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Biomedical subjects

R K Gupta

Publications and source records attributed to R K Gupta.

At least 757 records · Page 42Linked to original sources
PubMed1976

Fructose 1,6-bisphosphate: isomeric composition, kinetics, and substrate specificity for the aldolases.

13C NMR shows fructose 6-phosphate and fructose 1,6-bisphosphate to contain respectively 4.1 and 2.0% keto isomer at room temperature. The lower value for fructose 1,6-bisphosphate can be attributed to the electron-withdrawing effect of the C-1 phosphate. Measurements of the ring-opening rates of the alpha and beta anomers of fructose, 1,6-bisphosphate by an NMR line-broadening technique show them to be about 8 and 35 S-1, respectively, at pH 7.2, and 25degreesC. The value for the predominant beta anomer is threefold greater than the turnover rate of muscle aldolase so that, if the kinetic properties of the keto form were favorable, the reaction could proceed entirely through the keto form in solution. The kinetic properties of a fructose 1,6-bisphosphate(keto) analogue, 5-deoxyfructose, 1,6-bisphosphate, in the muscle aldolase reaction are more favorable (Vmax = 2.6, Km = 0.11 X 10(-6) M) than those of fructose 1,6-bisphosphate total (Vmax = 1, Km = 2.3 X 10(-6)M), giving a value of Vmax/Km that is 56 times greater for the 5-deoxy analogue. At the 2.0% concentration of the keto form this is sufficient to account for the steady-state rate and requires that the beta form, present at 40 times greater concentration, contributes little to the cleavage rate. With yeast aldolase the cleavage rate can be explained by the rapid spontaneous ring opening and reaction of the keto form with the enzyme. In view of the high rate of ring opening and the excellent properties of the keto form, previous rapid kinetic studies favoring action of cyclic forms may require reevaluation.

Fructose-Bisphosphate Aldolase↗
PubMed1976

Detection of tumor-associated antigen in human melanoma cell line supernatants.

Spent tissue culture medium (CDM-S) removed from a single cell line of human malignant melanoma grown in serum-free CDM, contained tumor-associated antigenic activity. Antibodies to CDM-S measured by complement fixation were detected in 44% (31/70) melanoma, 55% (15/27) sarcoma, 63% (24/38) carcinoma and 15% (11/72) normal sera. Delayed cutaneous hypersensitivity reactions (DCHR) were demonstrated in 4/5 melanoma patients at a 500 mug dose, 3/5 at a 100 mug dose and in 1/7 carcinoma patients at the 500 mug dose. One ml of CDM-S was shown to contain antigen equivalent to that obtained from the membranes of 2.9 X 10(7) tissue-cultured melanoma cells. After purification, 84% (16/19) sera from melanoma patients, 66% (12/18) from sarcoma and carcinoma patients and 8% (2/26) from normal controls were positive to the antigen by complement fixation.

Antibodies, Neoplasm↗
PubMed1976

Chromium(III)-adenosine triphosphate as a paramagnetic probe to determine intersubstrate distances on pyruvate kinase. Detection of an active enzyme-metal-ATP-metal complex.

The interaction of CrATP, a stable, substitution-inert, paramagnetic tridentate complex of ATP, with muscle pyruvate kinase has been studied by measuring the effects of CrATP on the kinetics of pyruvate enolization and on the longitudinal nuclear magnetic relaxation rate (1/T1) of the protons of water and the protons and carbon atoms of pyruvate to investigate the existence and activity of bimetallic enzyme-M(II)-CrATP complexes and to determine intersubstrate distances on a kinase. The paramagnetic effect of CrATP on 1/T1 of water protons is enhanced upon complexation with the enzyme. Titrations of the enzyme with CrATP yielded characteristic enhancements of 1/T1 for the binary enzyme-CrATP, ternary enzyme-Mg(II)-crATP, and quaternary enzyme-Mg(II)-crATP-pyruvate complexes of 3.5, 1.7, and 1.2 and dissociation constants of CrATP of 400, 200, and 200 muM, respectively. From the frequency dependence of 1/T1, the number of fast exchanging water protons in the coordination spheres of Cr(III) is approximately 6 in CrATP and in both the ternary enzyme-Mg(II)-CrATP complex and the quaternary enzyme-Mg(II)-CrATP-pyruvate complex. The paramagnetic effect of enzyme-bound Mn(II) on 1/T1 of water protons decreases upon the addition of CrATP. Titration of the binary enzyme-Mn(II) complex with CrATP decreases the characteristic enhancement due to Mn(II) from 24 +/- 3 to 6 +/- 1. Titration of the ternary eznyme-Mn(II)-pyruvate complex with CrATP decreases the enhancement from 6 +/- 1 to 0.5 +/- 0.1. The affinity of the enzyme for Mn(II) is increased 2-fold upon binding of CrATP as indicated by decreases in the amplitude of the EPR spectrum of free Mn(II). The dissociation constants of CrATP from the enzyme-Mn(II)-CrATP complex, the enzyme-CrATP-pyruvate complex, and the enzyme-Mn(II)-CrATP-pyruvate complex are all 200 muM. The observed titration behavior, the characteristic enhancement values, the tightening by Mg(II) of the binding of CrATP to the enzyme, and the tightening of the binding of Mn(II) to the enzyme by CrATP establish the existence of enzyme-M(II)-CrATP and enzyme-M(II)-CrATP-pyruvate complexes containing two cations, Mg(II) or Mn(II) and Cr(III), at the active site.

