Which functional processes control the short-term effect of grazing on net primary production in grasslands?

Grazing has traditionally been viewed as detrimental to plant growth, but it has been proposed that under certain conditions, grazing may lead to compensatory or overcompensatory growth. However, comprehensive information on the relative role of the main functional processes controlling the response of net primary production (NPP) to grazing is still lacking. In this study, a modelling approach was used to quantify the relative importance of key functional processes in the response of annual canopy NPP to grazing for a West African humid grassland. The PEPSEE-grass model, which represents radiation absorption, NPP, water balance and carbon allocation, was used to compute total and aboveground NPP in response to grazing pressure. Representations of grazing and mineral nitrogen input to the canopy were simplified to focus on the vegetation processes implemented and their relative importance. Simulations were performed using a constant or resource-driven root/shoot allocation coefficient, and dependence or independence of conversion efficiency of absorbed light into dry matter on nitrogen availability. There were three main results. Firstly, the response of NPP to grazing intensity emerged as a complex result of both positive and negative, and direct and indirect effects of biomass removal on light absorption efficiency, soil water availability, grass nitrogen status and productivity, and root/shoot allocation pattern. Secondly, overcompensation was observed for aboveground NPP when assuming a nitrogen-dependent conversion efficiency and a resource-driven root/shoot allocation. Thirdly, the response of NPP to grazing was mainly controlled by the effect of plant nitrogen status on conversion efficiency and by the root/shoot allocation pattern, while the effects of improved water status and reduced light absorption were secondary.

[Percutaneous closure of patent ductus arteriosus: results and costs compared to surgical closure]. / Fermeture du canal artériel par voie percutanée: comparaison des résultats et des coûts avec la fermeture chirurgicale.

The comparison of the clinical results and costs of the two methods of closure of patient ductus arteriosus was undertaken in two comparable groups of 40 patients treated in the same period in the same hospital. After transcatheter closure there was a 9% residual shunt rate at 3 years, the 2 patients with a residual continuous murmur being operated secondarily. The only complication was severe haemolysis which regressed after transcatheter ablation of the prosthesis. After surgical closure, there were no residual shunt. Some postoperative complications were observed in 20% of cases, usually benign (ventilatory problems, dysphonia or urinary infection), but occasionally more serious (peroperative lesion of the pulmonary artery). Morbidity, inherent to the technique of closure, was very different and much less in catheter closure. The average cost (daily cost x average length of hospital stay) was much less with transcatheter closure 38,558 francs versus 11,240 francs. On the other hand, the direct cost of transcatheter closure was greater than that of surgery: 32,798 francs versus 20,903 francs, the difference being related to the actual price of the prosthesis. The authors conclude that the 3 year results of transcatheter closure of patent ductus arterious make this technique a reasonable therapeutic alternative to surgery. From the safety point of view, the two techniques are comparable bu patient confort is greater with transcatheter closure for an increase in cost of the initial procedure which should decrease in relation to the types and prices of the prosthesis used.

[Double-chamber right ventricle, aortic subvalvular stenosis and interventricular septal defect. Apropos of 12 cases]. / Ventricule droit à double chambre, sténose sous-valvulaire aortique et communication interventriculaire. A propos de 12 cas.

The authors report 12 cases of double-chamber right ventricle associated with discrete subaortic stenosis and ventricle septal defect. The statistics derived from 3,292 surgical reports of congenital heart diseases operated on at the Marie-Lannelongue Surgical Center over an 8 years period show that this association is 7 times more frequent than the law of chance. Twenty-two per cent of double-chamber right ventricles had an associated discrete subaortic stenosis and, in 9% of cases of subaortic stenosis a double-chamber right ventricle was observed. The cause of this malformation could be a developmental defect of the primitive interampullar ring.

[Percutaneous mitral valvulotomy: comparison of 2 techniques in 100 matched-pair patients]. / Valvulotomie mitrale percutanée: comparaison de deux techniques chez 100 patients appariés.

