CYTOGENETIC ANALYSIS 503 



diploid or the original parental stemline karyotype is exceedingly rare. Consequently, 

 the value of transformed or altered forms in somatic genetic experimentation must 

 be reviewed with extreme caution. The commonly noted transition toward tetraploidy 

 during the course of proliferation may be regarded as representing an early phase of 

 progression and adaptability of the heteroploid in vitro. 605 • 782 Altered types of cells 

 rarely reflect properties of the parental stem cell in situ other than strain-specific 

 immunologic features. 391, 1030 Lines having only one or two extra normal chromo- 

 somes may be regarded as being more favorable than near-tetraploid forms for genetic 

 studies. Yet, the need for monosomaty and diploidy, as the more ideal forms, remains. 



Studies on somatic cells from induced malignancies in the house mouse, Mus 

 musculus, have been readily conducted on a short-term basis by Klein and his associates. 

 Since long-term tissue cultures and transplantable malignancies that retain their 

 original karyotype and immunologic properties are rare, replicable short-term cultures 

 employing normal-cell types may serve more effectively in the future. It is urged that 

 investigators who are actively pursuing basic trials with the house mouse assume 

 greater responsibilities for the development of cell lines of normal derivation that 

 retain the diploid or near-diploid status during the course of routine propagation in 

 vitro. 



The normal population of somatic cells is, of course, predominantly diploid, with a 

 small number of deviants or near diploids. Yet innumerable experimental designs 

 and theories regarding the malignant process are based on results with near-tetraploid 

 variants. Such studies must be scrutinized carefully and reevaluated in the light of 

 new evidences accumulated by Bayreuther. 63 The extreme and continued variation 

 in chromosomal numbers among the numerous sublines of normal and malignant cells 

 is evident from reports such as Levan's 781 registry of the numbers of chromosomes in 

 various sublines from human and rodent tissues. For the sake of economy and 

 greater productivity of experienced cytologists, the necessity and value for continuing 

 this determination and recording of chromosomal numbers is questioned. Of more 

 importance is the isolation of more appropriate lines of cells for conducting trials that 

 are truly definitive. 



TECHNICAL NOTES 



REFERENCES AND HELPFUL MANUALS 



Merchant, D. J., R. H. Kahn, and W. H. Murphy, Jr. : Handbook of Cell and Organ Culture. 

 Burgess Publishing Company, Minneapolis, Minnesota. 



Parker, R. C. : Methods of Tissue Culture. Third Ed. Paul B. Hoeber, Inc., New York, 1961. 



Paul, J.: Cell and Tissue Culture. Baltimore: Williams and Wilkins; London: E. and S. 

 Livingstone, 1959. 



Puck, T. T,: Quantitative Mammalian Cell Culture, Second Preliminary Edition. Depart- 

 ment of Biophysics, University of Colorado Medical Center, Denver, Colorado, 1957. 

 Address the Departmental Secretary. Cost: 82.00. 



Methods and Principles of Tissue Culture, Laboratory Manual of the Tissue Culture 

 Association Course, University of Wisconsin, Madison, Wisconsin, June-July, 1960. 



