家蚕五龄第1天与第4天后部丝腺蛋白质双向电泳图谱比较

【目的】家蚕后部丝腺是合成分泌占蚕丝总量75%～80%丝素蛋白的器官，通过后部丝腺蛋白的研究，有利于阐明家蚕分泌丝素蛋白及蚕茧优质、高产的机理。【方法】采用蛋白质双向电泳和图像分析技术，研究了家蚕不同品种五龄第1天和第4天后部丝腺细胞的蛋白质组成变化。【结果】发现各个品种五龄第1天和第4天后部丝腺细胞的蛋白质组成存在差异，但蛋白质水平的差异，远远小于从EST分析得出的基因表达水平的差异；不同家蚕品种，从五龄第1天到第4天，后部丝腺细胞的蛋白质组成的变化规律各不相同。【结论】暗示了家蚕丝素分泌的过程可能受到多种蛋白的调控，不同的品种，在调控位点及调控蛋白上存在着一定的差异，从而导致了不同品种家蚕后部丝腺细胞在分泌丝素能力上的差异。

A Study of the Effects of Different Grazing Intensities on Soil Physical Properties of Grassland and Forest Floor——For Example Hilly and Gully Regions on the Loess Plateau

【Objective】The objective of this article was to study the changes in soil physical properties with different grazing intensities. 【Method】With grazing field experiment, the effects of different grazing intensities and different types of livestock on physical properties of surface (0-10 cm) soil of grazing grassland and forest land with Caragana korshinskii Kom. were studied at hilly-gully regions on the Loess Plateau -Pianguan, Shanxi Province.【Result】The results showed that grazing intensity directly influenced the physical structure of soil of grazing grassland and Caragana korshinskii Kom. The soil bulk density increased along with the increase of grazing intensity, while water content and soil porosity decreased. Compared with goat selected as grazing livestock, sheep had a lesser that trampling effect on grazing land and the soil bulk density, was relatively small. The water content and soil porosity of the grazing land under sheep is higher than that №under goat. 【Conclusion】 Consequently, the soil properties of the surface layer (0-10 cm) grazing grassland and Caragana korshinskii Kom. are most sensitive to grazing intensity.