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Biomedical subjects

D Bonnet

Publications and source records attributed to D Bonnet.

At least 91 records · Page 5Linked to original sources
PubMed1999

CD8(+) minor histocompatibility antigen-specific cytotoxic T lymphocyte clones eliminate human acute myeloid leukemia stem cells.

Effective immunotherapy for human leukemia based on infusions of T lymphocytes requires the identification of effector T cells that target the leukemic stem cell. The transplantation of human acute myeloid leukemia into nonobese diabetic/severe combined immune deficient (SCID) mice has identified a rare leukemic progenitor termed the SCID leukemia-initiating cell, which is present in low frequency in the leukemic population and is essential for establishing leukemic hematopoiesis. Thus, this transplant model may be ideally suited to identify effector T cells with antileukemic activity. We report that CD8(+) cytotoxic T lymphocyte (CTL) clones specific for minor histocompatibility antigens inhibit the engraftment of human acute myeloid leukemia cells in nonobese diabetic/SCID mice and demonstrate that this inhibition is mediated by direct CTL recognition of SCID leukemia-initiating cells. These results indicate that CD8(+) minor histocompatibility antigen-specific CTL may be mediators of the graft-versus-leukemia effect associated with allogeneic hematopoietic cell transplantation and provide an experimental model to identify and select T cell clones for immunotherapy to prevent or treat relapse after allogeneic hematopoietic cell transplantation.

Animals↗
PubMed1999

Bone morphogenetic proteins regulate the developmental program of human hematopoietic stem cells.

The identification of molecules that regulate human hematopoietic stem cells has focused mainly on cytokines, of which very few are known to act directly on stem cells. Recent studies in lower organisms and the mouse have suggested that bone morphogenetic proteins (BMPs) may play a critical role in the specification of hematopoietic tissue from the mesodermal germ layer. Here we report that BMPs regulate the proliferation and differentiation of highly purified primitive human hematopoietic cells from adult and neonatal sources. Populations of rare CD34(+)CD38(-)Lin- stem cells were isolated from human hematopoietic tissue and were found to express the BMP type I receptors activin-like kinase (ALK)-3 and ALK-6, and their downstream transducers SMAD-1, -4, and -5. Treatment of isolated stem cell populations with soluble BMP-2, -4, and -7 induced dose-dependent changes in proliferation, clonogenicity, cell surface phenotype, and multilineage repopulation capacity after transplantation in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. Similar to transforming growth factor beta, treatment of purified cells with BMP-2 or -7 at high concentrations inhibited proliferation yet maintained the primitive CD34(+)CD38(-) phenotype and repopulation capacity. In contrast, low concentrations of BMP-4 induced proliferation and differentiation of CD34(+) CD38(-)Lin- cells, whereas at higher concentrations BMP-4 extended the length of time that repopulation capacity could be maintained in ex vivo culture, indicating a direct effect on stem cell survival. The discovery that BMPs are capable of regulating repopulating cells provides a new pathway for controlling human stem cell development and a powerful model system for studying the biological mechanism of BMP action using primary human cells.

Activin Receptors↗
PubMed1999

Detection of transposition of the great arteries in fetuses reduces neonatal morbidity and mortality.

BACKGROUND: Transposition of the great arteries (TGA) is a life-threatening malformation in neonates, but it is amenable to complete repair. Prenatal detection, diagnosis, and early management may modify neonatal mortality and mortality. METHODS AND RESULTS: Preoperative and postoperative morbidity and mortality were compared in 68 neonates with prenatal diagnosis and in 250 neonates with a postnatal diagnosis of TGA over a period of 10 years. The delay between birth and admission was 2+/-2.8 hours in the prenatal group and 73+/-210 hours in the neonatal group (P<0.01). Clinical condition at arrival, including metabolic acidosis and multiorgan failure, was worse in the neonatal group (P<0.01). Once in the pediatric cardiology unit, the management was identical in the 2 groups (atrioseptostomy, PGE1 infusion, operation date). Preoperative mortality was 15 of 250 (6%; 95% CI, 3% to 9%) in the neonatal group and 0 of 68 in the prenatal group (P<0.05). Postoperative morbidity was not different (25 of 235 versus 6 of 68), but hospital stay was longer in the neonatal group (30+/-17 versus 24+/-11 days, P<0.01). In addition, postoperative mortality was significantly higher in the neonatal group (20 of 235 versus 0 of 68, P<0.01); however, the known risk factors for operative mortality were identical in the 2 groups. CONCLUSIONS: Prenatal diagnosis reduces mortality and morbidity in TGA. Prenatal detection of this cardiac defect must be increased to improve early neonatal management. In utero transfer of fetuses with prenatal diagnosis of TGA in an appropriate unit is mandatory.

