Dynamic imbalance between cancer cell subpopulations induced by transforming growth factor beta (TGF-ß) is associated with a DNA methylome switch.

BACKGROUND: Distinct subpopulations of neoplastic cells within tumors, including hepatocellular carcinoma (HCC), display pronounced ability to initiate new tumors and induce metastasis. Recent evidence suggests that signals from transforming growth factor beta (TGF-ß) may increase the survival of these so called tumor initiating cells leading to poor HCC prognosis. However, how TGF-ß establishes and modifies the key features of these cell subpopulations is not fully understood. RESULTS: In the present report we describe the differential DNA methylome of CD133-negative and CD133-expressing liver cancer cells. Next, we show that TGF-ß is able to increase the proportion of CD133+ cells in liver cancer cell lines in a way that is stable and persistent across cell division. This process is associated with stable genome-wide changes in DNA methylation that persist through cell division. Differential methylation in response to TGF-ß is under-represented at promoter CpG islands and enriched at gene bodies, including a locus in the body of the de novo DNA methyl-transferase DNMT3B gene. Moreover, phenotypic changes induced by TGF-ß, including the induction of CD133, are impaired by siRNA silencing of de novo DNA methyl-transferases. CONCLUSIONS: Our study reveals a self-perpetuating crosstalk between TGF-ß signaling and the DNA methylation machinery, which can be relevant in the establishment of cellular phenotypes. This is the first indication of the ability of TGF-ß to induce genome-wide changes in DNA methylation, resulting in a stable change in the proportion of liver cancer cell subpopulations.

Microalgae adaptation as a strategy to recycle the aqueous phase from hydrothermal liquefaction.

Hydrothermal liquefaction (HTL) produces bio-crude oil from wet algae along with an aqueous phase (AP). This effluent contains minerals that can be reused for cultivating new microalgae but whose utility remains limited due to the presence of inhibitors. Reduced photosynthetic performance, growth, and null lipid accumulation were observed in wild-type Chlorella vulgaris NIES 227 cultivated in AP (1/200). Adaptive laboratory evolution was studied by batch transfers and turbidostat mode. Both methods effectively counterbalanced AP toxicity and restored the fitness of the microalgae. After adaptation, a higher AP addition was achieved, from 1/600 to 1/200, without inhibition. As compared with the wild typein control medium (0.261 g/L/d), both adapted-strains maintained competitive productivity (0.310 and 0.258 g/L/d) of lipid-rich biomass (37 %-56 %). The improved tolerance of the adapted strains persisted after the removal of AP and under axenic conditions. Adaptive laboratory evolution is suggested for AP reutilization in the algae production process.

Prolonged breastfeeding protects from obesity by hypothalamic action of hepatic FGF21.

Early-life determinants are thought to be a major factor in the rapid increase of obesity. However, while maternal nutrition has been extensively studied, the effects of breastfeeding by the infant on the reprogramming of energy balance in childhood and throughout adulthood remain largely unknown. Here we show that delayed weaning in rat pups protects them against diet-induced obesity in adulthood, through enhanced brown adipose tissue thermogenesis and energy expenditure. In-depth metabolic phenotyping in this rat model as well as in transgenic mice reveals that the effects of prolonged suckling are mediated by increased hepatic fibroblast growth factor 21 (FGF21) production and tanycyte-controlled access to the hypothalamus in adulthood. Specifically, FGF21 activates GABA-containing neurons expressing dopamine receptor 2 in the lateral hypothalamic area and zona incerta. Prolonged breastfeeding thus constitutes a protective mechanism against obesity by affecting long-lasting physiological changes in liver-to-hypothalamus communication and hypothalamic metabolic regulation.

Multi- and Transgenerational Outcomes of an Exposure to a Mixture of Endocrine-Disrupting Chemicals (EDCs) on Puberty and Maternal Behavior in the Female Rat.

