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Biomedical subjects

G Biswas

Publications and source records attributed to G Biswas.

At least 19 recordsLinked to original sources
PubMed2006

Instability and dynamics of thin viscoelastic liquid films.

The instability, rupture, and subsequent growth of holes in a thin Jeffreys-type viscoelastic film under the influence of long-range van der Waals force are investigated using both linear stability analysis and nonlinear numerical solutions. The linear stability analysis of full governing equations valid for arbitrary wave numbers shows that although fluid rheology does not influence the dominant length scale of the instability, it significantly affects the growth rate. It is shown that neglect of inertia and solvent dynamics results in a nonphysical singularity in the growth rate beyond a critical value of relaxation time. We further carry out numerical simulations of a set of long-wave, nonlinear differential equations (also derived in Rauscher et al., Eur. Phys. J. E 17, 373 (2005)) governing the evolution of the free surface. The nonlinear simulations, in their domain of validity, confirm the results of the linear analysis. Interestingly, results from nonlinear simulations further show that both for Newtonian and viscoelastic liquids, the shape and the dewetting dynamics of a hole are identical when examined in terms of a rescaled time which depends on rheological parameters. Thus, viscoelasticity of Jeffreys type merely accelerates the growth rate, without however affecting the important morphological characteristics.

Computer Simulation↗
PubMed2006

Controlling lymphatic filariasis and soil-transmitted helminthiasis together in South Asia: opportunities and challenges.

Lymphatic filariasis (LF) and the major soil-transmitted helminth (STH) infections are co-endemic in many countries, particularly in Asia. Control strategies for both groups of infections have increasingly focused on the use of mass chemotherapy. With the use of albendazole, there is now a tool that is common to both. However, there are also important differences in their modes of transmission and epidemiology, and, as a result, in the overall control strategies. The Global Programme for the Elimination of Lymphatic Filariasis aims to eliminate LF through time-limited mass drug administration programmes. Control activities for STH are more diffuse, aiming to piggy-back de-worming onto existing services, such as school health activities; controlling morbidity, rather than eliminating infection, is the stated goal. In order to maximize health benefits to communities that are endemic for one or both of these infections, it is vitally important that policy makers and programme managers have a clear understanding of both commonalities and differences, and implement control strategies that allocate available resources in an optimal manner.

Albendazole↗
PubMed2006

Primitive neuroectodermal tumor (PNET) as second malignancy after treatment of Hodgkin's disease.

Hodgkin's disease survivors are at an increased risk of developing second malignant neoplasms including secondary bone tumors. Common secondary bone tumors are osteogenic sarcoma and fibrosarcoma. Secondary primitive neuroectodermal tumor is extremely rare in this group. We present below, a rare case of secondary PNET in an 8-year-old child with Hodgkin's disease which developed unusually early outside the radiation portal and discuss potential factors responsible for its causation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2006

Rituximab (anti-CD20 monoclonal antibody) in lymphoproliferative malignancies: Tata Memorial experience.

Rituximab has been used extensively in lymphoproliferative disorders. We evaluated the results of 64 consecutive patients treated between 2001 and 2004 at our institution. This included 54 males and 10 females. The median age was 54 years (range 17 to 85 years). One-fourth of patients were above 60 years. The histology was aggressive NHL in 35, indolent NHL in 22 and 7 cases were diagnosed as CLL. Among NHL, sixteen were in early stage (I/II) and the remaining forty-one were in advanced stage (III/IV) of disease. B symptoms were present in 47% of cases. A total of 33 were de novo cases and 31 were previously treated. Rituximab monotherapy was used in 17 cases. Rituximab was used in combination with chemotherapy in the other 47 cases. Infusional toxicity included anaphylaxis in one, hypotension in one and minor infusional reactions in four others. The patient who developed anaphylaxis required discontinuation of further Rituximab. Growth factors were used in 25 patients. Febrile neutropenia occurred in 19 patients. The overall RR (CR + PR) was 72%. One patient had stable disease and progressive disease was documented in 17 patients. A total of seven patients died, three due to progressive disease, three due to chemotherapy related toxicity and one due to an unrelated cause. We conclude that Rituximab is a valuable addition to the treatment armamentarium of lymphoproliferative disorders.

Adolescent↗
PubMed2005

Metastatic gastric adenocarcinoma.

Gastrointestinal tumors represent less than 5% of all pediatric neoplasms. Within this subgroup carcinomas are rare, especially that of stomach. The authors present this rare entity with an equally rare presentation.

Adenocarcinoma↗
PubMed2005

Mechanism of mitochondrial stress-induced resistance to apoptosis in mitochondrial DNA-depleted C2C12 myocytes.

