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Biomedical subjects

S J Ritchey

Publications and source records attributed to S J Ritchey.

At least 37 records · Page 2Linked to original sources
PubMed1981

Plasma lipid and lipoprotein cholesterol concentrations in adult males consuming normal and high cholesterol diets under controlled conditions.

Twenty-three young adult males were fed diets containing either 400 or 1400 mg of cholesterol per day under controlled conditions for 4 wk. There were minimal differences between the two diets in total protein, carbohydrate, fat, and the P/S fatty acid ratio. In both diets 400 mg of cholesterol was supplied from nonegg food sources; the additional 1000 mg of cholesterol was from four whole eggs. Blood samples were collected after a 12- to 14-h fast at the beginning of the study, weekly throughout the experimental period, and 1 wk after completion of the study. Plasma total cholesterol and triglycerides and high-density, low-density, and very low-density lipoprotein cholesterol levels were measured. No significant differences in plasma total cholesterol, triglycerides, and lipoprotein cholesterol levels were observed between groups at any time. However, plasma cholesterol and cholesterol content of individual lipoproteins varied considerably among the individual subjects fed the high cholesterol diet. The importance of changes in the properties and metabolic activity of individual lipoproteins induced by dietary cholesterol with or without gross changes in the cholesterol levels remains to be determined.

Adult↗
PubMed1981

Copper and zinc utilization in elderly adults.

Elderly adults were provided with 2.33 mg of copper and either 7.80 or 23.26 mg of zinc daily during a 30-day metabolic study. Excretions of both minerals were measured throughout the study. The subjects were able to maintain apparent positive balance for copper, but were in negative balance for zinc on both levels off intake. Copper retention was significantly reduced by intake of the higher amount of zinc. These results support other reports indicating antagonism between the two nutrients. The hair content of zinc and copper was higher in females than in males and was in the ranges indicative of long-term adequate intakes. Recumbent length was significantly greater than standing height and should be investigated further as a more accurate measure of body height in the elderly.

Aged↗
PubMed1981

Carcass nitrogen as a predictor of protein requirement for mature female rats.

The minimal level of dietary protein required for maintenance of nitrogen equilibrium was investigated using Sprague-Dawley rats, 12 months of age. Rats were fed casein, supplemented with methionine, at levels ranging from 0.84 to 5.18% of the diet for 4, 8 or 12 weeks and were compared to a control group fed a similar diet containing 9.90% protein or to a baseline group fed a stock diet. The effect of dietary protein levels on total serum protein and on liver and carcass composition was assessed. Protein requirement levels with 95% confidence intervals were predicted by linear regression. Dietary protein levels of 2.14% or lower were not adequate to maintain body weight and serum protein levels, and animals fed these diets had elevated levels of liver lipid. Protein nutriture of rats fed 3.20% protein was generally intermediate between those fed 2.14% or less and those fed 3.62% or greater. Compared to carcass nitrogen, carcass water was not as reliable a parameter for determination of protein requirements. Using the baseline group for comparison and carcass nitrogen as the dependent variable, a dietary protein requirement was predicted for these animals of 3.91--4.19% with confidence intervals of 3.50--4.56% and 3.13--5.48%, respectively. This level is comparable to the maintenance protein requirement of 4% indicated by the National Research Council for adult rats.

Animals↗
PubMed1980

Effects of zinc intake on copper balance in adult females.

Adult women were fed dietary regimens that provided 2.0 mg of copper and either 8, 16, 24, mg of zinc daily in a 18-day controlled metabolic study. Zinc retentions were positive at all levels of intake, but the lowest level was probably not sufficient to maintain equilibrium. An intake of 16 mg of zinc was sufficient to maintain subjects in positive balance or at equilibrium, although this level may be marginal for individuals living in warm climates with potentially large sweat losses. None of the dietary groups was in positive balance on a copper intake of 2 mg/day, although the dietary level of zinc had no effect on copper retentions. Serum levels of copper decreased and zinc increased during the study.

