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281.
To investigate the evolution of the Rh blood-group system in anthropoid apes, New and Old World monkeys, and nonprimate animals, serologic typing of erythrocytes from these species with antibodies specific for the human Rh blood-group antigens was performed. In addition, genomic DNA from these animals was analyzed on Southern blots with a human Rh-specific cDNA.Consistent with earlier reports, serologic results showed that gorilla and chimpanzee erythrocytes had epitopes recognized by human Rh D and c antisera, and gibbon erythrocytes were recognized by the c antisera. Surprisingly, some Old and New World monkeys also expressed a Rh c epitope on their erythrocytes. No erythrocytes from the nonprimate animals reacted specifically with any of the human Rh antisera.Southern blot analysis with a human Rh-specific cDNA probe detected Rh-related sequences in anthropoid apes, all New and Old World monkeys, and in most nonprimate animals tested. Although some Rh-related restriction fragments were conserved across species lines in primates, the Rh locus was more polymorphic in chimpanzees and gorillas than in humans. In addition, restriction fragments segregating with the presence of the D antigen in humans were present in the primate species that expressed the D antigen. 相似文献
282.
283.
Summary The species composition of vesicular-arbuscular mycorrhizal (VAM) fungal communities changed during secondary succession of abandoned fields based on a field to forest chronosequence. Twenty-five VAM fungal species were identified. Seven species were clearly early successional and five species were clearly late successional. The total number of VAM fungal species did not increase with successional time, but diversity as measured by the Shannon-Wiener index tended to increase, primarily because the community became more even as a single species, Glomus aggregatum, became less dominant in the older sites. Diversity of the VAM fungal community was positively correlated with soil C and N. The density of VAM fungi, as measured by infectivity and total spore count, first increased with time since abandonment and then decreased in the late successional forest sites. Within 12 abandoned fields, VAM fungal density increased with increasing soil pH, H2O soluble soil C, and root biomass, but was inversely related to extractable soil P and percent cover of non-host plant species. The lower abundance of VAM fungi in the forest sites compared with the field sites agrees with the findings of other workers and corresponds with a shift in the dominant vegetation from herbaceous VAM hosts to woody ectomycorrhizal hosts. 相似文献
284.
Within a few years of field abandonment on the coastal dunes, a considerable number of species of trees and woody lianes of the climax evergreen forest enter the succession. At a relatively large-scale of analysis (a 100 m2 plot), there is no evidence of soil development during the early succession, with no accumulation of soil organic matter nor nutrients being detected. At this scale there is, therefore, little support for the facilitation model of succession. However, when smaller scales of analysis are employed (e.g. a plot equivalent to the canopy area of a sapling) a very different picture emerges; most recruitment of forest woody species occurs beneath saplings found in early succession. Nutrient concentrations were higher in soils under sapling canopies than in soils beyond sapling canopies. With increasing sapling size, an increasing number of seedlings of forest woody species were found and there is progressive soil amelioration. Thus, during the early succession, there is considerable small-scale patterning in soil development and recruitment. This pattern is largely established through bird dispersal, with the intensity of recruitment being dependent on the distance to seed sources. 相似文献
285.
Chr Westerkamp 《Plant biology (Stuttgart, Germany)》1990,103(4):366-371
Usually, bird-flowers are classified into New World flowers (used by hovering hummingbirds) and Old World species (adapted to perching birds). Since there are many observations which violate this classification the proposal is made to distinguish between blossoms adapted to hovering birds and those providing a well-defined perch. Characters and examples are given for both groups including the different ways a perch is provided by the plant and the distinct methods of hover-flight in birds. The diverse adaptive solutions for bird pollination within some taxa are exemplified. To understand bird-flowers the actual functioning of flowers must be in focus, and not the geographic distribution nor the systematic affiliation of their visitors. 相似文献
286.
Abstract. Two neighbouring even-aged 130-yr old Picea abies trees in a homogeneous stand can differ substantially with respect to their epiphytic vegetation. Sampled branches from the canopy of one tree harboured 781 specimens of the old forest lichen Usnea longissima of which only 50 could be seen from the ground, whereas no U. longissima were found on its nearest neighbour. Usnea longissima was most abundant on branch tips in lower parts of the canopy on branch segments having the highest biomass of other alectorioid species. Trees with and without U. longissima showed a different pattern in their mineral composition, suggesting that a tree-specific difference in nutritional status might contribute to explain the patchy distribution of this lichen within seemingly homogeneous stands. 相似文献
287.
