The Journal of nutrition
-
The Journal of nutrition · Aug 1992
Prolonged lactation contributes to depletion of maternal energy reserves in Filipino women.
This paper identifies determinants of women's postpartum weight and weight change in a large group of Filipino women followed for 24 mo. Longitudinal, multivariate models focused on the effects of lactation, while controlling for energy intake, energy expenditure, reproductive history and seasonality. Lactation was found to have a significant negative effect on weight of urban women. ⋯ Models of net postpartum weight change (from 2 to 24 mo) among nonpregnant women confirmed an important role for lactation. The likelihood of weight loss was significantly increased by lactation of more than 12-mo duration, by greater maternal age and by low dietary energy intake. The effects of lactation on maternal energy reserves can be mitigated substantially be increasing maternal dietary energy intakes.
-
The Journal of nutrition · Jul 1992
Comparative StudyA method for estimating the available energy of incompletely digested carbohydrates in rats.
We developed a method to estimate the available energy from carbohydrates that are unavailable or partially unavailable through direct digestion and absorption. Radiolabeled bacterial and plant cellulose and polydextrose were administered orally to germfree and conventional rats. Label in breath, feces, intestinal contents and carcass were determined with excellent total recovery of the administered label. ⋯ In conventional rats, 65% of the administered cellulose and 54% of the administered polydextrose were recovered in feces. In conventional rats, appreciable amounts of cellulose were fermented and an available energy value of 3.5 kJ/g was calculated. Calculation of the total availability of polydextrose, taking into account the direct absorption of small amounts of monomers present and the efficiency of fermentation, indicates an available energy value of 4.7 kJ/g.
-
The Journal of nutrition · Jan 1992
Determining optimal heat treatment of soybeans by measuring available lysine chemically and biologically with rats to maximize protein utilization by ruminants.
Soybeans were heated in a forced air oven at 120 and 130 degrees C for 60 and 180 min, and at 140, 150 and 160 degrees C for 10, 30, 60, 90 and 120 min. Two types of measurements were used to determine optimal heat treatment of soybeans to maximize protein utilization by ruminants. One was to estimate the rate and extent of protein degradation in the rumen using an in vitro ruminal system. ⋯ As temperature increased, the time required to maximize post-ruminal available lysine decreased. The optimal heat treatment for soybeans heated in a forced air oven was: 140 degrees C for 120 min or greater, 150 degrees C for 60 min or 160 degrees C for 30 min. A loss of 15-22% of chemically determined available lysine was necessary to achieve the heat treatment that resulted in maximal post-ruminal available lysine.
-
The Journal of nutrition · Oct 1991
Composition of nitrogen-containing fractions in digesta from the distal ileum of pigs fed a protein-free diet.
The levels of free, peptide-bound and protein-bound amino acid nitrogen in endogenous N at the distal ileum of the pig were determined when the digestion of protein after sample collection was minimized. Six 14-kg pigs were fed a protein-free diet and samples of digesta from the distal ileum were collected. The digesta were centrifuged and the supernatant ultrafiltered. ⋯ The mean amounts of nitrogen from individual amino acids (free + peptide) in the ultrafiltrate (expressed as percentages of the total nitrogen for the respective amino acid in whole ileal digesta) were low, ranging from 3.0% for isoleucine to 16.6% for proline. The finding that free amino acid N + peptide N is a small fraction of total N in endogenous ileal digesta supports the use of a new method for determining endogenous loss, whereby the animal is fed hydrolyzed casein and the ileal digesta are ultrafiltered. The high-molecular-weight fraction provides a measure of endogenous nitrogen loss.
-
The Journal of nutrition · Mar 1991
Comparative StudyChanges in Cu,Zn-superoxide dismutase, cytochrome c oxidase, glutathione peroxidase and glutathione transferase activities in copper-deficient mice and rats.
Dietary copper deficiency was produced in Swiss albino mice and Sprague Dawley rats to compare changes in selected antioxidant enzymes. A 5-wk dietary treatment was employed, starting approximately 1 wk after birth for mice (initially via dams) and 3 wk after birth for rats. An additional confirmatory experiment was conducted with mice using the postweanling paradigm. ⋯ Activity of cytochrome c oxidase (mice) and Cu,Zn-superoxide dismutase (mice and rats) was lower in all seven organs examined from Cu-deficient animals compared with Cu-adequate animals, although there were organ and species differences. Compared with Cu-adequate controls, glutathione peroxidase activity was lower in liver and plasma of Cu-deficient mice and rats. Hepatic glutathione transferase activity was markedly lower in those Cu-deficient mice started on treatment at 1 wk of age but not in those mice or rats subjected to postweanling copper deficiency.