Wet microwave digestion of diet and fecal samples for inductively coupled plasma analysis.
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Feces↗
Biomedical subjects
D B Milne
Publications and source records attributed to D B Milne.
Effects of dietary copper on human autonomic cardiovascular function.
Heart rate and blood pressure responses during supine rest, orthostasis, and sustained handgrip exercise at 30% maximal voluntary contraction were determined in eight healthy women aged 18-36 years who consumed diets varying in copper and ascorbic acid content. Copper retention and plasma copper concentration were not affected by diet. Enzymatic, but not immunoreactive, ceruloplasmin was lower (p less than 0.05) after the low copper and high ascorbic acid diet periods. Diet had no effect on resting supine heart rates, orthostatic responses in heart rate and blood pressure, or standing resting blood pressure. Systolic and diastolic blood pressures were increased significantly (p less than 0.05) during the handgrip test at the end of the low copper and ascorbic acid supplementation periods. Also, the ratio of enzymatic to immunoreactive ceruloplasmin decreased significantly during these dietary treatments. The mean arterial blood pressure at the end of the handgrip test was negatively (p less than 0.0004) correlated with the ceruloplasmin ratios. These findings indicate a functional alteration in human blood pressure regulation during mild copper depletion.
Adolescent↗
Ethanol metabolism in postmenopausal women fed a diet marginal in zinc.
Five postmenopausal women aged 50-63 y were fed a diet of mixed Western foods that supplied an average of 2.6 mg zinc/d for 6 mo. Plasma zinc did not change significantly during Zn depletion but increased slightly when Zn was fed. Zn content of blood cellular components and activities of Zn-containing enzymes were not affected by Zn intake. Ethanol tolerance tests performed at the end of control, middle of depletion, end of depletion, and end of repletion showed a change in ethanol metabolism at the end of the low-Zn intake period that was corrected within 1 mo with Zn supplementation. These data suggest that there are homeostatic mechanisms that maintain circulating levels of Zn. Zn and activity of Zn enzymes in tissues may be decreased before changes in circulating Zn levels are seen. Functional indices of Zn biochemistry, such as ethanol metabolism, may be more sensitive indicators of Zn stores and nutriture than circulating Zn.
Aged↗
Oxalate degradation by gastrointestinal bacteria from humans.
Anaerobic bacteria that metabolize oxalic acid have only recently been isolated from the rumen and from other gastrointestinal habitats. They constitute a new genus and species, Oxalobacter formigenes. This report presents the first comparison of cultural counts of these organisms from human feces and indicates that numbers as high as 10(7)/g may be present in feces from normal humans. Rates of oxalate degradation by mixed bacterial populations in feces from seven normal humans ranged from 0.1 to 4.8 mumol/(g X h). With fecal samples from eight patients that had undergone jejunoileal bypass surgery, rates were much lower [0-0.006 mumol/(g X h)]. We propose that oxalic acid degradation by Oxalobacter formigenes may influence absorption of oxalate from the intestine and that lower rates or lack of oxalate degradation in the colons of jejunoileal bypass patients may contribute to the increased absorption of dietary oxalate and the hyperoxaluria commonly associated with such patients.
Adult↗
Retinol, alpha-tocopherol, lycopene, and alpha- and beta-carotene simultaneously determined in plasma by isocratic liquid chromatography.
Retinol, alpha-tocopherol, lycopene, and alpha- and beta-carotene can be simultaneously determined in human plasma by reversed-phase liquid chromatography. Plasma--0.5 mL plus added internal standard, retinyl acetate--is deproteinized with 0.5 mL of ethanol, then extracted with 1.0 mL of petroleum ether. The organic layer is removed and evaporated, the residue is redissolved in 0.25 mL of ethanol, and 8-microL samples are injected into a 60 X 4.6 mm column of Hypersil ODS 3-microns particles at 35 degrees C. An isocratic methanol mobile phase, flow rate 0.9 mL/min, is used for the 9-min run. Retinol and retinyl acetate are monitored at 305 nm, the tocopherols at 292 nm, and the carotenoids at 460 nm. Between-run CVs were 3.1, 6.9, 6.1, and 6.5% for retinol, alpha-tocopherol, lycopene, and beta-carotene, respectively. Small sample requirement, simplicity of extraction, short run time, and good reproducibility make this procedure ideal for clinical or research use.
Carotenoids↗
Comparison of dietary histories and seven-day food records in a nutritional assessment of older adults.
