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101.
102.
Mathias H. Andersson Matz Berggren Dan Wilhelmsson Marcus C. Öhman 《Helgoland Marine Research》2009,63(3):249-260
With large-scale development of offshore wind farms, vertical structures are becoming more common in open water areas. To
examine how vertical structures of different materials may be colonized by epibenthic organisms, an experiment was carried
out using steel and concrete pilings constructed to resemble those commonly used in wind farm constructions as well as in
bridges, jetties and oil platforms. The early recruitment and succession of the epibenthic communities were sampled once a
month for the first 5 months and then again after 1 year. Further, the fish assemblages associated with the pillars were sampled
and compared to natural areas. The main epibenthic species groups, in terms of coverage, differed between the two materials
at five out of six sampling occasions. Dominant organisms on steel pillars were the barnacle Balanus improvisus, the calcareous tubeworm Pomatoceros triqueter and the tunicate Ciona intestinalis. On the concrete pillars, the hydroid Laomedea sp. and the tunicates Corella parallelogramma and Ascidiella spp. dominated. However, there was no different in coverage at different heights on the pillars or in biomass and species
abundance at different directions (north-east or south-west) 5 months after submergence. Fish showed overall higher abundances
and species numbers on the pillars (but no difference between steel and concrete) compared to the surrounding soft bottom
habitats but not compared to natural vertical rock walls. Two species were attracted to the pillars, indicating a reef effect;
Gobiusculus flavescens and Ctenolabrus rupestris. The bottom-dwelling gobies, Pomatoschistus spp., did not show such preferences.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
103.
Summary In a review of information on 444 patients with sporadic retinoblastoma, a correlation with increased fathers'age was demonstrated and no correlation with was found in the unilateral form. These data favor the hypothesis that the bilateral form is caused by a germinal mutation and the unilateral form is due to somatic mutations.
Zusammenfassung In einer Übersicht über 444 Patienten mit sporadischem Retinoblastom wurde eine Erhöhung des väterlichen Alters demonstriert. Bei den einseitigen Fällen wurde eine solche Erhöhung jedoch nicht gefunden. Die Daten sprechen dafür, daß die doppelseitige Form durch Keimzell-Mutation verursacht ist, während die einseitige form auf somatische Mutationen zurückgeht.相似文献
104.
Jenny Knapp Jean-Mathieu Bart Patrick Giraudoux Marie-Louise Glowatzki Isabelle Breyer Francis Raoul Peter Deplazes Georg Duscher Karel Martinek Pavol Dubinsky Marie-Hélène Guislain Florence Cliquet Thomas Romig Andrzej Malczewski Bruno Gottstein Renaud Piarroux 《PLoS neglected tropical diseases》2009,3(6)
Background
Alveolar echinococcosis (AE) is a severe helminth disease affecting humans, which is caused by the fox tapeworm Echinococcus multilocularis. AE represents a serious public health issue in larger regions of China, Siberia, and other regions in Asia. In Europe, a significant increase in prevalence since the 1990s is not only affecting the historically documented endemic area north of the Alps but more recently also neighbouring regions previously not known to be endemic. The genetic diversity of the parasite population and respective distribution in Europe have now been investigated in view of generating a fine-tuned map of parasite variants occurring in Europe. This approach may serve as a model to study the parasite at a worldwide level.Methodology/Principal Findings
The genetic diversity of E. multilocularis was assessed based upon the tandemly repeated microsatellite marker EmsB in association with matching fox host geographical positions. Our study demonstrated a higher genetic diversity in the endemic areas north of the Alps when compared to other areas.Conclusions/Significance
The study of the spatial distribution of E. multilocularis in Europe, based on 32 genetic clusters, suggests that Europe can be considered as a unique global focus of E. multilocularis, which can be schematically drawn as a central core located in Switzerland and Jura Swabe flanked by neighbouring regions where the parasite exhibits a lower genetic diversity. The transmission of the parasite into peripheral regions is governed by a “mainland–island” system. Moreover, the presence of similar genetic profiles in both zones indicated a founder event. 相似文献105.
Göran Englund Frank Johansson Patrik Olofsson Juha Salonsaari Johanna Öhman 《Ecology letters》2009,12(7):663-671
Diamond [Assembly of species communities. In: Ecology and Evolution of Communities (eds Cody, M.L. & Diamond, J.M.). Harvard University Press, Cambridge, pp. 342–444] proposed that resource competition leads to checkerboard-like distributions of competing species. This proposal prompted research that revealed checkerboard patterns within a wide range of communities, but the mechanisms that generate such patterns are still poorly understood. Here we present whole-lake natural experiments and analyses of species–environment relationships in small coastal lake fish communities that were fragmented when land uplift isolated these lakes from the Baltic Sea, showing that a combination of predation and habitat suitability generated checkerboard distributions. Checkerboard patterns developed because two piscivores, northern pike and Eurasian perch, caused the extinction of several prey species in deep lakes. Conversely, low oxygen levels in shallow lakes caused extinction of the piscivores, and these areas served as a refuge for tolerant prey species. Based on these findings, we suggest that habitat suitability and biotic interactions should be viewed simultaneously in null models of assembly rules. 相似文献
106.
