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Biomedical subjects

O Chavanon

Publications and source records attributed to O Chavanon.

At least 37 records · Page 2Linked to original sources

Prevalence and consequences of nutritional depletion in lung transplant candidates.

Nutritional status was studied in lung transplant (LT) candidates. The hypotheses were that nutritional depletion was highly prevalent and lean body mass depletion was a risk factor for a higher mortality both before and after LT. Of 78 consecutive patients listed for LT, 16 (21%) died while on the waiting list, eight (10%) were alive awaiting LT, and 54 (69%) received a graft. Mean age was 42.3+/-4.4 (mean+/-SD). Thirty-eight per cent had a diagnosis of bronchiectasis or cystic fibrosis (BRO/CF), 33% of emphysema, 20% of idiopathic pulmonary fibrosis (IPF) and 8% of primary pulmonary hypertension. Body mass index (BMI) was 20.4+/-4.3 kg.m2, weight was 87.9+/-16.6% of ideal body weight (IBW). Patients were classed into four nutritional groups according to IBW and creatinine height index (CHI): 1: weight <90% IBW and CHI <60% of predicted (28% of cases); II: weight <90% IBW and CHI > or =60% (27%); III: weight > or =90% IBW and CHI <60% (17%); IV: weight > or =90% IBW and CHI > or =60% (28%). Overall, 72% were depleted corresponding to groups 1, II and III. Lean body mass depletion occurred despite normal weight in 17% of the cases (group III). Subjects with BRO/CF were mostly in groups 1, II, III whereas IPF were concentrated in group II. Lean body mass depletion was associated with more severe hypoxaemia, reduced 6-minute walking distance and a higher mortality while awaiting. After LT, duration of mechanical ventilation, time spent in intensive care unit (ICU) was related to initial body composition. Survival after LT was lowest in group III. To conclude, nutritional depletion in lung transplant candidates is highly prevalent and should be more precisely assessed with a special reference to lean body mass since it has specific consequences both while awaiting and after lung transplant. Attempts should be made to increase lean body mass before lung transplant.

Adult↗

Furosemide inhibits thromboxane A2-induced contraction in isolated human internal mammary artery and saphenous vein.

Evidence suggests that, in addition to its diuretic property, furosemide also may exert direct vascular effects. Because thromboxane A2 (TXA2) has a role in the control of vascular tone, we investigated the effect of furosemide on the contraction induced by U46619 (a stable TXA2 mimetic) on isolated human internal mammary artery (IMA) and saphenous vein (SV). Concentration-response curves to U46619 were performed in the absence (vehicle) or the presence of furosemide (0.1-1 mM) on rings of IMA and SV. In addition, the relaxant effect of furosemide (0.1 microM-1 mM) also was evaluated on U46619-precontracted IMA and SV. The participation of cyclooxygenase derivatives was studied by pretreatment with indomethacin. Furosemide (0.1-1.0 mM) caused parallel rightward shifts of U46619 concentration-response curves without affecting the maximal responses in both IMA and SV. Treatment with indomethacin (1 microM) modified neither the inhibitory effect of furosemide on U46619-induced contractions, nor the relaxant effect of furosemide on U46619-induced contractions, nor the relaxant effect of furosemide on U46619-precontracted IMA and SV. In conclusion, furosemide at high concentrations inhibited U46619-induced contraction in human isolated IMA and SV and relaxed U46619-precontracted IMA and SV by mechanisms independent of the release of relaxant prostaglandins. These results suggest that blockade of TXA2 receptors by furosemide may contribute to explaining the therapeutic effects of furosemide in the treatment of severe heart failure.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

Endoscopic saphenectomy for coronary artery bypass surgery: comparison of two techniques with and without carbon dioxide insufflation.

OBJECTIVE: To compare the clinical results of an initial experience with two techniques of endoscopic saphenectomy with and without gas insufflation. DESIGN: A retrospective study was performed between September 1998 and March 1999 on 40 patients who underwent endoscopic saphenectomy for coronary artery bypass graft without (group 1, n=15) and with (group 2, n=25) carbon dioxide insufflation. INTERVENTIONS: In both groups, the site of harvesting was at the knee through a 2 cm incision. In group 1, dissection was performed using a hand-held dissector while in group 2 dissection was performed after ensuring that there was a seal at the knee and insufflation of carbon dioxide. Collaterals were controlled with an endoclipper in group 1 and bipolar scissors in group 2. Intraoperative procedure time, length of the harvested vein and aspect of the thigh (ecchymosis, hematoma, infection) were recorded. RESULTS: Vein trauma occurred in four patients in group 1 (four of 15, 27%) and in one in group 2 (one of 25, 4%). Hematomas developed in four patients in group 1 (four of 15, 27%) and in one patient in group 2 (one of 25, 4%). Wound infection occurred in no patients in group 1 and in one patient in group 2. One patient in group 2 suffered carbon dioxide embolism with no untoward consequences. Conversion to an open technique was necessary in five patients in group 1 (five of 15, 33%) and in two patients in group 2 (two of 25, 8%). CONCLUSIONS: Endoscopic saphenectomy both with and without carbon dioxide insufflation is associated with a low infection rate, but vein trauma and wound hematomas are more common without carbon dioxide insufflation.

