Biomedical subjects

M L Dubey

Publications and source records attributed to M L Dubey.

At least 19 recordsLinked to original sources

PubMed2006

Leishmania donovani: effect of verapamil on in vitro susceptibility of promastigote and amastigote stages of Indian clinical isolates to sodium stibogluconate.

Although pentavalent antimonials are the first-line drug for treatment of visceral leishmaniasis all over the world, yet, in India, increasing number of patients are being reported to be unresponsive to sodium stibogluconate. Verapamil, a calcium channel blocker, affects drug uptake by preventing its efflux and thereby accumulation within the cell. In the present study, effect of verapamil on in vitro susceptibility of both promastigote and amastigote stages of 15 clinical isolates and standard strain of Leishmania donovani to sodium stibogluconate was evaluated by detection of acid phosphatase. Amastigotes were found more susceptible to sodium stibogluconate than the promastigotes (p<0.05) and in the presence of verapamil, IC(50) value of sodium stibogluconate was reduced only for those isolates, which had a higher IC(50). Verapamil alone did not have any effect on the parasites. The results indicate that amastigotes are more susceptible to sodium stibogluconate than promastigotes and verapamil can reverse the in vitro drug resistance of L. donovani clinical isolates to sodium stibogluconate.

Animals↗

PubMed2006

Nitric oxide radicals in leucocytes and vaginal washes of Trichomonas vaginalis -infected symptomatic and asymptomatic women.

The clinical spectrum of Trichomonas vaginalis infection varies from asymptomatic to mild, moderate or severe vaginitis. Nitric oxide and other reactive nitrogen radicals produced by immune effector cells are important cytotoxic and cytostatic mediators against several microorganisms including parasites. In the present study, inducible nitric oxide synthase (iNOS) and reactive nitrogen intermediates (RNI) were determined in leucocyte cultures (stimulated with T. vaginalis in vitro) and vaginal washes (VWs) of 22 symptomatic and 20 asymptomatic T. vaginalis-infected and 20 healthy women by immunoblotting and Griess method respectively. The iNOS protein was detected in leucocytes and VWs of all the symptomatic and asymptomatic women, but was not detected in any of the samples from healthy women. Mean iNOS protein band intensity was significantly higher in leucocytes as compared to VWs (P<0.001) of both symptomatic and asymptomatic women and was also higher in leucocytes of asymptomatic as compared to symptomatic women (P<0.05). Mean RNI concentration was also significantly higher in leucocytes (P<0.01) and VWs (P<0.05) of asymptomatic as compared to symptomatic women, and was also higher in samples of infected as compared to healthy women (P<0.001). These results suggest that reactive nitrogen radicals may have a role in limiting T. vaginalis infection in asymptomatic women.

Animals↗

PubMed2005

Plasmodium falciparum: polymorphism in the MSP-1 gene in Indian isolates and predominance of certain alleles in cerebral malaria.

Polymorphism in the block-2 region of merozoite surface protein-1 gene in 69 North Indian Plasmodium falciparum isolates was studied by PCR and RFLP using Dra-1 endonuclease. On the basis of molecular weight of the PCR products, considerable size polymorphism in target gene was seen and 69 isolates were classified into five allelic types. On RFLP, the isolates in three allelic types were further divided into two sub-allelic types each and thus eight genetic types could be identified. Interestingly, all five allelic types were identified in 47 isolates from uncomplicated (non-cerebral) malaria patients while only two allelic types (Type 2 and 3) were seen amongst 22 isolates from cerebral malaria patients. Furthermore, on RFLP, one subtype (2A) was predominantly seen in cerebral malaria patients and one subtype (3A) was exclusively found in cerebral malaria patients. These observations suggest that a few, comparatively more virulent isolates prevalent in an area may cause severe disease (cerebral malaria) which can be identified by molecular techniques like PCR-RFLP.

