. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . Fig. 1. Electron micrograph of a single nucleus in a fraction prepared by the method of Philpot and Stanier. The nucleolus may be seen, but the nuclear membrane is absent. Inset. A high power micrograph of the nucleoplasm, showing filaments about 100 A in diameter. Fig. 2. Electron micrograph of a few mitochondria prepared in the dextran medium. The internal and external membranes may be seen. Inset. A micrograph at the same magnification of a particle in a light mitochondrial fraction, which might be a lysosome.
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . Fig. 1. Electron micrograph of a single nucleus in a fraction prepared by the method of Philpot and Stanier. The nucleolus may be seen, but the nuclear membrane is absent. Inset. A high power micrograph of the nucleoplasm, showing filaments about 100 A in diameter. Fig. 2. Electron micrograph of a few mitochondria prepared in the dextran medium. The internal and external membranes may be seen. Inset. A micrograph at the same magnification of a particle in a light mitochondrial fraction, which might be a lysosome. phosphate These nuclei (fig. 1) from rat liver are relatively clean of contaminating cytoplasm; this may be partially the result of the loss of the nuclear membrane, to which the cytoplasmic debris tends to adhere. There are. however, numerous small fila- ments (ca. 100 A diam.) dispersed throughout the nuclei (fig. 1, inset). These filaments which signifi- cantly have the same diameter as nucleo-protein filaments, may be an artifact due to the method of separation; however, it is also possible that they also exist in sections of whole tissue, but are rendered invisible by an interstitial substance, which is lost during separation, possibly as a consequence of the removal of the nuclear membranes. Methods for niitochondria.—The conventional me- thod for the separation of mitochondria uses M sucrose as a suspending medium (5). Mitochondria prepared by this method and by improved methods have been examined by several workers (1, 2, 6, 9). Mitochondria prepared in M sucrose are swollen, empty and usually contaminated with microsomal debris. We have described an improved complex medium containing M raffinose, 6 "o dextran and other additives. Mi- tochondria prepared in this medium (fig. 2) are not swollen and retain their internal double mem- branes and other contents. When the centrifugation conditions are carefully controlled it is possible to obtain cleane
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