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Biomedical subjects

M L Dubey

Publications and source records attributed to M L Dubey.

36 records · Page 2Linked to original sources
PubMed1993

Generation of reactive oxygen species by blood monocytes during acute Plasmodium knowlesi infection in rhesus monkeys.

The status and kinetics of monocyte activation during acute P. knowlesi infection was investigated by latex-induced, luminol-dependent chemiluminescence (CL) response. The contribution of various reactive oxygen species (ROS) to CL response was estimated before infection and at peak parasitaemia (day 7 post infection) by using scavengers of ROS (benzoate, catalase and superoxide dismutase). The chemiluminescence index (CLI) was not found to be significantly different from controls on day 2 postinfection, but was significantly higher on days 5 and 7 postinfection. Hydroxyl radical (OH.) production was considerably elevated, whereas superoxide anion (O2-.) and hydrogen peroxide (H2O2) production dropped following infection. These changes in generation of ROS are discussed in relation to the progression of parasitaemia to high levels, immunopathology and immunosuppression during acute P. knowlesi infection.

Animals↗
PubMed1992

Plasmodium falciparum induced perturbations of the erythrocyte antioxidant system.

Erythrocyte antioxidants catalase, superoxide dismutase, reduced glutathione and glutathione peroxidase were studied in cells harbouring different growth stages of Plasmodium falciparum. Catalase and superoxide dismutase showed significant decrease during parasite maturation indicating hampered metabolism of hydrogen peroxide and superoxide anions. Glutathione peroxidase also exhibited a downward trend during the growth of P. falciparum, while there was a moderate accumulation of reduced glutathione. These findings suggest decreased utilization of the reduction potential in detoxification of reactive oxygen species. The fall in all three antioxidant enzymes studied was highly significant (P less than 0.001) in erythrocytes with mature stages of the parasite (trophozoites, schizonts). The increased vulnerability of erythrocytes to damage, which parallels the growth phases of the parasite emphasizes the need for early treatment of P. falciparum malaria to minimise red cell destruction and the resulting anaemia.

Animals↗
PubMed1992

Oxidative damage of erythrocytes infected with Plasmodium falciparum. An in vitro study.

The extent of reduced glutathione, activity of glutathione peroxidase, amount of membrane lipid peroxidation products, and the extent of hemoglobin release from host erythrocytes during in vitro Plasmodium falciparum growth was studied. Highly synchronized parasite cultures were studied to examine the alterations caused by different growth stages of the parasite. There was a moderate increase in the reduced glutathione content as the parasite matured, which was significant only in schizont-rich erythrocyte lysates (p < 0.05) whereas the activity of glutathione peroxidase was significantly low in all the parasitized red blood cells (ring-infected RBC, p < 0.005; trophozoite- and schizont-infected RBC, p < 0.001). The lipid peroxidation product, malonyldialdehyde, of the host red cells increased gradually to more than fourfold in schizont-rich cells as compared with normal erythrocytes (p < 0.001). The hemoglobin release from cultured cells was significantly higher in all parasitized red cell cultures as well as in uninfected cells kept in in vitro, as compared with normal erythrocytes. The consequence of such changes induced by the malarial parasites in the host red cells in the pathogenesis of erythrocyte destruction and anemia of P. falciparum malaria is discussed.

Erythrocytes↗
PubMed1992

Effect of nifedipine treatment on oxidative metabolism of peritoneal macrophages and neutrophils of Plasmodium berghei-infected mice.

The oxidative metabolism of peritoneal macrophages (PM) and neutrophils from nifedipine (calcium channel blocker)-treated, Plasmodium berghei (NK 65)-infected and normal infected Swiss Albino mice was studied. A significant fall in oxidative metabolism as evidenced by decreased chemiluminescence (CL) response (P less than 0.001) was recorded both in PM and neutrophils from nifedipine-treated mice compared to the control animals. When the oxidative metabolism of these phagocytes was studied after infection of the host, higher CL response was recorded from both PM and neutrophils isolated during the early course of infection (0-1 and 5-10% parasitaemia) when compared to uninfected mice (P less than 0.001). A similar pattern was observed in the case of nifedipine-treated and infected mice even though the CL response was much lower. The increasing parasite load not only resulted in subnormal CL response but also prolonged the time required for the phagocytes to exhibit peak oxidative activity both in normal infected and CCB-treated infected mice, but the time taken to show peak CL response was shortened following drug administration compared to controls. These observations revealed the profound in vivo effect of CCB on the functioning of phagocytic leucocytes and thereby questions the use of CCB in combination with chloroquine for reversal of drug resistance.

