Comparative analysis of Krüppel-like factors expression in the retinas of zebrafish and mice during development and after injury.

The Krüppel-like factors (KLFs) have emerged as important transcriptional regulators of various cellular processes, including neural development. Some of them have been described as intrinsic factors involved in axon regeneration in the central nervous system (CNS) of vertebrates. Zebrafish are known for their ability to regenerate several tissues in adulthood, including the CNS, a capability lost during vertebrate evolution and absent in adult mammals. The role that KLFs could play in this differential ability remains unknown. Therefore, in this study, we analyzed the endogenous response of certain KLFs implicated in axon regeneration (KLFs 6, 7, 9, and 13) during retina development and after axon injury. The results showed that the expression of Klfs 6, 7, and 13 decreases in the developing retina of mice but not in zebrafish, while the mRNA levels of Klf9 strongly increase in both species. The response to injury was further analyzed using optic nerve crush (ONC) as a model of lesion. Our analysis during the acute phase (hours) demonstrated an induction of Klfs 6 and 7 expression exclusively in the zebrafish retina, while Klfs 9 and 13 mRNA levels increased in both species. Further analysis of the chronic response (days) showed that mRNA levels of Klf6 transiently increase in the retinas of both zebrafish and mice, whereas those of Klf7 decrease later after optic nerve injury. In addition, the analysis revealed that the expression of Klf9 decreases, while that of Klf13 increases in the retinas of zebrafish in response to optic nerve injury but remains unaltered in mice. Altogether, these findings support the hypothesis that KLFs may play a role in the differential axon regeneration abilities exhibited by fish and mice.

The importance of employing homologous serum free of thyronines in radioimmunoassays to assess circulating thyroid hormones in rainbow trout

A pesar de ser abundante, la información relacionada con los valores de tironinas circulantes en la trucha arcoiris, es confusa. El presente estudio demuestra la importancia de mantener especies sero-homólgoas durante la medición de tironinas con RIE para eviatar falsos resultados. La utilización de suero homólogo (trucha) libre de tironinas en la curva estándar permite la estandarización de radioinmunoensayos exactos y específcos para cuantificar los niveles circulates de T3 y T4 en 10 microl de suero de trucha arcoiris. El límite de detección fue de 50 pg para ambas tironinas. Los coeficientes de variación inter e intra ensayo fueron menores al 10 por ciento. Los valores promedio para T3 y T4 + - DEM en la población de truchas estudiadas (n=34) fueron 23.6 + - 1.2 y 12.0 + - 2.3 ng/ml respectivamente. Se obsevó una correlación positiva y significativa (p < 0.005) entre el peso corporal y T3 confirmando la participación activa de esta tironina en el proceso de crecimiento.