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Biomedical subjects

C M McCarthy

Publications and source records attributed to C M McCarthy.

At least 37 records · Page 2Linked to original sources
PubMed1987

Utilization of nitrate or nitrite as single nitrogen source by Mycobacterium avium.

Twenty L-amino acids and several inorganic compounds were tested individually, as a sole nitrogen source, for ability to support the growth of Mycobacterium avium LM1 serovar 1. Of the amino acids tested, only L-glutamine provided nutritional support comparable to that of ammonium chloride at 1 mM. With either 1 mM potassium nitrate or nitrite substituted for ammonium chloride, similar numbers of CFU were produced. M. avium cells were grown in potassium nitrate or nitrite concentrations of 0.25, 0.5, 1.0, and 2.0 mM, and the medium was assayed for remaining nitrogen compound at several times during growth. Rates of utilization were of first-order kinetics, with nitrite removed more rapidly than nitrate. The rates were approximately 10 times as rapid at 0.25 mM than at 2 mM for either nitrogen source. Nine clinical isolates that included M. avium serovars 1, 4, and 8 and Mycobacterium scrofulaceum serovar 43 were tested for rate of utilization of ammonia, nitrate, or nitrite. Ammonia and nitrite were utilized with first-order kinetics by all strains. Nitrate utilization occurred but was not at the same level for all strains. Clinical tests indicate that M. avium is negative for nitrate reductase; this is because of the rapid reduction of nitrite produced from nitrate.

Amino Acids↗
PubMed1987

Maximum growth rate of Mycobacterium avium in continuous culture or chronically infected BALB/c mice.

Mycobacterium avium is a human pathogen which may cause either chronic or disseminated disease and the organism exhibits a slow rate of growth. This study provides information on the growth rate of the organism in chronically infected mice and its maximal growth rate in vitro. M. avium was grown in continuous culture, limited for nitrogen with 0.5 mM ammonium chloride and dilution rates that ranged from 0.054 to 0.153 h-1. The steady-state concentration of ammonia nitrogen and M. avium cells for each dilution rate were determined. The bacterial saturation constant for growth-limiting ammonia was 0.29 mM (4 micrograms nitrogen/ml) and, from this, the maximal growth rate for M. avium was estimated to be 0.206 h-1 or a doubling time of 3.4 h. BALB/c mice were infected intravenously with 3 x 10(6) colony-forming units and a chronic infection resulted, typical of virulent M. avium strains. During a period of 3 months, the number of mycobacteria remained constant in the lungs, but increased 30-fold and 8,900-fold, respectively, in the spleen and mesenteric lymph nodes. The latter increase appeared to be due to proliferation in situ. The generation time of M. avium in the mesenteric lymph nodes was estimated to be 7 days.

Ammonia↗
PubMed1986

Recovery of Mycobacterium avium after treatment with chemical decontaminants.

Cell suspensions of a pathogenic strain of Mycobacterium avium, serovar 1, were tested for susceptibility to chemical disinfectants that are frequently used for decontamination of environmental samples. Kinetic data were obtained by determining the viability at 15-min intervals during 60 min of exposure at room temperature with aeration. After 60 min exposure to a combination of 0.094% Zephiran, and 10% trisodium phosphate, only 0.3% of the initial number of colony-forming units survived. Survival after 60 min treatment with 2% sodium hydroxide, 1% sodium hydroxide, or 0.04% hexadecylpyridinium chloride was 20, 46, and 57%, respectively. To assess the practical applications, the same agents were employed to extract M. avium that had been seeded into soil. Recovery of more than 25% of the initial number of colony-forming units was achieved with any of the treatments. Several combinations of chloramphenicol and antifungal drugs were tested for inhibition of soil microbiota that survived the decontamination procedures.

Disinfectants↗
PubMed1985

Influence of nitrogen source and growth status on glutamine synthetase and glutamate synthase activity in Mycobacterium avium.

An investigation was made of the activity of glutamine synthetase and glutamate synthase from batch-cultured cells of Mycobacterium avium. The bacteria were grown in medium with ammonium chloride concentrations of 0, 0.1, 0.25, 1, 5, or 25 mumol/mL or with glutamine at 0.1 or 1 mumol/mL. The specific activity of the two enzymes was determined at 0, 22, 45, and 70 h of incubation. Regardless of the ammonia concentration in the medium, glutamate synthase specific activity was two to five times higher in extracts from elongating cells, incubated 22 h, than in those from shortened cells, incubated 45 or 70 h. In contrast, there was no apparent difference in glutamine synthetase specific activity with regard to culture age; however, glutamine synthetase specific activity varied inversely with the concentration of ammonium chloride in the medium. Cells grown in glutamine had high activity of glutamine synthetase.

Ammonium Chloride↗
PubMed1984

Glutamine synthetase from Mycobacterium avium.

