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Biomedical subjects

S K Chaudhuri

Publications and source records attributed to S K Chaudhuri.

At least 19 recordsLinked to original sources
PubMed2002

Anaerobic biooxidation of Fe(II) by Dechlorosoma suillum.

Anaerobic microbial oxidation of Fe(II) was only recently discovered and very little is known about this metabolism. We recently demonstrated that several dissimilatory perchlorate-reducing bacteria could utilize Fe(II) as an electron donor under anaerobic conditions. Here we report on a more in-depth analysis of Fe(II) oxidation by one of these organisms, Dechlorosoma suillum. Similarly to most known nitrate-dependent Fe(II) oxidizers, D. suillum did not grow heterotrophically or lithoautotrophically by anaerobic Fe(II) oxidation. In the absence of a suitable organic carbon source, cells rapidly lysed even though nitrate-dependent Fe(II) oxidation was still occurring. The coupling of Fe(II) oxidation to a particular electron acceptor was dependent on the growth conditions of cells of D. suillum. As such, anaerobically grown cultures of D. suillum did not mediate Fe(II) oxidation with oxygen as the electron acceptor, while conversely, aerobically grown cultures did not mediate Fe(II) oxidation with nitrate as the electron acceptor. Anaerobic washed cell suspensions of D. suillum rapidly produced an orange/brown precipitate which X-ray diffraction analysis identified as amorphous ferric oxyhydroxide or ferrihydrite. This is similar to all other identified nitrate-dependent Fe(II) oxidizers but is in contrast to what is observed for growth cultures of D. suillum, which produced a mixed-valence Fe(II)-Fe(III) precipitate known as green rust. D. suillum rapidly oxidized the Fe(II) content of natural sediments. Although the form of ferrous iron in these sediments is unknown, it is probably a component of an insoluble mineral, as previous studies indicated that soluble Fe(II) is a relatively minor form of the total Fe(II) content of anoxic environments. The results of this study further enhance our knowledge of a poorly understood form of microbial metabolism and indicate that anaerobic Fe(II) oxidation by D. suillum is significantly different from previously described forms of nitrate-dependent microbial Fe(II) oxidation.

Aerobiosis↗
PubMed2001

Gamma-irradiated onions as a biological indicator of radiation dose.

Post-irradiation identification and dose estimation are required to assess the radiation-induced effects on living things in any nuclear emergency. In this study, radiation-induced morphological/cytological changes i.e., number of root formation and its length, shooting length, reduction in mitotic index, micronuclei formation and chromosomal aberrations in the root tip cells of gamma-irradiated onions at lower doses (50-2000 cGy) are reported. The capabilities of this biological species to store the radiation-induced information are also studied.

Cell Cycle↗
PubMed2001

Biogenic magnetite formation through anaerobic biooxidation of Fe(II).

The presence of isotopically light carbonates in association with fine-grained magnetite is considered to be primarily due to the reduction of Fe(III) by Fe(III)-reducing bacteria in the environment. Here, we report on magnetite formation by biooxidation of Fe(II) coupled to denitrification. This metabolism offers an alternative environmental source of biogenic magnetite.

Anaerobiosis↗
PubMed2000

Licania michauxii Prance root extract induces hsp 70 mRNA and necrotic cell death in cultured human hepatoma and colon carcinoma cell lines.

An extract of Licania michauxii Prance root was found to be cytotoxic to cultured human hepatoma (HepG2) and colon carcinoma (Caco-2) cells. Morphological and nuclear characteristics of treated cells were consistent with necrotic death. Increases in the chaperone protein hsp 70 and hsp 70 mRNA were dose dependent reaching peak mRNA levels (40-fold above control) at 6 h. Increases in nuclear localization of hsp 70 was also observed with treatment. Heat treatment of cells for 45 min to induce hsp 70 prior to treatment with the extract provided transient protection from the necrotic response.

Cell Death↗
PubMed2000

Flavonols from Heterotheca inuloides: tyrosinase inhibitory activity and structural criteria.

