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1.
造礁石珊瑚群落结构研究的概况,问题和前景   总被引:6,自引:0,他引:6  
造礁石珊瑚作为珊瑚礁生态系统中的关键生物类群,其群落结构是珊瑚礁系统研究中的一个重 要方面。本文回顾了20余年以来世界各国对造礁石珊瑚群落结构研究所取得的主要进展和认识,指出了目前研究中存在的问题并分析了不同空间范围研究结论之间的缺乏一致性和中等干扰假说的不足。 最后,结合珊瑚礁生态系统基础理论和应用发展的需求,本文探讨了造礁石珊瑚群落结构研究的前景。  相似文献   

2.
A risk analysis of in utero caffeine exposure is presented utilizing epidemiological studies and animal studies dealing with congenital malformation, pregnancy loss, and weight reduction. These effects are of interest to teratologists, because animal studies are useful in their evaluation. Many of the epidemiology studies did not evaluate the impact of the "pregnancy signal," which identifies healthy pregnancies and permits investigators to identify subjects with low pregnancy risks. The spontaneous abortion epidemiology studies were inconsistent and the majority did not consider the confounding introduced by not considering the pregnancy signal. The animal studies do not support the concept that caffeine is an abortafacient for the wide range of human caffeine exposures. Almost all the congenital malformation epidemiology studies were negative. Animal pharmacokinetic studies indicate that the teratogenic plasma level of caffeine has to reach or exceed 60 μg/ml, which is not attainable from ingesting large amounts of caffeine in foods and beverages. No epidemiological study described the "caffeine teratogenic syndrome." Six of the 17 recent epidemiology studies dealing with the risk of caffeine and fetal weight reduction were negative. Seven of the positive studies had growth reductions that were clinically insignificant and none of the studies cited the animal literature. Analysis of caffeine's reproductive toxicity considers reproducibility and plausibility of clinical, epidemiological, and animal data. Moderate or even high amounts of beverages and foods containing caffeine do not increase the risks of congenital malformations, miscarriage or growth retardation. Pharmacokinetic studies markedly improve the ability to perform the risk analyses.  相似文献   

3.
We have reviewed 43 studies related to dendroclimatology in Kazakhstan, and additionally 13 studies related to other subfields of dendrochronology, which have been published during the past 40 years. This review also includes studies published in Russian, Kazakh, German and Chinese languages, which are not easily accessible to international researchers.Dendroclimatic studies in Kazakhstan began back in the days of the Soviet Union and were actively conducted in the southern and northern parts of the country. With the collapse of the Soviet Union dendroclimatic studies stopped and resumed only 15-20 years later. Within the last 5 years, the intensity and quality of dendroclimatic studies increased significantly. Several research groups have investigated climate-growth relationships of Scots pine, Silver birch, Siberian larch, Siever’s apple and Schrenk spruce. Schrenk spruce was the most widely studied of these species, and several climatic reconstructions have been published based off their climate-growth relationships. Results of most studies on Schrenk spruce demonstrated good consistency, allowing the general patterns of climate-growth relationships to be accurately traced. Unfortunately, studies on other tree species have either lower level or represented just by one or two studies. It would therefore be premature to make any generalizations on these species at the current stage.We conclude that there is a good potential and good base for continuing dendroclimatic studies in Kazakhstan. There is a need to close several research gaps which limit our knowledge, such as chronologies’ length, application of new methods, species composition and spatial coverage. Closing these gaps let us significantly improve the dendrochronological network of Kazakhstan and provide important data for further hydrological and climate studies in Kazakhstan.  相似文献   

4.
《Cancer epidemiology》2014,38(6):647-653
BackgroundSmokeless tobacco is a possible risk factor for developing pancreatic adenocarcinoma. This systematic review addressed the question: Is there an association between smokeless tobacco use and pancreatic adenocarcinoma diagnosis?MethodsFive electronic databases, grey literature, and citations of relevant articles were searched to identify studies. Six researchers double-reviewed records for inclusion in the review. The information extracted from these studies was selected using criteria outlined in the Newcastle–Ottawa Quality Assessment Scale for observational studies. A qualitative synthesis of included studies was performed.ResultsThe search of electronic databases resulted in a total of 1747 citations. Eleven studies met the inclusion criteria for this review, including three cohort studies, seven case control studies and one study that pooled data from multiple case-control studies. Studies were heterogeneous in their assessment of exposure intensity and ascertainment of outcomes. Quality of the studies varied. Existing investigations of the association of interest appear to exhibit several types of biases including selection bias, information bias and bias in the analysis.ConclusionThe association between smokeless tobacco use and pancreatic adenocarcinoma is inconclusive. More definitive conclusions regarding this relationship await the results of more methodologically rigorous epidemiologic studies.  相似文献   

