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Biomedical subjects

L Wada

Publications and source records attributed to L Wada.

12 recordsLinked to original sources
PubMed1994

Trace element nutrition during pregnancy.

The best means to ensure an optimal intake of trace elements during pregnancy is the consumption of a well-balanced diet that includes both animal- and plant-food sources. Although vegetarian diets provide reasonable sources of trace elements, especially in dried beans and seeds, flesh foods contain higher concentrations of trace elements that are in a more readily absorbable form. Iron is the only trace element for which routine supplementation is recommended. In the United States, the iodine content of the food supply is sufficiently high to make supplementation unnecessary, but use of iodized salt is not contraindicated. There is no need to screen pregnant women routinely for trace element status, except to monitor hemoglobin and hematocrit as an indicator of iron status. The best indicators that a woman's trace element status may be at risk is a history of poor food selections, a clinical disorder that alters trace element use or excretion, or prior residence in a region of the world where the trace element content of the soil is low.

Female↗
PubMed1993

The effect of exercise on fructose absorption.

The effect of exercise on intestinal absorption of fructose was evaluated in 10 subjects after they consumed four beverages, each containing a total of 50 g carbohydrate: 100% fructose (100F), 95% fructose and 5% glucose (95F), 70% fructose and 30% glucose (70F), and 100% glucose (100G), as well as a water placebo. With 100F and 95F, breath hydrogen, which is an index of incomplete absorption, increased significantly in all subjects. In contrast, hydrogen excretion did not increase in any subject after consumption of 100G or water, or in five of seven subjects who consumed 70F. The rapid increase in hydrogen excretion observed when consumption of 100F was followed by exercise was not noted during a comparable nonexercise trial. These data suggest that intestinal capacity for absorption of fructose is readily saturated after ingestion of amounts as small as 50 g and that exercise, which reduces intestinal transit time, can cause incomplete absorption of fructose.

Fructose↗
PubMed1992

Kinetics of 1,25-dihydroxyvitamin D metabolism in the aging rat.

To determine whether postmaturational aging influences the kinetics of 1,25-dihydroxyvitamin D [1,25(OH)2D] metabolism in the rat, we measured the metabolic clearance (MCR) and production (PR) rates of 1,25(OH)2D in 6-, 12-, 18-, and 24-mo-old Fischer 344 rats using the constant infusion method. Plasma calcium, phosphorus, and parathyroid hormone (PTH), urinary calcium and phosphorus, and glomerular filtration rate (GFR) were also measured. MCR and PR increased 57 and 91%, respectively (when expressed per rat), and 32 and 39%, respectively (when expressed per kg body wt), between 6 and 24 mo of age, with the greatest increase occurring between 18 and 24 mo. The plasma concentration of 1,25(OH)2D remained unchanged. Plasma PTH, when compared with 6-mo-old animals, was significantly elevated at 18 mo (147%) and even higher at 24 mo (240%). GFR (51Cr-labeled EDTA clearance) remained unchanged through 18 mo but tended to be reduced at 24 mo. Plasma phosphorus tended to decrease with age, whereas plasma calcium, urinary calcium, and urinary phosphorus did not differ among the age groups. These data indicate that both clearance and production of 1,25(OH)2D increase with postmaturational aging in the rat. They also suggest that the early age-related rise in plasma PTH is neither a consequence of low plasma calcium nor of renal insufficiency.

Aging↗
PubMed1991

Hormonal mediators of amino acid-induced glomerular hyperfiltration in humans.

It has been speculated that glucoregulatory hormones and/or renal autacoids mediate the increase in glomerular filtration rate (GFR) induced by the administration of protein or amino acids. Because infusion of a mixture of amino acids (AA mix), but not of branched-chain amino acids (BCAA) alone, increases GFR, we performed a crossover study in seven normal subjects in which the glomerular hemodynamic effects of separate 3-h infusions of these two amino acid solutions were compared with changes in potential mediators of this response, i.e., glucoregulatory hormones, renin, vasodilatory prostaglandins (PGs), and guanosine 3',5'-cyclic monophosphate (cGMP). As expected, infusion of the AA mix but not BCAA resulted in a prompt and sustained increase in GFR. Both infusions caused a significant increase in plasma insulin, whereas glucagon increased only with the AA mix. Plasma growth hormone was initially unchanged with both infusions but increased after 2 h of BCAA. Neither infusion significantly increased the urinary excretion of PGE2, 6-keto-PGF1 alpha, or cGMP. Both infusions resulted in a small but significant decrease in plasma renin activity. Infusion of BCAA but not the AA mix resulted in a progressive decrease in plasma glucose and potassium concentrations and an increase in renal sodium reabsorption that may have resulted from stimulation of insulin secretion that was not counterbalanced by a simultaneous increase in glucagon. Thus only changes in glucagon exhibited a significant temporal relationship with changes in GFR, lending further support to a role for glucagon as a mediator of amino acid-induced glomerular hyperfiltration.