Tyrosinase inhibitory activity of flavonols, galangin, kaempferol and quercetin, was found to come from their ability to chelate copper in the enzyme. In contrast, the corresponding flavones, chrysin. apigenin and luteolin, did not chelate copper in the enzyme. The chelation mechanism seems to be specific to flavonols as long as the 3-hydroxyl group is free. Interestingly, flavonols affect the enzyme activity in different ways. For example, quercetin behaves as a cofactor and does not inhibit monophenolase activity. On the other hand, galangin inhibits monophenolase activity and does not act as a cofactor. Kaempferol neither acts as a cofactor nor inhibits monophenolase activity. However, these three flavonols are common to inhibit diphenolase activity by chelating copper in the enzyme.

Arnica↗
PubMed1999

Integrated approach to prediction of cervical intra-epithelial neoplasia status through a case-control study.

A case-control study on cervical intra-epithelial neoplasia (CIN) was carried out on 398 subjects in the state of West Bengal, India. These samples were taken from mass screening programs organized by the authors, maintaining the uniformity of sampling to the extent possible. The cervical smears were tested by the Papanicolaou (PAP) method, following the Bethesda system for reporting of CIN status. Odds ratios and correlation coefficients among different variables, assumed to produce carcinoma of the cervix, show that 6 out of 11 variables, i.e., age, education, socio-economic status, duration of marriage, age at marriage and body surface, are associated with CIN. Multivariate analysis of logistic regression was carried out using BMDP-LR with dichotomized response variables considering CIN (0 and 1) in one group and CIN (2 and 3) in the other group. The outcome of the analysis indicated that age and educational level are 2 contributing factors for CIN. The percentage of correct classification in this analysis has improved to 74.5%, with a probability of 0.90. Polychotomous regression analysis was carried out using BMDP-PR in the next step. This analysis showed that parity was a contributing factor, in addition to age and educational level. These 3 factors provide a predictive model for identifying the high-risk group in a rational way. This approach would restrict screening to approximately 10% of the population. Subsequently, the model has been validated in a confirmatory trial among 85 new cases and was found to work satisfactorily.

Adult↗
PubMed1999

A comparative study on the Mitsuda type response to antigens of chemoautotrophic nocardioform bacteria and to standard lepromin in leprosy patients.

Anergy, or contrarily, Mitsuda-type responses towards 4 chemoautotrophic nocardioform antigens (CAN-Ags) and a control standard lepromin were tested in 73 LL, TT and borderline cases of leprosy. The antigens injected per patient varied from a maximum of 5 to a minimum of 2. Complete anergy to CAN-Ags was seen in 92/92 instances tested on 24 LL cases. The anergy was weakly modified or unmodified in 3 other LL cases which had been vaccinated before. Concurrent studies with the same antigens tested on 33 TT cases showed clear-cut, dose-dependent, Mitsuda-type late responses in 80/81 instances. The CAN bacteria, therefore, despite their origin from different unrelated leprous human, mouse footpad (MFP) and armadillo tissues, appeared to be identical with each other and also probably related to the leprosy bacillus, on the basis of these parameters.

Actinomycetales↗
PubMed1998

Cell cycle control protein p34cdc2 homologue and its phase specific accumulation in synchronized onion (Allium cepa L.) root meristem cells.

A key regulator of the cell cycle is a highly conserved protein kinase whose catalytic subunit, p34cdc2, is encoded by cdc2 gene. Immunoblotting with a polyclonal antibody raised against PSTAIRE sequence (found in the N-terminal region of all cdc2 and cdc2 related proteins throughout the phylogenetic scale including higher plants), was used to study the presence of p34cdc2 in onion scale leaves and root tip cells. p34cdc2 homologues are beyond the detection level in scale leaves. PSTAIRE antibody was used to estimate p34cdc2 kinase protein levels during cell cycle in highly synchronous population of Allium cepa L. root meristem cells. p34cdc2 kinase protein showed gradual increase in their levels from S phase to G2 phase boundary. Immunoprecipitation followed by in vitro histone H1 kinase assays also depicted that its kinase activity increased parallel to the increase in p34cdc2 level.

