PubMed Health⌕ Search

Biomedical subjects

M Banai

Publications and source records attributed to M Banai.

At least 19 recordsLinked to original sources
PubMed2003

Delayed type hypersensitivity-associated disruption of splenic periarteriolar lymphatic sheaths coincides with temporary loss of IFN-gamma production and impaired eradication of bacteria in Brucella abortus-infected mice.

A major problem of infections with facultative intracellular bacteria is their chronic course. We comprehensively evaluated the host response in murine brucellosis to study mechanisms contributing to bacterial persistence in the presence of an established immune response. Evidence is presented that the decrease in eradication kinetics, reproducibly occurring 18 d after infection of mice with Brucella abortus S19, is related to a state of downregulation of defense mechanisms. This is not due to a Th1 to Th2 switch or prostaglandin-mediated suppression by macrophages but is most probably caused by a severe disruption of spleen morphology at the height of Brucella-induced delayed type hypersensitivity. This results in a profound depletion of both CD4(+) and CD8(+) T cells in periarteriolar lymphatic sheaths, a consecutive deleterious shift in the relation of permissive macrophages and protective lymphocytes and an impaired capacity of splenocytes to produce IFN-gamma in response to soluble Brucella antigen.

Animals↗
PubMed2002

The myth of Brucella L-forms and possible involvement of Brucella penicillin binding proteins (PBPs) in pathogenicity.

Brucella spp. L-forms have been proposed to be stationary phase organisms in the evolution of new variants and enduring entities in the host in complicated cases of brucellosis and during latent brucellosis. In vitro formation of Brucella L-forms has been achieved by treating the cells with sub-lethal doses of penicillin. Interestingly, Brucella spp. have classified during the evolution into two groups, penicillin susceptible or penicillin resistant, yet both types grow on 20 microg/ml of methicillin. Strains proven susceptible to penicillin grew in the presence of methicillin as L-forms as demonstrated by light and electron microscopy. In addition, the B. melitensis vaccine strain Rev.1, a penicillin susceptible organism, responded to sheep serum by development of L-form-like structures unlike wild type, strain 16M. The two strains grew normally in sheep macrophages. We propose, for the first time, a model that associates Brucella pathogenicity with the structure and activity of two of their penicillin binding proteins (PBPs). According to the model, PBP1 has evolved as the major cell wall synthesizing enzyme of the genus, capable of responding to host serum growth factor(s) necessary for Brucella survival in the host. This property is associated with high avidity to beta-lactam antibiotics. PBP2 complements the activity of PBP1. New beta-lactam antibiotics and improved vaccines might be developed based on this property.

Animals↗
PubMed2000

Exposure of hospital personnel to Brucella melitensis and occurrence of laboratory-acquired disease in an endemic area.

In 1997, 7 cases of laboratory-acquired Brucella melitensis infections were detected among the hospital personnel of a medical centre serving an endemic area in southern Israel. Although the onset of symptoms in 6 of the 7 patients occurred during a 2-week period, suggesting a point source exposure, biotype analysis showed that the outbreak was caused by 3 different B. melitensis serovars, indicating multiple exposures. Review of the laboratory records showed that during 1997, the microorganism was recovered from 146 blood and synovial fluid cultures, and that during the 2 months in which the laboratory-acquired cases occurred (April and June), 53 of 530 positive aerobic blood culture bottles (10.0%) grew B. melitensis. The epidemiological investigation did not reveal the source of the outbreak, and no noticeable breaches in laboratory safety practices could be demonstrated. It is concluded that in areas endemic for brucellosis, hospital personnel are frequently exposed to Brucella microorganisms. Under these circumstances, significant morbidity may occur despite observance of recommended safety practices. Biotyping of Brucella isolates may contribute to the elucidation of complex epidemiological situations.

Brucella melitensis↗
PubMed1997

Delayed-type hypersensitivity activity of the Brucella L7/L12 ribosomal protein depends on posttranslational modification.