The results of percutaneous mitral valvulotomy by the Double Balloon and the Inoue Balloon were compared in 100 patients referred to Marie-Lannelongue Hospital between 7/11/86 and 8/3/91, paired for age, sex and echocardiographic features of the mitral valve. The transvalvular diastolic pressure gradient at catheterisation or Doppler echocardiography decreased significantly and similarly with the two techniques: -65 +/- 19% versus -64 +/- 15% (p = 0.10) and -66 +/- 22% versus -58 +/- 23% (p = 0.20) for the Double-Balloon and the Inoue Balloon techniques respectively. Similarly, the mitral valve surface area measured by planimetry during echocardiography or calculated from the Gorlin formula increased by 0.9 +/- 0.39 cm2 with the Double Balloon and by 0.88 +/- 0.32 cm2 with the Inoué Balloon (p = 0.91) or by 0.98 +/- 0.62 cm2 versus 0.87 +/- 0.45 cm2 (p = 0.42). The number of commissures opened was the same with both techniques. The evolution of mitral regurgitation after dilatation was similar: stable or less severe in 61% dilated by the Double Balloon and 68% by the Inoue Balloon; aggravation by more than one grade in 7 and 5% respectively (p = 0.17). Complications were rare and comparable with both techniques. The results with the two methods were the same if patients with an optimal indication and those with more severe mitral valve disease were considered separately. The rapidity and simplicity of percutaneous mitral valvulotomy with the Inoué Balloon make it the technique of choice.

[Lung resection for cancer in coronary patients. Immediate and medium-term results. Retrospective study in a series of 51 patients]. / Exérèses pulmonaires pour cancer chez le malade coronarien. Résultats immédiats et à distance. Etude rétrospective d'une série de 51 malades.

Patients with both resectable lung cancer and coronary artery disease require preoperative cardiac evaluation in order to determine and prevent the surgical risk and to discuss the desirability of preventive myocardial revascularization. The results of thoracic surgery in coronary disease patients have been studied in a series of 51 patients operated upon for lung cancer at the Marie Lannelongue hospital, Paris, between 1985 and 1988. Thirty-two patients underwent non invasive exploration prior to surgery (exertion ECG in 22, myocardial radioisotope scanning in 10); 35 patients had coronary arteriography at the last moment, and 9 asymptomatic patients with an old history of myocardial infarction had no specific exploration. Forty-nine patients had lung surgery alone, preceded in 5 cases by percutaneous coronary angioplasty; one patient had pulmonary surgery and coronary surgery simultaneously, and another patient had coronary surgery first, later followed by lung surgery. No perioperative death was due to cardiovascular causes. A 75-year old male patient died of respiratory failure 30 days after lobectomy. The postoperative period was totally uneventful in 39 patients. No perioperative myocardial infarction was recorded; 4 patients experienced an episode of thoracic pain with ECG signs of myocardial infarction but no rise in serum enzyme concentrations. One patient had a cerebral vascular accident responsible for hemiplegia. Two late sudden deaths, probably of cardiac origin, occurred 4 and 11 months respectively after surgery. The actuarial survival rate at 3 months was 48 percent. In all survivors, the coronary symptoms were controlled by medical treatment. It seems, therefore, that perioperative complications in this type of patient can be avoided by preoperative evaluation of the coronary disease and by preventive myocardial revascularization in case of critical coronary stenosis.

[Endoluminal occlusion, using a catheter, of patent ductus arteriosus in an adult]. / Occlusion par voie endoluminale d'un canal artériel chez l'adulte.

The risk of surgical closure of the ductus arteriosus in the adult is greater than in children. The ductus arteriosus can now be occluded by venous catheterisation using a Rashkind umbrella. This procedure vas performed in a 63 year old woman. The diagnosis was confirmed and the anatomy of the lesion defined by catheterisation with aortography. The patent ductus was then occluded with a balloon catheter to assess the reversibility of the pulmonary hypertension. A 17 mm Rashkind umbrella was then used to completely occlude the ductus. The advantages of the method over surgical closure are: absence of morbidity related to thoracotomy, to general anaesthesia, to blood transfusion and the reduction of hospital stay to 3 days.

[Coaxial catheterization with an ultra-flexible catheter (Tracker) in coronary angioplasty]. / Intérêt du cathétérisme coaxial à l'aide d'un cathéter ultra-souple (Tracker) en angioplastie coronaire.

