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21.
The histone demethylase, lysine (K)-specific demethylase 2A (Kdm2a), is highly conserved and expressed ubiquitously. Kdm2a can regulate cell proliferation and osteo/dentinogenic, adipogenic and chondrogenic differentiation of mesenchymal stem cells (MSCs) derived from dental tissue. We used quantitative real-time RT-PCR analysis and immunohistochemistry to detect Kdm2a expression during development of the murine molar at embryonic days E12, E14, E16 and E17 and postnatal days P3 and P14. Immunohistochemistry results showed no positive staining of Kdm2a at E12. At E14, Kdm2a was expressed weakly in the inner enamel epithelium, stellate reticulum cells and dental sac. At E16, Kdm2a was expressed mainly in the inner and outer enamel epithelium, stratum intermedium and dental sac, but weaker staining was found in cervical loop and dental papilla cells adjacent to the basement membrane. At E17, the strongest Kdm2a staining was detected in the ameloblasts and stronger Kdm2a staining also was detected in the stratum intermedium, outer enamel epithelium and dental papilla cells compared to the expression at E16. Postnatally, we found that Kdm2a was localized in secretory and mature ameloblasts and odontoblasts, and dentin was unstained. Real-time RT-PCR showed that Kdm2a mRNA levels in murine germ cells increased from E12 to E14 and from E14 to E16; no significant change occurred at E16, E17 or P3, then the levels decreased at P14 compared to P3. Kdm2a expression may be closely related to cell proliferation, to ameloblast and odontoblast differentiation and to the secretion of extracellular enamel and dentin during murine tooth development. 相似文献
22.
Corn samples were collected in 1999 from three departments of Entre Réos province, Argentina, and were surveyed for mould
contamination and natural occurrence ofFusarium mycotoxins, ochratoxin A and aflatoxins.Fusarium verticillioides was the most prevalent fungal species recorded at all departments. Zearalenone, deoxynivalenol and ochratoxin A were not
found in any samples. Only one of the 52 corn samples analysed was contaminated with aflatoxin B1 (17 μg/kg). Fumonisin B1 was found in 58 % of samples (range of positive samples: 47– 3,347 μg/kg), fumonisin B2 in 33.0 % (range of positive samples: 23–537 μg/kg) and fumonisin B3 in 25.0 % (range of positive samples: 24–287 μg/kg) of them. This is the first report on the natural occurrence of mycotoxins
in corn from Entre Ríos province, Argentina. Levels of fumonisins were lower than detected in other Argentinian provinces. 相似文献
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Muha V Horváth A Békési A Pukáncsik M Hodoscsek B Merényi G Róna G Batki J Kiss I Jankovics F Vilmos P Erdélyi M Vértessy BG 《PLoS genetics》2012,8(6):e1002738
Base-excision repair and control of nucleotide pools safe-guard against permanent uracil accumulation in DNA relying on two key enzymes: uracil-DNA glycosylase and dUTPase. Lack of the major uracil-DNA glycosylase UNG gene from the fruit fly genome and dUTPase from fruit fly larvae prompted the hypotheses that i) uracil may accumulate in Drosophila genomic DNA where it may be well tolerated, and ii) this accumulation may affect development. Here we show that i) Drosophila melanogaster tolerates high levels of uracil in DNA; ii) such DNA is correctly interpreted in cell culture and embryo; and iii) under physiological spatio-temporal control, DNA from fruit fly larvae, pupae, and imago contain greatly elevated levels of uracil (200-2,000 uracil/million bases, quantified using a novel real-time PCR-based assay). Uracil is accumulated in genomic DNA of larval tissues during larval development, whereas DNA from imaginal tissues contains much less uracil. Upon pupation and metamorphosis, uracil content in DNA is significantly decreased. We propose that the observed developmental pattern of uracil-DNA is due to the lack of the key repair enzyme UNG from the Drosophila genome together with down-regulation of dUTPase in larval tissues. In agreement, we show that dUTPase silencing increases the uracil content in DNA of imaginal tissues and induces strong lethality at the early pupal stages, indicating that tolerance of highly uracil-substituted DNA is also stage-specific. Silencing of dUTPase perturbs the physiological pattern of uracil-DNA accumulation in Drosophila and leads to a strongly lethal phenotype in early pupal stages. These findings suggest a novel role of uracil-containing DNA in Drosophila development and metamorphosis and present a novel example for developmental effects of dUTPase silencing in multicellular eukaryotes. Importantly, we also show lack of the UNG gene in all available genomes of other Holometabola insects, indicating a potentially general tolerance and developmental role of uracil-DNA in this evolutionary clade. 相似文献
25.
