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Stop codon read-through (SCR) is a process of continuation of translation beyond a stop codon. This phenomenon, which occurs only in certain mRNAs under specific conditions, leads to a longer isoform with properties different from that of the canonical isoform. MTCH2, which encodes a mitochondrial protein that regulates mitochondrial metabolism, was selected as a potential read-through candidate based on evolutionary conservation observed in the proximal region of its 3′ UTR. Here, we demonstrate translational read-through across two evolutionarily conserved, in-frame stop codons of MTCH2 using luminescence- and fluorescence-based assays, and by analyzing ribosome-profiling and mass spectrometry (MS) data. This phenomenon generates two isoforms, MTCH2x and MTCH2xx (single- and double-SCR products, respectively), in addition to the canonical isoform MTCH2, from the same mRNA. Our experiments revealed that a cis-acting 12-nucleotide sequence in the proximal 3′ UTR of MTCH2 is the necessary signal for SCR. Functional characterization showed that MTCH2 and MTCH2x were localized to mitochondria with a long t1/2 (>36 h). However, MTCH2xx was found predominantly in the cytoplasm. This mislocalization and its unique C terminus led to increased degradation, as shown by greatly reduced t1/2 (<1 h). MTCH2 read-through–deficient cells, generated using CRISPR-Cas9, showed increased MTCH2 expression and, consistent with this, decreased mitochondrial membrane potential. Thus, double-SCR of MTCH2 regulates its own expression levels contributing toward the maintenance of normal mitochondrial membrane potential.  相似文献   
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Xiong N  Xiong J  Khare G  Chen C  Huang J  Zhao Y  Zhang Z  Qiao X  Feng Y  Reesaul H  Zhang Y  Sun S  Lin Z  Wang T 《PloS one》2011,6(6):e20677
3-methyl-1-phenyl-2-pyrazolin-5-one (edaravone), an effective free radical scavenger, provides neuroprotection in stroke models and patients. In this study, we investigated its neuroprotective effects in a chronic rotenone rat model for Parkinson's disease. Here we showed that a five-week treatment with edaravone abolished rotenone's activity to induce catalepsy, damage mitochondria and degenerate dopamine neurons in the midbrain of rotenone-treated rats. This abolishment was attributable at least partly to edaravone's inhibition of rotenone-induced reactive oxygen species production or apoptotic promoter Bax expression and its up-regulation of the vesicular monoamine transporter 2 (VMAT2) expression. Collectively, edaravone may provide novel clinical therapeutics for PD.  相似文献   
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Molecular and Cellular Biochemistry - DNA hydroxymethylation plays a very important role in some biological processes, such as DNA methylation process. In addition, its presence can also cause some...  相似文献   
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A clinically-related animal model of Parkinson''s disease (PD) may enable the elucidation of the etiology of the disease and assist the development of medications. However, none of the current neurotoxin-based models recapitulates the main clinical features of the disease or the pathological hallmarks, such as dopamine (DA) neuron specificity of degeneration and Lewy body formation, which limits the use of these models in PD research. To overcome these limitations, we developed a rat model by stereotaxically (ST) infusing small doses of the mitochondrial complex-I inhibitor, rotenone, into two brain sites: the right ventral tegmental area and the substantia nigra. Four weeks after ST rotenone administration, tyrosine hydroxylase (TH) immunoreactivity in the infusion side decreased by 43.7%, in contrast to a 75.8% decrease observed in rats treated systemically with rotenone (SYS). The rotenone infusion also reduced the DA content, the glutathione and superoxide dismutase activities, and induced alpha-synuclein expression, when compared to the contralateral side. This ST model displays neither peripheral toxicity or mortality and has a high success rate. This rotenone-based ST model thus recapitulates the slow and specific loss of DA neurons and better mimics the clinical features of idiopathic PD, representing a reliable and more clinically-related model for PD research.  相似文献   
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Trehalose synthase (TreS) catalyzes the reversible interconversion of trehalose (glucosyl-alpha,alpha-1,1-glucose) and maltose (glucosyl-alpha1-4-glucose). TreS was purified from the cytosol of Mycobacterium smegmatis to give a single protein band on SDS gels with a molecular mass of approximately 68 kDa. However, active enzyme exhibited a molecular mass of approximately 390 kDa by gel filtration suggesting that TreS is a hexamer of six identical subunits. Based on amino acid compositions of several peptides, the treS gene was identified in the M. smegmatis genome sequence, and was cloned and expressed in active form in Escherichia coli. The recombinant protein was synthesized with a (His)(6) tag at the amino terminus. The interconversion of trehalose and maltose by the purified TreS was studied at various concentrations of maltose or trehalose. At a maltose concentration of 0.5 mm, an equilibrium mixture containing equal amounts of trehalose and maltose (42-45% of each) was reached during an incubation of about 6 h, whereas at 2 mm maltose, it took about 22 h to reach the same equilibrium. However, when trehalose was the substrate at either 0.5 or 2 mm, only about 30% of the trehalose was converted to maltose in >or= 12 h, indicating that maltose is the preferred