Unveiling oxygen vacancy impact on lizardite thermo and mechanical properties.

Here, we performed a systematic DFT study assisted by the workflow framework SimStack for the mechanical and thermodynamic properties of the clay mineral lizardite in pristine and six different types of O vacancies configurations. In most cases, the defect caused a structural phase transition in the lizardite from the trigonal (pristine) to the triclinic phase. The results show that oxygen vacancies in lizardite significantly reduce the lattice thermal conductivity, accompanied by an elastic moduli reduction and an anisotropy index increase. Through the P-V relation, an increase in compressibility was evidenced for vacancy configurations. Except for the vacancy with the same crystalline structure as pristine lizardite, the sound velocities of the other vacancy configurations produce a decrease in these velocities, and it is essential to highlight high values for the Grüneisen parameter. We emphasize the great relevance of the punctual-defects introduction, such as O vacancies, in lizardite, since this microstructural design is responsible for the decrease of the lattice thermal conductivity in comparison with the pristine system by decreasing the heat transfer ability, turning lizardite into a promising candidate for thermoelectric materials.

Electrophysiological response to dialysis: the role of dialysate potassium content and profiling.

UNLABELLED: The task of dialysis therapy is, amongst other things, to remove excess potassium (K+) from the body. The need to achieve an adequate K+ removal with the risk of cardiac arrhythmias due to sudden intra-extracellular K+ gradient advises the distribution of the removal throughout the dialysis session instead of just in the first half. The aim of the study was to investigate the electrical behavior of two different K+ removal rates on myocardial cells (risk of arrhythmia and ECG alterations). Constant acetate-free biofiltration (AFB) and profiled K+ (decreasing during the treatment) AFB (AFBK) were used in a patient sample to understand, first of all, the effect on premature ventricular contraction (PVC) and on repolarization indices [QT dispersion (QTd) and principal component analysis (PCA)]. The study was divided into two phases: phase 1 was a pilot study to evaluate K+ kinetics and to test the effect on the electrophysiological response of the two procedures. The second phase was set up as an extended cross-over multicenter trial in patient subsets prone to arrhythmias during dialysis. Phase 1: PVC increased during both AFB and AFBK but less in the latter in the middle of dialysis (298 in AFB vs. 200 in AFBK). The PVC/h in a subset of arrhythmic patients was 404 +/- 145 in AFB and 309 +/- 116 in AFBK (p = 0.0028). QT interval (QTc) prolongation was less pronounced in AFBK than in AFB. Phase 2: The PVC again increased in both AFB and AFBK but less in the latter mid-way through dialysis (79 +/- 19 AFB vs. 53 +/- 13 AFBK). Moreover, in the most arrhythmic patients the benefit accruing from the smooth K+ removal rate was more pronounced (103 +/- 19 in AFB vs. 78 +/- 13 in AFBK). CONCLUSION: It is not the K+ dialysis removal alone that can be destabilizing from an electrophysiological standpoint, but rather its removal dynamics. This is all the more evident in patients with arrhythmias who benefit from the K+ profiling during their dialysis treatment.

Blood oxidative stress and lipoprotein oxidizability in haemodialysis patients: effect of the use of a vitamin E-coated dialysis membrane.

BACKGROUND: Oxidative stress has been shown in haemodialysis patients in relation with an increased production of free radicals due to membrane-induced complement and leukocyte activation. In order to minimize membrane bioincompatibility and thereby oxidative stress, more compatible filters have been perfected. Among them, a high-flux vitamin E-coated membrane (CL-EE) has been proposed recently. In vivo, little data is available on the consequences of the use of vitamin E-coated membranes. In the present study, the effects of a 3-month use of CL-EE dialysis membranes compared to conventional membranes have been evaluated in 12 haemodialysis patients on the blood oxidative stress status before and after the dialysis session. METHODS: We determined the lipid peroxidation status (plasma thiobarbituric acid-reactive substances) and antioxidant defence (erythrocyte Cu,Zn-superoxide dismutase and plasma and erythrocyte glutathione peroxidase activities, plasma vitamin E, beta-carotene, vitamin A and total antioxidant status). Also, we simultaneously determined the antioxidant content and the copper oxidizability of isolated low density- and high density-lipoproteins (LDLs and HDLs). RESULTS: The main consequence observed under these conditions was a marked enrichment of plasma with vitamin E, which was also significantly and selectively noted in HDLs (no changes in LDL vitamin E content), perhaps related to a specific storage capacity for vitamin E in HDLs of haemodialysis patients. The beta-carotene content of plasma, LDLs and HDLs was also higher after use of vitamin E-coated membranes than after use of high-flux biocompatible membranes. HDL copper oxidizability was reduced (as shown by an increased lag time) before dialysis after use of CL-EE membranes compared to conventional membranes, whereas LDL oxidizability remained unchanged. CONCLUSION: A 3-month use of vitamin E-coated membranes resulted in a significant increase in plasma and HDL vitamin E content, associated with a lower oxidizability of HDLs, which could be beneficial for haemodialysis patients.

A prospective randomised European multicentre study of medium-long run mortality and morbidity comparing acetate-free biofiltration and bicarbonate dialysis.