Humans↗
PubMed1999

Prenatal detection of a tetralogy of Fallot with origin of the left pulmonary artery from the ascending aorta in a familial 22q11 microdeletion.

Here we report a case of prenatal diagnosis of anomalous origin of the left pulmonary artery from the ascending aorta associated with a tetralogy of Fallot in a familial form of 22q11 deletion. The mother, who had a normal heart and a velo-cardio-facial syndrome, had a first child with a pulmonary atresia plus ventricular septal defect associated with a 22q11 deletion. Prenatal diagnosis during the second pregnancy identified the above-described cono-truncal anomaly and FISH study showed a recurrent 22q11 deletion. This case illustrates the intrafamilial variability of cardiac involvement in 22q11 deletion as well as the possibility of diagnosing complex cono-truncal malformations during fetal life.

Adult↗
PubMed1999

Reactivity of Lys(NH2)-containing peptides toward endopeptidases.

Lys(NH2)-containing peptides were subjected to various proteolytic enzymes which were selected for their well-documented specificity for arginyl and/or lysyl peptide bonds. Lys(NH2)-containing peptides were cleaved more rapidly by clostripain than the corresponding lysyl peptides. On the other hand, they proved to be resistant to Achromobacter protease I hydrolysis. The modified peptides synthesized in this study were more stable than the arginyl and lysyl analogues when incubated with trypsin or thrombin. The same tendency was observed when Lys(NH2)-containing peptides were incubated in diluted human serum, suggesting that the replacement of Arg or Lys by Lys(NH2) could be used to increase the stability of peptides in vivo.

Alcaligenes↗
PubMed1999

Surgical angioplasty of the main coronary arteries in children.

OBJECTIVE: To determine the safety and efficacy of surgical angioplasty of the coronary arteries in children. METHODS: We performed 9 surgical reconstructions of the left main coronary artery and 1 of the right coronary artery ostium in 10 children (mean age 5.7 years; range 2 months-15 years). The basic diseases included the following: congenital atresia of the left coronary artery (n = 2) and atresia of the right coronary artery in a patient with an aortoventricular tunnel (n = 1); stenosis of the left main coronary artery (1) in a patient with Williams syndrome (n = 1), (2) in a patient with familial hypercholesterolemia (n = 1), (3) after the arterial switch operation for transposition of the great arteries (n = 3), (4) after reimplantation of an anomalous left main coronary artery from the pulmonary artery (n = 1), and (5) by compression after a réparation à l'étage ventriculaire procedure (n = 1). Myocardial viability was assessed by single photon emission computed tomography (thallium 201; 7/10). The coronary artery stem was enlarged with a saphenous (n = 5), a pericardial (n = 4), or a polytetrafluoroethylene patch (n = 1). RESULTS: There was 1 hospital death and 9 patients are alive (mean follow-up 46 +/- 30 months; range 12 months to 10.5 years). Eight of 9 survivors had a selective coronary artery angiogram and had normal coronary artery ostia. Two patients had stenosis of the left anterior descending coronary artery, 1 of whom underwent successful internal thoracic artery grafting. CONCLUSIONS: Surgical angioplasty of the coronary stems restores physiologic coronary perfusion and conserves bypass material. It can be performed safely in children and provides encouraging midterm results.

Adolescent↗
PubMed1999

A new strategy for the surgical treatment of aortic coarctation associated with ventricular septal defect in infants using an absorbable pulmonary artery band.