Adenosine Triphosphate↗
PubMed1976

Arrangement and conformations of substrates at the active site of pyruvate kinase from model building studies based on magnetic resonance data.

Seventeen distances from two paramagnetic reference points, as determined by nuclear relaxation studies of six active complexes of rabbit muscle pyruvate kinase, have been used to construct molecular models of two composite enzyme complexes. In the model of the hypothetical pyruvate kinase-M(I)-M(II)-ATP-Cr(III)-P-enolpyruvate complex, overlap of the transferred phosphoryl groups of the two substrates, which is required to explain the observed competition, is incomplete, allowing greater than or equal to 1 A for the transition state to form. In the active enzyme-M(I)-M(II)-ATP-Cr(III)-pyruvate complex, the gamma-phosphoryl phosphorus of ATP is in molecular contact (3.0 +/- 0.5 A) with the carbonyl oxygen of pyruvate, consistent with direct phosphoryl transfer, indicating no need for intermediate phosphorylation of the enzyme. The enzyme-bound divalent cation, which forms second sphere complexes with the phosphoryl groups of P-enolpyruvate and ATP, may activate the transferred phosphoryl group indirectly, through a water ligand. By analogy with the position of Cr(III), a second divalent cation may participate more directly by coordination of the triphosphate chain of ATP.

Adenosine Triphosphate↗
PubMed1976

Human tumor cells grown in fetal calf serum and human serum: influences on the tests for lymphocyte cytotoxicity, serum blocking and serum arming effects.

Peripheral blood lymphoid cells (PBL) from cancer patients and normal donors were tested against three melanoma cell lines grown in either 10% fetal calf serum (FCS) or 2.5-5% human AB serum in order to determine if the heterologous membrane (HM) antigen or other FCS antigens acquired from the bovine serum supplement could influence lymphoid cell-mediated cytotoxicity in vitro. FCS-grown melanoma cells were more susceptible than the AB serum-grown subline to lymphocyte cytotoxic effects. Arming effects by autologous sera on normal donor lymphocytes and to a lesser extent on lymphocytes of cancer patients were more pronounced on the FCS-grown M12 melanoma cells. This effect was abrogated when the cells were grown in human AB serum for at least 8 weeks. The non-HM tumor-associated antigen remained at the same original low level. Blocking effects were more evident on the AB-grown M14 melanoma line. These data suggest that the FCS antigens on the cell surface may have been responsible for the augmented PBL cytotoxicity. The anti-FCS antibody present in normal and cancer patients' blood induced an antibody-dependent cellular cytotoxicity (ADCC). Elimination of arming activity against HM or other FCS antigens from AB-grown cells may have made the serum blocking factors more apparent. However, cytotoxicity against tumor cells by PBL from normal donors was still apparent even on the human serum-grown cells, suggesting that a different antigen-antibody system was also responsible for this "non-specific" activity.

Animals↗
PubMed1976

Magnetic resonance studies of the proximity and spatial arrangement of propionyl coenzyme A and pyruvate on a biotin-metalloenzyme, transcarboxylase.

A spin-labeled ester of CoA, R-CoA (3-carboxy-2,2,5,5-tetramethyl-1-pyrolidinyl-1-oxy CoA thioester), has been shown by competition studies using electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) to bind specifically to the propionyl-CoA binding sites of transcarboxylase. Titrations indicate 0.7 +/- 0.2 binding site for R-CoA per enzyme-bound biotin with a dissociation constant of 0.33 +/- 0.12 mM. Propionyl-CoA binds to this site with a 1.3-fold lower disonable agreement with kinetically determined inhibitor constants of CoA and propionyl-CoA and propionyl-CoA (D. B. Northrop (1969), J. Biol. Chem. 244, 5808). The bit of this spin-label on 1/T1 of water protons. The formation of a ternary transcarboxylase-R-CoA-pyruvate complex is suggested by the failure of pyruvate to displace R-CoA from the tight site and is established by the paramagnetic effects of enzyme-bound R-CoA on the relaxation rates of the protons and 13C atoms of enzyme-bound pyruvate. From the paramagnetic effects of R-CoA on the relaxation rates of the methyl protons of pyruvate at 40.5 and 100 MHz, and on the 13C-enriched carbonyl and carboxyl carbon atoms of pyruvate at 25.1 MHz, a correlation time of 7 nsec and distances from the bound nitroxide radical to the methyl protons, the carbonyl, and carboxyl carbon atoms of bound pyruvate of 7.9 +/- 0.7, 10.3 +/- 0.8, and 12.1 +/- 0.9 A, respectively, are calculated. These distances establish the close proximity of the CoA ester and keto acid sites on transcarboxylase. Together with the previously determined distances from the enzyme-bound (Co(II) to the methyl protons and 2 carbon atoms of bound pyruvate and to 12 protons and 3 phosphorus atoms of bound propionyl-CoA, the present distances are used to derive a composite model of the bound substrates in the overall transcarboxylation reaction. In this model the distance from the methyl carbon of pyruvate and the methylene carbon of propionyl-CoA, between which the carboxyl transfer takes place is only approximately 7 A. Depending on the detailed mechanism of the carboxyl transfer, the distance through which the carboxybiotin must migrate is therefore between 0 and 7 A. Hence the major role of the 14-A arm of carboxybiotin is not to permit a large carboxyl migration but, rather to permit carboxybiotin to traverse the gap which occurs at the interface of three subunits and to insinuate itself between the CoA and keto acid sites.

