Ascorbate content of wheat leaves is not determined by maximal l-galactono-1,4-lactone dehydrogenase (GalLDH) activity under drought stress

Although ascorbic acid (AA) is a high-abundance metabolite, relatively little is known about the factors controlling its accumulation in leaves. To address this issue, we examined the role of l -galactono-1,4-lactone dehydrogenase (GalLDH), the enzyme which catalyses the last step of this pathway, in the control of AA content under optimal and stress conditions. In a range of species, no clear relationship between AA content and leaf GalLDH protein and activity was found under optimal growth conditions. To explore the effect of drought stress on GalLDH activity and protein content, wheat (Triticum aestivum L.) was selected for detailed analysis, using two cultivars that differ in their constitutive AA level. In well-watered plants, the AA content of cv Buck Chambergo (BCH) was over twice that of cv Cooperativa Maipún (CM) but dehydroascorbic acid content was similar in both cv. In agreement with this, dehydroascorbate reductase and glutathione reductase activities were higher in cv BCH than in cv CM, indicating a higher capacity for AA regeneration. Neither leaf DHA content nor activities of AA regenerating enzymes were modified by drought. Although drought caused a substantial increase in GalLDH protein and activity in the low AA cv CM, this treatment had no effect on these parameters in cv BCH. Notably, leaf AA content was unaffected by drought in either cv. These results suggest that GalLDH protein and activity cannot be used as an indicator for changes in the capacity for ascorbate biosynthesis and that AA biosynthesis is constrained by other factors under stress. This can be explained by the importance of regeneration in maintaining AA levels and possibly also by redox regulation of GalLDH.     

大叶桃花心木中的柠檬苦素成分(英文)

为研究大叶桃花木(Swietenia macrophylla)的柠檬苦素类成分,采用柱层析的方法从大叶桃花心木的枝叶中分离得七个柠檬苦素分别为swimacronoid A(1)、mahonin(2)、methyl angolensate(3)、methyl 6-hydroxyango-lensate(4)、methyl 6-acetoxyangolensate(5)、swietmanin(6)、deacetylsecomahoganin(7)。其中化合物1为一个新的evodulone型的柠檬苦素,化合物7为首次从该种中分的。     

乳腺癌化疗现状及相关研究进展

乳腺癌是除非上皮来源肿瘤中女性最常见的恶性肿瘤,在美国平均每3名女性中就有一名患乳腺癌,是女性肿瘤致死中的第二大原因,给政府经济造成了很大的损失。目前,乳腺癌主要是以手术治疗为主,而化疗,放疗等也作为相当重要的辅助治疗应用于临床。这种手术加化疗的治疗方法一直可以取得很好的疗效,甚至于可以保住乳房。近年来,乳腺癌的化疗已逐步成为其治疗的首选方式,包括术后辅助化疗和术前的新辅助化疗。但由于化疗药物的滥用和肿瘤本身的异质性或是其他原因,越来越多的肿瘤耐药性报道给乳腺癌的化疗带来了很大的挑战。而这种肿瘤耐药性的分子机制尚不是很清楚。本文将从乳腺癌的概述,乳腺癌化疗的现状及乳腺癌化疗的前景来综述这一灾难性疾病。     

溃愈散对溃疡性结肠炎患者血清IL-4水平的影响及临床疗效观察

目的：探讨溃愈散对溃疡性结肠炎患者血清IL-4水平的影响及临床疗效观察。方法：将60例UC患者随机分为2组,治疗组和对照组各30例,治疗组用溃愈散保留灌肠治疗,对照组口服柳氮磺吡啶治疗。采用双抗体夹心ELISA法检测2组患者治疗前后血清IL-4水平,并与30例健康志愿者（空白组）对照。结果：治疗组临床总有效率为86．7％,对照组临床总有效率为70．0％,两组总有效率比较差别无统计学意义（P〉0．05）。两组肠黏膜病变疗效相当（P〉0．05）。治疗前两组血清IL-4水平明显低于空白组（P〈0．01）。治疗组与对照组治疗前相互比较,血清IL-4水平无统计学差异,治疗后两组血清IL-4水平较治疗前均明显上升（P〈0．01）,且治疗组上升程度高于对照组（P〈0．01）。结论：溃愈散对UC有良好的治疗作用并提高UC患者血清IL-4水平。