BACKGROUND: The effects of endocrine-disrupting chemicals (EDCs) on fertility and reproductive development represent a rising concern in modern societies. Although the neuroendocrine control of sexual maturation is a major target of EDCs, little is known about the potential role of the hypothalamus in puberty and ovulation disruption transmitted across generations. OBJECTIVES: We hypothesized that developmental exposure to an environmentally relevant dose of EDC mixture could induce multi- and/or transgenerational alterations of sexual maturation and maternal care in female rats through epigenetic reprograming of the hypothalamus. We investigated the transmission of a disrupted reproductive phenotype via the maternal germline or via nongenomic mechanisms involving maternal care. METHODS: Adult female Wistar rats were exposed prior to and during gestation and until the end of lactation to a mixture of the following 13 EDCs: di-n-butyl phthalate (DnBP), di(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA), vinclozolin, prochloraz, procymidone, linuron, epoxynaxole, dichlorodiphenyldichloroethylene, octyl methoxynimmate, 4-methylbenzylidene camphor (4-MBC), butylparaben, and acetaminophen. Perinatally exposed offspring (F1) were mated with unexposed males to generate germ cell (F2) and transgenerationally exposed (F3 and F4) females. Sexual maturation, maternal behavior, and hypothalamic targets of exposure were studied across generations. RESULTS: Germ cell (F2) and transgenerationally (F3) EDC-exposed females, but not F1, displayed delayed pubertal onset and altered folliculogenesis. We reported a transgenerational alteration of key hypothalamic genes controlling puberty and ovulation (Kiss1, Esr1, and Oxt), and we identified the hypothalamic polycomb group of epigenetic repressors as actors of this mechanism. Furthermore, we found a multigenerational reduction of maternal behavior (F1-F3) induced by a loss in hypothalamic dopaminergic signaling. Using a cross-fostering paradigm, we identified that the reduction in maternal phenotype was normalized in EDC-exposed pups raised by unexposed dams, but no reversal of the pubertal phenotype was achieved. DISCUSSION: Rats developmentally exposed to an EDC mixture exhibited multi- and transgenerational disruption of sexual maturation and maternal care via hypothalamic epigenetic reprogramming. These results raise concerns about the impact of EDC mixtures on future generations. https://doi.org/10.1289/EHP8795.

GnRH neurons recruit astrocytes in infancy to facilitate network integration and sexual maturation.

Neurons that produce gonadotropin-releasing hormone (GnRH), which control fertility, complete their nose-to-brain migration by birth. However, their function depends on integration within a complex neuroglial network during postnatal development. Here, we show that rodent GnRH neurons use a prostaglandin D2 receptor DP1 signaling mechanism during infancy to recruit newborn astrocytes that 'escort' them into adulthood, and that the impairment of postnatal hypothalamic gliogenesis markedly alters sexual maturation by preventing this recruitment, a process mimicked by the endocrine disruptor bisphenol A. Inhibition of DP1 signaling in the infantile preoptic region, where GnRH cell bodies reside, disrupts the correct wiring and firing of GnRH neurons, alters minipuberty or the first activation of the hypothalamic-pituitary-gonadal axis during infancy, and delays the timely acquisition of reproductive capacity. These findings uncover a previously unknown neuron-to-neural-progenitor communication pathway and demonstrate that postnatal astrogenesis is a basic component of a complex set of mechanisms used by the neuroendocrine brain to control sexual maturation.

From hepatitis to hepatocellular carcinoma: a proposed model for cross-talk between inflammation and epigenetic mechanisms.

Inflammation represents the body's natural response to tissue damage; however, chronic inflammation may activate cell proliferation and induce deregulation of cell death in affected tissues. Chronic inflammation is an important factor in the development of hepatocellular carcinoma (HCC), although the precise underlying mechanism remains unknown. Epigenetic events, which are considered key mechanisms in the regulation of gene activity states, are also commonly deregulated in HCC. Here, we review the evidence that chronic inflammation might deregulate epigenetic processes, thus promoting oncogenic transformation, and we propose a working hypothesis that epigenetic deregulation is an underlying mechanism by which inflammation might promote HCC development. In this scenario, different components of the inflammatory response might directly and indirectly induce changes in epigenetic machineries ('epigenetic switch'), including those involved in setting and propagating normal patterns of DNA methylation, histone modifications and non-coding RNAs in hepatocytes. We discuss the possibility that self-reinforcing cross-talk between inflammation and epigenetic mechanisms might amplify inflammatory signals and maintain a chronic state of inflammation culminating in cancer development. The potential role of inflammation-epigenome interactions in the emergence and maintenance of cancer stem cells is also discussed.

