Patterns of genic diversity and structure in a species undergoing rapid chromosomal radiation: an allozyme analysis of house mice from the Madeira archipelago.

The chromosomal radiation of the house mouse in the island of Madeira most likely involved a human-mediated colonization event followed by within-island geographical isolation and recurrent episodes of genetic drift. The genetic signature of such processes was assessed by an allozyme analysis of the chromosomal races from Madeira. No trace of a decrease in diversity was observed suggesting the possibility of large founder or bottleneck sizes, multiple introductions and/or a high post-colonization expansion rate. The Madeira populations were more closely related to those of Portugal than to other continental regions, in agreement with the documented human colonization of the island. Such a Portuguese origin contrasts with a study indicating a north European source of the mitochondrial haplotypes present in the Madeira mice. This apparent discrepancy may be resolved if not one but two colonization events took place, an initial north European introduction followed by a later one from Portugal. Asymmetrical reproduction between these mice would have resulted in a maternal north European signature with a nuclear Portuguese genome. The extensive chromosomal divergence of the races in Madeira is expected to contribute to their genic divergence. However, there was no significant correlation between chromosomal and allozyme distances. This low apparent chromosomal impact on genic differentiation may be related to the short time since the onset of karyotypic divergence, as the strength of the chromosomal barrier will become significant only at later stages.

Adaptive energetics in house mice, Mus musculus domesticus, from the island of Porto Santo (Madeira archipelago, North Atlantic).

The bioenergetic strategies of house mice (Mus musculus domesticus) from the island of Porto Santo were investigated and compared with those of mice from mainland Portugal. Energy obtained from food ingestion was 18.2% lower in Porto Santo mice than in mainland mice (1.53 vs. 1.87 kJ/g/day). The same pattern was observed for metabolisable energy intake, which was 19.2% lower in island specimens (0.87 vs. 1.08 kJ/g/day for mainland specimens). Apparent digestibility was similar in both groups of mice. Basal metabolic rate (BMR) of Porto Santo individuals was low (1.16 ml O(2)/g/h), representing only 56% of the predicted value, based on body mass, while mainland individuals exhibited a BMR closer to the expected value, corresponding to 87% of the predicted value (1.80 ml O(2)/g/h). Thermoregulatory abilities within the range of 10-28 degrees C ambient temperature did not differ between island and mainland mice. Results suggest an adaptation of Porto Santo mice to the environmental aridity of the island of Porto Santo, leading to a conservative energetic strategy.

Two deeply divergent mitochondrial clades in the wild mouse Mus macedonicus reveal multiple glacial refuges south of Caucasus.

A survey of 77 individuals covering the range of Mus macedonicus from Georgia in the East to Greece and Bulgaria in the West and Israel in the South has shown the existence of two deeply divergent mitochondrial clades. The southern clade was until now undetected and characterises mice from Israel. Nuclear genes also show some amount of regional differentiation tending to separate the southern M. macedonicus from the northern ones. These results point towards the fact that the eastern Mediterranean short-tailed mouse, which was seen as a fairly homogeneous monotypic species, has in fact a more complex phylogeographic history than has been suspected, and that it warrants the existence of two subspecies. The reasons for this non-uniformity probably ought to be looked for in the history of faunal movements linked to glacial periods, underlining the possible existence of at least two refugia south of the Caucasus.

Developmental instability in a riparian population of the Algerian mouse(Mus spretus) associated with a heavy metal-polluted area in central Portugal.

The adverse effects of heavy metals (mostly Cr, Mn, Fe, Cu, Zn, and Se) on the environment were appraised by comparing fluctuating asymmetry of dental characters (molars) in Algerian mice (Mus spretus) from polluted (Oeiras) and reference (Xévora) riparian areas, in central Portugal. The size of tooth traits was shown to be reduced in the contaminated area, and the developmental instability increased. The results suggest that Algerian mice may be used as indicators of heavy metal pollution and that fluctuating asymmetry represents a useful tool for monitoring ecological stresses, even when the contamination levels are low.

Molecular studies on the colonization of the Madeiran archipelago by house mice.

To study the colonization history of the house mouse (Mus musculus domesticus) on the Madeiran archipelago, complete mitochondrial D-loop sequences were obtained for 44 individuals from Madeira, Porto Santo and Ilhas Desertas. Altogether, 19 D-loop haplotypes were identified which formed part of a single clade in a phylogeny incorporating haplotypes from elsewhere in the range of M. m. domesticus, indicating that the Madeiras were colonized from a single source. Similarities between the sequences found in the Madeiras and those in Scandinavia and northern Germany suggest that northern Europe was the source area, and there is the intriguing possibility that the Vikings may have accidentally brought house mice to the archipelago. However, there is no record of Vikings visiting the Madeiras; on historical grounds, Portugal is the most likely source area for Madeiran mice and further molecular data from Portugal are needed to rule out that possibility.