OBJECTIVES: We propose a new strategy using coarctation repair together with a polidioxanone absorbable pulmonary artery banding to limit operative risk and to spare infants with aortic coarctation subsequent operations. BACKGROUND: The alternative for the surgical management of aortic coarctation associated with ventricular septal defect (VSD) is single-stage repair versus coarctation repair with or without banding of the pulmonary artery. METHODS: Eleven infants (mean weight 2,560 +/- 1,750 g, range 1,320 to 3,800 g) underwent a coarctation repair with a polydioxanone banding. Seven had a trabecular and four a perimembranous VSD. The mean size of the VSD was 5 +/- 0.7 mm (range 4 to 7 mm). The systolic pulmonary pressure was >80% of the aortic pressure in all. The pulmonary band was tightened until the systolic pulmonary pressure fell below 50% of the aortic pressure. RESULTS: There were no hospital deaths. The reabsorption of the banding was complete after 5.7 months in all patients (3 to 6.5 months). The VSD closed completely in four infants and partially in six, in whom the pulmonary artery pressure was normal without evidence for significant left-to-right shunt. One patient with a large trabecular VSD underwent surgical closure of his defect after four months. Finally, a subsequent open-heart surgery could be avoided in 91% (10/11) of patients. CONCLUSIONS: Provided the VSD belongs to types prone to close spontaneously, this policy may reduce the number of surgical procedures per infant as well as in-hospital mortality and morbidity rates. It should be proposed as an alternative to more complex procedures.

Absorbable Implants↗
PubMed1999

[What's new in pediatric cardiology?].

In recent years, close collaborations have been established between pediatric cardiology, medical and molecular genetics, fetal cardiology and pediatric radiology. As a consequence, several congenital heart defects and syndromes including cardiovascular malformations have been related to microdeletions such as 22q11 in Di George syndrome and 7q in Williams syndrome. Prenatal detection of heart malformations has become a crucial part of the management of life-threatening malformations of the neonate such as the transposition of the great arteries or the coarctation of the aorta. We are at the dawn of a new era of the development of preventive cardiovascular medicine starting from childhood thanks to new techniques of echo-tracking. Finally, three-dimensional reconstruction of heart defects by using ultrasound, X-ray or MRI have dramatically improved the diagnosis and the therapeutic strategies of cardiac diseases.

Cardiology↗
PubMed1999

Recognition and management of fatty acid oxidation defects: a series of 107 patients.

In a personal series of 107 patients, we describe clinical presentations, methods of recognition and therapeutic management of inherited fatty acid oxidation (FAO) defects. As a whole, FAO disorders appear very severe: among the 107 patients, only 57 are still living. Including 47 siblings who died early in infancy, in total 97 patients died, of whom 30% died within the first week of life and 69% before 1 year. Twenty-eight patients presented in the neonatal period with sudden death, heart beat disorders, or neurological distress with various metabolic disturbances. Hepatic presentations were observed in 73% of patients (steatosis, hypoketotic hypoglycaemia, hepatomegaly, Reye syndrome). True hepatic failure was rare (10%); cholestasis was observed in one patient with LCHAD deficiency. Cardiac presentations were observed in 51% of patients: 67% patients presented with cardiomyopathy, mostly hypertrophic, and 47% of patients had heart beat disorders with various conduction abnormalities and arrhythmias responsible for collapse, near-miss and sudden unexpected death. All enzymatic blocks affecting FAO except CPT I and MCAD were found associated with cardiac signs. Muscular signs were observed in 51% of patients (of whom 64% had myalgias or paroxysmal myoglobinuria, and 29% had progressive proximal myopathy). Chronic neurologic presentation was rare, except in LCHAD deficiency (retinitis pigmentosa and peripheral neuropathy). Renal presentation (tubulopathy) and transient renal failure were observed in 27% of patients. The diagnosis of FAO disorders is generally based on the plasma acylcarnitine profile determined by FAB-MS/MS from simple blood spots collected on a Guthrie card. Urinary organic acid profile and total and free plasma carnitine can also be very helpful, mostly in acute attacks. If there is no significant disturbance between attacks, the diagnosis is based upon a long-chain fatty acid loading test, fasting test, and in vitro studies of fatty acid oxidation on fresh lymphocytes or cultured fibroblasts. Treatment includes avoiding fasting or catabolism, suppressing lipolysis, and carnitine supplementation. The long-term dietary therapy aims to prevent periods of fasting and restrict long-chain fatty acid intake with supplementation of medium-chain triglycerides. Despite these therapeutic measures, the long-term prognosis remains uncertain.

Disease Management↗
PubMed1999

Synthesis of hydrazinopeptides using solid-phase N-electrophilic amination: extension to the Fmoc/tert-butyl strategy and chemistry of the N-N bond in strong acid media.

