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PubMed1983

Quinidine saliva concentrations: absence of correlation with serum concentrations at steady state.

Serum and saliva quinidine concentrations were measured in eight subjects with cardiac arrhythmias on various dosage regimens. There was good correlation between serum and saliva quinidine concentration after a single dose, but there was no such relationship after repeated dosing. Comparison of the area under a hysteresis loop, obtained by plotting the saliva/serum quinidine concentration ratio as a function of serum quinidine concentration over a dosing interval, indicated an exponential increase with increasing mean serum quinidine concentration. Salivary quinidine concentration predictions based on the Henderson-Hasselbalch equation did not correlate with the serum quinidine concentration under the steady-state conditions. These data suggest that quinidine concentration in saliva is not a direct reflection of its serum concentration in cardiac patients on maintenance (steady-state) therapy and hence not useful for therapeutic drug monitoring.

Administration, Oral↗

PubMed2006

Relationship between thiamine concentration and fermentation patterns in the rumen fluid of dairy cows fed with graded concentrate levels.

The objective of this study was to investigate the relationship between the thiamine concentration and the fermentation patterns [pH, concentration of short-chain fatty acids (SCFA)] in the free liquid (FRL) and particle-associated liquid (PARL) of the rumen in dairy cows fed with graded concentrate levels in the diet. Four ruminally cannulated Holstein cows in mid lactation were fed [semi-ad libitum, 18 kg dry matter (DM)/day] diets consisting of hay (H) and slowly degradable concentrate (C), offered in five different H:C ratios (% DM basis) in the following sequence: period 1, 30:70; period 2, 40:60; period 3, 50:50; period 4, 60:40 and period 5, 75:25. A negative quadratic relationship was observed between thiamine concentration in FRL and intake of dietary thiamine (R(2) = 0.36), of concentrate (R(2) = 0.38) and of digestible non-fibre carbohydrates (R(2) = 0.37). The thiamine concentration in PARL was higher (p < or = 0.05) compared to FRL. The ruminal thiamine concentration correlated negatively to pH and positively to concentrations of SCFA and propionate in the rumen. R(2) of these relationships varied markedly (0.002 and 0.77), depending on time after feeding and fluid digesta compartment. The higher R(2) were observed at 8 and 11 h after the morning feeding for FRL (R(2) 0.46-0.71) and PARL (R(2) 0.41-0.77), respectively.

Animal Feed↗

PubMed1996

Effect of prolonged high-concentrate feeding on ruminal protozoa concentrations.

Five ruminally cannulated steers, with ad libitum access to feed, were gradually adapted from an all-forage diet to a 75% concentrate diet over a 6-wk period. Three animals were then randomly assigned to an all-concentrate diet (87% whole corn) and the other two were fed a 90% concentrate plus 10% forage diet. These diets were fed for 17 wk and then reversed between groups for 11 additional weeks. Over the last 22 wk, addition of 10% forage to the all-concentrate diet had no effect on the concentration of total protozoa; however, Isotricha and Epidinium percentages increased (P < .05). Although concentrations varied markedly, protozoa persisted throughout the entire period of high-concentrate feeding (both diets) in three of the animals. In contrast, the other two animals were defaunated most of the time, except for the sporadic appearance of Entodinium species for 1- or 2-wk intervals. Average pH in these latter two animals was lower (P < .05) during the entire 28-wk high-concentrate feeding period. Because these two animals had a lower ruminal pH than the other three, even when fed all forage, it seems that the ruminal environment varies between individual animals. Thus, the maintenance of a protozoal population in animals fed high-concentrate diets may be related to physiological conditions such as rate and extent of salivary production, rate of fluid and particulate matter passage within each animal, and so on.

Animals↗

PubMed1984

Intracellular electrolyte concentrations in the frog skin epithelium: effect of vasopressin and dependence on the Na concentration in the bathing media.

