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Biomedical subjects

M Marchand

Publications and source records attributed to M Marchand.

At least 55 records · Page 3Linked to original sources
PubMed1995

Analysis of low-frequency lung impedance in rabbits with nonlinear models.

Lung mechanics was studied in six paralyzed tracheotomized rabbits ventilated with a specially devised computer-controlled ventilator. The target flow waveform contained noninteger multiple frequencies ranging from 0.83 to 6-10 Hz and met a neither-sum-nor-difference criterion to minimize the effects of nonlinearity (B. Suki and K. Lutchen. IEEE Trans. Biomed. Eng. 39: 1142-1151, 1992). The actual flow, however, contained harmonics of the two lowest frequencies. Measurements were performed at mean airway pressure (Paw) levels of 8 and 12 hPa and during histamine-induced bronchoconstriction. Smooth impedance curves were observed in unchallenged rabbits at low mean Paw levels. In contrast, unrealistic impedance fluctuations, suggestive of cross talk from the unwanted frequency components in the flow input, were seen at high mean Paw levels and during acute bronchoconstriction. Model analysis was performed by using the actual flow signal as an input to various nonlinear models. The impedance fluctuations observed at high mean Paw levels were well simulated by a model featuring a volume-dependent elastance, and those observed after histamine were almost perfectly reproduced by a model where resistance increased with the reciprocal of lung volume. We conclude that impedance data biased by cross talk may provide useful information on the presence and nature of respiratory system nonlinearities.

Airway Resistance↗
PubMed1995

[Influence of the valve position on the complications related to pericardial Carpentier-Edwards valve after 8 years].

Between July 1984 and December 1991, 541 Carpentier-Edwards pericardial prostheses were implanted in 536 patients (420 aortic and 121 mitral prostheses). The operative mortality was 2.9% for aortic and 3.3% for mitral valve replacement. All but 8 patients were followed up for an average of 3.9 years, making a total follow-up of 1930 patient-years. There were 61 deaths during follow-up (41 AVR, 20 MVR). The actuarial 8 year survival was 80 +/- 6% for AVR and 74 +/- 10% for MVR. There were 15 deaths related to the prostheses. The probability of absence of valve-related mortality was 97 +/- 3% for AVR and 92 +/- 6% for MVR (NS). The valve-related complications included 15 thromboembolic events (AVR: 12; MVR: 3), 10 endocarditis (AVR: 7; MVR: 3), 8 anticoagulant-related haemorrhages (AVR: 4; MVR: 4), 4 degeneration (AVR: 2; MVR: 2). There were no cases of cusp tear. The probability of absence of thromboembolic events at 8 years was 96 +/- 3% for AVR and 96 +/- 4% for MVR (NS), of absence of endocarditis 97 +/- 2% for AVR and 97 +/- 3% for MVR (NS) and of absence of valve degeneration 99 +/- 1% for AVR and 99 +/- 2% for MVR (NS). These results show that the position of the bioprosthesis had no influence on valve-related morbidity and that pericardium is a satisfactory tissue for the manufacture of mitral bioprostheses.

Actuarial Analysis↗
PubMed1995

[Systemic pulmonary shunts in the neonatal period. Short and medium-term results].

Systemic pulmonary shunts were performed in 41 consecutive neonates with congenital cyanotic heart disease between 1981 and 1992. The lesions comprised pulmonary atresia with intact interventricular septum (16 cases), pulmonary atresia with ventricular septal defect (9 cases), tetralogy of Fallot (5 cases), transposition of the great arteries (3 cases) and different complex cardiac lesions (8 cases). A polytetrafluoroethylene tube was used in 40 neonates, 5 mm in diameter in 39 cases, anastomosed to be subclavian artery in 21 patients (group A) and on the ascending aorta or innominate artery in 19 patients (group B). A retrospective analysis of the results was undertaken in all patients with a mean follow-up period of 6.5 years (range: 19 months-12.5 years). There were 4 early deaths (9.7%) and 8 late deaths (19.5%) giving a total mortality of 29.2%. Of the late deaths, 4 occurred in the first year, 3 suddenly at home and 4 in relation with the surgical correction. Occlusion of the shunt was suspected in only one case. The actuarial survival rate was 78% at one year, 75.5% at 7 years and 66% at 10 years. Eleven of the 12 deaths were in children with pulmonary atresia with intact interventricular septum (8 cases) and complex cardiac malformations (3 cases). Early complications were observed in 15 of the 37 survivors of the initial procedure. Cardiac failure occurred in 83% of group B and 22% of group A (p < 0.01). The probability of shunt efficacy was 89% at 1 year, 63% at 2 years and 45% at 3 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Anastomosis, Surgical↗
PubMed1994

