Effects of RNA on the developmental potentiality of the posterior primitive streak of the chick blastoderm

Studies on cell differentiation: inducing capacity of sulfhydryl-containing amino acids on post-nodal pieces of chick blastoderms

The inducing capacity of sulfhydryl (SH)-containing amino acids (cysteine and glutathione) on post-nodal pieces (PNPs) of stage 4 chick blastoderms was investigated. PNPs were treated for different lengths of time with chick Ringer's solution (control group) or chick Ringer's solution containing cysteine or glutathione, followed by culturing for 2-10 days on Spratt-Haas agar medium or on the chorioallantoic membrane of 8-day chick embryos. Control PNPs rarely showed differentiation, but those treated with the amino acids for six hours or longer developed structures such as neural tissue, notochord, somite mesoderm, and nephric tubules. The pulsatile tissue was only seen in the PNPs cultured for four days or longer. Two-four hours of treatment was too short to provoke induction in a statistically significant number of PNPs. The highest frequency of induction was noted in those pretreated with glutathione (8 mug/ml) for eight hours, followed by culturing for four days. The magnitude of the inducing capacity and toxicity of the amino acids were concentration dependent: a deleterious effect was observed at 14 mug/ml; the highest frequency of induction occurred at 8 mug/ml, but the frequency decreased as the concentration decreased; at 2 mug/ml all PNPs remained viable, but only a few (9-14%) showed differentiation. The inducing capacity of the amino acids was counteracted by equimolar concentrations of rho-chloromercuribenzoic acid or omega-chloroacetophenone. The effects of glutathione (8 mug/ml) differed from those of Hensen's node grafts in that the former caused sublethal cytolysis and inhibited H-3-uridine uptake in competent ectodermal cells during the first 18 hours of cultivation.

Partial characterization of the RNA stimulating growth of the seminal vesicle

RNA prepared from the seminal vesicles of intact adult rats, or of testosterone-treated castrate adult rats, produced a 30 per cent increase in the weight of the seminal vesicle and a 25 per cent increase in the incorporation of labeled amino acids into protein. RNA prepared from the liver or ventral prostate of the same animals produced only a 10 per cent increase in the weight of the seminal vesicle. RNA prepared from the liver of control or testosterone-treated adult female rats was ineffective in stimulating the growth of the seminal vesicle. Polyuridylic acid instilled into the lumen had no effect on the weight of the seminal vesicle, but increased the incorporation of labeled phenylalanine into protein. RNA sedimenting in the 18S area on sucrose density gradients was most effective in stimulating growth of the seminal vesicle of three-week-old rats. Treating homogenized tissue with deoxycholate greatly increased the effectiveness of the RNA extracted. RNA extracted from seminal vesicles by treatment with deoxycholate and dextran sulfate was biologically active, whereas the usual 4S RNA in the 100,000 x g supernatant is ineffective.

Competent chick ectoderm: nonspecific response to RNA

Presumptive chick neuroectoderm responds to RNA from brain and heart by forming neural tubes, but it does not respond to liver RNA. This dif ferential response can be correlated with the presence of Folin-positive material in those RNA preparations which elicit the formation of neural structures.