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991.
Previous work demonstrated that cystic fibrosis (CF) cells exhibit an increase in cAMP-mediated signaling as a characteristic response to lost CFTR function. Evidence for increased cAMP-mediated signaling in CF included increased phosphorylation of the cAMP response element binding protein (CREB) and elevated β-arrestin-2 (βarr2) expression. However, subsequent studies reveal that CREB activation in CF cells is independent of protein kinase-A (PKA). The goal of this study is to test the hypothesis that elevated βarr2 expression leads to increased CREB activation in a PKA-independent mechanism. βarr2-GFP expressing tracheal epithelial cells (βarr2-GFP) exhibit an increase of pCREB content and subsequent CRE activation compared to GFP expressing control cells. βarr2 activation of the ERK cascade represents a candidate mechanism leading to CREB activation. ERK exhibits increased activation in βarr2-GFP cells compared to cont-GFP cells, and ERK inhibition diminishes CRE activation in both GFP and βarr2-GFP cells. To test directly whether CREB regulation in CF is βarr2-dependent, nasal epithelium excised from wt mice (Cftr +/+; βarr2 +/+), CF mice (Cftr -/-; βarr2 +/+), and DKO mice (Cftr -/-; βarr2 -/-) were analyzed for pCREB protein content. Removal of βarr2 expression from CF mice reduces both pCREB and pERK content to wt levels. These data indicate that CF-related CREB regulation is mediated directly through βarr2 expression via the ERK pathway. 相似文献
992.
The influence of environmental gradients on the foliar nutrient economy of forests has been well documented; however, we have little understanding of what drives variability among individuals within a single forest stand, especially tropical forests. We evaluated inter‐ and intra‐specific variation in nutrient resorption, foliar nutrient concentrations and physical leaf traits of nine canopy tree species within a 1‐ha secondary tropical rain forest in northeastern Costa Rica. Both nitrogen (N) and phosphorus (P) resorption efficiency (RE) and proficiency of the nine tree species varied significantly among species, but not within. Both N and P RE were significantly negatively related to leaf specific strength. Green leaf N and P concentrations were strongly negatively related to leaf mass per area, and senesced leaf nutrient concentrations were significantly positively related to green leaf nutrient concentrations. This study reveals a strong influence of physical leaf traits on foliar nutrient and resorption traits of co‐occurring species in a secondary wet tropical forest stand. 相似文献
993.
994.
Brecknock S Dibbayawan TP Vesk M Vesk PA Faulkner C Barton DA Overall RL 《Planta》2011,234(4):749-758
Symplastic transport occurs between neighbouring plant cells through functionally and structurally dynamic channels called
plasmodesmata (PD). Relatively little is known about the composition of PD or the mechanisms that facilitate molecular transport
into neighbouring cells. While transmission electron microscopy (TEM) provides 2-dimensional information about the structural
components of PD, 3-dimensional information is difficult to extract from ultrathin sections. This study has exploited high-resolution
scanning electron microscopy (HRSEM) to reveal the 3-dimensional morphology of PD in the cell walls of algae, ferns and higher
plants. Varied patterns of PD were observed in the walls, ranging from uniformly distributed individual PD to discrete clusters.
Occasionally the thick walls of the giant alga Chara were fractured, revealing the surface morphology of PD within. External structures such as spokes, spirals and mesh were
observed surrounding the PD. Enzymatic digestions of cell wall components indicate that cellulose or pectin either compose
or stabilise the extracellular spokes. Occasionally, the PD were fractured open and desmotubule-like structures and other
particles were observed in their central regions. Our observations add weight to the argument that Chara PD contain desmotubules and are morphologically similar to higher plant PD. 相似文献
995.
