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1.
Usually the presence of the quiescent centre in roots is demonstrated by the absence of labelled nuclei following treatment of the root with appropriate radioactive markers. By modification of the pulselabelling technique, a negative image of the quiescent center, showing more intense labelling from [3H]thymidine than the surrounding area, was obtained in regenerating root apices of Zea mays L. 相似文献
2.
Organic Flocculation: an Efficient Second-Step Concentration Method for the Detection of Viruses in Tap Water 总被引:30,自引:26,他引:4 下载免费PDF全文
A method is described for second-step concentration of viruses from water. This method, combined with an adsorption-elution method, yields a mean recovery of about 75% 相似文献
3.
Isaac Cohen Tova Glaser Arthur Veis Joyce Bruner-Lorand 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,676(2):137-147
When platelet cytoplasmic Ca2+ is increased by the ionophore A23187 in the presence of the protease inhibitor leupeptin, there is the coincident appearance of a cross-linked polymer and the partial disappearance of monomeric protein and glycoprotein units. In the absence of leupeptin only 30% of the polymer was formed. The disappearance of monomeric protein bands, as detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis, is prevented by histamine, which as a pseudodonor amine is a known inhibitor of transglutaminase-catalyzed cross-linking. [14C]Histamine, at a tracer concentration, is incorporated into the polymer as well as into myosin, glycoproteins IIB and III, actin and tropomyosin. The lose of monomeric protein bands is mostly due to their conversion into polymers. Control measurements show that leupeptin effectively inhibited platelet Ca2+-dependent proteases. The cross-linking processes bringing about the observed increase in polymer formation are thus the result of a Ca2+-dependent platelet transglutaminase activity. The latter is located in the platelet cytosol and has been identified as platelet factor XIII on the basis of its specific cross-linking of fibrin. Platelet factor XIII, upon activation, may function physiologically to couple membrane proteins to cytoplasmic structural proteins. Thus, a new concept is proposed for the stabilization of platelet membranes and platelets as they form the hemostatic plug. 相似文献
4.
Cotyledons excised without the hypocotyl hook from 6-day-old etiolated cucumber ( Cucumis sativus L. var. Elem) seedlings accumulated a significantly higher amount of chlorophyll than cotyledons excised with hooks or intact cotyledons. It was found that maximum ehancement of greening was achieved after 2 h of dark incubation following excision. Pretreatments with red light effected an additive rise in chlorophyll level in subsequent white light after a dark incubation, suggesting that the effects of excision and phytochrome on greening act independently. Etiolated seedlings were variously dissected before greening and it was found that enhancement occurred only when cotyledons were excised at the level of the hypocotyl hook or above it. Similar results were obtained when the dissected plants were pre-treated with red light. 相似文献
5.
Exogenous nitric oxide triggers classic ischemic preconditioning by preventing intracellular Ca2+ overload in cardiomyocytes 总被引:1,自引:0,他引:1
The involvement of nitric oxide (NO) in the late phase of ischemic preconditioning is well established. However, the role of NO as a trigger or mediator of "classic preconditioning" remains to be determined. The present study was designed to investigate the effects of NO on calcium homeostasis in cultured newborn rat cardiomyocytes in normoxia and hypoxia. We found that treatment with the NO donor, sodium nitroprusside (SNP) induced a sustained elevation of intracellular calcium level ([Ca(2+)](i)) followed by a decrease to control levels. Elevation of extracellular calcium, which generally occurs during ischemia, caused an immediate increase in [Ca(2+)](i) and arrhythmia in cultures of newborn cardiomyocytes. Treatment with SNP decreased [Ca(2+)](i) to control levels and re-established synchronized beating of cardiomyocytes. A decrease in extracellular [Na(+)], which inhibits the Na(+)/Ca(2+) exchanger, did not prevent [Ca(2+)](i) reduction by SNP. In contrast, application of thapsigargin, an inhibitor of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a), increased [Ca(2+)](i), and in its presence, SNP did not reduce [Ca(2+)](i), indicating that Ca(2+) reduction is achieved via activation of SERCA2a. The results obtained suggest that activation of SERCA2a by SNP increases Ca(2+) uptake into the sarcoplasmic reticulum (SR) and prevents cytosolic Ca(2+) overload, which might explain the protective effect of SNP from hypoxic damage. 相似文献
6.
