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991.
Spector AA 《Journal of biomechanical engineering》2005,127(3):391-399
Cochlear outer hair cells are crucial for active hearing. These cells have a unique form of motility, named electromotility, whose main features are the cell's length changes, active force production, and nonlinear capacitance. The molecular motor, prestin, that drives outer hair cell electromotility has recently been identified. We reveal relationships between the active energy produced by the outer hair cell molecular motors, motor effectiveness, and the capacitive properties of the cell membrane. We quantitatively characterize these relationships by introducing three characteristics: effective capacitance, zero-strain capacitance, and zero-resultant capacitance. We show that zero-strain capacitance is smaller than zero-resultant capacitance, and that the effective capacitance is between the two. It was also found that the differences between the introduced capacitive characteristics can be expressed in terms of the active energy produced by the cell's molecular motors. The effectiveness of the cell and its molecular motors is introduced as the ratio of the motors'active energy to the energy of the externally applied electric field. It is shown that the effectiveness is proportional to the difference between zero-strain and zero-resultant capacitance. We analyze the cell and motor's effectiveness within a broad range of cellular parameters and estimate it to be within a range of 12%-30%. 相似文献
992.
A diverse Late Triassic (Late Norian) gastropod fauna is described from the Mission Creek Limestone of the Wallowa terrane
(Idaho, USA). Sample standardization by rarefaction analysis indicates that the fauna is even more diverse than the Late Triassic
gastropod fauna from the Pucara Formation (Peru) which represents the most diverse gastropod fauna from South America. The
gastropod fauna consists of 66 species; several genera are reported for the first time from North America. A high percentage
of the species are highly ornamented and several have distinct siphonal canals. This suggests that the appearance of truly
Mesozoic elements among the gastropods began before the Mesozoic Marine Revolution in other clades. The fauna is dominated
by high-spired strongly ornamented procerithiids, a group more characteristic for the Jurassic. Comparison of the present
fauna and the Iranian Nayband Formation gastropod fauna show that the procerithiids underwent a first global radiation in
the Late Triassic. The high number of new species in this fauna suggests that sampling of Late Triassic gastropod faunas is
still incomplete and hinders palaeobiogeographic considerations. Previous suggesions that gastropod faunas from the Wallowa
and Wrangellia terranes resemble each other and are distinct from those of Alexander, Chulitna, and Farewell terranes are
basically corroborated. The gastropod fauna of the Mission Creek Limestone differs considerably from that of the western and
central Tethys but shares several taxa with the Late Triassic gastropod fauna of the Pucara Formation in Peru. Thus, the Hispanic
corridor was probably not present in the Norian but opened only in the Early Jurassic.
The subfamily Andangulariinae is introduced and placed in the Zygopleuridae. The generaSpiniomphalus, Nodoconus, Gudrunella, Blodgettella, Idahospira, andSiphonilda and the subgenusCryptaulax (Wallowax) are introduced. 27 species are erected. A lectotype is designated forCryptaulax rhabdocolpoides
Haas, 1953.
相似文献
993.
Abarca-Grau AM Burbank LP de Paz HD Crespo-Rivas JC Marco-Noales E López MM Vinardell JM von Bodman SB Penyalver R 《Applied and environmental microbiology》2012,78(6):1644-1651
Rhizobium rhizogenes strain K84 is a commercial biocontrol agent used worldwide to control crown gall disease. The organism binds tightly to polypropylene substrate and efficiently colonizes root surfaces as complex, multilayered biofilms. A genetic screen identified two mutants in which these surface interactions were affected. One of these mutants failed to attach and form biofilms on the abiotic surface although, interestingly, it exhibited normal biofilm formation on the biological root tip surface. This mutant is disrupted in a wcbD ortholog gene, which is part of a large locus predicted to encode functions for the biosynthesis and export of a group II capsular polysaccharide (CPS). Expression of a functional copy of wcbD in the mutant background restored the ability of the bacteria to attach and form normal biofilms on the abiotic surface. The second identified mutant attached and formed visibly denser biofilms on both abiotic and root tip surfaces. This mutant is disrupted in the rkpK gene, which is predicted to encode a UDP-glucose 6-dehydrogenase required for O-antigen lipopolysaccharide (LPS) and K-antigen capsular polysaccharide (KPS) biosynthesis in rhizobia. The rkpK mutant from strain K84 was deficient in O-antigen synthesis and exclusively produced rough LPS. We also show that strain K84 does not synthesize the KPS typical of some other rhizobia strains. In addition, we identified a putative type II CPS, distinct from KPS, that mediates cell-surface interactions, and we show that O antigen of strain K84 is necessary for normal cell-cell interactions in the biofilms. 相似文献
994.
Background
Polyglutamine expansion is responsible for several neurodegenerative disorders, among which Huntington disease is the most well-known. Studies in the yeast model demonstrated that both aggregation and toxicity of a huntingtin (htt) protein with an expanded polyglutamine region strictly depend on the presence of the prion form of Rnq1 protein ([PIN +]), which has a glutamine/asparagine-rich domain.Principal Findings
Here, we showed that aggregation and toxicity of mutant htt depended on [PIN +] only quantitatively: the presence of [PIN +] elevated the toxicity and the levels of htt detergent-insoluble polymers. In cells lacking [PIN +], toxicity of mutant htt was due to the polymerization and inactivation of the essential glutamine/asparagine-rich Sup35 protein and related inactivation of another essential protein, Sup45, most probably via its sequestration into Sup35 aggregates. However, inhibition of growth of [PIN +] cells depended on Sup35/Sup45 depletion only partially, suggesting that there are other sources of mutant htt toxicity in yeast.Conclusions
The obtained data suggest that induced polymerization of essential glutamine/asparagine-rich proteins and related sequestration of other proteins which interact with these polymers represent an essential source of htt toxicity. 相似文献995.
