Experimental evaluation of porcine-valved conduits processed with a calcium-retarding agent (T6).

The effectiveness of a water-soluble C-12 alkyl sulfate (T6) (U.S. Patent No. 4,323,358) in retarding bioprosthetic calcification was evaluated in 23 porcine-valved conduits (13 T6-treated conduits and 10 controls) implanted in young sheep between the right ventricle and the pulmonary trunk. The grafts were divided into three groups according to the period of function: Group I, less than 2 months; Group II, 2 to 4 months; and Group III, 5 to 7 months. In Group I (four T6 and four controls), endocarditis occurred in five cases. In Group II (three T6 and three controls), four conduits showed severe fibrous peel ingrowth. In Group III (six T6 and three controls), fibrous peel was the main feature in four conduits and calcium deposits occurred in the porcine aortic wall in all cases, with cusp involvement in two; in both T6-treated and control conduits, chemical analysis showed a much lower calcium content of the cusps (8.45 +/- 80 versus 2.95 +/- 1.52 mg/gm dry weight, respectively) than that reported in other animal or human explants. The grade of calcification in control and T6-treated conduits was equal on x-ray analysis, and no differences in calcification patterns were noted on electron microscopy. This experimental model shows a low degree of cusp calcification and no significant differences between T6-treated and control conduits. Peel formation markedly interferes with performance of the porcine-valved conduit. The results of this analysis indicate that valved conduits are not the optimum model for evaluating calcium-retardant agents in biological valves.

Intrauterine versus postnatal repair of created pulmonary artery stenosis in the lamb. Morphologic comparison.

Experimental lamb models were used for intrauterine creation of pulmonary artery stenosis and later intrauterine repair or postnatal repair. Intrauterine creation of pulmonary artery stenosis was performed in 23 fetal lambs at 90 +/- 1 days of gestation. Eight lambs underwent intrauterine repair of pulmonary artery stenosis at 135 +/- 1 days of gestation and were studied 110 +/- 13 days after repair. Seven lambs underwent postnatal repair at 57 +/- 9 days after birth and were studied 162 +/- 32 days after repair. Eight fetal lambs with unrepaired pulmonary artery stenosis were studied 89 +/- 18 days after birth. All study lambs were compared with normal control lambs. The systolic right ventricular pressure was significantly higher after unrepaired stenosis (78.6 +/- 6.8 mm Hg) than in other lambs, but there was no statistically significant difference after intrauterine repair (23.3 +/- 2.9 mm Hg), postnatal repair (25.9 +/- 3.4 mm Hg), and normal lambs (21.6 +/- 1.1 mm Hg). The systolic pulmonary artery pressure was also not statistically different in these three groups. The weight measurements were age-adjusted for comparison of postnatal and intrauterine repair with normal lambs. The adjusted heart weights were similar in the three groups. The comparison of the adjusted heart weight/adjusted body weight ratio (10(-3) showed a significantly higher ratio in postnatal repair (7.4 +/- 0.1) than in intrauterine repair (6.1 +/- 0.1). The adjusted right ventricular weight/adjusted left ventricular weight ratio was significantly higher in the postnatal repair group (0.71 +/- 0.01) than in both the intrauterine repair group (0.59 +/- 0.01) and normal lambs (0.59 +/- 0.01). The transverse myocyte diameter was not statistically different in all groups of animals and there were no ultrastructural changes even when the pulmonary stenosis was unrepaired. We conclude that intrauterine repair was more satisfactory than postnatal repair in terms of age-adjusted heart weight results, but we did not find any advantages of intrauterine repair in terms of histologic and ultrastructural changes.

Intrauterine creation and repair of pulmonary artery stenosis in the fetal lamb. Weight and ultrastructural changes of the ventricles.

