Statistical Model for the Orientation of Nonspherical Particles Settling in Turbulence

The orientation of small anisotropic particles settling in a turbulent fluid determines some essential properties of the suspension. We show that the orientation distribution of small heavy spheroids settling through turbulence can be accurately predicted by a simple Gaussian statistical model that takes into account particle inertia and provides a quantitative understanding of the orientation distribution on the problem parameters when fluid inertia is negligible. Our results open the way to a parametrization of the distribution of ice crystals in clouds, and potentially lead to an improved understanding of radiation reflection or particle aggregation through collisions in clouds.

How are cytochrome b561 electron currents controlled by membrane voltage and substrate availability?

Direct recordings of electron currents mediated by cytochromes b561 (CYB561) are not available yet, despite the importance of these proteins in a variety of physiological functions, including neurotransmitter synthesis and dietary iron uptake. Here, we used the two-electrode voltage-clamp technique applied to Xenopus oocytes to demonstrate, for the first time, the generation of electron currents by a Drosophila member of the CYB561 superfamily named stromal cell-derived receptor 2 (SDR2). This experimental method, along with the theoretical development of a three-state kinetic model, supports the hypothesis that electron donor/acceptor concentrations and transmembrane voltage mutually control SDR2-mediated electron transport activity in a complex but predictable manner.

The role of the C-terminus for functional heteromerization of the plant channel KDC1

Voltage-gated potassium channels are formed by the assembly of four identical (homotetramer) or different (heterotetramer) subunits. Tetramerization of plant potassium channels involves the C-terminus of the protein. We investigated the role of the C-terminus of KDC1, a Shaker-like inward-rectifying K(+) channel that does not form functional homomeric channels, but participates in the formation of heteromeric complexes with other potassium alpha-subunits when expressed in Xenopus oocytes. The interaction of KDC1 with KAT1 was investigated using the yeast two-hybrid system, fluorescence and electrophysiological studies. We found that the KDC1-EGFP fusion protein is not targeted to the plasma membrane of Xenopus oocytes unless it is coexpressed with KAT1. Deletion mutants revealed that the KDC1 C-terminus is involved in heteromerization. Two domains of the C-terminus, the region downstream the putative cyclic nucleotide binding domain and the distal part of the C-terminus called K(HA) domain, contributed to a different extent to channel assembly. Whereas the first interacting region of the C-terminus was necessary for channel heteromerization, the removal of the distal K(HA) domain decreased but did not abolish the formation of heteromeric complexes. Similar results were obtained when coexpressing KDC1 with the KAT1-homolog KDC2 from carrots, thus indicating the physiological significance of the KAT1/KDC1 characterization. Electrophysiological experiments showed furthermore that the heteromerization capacity of KDC1 was negatively influenced by the presence of the enhanced green fluorescence protein fusion.

Solution structure of the phytotoxic protein PcF: the first characterized member of the Phytophthora PcF toxin family

The PcF protein from Phytophthora cactorum is the first member of the "PcF toxin family" from the plant pathogens Phytophthora spp. It is able to induce withering in tomato and strawberry leaves. The lack of sequence similarity with other proteins hampers the identification of the molecular mechanisms responsible for its toxicity. Here, we show that the six cysteines form a disulphide pattern that is exclusive for PcF and essential for the protein withering activity. The NMR solution structure identifies a novel fold among protein effectors: a helix-loop-helix motif. The presence of a negatively charged surface suggests that it might act as a site of electrostatic interaction. Interestingly, a good fold match with Ole e 6, a plant protein with allergenic activity, highlighted the spatial superimposition of a stretch of identical residues. This finding suggests a possible biological activity based on molecular mimicry.

