RESUMEN
Effects of twelve protease inhibitors on hatching of mouse embryos were investigated. Mouse hatching was strongly or moderately inhibited by trypsin inhibitors including p-toluenesulfonyl-Lys-CH2 Cl (TLCK) and chicken ovomucoid, while inhibitors for chymotrypsin and elastase showed weak or no inhibition. These results indicate the participation of a trypsin-like protease in the hatching of mouse embryos as a hatching enzyme., Since TLCK is the strongest and an irreversible inhibitor for the enzyme, timing of the participation of the hatching enzyme in the hatching process was examined by pulse treatment of embryos with TLCK before and during the zona shedding. The results indicated that a trypsin-like hatching enzyme functions before, but not during, the zona shedding of embryos, especially during a 15 h period immediately before the beginning of the shedding.
RESUMEN
To explore the substrate or subsite specificity of a mouse hatching enzyme, effects of leupeptin [acetyl(P4 )-Leu(P3 )-Leu(P2 )-argininal(P1 )] and its analogs (peptidyl argininals) on mouse blastocyst hatching were investigated. The compounds containing benzyloxycarbonyl group (Z) in the P4 position inhibited the hatching more strongly than those containing acetyl group or unprotected N-terminal amino acid. Among five Z-Leu-P2 -argininals, a derivative containing a P2 Ser residue was the most potent inhibitor, and the derivatives containing Leu, Thr, Pro, and Gly in the P2 position followed in this order. Then, we synthesized four Z-P3 -Ser-argininals and tested their effects on hatching. The result indicated that the compound with Phe residue in the P3 position was the strongest inhibitor, and the Leu-, Pro-, and Ala-containing derivatives were ranked in this order. Thus, among Z-dipeptidyl-argininals tested, Z-Phe-Ser-argininal most potently inhibited the mouse embryonic hatching, suggesting the preference of the mouse hatching enzyme for Phe(P3 )-Ser(P2 )-Arg(P1 ) sequence as a substrate.
RESUMEN
The karyotype of Cynops pyrrhogaster was determined on the mitotic chromosomes in the presumptive neural area of an early gastrula. 24 chromosomes of a diploid set consisted of 8 metacentric and 4 submetacentric pairs. Individual chromosomes were identified on the basis of their morphology and characteristic C-binding patterns. Sex chromosomes were not identified. Total length of the haploid chromosome set in the presumptive neural area decreased remarkably from morulae to gastrulae, further continued to decrease up to neurulae and thereafter remained unchanged till tail-buds. Chromosome shortening occurring from morulae to gastrulae was accompanied with a prominent decrease in chromosome volume, keeping chromosome width constant. Shortening took place evenly along the longitudinal axis of a chromosome. When gastrulae and neurulae were compared concerning their positions of the appearance of the C-bands, the basic pattern remained unchanged. In certain chromosomes, the number of C-bands decreased as the result of their fusion, as gastrulae proceeded to neurulae.
RESUMEN
Cell cycles have been analyzed in 10 divisions up to the time of hatching in the embryos of the sea urchin, Hemicentrotus pulcherrimus. In the first 5 cleavages, division synchrony is very high. On the average, TGC = 55.4 min, TG1 = 0 min, Ts = 12 min, TG2 =±0 min, TM = 42 min. In the remaining 5 cleavages, TGC becomes longer: 70 min for the 7th to 246 min for the 10th cleavage. G1 and G2 become definitely recognizable and become longer along with Ts . TM stays more or less constant. Plots of the changing lengths of the four compartments (G1 , S, G2 , M) on the Y-axis against TGC (X-axis) can be fitted to the following 4 regression equations; TG1 = 0.28TGC - 19.7, Ts = 0.609TGC - 15.2, TG2 = 0.104TGC - 4.72 and TM = 0.007TGC + 39.6.