Nonreproductive role of gonadotropin-releasing hormone in the control of ascidian metamorphosis.

BACKGROUND: Gonadotropin-releasing hormones (GnRHs) are neuropeptides that play central roles in the reproduction of vertebrates. In the ascidian Ciona intestinalis, GnRHs and their receptors are expressed in the nervous systems at the larval stage, when animals are not yet capable of reproduction, suggesting that the hormones have non-reproductive roles. RESULTS: We showed that GnRHs in Ciona are involved in the animal's metamorphosis by regulating tail absorption and adult organ growth. Absorption of the larval tail and growth of the adult organs are two major events in the metamorphosis of ascidians. When larvae were treated with GnRHs, they completed tail absorption more frequently than control larvae. cAMP was suggested to be a second messenger for the induction of tail absorption by GnRHs. tGnRH-3 and tGnRH-5 (the "t" indicates "tunicate") inhibited the growth of adult organs by arresting cell cycle progression in parallel with the promotion of tail absorption. CONCLUSIONS: This study provides new insights into the molecular mechanisms of ascidian metamorphosis conducted by non-reproductive GnRHs.

In vitro culture conditions using chemically defined media for in vitro matured and intracytoplasmically inseminated porcine oocytes.

The present study investigated in vitro culture methods [droplet and Well of the Well (WOW)] using semi-defined and defined media [modified porcine zygote medium (mPZM)] and the additional effects of insulin on in vitro matured and intracytoplasmically inseminated porcine oocytes. In Experiment 1, in vitro matured and intracytoplasmically inseminated porcine oocytes were cultured for 6 days in the following four groups: 1) mPZM-3 (containing bovine serum albumin) + droplet (30 mul), 2) mPZM-3 + WOW, 3) mPZM-4 (containing polyvinyl alcohol) + droplet, and 4) mPZM-4+ WOW. The culture media (mPZM-3 and mPZM-4) and methods (droplet and WOW) did not significantly affect the cleavage rate, but the blastocyst rate of the oocytes cultured in mPZM-3 was significantly (P<0.01) higher than that of mPZM-4 (20.1 and 9.4%, respectively). The blastocyst rates as percentages of the cleaved oocytes (51.8 and 16.9%) and the hatched blastocyst rate as percentages of the number of blastocysts (12.3 and 2.2%) were also significantly (P<0.01) higher in mPZM-3 compared with those in mPZM-4. There was significant interaction (P<0.05) between the two main factors; the effects of the culture media and methods on the rate of hatched blasyocysts as percentages of the blastocysts produced and, the hatched blastocyst rate (20.3%) as percentages of the number of blastocysts produced in mPZM-3 were significantly (P<0.05) higher than in the other groups. In Experiment 2, the additional effects of insulin (100 ng/ml) in mPZM-3 and mPZM-4 media was investigated in the WOW culture system. Insulin addition did not improve cleavage, blastocyst formation, or the number of cells in blastocysts. However, as in Experiment 1, mPZM-3 resulted in a significantly higher blastocyst rate as percentages of the cleaved oocytes than mPZM-4 (33.9 and 18.4%). These results indicate that a chemically defined medium (mPZM-4) needs to be improved to provide more suitable culture conditions for in vitro development of in vitro matured and intracytoplasmically inseminated porcine oocytes. However, the WOW system may be a useful IVC method for blastocyst development of in vitro matured porcine oocytes following ICSI when a semi-defined medium (mPZM-3) is used.

Sperm mitochondrial DNA transmission to both male and female offspring in the blue mussel Mytilus galloprovincialis.

In Mytilus mussels, paternal mitochondrial DNA (M type) from sperm is known to be transmitted to offspring. This phenomenon is called doubly uniparental inheritance (DUI). Under DUI, it has been reported that female mussels generally have only maternal mtDNA (F type). In this study, we examined the mode of mtDNA transmission in Mytilus galloprovincialis using M and F type-specific primer sets. The ratio of M and F types were measured in each sample by SNaPshot. The M type was detected in the adductor muscle and female gonad of all females. In unfertilized eggs spawned by 84.6% of females (22/26), M type was also detected. The F type was more abundant than the M type in all females. Although the ratio of M type in females was very low, all females contained the M type. From these results, we propose a new possibility about DUI inheritance. The presence of M type in unfertilized eggs indicates that the M type of eggs may also contribute to M type inheritance.

Influence of random noise on the contrast-to-gradient image resolution in scanning electron microscopy.

The contrast-to-gradient (CG) method has been proposed previously for the evaluation of image resolution in scanning electron microscopy (SEM). The CG resolution is based on the local resolution, which is defined as the distance to recognize the object's local surface at each pixel position. Then, the CG resolution R is inherently influenced by random noise contained in the image. The present study demonstrates the influence of random noise on the R-values using both personal computer-made dot patterns in various sizes and densities and SEM test micrographs. It is found that the R-values increase with increasing random noise intensity N and their increases are smaller for higher-density patterns, but the R-values are independent of their image sizes under constant pattern density. In addition, the standard CG algorithm is modified especially for straightly fabricated patterns along the x- (or y-) axis, resulting in an improvement in the measurement accuracy of y- (or x-) directional resolutions. The straightness as known information is utilized fully to recognize the local pattern in the random noise.