Evidence of a pluripotent human embryonic stem cell line derived from a cloned blastocyst     

Hwang WS  Ryu YJ  Park JH  Park ES  Lee EG  Koo JM  Jeon HY  Lee BC  Kang SK  Kim SJ  Ahn C  Hwang JH  Park KY  Cibelli JB  Moon SY 《Science (New York, N.Y.)》2004,303(5664):1669-1674

Somatic cell nuclear transfer (SCNT) technology has recently been used to generate animals with a common genetic composition. In this study, we report the derivation of a pluripotent embryonic stem (ES) cell line (SCNT-hES-1) from a cloned human blastocyst. The SCNT-hES-1 cells displayed typical ES cell morphology and cell surface markers and were capable of differentiating into embryoid bodies in vitro and of forming teratomas in vivo containing cell derivatives from all three embryonic germ layers in severe combined immunodeficient mice. After continuous proliferation for more than 70 passages, SCNT-hES-1 cells maintained normal karyotypes and were genetically identical to the somatic nuclear donor cells. Although we cannot completely exclude the possibility that the cells had a parthenogenetic origin, imprinting analyses support a SCNT origin of the derived human ES cells.  相似文献   

Sirt5 is a NAD-dependent protein lysine demalonylase and desuccinylase   总被引：1，自引：0，他引：1  

Du J  Zhou Y  Su X  Yu JJ  Khan S  Jiang H  Kim J  Woo J  Kim JH  Choi BH  He B  Chen W  Zhang S  Cerione RA  Auwerx J  Hao Q  Lin H 《Science (New York, N.Y.)》2011,334(6057):806-809

Silent information regulator 2 (Sir2) proteins (sirtuins) are nicotinamide adenine dinucleotide-dependent deacetylases that regulate important biological processes. Mammals have seven sirtuins, Sirt1 to Sirt7. Four of them (Sirt4 to Sirt7) have no detectable or very weak deacetylase activity. We found that Sirt5 is an efficient protein lysine desuccinylase and demalonylase in vitro. The preference for succinyl and malonyl groups was explained by the presence of an arginine residue (Arg(105)) and tyrosine residue (Tyr(102)) in the acyl pocket of Sirt5. Several mammalian proteins were identified with mass spectrometry to have succinyl or malonyl lysine modifications. Deletion of Sirt5 in mice appeared to increase the level of succinylation on carbamoyl phosphate synthase 1, which is a known target of Sirt5. Thus, protein lysine succinylation may represent a posttranslational modification that can be reversed by Sirt5 in vivo.  相似文献   

Molecular mechanisms for the functionality of lubricant additives     

Mosey NJ  Müser MH  Woo TK 《Science (New York, N.Y.)》2005,307(5715):1612-1615

Wear limits the life-span of many mechanical devices with moving parts. To reduce wear, lubricants are frequently enriched with additives, such as zinc phosphates, that form protective films on rubbing surfaces. Using first-principles molecular dynamics simulations of films derived from commercial additives, we unraveled the molecular origin of how antiwear films can form, function, and dissipate energy. These effects originate from pressure-induced changes in the coordination number of atoms acting as cross-linking agents to form chemically connected networks. The proposed mechanism explains a diverse body of experiments and promises to prove useful in the rational design of antiwear additives that operate on a wider range of surface materials, with reduced environmental side effects.  相似文献   

Graphoepitaxy of self-assembled block copolymers on two-dimensional periodic patterned templates     

Bita I  Yang JK  Jung YS  Ross CA  Thomas EL  Berggren KK 《Science (New York, N.Y.)》2008,321(5891):939-943

Self-assembling materials are the building blocks of bottom-up nanofabrication processes, but they need to be templated to impose long-range order and eliminate defects. In this work, the self-assembly of a thin film of a spherical-morphology block copolymer is templated using an array of nanoscale topographical elements that act as surrogates for the minority domains of the block copolymer. The orientation and periodicity of the resulting array of spherical microdomains are governed by the commensurability between the block copolymer period and the template period and is accurately described by a free-energy model. This method, which forms high-spatial-frequency arrays using a lower-spatial-frequency template, will be useful in nanolithography applications such as the formation of high-density microelectronic structures.  相似文献   

Cleavage of proBDNF by tPA/plasmin is essential for long-term hippocampal plasticity     

Pang PT  Teng HK  Zaitsev E  Woo NT  Sakata K  Zhen S  Teng KK  Yung WH  Hempstead BL  Lu B 《Science (New York, N.Y.)》2004,306(5695):487-491

Long-term memory is thought to be mediated by protein synthesis-dependent, late-phase long-term potentiation (L-LTP). Two secretory proteins, tissue plasminogen activator (tPA) and brain-derived neurotrophic factor (BDNF), have been implicated in this process, but their relationship is unclear. Here we report that tPA, by activating the extracellular protease plasmin, converts the precursor proBDNF to the mature BDNF (mBDNF), and that such conversion is critical for L-LTP expression in mouse hippocampus. Moreover, application of mBDNF is sufficient to rescue L-LTP when protein synthesis is inhibited, which suggests that mBDNF is a key protein synthesis product for L-LTP expression.  相似文献   

Recent biogenic phosphorite: concretions in mollusk kidneys     

Doyle LJ  Blake NJ  Woo CC  Yevich P 《Science (New York, N.Y.)》1978,199(4336):1431-1433

Phosphorite concretions have been detected in the kidneys of two widespread species of mollusks, Mercenaria mercenaria and Argopecten irradians, which have relatively high population densities. These concretions are the first documentation of the direct biogenic formation of phosphorite grains. The concretions are principally amorphous calcium phosphate, which upon being heated yields an x-ray diffraction pattern which is essentially that of chlorapatite. These concretions appear to be a normal formation of the excretory process of mollusks under reproductive, environmental, or pollutant-induced stress. Biogenic production of phosphorite concretions over long periods of time and diagenetic change from amorphous to crystalline structure, coupled with secondary enrichment, may account for the formation of some marine phosphorite desposits which are not easily explained by the chemical precipitation-replacement hypothesis.  相似文献   

