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H Bercovier

Publications and source records attributed to H Bercovier.

At least 55 records · Page 3Linked to original sources
PubMed1989

Duplication of the tuf gene: a new insight into the phylogeny of eubacteria.

The conservation and duplication of the tuf gene encoding the elongation factor EF-Tu were used to define phylogenetic relationships among eubacteria. When the tufA gene of Escherichia coli was used as a probe in hybridization experiments, duplicate tuf genes were found in gram-negative bacteria from three major phyla: purple bacteria, bacteroides, and cyanobacteria. Only a single copy of tuf was found in gram-positive bacteria, including mycobacteria and mycoplasmas. Gram-positive clostridia were found to carry two copies of tuf.

Bacteroides↗
PubMed1989

Characterization and taxonomic implications of the rRNA genes of Mycobacterium leprae.

The number of rRNA genes of Mycobacterium leprae was determined by restriction analysis of M. leprae total chromosomal DNA. A single set of rRNA genes was found. This set was subcloned from a cosmid library of M. leprae DNA into pUC13 and was characterized by restriction analysis and hybridization with Escherichia coli rRNA genes. The 16S, 23S, and 5S genes of M. leprae were clustered on a 5.3-kilobase DNA fragment. On one hand, restriction analysis of the set of rRNA genes showed the uniqueness of M. leprae among mycobacteria, but on the other hand, it suggested that M. leprae strains of several origins are very much alike. Quantitative hybridization studies between M. leprae rDNA and total DNA of various bacteria demonstrated a close relatedness between M. leprae and corynebacteria, nocardia, and mycobacteria, especially Mycobacterium tuberculosis.

Cloning, Molecular↗
PubMed1988

Lysis of murine macrophages infected with intracellular pathogens by interleukin 2-activated killer (LAK) cells in vitro.

To determine if murine lymphocytes activated by interleukin 2 (IL-2) were cytotoxic against syngeneic elicited peritoneal macrophages (M phi) infected with intracellular pathogens, splenocytes that had been cultured with IL-2 for 5 or 10 days were studied in vitro. These cells, [lymphokine-activated killer (LAK) cells] showed significantly greater cytotoxicity against M phi infected with Leishmania major or Legionella pneumophila than against uninfected M phi. Preferential cytotoxicity against infected M phi was best shown using effector-to-target-cell ratios of 1:1-20:1; when ratios greater than or equal to 40:1 were employed, uninfected M phi were also lysed. The extent to which M phi that had been incubated with L. major were lysed depended upon the proportion of M phi containing intracellular organisms. After infection with L. major, the duration of incubation did not appear to influence the degree of lysis by LAK cells.

Animals↗
PubMed1988

Haemophagocytosis and other haematological aspects of Mycobacterium lepraemurium disease of mice.

CBA mice inoculated i.v. with 2 x 10(8) viable MLM were observed at intervals for 5 months. In the bone marrow, haematopoietic cells were progressively displaced by MLM-laden phagocytes; depletion of erythroid cells began earlier and was more pronounced than that of myeloid cells. Transiently, mild anaemia and profound leucopenia were noted. The spleen was enlarged and the site of increasing histiocytosis and extramedullary haematopoiesis which was accompanied by displacement of splenic parenchyma. The liver was enlarged and its parenchyma contained scattered islands of haematopoietic elements. Lymph node cells had been largely replaced by MLM-laden macrophages by the end of the process. Thus, MLM infection exerts important effects on haematopoiesis of susceptible mice and is accompanied by active extramedullary haematopoiesis. In addition, the haemophagocytosis, observed most commonly in immuno-compromised patients infected with certain viral or mycobacterial pathogens, was observed late in the course of MLM disease of mice.

Animals↗
PubMed1988

Response of the murine hematopoietic system to chronic infection with Mycobacterium lepraemurium.

Mycobacterium lepraemurium infection of mice produces a chronic lethal disease that is characterized by massive accumulation of macrophages throughout the mononuclear-phagocyte system. We studied the influence of M. lepraemurium infection on the composition and function of the hematopoietic system. Medullary erythropoiesis was virtually abolished, as reflected by a small number of erythroid elements and a decrease in the number and frequency of erythroid progenitors in the bone marrow, together with reduced uptake of 59Fe into bone marrow hemin. On the other hand, erythropoiesis was observed in the spleen, as demonstrated by a large number of erythroid cells, a sixfold increase of 59Fe uptake, and a pronounced increase in the number of erythroid progenitors. A considerable increase of monocyte progenitors was observed in the spleen, and a more modest increase was observed in the bone marrow. This increase may be accounted for, at least in part, by greatly increased levels of macrophage-colony-stimulating factor in the serum of infected mice. Thus, M. lepraemurium infection produces important changes in the hematopoietic system, during the course of which the spleen becomes the major hematopoietic organ.

Animals↗
PubMed1987

beta-Glucosidase in Candida albicans and its application in yeast identification.