In recent years, the progressive increase in the mean age of the population entering chronic dialysis treatment has been responsible, on the one hand, for the growing number of patients undergoing regular dialysis, and on the other, for the high number of "critical" patients, both as a result of their age and the presence of concomitant morbidity. Thus, dialysis treatment today is not only aimed at waste removal and water-electrolyte homeostasis, but also at a reduction in morbidity and mortality, and at improving the patients' quality of life, thanks to the use of biocompatible materials and the achievement of good cardiovascular tolerance to treatment. Consequently, diffusive-convective dialysis procedures have been on the increase, since they combine better depuration with the use of biocompatible high-flux membranes. Acetate-free biofiltration (AFB) is a diffusive-convective dialysis procedure which utilises a high-flux membrane, AN69, post-dilution infusion of a sodium bicarbonate solution (NaHCO3), and a dialysate which is completely free of any buffer, and thus also free of acetate, which may have various negative effects on the patient. A number of studies have already shown the better hemodynamic stability and the reduction of intradialytic side-effects during AFB. All these, however, were short-term studies. To verify the beneficial effects of AFB in the long run, a three year multicentre randomised European trial has been proposed to compare bicarbonate hemodialysis (BD), a technique used in nearly 80% of the world's dialysis population, and AFB. The specific aim of the investigation is to verify, in a large number of patients, the results of hemodialysis treatment in terms of morbidity, mortality and quality of life. The study involves 80 hemodialysis units across Italy, France, Germany, Spain, Slovenia and Croatia, with enrollment of about 400 patients considered "critical" for at least one of the following reasons: age, diabetes, dialysis cardiovascular instability. Fifty percent of the patients are to undergo AFB with the AN69 membrane and bicarbonate solution infusion (NaHCO3 145 or 167 mEq/lt), and the other fifty percent are to be treated by BD, with any membrane except the nonmodified cellulosic one. Biochemical, cardiological, and nutritional parameters will be considered throughout the study. Mortality, morbidity both in terms of intra- and interdialysis symptoms - and hospitalisation rate, as well as the patients' quality of life, evaluated by the SF36 questionnaire, will be analysed.

Recurrent seizures alter renal function and plasma atrial natriuretic peptide levels in rats.

Status epilepticus can lead to impaired renal function, which has been attributed to complications of myoglobinuria. We confirmed changes in renal function in the absence of myoglobinuria by measuring renal hemodynamics, fluid and electrolyte excretions, and plasma levels of renin and atrial natriuretic peptide (ANP) before and after a 30-min period of recurrent generalized seizures in anesthetized, paralyzed rats. Renal plasma flow (RPF), renal blood flow (RBF) and glomerular filtration rate (GFR) decreased by approximately 60% after seizures. In contrast, urinary sodium excretion, urine flow, and plasma ANP levels increased approximately threefold. Urinary potassium excretion and plasma renin levels were unchanged. Renal function is profoundly altered after 30 min of seizures, primarily due to intense renal vasoconstriction precipitating a dramatic reduction in GFR. The concomitant increases in sodium and urine excretion may be mediated by the marked increase in plasma ANP levels. The decreases in GFR and RBF might contribute to the renal failure observed in some patients after status epilepticus.

[Popliteal artery entrapment syndrome in our experience]. / La sindrome da intrappolamento dell'arteria poplitea nella nostra esperienza.

Six cases of popliteal entrapment syndrome are presented with emphasis on the diagnostic difficulties related to this disease in its initial functional phase. The utility of Doppler ultrasonography associated with dynamic angiography is underlined. Normally surgical treatment of the disease is problem-free. The important determining factor seems to be medial gemellus hypertrophy. In this case the procedure of choice is thought to be vascular reconstruction associated with the disinsertion of this muscle followed by its reimplantation in a lower and medial position on the semi-membranous tendon muscle in order to avoid any secondary arterial compression.

Renal biofiltration.

Biofiltration is a hemodiafiltration technique performed with a base-free dialysate and simultaneous infusion in postdilution mode of isotonic bicarbonate solution. This technique has the advantages without the inconveniences of bicarbonate dialysis that result from complicated hardware and the need of frequent trouble shooting. In biofiltration, 1) the sodium dialysate concentration should be monitored according to the patient's body weight gain and to the sodium concentration of infusion fluid to obtain adequate sodium mass balance and 2) plasma bicarbonate is easily controlled because the final plasma bicarbonate concentration depends upon the bicarbonate infusion flow rate. Long-term follow-up evaluation (6-24 months) of 76 patients on a dialysis strategy of 3 hr three times a week from 17 European dialysis centers has shown that biofiltration is a simple and safe alternative to bicarbonate dialysis. It could be the way to fulfill the requirements of short time/high quality dialysis, which seems to be the developing trend of dialysis in the future. These advantages are, however, balanced by the extra cost of high flux dialyzers and infusion fluid.

[Is it possible to treat uremia by hemofiltration? Initial clinical results obtained with a poly-acrylo-nytril membrane]. / Peut-on traiter l'urémie par hémofiltration? Premiers résultats cliniques obtenus sur membrane poly-acrylo-nitrile

Following to work of Quellhorst, the authors used an RP6 haemodialyser as an ultrafilter and exchanged 20 litres of plasma ultrafiltrate against 18 to 20 litres of physiological solution during 200 sessions of 4 to 5 hours in 5 patients with uraemia, over a period of 3 to 10 months. The technique is simple and tolerance excellent. The possibility of a new approach to the treatment of uraemia without dialysate makes a large clinical trial worthwhile.

[Periodic hemodialysis. Application of new theories and technics to shortening the dialysis sessions]. / Hémodialyse périodique. Application des théories et techniques nouvelles au raccourcissement des séances de dialyse

Many attempts are now being made to reduce the time of dialysis in chronic uremia. The method developed by Funck-Brentano, Man and Sausse, which includes the use of a highly permeable membrane and precise control of ultrafiltration, is theoretically logical. It was easily applied to 22 unselected patients, treated nine hours weekly for two to eight months. Of course, the follow-up is insufficient. The dosage of products permitting the digestive elimination of phosphorus and potassium must be revised, but the improvement in physical and psychological tolerance of treatment is such that a return to long duration dialysis can no longer be considered possible.