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1.
M. H. Losvik 《Plant Ecology》1988,78(3):157-187
Well-drained mown hay meadows in Hordaland, western Norway, were investigated. The hay meadows are either managed in a traditional or in a semi-traditional way. Traditional management in the area involves little or no use of manure or fertilizer, mowing once or twice a year with a first cut later than June 23, clearing in spring and intensive grazing for short periods in spring and autumn. Semi-traditional management involves use of small to medium quantities of commercial fertilizer, often in addition to manure. Grazing may be irregular, light or lacking.Eight units of hay meadow vegetation are described, all assigned to the class Molinio-Arrhenatheretea, order Arrhenatheretalia; four units to the Atlantic alliance Cardaminion pratensis, association Cardamino pratensis-Conopodietum majoris (with three subassociations); one unit to the alliance Arrhenatherion elatioris, three units are provisionally grouped as Galium uliginosum-Knautia arvensis meadows.Continuous management of these meadows has resulted in characteristic species compositions, which vary along a west-east climatic gradient, and are related to the amount of commercial fertilizer used and the natural mineral-content of the soil.These hay meadows seem to be best maintained by continuing the traditional management regime. Grazing in spring and in autumn reduces fast growing dominants and creates openings for new seedlings of annuals and biennials. A late first cut allows for ripening of the seeds and creates openings for light for the species of the lower field layer. A list of species characteristic of traditionally managed permanent hay meadows is presented, and possible effects of present changes in management on the species composition of the meadows are discussed.The amount of organic matter in the topsoil is small in most stands. The pH values are between 4.0 and 5.6. The highest values were recorded in soil where little or no commercial fertilizer is used, and where the subsoil is naturally rich in minerals. A tendency to Mg impoverishment in the best fertilized stands is demonstrated. Species-rich stands on Ca-rich soils are poor in P.The expected changes in vegetation, future use, and conservation of permanent hay meadows in Hordaland are discussed.  相似文献   
2.
Summary This paper describes the analysis of the elimination of potato DNA from potato-tomato somatic cell hybrids. The hybrids were obtained by fusion of protoplasts of a cytoplasmic albino tomato genotype with leaf mesophyll protoplasts of a potato genotype carrying the -glucuronidase (GUS) gene of Escherichia coli. The potato protoplasts were either isolated from unirradiated plants or from plants irradiated with 50 or 500 Gy of -rays. Green calli were selected as putative fusion products. The hybridity of these calli was confirmed by isoenzyme analysis. All of the green calli tested contained a potato-specific chloroplast DNA restriction fragment, and most of the calli analysed were positive for -glucuronidase activity. In 72 of the hybrid calli we determined the percentage of potato nuclear DNA using species-specific probes. All of the tested green calli contained a considerable amount of potato genomic DNA, irrespective of the dose of irradiation of the potato parent. The limited degree of potato DNA elimination and the absence of true cybrids are discussed.  相似文献   
3.
Previous results from this laboratory have shown that very low chronic doses of gamma radiation can stimulate proliferation of the Cyanobacterium Synechococcus lividus. This modification of cell proliferation occurred during the first doubling. In this paper, we have compared the metabolism of cells cultivated in a normal environment or under chronic irradiation. Incubation of the cells in a new medium induced a high superoxide dismutase (EC 1.15.1.1, SOD) activity at the 18th hour and a degradation of phycocyanin, thus demonstrating that cells were submitted to a photooxidative stress. This increase in superoxide dismutase activity was followed by concomittant peaks of glutathione reductase (EC 1.6.4.2, GR) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49, G6P-DH) at the 24th hour. Irradiated cultures at a dose of 53.5 mGray/year show an earlier and higher peak of SOD, GR, and G6P-DH. In a second stage, cultures showed an earlier onset of photosynthesis under irradiation, as evidenced by an increase in pigment content and an enhancement of glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13, GAP-DH). These results show that the radiostimulation is related to the activation of enzymes protecting against peroxides that were induced under oxidative circumstances and to the activation of a glucose catabolism via the oxidative pentose phosphate pathway.Abbreviations mGy milli-Gray - SOD superoxide dismutase - G6P-DH glucose-6-phosphate dehydrogenase - GAP-DH glycer-aldehyde-3-phosphate dehydrogenase - GSSG oxidized glutathione  相似文献   
4.