In this report we attempt to explain the discrepancy between beta-glucosidase (EC 3.2.1.21) activity in Candida albicans as measured by commercial kits and that found in an experimental assay. beta-Glucosidase activity in American and Israeli isolates of C. albicans was evaluated with the API ZYM and YeastIdent systems (Analytab Products) and with experimental biochemical assays. Activity was found with whole cells and cell extracts of isolates from both sources. The greatest beta-glucosidase activity was found at pH 5.0 and with p-nitrophenyl-beta-glucopyranoside (PNP-BDG) as the substrate. In assays with beta-naphthyl-beta-D-glucopyranoside and 6-bromo-2-naphthyl-beta-D-glucopyranoside (6-Br-2-naphthyl-BDG), no enzyme activity was detected in whole cells and only limited activity was found in cell extracts of isolates from both sources. In studies with PNP-BDG at pH 5.0 and 7.5, 29 to 38% less activity was found at both pHs with American whole cells, and minor activity (20%) was found at pH 7.5 with isolates from both sources. Because assays with PNP-BDG in cell extracts of isolates from both sources showed no significant differences in activity, the more limited beta-glucosidase activity in American whole cells was most likely due to less efficient transport. Because the API ZYM system uses 6-Br-2-naphthyl-BDG as the substrate and because the substrate is buffered at pH 7.5 in the API YeastIdent kit, both systems appear to be of limited value for the detection of beta-glucosidase activity in C. albicans.

Candida albicans↗
PubMed1986

Mycobacteria possess a surprisingly small number of ribosomal RNA genes in relation to the size of their genome.

DNAs from Mycobacterium tuberculosis, M. intracellulare, M. phlei and M. smegmatis were digested by restriction enzymes and hybridized with three probes consisting of the 5' (16S rRNA), the middle (16S and 23S rRNA), and the 3' (23S and 5S rRNA) portions of the Escherichia coli rrnB operon. The resulting hybridization patterns indicate that slow-growing Mycobacteria species (i.e., M. tuberculosis and M. intracellulare), with genome size 3.13 - 4.29 X 10(9) daltons, appear to possess only one rRNA operon, whereas fast-growing species (i.e., M. phlei and M. smegmatis), with genome size 4.30 - 5.20 X 10(9) daltons, appear to possess two rRNA operons.

DNA↗
PubMed1986

Seasonal distribution of legionellae isolated from various types of water in Israel.

The presence of legionellae was investigated over 2 years in various types of water in Israel. Potable water, fish ponds, oxidation ponds and surface water were sampled on a monthly basis. Legionellae were not isolated during the cold months of the year (November to April), but were continually isolated during the rest of the year (May to October). Nineteen of 56 sources of water were found culture-positive for Legionella pneumophila serogroups 1, 2, 3, 4 and 6, L. bozemanii, L. israelensis and some nonspeciated Legionella. As irrigation water in Israel originates from the various types of water that we found to be culture-positive for Legionella, the public health implications of this finding were correlated with our previous seroepidemiological survey of irrigation workers.

Israel↗
PubMed1980

[Indigenous Legionnaires' disease. Importance of clinical symptoms (author's transl)].

The first case of legionnaires' disease indigenous to France is reported. Since rapid bacteriological and/or serological diagnostic procedures are lacking, the disease should be suspected clinically in patients presenting with febrile pneumonia typically associated with neurological, digestive and renal disorders. Antibiotic treatment with erythromycin should be initiated as early as possible.

Adult↗
PubMed1979

Yersinia enterocolitica among small wild mammals in France.

A survey of Yersinia enterocolitica was made in two French areas (Indre and Alsace) in several components of the terrestrial ecosystem. Y. enterocolitica has been isolated from several habitats and from numerous species of small mammals. The trap line method enabled us to estimate the density of the two abundant small mammal species, Microtus arvalis and Apodemus sylvaticus, and the densities of Y. enterocolitica carriers. The frequency of isolation was high when temperatures were low, but did not seem to be in direct relationship with animal densities. Infectious lesions were never found in spleens or intestines of 1893 captured animals. Samples of fresh water, fresh-water fish, soil and earthworms were occasionally collected. A total of 163 strains were isolated. Of these, 99 were of biochemical type 1; 20 different 0 serogroups were found.

Animals↗
PubMed1979

Contribution to the definition and the taxonomy of Yersinia enterocolitica.

The phenotypic study of 6,000 strains of Y. enterocolitica and Y. enterocolitica-like organisms by the biochemical reaction of the identification of Enterobacteriaceae on one hand and of 100 strains representing different chemiotypes by an auxanogram technique shows a large homogeneity of these strains which are apparated from the other Yersinia within Enterobacteriaceae. Six chemiotypes are described. The strains fermenting thamnose, similar to chemiotype I, can be subdivided in two groups according to the acidification of melibiose. The future and the denomination of these strains are discussed. The biochemical characteristics difining Y. enterocolitica and six chemiotypes are defined.

Ampicillin↗
PubMed1979

[Gas-liquid chromatography of non-volatile fatty acid produced by "Yersinia enterocolitica" (author's transl)].

The metabolic products (non-volatile fatty acids) of 24 strains belonging to four Yersinia enterocolitica groups (typical, sucrose negative, rhamnose positive, melibiose and rhamnose positive) were examined by gas liquid chromatography. All strains produced lactic, pyruvic and succinic acids. This technique did not allow any classification for taxonomic purpose. The evolution of lactic and succinic acid production was monitored for 72 h in shaked and non-shaked cultures. The concentration of both acids increased in the first 24 h, then decreased and increased again after 38 h. Shaked culture produced a lesser amount of lactic acid than did non-shaked culture. Only traces of succinic acid were detected in shaked culture. The quantities of metabolic products of the four strains grown in five media were significantly different. These observations suggest that the composition of the medium, the bacterial growth, inoculum size, incubation technique and the incubation time are important factors in metabolic production by aeroanerobic bacteria. Only constant results in the face of such varying factors could be of taxonomic value.

Chromatography, Gas↗