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Singaram?Gopalakrishnan Napo?KM?Cheung Bill?WP?Yip Doris?WT?AuEmail author 《Frontiers in zoology》2013,10(1):78
Introduction
Females having a longer telomere and lifespan than males have been documented in many animals. Such linkage however has never been reported in fish. Progressive shortening of telomere length is an important aging mechanism. Mounting in vitro evidence has shown that telomere shortening beyond a critical length triggered replicative senescence or cell death. Estrogen has been postulated as a key factor contributing to maintenance of telomere and sex-dependent longevity in animals. This postulation remains unproven due to the lack of a suitable animal system for testing. Here, we introduce a teleost model, the Japanese medaka Oryzias latipes, which shows promise for research into the molecular mechanism(s) controlling sex difference in aging.Results
Using the medaka, we demonstrate for the first time in teleost that (i) sex differences (female?>?male) in telomere length and longevity also exist in fish, and (ii) a natural, ‘menopause’-like decline of plasma estrogen was evident in females during aging. Estrogen levels significantly correlated with telomerase activity as well as telomere length in female organs (not in males), suggesting estrogen could modulate telomere length via telomerase activation in a sex -specific manner. A hypothetical in vivo ‘critical’ terminal restriction fragment (TRF, representing telomere) length of approximately 4 kb was deduced in medaka liver for prediction of organismal mortality, which is highly comparable with that for human cells. An age conversion model was also established to enable age translation between medaka (in months) and human (in years). These novel tools are useful for future research on comparative biology of aging using medaka.Conclusion
The striking similarity in estrogen profile between aging female O. latipes and women enables studying the influence of “postmenopausal” decline of estrogen on telomere and longevity without the need of invasive ovariectomy. Medaka fish is advantageous for studying the direct effect of increased estrogen on telomere length and longevity without the breast cancer complications reported in rodents. The findings strongly support the notion that O. latipes is a unique non-mammalian model for validation of estrogenic influence on telomere and longevity in vertebrates. This laboratory model fish is of potential significance for deciphering the ostensibly conserved mechanism(s) of sex-associated longevity in vertebrates.104.
Martijn Rolloos Marius H. C. Dohmen Paul J. J. Hooykaas Bert J. van der Zaal 《Molecular microbiology》2014,91(6):1240-1251
Agrobacterium tumefaciens cells carrying a tumour inducing plasmid (Ti‐plasmid) can transfer a defined region of transfer DNA (T‐DNA) to plant cells as well as to yeast. This process of Agrobacterium‐mediated transformation (AMT) eventually results in the incorporation of the T‐DNA in the genomic DNA of the recipient cells. All available evidence indicates that T‐strand transfer closely resembles conjugal DNA transfer as found between Gram‐negative bacteria. However, where conjugal plasmid DNA transfer starts via relaxase‐mediated processing of a single origin of transfer (oriT), the T‐DNA is flanked by two imperfect direct border repeats which are both substrates for the Ti‐plasmid encoded relaxase VirD2. Yeast was used as a model system to investigate the requirements of the recipient cell for the formation of T‐DNA circles after AMT. It was found that, despite the absence of self‐homology on the T‐DNA, the homologous repair proteins Rad52 and Rad51 are involved in T‐DNA circle formation. A model is presented involving the formation of T‐DNA concatemers derived from T‐strands by a process of strand‐transfer catalysed by VirD2. These concatemers are then resolved into T‐DNA circles by homologous recombination in the recipient cell. 相似文献
105.
Reactive oxygen species (ROS) and the heat stress response of Daphnia pulex: ROS‐mediated activation of hypoxia‐inducible factor 1 (HIF‐1) and heat shock factor 1 (HSF‐1) and the clustered expression of stress genes
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Summary In the first polar lobe ofBithynia eggs a special plasm, the vegetal body, is present. It consists of a cupshaped aggregate of small vesicles. Centrifugation of eggs prior to first cleavage may result in displacement of the vegetal body. In about 50% of thecentriguged eggs the vegetal body is found outside the polar lobe, in one of the blastomeres. Removal of the polar lobe from non-centrifuged eggs always leads to severe defects in development. When the lobe is removed from centrifuged eggs, however, about 50% of the eggs develop into normal embryos. It is concluded that the presence of the vegetal body in a blastomere suffices to ensure normal development and, hence, that the polar lobe-specific morphogenetic determinants are contained within the vegetal body. 相似文献
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Rat intestinal epithelial cells were isolated by EDTA-chelation, combined with gentle shaking (modified Weiser procedure) or with strong longitudinal vibration (Harrison/Webster procedure). Both methods yield large numbers of viable cells and are relatively easy to use. Electronmicroscopical and biochemical data indicate that cell fractions from different levels of the villous region can be obtained only by the modified Weiser procedure. When strong mechanical forces are involved (Harrison-Webster procedure) the villus epithelium is released according to an all-or-nothing process. The biotransformational capacity of cell fractions, obtained from different levels of the villi by the modified Weiser procedure, was investigated. It was shown that the rate of metabolism of 7-ethoxycoumarin and 1-naphthol was substantially higher in lower villous cells than in cells isolated from the upper villous region. O-Deethylation of 7-ethoxycoumarin decreases from 145 +/- 13 pmole/min mg cell protein (72 +/- 4% conjugated) in lower villous cells to 62 +/- 12 pmole/min mg cell protein (37 +/- 6% conjugated) in tip cells. Glucuronidation of 1-naphthol decreased from 495 +/- 23 pmole/min mg cell protein (lower villous cells) to 137 +/- 13 pmole/min mg cell protein (tip cells). 相似文献
110.
M Morgan Conn Joe Kappock Dale Drueckhammer Richard Cammack Dennis Hall Tony Cass Jon D Stewart Graham RL Cousins Jeremy KM Sanders Sabine Flitsch Philip AS Lowden Richard Newman 《Current opinion in chemical biology》1999,3(6):631
A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in chemical biology. 相似文献