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Posing the question of whether the precautionary principle has a role in risk assessment effectively constrains any debate of the issue within a framework predicated on the assumption that application of risk assessment is inevitable in the formulation of regulatory decisions. The question can equally validly be expressed in terms of whether there is a role for risk assessment in the formulation of precautionary legislation. This allows the debate then to turn on consideration of two questions: Firstly, does the precautionary principle have a role in policy development? and secondly, is this role consistent and compatible with a risk based approach to regulation? When recast in these terms, a more holistic comparison of the aims and objectives of both approaches and of their relative power in the formulation of regulation becomes possible. This leads to the conclusion that the precautionary principle is, when defined and applied correctly, scientifically more robust than risk assessment. Precautionary approaches utilize scientific information and conform robustly to a scientific process but also explicitly incorporate indeterminacies into the decision making framework. Moreover, the precautionary principle when applied to environmental regulation, is more likely to lead to regulation consistent with global sustainability. On this premise, this paper argues that risk based approaches are essentially incompatible with approaches based on the precautionary paradigm, and that of the two, risk assessment is more likely to lead to unsustainable underprotection of the environment.  相似文献   

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Is There a Role for the Apex in Shoot Geotropism?   总被引:3,自引:1,他引:2       下载免费PDF全文
Experiments with horizontal etiolated sunflower (Helianthus annuus L.) seedlings supported centrally such that both apical and basal ends are free to react to geostimulus, revealed that the apical end commences curvature 1 to 2 hours earlier than the basal end. The later curvature in the basal region is a consequence of the absence of growth in the initial period rather than merely slower growth. A comparison of zonal growth rates in a vertical and a horizontal seedling confirmed that geostimulus induces a renewal of growth in a region where growth had ceased. Removing the apical half of the hypocotyl showed that the curvature resulting from this growth initiation in the basal region is dependent on attachment to the apical region. Evidence that this dependence is unlikely to be due to energy deficiency is adduced. The prior response of the apical end to geostimulus and the apically dependent later initiation of new growth in the basal region are compatible with the delay inherent in message transport from apex to base and are considered as evidence for apical involvement in the totality of the seedling's georesponse.  相似文献   

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Astrogliosis, a cellular reaction with specific structural and functional characteristics, represents a remarkably homotypic response of astrocytes to all kinds of central nervous system (CNS) pathologies. Astrocytes play diverse functions in the brain, both harmful and beneficial. Mounting evidence indicates that astrogliosis is an underlying component of a diverse range of diseases and associated neuropathologies. The mechanisms that lead to astrogliosis are not fully understood, nevertheless, damaged neurons have long been reported to induce astrogliosis and astrogliosis has been used as an index for underlying neuronal damage. As the predominant source of proinflammatory factors in the CNS, microglia are readily activated under certain pathological conditions. An increasing body of evidence suggests that release of cytokines and other soluble products by activated microglia can significantly influence the subsequent development of astrogliosis and scar formation in CNS. It is well known that damaged neurons activate microglia very quickly, therefore, it is possible that activated microglia contribute factors/mediators through which damaged neuron induce astrogliosis. The hypothesis that activated microglia initiate and maintain astrogliosis suggests that suppression of microglial overactivation might effectively attenuate reactive astrogliosis. Development of targeted anti-microglial activation therapies might slow or halt the progression of astrogliosis and, therefore, help achieve a more beneficial environment in various CNS pathologies.  相似文献   

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A challenge to civilization is the growing incidence in the loss of sight and cognition due to increased life expectancy. Therefore, we are confronted with a rise in the occurrence of photoreceptor- and neuronal-survival failure, as reflected mainly by age-related macular degeneration (AMD) and Alzheimer’s disease (AD). Nervous system development is driven by neuronal apoptotic cell death, and thereafter, for the entire lifespan of an organism, neurons are postmitotic cells. In neurodegenerative diseases, apoptosis and other forms of cells death lead to selective neuronal loss. Although age is the main risk factor, not everyone develops these diseases during aging. Despite decades of important findings about neuronal cell death, the specific mechanisms that regulate neuronal survival remain incompletely understood.  相似文献   

