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Biomedical subjects

D K Bhattacharya

Publications and source records attributed to D K Bhattacharya.

At least 19 recordsLinked to original sources
PubMed2005

Pest control through viral disease: mathematical modeling and analysis.

This paper deals with the mathematical modeling of pest management under viral infection (i.e. using viral pesticide) and analysis of its essential mathematical features. As the viral infection induces host lysis which releases more virus into the environment, on the average 'kappa' viruses per host, kappain(1,infinity), the 'virus replication parameter' is chosen as the main parameter on which the dynamics of the infection depends. We prove that there exists a threshold value kappa(0) beyond which the endemic equilibrium bifurcates from the free disease one. Still for increasing kappa values, the endemic equilibrium bifurcates towards a periodic solution. We further analyse the orbital stability of the periodic orbits arising from bifurcation by applying Poor's condition. A concluding discussion with numerical simulation of the model is then presented.

Agriculture↗
PubMed2002

The activity of superoxide dismutase in hydroxyurea-treated E beta thalassemia.

AIM: To study the activity of superoxide dismutase (SOD) and the level of fetal hemoglobin (HbF) in hydroxyurea (HU)-treated E beta thalassaemia. METHODS: We have measured SOD level, HbF, mean corpuscular volume (MCV), packed cell volume (PCV) and hemoglobin (Hb) of E beta thalassaemia treated with HU (dose 30 mg/kg/day) for consecutive 90 days. RESULT: The increase of HbF synthesis without increase of Hb was observed in HU-treated patients. CONCLUSION: The decreased SOD level in long term and low dose of HU therapy in E beta thalassaemia may have some role to inhibit superoxide radical of erythrocyte. HU may act as inhibitor for oxidative damage of red cell in E beta thalassaemia.

Adolescent↗
PubMed2001

Splenectomy and splenic slice grafting in the management of thalassemia.

Over the last decade and a half, we performed a splenectomy along with slice grafting of the spleen in 170 (beta28 and Ebeta 142) transfusion-dependent, high-risk thalassemic patients. Of these, 17 were selected for study of the fate of the grafts and their immune status before and after operation. The procedure had equally good advantages of splenectomy and immunoconservation as partial splenectomy, partial splenic embolization, or partial splenic dearterialization, if not better, but none of the disadvantages of the other procedures.

Child↗
PubMed2001

O-acetyl sialic acid specific IgM in childhood acute lymphoblastic leukaemia.

Initial studies have revealed an enhanced surface expression of O-acetylated sialoglycoconjugates (O-AcSGs) on lymphoblasts concomitant with high titres of IgG in childhood Acute Lymphoblastic Leukaemia (ALL) (Mandal C, Chatterjee M, Sinha D, Br J Haematol 110, 801-12, 2000). In our efforts to identify disease specific markers for ALL, we have affinity-purified IgM directed against O-AcSGs that reacts with three disease specific O-AcSGs present on membrane proteins derived from peripheral blood mononuclear cells (PBMC) of ALL patients. Antibody specificity towards O-AcSGs was confirmed by selective binding to erythrocytes bearing surface O-AcSGs, decreased binding with de-O-acetylated BSM and following pretreatment with O-acetyl esterase. Competitive inhibition ELISA demonstrated a higher avidity of IgM for O-AcSG than IgG. Flow cytometry demonstrated the diagnostic potential of purified O-AcSA IgM as binding was specific with ALL patients and minimal with other haematological disorders and normal individuals. It therefore may be adopted as a non-invasive approach for detection of childhood ALL. Taken together, the data indicates that carbohydrate epitopes having terminal O-AcSA alpha2 --> 6 GalNAc determinants induce disease specific IgG and IgM, potentially useful molecular markers for childhood ALL.

Antibody-Dependent Cell Cytotoxicity↗
PubMed2001

Molecular characterization of hereditary persistence of foetal haemoglobin mutation by restriction fragment length polymorphism mapping.

