共查询到20条相似文献,搜索用时 31 毫秒
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Background: Various rare and endangered temperate ferns are being threatened by their recent population decline, but there is limited understanding of the causes behind it.Aims: This study attempted to identify the possible drivers of regional population decline and extinction in the globally distributed woodland fern Polystichum braunii.Methods: A comparison was undertaken of the climatic, edaphic and phytosociological characteristics of sites with increasing, decreasing or recently extinct populations in Germany.Results: A significantly higher frequency of episodes of low relative air humidity (<60%) was found at sites with decreasing or extinct populations compared to habitats with population increases. Sites with decreasing or extinct populations were also characterised as having less summer precipitation (<500 mm year?1) and a shorter duration of snow cover (<110 days year?1) than sites with increasing populations. The latter had significantly higher moss cover (56% of the forest floor), but less cover by a tree litter layer (23%) compared to decreasing (36% and 38%) or recently extinct populations (22% and 52%). All increasing populations were located in intact Tilia – Acer ravine forests, while those suffering population decline were mostly located in Fagus-dominated forests.Conclusions: It was concluded that the probable causes of the recent decline in German P. braunii populations are reduced air humidity levels, decreasing snow duration or a shift from moss-covered to tree litter-covered forest floors due to climate warming or altered forest management. 相似文献
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Longgen Xu Peng Han Yong Liu Hongwei Wang Yirong Yang Feng Qiu Wanling Peng Ligong Tang Jing Fu Xiaofeng Zhu Youhua Zhu 《Cell biochemistry and biophysics》2014,68(1):173-179
Even though the incidence of pregnancies in the female recipients is lower and also chronic renal disease in male patients is associated with impaired spermatogenesis, the health of the children born to these patients was not studied. In this report, we discuss information on the growth and development of offspring of 248 male and female kidney recipient patients. Physical and routine clinical measurements of the 252 offspring (129 male and 123 female) born to these transplantation patients were made along with the intelligence tests. In some of these children chest X-ray and immune indices were assessed. Among the recipients, 219 males fathered 223 children with an average birth weight of 3,255 ± 374 g and 29 female recipients gave birth to 29 children with an average birth weight of 2,923 ± 551. While most of these children were normal, we noticed a case of soft double toe, a case of short tongue tie, five cases of marginal mental retardation, three cases of proteinuria, six cases of microscopic hematuria, 15 cases of low hemoglobin, and 21 cases with recurrent respiratory tract infections. We conclude that kidney transplantation has no significant impact on the growth, development, health, and intelligence of the offspring born to recipients. 相似文献
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Tsutomu Ishikawa Tetsuya Tosa Ichiro Chibata 《Bioscience, biotechnology, and biochemistry》2013,77(9):581-585
In order to study the enzymatic properties of the ?-lysine acylase in Achromobacter pestifer EA, experiments were carried out with the pure enzyme preparation. As a result of the investigation, it was found that this enzyme readily hydrolyzes ?-N-acyllysine and shows no α-amino acylase activity, and that the enzyme is not specifically activated by metal ions unlike the other acylases. 相似文献
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Tsutomu Ishikawa Tetsuya Tosa Ichiro Chibata 《Bioscience, biotechnology, and biochemistry》2013,77(7):412-416
?-Lysine acylase of Achromobacter pestifer EA was purified by fractionations with ammonium sulfate and acetone, and by vertical zone electrophoresis. As a result, this bacterial ?-lysine acylase was obtained as an electrophoretically homogeneous protein, specific activity of which is the highest among ?-lysine acylases ever reported. 相似文献
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Tsutomu Ishikawa Tetsuya Tosa Ichiro Chibata 《Bioscience, biotechnology, and biochemistry》2013,77(3):193-198
Since Achromobacter pestifer EA isolated from soils shows markedly high ?-Iysine acylase activity compared with those of the other microorganisms ever tested, cultural conditions for the production of this enzyme were investigated.As a result, it was confirmed that simple medium containing 1% peptone, 5% glucose and some inorganic salts is most suitable for the enzyme production and that much more ?-Iysine acylase is produced by shaken culture or submerged culture in jar fermentor than by stationary culture. α-Amino acylase activity in this organism was also studied. 相似文献
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The 18S rRNA nucleotides close to the template nucleotide adjacent to the 80S ribosomal A-site codon on the 3′-end (i.e., the nucleotide in position +7 relative to the first nucleotide of the P-site codon) were identified using the affinity crosslinking approach. For this purpose, the photoreactive mRNA analogues with a perfluorophenylazide group attached through various linkers to the uridine C5, 3′-terminal phosphate or guanosine N7 were used. The position of the mRNA analogues on the ribosome was preset using tRNAPhe, which recognized the phenylalanine codon directed to the P-site. An analysis of the rRNAs isolated from the irradiated complexes of 80S ribosomes showed that all the analogues are almost equally crosslinked to the 18S rRNA nucleotides we attributed to the A-site codon environment: namely, to nucleotides A1823, A1824, and A1825 of the 3′-minidomain and to the 620–630 fragment of the 18S rRNA 5′-domain. In addition, we identified a new component of the mRNA binding site of human ribosomes, nucleotide C1698, belonging to the 18S rRNA 3′-minidomain, using analogues bearing a perfluorophenylazide group on uridine and guanine residues.__________Translated from Bioorganicheskaya Khimiya, Vol. 31, No. 3, 2005, pp. 295–302.Original Russian Text Copyright © 2005 by Demeshkina, Styazhkina, Bulygin, Repkova, Ven’yaminova, Karpova. 相似文献
