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排序方式: 共有103条查询结果,搜索用时 234 毫秒
91.
Mitochondrial DNA polymerase W748S mutation: a common cause of autosomal recessive ataxia with ancient European origin
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Hakonen AH Heiskanen S Juvonen V Lappalainen I Luoma PT Rantamaki M Goethem GV Lofgren A Hackman P Paetau A Kaakkola S Majamaa K Varilo T Udd B Kaariainen H Bindoff LA Suomalainen A 《American journal of human genetics》2005,77(3):430-41
Mutations in the catalytic subunit of the mitochondrial DNA polymerase gamma (POLG) have been found to be an important cause of neurological disease. Recently, we and collaborators reported a new neurodegenerative disorder with autosomal recessive ataxia in four patients homozygous for two amino acid changes in POLG: W748S in cis with E1143G. Here, we studied the frequency of this allele and found it to be among the most common genetic causes of inherited ataxia in Finland. We identified 27 patients with mitochondrial recessive ataxia syndrome (MIRAS) from 15 Finnish families, with a carrier frequency in the general population of 1 : 125. Since the mutation pair W748S+E1143G has also been described in European patients, we examined the haplotypes of 13 non-Finnish, European patients with the W748S mutation. Haplotype analysis revealed that all the chromosomes carrying these two changes, in patients from Finland, Norway, the United Kingdom, and Belgium, originate from a common ancient founder. In Finland and Norway, long, common, northern haplotypes, outside the core haplotype, could be identified. Despite having identical homozygous mutations, the Finnish patients with this adult- or juvenile-onset disease had surprisingly heterogeneous phenotypes, albeit with a characteristic set of features, including ataxia, peripheral neuropathy, dysarthria, mild cognitive impairment, involuntary movements, psychiatric symptoms, and epileptic seizures. The high carrier frequency in Finland, the high number of patients in Norway, and the ancient European founder chromosome indicate that this newly identified ataxia should be considered in the first-line differential diagnosis of progressive ataxia syndromes. 相似文献
92.
Short-term streamflow regulation (hydropeaking) affects the ecology of regulated rivers. We examined the longitudinal and temporal changes occurring in fish assemblages in a hydropeaking single river reservoir between two power plants by using electrofishing along the shoreline, hydroacoustics and test fishing in the open water. A longitudinally changing fish community was found among bottom-dwelling fish in the fast-flowing and highly disturbed upstream part of the reservoir progressing to generalists and pelagic fish in the lentic and most stable environment at the downstream end. The fish assemblage showed temporal patterns as fish density increased during night-time darkness and also towards autumn. Our work provides evidence for gradient effects of flow regulation and contributes to awareness of the effects of disturbance (flow/habitat variability) on biological systems. 相似文献
93.
Teppo Hiltunen Nelson G. Hairston Jr Giles Hooker Laura E. Jones Stephen P. Ellner 《Ecology letters》2014,17(8):915-923
Consumer–resource interactions are fundamental components of ecological communities. Classic features of consumer–resource models are that temporal dynamics are often cyclic, with a ¼‐period lag between resource and consumer population peaks. However, there are few published empirical examples of this pattern. Here, we show that many published examples of consumer–resource cycling show instead patterns indicating eco‐evolutionary dynamics. When prey evolve along a trade‐off between defence and competitive ability, two‐species consumer–resource cycles become longer and antiphase (half‐period lag, so consumer maxima coincide with minima of the resource species). Using stringent criteria, we identified 21 two‐species consumer–resource time series, published between 1934 and 1997, suitable to investigate for eco‐evolutionary dynamics. We developed a statistical method to probe for a transition from classic to eco‐evolutionary cycles, and find evidence for eco‐evolutionary type cycles in about half of the studies. We show that rapid prey evolution is the most likely explanation for the observed patterns. 相似文献
94.
Eero A. Haapala Anna-Maija Poikkeus Katriina Kukkonen-Harjula Tuomo Tompuri Niina Lintu Juuso V?ist? Paavo H. T. Lepp?nen David E. Laaksonen Virpi Lindi Timo A. Lakka 《PloS one》2014,9(9)
Background
There are no prospective studies that would have compared the relationships of different types of physical activity (PA) and sedentary behavior (SB) with academic skills among children. We therefore investigated the associations of different types of PA and SB with reading and arithmetic skills in a follow-up study among children.Methods
The participants were 186 children (107 boys, 79 girls, 6–8 yr) who were followed-up in Grades 1–3. PA and SB were assessed using a questionnaire in Grade 1. Reading fluency, reading comprehension and arithmetic skills were assessed using standardized tests at the end of Grades 1–3.Results
Among all children more recess PA and more time spent in SB related to academic skills were associated with a better reading fluency across Grades 1–3. In boys, higher levels of total PA, physically active school transportation and more time spent in SB related to academic skills were associated with a better reading fluency across the Grades 1–3. Among girls, higher levels of total PA were related to worse arithmetic skills across Grades 1–3. Moreover, total PA was directly associated with reading fluency and arithmetic skills in Grades 1–3 among girls whose parents had a university degree, whereas these relationships were inverse in girls of less educated parents.Conclusions
Total PA, physically active school transportation and SB related to academic skills may be beneficial for the development of reading skills in boys, whereas factors that are independent of PA or SB may be more important for academic skills in girls.Trial Registration
ClinicalTrials.gov: NCT01803776相似文献95.
