Protein deficiency in primates. IV. Pregnant rhesus monkey

The IGF axis in baboon pregnancy: placental and systemic responses to feeding 70% global ad libitum diet

Information on the influence of poor maternal nutrition on the regulation of responses to pregnancy, placental and fetal growth and development is critical to a better understanding of pregnancy physiology and pathophysiology. We determined normal changes and effects of controlled and monitored moderate nutrient restriction (NR) (global nutrient intake reduced to 70% of food consumed by mothers feeding ad libitum from 0.16 to 0.5 of gestation) in the baboon, on important hematological, biochemical, and hormonal indices of fetal growth and placental function. Serum IGF-I:IGFBP-3 ratio was lower in pregnant than control non-pregnant baboons feeding ad libitum. Serum concentrations of total and free IGF-I were decreased in NR mothers compared with controls (p<0.05). The decrease in fetal IGF-I did not reach significance (p=0.057). Serum IGF-I: IGFBP-3 ratio was decreased by NR in both mothers and fetuses. Maternal serum IGF-II was unchanged by NR. Placental IGF-I mRNA and protein abundance were similarly reduced whereas IGF-II mRNA increased in placental tissue of NR compared to control mothers. Systemic (maternal) and local (placental) IGFBP-1 and IGFBP-3 mRNA and protein abundance were unchanged by NR. Type 1 IGF receptor protein in the syncytiotrophoblast increased in NR. Type 2 IGF receptor protein was present in the stem villi core, and decreased after NR. We conclude that moderate NR in this important non-human primate model significantly disrupts the maternal and placental IGF-IGFBP axis and influences placental expression of this key system at the gene and protein level. Changes observed appear to be directed toward preserving placental growth.

Comparative and evolutionary dimensions of the energetics of human pregnancy and lactation

The purpose of this article is to compare the energetics of reproduction for human and other primates in order to evaluate the extent to which human reproductive energetics are distinct from other primates and other large-bodied placental mammals. The article also evaluates the energetics of human and primate gestation and lactation using data from a variety of different populations living under different environmental circumstances. Energetics refers to energy intake and expenditure, and changes in body fat stores. Human and nonhuman primates have longer periods of gestation and lactation and slower prenatal and postnatal growth than other mammals of similar size. This reduces daily maternal energy costs. The development of sizable fat stores is not unique to humans, but fat stores are typically greater in human females and may play a greater role in reproduction. The strategies used to meet the energy costs of pregnancy vary among populations of humans and nonhuman primates and among humans interindividual variability is high. In pregnancy, some increase energy intake but others apparently do not. Increases in metabolic efficiency are evident in some human populations, whereas decreases in physical activity occur, but are not seen in all human or primate populations. Lactation is more energetically costly on a daily basis among humans and nonhuman primates, but has not been as well studied. It appears that both nonhuman and human primates tend to increase energy intake to meet in part the cost of lactation. They also use other strategies such as relying on body tissue stores, reductions in physical activity, and/or increases in metabolic efficiency to meet the remainder of the cost. It is also clear that human females in different populations and different women in the same population use a different combination of strategies to meet the cost of lactation.

Intraday feeding patterns in infant rhesus monkeys and the effects of missing a meal

During the first month of life, infant rhesus monkeys (N = 96) were fed 7 times a day for the first 21 days and were fed 6 times a day thereafter. Fifty monkeys were fed SMA, a formula designed for human infants (9% protein, 43% carbohydrate, and 48% fat); 46 were fed one of three laboratory-confected diets varying in the amount of protein and carbohydrates provided. Although the diets had differential effects on weight gain, overall daily consumption was practically unaffected. A characteristic pattern was evident soon after birth: The first meal of the day (8:00 AM) was one of the largest, and the following two meals were usually the smallest; the next peak spanned the 4:00 PM and 8:00 PM feedings. The meal following a missed meal was slightly larger than normal. To some extent, the large meal at 8:00 AM can be attributed to the 10-hr absence of food during the night, but the peak at 4:00 PM and 8:00 PM cannot be so accounted for. The adult bicuspid pattern of eating hence appears to develop very early in life.

Changes in food intake during menstrual cycles and pregnancy of normal and diabetic rhesus monkeys

Food intake of control and streptozotocin-diabetic rhesus monkeys was measured during menstrual cycles and pregnancy. Intake of control monkeys was lower at the time of ovulation than during other phases of the menstrual cycle. Intake of control monkeys was also low during most of pregnancy, but this was accompanied by normal fetal growth and net maternal weight gain. Diabetic monkeys ate more than controls in all conditions and their intake did not vary reliably according to reproductive status. It is suggested that (1) oestrogen normally inhibits food intake during menstrual cycles and pregnancy, (2) food energy is utilized more efficiently during pregnancy than during non-pregnant states, and (3) the influence of oestrogen on food intake is either attenuated by insulinopenia or is obscured by the hyperphagia typically exhibited by the diabetic monkeys.

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.

Protein deprivation in primates: XII. food preferences of juvenile rhesus monkeys

21 male and 18 female juvenile rhesus monkeys whose mothers' prenatal diets varied according to protein content (either 1-, 2-, or 4-gm protein/kg body weight/day) were given a food-preference task. 20 monkeys were between 3 and 4 yr. old; 19 were between 1 1/2 and 2 1/2 yr. old. For each trial small pieces of the same type food were placed in 8 equally spaced wells about the circumference of a circular tray held outside each monkey's cage. Responsiveness to the 21 natural foods (assorted cheeses, meats, vegetables, nuts, cereals, fruits, and candies) offered 3 times on 3 different occasions was measured by recording number of pieces taken, number eaten, and elapsed time for taking all 8 pieces. All 3 measures were highly correlated. All diet groups exhibited the same general order of preference, males taking and eating more food pieces faster than females. Order of preference was significantly different for old versus young juveniles, with older juveniles' preferences more similar to those of adult female monkeys given the same task. The most notable differences in eating behavior were that younger juveniles played with their food and were less finicky about what they ate. Results suggest that food preferences of juvenile monkeys are not altered as a consequence of their mothers' prenatal protein deprivation.

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.