A novel class of low-molecular-weight organic gels has been developed; N,N′,N″-tristearyltrimesamide (TSTA) forms gels with various organic solvents, immobilizing solvent at a low concentration of TSTA. The gels, which form fibrous bundles leading to three-dimensional networks, exhibit well-defined sol-gel transitions. Both intermolecular hydrogen bonding and intermolecular inteactions between long alkyl chains are suggested to be responsible for the formation of gels.

Primordial germ cells (PGCs), collected from the blood of 2-day-old chick embryos, were concentrated by Ficoll density centrifugation. The blood contained 0.048% PGCs and the concentrated fraction contained 3.9% PGCs in blood cells. The PGCs were picked up with a fine glass pipette, and one hundred were then injected into the terminal sinuses of 2-day-old Japanese quail embryos (24 somites); bubbles were then inserted to prevent haemorrhage. The embryos were further incubated at 38 degrees C for 24 h, and then fixed. Serial sections were stained with the periodic acid-Schiff reagent (PAS) to demonstrate chicken PGCs and with Feulgen stain to identify quail cells. On the basis of the differences in staining properties, 63.6 +/- 5.3 chick PGCs were detected in the quail embryo in the area where the gonads develop. Furthermore, 39.3 +/- 4.5 chick PGCs were incorporated into the quail germinal epithelium within 24 h of the injection. A similar percentage of the host (quail) PGCs had also migrated to the germinal epithelium at the same stage of development. This technique for obtaining germ-line chimaeras will facilitate research on avian germ-line differentiation.

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Germline chimeric chickens were produced by transfer of primordial germ cells from White Leghorn to Barred Plymouth Rock, and vice versa. Blood was collected from stage 13-15 embryos and primordial germ cells were concentrated by Ficoll density gradient centrifugation. Approximately 200 primordial germ cells were injected into the bloodstream through the dorsal aorta of stage 14-15 recipient embryos from which blood had been drawn via the dorsal aorta prior to the injection. Intact embryos were also prepared as recipients for White Leghorns only. The manipulated embryos were cultured in recipient eggshells until hatching. Germline chimerism of the chickens reaching maturity was examined by mating them with Barred Plymouth Rocks and donor-derived offspring were identified based on their feather color. The efficiency of production of germline chimeras was 95% (19/20). When primordial germ cells were transferred from White Leghorn to Barred Plymouth Rock, the average frequency of donor-derived offspring was 81% for three male chimeras (96% for one female chimera), and it was approximately 3.5 times higher for transfer in the opposite direction (23% for 6 male chimeras). Removing blood from recipient embryos prior to primordial germ cell injection enhanced the frequency of donor-derived offspring by 10% in resulting male chimeras. Male chimeras produced donor-derived offspring more frequently (approximately 3.8 times) than female chimeras. Increases, decreases, or no changes were observed in the frequency of donor-derived offspring from the germline chimeras with increasing age.(ABSTRACT TRUNCATED AT 250 WORDS)

Conservation of genetic material in chickens was attempted by preserving primordial germ cells in liquid nitrogen. Primordial germ cells collected from the blood of embryos at stage 13-15 of White Leghorn and Barred Plymouth Rock breeds were concentrated by Ficoll density gradient centrifugation. The primordial germ cells were then suspended in a freezing medium containing 10% dimethyl sulfoxide. The temperature of the cell suspension was decreased by 1 degree C min-1 to -80 degrees C; the suspension was then placed in liquid nitrogen (-196 degrees C) and stored for 4-5 months. The cell suspension was thawed by taking it out of liquid nitrogen and placing it in water at 4 degrees C. The viability of the frozen-thawed primordial germ cells was 94.2%. One hundred frozen-thawed cells were injected into the bloodstream of recipient embryos (stage 14-15) from the other breed, from which blood had been drawn before the injection. These embryos were cultured in recipient eggshells until hatching. Viable offspring derived from the frozen-thawed primordial germ cells were obtained by mating male and female germline chimaeras or by mating the chimaeras with Barred Plymouth Rock chickens, and the offspring showed normal reproductive performance. This technique for cryopreservation of primordial germ cells giving rise to viable offspring makes it possible to conserve genetic material in avian species.