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991.
X. Yin E. Griesshaber A. Checa F. Nindiyasari-Behal I. Sánchez-Almazo A. Ziegler W.W. Schmahl 《Journal of structural biology》2021,213(2):107707
Shells of calcifying foraminifera play a major role in marine biogeochemical cycles; fossil shells form important archives for paleoenvironment reconstruction. Despite their importance in many Earth science disciplines, there is still little consensus on foraminiferal shell mineralization. Geochemical, biochemical, and physiological studies showed that foraminiferal shell formation might take place through various and diverse mineralization mechanisms.In this study, we contribute to benthic foraminiferal shell calcification through deciphering crystallite organization within the shells. We base our conclusions on results gained from electron backscattered diffraction (EBSD) measurements and describe microstructure/texture characteristics within the laminated shell walls of the benthic, symbiontic foraminifera: Ammonia tepida, Amphistegina lobifera, Amphistegina lessonii. We highlight crystallite assembly patterns obtained on differently oriented cuts and discuss crystallite sizes, morphologies, interlinkages, orientations, and co-orientation strengths.We show that: (i) crystals within benthic foraminiferal shells are mesocrystals, (ii) have dendritic-fractal morphologies and (iii) interdigitate strongly. Based on crystal size, we (iv) differentiate between the two layers that comprise the shells and demonstrate that (v) crystals in the septa have different assemblies relative to those in the shell walls. We highlight that (vi) at junctions of different shell elements the axis of crystal orientation jumps abruptly such that their assembly in EBSD maps has a bimodal distribution. We prove (vii) extensive twin-formation within foraminiferal calcite; we demonstrate (viii) the presence of two twin modes: 60°/[0 0 1] and 77°/~[6 –6 1] and visualize their distributions within the shells.In a broader perspective, we draw conclusions on processes that lead to the observed microstructure/texture patterns. 相似文献
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993.
The stability and shapes of domains with different bending rigidities in lipid membranes are investigated. These domains can
be formed from the inclusion of an impurity in a lipid membrane or from the phase separation within the membrane. We show
that, for weak line tensions, surface tensions and finite spontaneous curvatures, an equilibrium phase of protruding circular
domains or striped domains may be obtained. We also predict a possible phase transition between the investigated morphologies. 相似文献
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995.
Human infertility, defined as the inability to conceive after 1?year of unprotected intercourse, is a healthcare problem that has a worldwide impact. Genetic causes of human infertility are manifold. In addition to the chromosomal aneuploidies and rearrangements, single-gene defects can interfere with human fertility. This paper provides a review of the most common autosomal recessive and autosomal dominant single-gene disorders involved in human infertility. The genes reviewed are CFTR, SPATA16, AURKC, CATSPER1, GNRHR, MTHFR, SYCP3, SOX9, WT1 and NR5A1 genes. These genes may be expressed throughout the hypothalamic-pituitary–gonadal-outflow tract axis, and the phenotype of affected individuals varies considerably from varying degrees of spermatogenic dysfunction leading to various degrees of reduced sperm parameters, through hypogonadotropic hypogonadism reslting in pubertal deficiencies, until gonadal dysgenesis and XY and XX sex reversal. Furthermore, congenital bilateral absence of the vas deferens, as well as premature ovarian failure, have been reported to be associated with some single-gene defects. 相似文献
996.
Protein restriction without malnutrition is currently an effective nutritional intervention known to prevent diseases and promote health span from yeast to human. Recently, low protein diets are reported to be associated with lowered cancer incidence and mortality risk of cancers in human. In murine models, protein restriction inhibits tumor growth via mTOR signaling pathway. IGF-1, amino acid metabolic programing, FGF21, and autophagy may also serve as potential mechanisms of protein restriction mediated cancer prevention. Together, dietary intervention aimed at reducing protein intake can be beneficial and has the potential to be widely adopted and effective in preventing and treating cancers. 相似文献
997.
Human activities and climate variability drive fast‐paced change across the world's estuarine–coastal ecosystems 下载免费PDF全文
James E. Cloern Paulo C. Abreu Jacob Carstensen Laurent Chauvaud Ragnar Elmgren Jacques Grall Holly Greening John Olov Roger Johansson Mati Kahru Edward T. Sherwood Jie Xu Kedong Yin 《Global Change Biology》2016,22(2):513-529
Time series of environmental measurements are essential for detecting, measuring and understanding changes in the Earth system and its biological communities. Observational series have accumulated over the past 2–5 decades from measurements across the world's estuaries, bays, lagoons, inland seas and shelf waters influenced by runoff. We synthesize information contained in these time series to develop a global view of changes occurring in marine systems influenced by connectivity to land. Our review is organized around four themes: (i) human activities as drivers of change; (ii) variability of the climate system as a driver of change; (iii) successes, disappointments and challenges of managing change at the sea‐land interface; and (iv) discoveries made from observations over time. Multidecadal time series reveal that many of the world's estuarine–coastal ecosystems are in a continuing state of change, and the pace of change is faster than we could have imagined a decade ago. Some have been transformed into novel ecosystems with habitats, biogeochemistry and biological communities outside the natural range of variability. Change takes many forms including linear and nonlinear trends, abrupt state changes and oscillations. The challenge of managing change is daunting in the coastal zone where diverse human pressures are concentrated and intersect with different responses to climate variability over land and over ocean basins. The pace of change in estuarine–coastal ecosystems will likely accelerate as the human population and economies continue to grow and as global climate change accelerates. Wise stewardship of the resources upon which we depend is critically dependent upon a continuing flow of information from observations to measure, understand and anticipate future changes along the world's coastlines. 相似文献
998.
999.
1000.
利用RAPD标记和单株树大配子体构建马尾松的分子标记连锁图谱 总被引:39,自引:0,他引:39
利用300个随机的寡核苷酸引物和马尾松(Pinus massoniana Lamb.)种子的胚乳(大配子体)产生的随机扩增多态性DNA(RAPD)分子标记,进行马尾松标记连锁图谱的构建。经筛选共获得64个稳定的RAPD标记,利用多点连锁分析,其中的48个标记分属于13个不同的连锁群(连锁对),该图谱覆盖的基因组总长度约为692.5cM(centimorgan),标记间平均距离约为14.7cM,它为马尾松连锁图谱的构建提供了一个连锁框架。 相似文献