Biomedical subjects

P K Das

Publications and source records attributed to P K Das.

At least 19 recordsLinked to original sources

PubMed2002

Genetic variability of the human filarial parasite, Wuchereria bancrofti in South India.

The genetic variability of the lymphatic filarial parasite Wuchereria bancrofti, from three localities (one urban and two rural areas) in southern India, endemic for filariasis was studied using random amplified polymorphic DNA (RAPD) markers. The RAPD profiles were generated for 21 parasite populations (7 populations from each area), using a 10-mer random primer. The analysis of profiles indicated the existence of considerable genetic variability among parasite populations. The Nei's gene diversity between the individual populations in the 2 areas (one urban and another rural) was comparatively greater (0.3372+/-0.1462 & 0.2830+/-0.1764) than that of populations in another village (0.0490+/-0.1373). The greater genetic diversity among the former areas may be due to human migration, endemicity for long time and drug (diethyl-carbamazine citrate) pressure unlike the populations of latter village where the filariasis is relatively a recent introduction and which was never under active chemotherapy. The Nei's genetic distance was estimated and the phylogenetic tree was constructed using 'UPGMA'. These analyses indicated the prevalence of at least two genetically distinct clusters, among the populations studied, their maximum genetic distance being 0.2444. The finding of two genetic 'variants' of W. bancrofti, in the present study, may have important implications in filariasis epidemiology and control/elimination programmes.

Animals↗

PubMed2002

Aberrant expression of complement regulatory proteins, membrane cofactor protein and decay accelerating factor, in the involved epidermis of patients with vitiligo.

BACKGROUND: Vitiligo is a pigmentary disorder of the skin characterized by the complete absence of melanocytes from the lesion. Complement-activating antimelanocyte antibodies have been implicated in vitiligo pathogenesis. As membrane regulators of complement activation, membrane cofactor protein, decay accelerating factor and CD59 protect cells from elimination by autologous complement, their absence or downregulation on melanocytes may be associated with autoantibody and complement-mediated melanocyte destruction in vitiligo. OBJECTIVES: We studied the expression of these regulatory proteins in non-lesional, perilesional and lesional vitiligo skin compared with those of control specimens. METHODS: We used immunohistochemistry to study the expression of the regulatory proteins, and flow cytometric analysis of cultured melanocytes to investigate possible constitutive changes in the expression levels of these molecules. We also investigated whether melanocytes can influence keratinocyte susceptibility to autologous complement by regulating keratinocytic decay accelerating factor and membrane cofactor protein expression levels. RESULTS: Immunohistochemical data showed that expression of membrane cofactor protein and decay accelerating factor in whole epidermis was lower in lesional and perilesional skin in comparison with non-lesional skin. The reduced in situ expression appeared to be specific to vitiligo. However, coculture experiments indicated that melanocytes do not influence keratinocyte susceptibility to autologous complement. Further, flow cytometric analysis of cultured melanocytes convincingly demonstrated that non-lesional vitiligo and control melanocytes have comparable decay accelerating factor, membrane cofactor protein and CD59 expression levels. CONCLUSIONS: It is therefore concluded that there is no constitutive melanocyte defect per se that could be related to the in vivo expression of these molecules in vitiligo. Nevertheless, the present data suggest that both keratinocytes and melanocytes in the involved vitiliginous whole epidermis express lower levels of decay accelerating factor and membrane cofactor protein compared with controls that could render them more vulnerable to autologous complement attack.

Antigens, CD↗

PubMed2001

GOA, a novel gene encoding a ring finger B-box coiled-coil protein, is overexpressed in astrocytoma.

Serial analysis of gene expression (SAGE) was used to identify a gene named GOA (gene overexpressed in astrocytoma), which codes for a novel Ring finger B-box coiled-coil (RBCC) protein. Northern blot hybridization showed overexpression of GOA in 9 of 10 astrocytomas. Except for kidney, in which high expression was found, expression levels in normal tissues were low and comparable to normal brain. Immunohistochemistry demonstrated presence of GOA, with prominent nuclear staining, in astrocytoma tumor cells and astrocytes of fetal brain, but virtual absence in mature astrocytes. Overexpression was not due to amplification, since amplification of GOA was only found in one of 65 astrocytomas. GOA was localized to 17q24-25, a region that is frequently gained or amplified in a number of other tumor types. GOA contains two LXXLL motifs, which are thought to be important for nuclear receptor binding. Our data suggest an important role of GOA in the process of dedifferentiation that is associated with astrocytoma tumorigenesis and possibly with that of other tumor types as well.

