PubMed Health⌕ Search

Biomedical subjects

H Bercovier

Publications and source records attributed to H Bercovier.

At least 19 recordsLinked to original sources
PubMed1992

Cloning, sequencing and expression of the nhaA and nhaR genes from Salmonella enteritidis.

Na+/H+ antiporter activity is wide-spread and plays essential physiological roles. We found that several Enterobacteriaceae share conserved sequences with nhaA, the gene coding for an E. coli antiporter. A delta nhaA strain, which is sensitive to Na+ and Li+, was used to clone by complementation a DNA fragment from Salmonella enteritidis which confers resistance to the ions. The cloned fragment increased Na+/H+ antiport activity in membranes isolated from strains carrying the respective hybrid plasmid. DNA sequence analysis of the insert revealed two open reading frames. Both encode putative polypeptides which are closely homologous to the nhaA and nhaR gene products from Escherichia coli. The antiporter activity displays properties very similar to that of the E. coli NhaA, namely, it is activated by alkaline pH and recognizes Li+ with high affinity.

Amino Acid Sequence↗
PubMed1992

Molecular epidemiology of Shigella infections in Israel.

The DNAs of Shigella sonnei or Shigella dysenteriae type 1 strains isolated in outbreaks of shigellosis or in sporadic cases were analysed by restriction fragment length polymorphism (RFLP). Southern blots of the DNAs of 36 S. sonnei isolates digested by 8 restriction enzymes were hybridized with an Escherichia coli rRNA probe. The S. sonnei strains were unexpectedly diverse in their RFLP. Antibiotypes of the same isolates showed clusters of strains corresponding to the various outbreaks. On the other hand, RFLP analysis suggested concomitant multiple sources of infection rather than a common source and thereby introduced a new insight in the epidemiology of shigellosis. RFLP was also used to trace S. dysenteriae type 1 transmission in a recent cluster of clinical cases. Although antibiotic resistance patterns indicated the presence of more than one strain, RFLP analysis showed that the six isolates were identical clones and suggested the loss of an R episome after one person-to-person passage.

Blotting, Southern↗
PubMed1992

Cytokine-induced resistance to microbial infections in normal, immunosuppressed and bone marrow transplanted mice.

We studied the efficacy of in vivo and in vitro treatments with IL-1, IL-2, IL-3, and GM-CSF in the protection against bacterial (Salmonella typhimurium), fungal (Candida albicans) and viral (influenza virus A/PR8) infections, of normal, sublethally irradiated and lethally irradiated, bone marrow (BM) reconstituted mice. In parallel, the cytokines were tested for their ability to potentiate hematopoietic activity in vitro and in vivo. We demonstrate that, under the experimental conditions employed, IL-1 had the best protective activity against the three micro-organisms in both normal and immunocompromised mice when administered in vivo. Administration of IL-2 led to increased resistance in normal but not in immunodeficient mice, whereas GM-CSF had no beneficial effects. In contrast, preincubation of BM cells in these cytokines, singly or combined, prior to transplantation to lethally irradiated mice, did not confer protection against subsequent infection, although it increased the number of BM derived CFU-GM in culture (except in the case of IL-2). Administration of IL-1 or GM-CSF to BM transplanted mice facilitated WBC recovery, whereas IL-2 delayed it. Collectively, the data suggest that IL-1, alone or combined with other cytokines, may be beneficial in the prevention or treatment of microbial infections in immunocompromised and BM transplanted patients. It can also be concluded that enhanced hematopoietic recovery may not always coincide with the development of resistance to micro-organisms.

Animals↗
PubMed1991

Complete nucleotide sequence of the Mycobacterium leprae 23 S and 5 S rRNA genes plus flanking regions and their potential in designing diagnostic oligonucleotide probes.

The complete nucleotide sequences of the Mycobacterium leprae 23 S and 5 S rRNA genes and their flanking regions are presented. As compared to other eubacterial homologous molecules the 23 S rDNA exhibits two insertions. A 16 nucleotide long insertion is almost unique to members of the genus Mycobacterium, while the second represents an extended version of helix 54. The potential of both insertions to serve as target for diagnostic oligonucleotide probes was proven by comparative sequence analysis of 23 S rRNA of several Mycobacterium species and by dot blot hybridization. In addition, a 19-mer oligonucleotide probe is described, which can be considered genus Mycobacterium-specific.

