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Biomedical subjects

P Das

Publications and source records attributed to P Das.

At least 55 records · Page 3Linked to original sources
PubMed2001

Entamoeba histolytica trophozoites activated by collagen type I and Ca(2+) have a structured cytoskeleton during collagenase secretion.

A peculiar characteristic of Entamoeba histolytica trophozoites is their capacity to invade human tissues. One of the cellular determinants of invasion may include adhesion to extracellular matrix components such as collagen, induction, and secretion of electron-dense granules (EDG) and tissue digestion. The mechanism and receptors involved in this process are not well understood. Previous results suggested that cytoskeleton plays a very important role during EDG secretion. We present evidence suggesting that adhesion to collagen and activation of EDG secretion are integrin-dependent events, since beta1 subunits detected by antibodies are concentrated at membrane sites where collagen and actin were colocalized. Furthermore, the involvement of actin, vimentin, and tubulin in restructuring cytoskeleton during EDG secretion was evident, since cytoskeleton isolation was possible exclusively in activated cells. Studies of immunolocalization of tubulin, actin, and vimentin by immunofluorescence and transmission electron microscopy suggest a role for cytoskeleton in EDG secretion.

Actins↗
PubMed2001

Expression and purification of recombinant Giardia fibrillarin and its interaction with small nuclear RNAs.

Giardia lamblia, the ancient eukaryote does not have nucleolus but produces the fibrillarin protein that may be used for pre-rRNA processing. The nucleoli of eukaryotes contain complex population of small nucleolar RNAs, known as snoRNAs, several of which are required for rRNA processing. This report describes the full-length cloning of fibrillarin gene from Giardia lamblia, using RTPCR and the production of recombinant fibrillarin protein in Escherichia coli strain BL21 (DE3) as N-terminal His-tag protein. The condition for production of soluble protein was standardized. The expressed protein was purified by using Ni-chelation chromatography and used for functional studies. The small nuclear RNAs (snRNAs), RNA D, RNA J, and RNA H, containing box C, box D, and box C/D, respectively, of Giardia were also cloned by RTPCR. Antibody raised against the recombinant protein was used to identify the fibrillarin in giardial nuclear extract. The interaction of snRNAs with recombinant fibrillarin was followed using North-Western hybridization. Gel electrophoresis mobility shift assay demonstrated that bacterially expressed protein may participate in the in vitro interaction with RNA J, RNA H, and RNA D. Our results indicate that the recombinant fibrillarin by itself is able to bind and does not require the involvement of any other protein for this binding to the three snRNAs.

Animals↗
PubMed2001

Isolation of aflatoxigenic strains of Aspergillus and detection of aflatoxin B1 from feeds in India.

In a preliminary study, 256 feed samples collected from different parts of Northern India were examined for the presence of aflatoxigenic strains of Aspergillus favus/parasiticus and for detection of Aflatoxin B1 (AFB1). Out of 198 A. flavus and 15 A. parasiticus strains isolated, 76% and 86% respectively, were found to be toxigenic. Aflatoxin B1 content of these feeds, as estimated by thin layer chromatography (TLC) and enzyme linked immunosorbent assay (ELISA) were very high (average 0.412+/-0.154 ppm) in comparison to the permissible Indian regulation level (0.03 ppm). Seasonal variation of incidence and level of toxin in feed was recorded and it was high during monsoon/post monsoon period.

Aflatoxin B1↗
PubMed2001

Genomic organisation of the approximately 1.5 Mb Smith-Magenis syndrome critical interval: transcription map, genomic contig, and candidate gene analysis.

Smith-Magenis syndrome (SMS) is a multiple congenital anomalies/mental retardation syndrome associated with an interstitial deletion of chromosome 17 involving band p11.2. SMS is hypothesised to be a contiguous gene syndrome in which the phenotype arises from the haploinsufficiency of multiple, functionally-unrelated genes in close physical proximity, although the true molecular basis of SMS is not yet known. In this study, we have generated the first overlapping and contiguous transcription map of the SMS critical interval, linking the proximal 17p11.2 region near the SMS-REPM and the distal region near D17S740 in a minimum tiling path of 16 BACs and two PACs. Additional clones provide greater coverage throughout the critical region. Not including the repetitive sequences that flank the critical interval, the map is comprised of 13 known genes, 14 ESTs, and six genomic markers, and is a synthesis of Southern hybridisation and polymerase chain reaction data from gene and marker localisation to BACs and PACs and database sequence analysis from the human genome project high-throughput draft sequence. In order to identify possible candidate genes, we performed sequence analysis and determined the tissue expression pattern analysis of 10 novel ESTs that are deleted in all SMS patients. We also present a detailed review of six promising candidate genes that map to the SMS critical region.

Abnormalities, Multiple↗
PubMed2001

Heavy metal and nutrient concentration in soil and plants growing on a metalliferous chromite minespoil.

