Abstract # 44:

Scheduled for Thursday, August 17, 2006 04:30 PM-04:45 PM: Session 5 (Regency East #2) Oral Presentation

Litter size effects on differential placental tissue compartmentalization in Common Marmosets (Callithrix jacchus)

J. Rutherford Goehl and S. D. Tardif
Southwest National Primate Research Center, San Antonio, TX, USA
     Marmoset twins and triplets differ significantly in both intrauterine and postnatal growth patterns. It is hypothesized that placental structure may be related to differentiation of fetal growth trajectories. Stereological analysis of term twin and triplet marmoset placentas was undertaken to determine relations between litter size and placental structure. Stereology is a robust method of generating unbiased estimations of tissue volumes, which can readily be applied to histological specimens. 4 triplet and 6 twin placentas from the Southwest National Primate Research Center were analyzed, and volumes of placental trabeculae, intertrabecular space, fetal capillaries, and ischemic necrosis were calculated by point-counting. The average marmoset placenta comprised 47.6% trabecular tissue, 19.78% intertrabecular space, 4.94% fetal capillaries, and 2.52% ischemic necrosis. Increases in placental weight and volume were significantly correlated with an absolute increase of all tissue compartments (P<0.05). However, as placental size increases, there was a significant increase in the overall percentage of ischemic necrosis (P<0.05), suggesting that larger placentas are associated with greater loss of function. In this sample, litter size was not directly related to any stereological variable of placental structure. However, since litter size is related to placental size, it cannot be ruled out as a determinant of structural organization or function. Research supported in part by NIH grants R01-RR02022 and P51-RR1396 (SDT) and a Small Research Grant from the American Society of Primatologists (JRG).