Tova F. Fuller Anatole Ghazalpour Jason E. Aten Thomas A. Drake Aldons J. Lusis Steve Horvath 《Mammalian genome》2007,18(6-7):463-472
Systems-oriented genetic approaches that incorporate gene expression and genotype data are valuable in the quest for genetic
regulatory loci underlying complex traits. Gene coexpression network analysis lends itself to identification of entire groups
of differentially regulated genes—a highly relevant endeavor in finding the underpinnings of complex traits that are, by definition,
polygenic in nature. Here we describe one such approach based on liver gene expression and genotype data from an F2 mouse intercross utilizing weighted gene coexpression network analysis (WGCNA) of gene expression data to identify physiologically
relevant modules. We describe two strategies: single-network analysis and differential network analysis. Single-network analysis
reveals the presence of a physiologically interesting module that can be found in two distinct mouse crosses. Module quantitative
trait loci (mQTLs) that perturb this module were discovered. In addition, we report a list of genetic drivers for this module.
Differential network analysis reveals differences in connectivity and module structure between two networks based on the liver
expression data of lean and obese mice. Functional annotation of these genes suggests a biological pathway involving epidermal
growth factor (EGF). Our results demonstrate the utility of WGCNA in identifying genetic drivers and in finding genetic pathways
represented by gene modules. These examples provide evidence that integration of network properties may well help chart the
path across the gene–trait chasm.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.
Tova F. Fuller, Anatole Ghazalpour contributed equally to this work. 相似文献
7.
Enhanced Connexin-43 and α-Sarcomeric Actin Expression in Cultured Heart Myocytes Exposed to Triiodo-l-thyronine 总被引:2,自引:0,他引:2
Tribulova N Shneyvays V Mamedova LK Moshel S Zinman T Shainberg A Manoach M Weismann P Kostin S 《Journal of molecular histology》2004,35(5):463-470
This study examined whether triiodo-L-thyronine (T3) affects the expression of the major intercellular channel protein, connexin-43, and contractile protein alpha-sarcomeric actin. Cultured cardiomyocytes from newborn rats were treated on day three in culture with 10 or 100 nM T3 and examined 48 and 72 h thereafter. Treated and untreated cells were examined by immunofluorescence and electron microscopy. Expression levels of Cx43 and sarcomeric alpha-actin were monitored by Western blot analysis. Immunofluorescence labeling showed cell membrane location of Cx43 in punctuate gap junctions, whereby fluorescence signal area was significantly higher in cultured cardiomyocytes exposed to T3. This correlated with electron microscopical findings showing increased numbers and size of gap junction profiles, as well as with a significant dose-dependent increase of Cx43 expression detected by Western blot. Immunofluorescence of sarcomeric a-actin was enhanced and its expression increased dose- and time-dependently in T3-treated cultured heart myocytes. However, exposure to the higher dosage (100 nM) of T3 caused mild disintegration of sarcomeric a-actin in some myocytes, suggesting an over-dosage. The results indicate that T3 up-regulates Cx43 and accelerates gap junction formation in cultured neonatal cardiomyocytes. They suggest that thyroid status cannot only modulate the mechanical function of cardiomyocytes but also cell-to-cell communication essential for myocardial electrical and metabolic synchronizations. 相似文献
8.
9.
Brown AN Smith K Samuels TA Lu J Obare SO Scott ME 《Applied and environmental microbiology》2012,78(8):2768-2774
We show here that silver nanoparticles (AgNP) were intrinsically antibacterial, whereas gold nanoparticles (AuNP) were antimicrobial only when ampicillin was bound to their surfaces. Both AuNP and AgNP functionalized with ampicillin were effective broad-spectrum bactericides against Gram-negative and Gram-positive bacteria. Most importantly, when AuNP and AgNP were functionalized with ampicillin they became potent bactericidal agents with unique properties that subverted antibiotic resistance mechanisms of multiple-drug-resistant bacteria. 相似文献
10.