Precision measurement of the weak mixing angle in Møller scattering

We report on a precision measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: A(PV) = [-131 +/- 14(stat) +/- 10(syst)] x 10(-9), leading to the determination of the weak mixing angle sin2(thetaW(eff) = 0.2397 +/- 0.0010(stat) +/- 0.0008(syst), evaluated at Q2 = 0.026 GeV2. Combining this result with the measurements of sin2(thetaW(eff) at the Z0 pole, the running of the weak mixing angle is observed with over 6sigma significance. The measurement sets constraints on new physics effects at the TeV scale.

Long-term follow-up of open and endoscopic Hohmann procedures for lateral epicondylitis

PURPOSE

The long-term outcome of this new endoscopic technique was compared with that of the classical open Hohmann procedure.

TYPE OF STUDY

Retrospective cohort study.

METHODS

During 1992 and 1995, 37 patients were surgically treated with the Hohmann procedure after failed intensive conservative treatment. At an average of 92 months after the operation, 30 patients (81%) could be clinically re-examined and were evaluated with a standard questionnaire including the scores of Roles and Maudsley and Morrey et al.

RESULTS

Twenty of these patients were treated endoscopically and 10 with the open technique. There were no differences in demographic data between the 2 groups. At follow-up in both groups, similar results were seen for the function of the elbow, the scores of Roles and Maudsley and Morrey et al., the subjective rating of pain and function of the elbow, and complication rate. The results in the score of Morrey showed an average scoring of 93.2 for the endoscopic group and 87.5 for the open group (P > .05).

CONCLUSIONS

The endoscopic technique showed results comparable to the open technique and can therefore be recommended for wider surgical use so as to learn more details concerning possible complications and results of the new technique.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Multilevel genetic analyses of two European supercolonies of the Argentine ant, Linepithema humile

Some ants have an extraordinary unicolonial social organization, whereby individuals mix freely among physically separated nests. Recently, it was shown that the European population of Linepithema humile consisted of two enormous unicolonial supercolonies. Workers of the same supercolony are never aggressive to each other. In contrast, aggressiveness is invariably high between workers from different supercolonies. Here we investigated whether gene flow occurs between two supercolonies. We identified a contact zone in which we sampled 46 nests. For each nest, aggression tests were conducted against workers from reference nests from both supercolonies. Workers were always very aggressive towards workers of one of the supercolonies but not to workers of the other. Thus, all nests could be clearly assigned to one of the two supercolonies. For 22 of the 46 nests, we genotyped 15-16 workers at five microsatellite loci. A four-level hierarchical analysis of variance revealed very strong genetic differentiation between the two supercolonies (F(SUPERCOLONY-TOTAL) = 0.541) and low differentiation between sectors (i.e. group of nests connected together with trails) within supercolonies (F(SECTOR-SUPERCOLONY) = 0.064). The very high differentiation between the two supercolonies indicates a lack of ongoing gene flow, a conclusion further bolstered by the finding that the two supercolonies share no common alleles at two of the five microsatellite loci. A Bayesian clustering method also revealed the occurrence of two distinct clusters. These clusters exactly match the grouping obtained by aggression tests. None of the 332 genotyped individuals were admixed despite the fact that some nests of the two supercolonies were separated by less than 30 m. These results demonstrate that the two supercolonies have completely separate gene pools.

Loss of Wolbachia infection during colonisation in the invasive Argentine ant Linepithema humile

WOLBACHIA are maternally inherited bacteria, which are very common in arthropods and nematodes. Wolbachia infection may affect host reproduction through feminisation, parthenogenesis, male-killing, cytoplasmic incompatibility and increased fecundity. Previous studies showing discrepancies between the phylogenies of Wolbachia and its arthropod hosts indicate that infection is frequently lost, but the causes of symbiont extinction have so far remained elusive. Here, we report data showing that colonisation of new habitats is a possible mechanism leading to the loss of infection. The presence and prevalence of Wolbachia were studied in three native and eight introduced populations of the Argentine ant Linepithema humile. The screening shows that the symbiont is common in the three native L. humile populations analysed. In contrast, Wolbachia was detected in only one of the introduced populations. The loss of infection associated with colonisation of new habitats may result from drift (founder effect) or altered selection pressures in the new habitat. Furthermore, a molecular phylogeny based on sequences of the Wolbachia wsp gene indicates that L. humile has been infected by a single strain. Horizontal transmission of the symbiont may be important in ants as suggested by the sequence similarity of strains in the three genera Linepithema, Acromyrmex, and Solenopsis native from South and Central America.