Reaction of Cl with CD4 excited to the second C-D stretching overtone.

The effects of vibrational excitation on the Cl+CD(4) reaction are investigated by preparing three nearly isoenergetic vibrational states: mid R:3000 at 6279.66 cm(-1), |2100> at 6534.20 cm(-1), and |1110> at 6764.24 cm(-1), where |D(1)D(2)D(3)D(4)> identifies the number of vibrational quanta in each C-D oscillator. Vibrational excitation of the perdeuteromethane is via direct infrared pumping. The reaction is initiated by photolysis of molecular chlorine at 355 nm. The nascent methyl radical product distribution is measured by 2+1 resonance-enhanced multiphoton ionization at 330 nm. The resulting CD(3) state distributions reveal a preference to remove all energy available in the most excited C-D oscillator. Although the energetics are nearly identical, the authors observe strong mode specificity in which the CD(3) state distributions markedly differ between the three Cl-atom reactions. Reaction with CD(4) prepared in the |3000> mode leads to CD(3) products populated primarily in the ground state, reaction with CD(4) prepared in the |2100> mode leads primarily to CD(3) with one quantum of stretch excitation, and reaction with CD(4) prepared in the |1110> mode leads primarily to CD(3) with one quantum of C-D stretch excitation in two oscillators. There are some minor deviations from this behavior, most notably that the Cl atom is able to abstract more energy than is available in a single C-D oscillator, as in the case of |2100>, wherein a small population of ground-state CD(3) is observed. These exceptions likely result from the mixings between different second overtone stretch combination bands. They also measure isotropic and anisotropic time-of-flight profiles of CD(3) (nu(1)=1,2) products from the Cl+CD(4) |2100> reaction, providing speed distributions, spatial anisotropies, and differential cross sections that indicate that energy introduced as vibrational energy into the system essentially remains as such throughout the course of the reaction.

Optical control of ground-state atomic orbital alignment: Cl(2P3/2) atoms from HCl(v=2,J=1) photodissociation.

H(35)Cl(v=0,J=0) molecules in a supersonic expansion were excited to the H(35)Cl(v=2,J=1,M=0) state with linearly polarized laser pulses at about 1.7 microm. These rotationally aligned J=1 molecules were then selectively photodissociated with a linearly polarized laser pulse at 220 nm after a time delay, and the velocity-dependent alignment of the (35)Cl((2)P(32)) photofragments was measured using 2+1 REMPI and time-of-flight mass spectrometry. The (35)Cl((2)P(32)) atoms are aligned by two mechanisms: (1) the time-dependent transfer of rotational polarization of the H(35)Cl(v=2,J=1,M=0) molecule to the (35)Cl((2)P(32)) nuclear spin [which is conserved during the photodissociation and thus contributes to the total (35)Cl((2)P(32)) photofragment atomic polarization] and (2) the alignment of the (35)Cl((2)P(32)) electronic polarization resulting from the photoexcitation and dissociation process. The total alignment of the (35)Cl((2)P(32)) photofragments from these two mechanisms was found to vary as a function of time delay between the excitation and the photolysis laser pulses, in agreement with theoretical predictions. We show that the alignment of the ground-state (35)Cl((2)P(32)) atoms, with respect to the photodissociation recoil direction, can be controlled optically. Potential applications include the study of alignment-dependent collision effects.

H + CD4 abstraction reaction dynamics: product energy partitioning.

