Nuclear transfer studies of amoeba proteus after the inhibition of cell division by injection of non-homologous cytoplasm

Following the injection of the post-microsomal supernatant fraction of $\text{Amoeba discoides}$ cytoplasm into $\text{A.proteus}$, cell division is inhibited in at least 90% of the recipient cells. Nuclear transfers were performed to determine the site of inhibition in these injected cells. When nuclei from injected, inhibited cells one day after injection were transferred into new $\text{A.proteus}$ cytoplasms, 62% of the transfers divided. This ability to promote division declined with the length of time between transfer and the original_ injection. However, when nuclei from $\text{A.proteus}$ were transferred into injected, inhibited cytoplasms, only a low number of cells divided, comparable to the number obtained after the injection operation only, namely less than 10%. Thus although many nuclei could recover from inhibition, it was not possible to restore the cytoplasms of inhibited cells by new nuclei.     

Amoeba proteus: the nuclear periphery.

This study extends previous work on the nuclear envelope and associated structures. It illustrates that the cylindrical structures of the honeycomb lattice are not attached to the nuclear envelope, although generally perpendicular and closely apposed to it, and that there is a complex arrangement of fibrillar material between the cylinders of the lattice. The relationship of nuclear helices to these structures is described and the possible mode of their transfer from nucleus to cytoplasm is discussed.     

Observation of filaments of 10nm in the demembraned cytoplasm of Amoeba proteus

We report here the first observation of 10 nm filaments in a protozoan, Amoeba proteus. These intermediate sized filaments were observed in spread cytoplasmic preparations of amoeba as stable cytoplasmic components over a wide range of pH (5.0-9.0). Although their morphology is grossly similar to the vertebrate intermediate filaments by negative staining, the filaments of amoeba show a characteristic helical structure with a 25 nm axial periodicity and do not display fibrillar projection along their length or at their extremity.     

Pinocytosis and locomotion of amoebae. XIX. Immunocytochemical demonstration of actin and myosin in Amoeba proteus

The spatial distribution of cytoplasmic actin and myosin in 1. normal locomoting, 2. immobilized, and 3. pinocytosing Amoeba proteus was demonstrated by indirect immunofluorescence microscopy. In orthotactic and polytactic cells fixed during normal locomotion actin is mainly located in a cortical layer delineating the granuloplasm from the peripheral hyaloplasm. In cell areas lacking a hyaloplasmic sheet the actin layer immediately borders the plasma membrane. The amount of actin within the continuous layer seems to increase from the advancing front to the middle cell region and to decrease again toward the uroid. The distribution of myosin is largely congruent to the display of actin, with the exception that the myosin-based fluorescence of the cortical layer gradually increases from the front to the uroid. A considerable amount of actin and myosin is also distributed around the nucleus and the contractile vacuole. In immobilized cells contracted by the external application of 10(-4)M procaine hydrochloride the cortical layer distinctly increases in thickness. In contrast to normal locomoting cells actin and myosin show a uniform distribution within the cell cortex along the entire surface. In pinocytosing cells, up to three cortical layers conspicuously rich in actin are produced during the process of channel formation. One of these layers is located in close proximity to the plasma membrane of the pinocytotic channels and the vacuoles. The immunocytochemical results are discussed with respect to earlier observations on the distribution of actin and myosin in Amoeba proteus as obtained by other methods.     

Effects of pH and ATP on the cytoplasm of Amoeba proteus: relation between cytoplasm motility and actin polymerization

The effect of pH and ATP was studied on isolated cytoplasm of Amoeba proteus. These two parameters were shown to influence both the motility and the organization of actin filaments in the isolated cytoplasm. Furthermore, our results demonstrate that there is a relationship between the motility and the polymeric state of actin. When the isolated cytoplasm is non-motile, actin is highly polymerized into long filaments arranged parallel in bundles. When this cytoplasm is motile, however, actin can either be weakly polymerized, i.e. observed as few short filaments, or can be polymerized in long branched filaments forming a loose network.