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Biomedical subjects

S C Kundu

Publications and source records attributed to S C Kundu.

At least 19 recordsLinked to original sources
PubMed2001

Purification and characterization of fibroin from the tropical Saturniid silkworm, Antheraea mylitta.

The fibroin protein isolated from the posterior silkgland of the tropical Saturniid silkworm Antheraea mylitta, was solubilized in lithium dodecyl sulfate and purified by gel filtration. The major fraction from gel filtration was analyzed by SDS-PAGE under non-reducing and reducing conditions. One major protein band of ca 395 kDa was obtained under non-reducing conditions and a doublet band of approximately 197 kDa under reducing conditions. The appearance of a single spot in two-dimensional electrophoresis confirmed the purity of the protein indicating that it may be a homodimeric protein of two similar sized polypeptides. Amino acid composition analysis showed that, like other Saturniid fibroins, it is rich in glycine, alanine and serine amino acids. N-terminal amino acid sequence shows significant homology with other Antheraea species. The enzymatic deglycosylation analysis indicates that the fibroin protein is glycosylated and the oligosaccharides are O-linked to the protein backbone by N-acetylgalactoseamine moiety which conforms to a Core 1 mucin-type glycosylation pattern.

Amino Acid Sequence↗
PubMed2001

Differential expression of the fibroin gene in developmental stages of silkworm, Antheraea mylitta (Saturniidae).

Fibroin gene expression during the larval developmental stages of the Saturniid silkworm, Antheraea mylitta, was analyzed. Northern blot analysis of larval silk gland total RNA using the fibroin gene as a probe showed that fibroin is expressed in the intermoult stages and repressed during the moulting stages. Abundance of fibroin transcripts gradually increased from the third to fifth intermoult stage, reaching a peak in the fifth intermoult. Transcripts declined during the early spinning stage. Western blot analysis of fibroin protein production with anti-fibroin antibody confirmed the differential fibroin expression, in accordance with fibroin mRNA synthesis. Dot blot hybridization of genomic DNA isolated from each larval developmental stage with the labelled fibroin gene showed that at the genomic level, the relative concentration of the fibroin gene was constant throughout the developmental stages. Our data confirm that fibroin gene expression in A. mylitta, like in B. mori, is transcriptionally controlled and shows differential temporal variations.

Animals↗
PubMed2000

Characterization of cypovirus isolates from tropical and temperate Indian saturniidae silkworms.

Cytoplasmic polyhedrosis virus (cypovirus, CPV) isolates from larvae of saturniidae silkworms Antheraea mylitta, Antheraea proylei, and Antheraea assamensis were obtained and characterized. Scanning electron microscopic (SEM) studies revealed the presence of hexahedral (rhombic dodecahedron) polyhedral bodies of various size (1-4 microns) in individual hosts while transmission electron microscopic (TEM) studies of isolated virions showed their uniform (icosahedral) shape and size (approximately 55 nm). Genomes of these isolates were obtained from purified polyhedral bodies and analyzed by agarose and polyacrylamide gel electrophoresis. Eleven bands ranging from about 350 bp to 3.9 kb (total of 25.35 kb) were detected. These bands were completely degraded after treatment of the genome preparations with RNase A at low salt but not at high salt concentration. The banding pattern of the genomes remained unaffected by treatment of the respective preparations with DNase I, indicating that the genomes were composed of 11 double-stranded (ds) RNA segments. The RNA banding patterns of the CPV isolates from the saturniidae silkworms were similar to each other. These characteristics were similar to that of Antheraea mylitta cypovirus 4 (AmCPV-4) but different from that of Bombyx mori cypovirus 1 (BmCPV-1). In comparison to AmCPV-4 the isolates contained an additional, eleventh RNA segment and the size of the RNA segments was also different. Dot blot hybridization showed hybridization of the cloned 9th and 10th segment cDNAs from the A. mylitta CPV (AmCPV) isolate with RNAs from the A. proylei and A. assamensis CPV (ApCPV, AaCPV) isolates but not with RNA from BmCPV-1. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE) of polyhedral proteins from the AmCPV isolate showed the presence of 3 major and 5 minor bands of M(r) from 29.4 K to 163 K, but BmCPV-1 polyhedral bodies showed different protein banding pattern. Two heterologous cell lines infected with the AmCPV isolate showed very slow virus growth with the accumulation of polyhedral bodies in the cytoplasm of infected cells indicating a restricted host range of this CPV isolate.

Animals↗
PubMed1996

Scavenging of nitrogen dioxide, thiyl, and sulfonyl free radicals by the nutritional antioxidant beta-carotene.

