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Biomedical subjects

M Mandel

Publications and source records attributed to M Mandel.

At least 127 records · Page 7Linked to original sources
PubMed1977

The use of rec-bacteria for testing of carcinogenic substances.

A series of rec-Escherichia coli strains were tested for their sensitivity to four known carcinogenic compounds by examination of a zone of inhibited bacterial growth around a central well containing the test chemical. The mutants recA-, recB-, recC-, and recA- recB- recC- were all more sensitive to the mutagens than the parental strain AB1157. The recB- recC- strain was examined with a larger series of compounds and was found to respond to many of the substances in a similar way as the Salmonella typhimurium strains of Ames but with some notable exceptions. Nitrosamines, with rat liver microsomal activation, could be detected at lower levels and a group of aromatic amino compounds failed to react with these rec-E. coli. An unusual feature of these rec-mutants is their sensitivity to mixtures of nitrosamines and 2-acetyl amino-fluorene in the absence of microsomal activation.

2-Acetylaminofluorene↗
PubMed1977

Kinetic polarization deficiency in electrolyte solutions.

The prediction and experimental confirmation of a previously unsuspected kinetic effect occurring in electrolyte solutions are presented herein. Kinetic polarization deficiency may be described as a reduction, with respect to the pure solvent, in the static permittivity of the solution; the decrement in epsilon0 is shown to be proportional to the product of the dielectric relaxation time of the solvent and the low frequency conductivity of the solution. The kinetic ion-solvent interaction affects the capacitive admittance in two closely related ways: as an ion migrates, the surrounding volume elements of the liquid tend to rotate according to the laws of hydrodynamics, and although dielectric relaxation tends to restore an equilibrium polarization appropriate to the local electric field, this adjustment is not instantaneous; rather it lags behind by the dielectric relaxation time. Conversely, the force that an external field exerts on an ion does not develop its full strength instantly because the ion is driven partly by the external field and partly by the polarization that develops in response to the applied field, the polarization field evolving with a time constant that is the relaxation time for the orientation of solvent dipoles.

Electrolytes↗
PubMed1977

Gastrointestinal carcinoma in the Japanese of Hawaii: a status report.

The primary aim of the Japan--Hawaii Cancer Study was to identify factors that could explain the changes in cancer risk experienced by Japanese who migrated to Hawaii. Many investigations were conducted in this long-term prospective study since its inception in 1971. Among the findings that relate to gastrointestinal carcinoma were the following: 1) Bowel transit time does not appear to be related to the occurrence of large bowel cancer or to any of the benign conditions with which it is associated; 2) adenomatous and hyperplastic polyps, as well as diverticula, are much more prevalent among autopsy specimens from Japanese who had lived in Hawaii than of those in Japan; 3) adenomatous polyps and diverticula are positively associated with atherosclerosis in the necropsy population in Hawaii; 4) although the incidence of the diffuse histopathologic type of gastric cancer does not differ appreciably among the Japanese in Hawaii and Japan, the migrants have a significantly lower incidence of the intestinal type of stomach cancer; and 5) case-control studies indicated that the two conditions frequently associated with gastric carcinoma, i.e., gastric ulcer and intestinal metaplasia of the stomach, are associated with high salt intakes and adherence to the traditional Japanese diet.

Aged↗
PubMed1977

[Study of 14 denitrifying soil bacteria of the "pseudomonas stutzeri" group isolated by enrichment culture in the presence of nitrous oxide (author's transl)].

The strains were isolated from soil by enrichment in a liquid minimal medium containing ethanol, acetate, succinate, L-malate or tartrate, under an N2O atmosphere at 32 degrees C. All fourteen strains can use the following 25 sources of carbon and energy under aerobic conditions: glycerate, ethanol, propanol, acetate, butyrate, malonate, succinate, glutarate, sebacate, glycollate, L-lactate, D-lactate, L-malate, DL-3-hydroxybutyrate, pyruvate, fumarate, itaconate, mesaconate, crotonate, L-alpha-alanine, D-alpha-alanine, L-leucine, asparagine, L-tyrosine, and L-proline. They hydrolyze Tween 80 but not gelatin. Nitrate is used as nitrogen source. Nitrate reductase A and respiratory nitrite reductase are present. Four of the strains are clearly and easily distinguishable from the others on the basis of six characters: special morphology of colonies; in ability to use isovalerate and DL-valine, inability to use glucose, absence of exocellular amylase, and high level of metapyrocatechase. Their G + C content is 66-67%. One of the strains is distinct from the others by the yellow pigmentation of its colonies, its ability to use D-glucuronate, trehalose, D-sorbitol and citraconate, ability to grow at 4 degrees but not at 40 degrees, and a lower G + C content: 63%. One strain accumulates poly-beta-hydroxybutyrate. This work confirms the well-known, wide variability of the bacteria belonging to the P. stutzeri group. Denitrification by two of the strains was quantitatively studied using cell suspensions. Cells from NO-3-containing anaerobic cultures reduce NO-3, NO-2 and NO to N2O and N2; they reduce slowly N2O to N2. Cells grown in anaerobic cultures under N2O also reduce NO-3, NO-2 and NO to N2O and N2 but they reduce N2O rapidly to N2.

