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Biomedical subjects

H H Sandstead

Publications and source records attributed to H H Sandstead.

At least 91 records · Page 5Linked to original sources
PubMed1982

Copper bioavailability and requirements.

Knowledge of factors affecting the bioavailability of dietary copper is limited. Intestinal absorption of copper appears to be facilitated by L-amino acids. Picolinic acid has a favorable binding affinity for copper and may facilitate its absorption. Measurements of the dietary requirements for copper in adult men have shown the requirement to range from about 1.5 to 2.0 mg daily, levels similar to the 2.0 mg estimate suggested in the past. Comparison of the copper requirements with the levels of copper present in some contemporary diets suggests that marginal copper nutriture may not be rare. Persons who consume diets high in zinc and low in protein are at risk of copper deficiency. High intakes of sources of dietary fiber apparently increase the dietary requirement for copper. Studies in one man have shown that signs of mild copper deficiency can be produced experimentally when a conventional diet containing about 0.8 mg of copper is fed. At this time, the 2 to 3 mg daily intake of dietary copper suggested by the National Research Council (63) seems appropriate.

Adult↗
PubMed1982

Influence of dietary zinc on rat brain catecholamines.

Weanling rats were fed a 20% sprayed egg white, zinc-deficient diet for 9 or 10 days. One group (zinc-deficient) was fed ad libitum and given distilled deionized water; a second group was individually pair-fed to rats in the zinc-deficient group; a third group was fed ad libitum; a fourth group was also fed ad libitum, but was fasted overnight prior to slaughter. The latter three groups were given 25 ppm zinc (as zinc acetate) in the water. The brain was excised and the catecholamines were extracted with 0.1 M perchloric acid separated by reverse phase HPLC and measured electrochemically. There did not appear to be a correlation between food intake and brain catecholamine concentrations in any of the groups examined. Brain norepinephrine concentrations in the zinc-deficient rats, however, were significantly higher than in the pair-fed or ad libitum-fed rats.

Animals↗
PubMed1982

Mild zinc deficiency and undernutrition during the prenatal and postnatal periods in rats: effects on weight, food consumption, and brain catecholamine concentrations.

Rat dams were fed a 20% sprayed egg white diet, containing 10 ppm zinc, during gestation and lactation (ZD) and compared to zinc-adequate pair-fed (PF) and ad libitum fed (AL) control animals. AL dams consumed more food than the ZD group. Throughout gestation AL dams were heavier than PF and ZD dams. During lactation AL dams were heavier than the ZD dams which in turn were heavier than PF dams. Birth weights of ZD pups were less than the PF and AL pups. Postnatal daily weight gains of ZD pups were less than the PF pups which were less than AL pups. After weaning ZD pups fed commercial rat food gained less weight than PF and AL pups, and weight gain of PF and AL pups was similar. ZD dams had lower plasma zinc than control dams at parturition and at the end of lactation. Femur zinc of ZD, PF and AL dams was similar at parturition. ZD dams had lower femur zinc than PF and AL dams after lactation. Femur and liver zinc of ZD pups was lower than in PF and AL pups at birth. Regional brain catecholamine levels were not measured, but whole brain concentrations of catecholamines were not different among the groups. Thus, while mild zinc deficiency adversely affected growth of pups, effects on brain remain to be identified.

Animals↗
PubMed1982

Epiphyseal plate development in the zinc-deficient rat.

The effect of zinc deficiency on shearing strength, histological changes and proline utilization of the epiphyseal plate of the tibia of the weanling male rat was studied. A diet was fed based on sprayed egg white and containing less than 2 mg of zinc per kilogram. Over 27 day, the force required to displace the epiphysis of the zinc-deficient (ZD) rats was always less than that required for pair-fed (PF) controls. After 18 days, approximately 15% more force was required to displace the epiphysis of the PF rats than was required in the ZD rats. The thickness of the outside compact bone next to the epiphyseal plate region as determined by scanning electron microscopy was thicker in the ZD rats than in the PF controls of comparable age. The epiphyseal plates narrowed as the rats aged, and were clearly discernible in PF controls but not in ZD rats. The incorporation of L-[U-14C]proline into the epiphysis was significantly less in rats deprived of zinc for 16-22 days than in PF controls.

Animals↗
PubMed1981

Effect of zinc deficiency on appetite and plasma amino acid concentrations in the rat.

1. Levels of zinc in liver and plasma of the Zn-depleted rats fluctuated with the feeding cycle and were significantly higher at the bottom than at the top of the cycle. As Zn deficiency became more severe fluctuations in plasma Zn diminished. Concentrations of Zn in liver, in contrast to levels in plasma and femur, were not markedly lowered by day 15. 2. In contrast to ad lib-fed (AL) and overnight-fasted (OF) controls, some pair-fed (PF) controls had elevated levels of Zn in liver and plasma. 3. Intakes of water and food were significantly correlated in Zn-deficient rats. Packed cell volumes were significantly higher for Zn-depleted than for AL and PF rats. 4. Food intakes and plasma glucose concentrations were related in AL, OF and PF control rats but not in Zn-deficient rats. 5. At day 15 of Zn deficiency the order of total plasma amino acid concentrations in the groups of rats was AL greater than Zn-deficient greater than OF greater than PF. Many of the differences between the AL and OF groups for individual plasma amino acids also appeared in the Zn-deficient group at the top and bottom of the feeding cycle. Differences in individual amino acid concentrations at the top and bottom of the feeding cycle tended to be opposite in the PF and the Zn-deficient group. Levels of tyrosine and tryptophan in plasma were correlated (P less than 0.05) with the cyclic feeding pattern of the Zn-deficient group; however, the ratios tryptophan or tyrosine: sum of other large neutral amino acids did not correlate significantly with the eating habits of Zn-deficient rats.