Fetal lamb experimental models were employed for intrauterine creation and repair of pulmonary artery stenosis. The study group was composed of 51 fetal lambs including 29 models of pulmonary artery stenosis and 22 control lambs. Gestational age was 89 days at creation of pulmonary artery stenosis. Fourteen fetal lambs (Group A) were studied after creation of the stenosis at 131 days of gestation and compared to normal age-matched control lambs. The systolic right ventricular pressure was significantly higher after creation of pulmonary artery stenosis (76.6 +/- 17.8 versus 50.3 +/- 23.5 mm Hg), but the systolic pulmonary artery pressure was unchanged. The mean right ventricular weight and the mean right ventricular/left ventricular weight ratio were significantly greater after pulmonary artery stenosis than in normal control animals. The transverse myocyte diameter was not modified by pulmonary artery stenosis, but on electron microscopic study the myocytes appeared mature. Ten lambs (Group B) underwent intrauterine repair of pulmonary artery stenosis at 131 days of gestation without cardiopulmonary bypass. The pulmonary artery was clamped and patched. Immediately after repair the right ventricular pressure fell significantly from 85.8 +/- 18.9 to 62.2 +/- 14.6 mm Hg. At birth, 7 +/- 6 days after repair, Group B was compared to Group C (unrepaired pulmonary artery stenosis, five fetuses) and to normal control lambs. The mean right ventricular weight and the mean right ventricular/left ventricular weight ratio were not statistically different in Group B and in the control group. There were no ultrastructural changes after intrauterine repair. We conclude that intrauterine creation of pulmonary artery stenosis causes right ventricular hypertrophy with more mature myocytes. Intrauterine repair of pulmonary artery stenosis is feasible without cardiopulmonary bypass and rapidly abolishes the preponderance of right ventricular weight over left ventricular weight.

Biocompatibility of elastin-fibrin material in the rat.

Biocompatibility and biodegradability of a new elastin-fibrin material were investigated in several organs and tissues of the rat. It has been demonstrated that the material was quite well tolerated in all cases, except in bone marrow. Its use is considered in several aspects of reparative or constructive surgery.

Riluzole prolongs survival and delays muscle strength deterioration in mice with progressive motor neuronopathy (pmn).

The neuroprotective drug riluzole (Rilutek) is a sodium channel blocker and anti-excitotoxic drug which is marketed for the treatment of amyotrophic lateral sclerosis (ALS). Previous studies have shown that riluzole prolongs survival of transgenic mice harboring the mutated form of Cu,Zn-superoxide dismutase found in familial forms of the human disease. In this study we have examined the effect of treatment with riluzole in mice suffering from progressive motor neuronopathy (pmn), a hereditary autosomal recessive wasting disease which shares some symptoms of ALS. These mutants display hind limb weakness starting during the 3rd week of life and leading to paralysis and death during the 7th week of life. Daily treatment with 8 mg/kg of riluzole by oral route significantly retarded the appearance of paralysis, increased life span and improved motor performance on grip test and electromyographic results in the early stage of the disease. There was no effect of riluzole on weight gain. These data demonstrate that riluzole significantly prolongs life span, retards the onset of paralysis and slows the evolution of functional parameters connected with muscle strength in the pmn mouse model of motor neuron disease.

Morphological survey of a new pericardial valve prosthesis (Pericarbon): long-term animal experimental model.

A long-term experimental morphological study was carried out in 22 adult sheep to evaluate a new pericardial valve prosthesis (Pericarbon), which had been implanted in the tricuspid or mitral position. This prosthetic device differs substantially from others in that its construction design consists of two sheets of glutaraldehyde-fixed bovine pericardium and a low-profile flexible plastic stent (Delrin) covered by a pyrolytic carbon coated dacron fabric; one pericardium sheet forms the three cusp valve and is sutured to the second, which lines the inner surface of the plastic stent. Twenty animals were sacrificed at fixed intervals, while 2 are still living at about 3 years post-surgery. Tricuspid explants (mean duration, 295 days) showed significant fibrous sheathing and a mean calcium X-ray score of 1.75. Mitral medium-term explants (mean duration, 325 days) had fairly well preserved pliability and a mean calcium X-ray score of 2.5. Long-term explants (mean duration, 467 days) were all stiffened by calcification (mean score, 3.75). None of the explants had tears or perforations. Medium or long-term mechanical failure was not observed. A significant host tissue reaction took place in the tricuspid but not in the mitral position. Calcification mainly involved the collagen fibres and increased progressively with time. Ultrastructural studies invariably disclosed fair preservation of graft tissue structures, surface reendothelization and initial nuclei of calcification within the collagen fibres. These morphological findings confirm the potential advantages of this new prosthetic device and warrant long-term clinical trials to test its actual durability.