Factors that contribute to the mycoparasitism stimulus in Trichoderma atroviride strain P1          下载免费PDF全文

Woo S L　 Formisano E　 Fogliano V　 Cosenza C　 Mauro A　 Turrà D　 Soriente I　 Ferraioli S　 Scala F　 Lorito M 《浙江大学学报(农业与生命科学版)》2004,30(4):421-421

Trichoderma atroviride strain P1 has been used extensively to study the mycoparasitic mechanisms in the interaction between plant pathogenic host and beneficial antagonistic fungi. Mutants of P1 containing the green fluorescent protein (gfp) or glucose oxidase (gox) reporter systems and different inducible promoters (from the exochitinase nag1 gene, or the endochitinase ech42 gene of P1) were used to determine the factors that activate the biocontrol gene expression cascade in the antagonis…  相似文献   

Comparison of 1-deoxynojirimycin and aqueous mulberry leaf extract with emphasis on postprandial hypoglycemic effects: in vivo and in vitro studies     

Kwon HJ  Chung JY  Kim JY  Kwon O 《Journal of agricultural and food chemistry》2011,59(7):3014-3019

Carbohydrate digestion by α-glucosidase and subsequent glucose uptake at the brush border are critical for postprandial blood glucose control. Any specific inhibitors are useful as hyperglycemia modulating agents. In this study, it was postulated that an array of active components in mulberry leaf extract (MLE) may provide higher potency in inhibiting intestinal glucose absorption compared to the single component 1-deoxynojirimycin (DNJ), which is recognized as a promising inhibitor of intestinal glucose absorption. Both MLE and DNJ were active in inhibiting α-glucosidase. However, in Caco-2 cells, only MLE showed significant inhibition of 2-deoxyglucose uptake, whereas DNJ was ineffective. For glucose loading, co-administration of MLE resulted in potent inhibitions of glucose responses compared to those by DNJ in Sprague Dawley (SD) rats, but this was not found for maltose loading. These novel findings add evidence that the unabsorbed phytochemicals in MLE compete with glucose for intestinal glucose transporters, but DNJ itself does not. We also evaluated the timing of MLE consumption. By administering MLE for 30 min before glucose loading, the incremental area under the curve (IAUC) was significantly lowered in the rats, as compared to a simultaneously administered group. Similarly, cellular glucose uptake was significantly reduced in Caco-2 cells following pretreatment.  相似文献   

Pterocarpan profiles for soybean leaves at different growth stages and investigation of their glycosidase inhibitions     

Yuk HJ  Curtis-Long MJ  Ryu HW  Jang KC  Seo WD  Kim JY  Kang KY  Park KH 《Journal of agricultural and food chemistry》2011,59(23):12683-12690

Soybean leaves are eaten as seasonal edible greens in Korea. Analysis of the ethyl acetate extract of these leaves showed that it exhibited potent and selective neuraminidase inhibition, which began at the R3 stage and peaked at R7. Ten pterocarpans, including the new 6a-hydroxypterocarpan 10, were isolated from soybean leaves and their inhibition activities tested against a range of glycosidases. The relationship between structure and enzyme inhibition was investigated: 6a-hydroxypterocarpans exhibited much higher inhibition against neuraminidase (IC(50) = 2.4-89.4 μM) than α-glucosidase (IC(50) = 90.4-?>100 μM). Glyceollin VII (7) displayed 40-fold greater activity (IC(50) = 2.4 μM) against neuraminidase than α-glucosidase (IC(50) = 90.4 μM). On the other hand, coumestanes (1-3) were good α-glucosidase inhibitors (IC(50) = 6.0-42.6 μM). In kinetic analysis, the most potent neuraminidase inhibitors (5-10) were noncompetitive. HPLC analysis indicated that most pterocarpan synthesis began from the R3 stage, and a rapid change of pterocarpan concentrations was observed between the R4 and R7 stages.  相似文献   

Molecular characterization of tetracycline- and quinolone-resistant Aeromonas salmonicida isolated in Korea     

Ji Hyung Kim  Sun Young Hwang  Jee Soo Son  Jee Eun Han  Jin Woo Jun  Sang Phil Shin  Casiano Choresca  Jr  Yun Jaie Choi  Yong Ho Park  Se Chang Park 《Journal of veterinary science (Suw?n-si, Korea)》2011,12(1):41-48

The antibiotic resistance of 16 Aeromonas (A.) salmonicida strains isolated from diseased fish and environmental samples in Korea from 2006 to 2009 were investigated in this study. Tetracycline or quinolone resistance was observed in eight and 16 of the isolates, respectively, based on the measured minimal inhibitory concentrations. Among the tetracycline-resistant strains, seven of the isolates harbored tetA gene and one isolate harbored tetE gene. Additionally, quinolone-resistance determining regions (QRDRs) consisting of the gyrA and parC genes were amplified and sequenced. Among the quinolone-resistant A. salmonicida strains, 15 harbored point mutations in the gyrA codon 83 which were responsible for the corresponding amino acid substitutions of Ser⁸³→Arg⁸³ or Ser⁸³→Asn⁸³. We detected no point mutations in other QRDRs, such as gyrA codons 87 and 92, and parC codons 80 and 84. Genetic similarity was assessed via pulsed-field gel electrophoresis, and the results indicated high clonality among the Korean antibiotic-resistant strains of A. salmonicida.  相似文献