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Chloroplast thylakoids contain three classes of glycolipids, monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol (SQDG). We have investigated the stability of large unilamellar vesicles made from egg phosphatidylcholine (EPC) and different chloroplast glycolipids during freezing to -18 degreesC, as a function of the presence of three sugars: glucose, sucrose, or trehalose. Contrary to the situation in thylakoids, where cryoprotection increases from glucose < sucrose < trehalose, liposomes containing 50% DGDG showed the opposite behavior. In fact, carboxyfluorescein leakage increased over the control values (freezing in the absence of sugar) in the presence of trehalose. This effect was not seen in vesicles made from pure EPC, or a mixture of EPC and MGDG, or EPC and SQDG. Liposomes made from mixtures of all three glycolipids, however, showed even more leakage in the presence of trehalose than liposomes containing only DGDG and EPC. Copyright 1998 Academic Press. 相似文献
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Lack of geographic variation in anonymous nuclear polymorphisms in the American oyster, Crassostrea virginica 总被引:1,自引:0,他引:1
Comparing geographic variation of noncoding nuclear DNA polymorphisms,
which presumably are neutral to natural selection, with geographic
variation of allozymes is potentially a good way to detect the effects of
selection on allozyme polymorphisms. A previous study of four anonymous
nuclear markers in the American oyster, Crassostrea virginica, found
dramatic differences in allele frequency between the Gulf of Mexico and the
Atlantic Ocean. In contrast, 14 allozyme polymorphisms were fairly uniform
in frequency between the two areas. This led to the conclusion that all of
the allozyme polymorphisms were kept uniform in frequency by balancing
selection. To test the robustness of this pattern, six additional anonymous
nuclear DNA polymorphisms were surveyed in oysters from Panacea, Fla, and
Charleston, S.C. on the Gulf and Atlantic coasts, respectively. Unlike the
previously studied DNA markers, the six DNA polymorphisms examined here
show geographic variation that is not significantly greater than that of
allozymes. The reason for the discrepancy between the two sets of DNA
polymorphisms is unclear.
相似文献
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Natural selection and the molecular clock 总被引:13,自引:1,他引:12
46.
Christie M Bartels Jessica M Saucier Carolyn T Thorpe Amy JH Kind Nancy Pandhi Karen E Hansen Maureen A Smith 《Arthritis research & therapy》2012,14(4):R166
Introduction
Diabetes mellitus is a key predictor of mortality in rheumatoid arthritis (RA) patients. Both RA and diabetes increase the risk of cardiovascular disease (CVD), yet understanding of how comorbid RA impacts the receipt of guideline-based diabetes care is limited. The purpose of this study was to examine how the presence of RA affected hemoglobin A1C (A1c) and lipid measurement in older adults with diabetes.Methods
Using a retrospective cohort approach, we identified beneficiaries ≥65 years old with diabetes from a 5% random national sample of 2004 to 2005 Medicare patients (N = 256,331), then examined whether these patients had comorbid RA and whether they received guideline recommended A1c and lipid testing in 2006. Multivariate logistic regression was used to examine the effect of RA on receiving guideline recommended testing, adjusting for baseline sociodemographics, comorbidities and health care utilization.Results
Two percent of diabetes patients had comorbid RA (N = 5,572). Diabetes patients with comorbid RA were more likely than those without RA to have baseline cardiovascular disease (such as 17% more congestive heart failure), diabetes-related complications including kidney disease (19% higher), lower extremity ulcers (77% higher) and peripheral vascular disease (32% higher). In adjusted models, diabetes patients with RA were less likely to receive recommended A1c testing (odds ratio (OR) 0.84, CI 0.80 to 0.89) than those without RA, but were slightly more likely to receive lipid testing (OR 1.08, CI 1.01 to 1.16).Conclusions
In older adults with diabetes, the presence of comorbid RA predicted lower rates of A1c testing but slightly improved lipid testing. Future research should examine strategies to improve A1c testing in patients with diabetes and RA, in light of increased CVD and microvascular risks in patients with both conditions. 相似文献47.
C. Baud H. Hodak E. Willery H. Drobecq C. Locht M. Jamin F. Jacob-Dubuisson 《Molecular microbiology》2009,74(2):315-329
Sorting of proteins destined to the surface or the extracellular milieu is mediated by specific machineries, which guide the protein substrates towards the proper route of secretion and determine the compartment in which folding occurs. In Gram-negative bacteria, the two-partner secretion (TPS) pathway is dedicated to the secretion of large proteins rich in β-helical structure. The secretion of the filamentous haemagglutinin (FHA), a 230 kDa adhesin of Bordetella pertussis , represents a model TPS system. FHA is exported by the Sec machinery and transits through the periplasm in an extended conformation. From there it is translocated across the outer membrane by its dedicated transporter FhaC to finally fold into a long β-helix at the cell surface in a progressive manner. In this work, we show that B. pertussis lacking the periplasmic chaperone/protease DegP has a strong growth defect at 37°C, and the integrity of its outer membrane is compromised. While both phenotypes are significantly aggravated by the presence of FHA, the chaperone activity of DegP markedly alleviates the periplasmic stress. In vitro , DegP binds to non-native FHA with high affinity. We propose that DegP chaperones the extended FHA polypeptide in the periplasm and is thus involved in the TPS pathway. 相似文献
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It is commonly assumed that creatine kinase (CK) activity in plasma is related to the state of an inflammatory response at 24-48 h, and also it has shown biphasic patterns after a marathon run. No information is available on CK isoenzymes after an ultra-marathon run. The purpose of the present study is to examine the CK isoenzymes after a 200 km ultra-marathon run and during the subsequent recovery. Blood samples were obtained during registration 1 2 h before the 200-km race and during the race at 100 km, 150 km and at the end of 200 km, as well as after a 24 h period of recovery. Thirty-two male ultra-distance runners participated in the study. Serum CPK showed a marked increase throughout the race and 24 h recovery period (p < 0.001). Serum CK during the race occurs mostly in the CK-MM isoform and only minutely in the CK-MB isoform and is unchanged in the CK-BB isoform. High-sensitivity C-reactive protein (hs-CRP), oestradiol, AST and ALT increased significantly from the pre-race value at 100 km and a further increase took place by the end of the 200 km run. The results of our study demonstrate a different release pattern of creatine kinase after an ultra-distance (200 km) run compared to the studies of marathon running and intense eccentric exercise, and changes in several biomarkers, indicative of muscle damage during the race, were much more pronounced during the latter half (100–200 km) of the race. However, the increases in plasma concentration of muscle enzymes may reflect not only structural damage, but also their rate of clearance. 相似文献
50.