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E Fontaine

Publications and source records attributed to E Fontaine.

At least 55 records · Page 3Linked to original sources
PubMed1998

Regulation of the permeability transition pore in skeletal muscle mitochondria. Modulation By electron flow through the respiratory chain complex i.

We have investigated the regulation of the permeability transition pore (PTP), a cyclosporin A-sensitive channel, in rat skeletal muscle mitochondria. As is the case with mitochondria isolated from a variety of sources, skeletal muscle mitochondria can undergo a permeability transition following Ca2+ uptake in the presence of Pi. We find that the PTP opening is dramatically affected by the substrates used for energization, in that much lower Ca2+ loads are required when electrons are provided to complex I rather than to complex II or IV. This increased sensitivity of PTP opening does not depend on differences in membrane potential, matrix pH, Ca2+ uptake, oxidation-reduction status of pyridine nucleotides, or production of H2O2, but is directly related to the rate of electron flow through complex I. Indeed, and with complex I substrates only, pore opening can be observed when depolarization is induced with uncoupler (increased electron flow) but not with cyanide (decreased electron flow). Consistent with pore regulation by electron flow, we find that PTP opening is inhibited by ubiquinone 0 at concentrations that partially inhibit respiration and do not depolarize the inner membrane. These data allow identification of a novel site of regulation of the PTP, suggest that complex I may be part of the pore complex, and open new perspectives for its pharmacological modulation in living cells.

Animals↗
PubMed1998

Chemical modification of arginines by 2,3-butanedione and phenylglyoxal causes closure of the mitochondrial permeability transition pore.

We have investigated the role of arginine residues in the regulation of the mitochondrial permeability transition pore, a cyclosporin A-sensitive inner membrane channel. Isolated rat liver mitochondria were treated with the arginine-specific chemical reagent 2, 3-butanedione or phenylglyoxal, followed by removal of excess free reagent. After this treatment, mitochondria accumulated Ca2+ normally, but did not undergo permeability transition following depolarization, a condition that normally triggers opening of the permeability transition pore. Inhibition by 2,3-butanedione and phenylglyoxal correlated with matrix pH, suggesting that the relevant arginine(s) are exposed to the matrix aqueous phase. Inhibition by 2,3-butanedione was potentiated by borate and was reversed upon its removal, whereas inhibition by phenylglyoxal was irreversible. Treatment with 2,3-butanedione or phenylglyoxal after induction of the permeability transition by Ca2+ overload resulted in pore closure despite the presence of 0.5 mM Ca2+. At concentrations that were fully effective at inhibiting the permeability transition, these arginine reagents (i) had no effect on the isomerase activity of cyclophilin D and (ii) did not affect the rate of ATP translocation and hydrolysis, as measured by the production of a membrane potential upon ATP addition in the presence of rotenone. We conclude that reaction with 2,3-butanedione and phenylglyoxal results in a stable chemical modification of critical arginine residue(s) located on the matrix side of the inner membrane, which, in turn, strongly favors a closed state of the pore.

Animals↗
PubMed1998

Divergent responses to fluoxetine from two compulsive, food-related conditions: bulimia nervosa and compulsive water drinking.

BACKGROUND: The association of compulsive water drinking with bulimia nervosa is rarely encountered. Nevertheless similar behavior patterns could involve a common pathophysiological mechanism. METHODS: A case report with the association of those two disorders is described. Treatment with fluoxetine was introduced to alleviate the compulsive aspects of those disorders. RESULTS: Fluoxetine had a positive effect on bulimia nervosa but none on compulsive water drinking. CONCLUSIONS: The different response to pharmacologic treatment could mean that bulimia nervosa and compulsive water drinking are based on different physiological mechanisms.

Adult↗
PubMed1998

The mitochondrial permeability transition.

This review summarizes recent work on the regulation of the permeability transition pore, a cyclosporin A-sensitive mitochondrial channel that may play a role in intracellular calcium homeostasis and in a variety of forms of cell death. The basic bioenergetics aspects of pore modulation are discussed, with some emphasis on the links between oxidative stress and pore dysregulation as a potential cause of mitochondrial dysfunction that may be relevant to cell injury.

