Nuclear pore electron micrograph

Fig. 1 Ultrastructure of a nucleus from chicken liver and diagrammatic representation of the nuclear envelope. (A) Transmission electron micrograph of an ultrathin section through a nucleus from baby chick (cockerel) liver, showing the perinuclear cytoplasm (Cyt), nuclear envelope (NE), nuclear pore complex (NPC), and nucleoplasm (Nu). Scale bar, 1 /im. (B) Diagram showing prominent features of the nuclear envelope—the lamina (L), inner nuclear membrane (INM), outer nuclear membrane (ONM), nuclear pore complex (NPC), rough endoplasmic reticulum (RER), and ribosomes (R).

Fig. 2 Transmission electron micrograph of karyoskeletal protein-enriched fraction prepared from Drosophila embryos. The main panel shows a nucleuslike structure, bounded by a peripheral lamina (L) Inset Higher magnification showing tangential section through the periphery of karyoskeletal protein structure as shown in the main panel. Nuclear pore complex remnants can be readily appreciated as small ringlike structures.

Fig. 6 Dark-field electron micrographs of freeze-dried specimens, (A) Yeast nuclear pore complexes full-scale is 1.024 /urn (in collaboration with Qing Yang and Christopher Akey. Boston University). (B). Yeast spindle pole bodies with microtubules attached full-scale is 2,048 /xm (in collaboration with Esther Bullitt, Boston University).

On electron micrographs prepared from tissues fixed in osmic acid, the nuclear membrane appears as an envelope 250 A thick composed of three different layers an inner and an outer dense lining (each measuring 60 A in thickness) and a less dense median space (120 A thick). Unlike the cell or the mitochondrial membranes, the nuclear envelope (see Fig. 2-2) is not continuous, but is frequently interrupted by circular pores 1000 A in diameter [1-9]. 

---