Wiener J, Spiro D, Loewenstein W R
J Cell Biol. 1965 Oct;27(1):107-17. doi: 10.1083/jcb.27.1.107.
The fine structures of nuclear envelopes known to have different permeability properties were compared. Membranes of salivary gland cell nuclei of Drosophila (third instar) and Chironomus (prepupae), which are strong barriers to ion diffusion, and membranes of oocyte nuclei (germinal vesicle) of Xenopus and Triturus, which are much more ion-permeable, show no essential difference in size, frequency, and distribution of their membrane gaps ("pores") which could account for the marked disparities in membrane permeability. The gaps are occupied by diffuse electron-opaque material with occasional central regions of strong opacity. This material may possibly account for the high diffusion resistance of Drosophila and Chironomus nuclear envelopes, where the resistance is far too great to allow free diffusion through the gaps. But material of this kind is also present in the more permeable nuclear envelopes of Xenopus and Triturus oocytes, and there are no convincing structural differences discernible with the techniques employed.
对已知具有不同通透性的核膜精细结构进行了比较。果蝇（三龄幼虫）和摇蚊（预蛹）唾液腺细胞核的膜对离子扩散具有很强的屏障作用，而非洲爪蟾和蝾螈卵母细胞核（生发泡）的膜对离子的通透性要强得多，它们膜间隙（“孔”）的大小、频率和分布没有本质区别，而这种区别本可解释膜通透性的显著差异。这些间隙被弥漫性电子不透明物质占据，偶尔有强不透明的中心区域。这种物质可能是果蝇和摇蚊核膜具有高扩散阻力的原因，其阻力太大以至于无法让离子通过间隙自由扩散。但在非洲爪蟾和蝾螈卵母细胞通透性更强的核膜中也存在这种物质，并且用所采用的技术未发现明显的结构差异。