Amino Acid Motifs↗

PubMed2001

Successful therapy of lethal murine visceral leishmaniasis with cystatin involves up-regulation of nitric oxide and a favorable T cell response.

The virulence of Leishmania donovani in mammals depends at least in part on cysteine proteases because they play a key role in CD4(+) T cell differentiation. A 6-fold increase in NO production was observed with 0.5 microM chicken cystatin, a natural cysteine protease inhibitor, in IFN-gamma-activated macrophages. In a 45-day BALB/c mouse model of visceral leishmaniasis, complete elimination of spleen parasite burden was achieved by cystatin in synergistic activation with a suboptimal dose of IFN-gamma. In contrast to the case with promastigotes, cystatin and IFN-gamma inhibited the growth of amastigotes in macrophages. Although in vitro cystatin treatment of macrophages did not induce any NO generation, significantly enhanced amounts of NO were generated by macrophages of cystatin-treated animals. Their splenocytes secreted soluble factors required for the induction of NO biosynthesis, and the increased NO production was paralleled by a concomitant increase in antileishmanial activity. Moreover, splenocyte supernatants treated with anti-IFN-gamma or anti-TNF-alpha Abs suppressed inducible NO generation, whereas i.v. administration of these anticytokine Abs along with combined therapy reversed protection against infection. mRNA expression and flow cytometric analysis of infected spleen cells suggested that cystatin and IFN-gamma treatment, in addition to greatly reducing parasite numbers, resulted in reduced levels of IL-4 but increased levels of IL-12 and inducible NO synthase. Not only was this treatment curative when administered 15 days postinfection, but it also imparted resistance to reinfection. These studies provide a promising alternative for protection against leishmaniasis with a switch of CD4(+) differentiation from Th2 to Th1, indicative of long-term resistance.

Animals↗

PubMed2001

An automated method for the quantification of immunostained human Langerhans cells.

Allergic contact dermatitis is a frequent and increasing health problem. For ethical reasons, the current animal tests used to screen for contact sensitizers should be replaced by in vitro alternatives. Contact sensitizers have been shown to accelerate Langerhans cell (LC) migration from human organotypic skin explant cultures (hOSECs) more rapidly than non-sensitizers and it has been proposed that the hOSEC model could be used to screen for sensitizers. However, chemically induced decreases in epidermal LC numbers need to be accurately quantified if the alterations in epidermal LC numbers are to form the basis of an alternative system for screening contact sensitizers in vitro. As manual counting of LCs is labour intensive and subject to intra- and inter-personal variation we developed an image analysis routine, using the Leica QWin image analysis software, to quantify LCs in situ using immunohistochemically stained skin sections. LCs can be identified using antibodies against the membrane molecule CD1a or the Lag antibody, which recognises cytoplasmic Birbeck granules. Quantification of epidermal LC number using the image analysis software had a much lower inter-person variation than when the same specimens were counted manually, using both the anti-Lag and CD1a antibodies. The software-aided quantification of epidermal LCs provides an accurate method for measuring chemically-induced changes in LC numbers.

Antigens, CD1↗

PubMed2001

A symbiotic concept of autoimmunity and tumour immunity: lessons from vitiligo.

Vitiligo is a skin disease in which melanocytes (MCs) are eradicated from lesional epidermis, resulting in disfiguring loss of pigment. MCs are destroyed by MC-reactive T cells, as well as other non-immune and immune components. Similarities exist between the autoimmunity observed in vitiligo and the tumour immunity observed in melanoma immuno-surveillance. An analysis of these mechanisms might lead to the development of new therapies for both vitiligo and melanoma.

Autoimmunity↗

PubMed2001

Towards elimination of lymphatic filariasis in India.