Animals↗
PubMed1998

Renal transplantation in children with augmentation cystoplasty: long-term results.

PURPOSE: We assessed the long-term results of renal transplantation in children with augmentation cystoplasty. MATERIALS AND METHODS: We retrospectively reviewed the complications and followup in 14 pediatric renal transplant recipients with augmentation cystoplasty. The etiology of bladder dysfunction included posterior urethral valves in 10 cases, neurogenic bladder in 3 and vesicoureteral reflux in 1. All transplants were cadaver donor kidneys. Mean patient age at transplantation was 12.1 years (range 5 to 18). Augmentation cystoplasty was performed before and after transplantation in 10 and 4 cases, respectively. Detubularized ileum was used in 5 cases, tubular ileum in 4, tubular sigmoid in 4 and stomach in 1. RESULTS: Of the 14 transplanted kidneys 10 (71%) were functioning at a mean followup of 80 months (range 12 to 151). Serum creatinine was less than 1.4 mg./dl. in 9 patients. Four grafts were lost to chronic rejection. The 5 and 10-year graft survival rates were 84 and 73%, respectively. Two patients with a functioning kidney died of causes unrelated to augmentation cystoplasty. Complications included symptomatic urinary infections in 4 patients, hyperchloremic metabolic acidosis in 2, nephrolithiasis in the allograft in 2 and the hematuria-dysuria syndrome in 1. All patients were continent. CONCLUSIONS: Augmentation cystoplasty is a safe and effective method of restoring lower urinary tract function in the pediatric renal transplant population with a small noncompliant bladder.

Adolescent↗
PubMed1998

Zonal variation of apoptosis and proliferation in the normal prostate and in benign prostatic hyperplasia.

OBJECTIVE: To determine whether benign prostatic hyperplasia (BPH) results from an imbalance between cell proliferation and apoptosis, and the extent to which the rates of these opposing processes are altered with the expression of the anti-death oncoprotein bcl-2. MATERIALS AND METHODS: Ten prostate glands from normal men (mean age 43.7 years) were sampled according to McNeal's zonal anatomy, in addition to 30 prostate adenomas obtained from prostatectomy specimens from symptomatic patients (mean age 61.4 years). Tissue samples were fixed in formalin and embedded in paraffin. Proliferation and bcl-2 expression were assessed by immunostaining using Mib-1 and anti-bcl-2 antibodies, while apoptotic bodies were specifically stained using in situ nick translation. The percentage of positive cells was determined by optical microscopy. RESULTS: In normal epithelium, the rates of proliferation and apoptosis were increased in the peripheral zone (Mib-1 1.7%, apoptotic bodies 3.3%) compared with the central (0.2% vs 1.4%) and transition (0.1% vs 1.8%) zones. Proliferation was significantly greater in BPH than in normal prostate tissue (3.7%), contrasting with a stable rate of apoptosis (1.4%). In the normal prostate, bcl-2 was expressed by glandular and basal cells in the peripheral zone. In the central zone, bcl-2 was overexpressed in basal cells and in most glandular cells of the intraluminal ridges. Bcl-2 expression in the transition zone was limited to dispersed basal cells. In BPH, bcl-2 was strongly expressed by basal cells in mature glandular formations and in most cells of young small nodules. CONCLUSION: BPH may result from both an increase of proliferation within the basal compartment and a failure of apoptosis to counterbalance basal cell proliferation. Increased expression of bcl-2 may participate in this process by blocking apoptosis.

Adult↗
PubMed1998

Quantitative analysis of some mechanisms affecting the yield of oxidative phosphorylation: dependence upon both fluxes and forces.

