Protein deprivation in primates. V. Fetal mortality and neonatal status of infant monkeys born of deprived mothers

Maternal amino acid supplementation for intrauterine growth restriction

Maternal dietary protein supplementation to improve fetal growth has been considered as an option to prevent or treat intrauterine growth restriction. However, in contrast to balanced dietary supplementation, adverse perinatal outcomes in pregnant women who received high amounts of dietary protein supplementation have been observed. The responsible mechanisms for these adverse outcomes are unknown. This review will discuss relevant human and animal data to provide the background necessary for the development of explanatory hypotheses and ultimately for the development therapeutic interventions during pregnancy to improve fetal growth. Relevant aspects of fetal amino acid metabolism during normal pregnancy and those pregnancies affected by IUGR will be discussed. In addition, data from animal experiments which have attempted to determine mechanisms to explain the adverse responses identified in the human trials will be presented. Finally, we will suggest new avenues for investigation into how amino acid supplementation might be used safely to treat and/or prevent IUGR.

Regulation of placental growth and chorionic somatomammotropin in the rhesus monkey: effects of protein deprivation, fetal anencephaly, and placental vessel ligation

An isocaloric protein-deficient diet (0.5 gm/kg of body weight) was administered throughout pregnancy to 10 rhesus monkeys (Macaca mulatta). Ligation of the fetal interplacental bridging vessels (n = 6) and functional fetal hypophysectomy (experimental induction of anencephaly) (n = 10) were performed at midgestation. Monkey chorionic somatomammotropin (mCS) concentrations were measured serially in maternal plasma and in fetal plasma at birth. Fetal weight, trimmed placental weight, and placental DNA content were determined near term in the experimental groups and in controls matched for gestational age. Maternal mCS concentrations rose steadily until term and this rise paralleled the increase in placental weight (mCS at term = 16.5 +/- 0.90 microgram/ml in maternal plasma and 0.024 +/- 0.001 microgram/ml in fetal plasma). At term, maternal mCS correlated with placental DNA (r = 0.61, P less than 0.01) and placental weight (r = 0.49, P less than 0.01), but not fetal weight. Maternal mCS levels were not affected by protein deprivation, fetal anencephaly, or ligation of the interplacental bridging vessels. Maternal protein deprivation had a negative effect on fetal birth weight (409 +/- 22 versus 472 +/- 18 gm for controls, P less than 0.05) and maternal weight gain during pregnancy but had no effect on placental DNA or trimmed placental weight. Fetal anencephaly resulted in a 23% reduction in trimmed placental weight, no change in placental DNA, a 40% reduction in fetal body weight, and a reduced fetal/placental weight ratio. Ligation of interplacental bridging vessels resulted in atrophy of the secondary placental disc, an increase in weight and DNA content of the primary placenta, and normal fetal weight. We have concluded that the hemochorial placenta of the rhesus monkey responds to interruption of the fetal villous circulation in the first half of gestation by initiating compensatory hyperplasia. Placental cellular replication in the second half of rhesus pregnancy in minimally regulated by the fetal central nervous system or the pituitary gland. Secretion of mCS is primarily controlled by the mass of functioning trophoblast.

Loci of discriminanda and discrimination proficiency

Three groups of nine juvenile rhesus monkeys (Macaca mulatta) whose mothers were maintained on diets affording 3.35, 6.70, and 13.4 percent of calories as protein during gestation were tested in a series of discrimination-learning tasks in which the critical variable was the loci of the relevant cues. The stimuli used were two 75-mm x 75-mm plastic plaques. The loci of the discriminanda (colored dots on the plaque) varied according to a 3 x 3 grid. No significant differences were found among the diet groups. A gradient of discriminability appeared that accorded with the location of the discriminanda: The stimulus region closest to the monkey made for the least and the farthest region the most difficulty of discrimination, also discriminanda on the right part of the stimulus were easier to discriminate than those on the left. Animals rewarded for displacing the plaque containing a colored dot learned the discriminations faster than those reinforced for displacing the blank plaque. The differences in salience of different parts of a stimulus plaque, though systematic, are modest, not dramatic.

Effects of various degrees of undernutrition of mice on pregnancy and conceptus

Maternal intake of drastically (1/2 of control) and substantially (1/2 of control) reduced feeding was studied in pregnant mice during gestation and embryonic development. Resorptions, fetal mortality rate and fetal weight were significantly affected by maternal undernutrition during the treatment period. The number of fetuses with intrauterine weight retardation was also significant.

Protein deprivation in primates. VIII. Early behavior of progeny

Infant rhesus monkeys whose mothers were fed diets providing 1, 2, or 4 g of protein/kg body weight/day during pregnancy were tested on 13 behavioral tests during their first 60 days of life. (The diets had been shown to affect significantly the weights and blood protein concentrations of both pregnant and nonpregnant females.) The tests samples a wide range of behaviors, including visual and auditory perception, feeding reflexes, and locomotion. Despite the maternal dietary differences, the performances of infants on all tests were comparable in all groups. These data contrast with the finding of persistent deficit in rats born of protein-deprived mothers.