Amino Acids↗
PubMed1981

Methods for determining nutrient requirement in pregnancy--I.

There are several methods for evaluating nutritional requirements. Under appropriate circumstances, all can provide useful information. The most precise methods are those in which subjects live under controlled conditions. None of the methods is foolproof. The cost increases with the degree of control. Therefore, less expensive, less precise methods, may be appropriate for preliminary studies. If preliminary findings are positive, more carefully controlled studies should be done to obtain definitive information.

Adolescent↗
PubMed1981

Effects of dietary fiber from wheat, corn, and soy hull bran on excretion of fecal bile acids in humans.

Effects of dietary fiber on bile acid excretion and fecal bile acid concentration have been studied for seven subjects fed 26 g of either soft white wheat bran, corn bran, soybean hulls, or hard red spring wheat bran. Results indicate that even in a controlled study using a metabolic word, individual subject variation has a major impact on fecal bile acid excretion. This observation has not been fully appreciated in previous human studies. No significant change in the composition of fecal bile acids could be associated with the decrease in serum lipid levels previously reported. A method for the isolation and quantitation of fecal bile acids is described which does not require purification by thin-layer chromatography. A preliminary study of lyophilized fecal samples stored at -10 to -30 degrees C showed very little or no change in bile acid content. Samples stored at room temperatures for 11 months showed a substantial reduction in bile acid content.

Bile Acids and Salts↗
PubMed1981

Whole body surface loss of trace metals in normal males.

Whole body surface losses of zinc, copper, and iron were measured in 13 male volunteers who lived in a controlled environment for 4 to 9 months. For 88 daily samples, the mean losses for zinc, copper, and iron were 0.50, 0.34, and 0.33 mg/day (3.9, 26, and 2.1% of the mean dietary intakes, respectively). There was a large variance in metal losses with no significant differences in variance within-versus-between subjects or on the same-versus-different diets. The surface losses of zinc and iron increased the apparent dietary requirements determined by balance measurements only 5 and 3%, respectively, while the increase in copper requirement due to surface loss was 25 to 30%.

Adult↗
PubMed1981

Dietary fiber and personality factors as determinants of stool output.

We examined effects of fiber on stool output, since this is one of the primary mediating variables for the hypothesized relationship between fiber and disease. Total neutral detergent fiber in the dietary fiber source was predictive of stool weight but not frequency. Substantial individual differences in stool output remained when dietary factors were controlled. Personality measures were used to predict stool weight and frequency independently of diet, and accounted for about as much variance in stool output as did dietary fiber. These results suggest that personality factors predispose some persons to low stool output. These individuals may benefit particularly from dietary fiber.

Adolescent↗
PubMed1980

The human requirement for copper. I. Healthy men fed conventional, American diets.

Each of 13 men was fed diets made from conventional foods for two to seven periods lasting 30 days in a metabolic ward. There was a total of 47 experimental periods. Supplementation of the basal diet with each of several bran or other fiber sources was done in no particular order; each subject was fed the unsupplemented diet for at least one period. The diet was designed to contain amounts of essential nutrients close to the Recommended Dietary Allowances; it resembled the "average" American diet as it contained 16% protein, 40% fat, and 44% carbohydrate. Only minimal variation in energy intake and physical activity of the men was permitted; body weight remained constant within +/- 2%. Copper in food, feces, and urine was measured during the last 12 days of each period. Linear regression of balance (intake minus the sum of fecal and urinary losses) revealed a daily requirement of 1.30 mg (95% confidence limits of 1.24 to 1.35 mg). On consideration of a calculated surface loss of 0.25 mg/day, the requirement is 1.55 mg/day. The requirement was unaffected by the type of fiber source. A review of published data revealed that this requirement substantially exceeds the amount of copper found in many conventional diets.

Copper↗
PubMed1980

A mathematical model of creatine metabolism in normal males--comparison between theory and experiment.

Based upon knowledge that the body creatine pool in normal males undergoes a constant fractional conversion rate to creatinine and that 24-hr urinary creatinine excretion is dependent upon creatine and protein intakes, we developed a mathematical model with feedback which describes the creatine pool size and, consequently, the 24-hr urinary creatinine excretion as a function of time after change in diet. Validity of the model was tested by comparing calculated with experimental changes in 24-hr urinary creatinine excretion rates of male volunteers who were participating in studies of effects of "high" and "low" protein diets on mineral requirements. The model was further verified by comparing published changes in creatinine excretion rates with changes predicted by the model. It is concluded that the effects of changes in creatine and protein intakes upon the body creatine pool size in healthy males can be described mathematically by a model with a feedback component. It is also cautioned that 24-hr urinary creatinine excretion may not be a good reference for quantifying other urinary substances under circumstances where the creatine or protein intakes are not constant.

Adult↗