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1.
E. Conde A. M. Moreno I. Martin-Lacave A. Fernandez y H. Galera 《Anatomia, histologia, embryologia》1992,21(1):94-100
A systematic immunohistochemical study of the ultimobranchial tubule (UBT) has been carried out in 45 Wistar rats of different ages (0, 5, 10, 15, 20, 25, 30, 60 and 120 days). The existence of calcitonin immunoreactive cells in the UBT wall has been demonstrated in a 5-days old rat. In addition, immunohistochemical studies for thyroglobulin revealed positive staining in follicular cells connected to the UBT and, occasionally, in isolated cells lying within solid clusters from the UBT. These last results together with the continued and repeated existence of numerous mitosis and PAS (+) microfollicles, apparently rising from the UBT, support the hypothesis that the ultimobranchial body (UBB) may contribute partially to the formation of a part of the follicular component. 相似文献
2.
Juan Pablo Zoffoli Bernardo A. Latorre Paulina Naranjo 《Postharvest Biology and Technology》2009,51(2):183-192
Over 54,600 ha of table grapes (Vitis vinifera), mainly cvs. ‘Thompson Seedless’, ‘Flame Seedless’ and ‘Redglobe’, are planted in Chile. Almost the entire production is exported to the USA, Europe, Asia, or one of several Latin American countries, which typically requires 15–40 d of maritime transportation. During this period, several physical, physiological, and pathological factors cause table grape deterioration. Because berry size is the main quality factor in international markets, farmers often overuse the growth regulators, gibberellic acid (GA3) and forchlorfenuron (CPPU), in an effort to increase berry size. We examined the effect of preharvest growth regulators on seedless (‘Thompson Seedless’, and ‘Ruby Seedless’) and seeded (‘Redglobe’) table grape cultivars during cold (0 °C) storage plus a shelf life period of 3 d at 20 °C. The overuse of GA3, eight instead of two GA3 applications on Thompson Seedless, and the use of one GA3 application on Redglobe and ‘Ruby Seedless’, increased berry pedicel thickness and lowered cuticle content but induced shatter and predisposed grapes to gray mold caused by Botrytis cinerea. In contrast, CPPU increased berry pedicel thickness and cuticle content but did not increase shatter or gray mold incidence. Clusters that were subjected to overuse of combined GA3 and CPPU were highly sensitive to shatter, had the thickest pedicel, and developed a high gray mold incidence during cold storage. Hairline, a fine cracking developed during cold storage, was induced on ‘Thompson Seedless’ and ‘Ruby Seedless’ by growth regulators, but no hairline occurred on ‘Redglobe’ table grapes. Therefore, berry quality during cold storage is greatly influenced by growth regulator management in the vineyard. 相似文献
3.
4.
Mouillot Florent Ratte Jean-Pierre Joffre Richard Moreno Jose Manuel Rambal Serge 《Landscape Ecology》2003,18(7):665-674
Based on recent needs to accurately understand fire regimes and post-fire vegetation resilience at a supra-level for carbon cycle studies, this article focusses on the coupled history of fire and vegetation pattern for 40 years on a fire-prone area in central Corsica (France). This area has been submitted since the beginning of the 20th century to land abandonment and the remaining land management has been largely controlled by frequent fires. Our objectives were to rebuild vegetation and fire maps in order to determine the factors which have driven the spatial and temporal distribution of fires on the area, what were the feed backs on the vegetation dynamics, and the long-term consequences of this inter-relationship. The results show a stable but high frequency of small fires, coupled with forest expansion over the study period. The results particularly illustrate the spatial distribution of fires according to topography and vegetation, leading to a strong contrast between areas never burnt and areas which have been burnt up to 7 times. Fires, when occuring, affect on average 9 to 12% of the S, SE and SW facing slopes (compared to only 2 to 5% for the N facing slopes), spread recurrently over ridge tops, affect all the vegetation types but reburn preferentially shrublands and grasslands. As these fire-proning parameters have also been shown to decrease the regeneration capacity of forests, this study highlights the needs in spatial studies (both in terms of fire spread and vegetation dynamic) to accurately apprehend vegetation dynamic and functionning in fire-prone areas.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
5.
Mario Suwalsky Maritza BenitesBeryl Norris Carlos P Sotomayor 《Pesticide biochemistry and physiology》2003,77(2):44-53
The current study examines the acute effects of the organophosphorus pesticide chlorpyrifos on a sympathetic synapse of the frog Caudiverbera caudiverbera. Nerve stimulation was followed immediately by a transient increase in the short-circuit current (SCC) and in the potential difference (PD), which consisted of a rapid and then a slow component. Chlorpyrifos concentrations from 5 μM to 1.0 mM caused a dose-dependent block of both components to a 10% of their control values, which was reversed by washout. The pesticide blockade did not affect the skin response to noradrenaline. X-ray diffraction and fluorescence spectroscopy studies on membrane models showed marked phospholipid perturbation, which favors changes in ion channel conformation and interferes with receptor proteins, thus altering noradrenergic transmission and Cl− secretion in the mucous glands. The foregoing results may be interpreted as a reversible inhibition of the neuroepithelial synapse to nerve stimulation, possibly due to non-specific lip μd-protein perturbation, interference with synaptic transmission, and transient Cl− channel inactivation. 相似文献
6.
