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Biomedical subjects

S K Ghosh

Publications and source records attributed to S K Ghosh.

At least 163 records · Page 9Linked to original sources
PubMed1986

Purification of the constituent enzyme fractions of mycobacillin synthetase.

The final purification of the three-fraction enzyme complex mycobacillin synthetase was done by hydroxyapatite column chromatography and sucrose-density-gradient centrifugation; each of the fractions obtained migrates as a single component in SDS/polyacrylamide-gel electrophoresis and gel electrofocusing. The Mr of the enzyme fractions A, B and C by gel filtration is 260 000, 190 000 and 105 000, and that by SDS/polyacrylamide-gel electrophoresis is 252 000, 198 000 and 108 000 respectively. None of the enzyme fractions appears to possess subunit structure.

Centrifugation, Density Gradient↗
PubMed1986

Cloning and expression in Escherichia coli of a recA-like gene from Vibrio cholerae.

A library containing more than 80% of the Vibrio cholerae genome was constructed by cloning BamH1 restriction fragments into pBR322. Using interspecific complementation of an Escherichia coli recA mutant with plasmids containing the gene bank of V. cholerae, a recA-like gene was identified. The recombinant plasmid, designated as pDP145, contained a 1.45 kb segment of V. cholerae DNA which codes for a protein of molecular weight 39,000. The product of this gene confers methyl methane sulphonate resistance on the E. coli recA mutant, suppresses its ultraviolet (UV) light sensitive phenotype and has proteolytic activity on the phage lambda repressor. Induction of a 39,000 dalton protein in UV-irradiated V. cholerae cells was demonstrated.

Bacteriophage lambda↗
PubMed1986

Occupational health problems among workers handling Virginia tobacco.

The prevalence of "green symptoms" among 289 tobacco workers handling Virginia tobacco leaves was investigated. The frequency of these symptoms was high (53.29%). Urinary excretion rate of nicotine and cotinine increased significantly only among the subjects suffering from "green symptoms".

Agricultural Workers' Diseases↗
PubMed1986

Thomas-Fermi theory for atomic systems.

The classical Thomas-Fermi theory of the electrons in an atom is amended in a manner that produces continuity of the electron density rho. This is done by imposing the constraint that e(-2kr) [unk](2) rho dr should be finite, with k determined by the nuclear cusp condition, followed or preceded by an optimum coordinate scaling. Electron densities and total energies are shown to be vastly improved.

Journal Article↗
PubMed1986

A simple low-resistance flap valve for pulmonary ventilation studies.

Details of a simple low-resistance flap valve for pulmonary ventilation studies are presented. It has a space of 11 ml, weighs 28 g and is constructed from 3 mm thick perspex sheet. The opening pressure for both the inlet and the outlet is zero as its flaps normally remain open. The resistance of the valve to a flow of air at a rate of 20 l min-1 is 2.2 mm of water at the inlet and 4.2 mm of water at the outlet. At a rate of flow of 100 l min-1 the corresponding figures are 8.9 and 24.6 mm of water. All these values compare favourably with those obtained from three commercially available units. The valve has been in use over the past four years and the patient compliance has been found to be excellent.

Aerosols↗
PubMed1986

Membrane-associated glycoprotein (gp 160) identified on human lung tumors by a monoclonal antibody.

A monoclonal antibody (5E8) has been used to identify and structurally characterize a previously unreported macromolecule present on the surface of human lung tumors. This antibody was derived from a hybrid clone that was produced using spleen cells of mice immunized with a surgically excised squamous cell carcinoma. Using immunofluorescence, the 5E8 antibody was observed to stain many different human lung tumor cell lines and surgically excised human lung tumors including squamous cell carcinomas, adenocarcinomas, alveolar carcinomas, and a portion of the large cell tumors tested. With few exceptions, notably the basal layer of the skin, little or no detectable staining of 5E8 to normal human tissues (lung, brain, kidney, heart, stomach, breast, erythrocytes, or lymphocytes) was observed. The 5E8 antibody was used to immunoprecipitate detergent lysates of biosynthetically labeled or surface radioiodinated lung tumors. Analysis of the immunoprecipitates by sodium dodecyl sulfate gel electrophoresis revealed a major band and a faster migrating second minor band. The molecular weights of these two proteins were estimated to be 160,000 and 120,000, respectively. The addition of a reducing agent to the gels did not alter the migration pattern of the immunoprecipitated macromolecules. The removal of a terminal carbohydrate, sialic acid, did not restrict the binding of 5E8 to the tumor-associated antigen. However, labeling studies using galactose oxidase and tritiated borohydride revealed the presence of galactose on the immunoprecipitated protein. This major Mr 160,000 glycoprotein that was identified on two different human lung tumor cell lines was also found on a human large cell tumor tissue obtained by surgical biopsy. The 5E8 antibody and the Mr 160,000 glycoprotein that it recognizes represent two very useful components with which to test several new antibody-mediated drug delivery systems in the treatment of human lung tumors. The tumor-associated glycoprotein also represents a potential analyte for a diagnostic or prognostic immunoassay for lung cancer.

Antibodies, Monoclonal↗
PubMed1985

Functional characterization of constituent enzyme fractions of mycobacillin synthetase.

