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Biomedical subjects

D B Lowrie

Publications and source records attributed to D B Lowrie.

At least 73 records · Page 4Linked to original sources
PubMed1982

Benzylpenicillin transport and subcellular distribution in mouse peritoneal macrophage monolayers.

[14C]Benzylpenicillin was rapidly taken up into and eluted from mouse peritoneal macrophage monolayers and entered cytosol, lysosomes and phagolysosomes containing Staphylococcus aureus. Equilibrium concentrations in cytosol and lysosomes were consistent with transport by diffusion but partial membrane carrier dependence was evidenced by saturability (Km and Vmax 110 mM and 117 nmoles (10(6) cells)-1 (3 min)-1 respectively) and inhibition by probenecid. Partial dependence of transport on metabolic energy was shown by inhibition with cyanide plus 2-deoxyglucose and the temperature coefficient (Q10) was about 2. Some of the intralysosomal radiolabel accumulated as benzylpenicilloic acid.

Animals↗
PubMed1981

Hydrogen peroxide and superoxide release by alveolar macrophages from normal and BCG-vaccinated guinea-pigs after intravenous challenge with Mycobacterium tuberculosis.

The release of H2O2 and .O2- by alveolar macrophages from normal and BCG-vaccinated guinea-pigs was measured 3 h, 3 days and 6 days after i.v. challenge infection with Mycobacterium tuberculosis H37Ra. Vaccination did not affect the release of H2O2 or .O2- form macrophages that were removed from guinea-pigs 3 h after i.v. infection and tested as monolayers without a phagocytic stimulus. However, macrophages that were removed from vaccinated animals on the third and sixth days after i.v. infection released progressively more than macrophages that were removed after 3 h. This was not seen with cells from i.v.-infected normal animals. Exposure of macrophage monolayers to phorbol myristate acetate (PMA) and opsonized H37Ra caused increased release of H2O2 and .O2-. There was no difference in the response to PMA either between macrophages from normal animals and those from vaccinated animals or between macrophages taken 3 h, 3 days and 6 days after i.v. infection. Thus the response with PMA gave no indication of the development of local immunity. In contrast, with H37Ra as a phagocytic stimulus in vitro the amounts of H2O2 and .O2- released per cell-associated bacillus increased with the time elapsed since i.v. infection. This increase was greater with the macrophages from vaccinated animals than those from normal animals. The results support the hypothesis that H2O2 production by macrophages is involved in killing M. tuberculosis in vivo.

Animals↗
PubMed1981

The contribution of hydrogen peroxide resistance to virulence of Mycobacterium tuberculosis during the first six days after intravenous infection of normal and BCG-vaccinated guinea-pigs.

The course of infection with Mycobacterium tuberculosis strains H37Rv, H37Ra and their isoniazid-resistant, hydrogen peroxide-susceptible mutants in guinea-pig spleen and lung were assessed by measuring changes in number of viable bacteria during the first and second 3-day intervals after i.v. infection of normal and BCG-vaccinated animals. Vaccination had no effect on bacterial survival in the first 3 days of infection. The peroxide-susceptible mutants were killed or inhibited more than their parent strains; in normal animals this enhanced susceptibility was expressed equally during the first and second 3-day intervals while in vaccinated animals the effect was greater in the second 3-day interval. The results suggest that hydrogen peroxide is generated in significant amounts in the environment of tubercle bacilli lodged in normal tissues and in enhanced amounts when acquired immunity becomes expressed after a few days' lodgement in the tissues of vaccinated animals. Thus hydrogen peroxide resistance may contribute to virulence by protecting against both normal resident and immunologically activated macrophages.

Animals↗
PubMed1980

Analytical subcellular fractionation of rabbit alveolar macrophages with particular reference to the subcellular localisation of pyridine nucleotide-dependent superoxide-generating systems and superoxide dismutase.

Normal and Bacillus Calmette-Guerin (BCG) vaccine-induced rabbit alveolar macrophage homogenates were fractionated by isopycnic density gradient centrifugation. Superoxide dismutase-inhibitable NAD(P)H-dependent nitro-blue tetrazolium reductase was found localised to endoplasmic reticulum and mitochondria. The normal macrophages tended to contain more of this activity than the BCG-induced macrophages. Two superoxide dismutases were found: cyanide-sensitive superoxide dismutase was predominantly present in the cytosol, with a small proportion in mitochondria; cyanide-resistant superoxide dismutase was found confined to mitochondria. Neither differed in specific activity betw-en the normal and BCG-induced macrophages.

Animals↗
PubMed1980

The susceptibility of strains of Mycobacterium tuberculosis to catalase-mediated peroxidative killing.

At low pH and with continuous low concentrations of hydrogen peroxide generated in situ, catalase was able to replace peroxidase in the peroxidase/hydrogen peroxide/iodide microbicidal system. The system was effective against Escherichia coli and Mycobacterium tuberculosis. Iodide could not be replaced by chloride. The system was effective in lactate buffer, but not in citrate/phosphate buffer. Strains of M. tuberculosis with high and low virulence were equally susceptible. The observations are discussed in the context of an involvement of host-cell catalase in a possible intracellular killing mechanism against M. tuberculosis.

Buffers↗
PubMed1980

Properties and localisation of rabbit alveolar macrophage 5'-nucleotidase.

5'-Nucleotidase has been demonstrated in rabbit alveolar macrophages. This enzyme has been found to be localised on the plasma membrane as have alkaline phosphodiesterase I and leucyl-2-naphthylamidase. Heterogeneity of the plasma membrane has been evidenced by the behaviour of these enzymes during isopycnic centrifugation.

