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Biomedical subjects

A Datta

Publications and source records attributed to A Datta.

At least 91 records · Page 5Linked to original sources
PubMed1995

Studies on adhesion, haemagglutination and other biological properties of Vibrio cholerae O139.

The adhesive capabilities of eight Vibrio cholerae O139 epidemic strains to isolated rabbit intestinal epithelial cells (RIEC) were observed to be high similar to those observed with a Vibrio cholerae O1 strain isolated from patients. Toxin production by the strains, measured by accumulation of fluid in rabbit ileal loop model, was high and the toxin was lethal as the animal expired within 6 h. Culture filtrates of the strains exhibited the presence of vascular permeability factor which produce induration and necrosis in the adult rabbit and guinea pig skin. All the strains showed high to moderate haemagglutinin titres against chicken erythrocytes and produced El Tor-like haemolysin. SDS-PAGE of the outer membrane preparation of the strains showed the presence of major protein component at 38 kDa region. The lethality of the toxin, high adhesive activity, shifting of the major outer membrane protein band and production of thermolabile haemolysin on Wagatsuma agar were the major variations of these epidemic strains from V. cholerae O1 and V. cholerae non-O1 strains isolated previously.

Animals↗
PubMed1995

Haemagglutinating property & cell surface hydrophobicity of Vibrio cholerae 0139.

Cell-associated haemagglutinating activity was detected in all the epidemic strains of V. cholerae 0139 and 01, isolated in different parts of the country, with erythrocytes from rabbit, rat, chicken and guinea pig. Sheep erythrocytes were unresponsive to both groups of strains. While D-mannose, alpha-methyl-D-mannoside, glucosamine, N-acetyl-D-glucosamine, thyroglobuline were effective inhibitors of the haemagglutinating activity of the V. cholerae 0139 and 01 strains, galactose and N-acetyl-D-galactosamine sensitive haemagglutinins (HAs) were detected in the V. cholerae 01 but not in the V. cholerae 0139 strains. The best medium for expression of HAs in V. cholerae 01 and 0139 strains were observed to be penassay broth and tryptic soy broth respectively. The expression of HA in V. cholerae 01 was stimulated by Ca++ and Fe in the growth medium unlike that of V. cholerae 0139 which remained unaffected by these ions.

Animals↗
PubMed1994

ACPR, a STE12 homologue from Candida albicans, is a strong inducer of pseudohyphae in Saccharomyces cerevisiae haploids and diploids.

ACPR from Candida albicans encodes a protein antigenically related to the secretory acid proteinase of this yeast. Its amino terminal domain is highly similar to the amino terminal, DNA-binding domain of STE12 of Saccharomyces cerevisiae. STE12 is involved in mating of haploids and in pseudohyphae formation in diploids. ACPR, or its DNA-binding domain swapped into STE12, can support pseudohyphae formation in S. cerevisiae diploids. However, unlike STE12, these constructs affect the budding pattern and induce pseudohyphae formation in S. cerevisiae haploids as well, and this induction is independent of the nitrogen status of the medium. ACPR appears to be a stronger inducer of pseudohyphae than STE12 and is likely to be involved in the formation of pseudohyphae and hyphae in C. albicans.

Aspartic Acid Endopeptidases↗
PubMed1994

Identification of a putative transcription factor in Candida albicans that can complement the mating defect of Saccharomyces cerevisiae ste12 mutants.

We have isolated an acid proteinase-related gene, ACPR, from Candida albicans using a partial clone (Ganesan, K., Banerjee, A., and Datta, A. (1991) Infect. Immun. 59, 2972-2977) as a probe. Sequencing of the full-length gene revealed an open reading frame that can encode a protein of 699 amino acids. The deduced NH2-terminal amino acid sequence did not correspond with that determined from the purified secretory acid proteinase; however, the encoded protein is antigenically related to secretory acid proteinase and has a putative active site for acid proteinase. Interestingly, the amino acid sequence of the NH2-terminal 215 residues of Acprp is highly similar to the DNA binding domain of Ste12p of Saccharomyces cerevisiae. Gel retardation experiments showed that this region of Acprp, like Ste12p, could bind to S. cerevisiae pheromone response elements, suggesting that Acprp has a function similar to Ste12p. Chimeric constructs composed of S. cerevisiae STE12 and C. albicans ACPR genes complemented the mating defect of S. cerevisiae a or alpha ste12 mutants. Our results suggest the presence of a signal transduction system in C. albicans similar to that of S. cerevisiae mating pathway.

Amino Acid Sequence↗
PubMed1994

Structure-activity studies of antitumor taxanes: synthesis of novel C-13 side chain homologated taxol and taxotere analogs.

Taxol and taxotere analogs with one carbon homologated side chains were synthesized from 10-deacetylbaccatin III and a key oxazolidineacetic acid intermediate, which was synthesized in four steps from (S)-(+)-2-phenylglycine. 10-Deacetyl-1a'-homotaxol and 1a'-homotaxotere were at least 27 times less active than taxol in the microtubule assembly assay. The inability of these homologs to induce microtubule formation may be due to unfavorable solution conformations, preventing productive interactions with the taxol binding site on microtubules.

Docetaxel↗
PubMed1994

Mapping the lipoyl groups of the pyruvate dehydrogenase complex by use of gold cluster labels and scanning transmission electron microscopy.

