Testing quantum electrodynamics in extreme fields using helium-like uranium.

Quantum electrodynamics (QED), the quantum field theory that describes the interaction between light and matter, is commonly regarded as the best-tested quantum theory in modern physics. However, this claim is mostly based on extremely precise studies performed in the domain of relatively low field strengths and light atoms and ions1-6. In the realm of very strong electromagnetic fields such as in the heaviest highly charged ions (with nuclear charge Z ≫ 1), QED calculations enter a qualitatively different, non-perturbative regime. Yet, the corresponding experimental studies are very challenging, and theoretical predictions are only partially tested. Here we present an experiment sensitive to higher-order QED effects and electron-electron interactions in the high-Z regime. This is achieved by using a multi-reference method based on Doppler-tuned X-ray emission from stored relativistic uranium ions with different charge states. The energy of the 1s1/22p3/2 J = 2 → 1s1/22s1/2 J = 1 intrashell transition in the heaviest two-electron ion (U90+) is obtained with an accuracy of 37 ppm. Furthermore, a comparison of uranium ions with different numbers of bound electrons enables us to disentangle and to test separately the one-electron higher-order QED effects and the bound electron-electron interaction terms without the uncertainty related to the nuclear radius. Moreover, our experimental result can discriminate between several state-of-the-art theoretical approaches and provides an important benchmark for calculations in the strong-field domain.

Participation of ipsilateral cortical descending influences in bimanual wrist movements in humans.

There are contralateral and less studied ipsilateral (i), indirect cortical descending projections to motoneurons (MNs). We compared ipsilateral cortical descending influences on MNs of wrist flexors by applying transcranial magnetic stimulation (TMS) over the right primary motor cortex at actively maintained flexion and extension wrist positions in uni- and bimanual tasks in right-handed participants (n = 23). The iTMS response includes a short latency (~ 25 ms) motor evoked potential (iMEP), a silent period (iSP) and a long latency (~ 60 ms) facilitation called rebound (iRB). We also investigated whether the interaction between the two hands while holding an object in a bimanual task involves ipsilateral cortical descending influences. In the unimanual task, iTMS responses in the right wrist flexors were unaffected by changes in wrist position. In the bimanual task with an object, iMEPs in the right wrist flexors were larger when the ipsilateral wrist was in flexion compared to extension. Without the object, only iRB were larger when the ipsilateral wrist was extended. Thus, ipsilateral cortical descending influences on MNs were modulated only in bimanual tasks and depended on how the two hands interacted. It is concluded that the left and right cortices cooperate in bimanual tasks involving holding an object with both hands, with possible involvement of oligo- and poly-synaptic, as well as transcallosal projections to MNs. The possible involvement of spinal and transcortical stretch and cutaneous reflexes in bimanual tasks when holding an object is discussed in the context of the well-established notion that indirect, referent control underlies motor actions.

Local pesticide use intensity conditions landscape effects on biological pest control.

Complex landscapes including semi-natural habitats are expected to favour natural enemies thereby enhancing natural pest biocontrol in crops. However, when considering a large number of situations, the response of natural biocontrol to landscape properties is globally inconsistent, a possible explanation being that local agricultural practices counteract landscape effects. In this study, along a crossed gradient of pesticide use intensity and landscape simplification, we analysed the interactive effects of landscape characteristics and local pesticide use intensity on natural biocontrol. During 3 years, using a set of sentinel prey (weed seeds, aphids and Lepidoptera eggs), biocontrol was estimated in 80 commercial fields located in four contrasted regions in France. For all types of prey excepted weed seeds, the predation rate was influenced by interactions between landscape characteristics and local pesticide use intensity. Proportion of meadow and length of interface between woods and crops had a positive effect on biocontrol of aphids where local pesticide use intensity was low but had a negative effect elsewhere. Moreover, the landscape proportion of suitable habitats for crop pests decreased the predation of sentinel prey, irrespectively of the local pesticide use intensity for weed seeds, but only in fields with low pesticide use for Lepidoptera eggs. These results show that high local pesticide use can counteract the positive expected effects of semi-natural habitats, but also that the necessary pesticide use reduction should be associated with semi-natural habitat enhancement to guarantee an effective natural biocontrol.

Screening for Epstein-Barr virus (EBV) infection status in university freshmen: acceptability of a gingival swab method.

Prophylactic vaccines against Epstein-Barr virus (EBV) are under development. EBV-naïve college freshmen are ideal candidates for an efficacy trial, because their incidence of infectious mononucleosis (mono) during freshman year is as high as 20%. To assess perceptions about mono and a mono vaccine, and to learn if EBV immune status could be determined using a gingival swab rather than phlebotomy, we performed a cross-sectional study of 235 healthy students at the beginning of their freshman year. Subjects completed questionnaires and donated oral washes, gingival swabs and venous blood. Overall, 90% of students found the swab easy to use and 80% preferred the swab over venepuncture. Of the 193 students with sufficient samples, 108 (56%) had EBV antibodies in blood vs. 87 (45.1%) in the gingival swab. The sensitivity and specificity of the swab compared with blood for detecting EBV antibodies was 75.9% and 94.1%, respectively, with an accuracy of 89.3%. EBV DNA was detected in the oral wash and swab of 39.2% and 30.4% of blood-antibody-positive individuals, respectively. In conclusion, 44% of our freshmen were EBV-naïve and thus vaccine candidates, the gingival swab was an acceptable alternative to phlebotomy for detecting EBV antibody but needs improved sensitivity, and the perceived value of EBV vaccine was high (72% believed they would benefit).

