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Biomedical subjects

J B Ward

Publications and source records attributed to J B Ward.

At least 73 records · Page 4Linked to original sources
PubMed1984

Sperm count, morphology and fluorescent body frequency in autopsy service workers exposed to formaldehyde.

A battery of monitoring tests that could indicate genetic damage was used to investigate occupational formaldehyde exposure in a population of a hospital autopsy service workers. 11 exposed individuals and 11 matched controls were evaluated for sperm count, abnormal sperm morphology and 2F-body frequency. Subjects were matched for sex, age and customary use of alcohol, tobacco and marijuana. Additional information was collected on health, medications and other exposures to toxins. 10 subjects were employed for 4.3 months (range 1-11 months) prior to the first sample and 1 was employed for several years. Formaldehyde exposures were episodic but with a time weighed average between 0.61 and 1.32 ppm (weekly exposure range 3-40 ppm X h). Exposed and control subjects were sampled 3 times at 2-3 month intervals. Sperm morphology was also evaluated in B6C3F1 mice after 5 daily oral doses of 100 mg/kg formalin. No increase in abnormal morphology was detected in the treated animals. In humans, no statistically significant differences were observed between the exposed and control groups for the observed variables. Reduced sperm count correlated with increased abnormal morphology and 2F-body frequency in the exposed group but not in the control group. Evaluation of the impact of incidental exposures suggests a reduced count with marijuana use and increased abnormal morphology with medications used by controls. No effects on sperm were seen from formaldehyde or its metabolites in this population after occupational exposure, nor in mice following a high acute exposure. It is possible that minor effects might have occurred. The lack of an effect in this study may be due to a lack of statistical power to detect effects at this exposure level.

Air Pollutants, Occupational↗
PubMed1984

Purification and properties of autolytic endo-beta-N-acetylglucosaminidase and the N-acetylmuramyl-L-alanine amidase from Bacillus subtilis strain 168.

beta-N-Acetylglucosaminidase has been purified from the walls of Bacillus subtilis 168 and compared with the other known autolysin, N-acetylmuramyl-L-alanine amidase (amidase). The beta-N-acetylglucosaminidase was a dimer in LiCl buffers with a sub-unit molecular weight of 90000 and a pH optimum of about 5.0. It was very sensitive to proteolytic enzymes and was critically activated by 0.1 to 0.2 M-LiCl. It was insoluble in concentrations of LiCl lower than 0.05 to 0.1 M. It was less strongly bound to walls than was the amidase, which was a monomer of molecular weight 30000 to 40000 in LiCl buffers. The beta-N-acetylglucosaminidase is an endo-enzyme and showed no exo-activity. Lysozyme-like enzyme (muramidase) activity was undetectable in the wall extracts examined.

Acetylglucosaminidase↗
PubMed1983

The identification and characterization of a urinary mutagen resulting from cigarette smoke.

The urine of a cigarette smoker who excretes exceptionally mutagenic urine was analyzed for several factors affecting mutagenicity. S. typhimurium strain TA98 was always more sensitive to XAD-2 urine concentrates than TA100. With TA98, as high as 85 revertants per ml of urine were produced. It was observed that incubation with beta-glucuronidase was not required for expression of mutagenicity but that a complete S9 mix was needed to convert the material in the concentrate to the ultimate mutagenic species. TLC and HPLC separation of the XAD-2 urine concentrate resulted in the identification of trace amounts of the bladder carcinogen, 2-aminonaphthalene (beta-naphthylamine) and a considerable amount of a possible metabolite of 2-aminonaphthalene, 2-amino-7-naphthol. The identity of the compounds was confirmed by mass spectral analysis, and 2-amino-7-naphthol was shown to be a mutagen for TA100 and TA98 when activated by rat-liver S9.

Animals↗
PubMed1983

Combined phakomatoses: a case report of Sturge-Weber and Wyburn-Mason syndrome occurring in the same individual.

A patient exhibiting ocular and systemic manifestations of both Sturge-Weber and Wyburn-Mason syndrome is described. The ocular, dermatologic, and neurological findings are detailed. The simultaneous occurrence of more than one phakomatosis is rare, but several combinations have been described in the literature. This appears to be the first report of this particular combination of phakomatoses.

Adolescent↗
PubMed1983

Chromatography and isolation of the Kav 1.0 pheromone of female Nippostrongylus brasiliensis (Nematoda).

The Kav 1.0 pheromone from incubation of mouse-adapted females of Nippostrongylus brasiliensis was soluble in organic solvents, as shown by bioassay of males and presence of a peak at Kav 1.0 during gel filtration. Recovery of the biological activity from the females was enhanced when the Kav 1.0 component was purified by organic extraction-gel filtration, C-18 cartridge separation with 50% methanol, C-18 cartridge-gel filtration, and C-18 cartridge-TLC. The activity recovered from organic extraction, TLC, or gel filtration of solutions in which females had been incubated was less than the above combined techniques. Reverse-phase cartridges retained activity of 20,000 female-hr of incubation without loss and enabled storage of the pheromone component for 3 days at 4 C. The HPLC separation of incubate from females revealed an active peak(s) with a 4- to 5-min retention time. This peak(s) was present also in regions containing activity from other purification procedures.

