The genomes of many species are crowded with repetitive mobile sequences. In the case of endogenous retroviruses (ERVs) there is, for various reasons, considerable confusion regarding names assigned to families/groups of ERVs as well as individual ERV loci. Human ERVs have been studied in greater detail, and naming of HERVs in the scientific literature is somewhat confusing not just to the outsider. Without guidelines, confusion for ERVs in other species will also probably increase if those ERVs are studied in greater detail. Based on previous experience, this review highlights some of the problems when naming and classifying ERVs, and provides some guidance for detecting and characterizing ERV sequences. Because of the close relationship between ERVs and exogenous retroviruses (XRVs) it is reasonable to reconcile their classification with that of XRVs. We here argue that classification should be based on a combination of similarity, structural features, (inferred) function, and previous nomenclature. Because the RepBase system is widely employed in genome annotation, RepBase designations should be considered in further taxonomic efforts. To lay a foundation for a phylogenetically based taxonomy, further analyses of ERVs in many hosts are needed. A dedicated, permanent, international consortium would best be suited to integrate and communicate our current and future knowledge on repetitive, mobile elements in general to the scientific community. 相似文献
The population dynamics of the yellowjacket wasp (Vespula germanica Fabricus) in central Chile were analyzed for the first time. Using a simple Ricker logistic model and adding the effects of local weather variables (temperature and precipitation) and large-scale climate phenomena as El Niño Southern Oscillation (ENSO) and the Southern Annular Mode (SAM), we modeled the interannual fluctuations in nest density. The best model according to the Bayesian information criterion (BIC) included 1-year-lag negative feedback combined with the positive additive effects of ENSO and SAM. According to this model, yellowjacket nest density was favored by warm and dry winters, which probably influenced the survival of overwintering queens. Large-scale climatic variables [Southern Oscillation Index (SOI) and SAM] described the effect of exogenous factors in wasp fluctuations better than local weather variables did. Our results emphasize the usefulness of climate indices and simple theoretical-based models in insect ecological research. 相似文献
Since the results of the women health initiative study showing an overall negative risk-benefit ratio with 0.625 mg of conjugated estrogens plus 2.5 mg of medroxyprogesterone acetate, the use of the lowest effective dose of steroids in hormone replacement therapy (HRT) is recommended.
A low-dose regimen appears to induce less side effects such as breast tenderness or leg pain than do higher dose preparations.
The decrease in hot flashes with low-dose estrogens, range 60–70%, is less than the 80–90% reduction with standard dosing. But this mean that 60–70% of menopausal women do not need higher doses.
The same applies to bone preservation which is dose dependent: the number of non-respondant women will be higher than with standard doses. However, randomized double-blind, placebo controls trials have defined positive effects on bone of low doses of HRT with adequate calcium and Vitamin D in elderly women. The use of bone densitometry and of biochemical markers of bone turnover is mandatory in women using low or ultra-low-dose preparations.
In spite of the lack of trials conducted with low-dose HRT, this treatment seems to be safer:
• the plasma levels of estradiol are lower; as far as breast cancer risk is concerned, the decrease of this subrogate marker is considered as favourable;
• the increase in breast density is less pronounced;
• the nurses's health study found a dose relationship for stroke, with no increase in risk with low-dose of estrogens;
• the effects on subrogate markers of cardiovascular risk seem to be more favourable.
Beside the low-dose HRT, one must consider some other facts:
• the “critical window” theory: it is biologically plausible that HRT, if started early after the menopause can slow the progression of coronary atherosclerosis;
• the way of administration of HRT: some observational studies have shown no increase in the risk of venous thromboembolism risk among women treated with transdermal estrogens;
• the progestogen used: a French cohort study recently performed found no increase in breast cancer risk with the use of micronized progesterone meanwhile the increase in risk observed with other progestogens was similar to the findings of the WHI study.
In the future, it is conceivable that more comprehensive pharmacogenomic studies will lead to effective algorithms for individualizing the right dose of steroids to be used in HRT. 相似文献
Jasmonic acid (JA) is a naturally occurred growth regulator found in higher plants and a main signal molecule carrying information about injury. Its increased concentration in plants infested by herbivores can induce the wounded plants to produce defense responses which will affect herbivores. The application of exogenous JA to plants could imitate the effects of herbivores infestation. This study showed that applying exogenous JA on cabbage plants did not affect the survival of Plutella x vlostella larvae, but retarded their development and reduced the pupal weight and female fecundity. 相似文献
Despite the fact that estrogens cause hormonal disturbances in aquatic organisms, few studies on the estrogen contamination in our surface waters have been conducted. This study was thus conducted (1) to investigate the level of estrogens in the surface waters in Shenzhen and (2) to examine the estrogen levels in the sewage discharges in Hong Kong. Total estrogens (estrone E1, estradiol E2, and estriol E3) in the samples taken from two reservoirs, five rivers, and thirty sampling locations of the seawater in Shenzhen were measured by using ELISA kits. The preliminary results have revealed that the level of estrogens in the surface waters of Shenzhen is generally higher than that in the similar water bodies in well-developed nations. Sewage could be the major source of the estrogen contamination in these waters. The total estrogens levels in the Xili and Shenzhen Reservoirs were in a range of 3–11 ng/L with a mean value of 7 ng/L, where that in four rivers in Shenzhen were found to be 47–90 ng/L and 60.25 ng/L, respectively. In the seawater near the sewage discharge points they were 260–300 ng/L and 287 ng/L, respectively. The estradiol levels in the influent and effluent of three sewage treatment works (STWs) in Hong Kong were also monitored. The activated sludge process used in these STWs removed more than 80% whereas the chemical coagulation processed used at the Stonecutters Island STW removed less estrogens. Biological treatment appears to play a significant role in removing estrogens from wastewater. 相似文献