The evolution of sex determination

Sexual reproduction is a fundamental aspect of life. Sex-determination mechanisms are responsible for the sexual fate and development of sexual characteristics in an organism, be it a unicellular alga, a plant, or an animal. Surprisingly, sex-determination mechanisms are not evolutionarily conserved but are bewilderingly diverse and appear to have had rapid turnover rates during evolution. Evolutionary biologists continue to seek a solution to this conundrum. What drives the surprising dynamics of such a fundamental process that always leads to the same outcome: two sex types, male and female? The answer is complex but the ongoing genomic revolution has already greatly increased our knowledge of sex-determination systems and sex chromosomes in recent years. This novel book presents and synthesizes our current understanding, and clearly shows that sex-determination evolution will remain a dynamic field of future research. The Evolution of Sex Determination is an advanced, research level text suitable for graduate students and researchers in genetics, developmental biology, and evolution.

Space-time within general relativity : a structural realist understanding

ABSTRACT This dissertation investigates the, nature of space-time as described by the theory of general relativity. It mainly argues that space-time can be naturally interpreted as a physical structure in the precise sense of a network of concrete space-time relations among concrete space-time points that do not possess any intrinsic properties and any intrinsic identity. Such an interpretation is fundamentally based on two related key features of general relativity, namely substantive general covariance and background independence, where substantive general covariance is understood as a gauge-theoretic invariance under active diffeomorphisms and background independence is understood in the sense that the metric (or gravitational) field is dynamical and that, strictly speaking, it cannot be uniquely split into a purely gravitational part and a fixed purely inertial part or background. More broadly, a precise notion of (physical) structure is developed within the framework of a moderate version of structural realism understood as a metaphysical claim about what there is in the world. So, the developement of this moderate structural realism pursues two main aims. The first is purely metaphysical, the aim being to develop a coherent metaphysics of structures and of objects (particular attention is paid to the questions of identity and individuality of these latter within this structural realist framework). The second is to argue that moderate structural realism provides a convincing interpretation of the world as described by fundamental physics and in particular of space-time as described by general relativity. This structuralist interpretation of space-time is discussed within the traditional substantivalist-relationalist debate, which is best understood within the broader framework of the question about the relationship between space-time on the one hand and matter on the other. In particular, it is claimed that space-time structuralism does not constitute a 'tertium quid' in the traditional debate. Some new light on the question of the nature of space-time may be shed from the fundamental foundational issue of space-time singularities. Their possible 'non-local' (or global) feature is discussed in some detail and it is argued that a broad structuralist conception of space-time may provide a physically meaningful understanding of space-time singularities, which is not plagued by the conceptual difficulties of the usual atomsitic framework. Indeed, part of these difficulties may come from the standard differential geometric description of space-time, which encodes to some extent this atomistic framework; it raises the question of the importance of the mathematical formalism for the interpretation of space-time.

Enzyme-linked immunosorbent assay and Western blot antibody determination in sera from patients diagnosed with different helminthic infections with Anisakis simplex antigen purified by affinity chromatography

An evaluation of the sensitivity and the specificity of the Anisakis simplex antigens purified by affinity chromatography was performed using sera from patients diagnosed with Anisakis sensitisation and sera from patients previously diagnosed with different helminthic infections. Only the sera of the patients diagnosed with Schistosoma mansoni or Onchocerca volvulus parasitic infections were negative against the A. simplex antigen and its purified fractions (PAK antigen: A. simplex antigen purified using columns prepared with anti-A. simplex rabbit IgG and PAS antigen: PAK antigen purified using columns prepared with anti-Ascaris suum rabbit IgG). However all the sera were positive against the A. suum antigen. In all the sera from the patients diagnosed with Anisakis sensitisation, the antibody levels detected using the purified antigens (PAK and PAS antigens) were lower than the observed using the A. simplex crude extract with the highest diminution in the case of the IgG. When these same sera were tested against the A. simplex crude extract by Western blot, several bands of high molecular masses were observed as well as, intense bands at 60 and/or 40 kDa. A concentration of these last proteins was observed in the PAK and the PAS antigens. When the sensitivity and the specificity determinations were performed, only seven of the 38 patients diagnosed of Anisakis sensitisation were positive, as well as, the sera from the patients diagnosed with parasitisms by Echinococcus granulosus or Fasciola hepatica.

Determination of DNA persistence length by cryo-electron microscopy. Separation of the static and dynamic contributions to the apparent persistence length of DNA.

