RESUMO
We have investigated the shape of the OH/OD stretching Raman band of water as a function of the excitation wavelength in the deep UV region (200-266 nm). By analyzing the spectral profiles, we highlighted selective pre-resonance effects in the high wavenumber component of the OH/OD stretching band, associated to distorted H-bonded water configurations. A van't Hoff treatment of the temperature-dependent Raman spectra provides an estimate of the thermal energy associated to the change from ordered (ice-like) to disordered configurations that agrees with values obtained by related methods based on a two-state model of water. These results open the possibility of exploiting the observed pre-resonance deep-UV signal enhancement to investigate H-bonding properties in aqueous media.
RESUMO
Frontal midline θ (Fmθ) activity occurs in medial prefrontal cortices (mPFC), when expected and actual outcomes conflict. Cerebellar forward models could inform the mPFC about this mismatch. To verify this hypothesis we correlated the mPFC activation during a visuomotor tracking task (VM) with performance accuracy, in control and cerebellum-lesioned participants. Additionally, purely visual (V), motor (M) and a motor plus visual tasks (V + M) were performed. An Independent Component, with a mid-frontal topography scalp map and equivalent dipole location in the dorsal anterior cingulate cortex accounted for Fmθ. In control participants Fmθ power increased during VM, when the error level crossed a threshold, but not during V + M, M and V. This increase scaled with tracking error. Fmθ power failed to increase during VM in cerebellar participants, even at highest tracking errors. Thus, in control participants, activation of mPFC is induced when a continuous monitoring effort for online error detection is required. The presence of a threshold error for enhancing Fmθ, suggests the switch from an automatic to an executive tracking control, which recruits the mPFC. Given that the cerebellum stores forward models, the absence of Fmθ increases during tracking errors in cerebellar participants indicates that cerebellum is necessary for supplying the mPFC with prediction error-related information. This occurs when automatic control falters, and a deliberate correction mechanism needs to be triggered. Further studies are needed to verify if this alerting function also occurs in the context of the other cognitive and non-cognitive functions in which the cerebellum is involved.
Assuntos
Córtex Pré-Frontal , Ritmo Teta , Humanos , Ritmo Teta/fisiologia , Córtex Pré-Frontal/fisiologia , Função Executiva/fisiologia , Giro do Cíngulo/fisiologia , CerebeloRESUMO
Here we investigated the effects of physical training on cardiovascular autonomic control and cardiac morphofunctional parameters in spontaneously hypertensive rats (SHRs) subjected to ovarian hormone deprivation. Forty-eight 10-week-old SHRs were divided into two groups: ovariectomized (OVX, n=24) and sham (SHAM, n=24). Half of each group (n=12) was trained by swimming for 12 weeks (OVX-T and SHAM-T). Cardiac morphology and functionality were assessed using echocardiography, and autonomic parameters were assessed using double pharmacological autonomic block, baroreflex sensitivity (BRS), and analyses of heart rate variability (HRV) and blood pressure variability (BPV). Ovariectomy did not influence the cardiac autonomic tonus balance unlike physical training, which favored greater participation of the vagal autonomic tonus. Ovariectomy and aerobic physical training did not modify HRV and BRS, unlike BPV, for which both methods reduced low-frequency oscillations, suggesting a reduction in sympathetic vascular modulation. Untrained ovariectomized animals showed a reduced relative wall thickness (RWT) and increased diastolic and systolic volumes and left ventricular diameters, resulting in increased stroke volume. Trained ovariectomized animals presented reduced posterior wall thickness and RWT as well as increased final diastolic diameter, left ventricular mass, and stroke volume. Ovarian hormone deprivation in SHRs promoted morphofunctional adaptations but did not alter the evaluation of cardiac autonomic parameters. In turn, aerobic physical training contributed to a more favorable cardiac autonomic balance to the vagal autonomic component and promoted morphological adaptations but had little effect on cardiac functionality.