The global initiatives to eliminate lymphatic filariasis as a public health problem by the year 2020 have generated a great deal of debate in India, the largest endemic country. This has led to a shift in the focus from control to elimination of the disease. Although the campaign to eliminate filariasis has begun, much more needs to be done. Several recent research studies have provided an insight into various operational issues and prospects of elimination of lymphatic filariasis. In this article, the current scenario, recent research results, logistics and the prospects of eliminating lymphatic filariasis in India will be discussed.

Animals↗

PubMed2001

Effectiveness of community and health services-organized drug delivery strategies for elimination of lymphatic filariasis in rural areas of Tamil Nadu, India.

Lymphatic filariasis (LF) is targeted for global elimination. Repeated annual single-dose mass treatment with antifilarials has been recommended as the principal strategy to achieve LF elimination. This requires an effective and sustainable strategy to deliver the drug, diethylcarbamazine (DEC), to communities. In this study, a new drug delivery strategy - community-directed treatment (comDT) - was developed and implemented and its effectiveness compared with that of the traditional health services-organized drug delivery, in rural areas of Tamil Nadu, India. Qualitative and quantitative data showed that the communities and health services were able to distribute the drug in almost all villages. The drug distribution rate and treatment compliance rate of comDT and health services treatment were statistically compared after adjusting them for clustering. Under the comDT 68% (n=20 villages; range: 0-97%) of the population received DEC, compared with 74% (n=20 villages; range: 48-95%) with the health services treatment strategy (P > 0.05). However, only about 53% (range: 0-91%) of comDT recipients and 59% (range: 32-79%) of those who received DEC from the health services consumed the drug (P > 0.05). Although statistically not significant, the distribution and compliance rates were lower under the comDT strategy. Also, the strategy's operationalization appears to be difficult because of some social factors, and the tradition of communities' dependence on health services for treatment, whereas health services-organized distribution was much less cumbersome and found to be more acceptable to people. However, the distribution (74%) and compliance rates (59%) achieved by health services were also only moderate and may not be adequate to eliminate LF in a reasonable time frame. Health services manpower alone may not be sufficient to distribute the drug. We conclude that drug distribution by health services is the best option for India and participation of the community volunteers and village level government staffs in the programme is necessary to effectively distribute the drug and attain the desirable levels of treatment compliance to eliminate LF.

Adolescent↗

PubMed2001

Differential expression of functional guanylyl cyclases in melanocytes: absence of nitric-oxide-sensitive isoform in metastatic cells.

Nitric oxide (NO) is a reactive endogenous molecule with multiple functions and its cellular signaling activity is mainly mediated by activation of the soluble isoform of guanylyl cyclase, a heterodimeric (alpha/beta) hemeprotein. The expression of the NO-sensitive soluble isoform of guanylyl cyclase was studied in various cultured melanocytic cells by measuring the accumulation of guanosine 3',5'-cyclic monophosphate in the presence and absence of NO donors. Here we report that 3-morpholino-sydnonimine, a donor of NO redox species, and (Z)-1-[2- (2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate, a direct NO donor, induced a 20-fold increase in intracellular guanosine 3',5'-cyclic monophosphate in nonmetastatic melanoma cells and normal melanocytes in culture that could be related to cellular melanin content in a concentration-dependent manner. The increased intracellular guanosine 3',5'-cyclic monophosphate was due to stimulation of the activity of soluble guanylyl cyclase as such increase was completely abolished by using a specific inhibitor of soluble guanylyl cyclase. The involvement of functional soluble guanylyl cyclase was further confirmed by the presence of alpha1 and beta1 subunits in these cells at both mRNA and protein levels. In contrast, none of the NO donors induced guanosine 3',5'-cyclic monophosphate production in metastatic melanoma cells, which could be attributed to the absence of the beta1 subunit that is essential for catalytic activity of the soluble isoform of guanylyl cyclase. Metastatic melanoma cells produced higher levels of intracellular guanosine 3',5'-cyclic monophosphate in response to natriuretic peptides than other cell types, however, due to upregulation of membrane-bound guanylyl cyclase activities, but they are less pigmented or unpigmented. The present finding suggests that NO signaling in association with melanogenesis is dependent on the soluble isoform of guanylyl cyclase, whereas absence of soluble guanylyl cyclase but the presence of membrane-bound guanylyl cyclase correlates with the metastatic behavior of melanoma cells.

