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961.
962.
963.
Julien Bobe Jerôme Montfort Thaovi Nguyen Alexis Fostier 《Reproductive biology and endocrinology : RB&E》2006,4(1):39-16
Background
The hormonal control of oocyte maturation and ovulation as well as the molecular mechanisms of nuclear maturation have been thoroughly studied in fish. In contrast, the other molecular events occurring in the ovary during post-vitellogenesis have received far less attention. 相似文献964.
The Next Generation in Laser Treatments and the Role of the GreenLight High-Performance System Laser
Te AE 《Reviews in urology》2006,8(Z3):S24-S30
Lasers have evolved over the past decade, with technical refinements that have resulted in a procedure that can achieve transurethral-like results in a safe and efficacious manner. The physics and characteristics of the laser light, such as wavelength and power densities, influence efficiency of treatment and safety profiles of various laser techniques and systems. The currently commercially available 80-W potassium-titanyl-phosphate laser used for photoselective vaporization of the prostate gland in men with lower urinary tract symptoms and benign prostatic hyperplasia has been shown to be a safe and effective therapeutic alternative for a wide spectrum of prostate sizes and configurations. Refinements based on clinical experience as well as progress in available technologies have produced an advanced system with improvements in beam quality and an increase in power to provide an increase in vaporization efficiency and flexibility in technique. The refinements require adjustments to current technique. The advanced technological developments enhance the utility of this laser for application in benign prostatic hyperplasia and urology. 相似文献
965.
LRRK2 G2019S in families with Parkinson disease who originated from Europe and the Middle East: evidence of two distinct founding events beginning two millennia ago 下载免费PDF全文
Zabetian CP Hutter CM Yearout D Lopez AN Factor SA Griffith A Leis BC Bird TD Nutt JG Higgins DS Roberts JW Kay DM Edwards KL Samii A Payami H 《American journal of human genetics》2006,79(4):752-758
The leucine-rich repeat kinase 2 (LRRK2) G2019S mutation is the most common genetic determinant of Parkinson disease (PD) identified to date. It accounts for 1%-7% of PD in patients of European origin and 20%-40% in Ashkenazi Jews and North African Arabs with PD. Previous studies concluded that patients from these populations all shared a common Middle Eastern founder who lived in the 13th century. We tested this hypothesis by genotyping 25 microsatellite and single-nucleotide-polymorphism markers in 22 families with G2019S and observed two distinct haplotypes. Haplotype 1 was present in 19 families of Ashkenazi Jewish and European ancestry, whereas haplotype 2 occurred in three European American families. Using a maximum-likelihood method, we estimated that the families with haplotype 1 shared a common ancestor 2,250 (95% confidence interval 1,650-3,120) years ago, whereas those with haplotype 2 appeared to share a more recent founder. Our data suggest two separate founding events for G2019S in these populations, beginning at a time that coincides with the Jewish Diasporas. 相似文献
966.
Mixotrophic organisms combine light, mineral nutrients, and prey as supplementary resources. Based on theoretical assumptions and field observations, we tested experimentally the hypothesis that mixotrophs may invade established plankton communities depending on the trophic status of the system, and investigated possible effects on food web structure, species diversity, and nutrient dynamics. To test our hypothesis, we inoculated the mixotrophic nanoflagellate Ochromonas tuberculata into established planktonic food webs, consisting of specialist phototrophs, specialist phagotrophs, and bacteria at different supplies of soluble inorganic nutrients and dissolved organic carbon. Oligotrophic systems facilitated the invasion of O. tuberculata in two different ways. First, the combination of photosynthesis and phagotrophy gave mixotrophs a competitive advantage over specialist phototrophs and specialist phagotrophs. Second, low nutrient supplies supported the growth of small plankton organisms that fell into the food size spectrum of mixotrophs. Conversely, high nutrient supplies prevented O. tuberculata from successfully invading the food webs. Two important conclusions were derived from our experiments. First, in contrast to a paradigm of ecology, specialization may not necessarily be the most successful strategy for survival under stable conditions. Indeed, the use of several resources with lower efficiency can be an equally, or even more, successful strategy in nature. Second, when limiting nutrients promote the growth of bacterio- and picophytoplankton, invading mixotrophs may have a habitat-ameliorating effect for higher trophic levels, gauged in terms of food quantity and quality. Using given resources more efficiently, O. tuberculata generated higher biomasses and expressed an increased nutritional value for potential planktivores, due to decreased cellular carbon to phosphorus (C:P) ratios compared to specialized plankton taxa. Our findings may help to explain why energy transfer efficiency between phytoplankton and higher trophic levels is generally higher in oligotrophic systems than in nutrient rich environments. 相似文献
967.
Plants continuously generate organs at the flanks of their shoot apical meristems (SAMs). The patterns in which these organs
are initiated, also called patterns of phyllotaxis, are highly stereotypic and characteristic for a particular species or
developmental stage. This stable, predictable behaviour of the meristem has led to the idea that organ initiation must be
based on simple and robust mechanisms. This conclusion is less evident, however, if we consider the very dynamic behaviour
of the individual cells. How dynamic cellular events are coordinated and how they are linked to the regular patterns of organ
initiation is a major issue in plant developmental biology. 相似文献
968.
