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1.
Yunfei Jiang Rachid Lahlali Chithra Karunakaran Thomas D. Warkentin Arthur R. Davis Rosalind A. Bueckert 《Plant, cell & environment》2019,42(1):354-372
Field pea (Pisum sativum), a major grain legume crop, is autogamous and adapted to temperate climates. The objectives of this study were to investigate effects of high temperature stress on stamen chemical composition, anther dehiscence, pollen viability, pollen interactions with pistil and ovules, and ovule growth and viability. Two cultivars (“CDC Golden” and “CDC Sage”) were exposed to 24/18°C (day/night) continually or to 35/18°C for 4 or 7 days. Heat stress altered stamen chemical composition, with lipid composition of “CDC Sage” being more stable compared with “CDC Golden.” Heat stress reduced pollen viability and the proportion of ovules that received a pollen tube. After 4 days at 35°C, pollen viability in flower buds decreased in “CDC Golden,” but not in “CDC Sage.” After 7 days, partial to full failure of anthers to dehisce resulted in subnormal pollen loads on stigmas. Although growth (ovule size) of fertilized ovules was stimulated by 35°C, heat stress tended to decrease ovule viability. Pollen appears susceptible to stress, but not many grains are needed for successful fertilization. Ovule fertilization and embryos are less susceptible to heat, but further research is warranted to link the exact degree of resilience to stress intensity. 相似文献
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Cadmium is an important environmental pollutant and a potent toxicant to bacteria, algae, and fungi. Mechanisms of Cd toxicity and resistance are variable, depending on the organism. It is very clear that the form of the metal and the environment it is studied in, play an important role in how Cd exerts its effect and how the organism(s) responds. A wide range of Cd concentrations have been used to designate resistance in organisms. To date, no concentration has been specified that is applicable to all species studied under standardized conditions. Cadmium exerts its toxic effect(s) over a wide range of concentrations. In most cases, algae and cyanobacteria are the most sensitive organisms, whereas bacteria and fungi appear to be more resistant. In some bacteria, plasmid-encoded resistance can lead to reduced Cd2+ uptake. However, some Gram-negative bacteria without plasmids are just as resistant to Cd as are bacteria containing plasmids encoding for Cd resistance. According to Silver and Misra (1984), there is no evidence for enzymatic or chemical transformations associated with Cd resistance. Insufficient information is available on the genetics of Cd uptake and resistance in cyanobacteria and algae. Mechanisms remain largely unknown at this point in time. Cadmium is toxic to these organisms, causing severe inhibition of such physiological processes as growth, photosynthesis, and nitrogen fixation at concentrations less than 2 ppm, and often in the ppb range (Tables 2 and 3). Cadmium also causes pronounced morphological aberrations in these organisms, which are probably related to deleterious effects on cell division. This may be direct or indirect, as a result of Cd effects on protein synthesis and cellular organelles such as mitochondria and chloroplasts. Cadmium is accumulated internally in algae (Table 4) as a result of a two-phase uptake process. The first phase involves a rapid physicochemical adsorption of Cd onto cell wall binding sites, which are probably proteins and (or) polysaccharides. This is followed by a lag period and then a slow, steady intracellular uptake. This latter phase is energy dependent and may involve transport systems used to accumulate other divalent cations, such as Mn2+ and Ca2+. Some data indicate that Cd resistance, and possibly uptake, in algae and cyanobacteria is controlled by a plasmid-encoded gene(s). Although considerable information is available on Cd toxicity to, and uptake in fungi, further work is clearly needed in several areas. There is little information about Cd uptake by filamentous fungi, and even in yeasts, information on the specificity, kinetics, and mechanisms of Cd uptake is limited.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
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Nicholas A. Ashford 《人类与生态风险评估》2005,11(1):85-96
The Precautionary Principle is in sharp political focus today because (1) the nature of scientific uncertainty is changing and (2) there is increasing pressure to base governmental action on more “rational” schemes, such as cost-benefit analysis and quantitative risk assessment, the former being an embodiment of ‘rational choice theory’ promoted by the Chicago school of law and economics. The Precautionary Principle has been criticized as being both too vague and too arbitrary to form a basis for rational decision making. The assumption underlying this criticism is that any scheme not based on cost-benefit analysis and risk assessment is both irrational and without secure foundation in either science or economics. This paper contests that view and makes explicit the rational tenets of the