The intracellular electrolyte concentrations of the frog skin epithelium have been determined in thin freeze-dried cryosections using the technique of electron microprobe analysis. Stimulation of the transepithelial Na transport by arginine vasopressin (AVP) resulted in a marked increase in the Na concentration and a reciprocal drop in the K concentration in all epithelial cell layers. The effects of AVP were cancelled by addition of amiloride. It is concluded from these results that the primary mechanism by which AVP stimulates transepithelial Na transport is an increase in the Na permeability of the apical membrane. However, also some evidence has been obtained for an additional stimulatory effect of AVP on the Na pump. In mitochondria-rich cells and in gland cells no significant concentration changes were detected, supporting the view that these cells do not share in transepithelial Na transport. Furthermore, the dependence of the intracellular electrolyte concentrations upon the Na concentration in the outer and inner bathing solution was evaluated. Both in control and AVP-stimulated skins the intracellular Na concentration showed saturation already at low external Na concentrations, indicating that the self-inhibition of transepithelial Na transport is due to a reduction of the permeability of the apical membrane. After lowering the Na concentration in the internal bath frequently a Na increase in the outermost and a drop in the deeper epithelial layers was observed. It is concluded that partial uncoupling of the transport syncytium occurs, which may explain the inhibition of the transepithelial Na transport and blunting of the AVP response under this condition.

Amiloride↗

PubMed1999

Predicting starling chick carcass PCB concentrations from PCB concentrations in ingested animal matter.

Preremediation studies at Crab Orchard National Wildlife Refuge (CONWR) revealed statistically significant accumulations of polychlorinated biphenyls (PCBs) and effects in starling chicks (Sturnus vulgaris) from contaminated sites, including decreased nest attentiveness, decreased fledging success, and an increase in chick mortality. Although the expected route of exposure for starling chicks is thought to be via diet, this has not previously been documented at CONWR. The purpose of this study was to develop an equation to predict starling chick carcass PCB concentrations from PCB concentrations in ingested animal matter. During 1995 and 1996, stomach contents from 14 and 22 starling chicks collected from contaminated and reference sites, respectively, were evaluated. Animal, plant, and mineral matter in the stomach contents were separated and animal matter from stomachs of individuals from the same nest were combined, dried, and percent dry weight calculated. Composite samples of animal matter were then analyzed for the presence of PCBs (Aroclor 1254). Stomach contents were primarily composed of animal matter (76%), and the percent animal matter in the stomachs did not differ significantly among locations (range = 38.4% to 100%). The mean PCB concentration in composite samples of animal matter from stomachs of chicks collected from contaminated sites (1.82 +/- 1.17 mg/kg) was significantly greater than the concentrations in composite samples from two reference locations (<0. 24 mg/kg). PCB concentrations in stomach contents were correlated (Pearson correlation coefficient = 0.91, p < 0.005) with concentrations in carcasses of chicks from which the stomachs had been collected. The regression Y = 6.19 x X(1,398), where Y = starling chick carcass PCB concentration and X = starling stomach animal matter PCB concentration, indicated that PCB concentrations in consumed animal matter accounted for 82% of the variability in starling carcass concentrations.http://link.springer-ny. com/link/service/journals/00244/bibs/37n4p548.html</++ +HEA

Animals↗

PubMed1998

Temporal variation of thoron decay product concentration in the atmosphere and comparison with radon decay product concentration.

Seasonal and long-term variation of the airborne 212Pb concentration, representative of the equilibrium equivalent concentration of thoron decay products (EECRn220), was investigated from 1989 through 1996 at a semi-natural location in southern Germany. Continuous measurement yielded a long-term average concentration of 0.082 Bq m-3, while daily mean concentrations varied from < or = 0.01 to 0.34 Bq m-3. An average annual effective dose of 1.4 mSv due to outdoor thoron progeny concentration was estimated. This is about 2% of the dose due to the average short-lived radon progeny concentration (EECRn222) of 8.4 Bq m-3 measured for this location in the same period. In most years the seasonal pattern of 212Pb activity concentration in the atmosphere is characterized by two maxima: the first in May and the second one in September. Low concentrations are observed from November through February of each year. This is in contrast to the behaviour of the short-lived 222Rn progeny which exhibit enhanced concentrations exactly during these months. The most probable reason for the different temporal behaviour of 212Pb is the extremely reduced flux of thoron gas from the ground during the winter months.

Air Pollutants, Radioactive↗

PubMed2006

Effects of inspiratory oxygen concentration on endtidal carbon monoxide concentration.

