Origen y Migración de Células Troncales / Stem Cells Origin and Migration

La generación de progenitores celulares, su migración y distribución a través del organismo, es determinante en la generación de divergencia morfológica y evolución de las distintas especies de vertebrados. Las células progenitoras transitan por diferentes compartimentos durante el desarrollo embrionario y su exposición a diferentes medioambientes tisulares estimula la activación de programas específicos de diferenciación. En este capítulo discutiremos el origen de diferentes poblaciones de células migratorias, tales como las células madre embrionarias, las células germinales primordiales y las células de la cresta neural, con un enfoque en los distintos factores moleculares activados durante la migración hacia distintos compartimientos embrionarios.

Generation, migration and distribution of stem cells throughout the body are a major process in the generation of morphological divergence and evolution in different species of vertebrates. Progenitor cells pass through different compartments during embryonic development and the exposition to different tissue environments stimulates the activation of specific differentiation programs. In this chapter we discuss the origin of different migratory cell populations, such as embryonic stem cells, primordial germ cells and neural crest cells, with focus on the different molecular factors activated during migration to different embryonic compartments.

Epidemiology of neural tube defects in northern Iran, 1998-2003

We determined the rates of neural tube defects at a referral hospital in Gorgan, north Islamic Republic of Iran, and the relations of these abnormalities to sex, maternal ethnicity, maternal age and season. During 1998-2003, there were 109 cases among 37 951 births, a prevalence of 28.7 per 10 000 [24.8 and 32.8 per 10 000 among males and females respectively]. The rates in Turkmen, native Fars and Sistani ethnic groups were 40.5, 25.2 and 30.8 per 10 000 respectively. The rates of spina bifida and anencephaly were 16.3 and 11.3 per 10 000 respectively. The rate of affected newborns was highest in mothers aged over 35 years [50.7 per 10 000]. The peak prevalence was in December

Developmental changes of glycoconjugates in early mouse embryonic neuroepithlium, notochordal and surrounding mesenchymal interactions

During early neural tube formation, the notochord is essentialfor the induction of ectoderm and for the subsequent differentiation of theneuroepithelium forming diverse cell types in the neural tube. Due to thekey role of the glycoconjugates in many developmental events, the earlydistribution of these molecules in early notochordal interaction withadjacent tissues were studied. Material and Paraffin fixed 5m sections of days 10 to 14 of mouse embryo were processed for histochemical studies by using horseradish peroxidase labelled DBA, VVA-B4, WFA, UEA-1 and OFA lectins.These lectins have binding specificity for D-GalNac and a-fucose sidechains of the glycoconjugates. Histochemical analysis revealed that notochord and itsintermediate extracellular fluid show extensive reaction with the floor plateof neural tube on 10th day, using OFA. This reaction was absent in thenext day but a sever reaction was observed in the floor plate region. Theresults revealed a reaction in venteral portion of notochord with VVA-B4and it expanded in to gut tube. Furthermore, a WFA-reaction was observedin the notochord and some of adjacent mesenchymal cells, but UEA-1 and DBA, don't showed any reaction. The expression of the GalNac and also fucosilatedglycoconjugates is stage-dependent and thus probably geneticallyregulated. The timing and distribution of lectin reactions suggest that thesemolecules [GalNac and fucose] may play a role[s] in notochordalinteractions and subsequent formation of the adjacent tissues

Factor de crecimiento neuronal y sus posibles implicaciones terapéuticas en la actualidad / Nerve growth factor and its possible therapeutical implications today

Desde 1934 se realizaron estudios analizando los efectos que sobre las células sensitivas y neuronas motoras espinales que inervaban las extremidades de animales, producía la extirpación de primordios nerviosos. Las observaciones obtenidas de estos estudios (después de algunos años) permitieron el descubrimiento de un factor promotor del crecimiento neuronal, al cual se designó como factor de crecimiento neuronal (NGF). El NFG es la sustancia mejor caracterizada dentro de una familia de moléculas que se requieren para la supervivencia y el desarrollo de neuronas durante etapas embrionarias del crecimiento y durante la vida adulta. Se ha observado que, bajo ciertas circunstancias, la infusión exógena de BGF puede promover la supervivencia neuronal y la regeneración axonal, por lo cual, en la actualidad, se ha intentado la utilización de este factor para mejorar algunas condiciones patológicas en las cuales el principal componente es el daño neuronal, pudiendo producirse este último por diferentes mecanismos. Dado lo anterior, se ha postulado que la administración de BGF recombinante humano pudiera ser, en el futuro, de utilidad para el tratamiento de enfermedades del sistema nervioso central y periférico, ya que en algunos de los estudios realizados se ha demostrado que este factor puede tener efectos benéficos

Repercussöes neurológicas do hipertiroidismo congênito / Nurological repercussion of congenital hyperthyroidism

Na literatura disponível sobre os programas de rastreamento para o hipotireoidismo congênito tem-se mencionado como objetivo principal, a prevençäo das seqüelas neurológicas decorrentes do diagnóstico e tratamento tardios desta afecçäo. No entanto, tem-se observado que, mesmo com a disseminaçäo destes programas pelo mundo e o início precoce do tratamento, algumas disfunçöes neurológicas ainda säo notadas, o que leva um contigente significativo destas crianças a necessitarem de ensino especializado em tempo integral. Neste trabalho é feita uma revisäo bibliográfica sobre a embriologia do sistema nervoso e suas inter-relaçöes com o desenvolvimento do eixo hipotálamo-hipófise-tireoidiano fetal; as alteraçöes fisiopatológicas e bioquímicas que podem ocorrer no sistema nervoso em decorrência da hipotiroxinemia, seja de início pré-natal - quando é possível haver participaçäo materna na etiopatogenia -, seja de surgimento após o parto, quando a disfunçäo tireoidiana é exclusivamente oriunda do feto; e uma abordagem sobre as repercussöes a nível comportamental e de aprendizado. Embora o rastreamento neonatal tenha a sua indiscutível importância na melhoria das condiçöes de vida da populaçäo em geral, as lesöes ocorridas na fase pré-natal que näo säo evitadas com os programas de rastreamento neonatais convencionais, nos levam a pensar que o ideal seria incluir uma forma de rastreamento para o hipotireoidismo nas rotinas de acompanhamento pré-natal para que se possa garantir o desenvolvimento neurológico pleno desta populaçäo.