Quantification of electrical field-induced flow reversal in a microchannel

We characterize the electroosmotic flow in a microchannel with field effect flow control. High resolution measurements of the flow velocity, performed by micro particle image velocimetry, evidence the flow reversal induced by a local modification of the surface charge due to the presence of the gate. The shape of the microchannel cross-section is accurately extracted from these measurements. Experimental velocity profiles show a quantitative agreement with numerical results accounting for this exact shape. Analytical predictions assuming a rectangular cross-section are found to give a reasonable estimate of the velocity far enough from the walls.

The zinc binding site of the Shaker channel KDC1 from Daucus carota

KDC1 is a voltage-dependent Shaker-like potassium channel subunit cloned from Daucus carota which produces conductive channels in Xenopus oocytes only when coexpressed with other plant Shaker potassium subunits, such as KAT1 from Arabidopsis thaliana. External Zn(2+) determines a potentiation of the current mediated by the dimeric construct KDC1-KAT1, which has been ascribed to zinc binding at a site comprising three histidines located at the S3-S4 (H161, H162) and S5-S6 (H224) linkers of KDC1. Here we demonstrate that also glutamate 164, located in close proximity of the KDC1 S4 segment, is an essential component of the zinc-binding site. On the contrary, glutamate 159, located in symmetrical position with respect to E164 in the sequence E(159)XHHXE(164) but more distant from the voltage sensor, does not play any role in zinc binding. The effects of Zn(2+) can be expressed as a "shift" of the gating parameters along the voltage axis. Kinetic modeling shows that Zn(2+) slows the closing kinetics of KDC1-KAT1 without affecting the opening kinetics. Possibly, zinc affects the movement of the voltage sensor in and out of the membrane phase through electrostatic modification of a site close to the voltage sensor.

Stoichiometry studies reveal functional properties of KDC1 in plant shaker potassium channels

Functional heteromeric plant Shaker potassium channels can be formed by the assembly of subunits from different tissues, as well as from diverse plant species. KDC1 (K(+) Daucus carota 1) produces inward-rectifying currents in Xenopus oocytes when coexpressed with KAT1 and other subunits appertaining to different plant Shaker subfamilies. Owing to the presence of KDC1, resulting heteromeric channels display slower activation kinetics, a shift of the activation threshold toward more negative membrane potentials and current potentiation upon the addition of external zinc. Despite available information on heteromerization of plant Shaker channels, very little is known to date on the properties of the various stoichiometric configurations formed by different subunits. To investigate the functional properties of heteromeric nKDC1/mKAT1 configurations, we realized a series of dimeric constructs combining KDC1 and KAT1 alpha-subunits. We found that homomeric channels, formed by monomeric or dimeric alpha-subunit constructs, show identical biophysical characteristics. Coinjections of diverse tandem constructs, instead, displayed significantly different currents proving that KDC1 has high affinity for KAT1 and participates in the formation of functional channels with at most two KDC1 subunits, whereas three KDC1 subunits prevented the formation of functional channels. This article brings a contribution to the understanding of the molecular mechanisms regulating plant Shaker channel functionality by association of modulatory subunits.

KDC2, a functional homomeric potassium channel expressed during carrot embryogenesis

In Daucus carota, the model system for embryogenesis, it has been demonstrated that potassium and K(+) selective channels are involved in embryo development. Here, we report the isolation and cloning of a new carrot Shaker-like potassium channel, potassium D. carota channel 2 (KDC2), whose expression pattern during somatic embryogenesis proceeds along with the establishment of the polar axes and the settlement of the hypocotyl region. In plants, KDC2 transcript is localized at the shoot level, in the epidermis and guard cells, similarly to its Arabidopsis homolog KAT1. Electrophysiological assays indicated KDC2 as the first carrot subunit able to form homomeric functional channels in Xenopus oocytes, with properties similar to those of Arabidopsis KAT1.

