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1.
禾草内生真菌在宿主植物的茎叶等地上组织中普遍存在,不仅能够提高禾草对生物与非生物逆境的抗性,而且能够对周围环境中的不同微生物类群产生影响。主要总结了禾草Neotyphodium/Epichlo内生真菌对病原真菌、丛枝菌根真菌和土壤微生物的影响及其作用机理。发现禾草内生真菌普遍存在对病原真菌的抑制作用,而对丛枝菌根真菌存在不对称的竞争作用,且因种类而异。禾草内生真菌对土壤微生物群落的作用则会随着土壤类型和时间等外界因素发生变化。禾草内生真菌对不同类群微生物的影响机制主要包括:通过生态位竞争、抑菌物质分泌、诱导抗病性等对病原真菌造成影响;通过根系化学物质释放、营养元素调节、侵染条件差异等对丛枝菌根真菌造成影响;通过根际沉积物和凋落物等对土壤微生物群落造成影响。禾草内生真菌产生的生物碱能提高宿主植物对包括昆虫在内草食动物采食的抗性,影响病原菌的侵入、定殖和扩展;根组织分泌物中包含次生代谢产物能够抑制菌根真菌、土传病原真菌及其它土壤微生物的侵染与群落组成;也可能通过次生代谢物影响禾草的其它抗性。因此,禾草内生真菌在植物-微生物系统中的作用应该给予更多的关注和深入研究。  相似文献   

2.
盐碱会导致植株生长缓慢甚至抑制其正常发育,如何降低高盐和高p H对植物的不利影响,已成为农业持续发展的重大课题。近年来,内生和共生真菌对宿主植物在抗盐碱方面的有益作用也引起了研究人员的广泛兴趣。本综述评述了内生真菌对宿主禾草植物抗盐碱性影响的研究成果,首先评述了内生真菌对宿主禾草在盐碱胁迫下种子萌发和生长发育影响:表现在提高种子发芽率;促进胚芽和胚根生长;提高宿主禾草的分蘖数、叶片数、株高、生物量、根冠比、成熟花序长度、种子数和种子产量。但也有感染内生真菌对宿主在盐胁迫下无促进作用的。其次,评述了内生真菌在减少禾草盐碱胁迫的原初盐害方面作用:表现为影响膜透性、提高光合作用、增加水分利用效率、改变营养代谢和离子毒害、影响植物激素代谢。最后综述了内生真菌在减少禾草次生盐害方面作用,内生真菌具有促进禾草分泌抗氧化剂、增加抗氧化酶活性、调节有机渗透物质的作用。系统的归纳了内生真菌与宿主禾草抗盐碱性相关研究成果,提出未来可能的研究问题和方向为后期的科研提供参考。  相似文献   

3.
盐碱会导致植株生长缓慢,甚至抑制其正常发育,如何降低高盐和高p H对植物的不利影响,已成为农业持续发展的重大课题。近年来,内生和共生真菌对宿主植物在抗盐碱方面的有益作用也引起了研究人员的广泛关注。综述了内生真菌对宿主禾草植物抗盐碱性影响的研究成果,首先评述了内生真菌对宿主禾草在盐碱胁迫下种子萌发和生长发育影响表现在:提高种子发芽率;促进胚芽和胚根生长;提高宿主禾草的分蘖数、叶片数、株高、生物量、根冠比、成熟花序长度、种子数和种子产量。但也有感染内生真菌对宿主在盐胁迫下无促进作用的。其次,评述了内生真菌在减少禾草盐碱胁迫的原初盐害方面作用表现为:影响膜透性、提高光合作用、增加水分利用效率、改变营养代谢和离子毒害、影响植物激素代谢。最后综述了内生真菌在减少禾草次生盐害方面作用,内生真菌具有促进禾草分泌抗氧化剂、增加抗氧化酶活性、调节有机渗透物质的作用。系统的归纳了内生真菌与宿主禾草抗盐碱性相关研究成果,提出未来可能的研究问题和方向为后期的科研提供参考。  相似文献   

