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Biomedical subjects

Y Henis

Publications and source records attributed to Y Henis.

At least 37 records · Page 2Linked to original sources
PubMed1978

Localization of beta-(1,3)-glucanase in the mycelium of Sclerotium rolfsii.

The role of the lytic enzyme beta-(1,3)-glucanase in cell wall synthesis and its distribution in the mycelium of the fungus Sclerotium rolfsii were studied. Enzyme activity was determined after enzyme extraction with Triton X-100 from a cell wall preparation. Specific zones of immunofluorescence appeared in the hyphal tips, clamp connections, new septa, and lateral branching when a specific antiserum was used with the indirect method of the fluorescent antibody staining. Enzymatic activity in the cell wall preparation was inactivated by diethylpyrocarbonate. However, 69% of the total enzymatic activity was present in a latent form which was not affected by the ester. This result suggests that most of the beta-(1,3)-glucanase was present along the hyphal cell walls in a "masked" form. An active enzyme appeared only in those regions which showed immunofluorescence. The activity of glucan synthetase, an enzyme essential for wall formation, was higher in the branching funus grown on L-threonine-supplemented synthetic medium than in the synthetic medium-grown fungus.

Cell Wall↗
PubMed1977

A simple quantitative assay for bacterial motility.

It is argued that the average motility of bacterial populations should be identified with a diffusivity parameter. A simple capillary assay for quantifying this parameter is described, and some results obtained by using this procedure are presented. It is concluded that the assay combine speed and simplicity of operation with sufficient accuracy to make it a valuable tool in the assessment of motility.

Bacterial Physiological Phenomena↗
PubMed1977

The relationship between rhythmic hyphal growth and circadian formation of sclerotia in Sclerotium rolfsii Sacc.

The mycelium of the phytopathogenic fungus Sclerotium rolfsii type R (ATCC 26326) grown on a solid medium supplemented with 70 mM l-threonine exhibits a synchronous formation of sclerotia in circles whereas both leading and lateral hyphae enter into a rhythmic growth rate. A rhythmic activity of malate synthetase (malate synthase, EC 4.1.3.2) which accompanied the hyphal rhythm and preceded the formation of sclerotial circles was demonstrated. Both translocation of L-[14C]threonine and incorporation of L-[14C]leucine were significantly related to the circadian formation of sclerotia.

Circadian Rhythm↗
PubMed1977

Chemotaxis and movement of Physarum polycephalum and its responses to some neurotransmitters and psychomimetic compounds.

A method was developed for studying the effect of some neurotransmitters and drugs on the rate of movement and the chemotactic value of the plasmodium of Physarum polycephalum. Epinephrine (adrenaline) at a concentration of 1 mg/ml, reduced the rate of movement and shortened the length of the cycles of shuttle streaming, but did not affect the chemotactic response. The drugs DL-amphetamine, cannabinol and heroin diminished the rate of movement, whereas Na-barbitol misled the chemotactic response.

Amphetamine↗
PubMed1976

Metabolism of L-threonine and its relationship to sclerotium formation in Sclerotium rolfsii.

The activities of L-threonine dehydrogenase (I), 2-amino-3-oxybutyrate:CoA ligase (II), malate synthetase (III), isocitrate lyase (IV), glyoxylate dehydrogenase (V), glycine decarboxylase (VI), L-serine hydroxymethyltransferase (VII), glucan synthetase (VIII), glucose 6-phosphate dehydrogenase (IX) and succinic dehydrogenase (X) were detected in cell-free extracts prepared from the mycelium of the fungus Sclerotium rolfsii type R. Transfer of S. rolfsii to a threonine-containing medium resulted in a significant increase in the intracellular concentrations of L-threonine, glycine, serine and glyoxylate, and a decrease in oxalate. Incubation with 14C-labelled L-threonine resulted in an immediate output of 14CO2, and an accumulation of labelled glycine and serine in the mycelium. L-Threonine (10(-2)M) increased branching, favoured formation of sclerotia, and induced the formation of enzymes I to VIII, but not IX and X. Sodium oxalate (1-5 X 10(-2)M) inhibited branching, sclerotium formation and the activity of enzymes III and IV. Glycine (10(-1) M) inhibited branching, sclerotium formation and activity of I and II. Ammonium chloride (10(-1) to 10(-2) M) inhibited formation of sclerotia, threonine uptake and activity of III. Acetyl-CoA inhibited V and L-cysteine inhibited I as well as sclerotium formation and branching. It is suggested that hyphal morphogenesis and formation of sclerotia in S. rolfsii require an increased supply of carbohydrate intermediates and energy and that these are mainly supplied by the glyoxylate pathway.