Hsiao-Fen Li Chia-Hsuan Huang Li-Shuang Ai Chin-Kai Chuang Steve SL Chen 《Journal of biomedical science》2009,16(1):89-18
Background
Envelope (E) glycoprotein E2 of the hepatitis C virus (HCV) mediates binding of the virus to target cell receptors. Nevertheless, the precise role of E1 in viral entry remains elusive. 相似文献26.
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Despite the recent introduction of biological response modifiers and potent new small-molecule antirheumatic drugs, the efficacy of methotrexate is nearly unsurpassed in the treatment of inflammatory arthritis. Although methotrexate was first introduced as an antiproliferative agent that inhibits the synthesis of purines and pyrimidines for the therapy of malignancies, it is now clear that many of the anti-inflammatory effects of methotrexate are mediated by adenosine. This nucleoside, acting at one or more of its receptors, is a potent endogenous anti-inflammatory mediator. In confirmation of this mechanism of action, recent studies in both animals and patients suggest that adenosine-receptor antagonists, among which is caffeine, reverse or prevent the anti-inflammatory effects of methotrexate. 相似文献
28.
The ability of particular cell surface glycoproteins to recycle and become
exposed to individual Golgi enzymes has been demonstrated. This study was
designed to determine whether endocytic trafficking includes significant
reentry into the overall oligosaccharide processing pathway. The Lec1
mutant of Chinese hamster ovary (CHO) cells lack N -
acetylglucosaminyltransferase I (GlcNAc-TI) activity resulting in surface
expression of incompletely processed Man5GlcNAc2 N -linked
oligosaccharides. An oligosaccharide tracer was created by exoglycosylation
of cell surface glycoproteins with purified porcine GlcNAc-TI and
UDP-[3H]GlcNAc. Upon reculturing, all cell surface glycoproteins that
acquired [3H]GlcNAc were acted upon by intracellular mannosidase II, the
next enzyme in the Golgi processing pathway of complex N -linked
oligosaccharides (t1/2= 3-4 h). That all radiolabeled cell surface
glycoproteins were included in this endocytic pathway indicates a common
intracellular compartment into which endocytosed cell surface glycoproteins
return. Significantly, no evidence was found for continued oligosaccharide
processing consistent with transit through the latter cisternae of the
Golgi apparatus. These data indicate that, although recycling plasma
membrane glycoproteins can be reexposed to individual Golgi-derived
enzymes, significant reentry into the overall contiguous processing pathway
is not evident.
相似文献
29.
The role of site-specific N-glycosylation in secretion of soluble forms of rabies virus glycoprotein 总被引:1,自引:1,他引:0
Wojczyk BS; Stwora-Wojczyk M; Shakin-Eshleman S; Wunner WH; Spitalnik SL 《Glycobiology》1998,8(2):121-130
Rabies virus glycoprotein is important in the biology and pathogenesis of
neurotropic rabies virus infection. This transmembrane glycoprotein is the
only viral protein on the surface of virus particles, is the viral
attachment protein that facilitates virus uptake by the infected cell, and
is the target of the host humoral immune response to infection. The
extracellular domain of this glycoprotein has N- glycosylation sequons at
Asn37, Asn247, and Asn319. Appropriate glycosylation of these sequons is
important in the expression of the glycoprotein. Soluble forms of rabies
virus glycoprotein were constructed by insertion of a stop codon just
external to the transmembrane domain. Using site-directed mutagenesis and
expression in transfected eukaryotic cells, it was possible to compare the
effects of site-specific glycosylation on the cell-surface expression and
secretion of transmembrane and soluble forms, respectively, of the same
glycoprotein. These studies yielded the surprising finding that although
any of the three sequons permitted cell surface expression of full-length
rabies virus glycoprotein, only the N-glycan at Asn319 permitted secretion
of soluble rabies virus glycoprotein. Despite its biological and medical
importance, it has not yet been possible to determine the crystal structure
of the full-length transmembrane form of rabies virus glycoprotein which
contains heterogeneous oligosaccharides. The current studies demonstrate
that a soluble form of rabies virus glycoprotein containing only one sequon
at Asn319 is efficiently secreted in the presence of the N-glycan
processing inhibitor 1-deoxymannojirimycin. Thus, it is possible to purify
a conformationally relevant form of rabies virus glycoprotein that contains
only one N-glycan with a substantial reduction in its microheterogeneity.
This form of the glycoprotein may be particularly useful for future studies
aimed at elucidating the three-dimensional structure of this important
glycoprotein.
相似文献
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