Binding Sites↗
PubMed1976

Immunocytologic losses of isoantigens A, B, and H (O) in the endometrium and brain.

Formalin-fixed tissues from 100 endometria and 50 brains were grouped and studied by the technic of mixed-cell agglutination reaction (MCAR) for studying isoantigens A, B, and H (O). MCAR's were negative in all 45 of the endometria from subjects with endometrial carcinomas, where as MCAR's were positive in the epithelium of endometrial glands of the remaining 55 subjects (cyclic phases of endometrium and benign lesions). MCAR's were negative in all benign and malignant brain tumors and normal brain tissues used in this study. In view of the present findings and in the light of previous observations, the isonatigen loss in adenocarcinomas is greater than such losses in other types of malignancies so far studied. The cause of the negative MCAR's in normal brain tissue and brain tumours is not known, but they may be attributable to lack of isoantigens in normal brain tissue.

ABO Blood-Group System↗
PubMed1976

A double-blind comparison of lithium carbonate and maprotiline in the prophylaxis of the affective disorders.

A double-blind prospective study was carried out comparing the prophylactic effect of maprotiline and lithium carbonate over a period of one year in patients suffering from recurrent affective disorders. The average Affective Morbidity Index was lower, but not significantly so, in patients treated with lithium. A further analysis, based on dividing patients into those with no affective morbidity and those who showed some affective morbidity during the study, demonstrated lithium carbonate to be significantly superior to maprotiline both in the group as a whole and in unipolar depressives. A correlation between high plasma maprotiline concentration and low morbidity was observed and was in line with an earlier report. A highly significant negative correlation (r=-0-97; p less than 0-001) was found between plasma maprotiline concentration and body weight. Although the results showed lithium carbonate to be superior to maprotiline in the study, it should be emphasized that the plasma levels of lithium were constantly monitored and maintained at what is considered to be its optimum concentration, whereas the maprotiline treated patients were kept on a fixed dosage regime irrespective of plasma levels.

Adult↗
PubMed1976

Studies on the morphology and histology of the digestive tract of Bagarius bagarius (Ham).

1. The alimentary tract of Bagarius bagarius is long in accordance with its omnivorous nature and consists of buccal cavity, pharynx, oesophogus, stomach, intestine, and rectum. 2. The month is terminal and bounded by upper and lower lips, which are provided with many villiform teeth. 3. The buccal cavity and pharynx are dorso-ventrally flattened with smooth lining in the former and folded in the latter. Taste buds and mucous cells are present in these parts which help in selection of food and inlubricating the prey respectively. 4. The oesophagus is small but wide and produced into longitudinal folds. Histologically it is composed of the usual 4 layers viz. serosa, muscularis, submucosa and mucosa. The mucosa is stratified and bears mucous cells. 5. The stomach is large, sac-like and divided into a large cardiac and a small pyloric portion. In the submucosa of the cardiac part, gastric glands are present into the cryps of mucosa. 6. The intestine is distinguished into duodenum, ileum and rectum on the basis of folds. These folds are of honey comb type in duodenum, longitudinal in the ileum, and anatamosing in the rectum to form a honey comb. The muscularis of the duodenum is better developed than that of the ileum and is best formed in the rectum, where the mucosa contains abundant mucous cells. 7. The liver consists of 2 lobes and is formed of polygonal cells. Blood capillaries and hepatic ductules are present in it. The gall bladder lies in between the right lobe of liver and duodenum. It consists of connective tissues lined with columnar cells on inner side and serosa on the outer side. 8. The pancreas is diffused and lies concentrated between the liver, stomach and the coils of intestine. It is composed of polyhedral cells, which are aggregated to form acini. The pancreatic tissue is supplied with the pancreatic ductules and blood capillaries.

Animals↗
PubMed1976

Residues of DDT and its metabolites in human blood samples in Delhi, India.

Blood samples from 182 people in Delhi, India, were examined for DDT residues. All except 8 contained DDT and its metabolites. The average total DDT concentration in the whole blood ranged from 0.177 to 0.683 mg/litre in males and from 0.166 to 0.329 mg/litre in females. The DDT metabolites detected were p,p'-DDE, p,p'-DDD, and o,p'-DDT. DDE accounted for most of the total DDT.

Adolescent↗