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101.
Waterfowl can cause substantial reductions in plant standing crop, which may have ecological and economic consequences. However, what determines the magnitude of these reductions is not well understood. Using data from published studies, we derived the relationship between waterfowl density and reduction in plant standing crop. When waterfowl density was estimated as individuals ha−1 no significant relationship with reduction in plant standing crop was detected. However, when waterfowl density was estimated as kg ha−1 a significant, positive, linear relationship with reduction in plant standing crop was found. Whilst many previous studies have considered waterfowl species as homologous, despite large differences in body mass, our results suggest that species body mass is a key determinant of waterfowl impact on plant standing crop. To examine relative impacts of waterfowl groups based on species body mass, a measure of plant biomass reduction (R s) per bird per hectare was calculated for each group. Comparison of R s values indicated some differences in impact between different waterfowl groups, with swans having a greater per capita impact than smaller-bodied waterfowl groups. We present evidence that this difference is linked to disparities in individual body size and associated differences in intake rates, diet composition and energy requirements. Future research priorities are proposed, particularly the need for experiments that quantify the importance of factors that determine the magnitude of waterfowl impacts on plant standing crop. 相似文献
102.
LJ Schurgers IA Joosen EM Laufer ML Chatrou M Herfs MH Winkens R Westenfeld V Veulemans T Krueger CM Shanahan W Jahnen-Dechent E Biessen J Narula C Vermeer L Hofstra CP Reutelingsperger 《PloS one》2012,7(8):e43229
Background
Vitamin K-antagonists (VKA) are treatment of choice and standard care for patients with venous thrombosis and thromboembolic risk. In experimental animal models as well as humans, VKA have been shown to promote medial elastocalcinosis. As vascular calcification is considered an independent risk factor for plaque instability, we here investigated the effect of VKA on coronary calcification in patients and on calcification of atherosclerotic plaques in the ApoE−/− model of atherosclerosis.Methodology/Principal Findings
A total of 266 patients (133 VKA users and 133 gender and Framingham Risk Score matched non-VKA users) underwent 64-slice MDCT to assess the degree of coronary artery disease (CAD). VKA-users developed significantly more calcified coronary plaques as compared to non-VKA users. ApoE−/− mice (10 weeks) received a Western type diet (WTD) for 12 weeks, after which mice were fed a WTD supplemented with vitamin K1 (VK1, 1.5 mg/g) or vitamin K1 and warfarin (VK1&W; 1.5 mg/g & 3.0 mg/g) for 1 or 4 weeks, after which mice were sacrificed. Warfarin significantly increased frequency and extent of vascular calcification. Also, plaque calcification comprised microcalcification of the intimal layer. Furthermore, warfarin treatment decreased plaque expression of calcification regulatory protein carboxylated matrix Gla-protein, increased apoptosis and, surprisingly outward plaque remodeling, without affecting overall plaque burden.Conclusions/Significance
VKA use is associated with coronary artery plaque calcification in patients with suspected CAD and causes changes in plaque morphology with features of plaque vulnerability in ApoE−/− mice. Our findings underscore the need for alternative anticoagulants that do not interfere with the vitamin K cycle. 相似文献103.
David L. Jones Simon Gilroy Paul B. Larsen Stephen H. Howell Leon V. Kochian 《Planta》1998,206(3):378-387
Aluminum inhibition of root growth is a major world agricultural problem where the cause of toxicity has been linked to changes
in cellular calcium homeostasis. Therefore, the effect of aluminum ions (Al) on changes in cytoplasmic free calcium concentration
([Ca2+]c) was followed in root hairs of wild-type, Al-sensitive and Al-resistant mutants of Arabidopsis thaliana (L.) Heynh. Generally, Al exposure resulted in prolonged elevations in tip-localized [Ca2+]c in both wild-type and Al-sensitive root hairs. However, these Al-induced increases in [Ca2+]c were not tightly correlated with growth inhibition, occurring up to 15 min after Al had induced growth to stop. Also, in
32% of root hairs examined growth stopped without a detectable change in [Ca2+]c. In contrast, Al-resistant mutants showed little growth inhibition in response to AlCl3 exposure and in no case was a change in [Ca2+]c observed. Of the other externally applied stresses tested (oxidative and mechanical stress), both were found to inhibit root
hair growth, but only oxidative stress (H2O2, 10 μM) caused a prolonged rise in [Ca2+]c similar to that induced by Al. Again this increase occurred after growth had been inhibited. The lack of a tight correlation
between Al exposure, growth inhibition and altered [Ca2+]c dynamics suggests that although exposure of root hairs to toxic levels of Al causes an alteration in cellular Ca2+ homeostasis, this may not be a required event for Al toxicity. The elevation in [Ca2+]c induced by Al also strongly suggests that the phytotoxic action of Al in root hairs is not through blockage of Ca2+-permeable channels required for Ca2+ influx into the cytoplasm.
