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Biomedical subjects

B M Gmeiner

Publications and source records attributed to B M Gmeiner.

12 recordsLinked to original sources
PubMed1989

Phosphatidylserine modulates calf intestine alkaline phosphatase activity towards low and high molecular weight substrate.

Pretreatment of calf intestine alkaline phosphatase with phosphatidylserine resulted in an inhibition of the phosphatase activity towards low - (p-nitrophenylphosphate) and high (phosphohistone) molecular weight substrate. Phosphatidylcholine, irrespectively of the substrate used did not cause enzyme modulation. 12-O-tetradecanoylphorbol-13-acetate, 1,2-diolein as well certain retinoids, known to effect phosphatidylserine-sensitive enzyme systems (Castagna, M. et al. 1982, J. Biol. Chem. 257, 7847-7851; Gmeiner, B. 1986, Biochim. Biophys. Acta 856, 392-394) had no influence on the modulated phosphatase. The lipid interacting drug trifluoperazine inhibited the enzyme activity towards phosphohistone, but not towards p-nitrophenylphosphate as a substrate. The results indicate that acidic phospholipid may play a role in activity modulation of calf intestine membranous alkaline phosphatase activity.

Alkaline Phosphatase↗
PubMed1988

Co2+ is able to substitute for Mn2+ in some exogenous and endogenous galactosyltransferase reactions.

The ability of Co2+ to substitute for Mn2+ in exogenous and endogenous galactosyltransferase reactions was tested. Exogenous transfer was measured towards different high and low molecular weight galactose acceptors using galactosyltransferase from the following sources: crude serum, the serum enzyme partially purified by affinity chromatography and a pure enzyme preparation from milk. Endogenous transfer was estimated in preparations from human urinary bladder tumor cells and from rat liver microsomal fractions. The results show that Co2+ is able to substitute for Mn2+ in some exogenous and endogenous galactosyltransferase reactions. This ability seems to depend on the molecular structure of the galactose acceptor as well as on the nature of the enzyme.

Animals↗
PubMed1987

Phorbol ester, retinoic acid and diacylglycerol decrease ecto- but increase total basal-protein kinase activity of human fibroblasts.

Studies have been carried out on intact human lung fibroblasts (HLF) in situ to investigate the effect of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) and the anti-tumor promoter retinoic acid (RA) on ecto-protein kinases. The ecto-kinase reaction of the HLF-cells was cAMP-independent, showed an apparent Km for ATP of 6.99 +/- 0.35 (microM) and was substantially inhibited by TPA and RA. With the notable exception of a approximately 57 kD phosphoprotein both compounds decreased the overall phosphorylation of intact cells. In contrast to RA-treatment, however, TPA caused the release of a high molecular weight (approximately 210 kD) phosphoprotein from the HLF. RA was the most potent retinoid in reducing ecto-kinase activity. The physiological modulators of protein kinase C: 1,2- and 1,3-diolein as well the synthetic 1,2-dioctanoylglycerol decreased the ecto-kinase activity to an extent similar to that of TPA. The drop in ecto-kinase activity of HLF-cells in situ caused by TPA, RA and the diacylglycerols was accompanied by an increase in total basal-(Mg++-dependent) protein kinase activity present in extracts of treated cells. The results suggest an important role of ecto-kinase in the response of intact cells to TPA and RA.

Cells, Cultured↗
PubMed1986

The effect of retinoids on the activity of the membrane form of galactosyltransferase, studied in an enzyme/liposome model system.

In the present study the effect of retinoids on the membrane form of galactosyltransferase was tested. A model system consisting of pure bovine milk galactosyltransferase and phosphatidylserine vesicles was used for this investigation. Retinol, retinal and retinylphosphate were able to overcome the modulating effect of phosphatidylserine, that is, activated the enzyme. Retinoic acid and retinylpalmitate were ineffective in this system.

Animals↗
PubMed1985

Conversion of the amphiphilic galactosyltransferase from human mammary carcinoma cells to an active hydrophilic enzyme form by limited proteolysis.

As analyzed by a phase-separation technique, the Triton X-114 extract of human mammary carcinoma cells (MCF-7 cells) contain an amphiphilic form of galactosyltransferase (UDPgalactose: D-glucose 4-beta-D-galactosyltransferase, EC 2.4.1.22), while the galactosyltransferase activity released by these cells represents a hydrophilic form of the enzyme. When the amphiphilic galactosyltransferase was subjected to limited proteolysis with thermolysin, this treatment generated a hydrophilic form of the enzyme. With respect to Km for UDPgalactose the kinetic data were very similar for the amphiphilic, for the released and the hydrophilic galactosyltransferases produced by proteinase treatment. Differences were detected in electrophoretic and gel chromatographic properties. The hydrophilic enzymes showed a greater electrophoretic mobility on non-denaturing polyacrylamide gels than did the amphiphilic form. On Sepharose 6B column chromatography, the amphiphilic galactosyltransferase appeared to be of higher molecular weight than the hydrophilic enzyme.

Breast Neoplasms↗
PubMed1985

Galactosyltransferase activities in cultured urinary bladder tumor cells.

