Biomedical subjects
Publications and source records attributed to H Bernard.
A novel class of endothelin-A receptor ligands was discovered by high-throughput screening. Lead structure optimization led to highly potent antagonists which can be synthesized in a short sequence. The compounds are endothelin-A-selective, are orally available, and show a long duration of action.
We have isolated a hamster adrenal P45OC11 cDNA which shared 90 and 84% homology, respectively, with the nucleotide sequence and the amino acid sequence of the hamster adrenal P450aldo. Both P450C11 and P450aldo cDNA coding sequences were inserted in the plasmid pBluescript SK, transcribed and then translated using a rabbit reticulocyte system in the presence of [35S]methionine. The reaction products were immunoprecipitated with an anti-bovine P450C11 antibody for P450C11 and with an anti-hamster P450aldo for P450aldo. Immunoprecipitated proteins were analyzed by polyacrylamide gel electrophoresis. A single 35S-labeled protein band was detected for P450C11 and for P450aldo, respectively. P450C11 and P450aldo cDNAs were then both inserted into the expression vector pCMV5 containing a viral sequence specific for the attachment of ribosomes to mRNA. These constructions were transfected in COS-1 cells. 24 h after transfection, the presence of P450C11 and P450aldo mRNAs was determined by Northern blot analysis. In a time study experiment we found that P450C11 transformed the labeled-steroid into [14C]corticosterone, [14C]19-OH-deoxycorticosterone and [14C]18-OH-deoxycorticosterone in ratios of 1:1.11:0.07, after 2 h of incubation; no [14C]aldosterone could be detected. Cells transfected with plasmids harboring the P450aldo cDNA transformed [14C]deoxycorticosterone to [14C]corticosterone, [14C]aldosterone, [14C]18-OH-corticosterone, [14C]18-OH-deoxycorticosterone, [14C]19-OH-deoxycorticosterone and [14C]11-dehydrocorticosterone in ratios of 1:0.25:0.45:0.04:0.04:0.04 after 12 h of incubation. These results indicate that one P450 catalyzes the ultimate step of glucocorticoid formation and a separate P450 is involved in the final steps of aldosterone formation in hamster adrenals. The capacity of the hamster adrenal P450C11 to hydroxylate at positions 11beta and 19 in nearly equal ratio makes this animal an excellent model to study the mechanism of synthesis and inhibition of 19-OH-deoxycorticosterone, the precursor of 19-nor-deoxycorticosterone, a very potent mineralocorticoid involved in the development of essential hypertension.
The immunological characteristics of a recombinant beta-lactoglobulin were studied using monoclonal antibodies, polyclonal antiserum and sera from allergic patients. Recombinant beta-lactoglobulin (rBLG) was expressed in Escherichia coli strain DH5alpha and purified as described previously [Cho et al. (1994) J. Biol. Chem. 269, 11 102-11 107]. The method has been modified by adding an immunoaffinity purification step. A quantity of 5-10mg of purified rBLG per liter of medium culture can be produced. rBLG shared the same molecular weight as the natural BLG (nBLG) and also possessed at least one intrachain disulfide bridge. In HPLC, rBLG appeared as a single peak, and the purity was estimated to be greater than 95%. All the monoclonal antibodies (mAbs) used in this study recognized different epitopes of the BLG and presented compatible binding. No differences could be detected between rBLG and nBLG when tested in a Western blot with rabbit polyclonal antiserum or with three mAbs that bound preferentially the reduced and S-carboxymethylated form of BLG. In a competitive enzyme immunoassay (EIA) using either a rabbit polyclonal antiserum or four mAbs that recognized conformational epitopes, we could not distinguish between rBLG or nBLG. In direct ELISA using nBLG or rBLG as the immobilized allergen, we measured a similar concentration of specific anti-BLG IgE in five sera from allergic patients. The results of this study indicate that we have obtained a rBLG with biochemical and immunological properties very similar to nBLG.
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Some new derivatives of pyrido[2,3-d]pyrimidin-4(3H)-one A and 1,2,3,4-tetrahydro-pyrido[2,3-d]pyrimidines B were prepared. The study of their in vitro antiaggregating activity showed that the compounds A possessed an inhibitory potency when aggregation was induced with ADP. Their reduction to derivatives of 1,2,3,4-tetrahydro-pyrido[2,3-d]pyrimidine B led to a new series of molecules possessing a greater antiaggregating power. When compared to that of acetylsalicylic acid under the same conditions, this activity was weaker with collagen, the same with arachidonic acid-induced aggregation, but greater when aggregation was induced by ADP. However, they inhibited serotonin release only slightly. Compared to ginkgolide they remained weaker with PAF-induced aggregation.
We isolated a cDNA from a hamster adrenal cDNA library which was similar in sequence to those of the mouse and rat P450c18 cDNAs. The hamster P450c18 cDNA, however, was shorter than the rat and mouse P450c18 cDNAs at its 5'-end and the peptide leader sequence was absent. From a hamster genomic library we isolated and sequenced the first seven exons and a 5'-flanking region of the first P450c18 gene exon. With this information we were able to generate a P450c18 cDNA containing the peptide leader sequence using the polymerase chain reaction. Northern analyses were performed on adrenals from hamsters maintained on a low sodium diet for 0, 4, 7 and 10 days using a 32P-labeled sequence specific to P450c18; two mRNA bands were found at 2 and 3.4 kb. The intensity of both bands was increased about 3- to 5-fold under sodium restriction compared to controls. A distinct mRNA band of 2.3 kb hybridized with an oligonucleotide specific to P450(11) beta and its intensity did not change following low sodium intake. Immunoblotting analyses were performed using an antibovine adrenal P450(11) beta antibody that does not discriminate between P450(11) beta and P450c18 proteins. Three bands were detected at 52, 48 and 45 kDa in homogenate preparations of entire glands. Furthermore, the 45 kDa protein band was present in homogenates of the zona glomerulosa and absent in homogenates of the zone fasciculata-reticularis. In conclusion, these results show that the hamster adrenals express P450c18 as do mouse, rat and human adrenal glands. Furthermore, two P450c18 mRNAs, which are inducible by a low sodium intake, are present in the hamster adrenal vs one for the rat. The physiological role of these two hamster adrenal mRNA species remains to be elucidated.