This paper presents experimental and theoretical studies of the product energy partitioning associated with the H + CD4 (nu = 0) --> HD + CD3 reaction for the collision energy range 0.5-3.0 eV. The theoretical results are based on quasiclassical trajectories from (1) first principles direct dynamics calculations (B3LYP/6-31G), (2) an empirical surface developed by Espinosa-García [J. Chem. Phys. 2002, 116, 10664] (EG), and (3) two semiempirical surfaces (MSINDO and reparametrized MSINDO). We find that most of the energy appears in product translation at energies just above the reactive threshold; however, HD vibration and rotation become quite important at energies above 1 eV, each accounting for over 20% of the available energy above 1.5 eV, according to the B3LYP calculations. The barrier on the B3LYP surface, though being later than that on EG, predicts significantly higher HD vibrational excitation than EG. This deviation is contradictory to what would be expected on the basis of the Polanyi rules and derives from modest differences in the potential energy surfaces. The CD3 internal energy is generally quite low, and we present detailed rotational state distributions which show that the CD3 rotational distribution is largely independent of collision energy in the 0.75-1.95 eV range. The most populated rotational levels are N = 5 and 6 on B3LYP, with most of that excitation being associated with motion about the C2 axes, rather than C3 axis, of the CD3 product, in good agreement with the experimental results. Through our extensive studies in this and previous work concerning the scattering dynamics, we conclude that B3LYP/6-31G provides the best available description of the overall dynamics for the title reaction at relatively high collision energies.

H + CD4 abstraction reaction dynamics: excitation function and angular distributions.

We compare experimental photoloc measurements and quasi-classical trajectory calculations of the integral cross sections, lab-frame speed distributions, and angular distributions associated with the CD3 products of the H + CD4(nu = 0) --> CD3 + HD reaction at collision energies ranging from 0.5 to 3.0 eV. Of the potential energy surfaces (PES) we explored, the direct dynamics calculations using the B3LYP/6-31G** density functional theory PES provide the best agreement with the experimental measurements. This agreement is likely due to the better overall description that B3LYP provides for geometries well removed from the minimum energy path, even though its barrier height is low by approximately 0.2 eV. In contrast to previous theoretical calculations, the angular distributions on this surface show behavior associated with a stripping mechanism, even at collision energies only approximately 0.1 eV above the reaction barrier. Other potential energy surfaces, which include an analytical potential energy surface from Espinosa-García and a direct dynamics calculation based on the MSINDO semiempirical Hamiltonian, are less accurate and predict more rebound dynamics at these energies than is observed. Reparametrization of the MSINDO surface, though yielding better agreement with the experiment, is not sufficient to capture the observed dynamics. The differences between these surfaces are interpreted using an analysis of the opacity functions, where we find that the wider cone of acceptance on the B3LYP surface plays a crucial role in determining the integral cross sections and angular distributions.

Assessing the reliability and validity of a residency selection process examination: a preliminary study between the national board of medical examiners and the University of Panama Faculty of Medicine.

BACKGROUND: The Ministry of Health of the Republic of Panama is currently developing a national examination system that will be used to license graduates to practice medicine in that country, as well as to undertake postgraduate medical training. As part of these efforts, a preliminary project was undertaken between the National Board of Medical Examiners (NBME) and the Faculty of Medicine of the University of Panama to develop a Residency Selection Process Examination (RSPE). PURPOSE: The purpose of this study was to assess the reliability and validity of RSPE scores for a sample of candidates who wished to obtain a residency slot in Panama. METHODS: The RSPE, composed of 200 basic and clinical sciences multiple-choice items, was administered to 261 residency applicants at the University of Panama. RESULTS: The reliability estimate computed was comparable with that reported with other high-stakes examinations (Cronbach's alpha = 0.89). Also, a Rasch examinee proficiency item difficulty plot showed that the RSPE was well targeted to the proficiency levels of candidates. Finally, a moderate correlation was noted between local grade point averages and RSPE scores for University of Panama students (r = 0.38). CONCLUSIONS: Findings suggest that it is possible to translate and adapt test materials for use in other contexts.

A reinterpretation of the mechanism of the simplest reaction at an sp3-hybridized carbon atom: H + CD4 --> CD3 + HD.

A comparison between theory and experiment for the benchmark H + CD4 --> HD + CD3 abstraction reaction yields a reinterpretation of the reaction mechanism and highlights the unexpected contribution of a stripping mechanism. Whereas the best analytic surface fails to reproduce experiment, a first-principles direct-dynamics (on the fly) treatment is in good agreement, showing that the H + CD4 reaction exhibits extreme sensitivity to modest differences in the potential energy surface. We find that bent H-D-C transition state geometries play an important role in the dynamics. A simple model that relates the scattering angle impact parameter and cone of acceptance accounts well for the overall reaction dynamics.