The purpose of this work was to show how the quantitative definition of the different parameters involved in mitochondrial oxidative phosphorylation makes it possible to characterize the mechanisms by which the yield of ATP synthesis is affected. Three different factors have to be considered: (i) the size of the different forces involved (free energy of redox reactions and ATP synthesis, proton electrochemical difference); (ii) the physical properties of the inner mitochondrial membrane in terms of leaks (H+ and cations); and finally (iii) the properties of the different proton pumps involved in this system (kinetic properties, regulation, modification of intrinsic stoichiometry). The data presented different situations where one or more of these parameters are affected, leading to a different yield of oxidative phosphorylation. (1) By manipulating the actual flux through each of the respiratory chain units at constant protonmotive force in yeast mitochondria, we show that the ATP/O ratio decreases when the flux increases. Moreover, the highest efficiency was obtained when the respiratory rate was low and almost entirely controlled by the electron supply. (2) By using almitrine in different kinds of mitochondria, we show that this drug leads to a decrease in ATP synthesis efficiency by increasing the H+/ATP stoichiometry ofATP synthase (Rigoulet M et al. Biochim Biophys Acta 1018: 91-97, 1990). Since this enzyme is reversible, it was possible to test the effect of this drug on the reverse reaction of the enzyme i.e. extrusion of protons catalyzed by ATP hydrolysis. Hence, we are able to prove that, in this case, the decrease in efficiency of oxidative phosphorylation is due to a change in the mechanistic stoichiometry of this proton pump. To our knowledge, this is the first example of a modification in oxidative phosphorylation yield by a change in mechanistic stoichiometry of one of the proton pumps involved. (3) In a model of polyunsaturated fatty acid deficiency in rat, it was found that non-ohmic proton leak was increased, while ohmic leak was unchanged. Moreover, an increase in redox slipping was also involved, leading to a complex picture. However, the respective role of these two mechanisms may be deduced from their intrinsic properties. For each steady state condition, the quantitative effect of these two mechanisms in the decrease of oxidative phosphorylation efficiency depends on the values of different fluxes or forces involved. (4) Finally the comparison of the thermokinetic data in view of the three dimensional-structure of some pumps (X-ray diffraction) also gives some information concerning the putative mechanism of coupling (i.e. redox loop or proton pump) and their kinetic control versus regulation of mitochondrial oxidative phosphorylation.

ATP Synthetase Complexes↗
PubMed1998

[Clinical stage T3 prostate cancer: natural history, therapeutic choices and their results].

Clinical stage T3 prostate cancer is ambiguous both in terms of its definition and its place in the natural history of the disease, and there is no consensus concerning its treatment. In a review of the literature, 148 articles were selected and analysed from the Medline database over a 14-year period (1983-1997). Single-agent therapy: Radiotherapy and radical prostatectomy: it is unlikely that these treatments can cure clinical stage T3 prostatic cancer, except perhaps for a small minority of patients actually presenting with overstaged pT2 disease or certain forms of low-grade pT3. Neither treatment appears to have any advantage over the other-Endocrine therapy: it has been proposed as exclusive treatment at this stage. Few studies have been reported. However, many authors consider this choice to be legitimate, because one-half of patients already have lymph node involvement. Combination therapy: Radiotherapy and endocrine therapy: recent studies comparing exclusive external beram radiotherapy with endocrine therapy show an advantage in favour of combination therapy. Total prostatectomy and endocrine therapy: neoadjuvant endocrine therapy does not provide any advantage. Adjuvant endocrine therapy improves local control and progression-free survival. Adjuvant radiotherapy and radical prostatectomy provides no advantage for T3. The choice of treatment for stage T3, N0, M0 obviously depends on the patient's general state and life expectancy. If the option of a curative treatment in a young subject can be reasonably considered, combination therapy should be preferred.

Adult↗
PubMed1997

Study of regulation of mitochondrial respiration in vivo. An analysis of influence of ADP diffusion and possible role of cytoskeleton.