RESUMO
Medical devices are often colonized by bacteria which may cause severe infections. The aim of this work was to evaluate biofilm formation by S. maltophilia isolates from device-associated nosocomial infections. The 13 local isolates exhibited different capacities of biofilm formation on hydrophilic and hydrophobic surfaces. All isolates formed strong biofilms in polystyrene microplates, while strong, moderate or weak biofilms were detected in borosilicate (BS) or polypropylene (PP) tubes. The proficiency of biofilm formation was better evaluated by the level of crystal violet staining expressed relative to the final culture density. The microscopic analysis of biofilms formed on glass coverslips revealed the presence of a matrix of exopolysaccharides and microcolonies typical of biofilm architecture. Isolates with increased adhesion to BS showed larger microcolonies. According to our results, twitching correlated well with attachment to the three abiotic surfaces tested, while swimming only showed a slight correlation with biofilm formation on PP. Poor correlation was observed between cell surface hydrophobicity and biofilm formation. One of the highest biofilm-producing isolates adhered to urethral catheters of different materials, and exhibited an increased resistance to oxidative stress, one of the common stresses encountered by bacteria during the infection process due to the immune response.
El objetivo de este trabajo fue evaluar la formación de biopelículas por parte de aislamientos de Stenotrophomonas maltophilia. Los 13 aislamientos locales evaluados mostraron diferente capacidad de formar biopelículas en superficies hidrofílicas e hidrofóbicas. Todos ellos formaron biopelículas fuertes en microplacas de poliestireno (PS), mientras que se observaron biopelículas fuertes, moderadas o débiles en tubos de borosilicato (BS) o polipropileno (PP). La medida del cristal violeta unido a la biopelícula expresada en función de la densidad final de los cultivos permitió una mejor evaluación de la eficiencia de formación de biopelículas. El análisis microscópico de biopelículas formadas sobre cubreobjetos mostró la presencia de una matriz de exopolisacáridos y microcolonias típicas de la arquitectura de las biopelículas. Los aislamientos con mayor adhesión a BS mostraron microcolonias de mayor tamaño. La motilidad asociada a superficies ( twitching) presentó buena correlación con la adhesión a BS, PP y PS, mientras que la motilidad asociada a flagelos solo correlacionó ligeramente con la adhesión a PP. La correlación entre la hidrofobicidad de la superficie bacteriana y la formación de biopelículas fue escasa. Uno de los aislamientos productores de biopelículas fuertes evidenció capacidad de adhesión a catéteres uretrales de diferentes materiales y mayor resistencia al estrés oxidativo.
Assuntos
Humanos , Biofilmes/crescimento & desenvolvimento , Infecção Hospitalar/microbiologia , Infecções por Bactérias Gram-Negativas/microbiologia , Stenotrophomonas maltophilia/fisiologia , Aderência Bacteriana , Proteínas de Bactérias/análise , Cateterismo , Corantes/análise , Infecção Hospitalar/etiologia , Contaminação de Equipamentos , Vidro , Infecções por Bactérias Gram-Negativas/etiologia , Interações Hidrofóbicas e Hidrofílicas , Lipase/análise , Movimento , Estresse Oxidativo , Polipropilenos , Poliestirenos , Peptídeo Hidrolases/análise , Diálise Renal/instrumentação , Respiração Artificial/instrumentação , SilicatosRESUMO
The methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism is associated with the expression of a thermolabile enzyme with decreased activity that influences the pool of methyl-donor molecules. Several studies have reported an association between C677T polymorphism and susceptibility to colorectal cancer (CRC). Considering that methylation abnormalities appear to be important for the pathogenesis of CRC, we examined the correlation between the genotype of the MTHFR C677T polymorphism, hypermethylation of the promoter region of five relevant genes (DAPK, MGMT, hMLH1, p16(INK4a), and p14(ARF)), and microsatellite instability, in 106 patients with primary CRCs in Brazil. We did not find significant differences in the genotypic frequencies of the MTHFR C677T polymorphism when one or more loci were hypermethylated. However, we did find a significant excess of 677TT individuals among patients with CRC who had microsatellite instability. This strong association was independent of the methylation status of hMLH1 and of the biogeographical genomic ancestry of the patients. Although the mechanism responsible for the link between the C677T polymorphism and microsatellite instability was not apparent, this finding may provide a clue towards a better understanding of the pathogenesis of microsatellite instability in human colorectal cancer.