Mycobacterium avium was previously shown to be dependent upon ammonia or glutamine as a nitrogen source. In an effort to assess the physiology of ammonia assimilation by M. avium, a characterization of its glutamine synthetase was performed. The enzyme from M. avium was purified by streptomycin sulfate treatment, ammonium sulfate precipitation, and affinity chromatography. The enzyme was unusual in that it had a pH optimum of 6.4 and maximum enzyme activity was obtained between 50 and 60 degrees C as shown by the transferase assay. The glutamine synthetase activity from batch-cultured cells decreased with increasing concentration of ammonium chloride in the range of 0.25-5 mumol/mL of medium, which demonstrated a response to environmental supply of a nitrogen source. The mycobacterial enzyme was similar to the other bacterial glutamine synthetases in terms of molecular weight and sedimentation coefficient which were 600 000 and 19.5 S, respectively, and enzyme activity was lost by treatment with a glutamate analog, methionine sulfoximine. The isoelectric point was, however, pH 4.5. Treatment of the enzyme with snake venom phosphodiesterase resulted in an increase in specific activity. AMP was released by the phosphodiesterase treatment, thus demonstrating that M. avium glutamine synthetase was regulated by adenylylation modification.

Ammonium Chloride↗
PubMed1984

Free fatty acid and triglyceride content of Mycobacterium avium cultured under different growth conditions.

Previous investigations demonstrated that Mycobacterium avium has a requirement for fatty acid, which can be fulfilled by palmitic (C16:0) or oleic (C18:1) acids, and that it incorporates the fatty acid into triglycerides that are later utilized. Mycobacterium avium was grown in continuous culture or batch-cultured in medium that contained palmitic acid as the fatty acid source, but lacked albumin. Cells were extracted and free fatty acids and triglycerides were obtained by preparative thin-layer chromatography. The triglycerides were further purified by column chromatography. The free fatty acids were methylated and analyzed by gas chromatography. Oleic acid represented 40 to 64% of the total free fatty acids, except for cells batch-cultured and limited for nitrogen. The latter cells contained about 27% oleic acid, and 24% of the free fatty acids were of sizes greater than C24:0. The amount of palmitic acid varied considerably, but it and oleic acid together usually accounted for 70% of the total free fatty acids. The overall fatty acid content of the triglycerides was similar to that of the free fatty acids. However, two size classes of triglycerides were found that approximated the sizes of tristearin (C54) and tricaprylin (C24), molecular weights of 892 and 471 daltons, respectively. It is concluded that these types of studies may eventually lead to more accurate identification of pathogenic mycobacteria by means of gas chromatographic analyses.

Chromatography, Gas↗
PubMed1983

Register of chromosomal abnormalities in Queensland.

The development and use of the computer-aided retrieval of karyotypes (CAROK), a register of chromosomal abnormalities in Queensland, is described. The six independent cytogenetic laboratories serving the population of 2.2 million contribute data to the register which provides total population information on the occurrence of chromosomal abnormalities, without selection. CAROK policy on confidentiality, security, access, and safety of data is described in detail. A cytogenetic register such as this ensures a reliable permanent file of results, facilitates research, and provides a data base which will enable questions of clustering or secular trends to be answered efficiently. The register is complete for the years 1976-1981, and contains information on 880 consecutive abnormal cases; in this sense, the data constitute an unselected six-year series of diagnosed chromosomal abnormalities in Queensland. These figures show an average incidence figure (over a six-year period) for newly diagnosed cases of chromosomal abnormality of 6.61/100 000 general population per year.

Aneuploidy↗
PubMed1983

Continuous culture of Mycobacterium avium limited for ammonia.

Previous investigations demonstrated the utility of a cell-cycle technique for physiologic studies of lipid metabolism in Mycobacterium avium. Such a culture technique was not suitable for enzymic analyses. Therefore, continuous culture of M. avium was attempted. A modified culture medium, limited for ammonia nitrogen, was used to culture the organism at dilution rates of 0.08 to 0.175 per h. Measurements of colony-forming units, isotope incorporation, and cell protein during extended incubation times demonstrated that the organism was in steady state. Cells harvested from continuous culture had levels of glutamate synthase that increased proportionately to the dilution rate.

Ammonia↗
PubMed1981

Variation in isoniazid susceptibility of Mycobacterium avium during the cell cycle.

A strain Mycobacterium avium that had limited susceptibility to isonicotinic acid hydrazide (INH) at 5 micrograms/ml of medium was tested for its susceptibility under cell cycle conditions. The INH-susceptible cells of M. avium were prevented from elongating if INH was present in the medium and, although there was an initial lag of 15 to 20 h, INH was bactericidal for the susceptible cells. Resurgence of viability in the INH-treated cultures was due to multiplication of INH-resistant cells. Ethidium bromide, if present in the INH-treated cultures, prevented multiplication of the INH-resistant cells.

Cell Cycle↗