Adult↗
PubMed1987

Folic acid: effect on zinc absorption in humans and in the rat.

The effect of folic acid on zinc absorption and utilization was studied in humans and in rats. Serum Zn response curves after a 25-mg oral dose of Zn was measured for 4 h with and without 10 mg folic acid. The increase in serum Zn expressed as AUC (area under the curve) was 57 mumol/L for Zn alone and 65 mumol/L with folate. Zn intragastric intubation experiments with rats showed that adding 4.4 or 176 micrograms of folate to test meals containing 13 micrograms Zn did not affect the bioavailability of Zn as measured by the retention of 65Zn by the liver and kidney. A 3-wk feeding test carried out with diets containing either 6 or 12 mg Zn/kg diet showed that adding either 2 or 160 mg of folic acid had no effect on growth or Zn uptake by the femur. These results do not indicate any inhibition of Zn utilization by folic acid.

Absorption↗
PubMed1986

Effect of low zinc intakes on basal metabolic rate, thyroid hormones and protein utilization in adult men.

Basal metabolic rate (BMR), thyroid hormones and protein utilization were measured in six young men participating in a 75-d metabolic study of low zinc intakes. During metabolic period (MP) 1 (12 d) and MP 3 (9 d) the subjects received 16.5 mg Zn/d. During MP 2 (54 d) they received 5.5 mg Zn/d. Nitrogen intake averaged 12.6 g/d. Mean BMR significantly decreased from 1.00 +/- 0.06 to 0.91 +/- 0.05 kcal/(kg X h) (mean +/- SD) with the low zinc diet and tended to increase during period 3. Serum thyroid-stimulating hormone, thyroxine (T4) and free T4 tended to decrease during the low zinc period and to increase when the adequate zinc diet was fed; only the decrease in free T4 was significant at P less than 0.05, however. Among the measures of protein status, urinary urea excretion, serum prealbumin, albumin and retinol-binding protein levels all decreased significantly during the low zinc period. The results suggest that low zinc intakes may be associated with decreases in BMR. In addition, decreases in thyroid hormone levels and alterations in protein utilization may occur.

Adult↗
PubMed1985

Zinc utilization in young men fed adequate and low zinc intakes.

Zinc absorption and balances were measured in six young men who were confined while participating in a 75-d metabolic study. A diet of conventional food providing either 16.5 or 5.5 mg Zn/d was fed. Apparent absorption of zinc was calculated from the zinc balance data and from the absorption of a zinc stable isotope added to the diet. The apparent zinc absorption calculated from the isotope data was about 25% when 16.5 mg zinc was fed; it increased to about 53 and 49% after 13 and 42 d, respectively, when 5.5 mg zinc was fed. Total zinc absorption fell from 4.1 mg/d to 2.7-2.9 mg/d during the low zinc period, however. This zinc absorption was sufficient to maintain crude zinc balances in five of the six subjects. Neither serum nor urinary zinc levels changed significantly during the period of feeding low levels of zinc. It appears that zinc absorption readily responds to changes in dietary zinc and that an intake of 5.5 mg Zn/d for about 8 wk does not cause serum or urinary zinc level to fall.

Absorption↗
PubMedDate not supplied

Copper absorption in young men fed adequate and low zinc diets.

Copper absorption was measured at two levels of dietary zinc in six healthy young men who were confined to a metabolic unit for a 75 d study of zinc utilization. A diet of conventional foods was fed, providing either 16.5 or 5.5 mg zinc and 1.3 mg copper daily. Copper absorption was determined by feeding 65Cu, a stable isotope of copper, once during the 16.5 mg Zn diet and near the beginning and end of the 5.5 mg Zn diet. Apparent copper absorption averaged 48.1% when the 16.5 mg Zn diet was fed. This was significantly higher than the averages of 37.2 and 38.5% when the 5.5 mg Zn diet was fed. Absorption also differed significantly among subjects. Fecal copper did not differ between diets or among subjects. All subjects were in positive copper balance at both levels of dietary zinc. These results suggest that a dietary zinc intake slightly above the Recommended Dietary Allowance of 15 mg/d does not increase fecal copper loss and does not interfere with copper absorption.

Absorption↗