Expression of mage genes by non-small-cell lung carcinomas.

Human gene MAGE-I codes for an antigen that is recognized on melanoma cells by autologous cytolytic T lymphocytes (CTL). This antigen is potentially useful as a target for cancer immunotherapy because gene MAGE-I is not expressed in any normal tissues except the testis. We tested 46 surgical samples of non-small-cell lung carcinomas and observed MAGE-I expression in 16 of them (35%). Genes MAGE-2 and 3, which are closely related to MAGE-I, were expressed by a similar proportion of these tumors. Some small-cell lung tumors also express MAGE genes. The proportion of tumors expressing MAGE-I suggests that lung tumor patients may constitute the largest group of patients potentially eligible for pilot studies involving MAGE-I immunization.

Base Sequence↗
PubMed1994

New procedure to replace the aortic valve with autologous pericardium: a clinical case.

Primary tissue failure is a major problem with pericardial or porcine heterografts, and the causes of calcification of the tissue are not yet known. The deterioration of bioprostheses may be due in part to immunologic response. Using autologous tissue is a current approach of research. We present a case of replacement of the aortic valve using an original procedure with autologous pericardium.

Aortic Valve↗
PubMed1994

The Carpentier-Edwards pericardial aortic valve: intermediate results in 420 patients.

From July 1984 to December 1991, 420 patients underwent isolated aortic valve replacement with a Carpentier-Edwards pericardial bioprosthesis in our Institution. Of the patients 71.5% were male, the mean age was 66.9 +/- 11.9 years and 48% were in NYHA clinical stage III or IV. The operative mortality rate was 2.9% (12/420). All patients but six were followed up for an average of 3.9 years after their operation and total follow-up was 1444 patient-years. At this time of the study, over 80% of the patients are in NYHA class I or II, 6% are in atrial fibrillation and 7% receive anticoagulation treatment. There were 41 late deaths. After 8 years the actuarial survival rate is 80% +/- 6%. Nine patients died of valve-related causes (three endocarditis, three thromboembolic complication, one structural failure, and two sudden deaths). The actuarial rate of freedom from valve-related death was 97% +/- 3% at 8 years. Valve-related complications included 12 thromboembolic episodes (0.8% patient-year), 7 endocarditis (0.5% patient-year), 4 anticoagulant-related complications (0.2% patient-year), 6 reoperations (0.4% patient-year) and 2 structural valve failures (0.1% patient-year). After 8 years, freedom from thromboembolic complication was 96% +/- 3%, from endocarditis 97% +/- 2%, from reoperation 98% +/- 2% and from valve failure 99% +/- 1%. There were only two structural deteriorations (calcification and stenosis) and one explanation. No leaflet tear was observed. We conclude that these intermediate results are better than those obtained with previous pericardial bioprostheses.

Actuarial Analysis↗
PubMed1994

Electrocardiographic and electrophysiologic properties of cardiac allografts.

