Effect of chemicals on the duration of male meiosis in mice detected with laser scanning cytometry

Aneuploidy studies in sperm such as the sperm-FISH assay require a precise knowledge of the duration of spermatogenesis, especially of the meiotic stages. This is important in order to sample sperm from the epididymis at appropriate intervals after animal treatment. However, aneugens may delay the cell cycle. The progression from meiotic divisions to epididymal sperm was determined by labelling the last S-phase before meiosis with the thymidine analogue 5-bromo-2'-deoxyuridine (BrdU) and treating the animals 13 days later with the test chemicals. In a time frame of 20--24 days after treatment, BrdU-containing sperm were identified with a FITC-labelled anti-BrdU antibody and green fluorescent sperm were scored with a laser scanning cytometer (LSC). We studied the effects of the chemicals acrylamide, colchicine, diazepam, griseofulvin, taxol, thiobendazole, trichlorfon and vinblastine on the duration of meiotic divisions in male mice. Colchicine treatment prolonged the duration of meiotic divisions by about 48 h. On days 21 and 22, the frequencies of BrdU-labelled sperm in the colchicine group were 11.7 and 9.4%, respectively, while they were 28.4 and 30.6%, respectively, in the concurrent controls (P > 0.01). On day 24 after treatment, the frequency of labelled sperm in the colchicine group reached the control level. Etoposide treatment resulted in an elevation of BrdU-labelled sperm at 23 rather than 22 days. The other chemicals showed no significant effect of prolonging meiotic cell cycle progression. On the basis of the colchicine and etoposide data, it is suggested that the effect of a chemical on the meiotic cell cycle progression is determined first in order to chose the appropriate sperm sampling time to detect aneuploidy induction.

Automated evaluation of frequencies of aneuploid sperm by laser-scanning cytometry (LSC)

BACKGROUND

Laser-scanning cytometry (LSC) allows fast automated scoring of fluorescence signals directly on microscopic slides. Frequencies of spontaneous aneuploidies in murine and human sperm were evaluated by using this new LSC technique. Rapid detection may be of great interest in reproductive toxicology, as certain chemicals act as aneugens during meiosis, increasing the production of aneuploid germ cells. Materials and Methods Selected chromosomes were detected by using fluorescence in situ hybridization (FISH) and fluorochrome-labeled DNA-probes. Sperm chromatin was counterstained with propidium iodide. By scanning across the slide, fluorescence signals within sperm nuclei were detected and counted.

RESULTS

In murine sperm, the frequencies of disomies for chromosomes 8 and X were 0.019% and 0.021%, respectively. The automated assessment in human sperm resulted in disomy frequencies of 0.061% and 0.090% for chromosomes 13 and X, respectively. These results were comparable to data obtained from the same samples by manual microscopic scoring and to literature data.

CONCLUSIONS

Frequencies of genotypically abnormal sperm were not significantly different between automated and manual scoring. In conclusion, sperm aneuploidy was reliably determined and disomic sperm were successfully relocated by LSC. By virtue of rapid and reliable analyses, LSC has the powerful potential to replace manual microscopic FISH analysis in molecular cytogenetics.

Partial characterization of SUVi, a new mammalian gene induced by UV-C and expressed during the S phase of the cell cycle

By using a lacZ-based gene-trap approach, we identified a mammalian gene induced by UV-C in a Chinese hamster ovary cell clone (Menichini P et al. [1997]: Nucleic Acids Res 25:4803-4807). The activity of the encoded protein fused to a bacterial beta-galactosidase was followed through the hydrolysis of different beta-galactosidase substrates. In this study we describe how the expression of this gene is modulated during the cell cycle and in response to UV-irradiation. We show that the beta-galactosidase activity was virtually undetectable in quiescent cells (G[0]), started to increase when cells progressed in G(1), and reached a maximum in mid-S phase, indicating a possible role of the endogenous protein during DNA synthesis. Following UV-irradiation, besides a delay of the progression through the S phase, a twofold increase of the reporter protein activity in all phases of the cell cycle was observed. The partial sequence analysis showed that this gene, here named SUVi (for S phase UV-inducible), contains a domain that is highly conserved among different helicases. Together, these data suggest that the SUVi gene could be involved in DNA synthesis, a process that takes place both in the S phase and in the processing of UV-induced damage.

Stable expression of HIV-1 Nef induces changes in growth properties and activation state of human astrocytes

OBJECTIVE

Nef was shown to be the predominant viral protein expressed in HIV-1-infected astrocytes in vivo and in vitro suggesting a distinct role of Nef in this cell type. Nef-induced activation of T cells is well described, whereas the functional activities of Nef in astrocytes are unknown. Our aim was to examine the effect of Nef on growth properties and activation of astrocytes.

DESIGN

Human Nef-expressing astrocytic cell lines were established by stable transfection with different wild-type and mutant nef genes derived from laboratory isolates and brain tissue.

METHODS

Nef-expressing astrocytes were characterized in terms of growth properties (proliferation, growth in soft agar, focus formation) and morphology. Apoptotic cell death and expression of activation markers were determined by fluorescent antibody cell sorting.

RESULTS

Astrocytic cell lines revealed persistent Nef expression--detectable at the levels of mRNA and protein--and showed altered growth properties and morphology. Elevated expression of activation markers such as glial fibrillary acidic protein and CD88 (complement receptor C5a) was observed; these are regarded as markers for inflammatory processes in the brain. This effect was independent of the nef type or the expression level of the Nef protein. In contrast with previous reports no evidence for increased apoptotic cell death was found in astrocytes expressing Nef stably.

CONCLUSIONS

Our findings suggest that Nef changes the cellular properties of astrocytes, thus contributing to astrocyte activation and induction of astrogliosis in the central nervous system of individuals with AIDS.