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Biomedical subjects

D Sinha

Publications and source records attributed to D Sinha.

At least 55 records · Page 3Linked to original sources
PubMed1994

Ligand binding assays with recombinant proteins refolded on an affinity matrix.

This paper describes a procedure for performing ligand binding assays with recombinant proteins or protein fragments that can bind to an affinity matrix in the presence or absence of a denaturing agent but which require the presence of the denaturing agent to remain in solution. The method involves coupling of a known amount of the protein in a denaturing medium to a known amount of the affinity matrix, replacing the denaturing agent with a physiological buffer, and finally using the suspension of this protein-coupled matrix as the source of the recombinant protein to be studied for its functional properties. A constant volume of this suspension is incubated with different concentrations of a radiolabeled ligand. Radioactivity bound to the protein-coupled affinity matrix is determined after centrifugation and washing of the pellet. Nonspecific binding is determined either by using the uncoupled affinity matrix or by the standard technique of measuring the binding in the presence of excess unlabeled ligand.

Crotalid Venoms↗
PubMed1993

PCR to identify specific clones of interest for DNA sequencing.

We describe a rapid method for identifying specific clones of interest for the purpose of sequencing. The method essentially is polymerase chain reaction using one internal primer and one vector specific primer. The procedure is particularly useful when relatively large numbers of clones are to be examined either to establish the nucleotide sequence of a full-length cDNA or to find a specific section of a large DNA. The relative orientations of inserts in different clones can also be determined using the same procedure.

Animals↗
PubMed1992

Complete cDNA sequence of bovine alpha 1-antitrypsin.

A cDNA clone coding for the entire bovine alpha 1-antitrypsin molecule has been isolated from a lambda gt11 bovine liver cDNA library using a human alpha 1-antitrypsin cDNA as a probe. The bovine cDNA was sequenced by the dideoxynucleotide chain termination method. Comparison of the translated amino acid sequence of the bovine alpha 1-antitrypsin with those of the human, baboon, sheep, rat and mouse demonstrates the preservation of most of the critical structural determinants. The bovine and the sheep molecules have a sequence homology of 94% and both the molecules contain four cysteine residues; there is only one cysteine in the others.

Amino Acid Sequence↗
PubMed1992

A new scale for assessing behavioral agitation in dementia.

The primary purpose of the present study was to develop a reliable and valid rating instrument for assessing treatment efficacy for behavioral problems in the cognitively impaired elderly. The Behavioral and Emotional Activities Manifested in Dementia (BEAM-D) Scale was developed for the operational assessment of troublesome and disruptive behaviors in dementia. Each behavioral category of the BEAM-D was clinically considered to be a significant deviation from normative behavior for the geriatric dementia patient. The reliability and validity of the BEAM-D was assessed in a group of 45 patients diagnosed with primary degenerative dementia. The mean interrater reliability of BEAM-D items was 0.90. Concurrent validity was established by comparison with currently used rating scales, the Brief Psychiatric Rating Scale (BPRS) and the Sandoz Clinical Assessment-Geriatric (SCAG). Stepwise regression analysis revealed that the items of the BEAM-D had a strong relationship with conceptually similar behavioral dimensions on the BPRS and SCAG.

Aged↗
PubMed1991

Early experience with percutaneous transluminal coronary angioplasty in unstable angina.

Percutaneous transluminal coronary angioplasty was done in 13 of 105 patients with unstable angina, 10 of whom were males. Diagnostic coronary angiography revealed single vessel disease in 10 cases and two vessel disease in 3 cases; the degree of stenosis varied from 70-90%. Only a single major coronary artery was dilated. Immediate angiographic success was achieved in 12(92.3%) cases. The success rate at the time of discharge from hospital was 10 (76.9%) cases. Immediate complications encountered were acute myocardial infarction in 2 cases, they refused coronary artery bypass grafting and unsuccessful dilation in 1 case. No death occurred during the hospital stay. During follow-up of 6-9 months, 8 patients were symptom free (66.6%), 2 patients required repeat percutaneous transluminal coronary angioplasty and 2 patients died. In conclusion, percutaneous transluminal coronary angioplasty may be undertaken relatively safely in unstable angina, it leads to substantial improvement in symptoms during the early follow-up period. This therapeutic approach is highly beneficial particularly in single vessel disease.

Adult↗
PubMed1989

Functional domains in the heavy-chain region of factor XI: a high molecular weight kininogen-binding site and a substrate-binding site for factor IX.

