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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sulphaemoglobin production, induced by an oxidative stress (ascorbate and cyanide) has been studied in uraemic patients. Results are expressed as the ratio of optic density of sulphaemoglobin (620nm) to optic density of total haemoglobin (540nm). The mean (+/- SEM) ratio found was 0.35 +/- 0.03 in 28 controls and 0.56 +/- 0,03 in 51 uraemic subjects (p less than 0.001). Cross incubation tests demonstrated that the anomaly was caused by a plasma factor. In vitro studies - guanidinic compounds added to control erythrocyte suspensions before incubation - suggest that this factor might be guanidinic propionic acid.
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PMID:Plasma inhibitors of the erythrocyte hexose monophosphate shunt in uraemia. 54 90

Chloramines, compounds made up of chlorine and ammonia, when present in tap water used for dialysis cause methemoglobinemia and hemolysis. Ascorbic acid addition has been reported to effectively neutralize chloramines in vitro and in patients dialyzed with the single batch dialysis delivery system. We extended these observations to patients dialyzed with the proportioning dialysis delivery system where exposure time of ascorbic acid to chloramines is shorter. This may be important since we found that the half time of the reaction between ascorbic acid and chloramines is 4 minutes. Red cell oxidant sensitivity in 15 patients was assessed by incubating red cells with ascorbate-cyanide and measuring methemoglobin which averaged 2.17 +/- 0.42 g/100 ml (SEM) before dialysis and 2.87 +/- 0.52 g/100 ml after dialysis (NS). Reduced glutathione (GSH) levels were also measured as an index of red cell oxidant damage. GSH decreased from a mean of 7.40 +/- 0.59 micromoles/g Hb before dialysis to 6.98 +/- 0.52 micronmoles/g Hb after dialysis (P less than 0.01). In 2 patients there was no change in 51Cr red cell survival when dialyzed on either the proportioning system or other chloramine free systems. We conclude that addition of ascorbic acid to neutralize chloramines in tap water is also effective when using the proportioning dialysis delivery system.
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PMID:Prevention of chloramine-induced hemolysis in dialyzed patients. 69 6

The present study was designed to test the hypothesis that the active neurotransmitter processes of release and uptake affect the in vivo microdialysis recovery of dopamine (DA) in the nucleus accumbens (N ACC) of the rat. The in vivo recovery for DA was established for rats which had received either unilateral infusions of the neurotoxin 6-hydroxydopamine (6-OHDA, 8 micrograms) or vehicle (0.2 micrograms ascorbate). In the quantitative dialysis method used (point of no net flux method), DA is added to the perfusate at concentrations above and below the expected extracellular concentration (0, 5, 10 and 20 nM) and DA is measured in the dialysate from the brain to generate a series of points. A linear fit is performed, the slope of which is the in vivo recovery of the dialysis probe. The in vivo recovery of the 6-OHDA group was 30 +/- 3% which was significantly lower (P less than 0.002) than the in vivo recovery of the control group which was 60 +/- 3% (mean +/- SEM; n = 6/group). The zero intercept of this regression is the point of no net flux, which is the extracellular concentration of DA independent of the probe sampling characteristics. The extracellular DA concentration for the 6-OHDA group was 7.8 +/- 1.1 nM, which was not significantly different than the control group which was 6.9 +/- 0.7 nM.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The in vivo microdialysis recovery of dopamine is altered independently of basal level by 6-hydroxydopamine lesions to the nucleus accumbens. 180 Aug 51

Iron absorption from human milk and infant formula has received much attention, but experimental design problems have been common. In our study, iron retention from human milk, milk-based infant formula (IF) with and without supplemental ferrous sulfate, and IF supplemented with either human or bovine lactoferrin (Lf) was evaluated in infant rhesus monkeys. The exchange of 59Fe (III) Cl3 between the whey, casein, and fat fractions required up to 72 h to reach the same distribution as intrinsic iron, depending on the type of diet. Infant monkeys were intubated with labeled human milk or IF and counted in a whole body counter. Each infant received all five diets and was also intubated with a reference dose of 55Fe (II) ascorbate. There was no significant difference in iron retention (mean +/- SEM) from the experimental diets: human milk 32.5 +/- 5.1%; IF 32.1 +/- 8.0%; IF + Fe 23.0 +/- 3.9%; IF + human Lf 23.5 +/- 3.3%; IF + bovine Lf 22.7 +/- 4.9%. Therefore, infant monkeys absorb and retain iron similarly from human milk and infant formula. Supplementation of infant formula with human or bovine Lf resulted in similar iron retention to that of ferrous sulfate-supplemented infant formula.
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PMID:Iron retention from lactoferrin-supplemented formulas in infant rhesus monkeys. 231 47