Received: 24 October 1997 / Accepted: 6 March 1998 相似文献
104.
Mary F. Feitosa PhD Treva Rice Roland Rosmond Tuomo Rankinen Arthur S. Leon James S. Skinner Jack H. Wilmore Claude Bouchard D. C. Rao 《Obesity (Silver Spring, Md.)》2002,10(12):1222-1231
Objective: To investigate familial basis for the relationship between cortisol adiposity at baseline and their training responses. Research Methods and Procedures: Bivariate correlation and segregation analyses were employed between cortisol and several adiposity measures [body mass index, fat mass (FM), fat-free mass, percentage of body fat (% BF), abdominal visceral fat (AVF), abdominal subcutaneous fat (ASF), and abdominal total fat (ATF)] from 99 white families and 105 black families. Results: In both races, significant inverse phenotypic correlations were generally observed between cortisol and adiposity measures at baseline but not for training responses. Significant cross-trait familial correlations were found for cortisol with abdominal fat (ASF, AVF, ATF) and overall body adiposity (FM, % BF) measures at baseline, which accounted for 14% to 20% of the phenotypic variance in whites. The cross-trait correlations were not significant for baseline phenotypes in blacks, perhaps because of the small sample size. A bivariate segregation analysis showed evidence of polygenic pleiotropy for cortisol with both abdominal fat and overall adiposity measures that accounted for 14% to 17% of the phenotypic covariance, but major gene pleiotropy was not suggested in whites. However, when ASF, AVF, and ATF were additionally adjusted for FM, no familial cross-trait correlations or polygenic pleiotropy between cortisol and the abdominal fat measures remained. Discussion: Evidence was found for polygenic pleiotropy but not for pleiotropic major gene effects between cortisol and overall adiposity in whites. However, the covariation of cortisol with abdominal fat phenotypes is dependent on concomitant polygenic factors for total-body fat. 相似文献
105.
106.
107.
Polymorphisms and deduced amino acid substitutions in the coding sequence of the ryanodine receptor (RYR1) gene in individuals with malignant hyperthermia. 总被引:13,自引:0,他引:13
E F Gillard K Otsu J Fujii C Duff S de Leon V K Khanna B A Britt R G Worton D H MacLennan 《Genomics》1992,13(4):1247-1254
Twenty-one polymorphic sequence variants of the RYR1 gene, including 13 restriction fragment length polymorphisms (RFLPs), were identified by sequence analysis of human ryanodine receptor (RYR1) cDNAs from three individuals predisposed to malignant hyperthermia (MH). All RFLPs were detectable in PCR-amplified products, and their segregation was consistent with our initial finding of linkage to MH in the nine families previously informative for one or more intragenic markers (MacLennan et al., 1990, Nature 343:559-561). Four amino acid substitutions were identified in the study: Arg for Gly248, Cys for Arg470, Leu for Pro1785, and Cys for Gly2059. Of 45 families tested, a single family presented the Arg for Gly248 substitution where it segregated with malignant hyperthermia, making it a candidate mutation for predisposition to MH in man. The other three polymorphic substitutions failed to segregate with malignant hyperthermia in those families in which they occurred, implying that they represent polymorphisms with little or no effect on the function of the RYR1 gene. 相似文献
108.
