Bovine central nervous system development / Desenvolvimento do sistema nervoso central de bovinos

Central nervous system (CNS) development researches are extremely important to the most common congenital disorders and organogenesis comprehension. However, few studies show the entire developmental process during the critical period. Present research can provide data to new researches related to normal development and abnormalities and changes that occur along the CNS organogenesis, especially nowadays with the need for preliminary studies in animal models, which could be used for experimental research on the influence of viruses, such as the influence of Zika virus on the development of the neural system and its correlation with microcephaly in human newborns. Then, present study describes CNS organogenesis in cattle according to microscopic and macroscopic aspects, identifying structures and correlating to gestational period. Fourteen embryos and nine bovine fetuses at different ages were collected and analyzed. All individuals were measured in order to detect the gestational period. Bovine embryo at 17 days age has its neural tube, cranial neuropore, caudal neuropore and somites developed. After 24 days of development, were observed in cranial part of neural tube five encephalic vesicles denominated: telencephalon, diencephalon, mesencephalon, metencephalon and myelencephalon. In addition, the caudal part of neural tube was identified with the primitive spinal cord. The primordial CNS differentiation occurred from 90 to 110 days. The five encephalic vesicles, primordial spinal cord and the cavities: third ventricule, mesencephalic aqueduct, fourth ventricle and central canal in spinal cord were observed. With 90 days, the main structures were identified: (1) cerebral hemispheres, corpus callosum and fornix, of the telencephalon; (2) interthalamic adhesion, thalamus, hypothalamus and epythalamus (glandula pinealis), of the diencephalon; (3) cerebral peduncles and quadruplets bodies, of the mesencephalon; (4) pons and cerebellum, of the metencephalon; (5) medulla oblongata or bulb, of the myelencephalon; and (6) spinal cord, of the primitive spinal cord. After 110 days of gestation, the five encephalic vesicles and its structures were completely developed. It was noted the presence of the spinal cord with the cervicothoracic and lumbossacral intumescences. In summary, the results describes the formation of the neural tube from the neural plate of the ectoderm, the encephalic vesicles derived from the neural tube and subsequent structural and cavities subdivisions, thus representing the complete embryology of the central nervous system.(AU)

Os estudos que descrevem o desenvolvimento do sistema nervoso central (SNC) são de suma importância para compreensão da organogênese e identificação dos prováveis eventos que resultam em malformações congênitas. Estes dados podem subsidiar novas pesquisas relacionadas ao desenvolvimento normal, e interpretação de malformações e alterações que ocorrem ao longo da organogênese do SNC, considerando neste momento a necessidade de estudos preliminares em modelos animais, os quais poderiam ser utilizados para pesquisas experimentais sobre a influência de agentes infecciosos como o Zika vírus, no desenvolvimento do sistema nervoso e suas relações com a microcefalia em humanos recém-nascidos. O presente estudo teve como objetivo descrever os aspectos morfológicos macro e microscópicos da organogênese do SNC de bovinos, buscando correlacionar os achados morfológicos com a idade gestacional. Todos os animais foram mensurados para detectar o período gestacional. Foram coletados e analisados 14 embriões e nove fetos de bovinos de diferentes idades gestacionais. No embrião bovino a partir do décimo sétimo dia de gestação, encontra-se a formação do tubo neural, o neuroporo cranial e neuroporo caudal, e formação dos somitos. Após 24 dias de desenvolvimento, são observadas na parte cranial do tubo neural cinco vesículas encefálicas denominadas: telencéfalo, diencéfalo, mesencéfalo, metencéfalo e mielencéfalo; e na parte caudal do tubo neural, encontra-se a medula espinhal primitiva. Entre 90 a 110 dias de gestação, observa-se a total diferenciação das cinco vesículas do SNC. Com 90 dias, são identificas as principais estruturas: (1) do telencéfalo, os hemisférios cerebrais, corpo caloso e fórnix; (2) do diencéfalo, a aderência intertalâmica, tálamo, hipotálamo e epitálamo (glândula pineal); (3) do mesencéfalo, os pedúnculos cerebrais e os corpos quadrigêmios; (4) do metencéfalo, a ponte e o cerebelo; (5) do mielencéfalo, a medula oblonga (ou bulbo); e (6) da medula espinhal primitiva, a medula espinhal. Após 110 dias, as cinco vesículas encefálicas e as suas subdivisões se encontram completamente desenvolvidas. Notou-se a presença da medula espinhal com as intumescências cervicotorácica e lombossacral. Em resumo, os resultados demonstram a formação do tubo neural a partir da placa neural do ectoderma, as vesículas encefálicas provenientes do tubo neural e posteriormente as subdivisões das estruturas e das cavidades, que representam a completa embriologia do sistema nervoso central.(AU)

