Amoeba proteus

Protozoa Amoeba proteus Euglena viridis Paramecium caudatum Amorphous Spindle-shaped Slipper-shaped < 600 pm dia 40-65 x 14—20 pm 180-300 /rm length... 

Holothurin" is active in vitro against Amoeba proteus [24], holotoxins from Apostichopus japonicus are active against Trichomonas vaginalis [52]. The data on antiprotozoal activity of glycosides of Cucumaria echinata [49] were discussed above. These data were correlated with antifungal activities of the glycosides. 

No events have been described which uniquely characterize the G1 phase. The G1 phase appears to perform two functions the temporary or permanent arrest of cell division in eukaryotes is normally achieved by cells maintaining themselves in the G1 phase of the cell cycle (Prescott, 1970) also the terminal part of the G1 must contain events concerned with the initiation of DNA synthesis. Certain organisms, for example, the fission yeast Schizosaccharomyces pombe (Bostock et al., 1966), the multinucleate slime mold Physarum polycephalum (Guttes et al., 1967), and Amoeba proteus (Ord, 1968), do not exhibit a G1 phase. A number of mammaUan cells appear to lack a G1... 

Control of DNA synthesis in Amoeba proteus. Nature (London),... 

Fig. 10. An electron micrograph of the nucleus of Amoeba proteus. The helices are composed of particles that presumably contain D-RNA. The filament of the helix is about 110 A in width. (Electron micrograph provided by K. Murtl.)...

Prescott and Goldstein (1969) discovered in Amoeba proteus a protein fraction which moves from nucleus to cytoplasm and vice versa as determined from nuclear transplantation experiments. It may be that these migrating proteins correspond to IFF and are involved in mRNA transfer. 

Prescott, D. M., and L. Goldstein. 1969. Proteins in nuclear-cytoplasmic interactions in Amoeba proteus. Ann. Embryol. Morph., (Suppl. 1) 181-188. 

DNA sequencing has shown that genomes vary by size, but the significance of this remains unclear. The human genome contains about 3 billion base pairs, whereas the protozoan Amoeba proteus has 290 billion base pairs, which makes it one hundred times latter. Analysis of genetic variation has confirmed that humans are remarkably similar to other life-forms. Humans share 98 percent of their genetic material with chimpanzees, 90 percent with mice, 23 percent with yeast, and 12 percent with Escherichia coU. 

Protein synthesis and amino acid incorporation can take place in the total absence of DNA, as, for example, in nonnucleated halves of Amoeba proteus (393, 394), in enucleated Acetabularia mediterranea (396), in reticulocytes (30), and, of course, in the cell-free systems we have discussed in Section III. 

The presence of sialic acids in Amoeba remains uncertain. Treatment of Amoeba proteus with bacterial sialidase led to a reduction in pinocytotic activity compared to non-treated organisms (Chatterjee and Ray 1975). The same authors could also enhance lysolecithin-induced intercellular adhesion in A. proteus by sialidase treatment (Ray and Chatterjee 1975), although the release of Neu5Ac was not measured. These studies stand in opposition to those conducted with A. discoides (Allen et al. 1974, 1976), where no sialic acid was detected in biosynthetic and structural analytical experiments. 

Flickinger, C. J., 1968, The effects of enucleation on the cytoplasmic membranes of Amoeba proteus, J. Cell Biol. 37 300. 

Figure 17. Lysozyme stimulated pinocytosis in Amoeba proteus. Changes in heat output due to different lysozyme concentrations (0.04, 0.21 and 0.43 mg/mL). The baseline is indicated before the arrow, A represents the basic metabolism, B the heat output during pinocytosis [134],...

Note 6) (b) the induction of DNA synthesis in nuclei from G-2 phase Amoeba proteus transplanted into S-phase cells of the same species (Prescott and Goldstein, 1967) (c) the s)mchronous initiation of DNA synthesis in the normally monomacronucleate ciliate protozoan Euplotes into which a second nucleus is transplanted from a different animal (Kimball and Prescott, 1962) (Note 7). 

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