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排序方式: 共有107条查询结果,搜索用时 31 毫秒
41.
42.
UK-1 is a bis(benzoxazole) natural product displaying activity against a wide range of human cancer cell lines. A simplified analog of UK-1, 4-carbomethoxy-2-(2'-hydroxyphenyl)benzoxazole, was previously found to be almost as active as UK-1 against cancer cell lines, and similar to the natural product, formed complexes with a variety of metal ions such as Mg2+ and Zn2+. A series of 4-substituted-2-(2'-hydroxyphenyl)benzoxazole analogs of this 'minimal pharmacophore' of UK-1 were prepared. The anti-cancer activity of these analogs was examined in breast and lung cancer cell lines. Spectrophotometric titrations in methanol were carried out in order to assess the ability of UK-1 and these analogs to coordinate with Mg2+ and Cu2+ ions. Although none of the new analogs were more cytotoxic than 4-carbomethoxy-2-(2'-hydroxyphenyl)benzoxazole, some analogs were identified that display similar cytotoxicity to this simplified UK-1 analog with improved water solubility. UK-1 and all of these new analogs bind Cu2+ ions better than Mg2+ ions, and the nature of the 4-substituent is important for the Mg2+ ion binding ability of these 2-(2'-hydroxyphenyl)benzoxazoles. Previous studies of a limited number of UK-1 analogs demonstrated a correlation between Mg2+ ion binding ability and cytotoxicity; however, within this series of 4-substituted-2-(2'-hydroxyphenyl)benzoxazoles the variations in cytotoxicity do not correlate with either Mg2+ or Cu2+ ion binding ability. These results, together with recent ESI-MS studies of Cu2+-mediated DNA binding by UK-1 and analogs, indicate that UK-1 and analogs may exert their cytotoxic effects by interaction with Cu2+ or other transition metal ions, rather than Mg2+, and that metal ion-mediated DNA binding, rather than metal ion binding affinity, is important for the cytotoxic effect of these compounds. The potential role of Cu2+ ions in the cytotoxic action of UK-1 is further supported by the observation that UK-1 in the presence of Cu2+ displays enhanced cytotoxicity to MCF-7 and A549 cells when compared to UK-1 alone. 相似文献
43.
Denny P Hagen FK Hardt M Liao L Yan W Arellanno M Bassilian S Bedi GS Boontheung P Cociorva D Delahunty CM Denny T Dunsmore J Faull KF Gilligan J Gonzalez-Begne M Halgand F Hall SC Han X Henson B Hewel J Hu S Jeffrey S Jiang J Loo JA Ogorzalek Loo RR Malamud D Melvin JE Miroshnychenko O Navazesh M Niles R Park SK Prakobphol A Ramachandran P Richert M Robinson S Sondej M Souda P Sullivan MA Takashima J Than S Wang J Whitelegge JP Witkowska HE Wolinsky L Xie Y Xu T Yu W Ytterberg J Wong DT 《Journal of proteome research》2008,7(5):1994-2006
Saliva is a body fluid with important functions in oral and general health. A consortium of three research groups catalogued the proteins in human saliva collected as the ductal secretions: 1166 identifications--914 in parotid and 917 in submandibular/sublingual saliva--were made. The results showed that a high proportion of proteins that are found in plasma and/or tears are also present in saliva along with unique components. The proteins identified are involved in numerous molecular processes ranging from structural functions to enzymatic/catalytic activities. As expected, the majority mapped to the extracellular and secretory compartments. An immunoblot approach was used to validate the presence in saliva of a subset of the proteins identified by mass spectrometric approaches. These experiments focused on novel constituents and proteins for which the peptide evidence was relatively weak. Ultimately, information derived from the work reported here and related published studies can be used to translate blood-based clinical laboratory tests into a format that utilizes saliva. Additionally, a catalogue of the salivary proteome of healthy individuals allows future analyses of salivary samples from individuals with oral and systemic diseases, with the goal of identifying biomarkers with diagnostic and/or prognostic value for these conditions; another possibility is the discovery of therapeutic targets. 相似文献
44.
Fernando Zambrano Miguel Morales Nelson Fuentes Mireya Rojas 《The Journal of membrane biology》1981,63(1-2):71-75
Summary Sodium efflux was studied in22Na-loaded red blood cells in the presence of arylsulfatase, an enzyme that specifically hydrolyzes sulfatide. Sodium efflux was inhibited in proportion to the amount of arylsulfatase present. Maximum inhibition was almost as high as the efflux obtained in medium with K+ absent. At maximum inhibition 83.2% of the sulfatide content of the fragmented red blood cell membranes was hydrolyzed and ouabain-sensitive (Na++K+)-ATPase activity was inhibited by 100%. Sodium efflux, sulfatide content, and (Na++K+)-ATPase activity were unaffected with arylsulfatase in the presence of a high concentration of sulfatide. These results indicate that sulfatide plays a specific role in sodium and potassium ion transport. They also suggest that most sulfatide is localized externally in the red blood cell membrane. 相似文献
45.
Nelson Carvajal Mireya Fernández Juan Pablo Rodríguez Margarita Donoso 《Phytochemistry》1980,21(12):2821-2823
Urease (EC 3.5.1.5) was purified from Spirulina maxima by ammonium sulfate precipitation, DEAE-cellulose chromatography and gel filtration on Sephadex G-200. The enzyme had maximum activity at pH 8.7, a Km for urea of 0.12 mM and a MW of ca 232 000. A MW of 38 000 was determined for the subunits. The enzyme was inactivated by p-hydroxymercuribenzoate. 相似文献
46.
