Neurogenesis in the olfactory bulb of the frog Xenopus laevis shows unique patterns during embryonic development and metamorphosis.

We determined the time of origin of neurons in the olfactory bulb of the South African clawed frog, Xenopus laevis. Tritiated thymidine injections were administered to frog embryos and tadpoles from gastrulation (stage 11/12) through metamorphosis (stage 65), paraffin sections were processed for autoradiography, and the distribution of heavily and lightly labeled cells was examined. In the ventral olfactory bulb, we observed that the mitral cells were born as early as stage 11/12 and continued to be generated through the end of metamorphosis.

Neural pathway for aggressive display in Betta splendens: midbrain and hindbrain control of gill-cover erection behavior.

Horseradish peroxidase (HRP) was used to identify parts of the presumptive neural pathway for gill cover erection, a behavioral display pattern performed by Siamese fighting fish (Betta splendens) during aggressive interactions. Motor, motor integration and sensory areas were identified in the medulla and mesencephalon. Motor neurons of the dilator operculi muscle, the effector muscle for gill cover erection, are located in the lateral and medial parts of the caudal trigeminal motor nucleus.

Motor innervation of respiratory muscles and an opercular display muscle in Siamese fighting fish Betta splendens.

Horseradish peroxidase was used to identify motor neurons projecting to the adductor mandibulae, levator hyomandibulae, levator operculi, adductor operculi, and dilator operculi muscles in Siamese fighting fish, Betta splendens. These muscles participate in the production of respiratory and feeding movements in teleost fishes. The dilator operculi is also the effector muscle for gill-cover erection behavior that is part of Betta's aggressive display.

Neurogenesis in the vocalization pathway of Xenopus laevis.

We examined possible contributions of neurogenesis to sex differences in the vocalization pathway of the South African clawed frog, Xenopus laevis. Birthdates of neurons were obtained from autoradiograms of animals receiving tritiated thymidine from gastrulation through 1 month after metamorphosis. Thymidine availability studies showed that 80% of the [3H]-thymidine injected into embryos and tadpoles was incorporated into the DNA of dividing cells within 3 hours.

The ontogeny of androgen receptors in the CNS of Xenopus laevis frogs.

Androgenic steroids have been implicated in the development of sex differences in Xenopus laevis frogs. In order to determine when neurons first acquire the ability to concentrate androgen, we prepared autoradiograms of CNS in developing frogs following injection of tritiated dihydrotestosterone (DHT). X.