Axial deflection of DNA molecules in solution results from thermal motion and intrinsic curvature related to the DNA sequence. In order to measure directly the contribution of thermal motion we constructed intrinsically straight DNA molecules and measured their persistence length by cryo-electron microscopy. The persistence length of such intrinsically straight DNA molecules suspended in thin layers of cryo-vitrified solutions is about 80 nm. In order to test our experimental approach, we measured the apparent persistence length of DNA molecules with natural "random" sequences. The result of about 45 nm is consistent with the generally accepted value of the apparent persistence length of natural DNA sequences. By comparing the apparent persistence length to intrinsically straight DNA with that of natural DNA, it is possible to determine both the dynamic and the static contributions to the apparent persistence length.

Studies on antimicrobial activity, in vitro, of Physalis angulata L. (Solanaceae) fraction and physalin B bringing out the importance of assay determination

Complex physalin metabolites present in the capsules of the fruit of Physalis angulata L. have been isolated and submitted to a series of assays of antimicrobial activity against Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, S. aureus ATCC 25923, S. aureus ATCC 6538P, Neisseria gonorrhoeae ATCC 49226, Escherichia coli ATCC 8739; E. coli ATCC 25922, Candida albicans ATCC 10231 applying different methodologies such as: bioautography, dilution broth, dilution agar, and agar diffusion techniques. A mixture of physalins (pool) containing physalins B, D, F, G inhibit S. aureus ATCC 29213, S. aureus ATCC 25923, S. aureus ATCC 6538P, and N. gonorrhoeae ATCC 49226 at a concentration of 200 mg/µl, using agar dilution assays. The mixture was inactive against P. aeruginosa ATCC27853, E. coli ATCC 8739; E. coli ATCC 25922, C. albicans ATCC 10231 when applying bioautography assays. Physalin B (200 µg/ml) by the agar diffusion assay inhibited S. aureus ATCC 6538P by ± 85%; and may be considered responsible for the antimicrobial activity.

Automated systems in the identification and determination of methicillin resistance among coagulase negative staphylococci

Coagulase-negative staphylococci (CoNS) are an important cause of nosocomial bacteremia, specially in patients with indwelling devices or those submitted to invasive medical procedures. The identification of species and the accurate and rapid detection of methicillin resistance are directly dependent on the quality of the identification and susceptibility tests used, either manual or automated. The objective of this study was to evaluate the accuracy of two automated systems MicroScan and Vitek - in the identification of CoNS species and determination of susceptibility to methicillin, considering as gold standard the biochemical tests and the characterization of the mecA gene by polymerase chain reaction, respectively. MicroScan presented better results in the identification of CoNS species (accuracy of 96.8 vs 78.8%, respectively); isolates from the following species had no precise identification: Staphylococcus haemolyticus, S. simulans, and S. capitis. Both systems were similar in the characterization of methicillin resistance. The higher discrepancies for gene mec detection were observed among species other than S. epidermidis (S. hominis, S. saprophyticus, S. sciuri, S. haemolyticus, S. warneri, S. cohnii), and those with borderline MICs.

Redox dysregulation in schizophrenia : implication for oligodendrocyte maturation and structural connectivity