Dietary histories and seven-day food records were obtained for 54 apparently healthy older adults. The two dietary methods correlated for most nutrients, but mean differences were significant for several nutrients. Intakes below recommended levels occurred most frequently for energy, calcium, and zinc. Biochemical evidence of thiamin and riboflavin deficiency was unexpectedly frequent. Using food records, dietary iron correlated with serum ferritin. Using dietary histories, dietary protein correlated with serum albumin, and dietary zinc correlated with plasma zinc. Using either dietary method, plasma ascorbate was associated positively with both dietary ascorbate and ascorbate supplements, and negatively with cigarette smoking. Use of thiamin- or folate-containing supplements was associated with improved biochemical status for the respective vitamin. Though neither dietary histories nor food records give precise intake data for individuals, either method may be useful for epidemiologic studies with appropriate sample sizes.
Aged↗
Zinc content of blood cellular components and lymph node and spleen lymphocytes in severely zinc-deficient rats.
Several investigators have suggested that the measurement of leukocyte zinc may be useful for the assessment of zinc nutriture. However, in an earlier study, we found that the methods used did not adequately separate platelets from the different leukocyte populations. We subsequently developed a method which does adequately separate platelets, mononucleated cells (MNC), polymorphonucleated cells (PMN), and erythrocytes (RBC) from a single blood sample. This method was applied to a study of severe zinc deficiency in adult male rats. Significant reductions in plasma and femur zinc indicated severe zinc deficiency in the zinc-deficient animals compared with pair-fed or ad libitum-fed control rats in two separate experiments. However, we noted no differences in the zinc content of the MNC, PMN, RBC or lymph node lymphocytes, on a per cell basis, between the zinc-deficient and ad libitum- or pair-fed control groups of rats. A minor, but not significant (P greater than 0.05) reduction of platelet zinc was noted in zinc-deficient rats in two separate studies. These data indicate that the zinc contents of blood cellular components are not sensitive indicators of zinc deficiency in rats.
Animals↗
Zinc content of cellular components of blood: methods for cell separation and analysis evaluated.
Platelets, mononucleated cells, polymorphonucleated cells, and erythrocytes were separated from whole blood by use of discontinuous gradients of colloidal polyvinylpyrrolidone-coated silica ("Percoll"). We measured the zinc content of these cells by flame atomic absorption spectrophotometry, using a modified technique for micro-samples that obviated matrix interferences. Thus, results obtained by conventional flame atomic absorption and by the micro-method were identical. Inter-comparisons of separation methods indicated that separation of platelets and mononucleated cells by a two-gradient system of "Ficoll-Hypaque" (a synthetic polymer of sucrose) or Percoll was relatively poor, whereas there was a good separation when a tertiary gradient system of Percoll was used. The apparent zinc content of mononucleated cells depended on the degree of separation from the platelets, with contamination by platelets resulting in artificially high values for mononucleated cells.
Adult↗
Increased cholesterol in plasma in a young man during experimental copper depletion.
Signs of copper depletion were produced in a healthy man by an amount of dietary copper (0.83 mg/day) similar to that in some contemporary diets. Urinary and fecal loss of copper exceeded intake. Plasma copper, ceruloplasmin, and superoxide dismutase activity in erythrocytes decreased. Cholesterol in plasma increased, and hematologic indices were unchanged. Lipid metabolism may be a more sensitive index of copper nutriture than are changes in hematology. The findings support the hypothesis that inadequate copper nutriture or altered copper metabolism contributes to the occurrence of ischemic heart disease.
Adult↗
Iron status and brain function: serum ferritin levels associated with asymmetries of cortical electrophysiology and cognitive performance.
Levels of serum ferritin and iron were examined in relation to cognitive performance and quantitative EEG measures in 69 normal university students. Higher levels of serum ferritin were associated with greater activation of the left hemisphere relative to the right, indicated by less power in the EEG spectra from left hemisphere electrodes. Iron status was significantly related to cognitive performance on two of the cognitive tasks, and these relationships were consistent with the EEG asymmetries: higher ferritin predicted greater verbal fluency but poorer nonverbal auditory task performance. These results suggest that body iron stores are relevant to specific neurophysiological processes supporting attention.
Cognition↗
Effect of consuming fiber from corn bran, soy hulls, or apple powder on glucose tolerance and plasma lipids in type II diabetes.
The effects of consuming corn bran, soy hulls, or apple powder on glucose and lipid metabolism were investigated in two studies of persons with type II diabetes. Fiber sources, completely or partially added to bread, were incorporated into subjects' self-selected diets. Low fiber white bread served as a control. In study A, 10 subjects consumed 26 g fiber source daily; in study B, eight subjects consumed 52 g fiber source. Biochemical tests, including a 2-h postprandial glucose test using a low fiber formula meal, were scheduled after 2 and 4 wk of each dietary treatment. Soy hull consumption slightly improved some measures of glucose tolerance, with results varying between the studies. Consumption of 52 g corn bran decreased very low-density lipoprotein cholesterol, triglycerides, and glycosylated Hb, but subject tolerance was poor with the particle size used. Consumption of 52 g apple powder increased low-density lipoprotein and total cholesterol levels.