Animals↗
PubMed1983

Occupational exposure to formaldehyde in a medical center autopsy service.

The formaldehyde exposures occurring in the autopsy service of a medical complex were evaluated as part of a study to detect genetically harmful effects of chemical exposures. Determination of time-weighted average (TWA) exposures and characterization of the patterns of exposure experienced by individuals with different work responsibilities in this occupational setting were sought. Both general area and breathing zone samples were evaluated. Estimated weekly time-weighted average exposures for pathologists, residents and technicians were determined to be between 0.61 and 1.32 parts per million with little difference between work roles. While the averages were similar, the patterns of exposure of technicians and physicians were different. Technicians were exposed to a baseline level of formaldehyde for a prolonged period of time. In contrast, physicians were exposed for shorter times but experienced higher levels during specific tasks, particularly tissue-sectioning and examination. Evaluations of work procedures and environmental conditions in autopsy services are recommended to reduce personnel exposure to formaldehyde vapor.

Academic Medical Centers↗
PubMed1982

Experimental design and statistical analysis considerations for in vitro mammalian cell transformation assays with BALB/3T3 cells.

Many mammalian cell assays testing for mutagenic activity have common features which cause statistical estimation and analysis problems. Such assays measure the number of cell alterations occurring in a plate containing an unknown number of cells at risk. The number of cells at risk can be estimated from a parallel cytotoxicity study. While the Poisson distribution has been assumed to apply to standardized frequencies, this is questioned. The failure of standardized frequencies to follow a Poisson distribution is attributed to the relatively small and dosage-dependent number of susceptible cells per plate. A minimum number of such cells per plate or random cluster of plates has been determined for each dose so that the measured variable approximates a Poisson distribution. A transformation is suggested to achieve reasonable normality and variance equality, thereby allowing the use of parametric analysis of variance and regression methods and an estimation of required sample size.

Animals↗
PubMed1982

Benzylpenicillin-induced filament formation of Clostridium perfringens.

Growth of Clostridium perfringens with low concentrations of benzylpenicillin inhibited septum formation and division of the organisms. This resulted in continued growth of the organisms as aseptate filaments. The effect was reversed on removal of the antibiotic. The composition of walls isolated from organisms grown with the antibiotic was similar to that of walls from untreated bacteria. In addition, both contained non-N-acetylated glucosamine residues in their peptidoglycan. No differences were detected in the degree of cross-linkage of peptidoglycan. Clostridium perfringens contains six membrane-associated penicillin-binding proteins (PBPs) which have different affinities for [3H]benzylpenicillin. Concentrations of the antibiotic which were sufficient to cause filamentation of apparently all organisms in a culture caused almost complete saturation of PBPs 3, 4, 5 and 6. At these concentrations there was no measurable interaction with PBPs 1 and 2. Thus interaction of the antibiotic with the lower molecular weight PBPs is correlated with the inhibition of septum formation in C. perfringens.

Bacterial Proteins↗
PubMed1982

Purification and characterization of two phage PBSX-induced lytic enzymes of Bacillus subtilis 168: an N-acetylmuramoyl-L-alanine amidase and an N-acetylmuramidase.

After heat-induction of the defective phage PBSX in a xhi-1479 mutant of Bacillus subtilis 168, the culture lysed rapidly even if the lyt-2 mutation was present (which greatly reduces the amount of the bacterial autolysins). Two lytic enzymes, an N-acetylmuramoyl-L-alanine amidase and an endo-N-acetylmuramidase, were purified from the culture supernatant. The amidase was readily distinguished from the bacterial amidase by its low molecular weight. In addition, it was not inhibited by antibody directed against the bacterial enzyme. These results indicate that PBSX does not rely on the bacterial autolysins to accomplish lysis.

Amidohydrolases↗
PubMed1982

The biosynthesis and linkage of teichuronic acid to peptidoglycan in Bacillus licheniformis.

Membrane and wall-membrane preparations of Bacillus licheniformis 94 will, if supplied with the appropriate precursors, synthesize teichuronic acid and link it to peptidoglycan although teichuronic acid is absent from walls of this organism. B. licheniformis 94 lacks phosphoglucomutase activity and therefore cannot synthesize the precursor UDPglucuronic acid. The initial reaction of teichuronic acid biosynthesis is catalysed by a translocase and results in the formation of polyprenyl-diphospho-N-acetylgalactosamine and the release of UMP. This reaction is not inhibited by tunicamycin. The disaccharide repeating unit of the polymer is then formed by the transfer of glucuronic acid from UDPglucuronic acid with the release of UDP. Polymerization of the repeating units occurs by incorporation of new units at the reducing terminus of the growing teichuronic acid chain and the release of polyprenyl diphosphate. The subsequent dephosphorylation of the lipid diphosphate for reuse in the biosynthesis cycle is inhibited by bacitracin. Linkage to peptidoglycan occurs by the formation of a phosphodiester bond between the reducing N-acetylgalactosamine terminus of the teichuronic acid chain and a 6-hydroxyl group of a muramic acid residue in the glycan of peptidoglycan. Wall-membrane preparations synthesizing teichuronic acid, poly(glycerol phosphate) teichoic acid and peptidoglycan link the teichuronic and teichoic acids to different glycan chains.

