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N Bonnet

Publications and source records attributed to N Bonnet.

At least 37 records · Page 2Linked to original sources
PubMed2001

Elemental maps from EFTEM images using two different background subtraction models.

Acquisition of a great number of energy-filtered images in a TEM (EFTEM) around the characteristic signal with a low energy-selecting slit allows display of the electron energy loss (EEL)-spectrum of regions of interest (ROIs) of a sample. These EEL-spectra can be submitted to the different treatments already in use for electron energy loss spectroscopy (EELS). In particular, it is possible to fit the experimental background with different mathematical models, using images acquired below and above a characteristic ionization edge. After this fitting, elemental maps can be computed by subtraction of the extrapolated/interpolated background from the characteristic images. In this work, we compared two mathematical models for background fitting-the Egerton power law and the log-polynomial law. We studied the low-energy region (40-150 eV) and a higher-energy region (350-600 eV) with the aid of software for interactive processing of EFTEM image series that we developed. The analyzed elements were the constitutive elements: iron, phosphorus, nitrogen, and oxygen in several biological materials. Two analytical TEMs, one equipped with a post-column and the other with an in-column spectrometer, were used. Our experimental results confirm that the power law is very sensitive to the value of the energy loss of the pre-edge images when the background is computed by extrapolation. The log-polynomial model is less sensitive than the power law model to the value of the energy loss of the pre-edge images in the low energy region. For the oxygen K edge at 535 eV, it gives the best fit when it is combined with the interpolation method. The use of programs that facilitate the handling of EFTEM image series, and the controlled calculation of the background under the characteristic images, represent a step forward in the generation of elemental maps.

Animals↗
PubMed2001

Optimization of digital filters for the detection of trace elements in EELS. III--Gaussian, homomorphic and adaptive filters.

This paper is the third part of a series of papers dealing with the development of digital filters for the extraction of information from electron energy loss spectra, when the signal-to-background is very weak, as it is the case for elements in weak concentration. Three new filtering approaches are investigated: the use of high-order derivatives (typically, the fourth order derivative of a Gaussian), the use of homomorphic filtering (working on logarithmically-transformed spectra) and the use of adaptive filtering, taking into account the local background shape. These signal processing methods are applied to real spectra to demonstrate and comment their effects in three different cases of signal and background shapes related to calcium, phosphorus and boron detection in definite thickness organic matrix.

Boron↗
PubMed2001

Expanded polytetrafluoroethylene membranes to wrap surfaces of circulatory support devices in patients undergoing bridge to heart transplantation.

OBJECTIVE: Because of a lack of donor hearts, an increasing number of patients with heart failure must now undergo bridge to cardiac transplantation with a mechanical circulatory support device. Moreover, support periods have become longer. As a result, pericardial adhesions may develop while the support device is implanted, increasing the risk of injury at resternotomy and bleeding after transplantation. Use of expanded polytetrafluoroethylene (ePTFE) pericardial substitutes (membranes) may prevent such adhesions. PATIENTS AND METHODS: From January 1997 to December 1999, ePTFE membranes were used in 23 patients to wrap portions of an implanted left ventricular assist device (LVAD) or total artificial heart (TAH). Any complications during mechanical support or at cardiac transplantation were recorded. Six ePTFE membranes removed at transplantation were studied histologically. RESULTS AND CONCLUSIONS: At resternotomy for transplantation, the plane of dissection between tissues, ePTFE membranes, and surfaces of the mechanical support device were easily discerned. No adhesions were observed between tissues and membranes. There were no injuries during resternotomy and no patient had to undergo reoperation because of bleeding. One patient given a TAH had an infection during circulatory support that was controlled by antibiotic therapy. In another patient, clots developed between the device and an ePTFE membrane; these were removed successfully. Histologic studies of removed ePTFE membranes showed no infiltration of the membranes interstices by collagen or cellular components. Use of ePTFE membranes in patients undergoing bridge to transplantation with either an LVAD or a TAH limited adhesions between tissues and device surfaces without increasing the risk of infection.

Adolescent↗
PubMed2001

X-ray microanalysis of airway surface liquid collected in cystic fibrosis mice.