This paper describes the organization of lipoyl moieties within the pyruvate dehydrogenase (PDH) complex from Escherichia coli as studied in the scanning transmission electron microscope (STEM). The PDH complex is a multienzyme complex consisting of E1, pyruvate dehydrogenase, E2, dihydrolipoyl transacetylase, and E3, dihydrolipoyl dehydrogenase. The core of the complex is the cubic 24-subunit E2 component, which contains the lipoyl moieties bonded to lipoyl-bearing domains. E1 and E3 are associated along the edges (E1) and on the faces (E3) of the core. The lipoyl moieties were reduced with NADH and alkylated with a p-maleimidobenzoyl undecagold cluster complex. The gold labels were found to be bound very nearly specifically by dihydrolipoyl transacetylase (E2). Undecagold clusters were imaged directly by the STEM and also digitally mapped by radial mass analysis. The mass of the E2E3 subcomplex is about half that of the PDH complex. The PDH complex and GC-PDH are both about 420 A in diameter, as determined by radial mass analysis, and the E2E3 subcomplex and GC-E2E3 are 320 and 350 A, respectively. The outer boundary of the E2E3 subcomplex was clearly shown in STEM micrographs by the undecagold labels in GC-E2E3. Data obtained from radial mass analysis of GC-E2E3 and the unlabeled E2E3 subcomplex also showed that the size of the subcomplex is extended by the lipoyl-bearing domains surrounding the central E2 core. The capabilities of lipoyl moieties to undergo translocation over long distances through structural mobility in the lipoyl-bearing domains was confirmed by the observation that many of the lipoyl groups in E2E3 subcomplexes relax outward into space vacated by the removal of E1 during the preparation of the subcomplex from PDH complex. Radial mass analysis of the PDH complex and GC-PDH indicates that lipoyl groups are distributed over a large region of the PDH complex, extending from the central core to 170-180 A from the center of the complex, with the highest density at about 75 A from the particle centers, near the interface between E2 and the associated components E1 and E3.

Escherichia coli↗
PubMed1994

A knowledge acquisition tool in analytical pathology based on multi-media relational database.

The need for a knowledge based expert system for efficient decision making in the field of pathology has been well accepted. To build the knowledge-base for such an expert system is a painstaking task. This work is an attempt to provide the pathologists a powerful and user-friendly tool that will help them in the process of building the knowledge-base for medical diagnosis by closely looking at the specimen images and their extracted feature values. The tool is based on multi-media relational database and software like VAX Rally (4GL), ILIAD and SAS to provide a wide-range comparative study between feature data and image data; and also their statistical analysis.

Artificial Intelligence↗
PubMed1994

Infra-orbital nerve block for relief of postoperative pain following cleft lip surgery in infants.

The study was conducted on 20 infants scheduled for cleft lip repair surgery. Ten were randomly allocated to receive bilateral infra-orbital local anaesthetic nerve blocks at the conclusion of surgery with the other 10 receiving bilateral 'sham' blocks as controls. Postoperative pain relief was assessed using a pain assessment scoring system and by monitoring arterial blood pressure, heart rate and respiratory rate. The mean pain assessment score was significantly higher (i.e. better) (p < 0.05) in the infants receiving the local anaesthetic block. There were no significant statistical or clinical differences in the physiological measurements between the two groups. The infants receiving the block required less analgesia in the postoperative period. The results suggest that infra-orbital nerve block is a simple and effective means of achieving postoperative analgesia after cleft lip repair surgery in infants.

Blood Pressure↗
PubMed1994

Pathogenicity of Candida albicans: quest for a molecular switch.

Candida albicans is an opportunistic pathogen of human beings and other mammals. Two other features, besides its pathogenicity, have made it a popular organism for study. It exists in different cellular forms and can change from one form to another, depending on growth conditions. Thus, it is being used as a model system to study cellular differentiation. It can also heritably and reversibly switch its cellular and colony morphologies.

Aminoglycosides↗
PubMed1993

Molecular cloning and analysis of the NAG1 cDNA coding for glucosamine-6-phosphate deaminase from Candida albicans.

Candida albicans and other pathogenic Candida species can use N-acetylglucosamine as a sole carbon source for growth. GlcNAc induces the enzymes of GlcNAc catabolic pathway; besides, under certain conditions, GlcNAc also induces a change from the yeast to germ tube morphology. Glucosamine-6-phosphate deaminase (EC 5.3.1.10) is the terminal enzyme of the GlcNAc catabolic pathway. We have purified the deaminase from C. albicans and studied its characteristics. The size of the deaminase estimated from SDS-polyacrylamide gel electrophoresis is 28 kDa. N-Acetylglucosamine 6-phosphate, an allosteric activator of the Escherichia coli deaminase, has no effect on the activity of the C. albicans enzyme. The deaminase is induced over 100-fold by GlcNAc and its level is about 0.3-0.5% of the proteins in crude extract. Three cDNA clones were obtained from a lambda gt11 expression library by immunoscreening with deaminase antiserum. C. albicans genomic DNA blot hybridization revealed that the NAG1 gene, encoding the glucosamine-6-phosphate deaminase, is present in a single copy. Hybrid-selected translation and immunoprecipitation experiments revealed that the purified deaminase and the protein encoded by the clones were similar in size and in their antigenicity. DNA sequencing revealed that the largest cDNA clone contained the complete open reading frame, which can code for a 27.5-kDa protein. The NH2-terminal sequence (35 residues) determined from the purified deaminase was identical to the sequence of the deduced protein. The Nag1 protein has about 47% identity with the sequence of the E. coli glucosamine-6-phosphate deaminase. Furthermore, RNA blot hybridization showed that GlcNAc induces the expression of NAG1 gene.

Aldose-Ketose Isomerases↗