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Biomedical subjects

S Sarkar

Publications and source records attributed to S Sarkar.

At least 253 records · Page 14Linked to original sources
PubMed1993

Sensitization of periodontopathogenic bacteria to killing by light from a low-power laser.

Cultures of Porphyromonas gingivalis, Fusobacterium nucleatum and Actinobacillus actinomycetemcomitans were treated with a range of photosensitizers and then exposed to light from a 7.3 mW helium/neon laser for up to 80 s. Toluidine blue O (25 micrograms/ml) and methylene blue (25 micrograms/ml) were effective lethal photosensitizers of all 3 target organisms, enabling substantial light dose-related reductions in viable counts. Dihaematoporphyrin ester and aluminium disulphonated phthalocyanine were lethal photosensitizers only of P. gingivalis. In the absence of a photosensitizer, exposure to laser light had no significant effect on the viability of the cultures. If such low doses of light (22 J/cm2) are effective at killing bacteria in vivo, the technique may be useful as a means of eliminating periodontopathogenic bacteria from diseased sites.

Aggregatibacter actinomycetemcomitans↗
PubMed1993

Lethal photosensitization of bacteria in subgingival plaque from patients with chronic periodontitis.

Subgingival plaque samples from patients with chronic periodontitis were exposed to light from a 7.3 mW Helium/Neon laser for 30 s in the presence and absence of 50 micrograms/ml toluidine blue O as a photosensitizer. Viable counts of various groups and species of bacteria were carried out before and after irradiation. The median numbers of viable bacteria initially present in the 30-microliters aliquots irradiated were 1.13 x 10(5) cfu (aerobes), 4.08 x 10(5) cfu (anaerobes), 4.92 x 10(3) cfu (black-pigmented anaerobes), 4.75 x 10(2) cfu (Porphyromonas gingivalis), 6.15 x 10(3) cfu (Fusobacterium nucleatum) and 1.7 x 10(4) cfu (streptococci). The dye/laser combination achieved significant reductions in the viability of these organisms, the median reductions in the viable counts being 91.1% for aerobes, 96.6% for anaerobes, 100% for black-pigmented anaerobes, P. gingivalis and F. nucleatum and 94.2% for streptococci. Overall, the viability of bacteria in the 20 plaque samples was not significantly decreased by the dye alone. However, in a small minority of samples there were indications of light-independent, dye-induced toxicity. Low-power lasers, in conjunction with appropriate photosensitizers, may be a useful adjunct to mechanical debridement in the treatment of inflammatory periodontal diseases if a similar effectiveness against subgingival plaque bacteria can be achieved in vivo.

Adult↗
PubMed1993

Characterization of a rabbit fast skeletal troponin I cDNA: a comparative sequence analysis of vertebrate isoforms and tissue-specific expression of a single copy gene.

A cDNA encoding skeletal fast troponin I (TnIf) has been isolated and characterized from an adult rabbit fast skeletal muscle cDNA library. This cDNA contains the entire coding region of 549 base pairs (bp), the 3' untranslated (UT) segment of 78 bp and the 5' UT segment of 74 bp. The 3' UT segment shows the predicted stem-loop structure characteristic of eukaryotic mRNAs. The cDNA-derived amino acid sequence is not identical to the chemically-derived and the recently reported cDNA-derived amino acid sequences for rabbit TnIf, and thus enables to make the necessary corrections in the sequence information. The rabbit TnIf is encoded by a single copy gene which is expressed in adult fast skeletal muscle in a tissue-specific manner. Comparative sequence analysis of the vertebrate TnI isoforms and their cDNAs shows a high level of sequence conservation in the coding region among the TnIf interspecies isoforms. The sequence similarity is markedly decreased among the fast, slow and cardiac intra- and inter-species isoforms. The C-terminal halves of TnI isoforms including a segment believed to be involved in critical interactions with actin and troponin C (TnC) show high sequence conservation whereas the N-terminal halves show considerable difference in sequence and size. The significance of these results in relation to the biological function and evolution of members of the vertebrate TnI multigene family is discussed.

Amino Acid Sequence↗
PubMed1993

Mosquitoes of Sagar Island.

Twenty mosquito species belonging to five genera, viz. Aedes, Anopheles, Armigeres, Culex and Mansonia, were collected during 1992-93 from the northern, middle and southern regions of Sagar Island. This is the first record of mosquito fauna of this island.

Aedes↗
PubMed1993

Prevalence of dental caries in handicapped children of Calcutta.

A total of 1042, 3-14-year-old children with different types of handicapping conditions when recorded for dental caries using WHO 1987 caries recording index revealed that dental caries experience was higher in handicapped children than normal children. The prevalence of dental caries was highest in mentally retarded children followed by cerebral palsied, blind, epileptic, physically handicapped, children with Down's syndrome and deaf and dumb. Higher deft+DMFT was recorded in mandibular teeth compared to maxillary teeth.

Adolescent↗
PubMed1993

Cerebral palsy.

Explore the source record for details and available documents.

Cerebral Palsy↗
PubMed1993

Recurrent ameloblastoma of the mandible and maxilla.

Sixteen cases of recurrent ameloblastomas of the mandible and maxilla seen over a 14 year period at the Tata Memorial Hospital were analysed with emphasis on recurrence patterns, type of primary surgery and surgical management. Seventy-five percent of the cases had conservative surgery at the first instance. In our experience, recurrent tumors could be excised widely even in unusual locations with good results.

Adolescent↗
PubMed1993

Rapid spread of HIV among injecting drug users in north-eastern states of India.

