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Biomedical subjects

D Loisance

Publications and source records attributed to D Loisance.

269 records · Page 15Linked to original sources
PubMedDate not supplied

[Experimental study of a biodegradable micro-arterial prosthesis (author's transl)].

An experimental study of a micro-arterial prosthesis prepared from biological materials was carried out in the rat. The results obtained after two months were analysed in terms of permeability of the biochemical constituants of the vessel and of the neighbouring scar tissue, and endothelial healing. These studies showed the association with a process of proteolysis of the implanted vessel, of a process of reconstruction. They show moreover the quality of the endothelial scar on the internal surface of the vessel.

Animals↗
PubMedDate not supplied

Vascular substitute from human placental arteries: glycosaminoglycan and elastin synthesis in the neo-intimal hyperplasia.

Heparinized human placental arteries (internal diameter less than or equal to 1 mm) were cross-linked with glutaraldehyde and implanted in infrarenal aortas in rats (n = 78). At three months and one year following aortic replacement, the neo-intimal hyperplasia covering the patent conduits and the host intima media were excised. Glycosaminoglycans (GAGs) and elastin were metabolically labelled in vitro with radioactive glucosamine and valine, respectively. The incorporation of 3H glucosamine into GAGs decreased sixfold in both neo-intima and host intima media from three months to one year. At three months, the 3H label of hyaluronic acid accounted for 66 per cent and 43 per cent of the 3H GAGs in the neo-intima and host aorta, respectively. At one year, 55 per cent of the 3H GAG label were identified as 3H heparan sulphate in the neo-intima and host intima media. From three months to one year, the ratio of chondroitin 4 sulphate (CS 4) to chondroitin 6 sulphate (CS 6) decreased from 6 to 1.5 in the neo-intima, whilst the ratio of CS 4 to CS 6 (0.6) was constant in the host aorta during the experimental period. At one year, the neo-intima contained elastin. The radioactive incorporation pattern of GAGs and the biosynthetic label of valylproline dipeptides indicated a decrease in biosynthetic activity in neo-intimal and the host aortic cells with progressing time in vivo.

Animals↗
PubMedDate not supplied

[Extra-corporeal circulation. Experimental study. Comparative study of various oxygenators (author's transl)].

An experimental study of three different types of oxygenator was carried out in the dog during two hours extra corporeal circulation. The hemodynamic aspects and the characteristics of pulmonary elasticity that a previous study permitted us to choose as controls of the quality of extracorporeal perfusion, were studied. The results show that the pulmonary arterial resistances and the indices of pulmonary compliance do not recover during E.C.C. to their initial values, in the case of an E.C.C. using a bubble oxygenator. These results should be taken into consideration in the choice of the most suitable oxygenator.

Animals↗
PubMedDate not supplied

[Mechanical assistance of circulation. 42 cases].

OBJECTIVES: Mechanical circulatory support was proposed in patients in cardiogenic shock, as a bridge to cardiac transplantation or weaning. The aim of the present study is an analysis of the first 42 cases. METHODS: The 42 cases included 31 patients in cardiogenic shock unresponsive to medical therapy, good cardiac transplant candidates, and 11 patients unweanable off ventricular assist, or in shock in the intensive care unit. Results are evaluated in terms of transplantability and hospital survival. RESULTS: Overall success rate is 67%, ranging from 25% in previously transplanted patients to 46% following acute myocardial infarction and 57% in cardiomyopathy. Age and learning curve played a significative role. CONCLUSION: These data suggest that mechanical support improves survival in patients in cardiogenic shock. Earlier implantation should improve the patient outcome.

Adult↗
PubMedDate not supplied

[Cardiac transplantation. Operative risk factors].

An evaluation of the risks of heart transplantation, and in particular operative risk factors, should lead to optimal decision making in light of the lack of sufficient supply of transplantable organs. The optimal recipient for transplantation is the patient who will benefit best from the organ in terms of survival and quality of life and for whom the operative risk is the smallest. This study emphasized the preparing role of donors over 45, the poorer prognosis in recipients over 60, the situations limited by pulmonary resistance and the notion of retransplantation. The practical impact of these observations is of prime importance.

Adolescent↗
PubMedDate not supplied

Myocardial high-energy phosphate depletion in allograft rejection after orthotopic human heart transplantation.

The present study was designed to assess whether acute rejection affects myocardial energy content of the human orthotopically transplanted heart. Adenosine triphosphate content was measured in one tissue sample obtained during 46 routine right ventricular endomyocardial biopsies 6 to 455 days (98 +/- 110) after transplantation in 19 cyclosporine-treated transplant recipients. Tissue samples were immediately frozen in liquid nitrogen within 10 seconds after excision. Adenosine triphosphate analysis was performed with high performance liquid chromatography. Three groups of biopsy specimens were classified according to the standardized cardiac biopsy grading system. Group 1: Eight biopsy specimens without rejection; group 2: 24 biopsy specimens with mild rejection; group 3: 14 biopsy specimens with moderate or severe rejection. Graft systolic function evaluated by echocardiographic fractional shortening was in the normal range the day of biopsy. All patients had normal coronary angiograms within 1 month of the study. In the presence of mild rejection (grade 1A or 1B), adenosine triphosphate content was not significantly different from that of nonrejecting hearts (26.15 +/- 7.1 and 28.57 +/- 8.23 nmol/mg protein, respectively). By contrast, a significant decrease in adenosine triphosphate content was observed when moderate or severe rejection with focal or diffuse aggressive infiltrates were present (10.46 +/- 4.11 nmol/mg protein; p < 0.01 versus two other groups). In seven cases, sequential analysis showed a significant increase in adenosine triphosphate content after rejection therapy concomittant with histologic improvement: 10.19 +/- 2.9 before and 30.13 +/- 7.0 nmol/mg protein after treatment (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMedDate not supplied

