Sex determination: why so many ways of doing it?

Sexual reproduction is an ancient feature of life on earth, and the familiar X and Y chromosomes in humans and other model species have led to the impression that sex determination mechanisms are old and conserved. In fact, males and females are determined by diverse mechanisms that evolve rapidly in many taxa. Yet this diversity in primary sex-determining signals is coupled with conserved molecular pathways that trigger male or female development. Conflicting selection on different parts of the genome and on the two sexes may drive many of these transitions, but few systems with rapid turnover of sex determination mechanisms have been rigorously studied. Here we survey our current understanding of how and why sex determination evolves in animals and plants and identify important gaps in our knowledge that present exciting research opportunities to characterize the evolutionary forces and molecular pathways underlying the evolution of sex determination.

Spatial and temporal dynamics of jasmonate synthesis and accumulation in Arabidopsis in response to wounding.

A new metabolite profiling approach combined with an ultrarapid sample preparation procedure was used to study the temporal and spatial dynamics of the wound-induced accumulation of jasmonic acid (JA) and its oxygenated derivatives in Arabidopsis thaliana. In addition to well known jasmonates, including hydroxyjasmonates (HOJAs), jasmonoyl-isoleucine (JA-Ile), and its 12-hydroxy derivative (12-HOJA-Ile), a new wound-induced dicarboxyjasmonate, 12-carboxyjasmonoyl-l-isoleucine (12-HOOCJA-Ile) was discovered. HOJAs and 12-HOOCJA-Ile were enriched in the midveins of wounded leaves, strongly differentiating them from the other jasmonate metabolites studied. The polarity of these oxylipins at physiological pH correlated with their appearance in midveins. When the time points of accumulation of different jasmonates were determined, JA levels were found to increase within 2-5 min of wounding. Remarkably, these changes occurred throughout the plant and were not restricted to wounded leaves. The speed of the stimulus leading to JA accumulation in leaves distal to a wound is at least 3 cm/min. The data give new insights into the spatial and temporal accumulation of jasmonates and have implications in the understanding of long-distance wound signaling in plants.

Temporal patterns of fire sequences observed in Canton of Ticino (southern Switzerland)

Temporal dynamical analysis in fire sequences recorded from 1969 to 2008 in Canton Ticino (Switzerland) was carried out by using the Allan Factor statistics. The obtained results show the presence of daily periodicities, superimposed to two time-scaling regimes. The daily cycle vanishes for sequences of higher altitude fires, for which a single scaling behaviour is observed.

Temporal variability of antibiotics fluxes in wastewater and contribution from hospitals.

Significant quantities of antibiotics are used in all parts of the globe to treat diseases with bacterial origins. After ingestion, antibiotics are excreted by the patient and transmitted in due course to the aquatic environment. This study examined temporal fluctuations (monthly time scale) in antibiotic sources (ambulatory sales and data from a hospital dispensary) for Lausanne, Switzerland. Source variability (i.e., antibiotic consumption, monthly data for 2006-2010) were examined in detail for nine antibiotics--azithromycin, ciprofloxacin, clarithromycin, clindamycin, metronidazole, norfloxacin, ofloxacin, sulfamethoxazole and trimethoprim, from which two main conclusions were reached. First, some substances--azithromycin, clarithromycin, ciprofloxacin--displayed high seasonality in their consumption, with the winter peak being up to three times higher than the summer minimum. This seasonality in consumption resulted in seasonality in Predicted Environmental Concentrations (PECs). In addition, the seasonality in PECs was also influenced by that in the base wastewater flow. Second, the contribution of hospitals to the total load of antibiotics reaching the Lausanne Wastewater Treatment Plant (WTP) fluctuated markedly on a monthly time scale, but with no seasonal pattern detected. That is, there was no connection between fluctuations in ambulatory and hospital consumption for the substances investigated.

Spatio-temporal micromeasurements of the oxygen uptake in the developing chick embryo.

A method has been developed for the determination of the oxygen uptake of small areas (0.01 mm2) in an entire chick embryo cultured in vitro under defined metabolic conditions. It is based on the recordings of the spectral changes of the hemoglobin used as oxygen source for the respiring tissue (Barzu and Borza, 1967). Rapid scanning of the hemoglobin absorbance over the preparation allows a comparison of the O2 uptake of various regions. Values of the order of 10(-2) 1 O2 . min-2 are measured in less than 10 sec with a spatial resolution of 100 micron. The differentiation of embryonic tissue is not disturbed by the measurements. The O2 diffusion in the media and in the tissue has been analyzed by digital simulation. The O2 uptake of the Hensen's node was measured from embryos starting at the stage of definitive primitive streak (stage 4) up to the stage of 10 somites. It increases from 0.6 to 1.1 nl . h-1 with a marked acceleration between stages 4 and 5. The values corrected for the protein content of the Hensen's node at stage 4, 5, 6 and 8 are 32, 30 and 28 microliter . mg-1 . h-1 respectively. The first scanning results show different patterns of the O2 utake at the level of the Hensen's node and of the neural plate. At stage 6-7, the corrected O2 uptake is 30 microliter . mg-1 . h-1 for . the former and 43 microliter . mg-1 . h-1 for the latter.