4.
早熟禾亚科多种禾草可与Neotyphodium内生真菌形成禾草-内生真菌共生体,这种植物-微生物共生体性状较为稳定,且在自然界中广泛存在。禾草-内生真菌共生体稳定的互利共生关系不但保证了内生真菌所需的全部营养物质,而且共生体产生的次生代谢物又可显著提高宿主禾草对生物胁迫的抗逆性。众多研究表明,内生真菌的侵染可显著提高宿主禾草对虫害、病害及伴生植物等多种生物胁迫的抗性。据不完全统计,禾草内生真菌对蛛形纲、线虫纲、昆虫纲3个纲至少79个种的害虫表现出较明显的抗性,对至少22个种的病原真菌表现出明显的抗性。尽管利用内生真菌进行禾草品种选育及其品质改良的技术日趋成熟,但是内生真菌在不同宿主禾草之间高效的替代转化技术,及其在宿主体内遗传的稳定性仍有待于进一步深入探索。研究者把禾草内生真菌作为生防手段,在未来的应用过程中不应只考虑其与宿主禾草之间的共生特异性,而应更全面地分析禾草-内生真菌-生态环境之间的相互关系,让内生真菌更好地为人类服务。  相似文献   

5.
 近百年的禾草内生真菌研究历经了由浅入深的过程,从最初的家畜中毒事件认识到是一种共生内生真菌存在的缘故,到如今利用分子生物学技术揭示其共生机制,人类发现这类植物内生真菌并非想象中的对生态系统无足轻重。Epichloë及其无性型Neotyphodium与禾本科植物是系统发生的互利共生关系,尤其是Neotyphodium可提高宿主抵抗环境胁迫的能力和抵御动物的取食,增强植物的竞争力。禾草内生真菌有3种生活史:有性生活史、无性生活史和兼性生活史,后者表明真菌在不同的宿主及环境下既能营有性生殖也可营无性繁殖,是一种更灵活而有效的生活史对策。对内生真菌分子系统学、生活史以及与宿主禾草协同进化的研究发现,Neotyphodium起源于禾草致病真菌Epichloë的某些种,或是Epichloë与Neotyphodium的种间杂交后代。植物和内生真菌各异的生活史策略,真菌的种间杂交,两者的协同进化亦或种群间基因流的差异,都促成了共生体多样化的基因组合(Genetic combination ),也是其共生关系多样化的根源。内生真菌对宿主的有益作用只在特定基因型真菌、宿主和一定环境条件下才起作用,自然生态系统的共生关系要比农业系统复杂得多,是一个从互利共生至寄生关系的连续系统。未来对于更多共生体的遗传背景和基因与环境相互作用的阐明将有助于对禾草内生真菌共生关系本质更加深入的认识。  相似文献   

6.
禾草-内生真菌共生体在草地农业系统中的作用   总被引:24,自引:3,他引:21  
南志标  李春杰 《生态学报》2004,24(3):605-616
综述了国内外近年对禾草 -内生真菌 (N eotyphodium)的研究进展。全世界现已报道 14种禾草内生真菌 ,与 2 3个属的禾草形成共生体 ,我国已在 13属 2 5种天然草地禾草中发现内生真菌 ,其中发草属 (Descampsia)、大麦属 (H ord eum)和赖草属(L eymus)以往在国际文献中未曾报道。内生真菌在禾草体内产生的生物碱 ,致使采食带菌禾草的马、牛、羊、鹿等家畜产生中毒症状 ,每年给美国、新西兰等国造成的经济损失达 6.4亿美元之多 ,对其毒理研究取得了进展。已发现我国醉马草 (Achnatheruminebrians)对家畜的毒性与内生真菌的侵染有关。内生真菌侵染增加可使禾草对 42种害虫的抗性 ,并可增加对某些线虫和病害的抗性。与不带菌禾草相比 ,带菌禾草的另一特点是抗逆性强 ,牧草产量高。国际在该领域的研究主要集中在多年生黑麦草(L olium p erenne)和高羊茅 (Festuca arundinacea)。我国的研究发现 ,带菌布顿大麦草 (H ordeum bodg anii)和圆柱披碱草(Elymus cylind ricus)的牧草产量分别增加 3 3 .3 %和 2 78.8% ,分孽数分别增加 13 6.8%和 84.5%。目前 ,国际研究的重点包括大规模开展内生真菌生物学与生态学特性的研究 ,创造不含对家畜有害毒素的有益禾草 -内生真菌共生体 ,培育带内生真菌的草坪草品种 ,培育抗毒  相似文献   

