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Biomedical subjects

R Lubrano

Publications and source records attributed to R Lubrano.

At least 37 records · Page 2Linked to original sources
PubMed1988

Discrepancies between serum and erythrocyte concentrations of vitamin E in hemodialysis patients: role of HDL-bound fraction of vitamin E.

Recently, we have demonstrated that hemodialysis (HD) patients have higher serum and lower erythrocyte concentrations of vitamin E than controls. It is known that transfer of vitamin E from serum to erythrocyte is mostly due to high-density lipoproteins (HDL). For a better definition of the pattern of distribution of vitamin E in HD patients, we have dosed the amount of vitamin bound to serum HDL fraction. In 8 patients and in 8 healthy controls, we have determined the concentration of serum erythrocyte and HDL-bound vitamin E. The latest was obtained on an ultracentrifuged HDL fraction. HDL fractions from HD patients have been found to contain larger amounts of vitamin E than controls. The previously described higher serum and lower erythrocyte concentrations of vitamin E in HD patients have been confirmed in the study. The deficit of vitamin E in the membranes of erythrocytes from HD patients has been shown to be the result of increased consumption of the vitamin in the erythrocyte membranes, where it represents the major antioxidant agent. However, the finding of increased amounts of vitamin bound to HDL in HD patients suggests that the transfer of the vitamin to the erythrocyte membranes may also be defective.

Adult↗
PubMed1987

Red blood cell lipid peroxidation in predialysis chronic renal failure.

In hemodialysis patients the pentose-phosphate shunt activity is deficient. As a consequence, the lipid peroxidation of the erythrocyte membranes is increased as shown by the increase in malonyldialdehyde concentrations and is accompanied by a decrease of the level of vitamin E in RBC. In the present study we have found that increased lipid peroxidation of the erythrocyte membranes is present also in chronic renal failure patients in the predialysis state, provided that the serum creatinine levels are higher than 5 mg/dl.

Erythrocyte Membrane↗
PubMed1986

Vitamin E consumption by human blood platelets activated by latex particles.

Human blood platelet activation elicited by latex particles is associated to a 30% decrease in the cellular content of vitamin E. The vitamin E consumption is inhibited by the addition of catalase (500 U/ml) and azide (1 mM), but it is not affected by potassium cyanide (1 mM). It may be proposed that the challenge of platelets with particulate stimuli causes generation of oxygen reduction products, which leads to vitamin E depletion.

Azides↗
PubMed1986

Relationship between red blood cell lipid peroxidation, plasma hemoglobin, and red blood cell osmotic resistance before and after vitamin E supplementation in hemodialysis patients.

It has been reported that increased peroxidation of the polyunsaturated fatty acids in the erythrocyte membranes is one of the causes of chronic hemolysis in uremic patients on hemodialysis and that therapeutic doses of vitamin E are effective in reducing peroxidation, improving the hematocrit. The present study shows how the reduced peroxidation, induced by a course with therapeutic doses of vitamin E, is paralleled by a significant reduction of plasma hemoglobin concentrations at the end of the dialysis and by a significant improvement of erythrocyte osmotic resistance. The findings lead to the suggestion that the administration of tocopherol to patients on chronic hemodialysis for end-stage renal disease may be beneficial in improving anemia, acting via a reduction of lipid peroxidation of the red blood cell membranes. Whether this can reduce the need for the transfusions can be assessed only with a longitudinal long-term study, which is also necessary to determine whether the preliminary findings of this report have important clinical applications.

Adolescent↗
PubMed1986

Red blood cell membrane lipid peroxidation in continuous ambulatory peritoneal dialysis patients.

We have recently described that in the erythrocytes from uremic patients on chronic hemodialysis, the pentose-phosphate shunt is defective, the membrane concentrations of malonyldialdehyde, resulting from peroxidation of polyunsaturated fatty acids in the membranes themselves, are increased, and the concentrations of vitamin E, an antioxidizing agent, are reduced. In the present study we have analyzed these same metabolic aspects in a group of uremic patients in continuous ambulatory peritoneal dialysis. We have found normal function of the pentose-phosphate shunt, slightly elevated concentrations of malonyldialdehyde compared to controls, but definitely lower than in chronic hemodialysis patients, and higher tocopherol concentrations than in both controls and chronic hemodialysis patients.

