗
PubMed1977

Gastric secretion.

This review has attempted to cover some of the findings that have been made in the mechanism of gastric secretion in recent years. It is hard to offer any firm conclusions, whether at the level of stimulus, metabolism, or the terminal process of secretion. However, some generalizations may be possible. At least amphibian gastric secretion is stimulated by cAMP as a second messenger, with histamine presumably acting as the primary messenger. The resultant metabolic change is due largely to a direct stimulation of catabolism, which in dog appears to be the metabolism of hexose, through the glycolytic process, the hexose monophosphate shunt, and the Krebs' cycle with cytoplasmic reduction and mitochondrial oxidation of pyridine nucleotides. No evidence could be obtained for changes in high energy phosphate or for lipolysis. One would expect gastric mucosal membranes during secretion to contain an anion-restricted electrogenic H+ pump, but they in fact contain an ATPase stimulated by monovalent cations and are insensitive to ouabain. In addition, hog or dog gastric membranes have the vectorial properties of H+ absorption, Rb+ extrusion, and ANS fluorescence enhancement with the addition of ATP, as well as protein phosphorylation by 32P dependent on a K+ gradient.

3',5'-Cyclic-AMP Phosphodiesterases↗