Developmental stability in house mice heterozygous for single Robertsonian fusions.

Fluctuating asymmetry (FA) of tooth traits has been reported to be increased in Down syndrome patients as well as hybrids between chromosomal races of the house mouse differing in several Robertsonian (Rb) fusions. Developmental stability, assessed by FA, is thus thought to be impaired by spontaneous chromosomal abnormality or by chromosomal heterozygosity. Although the effect of a single fusion on developmental stability could theoretically be expected, it has never been documented. Crosses involving two chromosomal races of the house mouse diverging for one Rb fusion were performed to assess developmental stability in parental homozygous races as well as in their hybrids. Moreover, the occurrence of a spontaneous chromosomal mutation (WART type-b) allowed us to study the instantaneous effect of such a translocation on developmental stability. No difference in fluctuating asymmetry levels was detected among the groups considered in this study. This result suggested that a single stable or spontaneous balanced structural rearrangement did not inherently disturb developmental stability. In addition, the differential effect on developmental stability of one versus many heterozygous Rb fusions highlights the role of their quantitative accumulation in the disruption of coadaptation in chromosomal hybrids.

Spontaneous occurrence of a Robertsonian fusion involving chromosome 19 by single whole-arm reciprocal translocation (WART) in wild-derived house mice.

Chromosomal races of the house mouse (Mus musculus domesticus) bear Robertsonian (Rb) fusions, which consist of centric translocations between two non-homologous acrocentric chromosomes. The high level of diversity of these fusions in house mice is generated by de-novo formation of Rb fusions and subsequent whole-arm reciprocal exchanges (WARTs). This paper describes the spontaneous occurrence of a new Rb fusion, Rb(4.19), in progeny of wild-derived house mice segregating for Rb(4.12). The chromosomal mutation was traced to a female which exhibited germline and somatic mosaicism indicating an early embryonic origin of the mutation. FISH analysis of centromerically-located ribosomal genes suggested that no modification was observed on chromosomes 12 and 19 prior to or following the occurrence of Rb(4.19). Distribution of telomeric sequences showed that both Rb fusions lacked telomeres in their centromeric regions. It is argued that this spontaneous mutation most likely originated by single whole-arm reciprocal translocation (WART) between Rb(4.12) and an acrocentric chromosome 19, resulting in Rb(4.19) and a neo-acrocentric chromosome 12. Sequences required for centromeric function and proximal telomeres would have been transferred to the neo-chromosome 12 from chromosome 19 during the translocation. The existence of such WARTs which generate derived acrocentric chromosomes has several implications for chromosomal evolution in house mice.

Independence between developmental stability and canalization in the skull of the house mouse.

The relationship between the two components of developmental homeostasis, that is canalization and developmental stability (DS), is currently debated. To appraise this relationship, the levels and morphological patterns of interindividual variation and fluctuating asymmetry were assessed using a geometric morphometric approach applied to the skulls of laboratory samples of the house mouse. These three samples correspond to two random-bred strains of the two European subspecies of the house mouse and their F1 hybrids. The inter- and intraindividual variation levels were found to be smaller in the hybrid group compared to the parental ones, suggesting a common heterotic effect on skull canalization and DS. Both buffering mechanisms might then depend on the same genetic condition, i.e. the level of heterozygosity. However, related morphological patterns did not exhibit any congruence. In contradiction with previous studies on insect wing traits, we therefore suggest that canalization and DS may not act on the same morphological characters. The fact that this discrepancy could be related to the functional importance of the symmetry of the characters under consideration is discussed in the light of our knowledge of the genetic bases of both components of developmental homeostasis.

House mouse ancestor from late Pliocene Siwalik sediments of India.

A well preserved mouse skull has been recovered from a pedogenically modified mudstone layer (c. 2 millions years (MY) old) of Pinjor Formation (Upper Siwaliks) exposed east of Chandigarh, India. Comparison of the present skull with those of the extant species of the subgenus Mus reveals its closer relationship towards the house mouse Mus musculus lineage. The present fossil evidence is very much in line with the molecular, allozymic and ecological proposals for the time and place of origin of the subgenus Mus.

Fluctuating asymmetry in the Mus musculus hybrid zone: a heterotic effect in disrupted co-adapted genomes.

