Abstract.-Co-chromatography in a reversed-phase column was performed for 16 aminoacyl-tRNA's prepared from L-M cells grown in serum-free suspension culture and from tumors induced in irradiated C3H mice by subcutaneous injection of L-M/I cells. The results showed that between the two sources there were (1) marked differences in aspartyl-, histidyl-, phenylalanyl-, and tyrosyl-tRNA's; (2) significant quantitative differences in isoaccepting species of alanyl-, isoleucyl-, seryl-, and threonyl-tRNA's; and (3) similar to minimally different patterns of arginyl-, methionyl-, prolyl-, tryptophanyl-, valyl-, glycyl-, leucyl-, and lysyl-tRNA's. The differences were evident when synthetases prepared either from L-M cells or from the tumors were used. When the L-M tumors were brought back into in vitro culture, their tRNA patterns were like those of L-M cells. Addition of serum to the culture medium caused the L-M cells to show very minute, but detectable, amounts of the isoaccepting tRNA's found in the tumors. The cellular mechanisms which may be related to the changes of tRNA patterns in the L-M cells are discussed.The multiplicity of tRNA's accepting the same amino acid (isoaccepting tRNA's) has been well documented in lower and higher organisms (see Yang and Novellil for review). Apgar and Holley2 first reported that rat liver and yeast showed different patterns of isoaccepting tRNA's. Other studies have demonstrated that different chromatographic profiles of certain tRNA's were obtained during T2 phage infection in E. coli, I, 4 and during shifts of culture conditions in microorganisms.5 6 Similarly, different profiles have been demonstrated in organisms at different phylogenetic levels,7 in different mammalian tissues and organs,8 in tissues of the same kind that produce different proteins,9 in cells from different stages of development,10 and in cytoplasmic and mitochondrial fractions of cells.11 12 In this communication, we will present the results of a study on tumor formation by L-M cells, a subline of the clone 929 of L cells13 that has grown in a serum-free medium since 1958.14 These cells still retain the capacity of tumorigenesis in the C3H/Anf mice15 from which the original explant of normal subcutaneous connective tissue was taken in 1940.16 0.5% Bacto-peptone (199-P), were harvested by centrifugation and either used fresh or stored frozen at -700C until used. To obtain L-M tumors, 1 X 107 viable cells in 1 ml volume were injected into the left thigh of 7-week-old C3H/Anf male and female mice which had been irradiated with 425 R of X rays 4 hr previously. At 14 days the animals were decapitated and the tumors excised carefully from the surrounding tissue. The 1411

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SynopsisThe characteristics of Monvelle, a new biconstituent fiber from nylon 6 and a segmented polyurethane, are reviewed briefly, and some of the technical problems inherent in producing such a fiber are discussed. The characterization of two series of polyurethanes which can be melt spun is given in detail. The chemical composition of the hard segment was maintained constant, being derived from 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol1 in all polymers. In one series using poly(buty1ene adipate) of MW 2000 as the soft segment, the average hard segment content was varied from 33% to 54%. In the other series, the hard segment content was held at 43%, and three additional soft segments, each a t MW 2000, were used: poly(ethy1ene adipate), polycaprolactone and poly-1,Poxybutylene glycol (PBG).Characterizations include molecular weight distributions, thermal analysis, rheological studies, and selected small-angle and wideangle x-ray diffraction and polarized light microscopy. Crystallinity, melt viscosity, and activation energy of flow increased with increasing hardsegment content. Changes in the polyester soft segments had little effect on the properties studied, but with PBG the crystalline melting point of the polymer, without annealing, was higher and the melt viscosity was slightly higher than corresponding polyester-based samples, in agreement with previous reports of sharper phase separation in polyether urethanes, compared to polyester urethanes.

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A method for the induction of carcinomas in a circumscribed region of the hamster trachea is reported. By means of a special catheter, a solution of N-nitroso-N-methylurea was applied twice a week to about a 6-mm length of the trachea 10- to 16-mm distal from teh vocal cords. Slight alteration of this catheter allowed sampling of cytologic specimens directly from the surface of the carcinogen0exposed epithelium. This procedure permitted the simple and accurate correlation of sequential histologic and cytologic changes observed during tumor development in the hamsters. Noninvasive dysplastic and metaplastic lesions were seen in animals killed after 5 and 10 weeks of carcinogen application. These epithelial changes could be readily correlated with abnormal exfoliated cells abundantly present in cytologic specimens from these animals. Exposure to carcinogen for 15 weeks induced a 100% tumor incidence exclusively at the application site. More than 75% of the malignancies appeared within 15-20 weeks after the start of carcinogen administration. Most tumors were epidermoid carcinomas but some anaplastic large-cell carcinomas were also observed. Cytologic specimens of tumor-bearing animals had many cells conclusive of malignancy. The new experimental system lends itself to study of the effect of topically applied anticarcinogenic or cocarcinogenic agents on different carcinogen-induced epithelial lesions whose regression or progression can be followed by exfoliative cytology.