Adult↗
PubMed1980

Effects of oral contraceptive agents on copper and zinc balance in young women.

Young adult women were selected from a group of volunteers on the basis of present and past use of oral contraceptive agents. Subjects were either those who had never used oral contraceptives or those who had used an agent for a minimum of two menstrual cycles. All subjects were fed diets that provided 2.02 to 2.11 mg of copper and 9.15 to 9.10 mg of zinc daily in an 18-day controlled metabolic study. Both oral contraceptive users and nonusers were in negative zinc balance and zinc excretion as not different (P > 0.05) for the groups. Oral contraceptives did not alter (P > 0.05) the metabolic balance of copper; the mean copper retention values were -0.16 mg/day for the nonusers and -0.13 mg/day for the users of oral contraceptives. As anticipated from reports in the literature, the plasma copper levels were higher (P < 0.01) in the oral contraceptive group, but the levels of zinc were not different. Although blood levels of zinc and copper are usually changed with the use of oral contraceptives, the retention of the two nutrients appears not to be affected.

Adult↗
PubMed1979

Zinc retention and losses of zinc in sweat by preadolescent girls.

Preadolescent girls, ages 7 to 9 years, were fed levels of zinc ranging from 5.61 to 14.61 mg/day during an 18-day metabolic study. All other nutrients were provided at or above Recommended Dietary Allowance levels. The sweat loss of zinc was measured using an arm-bag method and whole body zinc loss was calculated from whole body nitrogen and arm loss of nitrogen and zinc. Fecal zinc reflected dietary zinc, but urinary zinc remained relatively stable. The mean daily loss of zinc through sweat was calculated to be 1.43 mg. Zinc retentions were not significantly different (P greater than 0.05) though the retention increased generally with intake of zinc. A comparison of these data with previously reported studies indicated that the absorption of zinc was usually in the range of 20 to 30%. Based on sweat losses reported by others and found in this study and on usual absorption of zinc, it appears that diets should provide a minimum of 7 mg of zinc daily for growing children.

Child↗
PubMed1979

Body weight and depot fat changes as influenced by exercise and dietary fat sources in adult BHE rats.

Adult male BHE rats were fed diets containing 15% of either corn oil (CO) or medium chain triglycerides (MCT) as the dietary source of fat. Further, rats were allowed to remain sedentary or were forced to exercise by swimming for 1 hour daily, for 3 weeks, followed by swimming for 2 hours daily for 3 weeks. The exercise for 3 weeks caused significant reductions in average body weight gains. After 6 weeks of exercise the lipid content of the adipose cells was reduced by about 50%. Fat cell numbers were not changed by either fat source or exercise, but fat cell size was significantly reduced after swimming daily for 6 weeks.

Adipose Tissue↗
PubMed1978

Position paper on RDA for protein for children.

The Recommended Dietary Allowances (RDA) by the National Academy of Sciences are revised approximately every five years. The RDA are compromise opinions of highly qualified nutritional scientists based on interpretations of available data. As with any interpretations of available data. As with any, interpretations and opinions not found on definitive information, they are subject to challenges. The RDA for protein for 7-to 9-uear-old children have been adjusted downward from 60 g in 1958 to 36 g in 1974, a 40% reduction. Data from our laboratories have shown positive apparent nitrogen balances on intakes as low as 18 g daily when no allowances were made for integumental and other nitrogen losses, however, based on accumulative data over several years we calculate the protein requirement to be 45 g daily from a typical American diet. If a safety factor of 30% is added the allowance would become 58.5 g. Currently the RDA for protein for the 7- to 10-year-old child supplies 6% of the RDA for Calories which contrasts to 8.30 and 9.20% for adult males and females, respectively. For comparison, energy from protein as a percentage of total energy for some common foods are: white bread, 12%; corn meal 10%; white rice 7%; and wheat flour 13%.

Adult↗
PubMed1977

The relationship of zinc to protein utilization in the preadolescent child.

