ABSTRACT Purpose: Bone repair aims to restore the anatomical, biomechanical, and functional integrity of the affected structure. Here we study the effects of ascorbic acid (AA) and epidermal growth factor (EGF) applied in a single dose and in combination on the repair of a noncritical bone defect model. Methods: Twenty-four rats were divided into four groups: an intact G-1 control group, and three groups that underwent a noncritical bone defect in the right tibia: G-2 treated with AA, G-3 treated with EGF, and G-4 treated with AA in combination with EGF. After 21 days of treatment, rats were sacrificed, the tibias were dissected and a destructive biomechanical analysis of three-point flexion test was performed in a universal testing machine; the values of stiffness, resistance, maximum energy, and energy at maximum load were statistically compared. Results: G-3 and G-4 recovered the biomechanical properties of strength and stiffness of an intact tibia 3 weeks after their application. Not so the energy and energy at maximum load. For G-2, only the stiffness of an intact tibia was recovered. Conclusions: EGF and AA-EGF applied to a noncritical bone defect in the rat tibia favors the recovery of bone resistance and stiffness.

SUMMARY: Gas exchange measurements were taken with an infrared gas analyzer (IRGA) and chlorophyll fluorescence with a modulated amplitude pulse fluorimeter (Mini-PAM) on fully developed leaves of ramon (Brosimum alicastrum Swartz) a tropical rainforest tree, grown in its natural habitat as to collect basic information of its physiological behavior. Data showed that maximum fixation of CO2 was 5 µmol m-2 s-1, photosynthetic efficiency was 0.67 while the photosystem II was found to saturate at a photonic flux density (PFD) of 500 µmol at 15 h. A high correlation was found between photosynthesis and transpiration. Highest water use efficiency occurred after 15 hours at a temperature of 30 °C, while chlorophyll levels remained constant. This is a shade tolerant, plant species thus it was found that initiates the photosynthetic process with low levels of light, presenting a light compensation point of 24 µmol m-2 s-1. In a parallel study, the same variables were measured in two sets of individuals of the same specie collected from two distant localities but growth in pots in the open. Photosynthetic variables of this plant species data showed very similar patterns. The results obtained suggest that, during the daylight hours and at higher temperatures, this species can carry out photosynthesis with high water use efficiency. Based on the results, the conclusion is that this plant species can adapt to a diversity of environmental conditions.

RESUMEN: Se realizaron mediciones de intercambio de gases con la ayuda de un analizador de gases en el infrarrojo (IRGA) y de fluorescencia de clorofilas con un fluorímetro de pulso de amplitud modulada (Mini-PAM) en hojas completamente desarrolladas del árbol del ramón (Brosimum alicastrum Swartz) en su hábitat natural para obtener información básica sobre su comportamiento fisiológico. Los resultados señalan que la máxima fijación de CO2 es de 5 µmol m-2 s-1, con una eficiencia fotosintética de 0.67 en tanto que el fotosistema II se satura con un flujo fotónico de 500 µmol a las 15 h. Se encontró una alta correlación entre fotosíntesis y transpiración. La máxima eficiencia fotosintética se detectó después de las 15 h a una temperatura de 30 °C, en tanto que los niveles de clorofila permanecieron constantes. Este árbol es una especie tolerante a la sombra por lo que el proceso de fotosíntesis se inicia a bajos niveles de luz, con un punto de compensación de luz a los 24 µmol m-2 s-1. En un estudio paralelo, las mismas variables fueron medidas en dos conjuntos de individuos de localidades muy distantes. Los patrones fotosintéticos fueron muy similares. Los resultados obtenidos sugieren que, durante el día a altas temperaturas, estos conjuntos desarrollan fotosíntesis con alta eficiencia de uso del agua. Basados en estos resultados se propone que esta especie puede adaptarse a diversas condiciones ambientales.

The present study shows the pattern of growth of the firsts years of Brosimum alicastrum (breadnut) developed in a commercial plantation in Yucatán, México. Trees were grown from seeds in nursery conditions and then transferred to the field. One year-old seedlings of 65 cm where transplanted in 2006, 2007 and 2009 to open-field conditions, each tree separated from the others by a 5 m distance. From 2010 to 2012, the trees were measured at the ages of 2, 4 and 5 years. Ten trees of each age were selected for the present study, and their height and stem diameter at 50cm from the ground level were measured once a month during 24 months. The growth rate of the seedlings during the first six months was found to be 65 cm year-1. Thereafter, they grew faster until the fifth year. At the sixth year, their endurance became apparent since the stem grew twice as much as during the previous years. A growth of 65 % in diameter and of 69 % in height was registered during the rainy season, compared to the growth during the dry season. This is a report on growth at the vegetative stage period, since at the beginning of the seventh year some of the trees began to bloom, signaling the end of their juvenile period.

El presente estudio proporciona información del crecimiento de Brosimum alicastrum (ramón) durante sus primeros años, en una plantación comercial localizada en Yucatán, México. Las plantas fueron desarrolladas a partir de semillas y cultivadas en vivero hasta la edad de un año de edad y 65 cm de altura, momento en el cual fueron transportadas al campo en donde se plantaron a una distancia de 5 m entre ellas. Los trasplantes se realizaron en los años 2006, 2007 y 2009 y las mediciones se hicieron del 2010 al 2012, cuando contaban con 2, 4 y 5 años de edad. Se eligieron 10 árboles de cada edad, y durante 24 meses se midió la altura máxima y el diámetro del tallo a 50 cm del suelo. Se determinó que las plántulas desarrolladas en vivero, en los primeros seis meses, crecen en forma lineal a una tasa de 0.65 m año-1, posteriormente, en condiciones de campo hasta los 7 años, el crecimiento fue exponencial. La fase de endurecimiento inicia a los 6 años, con un incremento en el diámetro del tallo superior al doble. Durante la época de lluvias se registraron 65 y 69 % del crecimiento en diámetro y altura respectivamente, comparado con el crecimiento en la época de sequía. Las edades de los árboles considerados en este trabajo se consignan como primera etapa de crecimiento, ya que algunos de los individuos de siete años iniciaron el proceso de floración, lo que indica el término del periodo juvenil de la planta.