7.
有关醉马草(Achnatherum inebrians)内生真菌(Epichlo?gansuensis, E. inebrians)共生体的研究,代表了我国禾草内生真菌研究领域的重要方向,使中国的醉马草-内生真菌与美国的苇状羊茅(Festuca arundinacea)-内生真菌(E. coenophiana)和新西兰的多年生黑麦草(Lolium perenne)-内生真菌(E. festucae var. lolii)成为禾草内生真菌国际三大研究分支。该文综述了近30年来对醉马草内生真菌共生体的系统研究,包括:内生真菌的分布、带菌率、检测方法、多样性,内生真菌提高宿主的抗旱、耐寒、耐盐碱、耐重金属、抗虫、抗病等抗逆性及其机理,共生体产生的生物碱等次生代谢物,对草食动物的毒性,及其在草地生态系统中的作用等。研究者实验证实了醉马草本身无毒,只有当内生真菌与醉马草共生并产生麦角新碱和麦角酰胺等麦角类生物碱后才能导致采食醉马草家畜中毒。文章展望了醉马草内生真菌基因组学和功能分析,利用杀菌剂杀死内生真菌进行醉马草脱毒,利用无毒内生真菌菌株进行饲用醉马草新品种选育,利用有毒醉马草内生真菌共生体进行抗虫防鸟的机场绿化新品种选育及生物源农药与医药开发等。  相似文献   

8.
《植物生态学报》2018,42(8):793
有关醉马草(Achnatherum inebrians)内生真菌(Epichloë gansuensis, E. inebrians)共生体的研究, 代表了我国禾草内生真菌研究领域的重要方向, 使中国的醉马草-内生真菌与美国的苇状羊茅(Festuca arundinacea)-内生真菌(E. coenophiana)和新西兰的多年生黑麦草(Lolium perenne)-内生真菌(E. festucae var. lolii)成为禾草内生真菌国际三大研究分支。该文综述了近30年来对醉马草内生真菌共生体的系统研究, 包括: 内生真菌的分布、带菌率、检测方法、多样性, 内生真菌提高宿主的抗旱、耐寒、耐盐碱、耐重金属、抗虫、抗病等抗逆性及其机理, 共生体产生的生物碱等次生代谢物, 对草食动物的毒性, 及其在草地生态系统中的作用等。研究者实验证实了醉马草本身无毒, 只有当内生真菌与醉马草共生并产生麦角新碱和麦角酰胺等麦角类生物碱后才能导致采食醉马草家畜中毒。文章展望了醉马草内生真菌基因组学和功能分析, 利用杀菌剂杀死内生真菌进行醉马草脱毒, 利用无毒内生真菌菌株进行饲用醉马草新品种选育, 利用有毒醉马草内生真菌共生体进行抗虫防鸟的机场绿化新品种选育及生物源农药与医药开发等。  相似文献   

9.
[目的]甘肃马先蒿与感染内生真菌的禾草(紫花针茅和麦宾草)建立根寄生关系,有关内生真菌对根寄生危害禾草光合作用调控方面的研究较少。[方法]本研究以紫花针茅和麦宾草带菌(E+)、不带菌(E-)植株为研究对象,研究甘肃马先蒿寄生和未寄生处理对紫花针茅和麦宾草E+、E-植株不同生长阶段光合特性影响的动态变化。[结果]甘肃马先蒿寄生显著降低紫花针茅和麦宾草的净光合速率、蒸腾速率和气孔导度,而胞间二氧化碳浓度和水分利用率却显著增加,这与禾草是否感染内生真菌无关。甘肃马先蒿寄生后E+紫花针茅的净光合速率、气孔导度和蒸腾速率高于E-植株,而麦宾草E+植株的净光合速率、气孔导度和蒸腾速率却低于E-植株;同时,根寄生条件下E+紫花针茅的胞间二氧化碳浓度和水分利用率低于E-植株;而E-麦宾草植株的胞间二氧化碳浓度和水分利用率却低于E+植株。[结论]内生真菌侵染影响甘肃马先蒿根寄生危害禾草的光合作用;甘肃马先蒿和内生真菌同时成为禾草营养消耗库时,内生真菌与禾草的共生关系处于一种互惠共生和相互拮抗的动态变化。  相似文献   