5.
A recurrent question in meta‐analyses is the validity of including both field and laboratory studies in a single analysis, given the differences in characteristics such as the duration or size of these experiments. In particular, are field studies consistently more variable, longer in duration, or do they differ from laboratory studies in other important ways? We examined these questions using an unusually large and comprehensive data set on grazing effects on benthic microalgae, consisting of 865 experiments including both field and lab studies and using marine, lotic or lentic communities of small benthic primary producers. We found there was greater variation in field than laboratory studies, but that this difference explained only 0.5% of the variance in the coefficient of variation. Field studies were longer, on average, than laboratory studies, but experiments in the two systems did not differ consistently in other ecological or design parameters. Thus, the common assumption that field studies have higher variances than laboratory studies, while true, explained only a tiny proportion of the heterogeneity in variation. Therefore, perhaps surprisingly, any conclusions from research syntheses would be unlikely to be affected by consistent differences in variance (or other parameters we examined) between the laboratory and field studies.  相似文献   

6.
Despite the success in using genome-wide association studies to identify many loci associated with human disease, there are several gaps in understanding of how common genetic diseases are manifested. Epigenetic studies, which focus on DNA and chromatin modifications, have the potential to complement genetic approaches and provide more insight into mechanism, environmental effects and modes of inheritance, including the potential for non-DNA-based heritability. However, there are considerable challenges in designing and interpreting epigenetic studies associated with disease. Here, I review recent studies focused on individual variation in chromatin, and outline how epigenome-based studies can be used to complement genetic studies. In particular, I see more benefit to epigenetic studies being performed in the context of genetic studies, rather than as separate investigations.  相似文献   

7.
The tiered approach to assessing ecological risk of insect-resistant transgenic crops assumes that lower tier laboratory studies, which expose surrogate non-target organisms to high doses of insecticidal proteins, can detect harmful effects that might be manifested in the field. To test this assumption, we performed meta-analyses comparing results for non-target invertebrates exposed to Bacillus thuringiensis (Bt) Cry proteins in laboratory studies with results derived from independent field studies examining effects on the abundance of non-target invertebrates. For Lepidopteran-active Cry proteins, laboratory studies correctly predicted the reduced field abundance of non-target Lepidoptera. However, laboratory studies incorporating tri-trophic interactions of Bt plants, herbivores and parasitoids were better correlated with the decreased field abundance of parasitoids than were direct-exposure assays. For predators, laboratory tri-trophic studies predicted reduced abundances that were not realized in field studies and thus overestimated ecological risk. Exposure to Coleopteran-active Cry proteins did not significantly reduce the laboratory survival or field abundance of any functional group examined. Our findings support the assumption that laboratory studies of transgenic insecticidal crops show effects that are either consistent with, or more conservative than, those found in field studies, with the important caveat that laboratory studies should explore all ecologically relevant routes of exposure.  相似文献   

8.
9.
The brain is a trait of central importance for organismal performance and fitness. To date, evolutionary studies of brain size variation have mainly utilized comparative methods applied at the level of species or higher taxa. However, these studies suffer from the difficulty of separating causality from correlation. In the other extreme, studies of brain plasticity have focused mainly on within‐population patterns. Between these extremes lie interpopulational studies, focusing on brain size variation among populations of the same species that occupy different habitats or selective regimes. These studies form a rapidly growing field of investigations which can help us to understand brain evolution by providing a test bed for ideas born out of interspecific studies, as well as aid in uncovering the relative importance of genetic and environmental factors shaping variation in brain size and architecture. Aside from providing the first in depth review of published intraspecific studies of brain size variation, we discuss the prospects embedded with interpopulational studies of brain size variation. In particular, the following topics are identified as deserving further attention: (i) studies focusing on disentangling the contributions of genes, environment, and their interactions on brain variation within and among populations, (ii) studies applying quantitative genetic tools to evaluate the relative importance of genetic and environmental factors on brain features at different ontogenetic stages, (iii) apart from utilizing simple gross estimates of brain size, future studies could benefit from use of neuroanatomical, neurohistological, and/or molecular methods in characterizing variation in brain size and architecture.  相似文献   

10.
11.