The increasing number of heart transplant patients requires that physicians be able to recognize the electrocardiographic (ECG) and electrophysiologic properties of cardiac allografts. Cardiac allografts are characterized by modifications of resting ECGs and frequent arrhythmias in the postoperative period, and the loss of autonomic nervous control illustrated by permanent tachycardia and loss of heart rate variability during 24-hour ambulatory ECG recording. Some clinical and experimental observations suggest a mid-term reinnervation of the cardiac allograft, but this requires histologic confirmation. The electrophysiologic characteristics of the denervated myocardium are similar to those of the innervated myocardium at rest. However, supersensitivity to circulating catecholamines has been observed in cardiac allografts as in experimentally denervated hearts, which is responsible for a progressive increase in heart rate during exercise and a slow decrease during recovery. Supersensitivity of the denervated heart to acetylcholine may explain the high prevalence of donor sinus dysfunction due to impairment of its automaticity. More often, the sinus node dysfunction is transient and can be treated with an adenosine antagonist, such as theophylline, before permanent implantation of a pacemaker. In the case of pacemaker implantation, synchronization of the donor atria with the recipient atria is desirable, and an endocardial lead implantation is preferred. Several electrophysiologic changes have been observed during acute cardiac allograft rejection. From experimental studies, the most important of these are the disturbance of conduction in the atria and the atrioventricular node and a decrease in the amplitude of the ventricular potential. Initial studies on isolated myocytes show profound changes in membrane conductance during experimental cardiac rejection. The development of new noninvasive detection methods of cardiac allograft rejection, such as intramyocardial voltage electrogram monitoring and high-resolution ECG, could help early diagnosis.

Animals↗
PubMed1994

[Partial pulmonary embolectomy without extracorporeal circulation. Apropos of a case].

The authors report a case of massive pulmonary embolism compromising the haemodynamic status of a 52 year old man with a formal contraindication to thrombolytic therapy. Unilateral pulmonary embolectomy was performed without cardiac pulmonary bypass, preceded by partial interruption of the inferior vena cava. Postoperative controls confirmed the success of the surgical procedure. Although the indications of surgical embolectomy are limited, especially without cardiopulmonary bypass, it may be considered for the treatment of certain cases of massive pulmonary embolism.

Cerebral Hemorrhage↗
PubMed1994

[Estimation of static lung volumes by nitrogen washout method. Single breath of oxygen].

Total lung capacity (TLC) and residual volume (RV) estimations were obtained from single-breath nitrogen washouts in 96 male and 77 female healthy never-smokers with normal spirometry from a non-polluted rural area in north-east France. TLC depended on height (both sexes) and diminished slightly with age in males, with the body-mass index (kg/m2) in females. RV increased with age in both sexes and with weight in males. The RV/TLC ratio was related only to age. When compared with values obtained using multiple-breath helium dilution, our results yielded lower predicted values. The test depends heavily on the subject's co-operation, and errors are frequent if a standard procedure is not observed. This method cannot thus be recommended for routine use in patients with respiratory diseases.

Adult↗
PubMed1993

Perspectives for immunization of HLA-A1 patients carrying a malignant melanoma expressing gene MAGE-1.

Many human melanoma tumors express antigens that are recognized in vitro by cytolytic T lymphocytes derived from the tumor-bearing patient. A gene has been identified that directs the expression of antigen MZ2-E on a human melanoma cell line. This gene, which has been named MAGE-1, shows no similarity to known sequences and belongs to a family of at least 3 closely related genes. Gene MAGE-1 is expressed in approximately 40% of melanoma tumor samples and by some tumors of other histological types. No expression has been observed in a panel of normal tissues. Antigen MZ2-E appears to be presented by HLA-A1, a HLA type found in approximately 25% of the population. Thus, precisely targeted experimental immunotherapy directed against antigen MZ2-E could be provided to individuals identified as HLA-A1 and MAGE-1 positive by HLA typing and analysis of the RNA of a small tumor sample.

Antigens, Neoplasm↗
PubMed1993

[Electrophysiological properties of the transplanted heart. Clinical applications].

