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Biomedical subjects

J Basu

Publications and source records attributed to J Basu.

At least 37 records · Page 2Linked to original sources
PubMed1997

Erythrophagocytosis and its relation to band 3 clustering in chronic myelogenous leukemia.

Band 3, a major erythrocyte membrane glycoprotein, undergoes topographic redistribution leading to enhanced clustering, in chronic myelogenous leukemia (CML). This is probably due to the binding of heme compounds to the CML erythrocyte membrane resulting from depletion of cellular levels of reduced glutathione (GSH). Band 3 clustering appears to be one of the factors associated with increased erythrophagocytosis in CML.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1997

Characterization of a beta-lactamase from Mycobacterium smegmatis SN2.

Beta-lactamases have been reported to be largely responsible for beta-lactam resistance in Mycobacteria. We report the characterization of a cell-associated beta-lactamase from Mycobacterium smegmatis. The enzyme hydrolyzed the "beta-lactamase-stable" oximinocephalosporins. Nitrocefin was the best substrate. 6-Beta-iodopenicillanate, clavulanate and sulbactam were effective inhibitors, whereas the Ki value for aztreonam was high. From its substrate and inhibitor profile, the enzyme appeared to be a cephalosporinase of group 2e.

Amino Acid Sequence↗
PubMed1997

Involvement of a 43-kilodalton outer membrane protein in beta-lactam resistance of Shigella dysenteriae.

A beta-lactam-sensitive strain (C152) of Shigella dysenteriae showed two major outer membrane proteins (OMPs) with M(r)s of 43,000 and 38,000, while the clinical isolate M2 lacked the 43,000-Mr OMP, which acted as a channel for beta-lactam antibiotics. Permeability of beta-lactams across the outer membrane (OM) of M2 was lower than that across the OM of C152. Mutants deficient in the 43-kDa OMP could be selected in vitro from strain C152 in the presence of cefoxitin. All beta-lactam-resistant strains were sensitive to imipenem.

Anti-Bacterial Agents↗
PubMed1997

Dual multimodular class A penicillin-binding proteins in Mycobacterium leprae.

The ponA gene of cosmid L222 of the Mycobacterium leprae genome library encodes a multimodular class A penicillin-binding protein (PBP), PBP1. The PBP, labelled with a polyhistidine sequence, has been produced in Escherichia coli, extracted from the membranes with 3-[(3-cholamidopropyl)-dimethylammonio]-1-propane-sulfonate (CHAPS) and purified by Ni2(+)-nitrilotriacetic acid-agarose chromatography. In contrast to the pon1-encoded class A PBP1, PBP1 undergoes denaturation at temperatures higher than 25 degrees C, it catalyzes acyl transfer reactions on properly structured thiolesters, and it binds penicillin with high affinity.

Acylation↗
PubMed1996

Biochemical characterization of the 49 kDa penicillin-binding protein of Mycobacterium smegmatis.

The 49 kDa penicillin-binding protein (PBP) of Mycobacterium smegmatis catalyses the hydrolysis of the peptide or S-ester bond of carbonyl donors R1-CONH-CHR2-COX-CHR2-COO- (where X is NH or S). In the presence of a suitable amino acceptor, the reaction partitions between the transpeptidation and hydrolysis pathways, with the amino acceptor, behaving as a simple alternative nucleophile at the level of the acyl-enzyme. By virtue of its N-terminal sequence similarity, the 49 kDa PBP represents one of the class of monofunctional low-molecular-mass PBPs. An immunologically related protein of M(r) 52,000 is present in M. tuberculosis. The 49 kDa PBP is sensitive towards amoxycillin, imipenem, flomoxef and cefoxitin.

Amino Acid Sequence↗
PubMed1996

Altered membrane phospholipid organization and erythrophagocytosis in E beta-thalassemia.

The underlying cause behind the accelerated destruction of erythrocytes in the bone marrow and in the peripheral circulation, accompanying the beta-thalassemic syndromes is still not clearly understood. The present investigation demonstrates that increased phagocytosis of erythrocytes in E beta-thalassemia is inhibited by the presence of phosphatidylserine (PS) vesicles, suggesting a PS-'PS-receptor' type of interaction in premature recognition of these erythrocytes by macrophages. Increased exposure of both aminophospholipids phosphatidylethanolamine (PE) and PS was demonstrated by fluorescamine labeling and annexin binding, respectively. The slower rate of translocation of PS across the bilayer suggested that this contributed towards the increased exposure of PS in E beta-thalassemic erythrocytes.

Annexins↗
PubMed1996

Identification and overexpression in Escherichia coli of a Mycobacterium leprae gene, pon1, encoding a high-molecular-mass class A penicillin-binding protein, PBP1.