Angioscopes↗

[Basaloid cancer of the esophagus].

BACKGROUND: Basaloid cancer of the esophagus is exceptional. The tumor probably develops from epithelial basal cells. This histological type is generally observed in ENT or bronchial localizations. CASE REPORT: A 62-year-old man underwent total pharyngo-laryngo-esophagectomy for a double tumor localization of a basaloid carcinoma of the esophagus and a hypophyayngeal squamous cell carcinoma. DISCUSSION: Basaloid carcinoma has specific histological features difficult to recognize at the pathology examination. Because of the high risk of metastasis, it may be important to propose radiotherapy and/or chemotherapy after surgical excision.

Antineoplastic Combined Chemotherapy Protocols↗

Reactivity of the Human Internal Mammary Artery and the Gastroepiploic Artery to Constrictor Substances.

The internal mammary artery (IMA) and the gastroepiploic artery (GEA) are frequently used to construct coronary artery bypass grafts. In order to determine and to compare their contractile properties, we studied the effects of constricting agents which are liberated or infused during coronary bypass surgery. IMA and GEA were arranged as ring segments and suspended in organ baths at optimal stretch using a normalization procedure. Concentration-contraction curves to angiotensin II, norepinephrine, U-46619, endothelin-1, leukotriene C(4) and KCl were performed. The sensitivity (pD(2)) of GEA and IMA to all the agents did not differ. However, GEA developed stronger maximal contraction force than IMA to angiotensin II (P < 0.001), norepinephrine (P < 0.05), U-46619 (P = 0.06), endothelin-1 (P < 0.01), and KCl (P < 0.01), whereas leukotriene C(4) did not induce a significant contraction on GEA and IMA. The higher contractility of GEA may explain that it is more prone to spasm than IMA in the clinical setting. This study reinforces IMA as a first-choice conduit for coronary artery bypass and emphasizes the need for antispastic drugs particularly when GEA is used as bypass vessel.http://link.springer-ny.com/link/service/journals/00547/bibs/8n4p187.html</hea

Journal Article↗

Effect of topical vasodilators on gastroepiploic artery graft.

BACKGROUND: Mobilization of the gastroepiploic artery (GEA) often results in a vasospasm with reduction of early graft flow. In order to prevent or suppress this highly reactive artery's spasm, we have compared the effect of 4 vasodilators, used in external application to prepare the GEA graft, prior to myocardial revascularization. METHODS: WE performed a double-blind clinical study to compare the effects of external application of vasodilators on gastroepiploic artery grafts. Fifty patients, whose gastroepiploic artery was used for coronary artery bypass grafting, were randomized into 5 groups of 10 patients. Gastroepiploic artery free flow and hemodynamic measurements were evaluated immediately after harvesting, before any pharmacological manipulation, and 10 minutes after the topical application of vasodilators, respectively: papaverine, linsidomine, nicardipine, glyceryl trinitrate, and normal saline solution. RESULTS: A significant increase in free flow occurred in all groups except for the normal saline solution group with measurements from 26.1+/-3.6 mL/min to 26.4+/-6.5 mL/min; p = 0.9. The most important increase in flow before and after local application occurred with glyceryl trinitrate and papaverine: from 25.5+/-2 mL/min to 50+/-6.1 mL/min (p < or = 0.01) and from 36.8+/-3.2 mL/min to 62+/-7.8 mL/min (p < 0.01) respectively. Nicardipine and linsidomine produced a less significant increase in flow: from 33.1+/-3.6 mL/min to 47.7+/-8.9 mL/min (p < 0.05) and from 28+/-3.8 mL/min to 39.8+/-7.5 mL/min (p < 0.05) respectively. When comparing percentage of flow increase, glyceryl trinitrate appeared to be significantly more efficient than nicardipine and linsidomine (p < 0.01 versus both groups). Although papaverine was more efficient than nicardipine and linsidomine, it did not reach statistical significance. CONCLUSIONS: During intraoperative preparation of the GEA graft, glyceryl trinitrate and papaverine to a lesser extent, used as topical vasodilators, appear to be more efficient in external application to increase the free flow of the GEA.

Administration, Topical↗

Accurate guidance for percutaneous access to a specific target in soft tissues: preclinical study of computer-assisted pericardiocentesis.