Developmental stability reflects the organism's ability to buffer minor developmental accidents and is often estimated by measuring the fluctuating asymmetry. Either implicitly or explicitly, numerous authors have assumed that developmental stability is correlated with overall fitness. If this is the case, changes in morphological asymmetry across a hybrid zone could be used as a measure of the selection on hybrid genomes. Developmental stability in hybrid populations is theoretically related to the genetic distance between hybridizing taxa, and results from a balance between the stabilizing effect due to increased heterozygosity and the disruptive effect caused by breakdown of genomic co-adaptation. Here we have compared the amount of fluctuating asymmetry across a transect of the hybrid zone between the two European subspecies of the house mouse (Mus musculus domesticus and M. m. musculus) in Denmark. For the first time in any natural hybrid zone we found an increased developmental stability in the populations with mixed genomes. Moreover, the apparently beneficial effect of hybridization on the developmental stability of the hybrid mice contrasts with the results of both genetic and parasitological studies which show that hybrid dysgenesis occurs in this zone. Our results suggest that the barrier to gene flow in the Mus musculus hybrid zone may result from the disruption of relatively few gene systems. They also lead us to reassess the relation between developmental stability expressed as fluctuating asymmetry, co-adaptation and overall fitness.

Fertility estimates in the Tunisian all-acrocentric and Robertsonian populations of the house mouse and their chromosomal hybrids.

The reproductive features of wild all-acrocentric and 2n = 22 Robertsonian (Rb) house mice (M. m. domesticus) from Tunisia were studied. The aim was to examine the possibility of a reproductive selective advantage associated with chromosomal change as well as to measure the effect of heterozygosity for a large number of Rb fusions on the fertility of hybrids. Results showed that litter sizes were significantly smaller in Rb than in all-acrocentric mice. This difference, which may represent a favourable demographic strategy related to the habitat segregation observed in the Tunisian mice, needs to be studied further. The F1 hybrids between the two chromosomal races showed a significantly reduced reproductive success and litter size (respectively, 53 per cent and 60 per cent less than either parental race). Analysis of the testicular histology of F1 and backcross males showed in some cases a breakdown of spermatogenesis. The degree of this disturbance was not related to the level of chromosomal heterozygosity suggesting that genetic incompatibilities between the two genomes might be involved. The strong reduction in fertility measured in these hybrids represents a reproductive isolating mechanism effectively reducing gene flow between the all-acrocentric and 22Rb mice populations of Tunisia.

[Acute poisoning by insecticides with anticholinesterase activity. Evaluation of the efficacy of a cholinesterase reactivator, pralidoxime]. / Intoxications aiguës par insecticides à action anticholinestérasique. Evaluation de l'efficacité d'un réactivateur des cholinestérases, le pralidoxime.

Pralidoxime is the most frequently used antidote in anticholinesterase insecticide poisoning, owing to its cholinesterase reactivating action. The efficiency of Pralidoxime has been retrospectively evaluated by comparing two groups of 31 patients, the first one treated by Pralidoxime in the most commonly used doses (1200mg/24H), the second one untreated. Age, sex and nature of poison were taken in consideration to make a matched distribution in both groups. The clinical and biological initial features were nearly the same in both groups; the other therapeutic measures were the same. There was no statistical difference between the both groups for evolutive criteria such as that mortality, duration of artificial ventilation, intubation, atropine administration, decrease in plasma cholinesterase. The results pleading against the use of Pralidoxime, at least at this dose, in anticholinesterase insecticide poisoning, warrant confirmation by prospective randomized studies. The efficiency of Pralidoxime warrants confirmation firstly in the course of poisonings by some clearly identified insecticides, to which pralidoxime is supposed to be the most effective, cater used in high doses, as recommended by some authors.

[Tamponade and total parenteral nutrition by central venous catheter]. / Tamponnade et alimentation parentérale totale sur cathéter veineux central.

Various complications are associated with the use of central venous catheters for total parenteral nutrition; cardiac tamponade is one of the most severe. Four cases are reported of cardiac tamponade during total parenteral nutrition: three of them were related to cardiac perforation by the tip of the catheter, placed in the right atrium; the fourth case may have been due to cardiac perforation or to an extraintestinal complication of inflammatory bowel disease. Hydropericardium may manifest itself soon after the catheter is inserted or, more usually, some days or weeks later. Immediate diagnosis is mandatory: a sudden and unexpected deterioration in a patient receiving total parenteral nutrition through a central venous catheter, with shock, heart failure, cyanosis, congestion of neck veins should arouse suspicion of hydropericardium. Long term undernutrition, a small atrophic heart, steroid treatment may also contribute to cardiac perforation. Immediate aspiration of the hydropericardium may be life-saving: if possible, the fluid is evacuated through the catheter while still in place; otherwise, pericardiocentesis must be immediately performed. Such complications can be prevented by: the use of flexible silicone or polyurethane catheters instead of rigid polyethylene catheters, especially for long term use; a correct positioning of the catheter tip in the superior vena cava in its extrapericardial sector, as it can be checked by chest X-ray. This examination, with opacification of the catheter with contrast medium, must be repeated because of the possibility of secondary displacement of the catheter.