Reconstitution of the Neurospora crassa plasma membrane H+-adenosine triphosphatase

AbstractThe purified H+-ATPase of the Neurospora crassa plasma membrane has been reconstituted by a gel filtration method into lipidic vesicles using sodium deoxycholate as the detergent. Reconstitution was performed for lipid/ATPase ratios ranging from 1000:1 to 5:1 (ww). Whatever the lipid/ATPase ratio, the ATPase molecules completely associate with the lipid vesicles. The ATPase specific activity is identical for all proteoliposomes regardless of the lipid/ATPase ratio, but the H+ transport decreases at high protein/lipid ratios, suggesting that the proteoliposomes are more leaky to H+ as the amount of protein inserted into the lipidic membrane increases. Analysis of the fragments generated by trypsin proteolysis in the presence and in the absence of MgATP + vanadate indicate that most of the reconstituted ATPase molecules are able to assume the transition state of the enzyme dephosphorylation reaction, and are therefore functional. The orientation (inside-out or rightside-out) of the ATPase molecules in the vesicles is independent of the lipid/ATPase ratio chosen for the reconstitution. For all the lipid/ATPase ratios tested, most of the ATPase molecules (> 99%) expose their cytoplasmic side to the outside of the n.-constituted proteoliposomes. The size of the vesicles increases parallel to the ATPase amount. Although the H+ leakiness of our preparation at low lipid/protein ratios prevents proton pumping measurements, the reconstitution procedure described here has the main advantage on other procedures to allow the obtention of vesicles at high protein-to-lipid ratios, facilitating further structural characterization of the ATPase by biochemical and biophysical techniques. Therefore, the procedure described here could be of general interest in the field of membrane protein study

Syndecan-3 and syndecan-4 are enriched in Schwann cell perinodal processes

BACKGROUND: Nodes of Ranvier correspond to specialized axonal domains where voltage-gated sodium channels are highly concentrated. In the peripheral nervous system, they are covered by Schwann cells microvilli, where three homologous cytoskeletal-associated proteins, ezrin, radixin and moesin (ERM proteins) have been found, to be enriched. These glial processes are thought to play a crucial role in organizing axonal nodal domains during development. However, little is known about the molecules present in Schwann cell processes that could mediate axoglial interactions. The aim of this study is to identify by immunocytochemistry transmembrane proteins enriched in Schwann cells processes that could interact, directly or indirectly, with axonal proteins. RESULTS: We show that syndecan-3 (S3) and syndecan-4 (S4), two proteoglycans expressed in Schwann cells, are enriched in perinodal processes in rat sciatic nerves. S3 labeling was localized in close vicinity of sodium channels as early as post-natal day 2, and highly concentrated at nodes of Ranvier in the adult. S4 immunoreactivity accumulated at nodes later, and was also prominent in internodal regions of myelinated fibers. Both S3 and S4 were co-localized with ezrin in perinodal processes. CONCLUSIONS: Our data identify S3 and S4 as transmembrane proteins specifically enriched in Schwann cell perinodal processes, and suggest that S3 may be involved in early axoglial interactions during development

Heart Rate Variability in Idiopathic Dilated Cardiomyopathy: Characteristics and Prognostic Value

AbstractObjectives. This study was designed to evaluate heart rate variability (HRV) in patients with idiopathic dilated cardiomyopathy (IDC), to determine its correlation with hemodynamic variables and ventricular arrhythmias and to evaluate its prognostic value in IDC.Background. Previous studies have shown that HRV could predict arrhythmic events in patients after infarction, but the characteristics of HRV in IDC have not been fully established.Methods. Time domain analysis of HRV on 24-h electrocardiographic (ECG) recording was performed in 93 patients with IDC, and results were compared with those in 63 control subjects.Results. Patients with IDC, even those without congestive heart failure, had significantly lower values for HRV than those of control subjects. HRV was related to left ventricular shortening fraction (R = 0.5, p = 0.0001) and to peak oxygen uptake (R = 0.53, p = 0.01). HRV was not different in patients with runs of ventricular tachycardia or in patients with late potentials on the signal-averaged ECG. During a mean follow-up period (±SD) of 49.5 ± 35.6 months, patients with reduced HRV had an increased risk of cardiac death or heart transplantation (p = 0.006). On multivariate analysis, cardiac events were predicted by increased left ventricular end-diastolic diameter (p = 0.0001), reduced standard deviation of all normal to normal RR intervals (p = 0.02) and increased pulmonary capillary wedge pressure (p = 0.04).Conclusions. Decreased HRV in patients with IDC is related to left ventricular dysfunction and not to ventricular arrhythmias. Analysis of HRV can identify patients with IDC who have an increased risk of cardiac death or heart transplantation