Plant K(in) and K(out) channels: approaching the trait of opposite rectification by analyzing more than 250 KAT1-SKOR chimeras

Members of the Shaker-like plant K(+) channel family share a common structure, but are highly diverse in their function: they behave as either hyperpolarization-activated inward-rectifying (K(in)) channels, or leak-like (K(weak)) channels, or depolarization-activated outward-rectifying (K(out)) channels. Here we created 256 chimeras between the K(in) channel KAT1 and the K(out) channel SKOR. The chimeras were screened in a potassium-uptake deficient yeast strain to identify those, which mediate potassium inward currents, i.e., which are functionally equivalent to KAT1. This strategy allowed us to identify three chimeras which differ from KAT1 in three parts of the polypeptide: the cytosolic N-terminus, the cytosolic C-terminus, and the putative voltage-sensor S4. Additionally, mutations in the K(out) channel SKOR were generated in order to localize molecular entities underlying its depolarization activation. The triple mutant SKOR-D312N-M313L-I314G, carrying amino-acid changes in the S6 segment, was identified as a channel which did not display any rectification in the tested voltage-range.

Vitamin E-coated dialyzers reduce oxidative stress related proteins and markers in hemodialysis--a molecular biological approach

BACKGROUND

Hemodialysis patients (HD) are exposed to oxidative stress which contributes to cardiovascular disease and accelerated atherosclerosis, major causes of mortality in these patients. A new dialysis membrane coated with vitamin E has been proposed against oxidative stress and atherosclerosis due to their ability to inhibit lipid peroxidation by interacting with scavengers. The mechanisms however are not completely clarified. This study evaluated, using a molecular biology approach, the effect of 6 months treatment with vitamin E-modified dialyzers, CL-E, on the gene expression of oxidative stress related proteins and markers.

PATIENTS AND METHODS

To this end, the gene expression of p22phox, a NAD(P)H oxidase subunit closely linked with the generation of superoxide anions and of Heme oxygenase-1 (HO-1), induced by and protective from oxidative stress, were evaluated by RT-PCR in mononuclear cells from 5 patients under 3 times a week chronic bicarbonate dialysis. Hydroperoxide (HPO) and total antioxidant power (AOP) plasma levels were evaluated at 3 and 6 months of treatment. HPO was also evaluated in 8 patients under CL-E treatment for 1 year and compared with 8 patients treated with cuprammonium-ryon filter (TAF).

RESULTS

p22phox mRNA decreased from 0.61 +/- 0.05 d.u. to 0.48 +/- 0.03, p < 0.01 while HO-1 increased from 0.55 +/- 0.04 d.u. to 0.62 +/- 0.03, p < 0.01. HPO decreased in CL-E treated patients: from 2.72 +/- 0.26 microM to 1.45 +/- 0.27 at 3 months (p < 0.001) to 0.87 +/- 0.11, p < 0.001 at 6 months, while AOP increased: from 752 +/- 90 mmol/L to 1057 +/- 105, p < 0.001 at 6 months. HPO was also reduced in 1 year Excebrane CL-E treated patients compared with cuprammonium treated patients: 2.25 +/- 0.3 vs. 1.42 +/- 0.11 microM, p < 0.001.

CONCLUSION

The reduced expression of oxidative stress related proteins and markers gives further support to the efficacy of the use of Vitamin E coated dialysers for the prevention or slowing progression of cardiovascular disease and atherosclerosis, major complications and causes of mortality in these patients in which oxidative stress plays a pivotal role.

DKT1, a novel K+ channel from carrot, forms functional heteromeric channels with KDC1

We report the isolation and characterisation of DKT1, a new carrot K+ channel alpha-subunit belonging to the Shaker-like family. DKT1 is expressed in many tissues of the adult plant, suggesting that it may play important roles in both nutrition and other important physiological processes. During embryo development, DKT1 is expressed at later phases implying the involvement of K+ in embryo maturation. When co-expressed with KDC1 in Xenopus oocytes, DKT1 is able to form functional, heteromeric channels, suggesting that possible interactions between these two ion channels in plant tissues may modulate K+ uptake.