Adolescent↗

PubMed2005

Antigenaemia and antibody response to Toxoplasma gondii in human immunodeficiency virus-infected patients.

Toxoplasma encephalitis in immunocompromised patients results from reactivation of previously acquired (latent) infection. The aim of the study is to assess the antigenaemia and antibody response to Toxoplasma gondii in human immunodeficiency virus (HIV)-infected patients to determine the best marker for early diagnosis of toxoplasmosis in such patients. Indirect enzyme-linked immunosorbent assay (ELISA) for detection of IgG, IgM and IgA anti-toxoplasma antibodies and double-sandwich ELISA for toxoplasma antigen is carried out in serum samples collected from 100 HIV seropositive patients and 75 controls. Toxoplasma-specific IgG, IgM and IgA antibody response and antigenaemia were detected in 12%, 6%, 7% and 14% of HIV-infected patients, respectively. On retrospective analysis of 14 patients with antigenaemia only one had central nervous system (CNS) symptoms attributable to toxoplasma infection. In this patient, the CD4+ cell count was below 50/microL and none of the specific immunoglobulin isotype responses could be detected. The patient showed clinical improvement following specific chemotherapy for toxoplasmosis. In 25 HIV-negative and anti-toxoplasma IgG antibody-positive controls, IgM was detected in two (8%), IgA in five (20%) and antigenaemia in 10 (40%), while 50 HIV seronegative healthy controls were negative for both antigen and antibody responses. The study indicates that detection of toxoplasma antigen in addition to IgG antibody response may prove to be a useful indicator in the early diagnosis of reactivated toxoplasmosis in HIV/AIDS patients.

Acquired Immunodeficiency Syndrome↗

PubMed2005

Antibody response to Toxoplasma gondii in saliva samples from human immunodeficiency virus-infected patients.

Toxoplasma gondii is an important opportunistic infection among human immunodeficiency virus (HIV)-infected patients as it causes fatal encephalitis. In the present study, antibody response to T. gondii is assessed in saliva samples from 100 HIV-seropositive patients and 25 HIV-negative healthy controls by indirect enzyme-linked immunosorbent assay (ELISA). Sensitivity and specificity for detection of IgG and IgM in saliva is calculated using a positive antibody response in serum samples (from an earlier study) as the gold standard. IgG and IgM antibodies were found in 20% and 25% patients, respectively. One control subject showed the presence of IgM antibody. Sensitivity for IgG and IgM antibodies was 64% and 81.25%, respectively, while specificity was 94.67% and 85.71%, respectively. This study indicates that saliva samples can be used as an alternative to serum samples to detect anti-toxoplasma antibodies, particularly IgM, for the diagnosis of toxoplasma encephalitis in HIV/acquired immune deficiency syndrome patients.

AIDS-Related Opportunistic Infections↗

PubMed2005

Association of parasitic infections and cancers.

Recent advances in the fields of molecular biology, epidemiology and infectious diseases have led to significant revelations to clarify the relationship between cancer and infective agents. This article reviews the relationship between parasitic infections and carcinogenesis and the possible mechanisms involved. Few parasites, e.g., Schistosoma haematobium and Opisthorchis viverrini have been found to be strongly associated with bladder cancer and cholangiocarcinoma respectively. The evidence for the association of several other parasites and cancers has also been postulated.

Animals↗

PubMed2005

Genetic polymorphism in Plasmodium falciparum vaccine candidate antigens.

Malaria is still a major public health problem in many tropical and subtropical countries. Malaria vaccine is highly desirable as an adjunct to existing malaria control measures. The polymorphisms in malaria vaccine candidates antigens might be a hurdle in developing an effective vaccine. The present article reviews the genetic polymorphism in several antigens expressed on the parasite surface, which are targets for immunological responses of the host and are good candidates for vaccine development against P. falciparum. Variable regions of most genes are generally dimorphic probably as a result of intragenic recombinations. Each allele in turn shows polymorphism resulting from point mutations, or other mechanisms. Several antigens like merozoite surface protein-1 and 2 (MSP-1 and MSP-2) and S antigen show high polymorphism while in others like circumsporozoite protein (CSP), apical membrane antigen-1 (AMA-1) and erythrocyte binding antigen-175 (EBA-175) functional constraints limit the degree of polymorphism. Polymorphism reported in these genes is discussed.