The enzyme fraction A, a constituent enzyme of the three-fraction enzyme mycobacillin synthetase, independently and sequentially activated five amino acids starting from L-proline, producing the pentapeptide Pro(Asp1,Glu1,Tyr1)Asp. The fractions B and C were unable to function independently. However, the fraction B synthesized the nonapeptide Pro(Asp3,Glu1,Tyr2,Ser1)Leu, sequentially activating the pentapeptide and next four amino acids, whereas the fraction C synthesized mycobacillin by the sequential activation of the nonapeptide and the remaining four amino acids. The pH optima of the above enzymes are almost identical (pH 7.8), but their Km values are a little different.

Adenosine Triphosphate↗
PubMed1985

Translocation of mycobacillin synthetase in Bacillus subtilis.

The extracellular release of mycobacillin from Bacillus subtilis first occurred in the medium at the onset of stationary phase and continued at a high rate even after 6 days. Mycobacillin synthetase activity appeared earlier than late-exponential phase in the cytosol of producer cells and was not sedimentable even at 105 000 g. The activity then quickly reached the maximum late in the stationary phase. With further increase in the age of the culture, the activity gradually disappeared from the cytosol, to reappear concomitantly in the membrane in an insoluble particulate form, even in absence of protein synthesis. The membrane-bound synthetase activity was sedimentable at 10 000 g and was fairly active even after 5 days.

Bacillus subtilis↗
PubMed1985

Accumulation of peptides by mycobacillin-negative mutants of Bacillus subtilis B3.

Thirteen mycobacillin-negative (My-) mutants of Bacillus subtilis B3 were isolated from an auxotrophically tagged mycobacillin producer organism. The wild-type producer, three feeble producers and three strictly My- mutants did not accumulate any ninhydrin-positive peptide in the culture medium while the remaining seven My- mutants did accumulate ten such peptides whose amino acid composition indicated that there might be only three different peptides. The N-terminal and C-terminal amino acid residues implicated one of these peptides as a pentapeptide intermediate in mycobacillin synthesis; this was further confirmed by its molecular weight and sequence. Studies on cell-free synthesis showed that only the enzyme system from the wild-type strain synthesized mycobacillin while the defective ones from all the My- mutants synthesized one and the same pentapeptide as found in the culture broth of some of the mutants. Further studies in which the enzymes responsible for mycobacillin synthesis by cell-free extracts were separated into three fractions, A, B and C, showed that seven of the mutants were defective in fraction B whereas the three other mutants had defects in both fractions B and C. Thus the pentapeptide Pro----Asp----Glu----Tyr----Asp appears to be implicated in mycobacillin biosynthesis.

Amino Acid Sequence↗
PubMed1985

Tissue typing in brucellosis.

The index case in this report was clinically, epidemiologically, and serologically proved to be suffering from acute brucellosis acquired in Britain and complicated by acute intractable reactive arthritis. HLA tissue typing was A1, A2, B7, and B27. As there is no information available about HLA typing in brucellosis in Britain, we examined further cases of human brucellosis retrospectively. Three further patients possessing B27 antigen were identified, only one of whom had had reactive arthritis. Eight of the 12 cases studied also carried A2, which is thus shown not to be protective against the development of brucellosis as had been suggested previously.

Adult↗
PubMed1984

A simple radioaerosol generator and delivery system for pulmonary ventilation studies.

Details of a simple radioaerosol generator and delivery system are presented. Aerosol streams of 99mTc-DTPA solution of different distributions were produced. The most useful distribution had an activity median aerodynamic diameter (AMAD) of 0.9 micron with a geometric standard deviation of 1.5. This distribution also had more than 96% of aerosol particles with aerodynamic diameter less than 2 micron. The system has been used for patient lung ventilation studies. The aerosol breathing-in period to achieve a satisfactory count rate was 1.8 +/- 0.38 min. The radioaerosol images were excellent and comparable to those obtained with 81mKr gas.

Aerosols↗
PubMed1984

Standardization of parameters for the mycobacillin synthetase activity.

An effective method of preparation involving sonication was developed for cell-free mycobacillin synthetase from Bacillus subtilis. The enzyme showed optimum activity at a buffer concentration of 50 mM (Tris-HCl) and pH 7.5. ATP and Mg2+ which were essential for synthesis showed an optimum requirement at a ratio of 1:1. The synthetase was markedly inhibited by ADP whereas AMP was without any effect. ATP or ATP-generating system could not be replaced by GTP, UTP or CTP. Co2+ and Mn2+ could to some extent substitute Mg2+. Mercapto reagents inhibited the antibiotic synthesis. Exogenous addition of pantothenic acid had no effect.

Bacillus subtilis↗
PubMed1984

Transcription of ground-state density-functional theory into a local thermodynamics.

The concepts of local temperature, local entropy, and local free energy density are introduced within the framework of the ground-state density-functional theory of many-electron systems, and a complete local thermodynamic picture is then developed. A view emerges of the electron cloud, as analogous to a classical inhomogeneous fluid moving under gradients of temperature, pressure, and an effective potential, described by a locally Maxwellian distribution.

Kinetics↗