Histidines are responsible for zinc potentiation of the current in KDC1 carrot channels

Unlike all plant inward-rectifying potassium channels, the carrot channel KDC1 has two histidine pairs (H161,H162) in the S3-S4 and (H224,H225) in the S5-S6 linkers. When coinjected with KAT1 in Xenopus oocytes, KDC1 participates in the formation of heteromultimeric KDC1:KAT1 channels and the ionic current is potentiated by extracellular Zn2+. To investigate the potential interactions between KDC1 and zinc, a KDC1-KAT1 dimer was constructed. The dimeric and heteromeric channels displayed similar characteristics and the same sensitivity to zinc and other metals; this result suggests that zinc binding is mediated by residues in a single channel subunit. The KDC1:KAT1 currents were also potentiated by external Pb2+ and Cd2+ and inhibited by Ni2+. To investigate further the role of KDC1-histidines, these amino acids were mutated into alanines. The single mutations H225A, H161A, and H162A did not affect the response of the heteromeric channels to zinc. Conversely, the single mutant H224A and the double mutants (H224A,H225A) and (H161A,H162A) abolished zinc potentiation, but not that induced by Pb2+ or Cd2+. These results suggest that Zn2+ potentiation cannot be ascribed to simple electrostatic interactions between zinc and channel residues and that histidine 224 is crucial for zinc but not for lead potentiation of the current.

ALEX (artificial liver for extracorporeal xenoassistance): a new bioreactor containing a porcine autologous biomatrix as hepatocyte support. Preliminary results in an ex vivo experimental model

Long-term maintenance of viability and expression of differentiated hepatocyte function is crucial for bioartificial liver support. We developed a new bioreactor design (ALEX), associated with a new extracellular autologous hepatocyte biomatrix (Porcine Autologous Biomatrix - PBM) support. To test this new bioreactor, we compared it to a standard BAL (BioArtificial Liver) cartridge in a ex vivo model using human plasma added to bilirubin, ammonium and lidocaine. A pathology study was performed on both bioreactors. The results suggest that ALEX allows a maximal contact between the perfusing plasma and the liver cells and a proper hepatocyte support by a cell-to-matrix attachment. ALEX is a suitable cell support bioreactor, guaranteeing long-term maintenance of the metabolic activity of hepatocytes when compared to a standard BAL cartridge.

Beneficial effects of L-carnitine in dialysis patients with impaired left ventricular function: an observational study

BACKGROUND

Recent studies have shown that L-carnitine may improve clinical status and reduce the need for erythropoietin in dialysis patients with cardiovascular diseases. In this observational study, we investigated whether the addition of L-carnitine to conventional therapy might improve cardiac function (as assessed by M-mode and two-dimensional echocardiography) and clinical status in dialysis patients with left ventricular dysfunction.

METHODS

Eleven dialysis patients with reduced left ventricular function (EF < 45%) were treated with L-carnitine for 8 months. Two-dimensional (2-D) echocardiography was performed at baseline and every 2 months up to the end of the treatment period. The dosage of erythropoietin was also monitored during the study and the patients' clinical status was assessed by a questionnaire.

RESULTS

Carnitine increased mean LV ejection fraction from 32.0% to 41.8% (p < 0.05 vs baseline). There was also a slight reduction of erythropoietin dosage and an improvement of clinical status.

CONCLUSIONS

Eight months' therapy with carnitine appears to improve LV function and clinical status in dialysis patients with impaired LVF.

Liver-kidney-transplantation in type 1 primary hyperoxaluria: description and comments on a case

BACKGROUND

Primary hyperoxaluria leads to oxalosis, a systemic illness with fatal prognosis in uremic youngsters because of systemic complications.

