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971.
Gabriella Lania Zhen Zhang Cinzia Caprio Anne M. Moon Antonio Baldini 《Developmental biology》2009,328(1):109-394
The thyroid develops within the pharyngeal apparatus from endodermally-derived cells. The many derivatives of the pharyngeal apparatus develop at similar times and sometimes from common cell types, explaining why many syndromic disorders express multiple birth defects affecting different structures that share a common pharyngeal origin. Thus, different derivatives may share common genetic networks during their development. Tbx1, the major gene associated with DiGeorge syndrome, is a key player in the global development of the pharyngeal apparatus, being required for virtually all its derivatives, including the thyroid. Here we show that Tbx1 regulates the size of the early thyroid primordium through its expression in the adjacent mesoderm. Because Tbx1 regulates the expression of Fgf8 in the mesoderm, we postulated that Fgf8 mediates critical Tbx1-dependent interactions between mesodermal cells and endodermal thyrocyte progenitors. Indeed, conditional ablation of Fgf8 in Tbx1-expressing cells caused an early thyroid phenotype similar to that of Tbx1 mutant mice. In addition, expression of an Fgf8 cDNA in the Tbx1 domain rescued the early size defect of the thyroid primordium in Tbx1 mutants. Thus, we have established that a Tbx1->Fgf8 pathway in the pharyngeal mesoderm is a key size regulator of mammalian thyroid. 相似文献
972.
Liyuan Zhao Tiezhu Mi Yu Zhen Mingyu Li Shanying He Jing Sun Zhigang Yu 《Hydrobiologia》2009,627(1):19-30
973.
The identification of brain tumor stem cells (BTSCs) leads to promising progress on brain tumor treatment. For some brain
tumors, BTSCs are the driving force of tumor growth and the culprits that make tumor revive and resistant to radiotherapy
and chemotherapy. Therefore, it is specifically significant to eliminate BTSCs for treatment of brain tumors. There are considerable
similarities between BTSCs and normal neural stem cells (NSCs), and diverse aspects of BTSCs have been studied to find potential
targets that can be manipulated to specifically eradicate BTSCs without damaging normal NSCs, including their surface makers,
surrounding niche, and aberrant signaling pathways. Many strategies have been designed to kill BTSCs, and some of them have
reached, or are approaching, effective therapeutic results. Here, we will focus on advantages in the issue of BTSCs and emphasize
on potential therapeutic strategies targeting BTSCs. 相似文献
974.
Purpose The low-density lipoprotein receptor (LDLr) mediates the uptake of LDL particles enriched with cholesterol, into several
tissues. In contrast to other tissues, the brain is thought to obtain cholesterol solely by de novo synthesis, yet certain
brain regions such as the brainstem are highly enriched with the LDLr. The goal of the present study was to assess the role
of the LDLr in maintaining cholesterol concentrations in the brainstem of wildtype and LDLr knockout (LDLr−/−) mice. Cholesterol
concentrations were also measured in the cortex, which served as a reference point, due to the lower expression of the LDLr,
as compared to the brainstem. Methods LDLr−/− and wildtype mice consumed an AIN-93G diet ad libitum until 7 weeks of age. After microwaving, the cortex and anterior
brain stem were isolated for cholesterol analysis. Cholesterol was extracted into chloroform/methanol, derivatized in trimethylsilyl
chloride and measured by gas chromatography/mass spectrometry. Results Concentrations of cholesterol in the brainstem did not differ statistically between LDLr−/− (18.8 ± 1.6 mg/g wet weight brain)
and wildtype (19.1 ± 2.0). Cortical cholesterol concentrations also did not differ statistically between LDLr−/− (11.0 ± 0.4 mg/g
wet weight brain) and wildtype (11.1 ± 0.2) mice. Conclusion The LDLr is not necessary for maintaining cholesterol concentrations in the cortex or brainstem, suggesting that other mechanisms
are sufficient to maintain brain cholesterol concentrations. 相似文献
975.