10.
以庞泉沟自然保护区4种不同群落类型林地和灌丛下的优势禾草为研究对象,调查不同禾草内生真菌感染率,研究内生真菌感染的禾草种群与原生生境的土壤理化性质、土壤酶活性及土壤微生物群落结构的相互关系。结果发现,影响紫羊茅、中亚薹草和野燕麦染菌率的主要因子是土壤水分含量和碳氮比,且土壤C、N、S以及土壤水分含量与紫羊茅的内生真菌染菌率成正相关,土壤蔗糖酶、脲酶和酸性磷酸酶与紫羊茅的感染率显著正相关,但中亚薹草与紫羊茅的结果相反。丝盖伞科是华北落叶松林和油松林土壤微生物群落的优势真菌,但不同染菌植被群落类型下的优势细菌微生物群落组成不同。总体看来,4种森林群落类型下禾草内生真菌染菌率与土壤理化性质相关性不同,且受到的生态因子影响大小也有差异,内生真菌感染导致各植被群落类型的土壤微生物群落结构具有差异,其优势土壤真菌和土壤细菌组成不同,这有助于进一步认识原生生境下不同感染率的禾草种群对土壤微生物群落结构的影响及其在生态系统中的各异生态学功能。  相似文献   

11.
Foot disorders are the main cause of dairy cow lameness and are considered to have a major impact on the welfare of dairy cattle. This study adopts a modeling approach, using a dynamic stochastic model, to provide more insight into the welfare impact of different types of foot disorders, both clinical and subclinical. The impact of specific foot disorders on welfare was assessed by simulating the incidence and duration of foot disorders and the pain associated with them. Pain assessment was based on locomotion scores, with underlying knowledge obtained from scientific literature and experts. The results demonstrated the seriousness of the welfare impact of foot disorders. The negative welfare impact was measured on a scale from 0 to 60, where the maximum outcome represents a cow having very severe pain during the whole year. On average, each cow achieves a welfare impact score of 12, which is 20% of the maximum welfare impact score. This welfare score equals having severe pain for a period of 3 months, indicating a serious impact on welfare. On average, digital dermatitis impacts most on welfare, which is caused by a high incidence of the painful clinical stage, followed by sole hemorrhages (SoH) and interdigital dermatitis and heel horn erosion (IDHE). The combination of a high incidence and long duration of SoH and IDHE causes this relatively high welfare impact of foot disorders that occur mostly subclinically. On average, over 1 year, 46% of the welfare impact due to foot disorders is caused by clinical foot disorders. The fact that subclinical foot disorders contribute more or less equally to the effects on welfare as clinical ones, indicates that farmers may readily underestimate the welfare impact by a factor two. Modeling welfare impact at cow level, individual cases of foot disorders, stresses the importance of pain intensity, indicating the importance of clinical foot disorders. This study demonstrated the serious welfare impact of foot disorders in dairy cattle and pointed out the considerable impact of subclinical foot disorders. Furthermore, the approach of welfare assessment, for example herd v. cow level, influenced the ranking of foot disorders for their impact on animal welfare. Potentially, this leads to different prioritization of specific solution strategies for dairy farmers, for example, focusing on cow comfort, hygiene or preventive medical treatments, foot trimming and/or health monitoring. The findings in this study support in raising awareness about this welfare issue.  相似文献   

12.
Predator impacts on stream benthic prey   总被引:4,自引:0,他引:4  
David Wooster 《Oecologia》1994,99(1-2):7-15
The impact that predators have on benthic, macroinvertebrate prey density in streams is unclear. While some studies show a strong effect of predators on prey density, others show little or no effect. Two factors appear to influence the detection of predator impact on prey density in streams. First, many field studies have small sample sizes and thus might be unable to detect treatment effects. Second, streams contain two broad classes of predators, invertebrates and vertebrates, which might have different impacts on prey density for a variety of reasons, including availability of refuge for prey and prey emigration responses to the two types of predators. In addition, predatory vertebrates have more complex prey communities than predatory invertebrates; this complexity might reduce the impact that predatory vertebrates have on prey because of indirect effects. I conducted a meta-analysis on the results of field studies that manipulate predator density in enclosures to determine (1) if predators have a significant impact on benthic prey density in streams, (2) if the impacts that predatory invertebrates and vertebrates have differ, and (3) if predatory vertebrates have different impacts on predatory prey versus herbivorous prey. The results of the meta-analysis suggest that on average predators have a significant negative effect on prey density, predatory invertebrates have a significantly stronger impact than predatory vertebrates, and predatory vertebrates do not differ in their impact on predatory versus herbivorous invertebrate prey. Three methodological variables (mesh size of enclosures, size of enclosures, and experimental duration) were examined to determine if cross correlations exist that may explain the differences in impact between predatory invertebrates and vertebrates. No correlation exists between mesh size and predator impact. Over all predators, no correlation exists between experimental duration and predator impact; however, within predatory invertebrates a correlation does exist between these variables. Also, a correlation was found between enclosure size and predator impact. This correlation potentially explains the difference in impact between predatory invertebrates and predatory vertebrates. Results of the meta-analysis suggest two important areas for future research: (1) manipulate both types of predators within the same system, and (2) examine their impacts on the same spatial scale.  相似文献   

