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111.
Diving ducks use their webbed feet to provide the propulsive force that moves them underwater. To hold position near the bottom while feeding, ducks paddle constantly to resist the buoyant force of the body. Using video sequences from two orthogonal cameras we reconstructed the 3-dimensional motion of the feet through water and estimated the forces involved with a quasi-steady blade-element model. We found that during station holding, near the bottom, ducks use drag based propulsion with the webbed area of the foot moving perpendicular to the trajectory of the foot. The body was pitched at 76±3.47° below the horizon and the propulsive force was directed 26±1.9° ventral to the body so that 98% of the propulsive force in the sagittal plane of the duck worked to oppose buoyancy. The mechanical work done by moving both feet through a paddling cycle was 1.1±0.2 J which was equivalent to an energy expenditure of 3.7±0.5 W to hold position while feeding at 1.5 m depth. We conclude that in shallow water the high energetic cost of feeding in ducks is due to the need to paddle constantly against buoyancy even after reaching the bottom. The mechanical energy spent on holding position near the bottom, while feeding, is approximately 2 fold higher than previous estimates that were made for similar bottom depths but based on the presumed motion of the body instead of motion of the feet. 相似文献
112.
113.
Edward J. Land Tulsi Mukherjee A.John Swallow J.Malcolm Bruce 《Archives of biochemistry and biophysics》1983,225(1):116-121
Pulse radiolysis of aqueous solutions containing adriamycin and redox indicators of known one-electron reduction potential (E1) shows that its E1 at pH 7 is ?328 mV (vs NHE). The variation E1 with pH in the range 6–12 shows that the net charge on the semiquinone at pH 7 is zero. As well as the pKa values of 2.9 and ≥ 14 established independently, the semiquinone has a pKa close to 9.2. The new data enable the structure and likely reactivity of the semiquinone to be specified. 相似文献
114.
115.
In most people worldwide intestinal lactase expression declines in childhood. In many others, particularly in Europeans, lactase
expression persists into adult life. The lactase persistence phenotype is in Europe associated with the −13910*T single nucleotide
variant located 13,910 bp upstream the lactase gene in an enhancer region that affects lactase promoter activity. This variant
falls in an Oct-1 binding site and shows greater Oct-1 binding than the ancestral variant and increases enhancer activity.
Several other variants have been identified very close to the −13910 position, which are associated with lactase persistence
in the Middle East and Africa. One of them, the −14010*C, is associated with lactase persistence in Africa. Here we show by
deletion analysis that the −14010 position is located in a 144 bp region that reduces the enhancer activity. In transfections
the −14010*C allele shows a stronger enhancer effect than the ancestral −14010*G allele. Binding sites for Oct-1 and HNF1α
surrounding the −14010 position were identified by gel shift assays, which indicated that −14010*C has greater binding affinity
to Oct-1 than −14010*G. 相似文献
116.
Franz Puttur Catharina Arnold-Schrauf Katharina Lahl Gulhas Solmaz Marc Lindenberg Christian Thomas Mayer Melanie Gohmert Maxine Swallow Christopher van Helt Heike Schmitt Lars Nitschke Bart N. Lambrecht Roland Lang Martin Messerle Tim Sparwasser 《PLoS pathogens》2013,9(9)
Plasmacytoid dendritic cells (pDCs) express the I-type lectin receptor Siglec-H and produce interferon α (IFNα), a critical anti-viral cytokine during the acute phase of murine cytomegalovirus (MCMV) infection. The ligands and biological functions of Siglec-H still remain incompletely defined in vivo. Thus, we generated a novel bacterial artificial chromosome (BAC)-transgenic “pDCre” mouse which expresses Cre recombinase under the control of the Siglec-H promoter. By crossing these mice with a Rosa26 reporter strain, a representative fraction of Siglec-H+ pDCs is terminally labeled with red fluorescent protein (RFP). Interestingly, systemic MCMV infection of these mice causes the downregulation of Siglec-H surface expression. This decline occurs in a TLR9- and MyD88-dependent manner. To elucidate the functional role of Siglec-H during MCMV infection, we utilized a novel Siglec-H deficient mouse strain. In the absence of Siglec-H, the low infection rate of pDCs with MCMV remained unchanged, and pDC activation was still intact. Strikingly, Siglec-H deficiency induced a significant increase in serum IFNα levels following systemic MCMV infection. Although Siglec-H modulates anti-viral IFNα production, the control of viral replication was unchanged in vivo. The novel mouse models will be valuable to shed further light on pDC biology in future studies. 相似文献
117.