Experimental cardioplasty using the latissimus dorsi muscle flap.

This study was undertaken to examine the possibility of using the latissimus dorsi muscular flap, divided in two parts thus covering the surfaces of the heart, and inserting it into the thoracic cavity by means of a segmental resection of the second rib. After cadaver case studies, 15 operations were performed on 5 Beagle dogs. The first group of 5 operations consisted of a latissimus dorsi flap graft over the heart. The second group and third group of operations (3 and 6 months later) consisted of reoperating for muscular and cardiac biopsies and electrical stimulation tests on the heart-muscle complex. The latissimus dorsi flap provided a sizable mass of contractile tissue. The haemodynamic studies showed no compressive or constrictive phenomenon of the muscle on the heart and revealed the preservation of an appropriate cardiac output for short intervals of time (2 hours), through phasic electrostimulation of the flap. The histopathological studies showed conserved muscular structure. The technical feasibility, histological adaptability and electrophysiological properties of this muscular flap makes it appropriate to develop a functional stimulation programme and perhaps adequate for the treatment of dysplasic, ischemic, tumoral and other acquired or congenital myocardial diseases.

Ethics committee recommendations for laboratory animals in private research in France.

Complementary to existing legislation, non-public research companies in France have been working together voluntarily within an organization known as Grice (Interprofessional Working Group on Ethics Committees for Laboratory Animals/Groupe de Réflexion Interprofessionnel sur les Comites d'Ethique appliquée à l'animal de laboratoire) with the objective of creating institutional ethics committees in an effort to promote animal welfare and good scientific procedures. Each company's commitment to the creation of these committees has been expressed by signing the Charter. Each ethics committee is composed of at least three members, including one who is not a scientist; a veterinarian is highly desirable. The committee examines all procedures and protocols involving animals and hands down a favourable or unfavourable opinion, or requests improvements, especially concerning animal well-being. Consensual approval of the protocol is an essential requirement before the purchase or allocation of animals. The committee examines every aspect of laboratory animal housing and care, and inspects all temporary or permanent animal housing facilities. Grice will continue its efforts in relation with public research organizations as well as with groups and in other countries whose objectives are in line with its own.

[Antenatal cardiac surgery. Creation of an experimental model of pulmonary stenosis in the fetus and repair in utero]. / Chirurgie cardiaque anténatale. Réalisation d'un modèle expérimental de sténose pulmonaire chez le foetus et réparation in utero.

An experimental model of pulmonary stenosis was created in ewes, fetus and repaired before birth by making use of the materno-foetal circulation. Eighteen ewes fetus underwent pulmonary artery banding at an average of 87 +/- 8 days' gestation (normal 135-145 days). All were reoperated before term at 132 +/- 6 days' gestation. They were divided into two groups : group I (7 fetus) was used to evaluate the experimental model of pulmonary stenosis by measuring right ventricular pressures (80 +/- 16 mmHg compared to 58 +/- 10 mmHg in control models), and the increase in right ventricular mass (2.8 +/- 0.5 X 10(-3) g vs 1.9 +/- 0.2 X 10(-3) g), left ventricular mass (2.2 +/- 0.3 X 10(-3) g vs 1.8 +/- 0.4 X 10(-3) g) and septal mass (1.8 +/- 0.3 X 10(-3) g vs 1.3 +/- 0.2 X 10(-3) g). In group II (11 fetus) the pulmonary stenosis was repaired by total clamping and patch repair. After repair and during the days just before birth, the ventricular masses decreased (RV = 2 +/- 0.3 X 10(-3) g; LV = 1.8 +/- 0.4 X 10(-3) g; septum = 1.8 +/- 0.3 X 10(-3) g) approaching values of normal control fetus. This experimental model shows that it is possible to correct cardiac lesions in utero by making use of the materno-fetal circulation and that antenatal repair of an arterial obstruction can rapidly reverse the reactional ventricular hypertrophy.

