. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 148 M. J. MISAMORE AND J. W. LYNN •° S. 80% a a — T 1 1 "0% b S o% ^ PWCtl DMSO 62uMCB 124uMCB Treatment tion when the sperm head was immediately (<10 /urn) subjacent to the cortex, the sperm head frequently pivoted around the entry point through angles exceeding 90° (Fig. Figure 8. Dose-dependent effects of cytochalasin B on sperm entry into the egg cortex during fertilization. Eggs were exposed to two concen- trations of the microfilament inhibitor cytochalasin B (CB). Unfertilized eggs were pretreated with periodi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 148 M. J. MISAMORE AND J. W. LYNN •° S. 80% a a — T 1 1 "0% b S o% ^ PWCtl DMSO 62uMCB 124uMCB Treatment tion when the sperm head was immediately (<10 /urn) subjacent to the cortex, the sperm head frequently pivoted around the entry point through angles exceeding 90° (Fig. Figure 8. Dose-dependent effects of cytochalasin B on sperm entry into the egg cortex during fertilization. Eggs were exposed to two concen- trations of the microfilament inhibitor cytochalasin B (CB). Unfertilized eggs were pretreated with periodic acid, then transferred to a solution of either /nM CB or CB in DMSO or to a control of either artificial pondwater (PW Ctl) or DMSO. Eggs were incubated 10 min and inseminated directly in the egg-inhibitor solution. Eggs were fixed at 10 min PI and scored for number of incorporated sperm (n = 100/trial). Values are mean ± standard error (n = 5). Letters indicate statistically significant differences based on a two-way ANOVA and Tukey multiple comparisons (P < ). (Fig. 9). Although a brief extrusion of cytoplasm was ob- served during the period of normal polar body formation (5 min PI), no cytoplasmic separation occurred and the extru- sion was reabsorbed by 10 min PI. Sperm entry into the egg cortex was not affected by inhibition of MT polymerization. In both normal (control) fertilizations and fertilizations in the presence of MT inhib- itors, D. polymorpha sperm bound to the egg surface within 30 s of insemination, and an insemination cone formed by 3 min PI. The insemination cones of both control and MT- inhibited trials were morphologically similar, and the sperm head and mitochondria passed through the oolemma and entered the egg cytoplasm within 4 min of binding (Fig. 9D, D'). Compared to the control, there was no significant difference (Fig. 10) in the numbers of eggs exhibiting sperm entry in the samples treated with colchicine (P
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