CASE REPORT

A 14-year old boy with primary type 1 hyperoxaluria who had a long-lasting history of nephrolithiasis and passed from normal renal function to end-stage renal disease within 7 months. MEASUREMENT of alanine: glyoxylate aminotransferase (AGT) catalytic activity in the liver biopsy disclosed very low activity which was not. responsive to pyridoxin., thus the patient entered onto a priority national waiting list for liver-kidney transplantation and a week later received a combined transplant. In order to increase body clearance of oxalate, the patient underwent medical treatment to increase urine oxalate solubility (sodium and potassium citrate oral therapy, magnesium supplementation and increase of diuresis) and intensive dialysis both before and after transplantation.

COMMENT

The medical approach to the treatment of this rare illness is discussed. Since the major risk for the grafted kidney is related to the oxalate burden, i.e. oxalate deposition from the body deposits to the kidney that becomes irreversibly damaged, treatment consists of increasing the body clearance of oxalate both by increasing oxalate solubility in the urine and with intensive dialysis performed both before and after combined transplantation. To the same extent (by limiting body oxalate deposits), a relatively early (native GFR 20-25 ml/minute) transplantation is advisable.

Reduction of homocysteine levels in coronary artery disease by low-dose folic acid combined with vitamins B6 and B12

An increased plasma homocysteine concentration is a risk factor for atherosclerosis. Folic acid lowers homocysteine but the optimal dose in patients with coronary artery disease (CAD) is unclear. This placebo-controlled, single-blind, dose-ranging study evaluates the effect of low-dose folic acid on homocysteine levels in 95 patients aged 61 +/- 11 years (mean +/- SD) with documented CAD. Patients in each group were given either placebo or 1 of 3 daily supplements of folic acid (400 microg, 1 mg, or 5 mg) for 3 months. Each active treatment arm also received 500 microg vitamin B12 and 12.5 mg vitamin B6. Total plasma homocysteine levels were measured after 30 and 90 days. Folic acid 400 microg reduced homocysteine levels from 13.8 +/- 8.8 to 9.6 +/- 2.0 micromol/L at 90 days (p = 0.001). On 1- and 5-mg folic acid, levels decreased from 13.0 +/- 6.4 to 9.8 +/- 4.0 micromol/L (p = 0.001) and from 14.8 +/- 6.9 to 9.7 +/- 3.3 micromol/L (p < 0.001), respectively. The decrease was similar in all treatment groups. There was no significant change with placebo. Although the sample size is small, these findings suggest that daily administration of 400 microg/day folic acid combined with vitamin B12 and vitamin B6 may be equivalent to higher doses in reducing homocysteine levels in patients with CAD.

The effect of metabolic control on development and progression of diabetic nephropathy

The progressively growing number of patients with end-stage renal failure (ESRF) associated with diabetes mellitus and requiring renal replacement therapy (RRT) stimulated both nephrologists and diabetologists to investigate the mechanisms linking hyperglycaemia to diabetic renal failure and to set up measures to prevent the onset and slow the progression of diabetic nephropathy. Over the last few decades, a large number of studies have investigated both the incidence of diabetic nephropathy and the relationship between metabolic control and the development of diabetic nephropathy. Chronologically, the first type of diabetes and diabetic nephropathy to be studied was type I, and it is only in recent years that metabolic control has been proven to be a contributor to the development of nephropathy in such patients. Recently, the DCCT demonstrated that metabolic control in the prealbuminuric phase was effective in reducing the incidence of microalbuminuria, even if it was unable to reduce the incidence of overt proteinuria in patients with type I diabetes and established proteinuria. On the other hand, in type II diabetes, the number of studies demonstrating a favourable effect of metabolic control on onset and progression of diabetic nephropathy is only slightly greater than those that failed to show a favourable effect. This feature may suggest that in type II patients, genetic and ethnic differences, nutritional aspects, lifestyle and other confounding factors may play a relevant role in the course of the disease. However, the trials performed and the retrospective analyses generally agree that glycated haemoglobin two standard deviations greater than the mean is related to a worsening in progression of diabetic nephropathy and to an enhanced risk of other complications. In general, a glycated haemoglobin < or =8% seems advisable. Moreover, in both type I and type II, greater emphasis should be placed on the major risk factors such as hypertension, smoking habits and hyperlipidaemia.