We have reviewed the current state of multidisciplinary knowledge of the photoprotective mechanism in the photosystem II antenna underlying non-photochemical chlorophyll fluorescence quenching (NPQ). The physiological need for photoprotection of photosystem II and the concept of feed-back control of excess light energy are described. The outline of the major component of nonphotochemical quenching, qE, is suggested to comprise four key elements: trigger (ΔpH), site (antenna), mechanics (antenna dynamics) and quencher(s). The current understanding of the identity and role of these qE components is presented. Existing opinions on the involvement of protons, different LHCII antenna complexes, the PsbS protein and different xanthophylls are reviewed. The evidence for LHCII aggregation and macrostructural reorganization of photosystem II and their role in qE are also discussed. The models describing the qE locus in LHCII complexes, the pigments involved and the evidence for structural dynamics within single monomeric antenna complexes are reviewed. We suggest how PsbS and xanthophylls may exert control over qE by controlling the affinity of LHCII complexes for protons with reference to the concepts of hydrophobicity, allostery and hysteresis. Finally, the physics of the proposed chlorophyll-chlorophyll and chlorophyll-xanthophyll mechanisms of energy quenching is explained and discussed. This article is part of a Special Issue entitled: Photosystem II. 相似文献
996.
Alexander A. Shestov Julien Valette Dinesh K. Deelchand Kamil U?urbil Pierre-Gilles Henry 《Neurochemical research》2012,37(11):2388-2401
Metabolic modeling of dynamic 13C labeling curves during infusion of 13C-labeled substrates allows quantitative measurements of metabolic rates in vivo. However metabolic modeling studies performed in the brain to date have only modeled time courses of total isotopic enrichment at individual carbon positions (positional enrichments), not taking advantage of the additional dynamic 13C isotopomer information available from fine-structure multiplets in 13C spectra. Here we introduce a new 13C metabolic modeling approach using the concept of bonded cumulative isotopomers, or bonded cumomers. The direct relationship between bonded cumomers and 13C multiplets enables fitting of the dynamic multiplet data. The potential of this new approach is demonstrated using Monte-Carlo simulations with a brain two-compartment neuronal-glial model. The precision of positional and cumomer approaches are compared for two different metabolic models (with and without glutamine dilution) and for different infusion protocols ([1,6-13C2]glucose, [1,2-13C2]acetate, and double infusion [1,6-13C2]glucose?+?[1,2-13C2]acetate). In all cases, the bonded cumomer approach gives better precision than the positional approach. In addition, of the three different infusion protocols considered here, the double infusion protocol combined with dynamic bonded cumomer modeling appears the most robust for precise determination of all fluxes in the model. The concepts and simulations introduced in the present study set the foundation for taking full advantage of the available dynamic 13C multiplet data in metabolic modeling. 相似文献
997.
Corina Nüesch Cora Huber Geert Pagenstert Vinzenz von Tscharner Victor Valderrabano 《Journal of electromyography and kinesiology》2012,22(6):939-946
Asymmetric osteoarthritis (OA) is a common type of OA in the ankle joint. OA also influences the muscles surrounding a joint, however, little is known about the muscle activation in asymmetric ankle OA. Therefore, the aim of this study was to characterize the patients’ muscle activation during isometric ankle torque measurements and level walking. Surface electromyography (EMG) was measured of gastrocnemius medialis (GM) and lateralis (GL), soleus (SO), tibialis anterior (TA), and peroneus longus (PL) in 12 healthy subjects and 12 ankle OA patients. To obtain time and frequency components of the EMG power a wavelet transformation was performed. Furthermore, entropy was introduced to characterize the homogeneity of the wavelet patterns.Patients produced lower plantar- and dorsiflexion torques and their TA wavelet spectrum was shifted towards lower frequencies. While walking, the patients’ muscles were active with a lower intensity and over a broader time–frequency region. In contrast to controls and varus OA patients, maximal GM activity of valgus OA patients lagged behind the activity of GL and SO. In both tasks, PL of the valgus patients contained more low frequency power. The results of this study will help to assess whether surgical interventions of ankle OA can reestablish the muscle activation patterns. 相似文献
998.
LEARNING OBJECTIVES: After reading this article, the participant should be able to: 1. Recognize the clinical features of chronic scapholunate and lunotriquetral ligament injuries and their long-term sequelae. 2. Describe the current management and latest techniques for treating chronic scapholunate and lunotriquetral ligament injuries and their long-term sequelae, such as wrist arthritis. SUMMARY: This article provides an update on the diagnosis, current management, and latest techniques for the treatment of chronic scapholunate and lunotriquetral ligament injuries and their long-term sequelae, such as wrist arthritis. 相似文献
999.
DNA error correcting codes over the edit metric consist of embeddable markers for sequencing projects that are tolerant of sequencing errors. When a genetic library has multiple sources for its sequences, use of embedded markers permit tracking of sequence origin. This study compares different methods for synthesizing DNA error correcting codes. A new code-finding technique called the salmon algorithm is introduced and used to improve the size of best known codes in five difficult cases of the problem, including the most studied case: length six, distance three codes. An updated table of the best known code sizes with 36 improved values, resulting from three different algorithms, is presented. Mathematical background results for the problem from multiple sources are summarized. A discussion of practical details that arise in application, including biological design and decoding, is also given in this study. 相似文献
1000.
Strom A Kolb H Martin S Herder C Simon MC Koenig W Heise T Heinemann L Roden M Schloot NC;DIATOR Study Group 《PloS one》2012,7(3):e33108