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1.
Mohsen A. Jafari 《Flexible Services and Manufacturing Journal》1989,2(1):63-86
We consider a flexible manufacturing system with a number of workstations, a single material transporter, and a common storage space of finite capacity. The material handling delay times are explicitly considered in the model and assumed to follow a two-stage Coxian distribution. The material processing times on a workstation also have a two-stage Coxian distribution. The routing of parts within the system follows a Markov chain. An approximate performance model is developed and the results are compared with the exact or simulation results. We also investigate how this performance model compares to a simulation with deterministic routing and processing times. Finally, we study the effect, on the performance measures, of ignoring the material transporter or of modeling the transporter as a central server with aggregation of routing information. 相似文献
2.
Cleavage of the HIV replication primer tRNALys,3 in human cells expressing bacterial anticodon nuclease.
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Anticodon nuclease is a bacterial restriction enzyme directed against tRNA(Lys). We report that anticodon nuclease also cleaves mammalian tRNA(Lys) molecules, with preference and site specificity shown towards the natural substrate. Expression of the anticodon nuclease core polypeptide PrrC in HeLa cells from a recombinant vaccinia virus elicited cleavage of intracellular tRNA(Lys),3. The data justify an inquiry into the possible application of anticodon nuclease as an inhibitor of tRNA(Lys),3-primed HIV replication. They also indicate that the anticodon region of tRNA(Lys) is a substrate recognition site and suggest that PrrC harbors the enzymatic activity. 相似文献
3.
Physiological implications of K accumulation in heart muscle 总被引:1,自引:0,他引:1
M Morad 《Federation proceedings》1980,39(5):1533-1539
K+-selective microelectrodes in conjugation with the voltage clamp technique were used to examine the voltage and time dependence of K+ efflux and accumulation in cardiac muscle. K+ efflux per action potential is about 10 to 30 pmoles/cm2 per sec. Accumulation of K+ in the paracellular space plays an important role in regulation of action potential duration, so that the [K+]o prior to generation of an action potential determines the duration of following action potential. This regulation is brought about by the shift of inward rectifying K+ current along the voltage axis, so at higher [K+]o there is more outward current at plateau potentials. Monitoring [K+]o after a period of rapid beating provides quantitative data regarding Na-pump activity. The data suggest the Na-pump is electrogenic, making it difficult to assess the extent of K+ accumulation from the measurements of resting potential alone. These studies indicate that changes in [K+]o not only reflect outward membrane currents and Na-pump activity, but also play an important physiological regulatory role in determining the duration of the action potential. 相似文献
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5.
Razieh Jafari Hajati Najmeh Ahmadian Chashmi 《Preparative biochemistry & biotechnology》2013,43(10):1010-1019
AbstractBetulin (B) and betulinic acid (BA) are two triterpenoids with a wide range of biological and medicinal activities in different organs of Betula pendula. This research aimed to increase the accumulation of B and BA in the hairy root culture of B. pendula by seven biotic and abiotic elicitors. Hairy root was induced in the stem’s inner bark of B. pendula using the C58C1 strain in the WPM (Woody Plant Medium). The effects of different concentrations of elicitors and different time of root harvest in hairy root culture of B. pendula showed that highest level of growth index (GI), B, and BA was acquired in treated hairy roots with chitosan (CTS), chlorocholine chloride (CCC) and chitosan nano-fiber (CTS NF). Highest GI of B. pendula hairy roots was 13 that was obtained in the roots treated with CTS 150?mg l?1 on the 8th day. The highest content of BA was 1.3?mg g?1 DW after treatment with 1?mg l?1CCC on the 4th and 6th days and 200?mg l?1CTS NF on the 10th day. The highest B content (0.94?mg g?1DW) was obtained in the treated hairy root by 2?mg l?1 CCC after 4 and 6?days. 相似文献
6.