OBJECTIVE: Carbon monoxide (CO) is eliminated mainly via the lungs so that exhaled carbon monoxide concentration reflects endogenous production. In this context, we studied the effects of inspiratory oxygen concentration and endotracheal intubation on endtidal CO concentrations. METHODS: In patients undergoing general anaesthesia, endtidal CO concentrations were measured while breathing room air, oxygen as well as after induction of general anaesthesia and endotracheal intubation. To exclude time-dependent effects, patients were assigned to two groups. Patients in group 1 (n = 20) were preoxygenated for 5 minutes, whereas patients in group 2 (n = 20) were preoxygenated for 10 minutes. We also studied the effects of different inspiratory oxygen concentrations in volunteers (n = 20) breathing room air, 50% and 100% oxygen. RESULTS: Breathing oxygen for 5 minutes increased endtidal carbon monoxide concentrations in all patients (in group 1 from 7.6+/-4.9 to 12.6+/- 5.0 ppm, p < 0.001; in group 2 from 7.1+/-6.1 to 16.4 +/- 8.6 ppm, p < 0.001). No further change of CO concentration was detected after 10 minutes of preoxygenation (16.4 +/- 9.0 vs. 16.4 +/- 8.6 ppm, p > 0.05). Endtidal CO values however significantly increased with induction of anaesthesia and endotracheal intubation (in group 1 to 21.5 +/- 6.3 ppm, p < 0.001, in group 2 to 26.1 +/- 13.1 ppm, p < 0.001). In volunteers, mean endtidal CO values increased from 10.7 +/-5.9 to 14.8+/-7.3 ppm after breathing 50% oxygen for 3 minutes (p < 0.001). Breathing pure oxygen had no additional effect on endtidal CO values (16.0 +/- 6.0 ppm, p > 0.05). CONCLUSIONS: Endtidal carbon monoxide levels are influenced by inspiratory oxygen concentrations. Induction of anaesthesia and endotracheal intubation further increases endtidal CO concentrations beyond the effects attributable to preoxygenation alone.

Aged↗

PubMed1978

Some effects of glucose concentration and anoxia on glycolysis and metabolite concentrations in the perfused liver of fetal guinea pig.

Effects of glucose concentration and anoxia upon the metabolite concentrations and rates of glycolysis and respiration have been investigated in the perfused liver of the fetal guinea pig. In most cases the metabolite concentrations in the perfused liver were similar to those observed in vivo. Between 50 days and term there was a fall in the respiratory rate and in the concentration of ATP and fructose 1,6-diphosphate and an increase in the concentration of glutamate, glycogen and glucose. Reducing the medium glucose concentration from 10 mM to 1 mM or 0.1 mM depressed lactate production and the concentration of most of the phosphorylated intermediates (except 6-phosphogluconate) in the liver of the 50-day fetus. This indicates a fall in glycolytic rate which is not in accord with the known kinetic properties of hexokinase in the fetal liver. Anoxia increased lactate production by, and the concentrations of, the hexose phosphates ADP and AMP in the 50-day to term fetal liver, while the concentration of ribulose 5-phosphate, ATP and some triose phosphates fell. These results are consistent with an activation of glycolysis, particularly at phosphofructokinase and of a reduction in pentose phosphate pathway activity, particularly at 6-phosphogluconate dehydrogenase. The calculated cytosolic NAD+/NADH ratio for the perfused liver was similar to that measured in vivo and evidence is presented to suggest that the dihydroxyacetone phosphate/glycerol 3-phosphate ratio gives a better indication of cytosolic redox than the lactate/pyruvate ratio. The present observations indicate that phosphofructokinase hexokinase and possibly pyruvate kinase control the glycolytic rate and that glyceraldehyde-3-phosphate dehydrogenase is at equilibrium in the perfused liver of the fetal guinea pig.

Adenine Nucleotides↗

PubMed2006

Association of increased serum heat shock protein 70 and C-reactive protein concentrations and decreased serum alpha(2)-HS glycoprotein concentration with the syndrome of hemolysis, elevated liver enzymes, and low platelet count.