Cosmid B577, a member of the collection of ordered clones corresponding to the genome of Mycobacterium leprae, contains a gene, provisionally called pon1, that encodes an 821-amino-acid-residue high-molecular-mass class A penicillin-binding protein, provisionally called PBP1. With similar amino acid sequences and modular designs, M. leprae PBP1 is related to Escherichia coli PBP1a and PBP1b, bienzymatic proteins with transglycosylase and transpeptidase activities. When produced in E. coli, His tag-labelled derivatives of M. leprae PBP1 adopt the correct membrane topology, with the bulk of the polypeptide chain on the surface of the plasma membrane. They defy attempts at solubilization with all the detergents tested except cetyltrimethylammonium bromide. The solubilized PBP1 derivatives can be purified by affinity chromatography on Ni2+-nitrilotriacetic acid agarose. They have low affinities for the usual penicillins and cephalosporins.

Amino Acid Sequence↗
PubMed1996

Border-crossing adjustment and personal health care spending by state.

This article presents the results of a pioneering effort by the Health Care Financing Administration (HCFA) to measure interstate border crossing for services used by Medicare and non-Medicare beneficiaries. A major focus is to provide estimates of per capita expenditures by State for individual services. Such estimates are not possible without adjustment for interstate border-crossing flows. This is HCFA's first attempt to furnish a unified per capita personal health care expenditures data base comprising all services and covering total population. The study also analyzes interstate differences in expenditure flows by computing rates of inflow and outflow of expenditures, and highlights Medicare/non-Medicare flow differences.

Catchment Area, Health↗
PubMed1996

Plasma levels of beta-carotene, lycopene, canthaxanthin, retinol, and alpha- and tau-tocopherol in cervical intraepithelial neoplasia and cancer.

Epidemiological studies continue to identify an association of dietary antioxidant micronutrients in cancer prevention. A number of case-control and cohort studies have demonstrated a relationship between high intake of foods rich in carotenoids, tocopherols, and vitamin C with a reduced risk of certain human malignancies. The purpose of this study was to investigate the comparative plasma levels of a profile of known dietary antioxidants, namely, beta-carotene, lycopene, canthaxanthin, retinol, alpha-tocopherol, and tau-tocopherol. The target population was women with a histopathological diagnosis of cervical intraepithelial neoplasia (CIN) or cervical cancer and a control group. All women resided in the same catchment area (Bronx Borough, New York City) and were of similar inner-city socioeconomic backgrounds representing a fairly homogenous population group. A cross-sectional sample of 235 women was recruited with informed consent. Plasma nutrient levels were measured by reverse-phase high pressure liquid chromatography under study codes. The mean plasma levels of carotenoids (beta-carotene, lycopene, and canthaxanthin), as well as alpha-tocopherol, were significantly lower in women with CIN and cervical cancer. In contrast, the mean plasma level of tau-tocopherol was higher among patients with CIN, while the mean plasma level of retinol was comparable among the groups. There were significant linear trends for all three carotenoids and quadratic trends for alpha- and tau-tocopherol with the degree of cervical histopathology. Plasma beta-carotene concentrations in cigarette smokers were significantly lower regardless of cervical pathology, whereas plasma lycopene and canthaxanthin levels were significantly lower in smokers with CIN. The findings of a decrease in all plasma antioxidant nutrient levels except tau-tocopherol in women with CIN and cancer suggest a potential role for antioxidant deficiency in the pathogenesis of CIN and carcinoma of the cervix, which requires further investigation.

Adult↗
PubMed1995

Persistent genital human papillomavirus infection as a risk factor for persistent cervical dysplasia.

BACKGROUND: Cervical dysplasia, also referred to as squamous intraepithelial lesion (SIL) in cytology or cervical intraepithelial neoplasia in histopathology, is thought to have the potential to advance in progressive stages to cervical cancer. However, not all cases of SIL progress, and most of the mild lesions spontaneously regress. Factors that govern regression, persistence, and progression of SIL are poorly understood. PURPOSE: Our analysis sought to identify factors that determined persistence or regression of SIL. METHODS: Seventy subjects with histopathologically confirmed cervical dysplasia were followed at 3-month intervals for 15 months. At each visit, the cervix was evaluated by Pap smear and colposcopy, and exfoliated cervicovaginal cells were analyzed for human papillomavirus (HPV) DNA. For each subject, data from every two consecutive visits were grouped as a pair. Persistent SIL was considered present if a lesion was detected at a visit (t) as well as at the next visit (t + 1) and absent if a lesion was detected at visit t but not at visit t + 1. A statistical model for time-dependent data correlated persistent SIL with various risk factors. RESULTS: Age, ethnicity, education, sexual behavior, smoking, and the use of oral contraceptives did not correlate with persistent SIL. The risk of persistent SIL was associated with continual HPV infection in visits t and t + 1 (HPV positive by Southern blot analysis: odds ratio [OR] = 3.91, and 95% confidence interval [CI] = 1.58-9.65; HPV positive by polymerase chain reaction [PCR]: OR = 2.42, and 95% CI = 1.03-5.67) and a persistent high viral load (OR = 4.07, and 95% CI = 1.35-12.30). When typed by PCR, individuals with type-specific persistent infection in visits t and t + 1, and particularly those with a continual high viral load (OR = 4.97; 95% CI = 1.45-17.02), had the highest risk for persistent SIL compared with those with a low level of type-specific persistent infection or non-type-specific persistent infection. The presence of persistent HPV infection in visits t-1 (the preceding time interval) was also predictive of persistent SIL in visits t and t + 1, although the strength of association was weaker, suggesting that persistent HPV and SIL occur synchronously. CONCLUSION: HPV infection and its associated cervical lesions tend to occur concurrently, and type-specific persistent HPV infection, particularly with a high viral load, produces chronic cervical dysplasia. IMPLICATIONS: The natural history of genital HPV infection directly influences the prognosis of cervical dysplasia as measured by persistence of the lesion. Testing for HPV infection may be valuable in the clinical management of women with cervical dysplasia.