Alcohol Oxidoreductases↗
PubMed1976

Factors affecting catalase level and sensitivity to hydrogen peroxide in Escherichia coli.

Composition of the culture medium, growth phase, and temperature play important roles in the sensitivity of Escherichia coli to H2O2. The medium and growth phase affected the sensitivity of the cells to H2O2 by modifying the amount of catalase synthesized by them, whereas the effect of temperature was due to the thermolability of the enzyme. Since catalase is unstable in the presence of its substrate, the correlation between the catalase level in the cells and their sensitivity to H2O2 could be observed only when the H2O2 concentration was not excessive in proportion to the amount of catalase.

Catalase↗
PubMed1975

Release of cell-bound polygalacturonase and cellulase from mycelium of Rhizoctonia solani.

Propagules of Rhizoctonia solani grown in modified Czapek's medium containing sodium polypectate or carboxymethyl cellulose as a sole carbon source produced both extracellular and cell-bound polygalacturonase (PG), and cellulase (Cx), respectively. The cell-bound enzymes can be released to various extents by shaking the germinating propagules in solutions of NaCl, KCl, phosphate buffer, Na2EDTA (ethylenediaminetetraacetate), detergents such as Triton X-100 (octyl phenoxypolyethoxyethanol), Tween 80 (polyoxyethylene sorbitan monooleate), Celmusol, and distilled water. Sodium dodecyl sulfate (SDS) inactivated both PG and Cx but did no affect Cx activity in phosphate buffer solution. PG was more easily released by salts from the mycelium of R. solani than Cx. The release of both enzymes was a passive process and was not due to an osmotic effect. The amount of the cell-bound fraction was correlated with the total amount of the extracellular fraction rather than with the mycelial growth. At least one-third of the cell-bound fractions of both enzymes was found to be associated with the cell wall fraction of the mycelium.

Cell Wall↗
PubMed1975

The effect of glucose and lactose on beta-D-galactosidase activity and formation of sclerotia in Sclerotium rolfsii.

Addition of 0.5% (w/v) lactose to a glucose-mineral mdeium (SM) induced formation of sclerotia and beta-D-galactosidase (beta-D-galactoside galactohydrolase)(EC 3.2.1.23) synthesis in Sclerotium rolfsii types A and R; These effects as well as lactose uptake were inversely related to glucose concentration within the tested range of 0.5 to 2.5% (w/v). Transfer of lactose-grown colonies to a glucose-supplemented medium nullified the inducible effect of lactose on formation of sclerotia, whereas transfer to water agar did not. It is concluded that glucose nullifies the effect of lactose on S. rolfsii by interfering with its active uptake.

Galactosidases↗
PubMed1975

Sequential production of polygalacturonase, cellulase, and pectin lyase by Rhizoctonia solani.

The sequence of appearance of cell wall degrading enzymes of Rhizoctonia solani propagules was followed. Polygalacturonase (PG; EC 3.2.1.15) was induced earlier by sodium polypectate (NaPP) as compared with the induction of cellulase (Cx; EC 3.2.1.4) by carboxymethyl cellulose (CMC), cellobiose, or fibrous cellulose powder. Increasing CMC concentration to 0.5% shortened the time of Cx appearance. In Czapek medium containing citrus pectin, pectin lyase (PL; EC 4.2.2.10) was produced faster and at higher amounts than in a medium containing NaPP as the sole carbon source. PG appearance also preceded that of PL in media simultaneously supplemented with their respective inducers. NaPP, which induced production of PG, repressed Cx production. Among the Cx inducers, only CMC and cellobiose repressed PG production to any extent. At pH 6.0, either in a synthetic medium or on autoclaved bean hypocotyl segments, a delay in PG production as compared with Cx and Pl production was observed. Optimal pH levels for enzyme production and activity were 4.0 and 5.0 for PG, and 5.5 for Cx, and 8.0 and 7.5 for PL. PG was less repressed than Cx by glucose, cellobiose, and monogalacturonic acid, while PL was not affected.

Carboxymethylcellulose Sodium↗
PubMed1973

Effect of biogenic amines and cannabinoids on bacterial chemotaxis.

The chemotactic response of Pseudomonas fluorescens was significantly enhanced by the stimulants dl-amphetamine and epinephrine. Acetylcholine, a physiological antagonist of epinephrine, and the cannabinoid tetrahydrocannabinol inhibited bacterial chemotaxis. It may be possible to use bacterial chemotaxis as a bioassay in biochemical studies of drug action.

Acetylcholine↗