The airway surface liquid (ASL) that lines the airway surface epithelium plays a major role in airway antibacterial defense and mucociliary transport efficiency, two key factors in cystic fibrosis (CF) disease. A major difficulty is to collect ASL in native conditions without stimulation or alteration of the underlying airway epithelium. Using a cryoprobe specifically adapted to collect native ASL from the tracheal mouse surface, we analyzed by X-ray microanalysis the complete ASL and plasma ion content in Cftr(tm1Hgu)/Cftr(tm1Hgu) mice compared with that in control littermates. ASL ion content from eight Cftr(tm1Hgu)/Cftr(tm1Hgu) mice and eight control littermates did not appear significantly different. The mean (+/-SE) concentrations were 2,352 +/- 367 and 2,058 +/- 401 mmol/kg dry weight for Na, 1,659 +/- 272 and 1,448 +/- 281 mmol/kg dry weight for Cl, 357 +/- 57 and 337 +/- 38 mmol/kg dry weight for S, 1,066 +/- 220 and 787 +/- 182 mmol/kg dry weight for K, 400 +/- 82 and 301 +/- 58 mmol/kg dry weight for Ca, 105 +/- 31 and 105 +/- 20 mmol/kg dry weight for Mg, 33 +/- 15 and 29 +/- 9 mmol/kg dry weight for P in non-CF and CF mice, respectively. This cryotechnique appears to be a promising technique for analyzing the complete elemental composition of native ASL in CF and non-CF tissues.

Animals↗
PubMed2001

Improved activity of an actin-resistant DNase I variant on the cystic fibrosis airway secretions.

In cystic fibrosis (CF), actin and DNA originating from inflammatory cells contribute to the thickness of airway secretions. Actin can bind to DNA-rich fibers and potently inhibit the enzymatic activity of rhDNase. The in vitro effects of the actin-resistant rhDNase variant (A114R) were analyzed and compared with those of the wild-type rhDNase. Frozen and thawed CF airway secretions were incubated for 30 min with different concentrations (0.1, 0.5, 1, 5, or 10 microg/ml) of either actin-resistant rhDNase or wild-type rhDNase. We observed that both the wild-type and the actin-resistant rhDNase significantly decreased (p < 0.05 and p < 0.001, respectively) the airway secretion viscosity. The decrease in airway secretion viscosity was significant even at low concentrations (0.1 microg/ml) of the actin-resistant variant. Incubation with the actin-resistant variant resulted in a significant decrease (p < 0.02) of the airway secretion contact angle and cough transport. A significantly higher (p < 0.01) increase in contact angle and cough transport of airway secretions was observed at 10 microg/ml with the actin-resistant variant as compared with the wild-type rhDNase. The present study had demonstrated that the actin-resistant rhDNase variant (A114R) has an enhanced capacity to improve the physical properties and cough transport of airway secretions from patients with cystic fibrosis.

Actins↗
PubMed2001

Aortic valve replacement with the composite Labcor porcine bioprosthesis in the elderly.

BACKGROUND: This paper presents the analysis of clinical results of the composite porcine Labcor bioprosthesis in the replacement of aortic valves in the elderly. METHODS: This retrospective study was carried out in the Thoracic and Cardiovascular Surgical Department, La Pitié-Salpétrière Hospital, Paris, for replacement of calcified, stenosed aortic valves between 1988 and 1995. It involved a series of 100 patients aged 70 and over (mean: 80+/-5 years ranging from 70 to 90). There were 63 female and 37 male patients. Preoperatively, five patients were in NYHA Class I, 23 in Class II, 65 in Class III and 7 in Class IV. RESULTS: Fifteen patients died in the early postoperative stage and 13 during the follow-up period. There was no evidence of valve failure. The average follow-up was 32 months and the actuarial survival rate at 5 years was 74+/-5%. Complications due to bleeding occurred in 3 patients taking anticoagulant treatment. There were neither valvular thrombosis nor embolism. Two patients presented with prosthetic endocarditis. Two patients received a reoperation because of leakage (1 septic). The five-year follow-up showed that 96% of patients did not require further surgery. When this study was completed, 83% of patients were in Class I or II versus 71% in Class III or IV prior to surgery. CONCLUSIONS: In the early/middle follow-up term, the results obtained when replacing the aortic valve with the composite Labcor bioprosthesis in the elderly are satisfying. Nevertheless, further long-term assessment is needed.

Aged↗
PubMed2001

[Changes in pharmacists practices (1996 - 2000) related to harm reduction policy (condoms, injecting equipment, methylmorphine) and maintenance therapy delivery (buprenorphine, methadone)].

