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Biomedical subjects

S Dasgupta

Publications and source records attributed to S Dasgupta.

At least 109 records · Page 6Linked to original sources
PubMed1994

A revised structure for the disialosyl globo-series gangliosides of human erythrocytes and chicken skeletal muscle.

Disialosyl globo-series gangliosides have previously been isolated from chicken skeletal muscle (E. L. Hogan, R. D. Happel, and J.-L. Chien (1982) Adv. Exp. Med. Biol. 152, 273-278; S. Dasgupta, J.-L. Chien, E. L. Hogan, and H. van Halbeek (1991) J. Lipid Res. 32, 499-506) and human erythrocytes (S. K. Kundu, B. E. Samuelsson, I. Pascher, and D. Marcus (1983) J. Biol. Chem. 258, 13857-13866). In both cases, the structure of this ganglioside was proposed to be NeuAc alpha 2-->3(NeuAc alpha 2-->6)Gal beta 1-->3GalNAc beta 1-->3Gal alpha 1-->Gal alpha 1-->4Gal beta 1-->1Cer (V3NeuAcV6NeuAcGb5Cer). We have reinvestigated the human erythrocyte antigen and now propose an alternative structure differing in the location of the NeuAc alpha 2-->6 residue: NeuAc alpha 2-->3Gal beta 1-->3 (NeuAc alpha 2-->6)GalNAc beta 1-->3Gal alpha 1-->4Gal beta 1-->4Glc beta 1-->1 Cer (V3NeuAcIV6NeuAcGb5Cer). This novel structure is supported by results of 1H-NMR spectroscopy, negative ion fast atom bombardment mass spectrometry, and methylation linkage analysis with capillary gas chromatography--mass spectrometry in both electron impact and chemical ionization modes. Furthermore, based on new results from negative ion fast atom bombardment mass spectrometry and linkage analysis, we propose that the chicken skeletal muscle antigen also has this revised structure, differing only in ceramide composition. The terminal tetrasaccharide of these gangliosides is identical to that of GD1 alpha, NeuAc alpha 2-->3Gal beta 1-->3(NeuAc alpha 2-->6)GalNAc beta 1-->4Gal beta 1-->4Glc beta 1-->1 Cer(IV3NeuAcIII6NeuAcGg4Cer), previously identified in a rat ascites hepatoma cell line (T. Taki, Y. Hirabayashi, H. Ishikawa, S. Ando, K. Kon, Y. Tanaka, and M. Matsumoto (1986) J. Biol. Chem. 261, 3075-3078) and a murine lymphoma cell line with low metastatic potential (K. Murayama, S. B. Levery, V. Schirrmacher, and S. Hakomori (1986) Cancer Res. 46, 1395-1402), although they appear to be immunologically distinct.

Animals↗
PubMed1994

Vaccination with the immediate-early protein ICP47 of herpes simplex virus-type 1 (HSV-1) induces virus-specific lymphoproliferation, but fails to protect against lethal challenge.

Assessing the immunobiological function of the individual proteins of herpes simplex virus-type 1 (HSV-1) continues to be important in elucidating virus-host interactions and for the rational design of subunit vaccines. In this report, the non-structural, immediate-early protein ICP47 of HSV-1 was examined for its ability to induce virus-specific immune responses. The ICP47 protein, when expressed from a recombinant vaccinia virus or when produced by cell-free, in vitro translation, induced a vigorous HSV-1-specific lymphoproliferative response. However, other common parameters of immunity such as neutralizing antibody, delayed-type hypersensitivity, and class I major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTL) were not induced by ICP47. Moreover, mice immunized with vaccinia-expressed ICP47 were unable to survive lethal challenge with virulent HSV, indicating that in spite of its ability to induce significant HSV-1-specific lymphoproliferation, ICP47 appears unable to afford protective immunity in vivo. Possible reasons for this failure and the implications of these results in terms of vaccine design are discussed.

Animals↗
PubMed1994

Fallacies of the fine needle aspiration cytology of surgical lesions of liver.

