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A Heitz

Publications and source records attributed to A Heitz.

At least 55 records · Page 3Linked to original sources
PubMed1989

Conformations, cation binding, and transmembrane ion transfer properties of a cyclooctapeptide built by an alternation of D and L residues.

The conformations of a cyclic octapeptide built with an alternation of D and L residues are investigated on the basis of 1H n.m.r. and CD data. The cyclooctapeptide can form structures which are specific to the alternating D-L sequence. This peptide can form two types of complexes with cations (peptide 2-cation and peptide-cation complexes) and the binding with monovalent cation is weak. This peptide is able to induce transmembrane ion transfer through both a carrier mechanism and pore formation.

Acetonitriles↗
PubMed1989

1H n.m.r. conformational studies on the C-terminal octapeptide of oxyntomodulin, a beta-turn locked by a salt bridge.

The octapeptide Lys-Arg-Asn-Lys-Asn-Asn-Ile-Ala (Arg4 in the human sequence) is the C-terminal part of porcine oxyntomodulin, an endogeneous peptide which is a potent inhibitor of stimulated acid secretion. This octapeptide exhibits the whole range of biological activities of the parent hormone. In the present work we report an 1H n.m.r. investigation of the conformational properties of the octapeptides of pig and human sequences in dimethylsulfoxide-d6 (DMSO) solution. The various resonances were assigned on the basis of two-dimensional COSY and NOESY experiments. Other experiments such as (i) temperature and concentration dependence of the amide proton chemical shifts, (ii) effects of ionic strength, (iii) comparison of the spectra with different analogues, were performed. We showed that in DMSO, the conformation of the octapeptide is directly related to the ionisation state of the C-terminus carboxyl group of alanine. In carboxylic state, the peptide adopts an extended conformation, while in the carboxylate state the four last residues (Asn-Asn-Ile-Ala) are involved in a type II beta-turn structure probably locked by a salt bridge between the carboxyl group of Ala8 and the epsilon ammonium group of Lys4 (or the guanidinium group of Arg4). These observations provide an insight into the possible conformational tendencies of this peptide in biological media.

Amino Acid Sequence↗
PubMed1988

Peptides mimicking the flap of human renin: synthesis, conformation, and antibody recognition.

Four peptides related to human renin flap region have been synthesized. Two of them are ring closed through appropriately designed disulfide bridges. Structure analysis involving IR and NMR techniques and recognition by polyclonal human renin antibodies provides support for a beta-hairpin secondary structure of the cyclized peptides identical with that presented by the flap section in the speculative human renin model [Blundell, T., Sibanda, B. L., & Pearl, L. (1983) Nature (London) 304, 273-275; Sibanda, B. L., Blundell, T., Hobart, P. M., Fogliano, M., Bindra, J. S., Dominy, B. W., & Chirgwin, J. M. (1984) FEBS Lett. 174, 102-111].

Antibodies↗
PubMed1988

Prolonged submaximal exercise and L-carnitine in humans.

Changes in the main physiological parameters and circulating indicators of carbohydrate, protein, lipid (and ketone body) metabolism were measured in ten exercising subjects before L-carnitine (L-carn) loading, after 4 weeks of daily loading with 2 g L-carn, and 6-8 weeks after terminating L-carn administration. Measurements were made on venous blood samples collected during each experiment at fixed time intervals over an initial rest of 45 min, 60 min bicycle exercise performed near 50% VO2max and 120 min recovery. Free and total plasma carnitine levels reached a plateau corresponding to an average rise of 25% for both fractions, 9-10 days after the beginning of the L-carn diet. These levels returned to their initial values 6-8 weeks after cessation of the supply. Generally L-carn supplementation did not significantly modify the physiological parameters and circulating metabolites. No distinct increase of the relative participation of endogenous lipids in the fuel supply of prolonged submaximal exercise was observed. In normal human subjects the increased demand for fatty acid oxidation resulting from exercise seems to be adequately supported by endogenous levels of carnitine.

Adult↗
PubMed1988

Low dose heparin versus low molecular weight heparin (Kabi 2165, Fragmin) in the prophylaxis of thromboembolic complications of abdominal oncological surgery.

Eighty patients undergoing pelvic or abdominal surgery for cancer were randomized in two groups for prevention of postoperative thromboembolism: 40 patients received a 15,000 IU day-1 Calciparine prophylaxis and 40 patients a 5000 anti-Xa U/d Fragmin prophylaxis for 10 days. In the Calciparine group, two patients (5%) developed postoperative pulmonary embolism but none developed it in the Fragmin group. Two patients in the Fragmin group (5%) developed isotopic DVT, which was not confirmed by phlebography. There was no deep vein thrombosis of the lower limbs in the two groups. Important postoperative bleeding (one patient in the Calciparine group and two patients in the Fragmin group) was similar in both groups. Moderate and minor bleeding were significantly lower in the Fragmin group. Haemoglobin and haematocrit changes, total blood loss and transfusion requirements were not different in both groups. It is concluded that, over a 10-day period, one daily 5000 U Fragmin prophylaxis was as effective and safe as three daily 5000 IU Calciparine injections.

