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Biomedical subjects

G Dreyfus

Publications and source records attributed to G Dreyfus.

At least 91 records · Page 5Linked to original sources
PubMed1989

Coupling of ATP hydrolysis to phosphate uptake in Rhodospirillum rubrum chromatophores under the influence of Ca2+ and Mg2+.

The Pi-ATP exchange and ATP hydrolytic reactions, by the F0F1 complex, were studied in Rhodospirillum rubrum chromatophores in the dark. An optimal pH between 7.0 and 8.5 was determined for the hydrolytic and exchange reactions. Under these conditions, the hydrolysis/exchange ratio was approximately 2. The kinetic analysis of the hydrolytic and exchange reactions using Mg-ATP as substrate showed a change in the hydrolysis/exchange ratio that varied between 2.0 and 2.8 as the substrate concentration was increased. With Ca-ATP, hydrolysis was not saturated up to a substrate concentration of 5.0 mM, and the hydrolysis/exchange ratios changed from 2 to 240 as the substrate concentration was increased from 0.06 to 5.0 mM. Free Mg2+ inhibited hydrolysis and phosphate uptake without altering the hydrolysis/exchange ratio. Nigericin induced an increase in the hydrolysis/exchange ratio from 2.7 to 130, whereas in the presence of valinomycin, this ratio increased from 2.7 to 21. From these results, it can be concluded that Ca-ATP hydrolysis is loosely coupled to phosphate uptake given that Pi-ATP exchange activity is extremely low, even at high rates of ATP hydrolysis.

Adenosine Triphosphate↗
PubMed1989

Aurovertin fluorescence changes of the mitochondrial F1-ATPase during multi- and uni-site ATP hydrolysis.

The aurovertin-F1 complex was used to monitor fluorescence changes of the mitochondrial adenosine triphosphatase during multi- and uni-site ATP hydrolysis. It is known that the fluorescence intensity of the complex is partially quenched by addition of ATP or Mg2+ and enhanced by ADP (Chang, T., and Penefsky, H. S. (1973) J. Biol. Chem. 248, 2746-2754). In the present study low concentrations of ATP (0.03 mM) induced a marked fluorescence quenching which was followed by a fast fluorescence recovery. This recovery could be prevented by EDTA or an ATP regenerating system. The rate of ATP hydrolysis by the aurovertin-F1 complex and the reversal of the ATP-induced fluorescence quenching were determined in these various conditions. ITP hydrolysis also resulted in fluorescence quenching that was followed by a recovery of fluorescence intensity. Under conditions for single site catalysis, fluorescence quenching was observed upon the addition of ATP. This strongly indicates that fluorescence changes in the aurovertin-F1 complex are due to the binding and hydrolysis of ATP at a catalytic site. Therefore the resulting ADP molecule bound at this catalytic site possibly induces the fluorescence recovery observed.

Adenosine Diphosphate↗
PubMed1989

Modulation of mitochondrial F0F1 catalysis by boundary and bulk phase phospholipids.

The importance of boundary and bulk phase phospholipids was studied on a mitochondrial ATPase complex isolated by AH-Sepharose chromatography as described by Dreyfus et al (1984, Anal. Biochem. 142,215-220), this preparation was devoid of the adenine nucleotide carrier. The presence of isoelectric or acidic phospholipids during the purification in the column allows the exchange of tightly bound phospholipids up to 95%. ATP hydrolysis and oligomycin sensitivity were slightly affected by the nature of boundary and bulk phase phospholipids, while Pi-ATP exchange was highly inhibited.

Adenosine Triphosphate↗
PubMed1989

Modified Danielson technique for recurrent aortic valve endocarditis.

Recurrent aortic valve endocarditis is frequently associated with paravalvular ring abscess that destroys the annulus. In occasional cases, the degree of necrosis, destruction of the annulus, and the presence of intramyocardial abscesses make it impossible to seat a new prosthesis. Danielson reported initial success in treating such patients by translocating the aortic valve to the ascending aorta and placing vein grafts to the coronary arteries. We recently treated a 17-year-old patient suffering recurrent aortic valve endocarditis using Danielson's technique, which we modified by implanting the left main coronary artery directly into the conduit. We believe that in young patients this modification can offer a beneficial alternative.