Assuntos
Humanos , Masculino , Feminino , Biomarcadores Tumorais/genética , Metilação de DNA , /genética , Neoplasias Colorretais/genética , Polimorfismo Genético/genética , Regiões Promotoras Genéticas , Estudos de Casos e Controles , Genótipo , Instabilidade Genômica/genética , Neoplasias Colorretais/enzimologia , Predisposição Genética para Doença , Repetições de Microssatélites/genéticaRESUMO
Levels of mtDNA(4977) deletions (DeltamtDNA(4977)) have been found to be lower in tumors than in adjacent non-tumoral tissues. In 87 cancer patients, DeltamtDNA(4977) was detected by multiplex polymerase chain reaction (PCR) amplification in 43 (49%) of the tumors and in 74 (85%) of the samples of non-tumoral tissues that were adjacent to the tumors. DeltamtDNA(4977) deletions were detected in 24% of the breast tumors, 52% of the colorectal tumors, 79% of the gastric tumors, and 40% of the head and neck tumors as compared with 77, 83, 100, and 90% of the adjacent respective non-tumoral tissues at the same DNA template dilution. Based on limiting dilution PCR of 16 tumors and their adjacent non-tumoral tissues, it was found that the amount of DeltamtDNA(4977) was 10- to 100-fold lower in the tumor than in the respective control non-tumoral tissues. Real-time PCR experiments were performed to quantify the number of DeltamtDNA(4977) deletions per cell, by determining the mitochondrial-to-nuclear DNA ratio. In all of the cases of breast, colorectal, gastric, and head and neck cancer the proportion of DeltamtDNA(4977) in tumors was lower than that of the respective non-tumoral tissue. Traces of DeltamtDNA(4977) in tumors were apparently due to contamination of tumor tissue with surrounding non-tumoral tissue, as evidenced by tumor microdissection and in situ PCR techniques, suggesting that tumors are essentially free of this mutation. Although the metabolic effect of DeltamtDNA(4977) may be minimal in normal (non-tumor) tissue, in tissue under stress, such as in tumors, even low levels of DeltamtDNA(4977) deletions may be intolerable.
Assuntos
Feminino , Humanos , Deleção de Sequência/genética , Mutação/genética , Neoplasias Colorretais/genética , Neoplasias Gástricas/genética , Neoplasias da Mama/genética , Neoplasias de Cabeça e Pescoço/genética , Estudos de Casos e Controles , DNA Mitocondrial/genética , Reação em Cadeia da Polimerase , Células Tumorais CultivadasRESUMO
Las cepas virulentas (Bvg+) de Bordetella pertussis expresan numerosos factores de virulencia. Estos factores están regulados por el locus bvg en respuesta a estímulos ambientales, a través del proceso reversible de modulación antigénica. A su vez, mutaciones en el locus bvg originan variantes avirulentas (Bvg-) que no expresan factores de virulencia en ninguna condición de cultivo. En este trabajo hemos seleccionado variantes espontáneas Bvg- de B. pertussis Tohama I y 10536, potencialmente útiles para el estudio de marcadores de virulencia, utilizando como medios selectivos Stainer-Scholte agarizado suplementado con 1 o/o de Casamino-acids (SSA-CAS) y Jones-Kendrick con 0,20 microgramos/ml de eritromicina (JK-Ery). Paralelamente hemos estudiado la eficiencia de recuperación de células de B. pertussis Tohama 1, 10536 y 40103 (cepas Bvg+) y de la cepa Bvg- 347 (control del fenotipo avirulento) en SSA-CAS y en Steiner-Scholte agarizado (SSA), y analizado el fenotipo de las células recuperadas a partir de ellos. Para la caracterización fenotípica se utilizaron los siguientes marcadores de fase virulenta: producción de hemólisis, producción de hemaglutininas y perfiles de proteínas de fracciones enriquecidas en membrana externa. Las tres cepas Bvg+ ensayadas mostraron diferente comportamiento en estos medios. B. pertussis Tohama 1 y 10646 no crecieron en SSA, mientras que la eficiencia de recuperación en el medio SSA-CAS fue inferior al 0,001 o/o, obteniéndose variantes Bvg- estables de la cepa Tohama 1, en cambio la cepa 10536 sufrió el fenómeno de modulación, ya que recuperó el fenotipo virulento al ser subcultivada en Bordel-Gengou. El medio JK-Ery permitió seleccionar variantes Bvg- estables de B. pertussis Tohama 1 y 10536. B. pertussis 40103 mostró alta eficiencia de recuperación en SSA y SSA-CAS y retuvo el fenotipo virulento en todos los medios ensayados. Por otra parte, B. pertussis 347, a pesar de ser avirulenta, presento una eficiencia de recuperación pobre en SSA y un crecimiento escaso en JK-Ery, corroborando que no todas las cepas Bv- adquieren la capacidad de crecer en medios que resultan inhibitorios para muchas cepas virulentas