Mauro Cristaldi

Environmental impact of the Chernobyl accident : mutagenesis in bank voles from Sweden

An investigation was carried out in Sweden aimed at studying the possible genetic effects of the Chernobyl fallout on wild small mammals. The bank voles (Clethrionomys glareolus Schreb.) were obtained from three differently contaminated areas in Sweden and, for control, in an area with negligible contamination by fallout. Radionuclide determinations to assess the content of 137Cs and mutagenicity tests (bone marrow micronucleus test and sperm abnormality assay) were performed. The results obtained showed a positive correlation between the increase of micronucleated polychromatic erythrocytes (MPCE/1000 PCE) and both 137Cs content in muscle and in soil contamination. The estimated doses absorbed by the animals were far lower than those required for the same effect in laboratory experiments. An explanation of this discrepancy between dose and measured biological effect is not available, yet similar results have been repeatedly reported after the Chernobyl accident and should be a matter for further discussion. An increased frequency of micronucleated cells might occur at minimal dose gradients, and the micronucleus test appears to be a valid tool to show such effects.

Genetic damage in urban mice exposed to traffic pollution

Wild rodents (Mus domesticus) were collected in three areas in Rome exposed to different traffic flows to ascertain a possible correlation between genetic damage and heavy metal concentration. The concentration of lead, cadmium and zinc were determined in liver, kidney and bones and two mutagenicity tests (micronucleus test and sperm abnormality assay) were employed. The results obtained showed that the contents of lead and cadmium were higher in animals collected in areas with high traffic flows than in those from control areas. A statistically significant increase of the frequency of micronucleated erythrocytes and of abnormal sperm cells was also obtained in animals collected in sites with high traffic flows. The investigation confirmed the suitability of using wild rodents as bioindicators of environmental pollution and as key-organisms in programs of pollution monitoring and environmental conservation.

MECHANISMS OF FIXATION AND ACCUMULATION OF CENTRIC FUSIONS IN NATURAL POPULATIONS OF MUS MUSCULUS L. I. KARYOLOGICAL ANALYSIS OF A HYBRID ZONE BETWEEN TWO POPULATIONS IN THE CENTRAL APENNINES

Chromosomal mutations causing partial sterility of the heterozygote are decisive in speciation processes in animals of limited vagility (e.g., Orthoptera and small mammals). In this regard the stasipatric speciation model (production of a heterozygous mutant, fixation in a small colony and subsequent spread of the homozygous mutant population) was proposed (see White, 1968, 1973, 1975, 1977), as opposed to the hypothesis of allopatric speciation (e.g., Key, 1974). Rodents offer several suitable characteristics for this type of study: 1) A variety of chromosomal rearrangements are involved: pericentric inversions, as in Spalax (Soldatovic and Savic, 1967; Wahrman et al., 1969; Lay and Nadler, 1972), Thomomys (Patton and Dingman, 1970), Perognathus (Patton, 1969), Peromyscus (Hsu and Arrighi, 1968) and, above all, centric fusions-and to a lesser extent, fissions-in Spalax (Wahrman et al., 1969; Lay and Nadler, 1972), Thomomys (Thaeler, 1968a; Nevo et al., 1974), Perognathus (Patton, 1969), Gerbillus (Wahrman and Gourevitz, 1973), Acomys (Wahrman and Goitein, 1972), Geomys (Selander et al., 1974) and Leggada (Matthey, 1970). 2) Different steps in the speciation process are evident: among different species of the same genus, among sibling species, among incipient species and among interbreeding populations. In Thomomys (Thaeler, 1968a, 1968b; Patton and Dingman, 1970;

The Comet assay for the detection of DNA damage in Mus spretus from Doñana National Park

Doñana Park (Spain), a protected area in Europe, was affected by an environmental disaster in April 1998 that caused the spreading of acidic water and mud full of toxic metals from the Aznalcollar pyrite mine. In order to assess the contamination in the area and to monitor the possible biological effects of the toxic spill, a series of coordinated studies was performed utilizing several animal species living in that area. We performed genotoxicity monitoring using the Comet assay on peripheral blood leukocytes of the Algerian mouse (Mus spretus), a nonprotected rodent suitable as a bioindicator. The mice were sampled in different areas 6 months after the ecological disaster and again 1 year later. Our results showed that in 1998 all the areas examined were contaminated, as determined by an increase in the Comet assay parameters in the analyzed animals, whereas a significant decrease in the values of these parameters was observed in the 1999 samples, which were collected in a riverside area subject to tide flows. Thus, the Comet assay has proven to be an interesting and sensitive tool in studies of environmental genotoxicity.

137Cs Determination and mutagenicity tests in wild Mus musculus domesticus before and after the Chernobyl accident

Wild rodents were collected alive in a suburban area to the north of Rome before, during, 6 months and 1 year after the Chernobyl accident. Radionuclide determinations to assess their content of (137)Cs and mutagenicity tests (bone-marrow micronucleus test and sperm abnormalities assay) were performed on the captured animals. The results obtained for the species Mus musculus domesticus (which was the rodent captured in highest numbers), compared with the results obtained before the fallout, showed an increase of both micronucleated polychromatic erythrocytes (MPCEs/1000 PCEs) and (137)Cs content during and after the fallout.