Samy A.F. Morad Jonathan C. Levin Su-Fern Tan Todd E. Fox David J. Feith Myles C. Cabot 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2013,1831(12):1657-1664
Acid ceramidase (AC), EC 3.5.1.23, a lysosomal enzyme, catalyzes the hydrolysis of ceramide to constituent sphingoid base, sphingosine, and fatty acid. Because AC regulates the levels of pro-apoptotic ceramide and mitogenic sphingosine-1-phosphate, it is considered an apt target in cancer therapy. The present study reveals, for the first time, that the prominent antiestrogen, tamoxifen, is a pan-effective AC inhibitor in the low, single digit micromolar range, as demonstrated in a wide spectrum of cancer cell types, prostate, pancreatic, colorectal, and breast. Prostate cancer cells were chosen for the detailed investigations. Treatment of intact PC-3 cells with tamoxifen produced time- and dose-dependent inhibition of AC activity. Tamoxifen did not impact cell viability nor did it inhibit AC activity in cell-free assays. In pursuit of mechanism of action, we demonstrate that tamoxifen induced time-, as early as 5 min, and dose-dependent, as low as 5 μM, increases in lysosomal membrane permeability (LMP), and time- and dose-dependent downregulation of AC protein expression. Assessing various protease inhibitors revealed that a cathepsin B inhibitor blocked tamoxifen-elicited downregulation of AC protein; however, this action failed to restore AC activity unless assayed in a cell-free system at pH 4.5. In addition, pretreatment with tamoxifen inhibited PC-3 cell migration. Toremifene, an antiestrogen structurally similar to tamoxifen, was also a potent inhibitor of AC activity. This study reveals a new, off-target action of tamoxifen that may be of benefit to enhance anticancer therapies that either incorporate ceramide or target ceramide metabolism. 相似文献
7.
8.
Mohieddin Jafari Mehdi Sadeghi Mehdi Mirzaie Sayed-Amir Marashi Mostafa Rezaei-Tavirani 《Mitochondrion》2013,13(6):668-675
Advances in organelle interactomics have led to new insights into organelle functions. In this study, we considered the common mitochondrial PIN of four evolutionarily distant eukaryotic species, namely Homo sapiens, Mus musculus, Drosophila melanogaster and Caenorhabditis elegans. By comparative interactomics analysis of mitochondrial PINs in these organisms, five conserved modules were identified. Modules comprise the main mitochondrial tasks, including proteins involved in translation process, mitochondrial import inner membrane proteins, TCA cycle enzymes, mitochondrial electron transport chain, and metabolic enzymes. Furthermore, we reemphasize that subgraphs of network, i.e., motifs and themes, may represent evolutionarily conserved topological units which are biologically significant. 相似文献
9.
Yalda Jafari Rosanna W. Peeling Sushmita Shivkumar Christiane Claessens Lawrence Joseph Nitika Pant Pai 《PloS one》2013,8(2)
Background
Rapid and point-of-care (POC) tests for syphilis are an invaluable screening tool, yet inadequate evaluation of their diagnostic accuracy against best reference standards limits their widespread global uptake. To fill this gap, a systematic review and meta-analysis was conducted to evaluate the sensitivity and specificity of rapid and POC tests in blood and serum samples against Treponema pallidum (TP) specific reference standards.Methods
Five electronic databases (1980–2012) were searched, data was extracted from 33 articles, and Bayesian hierarchical models were fit.Results
In serum samples, against a TP specific reference standard point estimates with 95% credible intervals (CrI) for the sensitivities of popular tests were: i) Determine, 90.04% (80.45, 95.21), ii) SD Bioline, 87.06% (75.67, 94.50), iii) VisiTect, 85.13% (72.83, 92.57), and iv) Syphicheck, 74.48% (56.85, 88.44), while specificities were: i) Syphicheck, 99.14% (96.37, 100), ii) Visitect, 96.45% (91.92, 99.29), iii) SD Bioline, 95.85% (89.89, 99.53), and iv) Determine, 94.15% (89.26, 97.66). In whole blood samples, sensitivities were: i) Determine, 86.32% (77.26, 91.70), ii) SD Bioline, 84.50% (78.81, 92.61), iii) Syphicheck, 74.47% (63.94, 82.13), and iv) VisiTect, 74.26% (53.62, 83.68), while specificities were: i) Syphicheck, 99.58% (98.91, 99.96), ii) VisiTect, 99.43% (98.22, 99.98), iii) SD Bioline, 97.95%(92.54, 99.33), and iv) Determine, 95.85% (92.42, 97.74).Conclusions
Rapid and POC treponemal tests reported sensitivity and specificity estimates comparable to laboratory-based treponemal tests. In resource limited settings, where access to screening is limited and where risk of patients lost to follow up is high, the introduction of these tests has already been shown to improve access to screening and treatment to prevent stillbirths and neonatal mortality due to congenital syphilis. Based on the evidence, it is concluded that rapid and POC tests are useful in resource limited settings with poor access to laboratories or screening for syphilis. 相似文献10.
Shahabzadeh Zeinab Darvishzadeh Reza Mohammadi Reza Jafari Morad 《Plant Molecular Biology Reporter》2020,38(2):175-186
Plant Molecular Biology Reporter - Fifty tall fescue (Festuca arundinacea Schreb.) half-sib families were screened under salinity stress during germination stage, and five tolerant and five... 相似文献