Papers by Rafael Eduardo Ramos Romero
Developmental Biology, 2010
Although patterning during regeneration in adult planarians has been studied extensively, very li... more Although patterning during regeneration in adult planarians has been studied extensively, very little is known about how the initial planarian body plan arises during embryogenesis. Herein, we analyze the process of embryo patterning in the species Schmidtea polychroa by comparing the expression of genes involved in the establishment of the metazoan body plan. Planarians present a derived ectolecithic spiralian development characterized by dispersed cleavage within a yolk syncytium and an early transient embryo capable of feeding on the maternally supplied yolk cells. During this stage of development, we only found evidence of canonical Wnt pathway, mostly associated with the development of its transient pharynx. At these stages, genes involved in gastrulation (snail) and germ layer determination (foxA and twist) are specifically expressed in migrating blastomeres and those giving rise to the temporary gut and pharyngeal muscle. After yolk ingestion, the embryo expresses core components of the canonical Wnt pathway and the BMP pathway, suggesting that the definitive axial identities are established late. These data support the division of planarian development into two separate morphogenetic stages: a highly divergent gastrulation stage, which segregates the three germ layers and establishes the primary organization of the feeding embryo; and subsequent metamorphosis, based on totipotent blastomeres, which establishes the definitive adult body plan using mechanisms that are similar to those used during regeneration and homeostasis in the adult.
The Manchester School, 2011
We investigate the weak form of the efficient capital market hypothesis through the detection of ... more We investigate the weak form of the efficient capital market hypothesis through the detection of a non-linear dynamic with potential for predictability of stock returns in the Mexican stock market. We apply the Hinich portmanteau bicorrelation test and the Brock, Dechert and Scheinkman test to the data. We observe that all the return series are characterized by a few brief periods of highly significant non-linearity. However, we cannot say that the Mexican market fails to satisfy the weak form of the efficient capital market hypothesis because the non-linear dependences appear on rare occasions and they are rapidly arbitraged away.
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Papers by Rafael Eduardo Ramos Romero