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排序方式: 共有215条查询结果,搜索用时 15 毫秒
51.
Chunyang Li Anneli Viherä-Aarnio Tuula Puhakainen Olavi Junttila Pekka Heino E. Tapio Palva 《Trees - Structure and Function》2003,17(2):127-132
Woody plants in the temperate and boreal zone undergo annual cycle of growth and dormancy under seasonal changes. Growth cessation and dormancy induction in autumn are prerequisites for the development of substantial cold hardiness in winter. During evolution, woody plants have developed different ecotypes that are closely adapted to the local climatic conditions. In this study, we employed distinct photoperiodic ecotypes of silver birch (Betula pendula Roth) to elucidate differences in these adaptive responses under seasonal changes. In all ecotypes, short day photoperiod (SD) initiated growth cessation and dormancy development, and induced cold acclimation. Subsequent low temperature (LT) exposure significantly enhanced freezing tolerance but removed bud dormancy. Our results suggested that dormancy and freezing tolerance might partially overlap under SD, but these two processes were regulated by different mechanisms and pathways under LT. Endogenous abscisic acid (ABA) levels were also altered under seasonal changes; the ABA level was low during the growing season, then increased in autumn, and decreased in winter. Compared with the southern ecotype, the northern ecotype was more responsive to seasonal changes, resulting in earlier growth cessation, cold acclimation and dormancy development in autumn, higher freezing tolerance and faster dormancy release in winter, and earlier bud flush and growth initiation in spring. In addition, although there was no significant ecotypic difference in ABA level during growing season, the rates and degrees of ABA alterations were different between the ecotypes in autumn and winter, and could be related to ecotypic differences in dormancy and freezing tolerance. 相似文献
52.
Nucleotide Sequence, Genomic Organization, and Chromosomal Localization of Genes Encoding the Human NMDA Receptor Subunits NR3A and NR3B 总被引:3,自引:0,他引:3
The N-methyl-D-aspartate (NMDA) receptors are glutamate-regulated ion channels that are critically involved in important physiological and pathological functions of the mammalian central nervous system. We have identified and characterized the gene encoding the human NMDA receptor subunit NR3A (GRIN3A), as well as the gene (GRIN3B) encoding an entirely novel subunit that we named NR3B, as it is most closely related to NR3A (57.4% identity). GRIN3A localizes to chromosome 9q34, in the region 13-34, and consists of nine coding exons. The deduced protein contains 1115 amino acids and shows 92.7% identity to rat NR3A. GRIN3B localizes to chromosome 19p13.3 and contains, as does the mouse NR3B gene (Grin3b), eight coding exons. The deduced proteins of human and mouse NR3B contain 901 and 900 amino acid residues, respectively (81.6% identity). In situ hybridization shows a widespread distribution of Grin3b mRNA in the brain of the adult rat. 相似文献
53.
Myc regulates keratinocyte adhesion and differentiation via complex formation with Miz1 总被引:3,自引:0,他引:3 下载免费PDF全文
Gebhardt A Frye M Herold S Benitah SA Braun K Samans B Watt FM Elsässer HP Eilers M 《The Journal of cell biology》2006,172(1):139-149
Myc plays a key role in homeostasis of the skin. We show that Miz1, which mediates Myc repression of gene expression, is expressed in the epidermal basal layer. A large percentage of genes regulated by the Myc-Miz1 complex in keratinocytes encode proteins involved in cell adhesion, and some, including the alpha6 and beta1 integrins, are directly bound by Myc and Miz1 in vivo. Using a Myc mutant deficient in Miz1 binding (MycV394D), we show that Miz1 is required for the effects of Myc on keratinocyte responsiveness to TGF-beta. Myc, but not MycV394D, decreases keratinocyte adhesion and spreading. In reconstituted epidermis, Myc induces differentiation and loss of cell polarization in a Miz1-dependent manner. In vivo, overexpression of beta1 integrins restores basal layer polarity and prevents Myc-induced premature differentiation. Our data show that regulation of cell adhesion is a major function of the Myc-Miz1 complex and suggest that it may contribute to Myc-induced exit from the epidermal stem cell compartment. 相似文献
54.
Understanding the interplay between climatic and anthropogenic factors is a major challenge in palaeo-ecology. In particular,
it is often difficult to distinguish anthropogenic and “natural” fire in the charcoal record. In this paper, analysis of fossil
pollen, charcoal, diatoms and isotopic evidence from Mapimbi, a small lake in the Kruger National Park, South Africa, suggests
that for most of the past ca. 700 years, the riverine gallery forests surrounding Mapimbi were primarily influenced by climate,
and benefited during warmer, wetter periods. The transitions between four, statistically different phases in the time-series
data coincide with regional climate records previously constructed from speleothem data, and are consistent with the transition
from the medieval warm period ending in the 14th century a.d. to the cooler, drier conditions prevailing during the little ice age of ca. a.d. 1400–1800. The data also suggest a period of significant, anthropogenic influence after a.d. 1800, when maize was grown and the incidence of localised fires increased. An increase in woody cover in recent decades may
be associated with the management of the area by Kruger National Park. A decline in cultivation occurred in the end of the
20th century linked with changes in socio-political organisation. 相似文献
55.