Mechanisms of free radical scavenging by the nutritional antioxidant beta-carotene have been investigated by pulse radiolysis. Free radicals, which can initiate the chain of lipid peroxidation, including nitrogen dioxide (NO2.), thiyl (RS.), and sulfonyl (RSO2.) radicals, are rapidly scavenged by beta-carotene. Absolute rate constant k[NO2. + beta-carotene] = (1.1 +/- 0.1) x 10(8) m-1 s-1 and for the glutathione thiyl radical k[GS. + beta-carotene] = (2.2 +/- 0.1) x 10(8) m-1 s-1 have been determined. The mechanisms however are mutually exclusive, the former involving electron transfer to generate the radical-cation [ beta-carotene]+. and the latter by radical-addition to generate an adduct-radical [RS... beta-carotene].. Rate constants for thiyl radical-addition reactions vary from 10(6) to 10(9) m-1 s-1 and correlate with the lipophilicity of the thiyl radical under study. Sulfonyl radicals undergo both electron abstraction, [ beta-carotene]+. and radical-addition, [RSO2... beta-carotene]. in an approximate 3:1 ratio. The beta-carotene radical-cation and adduct-radicals are highly resonance stabilized and undergo slow bimolecular decay to non-radical products. These carotenoid-derived radicals react differently with oxygen, a factor which is expected to influence the antioxidant activity of beta-carotene within tissues of varying oxygen tension in vivo.

Antioxidants↗
PubMed1990

Gemfibrozil in dyslipidaemia.

A new lipid regulating agent, Gemfibrozil was evaluated in different types of dyslipidaemias. Out of a total of 34 patients, all completed 12 weeks' treatment and 26 completed 24 weeks' of treatment. A significant reduction in total cholesterol, LDL-c triglyceride and apo-B and an increase in HDL cholesterol and its apoprotein--apo-A were observed. The patients belonged to hyperlipidaemias--types IIa, IIb, and IV. Patients' compliance was good and side effects were minimal.

Adult↗
PubMed1986

Sequential analysis of synaptonemal complexes in the repopulating spermatocytes of Rattus norvegicus after restricting the germ cell population to spermatogonia by gossypol treatment.

Synaptonemal complexes of the repopulating spermatocytes of male rats were analyzed day by day using silver-stained surface spread nuclei between 8 and 25 days after restricting the germ cell population to spermatogonia by treatment of gossypol acetic acid at 30 mg/kg body weight/day for 70 days. The method allowed sequential analysis of male meiotic prophase on successive days after the last day of treatment. The leptotene cells appeared on day 11 and were characterized by a network of lateral elements and large nucleolar bodies in a diffuse mass. On day 13 the unpaired lateral elements and short stretches of synaptonemal complexes characteristic for zygotene could be seen. Pachytene nuclei showing 20 autosomal synaptonemal complexes and XY axes appeared on day 15. The diplotene cells were defined on day 22 by the loss of a complete synaptonemal complex set and by the appearance of disjoined lateral elements and persistent segments of synaptonemal complexes.

Animals↗
PubMed1985

Effects of the male contraceptive agent gossypol on meiotic chromosomes of the male rat.

Synaptonemal complexes (SCs) of rat spermatocytes were analyzed in silver-stained meiotic preparations 10-24 days after treatment with gossypol acetic acid, 30 mg/kg/day, for 70 days. Gossypol did not affect SC formation or function, as judged by the absence of pairing anomalies, SC fragmentation, or presynaptic arrest. The unpaired lateral axes could be seen at zygotene, and at pachytene normal SCs could be observed. The behavior of the XY axes also appeared to be normal.

Animals↗
PubMed1982

The ultrastructural meiotic phenotype of the radiation sensitive mutant rad 6-1 in yeast.

An ultrastructural analysis of three yeast rad 6-1/rad 6-1 diploids on sporulation medium for 0, 6, 10, and 24 h shows that arrest occurs at meiotic prophase. Two strains, CL 139 and PU 6, fail to complete chromosome synapsis based on the continued presence of single chromosomal cores in arrested nuclei. A clone derived from CL 139, however, showed complete pairing as evident from the presence of 17 synaptonemal complexes. All three strains underwent spindle pole body duplication but the poles failed to form a proper metaphase I spindle. A revertant Rad 6+ isolated from CL 139 showed normal chromosome behaviour and normal kinetic functions. It is concluded that the absence of meiotic recombination in some Rad 6- strains may result from asynapsis, but that in other strains (e.g., CL 139s) recombination fails in spite of complete synapsis. In all cases the lack of sporulation is adequately explained by failure of the kinetic apparatus to form a metaphase I spindle.

Cell Nucleus↗