Animals↗

PubMed2003

Antigenaemia and antibody response to Leishmania donovani stage-specific antigens and rk39 antigen in human immunodeficiency virus-infected patients.

In order to define the possible markers for the early diagnosis of asymptomatic visceral leishmaniasis in human immunodeficiency virus (HIV)-infected individuals, the antigenaemia and antibody response to stage-specific Leishmania donovani and rk39 antigens is assessed by enzyme-linked immunosorbent assay (ELISA) and immunoreactivity to stage-specific antigens analysed by Western blot. Serum samples from two out of 100 HIV-infected individuals were found positive for antigenaemia, antibody response to stage-specific L. donovani antigens and rk39 antigen, and one sample was also positive for antigenaemia and antibody response to L. donovani antigens, while antibody detection to rk39 antigen was not carried on this sample. Additionally, one sample was found positive for amastigote antigenaemia and antibody response to amastigote antigen, while in this patient promastigote antigenaemia and antibody response to promastigote L. donovani and rk39 antigen could not be detected. One sample was found positive for antigenaemia, antibody response to amastigote antigen and negative for antibody response to promastigote antigen, while in this patient response to rk39 antigen was borderline. Although antibody response to rk39 antigen could be detected in 9/88 (10%) HIV-infected individuals, in six of these nine patients neither antigenaemia nor antibody response to stage-specific L. donovani antigens could be detected. All 10 confirmed visceral leishmaniasis and HIV-negative control patients had positive antigenaemia and antibody response to L. donovani amastigote and promastigote antigens, while all the normal healthy individuals were negative. The study indicated that detection of antibody response to rk39 antigen, amastigote antigenaemia and antibody response to amastigote antigen may prove to be better markers than detection of promastigote antigenaemia, antibody response to promastigote antigen and immunoblot reactivity.

AIDS-Related Opportunistic Infections↗

PubMed2003

Decreased level of 2,3-diphosphoglycerate and alteration of structural integrity in erythrocytes infected with Plasmodium falciparum in vitro.

2,3-Diphosphoglycerate (2,3-DPG), an intracellular metabolite of glycolytic pathway is known to affect the oxygen binding capacity of haemoglobin and mechanical properties of the red blood cells. 2,3-DPG levels have been reported to be elevated during anaemic conditions including visceral leishmaniasis. 2,3-DPG activity in P. falciparum infected red blood cells, particularly in cells infected with different stages of the parasite and its relationship with structural integrity of the cells is not known. Chloroquine sensitive and resistant strains of P. falciparum were cultured in vitro and synchronized cultures of ring, trophozoite and schizont stage rich cells along with the uninfected control erythrocytes were assayed for 2,3-DPG activity and osmotic fragility. It was observed that in both the strains, in infected erythrocytes the 2,3-DPG activity gradually decreased and osmotic fragility gradually increased as the parasite matured from ring to schizont stage. The decrease in 2,3-DPG may probably be due to increased pyruvate kinase activity of parasite origin, which has been shown in erythrocytes infected with several species of Plasmodium. The absence of compensatory increase in 2,3-DPG in P. falciparum infected erythrocytes may aggravate hypoxia due to anaemia in malaria and probably may contribute to hypoxia in cerebral malaria. As 2,3-DPG was not found to be increased in erythrocytes parasitized with P. falciparum, the increased osmotic fragility observed in these cells is not due to increased 2,3-DPG as has been suggested in visceral leishmaniasis.