The synthesis of hydrazinopeptides using solid-phase N-electrophilic amination was extended to the Fmoc/tert-butyl strategy. Both Boc/benzyl and Fmoc/tert-butyl strategies led to the isolation of by-products arising from the partial instability of the N-N bond during the final cleavage and deprotection step. Two paths of decomposition have been shown: the cleavage of the N-N bond leading to the regeneration of the amine and a Hofmann-type elimination yielding original dianisyl adducts. Our data suggest that the Fmoc/tert-butyl strategy is better suited for the synthesis of hydrazinopeptides.

Acids↗
PubMed1999

Cytokine treatment or accessory cells are required to initiate engraftment of purified primitive human hematopoietic cells transplanted at limiting doses into NOD/SCID mice.

Little is known about the cell types or mechanisms that underlie the engraftment process. Here, we have examined parameters affecting the engraftment of purified human Lin-CD34+CD38- normal and AML cells transplanted at limiting doses into NOD/SCID recipients. Mice transplanted with 500 to 1000 Lin-CD34+CD38- cord blood (CB) or AML cells required the co-transplantation of accessory cells (ACs) or short-term in vivo cytokine treatment for engraftment, whereas transplantation of higher doses (>5000 Lin-CD34+CD38- cells) did not show these requirements suggesting that ACs are effective for both normal and leukemic stem cell engraftment in this model. Mature Lin+CD34- and primitive Lin-CD34+CD38+ cells were capable of acting as ACs even though no repopulating cells are present. Cytokine treatment of NOD/SCID mice could partially replace the requirement for co-transplantation of AC. Furthermore, no difference was seen between the percentage of engrafted mice treated with cytokines for only the first 10 days after transplant compared to those receiving cytokines for the entire time of repopulation. Surprisingly, no engraftment was detected in mice when cytokine treatment was delayed until 10 days posttransplant. Together, these studies suggest that the engraftment process requires pluripotent stem cells plus accessory cells or cytokine treatment which act early after transplantation. The NOD/SCID xenotransplant system provides the means to further clarify the processes underlying human stem cell engraftment.

Acute Disease↗
PubMed1999

Total cavopulmonary and atriopulmonary connections are associated with reduced heart rate variability.

AIM: To determine whether cavopulmonary connections are associated with abnormalities of heart rate variability. METHODS: Heart rate variability was studied by 24 hour Holter monitoring in 39 patients (mean (SD) age 12.2 (4.1) years) who underwent cavopulmonary connection operations (partial in 12, total in 13, and atriopulmonary in 14). Two control groups were used: 18 healthy children (11.1 (2.5) years) and 16 patients (11.7 (4.3) years) undergoing cardiovascular surgery for biventricular repair of congenital heart disease. All patients were in sinus rhythm and had normal left ventricular function. Four time domain indices were calculated: mean duration of RR intervals (RR), standard deviation of all RR intervals (SD), square root of the mean squared differences of successive RR intervals (r-MSSD), and percentage differences of successive RR intervals of > 50 ms duration (pNN50). Four frequency domain indices were calculated: total power (TP), low frequency (LF), high frequency (HF), and the LF:HF ratio. RESULTS: Heart rate variability indices were identical in the two control groups. Significantly reduced heart rate variability was found in patients with total cavopulmonary connections and atriopulmonary connections compared with the two control groups. In patients with partial cavopulmonary connections, heart rate variability was reduced compared with healthy controls. No differences in heart rate variability could be related to clinical status (New York Heart Association functional class), number of surgical interventions, or presence of right atrial enlargement. CONCLUSIONS: Patients with cavopulmonary connections have significantly reduced heart rate variability and a particularly low vagal drive.

Adolescent↗
PubMed1999

[Compromise of the cardiac autonomic nervous system in patients with Fontan-type circulation: preliminary data].