Abstract Several studies have demonstrated that Bordetella pertussis has the ability to enter and survive intracellularly within human polymorphonuclear leukocytes (PMNL) and human monocytes/macrophages. The effects of human recombinant gamma interferon (IFN-γ) on the survival of B. pertussis in PMNL and human monocytes, and on the oxidative burst activity of PMNL and human monocytes in response to B. pertussis were assessed in this study. IFN-γ partially increased intracellular killing of phagocytosed B. pertussis in human monocytes, as determined by an orange acridine-crystal violet assay. In contrast, IFN-γ did not enhance intracellular killing of B. pertussis in PMNL. No significant increase of superoxide production was noted in human monocytes in response to B. pertussis when stimulated with various concentrations of IFN-γ. The partial increase of B. pertussis killing by IFN-γ within monocytes, together with poor production of superoxide may explain how B. pertussis can survive within human phagocytic cells, and thus cause a more prolonged course of the disease.  相似文献   
5.
Summary Asymmetric somatic hybrids were obtained by fusion of Solanum tuberosum (PDH40) protoplasts with 300- or 500-Gy irradiated protoplasts of S. brevidens. These radiation doses were sufficient to prevent the growth of the S. brevidens protoplasts. Putative hybrids were selected on the basis of phenotype from regenerated shoots and identified with a S. brevidens-specific probe. From these, 31 asymmetric hybrids were confirmed by morphological characteristics, isoenzyme patterns and RFLP analysis. The morphology of the asymmetric hybrids was intermediate between that of S. tuberosum and symmetric hybrids of both species (obtained without irradiation treatment). Chromosome counts from 17 asymmetric hybrids showed that the chromosome number of the hybrids ranged from 31 to 64. The asymmetric hybrids probably had one or two genome complements (i.e. either 24 or 48 chromosomes) from S. tuberosum and 7–22 chromosomes from S. brevidens. There was no clear correlation between the radiation dose and the degree of elimination of the S. brevidens genome.  相似文献   
6.
摘要 目的:观察中医正骨手法在桡骨远端伸直型骨折中的临床应用价值,并分析疗效的影响因素。方法:选择四川省骨科医院2020年1月~2022年1月期间收治的桡骨远端伸直型骨折患者152例,按照治疗方式的不同将患者分为对照组(给予石膏固定)和研究组(应用中医正骨手法治疗),例数分别为77例和75例。对比两组优良率、临床指标、腕关节活动度和X线相关影像学指标。同时采用多因素Logistic回归分析影响研究组腕关节功能疗效的相关因素。结果:治疗后,研究组的优良率明显高于对照组(P<0.05)。研究组手背消肿时间、疼痛缓解时间、骨折愈合时间均短于对照组(P<0.05)。两组治疗后12周掌屈、背伸、桡偏、尺偏、旋前、旋后活动度均扩大,且研究组均大于对照组(P<0.05)。两组治疗后12周掌倾角、尺偏角、桡骨高度均增加,且研究组均大于对照组(P<0.05)。单因素分析显示,研究组腕关节功能优良率与年龄、性别、骨质疏松、功能锻炼、掌倾角、尺偏角、桡骨高度、骨折端稳定性、受伤能量、利手情况有关(P<0.05),而与体质量指数、就诊时间、基础疾病、骨折类型、固定时间无关(P>0.05)。多因素Logistic回归分析显示:性别为女、骨质疏松、无功能锻炼、掌倾角偏小、桡骨高度偏短、骨折端不稳定、受伤能量为高能量、利手是影响腕关节功能优良率的危险因素(P<0.05)。结论:中医正骨手法可有效改善桡骨远端伸直型骨折患者腕关节功能,减少骨折愈合及疼痛缓解时间。此外,患者腕关节功能的优良率还受到性别、骨质疏松、功能锻炼、掌倾角、桡骨高度、骨折端稳定性、受伤能量、利手情况的影响,值得引起临床重视。  相似文献   
7.