Seventy-six cases of surgical hepatomegaly were subjected to fine needle aspiration cytology (FNAC) for initial diagnosis. Primary malignancies, as suspected clinically with adjunction of other investigative procedures, were 29 cases of whom 25 were confirmed by biopsy or therapy. Secondary deposits in liver were 27 of whom 15 were confirmed by therapy. Inflammatory lesions were 9 of whom 6 were confirmed by therapeutic response with specific therapy. Benign lesions were 10 of whom 5 were confirmed by surgery. Diagnosis of malignancies of liver is rather easier than that of benign lesions like hydatid cysts of liver which were Casoni's test negative; and hepatocellular adenoma, as the aspirate in the former is clear fluid and that of the latter is only normal looking liver cells. Thus, in respect of benign lesions of liver, FNAC diagnosis may be clinched after due consideration to the clinical findings, radiological and ultrasonographic findings and ultimately confirmed by exploration. Thus the fallacy lies in aspiration of normal looking liver cells whereby the histology may prove it to be hepatocellular adenoma, well differentiated hepatocellular carcinoma and secondary deposits where the exact site has not been hit. Ultrasonogram (USG) guidance helps in these cases where the same facility is available. This fallacy can again be avoided, where USG guidance is not available, by imparting due importance to clinical findings, USG findings and also by repeat smear.

Biopsy, Needle↗
PubMed1993

Cloning and sequencing of 5' flanking sequence from the gene encoding 2S storage protein, from two Brassica species.

Using oligodeoxyribonucleotide primers and the polymerase chain reaction, we have cloned and sequenced about 1.2 kb of upstream sequences from two members of the 2S seed storage protein-encoding gene family from Brassica juncea and B. oleracea. The two sequences bear more than 90% homology and have characteristic seed-specific promoter motifs. The high degree of sequence conservation indicates that this napin-encoding gene family evolved earlier than the divergence of the three primary Brassica species and their amphidiploids, and the sequences have been conserved due to some metabolic constraints in seed development.

2S Albumins, Plant↗
PubMed1993

Improved bacterial hosts for regulated expression of genes from lambda pL plasmid vectors.

The construction and use of a set of Escherichia coli strains with defective lambda prophages that facilitate expression of genes cloned in lambda pL-plasmid vectors is described. These bacteria allow high and regulated expression of such genes, whereas a kanamycin-resistance marker (KmR) on the prophage allows easy identification and genetic transfer from strain to strain. Optimal conditions for examining gene expression with the pL-vector systems using these strains are discussed.

Bacteriophage lambda↗
PubMed1993

Shuttle cosmid vectors for the trypanosomatid parasite Leishmania.

We have developed two shuttle cosmid vectors for the trypanosomatid protozoan parasite Leishmania. Cosmids cLHYG and cLNEO contain hyg and neo markers, conferring resistance to hygromycin B and G418, respectively, replicate extrachromosomally after transfection into promastigotes, and bear a unique BamHI cloning site. To ensure the representation of telomeric sequences, which represent about 5% of the Leishmania genome, random insert DNAs were prepared by shearing followed by blunt-end ligation with BamHI adapters. Representative genomic libraries from Leishmania species representing the four major pathogenic complexes were prepared using cosmid cLHYG. The cosmid libraries were efficiently transfected into Leishmania, and individual cosmids were readily recovered by transformation back into Escherichia coli. The relatively small size of the Leishmania genome (50 Mb) combined with the capacity and transfection efficiency of these cosmid libraries (> 1000 Leishmania transfectants/plate) suggests the feasibility of functional genetic complementation in this parasite.

Animals↗
PubMed1993

Biophysical characterization of Vibrio El Tor typing phage e5.

Vibrio cholerae typing phage e5, which can lyse only the El Tor strains of V. cholerae, was characterized. The phage had a polyhedral head 51 nm in diameter and a short tail 13 nm in length. It contained 13 structural polypeptides, with the molecular mass of the major component being 50 kDa. Phage chromosome comprised a 38.5-kb linear double-stranded DNA molecule with unique termini, as determined by restriction fragment analysis and electron microscopy, and had a G+C content of 35.5%. A physical map was constructed with the restriction endonucleases HaeII and HpaII. Adsorption of the phage to its host followed a biphasic kinetics and its intracellular growth was characterized by a latent period of 15 min and a burst size of 100 particles per infected cell. The phage was found to be moderately thermotolerant.