Anders Öhman Tommy Öman Mikael Oliveberg 《Protein science : a publication of the Protein Society》2010,19(1):183-189
The ribosomal protein S6 from Thermus thermophilus has served as a model system for the study of protein folding, especially for understanding the effects of circular permutations of secondary structure elements. This study presents the structure of a permutant protein, the 96‐residue P54‐55, and the structure of its 101‐residue parent protein S6wt in solution. The data also characterizes the effects of circular permutation on the backbone dynamics of S6. Consistent with crystallographic data on S6wt, the overall solution structures of both P54‐55 and S6wt show a β‐sheet of four antiparallel β‐strands with two α‐helices packed on one side of the sheet. In clear contrast to the crystal data, however, the solution structure of S6wt reveals a disordered loop in the region between β‐strands 2 and 3 (Leu43‐Phe60) instead of a well‐ordered stretch and associated hydrophobic mini‐core observed in the crystal structure. Moreover, the data for P54‐55 show that the joined wild‐type N‐ and C‐terminals form a dynamically robust stretch with a hairpin structure that complies with the in silico design. Taken together, the results explain why the loop region of the S6wt structure is relatively insensitive to mutational perturbations, and why P54‐55 is more stable than S6wt: the permutant incision at Lys54‐Asp55 is energetically neutral by being located in an already disordered loop whereas the new hairpin between the wild‐type N‐ and C‐termini is stabilizing. 相似文献
107.
Sorensen GS Cribb BW Merritt D Johnson ML Zalucki MP 《Arthropod Structure & Development》2006,35(1):3-13
This study provides comprehensive documentation of silk production in the pest moth Helicoverpa armigera from gland secretion to extrusion of silk thread. The structure of the silk glands, accessory structures and extrusion apparatus are reported. The general schema of the paired silk glands follows that found for Lepidoptera. Morphology of the duct, silk press, muscle attachments and spigot are presented as a three-dimensional reconstruction and the cuticular crescent-shaped profile of the silk press is demonstrated in both open and closed forms with attendant muscle blocks, allowing advances in our knowledge of how the silk press functions to regulate the extrusion of silk. Growth of the spigot across instars is documented showing a distinctive developmental pattern for this extrusion device. Its shape and structure are related to use and load-bearing activity. 相似文献
108.
Understanding the significance of electrophoretic variation is of interest for both ecological and evolutionary genetics. Although there has been a very active neutralist–selectionist debate about the patterns of electrophoretic variation in natural populations, it is only recently that charged amino acids have been shown to be important in enzyme adaptation. In this study we carried out a broad electrophoretic survey of amylase variation in 150 species of Drosophilids. The distribution of amylase electromorphs was found to be correlated with the geographical origin of the flies. Generally the faster migrating variants are found in warmer temperatures. There is also a correlation with the feeding habits of the species, in particular, fungus feeders consistently showed a deviating pattern of electrophoretic mobility. These correlations between ecological diversity and electrophoretic patterns indicate that at least some of the changes in charged amino acids are adaptive, and result from selection to cope with specific environments. 相似文献
109.
Novel mechanism for high-altitude adaptation in hemoglobin of the Andean frog Telmatobius peruvianus
Weber RE Ostojic H Fago A Dewilde S Van Hauwaert ML Moens L Monge C 《American journal of physiology. Regulatory, integrative and comparative physiology》2002,283(5):R1052-R1060
In contrast to birds and mammals, no information appears to be available on the molecular adaptations for O(2) transport in high-altitude ectothermic vertebrates. We investigated Hb of the aquatic Andean frog Telmatobius peruvianus from 3,800-m altitude as regards isoform differentiation, sensitivity to allosteric cofactors, and primary structures of the alpha- and beta-chains, and we carried out comparative O(2)-binding measurements on Hb of lowland Xenopus laevis. The three T. peruvianus isoHbs show similar functional properties. The high O(2) affinity of the major component results from an almost complete obliteration of chloride sensitivity, which correlates with two alpha-chain modifications: blockage of the NH(2)-terminal residues and replacement by nonpolar Ala of polar residues Ser and Thr found at position alpha131(H14) in human and X. leavis Hbs, respectively. The data indicate adaptive significance of alpha-chain chloride-binding sites in amphibians, in contrast to human Hb where chloride appears mainly to bind in the cavity between the beta-chains. The findings are discussed in relation to other strategies for high-altitude adaptations in amphibians. 相似文献
110.
S. Karsten Elena Voskoboeva Svetlana Tishkanina U. Pettersson Xcenia Krasnopolskaja Marie-Louise Bondeson 《Human genetics》1998,103(6):732-735
We present a mutational analysis of the iduronate-2-sulfatase (IDS) gene of 36 Russian patients with Hunter syndrome. Among
29 mutant alleles, there were 19 missense mutations, 1 nonsense mutation, 6 mutations affecting splice sites, and 3 major
structural alterations resulting in deletions. Of the 25 different mutations, 15 are novel and unique. Most of the missense
mutations result in intermediate or severe phenotypes.
Received: 1 June 1998 / Accepted: 27 July 1998 相似文献