Haemocyte changes in D. Melanogaster in response to long gland components of the parasitoid wasp Leptopilina boulardi: a Rho-GAP protein as an important factor.

The hymenopteran wasp Leptopilina boulardi (Figitidae) is a larval solitary parasitoid of Drosophila larvae of the melanogaster sub-group. The factors used by parasitoid females to prevent encapsulation of their eggs by the host are localized in the female long gland and reservoir. We report here the physiological effects of these factors on host haemocytes using in vivo injection experiments. The total number of haemocytes, the number of plasmatocytes and the number of crystal cells were not modified by injection of long gland extracts. In contrast, long gland extracts either from virulent or avirulent strains had a significant effect on the lamellocyte number. Compared to the Ringer control, the avirulent long gland products induced an increase of the lamellocyte number while virulent extracts induced a drastic decrease together with an alteration of the morphology of these cells. Interestingly, changes in the lamellocyte morphology were also observed following injection of the P4 protein, a major component of L. boulardi female long glands that displays a strong immune suppressive effect on Drosophila larvae. The implication of the P4 protein in suppressing the host cellular immunity is discussed in correlation with its predicted molecular function as a Rho-GAP protein.

A RhoGAP protein as a main immune suppressive factor in the Leptopilina boulardi (Hymenoptera, Figitidae)-Drosophila melanogaster interaction.

To protect its eggs, the endoparasitoid wasp Leptopilina boulardi injects immune suppressive factors into Drosophila melanogaster host larvae. These factors are localized in the female long gland and reservoir. We analyzed the protein content of these tissues and found that it strongly differed between virulent and avirulent parasitoid strains. Four protein bands present in virulent long glands were eluted and their immune suppressive effect was assessed in vivo, allowing demonstrating a major effect of one of these proteins. The corresponding cDNA encodes a predicted 30 kDa subunit containing a Ras homologous GTPase Activating Protein (RhoGAP) domain, suggesting a possible involvement in the regulation of actin cytoskeleton changes. Using Western-blot experiments, we showed that this protein is abundant in virulent female long glands but is undetectable in virulent females deprived of long glands or in long glands from avirulent wasps. Its potential role in modifying the morphology and the adhesive properties of the host lamellocytes, involved in Drosophila cellular immune responses, is discussed.

Active suppression of D. melanogaster immune response by long gland products of the parasitic wasp Leptopilina boulardi.

To develop inside their insect hosts, endoparasitoid wasps must either evade or overcome the host's immune system. Several ichneumonid and braconid wasps inject polydnaviruses that display well-studied immune suppressive effects. However, little is known about the strategies of immunoevasion used by other parasitoid families, such as figitid wasps. The present study provides experimental evidence, based on superparasitism and injection experiments, that the figitid species Leptopilina boulardi uses an active mechanism to suppress the Drosophila melanogaster host immune response, i.e. the encapsulation of the parasitoid eggs. The immune suppressive factors are localised in the long gland and reservoir of the female genital tractus, where virus-like particles (VLPs) have been observed. Parasitism experiments using a host tumorous strain indicate that these factors do not destroy host lamellocytes but that they impair the melanisation pathway. Interestingly, they are not susceptible to heating and are not depleted with prolonged oviposition experience, in contrast to observations reported for L. heterotoma, another figitid species. The mechanisms that prevent encapsulation of eggs from L. boulardi and L. heterotoma differ in several respects, suggesting that different physiological strategies of immunosuppression might be used by specialised and generalist parasitoids.

Preliminary experience with intraoperative transluminal balloon-catheter dilation and coronary artery bypass grafting for the treatment of symptomatic diffuse coronary artery disease.

Transluminal balloon-catheter dilation of coronary artery lesions has become increasingly common in the cardiac catheterization laboratory. We describe a method of intraoperative dilation that may improve surgical results when used in combination with coronary artery bypass graft (CABG) operations in patients with diffusely diseased coronary arteries. In 16 patients, long-segment intraoperative dilations were performed to enlarge luminal narrowings in 21 different regions. All of these patients had postoperative coronary angiography and left ventriculography so that we could objectively evaluate the coronary dilatations. There were no operative deaths or perioperative myocardial infarctions, and angina was relieved in all patients. Of the 21 dilated segments, 12 (57%) were unchanged, 2 (10%) became worse, and 7 (33%) were improved postoperatively. In addition, two new areas of intimal damage were detected in patients with unchanged postoperative liminal diameters. We conclude that further experience and longer follow-up are necessary before the efficacy of intraoperative coronary artery balloon-catheter dilation can be accurately determined.