Adult↗
PubMed1986

Vitamin E supplementation in hemodialysis patients: effects on peripheral blood mononuclear cells lipid peroxidation and immune response.

Lipid peroxidation and vitamin E levels in peripheral blood mononuclear cells (PBMC) were studied in 10 patients on maintenance hemodialysis. Significant increases of PBMC malonyldialdehyde (MDA) were detected, together with low vitamin E levels. After a fifteen-day-course of parenteral vitamin E supplementation, PBMC MDA reverted to normal values, while PBMC vitamin E levels remained lower than controls. In a parallel study an immunological monitoring was performed in the same patients before and after vitamin E supplementation. NK activity and PHA blastogenesis were not influenced by treatment, while a reduction of the number of OKT8+ lymphocytes were observed after vitamin E therapy. It is tempting to speculate that peroxidative damage of PBMC cell membranes in hemodialysis patients could, by impairing their functionality, influence immune responses and expression of functionally relevant membrane determinants.

Adult↗
PubMed1985

Pentose-phosphate shunt activity and red blood cell malonyldialdehyde levels in haemodialysis and in CAPD patients.

The baseline concentrations of MDA in the RBC membranes and the MDA production in the erythrocytes following stimulation with ascorbate and cyanide are compared in a group of uraemic patients on chronic haemodialysis and in one treated with CAPD. Lower baseline concentrations and smaller production of MDA following in vitro stimulation, point to a better function of the pentose-phosphate shunt in CAPD patients than in haemodialysis.

Adolescent↗
PubMed1985

Red blood cell membrane lipid peroxidation and chronic haemolysis in haemodialysis patients.

Pre dialysis concentrations of malonyldialdehyde (MDA) in the red blood cell membranes and pre and post dialysis percent variation of plasma haemoglobin levels are studied in a group of uraemic patients on maintenance haemodialysis both before and after a therapeutic trial with vitamin E. The findings show a significant correlation between MDA levels and percent variation of plasma haemoglobin during dialysis, thus indicating that reducing the amount of lipid peroxidation can help to reduce intradialytic chronic haemolysis.

Adolescent↗
PubMed1985

Biochemical and clinical effects of vitamin E administration in homozygous beta-thalassemia.

In beta-thalassemic homozygotes, low plasma levels of tocopherols may induce a red blood cell (RBC) lipid peroxidation and consequent hemolysis. This is an indication to treat these patients with vitamin E. In this study 26 beta-thalassemic homozygotes aged 2-14 years, were given vitamin E, 10 orally and 16 parenterally, 300 mg per day for 15 days. Prior to administration and blood transfusion, as compared to normal subjects of the same age, plasma and RBC tocopherols were significantly lower, whereas RBC malonyldialdehyde (MDA) was significantly increased. In both groups, after tocopherol administration, an increase in plasma and RBC tocopherols and a decrease in RBC MDA were found. The significance of these variations was greater in the parenterally treated group than in orally treated group. The treatment with vitamin E, appears to be effective to reduce the RBC oxidative damage in homozygous beta-thalassemia, principally when administered parenterally perhaps because of its poor intestinal absorption in these subjects.

Adolescent↗
PubMed1984

Evidence of red blood cell membrane lipid peroxidation in haemodialysis patients.

Some metabolic alterations of the pentose-phosphate shunt can increase susceptibility to red blood cell (RBC) lipid peroxidation in uraemic patients on maintenance haemodialysis. We investigated this phenomenon in 19 uraemic patients undergoing chronic haemodialysis by determining RBC malonyldialdehyde (MDA), a secondary product of lipid peroxidation and plasma and RBC tocopherols, which are powerful antioxidants. Evidence of RBC membrane lipid peroxidation was demonstrated by an increase of RBC MDA. RBC tocopherols were significantly decreased because of enhanced antioxidant activity. No significant variations of these parameters were found before and after dialysis.