The primary aim of this study was to determine serum Hsp70 concentrations in HELLP syndrome. We measured also the serum concentrations of three acute phase proteins: C-reactive protein (CRP), alpha(2)-macroglobulin (AMG) and alpha(2)-HS glycoprotein (AHSG). Ten severe preeclamptic patients with HELLP syndrome, 20 severe preeclamptic patients without HELLP syndrome and 20 normotensive, healthy pregnant women were included in this case-control study. Serum concentrations of Hsp70, CRP, AMG and AHSG were measured using an enzyme-linked immunosorbent assay (Hsp70), particle-enhanced immunoturbidimetric assay (CRP) and radial immunodiffusion (AMG, AHSG). The serum Hsp70 and CRP concentrations were significantly higher, whereas the serum AHSG concentration was significantly lower in the HELLP group (H) than the severe preeclamptic (P) and control (C) groups (median (25-75 percentile); Hsp70: 2.02 ng/ml (0.76-2.23) (H) versus 0.54 ng/ml (0.47-0.79) (P), p<0.01, and 0.30 ng/ml (0.27-0.33) (C), p<0.001; CRP: 43.9 mg/l (27.1-84.5) (H) versus 6.5 mg/l (2.7-10.7) (P), p<0.001, and 2.5 mg/l (1.1-6.7) (C), p<0.001; AHSG: 588 microg/ml (492-660) (H) versus 654 microg/ml (576-768) (P), p<0.05, and 738 microg/ml (666-804) (C), p<0.01, respectively). The serum AMG concentration did not differ between the study groups. In the HELLP group, there was a statistically significant negative correlation between serum Hsp70 concentration and platelet count (Spearman R=-0.69, p=0.026). In conclusion, serum Hsp70 and CRP concentrations are increased, whereas serum AHSG concentration is decreased, in HELLP syndrome. The maternal systemic inflammation seems to be more pronounced in HELLP syndrome than preeclampsia without HELLP syndrome, as suggested by the alterations in serum CRP and AHSG levels. However, it requires further investigation to determine whether these changes are causes or consequences of the disease.

Adult↗

PubMed2001

Relationship between endogenous estrogen concentrations and serum cholesteryl ester transfer protein concentrations in Chinese women.

BACKGROUND: CETP plays an important role in HDL metabolism and in the reverse cholesterol transport pathway. METHODS: The relationship between the changes of endogenous estrogen and the concentration of cholesteryl ester transfer protein (CETP) in the serum of Chinese women was investigated. Serum concentrations of estradiol (E(2)), follicle-stimulating hormone (FSH), CETP and lipid profile were determined in 196 Chinese women (52 premenopausal with ages ranging from 18 to 40 years, 57 perimenopausal from 41 to 60 years, and 87 postmenopausal from 61 to 81 years). RESULTS: Serum CETP concentration was significantly lower in postmenopausal women compared with those in perimenopausal and premenopausal women (1.39+/-1.06, 2.36+/-1.50 and 2.31+/-1.25 mg/l, respectively, P<0.0001). Even in the women around the menopausal, CETP concentration in postmenopause was significantly lower than that in premenopause (1.93+/-1.33 vs. 3.42+/-1.35 mg/l, P<0.01). In addition, CETP concentration had a highly positive correlation with serum concentration of E(2) (r=0.243, P<0.001), while negative correlation of CETP concentration with serum concentration of FSH was found (r=-0.273, P<0.001). CONCLUSIONS: Estrogen may affect the concentration of CETP.

Adolescent↗

PubMed2003

Increased concentrations of homocysteine and asymmetric dimethylarginine and decreased concentrations of nitric oxide in the plasma of patients with Alzheimer's disease.

