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1.
Characterization of cross-bridge elasticity and kinetics of cross-bridge cycling during force development in single smooth muscle cells 总被引:4,自引:2,他引:2
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Force development in smooth muscle, as in skeletal muscle, is believed to reflect recruitment of force-generating myosin cross-bridges. However, little is known about the events underlying cross-bridge recruitment as the muscle cell approaches peak isometric force and then enters a period of tension maintenance. In the present studies on single smooth muscle cells isolated from the toad (Bufo marinus) stomach muscularis, active muscle stiffness, calculated from the force response to small sinusoidal length changes (0.5% cell length, 250 Hz), was utilized to estimate the relative number of attached cross-bridges. By comparing stiffness during initial force development to stiffness during force redevelopment immediately after a quick release imposed at peak force, we propose that the instantaneous active stiffness of the cell reflects both a linearly elastic cross-bridge element having 1.5 times the compliance of the cross-bridge in frog skeletal muscle and a series elastic component having an exponential length-force relationship. At the onset of force development, the ratio of stiffness to force was 2.5 times greater than at peak isometric force. These data suggest that, upon activation, cross-bridges attach in at least two states (i.e., low-force-producing and high-force-producing) and redistribute to a steady state distribution at peak isometric force. The possibility that the cross-bridge cycling rate was modulated with time was also investigated by analyzing the time course of tension recovery to small, rapid step length changes (0.5% cell length in 2.5 ms) imposed during initial force development, at peak force, and after 15 s of tension maintenance. The rate of tension recovery slowed continuously throughout force development following activation and slowed further as force was maintained. Our results suggest that the kinetics of force production in smooth muscle may involve a redistribution of cross-bridge populations between two attached states and that the average cycling rate of these cross-bridges becomes slower with time during contraction. 相似文献
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A K Akatov F S Fluer G L Ratgauz I V Kushko 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1986,(10):15-20
The method for obtaining the preparation of toxic shock exotoxin (TSE) has been developed. This method comprises the following operations: the sorption of the toxin from the culture fluid on Amberlite CG-50, elution, dialysis, gel chromatography in a column with biogel P-2, isoelectric focusing, and gel chromatography in a column with Sephadex G-75. TSE is a relatively thermostable protein with a molecular weight of 24,000. Its isoelectric point is 7.2. Monospecific antiserum to TSE with precipitating antibody titer equal to 1:16, identical to the reference serum (M. S. Bergdoll), has been prepared. This antiserum has shown no cross reactions with the homogeneous preparations of staphylococcal enterotoxins. 相似文献
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Jamil M Neto Marina GM Viturino Galina Ananina Flvia F Bajano Sueli M da S Costa Alicia B Roque Gessica FS Borges Raissa Franchi Priscila HH Rim Flvio M Medina Fernando F Costa Mnica B de Melo Jos PC de Vasconcellos 《Experimental biology and medicine (Maywood, N.J.)》2021,246(21):2290
This study aimed to investigate the association among genetic variants of the complement pathway CFB R32Q (rs641153), C3 R102G (rs2230199), and CFH (rs1410996) with age-related macular degeneration (AMD) in a sample of the Brazilian population. In a case-control study, 484 AMD patients were classified according to the clinical age-related maculopathy grading system (CARMS) and compared to 479 unrelated controls. The genetic variants rs1410996 of complement H (CFH), rs641153 of complement factor B (CFB), and rs2230199 of complement 3 (C3) were evaluated through polymerase chain reaction (PCR) and direct sequencing. The associations between single nucleotide polymorphisms (SNPs) and AMD, adjusted by age, were assessed by using logistic regression models. A statistically significant association was observed between AMD risk and rs2230199 variant with an OR of 2.01 (P = 0.0002) for CG individuals compared to CC individuals. Regarding the comparison of advanced AMD versus the control group, the OR was 2.12 (P = 0.0036) for GG versus AA genotypes for rs1410996 variant. Similarly, the OR for rs2230199 polymorphism was 2.3034 (P = 5.47e-05) when comparing CG individuals to CC carriers. In contrast, the rs641153 variant showed a significant protective effect against advanced AMD for GA versus GG genotype (OR = 0.4406; P = 0.0019). When comparing wet AMD versus controls, a significant association was detected for rs1410996 variant (OR = 2.16; P = 0.0039) comparing carriers of the homozygous GG versus AA genotype, as well as in the comparisons of GG (OR = 3.0713; P = 0.0046) and CG genotypes (OR = 2.2249; P = 0.0002) versus CC genotype for rs2230199 variant, respectively. The rs641153 variant granted a significant protective effect against wet AMD for GA versus GG genotypes (OR = 0.4601; P = 0.0044). Our study confirmed the risk association between rs2230199 and rs1410996 variants and AMD, and the protective role against AMD for rs641153 variant. 相似文献