Amino Acid Sequence↗
PubMed1997

Monoclonal antibody raised against human mitotic cyclin B1, identifies cyclin B-like mitotic proteins in synchronized onion (Allium cepa L.) root meristem.

Cyclin B-like mitotic proteins have been detected in synchronized Allium cepa L. root tip cells by using mouse monoclonal anti-cyclin B1 antibody raised against human cyclin B1. Immunoblot shows two closely placed isoforms of cyclin B-like proteins having an apparent molecular weight around 54 kDa. In vivo [35S]-methionine labelling followed by immunoprecipitation and autoradiography indicates that cyclin B-like proteins are mainly synthesized in the G2 phase of the cell cycle and destroyed in late mitosis. Immunoblotting data depict that the level of cyclin B-like proteins reaches the maximum at the late G2 to early M phase; and it becomes degraded in the late hours of mitosis. Moreover, the cyclin B isoforms are stabilized in colchicine-arrested metaphase cells as already reported in animal cells.

Allium↗
PubMed1997

Effects of low concentrations of okadaic acid in HeLa cells.

HeLa cells treated for prolonged period with okadaic acid (OA; 5-10nM) inhibiting protein phosphatase 2A (PP2A) and also protein phosphatase 1 (PP1) partially showed prolonged effects on mitotic progression. In the presence of OA cells progressed normally in mitosis almost upto 4 hr, then a progressive accumulation of mitotic cells could be noticed. Most of the mitotic cells seemed to be arrested at the metaphase-anaphase transition point. In arrested mitotic cells the chromosomes remained arranged at the equiatorial plate, but with prolonged treatment the chromosomes got either scattered or clumped. However, a slow release into anaphase could also be observed after 15 hr treatment. Immunofluorescence studies for microtubules and electron microscope investigations indicated the dearrangement of spindle fibres, and a prolonged treatment led to the formation of multipolarity. This was also confirmed by spread preparations of chromosomes and the formation of multinucleate cells in preparations released from the mitotic block. Chromosomes became highly condensed showing mostly nondisjunction, but separation of sister chromatids could be observed in many cells. Immunoblot assays indicated a degradation of cyclin A, but the cyclin B1 level was significantly higher in the arrested mitotic cells after 12 hr treatment. After 24 hr of treatment the cyclin B1 level was slightly lower in arrested cells. Possible roles of protein phosphatase 2A inhibition and a prolonged partial inhibition of PP1 on the mitotic progression and the cyclin degradation at the metaphase-anaphase transition have been discussed.

Enzyme Inhibitors↗
PubMed1996

Cytotoxic and antioxidative sesquiterpenoids from Heterotheca inuloides.

Four sesquiterpenoids, beta-caryophyllene, beta-caryophyllene 4,5 alpha-oxide, 7-hydroxy-3,4-dihydrocadalin, and 7-hydroxycadalin, isolated from the dried flower of Heterotheca inuloides Cass. (Asteraceae), have been found to exhibit cytotoxic activity against several solid tumor cell lines. Among them, 7-hydroxy-3,4-dihydrocadalin and 7-hydroxycadalin have also been found to inhibit autoxidative and microsomal lipid peroxidation.

Animals↗
PubMed1995

Isolation and structural elucidation of pentacyclic triterpenoids from Maprounea africana.

Pentacyclic triterpenoids based on the taraxer-14-ene skeleton with a C-28 attached carboxylic acid group have been isolated from the roots of Maprounea africana. These compounds were identified as 1 beta,2 alpha-dihydroxyaleuritolic acid 2,3-bis-p-hydroxybenzoate [1], 2 alpha-hydroxyaleuritolic acid 3-p-hydroxybenzoate [2], 2 alpha-hydroxyaleuritolic acid 2,3-bis-p-hydroxybenzoate [4], aleuritolic acid 3-p-hydroxybenzoate [5], aleuritolic acid [6], and aleuritolic acid 3-acetate [7]. Compounds 1 and 2 are new triterpene esters. Compound 3 was previously reported as 7 beta-hydroxymaprounic acid 3-p-hydroxybenzoate [13]. However, based on detailed nmr studies, its structure has been revised.

Magnetic Resonance Spectroscopy↗