AIMS: To measure pharmacists involvement in harm reduction programs and in delivery of maintenance therapies in order to estimate their contribution to the new public health policy. METHOD: A longitudinal study was conducted among 327 pharmacies located in the southern suburban area of Paris (28 communities) using a standardized questionnaire. RESULTS: The response rate was 95% in 1996 and 92% in 2000. The number of condoms offered to intravenous drug users (IDU) decreased dramatically from 99% to 24% while delivered units decreased from 857 to 566 per day for needles and from 1200 to 760 per month per pharmacy for methylmorphine tablets (14.93 mg/tablet). Pharmacists delivered injecting equipment to some of their patients under opiate treatment: methylmorphine 19%, buprenorphine 35%, methadone 14%. Their contribution to the local healthcare network on addiction decreased from 38% to 20%. Nevertheless, the pharmacists attitude towards the IDU and public health policy was found to be improving with problems being mentioned for 62% of the cases in 1996 and for 16% in 2000. CONCLUSION: Pharmacists are rapidly and intensively changing their practices and are discovering a new comprehensive relationship with IDU. Better pharmacist involvement is associated with a shift in local healthcare network concentration, reinforcing the general practitioner-pharmacist partnership.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Motogenic effect of recombinant HGF on airway epithelial cells during the in vitro wound repair of the respiratory epithelium.

Cell migration is the earliest mechanism involved in the wound repair process of the respiratory epithelium and could be potentially enhanced by growth factors. In the present work, we investigated the localisation of the hepatocyte growth factor (HGF) receptor (c-Met) during wound repair and evaluated the effect of recombinant HGF (rHGF) on cell migration by using an in vitro model of airway epithelial wound repair. By using immunohistochemical methods, we observed that the immunoreactivity of the c-Met proto-oncogene was increased in epithelial cells engaged in the process of tissue repair. The incubation of wounded cultures with increasing concentrations of rHGF (0.2, 2, 20, and 200 ng/ml) induced a significant (P < 0.02) dose-dependent effect on the wound repair index, with a maximum effect produced at 20 ng/ml (+31.3%). The cell migration speed reached 50.2 micrometer/h at this concentration, compared to 20.4 micrometer/h in the absence of rHGF. No significant effect on cell proliferation was observed in the repairing area in the presence of rHGF. These results suggest that rHGF is able to improve the wound repair process of the airway epithelium by increasing cell migration.

Cell Movement↗
PubMed2000

Left ventricular alterations in a model of fetal left ventricular overload.

Congenital aortic coarctation is well tolerated by the fetus because the foramen ovale and ductus arteriosus equalize intracardiac and great arteries pressures and shunts. The pathologic consequences only emerge after birth with closure of the foramen ovale and ductus arteriosus. There is, however, no documentation of myocardial effects in utero of the left ventricular (LV) pressure overload induced by aortic banding. We investigated whether prenatal aortic banding could be detrimental at the structural and/or functional level. The goal of the present study was to investigate the cardiac effects of LV pressure overload in a fetal lamb model. Nine fetal lambs underwent preductal banding of the aortic arch in utero at midgestation (CoA group), whereas their twins underwent sham surgery. All fetuses were studied between 27 and 37 d after surgery for LV pressure, anatomic and histologic anomalies, and steady state sarcoendoplasmic reticulum calcium ATPase (SERCA 2a) mRNA and protein levels and pump activity. Surgery resulted in severe aortic coarctation in all the animals in the CoA group and was associated with a 65% increase in the LV weight to body weight ratio relative to the sham-operated group (p < 0.001). Hemodynamic and histologic studies showed an evolutionary pattern depending on duration of the experimental coarctation with a shift occurring at 30 d of coarctation. The initial response of cardiomyocytes to ventricular overload was hypertrophy of the myocytes, followed by myocyte hyperplasia. Compared with sham, there was an apparent decrease in the percentage of binucleated cells in the CoA group after 30 d of coarctation. The earliest response to LV pressure overload appears to occur at the molecular level. Indeed, sarcoendoplasmic reticulum calcium ATPase (SERCA 2a) mRNA levels fell significantly to only 28.6% of the sham group value (p = 0.023), independently of the duration of coarctation. In the fetal lamb, the pressure overload-induced hypertrophy resulting from progressive aortic coarctation leads to hemodynamic and lesional abnormalities and slows ontogenic maturation.