substrate. These incubations also produced up to 8-10% free glucose. The K(m) for maltose was approximately 10 mm, whereas for trehalose it was approximately 90 mm. While beta,beta-trehalose, isomaltose (alpha1,6-glucose disaccharide), kojibiose (alpha1,2) or cellobiose (beta1,4) were not substrates for TreS, nigerose (alpha1,3-glucose disaccharide) and alpha,beta-trehalose were utilized at 20 and 15%, respectively, as compared to maltose. The enzyme has a pH optimum of about 7 and is inhibited in a competitive manner by Tris buffer. [(3)H]Trehalose is converted to [(3)H]maltose even in the presence of a 100-fold or more excess of unlabeled maltose, and [(14)C]maltose produces [(14)C]trehalose in excess unlabeled trehalose, suggesting the possibility of separate binding sites for maltose and trehalose. The catalytic mechanism may involve scission of the incoming disaccharide and transfer of a glucose to an enzyme-bound glucose, as [(3)H]glucose incubated with TreS and either unlabeled maltose or trehalose results in formation of [(3)H]disaccharide. TreS also catalyzes production of a glucosamine disaccharide from maltose and glucosamine, suggesting that this enzyme may be valuable in carbohydrate synthetic chemistry.  相似文献   
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Curcumin is known for its anticancer properties, but its clinical application is limited due to its poor bioavailability and chemical stability. In this study we report the curcumin derivative, ST03 (1,2-bis[(3E,5E)-3,5-bis[(2-chlorophenyl)methylene]-4-oxo-1-piperidyl]ethane-1,2-dione) exhibits ∼ 14 fold better bioavailability compared to curcumin and is detectable in plasma up to 12 h. ST03 induces ROS, activates the intrinsic apoptotic pathway as evident by disruption of mitochondrial membrane potential, and induction of proapoptotic proteins in ovarian cancer lines PA1 and A2780. ST03 also blocked the migration of ovarian cancer cells. ST03 exerted its antitumor effect in-vivo in the EAC mouse model by activating the intrinsic apoptotic pathway. Our findings demonstrate ST03, a curcumin derivative, with better bioavailability and stability with no discernable toxicity in vivo to be a promising drug candidate for anticancer therapies.  相似文献   
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We compared the anatomical characteristics of vegetative organs, peduncle and mycorrhizal morphology of the two known species of Sirhookera (Epidendroideae, Orchidaceae) to identify anatomical markers for identification and the ecological adaptations of these species. The leaves are hypostomatic bearing tetracytic stomata and the walls of subsidiary cells are smooth in Sirhookera lanceolata and undulate in Sirhookera latifolia. On the adaxial and abaxial surfaces the leaves are covered by a thick cuticle. The hypodermis is dimorphic and present on both sides of the leaf; chlorenchyma is homogenous and the vascular bundles are collateral. The rhizome of Sirhookera possesses a single-layered epidermis, thick cuticle, thin-walled parenchymatous ground tissue containing starch grains and scattered collateral vascular bundles. A thick-walled sclerenchymatous band separates the cortex from the parenchymatous ground tissue comprising of banded cells in the peduncle. Starch grains are present in the ground tissue of the S. latifolia peduncle. The roots consist of the velamen, ∩-thickened exodermis, thin-walled cortex consisting of water-storage cells, O-thickened endodermis and a vascular cylinder with parenchymatous pith. Starch grains are present in the root cortical cells of S. lanceolata but absent in S. latifolia. Fungal pelotons that aids in nutrient acquisition were observed in the root cortical region of both species. The study revealed significant differences between the anatomical characteristics of the two species and that most of the anatomical features of Sirhookera relate to their ecological adaptations.  相似文献   
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In Parkinson''s disease (PD), neuronal cells undergo mitotic catastrophe and endoreduplication prior to cell death; however, the regulatory mechanisms remain to be defined. In this study, we investigated cell cycle regulation of DNA polymerase β (poly β) in rotenone-based dopaminergic cellular and animal models. Incubation with a low concentration (0.25 µM) of rotenone for 1.5 to 7 days resulted in a flattened cell body and decreased DNA replication during S phase, whereas a high concentration (2 µM) of rotenone exposure resulted in enlarged, multi-nucleated cells and converted the mitotic cycle into endoreduplication. Consistently, DNA poly β, which is mainly involved in DNA repair synthesis, was upregulated to a high level following exposure to 2 µM rotenone. The abrogation of DNA poly β by siRNA transfection or dideoxycytidine (DDC) treatment attenuated the rotenone-induced endoreduplication. The cell cycle was reactivated in cyclin D-expressing dopaminergic neurons from the substantia nigra (SN) of rats following stereotactic (ST) infusion of rotenone. Increased DNA poly β expression was observed in the substantia nigra pars compacta (SNc) and the substantia nigra pars reticulate (SNr) of rotenone-treated rats. Collectively, in the in vitro model of rotenone-induced mitotic catastrophe, the overexpression of DNA poly β promotes endoreduplication; in the in vivo model, the upregulation of DNA poly β and cell cycle reentry were also observed in the adult rat substantia nigra. Therefore, the cell cycle regulation of DNA poly β may be involved in the pathological processes of PD, which results in the induction of endoreduplication.  相似文献   
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