Characterization of hereditary persistence of foetal haemoglobin (HPFH) mutation in a family from West Bengal, India, was carried out by analysing the structure of the 5'-Ggamma-Agamma-psibeta-delta-beta-3' globin gene region by using the restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR) technique. The HPFH in this family was due to a deletion in the beta-globin gene cluster spanning at least from the Hin cII/5' psibeta to the Hin fI/3' beta RFLP site. This work indicates the importance of RFLP-PCR technique in characterization of the HPFH mutation.

Adolescent↗
PubMed2000

Identification and purification of cytolytic antibodies directed against O-acetylated sialic acid in childhood acute lymphoblastic leukemia.

Sialic acids typically present as terminal sugars of oligo-saccharides are reported to be modified by O-acetylation at the C-9 position on lymphoblasts of childhood acute lymphoblastic leukemia (ALL) patients (Sinha et al., 1999a, Leukaemia, 13, 119-125). We now report high titers of IgG antibodies directed against O-acetylated derivatives of sialic acids (O-AcSA) in serum of ALL patients. These antibodies were purified using bovine submaxillary mucin (BSM) and the IgG distribution was confined to IgG(1)and IgG(2)subclasses; their binding was totally abolished with de-O-acetylation confirming their specificity towards O-AcSA determinants. Flow cytometry demonstrated binding of these antibody fractions to peripheral blood mononuclear cells (PBMC) of both T- and B-ALL patients having increased cell surface 9-O-AcSA determinants. Western blotting of membranes derived from PBMC of ALL patients confirmed binding of the antibody to O-acetylated sialoglycoconjugates corresponding to 144, 135, 120, 90, and 36 kDa whereas binding to PBMC from normal individuals corresponded to 144 and 36 kDa. Specificity of the antibody fraction towards 9-O-AcSA was substantiated by hemagglutination and hemagglutination-inhibition assays. The antibody purified from ALL serum selectively mediates complement dependent cytolysis of lymphoblasts expressing O-AcSAs and thereby possibly confers passive protection. The enhanced anti O-AcSA antibody levels allowed for development of a serodiagnostic assay (BSM-ELISA) specific for ALL. Minimal crossreactivity was observed with other hematological disorders like acute myeloid leukemia (n = 16), chronic myeloid leukemia (n = 6), chronic lymphocytic leukemia (n = 7) and non-Hodgkin's lymphoma (n = 3) as well as normal healthy individuals (n = 28). The BSM-ELISA therefore provides a simple, noninvasive alternative diagnostic approach for ALL and merits clinical consideration.

Acetylation↗
PubMed1999

Development of a simple, blood based lymphoproliferation assay to assess the clinical status of patients with acute lymphoblastic leukemia.

Although childhood acute lymphoblastic leukemia (ALL) is highly responsive to chemotherapy, reliable techniques are needed to determine treatment outcome and predict relapse. Employing a 9-O-acetyl sialic acid binding lectin, ATN(H), we have identified two 9-O-acetylated sialogycoconjugates (9-OAcSGs) as novel biomarkers expressed selectively on leukemic blasts of ALL patients. Presently, we report a non-invasive, blood based lymphoproliferation assay, which employs the maximal lymphoproliferative dose of ATN(H) (MLD) to assess the status of 9-OAcSGs with progressive therapy. A low MLD (0.18 +/- 0.01 microg) in untreated patients reflects increased expression of 9-OAcSGs which decline following therapy (MLD = 2.10 +/- 0.60 microg), persist during maintenance therapy (MLD = 4.50 +/- 1.60 microg)/follow-up (MLD = 5.50 +/- 0.85 microg) and are re-induced with relapse (MLD = 0.25 +/- 0.01 microg). Since the assay detects lymphoblasts with a sensitivity of 10(-4), shows no cross-reactivity with other hematological disorders (n = 48) and has been tested in 212 patients, it meets clinical consideration.

Child↗
PubMed1999

A colorimetric assay to evaluate the chemotherapeutic response of children with acute lymphoblastic leukemia (ALL) employing achatininH: a 9-O-acetyl sialic acid binding lectin.