Background

Considering the uncertainty of safety of anti-malarial drugs in pregnancy, efficacy studies are one of the few sources of clinical safety data. Complete safety evaluation is not usually incorporated in efficacy studies due to financial and human resource constraints. This review reports the methods used for the assessment of safety of artemisinin-based and quinine-based treatments in efficacy studies in pregnancy.

Methods

Methodology of assessment and reporting of safety in efficacy studies of artemisinin-based and quinine-based treatment in pregnancy was reviewed using seven databases and two clinical trial registries. The protocol was registered to PROSPERO (CRD42017054808).

Results

Of 48 eligible efficacy studies the method of estimation of gestational age was reported in only 32 studies (67%, 32/48) and ultrasound was used in 18 studies (38%, 18/48). Seventeen studies (35%, 17/48) reported parity, 9 (19%, 9/48) reported gravidity and 13 (27%, 13/48) reported both. Thirty-eight studies (79%, 38/48) followed participants through to pregnancy outcome. Fetal loss was assessed in 34 studies (89%, 34/38), but the definition of miscarriage and stillbirth were defined only in 11 (32%, 11/34) and 7 (21%, 7/34) studies, respectively. Preterm birth was assessed in 26 studies (68%, 26/38) but was defined in 16 studies (62%, 16/26). Newborn weight was assessed in 30 studies (79%, 30/38) and length in 10 studies (26%, 10/38). Assessment of birth weight took gestational age into account in four studies (13%, 4/30). Congenital abnormalities were reported in 32 studies (84%, 32/38). Other common risk factors for adverse pregnancy outcomes were not well-reported.

Conclusion

Incomplete reporting and varied methodological assessment of pregnancy outcomes in anti-malarial drug efficacy studies limits comparison across studies. A standard list of minimal necessary parameters to assess and report the safety component of efficacy studies of anti-malarials in pregnancy is proposed.
  相似文献   

12.
Abstract. All participants at the conference ‘Species coexistence and diversity maintenance in temperate grassland ecosystems’, in Bed?ichov, Czech Republic, were asked to fill in a questionnaire about the spatio-temporal parameters, study type, and species performance measures used in studies presented at the conference. 57 out of 90 participants responded. Most of the reported studies were field experiments. The major differences in approach and spatial parameters divided the studies into singular or repeated recordings. Repeated recording studies tend to use more precise measures of species quantity for species (biomass, number of individuals) than one-time recording studies. Repeated recording studies cover whole range of plot sizes, whereas singular observation studies are confined to ranges from ca. 10?2 to 102 m. The plot size is not related to the extent in time duration, with several fine- scale studies of rather long duration. Most common experimental manipulations (biomass removal, nutrient addition) indicate that the species coexistence is addressed in a rather indirect way at the community level.  相似文献   

13.
Observational studies showed that tooth loss is associated with gastric cancer, but the findings are inconsistent. In this study, a meta-analysis was conducted to evaluate the relationship between tooth loss and gastric cancer. Relevant studies were screened in PubMed and Embase databases, and nine observational studies were considered eligible for the analysis. The combined relative risks for the highest versus the lowest categories of tooth loss were 1.86 (95% CI: 1.08–3.21) and 1.31 (95% CI: 1.12–1.53) in case control and cohort studies, respectively. However, unstable results were observed in the stratified and sensitivity analysis. The current evidence, based solely on four case-control studies and five cohort studies, suggested that tooth loss is a potential marker of gastric cancer. However, we can not concluded at this time that tooth loss may be a risk factor for gastric cancer due to significant heterogeneity among studies and mixed results between case-control studies and cohort studies. Additional large-scale and high-quality prospective studies are required to evaluate the association between tooth loss and risk of gastric cancer.  相似文献   