Vascular risk factors increase the risk of developing Alzheimer's disease. Increased concentrations of circulating homocysteine are associated with an increased risk of both vascular disease and Alzheimer's disease. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase. There is an increase in the concentration of ADMA in the circulation in vascular disease. We measured the concentrations of homocysteine, ADMA and nitric oxide (as nitrate and nitrite) in the plasma of 25 patients with Alzheimer's disease and 25 control subjects. There was a highly significant increase in the plasma concentration of homocysteine (P<0.001) and ADMA (P<0.0001) and a highly significant decrease in the plasma concentration of nitric oxide (P<0.0001) among the Alzheimer's patients. In the combined patient and control groups a highly significant positive correlation was found between the plasma concentrations of homocysteine and ADMA (r=0.782, P<0.0001). In addition, significant negative correlations were detected between the plasma concentration of nitric oxide and the plasma concentration of homocysteine (r=-0.592, P<0.0001) and ADMA (r=-0.789, P<0.0001). These significant correlations were found to persist, even when they were restricted to the Alzheimer's patients. The inhibition of endothelial nitric oxide synthesis by ADMA impairs cerebral blood flow, which may contribute to the development of Alzheimer's disease. Endothelial dysfunction is also associated with atherosclerosis and stroke, which are important risk factors for Alzheimer's disease. Inflammation plays an important role in Alzheimer's disease and the inhibition of endothelial nitric oxide by ADMA may increase the concentration of inflammatory mediators in the brain. The inhibition of neuronal nitric oxide synthesis by ADMA may cause cognitive dysfunction in Alzheimer's disease.

Aged↗

PubMed2006

Charge neutralization process of mobile species at any distance from the electrode/solution interface. 1. Theory and simulation of concentration and concentration gradients developed during potentiostatic conditions.

The theoretical framework of a general model for the simulation of concentration profiles of electroactive and nonelectroactive species, driven by an electrochemical process under potentiostatic conditions, is presented. Based on this analysis, finite differences simulations are performed to calculate the actual profiles under different experimental conditions. Furthermore, the effect of experimental parameters (diffusion coefficients of the ions of the redox couple or the supporting electrolyte, charge of the different species, etc.) on the concentration profiles is also examined. The results obtained when low and high concentrations of supporting electrolyte are compared aid understanding of the effect of the electrolyte on the measurements. The presented model also underlines the role of supporting electrolyte species when nonspecific techniques are employed to measure the concentration changes produced by electroactive species. On the other hand, if a highly specific technique were used to detect changes in the concentration or concentration gradient of a given species, then it would be possible to estimate the respective profiles of the other species. The simulations suggest that techniques measuring concentration gradients are more sensitive to determining concentration changes than those involving a measurable linearly related to concentration.

Journal Article↗

PubMed1999

A comparison of the plasma fructose concentrations in dogs and cats and changes in the fructose concentrations in dogs following intravenous administration of fructose.

The plasma concentrations of fructose, glucose, free fatty acids (FFA) and triglycerides (TG) were measured in dogs and cats. Changes in these concentrations were investigated in dogs by an intravenous fructose tolerance test (IVFTT) at a dose of 0.1 g/kg body weight. Fructose concentrations in the plasma of dogs were significantly higher than those of cats. There was no significant difference in plasma glucose concentrations between dogs and cats. Plasma FFA concentrations decreased and TG concentrations increased after feeding in both dogs and cats. During the IVFTT, the plasma fructose concentrations in the dogs increased rapidly to a peak by 2 min and then decreased to half of the peak by 5 min after the administration of fructose. Administration of fructose resulted in an increase in the plasma TG concentrations and reduced plasma FFA concentrations in the dogs. Only 4%, of the administered fructose was detected in the urine of dogs following IVFTT. Plasma fructose was considered to be rapidly absorbed and metabolized in both dogs and cats. However, as with glucose metabolism, there appear to be some differences in fructose metabolism between dogs and cats.

Animals↗

PubMed2005

Low plasma selenium concentrations, high plasma human immunodeficiency virus load and high interleukin-6 concentrations are risk factors associated with anemia in adults presenting with pulmonary tuberculosis in Zomba district, Malawi.