Preoperative prediction from cineangiograms of postrepair right ventricular pressure in tetralogy of Fallot.

To aid preoperative decision-making, we have related the ratio of postrepair peak pressure in the right and left ventricles (PRV/LV) to preoperative cineangiographic measurements in a retrospective study of 135 patients undergoing complete repair of tetralogy of Fallot or tetralogy of Fallot with pulmonary atresia. Postrepair PRV/LV was related to the preoperative diameter of right (DRPA) and left (DLPA) pulmonary arteries normalized to the descending thoracic aorta (DescThAo) in patients undergoing repair with transannular patching or a valved external conduit by the dquation: PRV/LV = 0.4840/(DRPA/DescThAO + DLPA/DesThAo) + 0.2007. Stenosis of the right pulmonary artery orifice and pulmonary artery arborization abnormalities incrementally increased postrepair PRV/LV. When a transannular patch was not used in classical tetralogy of Fallot, an increment of postrepair PRV/LV usually resulted, depending upon the size of the "anulus" measured intraoperatively: Incremental PRV/LV = 0.09437 . exp(-0.6344 . Z) where Z is a normalized expression in circumference terms of the diameter of the pulmonary arterial outflow tract (DPAOT) measured intraoperatively after infundibular dissection and valvotomy. DPAOT is itself related to the cineangiographically measured pulmonary valve anulus diameter (DPVA): DPAOT = 3.357 . DPVA0.5789 . BSA0.1551. In toto, these relations allow postrepair PRV/LV without transannular patching to be estimated from preoperative cineangiographic measurements. This allows preoperative predictiom in classical tetralogy of Fallot of the need for transannular patching, and in infants this can determine the choice between primary one-stage repair and two-stage repair. Prediction of postrepair PRV/LV when transannular patching or an external conduit is planned allows identification of patients in whom right and left pulmonary arteries are too small for safe complete repair, and in them an initial palliative operation should be done to enlarge the arteries.

The role of displacement of the mitral annulus in left atrial filling and emptying in the intact dog.

The variations in ventricular-atrial mitral annular position during the cardiac cycle and the simultaneous changes in left atrial silhouette area (obtained by angiography after injections of contrast material into the main pulmonary artery) were investigated in six experiments on intact dogs with chronically implanted intracardiac markers. Frame-by-frame measurements of the angiograms (120 frames/s) were used to determine, under various hemodynamic conditions, the duration, magnitude, and average rate of the mitral annular motion and of the simultaneous changes in left atrial area during atrial filling (ventricular systole) and atrial emptying (early in ventricular diastole). The mitral annulus was seen to move towards the ventricular apex during systole and towards the atrium early in diastole with the duration, average rate, and magnitude of displacement (although varying widely) showing good statistical correlations (P less than 0.0005-0.005) with the changes in projected left atrial area. These findings suggest that the duration, rate, and magnitude of atrial filling and emptying may be, in the intact heart, determined by the movements of the atrioventricular junction.

Sudden interruption of leaflet opening by ventricular contractions: a mechanism of mitral regurgitation.

The motion of both mitral cusps and the presence of valvular regurgitation during ventricular contractions were investigated in seven experiments on dogs in which radiopaque markers had been sutured to the cusps and the valve annulus 1-32 wk before the studies. Cineangiograms of the left ventricle were obtained during ventricular ectopic beats, interposed throughout the cardiac cycle (20-99% of cycle length) and during induced variations in the P-R interval (0-200 ms). Mitral regurgitation was observed only during a) weak, early ectopic beats (peak pressure below 34 mmHg) which were incapable of closing the cusps and b) when ventricular contractions suddenly interrupted normal leaflet motion toward the ventricle, during three well-defined periods of diastole (diastolic valve opening, diastolic rebound, and atrial opening). Valve closure following sudden reversal of cusp opening was slow and the leaflets often did not arrive simultaneously at their closed positions. These findings suggest that sudden interruption of leaflet opening by ventricular contractions is an important mechanism of transient mitral regurgitation in the normal heart.

Survey of mechanical assistance of the circulation and the present status of left-heart bypass.

The various types of mechanical circulatory assistance which recently have been developed are described. The techniques which appear to be most promising for clinical application are: veno-arterial bypass with oxygenation, synchronous arterial assistance, and closed-chest left-heart bypass.The effects of a left ventricular bypass on central hemodynamics and the oxygen requirements of the left ventricle are described. A bypass of 90% of the left ventricular output brings about a 30% reduction in the left ventricular myocardial oxygen requirement. Left atrial pressure is reduced. The central aortic mean pressure, the pulmonary artery pressure, and the right atrial pressure are not changed.