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71.
Role of the reticulum in the stability and shape of the isolated human erythrocyte membrane 总被引:12,自引:7,他引:5 下载免费PDF全文
In order to examine the widely held hypothesis that the reticulum of proteins which covers the cytoplamsic surface of the human erythrocyte membrane controls cell stability and shape, we have assessed some of its properties. The reticulum, freed of the bilayer by extraction with Triton X-100, was found to be mechanically stable at physiological ionic strength but physically unstable at low ionic strength. The reticulum broke down after a characteristic lag period which decreased 500-fold between 0 degrees and 37 degrees C. The release of polypeptide band 4.1 from the reticulum preceded that of spectrin and actin, suggesting that band 4.1 might stabilize the ensemble but is not essential to its integrity. The time-course of breakdown was similar for ghosts, the reticulum inside of ghosts, and the isolated reticulum. However, at very low ionic strength, the reticulum was less stable within the ghost than when free; at higher ionic strength, the reverse was true. Over a wide range of conditions the membrane broke down to vesicles just as the reticulum disintegrated, presumably because the bilayer was mechanically stabilized by this network. The volume of both ghosts and naked reticula varied inversely and reversibly with ionic strength. The volume of the naked reticulum varied far more widely than the ghost, suggesting that its deformation was normally limited by the less extensible bilayer. The contour of the isolated reticulum was discoid and often dimpled or indented, as visualized in the fluorescence microscope after labeling of the ghosts with fluoroscein isothiocyanate. Reticula derived from ghosts which had lost the ability to crenate in isotonic saline were shriveled, even though the bilayer was smooth and expanded. Conversly, ghosts crenated by dinitrophenol yielded smooth, expanded reticula. We conclude that the reticulum is a durable, flexible, and elastic network which assumes and stabilizes the contour of the membrane but is not responsible for its crenation. 相似文献
72.
73.
Localization of the forskolin photolabelling site within the monosaccharide transporter of human erythrocytes. 总被引:1,自引:0,他引:1
Chemical and proteolytic digestion of intact erythrocyte glucose transporter as well as purified transporter protein has been used to localize the derivatization site for the photoaffinity agent 3-[125I]iodo-4-azido-phenethylamino-7-O-succinyldeacetylforskol in [( 125I]IAPS-forskolin). Comparison of the partial amino acid sequence of the labelled 18 kDa tryptic fragment with the known amino acid sequence for the HepG2 glucose transporter confirmed that the binding site for IAPS-forskolin is between the amino acid residues Glu254 and Tyr456. Digestion of intact glucose transporter with Pronase suggests that this site is within the membrane bilayer. Digestion of labelled transporter with CNBr generated a major radiolabelled fragment of Mr approximately 5800 putatively identified as residues 365-420. Isoelectric focusing of Staphylococcus aureus V8 proteinase-treated purified labelled tryptic fragment identified two peptides which likely correspond to amino acid residues 360-380 and 381-393. The common region for these radiolabelled peptides is the tenth putative transmembrane helix of the erythrocyte glucose transporter, comprising amino acid residues 369-389. Additional support for this conclusion comes from studies in which [125I]APS-forskolin was photoincorporated into the L-arabinose/H(+)-transport protein of Escherichia coli. Labelling of this transport protein was protected by both cytochalasin B and D-glucose. The region of the erythrocyte glucose transporter thought to be derivatized with IAPS-forskolin contains a tryptophan residue (Trp388) that is conserved in the sequence of the E. coli arabinose-transport protein. 相似文献
74.
75.
Brigida TL Lucena Billy M dos Santos João LS Moreira Ana Paula B Moreira Alvaro C Nunes Vasco Azevedo Anderson Miyoshi Fabiano L Thompson Marcos Antonio de MoraisJunior 《BMC microbiology》2010,10(1):298
Background
Bacteria may compete with yeast for nutrients during bioethanol production process, potentially causing economic losses. This is the first study aiming at the quantification and identification of Lactic Acid Bacteria (LAB) present in the bioethanol industrial processes in different distilleries of Brazil. 相似文献76.
Background
Shoulder pain is a common complication of a stroke which can impede participation in rehabilitation programs and has been associated with poorer outcomes. The evidence base for current medical and therapeutic management options of hemiplegic shoulder pain is limited. This study will evaluate the use of suprascapular nerve block injection as part of an interdisciplinary approach to the treatment of shoulder pain following stroke. The technique has previously been proven safe and effective in the treatment of shoulder pain associated with rheumatoid arthritis and degenerative shoulder conditions but its usefulness in a stroke population is unclear. 相似文献77.
