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Biomedical subjects

H Ankel

Publications and source records attributed to H Ankel.

At least 55 records · Page 3Linked to original sources
PubMed1973

Antiviral effect of interferon covalently bound to sepharose.

Interferon, covalently bound to Sepharose 4B activated by cyanogen bromide, induces the antiviral state in sensitive cells. The antiviral effect is neutralized by antiserum specific to interferon and is recovered thereafter when the antibody is detached from the interferon by treatment at low pH. Binding interferon to Sepharose increases the stability of the molecule. It is likely that the interferon molecule acts on the cell receptor without being detached from the beads. However, the data do not exclude the possibility of a small loss of interferon, or fragments of it, after contact with the cell.

Animals↗
PubMed1973

Biosynthesis of glycogen and starch in Cryptococcus laurentii.

Cells of Cryptococcus laurentii, when grown in liquid culture on 2% glucose close to neutral pH, showed glycogen granules throughout the cytoplasm. Glycogen levels of C. laurentii cells reached maximal levels just before onset of stationary phase. Concomitantly, a sharp rise in total and specific activity of glycogen synthetase was observed. Conversely, glycogen phosphorylase reached its highest specific activity approximately 3 hr after the glycogen peaked and remained high until most of the endogenous glycogen was utilized. Uridine diphosphoglucose pyrophosphorylase activity was always an order of magnitude higher than glycogen synthetase during log phase, but fell off rapidly after the cells reached stationary growth. Kinetic properties of the glycogen synthetase showed that the enzyme is always activated by glucose-6-phosphate, although the degree of activation by glucose-6-phosphate was found to be somewhat variable. The accelerated uptake of glucose commencing with the onset of stationary phase is explained by the rapid formation of extracellular acidic polysaccharide, which continues as long as there is glucose in the medium. In cells grown at pH 3.4, where no detectable extracellular acidic polysaccharide was formed, glucose uptake drastically declined when the cells reached stationary phase. These cells also contained glycogen-like granules in the cytoplasm. The evidence presented indicates that these granules are in fact glycogen, and that its structure does not resemble that of the starch excreted by cells grown at acidic pH.

Carbon Isotopes↗
PubMed1971

Uridine diphosphate-4-keto-glucose, an intermediate in the uridine diphosphate-galactose-4-epimerase reaction.

When UDP-galactose 4-epimerase (EC 5.1.3.2) from Escherichia coli is incubated with UDP-galactose, then reduced with NaB(3)H(4), label is found in UDP-glucose and UDP-galactose. Enzymatic and chemical degradation demonstrates that the label is bound to carbon 4 of the glycosyl moieties. These results provide direct evidence for the existence of UDP-4-keto-glucose as an enzyme-bound intermediate in the epimerization reaction, and they exclude the formation of a 3-keto intermediate.

Alcohol Oxidoreductases↗
PubMedDate not supplied

Role of glycosilation in the susceptibility of "acid labile" interferon alpha to acid treatment.

Mononuclear cells from blood of healthy donors produce acid-labile interferon (IFN) alpha when stimulated with HIV-infected cells. A large proportion of this IFN appears to be glycosilated, as treatment with neuraminidase causes a shift of the isoelectric point (IP) from pH = 5.2-5.4 to pH = 5.8-6.2. To assess the role of glycosilation in determining the instability of antiviral activity after exposure to acid (pH lower than 4) peripheral blood mononuclear cells (PBMC) were induced to produce IFN with HIV-infected cells in the presence of tunicamycin, an inhibitor of glycosilation. The IFN produced under such experimental conditions (tu-IFN) was acid-stable. Tu-IFN was compared to a standard acid-labile IFN by affinity chromatography on Con A-sepharose. The elution pattern showed that tu-IFN does not bind to the gel, whereas the acid-labile IFN is eluted in two fractions, one unbound, which is stable at pH2, and one bound, which retains the initial acid-lability. These results suggest that acid-labile IFN alpha is largely glycosilated, and that the presence of glycosilated molecules contribute to render the IFN molecule unstable at acidic pH. It is to be determined whether some glycosilated molecule present in the IFN preparation, or glycosilation of the IFN molecule per se, is responsible for acid-lability of the antiviral activity.

Chromatography, Affinity↗