Development of the central nervous system in guinea pig (Cavia porcellus, Rodentia, Caviidae) / Desenvolvimento do sistema nervoso central em guinea pig (Cavia porcellus, Rodentia, Caviidae)

This study describes the development of the central nervous system in guinea pigs from 12th day post conception (dpc) until birth. Totally, 41 embryos and fetuses were analyzed macroscopically and by means of light and electron microscopy. The neural tube closure was observed at day 14 and the development of the spinal cord and differentiation of the primitive central nervous system vesicles was on 20th dpc. Histologically, undifferentiated brain tissue was observed as a mass of mesenchymal tissue between 18th and 20th dpc, and at 25th dpc the tissue within the medullary canal had higher density. On day 30 the brain tissue was differentiated on day 30 and the spinal cord filling throughout the spinal canal, period from which it was possible to observe cerebral and cerebellar stratums. At day 45 intumescences were visualized and cerebral hemispheres were divided, with a clear division between white and gray matter in brain and cerebellum. Median sulcus of the dorsal spinal cord and the cauda equina were only evident on day 50. There were no significant structural differences in fetuses of 50 and 60 dpc, and animals at term were all lissencephalic. In conclusion, morphological studies of the nervous system in guinea pig can provide important information for clinical studies in humans, due to its high degree of neurological maturity in relation to its short gestation period, what can provide a good tool for neurological studies.(AU)

Este estudo descreve o desenvolvimento do sistema nervoso central em guinea pig do 12º dia pós-concepção (dpc) até ao nascimento. No total, 41 embriões e fetos foram analisados macroscopicamente e por microscopia de luz e eletrônica. O fechamento do tubo neural foi observado no dia 14 e o desenvolvimento da medula espinhal e diferenciação das vesículas primitivas do sistema nervoso central foram observados no dia 20. Histologicamente, o tecido cerebral indiferenciado foi observado como uma massa de tecido mesenquimal entre os dias 18 e 20 e no 25º dia o tecido no interior do canal medular apresentou maior densidade. No dia 30 o tecido cerebral apresentou-se diferenciado, período no qual a medula espinhal preenchia todo o canal vertebral e foi possível observar os estratos cerebral e cerebelar. No dia 45 as intumescências cervical e lombar foram visualizadas e os hemisférios cerebrais estavam divididos, com uma clara distinção entre substância branca e cinzenta no cérebro e cerebelo. O sulco mediano dorsal da medula espinhal e a cauda equina foram evidentes apenas no dia 50. Não houve diferenças estruturais significativas em fetos de 50 e 60 dpc e animais a termo eram todos lisencefálicos. Estudos morfológicos do sistema nervoso em guinea pig podem fornecer informações importantes para estudos clínicos em seres humanos devido ao alto grau de maturidade neurológica em relação ao seu período de gestação curto, fato que servir como excelente ferramenta em estudos neurológicos.(AU)

Avaliação do comportamento fetal por meio da ultrassonografia de quarta dimensão: conhecimento atual e perspectivas futuras / Assessment of fetal behavior using four-dimensional ultrasonography: current knowledge and perspectives