V A McCormack I dos Santos Silva B L De Stavola R Mohsen D A Leon H O Lithell 《BMJ (Clinical research ed.)》2003,326(7383):248
ObjectiveTo investigate whether size at birth and rate of fetal growth influence the risk of breast cancer in adulthood.DesignCohort identified from detailed birth records, with 97% follow up.SettingUppsala Academic Hospital, Sweden.Participants5358 singleton females born during 1915-29, alive and traced to the 1960 census.ResultsSize at birth was positively associated with rates of breast cancer in premenopausal women. In women who weighed ⩾4000 g at birth rates of breast cancer were 3.5 times (95% confidence interval 1.3 to 9.3) those in women of similar gestational age who weighed <3000 g at birth. Rates in women in the top fifths of the distributions of birth length and head circumference were 3.4 (1.5 to 7.9) and 4.0 (1.6 to 10.0) times those in the lowest fifths (adjusted for gestational age). The effect of birth weight disappeared after adjustment for birth length or head circumference, whereas the effects of birth length and head circumference remained significant after adjustment for birth weight. For a given size at birth, gestational age was inversely associated with risk (P=0.03 for linear trend). Adjustment for markers of adult risk factors did not affect these findings. Birth size was not associated with rates of breast cancer in postmenopausal women.ConclusionsSize at birth, particularly length and head circumference, is associated with risk of breast cancer in women aged <50 years. Fetal growth rate, as measured by birth size adjusted for gestational age, rather than size at birth may be the aetiologically relevant factor in premenopausal breast cancer.
What is already known on this topic
There is some evidence that birth weight is related to risk of breast cancerThe exact nature of any association and whether it differs at premenopausal and postmenopausal ages is unclearFew studies have examined the effect of other measures of birth size and of gestational ageWhat this study adds
There are strong positive associations between measures of birth size and rates of breast cancer at premenopausal ages that persisted after adjustment for adult risk factorsFor a given birth size, gestational age was inversely associated with risk, suggesting that the rate of fetal growth may be aetiologically relevant to premenopausal breast cancerThere was no association between birth characteristics and rates of breast cancer at postmenopausal ages 相似文献109.
Membrane-aerated biofilms (MABs) are an effective means to achieve nitrification and denitrification of wastewater. In this
research, microsensors, fluorescence in situ hybridization (FISH), and modeling were used to assess the impact of bulk liquid
biological oxygen demand (BOD) concentrations on the activity and microbial community structure of nitrifying MABs. With 1 g
m−3 BOD in the bulk liquid, the nitrification rate was 1.3 g N m−2 day−1, slightly lower than the 1.5 g N m−2 day−1 reported for no bulk liquid BOD. With bulk liquid BOD concentrations of 3 and 10 g m−3, the rates decreased to 1 and 0.4 g N m−2 day−1, respectively. The percent denitrification increased from 20% to 100% when the BOD increased from 1 to 10 g m−3 BOD. FISH results indicated increasing abundance of heterotrophs with increasing bulk liquid BOD, consistent with the increased
denitrification rates. Modeling was used to assess the effect of BOD on nitrification rates and to compare an MAB to a conventional
biofilm. The model-predicted nitrification rates were consistent with the experimental results. Also, nitrification in the
MAB was much less sensitive to BOD inhibition than the conventional biofilm. The MAB achieved concurrent nitrification and
denitrification, whereas little denitrification occurred in the conventional biofilm. 相似文献
110.
Martine de Boer Maaike te Lintel Hekkert Jiang Chang Bibi S. van Thiel Leonie Martens Maxime M. Bos Marion G. J. de Kleijnen Yanto Ridwan Yanti Octavia Elza D. van Deel Lau A. Blonden Renata M. C. Brandt Sander Barnhoorn Paula K. Bautista-Niño Ilona Krabbendam-Peters Rianne Wolswinkel Banafsheh Arshi Mohsen Ghanbari Christian Kupatt Leon J. de Windt A. H. Jan Danser Ingrid van der Pluijm Carol Ann Remme Monika Stoll Joris Pothof Anton J. M. Roks Maryam Kavousi Jeroen Essers Jolanda van der Velden Jan H. J. Hoeijmakers Dirk J. Duncker 《Aging cell》2023,22(3):e13768