Bacteriophages↗
PubMed1993

Serotonergic-cholinergic neurotransmitters' function in brain during cadmium exposure in protein restricted rat.

Daily subcutaneous injection of cadmium chloride (0.3 mg/100g bw) for two weeks to normal and protein restricted (5% casein) rats shows significant decrease in 5-HT concentration in cerebellum, medulla oblongata-pons, hypothalamus, striatum-hippocampus, midbrain-thalamus-subthalamus, and cortex in both dietary regimens. No significant change occurs in concentration of ACh in cerebellum, but there is a significant increase in cortex, whereas significant decrease occurs in rest of the discrete regions of brain in both dietary conditions. Results also indicate that the intensity of cadmium effect is more evident in discrete brain regions in protein restricted dietary condition than in the normal group. The inhibitory action of Cd on both neurotransmitters has been discussed.

Acetylcholine↗
PubMed1993

Molecular characterization of gangliotetraosylceramide (GA1) in normal human brain and its developmental change.

Several neutral glycosphingolipids have recently been purified from normal human brain to the criterion of migration as homogeneous bands in two different solvent systems. One of these has been permethylated and analyzed by gas chromatography. Stepwise specific exoglycosidase hydrolysis confirms its structure as GAl or Gal beta 1-->3GalNAc beta 1-->4Gal beta 1-->4Glc beta 1-->1Cer. The neutral glycosphingolipids of rat CNS have been examined in order to investigate changes in GA1 during critical ages of brain development. Employing the highly sensitive techniques of digoxigenin (DIG) immunostaining and Fluorescence Assisted Carbohydrate Electrophoresis (FACE), we have identified several previously uncharacterized long chain neutral glycosphingolipids in brain and myelin. A major band with Rf close to that of nLcOse5Cer purified from bovine erythrocytes has been identified as GA1 by immuno-TLC using mono-specific polyclonal anti-GA1 antisera. It appears in 5 day-postpartum (P5) developing brain, increases until 21 days (P21) and subsequently declines. This phasic change along with changes in other nonsialylated glycosphingolipids of the developing brain strongly suggests that GA1 and other neutral glycosphingolipids may play a mediator role(s) in brain development and/or myelinogenesis.

Adult↗
PubMed1993

Design of helix ends. Amino acid preferences, hydrogen bonding and electrostatic interactions.

The amino acid sequence and chemical interactions at the ends of 163 helices were surveyed so as better to understand amino acid preferences previously observed [Richardson, J.S. & Richardson, D.C. (1988) Science 240, 1648-1652]. Amino acid preferences differed from the previous survey in some significant details and in ways that might affect the choice of amino acids during the design of a protein helix. The following major conclusions about helix ends were deduced from additional patterns of amino acid occurrence and interactions that were observed. (1) A specific pair of hydrogen bonds is often observed between a glutamic acid (or glutamine) side chain at the N3 position and the N-cap amide hydrogen, and between the N-cap side chain (often threonine) and the N3 amide hydrogen. This reciprocal interaction may be an important means of stabilizing the N-terminal end of a helix. (2) Negatively charged amino acids (aspartic acid and glutamic acid) at the N-terminal end of helices may be more important in stabilizing protein helices than positively charged residues (chiefly lysine) at the C-terminal end. (3) The identity of the residue at the N-cap position is correlated with the backbone conformation at that position. (4) Aspartic acid (or asparagine) at the N2 or N3 position may adopt a conformation that suggests a hydrogen-bonding interaction with the end of the helix, especially when the N-cap side chain does not form a hydrogen bond with the end of the helix.

Amino Acids↗
PubMed1992

Rolling-circle replication of a high-copy BPV-1 plasmid.

