Adverse effects associated with occupational exposure to benzene have often been reported in humans. It has been shown, that benzene causes chromosomal aberrations, sister chromatid exchanges and micronuclei in lymphocytes of exposed workers. In addition to evidence by conventional cytogenetic methods, the genotoxic effect of benzene has also been proved by a more specific approach based on fluorescence in situ hybridization with DNA probes. In the present paper, the nature of benzene-induced chromosomal aberrations and supposed consequence on human health is reviewed. The new possibilities in chromosomal alterations identification by molecular cytogenetic methods are also presented.
A 9-month-old Yorkshire terrier was admitted to the clinic because of abnormal sexual behaviour and clitoral hypertrophy. External examination confirmed standard development of caudal genital organs: vagina, vulva and cervix uteri. Serum profile of gonadotropin hormones 17 β- estradiol (<10.0 pg.ml−1) and testosterone (9.1 ng.ml−1) revealed the presence of testicular tissue. A midline laparotomy was performed to detect the cranial parts of the genital system. Gonads resembling testicles, structures indicating epididymis and rudimentary deferent ducts were resected, along with adherent part of the uterus. Cytogenetic analysis showed a male chromosomal complement 78, XY in all metaphases of the studied Yorkshire terrier dog. The chromosomal constitution was confirmed by fluorescence in situ hybridisation (FISH) with whole-chromosome painting probes specific for chromosomes X and Y, as well as by polymerase chain reaction (PCR) amplification of the 271- bp Y-linked fragment of SRY (the sex-determining region on the Y chromosome) gene. Sequencing of the dog’s SRY gene coding region did not reveal any mutation. To search for potential mutation in the SOX9 gene (Sry-box containing gene 9), which is considered to be one of the key genes involved in the sex determination process, the PCR fragments of exons 1, 2 and 3 originating from the canine patient were sequenced in order to compare with both male and female healthy control dogs. In the analysed regions of the SOX9 gene, no mutation was found.
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