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Biomedical subjects

M Barak

Publications and source records attributed to M Barak.

63 records · Page 4Linked to original sources
PubMed1984

Elucidation of the phagocytosis mechanism with the aid of luminous bacteria.

Phagocytosis of the luminous bacterium Vibrio cholerae var. albensis caused a similar decrease both in viable count and in the in-vivo luminescence. These effects of polymorphonuclear neutrophil leukocytes (PMN) were oxygen-dependent processes. Exposure of PMN to oxygen caused a prompt decrease in the luminescence of bacteria that had been ingested in anaerobic conditions. Cell-free supernates from active PMN suspensions caused a decrease in luminescence and as much as 10% of the killing could be attributed to extracellular killing. Similarly, bacteria entrapped on a membrane filter showed a decrease in luminescence upon addition of active PMN, even though they could not be ingested.

Aerobiosis↗
PubMed1983

The use of luminous bacteria for determination of phagocytosis.

The existing methods for phagocytosis evaluation are inadequate for assessing all the real events occurring during phagocytosis, or for continuously following the kinetics of the process. Our purpose is to establish the use of luminous bacteria as an object for phagocytosis. The bioluminescence test offers an easy and simple method to determine the kinetics of phagocytosis by following the luminescence of the bacteria. The terrestrial luminous bacteria Vibrio cholerae var. albensis are readily phagocytosed by polymorphonuclear (PMN) cells. The correlation coefficient between the decrease in luminescence and the decrease in viable count is 0.999. The rate of decrease in luminescence and the residual level of luminescence after 60 min of phagocytosis are proportional to the rate of increase in phagocytosis induced chemiluminescence, and to its maximal level, respectively. Opsonization requirements are comparable in both tests. Different inhibitors of the phagocytosis process caused similar changes in the rates of the bio- and chemiluminescence (correlation coefficient 0.974), and in the luminescence maximal level (correlation coefficient 0.804). The validity of the bioluminescence assay being proved, it is suggested as an alternative assay for phagocytosis assessment.

Azides↗
PubMed1983

Phagocytosis-induced mutagenesis in bacteria.

Dark mutants of the luminous bacteria Photobacterium fischeri reverted to hereditary stable luminescent forms when incubated with human polymorphonuclear neutrophils (PMN). The maximal mutagenic effect occurred during the first 15 min of phagocytosis, and was dependent on the phagocyte:bacterium ratio as well as on the integrity of the PMN cells. Heat-killed phagocytes or disintegrated phagocytes did not show any mutagenic activity, whereas the supernatant of the phagocytosis reaction exerted mutagenic activity. Scavengers of hydroxyl radical such as mannitol or benzoate and scavengers of singlet oxygen such as beta-carotene, as well as the presence of superoxide dismutase, prevented the mutations. The role of reactive oxygen metabolites in the phagocyte-mediated mutagenic process is discussed.

Anaerobiosis↗
PubMed1983

Determination of serum bactericidal activity with the aid of luminous bacteria.

Nonmarine luminous bacteria belonging to the genus Vibrio cholerae were extremely sensitive to the bactericidal activity of human serum. Luminous bacteria incubated in a medium containing serum showed a decrease in their in vivo luminescence that was directly proportional to the decrease in the viable count and was a function of the serum concentration. Both immunoglobulins and the complement system were required to exert the serum bactericidal activity. Serum lacking immunoglobulins or certain complement components, especially C3, did not affect the luminescence. The bactericidal effect of the serum on luminous bacteria was diminished by the presence of lipopolysaccharide or by pretreatment of the serum with different species of killed bacteria. As found in other systems, the bacteriolytic activity of serum was only augmented by lysozyme, but was not lysozyme dependent; although the luminous bacteria were converted into spheroplasts in serum containing 0.5 M sucrose, their in vivo luminescence was almost not affected. This system could easily distinguish between the C classical pathway and the properdin pathway. Ethylene glycol-bis (beta-aminoethyl ether)-N,N'-tetraacetic acid, which inhibits only the classical complement pathway, did not inhibit the decrease in luminescence as did EDTA. Thus, it was possible to distinguish between deficiencies in complement components participating in both pathways and complement components that were involved only in the classical pathway. This system could also be used as a substitute to the hemolytic system in complement fixation tests.

