We have isolated a number of emetine-resistant mutants from several different clones of CHO and CHL cells. Protein synthesis in extracts derived from each of the mutants is much more resistant to emetine than in the parental, emetine-sensitive cell lines, indicating the lesions affect the protein synthetic machinery directly. However, hybrid cell lines, derived from fusing either of two different emetine-resistant CHO mutants with either one of two different emetine-resistant CHL cells, are much more sensitive to growth inhibition by emetine than either parent. In addition, the incorporation of [3H] amino acids into protein in vivo and protein synthesis in vitro in extracts derived from these hybrids is much more sensitive to emetine inhibition than in either emetine-resistant parent. In contrast, no complementation was observed in hybrids derived from fusing two emetine-resistant CHO mutants or in hybrids derived from fusing two emetine-resistant CHL cell lines. These results indicate the CHO emetine-resistant mutants belong to one complementation group and the CHL emetine-resistant mutants belong to another. The genetic loci represented by these two complementation groups must both encode for gene products involved in protein synthesis.

We have isolated emetine-resistant cell lines from Chinese hamster peritoneal fibroblasts and have shown that they represent a third distinct class or complementation group of emetine-resistant mutants, as determined by three different criteria. These mutants, like those belonging to the two other complementation groups we have previously defined, which were isolated from Chinese hamster lung and Chinese hamster ovary cells, have alterations that directly affect the protein biosynthetic machinery. So far, there is absolute cell line specificity with respect to the three complementation groups, in that all the emetine-resistant mutants we have isolated from Chinese hamster lung cells belong to one complementation group, all those we have isolated from Chinese hamster ovary cells belong to a second complementation group, and all those isolated from Chinese hamster peritoneal cells belong to a third complementation group. Thus, in cultured Chinese hamster cells, mutations in at least three different loci, designated emtA, emtB, and emtC, encoding for different components of the protein biosynthetic machinery, can give rise to the emetine-resistant phenotype.

We investigated the characteristics of calcium phosphate cements (CPC) prepared by an exothermic acid-base reaction between NH4HzP04-based fertilizer (Poly-N) and calcium aluminate compounds (CAC), such as 3Ca0 .Al2O3 (C,A), CaO . A1203 (CA), and CaO * 2A1203 (CA,), in a series of integrated studies of reaction kinetics, interfacial reactions, in-situ phase transformations, and microstructure development. Two groups were compared: untreated and hydrothermally treated CPC specimens. The extent of reactivity of CAC with Poly-N al 25°C was in the following order: CA> C3A >> CA2. The formation of a NH4CaP04.xH20 salt during this reaction was responsible for the development of strength in the CPC specimens. The in-situ phase transformation of amorphous NH4CaP04 . xHLO into crystalline Ca5(P0&(OH) and the conversion of hydrous A1203 gel -y-AIOOH occur in cement bodies during exposure in an autoclave to temperatures up to 300°C. This phase transformation significantly improved mechanical strength.

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