Animals↗
PubMed1991

Malaria screening to prevent transmission by transfusion: an evaluation of techniques.

Transfusion-associated malaria is often severe or even fatal, because diagnosis is frequently delayed and it complicates an already serious underlying disorder. Detection of infected donors is difficult in endemic areas due to the lack of a suitable donor screening test. Blood smear staining techniques show poor results due to the low parasite concentration in many infected persons, and the antibody detection test is not helpful due to the universal presence of antibody in healthy donors in these areas. For comparative evaluation of various screening tests, 9131 blood smears from voluntary donors and a group of patients were screened by Giemsa staining. Ten (0.10%) subjects showed parasitaemia, whereas Acridine Orange fluorescence staining showed 13 (0.14%) parasitaemia in almost the same number of smears screened on the same samples. Significantly high levels of malarial antibody were detected in 12.6% and 19.86% of subjects by indirect fluorescent antibody and enzyme-linked immunoassay tests, respectively. Malarial antigen detection by monoclonal antibody showed positive results in 9.48% of subjects, demonstrating excellent results and showing direct evidence of infection. We recommend that this should be adopted as a screening technique by transfusion services in endemic areas in order to prevent post transfusion malaria.

Acridine Orange↗
PubMed1991

Plasmodial antigen detection by monoclonal antibody as a screening procedure for blood donors in transfusion medicine.

Very little information is available as regards the methods to be advocated to prevent transfusion malaria, especially in endemic countries. Most of the malaria non-endemic countries follow the rule of donor deferral for 3 years after malaria infection. This criterion cannot be followed in endemic areas since the majority of the population is continuously exposed to this infection. Therefore, there was a long felt need for a suitable screening procedure for blood donors to make the transfusion therapy safe. A total of 6,435 blood donors and 3,621 patients who received blood from these donors were studied by blood smears examination and malarial antigen detection by specific monoclonal antibody. Smear examination by Giemsa and acridine orange staining methods showed poor results (0.06% and 0.1% positivity respectively), probably due to low concentration of parasites. However, antigen detection by monoclonal antibody confirmed specific diagnosis in majority of these subjects. Blood smear examination failed to reveal malaria infection in 92.3% of antigen positive blood donors. It is, therefore, recommended that antigen detection by monoclonal antibody should be adopted as a routine screening procedure by the blood transfusion services in malaria endemic countries like India.

Animals↗
PubMed1991

Donor screening for malaria by antibody and antigen detection in endemic area.

Transfusion-associated malaria is one of the dreaded threats to the safety of transfusion services in this malaria endemic world. The main drawback in preventing this menace is that routine blood donor screening techniques are not very satisfactory. In this study, blood donors were screened for antimalarial antibody by micro ELISA and Indirect Fluorescence Antibody (IFA) test and malarial antigen by monoclonal antibody (MAB) technique. A total of 19.37% and 12.39% blood donors showed significantly high antibody by ELISA and IFA test respectively, and 0.35% donors showed the presence of antigen by the MAB technique. Solitary dependence on malarial antibody detection as a screening test might have led to rejection of 19.02% blood donors without any apparent infection. So antigen detection in blood donors with the help of the MAB technique seems to be more sensitive and a practically feasible screening test to prevent transfusion malaria.

Animals↗
PubMed1991

Generation of reactive oxygen species by blood monocytes in human Plasmodium falciparum and P. vivax infections.