In the field of percutaneous access to soft tissues, our project was to improve classical pericardiocentesis by performing accurate guidance to a selected target, according to a model of the pericardial effusion acquired through three-dimensional (3D) data recording. Required hardware is an echocardiographic device and a needle, both linked to a 3D localizer, and a computer. After acquiring echographic data, a modeling procedure allows definition of the optimal puncture strategy, taking into consideration the mobility of the heart, by determining a stable region, whatever the period of the cardiac cycle. A passive guidance system is then used to reach the planned target accurately, generally a site in the middle of the stable region. After validation on a dynamic phantom and a feasibility study in dogs, an accuracy and reliability analysis protocol was realized on pigs with experimental pericardial effusion. Ten consecutive successful punctures using various trajectories were performed on eight pigs. Nonbloody liquid was collected from pericardial effusions in the stable region (5 to 9 mm wide) within 10 to 15 minutes from echographic acquisition to drainage. Accuracy of at least 2.5 mm was demonstrated. This study demonstrates the feasibility of computer-assisted pericardiocentesis. Beyond the simple improvement of the current technique, this method could be a new way to reach the heart or a new tool for percutaneous access and image-guided puncture of soft tissues. Further investigation will be necessary before routine human application.

Animals↗

Antagonistic effects of losartan on thromboxane A2-receptors in human isolated gastroepiploic artery and saphenous vein.

In addition to its AT1-receptor antagonist activity, losartan has been shown to antagonize thromboxane A2 (TXA2)-induced contraction of animal vessels. We investigated for the first time in human isolated gastroepiploic artery (GEA) and saphenous vein (SV) the TXA2/PGH2-receptor antagonist activity of losartan in the presence of indomethacin (1 microM) and N(omega)-nitro-L-arginine (100 microg). Losartan at concentrations of > or =1 microM on GEA and from 10 microM on SV significantly shifted U46619-induced contractions to the right. In addition, 100 microM losartan decreased by 34% the amplitude of the contraction to U46619 on both GEA and SV. The potency of losartan for the TXA2 receptor was 50- and 80-fold lower than that for the AT1 receptor on human GEA and SV, respectively. This inhibitory effect of losartan appeared selective for angiotensin II and TXA2-induced contractions because 100 microM losartan did not modify either endothelin-1- or KCl-induced contraction in human SV, although a reduction of norepinephrine- and 5-hydroxytryptamine-induced contraction was observed in human GEA and SV, respectively. In conclusion, losartan is an antagonist of TXA2 receptor on human GEA and SV. However, this antagonist activity occurred for a relative high dose of losartan, suggesting that it contributes at a low level, if any, to its antihypertensive effect.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

Vasorelaxant actions of enoximone, dobutamine, and the combination on human arterial coronary bypass grafts.

Enoximone (a type III-selective phosphodiesterase inhibitor) and dobutamine (a beta-receptor agonist) are positive inotropic drugs frequently used in the postoperative management of coronary bypass surgery. The purpose of this study was to characterize their relaxant effects on the human internal mammary artery (IMA) and the gastroepiploic artery (GEA) and to test the hypothesis that their combination may have greater than additive relaxant effects. In organ baths, the relaxant effects of enoximone and dobutamine were tested on rings of IMA (n = 86) precontracted with U46619 (a thromboxane A2 mimetic), norepinephrine (NE), or KCl. The relaxant effects of dobutamine and enoximone also were tested on rings of GEA (n = 42) precontracted with U46619 and NE. The effect of the combination of enoximone and dobutamine were tested on rings of IMA (n = 24) precontracted with U46619 or NE. With respect to maximal relaxations induced by papaverine (10(-4) M), enoximone (< or =10(-3) M) caused full relaxations of IMA precontracted with NE, U46619, or KCI. Dobutamine (< or =10(-3) M) caused full relaxations of IMA precontracted with NE or KCI but only 46% (95% CI, 27-65) relaxation in the rings precontracted with U46619. Similar patterns of relaxation were observed in GEA rings, with dobutamine inducing partial relaxation in GEA precontracted with U46619. The pD2 values of enoximone and dobutamine were both significantly lower in segments precontracted with U46619. The in vitro threshold relaxant concentrations were in the upper limits or over the range of therapeutic plasma concentrations. The relaxant effect of the combination was significantly more important than the theoretic additive effect in IMA contracted with U46619 or NE. Enoximone and dobutamine are potent in vitro vasodilators but exert weak relaxant effects in IMA and GEA at concentrations in the therapeutic range. There is, however, a greater than additive vasorelaxant effect of the combination, suggesting that the vasorelaxant effect of the combination, in addition to the additive inotropic effect, may be beneficial to patients undergoing coronary bypass grafting.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

Functional comparison of the human isolated femoral artery, internal mammary artery, gastroepiploic artery, and saphenous vein.