Mendoza M Alvarado P Díaz de Torres E Lucena L de Albornoz MC 《Revista iberoamericana de micología》2005,22(3):151-156
We compared two methods for the preservation of fungi, Castellani's method and repeated passage in Sabouraud medium-agar, on five isolates of Sporothrix schenckii that were preserved for 18 years at room temperature by both procedures. They were evaluated for viability of the strains, growth rate, morphological and physiological characteristics, and in vitro sensitivity to iodide, itraconazole, terbinafine and posaconazole. 100% viability was observed in all of the isolates, with slower growth rate on strains preserved in water compared to strains periodically re-cultured. The typical morphological feature of these fungi was preserved by both methodologies. With regard to enzymatic activity, both groups gave urease reactions and were beta glucosidase-positive. Nevertheless, complete inhibition of the capacity to hydrolyse starch was observed only on the isolates preserved in water. This group also was more sensitive to potassium iodide at a concentration of 10 microM in the in vitro sensitivity tests. 相似文献
47.
High affinity leptin receptors are present in human mesenchymal stem cells (MSCs) derived from control and osteoporotic donors 总被引:2,自引:0,他引:2
There are disparate observations on central and peripheral effects of leptin, but several studies consistently support its role as a link between fat and bone. Bone marrow stroma contains mesenchymal stem cells (MSCs), which differentiate into osteoblasts and adipocytes, among others. In this study we assessed the expression of leptin receptors protein in MSCs from control and osteoporotic postmenopausal donors and their change during osteogenic and adipogenic differentiation. Also, we assessed the effects of leptin on osteogenic and adipogenic differentiation of these cells. We demonstrated high affinity leptin binding (KD = 0.36 +/- 0.02 nM) in both types of cells. Binding was very low under basal, but increased significantly (2-3 times) through osteogenic and adipogenic differentiation. Osteoporotic MSCs showed lower leptin binding capacity than control cells at an early osteogenic and adipogenic differentiation time, which could restrict cell sensitivity to the protective action of leptin. In this regard, we observed that leptin significantly inhibited adipocyte differentiation in control but not in osteoporotic MSCs, while it exerted a low stimulatory effect on calcium deposition (10%-20%) in both types of MSCs cells. In summary, we report the presence of high affinity leptin receptors on control and osteoporotic MSCs, which were modified distinctly by osteogenic and adipogenic stimulation and a direct and distinct effect of leptin on both type of cells. 相似文献
48.
Salas A Richards M Lareu MV Sobrino B Silva S Matamoros M Macaulay V Carracedo A 《American journal of physical anthropology》2005,128(4):855-860
During the period of the Atlantic slave trade (15th-19th centuries), millions of people were forced to move from Africa to many American destinations, changing dramatically the human landscape of the Americas. Here, we analyze mitochondrial DNA from two different American populations with African ancestry, with hitherto unknown European and Native American components. On the basis of historical records, African-Americans from Chocó (Colombia) and the Garífunas (or "Black Carib") of Honduras are likely to have had very different demographic histories, with a significant founder effect in the formation of the latter. Both the common features and differences are reflected in their mtDNA composition. Both show a minor component (approximately 16%) from Native Central/South Americans and a larger component (approximately 84%) from sub-Saharan Africans. The latter component is very diverse in the African-Americans from Chocó, similar to that of sub-Saharan Africans, but much less so in the Garífunas, with several mtDNA types elevated to high frequency, suggesting the action of genetic drift. 相似文献
49.
Mena-Rojas E Vázquez Cruz C Vaca Pacheco S García González O Pérez-Márquez VM Pérez-Méndez A Ibarra-Caballero J de la Garza M Zenteno E Negrete-Abascal E 《FEMS microbiology letters》2004,232(1):83-87
Haemophilus paragallinarum is the causal agent of infectious coryza, an economically important disease for the poultry industry. This bacterium secreted proteins of 25-110 kDa during its growth in brain heart infusion, tryptic soy broth, or Luria-Bertani glucose phosphate media, all lacking serum. Some of these proteins were recognized by sera from chickens experimentally infected with H. paragallinarum. A 110-kDa protein was recognized by a serum pool from convalescent-phase pigs naturally infected with Actinobacillus pleuropneumoniae, and also by a rabbit polyclonal serum against Apx I as well as a rabbit serum against Mannheimia haemolytica leukotoxin, suggesting the presence of an RTX-like protein in H. paragallinarum. H. paragallinarum secreted proteins could be important immunogens in the control of infectious coryza. 相似文献
50.
García González O García RM de la Garza M Vaca S Paniagua GL Mejía R Tenorio VR Negrete-Abascal E 《FEMS microbiology letters》2004,234(1):81-86
The complete amino acid and nucleotide sequence of a secreted metalloprotease produced by Actinobacillus pleuropneumoniae serotype 1 is reported. A clone showing proteolytic activity in cell-free culture media was selected from a genomic library of A. pleuropneumoniae serotype 1 in pUC 19. The sequence obtained contained an open reading frame encoding a protein with 869 amino acids. This protein was identified as a zinc neutral-metalloprotease belonging to the aminopeptidase family, with a predicted molecular weight of approximately 101 kDa. This sequence showed high homology with other predicted or sequenced aminopeptidases reported for different Gram-negative bacteria. Expression of the protease was observed in lung tissue from pigs that died of porcine pleuropneumonia suggesting a role in pathogenesis. 相似文献