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Biomedical subjects

R Chatterjee

Publications and source records attributed to R Chatterjee.

At least 109 records · Page 6Linked to original sources
PubMed1987

Immunogenicity of human immunodeficiency virus (HIV) reverse transcriptase: detection of high levels of antibodies to HIV reverse transcriptase in sera of homosexual men.

Immunoglobulin isolated from sera of homosexual men infected with human immunodeficiency virus (HIV) inhibited the reverse transcriptase (RT) activity of HIV. The inhibitory activity was specifically directed against HIV RT, and not against other mammalian retrovirus RT, including human T-lymphotropic virus type I. The relative titer of anti-RT antibody was significantly higher in asymptomatic men than in patients with lymphadenopathy or acquired immune deficiency syndrome (AIDS)-related complex. There was no correlation between the relative titer of anti-RT antibody and the relative titers of antibodies to major virion structural protein as determined by the enzyme-linked immunosorbent assay (ELISA) technique. These data suggest that antibodies to HIV RT may be related to the clinical status and possibly to the different degree of HIV replication in HIV-infected homosexual men.

AIDS-Related Complex↗
PubMed1986

Isolation and characterization of a new hemoglobin derivative cross-linked between the alpha chains (lysine 99 alpha 1----lysine 99 alpha 2).

Bis(3,5-dibromosalicyl) fumarate and a number of related bifunctional reagents react preferentially with oxyhemoglobin to cross-link the beta chains within the 2,3-diphosphoglycerate-binding site. In this report we describe a new derivative cross-linked between the alpha chains which is formed specifically in the reaction with deoxyhemoglobin. X-ray crystallographic studies show that the cross-link lies between Lys-99 alpha 1 and Lys-99 alpha 2, spanning the central cavity of the tetramer. Lys-99 alpha 1 and Lys-99 alpha 2 are located within a cluster of charged residues very near the middle of the hemoglobin molecule. In oxyhemoglobin, this site is completely inaccessible to the cross-linking agent. Competition experiments with inositol hexaphosphate indicate that the compound enters the central cavity in deoxyhemoglobin through the cleft between the alpha chains. Despite the presence of the cross-link between the alpha chains, the modified hemoglobin remains highly cooperative. The Hill coefficient for HbXL99 alpha is 2.6. The oxygen affinity of the cross-linked derivative is decreased by approximately 2-fold; at pH 7.0 in the presence of 0.1 M NaCl the P50 is 13.9 mm Hg compared to 6.6 mm Hg for HbA. This difference appears to be due to relatively small changes in both KR, the association constant for binding of oxygen to the R state, and the allosteric constant L. Surprisingly, the isoelectric point of oxyHbXL99 alpha is almost identical to that of oxyHbA, whereas in the deoxy form the isoelectric point of the cross-linked derivative is decreased relative to native hemoglobin as expected due to the loss of the two positive charges of the modified amino groups. In agreement with these findings, the alkaline Bohr effect of HbXL99 alpha is decreased by more than 50%. Earlier studies argue strongly against the possibility that Lys-99 alpha is directly responsible for this large fraction of the Bohr effect in HbA. Analysis of the structure suggests that in the cross-linked derivative Glu-101 beta, which is in close proximity to Lys-99 alpha in oxyhemoglobin, becomes an acid Bohr group.

Amino Acid Sequence↗
PubMed1986

The specificity of rabbit lung cathepsin I on biopeptides.

Ten peptides were tested as substrates for cathepsin I. The enzyme exerted both endopeptidase and aminopeptidase activities on 5 substrates, only aminopeptidase activity on 3 others, and only endopeptidase cleavage on one compound. One peptide was not significantly hydrolyzed. Aminopeptidase activity stopped one residue before a proline residue and endopeptidase cleavage took place one residue after a proline residue. With these substrates, this enzyme appears to have a broad specificity in its aminopeptidase action. However, cathepsin I appears to have a much narrower and more specific endopeptidase activity, hydrolyzing peptide bonds involving the nitrogen of branched chain or bulky or hydrophobic amino acids. Finally, some differences in the physical, chemical and biological properties of cathepsins H and I were discussed.

Amino Acid Sequence↗
PubMed1986

Concanavalin A-induced agglutination of Ehrlich ascites carcinoma cells during growth of the tumor in mice.

ConA-induced agglutination of Ehrlich ascites carcinoma (EAC) cells during development of the tumor in mice has been studied in vitro. EAC cells were incubated with different concentrations of ConA at 37 degrees C for various intervals of time and the cell aggregates of different sizes were scored under microscope. The older EAC cells (20-day-old) showed a decrease in cytoagglutination with respect to large aggregates formation compared to the younger (10-day-old) ones. The small aggregates formed by the 5-day-old EAC cells are dissociated by competition with alpha-methyl-D-mannoside but the large aggregates are not affected by the sugar treatment. The observed differences in the agglutination patterns are discussed in view of the influence of the lipid content of EAC cells and the ascites fluid on ConA-induced cytoagglutination.

