Evolutionary dynamics of autopolyploids in natural populations: the case of Turnera sidoides complex / Dinámica evolutiva de autopoliploides en poblaciones naturales: el caso del complejo Turnera sidoides

ABSTRACT Turnera sidoides (x=7) is one of the few well-studied South American autopolyploid complexes. Since polyploidy has played a prominent role within this complex, ongoing studies in T. sidoides focus on understanding the mechanisms involved in the origin and the establishment of polyploids using integrative approaches. This paper synthesises the results of more than 20 years of research on this topic. Cytogenetics analysis provided evidences for the production of unreduced male and female gametes, supporting the hypothesis of bilateral sexual polyploidization as the mechanism of origin of polyploids in T. sidoides. The finding of viable triploids suggested that unilateral sexual polyploidization could also be an important mechanism for the origin of tetraploids in T. sidoides. The occurrence of plants continuously forming many unreduced gametes would play a key role in the establishment of neopolyploids in natural populations. Also, the higher number of propagules that tetraploids contribute to subsequent generations, the ability to multiply asexually by rhizomes, and the occurrence of occasional cases of self-compatibility and successful illegitimate crosses in polyploids increase the likelihood that a low frequency of neopolyploids can be maintained in natural populations of T. sidoides. In addition, integration of cytogeographic and genetic divergence data together with past niche modelling provided further insights supporting the hypothesis that historical climatic and geomorphological events provided favourable conditions for the establishment of autopolyploids, with the wider distribution of tetraploids of T. sidoides being the result of their range expansion.

RESUMEN Turnera sidoides (x=7) es uno de los pocos complejos autopoliploides sudamericanos bien estudiados. Como la poliploidía ha tenido un papel destacado en el complejo, los estudios en curso en T. sidoides se centraron en la comprensión de los mecanismos implicados en el origen y el establecimiento de los poliploides mediante diferentes enfoques. En este trabajo se sintetizan los resultados de más de 20 años de investigación sobre este tema. El análisis citogenético proporcionó evidencias de la producción de gametos masculinos y femeninos no reducidos, sustentando la hipótesis de la poliploidización sexual bilateral como mecanismo de origen de los poliploides en T. sidoides. Sin embargo, el hallazgo de triploides fértiles sugirió que la poliploidización sexual unilateral también sería un mecanismo importante de origen de tetraploides en T. sidoides. La ocurrencia de plantas que forman continuamente gametos no reducidos desempeñaría un papel clave en el establecimiento de neopoliploides. Además, el mayor número de propágulos que los tetraploides aportan a las siguientes generaciones, la capacidad de multiplicación asexual por rizomas y los casos ocasionales de autocompatibilidad y cruzamientos ilegítimos exitosos aumentarían la probabilidad de que se mantenga una baja frecuencia de neopoliploides en las poblaciones naturales de T. sidoides. Asimismo, la integración de datos citogeográficos y de divergencia genética junto con el modelado de nicho en el pasado aportó información que sustenta la hipótesis de que los eventos climáticos y geomorfológicos históricos proporcionaron las condiciones favorables para el establecimiento y expansión de los tetraploides de T. sidoides.

Evaluation of the Induction of Cell-Mediated Immunity Against Candida albicans in a Model of Cutaneous Infection in Newborn 0-Day-Old Mice.

Candida albicans is a commensal fungus of the skin and mucous membranes in humans, but it is also responsible for mucocutaneous and systemic infections in immunocompromised patients like low birth weight neonates and premature newborns. The epicutaneous application of C. albicans is widely used to study the immune response against this pathogen in adult mice models. However, the immune response of newborns against infections caused by the genus Candida is poorly understood. In order to mimic premature human infection, we developed a model of C. albicans epicutaneous infection in newborn mice. We found that yeasts were able to colonize while the pseudohyphae invaded the epidermis. Recruitment of polymorphonuclear and mononuclear cells at the infection zone was observed. Fungal invasion, fungal burden and cellular infiltration displayed a time- and dose-dependent response. Interestingly, newborn mice were able to control C. albicans primary infection. Finally, we showed that the epicutaneous infection of C. albicans in newborn mice at birth results in the induction of cell-mediated immunity as evinced by delayed-type hypersensitivity assays.

Comparison of gait performance on different environmental settings for patients with chronic spinal cord injury.

STUDY DESIGN: Observational cross-section study. OBJECTIVES: The objective of our study was to determine if the influence of a community environment would impact on ASIA D spinal cord injured (SCI) gait performance patients. Our main hypothesis is that an outdoor community environment may influence gait speed and endurance on community ambulating patients. METHODS: Ten-Meter Walking (10MWT) and Six-Minute Walking (6MWT) tests were performed on community ambulating SCI research participants (n=18) in two different environmental conditions: (1) Experimental (indoors Gymnasium) and (2) Natural (community setting). Average gait speed and endurance values were obtained for the two different conditions and analyzed for statistical significance on the nonparametric two-tailed Wilcoxon signed rank test. RESULTS: While no difference was observed on the 10MWT we found an improvement on gait performance on the 6 MWT on a community setting. CONCLUSIONS: Our study showed mixed results on environmental influence on gait speed and endurance on ASIA D patient population. While there is no difference on the 10 MWT, there is an improvement on gait performance on the communitary 6MWT.

Transfer of the tibialis anterior for calcaneus deformity in myelodysplasia.

We evaluated the results of transfer of the tibialis anterior in the management of calcaneus deformity in young patients who had myelodysplasia; fifteen patients (twenty-two feet) were operated on between 1978 and 1985. The neural deficit was at the fourth and fifth lumbar levels. The average age at the time of the operation was seven years and two months (range, two to nineteen years). The average age at the latest follow-up was thirteen years (range, five to twenty-four years). The average duration of follow-up was five years and ten months (range, two to eleven years). Seventeen feet (twelve patients) had a good result (no ulceration of the heel or osteomyelitis and correction of the calcaneus deformity), and five feet (three patients) had a poor result (persistent ulceration, signs of osteomyelitis, recurrent or persistent calcaneus deformity, or the need for additional operative intervention). Children who were less than five years old had a better outcome, as determined by the Fisher exact test (p less than 0.5).

Neural tube defects: a study in Puerto Rico.

Recent literature reports an apparent decline in the incidence of neural tube defects throughout the world. A revision of stillbirth certificates and surgical reports of closure procedures for open neural tube defects was done in order to establish the incidence and its trend during a nine year period in Puerto Rico. The current prevalence of the syndrome was estimated using the death certificates in addition to the fore-mentioned surgical reports. Our results indicate that Puerto Rico carries probably the highest incidence of the US territories and that the trend is not declining one.