Alkaline Phosphatase↗
PubMed1979

Analytical subcellular fractionation of alveolar macrophages from normal and BCG-vaccinated rabbits with particular reference to heterogeneity of hydrolase-containing granules.

Macrophages were obtained by pulmonary lavage from normal rabbits or rabbits that had developed pulmonary granulomas after receiving intravenous BCG vaccine 2-3 weeks earlier. The cells were disrupted in iso-osmotic sucrose and a low-speed supernatant was fractionated by isopycnic centrifugation on a linear sucrose density gradient. Three populations of hydrolase-containing granules (putative lysosomes) were found in both normal and BCG-induced macrophages. They were distinguished by their different distributions in the gradient and different sensitivities to disruption by digitonin and were termed:type A, containing lysozyme; type B, containing N-acetyl-beta-glucosaminidase, beta-glactosidase, beta-glucuronidase and possibly some lysozyme; type C, containing cathepsin D. Acid phosphatase appeared to be about equally distributed between type B and C granules. Type A and B granules from BCG-induced macrophages showed markedly greater equilibrium density than did those from normal macrophages. Beta-glucuronidase and acid phosphatase had greater specific activity in the induced cells.

Animals↗
PubMed1979

Division and death rates of Salmonella typhimurium inside macrophages: use of penicillin as a probe.

In mouse peritoneal macrophages infected in vitro with Salmonella typhimurium the number of viable bacteria and the number of stainable bacteria detected by light microscopy both increased at similar rates with a doubling time of more than 1 h. Antibiotics were not present; instead extracellular bacteria were removed by frequently rinsing the cells. The bacterial doubling time in the same medium in the absence of macrophages was about 20 min. Penicillin added to macrophage monolayers rapidly entered the macrophages, reaching a diffusion equilibrium. The penicillin-induced bacterial death rate appeared to depend on the bacterial division rate as well as on the penicillin concentration. These properties of penicillin were used to monitor intracellular bacterial division and death rates. The results indicated that intracellular killing, with the disappearance of stainable bacteria, did not contribute to the extended doubling time in macrophages. It was concluded that the intracellular environment of the bacteria was probably growth inhibitory but not bactericidal.

Cell Division↗
PubMed1979

Phagolysosome formation, cyclic adenosine 3':5'-monophosphate and the fate of Salmonella typhimurium within mouse peritoneal macrophages.

Salmonella typhimurium did not inhibit fusion of lysosomes with the phagocytic vacuoles in infected macrophages and caused no increase in cyclic adenosine 3':5'-monophosphate. Glutaraldehyde-killed bacteria showed rapid ultrastructural degeneration within the phagolysosomes. In contrast, untreated bacteria were resistant to digestion by lysosomal enzymes. Intracellular survival of this species appears to depend on resistance to, and not evasion of, lysosomal enzymes.

Cyclic AMP↗
PubMed1979

Phagosome-lysosome fusion and cyclic adenosine 3':5'-monophosphate in macrophages infected with Mycobacterium microti, Mycobacterium bovis BCG or Mycobacterium lepraemurium.

When ingested by mouse peritoneal macrophage monolayers, live Mycobacterium microti caused a sustained increase in monolayer cyclic AMP content and fusion of lysosomes with the bacterium-containing phagosomes was impaired. Ingested live M. bovis BCG caused a transient increase in cyclic AMP and the defect in phagolysosome formation was less pronounced. Dead mycobacteria and live M. lepraemurium neither enhanced monolayer cyclic AMP content nor inhibited phagolysosome formation. Mycobacterium microti and BCG exceeded M. lepraemurium in cyclic AMP-synthesizing activity in vitro but the question of whether bacterial cyclic AMP contributed substantially to the increments in infected macrophages was not resolved. Antibody-coated BCG retained the ability to synthesize cyclic AMP and to enhance monolayer cyclic AMP but lost the ability to inhibit phagolysosome formation in macrophages, The observations are discussed in terms of possible control of phagolysosome formation by cyclic nucleotides.

Cyclic AMP↗
PubMed1978

Virulence and resistance to superoxide, low pH and hydrogen peroxide among strains of Mycobacterium tuberculosis.

Six strains of Mycobacterium tuberculosis of different virulence in guinea-pigs were compared with regard to their resistance to low pH, to hydrogen peroxide (H2O2) at different pH values and to superoxide (O2-). Low virulence was associated with susceptibility to H2O2 in native and isoniazid-resistant strains but not in laboratory-attenuated strain H37Ra. H2O2 resistance was only partly related to catalase content. Low virulence was not associated with susceptibility to an acid environment but the tuberculocidal effect of H2O2 was significantly increased at low pH. The strains were uniformly resistant to O2- and contained similar amounts of superoxide dismutase. The implications of these observations are discussed in the context of mechanisms of host defence in tuberculosis.

Animals↗
PubMed1978

Virulence of Mycobacterium tuberculosis and susceptibility to peroxidative killing systems.

At sub-bactericidal concentrations of hydrogen peroxide, Mycobacterium tuberculosis was killed by hydrogen peroxide/peroxidase/halide microbicidal systems. The halide cofactor could be either iodide or, with much lower efficiency, chloride. Omission of any one of the reactants eliminated the tuberculocidal effect. Differences in susceptibility between different strains of M. tuberculosis did not correlate with virulence differences. The observations are discussed in the context of host defence mechanisms against tuberculosis.

Chlorides↗