Effects of early-fruit removal on endogenous cytokinins and abscisic acid in relation to leaf senescence in cotton 总被引:7,自引:0,他引:7
Numerous studies have shown that early-fruit removal enhances vegetative growth and development of cotton (Gossypium hirsutum L.). However, few studies have examined changes in leaf senescence and endogenous hormones due to fruit removal. The objective
of this study was to determine the correlation between some endogenous phytohormones, particularly the cytokinins and abscisic
acid (ABA), and leaf senescence following fruit removal. Cotton was grown in pots and in the field during 2005 and 2006. Two
early-fruiting branches were excised from plants at squaring to form the fruit removal treatment while the non-excised plants
served as control. Plant biomass, seed cotton yield, cytokinins and ABA levels in main-stem leaves and xylem sap as well as
main-stem leaf photosynthetic rate (Pn) and chlorophyll (Chl) concentration were determined after removal or at harvest. Fruit
removals increased the leaf area, root and shoot dry weight and plant biomass at 35 days after removal (DAR), whether in potted
or field-grown cotton; under field conditions, it also improved plant biomass and seed cotton yield at harvest. The Pn and
Chl concentration in excised plants were significantly higher than in control plants from 5 to 35 DAR, suggesting that fruit
removal considerably delayed leaf senescence. Fruit-excised plants contained more trans-zeatin and its riboside (t-Z + t-ZR), dihydrozeatin and its riboside (DHZ + DHZR), and isopentenyladenine and its riboside
(iP + iPA) but less ABA in both main-stem leaves and xylem sap than control plants from 5 to 35 DAR. These results suggest
that removal of early fruiting branches delays main-stem leaf senescence, which can be attributed to increased cytokinin and/or
reduced ABA. Cytokinin and ABA are involved in leaf senescence following early fruit removal. 相似文献
976.
1植物名称红蒴立碗藓(Plryscomitriun eurystomum Sendtn.),也称尖口立碗藓、广口立碗藓。2材料类别配子体。3培养条件脱毒培养基:Knop(张献龙和唐克轩2004);愈伤组织诱导培养:MS+6-BA0.05mg·L-1;再分化培养基:MS。以上培养基均添加2%葡萄糖和1%琼脂。培养温度为(25±1)℃,光照强度为60-80μmol.m-2.s-1,光照时间为12h.d-1。4生长与分化情况4.1无菌材料的获得对采集得到的配子体植株先用75%酒精溶液消毒5S,无菌水清洗1次;再用0.25%新沽尔灭溶液表面消毒10S,无菌水漂洗3次;在无菌滤纸上将材料水分吸干,接种到不添加任何激素的Knop培养基上,培育获得无菌材料(图1)。 相似文献
977.
Feng ang ;Yanping Jing ;Zhen ang ;Tonglin Mao ;Jozef Samaj ;Ming Yuan ;Haiyun Ren 《Acta Botanica Sinica》2009,(2):113-121
Profilin is an actin-binding protein that shows complex effects on the dynamics of the actin cytoskeleton. There are five profilin isoforms in Arabidopsis thaliana L. However, it is still an open question whether these isoforms are functionally different. In the present study, two profilin isoforms from Arabidopsis, PRF1 and PRF2 were fused with green fuorescent protein (GFP) tag and expressed in Escherichia coil and A. thaliana in order to compare their biochemical properties in vitro and their cellular distributions in vivo. Biochemical analysis revealed that fusion proteins of GFP-PRF1 and GFP-PRF2 can bind to poly-L-proline and G-actin showing remarkable differences. GFP-PRF1 has much higher affinities for both poly-L-proline and G-actin compared with GFP-PRF2. Observations of living cells in stable transgenic A. thaliana lines revealed that 35S::GFP-PRF1 formed a filamentous network, while 35S::GFP-PRF2 formed polygonal meshes. Results from the treatment with latrunculin A and a subsequent recovery experiment indicated that filamentous alignment of GFP-PRF1 was likely associated with actin filaments. However, GFP-PRF2 localized to polygonal meshes resembling the endoplasmic reticulum. Our results provide evidence that Arabidopsis profllin isoforms PRF1 and PRF2 have different biochemical affinities for poly-L-proline and G-actin, and show distinctive Iocalizations in living cells. These data suggest that PRF1 and PRF2 are functionally different isoforms. 相似文献
978.
