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The murine-virus-infected erythroleukemia cell system provides an opportunity to examine regulatory mechanisms controlling cytodifferentiation. A cloned cell line (DR10c3) resistant to the erythropoiesis-inducing effect of dimethylsulfoxide (Me2SO).was isolated from the Me2SO-sensitive line DS19. DR10c3 is characterized as follows: (1) the uptake of [3H]Me2SO is similar to that in DS19; (2) The uptake of Me2SO was determined according to methods previously described (7). Chromosome analysis following 10 min of Colcemid arrest was performed by the method of quinacrine mustard staining according to techniques described elsewhere (8). Chromosomes were identified by their fluorescent banding patterns and arranged according to the standard mouse karyotype (9). Structurally rearranged (marker) chromosomes were given arbitrary numbers of M-1 through M-10.For determination of total protein or globin synthesis 108 cells were incubated in 10 ml of leucine-free Eagle's Basal Medium (GIBCO) with 250 ,uCi of [3H]leucine (New England Nuclear, specific activity 33.6 Ci/mmol) at 370 for 60 min. Aliquots (25 ,l) of the incubation mixture were removed at intervals, 50 ,ug of bovine serum albumin was added, and the mixture was precipitated with 10% trichloroacetic acid, collected on Millipore filters, washed with 5% trichloroacetic acid, and counted by liquid scintillation with 0.2 ml of formic acid and 10 ml of Bray solution, for total protein synthesis. For globin synthesis cells were lysed and glohin chains were isolated by chromatography as described elsewhere (10,11

To assess the value of high-frequency ultrasonography as a diagnostic imaging procedure in patients with colon carcinoma, we first evaluated the sonograms of 37 patients who had been already diagnosed with contrast enema and/or colonoscopy as having colon carcinoma. As a result, the sonographic criteria for diagnosis of a possible colon carcinoma were (1) a localized and irregular thickening of the colonic wall with heterogenous low echogenicity, (2) an irregular contour, (3) a lack of demonstrable movement or change of configuration of the bowel on real-time scanning, and (4) absence of wall stratification. During the last 4 years, 41 consecutive patients had findings meeting our sonographic criteria. In 37 patients (90%), the presence of colon carcinoma was confirmed by contrast enema and/or colonoscopy. Our study suggests that high-frequency real-time ultrasonography may be a useful imaging technique in diagnosis of colon carcinoma.

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