Animals↗
PubMed2000

[End-stage heart failure: role of various circulation assistance techniques].

There are currently 4 main types of cardiac assist devices: centrifugal pumps, paracorporeal pneumatic assist devices, implantable ventricular assist devices, total artificial heart. Although the efficacy of centrifugal pumps remains limited, that of the other 3 types of assist devices has now been clearly demonstrated. The choice between these various devices depends on the severity of heart failure at the time of implantation, the univentricular or biventricular disease, the potential for recovery, the patient's morphology and obviously the device or devices available to the team concerned. The results essentially depend on early implantation.

Chronic Disease↗
PubMed1999

Video-assisted coronary artery bypass in patients with preexisting tracheostomy.

A new technique allowing revascularization of the left coronary artery through a small thoracotomy after videoscopic harvesting of both mammary arteries is proposed in patients with total laryngectomy. This anterior thoracotomy approach, of real interest in patients with a preexisting tracheostomy, needs to be compared with a classic sternotomy in terms of functional recovery and the prevention of mediastinal sepsis in certain high-risk categories of patients (e.g., obesity, diabetes) for bilateral mammary artery harvesting.

Aged↗
PubMed1999

Biventricular repair approach in ducto-dependent neonates with hypoplastic but morphologically normal left ventricle.

OBJECTIVES: Increased afterload and multilevel LV obstruction is constant. We assumed that restoration of normal loading conditions by relief of LV obstructions promotes its growth, provided that part of the cardiac output was preoperatively supported by the LV, whatever the echocardiographic indexes. BACKGROUND: Whether to perform uni- or biventricular repair in ducto dependent neonates with hypoplastic but morphologically normal LV (hypoplastic left heart syndrome classes II & III) remains unanswered. Echocardiographic criteria have been proposed for surgical decision. METHODS: Twenty ducto dependent neonates presented with this anomaly. All had aortic coarctation associated to multilevel LV obstruction. Preoperative echocardiographic assessment showed: mean EDLW of 12.4 +/- 3.03 ml/m2 and mean Rhodes score of -1.73 +/-0.8. Surgery consisted in relief of LV outflow tract obstruction by coarctation repair in all associated to aortic commissurotomy in one and ASD closure in 2. RESULTS: There were 3 early and 2 late deaths. Failure of biventricular repair and LV growth was obvious in patients with severe anatomic mitral stenosis. The other demonstrated growth of the left heart. At hospital discharge the EDLVV was 19.4+/-3.12 ml/m2 (p = 0.0001) and the Rhodes score was -0.38+/-1.01 (p = 0.0003). Actuarial survival and freedom from reoperation rates at 5 years were 72.5% and 46%, respectively. CONCLUSIONS: Biventricular repair can be proposed to ducto dependent neonates with hypoplastic but morphologically normal LV provided that all anatomical causes of LV obstruction can be relieved. Secondary growth of the left heart then occurs; however, the reoperation rate is high.

Abnormalities, Multiple↗
PubMed1999

Vascular endothelium viability and function after total cardiopulmonary bypass in neonatal piglets.

Endothelium dysfunction with severe pulmonary hypertension may occur after total cardiopulmonary bypass (CPB) in infants as a result of a widespread inflammatory response. The aim of this study was to separate out the effects of lung ischemia-reperfusion from membrane oxygenator-induced activation of leukocytes on the function and viability of the pulmonary and systemic endothelia in neonatal piglets submitted to 90-min total CPB followed by 60-min reperfusion or in sham animals. Hemodynamics, gas exchange, endothelial-dependent relaxation in pulmonary and femoral arteries, and lung and skeletal muscle myeloperoxidase activity were assessed before, during, and after CPB, i.e., after reperfusion. Pulmonary and aortic endothelial cells and circulating leukocytes were harvested to assess reperfusion-induced changes in endothelial cells' viability and proliferation, and leukocyte-endothelial cell adhesion and cytotoxicity. Gas exchange worsened after reperfusion with pulmonary hypertension, increase in lung but not skeletal myeloperoxidase, and reduction of endothelial-dependent relaxation in pulmonary but not femoral arteries. After reperfusion, viabilities of pulmonary and aortic endothelial cells were reduced to 50%, endothelial cell growths were faster in pulmonary arteries than aorta, and leukocyte-pulmonary endothelial cell adhesion and cytotoxicity increased. These results suggest that in total CPB lung ischemia-reperfusion aggravates the inflammatory response and predisposes the lung endothelium to leukocyte-mediated injury.