Animals↗
PubMed1985

Clearance of glucose and sucrose from the saliva of human subjects.

The ability of 20 healthy people to clear test solutions of sucrose (0.73 M) and glucose (1.4 M) from the mouth was examined. Both sugars were cleared within 20 min in a two-step manner. Rapid clearance occurred between 0 and 6 min; much slower clearance occurred thereafter. It took 7.2 min with glucose and 6.3 min with sucrose for the saliva-sugar concentration to fall to 1 mg/ml. Salivary flow, stimulated during sugar exposure, decreased in a two-step pattern similar to sugar clearance. Evidently, clearance was dependent on the rate of flow of saliva which took about 1 h to return to its resting flow level. Comparison of the pattern of sugar clearance to the Stephan curve (the rapid pH fall followed by a slow pH rise seen after rinsing with sugar solutions) indicated that the pH-fall phase of the curve occurs during the initial period of rapid sugar clearance and salivary flow, and the pH-rise phase occurs during the subsequent period of slower clearance and slow saliva flow. Comparison with the data of Swenander-Lanke (1957) [Acta odont. scand. 15, 3-156], indicated that the clearance of sugar solutions also reflects the clearance of sugar-containing solid foods from the mouth.

Adult↗
PubMed1985

Chloroquine and premature evacuation of uterine conceptus in rats.

Bilateral spaying on day 18 of pregnancy in rats made the refractory uteri highly reactive to a single injection of chloroquine (25 mg/kg). Complete evaluation of the uterine conceptus resulted by 24-48 hours following chloroquine administration. It was moreover observed that the amount of luteal progesterone which was found to be sufficient to maintain pregnancy until term, failed to reverse the abortifacient efficacy of chloroquine.

Animals↗
PubMed1985

Phytohemagglutinin activation of the transcription of the bovine leukemia virus genome requires de novo protein synthesis.

Addition of supramitogenic doses of phytohemagglutinin (PHA) to short-term cultures of neoplastic or nonneoplastic lymphocytes infected with bovine leukemia virus increased the synthesis of the major core virion antigen (p25) by 5- to 10-fold. Such stimulation was not due to the mitogenic effect of PHA or to a generalized increase in cellular RNA or protein synthesis but rather to enhanced transcription of the viral genome by a PHA-induced protein.

Base Sequence↗
PubMed1985

Partial purification and characterization of tumor associated antigen in cervical carcinoma.

An identical component of tumor associated antigen (TAA) was detected in all clinical stages of the carcinoma of cervix (CaCx), in both premenopausal and postmenopausal patients, using heterologous antisera against the cancer tissues by immunodiffusion and immunoelectrophoretic tests. The TAA appeared to be cross-reacting specifically with carcinoma of other gynecological organs. A second TAA component was observed to be present only in CaCx, Stage II of premenopausal patients. The TAA component of CaCx common for all clinical stages, irrespective of climacteric states, was partially purified by subjecting postmeno CaCx, Stage II to gel filtration on Sephadex G-200. The antigen was found to be glycoprotein in nature, enzyme sensitive, highly thermostable and antigenically active at a pH range of 2.0-10.7. The approximate molecular weight of the component was found to be 67 000.

Adult↗
PubMed1984

Structural features required for the reactivity and intracellular transport of bis(3,5-dibromosalicyl)fumarate and related anti-sickling compounds that modify hemoglobin S at the 2,3-diphosphoglycerate binding site.

Bis(3,5-dibromosalicyl)fumarate (I) reacts preferentially with oxyhemoglobin to cross-link the two beta 82 lysine residues within the 2,3-diphosphoglycerate (DPG) binding site and as a result markedly increases the solubility of deoxyhemoglobin S. The cross-link acts by perturbing the acceptor site for Val 6 within the sickle cell fiber (Chatterjee, R., Walder, R. Y., Arnone, A., and Walder, J. A. (1982) Biochemistry 21, 5901-5909). In the present studies we have compared a large number of analogs of I to determine the structural features of the reagent required for specificity and for transport into the red cell. Both electrostatic and hydrophobic interactions contribute to the binding of these compounds at the DPG site. The optimal position for the negatively charged groups on the cross-linking agent for productive binding is adjacent to the ester as in the original salicylic acid derivatives. There is a direct correlation between the reactivity toward hemoglobin and the hydrophobicity of the substituent attached at the para position. Phenyl and substituted phenyl derivatives as in the analgesic, antiinflammatory drug diflunisal are particularly effective. These groups probably interact with hydrophobic residues of the amino-terminal tripeptide and the EF corner of the beta chains adjacent to the DPG binding site. Although bis(3,5-dibromosalicyl)fumarate is very reactive toward hemoglobin in solution, it is much less effective in modifying hemoglobin within the red cell. The reaction with intracellular hemoglobin was shown to be limited by competing hydrolysis of the reagent catalyzed at the outer surface of the erythrocyte membrane. Inactivation of the red cell membrane acetylcholinesterase with phenylmethylsulfonyl fluoride did not inhibit this reaction. Introduction of a single methyl group onto the carbon-carbon double bond of the fumaryl moiety decreases the lability of the ester 10-fold, due to steric effects, and allows the reagent to be taken up by the red cell and modify intracellular hemoglobin. The kinetics of transport of the methylfumarate derivative, bis(3,5-dibromosalicyl)mesaconate, are first-order, consistent with passive diffusion. The attachment of larger alkyl groups onto the cross-link bridge further enhances the transport of the reagent into the red cell. The solubility of deoxyhemoglobin S cross-linked with the butylfumarate derivative was found to be increased by almost 10% compared to the original fumarate diester.(ABSTRACT TRUNCATED AT 400 WORDS)