The isolated perfused working rat heart model of cardiopulmonary bypass and ischaemic cardiac arrest has been used to investigate whether addition of various organic anti-oxidants to the St Thomas' Hospital cardioplegic solution can enhance the recovery of function of the rat myocardium after normothermic (37 degrees C) global ischaemic arrest. Five anti-oxidants were studied: (i) ascorbate (1.0 and 10.0 mmol.litre-1), (ii) methionine (1.0 and 10.0 mmol.litre-1), (iii) reduced glutathione (1.0 and 10.0 mmol.litre-1), (iv) dimethylthiourea (0.1, 1.0, 10.0 and 50.0 mmol.litre-1), (v) N-2-mercaptopropionyl glycine (0.1, 1.0 and 10.0 mmol.litre-1). The recovery of aortic flow in control hearts which were free of anti-oxidant was 50.7(SEM 0.5)%; ascorbate (1.0 or 10.0 mmol.litre-1) improved this recovery to 72.1(1.7) and 70.2(0.3)% respectively; methionine (1.0 and 10.0 mmol.litre-1) improved the recovery to 74.1(5.7)% and 67.7(1.7)%, respectively; reduced glutathione (1.0 and 10.0 mmol.litre-1) improved the recovery to 66.7(1.4)% and 74.0(1.7)% respectively. In further studies, the addition of dimethylthiourea (0.1, 1.0 and 10.0 mmol.litre-1) to the cardioplegic solution failed to improve recovery of aortic flow [47.3(8.0), 24.6(7.3), 48.0(7.7)% respectively] when compared to its anti-oxidant free control value of 40.4(6.1)% and at a concentration of 50.0 mmol.litre-1 a very poor recovery of aortic flow of 7.7(4.8)% was observed. Mercaptopropionyl glycine (0.1, 1.0 and 10.0 mmol.litre-1) also failed to improve the recovery of aortic flow [34.7(1.6), 34.7(7.7) and 25.6(5.4)% respectively.2+ Since biological membranes are highly permeable to dimethylthiourea and mercaptopropionyl glycine, it is possible that they accumulate in the intracellular compartment.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Free radicals and cardioplegia: organic anti-oxidants as additives to the St Thomas' Hospital cardioplegic solution. 251 9

Plasma levels of vitamins were determined in eight patients who were nourished with long-term enteral feeding using commercial formulas. The type and quantity of the formula were individually tailored to the patients' needs. Caloric intake (mean +/- SEM) amounted to 1564 +/- 97 kcal/day. Vitamins intake from the formulas, expressed as percent of Recommended Daily Allowances (RDA), was as follows: pantothenic acid, 222 +/- 44%; vitamin B12, 206 +/- 34%; vitamin C, 376 +/- 51%; thiamine, 207 +/- 34%; niacin, 207 +/- 34%; riboflavin, 207 +/- 34%; pyridoxine, 222 +/- 17%; biotin, 113 +/- 13%; vitamin A, 93 +/- 4%; and folic acid, 104 +/- 14%. Plasma levels of thiamine, riboflavin, pyridoxine, pantothenic acid, folic acid, and vitamin B12 were within normal limits in all patients. Two patients had lower than normal plasma levels of nicotinic acid despite the high intake. Plasma biotin levels were above normal in all patients, with a mean of 931 +/- 140 pg/ml (N: 200-500 pg/ml). Ascorbic acid levels were within or above normal, but no correlation with intake was found. Carotene levels were measured in five patients and found to be below the lower limit of normal, a reflection of lack of intake from the enteral formulas. The plasma vitamin A levels were normal in all patients. It is concluded that feeding with commercial enteral formulas results in normal plasma levels of vitamins in patients maintained on these formulas for over 6 months. The excessive amounts of vitamins in the formulas do not result in elevated plasma levels, except for Biotin.
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PMID:Vitamin plasma levels in long-term enteral feeding patients. 251 94

Chitosan ascorbate, obtained by mixing chitosan with ascorbic acid and sodium ascorbate, was produced in a gel form suitable for the treatment of periodontitis according to current dental surgery. While chitosan ascorbate underwent degradation in vitro, especially in the presence of atmospheric oxygen and at pH 6.0, the protection from oxygen offered by the surgical cements and the physiological pH value permitted chitosan ascorbate to play an important biological role in vivo, where it kept a honeycomb structure, as indicated by SEM on biopsies taken on 10 patients. The proliferation and organization of the cells were thus favoured with a subsequent enhanced capability of reconstructing a histoarchitectural tissue. Chitosan was progressively reabsorbed by the host, with very satisfactory clinical recoveries of the 52 defects treated, for which tooth mobility and pocket depths were significantly reduced.
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PMID:Reconstruction of parodontal tissue with chitosan. 261 8