Jaana Vuosku Suvi Sutela Eila Tillman-Sutela Anneli Kauppi Anne Jokela Tytti Sarjala Hely H?ggman 《Plant signaling & behavior》2009,4(10):928-932
In plants, programmed cell death (PCD) is an important mechanism that controls normal growth and development as well as many defence responses. At present, research on PCD in different plant species is actively carried out due to the possibilities offered by modern methods in molecular biology and the increasing amount of genome data. The pine seed provides a favourable model for PCD because it represents an interesting inheritance of seed tissues as well as an anatomically well-described embryogenesis during which several tissues die via morphologically different PCD processes.Key words: conifer, developmental cell death, embryogenesis, megagametophyte, necrotic cell death, pine, seed development 相似文献
56.
Leili Saarse Eve Niinemets Anneli Poska Siim Veski 《Vegetation History and Archaeobotany》2010,19(1):17-28
Data from 59 sequences studied through pollen analysis were used to examine the decline in Alnus in Estonia during the Iron Age. Between a.d. 300 and 1300, the Alnus pollen frequency declined markedly in 30 records distributed evenly across the investigated area. The beginning of the decline
was time transgressive, coincidental with the start of extensive cultivation, and was frequently connected with the commencement
of rye cultivation and the availability of land suitable for cultivation. The greatest reduction in Alnus abundance occurred during the Late Iron Age between a.d. 900 and 1000. This spatially random asynchrony suggests that one or more factors affected Alnus populations across the whole northern region. Human impact is discussed as a plausible cause of the decline. To determine
the initiation of extensive crop farming in the eastern Baltic area, pollen diagrams from Latvia, Lithuania and the Novgorod
region were also examined. 相似文献
57.
58.
Anneli Hoikkala Jouni Aspi 《Evolution; international journal of organic evolution》1993,47(3):768-777
We examined sexual selection by Drosophila littoralis, D. montana, and D. ezoana females on male courtship sounds to determine whether the females use absolute or relative criteria when choosing their mates. Behavior of the females was observed, when they were courted by a single male producing normal sounds, or by a single wing-manipulated male producing abnormal sounds; and when they were courted by one or both of these males in a choice situation. The females usually accepted short-winged (but not wingless) males producing abnormal sounds, if they had no alternatives. However, if they heard the sound produced by a normal male, they rejected the deficient male. Drosophila littoralis and D. ezoana females selected between two wing-manipulated males with different wing areas. Our results suggest that the females choose their mates on the basis of relative criteria if the signals emitted by the courting males are within the range of acceptable cues. 相似文献
59.
Jaanika Ilisson Maksim Zagura Kersti Zilmer Erik Salum Kaire Heilman Anneli Piir Vallo Tillmann Jaak Kals Mihkel Zilmer Chris Pruunsild 《Arthritis research & therapy》2015,17(1)
IntroductionJuvenile idiopathic arthritis (JIA) is a frequent childhood rheumatic disease characterized by chronic inflammation. The latter has been related to impairment of arterial functional-structural properties, atherogenesis and later cardiovascular events. The objective of this study was to examine intima-media thickness (IMT) and the parameters of arterial stiffness in children with JIA at diagnosis and their correlation with JIA subtype and markers of inflammation and atherosclerosis.MethodsThirty-nine newly diagnosed patients with JIA (26 girls; mean age, 13.2 ± 2.6 years) and 27 healthy controls (9 girls; mean age, 13.6 ± 3.4 years) were included in the study. Twelve patients had oligoarthritis, fifteen had extended oligoarthritis and twelve had rheumatoid factor–negative polyarthritis. IMT of the common carotid artery was determined by ultrasonography, carotid-femoral pulse wave velocity (cfPWV) and augmentation index adjusted to a heart rate of 75 beats/min (AIx@75) were determined by applanation tonometry. The serum levels of atherosclerosis-related biomarkers, such as asymmetric dimethylarginine (ADMA), myeloperoxidase (MPO) and adiponectin, were measured by enzyme-linked immunosorbent assay.ResultsMean IMT (0.46 ± 0.04 vs. 0.42 ± 0.04 mm; p = 0.0003) and MPO concentration (115.2 [95 % confidence interval {95 % CI}, 97.4–136.3] vs. 57.6 [95 % CI, 47.1–70.3] ng/ml; p < 0.0001) were higher in the patients with JIA than in the control subjects. The cfPWV, AIx@75 and serum ADMA and adiponectin levels did not significantly differ between the groups and JIA subtypes. Serum adiponectin level correlated negatively with AIx@75 in patients with JIA (r = −0.38; p < 0.05).ConclusionsPatients with JIA have increased mean IMT and elevated MPO levels at early stages of the disease. AIx@75 was inversely independently associated with adiponectin level in the patients, suggesting that lower adiponectin levels might influence arterial subclinical stiffening in patients with newly diagnosed JIA. 相似文献
60.
Lise Graversen Thorkild I. A. S?rensen Liselotte Petersen Ulla Sovio Marika Kaakinen Annelli Sandb?k Jaana Laitinen Anja Taanila Anneli Pouta Marjo-Riitta J?rvelin Carsten Obel 《PloS one》2014,9(4)