Control of Protein Synthesis in Acanthamoeba castellanii

During development of Acanthamoeba castellanii in a non-nutrient medium, the pattern of synthesis of proteins changes. Comparison of in vivo and in vitro patterns of protein synthesis reveals concomitant relative increases of five proteins, indicating a control of synthesis of these proteins at the level of the RNA content. The decrease in the overall rate of protein synthesis and relative decreases in the synthesis of actin and ribosomal proteins during development, not accompanied by equivalent changes in the content of mRNA, suggest control mechanisms also at the level of translation. Patterns of ribosomal proteins do not change qualitatively during encystation, indicating that the inhibition in the overall rate of protein synthesis and the formation of inactive monosomes is not controlled by this mechanism; however, phosphorylation of one ribosomal protein, S 3, is observed occasionally during encystation. Phosphorylation of S 3 is also detected after transfer of stationary phase cells into fresh nutrient medium. It was found that only such cells having RNA of aberrant properties are able to phosphorylate S 3 after transfer into fresh nutrient medium. Since these changes in the property of RNA are never observed in cysts, in which phosphorylation of S 3 sometimes occurs, it is concluded that either other alterations in the properties of RNA than those detected or other parameters are responsible for changes in phosphorylation of S 3.     

Anatomy and affinities of pseudococculinid limpets (Mollusca, Archaeogastropoda)

The anatomy of 12 pseudococculinid species, representing the two subfamilies and 10 (of 11 known) genera, is described in detail. Three new genera are erected, Yaquinabyssia, Copulabyssia and Amphiplica. Subfamilial and generic systematics are reconsidered and additionally based on anatomical characters. Characters defining subfamilies and genera (Pseudoeoeculininae: Pseudococculina, Notocrater, Tentaoculus, Mcsopelex, Bandabyssia, Kurilabyssia; Caymanabyssiinae: Caymanabyssia, Colotrachelus, Yuquinabyssia, Copulabyssia, Amphiplica) are the modifications in shell and radula, the number and arrangement of gill-leaflets, the size of the pedal gland, the degree of eye-reduction and the modifications of the seminal groove and of the copulatory organ. Separation of the Pseudococculinidae Hiekman, 1983 from the Cocculinidae Dall, 1882 at the superfamilial level is confirmed by great differences in their anatomy. Whereas the Cocculinidae are closely related to the Bathysciadiidae (Cocculinoidea). the Lepctcllidae, Pyropeltidae, Pseudococculinidae,? Bathyphytophilidae, Osteopeltidae, Cocculinellidae, Addisoniidae and Choristellidae form a clearly separated supcrfamily (Lepetelloidea). Both superfamilies compose the Cocculiniformia. a primitive but highly specialized arehaeogastropod suborder.