排序方式: 共有283条查询结果,搜索用时 15 毫秒
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Wolf U. Blanckenhorn Paquita E. A. Hoeck Constanze Reim Yvonne Teuschl 《Evolutionary ecology》2011,25(4):875-884
Most life history traits are positively influenced by body size, while disadvantages of large size are poorly documented.
To investigate presumed intrinsic costs of large body size in yellow dung flies (Scathophaga stercoraria; Diptera: Scathophagidae), we allowed larvae from replicate lines artificially selected for small and large body size for
21 generations to compete directly with each other at 20°C (benign) and 25°C (stressful) and low and high food (dung) availability.
Greater mortality of large line flies was evident at low food independent of temperature, suggesting a cost of fast growth
and/or long development for genetically large flies during larval scramble competition under food limitation. Our results
are congruent with a previous study assessing mortality when competing within body size lines, so no additional mechanisms
affecting scramble or contest behavior of larvae need be invoked to explain the results obtained beyond the costs of longer
development and faster growth. Thus, artificial selection producing larger yellow dung flies than occur in nature revealed
some, albeit weak mortality costs of large body size that otherwise might have remained cryptic. We conclude, however, that
these costs are insufficient to explain the evolutionary limits of large body size in this species given persistently strong
fecundity and sexual selection favoring large size in both sexes. 相似文献
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Nossol C Diesing AK Walk N Faber-Zuschratter H Hartig R Post A Kluess J Rothkötter HJ Kahlert S 《Histochemistry and cell biology》2011,136(1):103-115
The specific function of the epithelium as critical barrier between the intestinal lumen and the organism’s internal microenvironment
is reflected by permanent maintenance of intercellular junctions and cellular polarity. The intestinal epithelial cells are
responsible for absorption of nutritional components, facing mechanical stress and a changing oxygen supplementation via blood
stream. Oxygen itself can regulate the barrier and the absorptive function of the epithelium. Therefore, we compared the dish
cell culture, the transwell-like membrane culture and the oxygen enriched air–liquid interface (ALI) culture. We demonstrated
strong influence of the different culture conditions on morphology and function of intestinal porcine epithelial cell lines
in vitro. ALI culture resulted in a significant increase in cell number, epithelial cell layer thickness and expression as
well as apical localisation of the microvilli-associated protein villin. Remarkable similarities regarding the morphological
parameters were observed between ALI cultures and intestinal epithelial cells in vivo. Furthermore, the functional analysis
of protein uptake and degradation by the epithelial cells demonstrated the necessity of sufficient oxygen supply as achieved
in ALI cultures. Our study is the first report providing marked evidence that optimised oxygen supply using ALI cultures directly
affects the morphological differentiation and functional properties of intestinal epithelial cells in vitro. 相似文献
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Stanca SE Csaki A Urban M Nietzsche S Biskup C Fritzsche W 《Biosensors & bioelectronics》2011,26(6):2911-2916
The investigation of the plasma membrane with intercorrelated multiparameter techniques is a prerequisite for understanding its function. Presented here, is a simultaneous electrochemical and topographic study of the cell membrane using a miniaturized amperometric enzymatic biosensor. The fabrication of this biosensor is also reported. The biosensor combines a scanning force microscopy (AFM) gold-coated cantilever and an enzymatic transducer layer of peroxidases (PODs). When these enzymes are brought in contact with the substrate, the specific redox reaction produces an electric current. The intensity of this current is detected simultaneously with the surface imaging. For sensor characterization, hydroquinone-2-carboxylic acid (HQ) is selected as an intrinsic source of H(2)O(2). HQ has been electrochemically regenerated by the reduction of antraquinone-2-carboxylic acid (AQ). The biosensor reaches the steady state value of the current intensity in 1 ± 0.2s. 相似文献
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Kubisch CH Logsdon CD 《American journal of physiology. Gastrointestinal and liver physiology》2007,292(6):G1804-G1812
Endoplasmic reticulum (ER) stress leads to the accumulation of misfolded proteins in the ER lumen and initiates the unfolded protein response (UPR). Components of the UPR are important in pancreatic development, and recent studies have indicated that the UPR is activated in the arginine model of acute pancreatitis. However, the effects of secretagogues on UPR components in the pancreas are unknown. The present study aimed to examine the effects of different types and concentrations of secretagogues on acinar cell function and specific components of the UPR. Rat pancreatic acini were stimulated with the CCK analogs CCK8 (10 pM-10 nM) or JMV-180 (10 nM-10 microM) or with bombesin (1-100 nM). Components of the UPR, including chaperone BiP expression, PKR-like ER kinase (PERK) phosphorylation, X box-binding protein 1 (XBP1) splicing, and CCAAT/enhancer binding protein homologous protein (CHOP) expression, were measured, as were effects on amylase secretion and intracellular trypsin activation. CCK8 generated a biphasic secretion dose-response curve, and high concentrations increased intracellular active trypsin levels. In contrast, JMV-180 and bombesin secretion dose-response curves were monophasic, and high concentrations did not increase intracellular trypsin activity. All three secretagogues increased BiP levels and XBP1 splicing. However, only supraphysiological levels of CCK8 associated with inhibited amylase secretion and trypsin activation stimulated PERK phosphorylation and expression of CHOP. The effects of CCK8 on UPR components were rapid, occurring within 5-20 min. In conclusion, ER stress response mechanisms appear to be involved in both pancreatic physiology and pathophysiology, and future efforts should be directed at understanding the roles of these mechanisms in the pancreas. 相似文献
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Elham Amini Jens V. Andersen Barnali Chakraborti Artem V. Diuba Tatsiana G. Dubouskaya Eric Ehrke Andiara Espindola de Freitas Guilherme Braga de Freitas Rafaella A. Gonçalves Deepali Gupta Richa Gupta Sharon R. Ha Isabel A. Hemming Minal Jaggar Emil Jakobsen Punita Kumari Navya Lakkappa Ashley P. L. Marsh Jessica Mitlöhner Yuki Ogawa Ramesh Kumar Paidi Felipe C. Ribeiro Ahmad Salamian Suraiya Saleem Sorabh Sharma Joana M. Silva Shripriya Singh Kunjbihari Sulakhiya Tesfaye Wolde Tefera Behnam Vafadari Anuradha Yadav Reiji Yamazaki Constanze I. Seidenbecher 《Journal of neurochemistry》2019,151(2):139-165
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Constanze Bickelmann James M. Morrow Jing Du Ryan K. Schott Ilke van Hazel Steve Lim Johannes Müller Belinda S. W. Chang 《Evolution; international journal of organic evolution》2015,69(11):2995-3003
The nocturnal origin of mammals is a longstanding hypothesis that is considered instrumental for the evolution of endothermy, a potential key innovation in this successful clade. This hypothesis is primarily based on indirect anatomical inference from fossils. Here, we reconstruct the evolutionary history of rhodopsin—the vertebrate visual pigment mediating the first step in phototransduction at low‐light levels—via codon‐based model tests for selection, combined with gene resurrection methods that allow for the study of ancient proteins. Rhodopsin coding sequences were reconstructed for three key nodes: Amniota, Mammalia, and Theria. When expressed in vitro, all sequences generated stable visual pigments with λMAX values similar to the well‐studied bovine rhodopsin. Retinal release rates of mammalian and therian ancestral rhodopsins, measured via fluorescence spectroscopy, were significantly slower than those of the amniote ancestor, indicating altered molecular function possibly related to nocturnality. Positive selection along the therian branch suggests adaptive evolution in rhodopsin concurrent with therian ecological diversification events during the Mesozoic that allowed for an exploration of the environment at varying light levels. 相似文献