Ho‐Kee Koon Pui‐Shan Chan Ricky Ngok‐Shun Wong Zhen‐Guo Wu Maria Li Lung Chi‐Kwong Chang Nai‐Ki Mak 《Journal of cellular biochemistry》2009,108(6):1356-1363
Epidermal growth factor receptor (EGFR), a receptor often expressed in nasopharyngeal carcinoma (NPC) cells, is one of the recently identified molecular targets in cancer treatment. In the present study, the effects of combined treatment of Zn‐BC‐AM PDT with an EGFR inhibitor AG1478 were investigated. Well‐differentiated NPC HK‐1 cells were subjected to PDT with 1 µM of Zn‐BC‐AM and were irradiated at a light dose of 1 J/cm2 in the presence or absence of EGFR inhibitor AG1478. Specific protein kinase inhibitors of downstream EGFR targets were also used in the investigation. EGFR, Akt, and ERK were found constitutively activated in HK‐1 cells and the activities could be inhibited by the EGFR inhibitor AG1478. A sub‐lethal concentration of AG1478 was found to further enhance the irreversible cell damage induced by Zn‐BC‐AM PDT in HK‐1 cells. Pre‐incubation of the cells with specific inhibitors of EGFR (AG1478), PI3k/Akt (LY294002), or MEK/ERK (PD98059) before light irradiation were found to enhance Zn‐BC‐AM PDT‐induced formation of apoptotic cells. The efficacy of Zn‐BC‐AM PDT can be increased through the inhibition of EGFR/PI3K/Akt and EGFR/MEK/ERK signaling pathways in NPC cells. Combination therapy with Zn‐BC‐AM PDT and EGFR inhibitors may further be developed for the treatment of advanced NPC. J. Cell. Biochem. 108: 1356–1363, 2009. © 2009 Wiley‐Liss, Inc. 相似文献
979.
To determine whether they could serve as non-toxic or less damaging alternative antifouling (AF) agents, 17 flavone and isoflavone derivatives were isolated from terrestrial plant extracts, purified and examined for their ability to inhibit the settlement of barnacle (Balanus amphitrite) cyprids. In larval bioassays, eight compounds showed strong anti-larval settlement activities, with EC(50) values <10 microg ml(-1). Through an analysis of the structure-activity relationship of these compounds, it was found that (1) the structural difference between flavones and isoflavones did not affect their AF activities; (2) the 5-hydroxyl group on the skeletons played a key role in AF activities; and (3) the presence of hydroxyl group or bulky group on C3 significantly reduced AF activities. A hydrolysis experiment using genistein, a typical active compound in this study, indicated that it was decomposed in the marine environment by hydrolysis reaction and that the degradation speed was significantly affected by pH. In a field AF test, genistein inhibited the attachment of B. amphitrite on panels coated with genistein-paint mixtures. 相似文献
980.
Chuck T. Chen Zhen Liu Melissa Ouellet Frédéric Calon Richard P. Bazinet 《Prostaglandins, leukotrienes, and essential fatty acids》2009,80(2-3):157-163
Analyses of brain phospholipid fatty acid profiles reveal a selective deficiency and enrichment in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), respectively. In order to account for this difference in brain fatty acid levels, we hypothesized that EPA is more rapidly β-oxidized upon its entry into the brain. Wild-type C57BL/6 mice were perfused with either 14C-EPA or 14C-DHA via in situ cerebral perfusion for 40 s, followed by a bicarbonate buffer to wash out the residual radiolabeled polyunsaturated fatty acid (PUFA) in the capillaries. 14C-PUFA-perfused brains were extracted for chemical analyses of neutral lipid and phospholipid fatty acids. Based on the radioactivity in aqueous, total lipid, neutral lipid and phospholipid fractions, volume of distribution (VD, μl/g) was calculated. The VD between 14C-EPA- and 14C-DHA-perfused samples was not statistically different for total lipid, neutral lipids or total phospholipids. However, the VD of 14C-EPA in the aqueous fraction was 2.5 times higher than that of 14C-DHA (p=0.025), suggesting a more extensive β-oxidation than DHA. Furthermore, radiolabeled palmitoleic acid, a fatty acid that can be synthesized de novo, was detected in brain phospholipids from 14C-EPA but not from 14C-DHA-perfused mice suggesting that β-oxidation products of EPA were recycled into endogenous fatty acid biosynthetic pathways. These findings suggest that low levels of EPA in brain phospholipids compared to DHA may be the result of its rapid β-oxidation upon uptake by the brain. 相似文献