Short-term outcome of diabetic patients in renal replacement therapy

BACKGROUND

Diabetic nephropathy or diabetes-related nephropathies represents one of the most relevant causes of renal failure in recent years. This complex pathological picture becomes particularly severe as time elapses and after starting renal replacement therapy (RRT).

METHODS

In an attempt to investigate the evolution of the major clinical features, a retrospective study was carried out on a cohort of 76 diabetic patients on RRT. Sixty-five have been treated by haemodialysis (HD) and 11 by peritoneal dialysis (CAPD), for at least 1 year. In these patients change in modality of treatment, metabolic control, cardiovascular, and ophthalmological complications, peripheral neuropathy, state of vascular access, and intradialytic complications were surveyed at initiation and after 1 year of treatment. A modified Karnofski's score was utilized, to evaluate the degree of rehabilitation. The comparison of prevalence was evaluated, using Student's t-test for paired samples.

RESULTS

After 1 year, 11 patients on CAPD remained on the same type of treatment. Out of 65 patients on standard bicarbonate HD, 11 were moved to acetate free biofiltration, two to paired filtration dialysis and one to haemofiltration. A worsening in arrhythmias was recorded with an increased prevalence from 25.0 to 35.0% (n.s.), and one more patient (15 vs 16 and 19 vs 20 respectively) experienced ischaemic cardiomyopathy and cerebrovascular insufficiency. Hypertension showed a significant improvement (72 vs 42, P<0.01). Nausea and vomiting, hypotensive episodes, and muscular cramps were more frequently observed. A worsening in patient's welfare was also recorded but without statistical significance.

CONCLUSIONS

This clinical evaluation even if retrospective and lasting 1 year, may suggest that RRT does not per se represent a cause of the development and progression of the major complications related to diabetic disease.

Prospective study of hyperhomocysteinemia as an adverse cardiovascular risk factor in end-stage renal disease

BACKGROUND

Retrospective and case-control studies show that hyperhomocysteinemia is an independent risk factor for atherosclerosis in patients with end-stage renal disease. We studied prospectively the association between total homocysteine and cardiovascular outcomes.

METHODS AND RESULTS

In all, 167 patients (93 men, 74 women; mean age, 56.3+/-14.7 years) were followed for a mean duration of 17.4+/-6.4 months. Cardiovascular events and causes of mortality were related to total homocysteine values and other cardiovascular risk factors. Cox regression analysis was used to identify the independent predictors for cardiovascular events and mortality. Fifty-five patients (33%) developed cardiovascular events and 31 (19%) died, 12 (8%) of cardiovascular causes. Total plasma homocysteine values ranged between 7.9 and 315.0 micromol/L. Levels were higher in patients who had cardiovascular events or died of cardiovascular causes (43.0+/-48.6 versus 26.9+/-14.9 micromol/L, P=.02). The relative risk (RR) for cardiovascular events, including death, increased 1% per micromol/L increase in total homocysteine concentration (RR, 1.01; CI, 1.00 to 1.01; P=.01).

CONCLUSIONS

These prospective observations confirm that hyperhomocysteinemia is an independent risk factor for cardiovascular morbidity and mortality in end-stage renal disease, with an increased RR of 1% per micromol/L increase in total homocysteine concentration. Interventional studies are needed to evaluate the possible effects of modifying this risk factor in these patients.

[Relationship between late ventricular potentials and ventricular arrhythmias in patients in chronic dialysis treatment]

BACKGROUND

Arrhythmias are frequent pathology in patients with chronic hemodialysis. We evaluated whether a relatively new technique, signal averaging, could be useful in predicting the development of complex arrhythmias in these patients.