Culture Media↗
PubMed1976

The isolation and properties of a denitrifying bacterium of the genus Flavobacterium.

A previously undescribed denitrifying bacterium was isolated from soil. The cells are small gram-negative rods, asporogenous, and non-motile. Colonies become yellow after long exposure to light. This colouring is due to the production of a carotenoid pigment. The organism shows no fermenting activity, and grows only in the presence of one of the following electron acceptors: NO2, N2O, and O2. It does not reduce nitrate. It gives a positive oxidase test and has a cytochrome c and catalase. It requires no growth factors, is a chemoorganotroph and uses only sugars as carbon and energy supply. The DNA base composition is 40.8 moles percent GC. Although presenting the physiological characteristics of a pseudomonad, the organism described has been placed in the genus Flavobacterium because of its pigmentation and its low GC percentage.

Aerobiosis↗
PubMed1976

[A new, sporulating, denitrifying, mesophilic bacterium: Bacillus azotoformans N. SP. (author's transl)].

The described bacterium was isolated by enrichment culture in peptone broth inoculated with garden soil, pasteurized and then put to incubate under N2O at 32 degrees. It is a Gram-negative rod, motile with peritrichous flagella, and producing oval spores without exosporium in swollen sporangia. However, cells have the thick walls, mesosomes and persistant septa characteristic of Gram-positive bacteria. It lacks fermentative activity, does not attack carbohydrates, has complex growth requirements, and will grow anaerobically only if one of the following electron acceptors is present: NO3, NO2, N2O, S4O6, and fumarate. Nitrate, nitrite, and nitrous oxide are denitrified with production of N2. The microorganism is mesophilic, gives a positive oxidase reaction, synthesizes a type of c cytochrome, and does not hydrolyse gelatin, starch nor "Tween 80". The following enzymes are present: nitrate reductase A, respiratory nitrite reductase, tetrathionate and fumarate reductases, L-glutamate dehydrogenase, and superoxide dismutase. The following enzymes are absent: thiosulfate reductase, urease, lecithinase, arginine dihydrolase, L-alanine dehydrogenase, phenylalanine desaminase, and catalase. The GC% of its DNA is 39. The bacterium described can be considered to be a new species. We propose the name Bacillus azotoformans n. sp.

Bacillus↗
PubMed1975

[Denitrifying bacteria of genus Alcaligenes isolated from soil].

The organism isolated is a small non-sporulating Gram-negative rod, motile by means of peritrichous flagellae. It is an oxidase-positive chemo-organotroph utilizing O2,NO-3,NO-2 and N2O as resiratory substrates. Primary alcohols as well as numerous organic and amino acids are utilized as carbon and energy sources. Carbohydrates are not assimilated. Poly-beta-hydroxybutyrate is accumulated intracellularly. The bacterium is assigned to the genus Alcaligenes and its phenotype characteristics are compared with those of A. faecalis.

Alcaligenes↗
PubMed1975

Characteristics of yellow-pigmented nonfermentative bacilli (groups VE-1 and VE-2) encountered in clinical bacteriology.

The morphological and physiological characteristics of 20 strains of motile, gram-negative, yellow-pigmented oxidative bacilli (groups VE-1 and VE-2) isolated in clinical bacteriology are described. Electron micrographs demonstrate the polar multitrichous flagella of group VE-1 and polar monotrichous flagella of group VE-2. Data obtained from guanine plus cytosine ratio studies of 56.8% for VE-1 and 68.9% for VE-2 distinguish the two groups of bacteria.

Bacteria↗