Reactividad cutánea de la población Panameña frente a tres antígenos fúngicos / Cutaneous reactivity of the Panamean population to 3 fungal antigens

Se determina la prevalencia de infección con tres hongos dimórficos mediante la administración intradérmica de sus respectivos antígenos a 555 individuos en la República de Panamá. Así se demuestra una prevalencia de infección con Histoplasma capsultum de 54.23%, con Paracoccidioides brasiliensis de 19.81% y con Sporothrix schenckii de 2.70%. Cabe señalar que antes de diagnosticarse el primer caso de paracoccidioidomicosis en Panamá, ya se tenía conocimiento de la infección por medio de la cutirreacción con el antígeno específico. Se observaron reacciones cruzadas entre los antígenos de H. capsulatum, P. brasiliensis y S. schenckii al constatar que hubo 96 personas sensibles a dos antígenos y que cinco, fueron reactivos a los tres antígenos utilizados en la encuesta

Motivación y educación en el control de infecciones nosocomiales / Motivation and education in control of nasocomial infections

Consideramos importante analizar el papel de la educación y la motivación en todo programa de control de infecciones nosocomiales, dado que éstos son y serán siempre uno de los riesgos ineludibles para todo paciente recluído en una institución de salud. Se establece la íntima relación existente entre educación y motivación, y planteamos como mecanismos para lograr la sensibilización los siguientes: el desarrollo y mantenimiento de programas de educación en servicio permanentes que abarcan todos los empleados; la edecuación de estos programas para el nivel del personal; y la inclusión de información sobre los principios y fundamentos de los reglamentos vigentes para el control de infecciones nosocomiales. Se describe el perfil del personal que desarrolla el programa de control de infecciones asociadas al hospital y se mencionan algunos de los obstáculos que dificultan el cumplimiento del programa. Finalmente, acetamos las limitaciones humanas y exhortamos a que éstas se mantengan a su mínima expresión

Evaluación microbiológica de la efectividad de un compuesto de clorhexidina al 0.2 (por ciento) frente a ciertos microorganismos periodontopáticos / Microbiological evaluation of the efectivity one compound the clorhexidina 0.2 (por ciento) front a some microorganism periodontopatics

Las enfermedades periodontales inflamatorias crónicas, causadas por bacterias gram negativas anaerobicas esencialmente, son responsables del 70 (por ciento) de las pérdidas dentales en los pacientes adultos. Hasta recientemente, la mejor manera de controlar estas enfermedades era mediante métodos mecánicos, pero ahora se ensaya con éxito, sobre todo en los países europeos, con el gluconato de clorhexidina para lograr este propósito. En el presente trabajo se evalúa la efectividad de este compuesto de clorhexidina producido localmente, mediendo su actividad inhibitoria en concentraciones predeterminadas frente a doce cepas microbianas estandarizadas, algunas periodontopáticas. Demostramos que el gluconato de clorhexidina requiere <30 segundos para tener acción letal sobre varios microorganismos, entre ellos especies periodontopáticas; tiene acción letal en una concentración de 0.2 (por ciento) frente a Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus viridans, Escherichia coli, Bacteroides melaninogenicus, Actinomyces viscosus y Candida albicans. Determinada la eficacia del producto local de gluconato de clorhexidina frente a varios microorganismos, nos encontramos en condiciones de estudiar la acción de este compuesto en el paciente para prevenir y/o eliminar la formación de la placa dentobacteriana

Infección por Paracoceidioides brasiliensis en la población panameña / Infection due to Paracoccidioides brasiliensis in a Panamenian population

Investigamos la prevalencia de infección con Paracoccidioides brasiliensis en la población panameña, mediante la intradermoreacción frente a la paracoccidioidina. El antígeno se aplicó a 893 personas de las distintas provincias de la República de Panamá. La reacción fue positiva en 205 (22.95%) personas, de las cuales 105 (51.2%) eran mujeres y 100 (48.8%) eran varones. La mayoría de los casos positivos eran de la provincia de Panamá (28.02%); la minoría, de la provincia de Bocas del Toro (14.47%). La alta inmunoprevalencia observada entre los agricultores del Darién confirmó la experiencia de otros investigadores, de la estrecha relación existente entre la infección y la actividad en el agro