Erik T Jansson Carolina L Trkulja Aikeremu Ahemaiti Maria Millingen Gavin DM Jeffries Kent Jardemark Owe Orwar 《Molecular pain》2013,9(1):1-8
The TRPV1 ion channel is expressed in nociceptors, where pharmacological modulation of its function may offer a means of alleviating pain and neurogenic inflammation processes in the human body. The aim of this study was to investigate the effects of cholesterol depletion of the cell on ion-permeability of the TRPV1 ion channel. The ion-permeability properties of TRPV1 were assessed using whole-cell patch-clamp and YO-PRO uptake rate studies on a Chinese hamster ovary (CHO) cell line expressing this ion channel. Prolonged capsaicin-induced activation of TRPV1 with N-methyl-D-glucamine (NMDG) as the sole extracellular cation, generated a biphasic current which included an initial outward current followed by an inward current. Similarly, prolonged proton-activation (pH 5.5) of TRPV1 under hypocalcemic conditions also generated a biphasic current including a fast initial current peak followed by a larger second one. Patch-clamp recordings of reversal potentials of TRPV1 revealed an increase of the ion-permeability for NMDG during prolonged activation of this ion channel under hypocalcemic conditions. Our findings show that cholesterol depletion inhibited both the second current, and the increase in ion-permeability of the TRPV1 channel, resulting from sustained agonist-activation with capsaicin and protons (pH 5.5). These results were confirmed with YO-PRO uptake rate studies using laser scanning confocal microscopy, where cholesterol depletion was found to decrease TRPV1 mediated uptake rates of YO-PRO. Hence, these results propose a novel mechanism by which cellular cholesterol depletion modulates the function of TRPV1, which may constitute a novel approach for treatment of neurogenic pain. 相似文献
118.
Cancer is a heterogeneous disease with different combinations of genetic alterations driving its development in different individuals. We introduce CoMEt, an algorithm to identify combinations of alterations that exhibit a pattern of mutual exclusivity across individuals, often observed for alterations in the same pathway. CoMEt includes an exact statistical test for mutual exclusivity and techniques to perform simultaneous analysis of multiple sets of mutually exclusive and subtype-specific alterations. We demonstrate that CoMEt outperforms existing approaches on simulated and real data. We apply CoMEt to five different cancer types, identifying both known cancer genes and pathways, and novel putative cancer genes.
Electronic supplementary material
The online version of this article (doi:10.1186/s13059-015-0700-7) contains supplementary material, which is available to authorized users. 相似文献119.
Bryony?L. Jones Tamiru?O. Raga Anke Liebert Pawel Zmarz Endashaw Bekele E.?Thomas Danielsen Anders?Krüger Olsen Neil Bradman Jesper?T. Troelsen Dallas?M. Swallow 《American journal of human genetics》2013,93(3):538-544
The persistent expression of lactase into adulthood in humans is a recent genetic adaptation that allows the consumption of milk from other mammals after weaning. In Europe, a single allele (−13910∗T, rs4988235) in an upstream region that acts as an enhancer to the expression of the lactase gene LCT is responsible for lactase persistence and appears to have been under strong directional selection in the last 5,000 years, evidenced by the widespread occurrence of this allele on an extended haplotype. In Africa and the Middle East, the situation is more complicated and at least three other alleles (−13907∗G, rs41525747; −13915∗G, rs41380347; −14010∗C, rs145946881) in the same LCT enhancer region can cause continued lactase expression. Here we examine the LCT enhancer sequence in a large lactose-tolerance-tested Ethiopian cohort of more than 350 individuals. We show that a further SNP, −14009T>G (ss 820486563), is significantly associated with lactose-digester status, and in vitro functional tests confirm that the −14009∗G allele also increases expression of an LCT promoter construct. The derived alleles in the LCT enhancer region are spread through several ethnic groups, and we report a greater genetic diversity in lactose digesters than in nondigesters. By examining flanking markers to control for the effects of mutation and demography, we further describe, from empirical evidence, the signature of a soft selective sweep. 相似文献
120.
Faecal pellet counts have been widely used to monitor the abundances of introduced ungulates in New Zealand, but ground-based sampling cannot be conducted safely in the steep non-forest habitats that are common in New Zealand's Southern Alps. Helicopter counts may be an effective technique for monitoring ungulates in steep non-forest habitat. We evaluated the relationship between faecal pellet and helicopter counts of ungulates (primarily feral goat Capra hircus) at 12 non-forest sites in the Southern Alps. Within each site we counted the numbers of ungulates from a helicopter on three occasions and the number of intact faecal pellets along 30 transects. Mean observed densities of feral goats derived from helicopter counts ranged from 0.0 to 20.2 km?2. There was a positive curvilinear (concave down) relationship between faecal pellet and helicopter counts. Compared with faecal pellet counts, helicopter counts were cheaper, could identify ungulate species and provided estimates of absolute density. Helicopter counts are a cost-effective method for monitoring ungulates in the steep non-forest habitats of New Zealand's Southern Alps. 相似文献