Aged↗
Influence of type and amount of dietary lipid on plasma lipid concentrations in endurance athletes.
Changes in plasma total cholesterol, triglyceride, and lipoprotein concentrations were assessed in three male endurance cyclists who consumed isoenergetic diets for 28-day periods in which carbohydrate, polyunsaturated fat, or saturated fat contributed about 50% of the daily energy intake. Dietary cholesterol was similar among the diets. Maximal aerobic capacity was maintained at 62 ml O2/(kg X min). Body weights were held within 3% of admission levels. The polyunsaturated fat diet significantly (p less than 0.05) reduced mean fasting plasma total cholesterol in comparison to the saturated fat and carbohydrate diets (160 versus 254 and 243 mg/dl, respectively). Similarly, the polyunsaturated fat diet depressed (p less than 0.05) mean plasma triglycerides relative to the saturated fat and carbohydrate diets (37 versus 62 and 79 mg/dl, respectively). No significant dietary effects were seen on high-density lipoprotein cholesterol. The observed changes in plasma total cholesterol were not significantly different than the values predicted by the Keys' equation, delta CHL = 1.35(2 delta S-delta P) + 1.5 delta Z. We conclude that under controlled conditions in which physical activity is constant l) dietary lipid differences influence fasting serum lipid and lipoprotein concentrations among men with high energy expenditures, and 2) the Keys' equation gives useful predictions of changes in plasma total cholesterol among vigorous men consuming different types and amounts of dietary lipid.
Adult↗
Effect of oral folic acid supplements on zinc, copper, and iron absorption and excretion.
Effects of folic acid supplements on zinc excretion patterns were seen during studies of mild zinc deficiency in men. During these studies eight men were fed diets containing 150 micrograms of folacin (by analysis) per day. Four of the men were supplemented with 400 micrograms of pteroylglutamic acid (folic acid) every other day. All of the men were fed diets containing about 3.5 mg/Zn per day which were supplemented with 4.0 mg/Zn day for 4 wk and unsupplemented for 16 wk, then supplemented with 30.0 mg/Zn day for 4 wk. Their body weights were kept constant by adjustments of energy intakes and expenditures. Duplicate diets, stools, and urines were analyzed for zinc, copper, and iron. Fecal zinc was significantly (p less than 0.001) higher in the group that received folic acid supplements during the initial control and low zinc intake periods. No significant differences were seen during the period of high zinc intake. During all dietary periods urinary zinc excretion was reduced by about 50% by folic acid supplementation. No apparent changes occurred in iron or copper excretion. These data indicate that supplemental folate influences zinc homeostasis, perhaps through formation of an insoluble chelate and impairment of absorption.
Adult↗
Maternal zinc, iron, folic acid, and protein nutriture and outcome of human pregnancy.
Four hundred fifty women were observed during pregnancy and postpartum. Forty-three variables including 12 laboratory indices of maternal nutrient status were assessed. Of the variance in fetal weight and head circumference 9.9 and 8.1%, respectively, were predictable by polynomial stepwise regression of laboratory indices of maternal nutriture. Maternal plasma zinc levels were inversely correlated with fetal weight. The occurrence of pregnancy complications in the highest and lowest quartiles of maternal plasma zinc, albumin, iron, and folic acid were compared. Using data only from the initial blood samples for which the trimester was identified precisely (n = 394), a significant association was found between the total occurrence of fetomaternal complications and zinc and albumin levels in the lowest quartile (zinc, p less than 0.02; albumin, p less than 0.02). Low zinc or low albumin were also associated with the specific complications of fetal distress (zinc, p less than 0.002; albumin p less than 0.002). High plasma folate was also associated with the total occurrence of complications (p less than 0.008) and with fetal distress (p less than 0.002). When all data (n = 713) including repeat blood samples and data from 56 mothers in whom the trimester could not be verified precisely were evaluated, associations between other complications and lowest quartile zinc and albumin and highest quartile folate were identified. Discriminant analysis of data from the initial blood samples revealed that plasma zinc was a discriminator for fetomaternal complications only in women in the lowest quartile for plasma zinc.
Adult↗
Changes in plasma zinc content after exercise in men fed a low-zinc diet.