We investigated the replicating form of a bovine papillomavirus type 1 (BPV-1) deletion mutant by direct electron-microscopic analysis of low molecular weight cellular DNA fractions. The detection of viral plasmid DNA replication intermediates was facilitated by the isolation of a spontaneously transformed mouse cell subclone containing an unusually high viral genome copy number (approx. 1000 per cell), and by employing a slight modification of the Hirt fractionation procedure to reduce the level of contaminating linear chromosomal DNA fragments. We observed exclusively rolling-circle-type viral DNA replication intermediates, at a frequency of detection of approximately one replication intermediate per 200 monomeric circular viral DNA molecules. The demonstration of rolling-circles with longer-than-genome-length tails indicated that this high-copy viral plasmid was not subject to a strict once-per-cell-cycle mode of DNA replication. Our observations provide further evidence in favour of an alternative replication mode of the BPV-1 genome, and may help to explain earlier conflicting findings concerning the mechanism of stable BPV-1 plasmid copy-number-control.

Animals↗
PubMed1992

Ganglio-N-tetraosylceramide (GA1) of bovine and human brain. Molecular characterization and presence in myelin.

During our studies of bovine brain neutral glycosphingolipids (Ngsl's), we have purified a compound that co-migrates on thin-layer chromatogram with standard GA1 (purified by acid hydrolysis of GM1) and close to penta- (nLc5Cer) glycosylceramide from bovien erythrocytes. The structure of the purified Ngsl from brain has been established by permethylation and by stepwise exoglycosidase hydrolysis. 600 MHz 1H NMR spectroscopy of the oligosaccharide obtained from the Ngsl after endoglycoceramidase hydrolysis confirms the structure as ganglio-N-tetraosylceramide (GgOse4Cer or GA1) as Gal beta 1----3GalNAc beta 1----4Gal beta 1----4Glc beta 1----1Cer. We have identified GA1 in bovine, rat and human brain and myelin by TLC-immunostaining with monospecific anti-GA1 antiserum.

Animals↗
PubMed1992

Hypertonic stress induces alpha B-crystallin expression.

Alpha B-crystallin, a major lens protein, was induced in primary cultures of dog lens epithelial cells and glomerular endothelial cells when they were grown under conditions of hypertonic stress. With Western blot analysis using a specific alpha B-crystallin antibody, we observed a significant increase in the concentration of alpha B-crystallin protein in cells grown for 4-6 days in media supplemented with 150 mM NaCl or 250 mM cellobiose. These supplements increased the osmolarity of the medium from 300 to 550-600 mosmol kg-1. Alpha B-crystallin mRNA was also increased reaching a maximum four-fold increase in lens and 16-fold increase in kidney cells within 1-2 days. These studies demonstrate a type of regulation of alpha B-crystallin expression in cells from lenticular and non-lenticular tissues.

Animals↗
PubMed1992

Direct visualization of plasmid DNA in bacterial cells.

The direct visualization of plasmid DNA inside Escherichia coli cells is demonstrated using phase-fluorescence microscopy of DAPI (4',6-diamidino-2-phenylindole)-stained bacteria. Small as well as large plasmids could be detected, both in minicells and in cells of larger size. For large plasmids, even single molecules appeared to be within the detection limit. The fluorescence generated from monomers of small plasmids was probably below this limit, and for these plasmids the observed signals may represent aggregates. The distribution of the fluorescence foci might reflect specific plasmid positioning during partition and/or replication.

Cell Division↗
PubMed1991

The E. coli cell cycle and the plasmid R1 replication cycle in the absence of the DnaA protein.

In E. coli strain EC::71CW chromosome replication is under the control of the R1 miniplasmid pOU71. A dnaA850::Tn10 derivative of EC::71CW was viable, which confirmed that R1 can replicate in the absence of the DnaA protein. The frequency of initiation of replication was, however, lowered and cell division was severely disturbed due to underreplication of the chromosome. Both replication and cell division could be restored to normal by increasing the production of RepA, the rate-limiting protein for initiation of replication from the integrated R1 origin. Therefore, the RepA protein seems to compensate for the absence of DnaA in the initiation of replication and assembly of replisomes. The role of the DnaA protein in the initiation of DNA replication, and as an overall regulator of the chromosome replication and cell division cycles of E. coli, is discussed in view of these results.

Bacterial Proteins↗