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991.
Preliminary observations on the morphology of the inner ear of the fetal narwhal (Monodon monoceros)
The inner ear of the narwhal (Monodon monoceros) was investigated on the basis of a complete series of microslides of an early fetus. In this well‐preserved specimen, the cochlea is about twice as large as the vestibular apparatus. The latter exhibits a high degree of specialization. Whereas the utriculus and sacculus are of normal size in comparison with those of other mammals, the semicircular canals are miniaturized but not obliterated, as in the case of some adult toothed whales. In comparison with other mammals, there is relatively little perilymphatic space around the vestibular organ, but the inner radius of the lymphatic ducts comes close to that of the adult human. Although there are some hints that the sensitivity of the vestibular system may be high in this species, detailed analysis of the adult narwhal ear is needed to confirm this inference. 相似文献
992.
993.
Presently, most simulations of ion channel function rely upon nonatomistic Brownian dynamics calculations, indirect interpretation of energy maps, or application of external electric fields. We present a computational method to directly simulate ion flux through membrane channels based on biologically realistic electrochemical gradients. In close analogy to single-channel electrophysiology, physiologically and experimentally relevant timescales are achieved. We apply our method to the bacterial channel PorB from pathogenic Neisseria meningitidis, which, during Neisserial infection, inserts into the mitochondrial membrane of target cells and elicits apoptosis by dissipating the membrane potential. We show that our method accurately predicts ion conductance and selectivity and elucidates ion conduction mechanisms in great detail. Handles for overcoming channel-related antibiotic resistance are identified. 相似文献
994.
Bacteriorhodopsin is a model system for membrane proteins. This seven transmembrane helical protein is embedded within a membrane structure called purple membrane. Its structural stability against mechanical stress was recently investigated by atomic force microscopy experiments, in which single proteins were extracted from the purple membrane. Here, we study this process by all-atom molecular dynamics simulations, in which single bacteriorhodopsin molecules were extracted and unfolded from an atomistic purple membrane model. In our simulations, key features from the experiments like force profiles and location of key residues that resist mechanical unfolding were reproduced. These key residues were seen to be stabilized by a dynamic network of intramolecular interactions. Further, the unfolding pathway was found to be velocity-dependent. Simulations in which the mechanical stress was released during unfolding revealed relaxation motions that allowed characterization of the nonequilibrium processes during fast extraction. 相似文献
995.
Recent theory suggests that both biodiversity and productivity are constrained by resource supply rates and ratios and that resource stoichiometry is the key to understanding the relationship between biodiversity and productivity. We experimentally tested this theory using pelagic metacommunities. We amended existing predictions by explicitly considering evenness as an aspect of biodiversity and including control of algal biomass by consumption in addition to competition. The metacommunities received a different phosphorus (P) supply and the three patches within each metacommunity differed in their nitrogen (N) supply, which created different N∶P ratios (2, 16, and 128). All patches were inoculated with a phytoplankton assemblage consisting of five species, and half of the metacommunities received two ciliate species as consumers. At the level of the entire metacommunity, algal biomass increased with increasing P supply, whereas species richness and evenness decreased with increasing P supply. Without consumers, resource use efficiency (RUE; realized biomass per unit of P) increased with increasing richness and evenness. Consumer presence reduced overall biomass and richness and precluded a correlation between RUE and biodiversity. At the patch level, local evenness correlated with higher RUE at both imbalanced N∶P ratios (2 and 128) but not at a balanced N∶P ratio. In conclusion, overall P supply constrained realized biomass and altered diversity, whereas resource stoichiometry shaped the relationship between biodiversity and RUE. 相似文献
996.