Effect of cardiopulmonary bypass on activated partial thromboplastin time waveform analysis, serum procalcitonin and C-reactive protein concentrations

Abstract Introduction Systemic inflammatory response syndrome (SIRS) is a frequent condition after cardiopulmonary bypass (CPB) and makes conventional biological tests fail to detect postoperative sepsis. Biphasic waveform (BPW) analysis is a new biological test derived from activated partial thromboplastin time that has recently been proposed for sepsis diagnosis. The aim of this study was to investigate the accuracy of BPW to detect sepsis after cardiac surgery under CPB. Methods We conducted a prospective study in American Society of Anesthesiologists' (ASA) physical status III and IV patients referred for cardiac surgery under CPB. Procalcitonin (PCT) and BPW were recorded before surgery and every day during the first week following surgery. Patients were then divided into three groups: patients presenting no SIRS, patients presenting with non-septic SIRS and patients presenting with sepsis. Results Thirty two patients were included. SIRS occurred in 16 patients (50%) including 5 sepsis (16%) and 11 (34%) non-septic SIRS. PCT and BPW were significantly increased in SIRS patients compared to no SIRS patients (0.9 [0.5-2.2] vs. 8.1 [2.0-21.3] ng/l for PCT and 0.10 [0.09-0.14] vs. 0.29 [0.16-0.56] %T/s for BPW; P < 0.05 for both). We observed no difference in peak PCT value between the sepsis group and the non-septic SIRS group (8.4 [7.5-32.2] vs. 7.8 [1.9-17.5] ng/l; P = 0.67). On the other hand, we found that BPW was significantly higher in the sepsis group compared to the non-septic SIRS group (0.57 [0.54-0.78] vs. 0.19 [0.14-0.29] %T/s; P < 0.01). We found that a BPW threshold value of 0.465%T/s was able to discriminate between sepsis and non-septic SIRS groups with a sensitivity of 100% and a specificity of 93% (area under the curve: 0.948 +/- 0.039; P < 0.01). Applying the previously published threshold of 0.25%T/s, we found a sensitivity of 100% and a specificity of 72% to discriminate between these two groups. Neither C-reactive protein (CRP) nor PCT had significant predictive value (area under the curve for CRP was 0.659 +/- 0.142; P = 0.26 and area under the curve for PCT was 0.704 +/- 0.133; P = 0.15). Conclusions BPW has potential clinical applications for sepsis diagnosis in the postoperative period following cardiac surgery under CPB

Insulin induces a positive relationship between the rates of ATP and glycogen changes in isolated rat liver in presence of glucose; a (31)P and (13)C NMR study