Human femoral, internal mammary, and gastroepiploic arteries and saphenous veins are used as bypass grafts for coronary surgery or for reconstruction in arterial occlusive disease. We have characterized the contractile responses of these vessels to various agents that are liberated during cardiac or vascular surgery. In organ baths, U46619 (a stable thromboxane A2 mimetic), norepinephrine, endothelin-1, angiotensin II, and KCl caused concentration-dependent contractions in all vessels tested. Leukotriene C4 did not induce any contraction in the arteries, whereas a contraction was obtained in the saphenous vein rings. U46619 induced the most powerful contraction in all vessels tested. The pD2 values for each agent did not differ among the different vessels. When responses were expressed as a percentage of KCl-induced contraction, the contraction of endothelin-1 (151+/-5%) and leukotriene C4 (43+/-5%) was more significant on saphenous veins than on arteries. In conclusion, thromboxane A2 appears to be the most potent endogenous constricting agent on different human vascular beds. Our second finding is that saphenous veins are more sensitive to contract to leukotriene C4 and endothelin-1 than arteries. These properties may influence early and (or) long-term vein graft patency.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

Glibenclamide inhibits thromboxane A2-induced contraction in human internal mammary artery and saphenous vein.

Glibenclamide, like other hypoglycemic sulfonylurea derivatives, is a potent blocker of ATP-regulated K+ channels. In addition, it is reported to inhibit prostanoid-induced contractions of isolated vascular smooth muscle from different animal species. We investigated the effect of glibenclamide on the thromboxane A2-mimetic U-46619 (9,11-dideoxy-9alpha,11alpha-methanoepoxy-prostaglandin F2alpha)-induced contractions in human isolated internal mammary arteries and saphenous veins. In the two vascular preparations, glibenclamide (3, 10 and 30 microM) caused a concentration-dependent shift to the right of the U-46619 contraction-response curve with a reduction, at the highest concentrations, in the maximal responses. This inhibitory effect appears selective for thromboxane A2-induced contractions since glibenclamide (30 microM) did not alter the contraction of internal mammary arteries in response to norepinephrine and of saphenous veins in response to 5-hydroxytryptamine (5-HT) and endothelin-1. However, glibenclamide reduced the endothelin-1-induced contraction in internal mammary arteries. The endothelin-1-induced contractions were similarly inhibited by GR 32191 ([1R-[1alpha(Z),2beta,3beta,5alpha]]-(+)-7-[5-([1,1'-b iphenyl]-4-ylmethoxy)-3-hydroxy-2-(1-piperidinyl)cyclopentyl]-4-++ +heptonoic acid, a thromboxane A2 receptor antagonist. These results suggest that glibenclamide also reduced the endothelin-1-induced contractions by inhibiting a thromboxane A2 receptor-mediated component of the contraction elicited by this peptide. In conclusion, glibenclamide clearly appears to exert a specific inhibitory influence on prostanoid-induced contractions in human internal mammary arteries and saphenous veins.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

EBV-B cells as antigen presenting cells in characterization of the self/donor context of allorecognition by T lymphocytes.

Alloreactivity is caused by T cell recognition of foreign histocompatibility antigens according to two models: (i) indirect recognition, in which processed allogeneic antigens are presented by self-major histocompatibility complexes like any other foreign antigen, and (ii) direct recognition, where the foreign MHC itself is recognized breaking the T cell recognition rule of self-restriction. This paper uses these two cases of alloantigen presentation as illustrative examples to investigate (i) the capacity of Epstein-Barr virus-transformed B cells (EBV-B cells) to process alloantigens, and (ii) in vitro assays with EBV-B cell lysate as a source of alloantigen, in order to characterize alloreactive T cell populations. A microculture system was established using donor EBV-B cell lysate as a source of the allogeneic antigen and donor or recipient EBV-B cells as antigen presenting cells to investigate whether alloantigen is recognized by effector T cells from the recipient. T lymphocytes produced after expansion in the presence of interleukin-2 from four samples of liver biopsies (three patients) and four samples of bronchoalveolar lavages (four patients) were used as effector cells. Upon human leucocyte antigen class II typing, these expressed the patient phenotype. When the T lymphocytes were from liver grafts, the recognition involved donor antigens presented by donor EBV-B cells (direct recognition). On the other hand, when the T lymphocytes were cultured from lung grafts, they mainly recognized antigens of donor EBV-B cell lysates in a self-restricted context (indirect recognition). These data suggest that EBV-B cells can provide allogeneic determinants recognized by T cells in donor or self-contexts, i.e. through either direct or indirect recognition.

Adult↗