Validation française de l'échelle d'expérience temporelle du plaisir [Validation of the Temporal Experience of Pleasure Scale (TEPS) in a French-speaking environment.]

INTRODUCTION: Anhedonia is defined as a diminished capacity to experience pleasant emotion and is commonly included among the negative symptoms of schizophrenia. However, if patients report experiencing a lower level of pleasure than controls, they report experiencing as much pleasure as controls with online measurements of emotion. OBJECTIVE: The Temporal Experience of Pleasure Scale (TEPS) measures pleasure experienced in the moment and in anticipation of future activities. The TEPS is an 18-item self-report measurement of anticipatory (10 items) and consummatory (eight items) pleasure. The goal of this paper is to assess the psychometric characteristics of the French translation of this scale. METHODS: A control sample was composed of 60 women and 22 men, with a mean age of 38.1 years (S.D.: 10.8). Thirty-six were without qualification and 46 with qualified professional diploma. A sample of 21 patients meeting DSM IV-TR criteria for schizophrenia was recruited among the community psychiatry service of the department of psychiatry in Lausanne. They were five women and 16 men; mean age was of 34.1 years (S.D.: 7.5). Ten obtained a professional qualification and 11 were without qualification. None worked in competitive employment. Their mean dose of chlorpromazine equivalent was 431mg (S.D.: 259). All patients were on atypical antipsychotics. The control sample fulfilled the TEPS and the Physical Anhedonia Scale (PAS). The patient sample fulfilled the TEPS and was independently rated on the Calgary Depression Scale and the Scale for Assessment of Negative Symptoms. For comparison with controls, patients were matched on age, sex and professional qualification. This required the supplementary recruitment of two control subjects. RESULTS: Results with the control sample indicate that the TEPS presents an acceptable internal validity with Crombach alphas of 0.84 for the total scale, 0.74 for the anticipatory pleasure scale and 0.79 for the consummatory pleasure scale. The confirmatory factor analysis indicated that the model is well adapted to our data (chi(2)/dl=1.333; df=134; p<0.0006; root mean square residual, RMSEA=0.064). External validity measured with the PAS showed R=-0.27 (p<0.05) for the consummatory scale and R=-0.26 for the total score. Comparisons between patients and matched controls indicated that patients were significantly lower than control on anticipatory pleasure (t=2.7, df(40), 2-tailed p=0.01; cohen's d=0.83) and on total score of the TEPS (t=2.8, df (40), 2-tailed p=0.01; cohen's d=0.87). The two samples did not differ on consummatory pleasure. The anticipatory pleasure factor and the total TEPS showed significant negative correlation with the SANS anhedonia, respectively R=-0.78 (p<0.01) for the anticipatory factor and R=-0.61 (p<0.01) for the total TEPS. There was also a negative correlation between the anticipatory factor and the SANS avolition of R=-0.50 (p<0.05). These correlations were maintained, with partial correlations controlling for depression and chlorpromazine equivalents. CONCLUSION: The results of this validation show that the French version of the TEPS has psychometric characteristics similar to the original version. These results highlight the discrepancy between results of direct or indirect report of experienced pleasure in patients with schizophrenia. Patients may have difficulties in anticipating the pleasure of future enjoyable activities, but not in experiencing pleasure once in an enjoyable activity. Medication and depression do not seems to modify our results, but this should be better controlled in a longitudinal study. The anticipatory versus consummatory pleasure distinction appears to be useful for the development of new psychosocial interventions, tailored to improve desire in patients suffering from schizophrenia. Major limitations of the study are the small size of patient sample and the under representation of men in the control sample.

Does locally delivered Zoledronate influence peri-implant bone formation? - Spatio-temporal monitoring of bone remodeling in vivo.

Bisphosphonates are known for their strong inhibitory effect on bone resorption. Their influence on bone formation however is less clear. In this study we investigated the spatio-temporal effect of locally delivered Zoledronate on peri-implant bone formation and resorption in an ovariectomized rat femoral model. A cross-linked hyaluronic acid hydrogel was loaded with the drug and applied bilaterally in predrilled holes before inserting polymer screws. Static and dynamic bone parameters were analyzed based on in vivo microCT scans performed first weekly and then biweekly. The results showed that the locally released Zoledronate boosted bone formation rate up to 100% during the first 17 days after implantation and reduced the bone resorption rate up to 1000% later on. This shift in bone remodeling resulted in an increase in bone volume fraction (BV/TV) by 300% close to the screw and 100% further away. The double effect on bone formation and resorption indicates a great potential of Zoledronate-loaded hydrogel for enhancement of peri-implant bone volume which is directly linked to improved implant fixation.