After experiencing problems of catheterisation during coronary angioplasty, the authors tried using a 3.2 F ultraflexible catheter with a 2.2 F tapered tip. In 2 patients, initial attempts at coronary catheterisation were failures but when this new catheter was used, angioplasty could be performed without any difficulty. This catheter was then used in 4 other patients and in all cases the Tracker enabled the operators to catheterise the coronary arteries and to perform angioplasty in 3 of the 4 cases. Therefore, this new ultraflexible catheter would seem to be a valuable alternative for catheterising particularly sinuous coronary arteries in which angioplasty is often technically difficult.

[Value of superior angiocardiography in the evaluation of the surgical excision of bronchial cancer. Respective role compared to thoracic x-ray computed tomography]. / Intérêt de l'angio-cavographie supérieure dans le bilan d'extirpabilité du cancer bronchique. Place respective par rapport à la tomodensitométrie thoracique.

The place of angiography-superior vena cavography in the assessment of the resectability of a lung cancer must be defined in comparison with the data provided by thoracic computed tomography. Sixty-six patients with proximal lung cancers of doubtful resectability were studied by means of angiography and computed tomography and the results of these preoperative investigations were correlated with the operative findings. The sensitivity of these two examinations for the diagnosis of vascular invasion preventing pulmonary resection is poor (53% and 47% respectively). The specificity and positive predictive value of angiography appear to be slightly superior to those of computed tomography (Sp: 96% and 82%, PPV: 78% and 47%, respectively). The diagnostic performance of these two examinations remains poor. Magnetic resonance imaging may replace these two examinations in the future.

[Treatment of rheumatic mitral stenosis in children and adolescents by a balloon catheter]. / Cure du rétrécissement mitral rhumatismal chez l'enfant et l'adolescent par un cathéter à ballonnet.

Between April 1986 and August 1987, eight children, 9 to 18 years old, with rheumatic mitral valve stenosis underwent a percutaneous balloon valvotomy. Immediate results were good. By echocardiographic measurements, mean transmitral gradients went from 23.7 +/- 7.1 mmHg to 5.8 +/- 4.7 mmHg (p less than 0.001), diastolic pressure half-times went from 299.0 +/- 15.6 msec to 123.3 +/- 42.3 msec (p less than 0.001) and mitral valve areas measured by planimetry went from 1.00 +/- 0.15 cm2/1.73 m2 to 2.68 +/- 0.71 cm2/1.73 m2 (p less than 0.001). Hemodynamic measurements showed a decrease in mean pulmonary artery pressure from 48.3 +/- 13.2 mmHg to 32.5 +/- 5.7 mmHg (p less than 0.01), a decrease in the mean left atrial pressure from 26.1 +/- 6.3 mmHg to 14.6 +/- 4.7 mmHg (p less than 0.02) and an increase in calculated mitral valve area (Gorlin formula) from 1.07 +/- 0.31 cm2/1.73 m2 to 2.73 +/- 1.17 cm2/1.73 m2 (p less than 0.02). The only complication observed was a grade III mitral insufficiency in a child with marked subvalvular fibrosis. Six patients had a very good result and one kept a moderate mitral stenosis. Percutaneous balloon valvotomy gives probably better results in children than in adults and obtains at least as good results as surgical closed mitral commissurotomy. Presently, this technique is the treatment of choice for rheumatic mitral stenosis in children. Contra-indications are intra-atrial thrombus and shortened, thickened subvalvular apparatus.

[Atrial septal defect and cyanosis. Apropos of 6 cases related to abnormal drainage of the inferior vena cava into the left atrium]. / Communication interauriculaire et cyanose. A propos de 6 observations en rapport avec un drainage anormal de la veine cave inférieure dans l'oreillette gauche.