Genotoxic damage in free-living Algerian mouse (Mus spretus) after the Coto Doñana ecological disaster

The Doñana National Park (Spain), one of the most important wildlife sites in the West of Europe, was affected (25 April 1998) by the spill of acidic waste rich in toxic metals (mainly zinc, lead, copper, etc.), arsenic and aromatic amines from the Aznalcollar mine accident. Micronuclei test with May Grunwald-Giemsa and with CREST-antikinetocore staining using DAPI as counter-staining were performed on peripheral blood erythrocytes from Algerian mice to evaluate genotoxic damage. Animals were collected in four locations each differently affected by the disaster. Higher frequencies of micronuclei and CREST-positive micronuclei were observed in the sites, which were reached by toxic sludge and contaminated water in comparison with those located within the park. The results obtained applying the two methods indicate that DAPI staining is more sensitive in detecting micronuclei. Genotoxic biomonitoring should be further carried out in the area to control the mutagenetic level in natural populations.

Clastogenicity and aneuploidy in newborn and adult mice exposed to 50 Hz magnetic fields

Purpose: To detect possible clastogenic and aneugenic properties of a 50 Hz, 650 μT magnetic field. Materials and methods: The micronucleus test with CREST (Calcinosis, Raynauds phenomenon, Esophageal dismotility, Sclerodactility, Telangectasia) antibody staining was performed on liver and peripheral blood sampled from newborn mice exposed to an ELF (Extremely Low Frequency) magnetic field during the whole intra-uterine life (21 days), and on bone marrow and peripheral blood sampled from adult mice exposed to the same magnetic field for the same period. Results: Data obtained in newborn mice show a significant increase in micronuclei frequencies. In absolute terms, most of the induced micronuclei were CREST-negative (i.e., formed by a chromosome fragment). However, in relative terms, ELF exposure caused a two-fold increase in CREST-negative micronuclei and a four-fold increase in CREST-positive micronuclei (i.e., formed by a whole chromosome). No significant effect was recorded on exposed adults. Conclusions: These findings suggest the need for investigation of aneugenic properties of ELF magnetic fields in order to establish a possible relationship to carcinogenesis.

New robertsonian metacentrics in another 22-chromosome mouse population in Central Apennines

New centric fusions (Rb 8-14 Rma) have been described in a 22-chromosome karyotype from a Mus musculus population in southern Central Italy. The diakinesis of hybrids obtained by crossing mice with different 22-chromosome complements show a ring-multivalent made up 16 metacentrics pairing arm-to-arm.

Sexual dimorphism of GABAA receptor levels in subcortical brain regions of a woodland rodent (Apodemus sylvaticus)

This is the first report of quantitative autoradiography results showing sex differences of GABAA receptor levels in brain regions of a wild rodent (wood mouse, Apodemus sylvaticus) living in its natural habitat. The labeling of this GABAergic site with its specific high affinity radioligand [3H] muscimol provided a heterogeneous and dimorphic binding pattern in some of the neural centers. In the female, higher (> or = 50 < or = 65%) to moderately higher (< 50%) binding levels than in the male, even after correction of the specific binding values using the calculated quenching coefficients, were observed in the substantia nigra pars reticulata and ventral lateral thalamic nucleus, brain centers that are relays of motor circuits. In the male, on the other hand, a higher level was only obtained in the caudateputamen. Relays of the stria terminalis-hypothalamic-central gray pathway such as the bed nucleus of the stria terminalis, the pontine central gray and the ventromedial hypothalamic nucleus, were among the other female brain areas with an extremely higher (> 65%) to higher and moderately higher binding activity than in the male. From the saturation analyses, it appeared that the binding differences were mainly due to Bmax variations, although closer examinations revealed that changes in the KD might have also accounted for [3H] muscimol binding differences, as shown by the high KD and Bmax values in the bed nucleus of the stria terminalis, the substantia nigra pars reticulata and the pontine central gray of the female wood mouse. These findings suggest that the dimorphic binding activity of GABAA receptors in the above brain regions might be involved in neuronal circuitry mechanisms related to sex-specific social behaviors in rodents living in their natural environmental conditions.

Chromosomal Polymorphism in an Alpine Population of Mus Musculus L.

Abstract Una popolazione alpina di Mus musculus L. e stata studiata dal punto di vista cromosomico ed ha rivelato numeri diploidi, nei 5 individui esaminati, pari a 2n = 27, 30, 32, 37; il numero fondamentale rimane pero inalterato ed uguale a quello che caratterizza Mus musculus, NF = 40. Lo studio delle diacinesi meiotiche e del cariotipo degli ibridi F1 ed F2 e R in esperienze di incrocio con topi albini di ceppo Suisse (2n = 40; NF = 40) dimostra la presenza di almeno 4 fenotipi cromosomici aploidi: n = 12, n = 13, n = 14, ed n = 19. I rapporti con il cariotipo di Mus poschiavinus Fatio (2n = 26; NF = 40) sono stati discussi.