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Claudia T Guimaraes Christiano C Simoes Maria Marta Pastina Lyza G Maron Jurandir V Magalhaes Renato CC Vasconcellos Lauro JM Guimaraes Ubiraci GP Lana Carlos FS Tinoco Roberto W Noda Silvia N Jardim-Belicuas Leon V Kochian Vera MC Alves Sidney N Parentoni 《BMC genomics》2014,15(1)
Background
Aluminum (Al) toxicity is an important limitation to food security in tropical and subtropical regions. High Al saturation on acid soils limits root development, reducing water and nutrient uptake. In addition to naturally occurring acid soils, agricultural practices may decrease soil pH, leading to yield losses due to Al toxicity. Elucidating the genetic and molecular mechanisms underlying maize Al tolerance is expected to accelerate the development of Al-tolerant cultivars.Results
Five genomic regions were significantly associated with Al tolerance, using 54,455 SNP markers in a recombinant inbred line population derived from Cateto Al237. Candidate genes co-localized with Al tolerance QTLs were further investigated. Near-isogenic lines (NILs) developed for ZmMATE2 were as Al-sensitive as the recurrent line, indicating that this candidate gene was not responsible for the Al tolerance QTL on chromosome 5, qALT5. However, ZmNrat1, a maize homolog to OsNrat1, which encodes an Al3+ specific transporter previously implicated in rice Al tolerance, was mapped at ~40 Mbp from qALT5. We demonstrate for the first time that ZmNrat1 is preferentially expressed in maize root tips and is up-regulated by Al, similarly to OsNrat1 in rice, suggesting a role of this gene in maize Al tolerance. The strongest-effect QTL was mapped on chromosome 6 (qALT6), within a 0.5 Mbp region where three copies of the Al tolerance gene, ZmMATE1, were found in tandem configuration. qALT6 was shown to increase Al tolerance in maize; the qALT6-NILs carrying three copies of ZmMATE1 exhibited a two-fold increase in Al tolerance, and higher expression of ZmMATE1 compared to the Al sensitive recurrent parent. Interestingly, a new source of Al tolerance via ZmMATE1 was identified in a Brazilian elite line that showed high expression of ZmMATE1 but carries a single copy of ZmMATE1.Conclusions
High ZmMATE1 expression, controlled either by three copies of the target gene or by an unknown molecular mechanism, is responsible for Al tolerance mediated by qALT6. As Al tolerant alleles at qALT6 are rare in maize, marker-assisted introgression of this QTL is an important strategy to improve maize adaptation to acid soils worldwide.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-153) contains supplementary material, which is available to authorized users. 相似文献6.
Use of the Aggregate-Hemagglutination Technique for Determining Exo-Enterotoxin of Bacillus cereus 总被引:2,自引:0,他引:2
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The possibility of using the aggregate-hemagglutination technique for detection of Bacillus cereus exo-enterotoxin in foodstuffs and culture media is shown. A 0.004-μg quantity of enterotoxin per ml can be detected by this method. 相似文献
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Background
Hyperplasia of usual type (HUT) is a common proliferative lesion associated with a slight elevated risk for subsequent development of breast cancer. Cell cycle-related proteins would be helpful to determine the putative role of these markers in the process of mammary carcinogenesis. The aim of this study was to analyze the expression of cell cycle related proteins in HUT of breast specimens of patients with and without breast cancer, and compare this expression with areas of invasive carcinomas. 相似文献9.
Fluer FS Prokhorov VIa Vesnina AF Akatov AK 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》2002,(6):65-68
An enzyme immunoassay (EIA) system for detection of staphylococcal enterotoxin, type C, has been developed. The sensitivity of the system is 1 ng/ml. The optimum EIA parameters have been worked out. The absence of false positive results with heterologous toxins confirms the specificity of the assay system. The possibility of the detection of staphylococcal enterotoxin, type C, in staphylococci isolated from different sources has been shown. 相似文献
10.
Fluer FS Prokhorov VIa Bondarenko VM Dmitrienko OA Lashenkova NN Men'shikova ED Vertiev IuV 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》2005,(5):3-6
The occurrence of Staphylococcus aureus strains producing enterotoxins of types SEA and SEB, which isolated from patients of different profile and caused the infectious process accompanied by pronounced intoxication without vomiting and enteric disturbances, was determined by means of the indirect hemagglutination test. The collection included 28 strains isolated in sepsis, 38 strains isolated in pneumonia, 57 strains isolated from patients with burns and 23, from the hands and nasopharynx of the medical staff. Among the staphylococcal strains isolated in sepsis, 75.6% synthesized SEA and 5.4%, SEB. The occurrence of SEA- and SEB-positive strains isolated in pneumonia was, respectively, 42.1% and 2.6%. From patients with burns SEA-positive staphylococci were mainly isolated (92.9%). Only 3% of the cultures isolated in wound infections produced SEA. From the medical staff, 13.4% of SEA-positive strains and 17.3% of SEB-positive strains were isolated. The data obtained from this study indicate the expediency of the determination of the enterotoxigenic properties of S. aureus clinical isolates in medical institutions for prophylactic measures with a view to the prevention of the spread of pathogenic clones. 相似文献