Anti-Bacterial Agents↗
PubMed1982

Synthesis of peptidoglycan in vivo in methicillin-resistant Staphylococcus aureus.

The cell-wall composition and degree of cross-linking of peptidoglycan in a strain of Staphylococcus aureus (strain MR-1) which is highly resistant to methicillin were similar to those of other strains of S. aureus. When the organism was grown in the presence of very low concentrations of methicillin (equivalent to 3 x 10(-4) x minimum growth-inhibitory concentration [MGIC] there was a large decrease in the degree of cross-linking of the peptidoglycan. Increasing concentrations of methicillin (up to 1.25 x 10(-2) x MGIC) caused a further decrease in cross-linkage but thereafter a minimum value was reached. This remained unchanged even after growth of the organisms in much higher concentrations of the antibiotic up to 0.3 x minimum growth-inhibitory concentration. S. aureus MR-1 was able to grow normally for many generations under these conditions and reduction in cross-linkage of peptidoglycan was the only change detected in wall chemistry. Growth in the presence of methicillin (up to 0.3 x MGIC) (or other beta-lactam antibiotics) did not lead to an imbalance in the biosynthesis of peptidoglycan since no soluble polymers were secreted into the growth medium and nucleotide-linked precursors did not accumulate intracellularly. High concentrations of beta-lactam antibiotics (5 x MGIC) were bacteriostatic not bactericidal and this may be related to an apparent deficiency in the endogenous autolytic enzymes of strain MR-1. Studies of the penicillin-binding proteins after growth in the presence of methicillin suggest that one of these proteins remains resistant to very high concentrations of the antibiotic. We propose that this protein acts as the primary transpeptidase responsible for the incorporation of newly synthesised peptidoglycan into the growing wall.

Bacterial Proteins↗
PubMed1981

Deficiency of autolytic activity in Bacillus subtilis and Streptococcus pneumoniae is associated with a decreased permeability of the wall.

Autolytic-deficient mutants of Bacillus subtilis which grow as chains of non-separated bacilli have been isolated by a procedure involving filtration of mutagenized cultures through glass-sinter filters. The mutants obtained were some 80-90% deficient in both autolysins, N-acetylmuramoyl-L-alanine amidase and endo-beta-N-acetylglucosaminidase. Treatment of one of these mutants with 5 M-LiCl extracted only about 20% of the protein obtained from an equivalent amount of the autolysin-containing bacilli. Similarly, a reduction of 40-60% in LiCl-extractable protein was obtained with autolytic-deficient Streptococcus pneumoniae whether these organisms lacked the autolytic enzyme or were phenotypically deficient by growth in ethanolamine-containing medium. Chromatography on Sephadex G-100 of the protein extracted from B. subtilis and S. pneumoniae revealed that the major difference between autolytic-deficient and parent organisms was a decrease in proteins of high molecular weight. Smaller differences were observed in a second fraction which contained low molecular weight material and proteins such as the autolysins, whose elution from the column was retarded by interaction with the Sephadex. Further examination of the fractionated protein from B subtilis by sodium dodecyl sulphate-polyacrylamide gel electrophoresis confirmed that the major difference between the extracts was in the amount of protein present and did not result from marked changes in the size of the extracted proteins. These observations suggest that autolysin deficiency in B. subtilis and S. pneumoniae results in a change in the porosity (permeability) of the bacterial wall.

Acetylglucosaminidase↗
PubMed1981

A role in vivo for penicillin-binding protein-4 of Staphylococcus aureus.

The degree of cross-linking of the peptidoglycan of Staphylococcus aureus H and mutants lacking penicillin-binding proteins 1 and 4 was studied. No major changes were observed in organisms lacking protein 1 whereas loss of protein 4 was accompanied by a marked reduction in the degree of cross-linking and the absence of a membrane-bound 'model' transpeptidase activity. A similar effect was achieved when cultures of the staphylococci were treated with the beta-lactam antibiotic cefoxitin. At low concentrations (0.05 microgram ml-1) cefoxitin shows highest affinity for protein 4 to which it appears to bind irreversibly. Treatment of the mutant lacking protein 4 with this concentration of the antibiotic did not affect the degree of cross-linkage. The possibility that the decrease in cross-linkage was a consequence of DD-carboxypeptidase activity on peptidoglycan precursors was investigated. Although both S. aureus H and the mutants possessed such activity it was insensitive to benzylpenicillin and cefoxitin and the role of this enzyme(s) in peptidoglycan biosynthesis remains unknown. We conclude that in vivo protein 4 acts as a transpeptidase involved in the secondary cross-linking of peptidoglycan and this activity is necessary to achieve the high degree of cross-linkage observed in the peptidoglycan of staphylococci.

Bacterial Proteins↗