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排序方式: 共有379条查询结果,搜索用时 781 毫秒
61.
62.
Arnon D. Jurberg Tiana Gonçalves Tatiane A. Costa Ana Carolina A. de Mattos Bernardo M. Pascarelli Pedro Paulo A. de Manso Marcelo Ribeiro-Alves Marcelo Pelajo-Machado José M. Peralta Paulo Marcos Z. Coelho Henrique L. Lenzi 《Development genes and evolution》2009,219(5):219-234
Schistosomiasis is a water-borne parasitic illness caused by neoophoran trematodes of the genus Schistosoma. Using classical histological techniques and whole-mount preparations, the present work describes the embryonic development
of Schistosoma mansoni eggs in the murine host and compares it with eggs maintained under in vitro conditions. Two pre-embryonic stages occur inside
the female worm: the prezygotic stage is characterized by the release of mature oocytes from the female ovary until its fertilization.
The zygotic stage encompasses the migration of the zygote through the ootype, where the eggshell is formed, to the uterus.
Fully formed eggs are laid still undeveloped, without having suffered any cleavage. In the outside environment, eight embryonic
stages can be defined: stage 1 refers to early cleavages and the beginning of yolk fusion. Stage 2 represents late cleavage,
with the formation of a stereoblastula and the onset of outer envelope differentiation. Stage 3 is defined by the elongation
of the embryonic primordium and the onset of inner envelope formation. At stage 4, the first organ primordia arise. During
stages 5 to 7, tissue and organ differentiation occurs (neural mass, epidermis, terebratorium, musculature, and miracidial
glands). Stage 7 is characterized by the nuclear condensation of neurons of the central neural mass. Stage 8 refers to the
fully formed larva, presenting muscular contraction, cilia, and flame-cell beating. This staging system was compared to a
previous classification and could underlie further studies on egg histoproteomics (morphological localizome). The differentiation
of embryonic structures and their probable roles in granulomatogenesis are discussed herein.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
63.
CaGLK2 regulates natural variation of chlorophyll content and fruit color in pepper fruit 总被引:1,自引:0,他引:1
64.
Light SH Minasov G Shuvalova L Peterson SN Caffrey M Anderson WF Lavie A 《Biochemistry》2011,50(12):2357-2363
Dehydroquinate dehydratase (DHQD) catalyzes the third step in the biosynthetic shikimate pathway. We present three crystal structures of the Salmonella enterica type I DHQD that address the functionality of a surface loop that is observed to close over the active site following substrate binding. Two wild-type structures with differing loop conformations and kinetic and structural studies of a mutant provide evidence of both direct and indirect mechanisms of involvement of the loop in substrate binding. In addition to allowing amino acid side chains to establish a direct interaction with the substrate, closure of the loop necessitates a conformational change of a key active site arginine, which in turn positions the substrate productively. The absence of DHQD in humans and its essentiality in many pathogenic bacteria make the enzyme a target for the development of nontoxic antimicrobials. The structures and ligand binding insights presented here may inform the design of novel type I DHQD inhibiting molecules. 相似文献
65.
McCullough BR Grintsevich EE Chen CK Kang H Hutchison AL Henn A Cao W Suarez C Martiel JL Blanchoin L Reisler E De La Cruz EM 《Biophysical journal》2011,(1):584-159
The actin regulatory protein, cofilin, increases the bending and twisting elasticity of actin filaments and severs them. It has been proposed that filaments partially decorated with cofilin accumulate stress from thermally driven shape fluctuations at bare (stiff) and decorated (compliant) boundaries, thereby promoting severing. This mechanics-based severing model predicts that changes in actin filament compliance due to cofilin binding affect severing activity. Here, we test this prediction by evaluating how the severing activities of vertebrate and yeast cofilactin scale with the flexural rigidities determined from analysis of shape fluctuations. Yeast actin filaments are more compliant in bending than vertebrate actin filaments. Severing activities of cofilactin isoforms correlate with changes in filament flexibility. Vertebrate cofilin binds but does not increase the yeast actin filament flexibility, and does not sever them. Imaging of filament thermal fluctuations reveals that severing events are associated with local bending and fragmentation when deformations attain a critical angle. The critical severing angle at boundaries between bare and cofilin-decorated segments is smaller than in bare or fully decorated filaments. These measurements support a cofilin-severing mechanism in which mechanical asymmetry promotes local stress accumulation and fragmentation at boundaries of bare and cofilin-decorated segments, analogous to failure of some nonprotein materials. 相似文献
66.