Animals↗
PubMedDate not supplied

Detection of genotoxicity of metallic compounds by the bacterial bioluminescence test.

Twenty metallic compounds were assayed for their genotoxic mutagenic activity by the bioluminescence test restoration of the luminescence of dark mutant of the luminous bacterium Photobacterium fischeri). The activity of the metals was tested in a liquid medium as well as on a solid medium. K2Cr2O7, MnCl2, BeCl2, KH2AsO4, ZnCl2 and Na2WO4 showed strong activity in liquid medium while AgNO3, Cd(OOCCH3)2, CoCl2, CuCl2, HgCl2, Na2SeO3 and Pb(NO3)2 were more active in the solid medium test. BaCl2, Na2MoO4, NaAsO2, NiSO4, Na2SeO4, RbCl, and SnCl2 were not active in the bioluminescence test. The correlation between the genotoxic activity of the tested metallic compounds in the bioluminescence test and other bacterial tests for genotoxic agents as well as the correlation between these results and the carcinogenicity of these compounds is discussed.

Luminescent Measurements↗
PubMedDate not supplied

Doppler echocardiographic study of the pulmonary artery and its branches in 114 normal neonates.

It has been shown that there are pressure gradients between the main pulmonary artery (MPA) and its two branches in infants undergoing catheterization. This study investigated the blood flow velocities and pressure gradients in the right and left pulmonary arteries (RPA and LPA, respectively) in normal neonates. The MPA and its two branches were examined echocardigraphically in 114 term consecutive healthy neonates aged 1-6 days. The pressure gradients between the MPA and RPA or LPA were calculated. Thirty neonates with pressure gradients above 2.5 mmHg were followed by 3-6 months. The peak velocities in the RPA and LPA (1.16 +/- 0.19 and 1.01 +/- 0.18 m/s) were significantly higher than that in the MPA (0.84 +/- 13 m/s) (both p < 0.001), with that in the RPA slightly higher than in the LPA (p < 0.001). There was an estimated pressure gradient of 2.5-8.3 mmHg between the MPA and RPA in 43% and of 2.5-6.6 mmHg between the MPA and LPA in 16.7% of all neonates. The gradients disappeared within 3-6 months in 12 (40%) of the 30 neonates with an initial gradient above 2.5 mmHg. The differences in blood flow velocities or pressure gradients in the RPA or LPA were probably attributable to the variations in pulmonary arterial pressure, cardiac output, age, and birth weight and can be considered physiologically characteristic in neonates.

Blood Flow Velocity↗
PubMedDate not supplied

The use of a seminal vesicle specific protein (MHS-5 antigen) for diagnosis of agenesis of vas deferens and seminal vesicles in azoospermic men.

Azoospermia is the cause of infertility in 8% of infertile male patients. Ten percent of those patients suffer from agenesis of the seminal vesicle (SV) and vas deferens (VD) agenesis. Currently, the diagnosis of SV and VD agenesis is based on low semen volume, low pH, and low fructose content of the seminal fluid of azoospermic men who have normal serum gonadotropins. In this study, an SV-specific sperm-coating antigen, the MHS-5 antigen, was used as a marker for the presence of SVs. The SV-specific protein (SVSP), MHS-5, was present in the control group but was not found in any of the seven samples from azoospermic men with proven agenesis of SV and VD. Another semen component, the prostate-specific antigen (PSA), whose presence in the semen is not influenced by the SV and VD agenesis, was found in both the study and the control groups. Its presence ruled out the possibility of azoospermia due to ejaculatory duct obstruction. The absence of MHS-5 antigen in seminal fluid can be used as a tool for a reliable diagnosis of agenesis of SV and VD in azoospermic men.

Biomarkers↗