Cui Guo Tsung Yu Ly-yun Chang Changqing Lin Hsiao Ting Yang Yacong Bo Yiqian Zeng Tony Tam Alexis K.H. Lau Xiang Qian Lao 《CMAJ》2021,193(32):E1240
Background:Exercise may exacerbate the adverse health effects of air pollution by increasing the inhalation of air pollutants. We investigated the combined effects of long-term exposure to fine particle matter (PM2.5) and habitual exercise on deaths from natural causes in Taiwan.Methods:We recruited 384 130 adults (aged ≥ 18 yr) with 842 394 medical examination records between 2001 and 2016, and followed all participants until May 31, 2019. We obtained vital data from the National Death Registry of Taiwan. We estimated PM2.5 exposure using a satellite-based spatiotemporal model, and collected information on exercise habits using a standard self-administered questionnaire. We analyzed the data using a Cox regression model with time-dependent covariates.Results:A higher level of habitual exercise was associated with a lower risk of death from natural causes, compared with inactivity (hazard ratio [HR] 0.84, 95% confidence interval [CI] 0.80–0.88 for the moderate exercise group; HR 0.65, 95% CI 0.62–0.68 for the high exercise groups), whereas a higher PM2.5 exposure was associated with a higher risk of death from natural causes compared with lower exposure (HR 1.02, 95% CI 0.98–1.07, and HR 1.15, 95% CI 1.10–1.20, for the moderate and high PM2.5 exposure groups, respectively). Compared with inactive adults with high PM2.5 exposure, adults with high levels of habitual exercise and low PM2.5 exposure had a substantially lower risk of death from natural causes. We found a minor, but statistically significant, interaction effect between exercise and PM2.5 exposure on risk of death (HR 1.03 95% CI 1.01–1.06). Subgroup analyses, stratified by PM2.5 categories, suggested that moderate and high levels of exercise were associated with a lower risk of death in each PM2.5 stratum, compared with inactivity.Interpretation:Increased levels of exercise and reduced PM2.5 exposure are associated with a lower risk of death from natural causes. Habitual exercise can reduce risk regardless of the levels of PM2.5 exposure. Our results suggest that exercise is a safe health improvement strategy, even for people residing in relatively polluted regions.Air pollution and physical inactivity are both major public health challenges worldwide.1 Air pollution was the fifth leading cause of disability related to health and accounted for 4.9 million deaths worldwide in 2017.2 More than 91% of the global population lives in areas where air quality does not meet the World Health Organization (WHO) guidelines.3 In addition, physical inactivity was the fourth leading risk factor for death globally, accounting for 5.3 million deaths worldwide in 2012.4 The WHO has challenged its member states to reduce physical inactivity by 15% by 2030.5As people exercise, their ventilation rate increases, which increases the volume of air pollutants they inhale. This may exacerbate the adverse health effects of air pollutants. Thus, the risk–benefit relation between air pollution and exercise needs to be assessed to understand whether it is safe to exercise regularly in polluted regions. Indeed, some studies have shown that acute exposure to air pollution when exercising may override the benefits of exercise.6,7 It is possible that the effects of long-term exposure to air pollution may be irreversible and cause a much larger disease burden than short-term exposure. Limited information exists on the combined effects of long-term exposure to air pollution and habitual exercise on human health, and findings have been inconsistent depending on health outcome. Three cohort studies have explored the relation between air pollution, physical activity and risk of death in Hong Kong,8 Denmark and the United States,9 with relatively small sample sizes.10 Therefore, we sought to investigate the combined effects of habitual exercise and long-term exposure to fine particle matter (PM2.5) on the risk of death from natural causes (i.e., deaths not attributable to accident, suicide or homicide) using a longitudinal cohort of adults in Taiwan, where the annual PM2.5 concentrations are 1.6 times higher than the WHO-recommended limit. We hypothesized that the beneficial effects of habitual exercise on risk of death may outweigh the risk of high levels of air pollutants inhaled during exercise. 相似文献
969.
Jordi Torres Jordi Miquel Juan-Carlos Casanova Alexis Ribas Carlos Feliu Serge Morand 《Biodiversity and Conservation》2006,15(14):4619-4632
We investigate the determinants of macroparasite species richness of Iberian carnivores. For this, we used the parasitological
data collected on 14 species of carnivores over a 10-year period. These previously unpublished data permitted to estimate
parasite species richness using estimators of species richness, i.e. Jackknife first order and Chao 2. Most of the parasite
species were rare, with low prevalence. Potential determinants were investigated as possible factors explaining the variability
of parasites species richness among carnivores host body mass, host geographical range, host longevity and host density. Using
independent contrasts, we found positive relationships between residuals of estimates of parasite species richness and residuals
in host density, and between residuals of estimates of parasite species richness and residuals in host range. These results
are discussed in terms of risk of extinction and invasion abilities related to a possible investment in immune defences correlated
with parasite diversity. 相似文献
970.
The common bile duct ligation in rat: a relevant in vivo model to study the role of mechanical stress on cell and matrix behaviour 总被引:2,自引:2,他引:0
Common bile duct ligation leads to bile accumulation and liver fibrosis. In this model, little attention has been dedicated to the modification of the common bile duct. We have studied by histochemistry and immunohistochemistry, 3 and 5 days after ligation, the connective tissue modifications of the common bile duct wall. After bile duct ligation, compared with normal bile duct, a strong increase of the bile duct diameter, due to bile stasis, and a thickness of the bile duct wall were observed; numerous myofibroblasts expressing α-smooth muscle actin appeared in parallel with the detection of many proliferating connective tissue cells. These myofibroblasts secreted very early high amount of elastic fibre components, elastin and fibrillin-1. Elastic fibre increase was also observed close to the epithelial cell layer. Procollagen type III deposition was also induced 3 days after ligation but decreased thereafter, underlining that myofibroblasts modify their synthesis of extracellular matrix components to comply with the request. We show here that common bile duct ligation represents an invaluable model to study myofibroblastic differentiation and extracellular matrix adaptation produced by an acute mechanical stress. 相似文献