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Objective: The relationships of gastric accommodation and satiety in moderately obese individuals are unclear. We hypothesized that obese people had increased gastric accommodation and reduced postprandial satiety. The objective of this study was to compare gastric accommodation and satiety between obese and non‐obese asymptomatic subjects. Research Methods and Procedures: In 13 obese (body mass index [BMI] ≥ 30 kg/m2; mean BMI, 37.0 ± 4.9 kg/m2) and 19 non‐obese control subjects (BMI < 30 kg/m2; mean BMI, 26.2 ± 2.9 kg/m2), we used single photon emission computed tomography to measure fasting and postprandial gastric volumes and expressed the accommodation response as the ratio of postprandial/fasting volumes. The satiety test measured maximum tolerable volume of ingestion of liquid nutrient meal (Ensure) and symptoms 30 minutes after cessation of ingestion. Results: Total fasting and postprandial gastric volumes and the ratio of postprandial/fasting gastric volume were not different between asymptomatic obese and control subjects. However, the fasting volume of the distal stomach was greater in obese than in control subjects. Maximum tolerable volume of ingested Ensure and aggregate symptom score 30 minutes later were also not different between obese and control subjects. Discussion: Asymptomatic obese individuals (within the BMI range of 32.6 to 48 kg/m2) did not show either increased postprandial gastric accommodation or reduced satiety. These datasuggest that gastric accommodation is unlikely to provide an important contribution to development of moderate obesity.  相似文献   

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Background

Research ethics consultation programs are being established with a goal of addressing the ethical, societal, and policy considerations associated with biomedical research. A number of these programs are modelled after clinical ethics consultation services that began to be institutionalized in the 1980s. Our objective was to determine biomedical science researchers'' perceived need for and utility of research ethics consultation, through examination of their perceptions of whether they and their institutions faced ethical, social or policy issues (outside those mandated by regulation) and examination of willingness to seek advice in addressing these issues. We conducted telephone interviews and focus groups in 2006 with researchers from Stanford University and a mailed survey in December 2006 to 7 research universities in the U.S.

Findings

A total of 16 researchers were interviewed (75% response rate), 29 participated in focus groups, and 856 responded to the survey (50% response rate). Approximately half of researchers surveyed (51%) reported that they would find a research ethics consultation service at their institution moderately, very or extremely useful, while over a third (36%) reported that such a service would be useful to them personally. Respondents conducting human subjects research were more likely to find such a service very to extremely useful to them personally than respondents not conducting human subjects research (20% vs 10%; chi2 p<0.001).

Conclusion

Our findings indicate that biomedical researchers do encounter and anticipate encountering ethical and societal questions and concerns and a substantial proportion, especially clinical researchers, would likely use a consultation service if they were aware of it. These findings provide data to inform the development of such consultation programs in general.  相似文献   

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alpha-Adrenoreceptor antagonists have become the primary medical treatment for lower urinary tract symptoms associated with benign prostatic hyperplasia (BPH). It was presumed that the primary mechanism by which alpha-blockers reduced lower urinary tract symptoms (LUTS) was by relaxation of smooth muscle in the prostate through a sympathetic response. Reduction of outlet resistance leads to changes in bladder function, thus improving both storage and voiding symptoms. However, it was observed that many patients with BPH-associated LUTS had significant improvement in storage symptoms without subjective or objective improvement in voiding. Storage symptoms associated with detrusor overactivity (frequency, urgency, and urge incontinence) are typically thought of as being parasympathetically mediated, and therefore anticholinergic medications have been the mainstay of pharmacological treatment, but recent work has suggested that several nonparasympathetic-mediated mechanisms may cause detrusor overactivity. Because alpha receptors appear to play a role in lower urinary tract function at multiple sites and levels, alpha-blockers could be used to treat voiding dysfunction not related to BPH. In addition, these nonprostate effects should be gender-independent, making the use of alpha-blockers plausible in women with specific types of voiding dysfunction.  相似文献   