Molecular phylogenetic evidence for an extracellular Cu Zn superoxide dismutase gene in insects

Representatives of three ancient gene families of the antioxidant enzyme superoxide dismutase (SOD) can be found in most metazoans. In mammals and Caenorhabditis elegans, there is at least one gene each of the cytoplasmic, mitochondrial and extracellular lineages of SOD genes. The cytoplasmic SOD was one of the first enzymes to be implicated in ageing due to its protection against damaging oxygen free radicals. In contrast to other metazoans, insects were thought to lack a gene for the extracellular SOD. We have cloned and sequenced an SOD mRNA in the ant Lasius niger that appears to belong to this extracellular family. Subsequent searches and analyses of SOD gene sequences in insect databases revealed that insects do indeed express all three SOD genes including the extracellular form. We conclude that insects as well as other metazoans appear to have the full repertoire of the three families of SOD.

Significant reproductive skew in the facultatively polygynous ant Pheidole pallidula

Reproductive skew - the extent to which reproduction is unevenly shared between individuals in a social group - varies greatly between and within animal species. In this study, we investigated how queens share parentage in polygynous (multiple queen) colonies of the Mediterranean ant Pheidole pallidula. We used highly polymorphic microsatellites markers to determine parentage of gynes (new queens), males and workers in P. pallidula field colonies. The comparison of the genotypes of young and adult workers revealed a very low queen turnover (less than 2%). The first main finding of the study of reproductive skew in these colonies was that there was a significant departure from equal contribution of queens to gyne, male and worker production. Reproductive skew was greater for male production than for queen and worker production. There was no relationship between the magnitude of the reproductive skew and the number of reproductive queens per colony, their relatedness and the overall colony productivity, some of the factors predicted to influence the extent of reproductive skew. Finally, our study revealed for the first time a trade-off in the relative contribution of nestmate queens to gyne and worker production. The queens contributing more to gyne production contributed significantly less to worker production.

The relationship between multiple mating by queens, within-colony genetic variability and fitness in the ant Lasius niger

Multiple mating has been suggested to benefit social insect queens because high genetic variation within colonies might decrease the load imposed by sterile diploid males, enhance resistance to parasites and pathogens, and lead to a more effective division of labour and/or a wider range of tolerable environmental conditions. We tested these hypotheses in the ant Lasius niger with three population samples from Switzerland and Sweden. We found no diploid males in young or mature colonies suggesting a lack of diploid male load. Colonies with multiply-mated queens were not larger nor did they produce more sexuals than colonies with singly-mated queens. We did find a significantly lower frequency of multiple mating among newly mated queens than among the queens heading mature colonies in one population sample (Switzerland 1997). However, this result was not repeated in the other study population, or in the following year in the Swiss population.

[Isolation of Plesiomonas shigelloides from a pediatric patient]

We report the isolation of P. shigelloides in the stools of a child with acute diarrhea living in the surroundings of Buenos Aires who usually drank untreated water. P. shigelloides has been implicated as an etiological agent in many sporadic cases of diarrhea, probably associated with drinking untreated water, eating uncooked seafood or foreign travel.

Restricted effective queen dispersal at a microgeographic scale in polygynous populations of the ant Formica exsecta

Ecological constraints on effective dispersal have been suggested to be a key factor influencing social evolution in animal societies as well as the shift from single queen colonies (monogyny) to multiple queen colonies (polygyny) in ants. However, little is known about the effective dispersal patterns of ant queens. Here we investigate the microgeographic genetic structure of mitochondrial haplotypes in polygynous populations of the ant Formica exsecta, both between pastures and among nests within pastures. An analysis of molecular variance revealed a very high genetic differentiation (phiST = 0.72) between pastures, indicating that queens rarely disperse successfully between pastures, despite the fact that pastures were sometimes as close as 1 km. Most of the pastures contained only a single haplotype, and haplotypes were frequently distinct between nearby pastures and even between groups of nests within the same pasture. In the three pastures that contained several haplotypes, haplotypes were not randomly distributed, the genetic differentiation between nests being phiST = 0.17, 0.52, and 0.69. This indicates that most queens are recruited within their parental colonies. However, a large proportion of nests contained more than one haplotype, demonstrating that colonies will sometimes accept foreign queens. The relatedness of mitochondrial genes among nestmates varied between 0.62 and 0.75 when relatedness was measured within each pasture and ranged between 0.72 and 1.0 when relatedness was assessed with all pastures as a reference population. Neighboring nests were more genetically similar than distant ones, and there was significant isolation by distance. This pattern may be due to new nests being formed by budding or by limited effective queen dispersal, probably on foot between neighboring nests. These results show that effective queen dispersal is extremely restricted even at a small geographical scale, a pattern consistent with the idea that ecological constraints are an important selective force leading to the evolution and maintenance of polygyny.