BACKGROUND: Although anemia is common among adults with pulmonary tuberculosis and human immunodeficiency virus (HIV) infection in sub-Saharan Africa, the factors contributing to its pathogenesis have not been well characterized. OBJECTIVE: To characterize the antioxidant micronutrient status, interleukin-6 (IL-6) concentrations, and HIV load in relationship with anemia in adults with pulmonary tuberculosis. SETTING: Zomba district, Malawi. METHODS: Erythropoietin, IL-6, plasma HIV load, and markers of micronutrient status (hemoglobin (Hb), plasma concentrations of retinol, alpha-tocopherol, carotenoids, ferritin, zinc, and selenium) were measured in 500 adults who presented with pulmonary tuberculosis in Zomba Central Hospital, Malawi. RESULTS: Among 370 HIV-positive and 130 HIV-negative adults, the prevalence of anemia was 88 and 77%, respectively (P = 0.002), and moderate to severe anemia (Hb < 80 g/l) occurred in 30 and 15%, respectively (P = 0.001). Geometric mean IL-6 concentration was 21.1 pg/ml, with no difference between HIV-positive and -negative adults. The erythropoietin response to anemia was not different between adults with elevated IL-6 and those with lower IL-6 concentrations. In a multivariate logistic regression model, HIV load, and lower plasma selenium concentrations were associated with moderate to severe anemia. In a final multivariate linear regression model, IL-6, plasma HIV load, and plasma selenium concentrations were associated with Hb concentrations. CONCLUSION: This study suggests that low selenium concentrations, high HIV load, and high IL-6 concentrations are associated with anemia in adults with pulmonary tuberculosis in sub-Saharan Africa.

Adult↗

PubMed1996

Effect of channelling on the concentration of bulk-phase intermediates as cytosolic proteins become more concentrated.

This paper shows that metabolic channelling can provide a mechanism for decreasing the concentration of metabolites in the cytoplasm when cytosolic proteins become more concentrated. A dynamic complex catalysing the direct transfer of an intermediate is compared with the analogous pathway lacking a channel (an "ideal" pathway). In an ideal pathway a proportional increase in protein content does not result in a change in the steady-state concentration of the bulk-phase intermediate, whereas in a channelling pathway the bulk-phase intermediate either decreases or increases depending on the elemental rate constants within the enzyme mechanisms. When the concentration of the enzymes are equal, the pool size decreases with increasing protein concentration if the elemental step depleting the bulk-phase intermediate exerts more control on its concentration than the step supplying the intermediate. Results are illustrated numerically, and a simplified dynamic channel is analysed in which the concentration of the enzyme-enzyme forms. For such a "hit-and-run" channel it is shown that, when the product-releasing step of the enzyme located upstream is close to equilibrium, the pool size decreases as the concentrations of the enzymes increase in proportion, regardless of the rate, equilibrium constants and concentration ratios of the two sequential enzymes.

Cytosol↗

PubMed2003

Risk factors for increased urinary inorganic arsenic concentrations from low arsenic concentrations in drinking water.

A large number of drinking water supplies worldwide have greater than 50 microg l(- 1) inorganic arsenic in drinking water, and there is increasing pressure to reduce concentrations. Few studies have specifically considered low concentrations of arsenic in water supplies and the significance of other factors which may contribute to increased exposure. This study aimed to investigate risk factors for increased urinary inorganic arsenic concentrations, in a population exposed to 10 - 100 microg l(- 1) of arsenic in drinking water, as well as a control population with lower arsenic concentrations in their drinking water. Inorganic arsenic in urine was used as the measure of exposure. The median drinking water arsenic concentration in the exposed population was 43.8 microg l(- 1) (16.0 - 73 microg l(- 1)) and less than the analytical limit of detection of 1 microg l(- 1) (<DL) (range<DL-8.0 microg l(- 1)) in the control group. The geometric mean urinary inorganic arsenic concentration for the exposed group was 4.24 microg l(- 1) (range<DL-18.8 microg l(- 1)) and for the control group was 1.18 microg l(- 1) (<DL-4.49 microg l(- 1)). In a random effects linear regression model, drinking water was the significant predictor of urinary inorganic arsenic concentrations with factors such as age, season and drinking water consumption important risk factors. These results show that concentrations of arsenic in drinking water, even at lower concentrations, make an important contribution to exposure. Further work is required to define the potential for absorption at these lower levels.

Adolescent↗

PubMed2004

Breakfast cereal fortified with folic acid, vitamin B-6, and vitamin B-12 increases vitamin concentrations and reduces homocysteine concentrations: a randomized trial.