The ribosomal protein L7/L12 isolated from Brucella melitensis induces a delayed-type hypersensitivity (DTH) reaction in brucella-sensitized guinea pigs. Surprisingly, the recombinant brucella L7/L12 protein expressed in Escherichia coli as a fusion protein with a six-histidine tag cannot elicit such a reaction. The six histidines tagged to the recombinant L7/L12 protein were removed enzymatically, but the resulting protein did not induce a DTH reaction in sensitized animals. Incubation of the recombinant L7/L12 fusion protein in a B. melitensis lysate endowed the recombinant protein with a DTH activity, suggesting that the recombinant protein was modified by this treatment. Glycosylation or phosphorylation of the recombinant L7/L12 protein could not be detected. On the other hand, radiolabeled palmitic acid was found to be incorporated to the recombinant protein during its incubation in the brucella lysate. This incorporation was specific for the brucella L7/L12 protein and was inhibited when the brucella lysate was frozen and thawed before the incubation. The data reported here indicate that posttranslational modification of L7/L12 protein comprising at least an acylation step is required for the brucella L7/L12 DTH activity.

Allergens↗
PubMed1996

Recombinant Brucella abortus proteins that induce proliferation and gamma-interferon secretion by CD4+ T cells from Brucella-vaccinated mice and delayed-type hypersensitivity in sensitized guinea pigs.

Optimal protective immunity to Brucella abortus infection is dependent on a coordinate interaction between different T-cell subsets which leads to an antigen-specific T-lymphocyte-mediated activation of macrophages, the main cellular reservoir for the bacterium. As an initial step in the identification of bacterial proteins that mediate cellular immunity, we have subcloned the B. Abortus ssb, uvrA, GroES, and GroEL genes into the prokaryotic expression vector pMAL-c2 using PCR. Escherichia coli DH5 alpha was transformed with the pMAL-ssb, pMAL-uvrA, pMAL-GroES, and pMAL-GroEL constructs separately, and gene expression was induced by isopropyl-beta-D-thiogalactopyranoside. The resulting fusion proteins were purified by affinity chromatography and confirmed by Western blot analysis using an anti-maltose-binding protein antibody. Furthermore, we have examined the pattern of T helper (Th) cell response from vaccinated BALB/c mice after in vitro stimulation with the recombinant (r) fusion proteins. In addition to T-cell proliferative responses, CD4+ T cells were tested for interleukin-2 (IL-2), IL-4, and gamma interferon (IFN-gamma) secretion. Primed CD4+ T cells proliferated to the rUvrA, rGroES, and rGroEL, but not to rSsb. The cytokine profile of the proliferating cells was characteristic of a Th1 type, as we detected IL-2 and IFN-gamma but not IL-4 in the T-cell culture supernatants. The recombinant B. abortus proteins were also screened in vivo to their ability to elicit DTH reaction in Brucella-sensitized guinea pigs. Moreover, the results of this study suggest that B. abortus rUvrA, rGroES, and rGroEL might be important sources of potentially protective molecules.

Animals↗
PubMed1996

The effects of hospital executives' personality traits on their perceptions and trust.

This field study examines the relationship between hospital executives' personality traits and both their perceptions of their subordinates' levels of skills and their level of trust in those subordinates. CEOs or senior executives of 37 acute care hospitals with at least 200 beds were surveyed. The high Nurturant manager did not perceive greater trust or skills than the low Nurturant manager. However, there was a significant and negative correlation between Person-Dominant managers and trust scores. Furthermore, the high Goal-Dominant managers varied significantly less than the low Goal-Dominant managers in their perceptions of their subordinates' skill. The study calls for a reexamination of the influence of personality traits on hospital executives' perceptions and trust. Power in the hands of certain managers may lead to the devaluation of the abilities and motivations of subordinates, and even the devaluation of their subordinates themselves.

Chief Executive Officers, Hospital↗
PubMed1995

Comparative evaluation of microagglutination test and serum agglutination test as supplementary diagnostic methods for brucellosis.