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Cyanobacterial cells accumulate substantial amounts of a membrane-associated 42 kilodalton polypeptide during adaptation to low CO2 conditions. The role of this polypeptide in the process of adaptation and in particular in the large increase in the ability to accumulate inorganic carbon (Ci), which accompanies this process, is not yet understood. We have isolated a mutant Synechococcus PCC7942 that does not accumulate the 42 kilodalton polypeptide. The mutant requires a high-CO2 concentration for growth and exhibits a very low apparent photosynthetic affinity for extracellular Ci. The latter might be attributable to the observed defective ability of the mutant to utilize the intracellular Ci pool for photosynthesis. The 42 kilodalton polypeptide does not appear to participate directly in the active transport of Ci, since the difference between the observed capabilities for CO2 and HCO3 uptake of the mutant and the wild type is not sufficient to account for their different growth and photosynthetic performance. Furthermore, high CO2-grown wild-type cells, where we could not detect the 42 kilodalton polypeptide, transported CO2 faster than the mutant. An analysis of the curves relating the rate of accumulation of Ci to the concentration of CO2 or HCO3 supplied, in the presence or absence of carbonic anhydrase, indicated that under the experimental conditions used here, CO2 was the preferred Ci species taken up by Synechococcus.  相似文献   

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Since there has been no significant increase in cancer cure rates in recent years that can be attributed to the treatment method alone, new and more radical procedures have been introduced in an effort to improve the results. In radiation therapy this has taken the form of supervoltage generators and in the use of high energy sources of radiation such as Cobalt 60 and Cesium 137. As this trend gains momentum, the place and future of orthovoltage therapeutic radiation (250 to 400 kilovolts) must be considered. General agreement is that supervoltage radiation offers an increase in depth dose and fewer local and systemic reactions, but it is too early to assess any change in cure rate. Measured against this is the danger of deep tissue damage, less relative biological efficiency and increased costs.In view of our ignorance regarding cancer, abandoning proved procedures prematurely is unjustified. The most promising trend lies in improved training and in the skillful use of what we have. While it may be that radiation of higher voltages will improve the morbidity and mortality rates, it would be better to concentrate these new modalities in centers where large numbers of cases are available.  相似文献   

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Achieving and maintaining effective suppression of serum testosterone levels in men treated with androgen ablation is one of the essential strategies in the management of prostate cancer. Historically, a serum testosterone below 50 ng/dL was considered to be the castrate level. Current data suggest that the new target for either surgical or chemical castration is a serum testosterone level of lower than 20 ng/dL in an attempt to maximize therapeutic outcomes. Testosterone breakthrough and the acute-on-chronic effects of administration of a luteinizing hormone-releasing hormone analogue may cause testosterone levels to periodically rise, sometimes to noncastrate levels. The goal of androgen ablation is to identify those agents that will most consistently achieve and maintain the lowest testosterone levels possible.Key words: Prostate cancer, Androgen ablation, LHRH analogues, LHRH antagonists, TestosteroneThe cornerstone of understanding the basic biology of prostate cancer relies upon the important discovery that prostate cancer is a hormonally responsive tumor. The current use of androgen ablation therapy in prostate cancer includes treatment based on serum prostate-specific antigen (PSA) only or local recurrence; neoadjuvant or adjuvant treatment of high-risk disease, usually in combination with radiation therapy; and treatment of patients with metastatic disease regardless of symptoms. The American Society of Clinical Oncology (ASCO) 2007 guidelines and National Comprehensive Cancer Network (NCCN) 2009 guidelines recommend either luteinizing hormone-releasing hormone (LHRH) agonists or bilateral orchiectomy as first-line therapy for men with advanced prostate cancer.1,2Medical or chemical castration is almost exclusively performed by the use of injectable LHRH analogues, with a minor role for estrogen and limited experience with LHRH antagonists. Surgical castration through bilateral orchiectomy is infrequently used today.Intermittent hormonal therapy (IHT) is being investigated as an alternative to continuous hormonal therapy with a potential for reduced morbidity and a delay of the progression to hormone-refractory disease.3 Although intermittent therapy may rely upon restoring a normal testosterone level, it is believed that the testosterone level should be as low as possible when the patient is on treatment, thus generating the lowest serum PSA level possible and likely improving outcome.4 Although the data on IHT are promising, trials reported thus far are relatively small and somewhat underpowered, and it is likely that its use will increase in the future as trials mature.There is growing recognition that many men may not achieve acceptable levels of testosterone using androgen ablation. This has led to a renewed interest in the significance of the testosterone level in the modern era of prostate cancer management. Can we define the best castration therapy for prostate cancer? Is this the therapy that provides the lowest and most consistent levels of testosterone suppression? To quote Dr. Claude Schulman in a recent editorial: “less is more.”5  相似文献   