Adult↗
PubMed1995

Nutrient antioxidants in the pathogenesis and prevention of cervical dysplasias and cancer.

The role of nutritional factors in biochemical interactions that are part of an oncogenic process or inhibit free radical proliferation have attracted considerable interest in relation to molecular mechanism(s) and the natural history of human cancer. Epidemiologic and experimental studies have drawn attention to the association between dietary micronutrient deficiencies and the incidence of neoplastic and malignant lesions. In the last two decades, the role(s) of retinoids, carotenoids, tocopherols and water-soluble antioxidant vitamins, and allegations of anti-tumor properties in the daily dietary consumption of fresh fruits and green leafy vegetables, have captured the attention of an increasingly sensitive diet- and health care-conscious public, the biochemical community, and industrial food producers. Moreover, recent epidemiologic and compelling advances in molecular biology have linked the presence of restricted human papillomavirus (HPV) subtypes to cervical carcinoma and precursor lesions. In the present report, we identify and review measurable effects of dietary deficiencies of selected antioxidant micronutrients (i.e., beta-carotene and vitamins A, C, and E) and their association with known cervix cancer risk factors in the pathogenesis and potential prevention of cervix dysplasias, presumed to be the precursor lesions of cervix cancer.

Anticarcinogenic Agents↗
PubMed1995

Medicare spending by state: the border-crossing adjustment.

As the first step in a pioneering effort by the Health Care Financing Administration (HCFA) to measure interstate border crossing for services used by both Medicare and non-Medicare beneficiaries, the authors study the spending behavior of Medicare beneficiaries for 10 Medicare-covered services. Based on interstate flow-of-expenditure data developed for calendar year 1991, the authors analyze the spending patterns of State residents by studying the inflow and outflow rates and the netflow ratios of expenditures incurred by Medicare patients. The report also provides per capita expenditure estimates with residence-based adjustments and evaluates the impact of the border-crossing adjustment for individual services and States.

Catchment Area, Health↗
PubMed1995

Lipid profile in women with preeclampsia: relationship between plasma triglyceride levels and severity of preeclampsia.

It has been hypothesized that, in preeclampsia, hypertriglyceridemia may lead to increased endothelial triglyceride accumulation that, in turn, may result in endothelial cell damage. The purpose of our study was to determine whether hypertriglyceridemia is associated with the severity of preeclampsia. We studied 29 preeclamptic patients and 46 normal pregnant women, aged 15 to 35 years, with singleton pregnancies, at 28 to 37 weeks' gestation. Total cholesterol, low-density lipoprotein cholesterol, and triglyceride levels were measured enzymatically. High-density lipoprotein cholesterol was determined using a dextran sulfate-magnesium precipitation method. Patients with mild preeclampsia had a significant increase in plasma triglyceride levels (P < .001), while patients with severe preeclampsia had triglyceride levels comparable to controls. Our findings suggest that there is no direct relationship between triglyceride levels and severity of preeclampsia.

Adolescent↗
PubMed1994

Mycotin: a lectin involved in the adherence of Mycobacteria to macrophages.

Pathogenic Mycobacteria colonize host macrophages. Attachment of these organisms to macrophages is the preliminary step prior to invasion of the macrophages by the bacteria. Western blot confirmed that walls of Mycobacterium avium and Mycobacterium tuberculosis contain molecules which are immunologically related to mycotin, a lectin found in Mycobacterium smegmatis. We have demonstrated that the adherence of Mycobacteria to macrophages is significantly inhibited by anti-mycotin antibody or the mycotin-specific sugar, mannan. These observations suggest that prevention of the interaction of mycotin-related molecules on the surfaces of Mycobacteria with mannose-specific receptors on macrophages, offers an important approach for blocking attachment of pathogenic Mycobacteria to macrophages, thereby preventing infection.

Animals↗
PubMed1994

Human erythrocyte membrane protein 4.2 is palmitoylated.

Protein 4.2 is a major protein of the human erythrocyte membrane. It has previously been shown to be N-myristoylated. After labeling of intact human erythrocytes with [3H]palmitic acid, radioactivity was found to be associated with protein 4.2 by immunoprecipitation of peripheral membrane proteins extracted at pH 11 from ghosts with anti-(4.2) sera, followed by SDS/PAGE and fluorography. The fatty acid linked to protein 4.2 was identified as palmitic acid after hydrolysis of protein and thin-layer chromatography of the fatty acid extracted in the organic phase. Protein 4.2 could be depalmitoylated with hydroxylamine, suggesting a thioester linkage. Depalmitoylated protein 4.2 showed significantly decreased binding to protein-4.2-depleted membranes, compared to native protein 4.2.

Blood Proteins↗