ZHOU Hua ZHANG Dai-fu SHAN Jiang SU Hai NIU Hui-yan WANG Juan YU Ping QI Wei-gang 《园艺学报》2004,20(12):2261-2264
AIM: To investigate the effects of angiotensin-converting enzyme inhibitors (ACEI), fosinopril, captopril and angiotensin II AT1 antagonists, valsartan on tissue factor (TF) expression on monocytes induced by lipopolysaccharide (LPS). METHODS: Mononuclear leukocytes from normal delivered female umbilical veins were incubated with bacterial LPS in presence or absence of different ACE inhibitors .At the end of incubation, the cells were disrupted by 3 freeze-thaw cycles. TF procoagulant activity was assessed by a one-stage clotting assay. RT-PCR was used to check TF mRNA expression, and GAPDH mRNA was used for parallel assay. RESULTS and CONCLUSION: The results showed that increased expression of TF mRNA induced by LPS was inhibited by fosinopril, captopril and valsartan, respectively, and the procoagualant activity of monocytes was also reduced. 相似文献
7.
脊椎动物性别分化和性腺发育的分子机制保守,但不同类群的最上游的性别决定基因却大不相同,尤其是鱼类,其性别决定基因表现出明显的多样性。性别决定包括环境性别决定和遗传性别决定,环境性别决定主要受温度、光照、激素和pH等的影响,而遗传性别决定一般由位于性染色体上的性别决定基因决定。转化生长因子-β(transforming growth factorβ, TGF-β)信号通路参与介导了多种生物学过程,近年来很多研究表明,鱼类有多个性别决定基因都是TGF-β信号通路的成员,且该信号通路对于鱼类的性别分化也有重要的作用。本文总结了鱼类已报道的性别决定基因或候选基因,详细综述了TGF-β信号通路在鱼类性别决定与分化中的各种功能,并探讨了该信号通路参与鱼类性别决定的可能机制,这对认识TGF-β信号通路在鱼类性别决定、分化中的作用和性控育种有重要意义。 相似文献
8.
基于不同分析方法研究磷酸根在矿物表面吸附机制的进展 总被引:3,自引:1,他引:2
磷素是植物生长必需的营养元素,也是联系生态系统中生物与非生物作用的关键元素。对磷酸根在矿物表面吸附反应机制的深入认识,有助于了解其在陆地和水环境中的形态、迁移、转化和生物有效性。本文主要综述了磷酸根在常见(土壤)矿物表面吸附机制的研究进展。各种分析技术或方法,如OH–释放量分析、Zeta电位分析(电泳迁移率测试)、等温滴定量热法、原子力显微镜、X射线光电子能谱、红外光谱、核磁共振波谱、X射线吸收光谱、表面络合模型、量子化学计算等,均以不同方式揭示磷酸根在不同矿物体系的吸附机制。磷酸根在矿物(尤其是铁、铝氧化物)表面的吸附通常伴随着水基和羟基的交换。一般认为磷酸根在矿物表面主要形成双齿双核、单齿单核内圈络合物,且受pH的影响较大。pH以及磷酸根在矿物表面的吸附密度影响内圈络合物的质子化状态。在低pH、高磷浓度、较高反应温度、较长吸附时间,以及弱晶质矿物吸附等条件下矿物表面吸附的磷可在矿物表面转化形成含磷的表面沉淀,造成矿物溶解转化以及磷生物有效性的进一步降低。最后展望了磷酸盐在矿物-水界面吸附有关的研究热点和方向。 相似文献
9.
脑部特异表达rtTA调控元件转基因小鼠的构建 总被引:1,自引:1,他引:0
为获得一种可调控基因表达系统,避免传统转基因在胚胎发育早期表达的毒性作用或致死作用以及基因过度表达而造成难于分析的复杂多表型,应用分子生物学方法将四环素反式激活子rtTA克隆到仅在脑部能被激活的钙调蛋白依赖性蛋白激酶CaM kinase Ⅱα亚基启动子之后,将其通过显微注射方法注入FVB小鼠受精卵雄原核中获得四环素调控系统中反应组分的转基因工具鼠.经PCR及Southern检测,最终得到3只阳性小鼠(1公2母),表达检测结果显示,其中仅2只(1公1母)后代检测到rtTA表达产物.结果表明已成功构建四环素调控系统中的转基因工具鼠,为今后研究其他脑部基因功能提供便利. 相似文献
10.
不同贮存温度和时间对蜂王浆中游离氨基酸的影响 总被引:3,自引:2,他引:1
将新鲜蜂王浆分别贮藏在不同时间和温度下,对比分析游离氨基酸的含量及组成。结果测得蜂王浆中含有21种游离氨基酸,以脯氨酸含量最高。在室温下贮藏时,苏氨酸变化最大;-20℃时,丝氨酸变化最大;甲硫氨酸和组氨酸在-20℃下较稳定,含量几乎不变,在室温下15d内分别下降12.5%和17.4%,30d后分别下降37.5%和40.0%。由此我们可以推测甲硫氨酸和组氨酸在一定程度上可以代表蜂王浆的新鲜度。 相似文献