BACKGROUND: High homocysteine and low B vitamin concentrations have been linked to the risk of vascular disease, stroke, and dementia and are relatively common in older adults. OBJECTIVE: We assessed the effect of breakfast cereal fortified with folic acid, vitamin B-6, and vitamin B-12 on vitamin and homocysteine status. DESIGN: A randomized, double-blind trial was conducted in 189 volunteers aged 50-85 y. The subjects had no history of hypertension, anemia, asthma, cancer, or cardiovascular or digestive disease and did not regularly consume multiple or B vitamin supplements or highly fortified breakfast cereal. Subjects were randomly assigned to consume 1 cup (0.24 L) breakfast cereal fortified with 440 microg folic acid, 1.8 mg vitamin B-6, and 4.8 microg vitamin B-12 or placebo cereal for 12 wk. Blood was drawn at 0, 2, 12, and 14 wk. Methionine-loading tests were conducted at baseline and week 14. RESULTS: Final baseline-adjusted plasma homocysteine concentrations were significantly lower and B vitamin concentrations were significantly higher in the treatment group than in the placebo group (P < 0.001). The percentage of subjects with plasma folate concentrations < 11 nmol/L decreased from 2% to 0%, with vitamin B-12 concentrations < 185 pmol/L from 9% to 3%, with vitamin B-6 concentrations < 20 nmol/L from 6% to 2%, and with homocysteine concentrations > 10.4 micromol/L (women) or > 11.4 micromol/L (men) from 6.4% to 1.6%. The percentage of control subjects with values beyond these cutoff points remained nearly constant or increased. CONCLUSIONS: In this relatively healthy group of volunteers, consumption of 1 cup fortified breakfast cereal daily significantly increased B vitamin and decreased homocysteine concentrations, including post-methionine-load homocysteine concentrations.

Aged↗

PubMed1998

Rapid automated determination of lipid hydroperoxide concentrations and total antioxidant status of serum samples from patients infected with HIV: elevated lipid hydroperoxide concentrations and depleted total antioxidant capacity of serum samples.

Excessive production of oxygen free radicals causes the oxidation of circulating or membrane lipids, proteins, and DNA. Patients infected with HIV usually have severe malnutrition in the AIDS stage of disease. Therefore, they may be at higher risk of oxidative stress. We measured lipid hydroperoxide concentration, antioxidant status, cholesterol, triglyceride, iron, ceruloplasmin, and transferrin concentrations in the serum samples of 14 patients infected with HIV and compared our results with the results from 14 volunteers who served as controls. Lipid hydroperoxide concentrations in serum samples were measured by a colorimetric assay in which hemoglobin catalyzes the reaction of lipid hydroperoxide with a methylene blue derivative, yielding methylene blue. The total antioxidant capacity of serum was measured by the ability of serum to inhibit the formation of ferrylmyoglobin by metmyoglobin and hydrogen peroxide. Both assays were automated on the Syva-30R analyzer (Behring, San Francisco, Calif). We measured serum cholesterol and triglyceride concentrations by using the Vitro 950 analyzer (Johnson & Johnson, Rochester, NY). The lipid hydroperoxide concentrations were significantly elevated (mean, 1.44; SD, 0.95 micromol/L) in patients with HIV compared with control subjects (mean, 0.25; SD, 0.24 micromol/L). In contrast, the total antioxidant capacity was significantly lower in patients with HIV (mean, 1.04; SD, 0.13 mmol/L of trolox equivalent) compared with control subjects (mean, 1.66; SD, 0.09 mmol/L). We observed a fair correlation between serum lipid hydroperoxide concentrations and serum triglyceride concentrations in patients with AIDS. The correlation between serum hydroperoxide concentration and antioxidant status of serum was relatively poor. The lipid hydroperoxide assay was linear, from 0.1 micromol/L to 50 micromol/L. The within-run and between-run coefficients of variation were 3.5% and 4.5%, respectively, at a lipid hydroperoxide concentration of 2.5 micromol/L. The total antioxidant capacity assay was linear, from 0.1 to 2.5 mmol/L of trolox equivalent. The within-run and between-run coefficients of variation were 1.4% and 4.2% for the standard, with a target total antioxidant capacity of 1.5 mmol/L of trolox equivalent. We conclude that our automated assays for determination of total antioxidant status of serum and lipid hydroperoxide products may be helpful screening tests followed by measuring individual antioxidants, such as tocopherol, ascorbic acid, and other antioxidants for patients with severe deficiency of antioxidant status.

Antioxidants↗