In this study, we show that partial mitochondrial DNA (mtDNA) depletion (mitochondrial stress) induces resistance to staurosporine (STP)-mediated apoptosis in C2C12 myoblasts. MtDNA-depleted cells show a 3-4-fold increased proapoptotic proteins (Bax, BAD and Bid), markedly increased antiapoptotic Bcl-2, and reduced processing of p21 Bid to active tBid. The protein levels and also the ability to undergo STP-mediated apoptosis were restored in reverted cells containing near-normal mtDNA levels and restored mitochondrial transmembrane potential. Inhibition of apoptosis closely correlated with sequestration of Bax, Bid and BAD in the mitochondrial inner membrane, increased Bcl-2 and Bcl-X(L), and inability to process p21 Bid. These factors, together with the reduced activation of caspases 3, 9 and 8 are possible causes of mitochondrial stress-induced resistance to apoptosis. Our results suggest that a highly proliferative and invasive behavior of mtDNA-depleted C2C12 cells is related to their resistance to apoptosis.

Apoptosis↗
PubMed2004

Amyloidosis complicating rhinophyma.

Rhinophyma is the advanced stage of acne rosacea and a source of embarrassment for the patient. Secondary localized cutaneous amyloidosis complicating rhinophyma is not reported in the literature. A patient with rhinophyma was treated by excision and primary closure. The histologic examination showed amyloidosis.

Adult↗
PubMed2002

The use of spatial analysis in mapping the distribution of bancroftian filariasis in four West African countries.

The geographical distribution of human infection with Wuchereria bancrofti was investigated in four West African countries (Benin, Burkina Faso, Ghana and Togo), using a commercial immunochromatographic test for filarial antigen. Efforts were made to cover each health-system implementation unit and to ensure no sampling point was >50 km from another, but otherwise the 401 study communities were selected at random. The aim was to enable spatial analysis of the data, to provide a prediction of the overall spatial relationships of the infection. The results, which were subjected to an independent random validation in Burkina Faso and Ghana, revealed that prevalence in the adult population of some communities exceeded 70% and that, over large areas of Burkina Faso, community prevalences were between 30% and 50%. Most of Togo, southern Benin and much of southern Ghana appeared completely free of the infection. Although there were foci on the Ghanaian coast with prevalences of 10%-30%, such high prevalences did not extend into coastal Togo or costal Benin. The prevalence map produced should be useful in prioritizing areas for filariasis control, identifying potential overlap with ivermectin-distribution activities undertaken by onchocerciasis-control programmes, and enabling inter-country and sub-regional planning to be initiated. The results indicate that bancroftian filariasis is more widely distributed in arid areas of Burkina Faso than hitherto recognized and that the prevalences of infection have remained fairly stable for at least 30 years. The campaign to eliminate lymphatic filariasis as a public-health problem in Africa will require significantly more resources (human, financial, and logistic) than previously anticipated.

Adolescent↗
PubMed2001

Evolutionarily divergent electron donor proteins interact with P450MT2 through the same helical domain but different contact points.

We have investigated the sites of N-terminally truncated cytochrome P4501A1 targeted to mitochondria (P450MT2) which interact with adrenodoxin (Adx), cytochrome P450 reductase (CPR) and bacterial flavodoxin (Fln). The binding site was mapped by a combination of in vitro mutagenesis, in vivo screening with a mammalian two-hybrid system, spectral analysis, reconstitution of enzyme activity and homology-based structural modeling. Our results show that part of an aqueous accessible helix (putative helix G, residues 264-279) interacts with all three electron donor proteins. Mutational studies revealed that Lys267 and Lys271 are crucial for binding to Adx, while Lys268 and Arg275 are important for binding to CPR and FLN: Additive effects of different electron donor proteins on enzyme activity and models on protein docking show that Adx and CPR bind in a non-overlapping manner to the same helical domain in P450MT2 at different angular orientations, while CPR and Fln compete for the same binding site. We demonstrate that evolutionarily divergent electron donor proteins interact with the same domain but subtly different contact points of P450MT2.

Adrenodoxin↗
PubMed2001

Mitochondria-to-nucleus stress signaling induces phenotypic changes, tumor progression and cell invasion.

Recently we showed that partial depletion of mitochondrial DNA (genetic stress) or treatment with mitochondrial-specific inhibitors (metabolic stress) induced a stress signaling that was associated with increased cytoplasmic-free Ca(2+) [Ca(2+)](c). In the present study we show that the mitochondria-to-nucleus stress signaling induces invasive phenotypes in otherwise non-invasive C2C12 myoblasts and human pulmonary carcinoma A549 cells. Tumor-specific markers cathepsin L and transforming growth factor beta (TGFbeta) are overexpressed in cells subjected to mitochondrial genetic as well as metabolic stress. C2C12 myoblasts subjected to stress showed 4- to 6-fold higher invasion through reconstituted Matrigel membrane as well as rat tracheal xenotransplants in Scid mice. Activation of Ca(2+)-dependent protein kinase C (PKC) under both genetic and metabolic stress conditions was associated with increased cathepsin L gene expression, which contributes to increased invasive property of cells. Reverted cells with approximately 70% of control cell mtDNA exhibited marker mRNA contents, cell morphology and invasive property closer to control cells. These results provide insights into a new pathway by which mitochondrial DNA and membrane damage can contribute to tumor progression and metastasis.

Animals↗