Generation of reactive oxygen radicals by peripheral blood monocytes was measured by luminol-dependent chemiluminescence in 23 P. vivax- and 7 P. falciparum-infected patients. The chemiluminescence index (CLI) was not found to be significantly higher in P. vivax-infected cases than in healthy controls. But in patients with P. falciparum infection, the CLI was significantly higher compared to controls as well as to P. vivax-infected patients. In two severe and complicated P. falciparum-infected cases, CLI was found to be higher than in mild cases. As immunosuppression is more marked in falciparum malaria than in vivax cases, the role of oxygen radical generation in immunopathology and causation of immunosuppression in falciparum malaria needs further investigation.

Animals↗
PubMed1990

Post-transfusion malaria in thalassaemia patients.

A total of 125 beta-thalassaemia patients receiving repeated blood transfusions were screened by Giemsa stain, Acridine-orange stain and antigen detection for evidence of malaria infection on each visit. A total of 8 (6.4%) of the patients developed post-transfusion malaria (PMT) as confirmed by tracing the infected blood donors. A high incidence of PTM in thalassaemia patients appears to be due to the use of fresh blood and the high frequency of blood transfusions required by these patients. Antigen detection using monoclonal antibody was found to be more sensitive for diagnosis of PTM and for screening suspected donors than the conventional blood smear examination methods and is therefore recommended for routine blood donor screening to rule out malaria infection.

Animals↗
PubMed1990

Isolation rates of different mycobacterial species from Chandigarh (north India).

A total of 4958 patients, clinically suspected to have tuberculosis were screened for mycobacteria by acid fast staining and culture procedures. Mycobacterial species were isolated from 462 (9.3%) patients while acid fast bacilli were demonstrated on smear examination in 83 (1.7%) patients. Mycobacterium tuberculosis was the most common isolate (92%). Among the nontuberculous mycobacteria, M. fortuitum was isolated in 13 (2.8%), M. avium in 2 (0.4%) and M. szulgai in 1 (0.2%). In 22 individuals clinically suspected of tubercular pleural effusion, pleural biopsy specimen gave higher isolation of mycobacteria (27.3%) as compared to isolations from pleural fluid specimens (9.1%).

Child↗
PubMed1989

Seroepidemiological study of malaria in a rural population of Chandigarh.

A total of 1689 peripheral blood smears and serum samples were collected from healthy subjects from four villages of U.T. Chandigarh during the pre-monsoon season (February to May 1987) while 1809 such samples were collected during the post-monsoon season (October 1987-January 1988). None of the peripheral blood smears examined by Giemsa and acridine-orange stains showed malarial parasite. Out of 1689 serum samples tested by indirect haemagglutination (IHA) test during pre-monsoon season, 81 per cent showed malarial antibody titres of less than 1:8 and only 19 per cent showed titres of 1:8 or above. In contrast, out of 1809 serum samples tested during post-monsoon season, 58.3 per cent showed antibody titres of less than 1:8 while 41.6 per cent samples showed titres of 1:8 and above. Total number of malaria cases from these villages from June 1987 to January 1988 was also low (total 65 cases) as compared to corresponding period of previous year (total cases 191). Serological findings independent of positive cases of malaria suggest that though, no proved clinical cases of malaria were observed in the population surveyed, malaria transmission had certainly taken place as evidenced by higher antibody titres observed during the post-monsoon season compared to pre-monsoon season.

Adolescent↗
PubMed1987

Incidence of shigellosis and multi-drug resistant Shigellae: a 10 year study.

Between 1976 and 1985 a total of 12,709 faecal samples were cultured. From these samples 760 strains (6.0%) of Shigellae were isolated. Shigella flexneri was the commonest isolate (55%), followed by S. dysenteriae (29.7%). A total of 15.7% of children under 5 years of age were positive for Shigellae. The rate of isolation was lower during the winter months than in the summer months. Only 25 strains (3.3%) were sensitive to all five antibiotics tested. A total of 617 (81.2%) were resistant to three or more antibiotics (multi-drug resistant). The minimum inhibitory concentrations (MICs) of five drugs were calculated in 100 strains. Streptomycin showed an MIC of 25 micrograms ml-1 or less for only seven strains. MICs of chloramphenicol tetracycline and ampicillin were found to be as high as 100-1000 micrograms ml-1 for the majority of strains. Sulphonamide showed an MIC of 1000 micrograms ml-1 for 93 strains.

Anti-Bacterial Agents↗