Schizophrenia, which results from an interaction between gene and environmental factors, is a psychiatric disorder characterized by reality distortion. The clinical symptoms, which are generally diagnosed in late adolescence or early adulthood, partly derive from altered brain connectivity especially in prefrontal cortex. Disruption of neuronal networks implies oligodendrocyte and myelin abnormalities in schizophrenia pathophysiology. The mechanisms of these impairments are still unclear. Converging evidences indicate a role of redox dysregulation, generated by an imbalance between pro-oxidants and antioxidant defense mechanisms, in the development of schizophrenia pathophysiology. In particular, genetic and biochemical data indicate impaired synthesis of glutathione, the main cellular antioxidant and redox regulator. As oligodendrocyte maturation is dependent on redox state, we evaluated whether abnormal redox control could contribute to oligodendrocyte and myelin impairments in schizophrenia. We found that glutathione in prefrontal cortex of early psychosis patients and control subjects positively correlated with white matter integrity. We then further explored the interplay between glutathione and myelin using a translational approach. Our data showed that in mice with genetically impaired glutathione synthesis, oligodendrocyte late maturation as well as myelination was delayed in the anterior cingulate cortex. Specifically, oligodendrocyte number and myelin levels were lowered at peripubertal age, coincident in time with the peak of myelin- related gene expression during normal brain development. These data suggest that early adolescence is a vulnerable developmental period during which an adequate redox control is required for oligodendrocyte maturation and active myelination process. Consistently, oxidative stress mediated by psychosocial stress also delayed myelination in peripubertal mice. At cellular levels, impaired glutathione synthesis altered oligodendrocyte development at several levels. Using oligodendrocyte progenitor cells cultures, our data showed that glutathione deficiency was associated with (i) cell cycle arrest and a reduction in oligodendrocyte proliferation, and (ii) an impairment in oligodendrocyte maturation. Abnormal oligodendrocyte proliferation was mediated by upregulation of Fyn kinase activity. Consistently, under oxidative stress conditions, we observed abnormal regulation of Fyn kinase in fibroblasts of patients deficient in glutathione synthesis. Together, our data support that a redox dysregulation due to glutathione deficit could underlie myelination impairment in schizophrenia, possibly mediated by dysregulated Fyn pathway. Better characterization of Fyn mechanisms would pave the way towards new drug targets. -- La schizophrénie est une maladie psychiatrique qui se définit par une distorsion de la perception de la réalité. Les symptômes cliniques sont généralement diagnostiqués durant l'adolescence ou au début de l'âge adulte et proviennent de troubles de la connectivité, principalement au niveau du cortex préfrontal. Les dysfonctionnements des réseaux neuronaux impliquent des anomalies au niveau des oligodendrocytes et de la myéline dans la pathophysiologie de la schizophrénie. Les mécanismes responsables des ces altérations restent encore mal compris. Dans le développement de la schizophrénie, des évidences mettent en avant un rôle de la dérégulation rédox, traduit par un déséquilibre entre facteurs pro-oxydants et défenses antioxydantes. Des données génétiques et biochimiques indiquent notamment un défaut de la synthèse du glutathion, le principal antioxydant et rédox régulateur des cellules. Etant donné que la maturation des oligodendrocytes est dépendante de l'état rédox, nous avons regardé si une dérégulation rédox contribue aux anomalies de la myéline dans le cadre de la schizophrénie. Dans le cortex préfrontal des sujets contrôles et des patients en phase précoce de psychose, nous avons montré que le glutathion était positivement associé à l'intégrité de matière blanche. Afin d'explorer plus en détail la relation entre le glutathion et la myéline, nous avons mené une étude translationnelle. Nos résultats ont montré que des souris ayant un déficit de la synthèse du glutathion présentaient un retard dans les processus de maturation des oligodendrocytes et de la myélinisation dans le cortex cingulaire antérieure. Plus précisément, le nombre d'oligodendrocytes et le taux de myéline étaient uniquement diminués durant la période péripubertaire. Cette même période correspond au pic de l'expression des gènes en lien avec la myéline. Ces données soulignent le fait que l'adolescence est une période du développement particulièrement sensible durant laquelle un contrôle adéquat de l'état rédox est nécessaire aux processus de maturation des oligodendrocytes et de myélinisation. Ceci est en accord avec la diminution de myéline observée suite à un stress oxydatif généré par un stress psychosocial. Au niveau cellulaire, un déficit du glutathion affecte le développement des oligodendrocytes à différents stades. En effet, dans des cultures de progéniteurs d'oligodendrocytes, nos résultats montrent qu'une réduction du taux de glutathion était associée à (i) un arrêt du cycle cellulaire ainsi qu'une diminution de la prolifération des oligodendrocytes, et à (ii) des dysfonctionnements de la maturation des oligodendrocytes. Par ailleurs, au niveau moléculaire, les perturbations de la prolifération étaient générées par une augmentation de l'activité de la kinase Fyn. Ceci est en accord avec la dérégulation de Fyn observée dans les fibroblastes de patients ayant une déficience en synthèse du glutathion en condition de stress oxydatif. Les résultats de cette thèse soulignent qu'une dérégulation rédox induite par un déficit en glutathion peut contribuer aux anomalies des oligodendrocytes et de la myéline via le dysfonctionnement des voies de signalisation Fyn. Une recherche plus avancée de l'implication de Fyn dans la maladie pourrait ouvrir la voie à de nouvelles cibles thérapeutiques.

Determination of nicotine and nicotine metabolites in urine by hydrophilic interaction chromatography-tandem mass spectrometry: Potential use of smokeless tobacco products by ice hockey players.