Adolescent↗
PubMed1989

Aberrant right subclavian artery aneurysm: report of a case and review of the literature.

Aneurysms of an aberrant subclavian artery are rare. They are usually secondary to atherosclerosis. Dysphagia is the most common presenting symptom. The diagnosis of these lesions is most easily established by CT scan. Biplane arteriography is necessary in order to clearly analyze the aortic arch and its branches. Surgical resection is usually indicated. Numerous procedures have been proposed to treat these lesions and controversy exists concerning the best surgical technique. We treated a patient who suffered from an aneurysm of an aberrant subclavian artery. The surgical technique is detailed as well as a review of all the cases of the literature.

Aged↗
PubMed1989

[Right ventricular assistance by intrapulmonary counterpulsation].

Right ventricular failure is relatively frequent and constitutes one of the causes of post-operative heart failure. Few drugs are available to treat right ventricular failure. We present a simple and effective means of mechanical support available in all cardiovascular units: counterpulsation in the pulmonary artery. Our experience and a review of the literature have enabled us to determine the indications for this method to support a failing heart.

Assisted Circulation↗
PubMed1989

[Limitations of the feasibility of right catheterization in the evaluation for cardiac transplantation].

The number of patients who survive heart transplantation has considerably increased in recent years, but mortality during the first 3 months still reaches 10 to 20 p. 100 depending on the authors. Among the various causes of death, acute graft deficiency due to pulmonary arterial hypertension plays an important role. In most cases, pulmonary vascular resistance has been misevaluated or its progress has not been foreseen. Between January 1985 and June 1988, 96 heart transplantations were performed at the Broussais Hospital, Paris. We thought that pulmonary vascular resistance could be better evaluated by using dobutamine to mimick transplantation and to assess pulmonary pressure and resistance variations associated with the increase in cardiac output. High doses of dobutamine ranging from 10 to 30 mcg/kg/min were administered to bring the basal cardiac output level up to the theoretical output level or to increase it by 50 p. 100. The 96 patients who had heart transplantation during the aforementioned period were divided into two groups: group I comprised 35 patients who were transplanted before dobutamine was used, while group II comprised 61 patients for whom the dobutamine test was always considered. The mortality rate was 11.75 p. 100 (4/35) in group I and nil in group II as regards death from pulmonary arterial hypertension (p = 0.04). We demonstrate that a single resistance value is not reliable, even when it is normal, when the cardiac output is low. Furthermore, there is no threshold value for contraindication, and indexing resistance alters the scale of values but does not enable normality to be defined. By using the dobutamine test we were able to reduce considerably the mortality due to pulmonary arterial hypertension and also to exclude orthotopic transplantation in some patients.

Arterioles↗
PubMed1989

Monitoring of heart allograft rejection by simultaneous measurement of serum beta 2-microglobulin and urinary neopterin.

In patients with heart transplant, the combined determination of serum beta 2-microglobulin and urinary neopterin, as rejection marker, prevented the interference by renal function and cyclosporin therapy. Unfortunately, the simultaneous measurement of these two parameters cannot distinguish between a rejection episode and the early stage of viral infection.

Biopterins↗
PubMed1989

[Postoperative iatrogenic coronaro-ventricular fistula].

Acquired coronary cardiac fistulas are rare. To date, thirty cases have been published in the literature, all secondary to thoracic trauma. The right cardiac chambers were more frequently involved. A recent continuous cardiac murmur is the most constant finding. Nontreated, these lesions tend to induce coronary insufficiency and congestive heart failure. 22 of the 30 reported cases were managed surgically. We hereby report a case of postoperative coronary cardiac fistula secondary to left ventricular venting, in which the fistula involved the left ventricular cavity.

Aortic Valve↗