Brownstein D Miller MA Oates SC Byrne BA Jang S Murray MJ Gill VA Jessup DA 《Journal of wildlife diseases》2011,47(2):278-292
Bacterial infections are an important cause of sea otter (Enhydra lutris) mortality, and some of these infections may originate from terrestrial and anthropogenic sources. Antimicrobials are an important therapeutic tool for management of bacterial infections in stranded sea otters and for prevention of infection following invasive procedures in free-ranging otters. In this study, susceptibility to commonly used antimicrobials was determined for 126 isolates of 15 bacterial species or groups from necropsied, live-stranded injured or sick, and apparently healthy wild sea otters examined between 1998 and 2005. These isolates included both gram-positive and gram-negative strains of primary pathogens, opportunistic pathogens, and environmental flora, including bacterial species with proven zoonotic potential. Minimal evidence of antimicrobial resistance and no strains with unusual or clinically significant multiple-drug resistance patterns were identified. Collectively, these findings will help optimize selection of appropriate antimicrobials for treatment of bacterial diseases in sea otters and other marine species. 相似文献
996.
Borck G Wunram H Steiert A Volk AE Körber F Roters S Herkenrath P Wollnik B Morris-Rosendahl DJ Kubisch C 《Human genetics》2011,129(1):45-50
Warburg Micro syndrome and Martsolf syndrome are clinically overlapping autosomal recessive conditions characterized by congenital
cataracts, microphthalmia, postnatal microcephaly, and developmental delay. The neurodevelopmental and ophthalmological phenotype
is more severe in Warburg Micro syndrome in which cerebral malformations and severe motor and mental retardation are common.
While biallelic loss-of-function mutations in RAB3GAP1 are present in the majority of patients with Warburg Micro syndrome; a hypomorphic homozygous splicing mutation of RAB3GAP2 has been reported in a single family with Martsolf syndrome. Here, we report a novel homozygous RAB3GAP2 small in-frame deletion, c.499_507delTTCTACACT (p.Phe167_Thr169del) that causes Warburg Micro syndrome in a girl from a consanguineous
Turkish family presenting with congenital cataracts, microphthalmia, absent visually evoked potentials, microcephaly, polymicrogyria,
hypoplasia of the corpus callosum, and severe developmental delay. No RAB3GAP2 mutations were detected in ten additional unrelated patients with RAB3GAP1-negative Warburg Micro syndrome, consistent with further genetic heterogeneity. In conclusion, we provide evidence that RAB3GAP2 mutations are not specific to Martsolf syndrome. Rather, our findings suggest that loss-of-function mutations of RAB3GAP1 as well as functionally severe RAB3GAP2 mutations cause Warburg Micro syndrome while hypomorphic RAB3GAP2 mutations can result in the milder Martsolf phenotype. Thus, a phenotypic severity gradient may exist in the RAB3GAP-associated disease continuum (the “Warburg–Martsolf syndrome”) which is presumably determined by the mutant gene and the
nature of the mutation. 相似文献
997.
Deborah J. Shafer James E. Kaldy Timothy D. Sherman Katharine M. Marko 《Aquatic Botany》2011,95(3):214-220
Photosynthetic responses were quantified for two Zostera japonica Aschers. and Graebn. populations from the northern and southern limits of distribution exposed to a range of salinities along the Pacific Coast of North America. Plants were collected from Padilla Bay, Washington (northern) and Coos Bay, Oregon, USA (southern) and cultured together in experimental tanks at 3 salinities (5, 20 and 35) under saturating irradiance for 3 weeks. Subsequently, photosynthesis–irradiance (P vs. E curves) relationships for leaf segments from the two populations were assessed using an oxygen electrode system. We found no evidence for diel rhythms in either light saturated photosynthesis (Pmax) or dark respiration (Rd). For the Padilla Bay population, Pmax ranged from 192 to 390 μmol O2 g DW−1 h−1; for the Coos Bay population Pmax ranged from 226 to 774 μmol O2 g DW−1 h−1. Photosynthetic maxima of the Coos Bay plants occurred at a salinity of 20, whereas salinity had no effect on the photosynthetic maxima of the Padilla Bay plants. There were significant differences in leaf tissue Rd among salinity treatments but the two populations responded similarly to salinity. North American populations of Z. japonica are best adapted to intermediate salinities, displaying minimum Rd rates, lower compensation irradiance, higher saturation irradiance, and greater Pmax rates at a salinity of 20. Additionally, the southern population may be better adapted to southward expansion along the Pacific Coast and changes associated with global climate change. 相似文献
998.