The diagnosis of brucellosis in cattle and small ruminants requires the use of more than one serological test. The complement fixation test (CFT), the rose bengal test (RBT), and the serum agglutination test (SAT) are among the most useful tests for routine diagnosis. The microagglutination test (MAT) was developed as a simpler and more efficient test than the SAT. The relative efficacy of this test compared with that of the SAT was evaluated by using brucella-free sheep and goats prior to and after vaccination treatment. The specificities of the MAT and the SAT were 100%. Of the ewes and goats with a vaccination history, one ewe, expectedly a negative responder, had reactions in the MAT, the complement fixation test, and the rose bengal test but not in the SAT, suggesting a lower sensitivity of the SAT in this case. The calculated sensitivities of the MAT and the SAT were 93.9%. The agreement between MAT and SAT results from nonresponders was examined by using sera from unvaccinated lambs and kids (95.2% agreement), unvaccinated ewes and goats (84.4%), and ewes and goats with a vaccination history (43.9%). For the latter group higher levels of agglutination units were observed by the MAT than by the SAT in 51.5% of the samples. In testing sera from positive reactors after vaccination neither method was superior (MAT values were greater than SAT values for 23.5% of the samples, and MAT values were less than SAT values for 21.9% of the samples). Comparison of the methods on the individual sample level revealed a significant correlation between the MAT and the SAT (r = 0.96 +/- 0.005; P < 0.001). Since the MAT is simpler to perform than the SAT and can potentially be automated, the inclusion of the MAT as a supplementary test in brucellosis control programs is recommended.

Agglutination Tests↗
PubMed1994

Identification and nucleotide sequence of Brucella melitensis L7/L12 ribosomal protein.

DNA sequencing of the gene encoding a Brucella melitensis 12-kDa protein revealed that this protein was the ribosomal protein L7/L12. The B. melitensis L7/L12 DNA sequence was identical to that of the corresponding B. abortus gene, showing the near identity of these two organisms. When comparing the sequence of this protein to that of other organisms some domains were highly conserved, especially the C-terminus, which contrasted with the lack of conservation of the sequences at the N-terminus. The finding that the ribosomal protein L7/L12 of Brucella is an immunodominant antigen provides a new rationale to explain the activity of ribosomal vaccines.

Amino Acid Sequence↗
PubMed1994

Brucella ribosomal protein L7/L12 is a major component in the antigenicity of brucellin INRA for delayed-type hypersensitivity in brucella-sensitized guinea pigs.

A delayed-type hypersensitivity (DTH) reaction in the course of brucellosis in humans and animals can be revealed by the brucellin INRA (Brucellergen) skin test. Brucellergen is composed of more than 20 proteins of different molecular weights. A 12-kDa protein eliciting DTH in Brucella melitensis Rev1-sensitized guinea pigs was found to be a significant component for the allergenic properties of Brucellergen. Sequencing of the gene encoding this protein identified it as the L7/L12 ribosomal protein. The L7/L12 gene of B. melitensis was amplified by PCR and subcloned in the Escherichia coli pQE30 plasmid. The resulting recombinant protein did not produce a DTH reaction in sensitized animals. It was used to raise specific antibodies in a rabbit. Affinity chromatography with these antibodies was used to isolate a single protein from Brucellergen and from B. melitensis cytosol preparations which produced a DTH reaction in guinea pigs sensitized with B. melitensis Rev1. N-terminal amino acid sequencing of the protein confirmed that it was the L7/L12 ribosomal protein. This is the first complete report on the involvement of a defined bacterial ribosomal protein in the DTH response of animals infected with intracellularly multiplying bacteria.

Allergens↗
PubMed1994

Situational determinants of the delegation of authority among hospital senior executive officers.

This field study examined the relationship between hospital senior managers' delegation and task importance, the senior managers' trust in their subordinates, and their perception of subordinates' levels of skills. The responses of 32 hospital CEOs or senior executives were compared with the responses of their three most important subordinate managers (for a total of 96 subordinates). Trust scores were uniformly high with little variation, and most of the tasks studied were delegated frequently or occasionally. Although delegation was positively related to the managers' perception of their subordinates' skills, it was not related to the importance of the tasks. These findings confirmed the importance of situational factors in delegation and raised serious questions about senior managers' maximization of the scarce and costly resource that their management staff represent.