[Anastomoses of the small intestine in a septic environment protected by polyglactin 910-collagen mesh. Experimental study in rats]. / Anastomoses de l'intestin grêle en milieu septique protégées par un treillis de polyglactine 910-collagène. Etude expérimentale chez le rat.

An experimental study was carried out in rats to evaluate the outcome of small bowel anastomoses in the presence of peritonitis with and without protection by a polyglactin 910 mesh. One hundred and thirty rats were operated. 1) Thirty small bowel anastomoses were performed in a sterile environment to evaluate the morbidity and mortality due to the surgical procedure itself. All these animals had an uneventful course. 2) Forty anastomoses were performed in a septic environment without protection. Twelve rats died immediately after the procedure. Six rats developed an anastomotic fistula and 22 had an uneventful course. 3) Sixty anastomoses were performed in a septic environment and protected by a polyglactin 910 mesh. Seventeen rats died immediately after the procedure. There were no anastomotic disruptions. Seventeen rats had an uneventful course, and 28 (65%) developed stenosis of the anastomosis. Protection of small bowel anastomoses by a polyglactin 910 mesh appears to effectively prevent disruptions (no anastomotic fistulae or locoregional infections were recorded). However, the mesh is responsible for an intense inflammatory reaction, that often results in intestinal obstruction.

Intervessel (arteries and veins) and heart/vessel selectivities of therapeutically used calcium entry blockers: variable, vessel-dependent indexes.

The intervessel selectivity indexes of the calcium entry blockers amlodipine, felodipine, isradipine, nicardipine, nifedipine, nitrendipine, diltiazem and verapamil were assessed by determining the potency of these compounds [concentration decreasing tension developed by KCl in blood vessels by 50% (bvlC50)] to relax several KCl-precontracted blood vessels (femoral, jugular and saphenous veins and left anterior descending and left circumflex coronary and renal arteries) precontracted with KCl. The concentrations of KCl (25 mM for arteries and 50 mM for veins) used gave a similar response in these vessels. Intervessel selectivity indexes are the ratios of the bvlC50 determined in two different vessels. The negative inotropic potency (hlC50) was ascertained in paced (2 Hz), isoproterenol-(10 nM) supported atrial strips, and for three of the compounds, in papillary muscles. This allowed calculation of heart/vessel selectivity or vasoselectivity (ratio of hlC50 and bvlC50). All compounds overcame almost entirely (85-100%) the vessel contractile response to KCl and strongly reduced (65-90%) the tension developed by myocardial preparations. The rank order for vasorelaxant potency (bvlC50 from approximately 1 to approximately 700 nM) was generally as follows: isradipine > or = nifedipine > or = nitrendipine > or = amlodipine > or = verapamil > or = felodipine > or = nicardipine > or = diltiazem. However, the rank order for negative inotropic potency (hlC50 spanning from approximately 200 to approximately 6000 nM) was isradipine > or = nifedipine > or = verapamil > or = diltiazem > or = amlodipine > or = nitrendipine > or = felodipine > or = nicardipine. All compounds were generally more potent in relaxing capacitance than conductance vessels. Furthermore, of the capacitance vessels, the jugular vein was the least susceptible to relaxation; among the conductance vessels, five of the eight compounds relaxed renal arteries with greater potency than coronary arteries. Consequently, the value of the heart/vessel selectivity index is intrinsically dependent on the vessel used to calculate it. Overall, nitrendipine was the most vasoselective calcium entry blocker studied, with selectivity indexes ranging from 28 to 523. In conclusion, 1,4-dihydropyridine calcium entry blockers generally have a much greater affinity for calcium channels present in micropig veins than in heart muscle myocytes. This is possibly due to tissue-specific features of L-type calcium channels. Finally, comparing the vasoselectivity index of various compounds has validity only if this index is calculated by using the same experimental procedure applied to the same vascular tissue and the same heart preparation taken from the same species.

Glutaraldehyde-fixed bovine iliac veins used as bioprosthetic conduits: an experimental animal study.

