Cytogenetic effects of inhaled ozone

We have repeated as closely as possible the experiments of Zelac et al., who observed significantly elevated levels of chromosome aberrations in short-term cultures of peripheral lymphocytes from Chinese hamsters that had inhaled ozone. Unlike Zelac et al., we observed no increase in chromosome-type aberration levels, though a small increase in chromatid-aberration levels similar to that reported for exposed human subjects by Merz et al. was seen. No increase in the levels of any chromosomal aberration type was seen in parallel direct bone-marrow preparations. Sister-chromatid exchange (SCE) levels and cell-replication rates, which were determined in the Chinese hamster peripheral lymphocyte cultures and also in bone-marrow samples from similarly treated mice, failed to show any ozone-induced changes.

Factors influencing the frequency of mitomycin C-induced sister-chromatid exchanges in 5-bromodeoxyuridine-substituted human lymphocytes in culture

Newly developed techniques for the detection of sister-chromatid exchanges (SCE) require the substitution of 5-bromodeoxyuridine (BrdU) for thymidine in DNA. We investigated the possibility of interactions between BrdU and one mutagen--carcinogen, mitomycin C (MMC) for the induction of both chromosomal aberrations and SCE in human peripheral lymphocytes in culture. No effect on aberration yield was found. Neither comparisons between the yields of SCE by BrdU substitution and differential staining and those detected by tritiated thymidine incorporation and autoradiography nor between the yields of SCE for different levels of BrdU incorporation provided any evidence of synergism. It was found, however, that MMC persists in cultures and continues to increase SCE frequencies for about 30 h. It was also observed that some MMC-induced DNA lesions persist long enough so that some of those present prior to S phase of the first cell cycle cause additional SCE in the third cycle.

Caffeine inhibition of prereplication repair of mitomycin C-induced DNA damage in human peripheral lymphocytes

Caffeine increases the number of sister-chromatid exchanges (SCE) induced by mitomycin C (MMC) in human peripheral lymphocytes in culture. This enhancement decreases when the treated cells are held in medium before phytohemagglutinin (PHA) stimulation, or when caffeine is added to cultures some time after PHA stimulation but prior to DNA synthesis. There thus appears to be a caffeine-sensitive prereplication repair system, presumably an excision mechanism, capable of repairing a fraction of the MMC-induced DNA lesions.

X-ray and UV-induced chromatid aberrations: evidence for polynemic chromosomes?

Ikushima and Wolff have recently interpreted both their observation of chromatid aberrations in second and third mitoses following X-irradiation and the production of chromatid type chromosomal aberrations by UV light administered during the G1 phase of the cell cycle in terms of a polyneme model of eukaryote chromosome structure. They were led to do so, however, largely because of their X-ray data, which the interpreted as evidence for the induction of sub-chromosomal lesions (by G1 irradiation; sub-chromatid for G2 irradiation) which appear as chromatid type aberrations only in later divisions. We here report data from similar X-ray experiments in which synchronized Chinese hamster tissue culture cells were irradiated in either G1 or G2 and then scored for chromatid aberrations in their first, second and third post-irradiation mitoses. Our results do not show the effect reported by Ikushima and Wolff. We conclude that all of the data available of aberration production is compatible with a simple mononeme model of eukaryote chromosome structure.

An evaluation of 99mTc-sulfur colloid liver scintiscans and their usefulness in metastatic workup: a review of 1,424 studies

To determine the clinical usefulness of liver scintiscanning in detecting metastatic disease of the liver, 1,424 liver studies performed on 1,115 patients were reviewed along with their charts. Five hundred eighty-one patients had histopathological evaluation by needle biopsy of the liver, laparotomy, and/or autopsy within a mean period of 40 days of liver scan. The histopatholigical findings were correlated with the liver sicntiscan findings and the latter gave an overall accuracy of 77.3%.

A 14/14 marker chromosome lymphocyte clone in ataxia telangiectasia

A lymphocyte clone with a 45, XY karyotype with a 14/14 tandem translocation marker, the frequency of which is time-variable, has been observed in an ataxia telangiectasia patient. Cells with the marker chromotosome were not observed in fibroblasts cultures derived from a skin biopsy, nor was the marker observed in leukocyte cultures from the patient's two affected sibs.

Photoreactivation of ultraviolet-induced chromosomal aberrations

Ultraviolet induces only chromatid-type aberrations in synchronized G(1) V-79 Chinese hamster and A8W243 Xenopus tissue culture cells. Posttreatment with white light prevents expression of most potential aberrations in the A8 toad cell, which possesses a photoreactivation enzyme. We conclude that the major ultraviolet-induced DNA lesion leading to chromosomal aberrations is the pyrimidine dimer.

Chromosome 16: a specific chromosomal pathway for the origin of human malignancy?

Minkler, Gofman and Tandy (1970a, b) have recently reported data on the karyotype constitutions of human tissue culture cell lines and human tumours, as gathered by a semi-automatic chromosome analysis system. The data appears to show a relationship between the relative number of "number 16" chromosomes and malignancy. We have tested the ability of the "cutting line" approach they used to correctly classify chromosomes from a sample of 723 cells from 100 normal subjects. The cutting line scheme gave very different results from those of an experienced cytogeneticist. The method also failed to give correct average numbers of chromosomes per class. We are thus led to question the conclusions reached by Minkler et al. It appears possible that their relatively consistent finding of an excess of "number 16" chromosomes in their largely hyperploid material may be an artefact of their classification scheme, arising from measurement normalization problems, rather than a reflection of a real excess of "number 16" or even of "number 16-like" chromosomes.

Statistical analysis of the normal human karyotype

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