Consumption of nicotine in the form of smokeless tobacco (snus, snuff, chewing tobacco) or nicotine-containing medication (gum, patch) may benefit sport practice. Indeed, use of snus seems to be a growing trend and investigating nicotine consumption amongst professional athletes is of major interest to sport authorities. Thus, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the detection and quantification of nicotine and its principal metabolites cotinine, trans-3-hydroxycotinine, nicotine-N'-oxide and cotinine-N-oxide in urine was developed. Sample preparation was performed by liquid-liquid extraction followed by hydrophilic interaction chromatography-tandem mass spectrometry (HILIC-MS/MS) operated in electrospray positive ionization (ESI) mode with selective reaction monitoring (SRM) data acquisition. The method was validated and calibration curves were linear over the selected concentration ranges of 10-10,000 ng/mL for nicotine, cotinine, trans-3-hydroxycotinine and 10-5000 ng/mL for nicotine-N'-oxide and cotinine-N-oxide, with calculated coefficients of determination (R(2)) greater than 0.95. The total extraction efficiency (%) was concentration dependent and ranged between 70.4 and 100.4%. The lower limit of quantification (LLOQ) for all analytes was 10 ng/mL. Repeatability and intermediate precision were ?9.4 and ?9.9%, respectively. In order to measure the prevalence of nicotine exposure during the 2009 Ice Hockey World Championships, 72 samples were collected and analyzed after the minimum of 3 months storage period and complete removal of identification means as required by the 2009 International Standards for Laboratories (ISL). Nicotine and/or metabolites were detected in every urine sample, while concentration measurements indicated an exposure within the last 3 days for eight specimens out of ten. Concentrations of nicotine, cotinine, trans-3-hydroxycotinine, nicotine-N'-oxide and cotinine-N-oxide were found to range between 11 and 19,750, 13 and 10,475, 10 and 8217, 11 and 3396, and 13 and 1640 ng/mL, respectively. When proposing conservative concentration limits for nicotine consumption prior and/or during the games (50 ng/mL for nicotine, cotinine and trans-3-hydroxycotinine and 25 ng/mL for nicotine-N'-oxide and cotinine-N-oxide), about half of the hockey players were qualified as consumers. These findings significantly support the likelihood of extensive smokeless nicotine consumption. However, since such conclusions can only be hypothesized, the potential use of smokeless tobacco as a doping agent in ice hockey requires further investigation.

Micro-Structural Brain Alterations in Aviremic HIV+ Patients with Minor Neurocognitive Disorders: A Multi-Contrast Study at High Field.

OBJECTIVE: Mild neurocognitive disorders (MND) affect a subset of HIV+ patients under effective combination antiretroviral therapy (cART). In this study, we used an innovative multi-contrast magnetic resonance imaging (MRI) approach at high-field to assess the presence of micro-structural brain alterations in MND+ patients. METHODS: We enrolled 17 MND+ and 19 MND- patients with undetectable HIV-1 RNA and 19 healthy controls (HC). MRI acquisitions at 3T included: MP2RAGE for T1 relaxation times, Magnetization Transfer (MT), T2* and Susceptibility Weighted Imaging (SWI) to probe micro-structural integrity and iron deposition in the brain. Statistical analysis used permutation-based tests and correction for family-wise error rate. Multiple regression analysis was performed between MRI data and (i) neuropsychological results (ii) HIV infection characteristics. A linear discriminant analysis (LDA) based on MRI data was performed between MND+ and MND- patients and cross-validated with a leave-one-out test. RESULTS: Our data revealed loss of structural integrity and micro-oedema in MND+ compared to HC in the global white and cortical gray matter, as well as in the thalamus and basal ganglia. Multiple regression analysis showed a significant influence of sub-cortical nuclei alterations on the executive index of MND+ patients (p = 0.04 he and R(2) = 95.2). The LDA distinguished MND+ and MND- patients with a classification quality of 73% after cross-validation. CONCLUSION: Our study shows micro-structural brain tissue alterations in MND+ patients under effective therapy and suggests that multi-contrast MRI at high field is a powerful approach to discriminate between HIV+ patients on cART with and without mild neurocognitive deficits.

Intermediary and structural determinants of early childhood health in Colombia: exploring the role of communities

This study examines how structural determinants influence intermediary factors of child health inequities and how they operate through the communities where children live. In particular, we explore individual, family and community level characteristics associated with a composite indicator that quantitatively measures intermediary determinants of early childhood health in Colombia. We use data from the 2010 Colombian Demographic and Health Survey (DHS). Adopting the conceptual framework of the Commission on Social Determinants of Health (CSDH), three dimensions related to child health are represented in the index: behavioural factors, psychosocial factors and health system. In order to generate the weight of the variables and take into account the discrete nature of the data, principal component analysis (PCA) using polychoric correlations are employed in the index construction. Weighted multilevel models are used to examine community effects. The results show that the effect of household’s SES is attenuated when community characteristics are included, indicating the importance that the level of community development may have in mediating individual and family characteristics. The findings indicate that there is a significant variance in intermediary determinants of child health between-community, especially for those determinants linked to the health system, even after controlling for individual, family and community characteristics. These results likely reflect that whilst the community context can exert a greater influence on intermediary factors linked directly to health, in the case of psychosocial factors and the parent’s behaviours, the family context can be more important. This underlines the importance of distinguishing between community and family intervention programmes.