Animals↗

PubMed2001

Role of 67 kDa cell surface laminin binding protein of Leishmania donovani in pathogenesis.

The role that interaction with laminin may play in Leishmania donovani infection was investigated. Binding of (125)I-radiolabeled laminin, in a liquid-phase assay, by the parasite was rapid, saturable, specific, reversible, and of high affinity. Using a Western blotting procedure, a 67 kDa laminin-binding protein (LBP) was identified from the membrane of both the promastigote and amastigote forms of L. donovani. Subsequently, the protein was purified by affinity chromatography. Immunofluorescence with a polyclonal antibody against LBP as well as flow cytometric analysis demonstrated its presence at the parasite surface. After stimulation with phorbol-12-myristate-13-acetate (PMA), U937 cells exhibited the ability to adhere to laminin and LBP specifically inhibited this adhesion. The reduced parasite adhesion after tunicamycin treatment suggested the importance of sugar residues in cell adhesion. Although co-administration of either laminin or LBP or anti LBP antibody reduced parasite virulence, resulting in a lower level of infection in the BALB/c mouse model, an in vitro macrophage culture-enhanced level of infection was observed in the case of laminin-coated parasites. The results collectively suggest a role for LBP in the interaction of the parasite with extracellular matrix elements, which may constitute a basis for the homing of the parasite to its physiological address.

Animals↗

PubMed2001

Distribution of ABO and Rh-D blood groups among blood donors in a tertiary care centre in South India.

The distribution of ABO and Rh-D blood groups was studied among 150,536 blood donors screened at the Dr John Scudder Memorial Blood Bank, Christian Medical College Hospital, Vellore, over a period of 11 years (April 1988 to March 1999). The most common blood group was found to be group O [58,330 (38.75%)], followed by group B [49,202 (32.69%)], and group A [28,372 (18.85%)]. The least common blood group was AB group [7,930 (5.27%)]. A2 or A2B groups were found in 3.01% and 1.43% of donors, respectively. The prevalence of Rh-D negative group was found in 8,225 (5.47%) donors. Bombay group (H negative non-secretor, genotype hh phenotype Oh) was found in six donors (0.004%). Although the incidence of Rh-D negative group was identical to previously published data from North India, the most common blood group was O group in our study as opposed to B group.

ABO Blood-Group System↗

PubMed2001

Quantifying mosquito biting patterns on humans by DNA fingerprinting of bloodmeals.

A major debate in infectious disease epidemiology concerns the relative importance of exposure and host factors, such as sex and acquired immunity, in determining observed age patterns of parasitic infection in endemic communities. Nonhomogeneous contact between hosts and vectors is also expected to increase the reproductive rate, and hence transmission, of mosquito-borne infections. Resolution of these questions for human parasitic diseases has been frustrated by the lack of a quantitative tool for quantifying the exposure rate of people in communities. Here, we show that the polymerase chain reaction (PCR) technique for amplifying and fingerprinting human DNA from mosquito bloodmeals can address this problem for mosquito-borne diseases. Analysis of parallel human and mosquito (resting Culex quinquefasciatus) samples from the same households in an urban endemic focus for bancroftian filariasis in South India demonstrates that a 9-locus radioactive short-tandem repeat system is able to identify the source of human DNA within the bloodmeals of nearly 80% of mosquitoes. The results show that a person's exposure rate, and hence the age and sex patterns of exposure to bites in an endemic community, can be successfully quantified by this method. Out of 276 bloodmeal PCR fingerprints, we also found that on average, 27% of the mosquitoes caught resting within individual households had fed on people outside the household. Additionally, 13% of mosquitoes biting within households contained blood from at least 2 people, with the rate of multiple feeding depending on the density of humans in the household. These complex vector feeding behaviors may partly account for the discrepancies in estimates of the infection rates of mosquito-borne diseases calculated parasitologically and entomologically, and they underline the potential of this tool for investigating the transmission dynamics of infection.

