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B Vitoux

Publications and source records attributed to B Vitoux.

28 records · Page 2Linked to original sources
PubMed1989

Conformational perturbations in retro-analogs of the tBuCO-Ala-Gly-NHiPr dipeptide. Crystal structure of the retro-dipeptide with a reversed Ala-Gly amide bond.

The three retro-analogs of the tBuCO-Ala-Gly-NHiPr dipeptide, in which each amide bond had been successively reversed, were studied in solution by 1H-n.m.r. and i.r. spectroscopy with reference to the conformational properties of their parent dipeptide. Reversal of the Ala-Gly amide bond proved to perturb the folding tendency of the backbone less than the inversion of either of the terminal amide bonds. The crystal structure of the retro-peptide containing a reversed Ala-Gly amide bond was also solved by X-ray diffraction and constitutes the first available data for this retro-peptide series. In contrast to the beta II-folded structure of the parent dipeptide, the retro-peptide molecule adopts an open conformation in the crystal.

Dipeptides↗
PubMed1989

[Evaluation by two-dimensional and doppler echocardiography of the results of percutaneous mitral valvuloplasty].

The purpose of this study was to determine the value of two-dimensional echocardiography and doppler ultrasound in the evaluation of the results and mechanism of percutaneous mitral valvuloplasty. The study involved 200 patients (77 p. 100 female) of mean age 43 +/- 15 years (range 13 to 79 years), most of whom were in NYHA class III or IV. The patients were divided into three groups according to the severity of the anatomical lesions. Group I patients (n = 58) had flexible valves and only minor alterations of the subvalvular structures; group II patients (n = 75) had flexible valves but deeply altered subvalvular structures; group III patients (n = 67) had calcified valves. Following valvuloplasty, the mean transmitral doppler gradient fell from 16 to 5 mmHg (p less than 0.0001) and the mitral valve area, as measured by two-dimensional echocardiography, increased from 1 to 1.9 cm2 (p less than 0.00001); the corresponding values at doppler measurement were 1 and 2 cm2 respectively. In patients successfully dilated, two-dimensional echocardiography showed that the mechanism involved was complete opening of one or both commissures. Before dilatation, 68 patients (34 p. 100) had an usually small degree of mitral regurgitation. After dilatation, grade 3/4 mitral regurgitation was observed in 9 patients (4.5 p. 100). The quality of the results obtained depended on the anatomical lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

[Transesophageal echography. Value of the technic apropos of a preliminary experiment in 320 patients (385 examinations)].

The authors discuss the clinical utility and feasibility of trans-esophageal echocardiography. Between April and October 1988, 385 examinations were performed in 320 patients (mean age: 54 yr, range: 17-89). In 9 patients (2.4 p. 100), the transesophageal transducer could not be introduced. The only complication was one case of bacteremia without sequela, that occurred early in our use of this technique. Transesophageal echocardiography proved to be useful in the following indications: mitral stenosis (n = 50), mainly by detecting thromboses of the left atrium (n = 5); infectious endocarditis (n = 21), especially for diagnosing aortic ring abscesses (n = 3); severe mitral insufficiency (n = 26), to assess the mechanism of regurgitation and to visualize chordal rupture (n = 13). We conclude from this preliminary study that transesophageal echocardiography is particularly useful in the pathologies described above as a complementary procedure to conventional echocardiography.

Adolescent↗
PubMed1988

Mitral calcification in aortic stenosis.

To appreciate the incidence, the promoting factors and the consequences of mitral calcification in aortic stenosis (AS), the data from 675 patients operated on for AS were reviewed. Mitral calcification was revealed by fluoroscopy, echocardiography and/or surgery. Mitral annular calcification (MAC) was observed in 169 patients (25%). In patients with MAC, females were more frequent (42.3 vs. 17.9%, P less than 0.0001), age was greater (64 vs. 58 years, P less than 10(-7)), AS was more severe (0.6 vs. 0.7 cm2, P less than 0.002), and LV walls were thicker (interventricular septum 13.5 vs. 12 mm, P less than 0.0003 posterior wall 12.8 vs. 11.9 mm, P less than 0.004). First-degree AV block was more frequent in patients with MAC but did not lead to more frequent pacemaker implantation. Mitral anterior leaflet calcification was noted in 215 patients (31.8%). When massive, it created mitral stenosis which, in one case, required later mitral replacement. Five- and ten-year actuarial survival rates were not different in patients with or without mitral calcification. We conclude that mitral calcification is frequent in AS. Promoting factors for MAC are age, severity of AS, and female gender.

Adult↗
PubMed1988

[Percutaneous mitral commissurotomy. Apropos of 130 cases].

