2 results
Morphogenesis of exogut isolated from vegetalised embryo of sea urchin
- Yasuyuki Kamata, Kazuyuki Endo, Hiroyuki Nozaki, Akiko Fujiwara, Ikuo Yasumasu
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It is well known that sea urchin embryos treated with lithium chloride (LiC1) develop to abnormally into vegetalised embryos, in which differentiation of ectodermal cells is inhibited. When embryos of the sea urchins, Hemicentrotus pulcherrimus and Anthocidaris crassispina were treated with 20 mM LiC1 from the 8-cell stage to the corresponding early gastrula stage, they developed to vegetalised embryos with a large exogut 45 h after fertilisation. In these vegetalised embryos, high activity of alkaline phosphatase (AP) was detected histochemically at the end of the exogut where it is attached to the embryo body. High activity of AP is known to be detected specifically in the gut of sea urchin pluteus larvae by the same procedure as used in this study. Hence, we concluded that this part of the exogut is composed of the cells which develop into the cells of the gut in normal development.
When exogut isolated from vegetalised embryos was cultured in the extract obtained from eggs or embryos, the end composed of the cells in which high AP activity was detected, expanded during culture and formed a large spherical structure about 24 h after the initiation of culture. The minimum concentration of extract to cause expansion of isolated exogut was 5 × 103 egg or embryo equivalent/ml ASW (artificial seawater). The extract boiled at 95 °C for 1 h also caused expansion of isolated exogut at the same concentrations as non-boiled extract. On the other hand, the extract obtained from eggs or embryos by chloroform–methanol extraction did not cause any expansion of exogut, but the aqueous phase, heat-dried and dissolved in ASW, induced expansion of isolated exogut.
Light-induced reactivation of movement in degenerated sperm of echiuroid, oyster and sea urchin
- Yasuyuki Kamata, Akiko Fujiwara, Ken Yamazaki, Eigoro Tazawa, Ikuo Yasumasu
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Previously, it has been reported that NADH cytochrome c reductase and succinate cytochrome c reductase, in which the redox reaction in cytochrome b is involved, are activated by light irradiation with peaks of photo-activation at wavelengths of 430, 530 and 570 nm corresponding to those in the absorption spectrum of reduced cytochrome b in mitochondria isolated from sperm of echiuroid, oyster and sea urchin (Tazawa et al., 1996). In sperm of these species, augmentation of respiration due to photo-activation of the cytochrome b reaction is observed only when the electron transport in this span of the mitochondrial respiratory chain is inhibited by carbon monoxide (Fujiwara et al., 1991; Yasumasu et al., 1991) or by a decrease in the amount of cytochrome b due to sperm ageing. In sperm cultured for a long time, the respiratory rate was very low and almost all sperm became immotile. In these sperm, respiration was reactivated by light irradiation at the wavelengths of 430, 530 and 570 nm (Fujiwara et al., 1999).
In the present study, photo-reactivation of movement in these somewhat degenerated sperm incubated for a long time was also found to occur, with peaks at the above-mentioned wavelengths. We concluded that photo-reactivation of movement in these sperm, in which the cytochrome b reaction probably became rate-limiting in the respiration chain, is supported by reactivation of respiration by light irradiation. On the other hand, though the ATP level decreased to a rather low level at about 30 min after the initiation of incubation in sperm of all species examined, sperm swam for more than 10 h, by which time the ATP level was quite low. Light irradiation induced reactivation of movement but did not alter the rather low ATP level in these sperm. Thus the ATP level does not seem to be responsible for making sperm immotile. In sperm treated with Triton X-100, movement was induced by adding ATP and Mg2+, even when many sperm had become immotile after a long incubation. Hence, capacity for movement does not seem to be reduced by a long incubation time. The movement of sperm treated with Triton X-100 was not activated bv light irradiation.