Ape Plasmodium parasites as a source of human outbreaks.

Recent studies have revealed a remarkable molecular diversity of Plasmodium parasites in great apes in Africa, as well as parasite exchange events between these primates and humans. We review the different points of view proposed on the origin of human malaria, and discuss ape Plasmodium parasites as a source of human outbreaks.

Aggressive and neutral interventions in conflicts in captive groups of brown lemurs (Eulemur fulvus fulvus).

Third-party interventions in conflicts have revealed complexity in primate social relationships. This type of intervention has seldom been analyzed in prosimians, although many of these species exhibit complex (multimale/multifemale) social organizations. The present study on captive brown lemurs (Eulemur fulvus fulvus) shows that dominant individuals were more likely to intervene in conflicts. Both males and females intervened aggressively in conflicts. Female aggressive interventions occurred mainly on behalf of close kin, whereas males mainly intervened on behalf of juveniles. This study also provides the first record of neutral or peaceful interventions in lemurs. Although females intervened neutrally, almost all neutral interventions were by dominant males. Dominant males intervened in conflicts neutrally more often than aggressively, principally in conflicts between adults and juveniles or between juveniles. Neutral interventions by males always ended the conflicts and were often followed by affiliative contacts between participants (intervenors and opponents). In lemurs, female interventions can be explained by kin selection, while the nature of dominant males' interventions suggests a control role. Interventions by males on behalf of juveniles may increase the formers' fitness.

Cellular determinants of the mutational specificity of 1-nitroso-6-nitropyrene and 1-nitroso-8-nitropyrene in the lacI gene of Escherichia coli.

We have characterized 202 lacI(-) mutations, and 158 dominant lacI(-d) mutations following treatment of Escherichia coli strains NR6112 and EE125 with 1-nitroso-6-nitropyrene (1,6-NONP), an activated metabolite of the carcinogen 1,6-dinitropyrene. In all, 91% of the induced point mutations occurred at G:C residues. The -(G:C) frameshifts were the dominant mutational class in the lacI(-) collections of both NR6112 and EE125, and in the lacI(-d) collection of NR6112. Frameshift mutations occurred preferentially in runs of guanine residues, and their frequency increased with the length of the reiterated sequence. In strain EE125, which contained the plasmid pKM101, there was a marked stimulation in the frequency of base substitution mutations that was particularly apparent in the lacI(-d) collection. This study completes a comprehensive analysis of 1194 lacI(-) and 348 lacI(-d) mutations induced by either 1,6-NONP or its positional isomer 1-nitroso-8-nitropyrene (1,8-NONP) in strains of E. coli that differ with regard to their ability to carry out nucleotide excision repair and/or their ability to express the translesion synthesis DNA polymerase RI (MucAB) encoded by plasmid pKM101. Among the mutations are 763 frameshift mutations, 367 base substitutions and 47 deletions; these mutations have been characterized at more than 300 distinct sites in the lacI gene. Our studies provide detailed insight into the DNA sequence alterations and mutational mechanisms associated with dinitropyrene mutagenesis. We review the mutational spectra, and discuss cellular lesion repair or tolerance mechanisms that modulate the observed mutational specificity.

The mutational specificity of 1-nitroso-6-nitropyrene in the lacI gene of Escherichia coli strains deficient in nucleotide excision repair.

We have examined the mutational specificity of 1-nitroso-6-nitropyrene (1,6-NONP), an activated metabolite of the carcinogen 1,6-dinitropyrene, in the lacI gene of Escherichia coli strains which are deficient in nucleotide excision repair (strain NR6113, delta uvrB; strain CM6114, delta uvrB, plasmid pKM101). Separate collections of lacI- mutations and dominant lacI-d mutations, which contain DNA sequence alterations in the region of the lacI gene that encodes the DNA binding domain of the lacI repressor, were made following 1,6-NONP treatment. The DNA sequence of 418 mutations was determined, of which 228 were lacI- mutations and 190 were lacI-d mutations. Ninety three percent of the induced point mutations occurred at G:C residues.0 -(G:C) frameshifts were the dominant mutational class in the lacI- collections of both NR6113 and CM6114, and in the lacI-d collection of NR6113. The frameshift mutations occurred preferentially in runs of guanine residues and their frequency increased markedly with the length of the reiterated sequence. In strain CM6114, which contained the plasmid pKM101, there was a marked stimulation in the frequency of G:C-->T:A transversions that was particularly apparent in the lacI-d collection. We discuss models which might account for the apparent differences in mutational specificity resulting from the presence of the UmuD/C and MucA/B proteins. The results suggest that major classes of mutation are recovered in both the lacI- and lacI-d collections. However, the proportions of the major classes of mutations within the two collections can differ significantly. Depending on the genetic background of the host strain, the relative ratios of base substitutions to frameshift mutations in the lacI-d target can differ by almost an order of magnitude as compared with the lacI- target. This is primarily a function of the relative mutational target size of the different classes of mutation.