Several maximum likelihood and distance matrix methods for estimating phylogenetic trees from homologous DNA sequences were compared when substitution rates at sites were assumed to follow a gamma distribution. Computer simulations were performed to estimate the probabilities that various tree estimation methods recover the true tree topology. The case of four species was considered, and a few combinations of parameters were examined. Attention was applied to discriminating among different sources of error in tree reconstruction, i.e., the inconsistency of the tree estimation method, the sampling error in the estimated tree due to limited sequence length, and the sampling error in the estimated probability due to the number of simulations being limited. Compared to the least squares method based on pairwise distance estimates, the joint likelihood analysis is found to be more robust when rate variation over sites is present but ignored and an assumption is thus violated. With limited data, the likelihood method has a much higher probability of recovering the true tree and is therefore more efficient than the least squares method. The concept of statistical consistency of a tree estimation method and its implications were explored, and it is suggested that, while the efficiency (or sampling error) of a tree estimation method is a very important property, statistical consistency of the method over a wide range of, if not all, parameter values is prerequisite.  相似文献   
8.
A. Danin 《Plant Ecology》1978,36(2):83-93
Summary Lists of vascular plant species for each of the 12 ecological districts of Sinai were prepared. In all 78,000 observations on altogether 812 species were analyzed. The number of districts where each species occurred was also counted. Linear regressions were calculated for the log-transformed values of species/area, species/altitude and multiple regression of species on both area and altitude.The regression of species on area for the 12 ecological districts of Sinai gave the equation: log S = 1.0309+0.3 log A The value of z=0.3 is higher than 0.222—the measured overall value for the continents and higher than the values for the Sahara, California mainland, the British Isles, and the Netherlands. However, it is lower than the values for the Galápagos Archipelago and the California Islands.The number of species supported in districts characterized by fissured limestone, gravel plains, chalk, marl, sandstones, sands or fissured magmatic and metamorphic rocks is close to the regression of species on area, whereas large outcrops of smooth-faced rocks are relatively richer in total number of species as well as in stenotople species.It is suggested that the high gamma diversity of Sinai as compared with other parts of the world is primarily due to its environmental heterogeneity. Sinai being a meeting place of three phytogeographical regions and to past climatic changes. The effect of smooth-faced rock outcrops as conducive to providing refugia must also be taken into account.This work is based on a comprehensive study of the vegetation of Sinai directed by Prof. G. Orshan, with the collaboration of Dr. A. Shmida, the present author and the late Prof. N.H. Tadmor and Dr. G. Halevy.  相似文献   
9.
Summary Asymmetric somatic hybrids were recovered following fusion of tomato leaf mesophyll protoplasts with irradiated protoplasts isolated from Lycopersicon pennellii suspension cells. The asymmetry was determined by scoring the regenerants at between 20 and 24 loci using isozymes and restriction fragment length polymorphisms. In addition, three quantitative traits, fruit size, leaf shape, and stigma exsertion, were measured in the regenerants. The recovery of asymmetric somatic hybrids was as high as 50% of the regenerants, and there was no requirement for the transfer of a selectable marker gene from the irradiated partner. The amount of nuclear DNA transferred from the irradiated protoplast fusion partner was found to be inversely proportional to the radiation dose. It was possible to recover tomato asymmetric somatic hybrids which were self-fertile and contained limited amounts of genetic information from L. pennelli.  相似文献   
10.
The design and synthesis of a novel series of potent gamma secretase modulators is described. Exploration of various spacer groups between the triazole ring and the aromatic appendix in 2 has led to anilinotriazole 28, which combined high in vitro and in vivo potency with an acceptable drug-like profile.  相似文献   
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