Ontogeny in Iguanodontia

I-1: Spermatogonial Ontogeny in Mice

Background:Spermatogenesis is maintained by a pool of the spermatogonia. The group formed by As, Apr and Aal is known as undifferentiated type a spermatogonia (Aund). The Aal spermatogonia will differentiate, with no mitotic division, to the differentiating type A1 spermatogonia. The type A1 spermatogonia undergo 6 successive mitotic divisions to yield A2, A3, A4, intermediate-type (In), and ty...

Ontogeny in the family.

When ontogeny takes place in a family, and parents provide essential resources for development, the parents become an environmental component to the development of a wide range of offspring traits. Because differences among parents may partly reflect genetic variation, this environmental component contains genes and may itself evolve. Also, when offspring play an active role in family interacti...

Ontogeny in Dysalotosaurus lettovorbecki

Oxytocin in cardiac ontogeny.

Previous studies demonstrated the presence of oxytocin (OT) and oxytocin receptors (OTRs) in the heart. The present work provides results supporting a potential role of OT in cardiomyogenesis. Here, we show a maximal OT and OTR protein level in the developing rat heart at day 21 of gestation and postnatal days 1-4, when cardiac myocytes are at a stage of intense hyperplasia. Between postnatal d...

Bone Histology in Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia) – Variation, Growth, and Implications

BACKGROUND Dysalotosaurus lettowvorbecki is a small ornithopod dinosaur known from thousands of bones and several ontogenetic stages. It was found in a single locality within the Tendaguru Formation of southeastern Tanzania, possibly representing a single herd. Dysalotosaurus provides an excellent case study for examining variation in bone microstructure and life history and helps to unravel th...