Macdonald TE Helma CH Shou Y Valdez YE Ticknor LO Foley BT Davis SW Hannett GE Kelly-Cirino CD Barash JR Arnon SS Lindström M Korkeala H Smith LA Smith TJ Hill KK 《Applied and environmental microbiology》2011,77(24):8625-8634
A total of 41 Clostridium botulinum serotype E strains from different geographic regions, including Canada, Denmark, Finland, France, Greenland, Japan, and the United States, were compared by multilocus sequence typing (MLST), amplified fragment length polymorphism (AFLP) analysis, variable-number tandem-repeat (VNTR) analysis, and botulinum neurotoxin (bont) E gene sequencing. The strains, representing environmental, food-borne, and infant botulism samples collected from 1932 to 2007, were analyzed to compare serotype E strains from different geographic regions and types of botulism and to determine whether each of the strains contained the transposon-associated recombinase rarA, involved with bont/E insertion. MLST examination using 15 genes clustered the strains into several clades, with most members within a cluster sharing the same BoNT/E subtype (BoNT/E1, E2, E3, or E6). Sequencing of the bont/E gene identified two new variants (E7, E8) that showed regions of recombination with other E subtypes. The AFLP dendrogram clustered the 41 strains similarly to the MLST dendrogram. Strains that could not be differentiated by AFLP, MLST, or bont gene sequencing were further examined using three VNTR regions. Both intact and split rarA genes were amplified by PCR in each of the strains, and their identities were confirmed in 11 strains by amplicon sequencing. The findings suggest that (i) the C. botulinum serotype E strains result from the targeted insertion of the bont/E gene into genetically conserved bacteria and (ii) recombination events (not random mutations) within bont/E result in toxin variants or subtypes within strains. 相似文献
67.
Effects of exogenous apo E-3 and of cholesterol-enriched meals on the cellular metabolism of human chylomicrons and their remnants 总被引:1,自引:0,他引:1
The effects of exogenous apo E-3 and of cholesterol-enriched meals on the binding, cell association and proteolytic degradation of human chylomicrons and their remnants were determined in cultured human skin fibroblasts. Chylomicrons were prepared from plasma of normolipemic humans 4 h after a fat meal with normal or high cholesterol content. Remnants were obtained after incubation of chylomicrons with lipoprotein lipase in vitro. Cellular metabolism of chylomicrons was minimal, less than 10% that of LDL. Exogenous apo E-2 enhanced chylomicron metabolism by 3-4-fold. The cellular metabolism of remnants was 2.5-3.5-fold higher as compared to intact chylomicrons but their response to exogenous apo E-3 was considerably lower. The cellular metabolism of chylomicrons and chylomicron remnants obtained from subjects eating cholesterol-enriched fat meal was the highest either without or with added exogenous apo E-3. Yet, even in the preparation that exhibits the highest metabolic activity (apo E-3 enriched remnants from cholesterol-enriched meals) the absolute proteolytic degradation was about two-thirds that of LDL. We conclude that although LDL-receptors take up and degrade chylomicron remnants, the rate of catabolism of remnants by this route can not explain the rapid and complete remnant removal process as observed in vivo. 相似文献
68.