Precautionary Principle within an analytical framework as rigorous as uncertainties permit, and one that mirrors democratic values embodied in regulatory, compensatory, and common law. Unlike other formulations that reject risk assessment, this paper argues that risk assessment can be used within the formalism of tradeoff analysis—a more appropriate alternative to traditional cost-benefit analysis and one that satisfies the need for well-grounded public policy decision making. This paper will argue that the precautionary approach is the most appropriate basis for policy, even when large uncertainties do not exist, especially where the fairness of the distributions of costs and benefits of hazardous activities and products are a concern. Furthermore, it will offer an approach to making decisions within an analytic framework, based on equity and justice, to replace the economic paradigm of utilitarian cost-benefit analysis. 相似文献
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Short men are less likely to be married or live in a permanent relationship than their taller counterparts. This pattern is not due to their social status. While blue-collar workers are shorter on average than managers, the effects of height on finding a mate are similar in the two social groups. Being tall is also economically advantageous for men. With identical educational attainment levels, tall men have better careers than short men as they are given greater supervisory responsibilities. In making a commitment, some women might take height into account as an anticipated indicator of future resources of the household. Choice of partner is also influenced by social norms--i.e., partners should be physically well-matched--which is more difficult for shorter men. 相似文献
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Aydin E Cumurcu T Ozugurlu F Ozyurt H Sahinoglu S Mendil D Hasdemir E 《Biological trace element research》2005,108(1-3):33-41
The purpose of this study was to investigate iron (Fe), zinc (Zn), and copper (Cu) levels of aqueous humor, lens, and serum
in nondiabetics and diabetics and to determine the effects of diabetes on Fe, Zn, and Cu contents in the lens. Fe, Zn, and
Cu contents of aqueous humor, lens, and serum samples of 19 patients (9 nondiabetic patients with a mean age of 62.3±5.4 yr,
and 10 diabetic patients with a mean age of 59.5±5.9 yr) were analyzed by atomic absorption spectrometry using a prospective
study design. The lens levels of Cu in diabetic patients were significantly higher compared with nondiabetic patients (p=0.02); however; there was no difference in the other elements (Zn, Fe; p=0.28, p=0.74, respectively). The levels of Fe, Zn, and Cu in the aqueous humor and serum of diabetic patients were not found to be
statistically significant when compared to nondiabetics (p=0.46, p=0.11, p=0.18, and p=0.22, p=0.43, p=0.72, respectively). These results demonstrate that increased Cu content of the lens presumably has a greater association
with the development of lens opacification in diabetics than Zn and Fe content. 相似文献
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Background
This cross-sectional study assessed the frequency of discrimination, harassment, and violence and the associated factors among a random sample of 1000 lesbian, gay men, and bisexual women and men recruited from randomly selected public venues in Italy.Methods
A face-to-face interview sought information about: socio-demographics, frequency of discrimination, verbal harassment, and physical and sexual violence because of their sexual orientation, and their fear of suffering each types of victimization.Results
In the whole sample, 28.3% and 11.9% self-reported at least one episode of victimization because of the sexual orientation in their lifetime and in the last year. Those unmarried, compared to the others, and with a college degree or higher, compared to less educated respondents, were more likely to have experienced an episode of victimization in their lifetime. Lesbians, compared to bisexual, had almost twice the odds of experiencing an episode of victimization. The most commonly reported experiences across the lifetime were verbal harassment, discrimination, and physical or sexual violence. Among those who had experienced one episode of victimization in their lifetime, 42.1% self-reported one episode in the last year. Perceived fear of suffering violence because of their sexual orientation, measured on a 10-point Likert scale with a higher score indicative of greater fear, ranges from 5.7 for verbal harassment to 6.4 for discrimination. Participants were more likely to have fear of suffering victimization because of their sexual orientation if they were female (compared to male), lesbian and gay men (compared to bisexual women and men), unmarried (compared to the others), and if they have already suffered an episode of victimization (compared to those who have not suffered an episode).Conclusions
The study provides important insights into the violence experiences of lesbian, gay men, and bisexual women and men and the results may serve for improving policy initiatives to reduce such episodes. 相似文献8.