The effects of zinc intake on nitrogen utilization was investigated during a 20-day balance study with 23 preadolescent girls. The children were fed a diet which provided 4.17 g of nitrogen and 5.5 mg of zinc daily; the diet was supplemented with a combination of 5 mg of zinc and/or nitrogen supplied from either amino acids or nonspecific nitrogen. Complete collections of excreta were made throughout the study. Neither the supplementation of amino acids nor zinc improved the retention of nitrogen. Urinary excretion of urea nitrogen, uric acid, and creatinine were not different as a result of zinc supplementation. Subjects consuming the lower level of zinc were in negative zinc balance, but the subjects consuming 10.5 mg of zinc were in positive balance. The supplementation of this low protein diet with amino acids did not improve nitrogen retention.

Amino Acids↗
PubMed1976

The effects of sweat nitrogen losses in evaluating protein utilization by preadolescent children.

A nitrogen balance study was conducted to determine the effects of three levels of nitrogen intake on the loss of nitrogen through sweat and to assess further the impact of sweat nitrogen on protein needs of preadolescent children. Values were determined through the collection of 24-hr, total body sweat samples from twelve healthy boys having a mean age of 8 years, 8 months. Mean height and weight of the subjects were 131.4 cm and 31.0 kg, respectively. Environmental conditions were relatively constant during the study. Mean sweat nitrogen losses were 208, 287, and 368 mg/day on daily protein intakes of 29, 54, and 84 g, respectively. Mean nitrogen balances per day were 0.39, 0.09, and 1.95 g when sweat nitrogen losses were included in the calculations. At the lower and moderate levels of protein intake, nine and six subjects were in negative nitrogen balance when sweat losses were considered. Sweat nitrogen losses in the boys were similar to a previous study with preadolescent girls. Based upon published basal metabolic rates and mean sweat nitrogen losses of 261 and 288 mg/day for girls and boys, the nitrogen lost through sweat was 0.25 mg/basal kcal for both sexes. An estimation of 0.5 mg/basal kcal for integumental nitrogen loss appears realistic for this age group.

Body Surface Area↗
PubMed1976

An estimation of mineral losses through arm sweat of preadolescent children.

Balance studies were conducted to determine the effects of three levels of nitrogen intake on the loss of nitrogen through sweat in preadolescent boys and girls. During the studies, the losses of calcium, iron, magnesium, manganese, potassium, sodium, and zinc were determined in the arm sweat of the subjects. Sweat from the forearm was collected in a polyethylene bag for 1 hr on three different occasions. Using the concentrations of nitrogen in the arm bag and in the whole body collection and the concentration of minerals in the arm bag, the total body loss of minerals were estimated. Losses of minerals through sweat, expressed as a percentage of intake, ranged from 0.12 to 1.10%. Under conditions of these studies, sweat losses of the essential minerals were not a significant factor in estimating total losses.

Calcium↗
PubMed1975

Sweat nitrogen losses by and nitrogen balance of preadolescent girls consuming three levels of dietary protein.

A nitrogen balance study was undertaken to determine the effects of three levels of nitrogen intake on the loss of nitrogen through sweat and to assess the impact of sweat nitrogen on the protein needs of preadolescent girls. Values were determined through the collection of 24-hour, total body sweat samples from 15 healthy girls with a mean age of 8 years, 7 months. Mean height and weight of the subjects were 132 cm and 28.9 kg, respectively. Mean sweat nitrogen losses, collected under uncontrolled environmental conditions, were 201 mg, 263 mg and 319 mg/day on 34 g, 57 g and 88 g of protein intake. The environmental conditions throughout the study remained fairly constant. Mean nitrogen balances per day were 0.04 g, 0.55 g and 1.42 g on the respective levels of nitrogen intake, with the inclusion of sweat nitrogen loss, however, a negative nitrogen balance per day was found in 8 and 2 subjects on 34 g and 57 g protein intake. After considering nitrogen retention of 0.3 g which has been recommended by NRC for the minimum nitrogen allowance for growth of preadolescent children, protein intakes higher than that recommended by the NRC-RDA for preadolescent girls may be required for support of normal growth.

Body Surface Area↗