BACKGROUND: There is an emerging theory suggesting that insulin, which is known to be the predominant postprandial anabolic hormone, is also a major regulator of mitochondrial oxidative phosphorylation in human skeletal muscle. However, little is known about its effects in the liver. Since there is a theoretical relationship between glycogen metabolism and energy status, a simultaneous and continuous investigation of hepatic ATP and glycogen content was performed in intact and isolated perfused liver by (31)P and (13)C nuclear magnetic resonance (NMR) The hepatic rates of ATP and glycogen changes were evaluated with different concentrations of insulin and glucose during continuous and short-term supply. RESULTS: Liver from rats fed ad libitum were perfused with Krebs-Henseleit Buffer (KHB)(controls) or KHB containing 6 mM glucose, 30 mM glucose, insulin alone, insulin + 6 mM glucose, insulin + 30 mM glucose. In the control, glycogenolysis occurred at a rate of -0.53 ± 0.021 %·min(-1) and ATP content decreased at a rate of -0.28 ± 0.029 %·min(-1). In the absence of insulin, there was a close proportional relationship between the glycogen flux and the glucose concentration, whereas ATP rates never varied. With insulin + glucose, both glycogen and ATP rates were strongly related to the glucose concentration; the magnitude of net glycogen flux was linearly correlated to the magnitude of net ATP flux: flux(glycogen )= 72.543(flux(ATP)) + 172.08, R(2 )= 0.98. CONCLUSION: Only the co-infusion of 30 mM glucose and insulin led to (i) a net glycogen synthesis, (ii) the maintenance of the hepatic ATP content, and a strong positive correlation between their net fluxes. This has never previously been reported. The specific effect of insulin on ATP change is likely related to a rapid stimulation of the hepatic mitochondrial oxidative phosphorylation. We propose that variations in the correlation between rates of ATP and glycogen changes could be a probe for insulin resistance due to the action of substrates, drugs or pathologic situations. Consequently, any work evaluating insulin resistance on isolated organs or in vivo should determine both ATP and glycogen fluxes

Les habitudes des enseignants et les intentions didactiques des nouveaux programmes d'électricité en classe de quatrième

La mise en place de nouveaux programmes nécessite, de la part des enseignants, une prise en compte des intentions des rédacteurs puis une traduction de celles-ci en actes pédagogiques. Nous nous intéressons ici à la perception que les enseignants ont des intentions didactiques contenues dans le nouveau programme d'électricité de la classe de quatrième en France. Des entretiens semi-directifs, conduits avec neuf enseignants, semblent montrer que leur expérience professionnelle, leurs habitudes, limitent leur perception des nouveautés malgré une bonne connaissance des difficultés que les modifications de programme visent à résoudre. Les formes particulières de cet effet de filtrage sont analysées. On observe à ce propos qu'il peut être utile d'associer des intentions didactiques nouvelles à un objet matériel lui-même nouveau qui leur serve de support

Impact of timing administration of mesenchymal stromal cells on serum creatinine following renal ischemia/ reperfusion in rats

peer reviewedExperimental models of renal ischemia/reperfusion (I/R) have suggested protective effects of mesenchymal stromal cells (MSC) therapy. Still, param- eters of MSC injection, including volume, route and timing of cell administration, remain largely debated. Particularly, MSC infusion in mouse has been shown to be beneficial “a priori” but deleterious “a posteriori” of renal I/R injury. In order to further investigate the influence of the timing of MSC administration, we used 10-week-old Lewis rats categorized in 4 groups. Groups 1 (MSC D-7, n = 10) and 2 (MSC D + 1, n = 7) received caudal i.v. injection of MSC (1.5 9 106 in 1 ml of saline) 7 days before or 1 day after renal I/R, respectively. Control groups 3 (saline D-7, n = 6) and 4 (saline D + 1, n = 6) received equal volume of saline at similar time points. Left renal ischemia (by clamping of the renal pedicle) lasted 45 min. Right nephrectomy was simultaneously performed. Blood sample was collected from inferior vena cava at 48 h post reperfusion. MSC phenotype was confirmed by FACS analysis. In groups 1 and 3, serum creatinine (SCr) reached 1.4 ` 0.7 versus 2.4 ` 0.8 mg/dl, respectively (p < 0.05). In groups 2 and 4, SCr was 4.9 ` 0.7 versus 3.3 ` 0.9 mg/dl, respectively (p < 0.001). Furthermore, SCr levels were statistically worse when MSC were administered after renal I/R in comparison to a priori infusion (p < 0.0001). In conclusion, MSC administration 7 days prior to renal I/R attenuates kidney injury in comparison to (i) saline infusion or (ii) MSC infusion 1 day after renal I/R. Conversely, on the basis of SCr levels, MSC therapy performed after renal I/R worsens kidney injury in rats