In order to evaluate the effectiveness and risks of percutaneous mitral commissurotomy (PMC), we tried this procedure in 130 patients. Nine attempts were unsuccessful due to pre-PMC complications (haemopericardium 2, air embolism 1) or to technical failure (6 cases, 5 of which occurred in the first 15 attempts). PMC could be performed in 121 patients: 88 women and 33 men aged from 13 to 79 years (mean 42 + 15 years); 22 patients had previously been operated upon, 5 had a history of embolism, 99 were in functional stage III or IV. Echocardiography divided these patients into 3 groups: 29 had calcified leaflets (group 1), 42 had flexible leaflets and little alteration of the subvalvar system (group 2), and 49 had flexible leaflets with alteration of the subvalvar system (group 3). Mitral regurgitation grade 1/4 was present in 32 cases. PMC was performed with one balloon (Trefoil 3 x 12 mm) in 14 patients and therafter with two balloons (Trefoil 3 x 10 mm plus conventional 15 or 19 mm balloon) in 107 patients. PMC resulted in significant improvement in haemodynamic values: the mean capillary pressure fell from 20 +/- 7 to 11 +/- 5 mmHg (p less than 0.0001) and the mean mitral gradient from 16 +/- 6 to 6 +/- 2 mmHg (p less than 0.0001), while the cardiac index rose from 2.7 +/- 0.6 to 3.1 +/- 0.7 l/mn/m2 (p less than 0.001) and the mitral valve area (MVA) from 1.1 +/- 0.2 to 2.2 +/- 0.5 cm2 (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

[Doppler measurement of transvalvular gradients. Simultaneous Doppler-catheterization recordings on 78 patients].

Several studies have demonstrated the value of Doppler ultrasound as a means of measuring gradients across cardiac valves. However, in view of sudden variations in cardiac output gradients should be measured simultaneously by Doppler and catheterization in order to validate the former method and determine its accuracy. We conducted a prospective study with simultaneous recordings in 78 patients with aortic valve stenosis (33) or mitral valve stenosis (19) or cardiac valve prosthesis (26). Mean age of the patients was 55 +/- 14 years, and 50% of them were male. Subjects with pure or predominant regurgitation were excluded from the study. In the whole of the population studied, correlation between Doppler ultrasound and haemodynamics was very good with r = 0.98, p less than 0.001 for maximum gradient and r = 0.96, p less than 0.001 for mean gradient. The perfect simultaneity of the haemodynamic and ultrasonic recordings was confirmed by comparing the duration of gradients measured by the two methods (r = 0.996, p less than 0.001). There also was very close correlation between ultrasounds and catheter in patients with mitral stenosis (maximum gradient r = 0.98, p less than 0.001; mean gradient r = 0.97, p less than 0.001). Mean Doppler-catheter differences were not significant, and no underestimation by Doppler reached or exceeded 5 mmHg. Correlations were also satisfactory in patients with aortic stenosis (maximum gradient r = 0.97, p less than 0.01; mean gradient r = 0.90, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve Stenosis↗
PubMed1981

N-methyl peptides. III. Solution conformational study and crystal structure of N-pivaloyl-L-prolyl-N-methyl-N'-isopropyl-L-alaninamide.

The study of tBuCO-L-Pro-Me-L-Ala-NHiPr (1) by i.r. and n.m.r spectroscopies has indicated that the middle amide group accommodates preferentially the cis arrangement in inert (CCl4) and aprotic (DMSO) solvents. Cis conformers are folded by a strong intramolecular hydrogen bond involving both terminal CO and NH groups whereas the minor trans conformers accommodate an open conformation. The cis folded form is retained in the solid state and its crystal structure was fully characterized by X-ray diffraction.

Crystallization↗
PubMed1981

N-Methyl peptides. IV. Water and beta-turn in peptides. Crystal structure of N-pivaloyl-L-prolyl-N,N'-dimethyl-D-alaninamide in the anhydrous and monohydrated states.

The model tripeptide tBuCO-L-Pro-Me-D-Ala-MHMe crystallizes in both anhydrous (1) and monohydrated (2) states: 1, monoclinic space group C2 with a = 20.030 (2) A, b = 5.836 (2) A, c = 14.958 (3) A and beta = 94.11 (1) degrees; 2, orthorhombic space group P212121 with a = 6.971 (6) A, b = 11.766 (3) A, and c = 22.394 (8) A. Both crystal structures were solved by X-ray diffraction in order to characterize the influence of water on the molecular structure. The anhydrous molecule accommodates the well-known, beta II-folded conformation with three trans amide functions and an intramolecular i + 3 leads to hydrogen bond. In the hydrated molecule, water is inserted in a loop containing 12 atoms and induces some conformational changes of the peptide backbone.

Dipeptides↗