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Biomedical subjects

D Loisance

Publications and source records attributed to D Loisance.

At least 163 records · Page 9Linked to original sources
PubMed1985

Age-related changes of action potential plateau shape in isolated human atrial fibers.

Because the frequency of atrial arrhythmia increases dramatically with age in humans, we investigated age-related changes of cellular electrical activity in human atrial fibers, utilizing standard microelectrode techniques. Twenty-four atrial samples, uniformly exhibiting fast responses, were selected. Patients were in two different age groups: 10.0 +/- 7.0 mo and 54.4 +/- 9.7 yr. Although mean maximum diastolic electrical potential did not significantly differ, the two groups showed marked dissimilarities in action potential (AP) shape. Adult-type APs always exhibited an initial notch followed by a low-level prolonged plateau, whereas APs of the young were more triangular and had a short plateau approaching zero potential. 4-Aminopyridine (0.5 mM) markedly increased the level of the adult AP plateau without suppressing the initial notch, which disappeared after further addition of caffeine (10 mM). The simultaneous action of the two drugs changed an adult-type AP into a young type. The drug effects were much less marked in young atria. Our results suggest that an age-related increase in transient outward currents can account for the differences in plateau shape described. Moreover, age-related differences in plateau configuration in response to a period of rest suggest a faster repriming kinetic of these currents in adults.

4-Aminopyridine↗
PubMed1984

[Cardiac transplantation: noninvasive detection of rejection by echocardiography].

The main objective of follow-up of cardiac transplant patients is early recognition of acute rejection of the allogenic myocardium. Two patients followed up by the usual protocol also underwent routine M-mode and 2D echocardiography. The data was digitalized and memorized to allow systematic study of the pericardial and cardiac structures, and a comparison of their evolution. Acute rejection was associated with an increase in the acoustic density of the myocardium, especially of the interventricular septum, and an increase in myocardial mass as calculated from M-mode data; an increase of 5 p. 100 of this parameter with respect to an average reference value was judged to be significant. Comparisons were made with electrocardiographic data, especially with an index of voltage. The variability of this index which may be unrelated to rejection was apparent; in addition, there was an interval of about 5 days between the echocardiographic changes and the recording of significant reductions of the electrocardiographic index. Previously reported histological changes explain the precocity and reliability of the echocardiographic results obtained by a non-invasive and reproducible method.

Adult↗
PubMed1984

[Experimental study of a biological micro-arterial prosthesis].

An arterial prosthesis prepared from human placental arteries, diameter 1.0 mm, length 20 mm, was evaluated after implantation into the infrarenal region of the aorta of the rat. The permeability rate after one year (70%) compares favorably with results after fresh arterial autografts. Histology showed that the prosthesis acted as a matrix colonizable by the tissues of the recipient. The internal surface of the tube was covered by a tissular layer in which fibrillary elements suggestive of elastic fibers were developing.

Animals↗
PubMed1984

[Types and choice of valve prosthesis].

A great variety of valvular prostheses are available to the surgeon when conservative valvular repair techniques are not indicated. The choice of a prosthesis is dependent on many diverse factors including the patient himself, local anatomic considerations, and the mechanical characteristics and thromboembolic risk of the prosthesis itself. Two types of prostheses are available: the mechanical prostheses with their well known durability requiring, however, indefinite anticoagulant therapy, or the bioprostheses which provide greater comfort and freedom, but whose long term reliability is uncertain.

Bioprosthesis↗
PubMed1983

Healing of biodegradable vascular prosthesis. Incorporation of 3H-valine into proteins in the subendothelial scar and host intima-media of rat aorta.

Heparin treated and aldehyde crosslinked rat aorta segments were implanted in infrarenal aorta of homologous rats. One year following aortic replacement, the subendothelial scar and the prosthetic remnants were excised. The scar and the host intima-media were incubated with 3H-valine for 4 h and extracted with 5 M guanidinium chloride--0.05 M dithiothreitol--0.1 M Tris--0.1% EDTANa2 at pH 7.5 prior (Extract 1) and following (Extract 2) hydrolysis of collagen. The radioactivity of extract 1 accounted for approximately 80% of the total label incorporated in the scar and host intima-media. The 3H-label of extract 1 adjusted for the tissue collagen content was about twenty times higher in the scar than in the host aorta. The major 3H protein peaks from Extract 1 of scar and host aorta were of 130 K, 100 K and 70 K apparent molecular weight, based on polyacrylamide gel electrophoresis in SDS. Hydrolysis with 2N KOH of the extraction residue from the host aorta and scar yielded 3H-val-pro dipeptides and hydrolysis with 6N HCl desmosines. The incorporation pattern of 3H-valine into proteins and the presence of elastin synthesized de novo in the scar replacing the prosthesis indicate macromolecular repair of the host aortic wall.

