The so-called “megasporophylls” of Ginkgoales, Coniferales, and Gnetales have been proven metamorphosed shoots, making “megasporophyll” of Cycas the last one resembling a leaf. Why and how it is so in Cycas (the m...The so-called “megasporophylls” of Ginkgoales, Coniferales, and Gnetales have been proven metamorphosed shoots, making “megasporophyll” of Cycas the last one resembling a leaf. Why and how it is so in Cycas (the most ancient seed plant dated back to the Palaeozoic) become key questions because their answers are hinged with the fates of several hypotheses in botany. Here, we performed a controlled developmental experiment on the ovulate parts (megasporophylls) in a single strobilus of Cycas sexseminifera. By removing the neighboring ones, two of the ovulate parts were left isolated spatially from others, in contrast to others left intact. A half-year-long continuous observation indicates that the isolated ovulate parts change their ovule arrangement from initial pinnate into helical pattern, while the intact ones in the same strobilus remain pinnate as usual. Since all ovulate parts are in the same strobilus and controlled by the same genome in this case and the only difference is lack of pressure from neighbors for the isolated ones, the changes in ovule orientation and ovulate part morphology can only be attributed to the lack of mechanical pressure among the ovulate parts. Therefore, we conclude that mechanical pressure, not genes, controls the morphology of ovulate parts and contributes to the leaf-like ovulate part morphology in Cycas. This conclusion cautions previous superficial interpretations of plant morphology.展开更多
目的研究压力对体外培养的人脐静脉内皮细胞ECV-304形态和结构的影响,探讨压力增高对血管内皮细胞形态和结构的影响及在门脉高压症血管内皮病变中的意义。方法对静态培养及不同压力、不同时间条件下体外培养的人脐静脉内皮细胞ECV-304...目的研究压力对体外培养的人脐静脉内皮细胞ECV-304形态和结构的影响,探讨压力增高对血管内皮细胞形态和结构的影响及在门脉高压症血管内皮病变中的意义。方法对静态培养及不同压力、不同时间条件下体外培养的人脐静脉内皮细胞ECV-304用倒置显微镜和透射电镜进行形态和结构观察,并用计算机图像分析系统进行形态参数的定量分析。结果施加生理范围和超生理范围的压力干预后,在倒置相差显微镜下可见内皮细胞的形态发生改变,表现为细胞形状梭形化或变为不规则形,部分细胞轮廓不清,胞核增大,大多数细胞胞浆有暗色颗粒,细胞排列紊乱,以40 mm Hg 24 h组最为明显。形态参数的定量分析结果显示在40 mm Hg压力下培养24 h后,血管内皮细胞的细胞面积、胞核面积和形状因子与正常组和生理压力组相比均有极显著性改变(P均<0.01)。透射电镜观察则见加压组有空泡的细胞数明显多于正常组,胞质中空泡的数目也明显增多,且大小不一,细胞内的吞噬溶酶体也明显增多。结论血管内皮细胞对机械压力有一s定的耐受能力,但长时间超生理范围的压力对血管内皮细胞的形态和结构有显著影响。门静脉高压症的血管内皮病变的形成与其内皮细胞长期受高压刺激有关。展开更多
文摘The so-called “megasporophylls” of Ginkgoales, Coniferales, and Gnetales have been proven metamorphosed shoots, making “megasporophyll” of Cycas the last one resembling a leaf. Why and how it is so in Cycas (the most ancient seed plant dated back to the Palaeozoic) become key questions because their answers are hinged with the fates of several hypotheses in botany. Here, we performed a controlled developmental experiment on the ovulate parts (megasporophylls) in a single strobilus of Cycas sexseminifera. By removing the neighboring ones, two of the ovulate parts were left isolated spatially from others, in contrast to others left intact. A half-year-long continuous observation indicates that the isolated ovulate parts change their ovule arrangement from initial pinnate into helical pattern, while the intact ones in the same strobilus remain pinnate as usual. Since all ovulate parts are in the same strobilus and controlled by the same genome in this case and the only difference is lack of pressure from neighbors for the isolated ones, the changes in ovule orientation and ovulate part morphology can only be attributed to the lack of mechanical pressure among the ovulate parts. Therefore, we conclude that mechanical pressure, not genes, controls the morphology of ovulate parts and contributes to the leaf-like ovulate part morphology in Cycas. This conclusion cautions previous superficial interpretations of plant morphology.
文摘目的研究压力对体外培养的人脐静脉内皮细胞ECV-304形态和结构的影响,探讨压力增高对血管内皮细胞形态和结构的影响及在门脉高压症血管内皮病变中的意义。方法对静态培养及不同压力、不同时间条件下体外培养的人脐静脉内皮细胞ECV-304用倒置显微镜和透射电镜进行形态和结构观察,并用计算机图像分析系统进行形态参数的定量分析。结果施加生理范围和超生理范围的压力干预后,在倒置相差显微镜下可见内皮细胞的形态发生改变,表现为细胞形状梭形化或变为不规则形,部分细胞轮廓不清,胞核增大,大多数细胞胞浆有暗色颗粒,细胞排列紊乱,以40 mm Hg 24 h组最为明显。形态参数的定量分析结果显示在40 mm Hg压力下培养24 h后,血管内皮细胞的细胞面积、胞核面积和形状因子与正常组和生理压力组相比均有极显著性改变(P均<0.01)。透射电镜观察则见加压组有空泡的细胞数明显多于正常组,胞质中空泡的数目也明显增多,且大小不一,细胞内的吞噬溶酶体也明显增多。结论血管内皮细胞对机械压力有一s定的耐受能力,但长时间超生理范围的压力对血管内皮细胞的形态和结构有显著影响。门静脉高压症的血管内皮病变的形成与其内皮细胞长期受高压刺激有关。
