A cross-sectional study (n = 99) was made of male baboons (Papio cynocephalus) aged 3 weeks to > 10 years. Serum testosterone and testicular size were compared with body weight and crown-rump length. Pubertal onset in baboons occurs at 3-4 years of age; data were analyzed, therefore in three groups: 0-3 years; 3-4 years; and greater than 4 years. Testicular volume index increased minimally prior to 3 years of age. Between 3 and 4 years of age, there was a n increase (P < .05) in testicular growth, which was followed after 4 years of age by a return to the prepubertal rate. Plasma testosterone decreased from birth to 3 years of age. Between 3 and 4 years of age, there was an increase (P < .05) in testosterone. The levels of which remained unchanged after 4 years of age. A linear increase in body weight was observed for the first 3 years which was followed by an increase (P < -05) in the rate of weight gain between 3 and 4 years of age. After 4 years of age, body weight continued to increase but at a rate less than those of the two earlier periods. A linear increase in crown-rump length was observed over the first 3 years. Between 3 and 4 years of age there was a slight increase (P > .06) in crown-rump length, which approached zero after 4 years of age. These data demonstrate many similarities between the pubertal development of male baboons and humans. Male baboons appear to be appropriate for the study of reproductive and endocrine development and the factors involved in the pubertal growth spurt of the human male.

Water contents of various body water compartments were estimated within nine hours of birth in 11 preterm and eight term baboon (Papio cynccephalus neonates. Estimated water contents of all body compartments (in ml) increased linearly with birthweight (r = 0.52 to 0.90, P 0.007) andwith gestational age (r = 0.46-0.94, P < 0.05). When body water estimates were expressed in proportion to bodyweight (in mlkg), preterm neonates had significantly larger mean antipyrine space and intracellular water than their term peers. Mean corrected bromide space, interstitial water, plasma volume, blood volume, and red cell volume were similar in preterm and term neonates. Although there are minor differences in body water contents and distribution between baboon and human neonates, baboon data are sufficiently similar to human data to justify using the baboon fetus and neonate as a model for investigations of human development.

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Amniotic fluid volume (AFV) and amniotic fluid ingestion rate (or fetal swallowing rate, FSR) were estimated by inulin and para-aminohippurate (PAH) dilution in 14 normal baboon pregnancies. Mean (f SE) AFV was significantly lower at 137-140 days of pregnancy (preterm) than at 173-178 days (term) (inulin: 326 f 22.9 ml vs 483 55.9 ml, P = 0.014; PHA: 269 -+ 39.4 ml vs 471 f 39.4 ml, P = 0.002). In proportion to fetal weight, however, mean AFV was similar throughout the third trimester of pregnancy (inulin: 582 5 40.9 mlkg; PAH: 541 & 39.8 mlkg). Mean FSR was lower in preterm than in term animals when estimated by inulin dilution (587 & 55.5 ml/day vs 784 f 55.0 ml/day, P = 0.030) but not when estimated by PAH dilution (753 65.7 mliday vs 625 f 50.6 mliday). In proportion to their weights, however, preterm fetuses swallowed amniotic fluid more rapidly than term fetuses (inulin: 1,216 f 117.6 ml/kg/day vs 840 f 67.5 ml/ kgiday, P = 0.025; PAH: 1,561 & 142.9 ml/kg/day vs 682 & 62.7 mlkg/day, P < 0.001). Furthermore, our data suggest that the commonly accepted technique for estimating AFV may be based on inaccurate premises, that insulin may be a better marker than PAH to estimate AFV and FSR, and that needle aspiration of amniotic fluid does not appear to be an adequate technique to validate chemical dilution methods. Our data, however, provide estimates which indicate that the baboon is an appropriate animal model in which to seek refinements and validation of our techniques.