Base Composition↗
PubMed1991

Prevalence and correlates of diphtheria toxin antibodies among young adults in Israel.

The paucity of information about immunity against diphtheria of young adults in Israel prompted us to analyse sera from a random sample of 480 recruits (263 males and 217 females) aged 18-19 years. Antitoxin antibody levels were determined by means of ELISA. Of the recruits 58.1% had antibody values greater than 0.1 IU/ml; 38.5% had amounts between 0.01 and 0.1 IU/ml, which is considered low when using the ELISA method, and 3.3% had less than 0.01 IU/ml. The results of this study suggest that a booster dose of antidiphtheria vaccine should be given to adults in Israel in order to ensure adequate antibody levels.

Adolescent↗
PubMed1991

Crossed immunoelectrophoretic analysis of Mycobacterium paratuberculosis.

Antigenic analysis of M. paratuberculosis revealed extensive cross-reactivity with M. avium; however, the number of cross-reactive antigens found was dependent on the strain of M. avium tested. One antigen was shown to be the common antigen while another appeared to be iron-regulated in its production. A commercial polyclonal antibody to M. paratuberculosis produced a CIE precipitin pattern comparable to that of the antibody produced for the present study. An antigen designated no. 6 was consistently precipitated by sera from cattle infected with M. paratuberculosis. This antigen exhibited complete cross-reaction with M. avium and partial cross-reaction with M. phlei. Among three commercially available complement fixation (CF) antigen that could be precipitated by M. paratuberculosis antibodies. A commercial antigen for use in an agar gel immunodiffusion test for Johne's disease diagnosis produced 12 precipitins with the M. paratuberculosis antibody, one of which was identical with antigen 6.

Animals↗
PubMed1991

Legionellosis at Hadassah University Hospital: a 1-year survey.

During 1985 in the Hadassah University Hospital we studied all hospitalized patients whose serum had been submitted for Legionella antibodies. Of 133 patients, 12 (9%) had legionellosis as diagnosed by serology, direct fluorescence, or culture. All Legionella cases appeared to be sporadic, nonseasonal, community-acquired pneumonia. There were no specific environmental co-factors or clustering. A significant predilection of the disease for immunosuppressed individuals was observed; the in-hospital mortality was high (5/12), especially if erythromycin therapy was delayed. L. pneumophila and L. bozemanii were the dominant etiological species. In Jerusalem, Legionella is not infrequently the etiological agent in community-acquired pneumonia in immunosuppressed patients.

Adult↗
PubMed1990

Development of sensitive methods for the detection of mycobacteria by DNA probes.

A sensitive method allowing the detection of mycobacteria by DNA probing has been developed. Besides the choice of a relevant probe encoding for part of the ribosomal RNA genes, the critical step allowing this high sensitivity was the method by which mycobacteria were lysed. Sonication of mycobacteria in the presence of chloroform followed by dot blot by this lysate gave the highest sensitivity in the detection of sequences homologous to the DNA probes.

Cloning, Molecular↗
PubMed1990

Detection of interleukin-3 in the serum of mice infected with Mycobacterium lepraemurium.

Infection of mice by Mycobacterium lepraemurium is accompanied by ablation of erythropoiesis in the bone marrow and gross enlargement of the spleen. This, together with increased monocytopoiesis and the earlier demonstration of macrophage colony-stimulating factor in the serum of infected mice, suggested the activity of additional cytokines. Eight weeks after infection of mice by M. lepraemurium, interleukin-3 (IL-3) activity was demonstrated in the serum (titer, 1:3200). The serum titer of IL-3 activity was maximal after 13 weeks (greater than 1:6400) and was slightly reduced after 18 weeks (1:6400). That the IL-3 activity detected in the serum of the M. lepraemurium-infected mice reflected the presence of IL-3 itself was confirmed by a neutralization assay using anti-murine IL-3 antibodies; IL-3 activity in the serum of mice 13 weeks after infection was completely abolished by the anti-IL-3 antibodies. Finally, a 1-kb signal of IL-3 RNA was detected in the spleens of M. lepraemurium-infected mice 13 weeks after infection.

