. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. POLARITY AND ME1OSIS IN OOCYTES 269 ill., 1988) and in enucleated sea urchin embryos (Lorch, 1952; Sluder /oc\'ii'.i Fragments' No. of asters2 Transection Pole No. 2 1 Undetected A + 23 22(12) 0 1 B + 21 21 (21) 0 0 C + 14 14(8) Q 0 D 15 0 0 15 ' Prophase-arrested oocytes were transected in various directions (Fig. 4). and GV-enucleate fragments either containing the pole ( + ) or lacking the pole (-) were treated with 1 DTT and observed from about 20 mm to about 40 min at room temperature (24-27°C). The fragments lacki
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. POLARITY AND ME1OSIS IN OOCYTES 269 ill., 1988) and in enucleated sea urchin embryos (Lorch, 1952; Sluder /oc\'ii'.i Fragments' No. of asters2 Transection Pole No. 2 1 Undetected A + 23 22(12) 0 1 B + 21 21 (21) 0 0 C + 14 14(8) Q 0 D 15 0 0 15 ' Prophase-arrested oocytes were transected in various directions (Fig. 4). and GV-enucleate fragments either containing the pole ( + ) or lacking the pole (-) were treated with 1 DTT and observed from about 20 mm to about 40 min at room temperature (24-27°C). The fragments lacking the pole were examined further up to about 100 min. : The number of asters detected is indicated. The number in paren- theses indicates the fraction of cases in which the site of the pole was recognizable. In these cases, the asters appeared in a cytoplasmic region close to the pole. Discussion Poles as associated sites ofceiilrosomes The present study has revealed a pair of asters at the pole of living sea cucumber oocytes during maturation. The occurrence of fibrillar structures (Ohshima, 1921, 1925; Inaba. 1930) and microtubules (Smiley and Cloney, 1985) at the pole in prophase-arrested oocytes suggests that the asters may pre-exist in some form in immature oocytes. And Oka (1940) reported a fibrillar structure even in growing oocytes. The present study demonstrates that the organizing centers of the meiotic spindle are derived from the pole in prophase-arrested oocytes. These findings imply that the fibrillar structure at the pole is a structure. Figure 5. Aster formation in a GV-enucleate fragment with the pole (A-D), and chromosome arrange- ments in GV-nueleate fragments without (E), and with (F), the pole. The fragment in A-D was obtained from transection A (Fig. 4). and those in E and F were obtained from transections C and D, respectively. A: 9 min. The pole (arrow-head) looks clear. B: 15 min. C: 21 min. A pair of asters (arrows; also in D) form at the pole. D: 30
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