Manipur, a north-eastern state of India bordering Myanmar, has experienced very rapid transmission of the human immunodeficiency virus (HIV) among its vast drug-injecting population. Seroprevalence among intravenous drug users increased from 0 per cent in September 1989 to 50 per cent within six months. With a minimum injecting population of 15,000 and seropositivity of over 50 per cent, the infection quickly spread to the population at large. One per cent of antenatal mothers tested seropositive by 1991. Forming part of the area of South-East Asia known as the Golden Triangle, and producing opium and its derivatives, Myanmar shares a long international border with four States of the region, and populations with a common language and culture move freely across borders. Two other north-eastern states of India bordering Myanmar have faced a similar epidemic within a short period of time. As a result of serosurveillance for HIV since 1986, the epidemic could be detected at an early stage. The present paper provides an account of the results of ongoing comprehensive studies conducted in the north-eastern states of India on drug-related HIV infection, already a serious problem, but possibly still restricted to that region of the country. The prevalence of intravenous drug users, their HIV serological status, the demographic profile, risk behaviour, the spread of the infection to other groups and the problems of harm minimization are also covered.

Adolescent↗
PubMed1993

Transformation by the vRel oncoprotein requires sequences carboxy-terminal to the Rel homology domain.

The vRel oncoprotein of the avian Rev-T retrovirus is a member of the Rel/NF-kappa B family of transcription factors. The highly conserved amino-terminal Rel Homology (RH) domain in these proteins is required for DNA binding, protein-protein interactions and nuclear localization, and many mutations within this domain abolish transformation by vRel. We demonstrate here that overexpression of the vRel RH domain alone is insufficient to induce transformation of chicken spleen cells, indicating that sequences from the nonconserved carboxy terminus are necessary for the vRel transforming function. Therefore, we constructed and assayed several vRel mutants with deletions of carboxy-terminal sequences. These mutant vRel proteins did not transform spleen cells with equal efficiency, even though they were functionally similar by several other criteria. Our results demonstrate that there are two regions (aa 389 to 432 and aa 437 to 503) within the carboxy-terminal half of vRel that are important for transformation: mutant vRel proteins containing the RH domain and one or both of these carboxy-terminal regions can transform at roughly wild-type levels. Analysis of Gal4 fusion proteins containing carboxy-terminal sequences from the vRel mutants indicated that there is a correlation between the ability of these mutant proteins to transform avian spleen cells and their ability to activate transcription. These observations suggest that vRel induces malignant transformation by directly altering gene expression.

Animals↗
PubMed1992

Antileishmanial activity of hamycin: a polyene antibiotic.

Hamycin, a polyene antibiotic, now in extensive use in the treatment of candidiasis and otomycosis, is found to be remarkably effective in killing Leishmania donovani promastigotes in a liquid medium at a concentration of 0.2 microgram/ml. The glucose stimulated respiration and the uptake of 2-deoxy-D[U-14C]-glucose was inhibited in cells treated with the drug at a growth inhibitory concentration. An immediate release of isotopic glucose from preloaded cells could be demonstrated after exposure to hamycin. All the above effects could be effectively prevented in the presence of ergosterol. The primary site of action of hamycin on L. donovani promastigote cells appears to be membrane sterols that result in the loss of the permeability barrier to small metabolites. The lower minimum inhibitory concentration of hamycin compared to other established drugs warrants further study in the context of increasing reports of clinical resistance to pentavalent antimonials.

Amphotericin B↗
PubMed1992

On fluctuation analysis: a new, simple and efficient method for computing the expected number of mutants.

Fluctuation analysis, which is often used to demonstrate random mutagenesis in cell lines (and to estimate mutation rates), is based on the properties of a probability distribution known as the Luria-Delbrück distribution (and its generalizations). The two main new results reported in this paper are (i) a simple, completely general, and computationally efficient procedure for calculating probability distributions arising from fluctuation analysis and (ii) the formula for this procedure when cells in a colony have only grown for a finite number of generations after initial seeding. It is also shown that the procedure reduces to one that was developed earlier when an infinite number of generations is assumed. The derivation of the generating function of the distribution is also clarified. The results obtained should also be useful to experimentalists when only a relatively short time elapses between seeding and harvesting cultures for fluctuation analysis.

Cell Line↗
PubMed1992

Studies on endoplasmic reticulum--Golgi complex cycling pathway in herpes simplex virus-infected and brefeldin A-treated human fibroblast cells.

Brefeldin A (BFA), a fungal metabolite, significantly inhibited the release of herpes simplex virus type 1 (HSV-1) from infected human fibroblast cells. Electron micrographs of HSV-1-infected and BFA-treated human cells demonstrated the presence of enveloped particles trapped between outer and inner nuclear membranes. Analyses of viral glycoproteins B, C, and D (gB, gC, and gD) showed faster migrating, immature forms in BFA-treated cells when compared to the mature glycoproteins, as observed in the untreated control cells. The shift in mobilities of the glycoproteins in BFA-treated cells apparently was due to the disassembly of the Golgi complex when evaluated by an indirect immunofluorescence assay. The immature forms of gB, gC, and gD could not be detected on the surface of BFA-treated human fibroblast cells. Removal of BFA resulted in a reorganization of the Golgi complex and formation of fully glycosylated gB, gC, and gD. Moreover, the HSV-1 particles released from the treated cells after the removal of BFA completely restored the infectivity of the viral particles. Our results indicate that human fibroblast cells have an endoplasmic reticulum-Golgi cycling pathway.

Animals↗