The ideal prosthetic conduit for surgical repair of complex congenital heart disease has yet to be found. Twenty conduits were implanted between the right ventricle and pulmonary artery in growing sheep as follows: four Dacron porcine valve conduits (mean time in place, 142 days); four avalved glutaraldehyde-fixed bovine iliac veins (mean 132 days); and 12 glutaraldehyde-fixed bovine iliac veins containing a porcine valve (mean 180 days). Fifteen conduits were left in place from 167 to 244 days (mean 204 days), and five were explanted earlier (mean 54 days). Pathological study included gross, x-ray, histological, and ultrastructural investigation. Five conduits failed because of infective endocarditis. The valved Dacron conduits showed significant tissue ingrowth and calcification of the valve graft. The valved bovine iliac veins presented calcification at the valve level and vein wall, as well as a valvelike calcific fibrous ridge at the proximal anastomosis with the right ventricle. The avalved bovine iliac veins also presented calcific deposits along the wall and a valvelike calcific ridge at the ventricular anastomosis. Histological and ultrastructural studies of the vein tunica media revealed the phenomena of inflammatory rejection and foreign body reaction with loss of smooth muscle cells (medionecrosis) and fibrotic replacement. In conclusion, bovine iliac veins undergo inflammation with medionecrosis indicating that smooth muscle cell antigenicity is not attenuated by glutaraldehyde fixation.

[Intestinal transplantation in children]. / La transplantation intestinale chez l'enfant.

A long period of experimental work has allowed to study successively hypothermic preservation of the small bowel, autotransplantation and finally allotransplantation. After this initial phase of experimental surgery, a certain number of intestinal transplantations in humans could be attempted as cyclosporine became available. Following a brief of report of 3 intestinal transplantations recently performed by the group of the hôpital des Enfants-Malades in Paris, indications for intestinal transplantation are provided. Subtotal resections of the small bowel in children or adolescents and extensive resections in neonates account for most of the indications. Despite significant progress, further advances in intestinal transplantation need to be made, because the small bowel poses unique problems in that it seems to represent a compendium of all the particularities and difficulties of other organ transplantations.

Evaluation of Pericarbon valve prosthesis: in vitro, ultrastructural, and animal studies.

Pericarbon, a new generation pericardial valve, is characterized by a single, three cuspal shaped pericardium sheet, which is sutured to a second sheet lining the inner surface of the plastic, low profile stent. A coating of hemocompatible carbon film covers all the exposed, nonbiological surfaces. Optimal preservation of collagen and graft cells is achieved by fresh tissue glutaraldehyde fixation and cusp shaping without mold. Accelerated fatigue testing showed a duration of over 150 million cycles, a figure much higher than that observed when current pericardial and porcine valves were tested with the same apparatus. Results of long-term (greater than 7 months, average 10.5) implantation in 20 sheep (13 mitral, 7 tricuspid) disclosed no case of mechanical failure, mild to moderate primary calcification in older explants, and significant fibrous tissue overgrowth only in the tricuspid position. Transmission electron microscopy studies revealed collagen and elastic fiber integrity, no significant plasma protein insudation, and well-preserved graft cells. Re-endothelialization by host cells was a regular finding on scanning electronic microscopy. Early ultrastructural nuclei of calcification were seen mostly on collagen fibers. Pericarbon presents basic changes in pericardial valve design, and optimal morphological preservation is obtained after industrial processing. Accelerated fatigue tests in vitro show long duration. At medium long-term animal experimental follow-up, mechanical failure was not observed; significant host tissue reaction occurred in the tricuspid but not in the mitral position; primary calcification increased progressively with time and involved mainly collagen fibers.

Relationship between parietal blood flow studies in the left colon and the rectum in dogs. Colonic pressure and blood flow.

An animal model was proposed to clarify the difference in occurrence of enterocolitis in congenital aganglionosis. When gaseous distention of the colon was localized to the rectosigmoid area, enterocolitis never occurred. On the contrary, when it involved the left colon, enterocolitis occurred in 13 of 15 patients. Intestinal blood flow rates were simultaneously measured in the left colon and rectum of six dogs by using labeled microspheres and expressed in function of the intraluminal pressure. Results show that for elevated values of intraluminal pressure, blood flow was significantly lower in the left colon than in the rectum. These results may explain why ischemia and necrosis occurred more frequently in the left colon than in the rectum.