With the improvement in the results of cardiac transplantation, more and more cardiologists are called on to follow up cardiac transplant patients. Cardiological follow-up requires a knowledge of the electrocardiographic and electrophysiological features of the transplanted heart after surgery and the suppression of autonomic innervation. The transplanted heart ECG is characterised by the presence of 2 P waves of different morphology and frequency (from the native and transplanted atria), an acceleration of the sinus rhythm, clockwise rotation of the longitudinal axis, right bundle branch block and ST-T segment changes. The increase in heart rate during exercise is catecholamine-dependent, more progressive and less important than in normal subjects, as is the deceleration of the cardiac rhythm when exercise is stopped. The observation of early sinus node dysfunction is not rare (6.6%) and though usually asymptomatic and transient, implantation of a pacemaker is commonly proposed with different modes of stimulation (VVI, VVIR, AAIR, AAT). The authors have observed changes in the electrophysiological properties of experimental transplanted hearts during acute rejection. The most important of these were in the conduction of the activation within the atrium and in the atrioventricular node, and a reduction in the amplitude of the ventricular potential. The recording of these changes in humans by a non-invasive method could help early diagnosis of acute rejection and limit the number of endomyocardial biopsies. Of the non-invasive techniques under assessment, signal-averaged electrocardiography (temporal and/or frequency analysis) seems to be the most promising.

Animals↗
PubMed1992

Implications of lower- and upper-limb training procedures in patients with chronic airway obstruction.

In assessing the effectiveness of lower-limb and upper-limb nonspecific physical training, we have considered 3 objectives in this study: (1) determination of clinical and functional actual state in patients with chronic airway obstruction (CAO), before and after training; (2) determination of the tests, level of work, and duration of the session training as well as how to increase the training load throughout the training program; and (3) the "particular" upper-limb exercise training in patients with CAO. Many personal factors such as psychologic (personality, degree of patient motivation), alcohol and smoking habits, physical activity, malnutrition, as well as routine tests, at rest and maximal exercise, including the control of metabolic acidosis (lactate) and arterial blood gases (or at least of SaO2), should be considered. Exercise training has the potential to improve exercise tolerance in those who develop metabolic acidosis. The pattern of lactates during exercise represents a good criterion on the selection of patient's training. Two ergospirometric strategies, at high intensity exercise, established from the anaerobic threshold (AT) are described: (a) the above AT 45 min constant exercise (high work rate), at 60% of the difference between AT and maximum VO2 or 80% of the maximal tolerated power (MTP), and (b) the "45 min square-wave endurance exercise test" (SWEET), simulating an interval training session, established from the MTP and the AT. To the SWEET's base (% MTP from AT or aerobic training), a peak of 60 s at MTP (anaerobic training) is added every 5 min. While those 2 protocols, after 6 to 8 weeks of training, lactate and ventilation were lower for identical work rate. In addition, endurance (time in "a" and total physical work in "b") increased up to 60%. Further, maximal exercise ventilation and maximum VO2 increased after SWEET training. Roughly every 7 training sessions, a 10% to 15% reduction in heart rate (HR), during the training program, allows the patient to increase the work rate of the sessions. Evaluation of training the upper limb in patients with CAO requires measurements of MTP and maximum VO2. With the upper limb (wheelchair ergometer), Wmax, maximum VO2, and HR represent 30%, 65%, and 95%, respectively, of the lower limb (ergometer). Further, some expiratory and inspiratory accessory muscles show electromyographic fatigue at the MTP upper-limb level. This may contribute to the rationale for training respiratory muscles.(ABSTRACT TRUNCATED AT 400 WORDS)

Acidosis, Lactic↗
PubMed1991

The cytosolic and glycosomal isoenzymes of glyceraldehyde-3-phosphate dehydrogenase in Trypanosoma brucei have a distant evolutionary relationship.