2,3-Diphosphoglycerate↗
PubMed1984

The interaction of hemoglobin with the cytoplasmic domain of band 3 of the human erythrocyte membrane.

Previous studies point to the acidic amino-terminal segment of band 3, the anion transport protein of the red cell, as the common binding site for hemoglobin and several of the glycolytic enzymes to the erythrocyte membrane. We now report on the interaction of hemoglobin with the synthetic peptide AcM-E-E-L-Q-D-D-Y-E-D-E, corresponding to the first 11 residues of band 3, and with the entire 43,000-Da cytoplasmic domain of the protein. In the presence of increasing concentrations of the peptide, the oxygen binding curve for hemoglobin is shifted progressively to the right, indicating that the peptide binds preferentially to deoxyhemoglobin. The dissociation constant for the deoxyhemoglobin-peptide complex at pH 7.2 in the presence of 100 mM NaCl is 0.31 mM. X-ray crystallographic studies were carried out to determine the exact mode of binding of the peptide to deoxyhemoglobin. The difference electron density map of the deoxyhemoglobin-peptide complex at 5 A resolution showed that the binding site extends deep (approximately 18 A) into the central cavity between the beta chains, along the dyad symmetry axis, and includes Arg 104 beta 1 and Arg 104 beta 2 as well as most of the basic residues within the 2,3-diphosphoglycerate binding site. The peptide appears to have an extended conformation with only 5 to 7 of the 11 residues in contact with hemoglobin. In agreement with the crystallographic studies, binding of the peptide to deoxyhemoglobin was blocked by cross-linking the beta chains at the entrance to the central cavity. Oxygen equilibrium studies showed that the isolated cytoplasmic fragment of band 3 also binds preferentially to deoxyhemoglobin. The binding of the 43,000-Da fragment to hemoglobin was inhibited in the cross-linked derivative indicating that the acidic amino-terminal residues in the intact cytoplasmic domain also bind within the central cavity of the hemoglobin tetramer.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1984

Studies on concanavalin A receptor sites of tumour cells following ultraviolet exposure.

Alteration of surface receptor of Ehrlich tumour cells by concanavalin A (Con A), shortwave UV and UV plus Con A have been studied. DNA of nuclear chromatins is highly sensitive to UV but receptor glycoprotein sites are UV resistant as evidenced by their retention of agglutination properties after radiation. Con A and UV plus Con A treatments of tumour cells delay the in vivo growth of solid tumour which may be due to some immunological mechanism.

Agglutination Tests↗
PubMed1984

Purification and partial characterization of a murine mammary tumor-associated antigen.

A mammary tumor-associated antigen (MTAA) of the murine mammary tumor virus (MuMTV)-induced spontaneous mammary tumors of C3H/J mice was purified and partially characterized. The crude extract of the mammary tumor, when subjected to DEAE-cellulose chromatography and eluted with a discontinuous NaCl gradient, provided three major protein peaks, of which only the first (F1) possessed the MTAA activity. The antigen was further purified by subjecting F1 to polyacrylamide gel electrophoresis. The MTAA was a glycoprotein with a molecular weight of approximately 83,000. The antigen was localized in the plasma membrane and was different from the MuMTV structural antigens. Circulating antibodies against the MTAA were observed in the sera of tumor-bearing mice but not in that of tumor-free mice.

Animals↗
PubMed1984

Circulating immune complexes in sera of patients with oral cancer.

Circulating immune complexes (IC) in the sera of patients with oral cancer have been measured by using polyethylene glycol (PEG) precipitation assay. At least 60% of patients with carcinomatous buccal mucosa were found to have markedly higher amounts of IC. Results have been discussed in view of other types of cancer and the various methods used for the assay of IC.

Adult↗
PubMed1983

Theory of long-range coherence in biological systems. I. The anomalous behaviour of human erythrocytes.

In this paper, an explicit expression of the interaction potential has been obtained, based on the Fröhlich model of long-range coherence in biological cells. These theoretical expressions are used to correlate with the experimental data obtained from the light scattering and the Brownian motion for the red blood cells (human erythrocytes). The necessary conditions are derived for the formation of rouleaux in human erythrocytes in the presence of long range interactions. The kinetics of rouleaux formation in terms of the properties of the diffusion coefficient has been investigated. It is concluded that both types of experimental data can be interpreted satisfactorily by this model.

Cell Movement↗