BACKGROUND: Rhythm disturbances are frequent after Fontan operations. Arrhythmias related to reduced heart rate variability (HRV) have been described in various cardiovascular diseases. METHODS: We attempted to investigate HRV in 12 patients who underwent Fontan operation (age 11.4 +/- 3 years). Results were compared to a control group of 13 children matched for age, sex and heart rate (10.4 +/- 3 years). All patients underwent 24-hour Holter monitoring. The following time domain indexes were calculated: mean duration of RR intervals, standard deviation of all RR intervals (SD), square root of the mean squared differences of successive RR intervals (r-MSSD), percentage of differences between adjacent RR intervals > 50 msec (pNN50). The following frequency domain indexes were calculated: total power (TP), low frequency (LF), high frequency (HF), LF/HF ratio. RESULTS: The following indexes were significantly reduced in Fontan patients: SD (p < 0.0001), r-MSSD (p < 0.0001), pNN50 (p = 0.0002), TP (p < 0.0001), LF (p < 0.0001), HF (p = 0.0001). LF/HF increased significantly (p = 0.04). No differences were detected according to the type of operation (cavopulmonary connection vs atriopulmonary connection) or clinical status. CONCLUSIONS: Patients with Fontan circulation had a significantly reduced HRV and particularly abnormal sympatho-vagal balance. Surgery on the caval veins and the atria alters the intracardiac ganglia that are abundant at the cavo-atrial junction and in the myocardium of the right atrium. Abnormalities of HRV in Fontan patients may act as a co-factor in the initiation of arrhythmia in these patients.

Adolescent↗
PubMed1999

Cystic dystrophy in heterotopic pancreas of the duodenal wall: medical and surgical treatment.

A patient with cystic dystrophy in heterotopic pancreatic tissue, localized in the second duodenum, is described. Diagnosis was assessed by computed tomography, endosonography and magnetic nuclear resonance (MNR). Medical treatment with octreotid during three weeks was effective but duodenal stenosis persisted. Finally, pylorus preserving pancreaticoduodenectomy was performed. Microscopy examination confirmed the diagnosis and the efficiency of medical treatment. A review of the literature about cystic dystrophy is done.

Antineoplastic Agents, Hormonal↗
PubMed1999

[A new anatomical approach to congenital valve diseases by three-dimensional echocardiography].

Congenital valvular heart disease in childhood is often complex. Conventional echocardiography provides two-dimensional views which require mental reconstruction for three-dimensional assessment. This problem may be solved by the use of three-dimensional (3D) echocardiography which obtains images of valves comparable to those seen at surgery. This was confirmed by 4 cases of congenital valvular heart disease studied by 3D echocardiography: stenotic bicuspid aortic valve disease, parachute mitral valve and two cases of mitral regurgitation in patients with atrioventricular canal. The 3D views of the aortic valve showed the commissural opening after percutaneous balloon valvuloplasty of the bicuspid valve. The surface of the aortic orifice and the surface of the two mitral leaflets were measured from 3D reconstructions. The longitudinal 3D view analysed the extension of the single obstructive mitral papillary muscle of the parachute malformation. The 3D ventricular views allowed assessment of the extension of the cleft and the surface of the three mitral leaflets of the 2 cases of atrioventricular canal. In one of these cases, the results of surgical valvuloplasty were evaluated after 3D reconstruction of the valve. 3D echocardiography is not only a diagnostic tool for congenital heart disease but also a very useful complementary investigation for accurate evaluation of congenital valvular lesions to optimise possible valve repair.

Adolescent↗
PubMed1999

[Treatment of obstruction of prosthetic conduct by percutaneous implantation of stents].

Prosthetic conduits, with or without biological valves, are often inserted in surgical procedures to correct or palliate cardiac malformations. The principal problem is degeneration which causes variable degrees of obstruction requiring reoperation for their replacement. The aims of this study were to assess the feasibility, safety and efficacy of a non-surgical method of treating these obstructive prostheses by dilatation-implantation of a metallic vascular endoprosthesis (stenting). Thirteen patients were treated (age range 7.7 to 36 years; mean: 15 years). Eight had pulmonary atresia with a ventricular septal defect corrected by a valved conduit from the right ventricle to the pulmonary artery which became obstructive nearly 10 years later: the implantation of the stent reduced the transconduit pressure gradient in all cases except one who had not undergone closure of the septal defect in which the cyanosis was improved. There are two cases of obstruction of a modified Blalock anastomosis in which the stent revascularised the shunt with improvement in cyanosis. In the final 3 cases, the whole Fontan procedure was compromised by obstruction of a conduit incorporated in the system, and which dilatation with stenting considerably improved. The efficacy of the procedure was constant with no complications other than rupture of the balloon in 3 cases. The good results were maintained for an average of 7.3 months (range 1 to 25 months), but it was necessary to redilate one restenosed stent after 8 months. Dilatation followed by stenting in obstructive cardiovascular prostheses is a simple, safe and effective alternative to surgical reoperation.

Adolescent↗