Sousa PM Silva ST Hood BL Charro N Carita JN Vaz F Penque D Conrads TP Melo AM 《Biochimie》2011,93(3):418-425
The organization of respiratory chain complexes in supercomplexes has been shown in the mitochondria of several eukaryotes and in the cell membranes of some bacteria. These supercomplexes are suggested to be important for oxidative phosphorylation efficiency and to prevent the formation of reactive oxygen species.Here we describe, for the first time, the identification of supramolecular organizations in the aerobic respiratory chain of Escherichia coli, including a trimer of succinate dehydrogenase. Furthermore, two heterooligomerizations have been shown: one resulting from the association of the NADH:quinone oxidoreductases NDH-1 and NDH-2, and another composed by the cytochrome bo3 quinol:oxygen reductase, cytochrome bd quinol:oxygen reductase and formate dehydrogenase (fdo). These results are supported by blue native-electrophoresis, mass spectrometry and kinetic data of wild type and mutant E . coli strains. 相似文献
999.
An optode device for net-photosynthesis measurements, based on oxygen-depending quenching of fluorescence from O2-specific sensors, and PAM fluorometry have been used to study diurnal courses of net-photosynthesis and the Fv/Fm ratio of the submerged plant Lagarosiphon major. Plants were pre-cultivated and studied in large mesocosm flow-through outdoor tanks under 50% and 80% shade cloth, respectively. Growth under the different shade cloths resulted in similar light compensation points (∼20 μmol photons m−2 s−1), but strongly different light saturation levels, with about 150 μmol m−2 s−1 for plants grown under 80% shade cloth and about 350 μmol m−2 s−1 for plants grown under 50% shade cloth. Plants under both growth conditions showed a transient reduction of the maximum Fv/Fm value in the afternoon (down to 70% of the morning control values under 80% shade cloth and down to 85% under 50% shade cloth), which was not accompanied by a reduction of the net photosynthetic rate. This indicated that the fluorescence parameter Fv/Fm must not be a reliable indicator of the rate of photosynthesis under all conditions. The new photo-optical device became evidenced as a valuable tool not only for laboratory experiments, but also for field studies of gas exchange of submerged plants. 相似文献
1000.
Hayes JE Wallace MR Knopik VS Herbstman DM Bartoshuk LM Duffy VB 《Chemical senses》2011,36(3):311-319
The 25 human bitter receptors and their respective genes (TAS2Rs) contain unusually high levels of allelic variation, which may influence response to bitter compounds in the food supply. Phenotypes based on the perceived bitterness of single bitter compounds were first linked to food preference over 50 years ago. The most studied phenotype is propylthiouracil bitterness, which is mediated primarily by the TAS2R38 gene and possibly others. In a laboratory-based study, we tested for associations between TAS2R variants and sensations, liking, or intake of bitter beverages among healthy adults who were primarily of European ancestry. A haploblock across TAS2R3, TAS2R4, and TAS2R5 explained some variability in the bitterness of espresso coffee. For grapefruit juice, variation at a TAS2R19 single nucleotide polymorphism (SNP) was associated with increased bitterness and decreased liking. An association between a TAS2R16 SNP and alcohol intake was identified, and the putative TAS2R38-alcohol relationship was confirmed, although these polymorphisms did not explain sensory or hedonic responses to sampled scotch whisky. In summary, TAS2R polymorphisms appear to influence the sensations, liking, or intake of common and nutritionally significant beverages. Studying perceptual and behavioral differences in vivo using real foods and beverages may potentially identify polymorphisms related to dietary behavior even in the absence of known ligands. 相似文献