Abdominal Neoplasms↗
PubMed1987

1H and 13C n.m.r. studies of pseudo-peptide analogues of the C-terminal tetrapeptide of gastrin.

1H and 13C n.m.r. study of pseudo-peptide analogues of the C-terminal tetrapeptide of gastrin, obtained by replacing each peptide bond by a "reduced peptide bond", one at a time, e.g. Boc-Trp psi (CH2NH)Leu-Asp-Phe-NH2 2, Boc-Trp-Leu psi (CH2NH) Asp-Phe-NH2 3, Boc-Trp-Leu-Asp psi (CH2NH)Phe-NH2 4, were reported. The CH2NH bond was completely characterized. 1H and 13C spectroscopic data were reported. It appeared from the present work that the modifications produced by the replacement of a peptide bond by a CH2NH bond were localized around the CH2NH.

Carbon Isotopes↗
PubMed1987

Cyclic tetrapeptides with sequences related to HC toxin. Conformations and cation binding.

Peptides with sequences related to HC toxin (cyclo(LAla-DAla-L-Aoe-DPro] can adopt a conformation locked by three gamma turns. A "structure--spectroscopy characteristics" relationship is proposed. These peptides can complex Mg++ cations and the binding is accompanied by a transconformation of the peptide backbone. The relevance with the biological activity of the toxin is discussed.

Amino Acid Sequence↗
PubMed1987

[Diffuse leiomyomatosis of the stomach].

Sonography and computed tomography were the first imaging methods enabling the visualization of intramurally growing tumours of the stomach. The article reports on a rare case of a diffuse leiomyoma that was diagnosed by means of computed tomography.

Aged↗
PubMed1986

Conformations of gramicidin A and its 9,11,13,15-phenylalanyl analog in dimethyl sulfoxide and chloroform.

In order to understand the difference in single channel behavior of gramicidin A as compared to that of gramicidin M- which is the mirror image of gramicidin M (all four tryptophanyl residues substituted by phenylalanine), conformational investigations were made under several experimental conditions. It is shown that, when examined under identical conditions, both molecules adopt the same conformations which could be identified in dimethyl sulfoxide (DMSO) and chloroform. In DMSO the conformation is based on a succession of beta-turns while in chloroform gramicidin A and M- can adopt a dimeric hybrid structure: a double helix terminated by two single-stranded helices involving the N- and C-terminal parts, respectively. It is therefore concluded that the difference in the energy profile between both gramicidins which was deduced from the ion transfer data has its origin in the nature of the aromatic side chains.

Chloroform↗
PubMed1986

Solution synthesis of antigenic and inhibiting peptides of the human renin prosegment-1. [Tyr47, Nle53] preprorenin-(47-60) peptide methyl ester.

The [Tyr47, Nle53] preprorenin (47-60) peptide methyl ester, a tetradecapeptide related to the human renin prosegment, has been synthesized using a three-segment coupling strategy. Selective deprotection of the segments before coupling allowed an easy removal of the final tetradecapeptide side chain-protecting groups by acidolysis and an easy purification. Antibodies raised against this peptide bound the plasmatic inactive renin.

Amino Acid Sequence↗
PubMed1986

Solution synthesis of antigenic and inhibiting peptides of the human renin prosegment-2. [Tyr40] preprorenin-(40-50) peptide methyl ester.

The [Tyr40] preprorenin (40-50) peptide methyl ester, an undecapeptide related to the human renin prosegment, has been synthesized using a stepwise strategy with hydrogenolisable protections on the side chains. The final deprotection was very difficult as observed by 1H NMR and reversed phase HPLC. 2D 1H NMR spectroscopy of the purified peptide allowed the assignment of all protons.

Amino Acid Sequence↗
PubMed1986

Work rate-dependent lactate kinetics after exercise in humans.

Arterial blood lactate concentrations were measured on 19 subjects before, during, and after a 3-min bicycle exercise at several work rates, and the concentrations during the recovery phases were fitted to a biexponential time function consisting of a rapidly increasing and a slowly decreasing component. Highly significant correlations with the work rate of the exercise preceding the recovery were found for all the parameters of the fitted equation. The two velocity constants show inverse linear relationships, whereas the other parameters vary according to a definite power function. A functional meaning has been given to the two velocity constants, namely the ability of the tissues to exchange and to remove lactate. For the group of subjects studied, after exercises at work rates below about 3.5 W/kg, the tissue's ability to utilize, and possibly to exchange lactate, increases over values generally reported for resting conditions, whereas after exercises at higher work rates the inverse occurs. Lactate kinetics during recovery appear to be the result of two underlying processes, one enhancing the ability of the tissues to exchange and remove lactate and the other restraining it.