Gilad Twig Estela Derazne Ziona Haklai Nehama Goldberger Arnon Afek Hertzel C. Gerstein Jeremy D. Kark Tali Cukierman-Yaffe 《Cardiovascular diabetology》2018,17(1):154
Background
Epidemiological studies have demonstrated a relationship between cognitive function in youth and the future risk of death. Less is known regarding the relationship with diabetes related death. This study assessed the relationship between cognitive function in late adolescence and the risk for diabetes, cardiovascular- (CVD) and all-cause mortality in adulthood.Methods
This retrospective study linked data from 2,277,188 16–19 year olds who had general intelligence tests (GIT) conducted during pre-military recruitment assessment with cause of death as coded by the Israel Central Bureau of Statistics. The associations between cognitive function and cause-specific mortality were assessed using Cox models.Results
There were 31,268 deaths that were recorded during 41,916,603 person-years of follow-up, with a median follow-up of 19.2 (IQR 10.7, 29.5) years. 3068, 1443, 514 and 457 deaths were attributed to CVD, CHD, stroke, and diabetes, respectively. Individuals in the lowest GIT vs. highest GIT quintiles in unadjusted models had the highest risk for all-cause mortality (HR 1.84, 95% CI 1.78, 1.91), total CVD (HR 3.32, 95% CI 2.93, 3.75), CHD (HR 3.49 95% CI 2.92, 4.18), stroke (HR 3.96 95% CI 2.85, 5.5) and diabetes-related (HR 6.96 95% CI 4.68, 10.36) mortality. These HRs were attenuated following adjustment for age, sex, birth year, body-mass index, residential socioeconomic status, education and country of origin for all-cause (HR 1.23, 95% CI 1.17, 1.28), CVD (HR 1.76, 95% CI 1.52, 2.04), CHD (HR 1.7 95% CI 1.37, 2.11), stroke (HR 2.03, 95% CI 1.39, 2.98) and diabetes-related (HR 3.14 95% CI 2.00, 4.94) mortality. Results persisted in a sensitivity analyses limited to participants with unimpaired health at baseline and that accounted competing risk.Conclusions
This analysis of over 2 million demonstrates a strong relationship between cognitive function at youth and the risk for diabetes, all-cause and CVD-related mortality independent of adolescent obesity.69.
Amanda M. Schalk Aleksandar Antansijevic Michael Caffrey Arnon Lavie 《The Journal of biological chemistry》2016,291(10):5088-5100
Bacterial l-asparaginases play an important role in the treatment of certain types of blood cancers. We are exploring the guinea pig l-asparaginase (gpASNase1) as a potential replacement of the immunogenic bacterial enzymes. The exact mechanism used by l-asparaginases to catalyze the hydrolysis of asparagine into aspartic acid and ammonia has been recently put into question. Earlier experimental data suggested that the reaction proceeds via a covalent intermediate using a ping-pong mechanism, whereas recent computational work advocates the direct displacement of the amine by an activated water. To shed light on this controversy, we generated gpASNase1 mutants of conserved active site residues (T19A, T116A, T19A/T116A, K188M, and Y308F) suspected to play a role in hydrolysis. Using x-ray crystallography, we determined the crystal structures of the T19A, T116A, and K188M mutants soaked in asparagine. We also characterized their steady-state kinetic properties and analyzed the conversion of asparagine to aspartate using NMR. Our structures reveal bound asparagine in the active site that has unambiguously not formed a covalent intermediate. Kinetic and NMR assays detect significant residual activity for all of the mutants. Furthermore, no burst of ammonia production was observed that would indicate covalent intermediate formation and the presence of a ping-pong mechanism. Hence, despite using a variety of techniques, we were unable to obtain experimental evidence that would support the formation of a covalent intermediate. Consequently, our observations support a direct displacement rather than a ping-pong mechanism for l-asparaginases. 相似文献
70.
Tobacco plants (Nicotiana rustica L.) pre-exposed to leaf dehydration, mineral deprivation, salination, or BO33− toxicity exhibited increased resistance to subzero temperature and to reduced oxygen in the root medium. The stressed plants all showed an elevated content of leaf abscisic acid. Upon transfer of mineral deprived and salinated plants to prestress conditions, a decline in leaf abscisic acid content to prestress levels took place together with a loss of the increased resistance to subzero temperature and to deprivation of root oxygen. Treatment with abscisic acid by direct application to the leaves or by addition to the root medium improved leaf resistance to subzero temperature and to deprivation of root oxygen. A common hormone-regulation mechanism involving abscisic acid is suggested for this phenomenon of “cross-adaptation” by which a given stress confers increased resistance to other, apparently unrelated stresses. 相似文献