14.
外来植物入侵的全境性研究进展与展望   总被引:4,自引:0,他引:4  
由于外来种入侵地一般都远离其自然分布区(原产地), 如果只在其入侵地或者原产地进行研究, 很难真正发现其入侵性形成和成功入侵的根本原因。目前, 许多学者开始关注和倡导对入侵种在原产地和入侵地的表现同时进行研究, 即入侵种的全境性研究(whole-range studies), 为入侵生物现有地理分布格局的形成原因和入侵机制等提供解释。本文结合国内外关于入侵植物全境性研究的进展和成果, 分别针对研究的主要目的、内容、意义等进行了全面的阐述, 探讨了存在的问题与不足, 并对未来相关研究进行了展望。目前已有的全境性研究主要是通过野外直接观测和同质种植园实验来比较入侵种在入侵地和原产地的生长、繁殖和生理生态等表型性状的差异, 以及应用分子标记方法比较入侵地种群和原产地种群遗传多样性的差异, 进行入侵植物的分子系统地理学研究, 从而有效检验生物入侵机制的理论和假说, 深入阐明植物入侵的机制, 为制定入侵植物的防控策略提供指导。值得注意的是, 由于外来植物入侵的全境性研究起步较晚, 现有研究的方法和内容还不够完善, 今后需要在加强国际合作的基础上进一步改善。  相似文献   

15.
Pharmaceuticals have been used on adults and children; however, they were previously investigated only by adult human clinical studies and adult animal nonclinical studies. The US FDA finalized the guidance of juvenile animal toxicity studies in 2006, and EMEA was finalized in 2008. At that point, juvenile animal toxicity studies were encouraged to investigate the safety of the pediatric population. In Japan, the awareness of the development of pediatric drugs is increasing, and many scientific meetings about juvenile animal studies are being held. A Japanese guideline for juvenile animal toxicity studies has been long awaited by many Japanese pharmaceutical companies because concrete directionality has not been available in Japan thus far. The Ministry of Health, Labour, and Welfare started to prepare the guideline for nonclinical safety studies in juvenile animals since October 2010. After completion of the Japanese guideline, guidelines would exist in the three regions: Japan, US, and Europe. Then, global development of pediatric pharmaceuticals would be accelerated effectively.  相似文献   

16.
BackgroundNumerous biomechanical studies have addressed normal shoulder function and the factors that affect it. While these investigations include a mix of in-vivo clinical reports, ex-vivo cadaveric studies, and computer-based simulations, each has its own strengths and limitations. A robust methodology is essential in cadaveric work but does not always come easily. Precise quantitative measurements are difficult in in-vivo studies, and simulation studies require validation steps. This review focuses on ex-vivo cadaveric studies to emphasize the best research methodologies available to simulate physiologically and clinically relevant shoulder motion.MethodsA PubMed and Web of Science search was conducted in March 2017 (and updated in May 2018) to identify the cadaveric studies focused on the shoulder and its function. The key words for this search included rotator cuff (RC) injuries, RC surgery, and their synonyms. The protocol of the study was registered on PROSPERO and is accessible at CRD42017068873.ResultsThirty one studies consisting of 167 specimens with various biomechanical methods met our inclusion criteria. All studies were level V cadaveric studies. Cadaveric biomechanical models are widely used to study shoulder instability and RC repair. These models are commonly limited to the glenohumeral joint by a fixed scapula, passively and discretely move the humerus, and statically load the RC without regard for the integrity of the glenohumeral capsule.ConclusionAll studies captured in this review evaluated shoulder biomechanics. Recent studies in patients suggest that some assumptions made in this space may not fully characterize motion of the human shoulder. With reproducible scapular positioning, dynamic RC activation, and preservation of glenohumeral capsule integrity, cadaveric studies can facilitate proper validation for simulation models and broaden our understanding of the shoulder environment during motion in healthy and disease states.  相似文献   

