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Biomedical subjects

A M Harris

Publications and source records attributed to A M Harris.

At least 73 records · Page 4Linked to original sources
PubMed1985

Human mononuclear phagocyte antiprotozoal mechanisms: oxygen-dependent vs oxygen-independent activity against intracellular Toxoplasma gondii.

To determine if the oxygen-dependent and -independent antiprotozoal mechanisms with which the human mononuclear phagocyte is equipped to act against Leishmania donovani operate against other intracellular parasites, oxidatively intact and deficient cells were challenged with Toxoplasma gondii. Fresh monocytes and lymphokine- or gamma-interferon (IFN-gamma)-activated macrophages from normal individuals killed 35% and 50% of T. gondii within 6 hr, respectively, and each of these cell populations inhibited the replication of surviving parasites 20 hr after infection. This activity was associated with the capacity to release large amounts of H2O2 (572 to 971 nmol/mg) and to respond to toxoplasma ingestion with respiratory burst activity. Impairing the ability to generate oxygen intermediates by glucose deprivation or treatment with superoxide dismutase, catalase, or mannitol inhibited toxoplasmacidal activity by greater than 80% and permitted a 2.6- to 4.3-fold increase in the number of intracellular toxoplasmas. In contrast to normal cells, fresh monocytes from patients with chronic granulomatous disease (CGD) killed less than 8% of toxoplasmas and exerted 50% less toxoplasmastatic activity. However, although associated with the induction of only modest toxoplasmacidal effects (18 to 20% killing), lymphokine stimulation did induce CGD monocytes and macrophages as well as oxidatively inactive human endothelial cells to display near normal levels of toxoplasmastatic activity. Similar to oxygen-dependent mechanisms, the enhancement of oxygen-independent activity by crude lymphokines could be abolished by a monoclonal anti-IFN-gamma antibody and could be achieved by treatment with recombinant IFN-gamma alone. Unstimulated CGD monocytes, however, were found to lose all antitoxoplasma activity after two days in culture, whereas normal cells continued to effectively inhibit T. gondii replication, suggesting that oxygen-independent responses may not actually be required for the normal monocyte to act against T. gondii. Taken together with previous findings with L. donovani, these results indicate that the human mononuclear phagocyte possesses an oxygen-independent antiprotozoal mechanism and that its effects can be enhanced by lymphokines (IFN-gamma), but that nevertheless this cell's primary response to intracellular protozoa is largely oxygen dependent.

Endothelium↗
PubMed1981

Prevention of post weaning mastitis in ewes.

The efficacy of a dry cow cerate in protecting the dry ewe against mastitis was tested in three flocks. Of 931 ewes, 462 were infused, shortly after their lambs were weaned, with a dry cow cerate containing 1 g procaine penicillin and 0.5 g dihydrostreptomycin sulphate. The remaining 469 served as untreated controls. At tupping, when the sheep were examined for clinical evidence of mastitis, 21 cases (4.5 per cent) were recorded among the controls but only seven (1.5 per cent) among the treated ewes. There was variation in the distribution of cases between individual flocks but overall the incidence of mastitis in the treated sheep was lower and significantly different from that among the control ewes.

Animals↗
PubMed1981

The Mayo three-community hypertension control program. V. Cost-effectiveness of intervention.

This paper compares the costs of a categorical clinic model for community hypertension intervention with the costs of two less resource-intensive hypertension programs. Three categories of costs are measured for each program: program costs, patient costs, and time costs. Total costs are expressed in terms of costs per hypertensive patient controlled under each program. When adjusted for differences in hypertension prevalence and screening costs in the three community programs, the cost-effectiveness of the categorical clinic model is questionable. These results suggest that careful analyses of the categorical clinic model in other communities should be conducted before public resources are committed to the establishment of such models on a widespread basis.

Community Health Services↗
PubMed1976

Identification of beta-lactamases by analytical isoelectric focusing: correlation with bacterial taxonomy.

beta-Lactamases (EC. 3.5.2.6) can be directly compared by analytical isoelectric focusing. Using this technique, 242 strains from five Gram-positive and 16 Gram-negative genera were examined. A preparation of each strain focused as a single group of bands which did not match the pattern of any R factor-associated beta-lactamase. None of the strains was known to carry an R factor and resistance transfer experiments were unsuccessful. The enzymes studied were therefore thought to be chromosomally mediated. The isoelectric points ranged from 3.9 to 8.7 and were not related to the substrate profiles or other biochemical properties. The chromosomal beta-lactamases appeared to be specific for genus, species and sub-species, and strains that produced identical beta-lactamases had identical bacterial characteristics. Correlation of bacteriological differences with differences in beta-lactamase patterns is discussed with particular reference to strains of Escherichia coli and Klebsiella spp. Since beta-lactamases may be universally produced by bacteria, separation of the enzymes by analytical isoelectric focusing could be used in bacterial taxonomy.

Bacteria↗
PubMed1976

A study of once daily tenormin (atenolol) in hypertension: some implications in patient compliance.

A clinical study is described in which hypertensive patients on no drug therapy were given atenolol in increasing doses from 50 mg twice daily to 200 mg twice daily until the diastolic blood pressure was 90 mm Hg or below. At this stage the drug was withdrawn until blood pressure readings had risen to pre-treatment levels. The same dose of atenolol was then re-introduced but now given once-a-day (in the morning) and was continued for four weeks. Of the elevel patients entering the study, one withdrew as his blood pressure was not controlled on a dose of 200 mg of atenolol twice daily, and another because on withdrawal of atenolol his blood pressure did not rise to pre-treatment levels. The remaining nine patients completed the study. There was a statistically significant fall in blood pressure on both atenolol regimes and there was no significant difference between the blood pressure control achieved on twice-a-day and once-a-day administration. Only one patient developed side-effects; this being an asthmatic who developed mild dyspnoea on atenolol which did not necessitate withdrawal of the drug. It is concluded that once-a-day administration of a given dose of atenolol is therapeutically equivalent to twice-a-day administration. The implications of this in terms of better patient compliance, and thus better prognosis, are discussed.

Adult↗