Adolescent↗

PubMed2001

Oviposition attractancy of an infusion from a wood inhabiting fungus for vector mosquitoes.

BACKGROUND & OBJECTIVES: Review of literature indicates that none of the chemicals so far studied for oviposition attractancy was found to be promising for operational use. Efforts are being made to find an effective substance to corner a large number of ovipositing females to selective breeding sites for ease of control operation. This will reduce insecticidal consumption and will be cost-effective. This study is aimed to evaluate the oviposition attractancy of aqueous infusion from a wood inhabiting fungus (Polyporus spp.) for vector mosquitoes both in the laboratory and under field conditions. METHODS: An aqueous infusion (10%) was prepared by soaking 10 g of fungal powder in 100 ml of chlorine-free tap water. The mixture was shaken thoroughly and filtered through Whatman No. 1 filter paper. The filtered infusion was tested for oviposition attractancy against vector mosquitoes both in the laboratory and under field conditions. RESULTS: The laboratory study on the dose-effect relationship indicated that at an optimum concentration of 4 ppm, maximum attractancy was observed. Water treated with aqueous fungal infusion (AFI) at 4 ppm received significantly more egg rafts/eggs of vector mosquitoes than other substrates like rearing water, natural breeding water and tap water. Trials conducted in the field showed that mud pots treated with AFI placed in both indoor and outdoor locations received significantly more Aedes aegypti eggs than the control. Similarly, treated pots placed in paddy fields attracted significantly more gravid Anopheles subpictus for oviposition than untreated pots. In contrast, the number of egg rafts of Culex quinquefasciatus laid in AFI treated pots was significantly less than in the control ones owing to strong natural olfactory factors associated with the breeding habitat. INTERPRETATION & CONCLUSION: The results indicated that there is scope for developing a trap incorporating this oviposition attractant along with insect growth regulator(s) (IGR) for surveillance and/or control of Ae. aegypti and other vector mosquitoes breeding in paddy fields.

Animals↗

PubMed2001

Mucopolysaccharides from psyllium involved in wound healing.

Mucopolysaccharides derived from the husk of psyllium (Plantago ovata) have properties beneficial for wound cleansing and wound healing. Recent studies indicate that these mucopolysaccharides also limit scar formation. Our in vitro and in vivo studies aimed to investigate the mechanisms involved, e.g., fluid absorption, bacterial adherence and in vitro stimulatory effects on macrophages, which are pivotal in wound healing. The mucopolysaccharides contained in a sachet (Askina Cavity) or in a hydrocolloid mixture (Askina Hydro) were found to have a gradual and sustained absorbency over a period of 7 days, amounting to 4-6 times their weight in water. The swelling index was 9 mm after 312 h. Adherence of wound bacteria to the mucopolysaccharides started after 2 h and was more pronounced after 3 h. Semiquantitative measurements of bacterial adherence used centrifugation and subsequent optical density determinations of supernatant. These confirmed the strong adherence potential of psyllium particles. Lactic acid dehydrogenase staining of pretreated cultured human skin explants did not reveal toxicity of the mucopolysaccharides derived from psyllium husk. Langerhans' cell migration from the epidermis was negligible and interleukin-1 beta expression in the explants was not significant, supporting the very low allergenic potential of psyllium. The characteristics of mucopolysaccharide granulate derived from psyllium husk in Askina Cavity and Askina Hydro related to fluid absorption, bacterial adherence, biocompatibility, stimulation of macrophages, irritancy response and allergenicity showed an optimal profile, supporting the good clinical performance of wound healing products containing psyllium husk.

Absorption↗

PubMed2000

Efficacy of aqueous suspension and granular formulations of Bacillus thuringiensis (Vectobac) against mosquito vectors.