Whole blood ascorbate, plasma oxalate, serum cholesterol, and capillary fragility were measured at monthly intervals for 3 mth in 7 patients receiving continuous ambulatory peritoneal dialysis and 4 receiving haemodialysis, to whom ascorbate supplements had not been prescribed for at least 12 mth. Ascorbate supplements, 25 mg/day, were prescribed for the first month and 50 mg/day for the second month; in the final month patients received no supplements. Whole blood ascorbate was below normal in 6/11 patients at the start of the study but was normal in 10/11 patients when taking ascorbate 50 mg/day. No significant changes in plasma oxalate were observed with these doses of ascorbate, and correction of ascorbate deficiency had no effect on serum cholesterol, mean cell volume, or the results of capillary fragility tests. In a supplementary study, ascorbic acid 500 mg/day was administered for 3 wk to 11 patients. This resulted in a significant rise in mean plasma oxalate from 30.3 (SEM 3.5) to 48.4 (SEM 20.3) mumol/l.
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PMID:Correction of subclinical ascorbate deficiency in patients receiving dialysis: effects on plasma oxalate, serum cholesterol, and capillary fragility. 274 78

Commercial oral iron preparations (drops) containing trivalent iron either as a citrate (C) or hydroxide-polymaltose complex (HP) were labelled with 59Fe in the thermal neutron flux of a research reactor. No measurable differences were observed between the original commercial preparation and the neutron-activated samples. In an intraindividual comparison oral doses of 100 mg 59Fe were administered as an aqueous 59Fe(II)-ascorbate solution (= reference), C (-59Fe) and HP (-59Fe) to starved subjects with normal and depleted iron stores. Two weeks later the whole body retention of absorbed 59Fe was measured and used for the calculation of 59Fe-absorption. Subjects with normal Fe-stores absorbed means a +/- SEM +/- SD = 8.53 +/- 0.29 +/- 1.2% of the 59Fe from the aqueous 59Fe(II)-ascorbate solution, 1.58 +/- 0.12 +/- 0.49 of the C-59Fe and 0.81 +/- 0.06 +/- 0.27% of the HP-59Fe. Subjects with depleted Fe-stores absorbed means a +/- SD = 17 +/- 3% of the 59Fe from the aqueous 59Fe(II)-ascorbate solution and only 2.4 +/- 1% from the HP-59Fe. The relative bioavailabilities were reduced from 100% (reference = Fe(II)-ascorbate) to 19% for the C-Fe and to 9.5% for the HP-Fe in subjects with normal Fe-stores. In subjects with depleted iron stores the relative bioavailability was decreased from 100 to 14% for the HP-Fe. Oral iron preparations with a relative bioavailability less than 10% or less than 30% are considered to be therapeutically ineffective or insufficient, respectively.
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PMID:Intestinal absorption of 59Fe from neutron-activated commercial oral iron(III)-citrate and iron(III)-hydroxide-polymaltose complexes in man. 356 63

Plant foods were digested in vitro and the proportion of iron which diffused across a semi-permeable membrane was used as an index of Fe availability. The mean (with SEM) Fe diffusibility from a group of eighteen cereals, legumes and nuts was very low, 2.1 (0.25)%, whereas from a group of sixteen fruits and vegetables it was high, 31.7 (1.09)%. The difference between the two food groups was highly significant (P less than 0.001). The results for Fe diffusibility correlated well with literature values for the in vivo absorption of Fe from similar foods (r0.84, P less than 0.01). When phytate, citrate and ascorbate were added to selected foods in amounts corresponding to endogenous levels, only phytate and citrate gave the expected effects on Fe diffusibility. Ascorbate only enhanced Fe diffusibility to the expected extent when it was added in much larger amounts, not normally found in foods. When added to cereal foods, orange juice was found to enhance greatly Fe diffusibility even when its content of ascorbate was completely destroyed by boiling followed by prolonged storage. When citrate and ascorbate were added to cereal foods in amounts equivalent to those found in fresh orange juice, both enhanced Fe diffusibility but citrate was far more effective. It is concluded that phytate is a major inhibitor of Fe diffusibility in cereals, legumes and nuts. However, citrate rather than ascorbate would appear to be the major enhancer of Fe diffusibility from many fruits and vegetables. The implications of the present results are discussed in relation to the relative influence of phytate, citrate and ascorbate on dietary Fe availability.
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PMID:In vitro estimation of iron availability from a range of plant foods: influence of phytate, ascorbate and citrate. 356 34


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