The fish community in the littoral areas of eight regulated lakes and five reference lakes in Finland was sampled by electrofishing.
No significant effect of winter drawdown on species richness was recorded across lakes. Total fish density for stony bottoms
of the regulated and reference lakes averaged 19.3 and 32.7 individuals per 100 m2, respectively, but this difference was not statistically significant. The combined proportion of littoral fish species, including
minnow (Phoxinus phoxinus), bullhead (Cottus gobio), alpine bullhead (Cottus poecilopus), nine-spined stickleback (Pungitius pungitius), and stone loach (Barbatula barbatula), supplemented with zoobenthos feeders ruffe (Gymnocephalus cernuus) and young burbot (Lota lota), was much lower in the regulated lakes than in the reference lakes. Besides winter drawdown, other variables, such as nutrient
level and lake size, affected the fish community.
Guest editors: K. M. Wantzen, K.-O. Rothhaupt, M. M?rtl, M. Cantonati, L. G.-Tóth & P. Fischer
Ecological Effects of Water-Level Fluctuations in Lakes 相似文献
96.
97.
Teppo Hiltunen Jouni Laakso Veijo Kaitala Lotta-Riina Suomalainen Minna Pekkonen 《Acta Oecologica》2008,33(3):291-299
Competition theory generally predicts that diversity is maintained by temporal environmental fluctuations. One of the many suggested mechanisms for maintaining diversity in fluctuating environments is the gleaner-opportunist trade-off, whereby gleaner species have low threshold resource levels and low maximum growth rates in high resource concentration while opportunist species show opposite characteristics. We measured the growth rates of eight heterotrophic aquatic bacteria under different concentrations of chemically complex plant detritus resource. The growth rates revealed gleaner-opportunist trade-offs. The role of environmental variability in maintaining diversity was tested in a 28-day experiment with three different resource fluctuation regimes imposed on two four-species bacterial communities in microcosms. We recorded population densities with serial dilution plating and total biomass as turbidity. Changes in resource availability were measured from filter-sterilised medium by re-introducing the consumer species and recording short-term growth rates. The type of environmental variation had no effect on resource availability, which declined slowly during the experiment and differed in level between the communities. However, the slowly fluctuating environment had the highest Shannon diversity index, biomass, and coefficient of variation of biomass in both communities. We did not find a clear link between the gleaner-opportunist trade-off and diversity in fluctuating environments. Nevertheless, our results do not exclude this explanation and support the general view that temporal environmental variation maintains species diversity also in communities feeding chemically complex resource. 相似文献
98.
99.
Lise Comte Juan Carvajal‐Quintero Pablo A. Tedesco Xingli Giam Ulrich Brose Tibor Ers Ana F. Filipe Marie‐Jose Fortin Katie Irving Claire Jacquet Stefano Larsen Sapna Sharma Albert Ruhi Fernando G. Becker Lilian Casatti Giuseppe Castaldelli Renato B. Dala‐Corte Stephen R. Davenport Nathan R. Franssen Emili García‐Berthou Anna Gavioli Keith B. Gido Luz Jimenez‐Segura Rafael P. Leito Bill McLarney Jason Meador Marco Milardi David B. Moffatt Thiago V. T. Occhi Paulo S. Pompeu David L. Propst Mark Pyron Gilberto N. Salvador Jerome A. Stefferud Tapio Sutela Christopher Taylor Akira Terui Hirokazu Urabe Teppo Vehanen Jean R. S. Vitule Jaquelini O. Zeni Julian D. Olden 《Global Ecology and Biogeography》2021,30(1):38-50
100.
The role of transferrin receptors and iron delivery in mouse embryonic morphogenesis 总被引:1,自引:0,他引:1
Irma Thesleff Anna-Maija Partanen William Landschulz Ian S. Trowbridge Peter Ekblom 《Differentiation; research in biological diversity》1985,30(2):152-158
The iron-carrying serum protein transferrin is required for the proliferation and differentiation of embryonic tissues in culture. We studied the expression and role of transferrin receptors in two model systems using a monoclonal antibody against the transferrin receptor of mice. The addition of 20-100 micrograms/ml antibody to a chemically defined culture medium containing transferrin (10 micrograms/ml) inhibited morphogenesis and cell proliferation in kidneys and teeth. However, the antibody did not inhibit development when iron was delivered to the cells by a lipophilic iron chelator i.e., by-passing the receptor-mediated pathway. Hence, the binding of the receptor antibody to the receptor apparently did not affect cell proliferation, and the antibody was not toxic to the tissues. Our results suggest that the antibody to the transferrin receptor inhibits development by blocking the normal endocytotic route of iron delivery. Cells derived from embryonic kidneys and teeth expressed the transferrin receptor when cultured as monolayers. However, using immunofluorescent techniques, we were unable to detect the receptor in frozen tissue sections. It is possible that the seeding of cells in monolayer cultures affects the expression of the transferrin receptor, since it is known that all types of cells require transferrin for continued proliferation in culture. Organ-cultured kidney mesenchymal cells are not initially responsive to transferrin, but they acquire responsiveness as a consequence of an inductive tissue interaction. Although it remains unknown as to whether the acquisition of transferrin responsiveness is directly related to the expression of transferrin receptors, our results suggest that transferrin and its receptors play a role in embryonic morphogenesis. 相似文献