Trypanosoma brucei contains two isoenzymes for glyceraldehyde-3-phosphate dehydrogenase: one enzyme resides in a microbody-like organelle, the glycosome; the other is found in the cytosol. Previously we have reported the characterization of the gene for the glycosomal enzyme [Michels, P. A. M., Poliszczak, A., Osinga, K. A., Misset, O., Van Beeumen, J., Wierenga, R. K., Borst, P. & Opperdoes, F. R. (1986) EMBO J. 5, 1049-1056]. Here we describe the cloning and analysis of the gene that codes for the cytosolic isoenzyme. The gene encodes a polypeptide of 330 amino acids, with a calculated molecular mass of 35440 Da. The two isoenzymes are only 55% identical. The cytosolic glyceraldehyde-3-phosphate dehydrogenase differs from the glycosomal enzyme in the following respects: (a) its subunit molecular mass is 3.4 kDa smaller due to the absence of insertions and a small C-terminal extension which are unique to the glycosomal protein; (b) the cytosolic enzyme has a lower pI (7.9, as compared to 9.3 for the glycosomal isoenzyme), which is due to a reduction in the excess of positively charged amino acids (the calculated net charges of the polypeptides are +2 and +11, respectively). We have compared the amino acid sequences of the two T. brucei glyceraldehyde-3-phosphate dehydrogenases, with 24 available sequences of the corresponding enzyme of other organisms from various phylogenetic groups. On the basis of this comparison an evolutionary tree was constructed. This analysis strongly supports the theory that T. brucei diverged early in evolution from the main eukaryotic branch of the phylogenetic tree. Further, two separate branches for the lineages leading to Trypanosoma are inferred from the amino acid sequences, suggesting that the genes for the two glyceraldehyde-3-phosphate dehydrogenases of the trypanosome are distantly related and must have been acquired independently by the trypanosomal ancestor. The branching determined with the glycosomal enzyme precedes that found with the cytosolic enzyme. The available data do not allow us to decide which of the two genes originally belonged to the trypanosome lineage and which entered the cell later by horizontal gene transfer.

Amino Acid Sequence↗
PubMed1991

Intraoperative measurements of cerebral haemodynamics during ductus arteriosus ligation in preterm infants.

Intraoperative Doppler sonographic examinations were carried out on seven preterm neonates to measure cerebral blood flow velocity changes in the anterior cerebral arteries during ductus arteriosus ligation. Age at surgery was 12 +/- 6 days. Continuous recordings during the operative procedure showed a rapid increase in diastolic blood pressure (P less than 0.01), whereas systolic blood pressure was not significantly higher compared with pre-occlusion values. In the anterior cerebral arteries, ductal closure led to a decrease in resistance index of Pourcelot (mean = 1.02 +/- 0.08 vs 0.65 +/- 0.07 (P less than 0.001)) and to an increase in area under the velocity curve (mean = 3.64 +/- 0.38 vs 8.16 +/- 1.07 (P less than 0.001)). These changes were associated with a corresponding increase of the end diastolic flow velocity (P less than 0.001) but no change in the peak systolic velocity. The heart rate did not change significantly during ductal closure. TcPO2, TcPCO2 remained normal during the study period. These data indicate that changes in cerebral blood flow velocity during surgical ligation are principally determined by changes in systemic diastolic pressure. Systolic blood pressure and peak systolic flow velocity remain unchanged or slightly higher than preligation values, thereby restoring normal cerebral blood flow velocity pattern without increasing the stress on the wall of cerebral vessels and thus the risk of peri-intraventricular haemorrhage.

Blood Flow Velocity↗
PubMed1991

Vibrio navarrensis sp. nov., a species from sewage.

A group of 11 strains, mostly isolated from sewage water in the Province of Navarra, Spain, were found to constitute a DNA relatedness group which is 2 to 39% related to 23 species of the genus Vibrio and 2 to 3% related to two Aeromonas species. Phenotypically, these strains have all of the properties that define the genus Vibrio. However, they differ from the previously described species by three or more properties. The strains are negative for arginine, ornithine, and lysine decarboxylase activities and the Voges-Proskauer test and are unable to utilize putrescine, gluconate, glucuronate, and histidine. They utilize and produce acid from sucrose and grow at 40 degrees C. All strains grow in the presence of 0.5% (wt/vol) NaCl, and seven strains grow weakly in peptone water lacking NaCl. The group of strains which we studied can also be differentiated from other Vibrio species by fatty acid content. The G+C ratio of the DNA is 45 to 47 mol%. The name Vibrio navarrensis sp. nov. is proposed for these strains; strain 1397-6 (= CIP 103381) is the type strain.

Base Composition↗