Transportation selection mechanism between nucleus and cytoplasm in the nuclear pore complex Approach from morphology

在冷冻破裂过程中，通过调节固定剂的浓度和种类和/或控制防冻液的浓度，暴露了大鼠胰腺腺泡细胞核膜的全部8种表面(外、内核膜的4个真面，外、内核膜的4个断裂面)。用高分辨扫描电子显微镜(SEM)对暴露表面进行了离子包裹，发现在0.1%Os溶液浸泡处理过程中，含有核孔复合体(NPC)的蛋白质趋于消失，因此可以从细胞质侧和核侧观察到直径约为45~65 nm的NPC核孔。核孔周围的膜稍有隆起，内核膜的真表面上似乎形成了直径约90 nm的环状。扫描电子显微镜观察，细胞质一侧的REVE…更重要的是，构成鼻咽癌细胞质部分的8个颗粒不是球形的，而是椭圆形的。由于这些颗粒在浸渍处理过程中很容易消失，因此可以在没有颗粒的情况下观察到外核膜的真实表面。表面光滑平整，看起来完好无损。这一结果表明，颗粒位于核膜外的真实表面，与膜几乎没有联系。输送物质(“中心塞”或“货物”或“货物和运输因子”)的直径约为25-30 nm。鼻咽癌中心部围绕运输材料形成内径约10~35 nm、外径约45~65 nm的中心环。它由16个粒子组成。位于核周的内径约45~65 nm、外径约90~100 nm的环状结构也由16个颗粒组成。核周和核孔中心的蛋白质颗粒似乎在膜上形成一个紧密相连的环，很可能是以较暗单元的形式存在。较少

All eight kinds of surfaces of nuclear membranes (four true surfaces of the outer and inner nuclear membranes, four fracture faces of the outer and inner nuclear membranes) in the rat pancreatic acinar cell were exposed by adjusting the density and the kind of fixatives and/or by controlling the density of antifreeze solution at the freeze cracking process. The exposed surfaces were ion-coated with osmium and they were investigated with high-resolution scanning electron microscope(SEM).As the proteins consisting nuclear pore complex(NPC) were tend to disappear at the maceration treatment process with 0.1% osmium solution, the observation of the nuclear pore without proteins of NPC about 45-65 nm in diameter could be possible both from the cytoplasm side and nucleus side. The membrane surrounding the nuclear pores rose slightly like the bank, and it seemed to form a ring of about 90 nm in diameter on the true surface of inner nuclear membrane.SEM observation from the cytoplasm side reve … More aled that eight particles consisting the cytoplasmic part of NPC were not spherical but ovoid in shape. Since these particles disappeared rather easily at the maceration treatment process, it became possible to observe the true surface of outer nuclear membrane without the particles. The surface was smooth and flat appearance, and so it seemed to remain intact. This result indicates that the particles are situated on the true surface of outer nuclear membrane having little connection with the membrane.The size of transporting material ("central plug" or "cargo" or "cargo and transport factors") was about 25-30 nm in diameter. The central part of NPC surrounding the transporting materiel formed a central ring of about 10-35 nm in inner diameter, 45-65 nm in outer diameter. It was composed of sixteen particles. The ring like structure of about 45-65 nm in inner diameter and about 90-100 nm in outer diameter situated in the perinuclear space was also composed of sixteen particles. The both composition protein particles in the perinuclear space and in the center of nuclear pore seemed to form a ring connecting tightly to each other across the membrane probably in the form of dimmer units. Less