Central corneal thickness, intraocular pressure, and degree of myopia in an adult myopic population aged 20 to 40 years in southeast Spain: determination and relationships

Objective: To determine the values of, and study the relationships among, central corneal thickness (CCT), intraocular pressure (IOP), and degree of myopia (DM) in an adult myopic population aged 20 to 40 years in Almeria (southeast Spain). To our knowledge this is first study of this kind in this region. Methods: An observational, descriptive, cross-sectional study was done in which a sample of 310 myopic patients (620 eyes) aged 20 to 40 years was selected by gender- and age-stratified sampling, which was proportionally fixed to the size of the population strata for which a 20% prevalence of myopia, 5% epsilon, and a 95% confidence interval were hypothesized. We studied IOP, CCT, and DM and their relationships by calculating the mean, standard deviation, 95% confidence interval for the mean, median, Fisher’s asymmetry coefficient, range (maximum, minimum), and the Brown-Forsythe’s robust test for each variable (IOP, CCT, and DM). Results: In the adult myopic population of Almeria aged 20 to 40 years (mean of 29.8), the mean overall CCT was 550.12 μm. The corneas of men were thicker than those of women (P = 0.014). CCT was stable as no significant differences were seen in the 20- to 40-year-old subjects’ CCT values. The mean overall IOP was 13.60 mmHg. Men had a higher IOP than women (P = 0.002). Subjects over 30 years (13.83) had a higher IOP than those under 30 (13.38) (P = 0.04). The mean overall DM was −4.18 diopters. Men had less myopia than women (P < 0.001). Myopia was stable in the 20- to 40-year-old study population (P = 0.089). A linear relationship was found between CCT and IOP (R2 = 0.152, P ≤ 0.001). CCT influenced the IOP value by 15.2%. However no linear relationship between DM and IOP, or between CCT and DM, was found. Conclusions: CCT was found to be similar to that reported in other studies in different populations. IOP tends to increase after the age of 30 and is not accounted for by alterations in CCT values.

Predicting random level and seasonality of hotel prices. A structural equation growth curve approach

This article examines the effect on price of different characteristics of holiday hotels in the sun-and-beach segment, under the hedonic function perspective. Monthly prices of the majority of hotels in the Spanish continental Mediterranean coast are gathered from May to October 1999 from the tour operator catalogues. Hedonic functions are specified as random-effect models and parametrized as structural equation models with two latent variables, a random peak season price and a random width of seasonal fluctuations. Characteristics of the hotel and the region where they are located are used as predictors of both latent variables. Besides hotel category, region, distance to the beach, availability of parking place and room equipment have an effect on peak price and also on seasonality. 3- star hotels have the highest seasonality and hotels located in the southern regions the lowest, which could be explained by a warmer climate in autumn

Determination of chlorzoxazone and 6-hydroxychlorzoxazone in plasma by gas chromatography--mass spectrometry.

A gas chromatographic-mass spectrometric method is presented which allows the determination of chlorzoxazone and 6-hydroxychlorzoxazone after derivatization with the reagent N-tert.-butyldimethylsilyl-N-methyltrifluoroacetamide. No interference was observed from endogenous compounds following the extraction of plasma samples from six different human subjects. The standard curves were linear over a working range of 20 to 4000 ng/ml and of 20 to 1000 ng/ml for chlorzoxazone and 6-hydroxychlorzoxazone, respectively. Recoveries ranged from 65 to 97% for the two compounds and intra- and inter-day coefficients of variation were always less than 9%. The limit of quantitation of the method was found to be 5 ng/ml for the two compounds, hence allowing its use for single low dose pharmacokinetics.

Non-invasive dry mass determination and monitoring at the single cell level with digital holographic microscopy

Digital holography microscopy (DHM) is an optical microscopy technique which allows recording non-invasively the phase shift induced by living cells with nanometric sensitivity. Here, we exploit the phase signal as an indicator of dry mass (related to the protein concentration). This parameter allows monitoring the protein production rate and its evolution during the cell cycle. ©2008 COPYRIGHT SPIE