Thoracoscopic treatment for delayed presentation of congenital diaphragmatic hernia in the infant. A report of three cases

BACKGROUND

Delayed presentations of congenital hernia occurring outside of the neonatal period have been reported for all ages. Classically, repair of the hernia defect involves a transverse subcostal laparotomy in the pediatric age group and usually a thoracotomy in the adult. The first report describing a laparoscopic repair of a congenital diaphragmatic hernia in a 6-month-old infant was published in 1995. During the past 25 years, 17 patients with delayed presentation of congenital diaphragmatic hernias have been managed by our pediatric surgery team. The last three patients underwent surgery thoracoscopically.

PATIENTS AND METHODS

This study involved two boys (ages, 8.3 and 19 months, respectively) and one girl (age, 9 months) weighing 8 to 13 kg. All three infants underwent surgery using a thoracoscopic approach with general anesthesia. A thoracic epidural catheter was placed systematically for postoperative analgesia during the first 24 hours. Reduction of the hernia contents using one optical trocar and two operating trocars was difficult in the case without any hernia sac. In the cases with a hernia sac, reduction was easily and quickly obtained with a pleural insufflation of carbon dioxide (~8 mmHg). The hernia defect was repaired using interrupted sutures of 2/0 Ethibond. For two of the three patients, this repair was reinforced with staples in the one case and a nonresorbable mesh in the other case.

RESULTS

The mean operative time was 78 min. The chest tube was removed on the first or second postoperative day and the patients were discharged on the fourth or fifth postoperative day. At the 19-month follow-up assessment in one case, the chest x-ray was perfectly normal and diaphragmatic motion also was confirmed to be normal by ultrasonography.

CONCLUSIONS

The thoracoscopic approach for the repair of delayed-presentation congenital diaphragmatic hernia is feasible. Our results demonstrate the safety and efficiency of this surgery, as well as a remarkable functional and cosmetic result and a very quick recovery.

Queen control of sex ratio in fire ants

The haplodiploid sex-determination system of ants gives rise to conflict between queens and workers over colony sex ratios, and the female-biased allocation ratios seen in many species suggest that workers often prevail in this conflict. We exchanged queens between male- and female-specialist colonies of the fire ant Solenopsis invicta. These exchanges quickly reversed the sex-ratio biases of adopting colonies. The sex ratio of queen-laid eggs differed strongly between male- and female-specialist colonies. These findings suggest that queens can force workers to raise male sexuals by limiting the number of female brood and help to explain why sex investment ratios lie between the queen and worker equilibria in this and many other ant species.

Sex ratio and Wolbachia infection in the ant Formica exsecta

Sex allocation data in social Hymenoptera provide some of the best tests of kin selection, parent-offspring conflict and sex ratio theories. However, these studies critically depend on controlling for confounding ecological factors and on identifying all parties that potentially manipulate colony sex ratio. It has been suggested that maternally inherited parasites may influence sex allocation in social Hymenoptera. If the parasites can influence sex allocation, infected colonies are predicted to invest more resources in females than non-infected colonies, because the parasites are transmitted through females but not males. Prime candidates for such sex ratio manipulation are Wolbachia, because these cytoplasmically transmitted bacteria have been shown to affect the sex ratio of host arthropods by cytoplasmic incompatibility, parthenogenesis, male-killing and feminization. In this study, we tested whether Wolbachia infection is associated with colony sex ratio in two populations of the ant Formica exsecta that have been the subject of extensive sex ratio studies. In these populations colonies specialize in the production of one sex or the other. We found that almost all F. exsecta colonies in both populations are infected with Wolbachia. However, in neither population did we find a significant association in the predicted direction between the prevalence of Wolbachia and colony sex ratio. In particular, colonies with a higher proportion of infected workers did not produce more females. Hence, we conclude that Wolbachia does not seem to alter the sex ratio of its hosts as a means to increase transmission rate in these two populations of ants.