The efficacy of aqueous suspension (AS) and granular (G) formulation of Bacillus thuringiensis var. israelensis (Vectobac) was tested against the immatures of mosquito vectors in the laboratory and under field conditions. Laboratory tests showed that the aqueous suspension was relatively more effective against Culex quinquefasciatus than Aedes aegypti and Anopheles stephensi, the respective LC(50) values being 0.046, 0.060 and 0.190 mg/l. In stream pools, with the application of Vectobac AS at 1.2 l/ha, more than 80% reduction in immature density of Anopheles larvae (Anopheles fluviatilis and Anopheles culicifacies) was observed for 2-8 days, and at 2.4 l/ha for 3.5-9.0 days. At the dosage of 7.0 kg/ha of the granular formulation, a reduction in immature density by more than 80% was observed for 2-9 days. In polluted habitats such as cesspits, U-drains and cement tanks, the effectiveness of Vectobac AS lasted for 1-4 days when applied at 1.2 and 2.4 l/ha, and Vectobac G was effective for 1-3 days at application rates of 7. 0 and 14.0 kg/ha against C. quinquefasciatus. There was no significant difference in the effectiveness between the two formulations and the two application rates.

Aedes↗

PubMed2000

Micro-anatomy related antigen expression in melanocytic lesions.

The in situ expression of antigens associated with melanosomes (gp-100), pigmentation (PAA), tyrosinase (TRP-1), melanoma (MAA-1/MAA-2), and HLA-DR was investigated immunohistochemically in frozen archival specimens of common acquired melanocytic naevi, in dysplastic melanocytic naevi, and in lymph node metastases of melanoma. Expression of these antigens was also studied in established cultured normal human melanocytes, naevus-derived melanocytes and melanoma cell lines of varying metastatic potential, by immunohistochemistry and flow cytometry. Compared with normal melanocytes, melanocytic naevi exhibited increased expression of gp-100, PAA, and TRP-1 in the lesional cells at or very near the dermo-epidermal junction, but with diminishing expression towards the intra-dermal base of the lesions. In contrast, expression of MAA-1 and MAA-2 was observed in melanocytes throughout the dermal part of the naevi. Melanocytes located at the basal layer of the epidermis were positive only for gp-100, PAA, and TRP-1 antigens. Dysplastic melanocytic naevi showed staining of gp-100, PAA, TRP-1, HLA-DR, MAA-1, and MAA-2 of junctional lesional melanocytes, but less intense than that of common acquired naevi. These antigens were not detectable in the dermal part of the dysplastic naevi. Expression of these antigens in lymph node metastases of melanoma was either positive or negative. Similar results regarding antigen expression were observed in all cultured melanocytic cells, both by immunohistochemistry and by flow cytometry. The present data suggest that analysis of these antigens may contribute to the discrimination of common acquired melanocytic naevi from their dysplastic counterparts. Furthermore, variations in the levels of expression in naevi may be consistently related to the micro-anatomy of the lesions, indicating that the micro-environment may have an influence on the expression levels of these antigens in different lesional melanocytes.

Antigens, Neoplasm↗

PubMed2000

The economic burden of lymphatic filariasis in India.

Lymphatic filariasis affects 119 million people living in 73 countries, with India accounting for 40% of the global prevalence of infection. Despite its debilitating effects, lymphatic filariasis is given very low control priority. One of the reasons for this is paucity of information on the economic burden of the disease. Recent studies in rural areas of south India have shown that the treatment costs and loss of work time due to the disease are considerable. Based on the results of these studies, Kapa Ramaiah et al. here estimate the annual economic loss because of lymphatic filariasis for India and discuss the implications of their findings.

Adolescent↗

PubMed2000

Studies of solvation of ketocyanine dyes in homogeneous and heterogeneous media by UV/Vis spectroscopic method.

Solvation characteristics of ketocyanine dyes (I-VI) have been investigated in pure solvents and heterogeneous media by absorption and fluorescence studies. The dyes are good reporters of solvent polarity. In protic solvents they exist as equilibrium mixtures of bare and hydrogen-bonded form in the ground state (S0), the latter being the emitting species. In aprotic solvents of low polarity association of the S1 state of the dye takes place. In aqueous micellar media the dye resides at the micelle water interface. The binding constant for dye-micelle interaction has been determined. Fluorescence data in beta-cyclodextrine solution resemble that for that neutral micellar solution indicating that the interaction between the -OH group of the heterogeneous part (micelle/cyclodextrine cavity) and the carbonyl oxygen of the dye is important in both the cases.

Alkenes↗