Isolated from an Escherichia coli strain MEN-1 is a plasmid-mediated beta-lactamase that confers resistance to methoxy imino third-generation cephalosporins. The protein purified to homogeneity was digested by trypsin, chymotrypsin and endoproteinase Asp-N. Amino acid sequence determinations of the resulting peptides gave rise to the alignment of the 263 residues of the beta-lactamase. From amino acid sequence comparison MEN-1 was found to share more than 72% identity with the chromosomally mediated beta-lactamases of Klebsiella oxytoca. Therefore, MEN-1 is the first transferable extended-spectrum beta-lactamase which is not directly derived from the widespread TEMs or SHV-1 penicillinases with which it presents less than 39% identity.
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Some derivatives of thieno[2,3-d]pyrimidin-4(3 H)-one A and their 1,2-dihydrogenated homologues B were synthesized. The study of their in vitro antiaggregating activity showed that the first compounds exhibited significant inhibiting power when aggregation was induced with ADP. Their reduction to derivatives of 1,2-dihydrothieno[2,3-d]pyrimidin-4(3 H)-one led to a new series of molecules possessing a large antiaggregant activity. When compared to that of acetylsalicylic acid under the same conditions, this activity was the same with collagen or arachidonic acid-induced aggregation, but greater when aggregation was induced by ADP. Serotonin release was also inhibited.
Some new 4-quinazolinones were prepared. Their antiplatelet activity was evaluated in vitro with respect to aggregation induced by ADP, collagen, arachidonic acid and the platelet serotonin release reaction. Most molecules showed an inhibiting power similar to that of acetylsalicylic acid under the same conditions, and even greater when aggregation was induced by ADP. Reduction of the 4-quinazolinone derivatives to their 1,2,3,4-tetrahydroquinazoline homologues produced an increase in platelet inhibitory action except when ADP is the inductor.
Twenty salicylate derivatives were tested for their antagonistic activity on the inhibitory effect of aspirin on platelet aggregation. The blocking effect was not limited to the salicylate but also characterised some of its substituted compounds. The substituant influence did not seem to be related to electronic or size parameters. This antagonistic activity of these derivatives decreased as concentrations increased, owing to the emergence of their own inhibitory activity: several salicylate derivatives showed dual inhibitory and inhibition antagonistic activity, with both properties present at the same concentration. A mechanism involving dissociated activities on the two enzymatic sites of cyclooxygenase is proposed.
This study uses a new database containing clinical risk factors for cardiac surgery to investigate the relationship between surgical volume (hospital and surgeon) and inhospital mortality rate for all patients receiving coronary artery bypass surgery in New York State in 1989. Also, hospitals with significantly higher and lower mortality rates than expected on the basis of patient preoperative risk factors are identified. The results demonstrate that both annual surgeon volume and annual hospital volume are significantly (inversely) related to mortality rate. The 36% of all coronary bypass operations performed in hospitals with annual bypass volumes of 700 or more by surgeons with annual bypass volumes of 180 or more had a risk-adjusted mortality rate of 2.67% in comparison to a risk-adjusted mortality rate of 4.29% for other bypass operations. Furthermore, low surgical volumes were a major contributor to the outlier status of four of the five hospitals with significantly higher mortality rates than expected.
The in vitro antiaggregating action of paracetamol and ten of its derivatives was studied by observing their action on collagen, adenosine-5 diphosphate (ADP) and arachidonic acid-induced platelet aggregation. It is established that in vitro activity appears not only with paracetamol but also with its positional isomers and its isosteric derivatives; this involves the replacement of oxygen by sulfur and that of the NH group of oxygen. Paracetamol and its derivatives also have an inhibiting effect on the serotonin release and the thromboxane synthesis of collagen-stimulated platelets.
Thirteen aspirin-related compounds were tested for inhibitory activity on platelet aggregation in human platelet rich plasma (PRP) induced with ADP, collagen and arachidonic acid. The following structure-activity relationships were found: none of the functional groups used to replace the acetyl group retained the significant antiaggregant activity of aspirin; anti-aggregant activity was enhanced when the carboxylic group was replaced with a hydroxyl or an acetylated hydroxyl group. The activity of these mono and diacetylated pyrocatechol derivatives was unaffected by incubation of PRP with sodium salicylate.
A dozen acetoxy benzene derivatives (mono- or diacetylated diphenols) were tested for inhibitory activity on platelet aggregation in human platelet rich plasma induced with collagen, ADP and arachidonic acid. All the compounds tested showed an activity, and the results emphasize the antiaggregant properties of diacetylated derivatives which are more potent than aspirin. Unlike aspirin, their action is not prevented by salicylate. However, the large inhibition of serotonin release and thromboxane synthesis localizes their activity in arachidonic acid metabolism.