Animals↗
PubMed1999

[Angioplasty with stent of the common trunk of the left coronary artery with abnormal origin at the level of the right anterior sinus and with a retro-aortic trajectory].

The authors report a case of angioplasty with implantation of a stent in an anomalous left main coronary artery arising from the right anterior sinus of Valsalva with a retro-aortic trajectory. The introduction of stenting has made angioplasty of anomalous coronary arteries a possible alternative to surgery with the reserve of a high risk of restenosis when the lesion is distal and situated at a bifurcation.

Aged↗
PubMed1999

[Preservation of the native aortic valve in the treatment of aortic aneurysmal dilatation].

Mechanical valve conduit replacement of the aortic root is a durable and appropriate procedure for aortic root dilatation with or without aortic aortic insufficiency. But this procedure may sacrifice an anatomically salvageable aortic valve and requires a life-long anticoagulation with its attendant thromboembolic versus haemorrhagic risks, which is not ideal for young active patients. Recently, two techniques of aortic root replacement with aortic valve sparing have been described, based on experimental data. The first one is Yacoub's procedure (1983), where the correction of the aortic root is performed by correcting the sinotubular junction and replacement of the aortic sinuses with an appropriately tailored Dacron graft (remodelling). The second technique was described by David (1992). In this one, the aortic root reconstruction is performed by reimplanting the aortic valve in a tubular Dacron graft (reimplantation). Since 1993, we have been interested in these procedures and the aim of this study was to examine the perioperative and intermediate term results of these techniques. From 1993 to 1998, 14 patients had either reimplantation of the aortic valve (3 patients) or remodelling of the aortic root (11 patients). Patients' ages ranged from 17 to 57 years (40.2 +/- 7.9 years). Four patients had Marfan's syndrome (29%). There were 11 cases of aortic insufficiency, three 1+ (21.4%), 3+ (21.4%), seven 2+ (50%) and one 3+ (7.2%). All the patients had morphologically normal aortic leaflets. The mean diameter of the sinuses was 57 +/- 4 mm. There was no acute or chronic dissection. The left ventricular function was measured as the percentage of the fractional shortening of the left ventricular diameter. The mean of the fractional shortening was 38.3 +/- 4%. There was no mortality and all patients underwent early and late follow-up echocardiography. The 14 patients have only mild or no insufficiency, which has not progressed in any patient. No other valve-related complication has occurred. Aortic valve-sparing replacement of the aortic root is an excellent procedure for patients with aortic root dilatation and anatomically salvageable valves. The long-term results are still unknown but it seems an attractive alternative to composite replacement of the aortic valve and descending aorta. Morbidity and mortality rates are very low, even lower than a Bentall procedure, while the savings in cost and human lives due to the absence of a mechanical valve prosthesis are significant.

Adolescent↗
PubMed1999

Perioperative management in minimally invasive coronary surgery.

OBJECTIVE: It is important to apply the same rules used for classical coronary revascularization to beating heart coronary surgery. The surgeons must have a strategy, and be prepared for adverse events, and complications. METHODS: A careful analysis of the coronarography is essential to predict eventual contraindications or causes of possible operative difficulties. All the team must be involved in the surgical protocol. Three main problems need to be solved: the prevention of ischemia during the procedure, good stabilization of the anastomotic site and arterial occlusion. The first goal is reached by using a pre-conditioning technique or an intracoronary shunt. Vessel stabilization may be obtained by several methods: pressure adhesion devices, patch technique or suction devices. The final problem is to have a blood free field, this requires arterial occlusion which may be achieved in several ways: silastic Snares or sutures, aclan clamps, coronary occluder. RESULTS: We have developed at la Pitié a protocol to apply all these principles. From February 1997 to November 1998, multiple revascularization was performed on 167 patients. A total of 344 coronary anastomosis were carried out (mean: 2.05 graft/patient). CONCLUSION: Some simple rules had to be applied to reduce the rate of complications to the minimum: a good clinical case selection, use of a routine protocol, and recognize the need to adapt the indications to the learning curve of the operator.

Coronary Angiography↗