13.
The hunting impact on waders in Spain was studied to test the efficiency of species protection measures. Using information on ringed bird recoveries in Spain of 28 species a hunting impact index was calculated. The results show a high hunting pressure similar to that of other groups of birds. The hunting impact on quarry species was higher than on protected species. The change of protection level in a group of species from quarry to protected species resulted in a decrease in hunting impact. A negative trend in the hunting impact was found during a 15-year period. This result could be due to under-reporting or falsification of death causes in the recovery report. However, recoveries of shot and dead birds showed a positive relationship in contrast with expected if found dead reports increased by falsification, suggesting that there has not been a falsification of the ring recovery reports. Nevertheless, in spite of the decrease in the hunting pressure when protection measures were applied, hunting impact remains very high on protected species for a long time and studies evaluating the impact of hunting on the population dynamics of waders needs further study.  相似文献   

14.
马奔  严冬  温亚利 《生态学报》2023,43(10):4202-4211
国家公园内人与野生动物冲突严重,建立野生动物肇事保险机制是减缓冲突的重要举措。以大熊猫国家公园周边社区为例,分析建立国家公园以及农户风险偏好对野生动物肇事保险购买意愿的影响,并探讨冲突程度和制度信任的中介效应。研究结果表明建立国家公园显著增加了农户野生动物肇事保险购买意愿,而农户风险偏好对保险购买意愿会产生负向显著影响。冲突程度和制度信任是重要的中介变量,冲突程度和制度信任均对农户保险购买意愿产生正向显著影响。建立国家公园显著增加了人与野生动物冲突严重程度,进而对保险购买意愿产生正向影响。此外,建立国家公园显著降低了农户制度信任,进而对保险购买意愿产生负向影响。农户风险偏好对野生动物肇事损失程度产生正向显著影响,进而对保险购买意愿产生正向影响。农户风险偏好对制度信任影响并不显著。基于此,研究提出吸纳社会资本参与,拓宽野生动物肇事保险资金来源,开展社区共管、地役权补偿等措施提升社区信任以及建立基于农户自主防护行为的野生动物肇事保险机制等政策建议。  相似文献   

15.
赵雪雁  毛笑文 《生态学报》2013,33(17):5397-5406
农户作为我国最主要的经济活动主体与最基本的决策单位,已成为影响生态环境的最重要单元,当前急需理解农户的环境影响,并依此为依据找寻缓解环境压力的对策.以甘肃省张掖市、甘南藏族自治州、临夏回族自治州为研究区,以生态足迹作为测度环境影响的指标,利用入户调查资料,基于成分法核算了农户的生态足迹,对比分析了汉、藏、回族地区农户的环境影响,并利用STIRPAT模型分解了各因素对农户环境影响的作用.研究发现:(1)甘南州农户的人均生态足迹高于张掖市与临夏州,其中甘南州农户的人均草地足迹远高于张掖市与临夏州,而张掖市农户的人均化石能源地足迹远高于甘南州与临夏州;(2)3个地区农户对耕地影响的差距均较小,但对水域、林地、草地影响的差距都较悬殊;(3)农户的家庭规模、富裕水平、受教育程度、非农化水平是影响生态环境的主要驱动因子,扩大家庭规模、提高富裕水平将加剧对环境的影响,而提高农户的受教育程度及非农化水平将减缓对环境的影响,但它们引起的环境影响变化速度均低于其自身的变化速度;(4)民族属性对农户的环境影响具有显著作用,张掖市、甘南藏族自治州、临夏回族自治州的现有样本数据支持环境Kuznets曲线假说.  相似文献   