Adolescent↗
PubMed1984

Effects of alpha-tocopherol administration on red blood cell membrane lipid peroxidation in hemodialysis patients.

The result of vitamin E treatment in 19 uremic patients in chronic hemodialysis is evaluated. In particular, the levels of erythrocyte malonyldialdehyde (MDA) and vitamin E were determined, and the fatty acid composition of red blood cell (RBC) membrane before and after treatment with parenterally administered vitamin E. A decrease of RBC MDA levels, an increase of RBC vitamin E concentrations, and a decreased saturated fatty acid to unsaturated fatty acid ratio were found after treatment with vitamin E. There was a statistically significant increase of the packed RBC volume.

Adolescent↗
PubMedDate not supplied

Disappearance of oxidative damage to red blood cell membranes in uremic patients following renal transplant.

Hemodialysis patients display increased oxidative damage to red blood cell (RBC) membranes, characterized by elevated levels of malonyldialdehyde (MDA), a short chain aldehyde produced by the oxidation of the polyunsaturated fatty acids (PUFA) in the RBC membranes. This is the result of a metabolic blockage of the pentose-phosphate shunt in uremic patients, which causes reduced detoxification of highly oxidative free radicals. The oxidative damage induces increased RBC rigidity and decreased RBC deformability, therefore favoring hemolysis. The aim of this work was to determine if a functioning renal graft would restore normal erythrocyte metabolism, reducing the oxidative damage. To this end, we have determined RBC MDA concentrations in 20 hemodialysis (HD) patients (RBC MDA 18.22 +/- 4.36 micrograms/ml packed RBC), 20 renal transplant (T) patients with well functioning grafts (serum creatinine less than 2 mg%) (RBC MDA 1.2 +/- 0.4 micrograms/ml packed RBC) (T vs. HD P less than 0.005) and 20 healthy controls (HC) (RBC MDA 1.44 +/- 0.6 micrograms/ml packed RBC) (HC vs. HD P less than 0.005; HC vs. T NS). Our findings show that a well-functioning renal graft restores normal RBC metabolism and eliminates the oxidative damage induced by uremia.

Adolescent↗
PubMedDate not supplied

Oxidative damage to RBC membranes and pentose phosphate shunt activity in hemodialysis patients after suspension of erythropoietin treatment.

During follow-up of anemic hemodialysis patients (HDP) treated with recombinant human erythropoietin (rHuEpo), it was noticed that in five HDP, some time after suspension of rHuEpo, hemoglobin (Hb) levels remained at acceptable levels. A metabolic block of the pentose phosphate shunt (PPS) has been described in HDP, which leads to increased oxidative damage of red blood cell (RBC) membranes and increased susceptibility to hemolysis. The increased production of short-chain fatty aldehydes, including malonyldialdehyde (MDA), is an appropriate index of oxidative damage. This study aimed to verify whether the maintenance of acceptable levels of Hb was related to a change in RBC membrane oxidative damage and pentose phosphate shunt activity. In the five HDP in question who required rHuEpo (150 U/kg/week) for severe anemia (Hb = 7.48 +/- 0.95 g/dl), after a stable level of Hb > 10 g/dl was reached for at least 1 month, rHuEpo treatment was stopped. Hb levels remained adequate (Hb = 10.68 +/- 0.77 g/dl) after 14.6 +/- 7.64 months. The oxidative damage was evaluated by measuring RBC MDA (microgram/ml packed RBC) basal levels, and PPS activity by measuring MDA levels after incubation with ascorbate and cyanide (delta % RBC MDA production). Ten anemic HDP not treated with rHuEpo were used as controls (Hb = 8.12 +/- 1.32 g/dl). It was found that the maintenance of adequate levels of serum Hb after suspension of rHuEpo therapy is related to a decrease in RBC membrane oxidative damage (RBC MDA HDP = 2.40 +/- 0.41 vs. RBC MDA controls = 18.23 +/- 6.56; P < 0.005) in consequence of the normalization of pentose phosphate shunt activity.

Aged↗