The purpose of this work was to investigate the mechanism of regulation of mitochondrial respiration in vivo in different muscles of normal rat and mice, and in transgenic mice deficient in desmin. Skinned fiber technique was used to study the mitochondrial respiration in the cells in vivo in the heart, soleus and white gastrocnemius skeletal muscles of these animals. Also, cardiomyocytes were isolated from the normal rat heart, permeabilized by saponin and the "ghost" (phantom) cardiomyocytes were produced by extraction of myosin with 800 mM KCl. Use of confocal immunofluorescent microscopy and anti-desmin antibodies showed good preservation of mitochondria and cytoskeletal system in these phantom cells. Kinetics of respiration regulation by ADP was also studied in these cells in detail before and after binding of anti-desmine antibodies with intermediate filaments. In skinned cardiac or soleus skeletal muscle fibers but not in fibers from fast twitch skeletal muscle the kinetics of mitochondrial respiration regulation by ADP was characterized by very high apparent Km (low affinity) equal to 300-400 microM, exceeding that for isolated mitochondria by factor of 25. In skinned fibers from m. soleus, partial inhibition of respiration by NaN3 did not decrease the apparent Km for ADP significantly, this excluding the possible explanation of low apparent affinity of mitochondria to ADP in these cells by its rapid consumption due to high oxidative activity and by intracellular diffusion problems. However, short treatment of fibers with trypsin decreased this constant value to 40-70 microM, confirming the earlier proposition that mitochondrial sensitivity to ADP in vivo is controlled by some cytoplasmic protein. Phantom cardiomyocytes which contain mostly mitochondria and cytoskeleton and retain the normal shape, showed also high apparent Km values for ADP. Therefore, they are probably the most suitable system for studies of cellular factors which control mitochondrial function in the cells in vivo. In these phantom cells anti-desmin antibodies did not change the kinetics of respiration regulation by ADP. However, in skinned fibers from the heart and m. soleus of transgenic desmin-deficient mice some changes in kinetics of respiration regulation by ADP were observed: in these fibers two populations of mitochondria were observed, one with usually high apparent Km for ADP and the second one with very low apparent Km for ADP. Morphological observations by electron microscopy confirmed the existence of two distinct cellular populations in the muscle cells of desmin-deficient mice. The results conform to the conclusion that the reason for observed high apparent Km for ADP in regulation of oxidative phosphorylation in heart and slow twitch skeletal muscle cells in vivo is low permeability of mitochondrial outer membrane porins but not diffusion problems of ADP into and inside the cells. Most probably, in these cells there is a protein associated with cytoskeleton, which controls the permeability of the outer mitochondrial porin pores (VDAC) for ADP. Desmin itself does not display this type of control of mitochondrial porin pores, but its absence results in appearance of cells with disorganised structure and of altered mitochondrial population probably lacking this unknown VDAC controlling protein. Thus, there may be functional connection between mitochondria, cellular structural organisation and cytoskeleton in the cells in vivo due to the existence of still unidentified protein factor(s).

Adenosine Diphosphate↗
PubMed1997

Inhibition of the mitochondrial cyclosporin A-sensitive permeability transition pore by the arginine reagent phenylglyoxal.

The mitochondrial permeability transition pore, a cyclosporin A-sensitive channel, is controlled by the transmembrane electric potential difference across the inner membrane. Here, we show that treatment of rat liver mitochondria with the arginine reagent phenylglyoxal inhibits the permeability transition pore triggered by depolarization with uncoupler after Ca2+ accumulation. Phenylglyoxal does not change the extent of mitochondrial Ca2+ uptake or the extent of membrane depolarization, indicating that covalent modification of arginine (and possibly lysine) residues directly affects the open probability of the pore. We propose that arginine residues play a role in the physiological control of the permeability transition pore by the mitochondrial transmembrane potential.

Animals↗
PubMed1997

Reactivity to endothelium-dependent and -independent vasoactive substances is maintained in coronary resistance vessels of the failing hamster heart.