Metal contamination in soil and plant samples from a chromite mine and its adjoining regions was determined. The metal concentration varied in stem, leaf and root of different tree species. In the case of shrubs, the highest concentration of iron (18.5 mg kg(-1) was detected in the stem of Combretum roxburghii. The concentration of aluminium varied from 1.8 - 5.3 mg kg(-1) dry weight, whereas the nickel content was found to be the highest in the stem of Calotropis gigantea. In the case of herbs, chromium concentration was highest (60.9 mg kg(-1) dry weight) in Evovulus alsenoides and the lowest (18.8 mg kg(-1) dry weight) in Andrographis paniculata. There was a significant correlation observed between chromium in soil with the root of tree species like Lagerstroemia parviflora, Madhuca longifolia, Anogeissus latifolia and Haldina cordyfolia. Nickel in soil was significantly correlated with the stem and leaf of all the tree species except Chlroxylon sweitenta. Iron in soil showed correlation with the stem and leaf of Chloroxylon sweitenia. Among the shrubs (Calotropis gigantea, Combretum roxburghii and Smilax zeylancia), chromium in soil showed a correlation with the root. Nickel in soil was positively correlated with the stem and leaf of Calotropis gigantea and Combretum roxburghii. Among the herbs, chromium in the whole plant of Evolvulus alsenoids, Solanum surattense and Phyllanthus fraternus showed significant positive correlation with soil; nickel in Solanum surattense showed significant positive correlation with soil. The positive correlation coefficient was observed between iron in the whole plant and soil on Phyllanthus virgatus, Phyllanthus fraternus and Andrographis paniculata. The above information would be useful for the establishment of a vegetation cover on the minewaste heaps.

Chromium↗
PubMed2001

Nipah virus infection among abattoir workers in Malaysia, 1998-1999.

BACKGROUND: An outbreak of encephalitis primarily affecting pig farmers occurred during 1998-1999 in Malaysia and was linked to a new paramyxovirus, Nipah virus, which infected pigs, humans, dogs, and cats. Because five abattoir workers were also affected, a survey was conducted to assess the risk of Nipah infection among abattoir workers. METHODS: Workers from all 143 registered abattoirs in 11 of 13 states in Malaysia were invited to participate in this cross-sectional study. Participants were interviewed to ascertain information on illness and activities performed at the abattoir. A serum sample was obtained to test for Nipah virus antibody. RESULTS: Seven (1.6 %) of 435 abattoir workers who slaughtered pigs versus zero (0%) of 233 workers who slaughtered ruminants showed antibody to Nipah virus (P = 0.05). All antibody-positive workers were from abattoirs in the three states that reported outbreak cases among pig farmers. Workers in these three states were more likely than those in other states to have Nipah antibody (7/144 [4.86%] versus 0/291 [0%], P < 0.001) and report symptoms suggestive of Nipah disease in pigs admitted to the abattoirs (P = 0.001). CONCLUSIONS: Nipah infection was not widespread among abattoir workers in Malaysia and was linked to exposure to pigs. Since it may be difficult to identify Nipah-infected pigs capable of transmitting virus by clinical symptoms, using personal protective equipment, conducting surveillance for Nipah infection on pig farms which supply abattoirs, and avoiding handling and processing of potentially infected pigs are presently the best strategies to prevent transmission of Nipah virus in abattoirs.

Abattoirs↗
PubMed2000

Development, expression, and murine testing of a multistage Plasmodium falciparum malaria vaccine candidate.

A synthetic gene encoding twelve B cell epitopes, six T-cell proliferative epitopes, and three cytotoxic T lymphocyte (CTL) epitopes from nine stage-specific antigens, representing the sporozoite, liver stage, asexual blood-stage, and sexual-stage antigens of Plasmodium falciparum, was constructed by assembling overlapping oligonucleotides followed by PCR extension and annealing. A three-step PCR protocol using twelve long oligonucleotides was employed to generate a 1053 base-pair synthetic gene, the identity of which was confirmed by sequencing. This synthetic gene, named CDC/NII MAL VAC-1, was cloned, and the recombinant protein was expressed in the Baculovirus Expression Vector System (BEVS). The selection of malarial epitopes for inclusion in this vaccine construct was based on immunoepidemiological studies in malaria endemic area, in vitro, and in vivo protection studies in model systems. The 41 kDa BEVS-expressed recombinant protein reacted with mouse antibodies specific for individual B cell epitopes in the vaccine construct and with sera from clinically immune Kenyan adults. An immunization study in three strains of mice that differ at the H-2 locus demonstrated that the BEVS-expressed recombinant protein is immunogenic; the candidate vaccine antigen induced high titer antibodies, and lymphocyte proliferative and IFN-gamma responses. These results demonstrate that individual B and T cell epitopes can be assembled to create synthetic genes that encode proteins capable of eliciting specific antibody and T cell responses.

Adult↗
PubMed2000

PCR detection of Giardia lamblia in stool: targeting intergenic spacer region of multicopy rRNA gene.