2,3-Diphosphoglycerate↗

PubMed2002

Seroepidemiological study of toxoplasmosis in different sections of population of Union Territory of Chandigarh.

Infections with Toxoplasma gondii in humans are usually asymptomatic or in the form of mild febrile illness. Primary infection in pregnant women may result in congenital toxoplasmosis while infection in immunocompromised subjects like AIDS patients may cause potentially fatal toxoplasma encephalitis. In India, only a few studies in hospital based patients have shown prevalence of toxoplasmosis to be between 1.5 and 21%. No field study involving general population is available. The present study investigates the prevalence of toxoplasmosis in subjects from rural, urban and urban slum populations of Union Territory, Chandigarh. Serum samples from 500 subjects from each group were collected and antitoxoplasma IgM and IgG was detected by conventional micro ELISA technique using soluble Toxoplasma gondii tachyzoite antigen. Overall 5.4% subjects were positive for IgM while 4.66% showed IgG antitoxoplasma antibodies. Amongst the three groups, significantly higher number of subjects in slum area (7.8%) showed IgM antibodies as compared to urban and rural areas (4.2% each). There was no significant difference in IgG positivity between three study areas. Prevalence of T. gondii specific IgG antibodies was significantly higher amongst females of both slum (7.31%) and rural area (8.44%) as compared to the males (2.85% and 3.27% respectively) in the same areas (p<0.05) and also to females of the urban area (2.98%, p<0.05). Prevalence of IgM antibodies was significantly higher (p<0.05) in females in the slum area (10.5%) as compared to females in the urban area (2.55%). In both urban and slum areas, highest IgM seropositivity was observed in age group 6-12 years (10% and 13.3% respectively), while in the rural area the highest IgM seropositivity was seen in the age group > or = 5 years (17.7%). These data indicate that majority of children are exposed to toxoplasma before 12 years of age and particularly in rural areas higher number of subjects acquire Toxoplasma gondii infection early in childhood probably as a result of higher exposure due to farming, poor hygiene and handling of animals.

Adolescent↗

PubMed1999

Comparative evaluation of methods of malaria parasite density determination in blood samples from patients & experimental animals.

Three methods for the quantitation of parasitaemia in malaria were compared with the standard method for ascertaining the accuracy in patients, Plasmodium berghei infected mice and P. knowlesi infected Rhesus monkeys. Technique I, where parasitaemia was calculated from the number of PRBCs in 10,000 RBCs in thin blood film and the total RBC count of the host, was used as the standard. Technique II, where parasitaemia was calculated based on the number of PRBCs per WBC and average total WBC count (8000/microliter), was least accurate. Technique IV, where parasitaemia was calculated from the number of PRBCs per oil immersion field (OIF) of microscope and the estimated amount of blood in one OIF of a thick smear, was most accurate when parasitaemia was low as in malaria patients and experimental animals with < 1 per cent parasitaemia. In mice with moderate parasitaemia (5-10%) and in falciparum malaria cases (with 3-7% parasitaemia) also technique IV was most accurate. In both animal models showing high (15-25%) and in monkeys with moderate parasitaemia, technique III based on the number of PRBCs per WBC and actual total WBC count, was the most accurate. Thus, technique IV being simpler and cost effective, with standardization of the amount of blood used in making a thick smear, may be used routinely for quantitation of parasitaemia.

Animals↗

PubMed1997

Biochemical changes induced by malarial parasites.

The morbidity associated with malaria plays a key role in the staggering of the social and economic development of human race. The investigations on the cellular, biochemical and molecular organisation of the malarial parasite are important to understand the host parasite interactions in a better way. The parasite induces several biochemical and biophysical alterations in the host red cells. It is well recognized that cation homeostasis is vital to basic aspects of cell functions. Though the pathogenesis of anaemia associated with Plasmodium falciparum infection is multifactorial, the complex mechanisms involving the role of oxidant stress and calcium imbalance of infected red cells plays an important role.