Pregnant women in developing countries are vulnerable to multiple micronutrient deficiencies. Studies assessing serum levels
of the micronutrients and magnitude of their deficiencies are very scarce in African subjects. This study was aimed at determining
serum levels of micronutrients in 375 pregnant (42 HIV seropositive) and 76 non-pregnant women (20 HIV seropositive) who visited
the University of Gondar Hospital, Gondar, Ethiopia. Serum concentrations of zinc,\ copper, selenium, calcium, and magnesium
were determined using an inductively coupled plasma mass spectrometer. Irrespective of HIV serostatus, pregnant women had
significantly higher serum concentrations of copper and copper/zinc ratio and significantly lower magnesium compared to those
in non-pregnant women (P < 0.05). Except for selenium, which was significantly lower in HIV-seropositive pregnant women (P < 0.05), the mean serum concentrations of zinc, copper, calcium, and magnesium were not significantly different between pregnant
women by HIV serostatus. The prevalence of deficiency in zinc, magnesium, selenium, and calcium in the pregnant women, irrespective
of their HIV serostatus, was 66.7%, 25.6%, 21.9%, and 9.3%, respectively. The magnitude of deficiency in zinc, magnesium,
and selenium was significantly higher in HIV seropositive pregnant women (76.2%, 52.4%, and 45.2%) than that in HIV-seronegative
pregnant women (65.5%, 22.2%, and 18.9%) and in HIV-seronegative non-pregnant women (42.9%, 8.1%, and 30.4%; P < 0.05). Deficiency in one, two, three, or four mineral elements was observed in 44.8%, 14.4%, 9.9%, and 5.1% of the pregnant
women, respectively. Only 25.9% of the pregnant women and 44.7% of the non-pregnant women were not deficient in any of the
micronutrients. The high prevalence of micronutrient deficiencies in pregnant and non-pregnant women in Gondar, Ethiopia warrants
the need for strategies on prevention and control of the deficiencies. 相似文献
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Leslie M. Klevay 《Biological trace element research》1982,4(2-3):95-104
Meals of 12 diets were prepared from conventional foods with precautions against contamination by metallic elements because
of epidemiologic associations between ischemic heart disease and the metabolism of magnesium, calcium, copper, and zinc. Magnesium,
calcium, copper, and zinc were measured by atomic absorption spectrometry with satisfactory accuracy and precision.
The mean daily amount of copper in the diets was less than the apparent adult requirement. Mean amounts of magnesium and zinc
were close to apparent requirements; however, adults consuming amounts less than one standard deviation below these means
may be depleting body stores and be at risk of pathology.
Magnesium and copper were highly correlated (r=0.849,P=0.0001) in meals. This and other significant correlations probably will prevent the relationships of these elements to ischemic
heart disease from being elucidated by epidemiology. Metabolic experiments will be necessary to differentiate among several
hypotheses. 相似文献
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A vast literature has explored the genetic interactions among the cellular components regulating gene expression in many organisms. Early on, in the absence of any biochemical definition, regulatory modules were conceived using the strict formalism of genetics to designate the modifiers of phenotype as either cis- or trans-acting depending on whether the relevant genes were embedded in the same or separate DNA molecules. This formalism distilled gene regulation down to its essence in much the same way that consideration of an ideal gas reveals essential thermodynamic and kinetic principles. Yet just as the anomalous behavior of materials may thwart an engineer who ignores their non-ideal properties, schemes to control and manipulate the genetic and epigenetic programs of cells may falter without a fuller and more quantitative elucidation of the physical and chemical characteristics of DNA and chromatin in vivo. 相似文献
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G. Nugent 《New Zealand journal of zoology.》2013,40(3-4):75-90
Abstract A postal survey of 8639 licensed firearm owners in 1989 indicated that an estimated 117 200 ± 6300 New Zealanders (3.5% of the total population) did some hunting in 1988. An estimated 33 100 former hunters did not hunt in 1988 but thought it likely that they would hunt again in future. The survey provided useful estimates of 1988 national totals for hunting effort (4.4 million hunter days), gross expenditure ($NZ100 million), and harvest (6.5 million animals). Small-game hunting dominated, involving 81% of hunters, 59% of total hunting effort, and 86% of total numerical harvest: rabbits (Oryctolagus cuniculus) and possums (Trichosurus vulpecula) each comprised 40% of the national bag. Gamebird hunting involved 48% of hunters, 19% of effort, and 11% of total harvest: ducks comprised 73% of the gamebird harvest. Although big-game hunting attracted the fewest hunters (42%) it ranked second for hunting effort (21%). Big game formed 3% of the total numerical harvest: pigs (Sus scrofa), goats (Capra hircus), and red deer (Cervus elaphus scoticus) were the most commonly taken. Big-game were estimated to comprise 49% of total harvest biomass, followed by small-game (47%), and gamebirds (4%). Most deer (nearly 60%) were taken for recreation, with helicopter-based hunting accounting for only one-third the total deer harvest. A quarter of those people hunting in 1988 hunted on five or fewer days that year, and a relatively small group of mainly professional hunters accounted for a disproportionately large share of the overall harvest Hunters reported spending an average of $851 each on hunting in 1988. Expenditure on big-game comprised 44% of the total, small-game 23%, and gamebirds 33%. Expenditure per animal harvested or per day hunted was greater for big-game animals (other than goats) than for gamebirds, which were more expensive to hunt than small-game. Total hunting effort was inversely related to the average expenditure per animal harvested, regardless of the type of game. 相似文献
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The respiratory system has ideal tissue structure and cell types for efficient gas exchange to intake oxygen and release carbon dioxide. This complex system develops through orchestrated intercellular signaling among various cell types, such as club, ciliated, basal, neuroendocrine, AT1, AT2, endothelial, and smooth muscle cells. Notch signaling is a highly conserved cell–cell signaling pathway ideally suited for very short-range cellular communication because Notch signals are transmitted by direct contact with an adjacent cell. Enthusiastic efforts by Notch researchers over the last two decades have led to the identification of critical roles of this signaling pathway during development, homeostasis, and regeneration of the respiratory system. The dysregulation of Notch signaling results in a wide range of respiratory diseases such as pulmonary artery hypertension (PAH), chronic obstructive pulmonary disease (COPD), interstitial pulmonary fibrosis (IPF), and lung cancer. Thus, a deep understanding of the biological functions of Notch signaling will help identify novel treatment targets in various respiratory diseases. 相似文献
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ABSTRACTMacroautophagy/autophagy deregulation has been observed in perpetuated inflammation and the proliferation of tumor cells. However, the mechanisms underlying these changes have yet to be well-identified. UVRAG is one of the key players of autophagy, but its role in vivo remained puzzling. Our recent study utilized a mouse model with inducible expression of a cancer-derived frameshift (FS) mutation in UVRAG that dominant-negatively inhibits wild-type UVRAG, resulting in impaired stimulus-induced autophagy. The systemically compromised autophagy, particularly mitophagy, notably increases inflammation and associated pathologies. Furthermore, our discovery indicates that time-dependent autophagy suppression and ensuing CTNNB1/β-catenin activation may serve as one tumor-promoting mechanism underpinning age-related cancer susceptibility. 相似文献
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Lujan HL Janbaih H Feng HZ Jin JP DiCarlo SE 《American journal of physiology. Regulatory, integrative and comparative physiology》2012,302(12):R1384-R1400
In the United States alone, the National Heart, Lung, and Blood Institute (NHLBI) has invested several hundred million dollars in pursuit of myocardial infarct-sparing therapies. However, due largely to methodological limitations, this investment has not produced any notable clinical application or cardioprotective therapy. Among the major methodological limitations is the reliance on animal models that do not mimic the clinical situation. In this context, the limited use of conscious animal models is of major concern. In fact, whenever possible, studies of cardiovascular physiology and pathophysiology should be conducted in conscious, complex models to avoid the complications associated with the use of anesthesia and surgical trauma. The mouse has significant advantages over other experimental models for the investigation of infarct-sparing therapies. The mouse is inexpensive, has a high throughput, and presents the ability of one to create genetically modified models. However, successful infarct-sparing therapies in anesthetized mice or isolated mouse hearts may not be successful in more complex models, including conscious mice. Accordingly, a conscious mouse model of myocardial ischemia and reperfusion has the potential to be of major importance for advancing the concepts and methods that drive the development of infarct-sparing therapies. Therefore, we describe, for the first time, the use of an intact, conscious, and unrestrained mouse model of myocardial ischemia-reperfusion and infarction. The conscious mouse model permits occlusion and reperfusion of the left anterior descending coronary artery in an intact, complex model free of the confounding influences of anesthetics and surgical trauma. This methodology may be adopted for advancing the concepts and ideas that drive cardiovascular research. 相似文献