METHODS

Thirty-three patients, 18 male and 15 female, subjected to thrice weekly chronic hemodialytic treatment with various dialysis techniques, were studied. Exclusion criteria were the presence of antiarrhythmic and inotropic treatment. The following examinations were carried out in all patients: a Holter dynamic electrocardiography for a duration of 24 hours, begun on the day of dialysis, high resolution ECG pre- and post-dialysis to find out if there were any ventricular late potential (VLP). Four hundred beats were examined in order to obtain a background noise of less than 0.7 microV and a better definition of the signal. The following parameters were considered significant for the presence of VLP: a) filtered QRS duration > 120 msec; b) the root mean square of the signal expressed in the terminal portion of QRS (RMS) < 25 microV) high frequency low amplitude signals duration (HFLA) > 40 msec. A positive value in two of these parameters was considered indicative of the presence of VLP. In addition various pre and post-dialysis indices of dialytic efficiency and a mono and two-dimensional echocardiogram with pulsed and color Doppler were carried out. Of the 33 patients studied, ten were excluded because they presented too high a background noise at the high resolution ECG. Of the remaining 23 patients, 13 (56%) presented VLP and nine of these (69%) presented complex arrhythmias. Of the ten patients without VLP, 5 (50%) presented complex arrhythmias. The incidence of arrhythmias was highest during the last two hours of dialysis and in the two hours following it. The patients were then divided into two groups (A and B) according to the ejection fraction (EF) found at the echocardiogram. Group A was composed of 17 patients of whom 8 (47%) presented complex arrhythmias; group B (EF < 45%) was composed of the remaining six patients, who all presented complex arrhythmias. In group A nine patients (53%) out of 17 had LVP, in group B four out of six (66%) had it. All the patients except one presented an increase in the thickness of the ventricular wall and alterations of Doppler transmitral filling rate. Left ventricular hypertrophy was diagnosed in 22 out of the 23 patients. Four patients also had chronic ischaemic heart disease; of these three had LVP. There was no correlation between the presence of LVP and the hemodialytic indices and between the latter and complex arrhythmias.

CONCLUSIONS

Our study showed that arrhythmias are more frequent in patients with LVP before dialysis than in those without. The difference was statistically significant (p < 0.006); the incidence of arrhythmias was higher in patients with FE < 45% (p < 0.001). The majority of patients (95%) had left ventricular hypertrophy; only four (17%) had ischaemic heart disease too. It is highly probable that the presence of LVP in our patients can be attributed to hypertension and subsequent left ventricular hypertrophy. As patients with LVP at the end of dialysis had a greater incidence of arrhythmias than those without LVP, we suggest that this method could be useful as a first screening in dialysed patients.

Tissue factor pathway inhibitor (TFPI) activity in uremic patients during hemodialysis

We studied tissue factor pathway inhibitor (TFPI) activity during hemodialysis in 10 uremic patients who were not receiving anticoagulant for at least 120 minutes. TFPI activity before dialysis was normal (patients 107 +/- 5.8%, controls 104 +/- 4.5%). During extracorporeal circuit it rose progressively with a statistically significant difference, reaching a plateau between 60 and 120 minutes. Since thrombin induces a marked redistribution and release of TFPI from stimulated endothelial cells and platelets contain about 10% of TFPI activity that is secreted following activation it is possible that thrombin-induced release of TFPI by endothelium and platelets could account for the increased TFPI we found during hemodialysis. To investigate this possibility we measured during dialysis beta-thromboglobulin (beta-TG), thrombin-antithrombin complex (TAT) and prothrombin fragment 1.2 (F 1.2). The increased levels of beta-TG, TAT and F1.2 we noted during extracorporeal circuit are in keeping with this concept. One hundred eighty minutes after initiation of dialysis, by which time all patients were receiving heparin there was a further increase in TFPI (to more than 200% of baseline), due to the presence of the glycosaminoglycan. This was due the previously reported displacement by heparin of the major intravascular pool of TFPI, from endothelial cell surfaces.