Theiler S Mela P Diamantouros SE Jockenhoevel S Keul H Möller M 《Biotechnology and bioengineering》2011,108(3):694-703
The potential of novel functional star‐shaped poly(ε‐caprolactone)s of controlled molecular weight and low molecular weight distribution bearing acrylate end groups as material for biomedical applications was demonstrated in this study. The polymers were functionalized via Michael‐type addition of amino acid esters containing amino or thiol groups showing the potential for immobilization of biomolecules. Furthermore, scaffolds of different geometries were prepared by uniaxial freezing of polymer solutions followed by freeze drying. Different solvents and polymer concentrations were investigated, resulting in scaffolds with porosities between 76 and 96%. Mechanical properties of the scaffolds were investigated and the morphology was determined via scanning electron microscopy. Scaffolds with interconnected channels were prepared using benzene, 1,2‐dichloroethane or dioxane as solvent. The tubular longitudinal pores in honeycomb arrangement extend throughout the full extent of the scaffolds (typical pore sizes: 20–100 µm). Biotechnol. Bioeng. 2011; 108:694–703. © 2010 Wiley Periodicals, Inc. 相似文献
997.
Helmut F. van Emden Elizabeth A. Wild 《Entomologia Experimentalis et Applicata》2020,168(6-7):582-586
We have been able to maintain a continuous culture of Myzus persicae (Sulzer) (Hemiptera: Aphididae) on a fully defined artificial diet at Reading, UK, for over 30 years, without any return to plants. Following multiple requests from aphid researchers, here we provide the details of our culturing method. Detailed instructions are given for rearing M. persicae on the diet. An improved recipe is included as well as the construction and changing of diet sachets. 相似文献
998.
Georgakopoulos Nikitas Prior Nicole Angres Brigitte Mastrogiovanni Gianmarco Cagan Alex Harrison Daisy Hindley Christopher J. Arnes-Benito Robert Liau Siong-Seng Curd Abbie Ivory Natasha Simons Benjamin D. Martincorena Inigo Wurst Helmut Saeb-Parsy Kourosh Huch Meritxell 《BMC developmental biology》2020,20(1):1-7
999.
Hosny El-Adawy Helmut Hotzel Herbert Tomaso Heinrich Neubauer Eduardo N. Taboada Ralf Ehricht Hafez M. Hafez 《PloS one》2013,8(2)
Campylobacter is genetically highly diverse and undergoes frequent intraspecific recombination. Turkeys have been identified as an important reservoir for Campylobacter jejuni which is of public health significance. The assessment of the genetic diversity among Campylobacter population is critical for our understanding of the epidemiology of this bacterium. The genetic profiles were different according to the molecular typing methods used. The performance of established flaA genotyping, multilocus sequencing typing (MLST) and DNA microarray assay based on the ArrayTube™ technology was evaluated using 14 Campylobacter jejuni isolated from a commercial turkey flock. The flaA typing was performed using PCR-RFLP with restriction enzymes Sau3AI, AluI, a ‘composite’ flaA analysis of AluI and Sau3AI and DdeI. The 14 isolates were differentiated into 3, 5, 7 and 9 genotypes, respectively. Entire flaA gene and short variable region (SVR) sequences were analysed. Sequencing of the entire flaA provided 11 different genotypes. flaA-SVR sequence analysis detected 8 flaA alleles and 4 flaA peptides. One new flaA allele type (528) was identified. MLST analysis represented 10 different sequence types (STs) and 5 clonal complexes (CCs). The microarray assay recognised 14 different genotypes. The discriminatory indices were 0.560, 0.802, 0.857, and 0.912 for flaA-RFLP depending on the used enzymes, 0.890 for flaA-SVR, 0.967 for entire flaA sequencing, 0.945 for MLST and 1.00 for the DNA microarray assay. The flaA gene was genetically stable over 20 passages on blood agar. In conclusion, the different typing tools demonstrated a high level of genetic heterogeneity of Campylobacter jejuni in a turkey flock, indicating that a single flock can be infected by multiple genotypes within one rearing cycle. DNA microarray-based assays had the highest discriminatory power when compared with other genotyping tools. 相似文献
1000.
Manfred Georg Moertl Helmut Karl Lackner Ilona Papousek Andreas Roessler Helmut Hinghofer-Szalkay Uwe Lang Vassiliki Kolovetsiou-Kreiner Dietmar Schlembach 《PloS one》2013,8(4)