LaPara TM Cole AC Shanahan JW Semmens MJ 《Journal of industrial microbiology & biotechnology》2006,33(4):315-323
The purpose of this study was to examine the effects of different nutrient (carbon, nitrogen, oxygen) concentrations on the
microbial activity and community structure in membrane-aerated biofilms (MABs). MABs were grown under well-defined conditions
of fluid flow, substrate concentration, and membrane oxygen partial pressure. Biofilms were then removed and thin-sliced using
a cryostat/microtome parallel to the membrane. Individual slices were analyzed for changes with depth in biomass density,
respiratory activity, and the population densities of ammonia-oxidizing and denitrifying bacteria populations. Oxygen-sensing
microelectrodes were used to determine the depth of oxygen penetration into each biofilm. Our results demonstrated that ammonia-oxidizing
bacteria grow near the membrane, while denitrifying bacteria grow a substantial distance from the membrane. However, nitrifying
and denitrifying bacteria did not grow simultaneously when organic concentrations became too high or ammonia concentrations
became too low. In conclusion, membrane-aerated biofilms exhibit substantial stratification with respect to community structure
and activity. A fundamental understanding of the factors that control this stratification will help optimize the performance
of full-scale membrane-aerated biofilm reactors for wastewater treatment. 相似文献
78.
Nguyen Thuy Duong Glenn E. Morris Le Thanh Lam Qiuping Zhang Caroline A. Sewry Catherine M. Shanahan Ian Holt 《PloS one》2014,9(4)
Nesprin-1-giant and nesprin-2-giant regulate nuclear positioning by the interaction of their C-terminal KASH domains with nuclear membrane SUN proteins and their N-terminal calponin-homology domains with cytoskeletal actin. A number of short isoforms lacking the actin-binding domains are produced by internal promotion. We have evaluated the significance of these shorter isoforms using quantitative RT-PCR and western blotting with site-specific monoclonal antibodies. Within a complete map of nesprin isoforms, we describe two novel nesprin-2 epsilon isoforms for the first time. Epsilon isoforms are similar in size and structure to nesprin-1-alpha. Expression of nesprin isoforms was highly tissue-dependent. Nesprin-2-epsilon-1 was found in early embryonic cells, while nesprin-2-epsilon-2 was present in heart and other adult tissues, but not skeletal muscle. Some cell lines lack shorter isoforms and express only one of the two nesprin genes, suggesting that either of the giant nesprins is sufficient for basic cell functions. For the first time, localisation of endogenous nesprin away from the nuclear membrane was shown in cells where removal of the KASH domain by alternative splicing occurs. By distinguishing between degradation products and true isoforms on western blots, it was found that previously-described beta and gamma isoforms are expressed either at only low levels or with a limited tissue distribution. Two of the shortest alpha isoforms, nesprin-1-alpha-2 and nesprin-2-alpha-1, were found almost exclusively in cardiac and skeletal muscle and a highly conserved and alternatively-spliced exon, available in both nesprin genes, was always included in these tissues. These “muscle-specific” isoforms are thought to form a complex with emerin and lamin A/C at the inner nuclear membrane and mutations in all three proteins cause Emery-Dreifuss muscular dystrophy and/or inherited dilated cardiomyopathy, disorders in which only skeletal muscle and/or heart are affected. 相似文献
79.
Hudacek DL Kuruvilla S Kim N Semrau K Thea D Qazi S Pleasant A Shanahan J 《PloS one》2011,6(6):e20438
Background
Pneumonia, diarrhea and measles are the leading causes of death in children worldwide, but have a disproportionately low share of international funding and media attention [1]–[3]. In comparison, AIDS, tuberculosis and malaria - diseases that also significantly affect children – receive considerably more funding and have relatively high media coverage. This study investigates the potential relationship between media agenda setting and funding levels in the context of the actual burden of disease.Methods
The news databases Lexis Nexis, Factiva, and Google News Archive were searched for the diseases AIDS, TB and Malaria and for lower funded pediatric diseases: childhood pneumonia, diarrhea, and measles. A sample of news articles across geographic regions was also analyzed using a qualitative narrative frame analysis of how the media stories were told.Results
There were significantly more articles addressing the Global Fund diseases compared to the lower funded pediatric diseases between 1981 and 2008 (1,344,150 versus 291,865 articles). There were also notable differences in the framing of media narratives: 1) There was a high proportion of articles with the primary purpose of raising awareness for AIDS, TB and malaria (46.2%) compared with only 17.9% of the pediatric disease articles. 2) Nearly two-thirds (61.5%) of the AIDS, tuberculosis and malaria articles used a human rights, legal or social justice frame, compared with 46.2% for the lower funded pediatric disease articles, which primarily used an ethical or moral frame.Conclusion
This study demonstrates that lower funded pediatric diseases are presented differently in the media, both quantitatively and qualitatively, than higher funded, higher profile diseases. 相似文献80.