Search

Introducción: La persistencia de los polimorfismos del color del pelaje, como la coexistencia del color del pelaje melánico (negro) y el "tipo salvaje" (manchado), es un enigma evolutivo. Objetivo: Probamos las predicciones de la Regla de Gloger y la hipótesis de la Segregación Temporal que proponen que los individuos melánicos (a) ocurrirán con mayor frecuencia en el bosque tropical cerrado que en el hábitat abierto debido a las ventajas del camuflaje y la termorregulación, y (b) serán más activos durante las épocas más brillantes del ciclo circadiano y lunar porque la pigmentación negra es críptica bajo una iluminación brillante. Métodos: Con base en 10 años de registros de cámaras trampas de jaguar y tigrillo de un denso bosque tropical en Costa Rica, comparamos la actividad y la abundancia relativa de formas no melánicas (rosetones o manchados) versus formas melánicas. Resultados: El 25% de los registros de jaguares en bosques densos fueron melánicos en comparación con el promedio global del 10% en hábitats abiertos y cerrados; el 32% de los registros de tigrillo fueron melánicos en comparación con el 18% en general en Brasil. El análisis de superposición indicó que los jaguares melánicos eran más activos durante las horas del día en comparación con los jaguares no melánicos, que eran más nocturnos y crepusculares. Asimismo, el tigrillo melánico era más diurno que el tigrillo no melánico. El tigrillo melánico también fue más activo durante la luna llena, mientras que el tigrillo no melánico fue menos activo. Conclusión: Estos resultados implican que los jaguares y tigrillos melánicos disfrutan de los beneficios adaptativos de un camuflaje superior cuando habitan en un bosque denso y acumulan una ventaja de aptitud cuando cazan en condiciones de iluminación más brillante. Si es cierto, la selección natural aseguraría que los individuos melánicos persistan cuando se retiene el bosque denso, pero pueden verse amenazados por la deforestación y la presencia humana acelerada.

This study was designed to determine the optimal intensity for verification phase testing (VP) in healthy, young adults. Thirty one young, active participants (16 females) completed a cycle ergometer graded exercise test (GXT) VO2max test and 4 VP tests at 80, 90, 100, and 105% of the maximum wattage achieved during the GXT. GXT and VP VO2max values showed a significant test x sex interaction (p = 0.02). The males elicited significantly higher VO2max values during the GXT, 80%, and 90% when compared to the 105%, (105 vs. GXT: p = 0.05; 105% vs. 80%: p < 0.01; 105% vs. 90%: p = 0.02). There were no significant differences in VO2max across the tests in the females (p > 0.05); 80% of the males achieved their highest VP VO2max during a submaximal VP test compared to only 37.5% of the females. A secondary study conducted showed excellent reliability (ICCs > 0.90) and low variation (CVs < 3%) for the 90% VP. Our findings show that a submaximal verification phase intensity is ideal for young healthy males to elicit the highest VO2max during cycle ergometer testing. For females, a range of intensities (80–105%) produce similar VO2max values. However, the 80% VP yields an unnecessarily high time to exhaustion.

Self-transmissible and mobilizable plasmids contribute to the emergence and spread of multidrug-resistant bacteria by enabling the horizontal transfer of acquired antibiotic resistance. The objective of this study was to capture and characterize self-transmissible and mobilizable resistance plasmids from a coastal wetland impacted by urban stormwater runoff and human wastewater during the rainy season. Four plasmids were captured, two self-transmissible and two mobilizable, using both mating and enrichment approaches. Plasmid genomes, sequenced with either Illumina or PacBio platforms, revealed representatives of incompatibility groups IncP-6, IncR, IncN3, and IncF. The plasmids ranged in size from 36 to 144 kb and encoded known resistance genes for most of the major classes of antibiotics used to treat Gram-negative infections (tetracyclines, sulfonamides, β-lactams, fluoroquinolones, aminoglycosides, and amphenicols). The mobilizable IncP-6 plasmid pLNU-11 was discovered in a strain of Citrobacter freundii enriched from the wetland sediments with tetracycline and nalidixic acid, and encodes a novel AmpC-like β-lactamase (blaWDC-1), which shares less than 62% amino acid sequence identity with the PDC class of β-lactamases found in Pseudomonas aeruginosa. Although the IncR plasmid pTRE-1611 was captured by mating wetland bacteria with P. putida KT2440 as recipient, it was found to be mobilizable rather than self-transmissible. Two self-transmissible multidrug-resistance plasmids were also captured: the small (48 kb) IncN3 plasmid pTRE-131 was captured by mating wetland bacteria with Escherichia coli HY842 where it is seemed to be maintained at nearly 240 copies per cell, while the large (144 kb) IncF plasmid pTRE-2011, which was isolated from a cefotaxime-resistant environmental strain of E. coli ST744, exists at just a single copy per cell. Furthermore, pTRE-2011 bears the globally epidemic blaCTX-M-55 extended-spectrum β-lactamase downstream of ISEcp1. Our results indicate that urban coastal wetlands are reservoirs of diverse self-transmissible and mobilizable plasmids of relevance to human health.

Tumor angiogenesis is critical for the growth and progression of cancer. As such, angiostasis is a treatment modality for cancer with potential utility for multiple types of cancer and fewer side effects. However, clinical success of angiostatic monotherapies has been moderate, at best, causing angiostatic treatments to lose their early luster. Previous studies demonstrated compensatory mechanisms that drive tumor vascularization despite the use of angiostatic monotherapies, as well as the potential for combination angiostatic therapies to overcome these compensatory mechanisms. We screened clinically approved angiostatics to identify specific combinations that confer potent inhibition of tumor-induced angiogenesis. We used a novel modification of the ex ovo chick chorioallantoic membrane (CAM) model that combined confocal and automated analyses to quantify tumor angiogenesis induced by glioblastoma tumor onplants. This model is advantageous due to its low cost and moderate throughput capabilities, while maintaining complex in vivo cellular interactions that are difficult to replicate in vitro. After screening multiple combinations, we determined that glioblastoma-induced angiogenesis was significantly reduced using a combination of bevacizumab (Avastin®) and temsirolimus (Torisel®) at doses below those where neither monotherapy demonstrated activity. These preliminary results were verified extensively, with this combination therapy effective even at concentrations further reduced 10-fold with a CI value of 2.42E-5, demonstrating high levels of synergy. Thus, combining bevacizumab and temsirolimus has great potential to increase the efficacy of angiostatic therapy and lower required dosing for improved clinical success and reduced side effects in glioblastoma patients.