Data Collection↗
PubMed1990

Isolation, identification, and characterization in Israel of Brucella melitensis biovar 1 atypical strains susceptible to dyes and penicillin, indicating the evolution of a new variant.

During characterization by conventional biotyping tests of numerous Brucella melitensis isolates obtained in Israel in the last 2 years, we identified several strains of the biovar 1 serotype that are atypically susceptible to dyes and penicillin. Their coisolation from two brothers in a family that rears sheep and from the milk of one of their sheep and the prevalence of such strains in two distinct geographical zones in Israel provide epidemiological support for the notion that a new variant has been identified.

Animals↗
PubMed1985

Streptococcus faecalis R plasmid pJH1 contains a pAM alpha 1 delta 1-like replicon.

Streptococcus faecalis R plasmid pJH1 did not transform competent strains of Streptococcus sanguis. A hybrid plasmid, pDL310, consisting of virtually all of the S. faecalis hemolysin-bacteriocin plasmid pJH2 and a segment of pJH1 DNA that included the tetracycline resistance determinant, yielded tetracycline-resistant transformants at a frequency of less than 10(-8) transformants per CFU, when it was added to a competent culture of S. sanguis Wicky. Four of the transformants contained a 4.7-kilobase plasmid (pDL316) that transformed strain Wicky at a frequency of 8.6 X 10(-8). Restriction endonuclease digests, agarose gel electrophoresis, and Southern blot hybridizations indicated that pDL316 consisted entirely of pJH1-derived DNA. Additional restriction studies, Southern blot hybridizations, and heteroduplex analyses indicated that pDL316 was very closely related to 4.6-kilobase tetracycline resistance plasmid pAM alpha 1 delta 1, a derivative of 9.0-kilobase S. faecalis plasmid pAM alpha 1.

Bacteriocins↗
PubMed1984

Streptococcus faecalis R plasmid pJH1 contains an erythromycin resistance transposon (Tn3871) similar to transposon Tn917.

The R plasmid pJH1 contains a 5.1-kilobase transposon ( Tn3871 ) that mediates inducible resistance to erythromycin. Three AvaI digestion fragments from this transposon are identical in size to and homologous with three AvaI-derived fragments from the previously described erythromycin resistance transposon Tn917 . These three DNA fragments account for greater than 90% of both transposons.

Base Sequence↗
PubMed1983

Genetic, molecular, and functional analysis of Streptococcus faecalis R plasmid pJH1.

Streptococcus faecalis JH1 contains two conjugative plasmids, pJH1, an R plasmid that codes for resistance to kanamycin, streptomycin, erythromycin, and tetracycline, and pJH2, a hemolysin-bacteriocin plasmid. Strain JH1 was used as an antibiotic resistance donor in conjugation experiments with two plasmid-free S. faecalis recipient strains, JH2-2 and OG1-RF1. Plasmid pJH1 was purified from one transconjugant, DL77, and subjected to restriction endonuclease analyses. Five restriction enzymes, EcoRI, XbaI, BamHI, SalI, and XhoI, yielding 10, 9, 3, 2, and 2 fragments, respectively, were used to determine the size (80.7 kilobases) of pJH1 and to construct a restriction endonuclease map of the plasmid. Twenty-eight percent of the antibiotic-resistant transconjugants examined expressed only part of the resistance pattern (Kmr Smr Emr Tcr) associated with pJH1, that is, they were resistant to kanamycin, streptomycin, and erythromycin; to erythromycin and tetracycline; or to erythromycin or to tetracycline only. Most of these strains also produced hemolysin and bacteriocin, and several contained a hybrid plasmid consisting of pJH2 and specific segments of pJH1 DNA. Several of these hybrid plasmids, as well as a deletion derivative of pJH1 that coded for resistance to tetracycline but not to kanamycin, streptomycin, or erythromycin, were purified and used to confirm the arrangement of restriction endonuclease fragments on the pJH1 map and to locate the resistance determinants on this map.