The authors report six cases of atrial septal defect (ASD) associated with abnormal drainage of the inferior vena cava into the left atrium responsible for right-to-left shunting, without pulmonary hypertension. The abnormal drainage could be due either to an anatomical malposition of the inferior vena cava opening into the left atrium, or to an abnormal blood flow from this vein, normally located through a low ASD, under the influence of anatomical, mechanical and haemodynamic factors. Clinically, all patients presented with light cyanosis and with the usual signs of ASD. None of them had elevated pulmonary pressure. The lesion, suggested by clinical findings, was diagnosed either at angiography, which in four cases demonstrated an abnormal pulmonary venous return, or at colour-coded doppler echocardiogram, or at surgery. In every case, surgical correction consisted of closure of the often low-sited ADS by a patch which diverted the inferior vena cava into the right atrium and the abnormal venous return towards the left atrium. The short--and long-term results of surgery were excellent. The authors review the literature concerning this unusual association of ASD with an abnormal drainage of the inferior vena cava into the left atrium.

[Endoluminal mitral valvuloplasty in young adults and children. Apropos of 10 cases]. / Valvuloplastie mitrale endoluminale chez l'adulte jeune et l'enfant. A propos de 10 cas.

Between April 1 and May 15, 1986, transluminal dilatation of the mitral valve was performed at the Marie-Lannelongue Hospital, near Paris, in 10 patients aged from 12 to 48 years (mean 25,3 years) suffering from rheumatic mitral stenosis with supple valve leaflets. The procedure, carried out under local anaesthesia, included trans-septal catheterization followed by installation of one, then usually two balloons opposite the mitral orifice. The total diameter of the balloons was often greater than that of the mitral annulus. No haemorrhage, embolism or arrhythmia was observed. A significant left-to-right shunt, evaluated by radioisotope exploration with technetium pyrophosphate performed on the 8th day, was present in only one patient. The LV-LA end-diastolic gradient fell from 14.4 +/- 9.8 to 4.6 +/- 3.4 mmHg (p less than 0.01). The mean pulmonary arterial pressure was reduced less significantly from 39.9 +/- 18.4 to 27.2 +/- 11.3 mmHg (p less than 0.02). The cardiac output was only moderately increased from 2.52 +/- 0.48 to 2.88 +/- 0.66 l/min/m2. The mitral valve area, measured from the smaller axis on 2-dimensional echocardiography, more than doubled, reaching a mean value of 1.99 +/- 0.56 cm2. This figure was confirmed by the reduction, at Doppler velocimetry, of the gradient half-regression time from 267 +/- 62 to 118 +/- 46 ms (p less than 0.01). Similarly, the end-systolic gradient evaluated by Doppler, fell from 17.5 +/- 8.9 to 5.3 +/- 4.7 mmHg (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

[Percutaneous transluminal angioplasty in complex congenital cardiopathies. Apropos of 2 cases]. / Angioplastie transluminale percutanée dans des cardiopathies congénitales complexes. A propos de deux cas.

Percutaneous transluminal angioplasty (PTA), already widely used in stenosis of peripheral, renal or coronary arteries, has now been extended to congenital heart diseases. Thus, in pulmonary or aortic orificial stenosis this simple and fairly safe method has proved to be a suitable alternative to surgery. In other cases it may be used for tiding the patient over a critical period pending surgery. Finally, PTA may be performed as a palliative treatment of lesions that are too complex for surgery or carry an excessively high operative risk. This applies to the two cases reported here, where PTA enabled us to dilate: the ductus arteriosus in a patient with single ventricle--an application which, to our knowledge, has not yet been reported--and a strongly stenotic pulmonary orifice associated with a complex heart disease. In both cases PTA was successful both haemodynamically and angiographically and was followed by marked clinical improvement. The published cases of complex congenital heart diseases where PTA has been used are reviewed.

[Rheumatic mitral stenosis. The medical solution]. / Rétrécissement mitral rhumatismal. La solution médicale.

The first case of balloon catheter valvular dilatation for rheumatic mitral stenosis is reported in a 13 year-old child. The technique, under local anesthesia, required a transseptal access, then the introduction of one, then simultaneously 2 balloon catheters through the mitral valve. A perfect opening of the valve, without mitral insufficiency was obtained. This technique, even if difficult, seems to be adaptable to most children with rheumatic mitral stenosis.