Animals↗
PubMed1990

Nucleotide sequence and codon usage of the elongation factor Tu(EF-Tu) gene from Mycoplasma pneumoniae.

The Mycoplasma pneumoniae tuf gene, encoding the elongation factor protein Tu, was cloned and sequenced. The nucleotide sequence of the mycoplasmal gene showed about 60% homology to the sequences of tuf genes of other prokaryotes, yeast mitochondria and Euglena gracilis chloroplasts, and about 75% similarity was found when comparing the deduced amino acid sequences of the various Tu proteins. The relatively low G + C content (40%) of the M. pneumoniae DNA was reflected in a low G + C content (44.6%) of the tuf gene, and in a preferential use of adenine and uracil at the third position of codons, yet codon usage analysis revealed the presence of almost all of the codons of the genetic code in the mycoplasmal gene. Southern blot hybridization of digested DNAs of 11 Mollicutes species with the entire M. pneumoniae tuf gene and with its 5' part suggested the presence of one copy only of this gene in the representative species of the Mollicutes. In this respect, the Mollicutes resemble Gram-positive bacteria and differ from the Gram-negative bacteria, which carry two copies of the tuf gene.

Amino Acid Sequence↗
PubMed1990

The disease of CBA and BALB/c mice that follows inoculation of a small number of Mycobacterium lepraemurium into the hind foot pad.

To learn if the lack of an immune response in mice infected with Mycobacterium lepraemurium (MLM) was a consequence of the organisms, we studied the disease that followed inoculation of less than or equal to 5000 organisms into the hind foot pads of CBA and BALB/c mice. The mice of both strains demonstrated a rapid increase of bacterial numbers soon after inoculation, with a slowing of the rate of multiplication once the number of organisms per foot pad passed 3 x 10(7). By 1 year after inoculation, the numbers of organisms had reached levels greater than or equal to 10(11) in the spleen and liver, and greater than or equal to 10(8) in the femoral bone marrow. In mice that had been inoculated with as few as 5 MLM or 50 MLM, the organisms had multiplied to numbers greater than 10(8) in the foot pads and to greater than or equal to 10(9) in the spleens, suggesting that the ID50 of viable MLM may be less than or equal to 5 organisms per foot pad. No protection against superinfection could be demonstrated. On the other hand, initial multiplication of MLM in the foot pads was followed virtually immediately by the death of at least 97% of the organisms.

Animals↗
PubMed1989

Cloning and restriction analysis of ribosomal RNA genes from Mycobacterium smegmatis.

A genomic library of Mycobacterium smegmatis DNA was constructed in phage EMBL3. A clone (gamma HB85) containing rRNA genes was isolated using as probes, fragments of E. coli rRNA cistron B. This cloned DNA fragment was mapped by restriction analysis and was shown to contain one complete set of rRNA genes (rRNA A). The physical mapping of the second set of rRNA genes of M. smegmatis (rRNA B) was done by restriction analysis of total chromosomal DNA. The two sets of rRNA genes showed highly conserved restriction sites within the respective sets but not in the flanking regions. The two rRNA sets of genes are organised like in the other eubacteria in the order 16S-23S-5S.

Cloning, Molecular↗
PubMed1989

Doubling time of Mycobacterium lepraemurium in mouse footpads.

The doubling time of Mycobacterium lepraemurium (MLM) was measured in CBA/Ca mice. In eight experiments, 5 X 10(3) MLM were inoculated into the hind footpads of groups of mice, and the organisms were harvested from 1-45 days later. The harvested organisms were enumerated, and the doubling time was calculated assuming that MLM had multiplied without a lag phase and that multiplication continued at a constant rate from inoculation to harvest. Simultaneously, the proportions of viable organisms in the inocula were determined by inoculation of serially diluted suspensions into the footpads of other mice, harvesting 4 months later and calculating the most probable number. MLM were observed to multiply rapidly during the first several days, and more slowly thereafter; the mean initial doubling time was determined to be 0.5 days, a value much smaller than those previously reported by other workers.

Animals↗
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↗