OBJECTIVES: Several studies suggest that regulation of coronary vasomotion is abnormal in heart failure, but controversies exist as to whether an altered endothelium-dependent dilation of the coronary vasculature contributes to these abnormalities. In the present study we evaluated the coronary reactivity to endothelium-dependent and -independent vasoactive substances in a model of chronic heart failure. METHODS: Isolated hearts from > 200-day-old cardiomyopathic hamsters (UM-X7.1) and age-matched normal Syrian hamsters were mounted on a Langendorff apparatus and retrogradely perfused at constant pressure (100 mmHg). Heart rate, left ventricular developed pressure (LVP) and coronary flow (CF) were measured. A first group of normal and failing hearts were challenged with increasing doses of acetylcholine (Ach), 1-1000 nM, and sodium nitroprusside (SNP), 0.01-10 microM. A second group was challenged with Ach (100 nM) and SNP (1 microM) before and during infusion of the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). Finally, normal and failing hearts were challenged with Ach (100 nM) before and during infusion of indomethacin (10 microM) or tetraethylammonium (1 mM). RESULTS: Myocardial contractility and coronary flow were significantly impaired in failing hearts (LVP = 32 +/- 5 vs. 50 +/- 4 mmHg in normal hearts; CF = 4.7 +/- 0.6 vs. 6.7 +/- 0.6 ml/min in normal hearts). Coronary flow increases with increasing doses of Ach (EC50 = 84 +/- 15 nM for failing hearts and 100 +/- 3 nM for normal hearts, P = ns). At concentrations exceeding the EC50, failing hearts were more sensitive to the coronary dilator effects of Ach. The reduction in coronary flow elicited by L-NAME was similar in normal (-41 +/- 2%) and failing hearts (-40 +/- 3%); in both normal and failing hearts, the acetylcholine vasodilator response was not significantly affected by L-NAME. Indomethacin infusion resulted in a slight increase in coronary flow and significantly reduced the coronary dilator effects of acetylcholine. Tetraethylammonium had no significant effects on basal coronary perfusion of normal and failing hearts. However, in the latter group, acetylcholine vasodilator response was significantly attenuated. CONCLUSION: Results obtained in isolated failing hamster hearts allow us to conclude that (1) significant coronary dysfunctions are present in this model of chronic heart failure, (2) neither the NO-synthase nor the cyclo-oxygenase pathway contributes to these coronary dysfunctions, and (3) an adequate coronary vasodilator response appears to be present in this model of chronic heart failure.

Acetylcholine↗
PubMed1997

Posterior urethral valves: long-term renal function consequences after transplantation.

PURPOSE: We assessed the long-term efficacy of renal transplantation in children with posterior urethral valves. MATERIALS AND METHODS: We retrospectively compared the outcomes of renal transplantation in 66 children with posterior urethral valves and 116 with malformation uropathies (controls). RESULTS: Graft survival in the posterior urethral valves and control groups was 69 and 72% at 5 years, and 54 and 50% at 10 years, respectively (not statistically significant). A statistically significant increase in serum creatinine was noted at 10 years in children with posterior urethral valves but not in controls (p < 0.05). CONCLUSIONS: Renal transplantation in children with posterior urethral valves is not associated with a high rate of failure. However, long-term deterioration of graft function is likely related to lower urinary tract dysfunction.

Child↗
PubMed1997

Twenty-year experience with jejunal conduits.

OBJECTIVES: To assess the results of jejunal conduit urinary diversion, with particular attention to electrolyte imbalance and long-term renal function. METHODS: From 1976 to 1994, 50 patients underwent urinary diversion using a short jejunal loop (10 to 12 cm) placed transperitoneally. Of these patients, 18 received pelvic irradiation before diversion. Renal function and configuration of the upper urinary tract were assessed by creatinine clearance and excretory urography. RESULTS: Median follow-up was 26 months (3 to 204). Of 50 patients, 22 had a follow-up more than 5 years later (median 86 months). Eight patients (16%) underwent 10 revision procedures postoperatively. Late complications related to urinary diversion included renal calculi (12%), parastomal hernia (6%), pyelonephritis (4%), ureterojejunal obstruction (4%), and stomal prolapse (2%). Electrolyte imbalance occurred in 2 patients (4%) and was easily corrected by 4 g sodium bicarbonate. No significant decrease in creatinine clearance (P = 0.6) was found in 22 patients with a follow-up of more than 5 years; however, of these patients, 2 had a decrease in creatinine clearance of greater than 20%, due to ureterojejunal obstruction. Of 42 ureterorenal units, hydronephrosis occurred and increased in 1 and 2 cases, respectively, and renal scarring occurred and progressed in 2 and 2 cases, respectively. CONCLUSIONS: Urinary diversion using a short length of jejunum placed transperitoneally is a reliable procedure and gives good long-term renal function. Electrolyte imbalances are rare. Moreover, jejunal conduit can be used in almost all situations, especially after pelvic irradiation.