Adult↗
PubMed1985

Synthesis of aldehydic peptides inhibiting renin.

Reduction of peptidyl N, O-dimethyl hydroxamates with lithium aluminium hydride in diethyl ether at 0 degree allowed the preparation of peptidyl aldehydes in excellent yield and optical purity. These aldehydic peptides are able to inhibit renin activity. They are the shortest renin inhibitors known to date.

Aldehydes↗
PubMed1985

[Immediate coronary angioplasty in the acute phase of myocardial infarction. French multicenter study: December 1983].

Following the introduction of intracoronary thrombolysis in the acute phase of myocardial infarction (AMI), transcutaneous coronary angioplasty (TCA) was originally conceived as a logical complementary procedure to treat residual stenosis and so prevent the frequent post-thrombolysis reocclusion (20-30 p. 100 of cases). With increasing experience TCA of first intent appeared rational, more rapid and effective, ensuring coronary recanalisation (CR), suppression of residual stenosis and the prevention of reocclusion in the same procedure with with the objective of reducing the number of coronary bypass grafts (CBG) in patients with single vessel disease. A French multicentre study of 22 cases was organised by 9 centres. The average period between onset of symptoms and intervention was 2 hours 10 mins (range 30 mins-5 hours 30 mins). The average duration of the procedure was only 30 mins. 16 patients had anterior and 6 patients inferior AMI. Coronary angiography showed 12 occlusions (54.5 p. 100) and 10 sub-occlusions with 6 cases of delayed opacification. All patients had successful initial TCA with no major complications. The arterial occlusions decreased from 100 p. 100 to 31 p. 100 and the subocclusions from 94 to 12 p. 100. 2 patients died in the hospital period, one at the 48th hour of controlateral AMI and the other one at the 5th day of reocclusion. Three patients developed reocclusion at the site of the original TCA. Complete regression of ECG changes was observed in 31.8 p. 100 of cases. Complete recovery of normal left ventricular function was observed in 8 of the 17 patients who underwent follow-up investigations (47 p. 100 of cases).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Aldehydic peptides inhibiting renin.

Aldehydic peptides in which the C terminal residue is leucinal or phenylalaninal were synthesized. These compounds exhibited potent inhibition of renin activity and appeared to be precursors of transition state analogues for renin-catalysed amide bond hydrolysis.

Aldehydes↗
PubMed1983

Beta-adrenoceptors of the human myocardium: determination of beta 1 and beta 2 subtypes by radioligand binding.

beta-Adrenoceptors of the human myocardium were investigated with binding studies using 125iodocyanopindolol (ICYP) as ligand. Inhibition of ICYP-binding by betaxolol (a selective beta 1-antagonist) and ICI 118551 (a selective beta 2-blocking drug) resulted in non-linear Scatchard-plots suggesting that both beta-adrenoceptor subtypes are present in human left atrium and left ventricle. Computer analysis of the data gave a beta 1/beta 2-adrenoceptor ratio of approximately 65:35 both for left atrium and for left ventricle.

Binding, Competitive↗
PubMed1981

[Ductus arteriosus in neonatal cyanotic cardiopathies. Value of the recording of the cutaneous partial pressure of oxygen].

Adaptation to extrauterine life is always precarious in the newborn with cyanotic cardiac malformations. Limited survival is possible in cases with obstructive lesions of the right heart providing ductal closure is delayed. This was monitored in 3 cyanotic neonates with ductal dependant cardiac malformations (tricuspid atresia, transposition of the great arteries with atresia or severe stenosis of the pulmonary valve) by continuous measurement of the cutaneous pO2. The value of cutaneous pO2 monitoring has already been established. It is a reliable indicator of arterial pO2 in the neonatal period. Its major advantage, apart from the possibility of continuous monitoring, is that it is non-invasive and may be performed at the bedside. Analysis of curves recorded over several hours or days showed the cyclical nature of cutaneous pO2, probably related to slow variations in ductal diameter equilibrating effective pulmonary flow, arterial pO2 and ductal constriction. Prolonged hyperoxygenation of these desaturated children does not usually improve their condition; progressive deterioration due to the constrictive effect of oxygen on the ductus may be observed. When a clear decrease in the amplitude of oscillation is recorded ductal closure is imminent and palliative surgery should be undertaken whenever possible.

Ductus Arteriosus, Patent↗