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The incidence of testicular cancer, primarily seminoma, has been increasing in many countries, including the United States. The testis is often the site of residual cancer after adequate treatment with systemic chemotherapy. The blood-testis barrier is commonly cited as the explanation for residual tumor within the gonad after chemotherapy and as the indication for delayed orchiectomy. Conversely, complete eradication of viable tumor from the primary site is common and argues against the testis as a "tumor sanctuary." Residual tumor is also demonstrated within metastatic foci, and the disparity between the histopathologic response of the primary tumor and metastatic sites may be best explained by tumor heterogeneity and multiple tumor clones. Regardless of the scientific and academic arguments, delayed radical orchiectomy remains an important part of treatment for patients undergoing primary chemotherapy.  相似文献   

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The prevalence of metal dysregulation in many neurodegenerative and neurocognitive disorders has compelled many studying such diseases to investigate the mechanisms underlying metal regulation in the central nervous system. Metal homoeostasis is often complex, with sophisticated, multilayered pathways in operation. G protein-coupled receptors are omnipresent on cell membranes and have intriguing mechanisms of endocytosis and trafficking that may be useful in metal homoeostasis. Indeed, many receptors and/or their cognate ligands are able to bind metals, and in many cases metals are considered to have neuromodulatory roles as a result of receptor binding. In this mini-review, we outline the structural and functional aspects of G protein-coupled receptors with a focus on the mechanisms leading to endocytosis and cellular trafficking. We further highlight how this may help in the trafficking of metal ions, notably copper.  相似文献   

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Regional ex-vessel markets for cannery-grade skipjack tuna throughout the globe are spatially integrated by price, but such markets for yellowfin tuna are spatially independent. The Americas exert primary price leadership in ex-vessel skipjack markets, but Bangkok and American Samoa also exert price leadership, and Ivory Coast, Japan, and Spain are largely price followers. Regional ex-vessel markets for skipjack and yellowfin are not integrated by prices. While price effects of this nature are simply evidence of a pecuniary externality, and thereby do not necessarily affect the overall size of global net benefits, in practice such price effects affect distribution among players—who wins and who loses—and in this manner, the eventual formation of, and compliance with, different management policies.  相似文献   

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Background

Functional MRI combined with electromyography (EMG-fMRI) is a new technique to investigate the functional association of movement to brain activations. Thalamic stereotactic surgery is effective in reducing tremor. However, while some patients have satisfying benefit, others have only partial or temporary relief. This could be due to suboptimal targeting in some cases. By identifying tremor-related areas, EMG-fMRI could provide more insight into the pathophysiology of tremor and be potentially useful in refining surgical targeting.

Objective

Aim of the study was to evaluate whether EMG-fMRI could detect blood oxygen level dependent brain activations associated with tremor in patients with Essential Tremor. Second, we explored whether EMG-fMRI could improve the delineation of targets for stereotactic surgery.

Methods

Simultaneous EMG-fMRI was performed in six Essential Tremor patients with unilateral thalamotomy. EMG was recorded from the trembling arm (non-operated side) and from the contralateral arm (operated side). Protocols were designed to study brain activations related to voluntary muscle contractions and postural tremor.

Results

Analysis with the EMG regressor was able to show the association of voluntary movements with activity in the contralateral motor cortex and supplementary motor area, and ipsilateral cerebellum. The EMG tremor frequency regressor showed an association between tremor and activity in the ipsilateral cerebellum and contralateral thalamus. The activation spot in the thalamus varied across patients and did not correspond to the thalamic nucleus ventralis intermedius.

Conclusion

EMG-fMRI is potentially useful in detecting brain activations associated with tremor in patients with Essential Tremor. The technique must be further developed before being useful in supporting targeting for stereotactic surgery.  相似文献   

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We argue that there is not enough science to appropriately support many of the conservation measures currently being proposed, and hence, we cannot be sure of the objectivity of the conservation actions being implemented. The objectivity claimed to be underlying conservation actions is more assumed than real. We also suggest that the approach to conservation is driven more by moral commitments than by tested concepts, and it is further biased by our anthropocentric evaluation of ecological processes and their outcomes. Conservation science is a young subject, which needs to be nourished while it continues to feed on its roots-ecology and evolutionary biology.  相似文献   

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