[Sensorimotor polyneuropathy in a flare-up of Crohn disease]. / Polyneuropathie sensitivomotrice au cours d'une poussée de maladie de Crohn.

A 22-year-old man developed an axonal sensorimotor polyneuropathy and an episode of pyloroduodenal stenosis at the same time. Rectal biopsy established the diagnosis of Crohn's disease. The etiologic investigations were negative. The neurological and gastrointestinal troubles improved and followed a parallel course. Without vitamin deficiency or metronidazole treatment, peripheral polyneuropathy is a rare event in Crohn's disease. An autoimmune cause is suspected.

Multiple calcified brain metastases revealing a lung carcinoma.

The case of a 50-year-old man with multiple calcified brain metastases revealing an undifferentiated lung carcinoma after a delay of two months, is reported. A slow and progressive clinical evolution was noted. Eight months after the brain lesion had been discovered, intramedullary and epidural spinal metastases appeared. However, the calcified brain metastases remained stable 11 months after the diagnosis. One month later the patient died after several episodes of generalized seizures.

[Recovery following anesthesia with diazepam-ketamine and fentanyl-methohexital]. / Réveil après anesthésie par diazépam-kétamine et fentanyl-méthohexital.

The quality of recovery from general anaesthesia for day-case surgery is assessed by the Trailmaking test in a randomized study of 100 women scheduled for termination of pregnancy on an outpatients basis. All patients are in ASA group I or II. Recovery following diazepam-ketamine based anaesthesia is compared to that following fentanyl-methohexital based anaesthesia. In group A, 5 min after intravenous injection of diazepam (0,2 mg.kg-1), anaesthesia is induced with ketamine (1 mg.kg-1). If necessary, in response to spontaneous movement, for maintenance of anaesthesia, 1 or 2 supplementary doses of ketamine (0,5 mg.kg-1) are administered. In group B, 5 min after intravenous injection of fentanyl (1 microgram.kg-1), anaesthesia is induced with methohexital (2 mg.kg-1). If necessary, in response to spontaneous movement, for maintenance of anaesthesia, 1 or 2 supplementary doses of methohexital (0,7 mg.kg-1) are administered. The quality of recovery is assessed by Trailmaking test 1/2 h and 1 h after surgery and compared with pre-anaesthetic score. The two groups are comparable with regard to age, weight, educational level and average duration of anaesthesia. In group A, the mean score for the two parts of the test is not significantly different 1 h after surgery from the pre-anaesthetic score. In group B, the mean score for the two parts of the test is not significantly different 1/2 h after surgery than the pre-anaesthetic score. This better post-anesthetic score is explained by a learning effect of the test when used several times.(ABSTRACT TRUNCATED AT 250 WORDS)

Human optokinetic afternystagmus. Charging characteristics and stimulus exposure time dependence in the two-component model.

The dependence of human optokinetic afternystagmus (OKAN) velocity storage (charging) and optokinetic nystagmus (OKN) characteristics on optokinetic (OK) stimulus exposure time was investigated, using the two-component double exponential model for OKAN decay. Results are compatible with our previously proposed concept of two velocity storage integrators, one responsible for the short time constant decay (pursuit-mediated) and the other for the long time constant decay (OK system-mediated). The dependence of the long time constant integrator of OKAN on stimulus exposure time was clearly demonstrated. The short time constant integrator appeared to be independent of stimulus exposure time within the range studied. We conclude that the charging time-course of each component is distinct from that of the other. The time constants of each component decay were found to be invariant. A left-right asymmetry observed in both OKN and OKAN responses suggests that the integrators are direction sensitive.

Human optokinetic afternystagmus. Stimulus velocity dependence of the two-component decay model and involvement of pursuit.

The dependence of human OKAN characteristics on optokinetic (OK) stimulus velocity was examined using the two-component double exponential model for OKAN decay. Drum velocities studied were between 10 degrees and 70 degrees deg/sec over a constant exposure period of 60 sec. Results reveal two distinct types of response: a 'low'-level response at lower drum velocities (10 degrees, 20 degrees, 30 degrees/sec) and a 'high'-level response at higher drum velocities (40 degrees, 60 degrees, 70 degrees /sec). These findings support our previous proposal that OKAN decay is a two-component process, and extend it by demonstrating that these two components have differing stimulus velocity sensitivities, as would be predicted if it were assumed that they represented direct (pursuit) and indirect (non-pursuit) pathways respectively.