Adolescent↗
PubMed1997

Myocardial reactive hyperemia in experimental chronic heart failure: evidence for the role of K+ adenosine triphosphate-dependent channels and cyclooxygenase activity.

BACKGROUND: Several studies suggest that coronary perfusion is abnormal in heart failure. The fact that these deficits may results in an altered coronary reserve remains controversial. Therefore, coronary adaptability to short-duration ischemia and the resultant myocardial reactive hyperemia were investigated in a model of chronic heart failure. METHODS AND RESULTS: Experiments were performed in normal and failing hamster hearts (UM-X7.1, aged > 225 days). Heart rate, left ventricular developed pressure, and coronary flow were recorded continuously before and after each 30-second ischemia in isolated perfused heart preparations. Studies were conducted under control conditions and in the presence of four inhibitors of potential mediators of the reactive hyperemia response: the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (30 microM), the adenosine antagonist 8-(p-sulfophenyl)theophylline (50 microM), the K+ cyclic adenosine triphosphate-dependent channel antagonist glibenclamide (10 microM), and the cyclooxygenase inhibitor indomethacin (10 microM). Baseline hemodynamic parameters were all significantly impaired in failing hearts. Under control conditions, failing hearts were able to respond adequately to a 30-second ischemia: repayment-to-debt ratio averaged 1.02 +/- 0.09 as compared with 1.10 +/- 0.09 in normal hearts (P = NS). All inhibitors significantly reduced basal coronary perfusion except for indomethacin. Of the four inhibitors of potential mediators of the myocardial reactive hyperemic response, only glibenclamide and indomethacin impaired the repayment-to-debt ratio. In their presence, repayment-to-debt ratio was reduced by 40% of the baseline response (P < .01) without significant difference between normal and failing hearts. On the contrary, NG-nitro-L-arginine methyl ester and 8-(p-sulfophenyl)theophylline did not alter the repayment-to-debt ratio. CONCLUSIONS: These observations demonstrate the capacity of the failing heart to tolerate short-duration ischemia despite the presence of significant alterations in its basal coronary perfusion. In addition, results suggest that activation of K+ adenosine triphosphate-dependent channels and the presence of cyclooxygenase by-products are important determinants of coronary adaptation to short-duration ischemia in this model of chronic heart failure.

Animals↗
PubMed1997

Long-term results of renal transplantation in children with the prune-belly syndrome.

PURPOSE: We assessed the long-term efficacy of renal transplantation in children with the prune-belly syndrome. MATERIALS AND METHODS: We retrospectively compared the outcomes of renal transplantation in 9 children with the prune-belly syndrome and 100 with malformative uropathy. RESULTS: Graft survival in the prune-belly syndrome and control groups was 50 and 72% at 5 years, and 50 and 47% at 10 years, respectively (not statistically significant). No statistically significant increase in serum creatinine was noted at 10 years in children with the prune-belly syndrome. Two patients with the prune-belly syndrome underwent internal urethrotomy after transplantation. All patients voided well and did not require intermittent catheterization. CONCLUSIONS: Renal transplantation in children with the prune-belly syndrome is not associated with a high rate of failure. However, these patients must be followed with regular urological evaluation since voiding efficiency may deteriorate.

Child↗
PubMed1997

Combined modified rectus fascial sling and augmentation ileocystoplasty for neurogenic incontinence in women.

PURPOSE: We assessed results of a combined modified rectus fascial sling procedure and augmentation ileocystoplasty in women with neurogenic urinary incontinence. MATERIALS AND METHODS: We prospectively evaluated 21 patients (mean followup 28.6 months). RESULTS: A total of 20 patients (95.2%) was dry during the day on intermittent catheterization and none had difficulty with catheterization. Subsequently surgery was necessary in 1 case for perforation of the augmented bladder. CONCLUSIONS: A combined modified rectus fascial sling procedure and augmentation ileocystoplasty are safe and effective when all available pharmacological treatments and clean intermittent catheterization have failed.

Adolescent↗