[Non-surgical treatment of pulmonary valve stenosis]. / Cure non chirurgicale de la sténose pulmonaire valvulaire.

Percutaneous pulmonary valve valvuloplasty was attempted 17 times in 16 infants and children aged 15 days to 18 years. Valvuloplasty was performed during cardiac catheterization without general anesthesia. Balloon catheter was positioned across the pulmonary valve using a guide wire previously introduced in the right or left pulmonary artery. All patients experienced a decrease in the right ventricular peak systolic pressure from 111.5 +/- 35.9 to 69 +/- 28.9 mmHg (p less than 0.001), a decrease in the ratio of right ventricular pressure to systemic systolic pressure from 1.08 +/- 0.34 to 0.65 +/- 0.28 (p less than 0.001) and a decrease in right ventricular to pulmonary artery gradient from 88.52 +/- 37.2 to 54.82 +/- 29.4 mmHg (p less than 0.001). A child with a history of postoperative seizures had convulsions after the procedure and died 72 hours later. Four other patients are considered as a failure of the technique, 4 had clear hemodynamic improvement but right ventricular pressure remained above 50 mmHg, and 8 had satisfactory relief of their stenosis with a right ventricular pressure below or equal to 50 mmHg and a right ventricular to pulmonary artery gradient below 30 mmHg. These good results were confirmed in 2 patients, one year after the dilatation. Percutaneous balloon valvuloplasty is probably now the best treatment for pulmonary valvular stenosis. Short-term and results at distance from the procedure are good, and morbidity and cost are less than those for a surgical cure.

[Adult pulmonary valvular stenosis, major stenosing right ventricular hypertrophy and tricuspid insufficiency. Apropos of 2 cases]. / Sténose valvulaire pulmonaire vieillie, hypertrophie ventriculaire droite sténosante majeure et insuffisance tricuspidienne. A propos de 2 observations.

2 cases of severe pulmonary valvular stenosis in two young adults aged 21 and 29 years respectively are presented. Despite the degree of stenosis (4 mm jet), the right ventricular pressures did not exceed systemic pressures because of severe tricuspid regurgitation. This dominated the clinical and anatomical findings, causing aneurysmal dilatation of the right atrium and displacement of the tricuspid valve to the left. The diagnosis of Ebstein's anomaly was raised in one case but excluded by echocardiography and angiocardiography. In spite of the severity of the symptoms and peripheral clinical signs, surgery of the right ventricular outflow tract, tricuspid valvuloplasty and resection of part of the right atrium led to a complete and rapid cure, confirmed by catheterisation one month after operation.

[Malformations of the tricuspid valve associated with Fallot's tetralogy. Apropos of a series of 224 surgically treated Fallot's tetralogies]. / Malformations de la valve tricuspide associées à la tétralogie de Fallot. A propos d'une série de 224 tetralogies de Fallot opérées.

This study was based on 7 children aged 20 months to 13 years with tetralogy of fallot (TOF) and tricuspid valve defects. Cases of endocardial cushion defects (8 cases of atrioventricular) were excluded. Three types of tricuspid valve defect were observed: 4 tricuspid valve prolapse (with one associated mitral valve prolapse); 2 accessory tricuspid valves passing through a ventricular septal defect to prolapse in diastole under the aortic valve; 1 Ebstein anomaly. The prevalence of tricuspid valve defects associated with TOF 3 p. 100 in this series. The diagnosis can: usually be made by 2D echocardiography. Tricuspid valve prolapse (usually the septal leaflet) is visualised in the apical 4 chamber view. The passage of accessory tricuspid tissue across the VSD into the left ventricular outflow tract is visible in the parasternal long axis or subcostal long axis views. Ebstein anomaly can be demonstrated in apical 4-chamber views showing the abnormally apical site of insertion of the septal leaflet of the tricuspid valve and "atrialisation" of part of the right ventricle. Tricuspid valve defects did not pose any special surgical problems during complete repair of TOF but this series did not include any cases of tricuspid hypoplasia or parachute tricuspid valve which have been reported in the literature and which do complicate surgery. Tricuspid valve and subendocardial cushion defects should be looked for systematically in patients with TOF undergoing 2D echocardiography.