DNA Restriction Enzymes↗
PubMed1982

Effects of ionophores and dicyclohexylcarbodiimide on Mycoplasma gallisepticum adherence to erythrocytes.

To test the influence of the electrochemical ion gradient across mycoplasma membranes on the capacity of organisms to adhere to host cells, Mycoplasma gallisepticum cells were treated with valinomycin, carbonylcyanide m-chlorophenylhydrazone, and N,N'-dicyclohexylcarbodiimide (DCCD) singly or in combination. Uptake of [3H]tetraphenylphosphonium by the treated cells was employed as a measure of the effects of the ionophores on membrane potential. In the absence of K+, valinomycin increased, whereas carbonylcyanide m-chlorophenylhydrazone, and DCCD decreased [3H]tetraphenylphosphonium uptake. However, with a high level of K+ or with DCCD, uptake of [3H]tetraphenylphosphonium in the presence of valinomycin decreased below control levels, indicating that, generally, the ionophores affected membrane potential in the expected manner. The treated organisms were tested for their capacity to attach to glutaraldehyde-fixed human erythrocytes. DCCD was the best inhibitor of mycoplasma attachment, and in combination with valinomycin attachment, capacity decreased by about 40%. The combination of valinomycin plus carbonylcyanide m-chlorophenylhydrazone was less effective; it decreased attachment by about 15 to 25%. It was concluded that the dissipation of ion gradients across cell membranes decreases only partially mycoplasma adherence, in line with previous findings that isolated mycoplasma membranes retain the major part of the attachment capacity of intact cells.

Adhesiveness↗
PubMed1981

Adhesion of mycoplasmas to eukaryotic cells.

Many pathogenic mycoplasmas are surface parasites, adhering to the epithelial linings of the respiratory and urogenital tracts. Since mycoplasmas lack cell walls their plasma membrane comes in close contact with that of their host, allowing exchange of components between the two membranes and possibly fusion. The tight association of the parasite with its host is illustrated in scanning electron micrographs of Mycoplasma pneumoniae and M. gallisepticum adhering to human red blood cells. Specialized structure at the tips of the mycoplasma cells appear to function as attachment organelles. Our main aim has been to chemically define the receptors on the host cell and the binding sites on the mycoplasma cells responsible for adhesion. Glycophorin (the major sialoglycoprotein of human red blood cells) serves as the main or sole receptor for M. gallisepticum whereas M. pneumoniae binds to additional receptors on human red blood cells. Trypsin treatment of M. pneumoniae cells abolishes their ability to attach to human red cells, suggesting the protein nature of the binding sites. M. pneumoniae membranes solubilized by detergents were subjected to affinity chromatography on glycophorin-Sepharose so that membrane components with high affinity for glycophorin could be isolated. The fraction isolated consisted of several proteins (relative molecular mass 25 000 and 45 000). The binding of this fraction to red cells was relatively low but appeared to be specific, as it was inhibited by glycophorin but not by its hydrophobic moiety. The possibility is discussed that the exposure of the binding sites on the mycoplasma cell surface is influenced by the electrochemical ion gradient across the membrane.

Adhesiveness↗
PubMed1981

Attachment of killed Mycoplasma gallisepticum cells and membranes to erythrocytes.

To correlate viability with attachment capacity, Mycoplasma gallisepticum cell harvested at different growth phases and treated by various agents were tested for their capacity to attach to human erythrocytes. The results show that viability per se is not essential for M. gallisepticum attachment to erythrocytes, as cells killed by ultraviolet irradiation anmd membranes isolated by lysing M. gallisepticum cells by various means retained attachment capacity. However, treatment of the mycoplasmas by protein-denaturing agents, such as heart, glutaraldehyde, or prolonged exposure to low pH, drastically affected or even abolished attachment, supporting the protein nature of the mycoplasma membrane components responsible for specific binding to the sialoglycoprotein receptors on the erythrocytes.

Adhesiveness↗