To probe the molecular interactions of factor XI we have prepared two monoclonal antibodies (MoAbs; 5F7 and 3C1), each of which binds the heavy chain of reduced and alkylated factor XIa. Competitive solid phase radioimmunoassay (RIA) binding studies revealed that 5F7 and 3C1 are directed against different epitopes within factor XI. One antibody (5F7) blocked the surface-mediated proteolytic activation of factor XI and its binding to HMW kininogen, but had no effect on factor-XIa-catalyzed factor IX activation. The other antibody (3C1) is a competitive inhibitor of factor-IX activation by factor XIa, but blocked factor-XI binding to HMW kininogen only at 1,000-fold higher concentration than 5F7. Moreover, HMW kininogen had no effect on the kinetics of factor-XIa-catalyzed factor-IX activation. Furthermore, factor XI CNBr peptide fragments that bind to the 5F7 and 3C1 antibodies were isolated. The peptides that bound to the 5F7 antibody blocked the binding of HMW kininogen to factor XI but did not inhibit factor-XIa-catalyzed factor-IX activation. However, the peptides isolated by the 3C1 antibody inhibited factor-XIa-catalyzed factor-IX activation and had no effect on factor-XI binding to HMW kininogen. Our results indicate that distinct functional domains within the heavy chain region of factor XI are important for the binding of factor XI to HMW kininogen and for activation of factor IX by factor XIa.

Antibodies, Monoclonal↗
PubMed1988

Carcinogenicity of aromatic hydrocarbons directly applied to rat mammary gland.

To obtain some initial evidence on the mechanism(s) of activation of PAH in rat mammary gland, we studied the carcinogenicity of a series of PAH directly applied to this tissue. A series of PAH which are or are not expected to be activated by one-electron oxidation because of their low or high ionization potential (IP), respectively, were tested. The compounds were dispersed as fine powders on an exposed mammary gland of female Sprague-Dawley rats. 5-Methylchrysene, dibenz[a,h]anthracene and benz[a]anthracene, which have relatively high IP, were inactive. In contrast, three PAH with relatively low IP, 7,12-dimethylbenz[a]anthracene, benzo[a]pyrene (BP), and 3-methylcholanthrene (MC), were potent carcinogens, 6-MethylBP, with low IP, and 7-methyl-benz[a]anthracene, with borderline IP, elicited only mesenchymal tumors, whereas BP 7,8-dihydrodiol and cyclopenta[cd]pyrene were inactive. A series of MC derivatives substituted at C-1 or C-2 was tested. Substituents at C-1, the position of activation in the one-electron oxidation pathway, generally suppressed carcinogenic activity. Substitution at C-2 did not eliminate carcinogenic activity, with the exception of MC2-one. These results provide initial information suggesting that one-electron oxidation may be a mechanism of activation for PAH in the mammary gland.

Animals↗
PubMed1987

Role of calcium ions and the heavy chain of factor XIa in the activation of human coagulation factor IX.

Since optimal rates of factor IX activation by factor XIa require the presence of calcium ions and the heavy chain of the enzyme as well as the active-site-containing light chain, we have studied the effects of calcium ions and the heavy chain on the reaction kinetics. Whereas the amidolytic activities of factor XIa and of its active-site-containing light chain were almost indistinguishable, the two enzymes behaved quite differently when factor IX was the substrate. Factor XIa was 100-fold more potent in the presence of Ca2+ than in its absence. On the contrary, the presence or absence of Ca2+ made very little difference in the case of the isolated light chain of factor XIa. Moreover, the enzymatic activity of the light chain was almost identical with that of intact factor XIa when Ca2+ was absent. Using an optimal concentration of Ca2+, we studied the activation in the presence of various concentrations of two monoclonal antibodies, one (5F4) directed against the light chain of factor XIa and the other (3C1) against its heavy chain. Analysis of 1/V vs. 1/S plots showed that whereas inhibition by 5F4 was noncompetitive, 3C1 neutralized the enzyme in a classical competitive fashion. We conclude that in the calcium-dependent activation of factor IX by factor XIa the heavy chain of the enzyme is involved in the binding of the substrate and this is essential for optimal reaction rates.

Antibodies, Monoclonal↗
PubMed1987

Drug levels and antiparkinsonian drugs in neuroleptic-treated schizophrenic patients.

The limitations of antiparkinsonian treatment strategy when using anticholinergic drugs are determined by their side effects induced through excessive inhibition of parasympathetic functions. In the present study we have investigated the peripheral effects of antiparkinsonian agents on blood levels of concomitantly administered neuroleptic drugs. We have compared the anticholinergic and a dopamine mimetic antiparkinsonian agent in their effects on serum neuroleptic activity (SNA) and serum anticholinergic activity (SAA). Sixteen schizophrenic patients on chronic neuroleptic therapy with steady state neuroleptic levels were receiving either amantadine, 200 mg/day, or anticholinergic drugs (trihexyphenidyl, 10 mg/day, or benztropine, 6 mg/day) for the first 2 weeks, after which the amantadine group was crossed over to anticholinergic and the anticholinergic group to amantadine for the following 2 weeks. Blood samples were obtained once a week along with clinical testing. The results indicate that SAA was fivefold higher with benztropine than with trihexyphenidyl and that amantadine had no effect on SAA. Moreover, SNA was not altered either by anticholinergics or amantadine coadministration, indicating that the therapeutic blood neuroleptic levels are not compromised by antiparkinsonian administration.

Adult↗
PubMed1987

Regulation of factor XIa activity by platelets and alpha 1-protease inhibitor.

