The frequencies of sister-chromatid exchanges (SCE) were investigated in lymphocytes in 32 normal adult individuals of both sexes with no interracial familial backgrounds from Caucasian, American black, oriental and native American races. There was no significant difference in the average frequency of SCEs in the 4 races

Butler, Merlin G.

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SISTER-CHROMATID EXCHANGE IN 4 HUMAN RACESMERLIN G. BUTLERDepartment of Medical Genetics, Indiana University School of Medicine, Indianapolis, IN 46223 (U.S.A.)SUMMARYThe frequencies of sister-chromatid exchanges (SCE) were investigated in lymphocytes in 32 normal adult individuals of both sexes with no interracial familial backgrounds from Caucasian, American black, oriental and native American races. There was no significant difference in the average frequency of SCEs in the 4 races.Sister-chromatid exchanges (SCE) are the result of apparent exchanges of DNA between chromatids and may be visualized in metaphase chromosomes after growth of cells for 2 cycles in bromodeoxyuridine and appropriate staining procedures. The frequency of SCEs is thought to be a sensitive indicator of genetic instability and early chromosome changes (Perry and Evans, 1975; Solomon and Bobrow, 1975; Vogel and Bauknecht, 1976; Carrano, 1978).The analysis of SCEs is useful in the detection of genetic damage in humans exposed to various mutagens and carcinogens (Allen and Latt, 1976; Craig-Holmes and Shaw, 1977; Butler et al., 1980). In order to conduct SCE experiments with human subjects in which individuals of different races are included, the SCE frequency of normal individuals of the human races should be considered. Herein, SCE data are presented in 32 normal individuals from 4 human races to examine differences, if any, in the SCE frequencies between races.Materials and methods32 healthy adult individuals of both sexes with no history of significant illnesses, medication or X-ray exposure within the past 6 months were sampled from Caucasian, American black, oriental, and native American subjects. The subjects selected were not related and denied genetic impurity or interracial familial backgrounds. All subjects were living in the United States and selected from the American population. The oriental group consisted of individuals from Chinese or Japanese descent. The native Americans were members of the Nebraska Omaha tribe. The subjects had not been knowingly exposed to environmental or occupational hazards.Peripheral blood (0.4 ml) was added to 8 ml of Basal medium–Eagles supplemented with 20% fetal calf serum, penicillin (40 U/ml), streptomycin (40 μg/ml), phytohemagglutinin, and 20 μM 5-bromodeoxyuridine. The cultures were incubated at 37°C in the dark. Colcemid was added after 69 h of incubation and the cells harvested at 72 h then treated with hypotonic saline (0.075 M KCl) and fixed in 3:1 methanol–acetic acid. Air-dried slides were stored in the dark for 1 day then stained with the fluorescence plus Giemsa (FPG) HHS Public AccessAuthor manuscriptMutat Res. Author manuscript; available in PMC 2016 October 05.Published in final edited form as:Mutat Res. 1981 ; 91(4-5): 377–379.Author ManuscriptAuthor ManuscriptAuthor ManuscriptAuthor Manuscripttechnique (Perry and Wolff, 1974). The slides were analyzed for SCEs at the microscope. The SCE frequency for each subject was based on the number of SCEs in a minimum of 20 cells.Results and discussionThe use of sister-chromatid exchanges (SCE) to determine genetic instability has increased in recent years. With expanded SCE experimentation in human disorders, the emphasis on SCE standardization between laboratories becomes apparent. To aid in accomplishing SCE standardization, factors which are known to influence the SCE frequency should be controlled (Speit, 1980). To keep other extraneous factors at a minimum and to analyze the effect of a particular factor, such as race on the number of SCEs, a careful medical history and screening program should be followed.In order to conduct SCE experiments with human subjects in which individuals of different races are included the racial difference, if any, in the SCE frequency should be known. Therefore, an attempt to examine the SCE data of individuals in 4 human races was made.The average SCE frequency and standard deviation from the 4 groups were: Caucasian, 8.1 ± SD 0.48; American black, 8.2 + SD 0.84; oriental, 8.7 + SD 0.65; native American, 8.6 ± SD 0.57 (Table 1). The Kruskal–Wallis one-way analysis of variance test by ranks (Kruskal and Wallis, 1952) was applied to the SCE data (H = 5.01, 3 degrees of freedom, 0.1 < p < 0.2 from chi-square distribution). The value obtained was not considered significant, therefore no significant difference in the SCE frequency between races could be detected by the method described. Also there was no correlation between the age or sex of the individual and the SCE frequency.AcknowledgmentsThis research was supported by the following grants: PHS-T32 GMO7468 and American Cancer Society, Institution 57-838-02. I thank Dr. Catherine Palmer for reviewing the manuscript.ReferencesAllen JW, Latt SA. Analysis of SCE formation in vivo in mouse spermatogonia as a new test system for environmental mutagens. Nature (London). 1976; 260:449–451. [PubMed: 1256591] Butler MG, Sanger WG, Veomett GE. Increased frequency of sister chromatid exchanges in alcoholics. Mutation Res. 1980 in press. Carrano AV. SCE as indicators of mutagenesis. Nature (London). 1978; 271:551–553. [PubMed: 622190] Craig-Holmes AP, Shaw M. Effects of six carcinogens on SCE frequency and cell kinetics in cultured human lymphocytes. Mutation Res. 1977; 46:375–384.Kruskal WH, Wallis WA. Use of ranks in one-criterion variance analysis. J Am Stat Assoc. 1952; 47:583–621.Perry P, Evans HJ. Cytological detection of mutagens–carcinogen exposure by sister chromatid exchange. Nature (London). 1975; 258:121–125. [PubMed: 52847] Perry P, Wolff S. New Giemsa method for the differentiation staining of SCE. Nature (London). 1974; 251:156–158. [PubMed: 4138930] Solomon E, Bobrow M. SCE – a sensitive assay of agents damaging human chromosomes. Mutation Res. 1975; 30:273–278. [PubMed: 1207711] BUTLER Page 2Mutat Res. Author manuscript; available in PMC 2016 October 05.Author ManuscriptAuthor ManuscriptAuthor ManuscriptAuthor ManuscriptSpeit G. Effects of temperature on sister chromatid exchanges. Hum Genet. 1980; 55:333–336. [PubMed: 7203467] Vogel W, Bauknecht T. Differential chromatid staining by in vivo treatment as a mutagenicity test system. Nature (London). 1976; 260:448–449. [PubMed: 1256590] BUTLER Page 3Mutat Res. Author manuscript; available in PMC 2016 October 05.Author ManuscriptAuthor ManuscriptAuthor ManuscriptAuthor ManuscriptAuthor ManuscriptAuthor ManuscriptAuthor ManuscriptAuthor ManuscriptBUTLER Page 4TABLE 1SISTER-CHROMATID EXCHANGE (SCE) DATA IN CAUCASIANS, AMERICAN BLACKS, ORIENTALS AND NATIVE AMERICANSGroupNumber of subjectsAgeSexAverage number of SCE per cell per individualTotal number of cells analyzedMeanRangeM/FGroups mean ± SDRangeCaucasian932.025–585/48.1 ± 0.487.2–9.0215American Black825.221–363/58.2 ± 0.847.4–9.8185Oriental827.923–314/48.7 ± 0.658.1–9.8190Native American732.424–414/38.6 ± 0.577.8–9.5174Mutat Res. Author manuscript; available in PMC 2016 October 05.

Sister-chromatid exchange in 4 human races

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Sister-chromatid exchange in 4 human races

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