Animals↗

PubMed1995

Plasmodium falciparum: role of activated blood monocytes in erythrocyte membrane damage and red cell loss during malaria.

The role of Plasmodium falciparum and blood monocytes in the erythrocyte damage and pathogenesis of anemia has been investigated using two strains of the parasite; one laboratory-established strain (FSJ-M) and one wild, fresh, clinical isolate (PfPGI). Peripheral blood monocyte-induced growth inhibition of the parasites, erythrocyte membrane lipid peroxidation as seen by the formation of lipid peroxide products, and sensitivity to peroxide hemolysis at atmospheric oxygen were evaluated. The growth inhibition of FSJ-M by activated blood monocytes was greater than that of PfPGI. The extent of lipid peroxidation and sensitivity to hemolysis increased significantly as the parasites matured. These adverse effects were more marked following exposure to activated monocytes, especially in synchronized, parasitized RBCs. In addition, uninfected erythrocytes within the PfPGI parasite culture revealed a significant increase in the lipid peroxide formation (P < 0.01) and susceptibility to lysis (P < 0.05) under similar oxidant stress induced by monocytes from normal healthy donors. Furthermore, there was a direct correlation between membrane lipid peroxidation and peroxide hemolysis, both before and after monocyte exposure, suggesting a primary role of membrane peroxidation in red cell lysis. The contribution of intraerythrocytic parasites and nonspecific activation of blood monocytes in the pathophysiology of erythrocyte damage and anemia of P. falciparum infection is discussed.

Adult↗

PubMed1994

Plasmodium falciparum and blood monocyte induced abnormalities in human erythrocyte cation homeostasis.

The role of Plasmodium falciparum and activated blood monocytes in bringing about erythrocyte membrane lipid peroxidation and in altering the enzyme activity associated with Ca2+ and K+ efflux was studied. An attempt was made to investigate the role of parasite and monocyte-mediated reactive oxygen species (ROS) in inhibiting Ca(2+)-Mg2+ ATPase and Na(+)-K+ ATPase in order to find out the cause of reported high intra-erythrocytic calcium and depleted potassium levels in parasitized erythrocytes (PRBC). The PRBC showed enhanced lipid peroxidation as indicated by increased malonyldialdehyde (MDA) formation which coincided with the maturity of the parasite. This was further enhanced following exposure of PRBC to activated blood monocytes. The Ca(2+)-Mg2+ ATPase activity was decreased as the parasite matured and was further hampered significantly in mature parasite-infected red cells exposed to activated blood monocytes. There was a good negative correlation between MDA formation and Ca(2+)-efflux from red blood cells suggesting the negative influence of ROS on Ca(2+)-efflux. The Na(+)-K+ ATPase activity did not reveal any significant change, both during parasite maturation as well as upon exposure to ROS from activated monocytes. We therefore suggest that inhibition of Ca(2+)-efflux and the resulting increased cytosolic Ca2+ in PRBC might have a role in structural and functional abnormalities of red blood cell, thus enhancing the red cell loss during P. falciparum infection.

Animals↗

PubMed1994

Increased glutathione cycling and vitamin E of P. falciparum infected erythrocytes fail to prevent spontaneous haemolysis.

In an attempt to understand the pathogenesis of anaemia in Plasmodium falciparum infection, the status of erythrocyte glutathione and vitamin E content in relation to the susceptibility of infected red cells to peroxide haemolysis was examined. Synchronized cultures of the parasite with either ring-, trophozoite or schizont-infected red cells showed a gradual increase in the reduced glutathione content which was significantly higher (p < 0.05) in schizont-infected cells. Trophozoite-infected cells revealed significant increase in oxidized glutathione (p < 0.01) suggesting an increase in glutathione utilization during active erythrocytic schizogony of the parasites. The membrane antioxidant vitamin E also showed an increased accumulation in trophozoite- and schizont-infected red cells (p < 0.05) but not in the uninfected or ring-infected erythrocytes. Despite a favourable change in these antioxidants, the infected as well as uninfected red cells from parasite cultures showed enhanced peroxide haemolysis (uninfected, p < 0.05; ring-rich, p < 0.05, trophozoite- and schizont-rich, p < 0.001). The study provided direct evidence for enhanced susceptibility of red cells to lysis, including those of uninfected cells exposed to parasite products. This might explain the cause for much higher red cell loss and anaemia during P. falciparum infection than all the infected cells put together.