17.
Europe’s Great Recession provides an opportunity to study the impact of increased financial insecurity on health. A number of studies explored the impact of the Recession on health, but they often reached different conclusions. To understand the root of this debate, we undertook a systematic literature review. Articles were analysed thematically based on: geography, data type, operationalisations of wealth and health, and study design. A critical appraisal was also undertaken. Forty-two studies, published from January 2010 to October 2018, were included in our review. Twenty-six of the forty-two studies found that the Great Recession worsened physical health indicators in the Eurozone. In terms of geography, a large concentration of studies focussed on Spain and Greece, indicating that there may be a gap in understanding the health consequences for EU countries with less severe experiences of the Recession. Regarding data type, nearly all studies used secondary datasets, possibly meaning that studies were constrained by the data available. In terms of operationalisations of wealth and health, a majority of studies used single/simple measures of both, so that these multi-faceted concepts were not fully reflected. Further, fewer than half included studies used panel data, with the remaining studies unable to undertake more causal analyses. The results of the critical appraisal showed that lower-quality studies tended to not find a negative impact of the Recession on health, whereas higher quality studies generally did. In future, we recommend conducting cross-country comparisons, using (inter)nationally-representative panel data conducted over a minimum of a ten-year time horizon, and employing multi-faceted operationalisations of wealth and health. This could provide more common ground across studies, and a clearer indication of whether the Recession impacted health.  相似文献   

18.
Ariella Binik 《Bioethics》2020,34(4):420-430
Controlled human infection model (CHIM) studies involve the intentional exposure of healthy research volunteers to infectious agents. These studies contribute to knowledge about the cause or development of disease and to the advancement of vaccine research. But they also raise ethical questions about the kinds of risks that should be permissible and whether limits should be imposed on research risks in CHIM studies. Two possible risk thresholds have been considered for CHIM studies. The first suggests constraining ethically permissible risks according to a minimal risk threshold and the second endorses a higher risk threshold that excludes irreversible or fatal infections. I argue that neither of these thresholds is persuasive and situate questions about risk thresholds in CHIM studies within a broader debate about permissible risks in research. I argue that risks in CHIM studies should be constrained according to limits on research risks that do not offer corresponding benefits in all studies rather than developing a unique risk threshold for CHIM studies. I then propose five recommendations for the ethical assessment of risk in CHIM studies.  相似文献   

19.
Drug metabolism studies constitute an important and necessary step in the evaluation of drug efficacy and safety. In vivo drug metabolism studies suffer from many disadvantages. Hence there is a rise in validation of in vitro microbial models. This review describes the transformation studies of drugs by the fungus, Cunninghamella and correlating them with the metabolism/biotransformation in animal systems and providing technical methods to develop microbial models. Emphasis is laid on the potential of Cunninghamella fungus to mimic mammalian drug biotransformations and to use as in vitro model for drug metabolism studies and for further toxicological and pharmacological studies of metabolites.  相似文献   

20.
The literature concerning regret among women following voluntary sterilization shows a lack of methodological rigor. This paper reviews the 7 prospective studies of voluntary sterilization conducted since 1973 that are judged to have adequate design and measurement standards, and suggests methodological considerations for future research. 3 of the studies were conducted in the US, 2 in the UK, 1 in Thailand, and 1 in Pakistan. Only 3 of the 7 studies used control groups and only 3 used standardized pre- and posttest psychological measures. Subjects in all the studies requested sterilization on a voluntary basis. 4 of the 7 studies evaluated contraceptive and menstrual histories before and after sterilization. All the studies varied in their poststerilization follow-up intervals ranging from 2 months and 1 year to 18 months and 2 years. Attrition rates also varied widely across the studies. Although none of these studies presented percentages for precise measures of regret, the overall effect of the sterilization procedure was found to be positive. The relationship between regret and purported indicators of regret, such as depression, anxiety, menstrual difficulties, and desire for reversal, should be documented in prospective, controlled studies. Longer poststerilization follow-up periods are recommended. Responses of childless women and male partners to sterilization should also be considered in future studies. Finally, since repeated references are made to menstrual problems following voluntary sterilization, it is important that studies assessing poststerilization responses control for oral contraceptive (OC) use because OCs reduce menstrual flow and their discontinuation results in a return to normal, although heavier, menstrual flow.  相似文献   

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