Reduced production of the deleterious hydroxyl free radical during the final reperfusion of isolated rabbit heart with the use of an improved sodium lactobionate-based cardioplegic medium.

The production of free radicals during the reperfusion of hearts after prolonged ischemia might be responsible for the deleterious effects observed. Several strategies have attempted to limit this production or trap the radicals produced. This study aimed to evaluate the efficacy of a sodium lactobionate-based solution supplemented with 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, a stable nitroxide free radical, in scavenging hydroxyl radicals produced during the reperfusion of the isolated rabbit heart. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl was administered just before the end of the storage period (6 hours) in a cardioplegic solution, either crystalloid solution or sodium lactobionate-based solution. The production of hydroxyl radicals was assessed through the production of dihydroxybenzoic acid, a reaction compound of hydroxyl radicals with salicylate. Two main isomers of dihydroxybenzoic acid were found in the coronary effluents: 2,3 and 2,5 dihydroxybenzoic acid. The production was 40-fold lower when the hearts received sodium lactobionate-based solution than when they received crystalloid solution (p < 0.001). The presence of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl had no influence on the production of hydroxyl radicals. The production of hydroxyl radicals was maximal during the first minute of the reperfusion. Iron ions, directly involved in the production of hydroxyl radicals, were shown to be complexed by sodium lactobionate in vitro. These results underlie the important role of lactobionate in the prevention of the reperfusion injury and the inefficacy of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl to decrease the production of hydroxyl radicals.

Adenine↗
PubMedDate not supplied

A lactobionate-based extracellular-type solution for donor heart preservation.

The University of Wisconsin solution, which contains the impermeant lactobionate and has an intracellular-type electrolyte composition, has been shown to improve donor heart preservation. Because a deleterious effect of the intracellular-type solutions has been reported, we evaluated a new lactobionate-based extracellular-type solution, by comparing it with University of Wisconsin solution and a crystalloid cardioplegic solution in 45 rabbit hearts. Hearts were arrested by infusion of these solutions and immersed in the same solution (lactobionate-based extracellular-type solution, University of Wisconsin solution) or in the lactated Ringer's solution (crystalloid cardioplegic solution) for 6 hours at 4 degrees C. A Langendorff circuit was used for reperfusion. Left ventricular compliance was better preserved with both lactobionate-based solutions than with the crystalloid cardioplegic solution. Adenosine triphosphate was best preserved with the lactobionate-based extracellular-type solution after arrest and after reperfusion, whereas reperfusion arrhythmias were less marked with the University of Wisconsin solution. These results suggest that lactobionate plays an important role in the preservation of ventricular compliance and that the lactobionate-based extracellular-type solution is preferable for adenosine triphosphate preservation. Further study will be required to assess the factors predisposing to reperfusion arrhythmias.

Adenine↗
PubMedDate not supplied

Right ventricular late filling termination time and its relation to interstitial collagen content in early transplanted heart: a color M-mode Doppler digital analysis.

BACKGROUND: Histologic changes in cardiac allografts resulting from fibrosis or acute rejection can modify ventricular diastolic function and ventricular inflow characteristics. These abnormalities may be detected by color M-mode Doppler echocardiography which has been shown to be sensitive in assessing ventricular diastolic function. METHODS: Twelve cardiac allograft recipients were prospectively studied with serial color M-mode and single-gated Doppler echocardiography, as well as with endomyocardial biopsy, with a follow-up of approximately 10 weeks. The myocardial interstitial collagen content as evaluated by videodensitometry was compared with right and left ventricular late filling termination times measured in the absence of a severe episode of rejection. RESULTS: A positive and significant correlation was found between the collagen content and the corresponding right ventricular late filling termination time (r = 0.89, p < 0.0001), but no correlation was found with the left ventricular late filling termination time. Moreover, variations in collagen content and variations in right ventricular late filling termination time were also highly correlated (r = 0.91, p < 0.0001). In allograft recipients who had episodes of rejection of grade 3A or greater, both right and left ventricular late filling termination times were significantly increased during rejection. CONCLUSIONS: Measurements of right ventricular late filling termination time by color M-mode Doppler echocardiography performed in the absence of acute rejection can be use to monitor the evolution of interstitial collagen content in cardiac allografts. The early detection of abnormally prolonged late filling termination time could be followed by endomyocardial biopsy to confirm the histologic changes.

Adult↗