Animals↗

PubMed1993

Effect of nifedipine on oxidative damage of erythrocytes in Plasmodium berghei-infected mice.

It is known that the calcium channel blocker (CCB), nifedipine, can inhibit phagocyte oxidative burst in Plasmodium berghei-infected mice. The extent of immunopathological changes as seen by the course of infection and membrane lipid peroxidation in nifedipine-treated mice was examined in comparison with untreated mice at different parasite loads. The glutathione antioxidant system was also studied in these animals to assess its capacity to neutralize reactive oxygen species (ROS) in infected erythrocytes. The survival period of nifedipine-treated, infected mice decreased significantly. It was observed that the accumulation of reduced glutathione was greater and the decrease in glutathione peroxidase activity was less marked in drug-treated animals, suggesting better protection of the parasites against oxidative injury. The accumulation of the lipid peroxidation product, malonyldialdehyde was significantly lower in nifedipine-treated animals at all parasitemia levels studied, indicating decreased ROS generation and parasite damage. These observations reveal the shortcomings of using CCB to reverse the chloroquine resistance in malaria as this would minimize oxidative damage of parasitized red cells and phagocyte-mediated parasite killing.

Animals↗

PubMed1993

Effect of nifedipine on calcium status and chemiluminescence response of phagocytes during Plasmodium berghei infection in mice.

The macrophages and neutrophils from nifedipine-treated mice, both Plasmodium berghei-infected and uninfected, showed suppressed capacity to generate oxygen free radicals as compared with untreated controls. Nifedipine treatment did not affect resting state free calcium levels in these cells. But the rise in intracellular calcium levels of macrophages and neutrophils following P. berghei infection was significantly less (P < 0.05) in nifedipine-treated mice as compared with untreated groups at various parasitaemia levels. Probably this reflects a more potent effect of nifedipine on these cells in the depolarized state. Similarly, the rise in intracellular calcium levels of these cells following formyl-Met-Leu-Phe (fMLP) stimulation was also significantly less in nifedipine-treated groups than in untreated controls at different parasitaemia levels. A positive correlation between this fMLP-stimulated rise in calcium levels and the chemiluminescence response of macrophages and neutrophils was observed in nifedipine-treated and untreated groups at various parasitaemia levels. Thus the respiratory-burst responses of these cells during P. berghei infection depend on the calcium homeostasis in the cells. The disturbances of the calcium-regulating mechanisms by nifedipine treatment resulted in subnormal phagocytic cell responses which lead to more severe and rapidly fatal P. berghei infection in these animals.

Amino Acid Sequence↗

PubMed1993

Altered course of Plasmodium berghei infection by nifedipine treatment.

The effect of nifedipine (a calcium channel blocker) on the course of P. berghei infection was examined. It was observed that mice receiving a daily dose of 0.015 mg/kg of nifedipine had significantly shorter prepatent, patent and survival periods as compared to untreated P. berghei-infected animals (p < 0.001). This shows that the calcium channel blockers, in addition to possessing the property of reversing drug resistance during combined therapy with chloroquine, may also alter the pathophysiology of malaria infection. The decreased resistance of the host to the invading parasite suggests that the effect of CCB on the host-parasite interaction in human malaria needs to be investigated further before CCB can be used in combination with chloroquine for the treatment of chloroquine-resistant malaria or for chemoprophylaxis.

Animals↗