SESAM - a new framework integrating macroecological and species distribution models for predicting spatio-temporal patterns of species assemblages

Two different approaches currently prevail for predicting spatial patterns of species assemblages. The first approach (macroecological modelling, MEM) focuses directly on realised properties of species assemblages, whereas the second approach (stacked species distribution modelling, S-SDM) starts with constituent species to approximate assemblage properties. Here, we propose to unify the two approaches in a single 'spatially-explicit species assemblage modelling' (SESAM) framework. This framework uses relevant species source pool designations, macroecological factors, and ecological assembly rules to constrain predictions of the richness and composition of species assemblages obtained by stacking predictions of individual species distributions. We believe that such a framework could prove useful in many theoretical and applied disciplines of ecology and evolution, both for improving our basic understanding of species assembly across spatio-temporal scales and for anticipating expected consequences of local, regional or global environmental changes. In this paper, we propose such a framework and call for further developments and testing across a broad range of community types in a variety of environments.

Temporal patterns of nucleotide misincorporations and DNA fragmentation in ancient DNA.

DNA that survives in museum specimens, bones and other tissues recovered by archaeologists is invariably fragmented and chemically modified. The extent to which such modifications accumulate over time is largely unknown but could potentially be used to differentiate between endogenous old DNA and present-day DNA contaminating specimens and experiments. Here we examine mitochondrial DNA sequences from tissue remains that vary in age between 18 and 60,000 years with respect to three molecular features: fragment length, base composition at strand breaks, and apparent C to T substitutions. We find that fragment length does not decrease consistently over time and that strand breaks occur preferentially before purine residues by what may be at least two different molecular mechanisms that are not yet understood. In contrast, the frequency of apparent C to T substitutions towards the 5'-ends of molecules tends to increase over time. These nucleotide misincorporations are thus a useful tool to distinguish recent from ancient DNA sources in specimens that have not been subjected to unusual or harsh treatments.

Maladies auto-immunes neuromusculaires: diagnostic et prise en charge [Dysimmune neuromuscular disorders: diagnostic challenges and new ways of management].

This review describes some dysimmune neuromuscular disorders and their recent management: syndrome of peripheral nerve hyperexcitability (treatment of cramps, immunosuppressors); Guillain-Barré syndrome (new mechanisms and consensus treatment); chronic inflammatory demyelinating polyradiculoneuropathy (new indication for the use of pulse dexamethasone, new scores of activity); importance of subcutaneous immunoglobulin in multifocal motor neuropathy and of infusions of rituximab in myasthenia gravis; new entities in myositis and their treatment.

Ecological temporal stability of Staphylococcus aureus nasal carriage.

We described the colonization dynamics of Staphylococcus aureus in a group of 266 healthy carriers over a period of approximately 1 year. We used precise genotyping methods, i.e., amplified fragment length polymorphism (AFLP), spa typing, and double-locus sequence typing (DLST), to detect changes in strain identity. Strain change took place rather rarely: out of 89 carriers who had initially been colonized, only 7 acquired a strain different from the original one. Approximately one-third of the carriers eliminated the colonization, and a similar number became newly colonized. Some of these events probably represent detection failure rather than genuine colonization loss or acquisition. Lower bacterial counts were associated with increased probability of eliminating the colonization. We have confirmed a high mutation rate in the spa locus: 6 out of 53 strains underwent mutation in the spa locus. There was no overall change in S. aureus genotype composition.

Fractal temporal organisation of motricity is altered in major depression.

OBJECTIVE: Motor changes in major depression (MD) may represent potential markers of treatment response. Physiological rhythms (heart rate/gait cycle/hand movements) have been recently shown to be neither random nor regular but to display a fractal temporal organisation, possibly reflecting a unique central "internal clock" control. Sleep and mood circadian rhythm modifications observed in MD also suggest a role for this "internal clock". We set out to examine the fractal pattern of motor activity in MD. METHODS: Ten depressed patients (46±20 years) and ten age- and gender-matched healthy controls (48±21 years) underwent a 6-h ambulatory monitoring of spontaneous hand activity with a validated wireless device. Fractal scaling exponent (α) was analysed. An α value close to 1 means the pattern is fractal. RESULTS: Healthy controls displayed a fractal pattern of spontaneous motor hand activity (α: 1.0±0.1), whereas depressed patients showed an alteration of that pattern (α:1.2±0.15, p<0.01), towards a smoother organisation. CONCLUSION: The alteration of fractal pattern of hand activity by depression further supports the role of a central internal clock in the temporal organisation of movements. This novel way of studying motor changes in depression might have an important role in the detection of endophenotypes and potential predictors of treatment response.