A PCR based detection that amplifies the 552-bp intergenic spacer (IGS) region of multicopy rRNA gene of Giardia lamblia and 320-bp internal sequences to first PCR product has been used in diagnosis of giardiasis in stool sample. The primers were found highly specific to Giardia spp. only, because no amplification was observed with DNAs from other enteric pathogens like Escherichia coli, Shigella dysenteriae and Entamoeba histolytica. The test could detect even less than 2 pg of genomic DNA from Giardia trophozoites. In direct diagnosis of Giardia lamblia in stool samples, it was observed that PCR amplification of IGS followed by nested PCR could enhance the sensitivity and specificity of the tests manifold and the system was able to detect as low as 10 parasites in 100 microl of stool. The comparative evaluation of the present system with conventional microscopy, CIEP and ELISA in the diagnosis of giardiasis from diarrhoeic stool samples and control subjects demonstrated a 100% correlation among nested PCR, microscopic examination and ELISA in patients suggestive of giardiasis (Group I) and control subjects (Group II). In Group I cases (patients suffering from other than giardiasis), CIEP, ELISA and nested PCR showed better results than microscopic examination. However, among them, PCR was found most sensitive and specific because 20% positivity was noticed by PCR whereas CIEP and ELISA showed only 7.14% and 12.85%, respectively. Break-up results showed that all the samples which were positive by CIEP or ELISA, also found positive by PCR. The present observation clearly suggests the use of PCR that amplifies the intergenic spacer region of multicopy rRNA gene of Giardia lamblia followed by nested PCR for routine, quick and reliable detection of Giardia lamblia in stool samples.

Animals↗
PubMed2000

Effects of chromium and nickel on germination and growth in tolerant and non-tolerant populations of Echinochloa colona (L.) Link.

The tolerance of populations of a grass, Echinochloa colona, growing abundantly on chromite minewaste dumps, was tested in two separate experiments. Seed-based experiments indicate that the populations growing naturally on uncontaminated sites, germinated better in nutrient solutions without metal than those collected from minewaste dumps. Metal tolerance indices were greater in the plant populations derived from metal contaminated sites and better growth of these plants was noted on mine spoil soil-mix in the ratio of 1:1; the percentage of seed germination and the rate of seedling growth, however, declined in a soil compost containing 25% mine spoil and 75% uncontaminated (control) soil. Populations of Echinochloa colona occurring naturally on chromite mine spoils, therefore, appear to have developed metal tolerance. It is maintained by a balanced and stable genetic system built up and adjusted by natural selection. Such material is very suitable to be used in restoration work designed to produce an effective vegetation cover to improve the derelict land and to reduce erosion. This finding might be useful in revegetation programmes on metalliferous minewastes.

Chromium↗
PubMed2000

Complementation between specific HLA-DR and HLA-DQ genes in transgenic mice determines susceptibility to experimental autoimmune encephalomyelitis.

To investigate the contribution of human leukocyte antigen (HLA) class II molecules in susceptibility to inflammatory demyelination, we induced experimental autoimmune encephalomyelitis (EAE) in transgenic (tg) mice expressing the HLA-DR3, HLA-DQ8 and HLA-DQ6 molecules in the absence of endogenous class II (Ab(o)). Following immunization with mouse myelin, HLA-DR3 tg mice mounted strong T-cell proliferative responses, and developed inflammatory lesions and demyelination in the central nervous system with mild to moderate clinical symptoms of EAE. HLA-DQ8 and HLA-DQ6 tg mice elicited weak T-cell proliferative responses and did not develop clinical symptoms of EAE. HLA-DR3/DQ6 double tg mice immunized with mouse myelin experienced clinical disease similar to the single tg HLA-DR3 tg mice, indicating that expression of DQ6 in this line had no effect on disease. In contrast, HLA-DR3/DQ8 double tg mice developed severe inflammatory lesions and clinical disease in response to immunization with mouse myelin. Our data suggest that in the presence of two susceptible class II alleles, namely HLA-DR3 and DQ8, there is additional selection and expansion of potential autoreactive T cells, resulting in enhanced severity of disease.

Animals↗
PubMed2000

In vitro manipulation and propagation of medicinal plants.

Well developed techniques are currently available to help growers meet the demand of the pharmaceutical industry in the next century. These protocols are designed to provide optimal levels of carbohydrates, organic compounds (vitamins), mineral nutrients, environmental factors (e.g. light, gaseous environment, temperature, and humidity) and growth regulators required to obtain high regeneration rates of many plant species in vitro and thereby facilitate commercially viable micropropagation. Well-defined cell culture methods have also been developed for the production of several important secondary products. An overview of the regeneration of medicinal plants by direct and indirect organogenesis and by somatic embryogenesis from various types of explants is presented, and the use of these techniques combined with other biotechnological approaches to improve medicinal plants through somaclonal variation and genetic transformation is reviewed.

Journal Article↗