Nitric oxide synthase in chick embryo retina during development

High levels of nitric oxide synthase were found in the early stages of developing chick embryo retina. The enzyme activity sharply decreased up to 13-day-old chick embryo retina, when the level of the last embryonic day was reached. The results show that nitric oxide is synthesized in chick embryo retina prior to synaptogenesis. The incubation of chick embryo retinas in presence of NMDA increased the synthesis of nitric oxide, thus, the appearance of nitric oxide production before the synaptogenesis in the retina as well as in the brain may be considered as signal for the development and shaping of neuronal and non-neuronal cells.

[Study of the arrhythmia in patients with chronic uremia in periodic hemodialysis with Holter dynamic electrocardiography]

For the purpose of evaluating cause, frequency, type and seriousness of arrhythmias in dialysis patients, 14 chronic uremics, 8 on bicarbonate-dialysis, 6 on acetate-dialysis underwent a basal ECG, echocardiography and a Holter dynamic electrocardiography (ECGD) for a duration of 96 hours. Before and after dialysis PAO, body weight, serum electrolytes and arterial pH were controlled. In 11 patients (78%) supraventricular and ventricular arrhythmias were discovered of equal frequency and seriousness both in the inter and intra dialytic phase, even if more frequent in ventricular hypertrophic patients (IVSn) the complex ventricular arrhythmias (Lown greater than 2). The seriousness and frequency of ventricular and supraventricular arrhythmias in the dialytic phase did not seem to depend either on the type of tampon or on the presence or absence of cardiopathies while in the inter-dialytic phase the seriousness of ventricular arrhythmias seems to depend upon the presence of cardiopathies. The Authors conclude that the pathogenesis of arrhythmias in uremic patients on dialysis is multifactorial and that their elevated incidence makes the use of a Holter in these patients recommendable.

Biofiltration vs. bicarbonate dialysis: influence on plasma volume changes and extravascular fluid mobilization

The present study compares the effects of bicarbonate hemodialysis (Bic. HD) and biofiltration (BF), a new hemodiafiltration technique, on plasma volume (PV) changes and extravascular fluid mobilization (Vfm). Ten uremic patients underwent one experimental session of Bic. HD and, one week later, one of BF, both on the second dialysis of the week. Net ultrafiltration rate was limited to 700 ml/min. At the start of each session, whole blood volume (WBV), PV and red cell volume (RCV) were determined using 5 mu Ci of radioiodinated serum albumin (RISA). PV and Vfm were calculated at hourly intervals using a serial hematocrit method. On Bic. HD, PV increased at 60 min. then decreased at 120 and 180 min., with efficient Vfm only during the first hour. On BF, PV increased throughout treatment, with greater Vfm. It would appear that PV is better preserved in BF, on account of more efficient Vfm.

Carnitine deficiency induced during hemodialysis and hyperlipidemia: effect of replacement therapy

Plasma carnitine levels were studied in 14 uremic patients before, during, and after hemodialysis. The predialysis plasma carnitine levels were normal but fell during dialysis (half-life of 3.6 h). Plasma carnitine levels rose quickly in the first 6 h after dialysis, after which time the rise was more gradual. Muscle carnitine was significantly reduced in the dialyzed patients (p less than 0.005) compared with controls. In four patients lipid droplets were observed in muscle. Ten patients on maintenance hemodialysis exhibited plasma hyperlipidemia and low muscle carnitine. These individuals were given DL-carnitine (50 mg/kg body weight) intravenously after each dialysis. At the end of a 2-month carnitine treatment, plasma triglyceride levels were found to be reduced (p less than 0.001) and muscle carnitine content significantly increased (p less than 0.005). These findings suggest that carnitine may be useful in treatment of hypertriglyceridemia and muscle carnitine deficiency states induced during maintenance hemodialysis.