No abstract

The effect of 5-hydroxytryptamine (5-HT) on steroidogenesis and oocyte maturation in pre-ovuiatory follicles of the medaka Oryzias lafipes was examined using in vitro culture system. The earliest breakdown of the germinal vesicle of intrafollicular oocytes occurred about 17 hr after the beginning of incubation in the presence of 5-HT at concentration of 10 ng/ml or more. 5-HT induced oocyte maturation in a dosedependent manner. Cyanoketone inhibited this stimulation. The concentration of 5-HT required to induce oocyte maturation corresponded to that required to enhance the production (secretion) of estradiol-17p and 17a,2Op-dihydroxy-4-pregnen-3-one b y pre-ovulatory follicle cells. At a concentration of 1 pglml, the follicle had to be exposed to 5-HT for at least 4 hr for oocyte maturation accompanied by ovulation to occur. These results indicate that 5-HT induces in vitro maturation of medaka oocytes by stimulating 17a,20p-dihydroxy-4pregnen-3-one production by pre-ovulatory follicular cells. 625

The DnaK/Hsp70 family is a molecular chaperone that binds non-native states of other proteins, and concerns to various physiological processes in the bacterial, plant and animal cells. Previously, we showed that overexpression of DnaK from a halotolerant cyanobacterium Aphanothece halophytica (ApDnaK) enhances tolerance to abiotic stresses such as high salinity and high temperature in tobacco plants. Here, we tested the transformation of poplar (Populus alba) with ApDnaK for enhancing the growth of transformed poplar plants. Under control growth conditions, transgenic poplar plants exhibited similar growth rates with the wild-type plants during young seedlings under low light intensity, whereas they showed faster growth, larger plant size, and higher cellulose contents when poplar plants were grown under high light intensity. Transgenic young poplar plants exhibited more rapid recovery from the stresses of high salinity, drought, and low temperature compared with those of the wild type plants when poplar plants were grown under low light intensity. These results suggest that ApDnaK could be useful to enhance the growth rate as well as to increase the stress tolerance.

No abstract