Establishment of the axis in chordates: facts and speculations.

A master plan for the early development of all chordates is proposed. The radial symmetry of the chordate ovum is changed at or after fertilization into a bilateral symmetry by an external signal. Until now two alternative triggers, sperm entry and gravity, have been demonstrated.

The spatial and temporal dynamics of Sax1 (CHox3) homeobox gene expression in the chick's spinal cord.

Sax1 (previously CHox3) is a chicken homeobox gene belonging to the same homeobox gene family as the Drosophila NK1 and the honeybee HHO genes. Sax1 transcripts are present from stage 2 H&H until at least 5 days of embryonic development. However, specific localization of Sax1 transcripts could not be detected by in situ hybridization prior to stage 8-, when Sax1 transcripts are specifically localized in the neural plate, posterior to the hindbrain.

A direct approach to the study of the effect of gravity on axis formation in birds.

A system has been developed to enable the normal development of aborted very early uterine avian embryos, outside the female's uterus. The shell-less aborted egg was put into a foster shell of a sister egg, previously laid by the same female. The empty space between the shell and aborted egg was filled with artificial uterine fluid.

Changes in uterine fluid composition and acid-base status during shell formation in the chicken.

The aim of this study was to characterize the dynamic changes in uterine fluid composition and acid-base status during shell calcification in the chicken. Uterine eggs at timed intervals were manually aborted and the accompanying fluid collected and analyzed for composition of osmolytes, enzymes, and acid-base parameters. Blood samples were analyzed for comparison.

Immunohistochemical analysis of the segregation process of the quail germ cell lineage.

An antiserum against quail 7 day gonadal germ cells was found to react specifically with gonadal germ cells of both sexes. Transverse sections from a range of early quail developmental stages were submitted to the antibody PAP reaction. Blastodiscs from the earliest uterine stages (II to X E.