The unique organization of filamentous actin in the medullary canal of the medulla oblongata

In the central canal, F-actin is predominantly localized in the apical region, forming a ring-like structure around the circumference of the lumen. However, an exception is found in the medulla oblongata, where the apical F-actin becomes interrupted in the ventral aspect of the canal. To clarify the precise localization of F-actin, the fluorescence signals for F-actin were converted to the peroxidase/DAB reaction products in this study by a phalloidin-based ultrastructural technique, which demonstrated that F-actin is located mainly in the microvilli and terminal webs in the ependymocytes. It is because the ventrally oriented ependymocytes do not possess well-developed microvilli or terminal web that led to a discontinuous labeling of F-actin in the medullary canal. Since spinal motions can change the shape and size of the central canal, we next examined the cytoskeletons in the medullary canal in both rats and monkeys, because these two kinds of animals show different kinematics at the atlanto-occipital articulation. Our results first demonstrated that the apical F-actin in the medullary canal is differently organized in the animals with different head-neck kinemics, which suggests that the mechanic stretching of spinal motions is capable of inducing F-actin reorganization and the subsequent cell-shape changes in the central canal.     

Effects of CEPA and 1-MCP on Flower Bud Differentiation of Apple cv. ‘Nagafu No.2’ Grafted on Different Rootstocks

Journal of Plant Growth Regulation - The apple (Malus domestica Borkh.) has a relatively long sapling stage which prevents fruit breeding. The understanding of the flowering system is important to...     

葡萄枝条水分含量变化与抗寒性关系

以12个葡萄品种1年生枝条为试材,通过0、-15、-18、-21、-24、-27、-30、-133℃8个低温处理24h后,测定不同低温胁迫下葡萄枝条的,6-含水量、束缚水含量、自由水含量和束缚水与自由水的比值。结果表明：随着处理温度的降低,同一品种枝条的总含水量基本恒定,自由水含量呈先下降再升高的趋势,束缚水含量和束缚水与自由水的比值均呈现为先升高再下降的趋势;束缚水与自由水的比值随低温胁迫的变化呈Cubic方程,不同品种束缚水与自由水的比值达到最高点的温度不同,‘双红’、‘北冰红’、‘左优红’的拐点温度在-25℃以下,‘775’、‘巨峰’的拐点温度在-20℃左右,‘雷司令’、‘黑比诺’、‘霞多丽’的拐点温度在-18℃左右,‘赤霞珠’、‘梅鹿特’、‘白比诺’、‘红地球’拐点温度在-16～17℃。对葡萄休眠枝条进行低温处理后,通过测定束缚水与自由水含水量变化鉴定葡萄品种的抗寒性是可行的。     

甘肃白水江自然保护区瘦枝Xiu生物学特性及防治

白水江瘦枝Macellina baishuijiangia Chen是甘肃白水江自然保护区所辖林区的主要森林害虫之一。1992年调查其成灾面积达133 hm2,其中范坝、碧口、刘家坪等保护站受害最严重,虫口密度高达150～200头／株。连续两年危害可导致成片锐齿栎树枯死,造成的直接经济损失1年就达85.3万元,且影响森林自然景观及破坏区域生态平衡。为确切掌握该虫在这一地区的发生规律及其习性,作者于1996～1997年进行了定点观测。 1 观测方法 此项研究采取室内饲养观察与野外调查试验相结合的方法进行。 1.1 室内饲养 在室内设置尼龙纱笼80cm×100cm×150cm 1个,30cm×40cm×60cm 3个,野外也同样设置上述4个纱笼,放置于少人为干扰的自然环境中,从野外采集虫体健康,跗肢齐全的若虫放入饲虫笼内,在每个笼内同时放入锐齿栎的鲜嫩枝条供若虫取食,并用罐头瓶加水保湿。在每笼分别放入10头初龄若虫,任其自由取食,每日定时记录个体若虫取食量,同时采用上述方法对若虫进行个体单独饲养,并记录某个体取食量、蜕皮次数、产卵的始、盛、末期、产卵量、寿命和遗腹卵数量。 1.2 野外调查 采取随机抽样的方式进行,在边长28.28m×28.28m的标准样地内,采用双对角线的方法进行调查,逐株详细调查虫口密度,并记录受害程度与寄主植物。     

地衣芽胞杆菌来源角蛋白酶N端对活力及其热稳定性的影响

【目的】通过对一株地衣芽孢杆菌来源的角蛋白酶N端进行分子改造,研究其对角蛋白酶活力和热稳定性的影响,进而提高角蛋白酶的热稳定性。【方法】将角蛋白酶N端前5个氨基酸进行分段缺失,并通过序列比对将N端的前5个氨基酸替换为来源于Thermoactinomyces vulgaris的嗜热蛋白酶的N端,将野生型和突变体角蛋白酶基因在枯草芽孢杆菌WB600中进行表达,并对重组酶进行纯化与酶学性质研究。【结果】角蛋白酶N端不同长度的缺失大幅度地降低了角蛋白酶的活力,其中缺失前5个氨基酸完全丧失了酶活力。将角蛋白酶N端前5个氨基酸替换为嗜热蛋白酶N端前12个氨基酸,虽然降低了近70%的活力,但是却增加了角蛋白酶的热稳定性,60°C条件下的半衰期t1/2由原来的9 min提高到20 min。【结论】角蛋白酶的N端对其酶活力具有较大的影响,与嗜热蛋白酶来源的N端进行替换可以有效提高角蛋白酶的热稳定性。