We have studied the complex interrelationships between platelets, Factor XIa, alpha 1-protease inhibitor and Factor IX activation. Platelets were shown to secrete an inhibitor of Factor XIa, and to protect Factor XIa from inactivation in the presence of alpha 1-protease inhibitor and the secreted platelet inhibitor. This protection of Factor XIa did not arise from the binding of Factor XIa to platelets, the presence of high molecular weight kininogen, or the inactivation of alpha 1-protease inhibitor by platelets. The formation of a complex between alpha 1-protease inhibitor and the active-site-containing light chain of Factor XIa was inhibited by activated platelets and by platelet releasates, but not by high molecular weight kininogen. These results support the hypothesis that platelets can regulate Factor XIa-catalyzed Factor IX activation by secreting an inhibitor of Factor XIa that may act primarily outside the platelet microenvironment and by protecting Factor XIa from inhibition, thereby localizing Factor IX activation to the platelet plug.

Blood Platelets↗
PubMed1986

Mechanism of activation of coagulation factor XI by factor XIIa studied with monoclonal antibodies.

The interaction of Factor XIIa with Factor XI was investigated using two monoclonal antibodies, one (3Cl) directed against the heavy chain of Factor XIa and the other (5F4) against its light chain. 3C1 either as intact IgG or as Fab' fragment, enhanced the rate of Factor XIa generation in the fluid phase but inhibited it in the presence of kaolin and high molecular weight (HMW) kininogen. In contrast, the Fab' fragments of 5F4 inhibited only the fluid phase activation and had no effect on the surface-mediated activation. 3C1 was found to block the binding of Factor XI to HMW kininogen, whereas 5F4 did not. We conclude: a domain on the heavy chain region of Factor XI is essential for binding to HMW kininogen and for optimal surface-mediated activation by Factor XIIa; and binding of 3C1 to Factor XI changes its conformation rendering it a more favorable substrate for Factor XIIa in the fluid phase.

Antibodies, Monoclonal↗
PubMed1986

Functional characterization of platelet-bound factor XIa: retention of factor XIa activity on the platelet surface.

Previously we have shown that both factor XI and factor XIa are bound specifically to distinct, high-affinity sites on the surface of activated platelets in the presence of high Mr kininogen. To determine the functional significance of factor XIa binding to platelets, bound factor XIa has now been compared with the unbound enzyme. Platelets incubated with thrombin, high Mr kininogen, and 125I-labeled factor XIa bound 130 to 500 molecules of factor XIa per platelet. Scatchard analysis of binding data give a dissociation constant (Kd) of 822 pmol/L +/- 140 (SEM). Rates of factor IX activation, assayed by release of trichloroacetic acid-soluble 3H-labeled activation peptide from purified [3H]-factor IX, were similar when factor XIa was bound to platelets and when it was free in solution. The platelet-bound factor XIa was isolated by centrifugation through 20% sucrose and was functionally characterized both in a factor XIa coagulation assay and in the factor IX activation peptide release assay in comparison with unbound factor XIa in the presence of treated platelets. The functional activity of platelet-bound factor XIa as a factor IX activator as well as its structural integrity were shown to be fully retained on the platelet surface. Since platelets bind factor XI and promote its proteolytic activation to factor XIa, factor XIa binding to platelets may serve to localize factor IX activation to the hemostatic plug, where factor XIa is protected from inactivation by plasma protease inhibitors and where acceleration of subsequent coagulation reactions can occur.

Binding Sites↗
PubMed1985

Functional characterization of human blood coagulation factor XIa using hybridoma antibodies.

During the initiation of intrinsic coagulation factors XI and XIa interact intimately with several other coagulation proteins (factor XIIa, high Mr kininogen, and factor IX) as well as with the platelet surface. To help elucidate these complex intramolecular interactions, we have prepared a collection of monoclonal antibodies directed against various epitopes in factor XI. We have utilized these reagents to isolate factor XI and the light chain of factor XIa on affinity columns, and to probe structure-function relationships involved in the interactions of factor XIa with factor IX. The isolated light chain of factor XIa retained greater than 90% of its amidolytic activity against the oligopeptide substrate pyro-Glu-Pro-Arg-pNA (S-2366), but only 3.8% of its clotting activity in a factor XIa assay and 1% of its factor IX activating activity in an activation peptide release assay. This suggests that regions of the heavy chain are required for development of coagulant activity and specifically for the interaction of factor XIa with factor IX. To test this hypothesis, the effects of three of the monoclonal antibodies (5F4, 1F1, and 3C1) on the function of factor XIa were examined. The results show that in a clotting assay the light chain-specific antibody (5F4) inhibits 100% of the factor XIa activity, whereas of the heavy chain-specific antibodies, one (3C1) inhibits 75% and another (1F1) only 17%. Similarly in the factor IX activation peptide release assay, antibody 5F4 inhibits 100% of the factor XIa activity, whereas 3C1 inhibits 75% and 1F1 inhibits 33%. We conclude that regions located in the heavy chain, in addition to those in the light chain, are involved in the interaction of factor XIa with factor IX and in the expression of the coagulant activity of factor XI.

Antibodies, Monoclonal↗