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Brains of 1664 subjects (895 males and 769 females) aged from 20 to 89 years have been studied. The whole material being investigated was divided, within sex groups, into body-height classes and age classes. The class interval within the age classes was 10 years, that in height classes 5 cm. Mean arithmetics, standard deviations, standard error as well as coefficients of variation and correlation for respective classes have been calculated. It has been ascertained that the brain weight depends on the body height. In tall subjects no brains of extremely low absolute weight are encountered and, adversely, high brain weight is seldom met in short individuals. The body height also exerts certain influence upon the relative weight of the brain. More favourable proportion between the brain weight and the body length has been revealed in short subjects. Tall individuals are characterized by a low relative weight of the brain. It should be supposed that the spinal cord weight is higher in the latter subjects. The differences between the mean absolute weight of women's brains and that in men of the same age class are conditioned by the difference in the body length. A constant magnitude of difference in the mean brain weight in subjects of the same body height claims 100 g. The paper provides 2 enclosed tables representing obtained results for arithmetic mean of the absolute brain weight both in the age classes and body height classes. The differences between the mean weights of brains in women as well as in men are not significant. The coefficient of correlation between the brain weight and the body height is for men r male1 = 0.2008 for women r female1 = 0.2630, wherease the coefficient of regression for the brain weight is r male2 = 3.67 and r female2 = 3.906 respectively. 相似文献
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Estela Sánchez De Jiménez J. Torres Victoria E. Valles J. Solís G. Soberón 《The Biochemical journal》1965,97(3):887-891
1. Starvation for 3 days produces a decrease in methaemoglobin-reductase and glutathione-reductase activities, but it does not alter the glucose 6-phosphate-dehydrogenase activity of the rat erythrocyte. 2. The feeding of a protein-free diet for 11 days causes greater changes in the first two enzymes and also a diminution of the third. Under this experimental condition slight decreases in protein and haemoglobin contents were noted. 3. The experimental animals did not show methaemoglobinaemia, probably because the activity of methaemoglobin diaphorase is preserved. 4. The GSH content was not affected but the stability of the tripeptide in the presence of an oxidizing agent was diminished. 相似文献
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Renee J. Brooks Paul J. Schulte Barbara J. Bond Robert Coulombe Jean-Christophe Domec Thomas M. Hinckley Nate McDowell Nathan Phillips 《Trees - Structure and Function》2003,17(2):101-108
Do branchlets within a branch have autonomous water supplies, or do they share a common water supply system? We hypothesized that if branchlets shared a common water supply, then stomatal conductance (gs) on sunlit foliage would increase with reduced transpiration of competing foliage on the branch. We reduced transpiration of other foliage on the branch through bagging and shading, and we monitored the gas-exchange responses of the remaining sunlit foliage on the branch relative to control branches for several age classes of Douglas-fir trees (aged ~10 years, 20 years, and 450 years old). Contrary to our hypothesis, we found no increases in gs in either young or old trees following transient reductions in the amount of transpiring leaf area. The diurnal change in water potential, mid-day stomatal closure and associated photosynthetic decline occurred at the same time and were of the same magnitude on both treated and untreated branches, with the exception of photosynthesis in one 450-year-old tree. Hydraulic conductance measurements of branch junctions indicate that xylem within branches is only partially interconnected which would reduce the effectiveness of shading as a means of increasing water supply to the remaining sunlit foliage. The lack of a response implies that when a branch is in partial shade, the remaining sunlit foliage has no advantage with respect to water status over foliage on a branch completely in the sun. 相似文献
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This paper explores the relationship between the economic turmoil generated by the Great Recession and the increase of secessionism. Some authors have stressed that the Great Recession triggered changes in territorial preferences and, in the context of a conflict between the centre and the periphery, fuelled secessionism as a radical shift of the institutional setup. Nevertheless, other researchers have remarked that a recession may enhance the status quo bias and decrease the likelihood of changes. Our paper aims at contributing to this debate by analysing the case of Catalonia. We use an aggregate and an individual-level empirical design to explore the relationship between the deterioration of the economic situation and the increase of preferences for secession among the Catalan population. The findings from the analysis of our empirical models do not support the hypothesis that the effects of the Great Recession had any significant impact on political preferences in Catalonia. 相似文献
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N. Rashevsky 《Bulletin of mathematical biology》1972,34(1):65-69
By generalizing a previous paper on periodicities in the endocrine system (Bull. Math. Biophysics,30, 735–749, 1968), it is shown that nonperiodic, sporadic oscillations in the system are also possible. A procedure of describing
the feedback mechanism between the endocrine system and the central nervous system is suggested. It is shown that the combined
system: endocrine—CNS, also may show sporadic fluctuations. 相似文献