Amino acids as wetting agents: surface translocation by Porphyromonas gingivalis.

Our understanding of how oral microbiota adapt in response to changes in their surroundings remains limited. This is particularly true of the slow-growing anaerobes that persist below the gum line. Here, we report that the oral anaerobe Porphyromonas gingivalis strain 381 can surface translocate when sandwiched between two surfaces. We show that during movement, this bacterium alters its metabolism, specifically side products of arginine utilization including citrulline and ornithine accumulated in the translocating cells; while arginine, N-acetyl-arginine, and the polyamine putrescine, which is produced from arginine were consumed. In addition, our results indicate that movement requires modification of the surrounding environment via proteolysis, cell dispersion, cell-on-cell rolling, and sub-diffusive cell-driven motility. We also show that production of fimbriae and fimbriae-associated proteins; as well as the regulation of contact-dependent growth inhibition genes, which are known to be involved in self-nonself discrimination, and the type IX secretion system are central to surface translocation. These studies provide a first glimpse into P. gingivalis motility and its relationship to ecological variables.

Hydration practices of runners during training vs competition / Prácticas de hidratación en corredores durante el entrenamiento vs la competición

Background: Appropriate hydration ensures that the athlete is in ideal condition during exercise. Inadequate hydration practices are still present among athletes participating in different types of sports. This could be the result of a low level of knowledge concerning the importance of hydration for athletic performance. The purpose of this study was to evaluate the level of knowledge and the hydration practices of the runners in training and competition. Method: This study used an exploratory method involving a questionnaire containing 19 objective questions related to hydration habits and level of knowledge about hydration, as reported in prior studies, which included questions categorized into three parts: demographic characteristics, hydration habits during competition and training, and hydration knowledge. A total of 412 athletes (36.1 ± 12.9 years old) with a high experience in the sport (11.2 ± 10.9 years) were evaluated. Results: A significant difference (p = 0.0012) was observed for reported hydration practices between training and competitions. Moreover, the data revealed that a large number of runners (41 % in competitions and 54.4% in training) had inadequate hydration habits because they did not always consume fluids. Increased consumption of fluids in the competitions was also observed. Only 35.4% of athletes consumed sports drinks, while 3.88 % had never consumed fluids during training, and 1.5% never consumed fluids in competition. Few athletes (23.2%) weighed themselves before and after exercising. Participants answered 66.6% of hydration knowledge questions correctly. Conclusion: Runners were not able to transfer their knowledge about proper hydration during both training and competition practices

Introducción: Una hidratación adecuada asegura que el atleta está en condición ideal durante el ejercicio. Se suelen presentar prácticas de hidratación inadecuadas entre los deportistas de diferentes disciplinas que podrían deberse a un bajo nivel de conocimiento sobre la importancia de una correcta hidratación para el rendimiento deportivo. El objetivo del estudio fue evaluar el nivel de conocimiento y las prácticas de hidratación en corredores durante el entrenamiento frente a la competición. Métodos: Este estudio utilizó un método exploratorio que incluía un cuestionario con 19 preguntas objetivas relacionadas con los hábitos de hidratación y el nivel de conocimiento sobre hidratación, según lo informado en estudios previos, cuyas preguntas estaban divididas en tres partes: características demográficas; hábitos de hidratación durante el entrenamiento y competición, y conocimientos sobre hidratación. Se evaluaron 412 corredores (36,1 ± 12,9 años) con una elevada experiencia en la práctica del atletismo (11,2 ± 10,9 años). Resultados: Hubo diferencia significativa (p = 0,0012) de las prácticas de hidratación durante los entrenamientos y la competición, con mayor consumo de líquidos durante las competiciones. Por otra parte, los datos revelaron que un gran número de corredores (41,0% en competición y 54,4 % en entrenamiento) tenían hábitos de hidratación inadecuados al no consumir siempre líquidos. Sólo el 35,4 % de los atletas declararon consumir bebidas deportivas. La ingesta de líquidos era inexistente en el 3,8% de los atletas durante el entrenamiento y el 1,5% en competiciones. Sólo el 23,2% de los encuestados controlaban el peso corporal antes y después del ejercicio. Los participantes respondieron correctamente al 66,6% de las preguntas sobre conocimiento de hidratación. Conclusiones: Los corredores participantes no fueron capaces de trasladar sus conocimientos sobre el tema de hidratación en prácticas adecuadas tanto en entrenamiento como en competición

Finite element modeling of the cyclic wetting mechanism in the active part of wheat awns.

Many plant tissues and organs are capable of moving due to changes in the humidity of the environment, such as the opening of the seed capsule of the ice plant and the opening of the pine cone. These are fascinating examples for the materials engineer, as these tissues are non-living and move solely through the differential swelling of anisotropic tissues and in principle may serve as examples for the bio-inspired design of artificial actuators. In this paper, we model the microstructure of the wild wheat awn (Triticum turgidum ssp. dicoccoides) by finite elements, especially focusing on the specific microscopic features of the active part of the awn. Based on earlier experimental findings, cell walls are modeled as multilayered cylindrical tubes with alternating cellulose fiber orientation in successive layers. It is shown that swelling upon hydration of this system leads to the formation of gaps between the layers, which could act as valves, thus enabling the entry of water into the cell wall. This supports the hypothesis that this plywood-like arrangement of cellulose fibrils enhances the effect of ambient humidity by accelerated water or vapor diffusion along the gaps. The finite element model shows that a certain distribution of axially and tangentially oriented fibers is necessary to generate sufficient tensile stresses within the cell wall to open nanometer-sized gaps between cell wall layers.

[Corneal contact time of artificial tear solutions]. / Untersuchungen zur Verweildauer von Tränenersatzmitteln.

In 30 subjects without ophthalmological disease the corneal contact time of a new artificial polyacrylic-based tear gel (Vidisic, produced by Dr. Mann, Berlin) was compared with a well-known artificial polyvinyl alcohol-based tear solution. The Vidisic concentration remained in the corneal tear film 7 times longer than the substance it was compared with. In a second study including 7 normal subjects and 5 patients with keratoconjunctivitis sicca, the influence of Vidisic on break-up time (BUT) and the Schirmer test was demonstrated. It was found that tear secretion improved for 2-4 hours (Schirmer test) and the stability of the tear film (BUT) improved for about 6 hours with Vidisic. These results suggest that application of Vidisic four times a day is sufficient for efficatious therapy even in cases of severe keratoconjunctivitis sicca.