Employing a 9-O-acetyl sialic acid binding lectin, Achatinin(H) (ATNH), we have reported a non-invasive, blood based lymphoproliferation assay which measures the maximal lymphoproliferative dose (MLD) of ATN(H) to assess the status of 9-O-acetylated sialoglycoconjugates (9-OAcSGs) in patients with Acute lymphoblastic leukemia (ALL) (Mandal C, Sinha D, Sharma V, Bhattacharya DK. O-acetyl sialic acid binding lectin, as a probe for detection of subtle changes on the cell surface induced during acute lymphoblastic leukemia [ALL] and its clinical application. Ind J Biochem Biophys 1997;34:82; Sinha D, Mandal C, Bhattacharya DK. Development of a simple blood based lymphoproliferation assay to assess the clinical status of patients with acute lymphoblastic leukemia. Leuk Res 1999;13:309-312; Sinha D, Mandal C, Bhattacharya DK. A novel method for prognostic evaluation of childhood acute lymphoblastic leukemia. Leukemia 1999;13[in press]). Although the expression of 9-OAcSGs clearly serves as an index of treatment outcome, the assay has limitations in that it requires radioisotopes, i.e. [3H]-TdR. Therefore a colorimetric assay was developed as an alternative approach. The pre-treatment MLD, as measured by the colorimetric assay, was 0.15 +/- 0.02 microg which progressively increased during consolidation therapy (1.40 +/- 0.39 microg), maintenance therapy (4.20 +/- 1.60 microg) and in followed-up cases (5.20 +/- 0.43 microg) but sharply declined following relapse (0.25 +/- 0.02 microg). The colorimetric assay also showed a good correlation with radiometric assay (r = + 0.93) and their mean coefficient of inter-assay precision were also comparable (15.53% versus 14.86%). We therefore propose that the colorimetric assay is a safe, non-radiometric, user-friendly alternative for assessing individual chemotherapeutic responses in childhood ALL.

Acetylation↗
PubMed1999

Identification of 9-O acetyl sialoglycoconjugates (9-OAcSGs) as biomarkers in childhood acute lymphoblastic leukemia using a lectin, AchatininH, as a probe.

Neoplastic transformation causes changes in cell surface architecture, most notably, aberrant sialylation. Exploiting the restricted specificity of a 9-O acetyl sialic acid (9-OAcSA) binding lectin, AchatininH (ATN(H)), we have identified two 9-O acetyl sialoglyconjugates (9-OAcSGs) on lymphoblasts of 87 children suffering from acute lymphoblastic leukemia (ALL). The preferential binding of ATN(H) to lymphoblasts induces their 11-fold increased agglutination (81 +/- 7.8%) compared to peripheral blood mononuclear cells (PBMC) of normal donors (8 +/- 4.3%) which corroborates with flow cytometry studies. Agglutination of MOLT-4 (87 +/- 4.8%), a lymphoblastoid cell line and MDCK (91.25 +/- 0.01%), a cell line expressing surface 9-OAcSA, confirms the preferential binding of ATN(H) to lymphoblasts through their surface 9-OAcSGs. Furthermore, fluorometric quantitation reveals a 4.6-fold increase in % of 9-OAcSA on lymphoblasts of ALL patients (42.1 +/- 4.1%) compared to normal donors (9.2 +/- 3.4%). Western blotting confirms that ATN(H) recognizes two membrane sialoglycoconjugates, of MW 120 kDa and 90 kDa, both having 9-OAcSA alpha2 --> 6 GalNAc terminal sugar moiety as their lectinogenic epitope. We propose that these 9-OAcSGs may serve as biomarkers for detection and monitoring of lymphoblasts in ALL and accordingly merit therapeutic considerations.

Agglutination Tests↗
PubMed1999

The prevalence of antiphospholipid antibodies in cases of recurrent pregnancy loss.