Animals↗
PubMed1982

[Surgical treatment of subvalvular aortic obstructions. A new approach].

Approaching the region below the aortic valve is notoriously difficult. The new technique described, derived from the Konno-Restan technique, provides wide exposure of the infra-aortic canal through the right ventricle, the aorta and the septum. Experiments on animals have shown that it entails no risk of heart damage. This technique was used on one patient with sub-aortic fibromuscular tunnel with excellent post-operative results.

Aorta↗
PubMed1982

[Extracorporeal circulation with membrane oxygenation in high-risk coronary surgery].

The case of a patient operated for left main stem disease in which cardiopulmonary bypass (CPB) lasted 7 hours because of acute severe myocardial failure is reported. A satisfactory recovery of autonomous hemodynamic function was achieved. This case illustrates the technical progress which has been made in CPB: reduction of blood cell trauma in the bypass circuits, improved oxygenation reducing the disturbances of tissue perfusion usually associated with bubble oxygenators. The use of hypothermia in vasoplegic patients also contributes to the reduction in the incidence of complications. These improvements result in the optimal recovery of ischemic myocardial fibres and reduce the need for pharmacological support which is always difficult to manage and which is often associated with unwanted side effects.

Cardiopulmonary Bypass↗
PubMed1982

[Experimental test of two tissue adhesives (GRF and IBC 2) in vascular microsurgery in the rat (author's transl)].

Tissues adhesives have been evaluated on rats, during microvascular surgery: the IBC 2 and the GRF glues. The short and long term evolution is studied. The patency rate of the anastomosis is analyzed and the histological aspect is studied. The GRF glue exhibits a rapid resorption rate, but the long term results show a high toxicity against the muscular layers of the artery. The IBC 2 glue has a slower resorption rate and its long term effect are restricted to a foreign body reaction.

Animals↗
PubMed1981

[Small-caliber vascular prosthesis].

Further research on biomaterials should permit the development of an adequate microarterial prosthesis. This program should also allow improvements of the presently available arterial substitutes. Various types of conduits have been tested on an experimental model: prosthetic tube, biological conduits either preserved or chemically modified. The most encouraging results have been observed with an arterial conduit, prepared from fresh aorta, treated by trypsin and glycosaminoglycans.

Animals↗
PubMed1981

[False failure of an aortocoronary bypass. Spasm of an artery revascularized by 2 saphenous vein graft].

The cause of recurrent resting angina one year after aorto-coronary bypass is presented. A 65 year old female with effort and resting angina with syncope had an isolated narrowing of the proximal portion of the left anterior descending artery on coronary angiography. Saphenous vein aorto-coronary bypass and cardiac plexectomy were performed on the 18 . 12 . 78, and an excellent result was obtained in the first postoperative year. Nocturnal angina with syncope recurred on the 31 . 12 . 79 and anterior subendo-cardial ischaemic changes were noted on the post critical electrocardiogramme. On control angiography 10 days later, the bypass graft was shown to be patent. A provocative test with methylergometrine showed spasm of the whole of the revascularised artery without any changes in the other vessels. Attacks of spontaneous angina with ST depression on Holter monitoring continued despite treatment with Nifedipine (6 capsules/day). The substitution of Diltiazem (3 capsules/day) prevented further recurrence with a follow-up of three months. The authors conclude that spontaneous angina after aorto-coronary bypass is not synonymous with graft dysfunction, and suggest that the effects of cardiac denervation in vasospastic angina, where Nifedipine and Diltiazem seem to have different modes of action, need further confirmation.

Aged↗
PubMed1981

Studies on elastic tissue of aorta in aortic dissections and Marfan syndrome.

Insoluble elastins were isolated from control and aneurytic aortas by a sequential extraction procedure involving the use of purified collagenase. Marked differences in amino acid analyses and susceptibilities to pancreatic elastase were observed between normal and pathological samples. The incorporation of either 14C-lysine or 14C-glucosamine into proteins of the vessel wall was also studied. In addition, high amounts of elastase-type activity was extractable from pathological aorta specimens which may contribute significantly to the loss of elastic tissue evidenced by ultra-structural studies and confirmed by the biochemical technics. We propose therefore that increased elastase-type protease activity in these pathological aortas does significantly contribute to the weakening of the aortic wall and also may well be the main cause of the rupture of aneurysms observed occasionally.

Adult↗