16.
This laboratory has developed a subfracture, joint trauma model in rabbits. Using a dropped impact mass directed onto a slightly abducted joint, chronic softening of retropatellar cartilage and thickening of underlying subchondral bone are documented in studies to 1 year post-insult. It has been hypothesized that these tissue changes are initiated by stresses developed during impact loading. A previous analytical study by this laboratory suggests that tensile strains in retropatellar cartilage can be significantly lowered, without significantly changing the intensity of stresses in the underlying subchondral bone, by reorientation of patellar impact more centrally on the joint. In the current study comparative experiments were performed on groups of animals after either an impact directed on the slightly abducted limb or a more central impact. One-year post-trauma in animals subjected to the central-oriented impact no degradation of the shear modulus for the retropatellar cartilage was documented, but the thickness of the underlying subchondral bone was significantly increased. In contrast, alterations in cartilage and underlying bone following impact on the slightly abducted limb were consistent with previous studies. The current experimental investigation showed the sensitivity of post-trauma alterations in joint tissues to slight changes in the orientation of impact load on the joint. Interestingly, for this trauma model thickening of the underlying subchondral plate occurred without mechanical degradation of the overlying articular cartilage. This supports the current laboratory hypothesis that alterations in the subchondral bone and overlying cartilage occur independently in this animal model.  相似文献   

17.
AIM: To study the effect of a single impact on the structure and mechanical properties of cartilage. MATERIALS AND METHOD: Osteochondral plugs harvested from bovine femora were subjected each to a single impact using an in-house designed drop-tower. Impact masses of different values were released from different drop heights in selected combinations to apply stresses at strain rates and impact energies within specific ranges. Changes in the storage and loss moduli were estimated from cyclic compressive loading test undertaken before and after impact. The conditions of these tests were set to those occurring during walking and running. The extent of the damage on cartilage surface and depth was assessed using optical and confocal microscopy. RESULTS: The storage modulus varied slightly at level walking and running after performing impact tests up to the impact energy of 0.736 J. However, the decrease in the storage modulus was considerable at the impact energy of 1.962 J for test conditions representing both walking and running. This impact energy resulted in strain rate of 1500 s(-1), stress of 25 MPa and energy absorbed per unit volume of 12.79 mJ/mm(3). After impact the loss modulus increased over the loading cycles at all energies. Severe fissures were observed across the cartilage surface and through its thickness at levels of impact energy equal or greater than 1.472 J. CONCLUSIONS: This study identified thresholds for the strain rate, impact stress and impact energy, which caused permanent changes in the mechanical properties and damage to structure of cartilage.  相似文献   

18.
There is insufficient information regarding the factors affecting the environmental impacts of alien species. In particular, little is known about whether there is any relationship between the invasiveness (establishment and spread) of an introduced species and its per capita impact. We experimentally assessed the relationship between the extent of spread of up to 29 alien plant species and their impact on recruitment of native tree species in Amani Botanical Garden, Tanzania. We also studied the effects of allelochemicals of selected alien on native plant species to assess potential mechanisms of impact. We found no relationship between the extent of spread of an alien tree species and their impact on seed germination, seedling survival, and seedling communities of native trees in their understory, and no indication that allelochemicals consistently explain their effects on recruitment of the studied species. These results suggest that extent of spread cannot be used as a proxy for impact. Hence, managers should continue assessing both the spread and the impact of alien species when prioritizing alien species for management.  相似文献   

19.
This paper is a preliminary report on the development of a new instrument, the Impact of Weight on Quality of Life (IWQOL) questionnaire, that assesses the effects of weight on various areas of life. We conducted two studies utilizing subjects in treatment for obesity at Duke University Diet and Fitness Center. The first study describes item development, assesses reliability, and compares pre- and post-treatment scores on the IWQOL. In the second study we examined the effects of body mass index (BMI), gender, and age on subjects' perceptions of impact of weight on quality of life. Results indicate adequate psychometric properties with test-retest reliabilities averaging .75 for single items, and .89 for scales. Scale internal consistency averaged .87. Post-treatment scores differed significantly from pre-treatment scores on all scales, indicating that treatment produced positive changes in impact of weight on quality of life. The results of the second study indicate that the impact of weight generally worsened as the patients' size increased. However for women there was no association between BMI and impact of weight on Self-Esteem and Sexual Life. Even at the lowest BMI tertile studied, women reported that weight had a substantial impact in these areas. There were also significant gender differences, with women showing greater impact of weight on Self-Esteem and Sexual Life compared with men. The impact of age was a bit surprising, with some areas showing positive changes and others showing no change.  相似文献   

20.
Summary The effect of homogeniser impact distance on the disruption efficiency of stationary and growth-phase Escherichia coli is examined. Disruption efficiency decreases as impact distance increases as seen previously for yeasts. However, the dependence on impact distance is considerably less than previously reported for yeast. Results suggest that homogeniser performance can be improved by decreasing impact distance. This effect is modelled.  相似文献   

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