Antiphospholipid antibodies (aPL) are a diverse family of autoantibodies reactive against negatively charged phospholipid-protein complexes. The clinically significant members include lupus anticoagulant (LA), anticardiolipin antibody (aCL) and reaginic antibodies causing biological false positive (BFP) venereal disease laboratory test (VDRL). Although detected in various clinical scenarios, unexplained fetal loss in women of reproductive age group is the commonest association. Fifty pregnant women of first and second trimester with a history of two or more unexplained pregnancy losses were studied for the presence of LA, aCL and reaginic antibodies. Thirty pregnant women of the same trimester without any history of fetal loss were taken as control. LA was detected in nine (18%) cases and aCL in 12 (24%) cases of the study group. The control group was negative for any autoantibody. The prevalence of aPL in the study group found to be statistically significant. Detection of aPL must be considered in women with previous pregnancies complicated by unexplained fetal wastage.

Abortion, Habitual↗
PubMed1997

The occurrence of beta-thalassemia mutation and its interaction with hemoglobin E in the eastern India.

The distribution of variant hemoglobin in India has been related to various ethnic groups among other factors. beta-Thalassemia is the most frequent monogenic disorder in the country. Analysis of hemoglobin of 435 cases from Eastern India was performed by electrophoresis and by other quantitative methods. Analysis of the beta-globin gene of 112 cases used ARMS (amplification refractory mutation system)-PCR (polymerase chain reaction) techniques showing that IVS-1 nt 5 (G-->C) is the most prevalent mutation in populations from Eastern India. IVS-1 nt 5 (G-->C) interacts with the codon 26 (G-->A) mutation to produce E beta-thalassemia phenotype in the samples from West Bengal, India.

Hemoglobin E↗
PubMed1997

Image contrast of biological materials in high-voltage electron microscopy.

A new and simple expression has been formulated for the estimation of contrast of amorphous specimens in the tilted-beam mode of dark-field (DF) imaging in a high-voltage electron microscope. DF contrasts have been calculated for AIDS1.DNA, Salmonella typhimurium DNA, human haemoglobin and myoglobin of sperm whale in the range 0.1-3.0 MV and compared with the corresponding bright-field (BF) contrasts. DF contrast is seen to be significantly greater than BF contrast for a wide range of microscope apertures (alpha) and voltages (phi). The ratio of DF to BF contrast was observed to increase with increasing phi and alpha for all the aforesaid specimens.

DNA↗
PubMed1997

Image contrast of biological macromolecules in electron microscopy under accelerated voltage.

Image contrast in the tilted beam mode of dark field (DF) imaging with a conventional transmission electron microscope has been estimated theoretically for two well-known biological macromolecules viz. lambda-phage DNA and BSA precursor protein. The DF contrast for electron accelerating voltage 0.1 to 3.0 MV has been compared with the corresponding bright field (BF) contrast. The DF contrast is seen to be so overwhelmingly greater than the BF contrast, for a wide range of accelerating voltage (phi) and aperture (alpha), that even an unstained bio-macromolecule should become visible under high voltage DF imaging.

DNA, Viral↗
PubMed1996

Bionomic equilibrium of two-species system. I.

The concept of bionomic equilibrium is used to obtain limits of cost per unit effort and maximum value of effort for the joint harvesting of three types of two-species system: (1) a logistic growth model of two ecologically independent species, (2) a logistic growth model of two species that have competitive interactions, and (3) a Lotka-Volterra model of one prey and one predator. In each case, the existence of feasible bionomic equilibrium points and that of partially feasible bionomic equilibrium points are considered separately. First it is shown that cost per unit effort has both upper and lower threshold values if feasible bionomic equilibrium points occur, whereas it has only the upper threshold values if partially feasible bionomic equilibrium points occur. Further, the threshold values depend solely on the catchability coefficients, the selling prices of unit biomasses, and the parameters of the given model, namely the biotic potentials, carrying capacities, etc. Next, it is proven that for the first type of feasible point, if the cost per unit effort is kept under proper threshold values, then corresponding to each such value, the maximum value of the efforts exerted can be calculated in terms of the given parameters only. Moreover, the set of all such maximum values of the efforts for different choices of cost per unit effort is always bounded and the supremum of these maximum efforts is independent of the choice of cost per unit effort.

Animals↗