摘要 目的:探讨高龄瘢痕子宫再妊娠孕产妇剖宫产术终止妊娠直接病因及预后影响因素分析。方法:回顾性分析2016年1月-2020年10月在我院收治的400例高龄瘢痕子宫再妊娠孕妇。按照是否终止妊娠将400例孕妇分为终止妊娠组(200例)和未终止妊娠组(200例)。并对200例终止妊娠孕妇进行2年随访,按照2年内再妊娠情况分为再妊娠成功组(150例)和再次终止妊娠组(50例)。采用Spearman检验进行相关性分析;采用logistics回归模型进行回归分析。结果:200例终止妊娠孕妇中瘢痕妊娠60(30.00 %)例,死胎13(6.50 %)例,胎儿畸形25(12.50 %)例,子痫前期81(40.50 %)例,胎膜早破11(5.50%)例,妊娠意外事件10(5.00 %)例。高龄瘢痕子宫孕妇终止妊娠后再妊娠与教育水平、是否有固定职业、家庭月收入无关(P>0.05);与年龄、孕次、产次、剖宫产手术史、终止妊娠病因有关(P<0.05);200例终止妊娠孕妇预后再妊娠与年龄、孕次、产次、剖宫产手术史、终止妊娠病因密切相关(P<0.05);多因素分析结果显示,年龄、孕次、产次、剖宫产手术史、终止妊娠病因是独立危险因素(P<0.05)。结论:高龄瘢痕子宫孕妇终止妊娠的主要病因为瘢痕妊娠,死胎,胎儿畸形例,子痫前期,胎膜早破,妊娠意外事件。年龄、孕次、产次、剖宫产手术史、终止妊娠病因是影响高龄瘢痕子宫孕妇预后再妊娠的独立危险因素。 相似文献
288.
摘要 目的:探讨综合康复方案联合心理干预对老年肌少-骨质疏松症(SOP)患者的影响,以期为SOP患者的康复提供合理方案。方法:前瞻性选取徐州医科大学附属医院2021年3至2021年8月收治的64例老年SOP患者为研究对象,按照随机数字表法将所有的患者分为观察组和对照组,每组32例。对照组予以常规干预,观察组在对照组的基础上予以综合康复方案联合心理干预。观察两组患者骨骼肌肉恢复情况、机体功能、骨密度以及心理状况。结果:干预6个月后两组患者外周骨骼肌质量(ASM)、外周骨骼肌指数(SMI)以及握力均较干预前以及干预3个月后上升,且观察组高于对照组(P<0.05)。干预6个月后两组患者平衡测试、4 m步速测试、5次椅上坐-站测试评分均较干预前以及干预3个月后上升,且观察组高于对照组(P<0.05)。干预6个月后两组患者骨密度较干预前以及干预3个月后上升,且观察组高于对照组(P<0.05)。干预3个月后以及干预6个月后两组患者心理痛苦与管理筛查工具量表(DMSM)、汉密尔顿焦虑量表(HAMA)、汉密尔顿抑郁量表(HAMD)评分均较干预前下降,且观察组低于对照组(P<0.05)。结论:综合康复方案联合心理干预可促进老年SOP患者骨骼肌肉恢复,提升机体功能,改善骨密度及心理状况,是老年SOP患者的理想康复方案,值得临床借鉴应用。 相似文献
289.
Gregory M. Crutsinger Melissa N. Habenicht Aimée T. Classen Jennifer A. Schweitzer Nathan J. Sanders 《Plant and Soil》2008,303(1-2):95-103
Plant–insect interactions can alter ecosystem processes, especially if the insects modify plant architecture, quality, or
the quantity of leaf litter inputs. In this study, we investigated the interactions between the rosette gall midge Rhopalomyia solidaginis and tall goldenrod, Solidago altissima, to quantify the degree to which the midge alters plant architecture and how the galls affect rates of litter decomposition
and nutrient release in an old-field ecosystem. R. solidaginis commonly leads to the formation of a distinct apical rosette gall on S. altissima and approximately 15% of the ramets in a S. altissima patch were galled (range: 3–34%). Aboveground biomass of galled ramets was 60% higher and the leaf area density was four
times greater on galled leaf tissue relative to the portions of the plant that were not affected by the gall. Overall decomposition
rate constants did not differ between galled and ungalled leaf litter. However, leaf-litter mass loss was lower in galled
litter relative to ungalled litter, which was likely driven by modest differences in initial litter chemistry; this effect
diminished after 12 weeks of decomposition in the field. The proportion of N remaining was always higher in galled litter
than in ungalled litter at each collection date indicating differential release of nitrogen in galled leaf litter. Several
studies have shown that plant–insect interactions on woody species can alter ecosystem processes by affecting the quality
or quantity of litter inputs. Our results illustrate how plant–insect interactions in an herbaceous species can affect ecosystem
processes by altering the quality and quantity of litter inputs. Given that S. altissima dominates fields and that R. solidaginis galls are highly abundant throughout eastern North America, these interactions are likely to be important for both the structure
and function of old-field ecosystems. 相似文献
290.