After demonstrating that three bladder cancer cell lines (human bladder transitional cell carcinoma, MGH-U1; rat bladder transitional cell carcinoma, RBTCC; Nara rat bladder epidermal carcinoma, NBT-II) had galactosyltransferase (GT) activity in their cell surfaces, we investigated the effect of increasing cell density on the activity of this enzyme. All three cell lines responded to increased cell density by increased activity of cell-surface GT towards endogenous acceptor. By the use of exogenous acceptor, we showed that in the two transitional cell carcinoma lines (human and rat), the increased activity was probably caused by increased levels of endogenous acceptor rather than enzyme. In the rat bladder epidermal carcinoma line, on the other hand, increased GT activity seemed to be the result of increased levels of the enzyme. These conclusions were supported by the increased shedding of GT into the medium with increasing cell density in case of the epidermal carcinoma cells, but not the two transitional cell carcinoma lines. Total cell-associated GT activity would indicate that, in contrast to the two transitional cell carcinoma lines, the bladder epidermal carcinoma cells may have an increased rate of synthesis of GT as confluence is approached.

Animals↗
PubMed1976

Influences of retinoic acid and retinoid on skin metabolism. Investigations of oxygen consumption and enzymatic activities of human skin.

All-trans retinoic acid and its derivative retinoid, two new compounds with expanding therapeutic spectrum in dermatology, were investigated in biochemical assays. Both substances provoke an increase in oxygen consumption of rat skin whereas in human skin only retinoid was found active in this respect. In resting yeast cells, both substances failed to exert any significant influence on oxygen consumption.--Pure G-6-PDH was inhibited by retinoic acid and retinoid in concentrations as low as 5 mug/ml. In human skin homogenates, LDH-, GAPDH-, and G-6-PDH-activities were inhibited by retinoic acid whereas GOT-, LAP-, and ALD-activites remained practically unchanged following an incubation with retinoic acid in concentrations between 1 and 100 mug/ml for 60 min.--The data collected in this study were briefly discussed with regard to the use of retinoic acid and its derivatives in psoriasis.

Animals↗
PubMed1976

Enzyme inhibition in human skin homogenates by hydrocortisone, hydrocortisone acetate and hydrotisone butyrate.

In fresh human skin homogenates, the activities of four enzymes, lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G-6-PDH), "acid" phosphatase (AcP), and "leucine aminopeptidase" (LAP) were assayed following an incubation with hydrocortisone, hydrocotisone acetate, or hydrocortisone-17-butyrate, respectively. Concentration of the three compounds measured 2.75 mMol/l. Hydrocortison butyrate inhibited LDH-G-6-PDH-, and AcP-activities. Hydrocortisone and hydrocortisone acetate exerted a significant inhibitory action only in the case of G-6-PDH-activity.--On pure G-6-PDH from yeast, the inhibition exerted by hydrocortisone butyrate was significantly stronger than the inhibition exerted by the two other steroids. Time/action diagrams revealed the fact that hydrocortisone butyrate is superior to the other two compounds from the beginning of the incubation period.--The date sustain the assumption that hydrocortisone butyrate exerts biochemical-pharmacological actions of its own and that it may not be considered just as an esterified transport form of hydrocortisone.

Acetates↗
PubMed1976

The influence of D-penicillamine on enzymatic activities: glucose-6-phosphate dehydrogenase. Correlation with serum levels measured in humans.

The influence of D-penicillamine on glucose-6-phosphate dehydrogenase of yeast (pure enzyme), human hemolysate, and human skin homogenate were determined. In high concentrations, D-penicillamine inhibits glucose-6-phosphate dehydrogenase activity (concentrations above 6.7 mmol/l, i. e. l g/l). In low concentrations, D-penicilliamine exerts an indirect influence by removing some inhibiting metal ions, such as zinc. In human skin homogenates, an activating action of D-penicillamine on glucose-6-phosphate dehydrogenase activity occurs due to the chelation of metal ions.

Enzyme Activation↗
PubMed1975

Inhibition of glucose-6-phosphate dehydrogenase activity by betamethasone and three of its esters with dermatological importance.

Betamethasone, betamethasone-17-valerate, betamethasone-17-benzoate, and betamethasone-17,21-diproprionate were investigated for their inhbitory action on glucose-beta-phosphate dehydrogenase (G-6-PDH) activity (pure enzyme from yeast, enzyme from human skin homogenate). Between these four compounds, marked differences were encountered which could not be attributed to the presence of an esterified or unesterified steroid. According to these data it does not seem to be justified to consider betamethasone esters simply as the transport forms of the topically inactive betamethasone but one must consider the betamethasone esters having biochemical actions of their own.

Betamethasone↗
PubMed1975

Influence of ultraviolet light, various temperatures, and zinc ions on anthralin (dithranol). Biochemical and chemical investigations.

The changes of anthralin under various physical conditions (temperature, ultraviolet irradiation) were investigated by biochemical assay (inhibition of G-6-PDH activity), by oxygen monitor (increased oxygen consumption in the presence of zinc ions), and by recording the absorption spectra. Higher temperatures and exposure to ultraviolet light provoke the formation of a biochemically highly active compound within short periods of time. In clinical therapy, this compound may easily be formed when anthralin is used together with ultraviolet irradiation (Ingram method). Changes in the biochemical activity of anthralin are accompanied by changes in the absorption spectra. Oxidation (e.g. in the presence of zins ions) or inhibition of oxidation (e.g. in the presence of salicylic acid) may easily be detected by spectroscopic assay.

Absorption↗