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Biomedical subjects

T A Morck

Publications and source records attributed to T A Morck.

9 recordsLinked to original sources
PubMed1991

Studies of the permeability of isolated porcine peritoneum to nutrients: saccharides.

Isolated peritoneal membrane, freshly harvested from pigs, was studied in vitro to determine the permeability of the membrane to saccharide nutrients. Studies were performed with glucose and sucrose at various transmembrane gradients ranging from 150 to 600 mosm/liter (mmol/liter) and with polysaccharide at a 300 mosm/liter gradient. Findings indicate that flux of these nutrients across the isolated peritoneum is related to molecular weight and that sufficient kilocalories will traverse the membrane to provide for adequate carbohydrate nutrition (calculated to deliver more than 3000 kcal/day at gradients of 150 mosm/liter). Polysaccharide flux studies suggest that carbohydrate calories may be provided in the form of complex molecules and not only in the form of glucose. Studies of 1:1 serum and polysaccharide mixtures showed the conversion of polysaccharide to glucose by serum in vitro. When rats were given intraperitoneal polysaccharide their blood glucose levels rose promptly although they remained fasting, suggesting an in vivo conversion also occurs. These findings provide support for use of polysaccharides intraperitoneally as means to reduce the osmolarity of fluid administered for nutritional support; this would increase tolerance while still providing ample calories. The in vitro apparatus used in these studies provides a mechanism to study individual nutrients and yields highly reproducible results. These studies add further evidence that intraperitoneal nutrition is feasible.

Animals↗
PubMed1985

Soy protein products and heme iron absorption in humans.

Dual radioiron tags were used to measure both heme and nonheme iron absorption simultaneously from meat-containing meals in 76 healthy male volunteers. Partial substitution of beef with soy flour reduced the availability of nonheme iron but improved the percentage absorption of heme iron significantly (27 to 59% rise). In contradistinction three other powerful inhibitors of nonheme iron absorption, bran, tea, and desferrioxamine, had no appreciable effect on heme. Ascorbic acid (100 mg and 1000 mg in separate experiments) improved nonheme iron uptake markedly but also failed to alter the assimilation of heme. These studies demonstrate that the deleterious effects on iron nutrition of substituting soy protein for beef are partially offset by improved availability of the remaining heme iron as well as by an increase in the nonheme iron content of the meal.

Adolescent↗
PubMed1983

Inhibition of food iron absorption by coffee.

Dual isotope studies were performed in iron replete human subjects to evaluate the effect of coffee on nonheme iron absorption. A cup of coffee reduced iron absorption from a hamburger meal by 39% as compared to a 64% decrease with tea, which is known to be a potent inhibitor of iron absorption. When a cup of drip coffee or instant coffee was ingested with a meal composed of semipurified ingredients, absorption was reduced from 5.88% to 1.64 and 0.97%, respectively, and when the strength of the instant coffee was doubled, percentage iron absorption fell to 0.53%. No decrease in iron absorption occurred when coffee was consumed 1 h before a meal, but the same degree of inhibition as with simultaneous ingestion was seen when coffee was taken 1 h later. In tests containing no food items, iron absorption from NaFeEDTA was diminished to the same extent as that from ferric chloride when each was added to a cup of coffee. These studies demonstrate that coffee inhibits iron absorption in a concentration-dependent fashion.

Adolescent↗
PubMed1983

Effect of fiber on nonheme iron absorption.

The effect of fiber on the absorption of food iron was examined by performing multiple radioiron absorption tests in normal male and female subjects. In an initial study, we added bran, pectin, or cellulose to muffins prepared with wheat flour. Because of the low values obtained in this study, another study was done in which apple juice containing 50 mg of ascorbic acid was added to the meal to increase iron absorption averaged 2.26% from plain muffins, 1.07% from bran muffins, 1.89% from pectin muffins, and 2.26% from cellulose muffins. Only the effect of bran was statistically significant. We next designed two complex meals that differed maximally in their content of naturally occurring fiber but that were matched with respect to macronutrient, mineral, iron, and ascorbic acid contents. Mean absorptions from the low- and high-fiber meals were significantly different, averaging 6.07% and 2.96%, respectively. These results demonstrate that inhibition of iron absorption is not a universal property of all fiber sources. Moreover, the relatively modest effect of maximally altering the natural fiber content of a meal suggests that fiber is not a major determinant of food iron availability in humans.

Adolescent↗
PubMed1982

Reduction of the soy-induced inhibition of nonheme iron absorption.

Recent studies in normal men have demonstrated that soy products have a pronounced inhibitory effect on the absorption of nonheme dietary iron. The purpose of the present investigation was to explore approaches to overcoming this inhibition. A modest but significant increase in iron absorption was observed when test meals containing either isolated soy protein or whole soybeans were baked at 200 degrees C. The addition of 100 mg ascorbic acid to a meal containing isolated soy protein had a more dramatic effect, increasing mean absorption from 0.6 to 3.2%. A similar but less pronounced increase was observed when meat was added to the isolated soy protein meal. These results indicate that the inhibitory effect of soy can be reversed to some extent by substances known to enhance nonheme iron absorption.

Adolescent↗
PubMed1981

The inhibitory effect of soy products on nonheme iron absorption in man.

Radioiron absorption studies were performed in male volunteer subjects to determine the effect on nonheme iron absorption of various semipurified proteins. When egg albumen and casein were substituted in protein-equivalent quantities in a semisynthetic meal, similar mean absorptions of 2.5 and 2.7% were observed. In contrast, isolated soy protein reduced absorption sharply, to an average of 0.5%. When egg albumen in the semisynthetic meal was replaced with full fat soy flour, textured soy flour, and isolated soy protein, absorption fell from 5.5 to 1.0, 1.9, and 0.4%, respectively, indicating an inhibitory effect by a wide range of soy products. The effect of substituting textured soy flour for meat in a meal containing a hamburger, french fries, and a milkshake was also evaluated. With 3:1 and 2.1 ratios of meat to unhydrated textured soy flour, absorption decreased by 61 and 53%, respectively. The soy products tested in this study have a pronounced inhibitory effect on the absorption of nonheme iron.

Absorption↗
PubMed1981

Iron availability from infant food supplements.

Radioiron absorption tests are performed in human volunteer subjects to measure iron absorption from five infant food supplements. These products included corn-soya-milk, corn-soy blend, wheat-soy blend, wheat protein concentrate blend, and whey-soy drink mix. In iron replete adult males, mean percentage absorption ranged from 0.6 to 1.4%. By relating these results to absorption from a reference dose of inorganic iron, it was estimated that iron-deficient infants would absorb between 1.7 and 4.1% of the iron contained in the infant foods. These results indicate that this fortification iron is poorly absorbed, and probably supplies only about half of the daily iron requirement for iron deficient children between 6 months and 3 yr of age.

Absorption↗
PubMed1981

Iron requirements of White Leghorn hens.

Studies were conducted to determine the iron requirements of laying and breeding hens (Gallus domesticus). Single Comb White Leghorn hens fed a purified diet containing 15 ppm iron exhibited a rapid decline in hematocrit, blood hemoglobin, egg iron concentrations and hatchability of fertile eggs. No effects of the low iron diet on body weight, feed consumption, or fertility were observed. When hens were fed graded levels of iron from 15 to 65 ppm at 10 ppm increments, a dose response was observed for hematocrit and hatchability. The iron requirement for maintenance of hematocrit was between 35 and 45 ppm iron. Fifty-five parts per million iron were required for maximum hatchability of fertile eggs.

Anemia, Hypochromic↗