For 30 days five healthy men aged 23-57 yr consumed a diet adequate in zinc (8.6 mg/day); they ate a low-zinc diet (3.6 mg/day) for the next 120 days and then received a zinc-supplemented (33.6 mg/day) diet for 30 days. Copper intake was constant at 1.8 mg/day. Aerobic capacity was determined periodically during each diet period. Relative zinc balance (% of control) declined during depletion (r = -0.28, P less than 0.009). Pre- and postexercise zinc concentrations decreased when dietary zinc was restricted (r = -0.61, P less than 0.0001 and r = -0.78, P less than 0.0001) and increased with supplementation (r = 0.61, P less than 0.008 and r = 0.76, P less than 0.0003, respectively). Both plasma zinc and hematocrit increased (P less than 0.01) after maximal exercise. To minimize the effect of hemoconcentration during exercise, the van Beaumont quotient (J. Appl. Physiol. 34: 102-106, 1973) was calculated using pre- and postexercise hematocrit and plasma zinc. The initial quotient of 1.8 +/- 1.8% (mean +/- SE) declined (P less than 0.05) to -7.4 +/- 2.3% during depletion. With zinc repletion, the quotient increased to 6.9 +/- 3.6%, which was greater (P less than 0.05) than the quotient in depletion but similar to the initial quotient. The quotient was a strong predictor (r = 0.71, P less than 0.0005) of the change in relative zinc balance during zinc depletion. In contrast, no changes were found in plasma copper content. These data suggest that zinc mobilization from tissues is impaired during zinc depletion, and they validate the use of the van Beaumont quotient as an index of change in body zinc stores.
Adult↗
Effect of a moderate increase in dietary protein on the retention and excretion of Ca, Cu, Fe, Mg, P, and Zn by adult males.
Mineral utilization was studied by metabolic balance techniques in 10 healthy male volunteers fed diets containing 65 and 94 g protein. Both diets contained approximately 650 mg calcium, 1 mg copper, 16 mg iron, 250 mg magnesium 1000 mg phosphorus, and 7 mg zinc. The diet consisted of conventional foods; the additional 29 g protein was egg white protein mixed into a beverage and fed twice per day. Plasma mineral levels were not affected by the increase in dietary protein. When the diet provided 94 g of protein, urinary calcium and zinc were slightly, but significantly, increased by an average of 35 mg (p less than 0.05) and 0.15 mg (p less than 0.001), respectively. Apparent mineral absorption and balance were unchanged by this modest increase in dietary protein.
Absorption↗
Maximal oxygen consumption as related to magnesium, copper, and zinc nutriture.
Forty-four healthy male university athletes and 20 untrained men underwent maximal treadmill exercise testing to determine the relationship between maximal oxygen consumption and various measurements of elemental nutriture. Hb and mean plasma and erythrocyte concentrations of magnesium, copper, and zinc were within established norms for both groups after a 12-h fast. Mean plasma copper concentration was significantly (p less than 0.01) higher in the athletes (90 +/- 14.3 versus 81 +/- 8.0 micrograms/dl). Average maximal oxygen consumption also was significantly (p less than 0.001) higher in the athletes [4.5 +/- 0.5 versus 3.3 +/- 0.6 L/min and 55.5 +/- 7.1 versus 47.0 +/- 6.0 ml/(kg x min)]. Plasma magnesium was significantly correlated (r = 0.46; p less than 0.002) with maximal oxygen consumption, ml/(kg x min), among the athletes. This relationship persisted when the effect of Hb concentration was removed by covariance analysis (p less than 0.005). Only a weak association (r = -0.32; p = 0.17) was found between oxygen consumption and plasma magnesium in the untrained men. We hypothesize that ionic magnesium may facilitate oxygen delivery to working muscle tissue in trained subjects.
Adult↗
Folate status of adult males living in a metabolic unit: possible relationships with iron nutriture.
Folate and iron status was monitored at monthly intervals in 40 adult males who were living in a metabolic unit for 2 to 8 months and consuming diets containing 150 to 250 micrograms of folate per day. There were significant (p less than 0.02) declines in hematocrit, serum folate, and serum ferritin. Men who participated in studies for 6 months or more or those with initial serum folate levels more than 10.5 ng/ml and erythrocyte folate levels more than 481 ng/ml also exhibited a highly significant (p less than 0.001) decline in red blood cell folate. Men with erythrocyte folate below 480 ng/ml or serum folate below 10 ng/ml and who participated in the studies for less than 5 months showed little or no change in folate status. The findings may reflect adjustments in body folate to reflect dietary intakes. Also a folate intake of 200 +/- 68 micrograms/day appeared to be adequate for maintenance of folate stores in adult males. A correlation between iron stores and folate status was also observed. However, this relationship may be coincidental.
Adult↗