Durante as últimas décadas, o desenvolvimento da ultrassonografia em tempo real tem possibilitado a visibilização direta do feto no útero, bem como a avaliação de sua atividade. Com o advento da ultrassonografia tridimensional (3D) no final dos anos 1980, iniciou-se uma nova era no diagnóstico por imagem em Obstetrícia, ampliando-se sobremaneira a possibilidade do estudo fetal. Recentemente, uma técnica que permitiu que a imagem 3D fosse transformada em um modo em tempo real foi introduzida e tem sido chamada de ultrassonografia em quarta dimensão (4D), a qual permite o monitoramento contínuo da face fetal e de outras áreas da superfície do feto, como, por exemplo, suas extremidades. Alguns estudos já se ocuparam em avaliar esta nova metodologia na observação do comportamento fetal durante diferentes estágios da gestação, na tentativa de melhor entender as relações entre a maturação do sistema nervoso central do feto e suas implicações em seu padrão de comportamento. No presente artigo, os autores realizam uma revisão sobre o uso atual da ultrassonografia 4D na avaliação do comportamento fetal, discorrendo sobre as perspectivas da técnica em espelhar, por meio da observação de padrões de movimentos e expressões faciais, o desenvolvimento neurológico do feto, destacando as potenciais aplicabilidades dessa tecnologia como nova área de pesquisa em medicina fetal.

In the last decades, the development of real-time ultrasonography has allowed the direct view of the fetus in the uterus, as well as assessing its activity. The advent of threedimensional ultrasonography (3D) at the end of the 80s initiated a new era in diagnostic imaging for Obstetrics, dramatically increasing the possibility of studying the fetus. Recently, a new technique allowing the 3D image to be transformed into real-time was introduced: the four-dimensional (4D) ultrasonography. It allows the continuous monitoring of fetal face and other surface areas, such as the extremities. Some studies have already assessed this new methodology for fetal behavior observation during different stages of pregnancy, trying to understand better the relationship between fetal central nervous system maturation and the implications for its behavior. In this article, the authors review the current use of 4D ultrasonography in the assessment of fetal behavior, and discuss the possibilities of the technique to show the neurological development of the fetus, by means of watching movement and facial expressions. They also highlight the potential applicability of this new method in this new research area of fetal medicine.

Desarrollo embrionario del sistema nervioso central y órganos de los sentidos: revisión / Embryonic central nervous system and sense organ development: review

El sistema nervioso tiene origen en la capa germinal ectodérmica. Así como en la vida posnatalel sistema nervioso está claramente diferenciado en sistema nervioso central y periférico,en su etapa embrionaria la formación de cada uno sigue caminos diferentes, pero cercanos.Esta revisión hace hincapié en la formación del sistema nervioso central y de estructurasespecíficas, como los órganos de los sentidos. Se presenta un breve recorrido por procesoscomo la gastrulación, la neuralización y la formación de placodas hasta llegar a las diferentesestructuras que conforman el sistema nervioso central y los órganos de los sentidos...

The nervous system has its origin in the well-known ectodermic germinal layer. During thepostnatal life, the nervous system is clearly differentiated in central nervous system andperipheral nervous system. During the embryonic stage, all the components follow differentpaths but they are still close to each other. This review focuses on the central nervoussystem and development of the sense organs. It includes a brief review of processes suchas gastrulation, neurulation and development of cranial placodes and the structures thatmake up the central nervous system and the sense organs...

Chronic stress effects on NPY neuronal population during rat development / Efectos del stress crónico sobre la población neuronal NPY durante el desarrollo de ratas

The aim of this work was to determine the chronical stress effects on the encephalic NPY neurons population during the fetal Central nervous system development. Immunocytochemical techniques were used for this purpose: NPY neurons presented a similar morphology during the gestation days studied but their distribution varied in the anterior, medium and posterior brain. Statistical Highly significant differences in number of NPY positive neurons (p<0.01) among anterior, medium and posterior brain of stressed fetus (SF) were determined depending on the gestation period and the brain area. The NPY neurons were increased in ARC (Arcuate Hypothalamic Nucleus), PH (Posterior Hypothalamic Area) and DM (Dorsomedial Hypothalamic Nucleus) in stressed fetuses (SF) of 17 days, and in ARC of 19 days SF (p< 0.01) were detected in the different brain nucleus. The NPY population increased in PnO (Pontine Reticular Nu, Oral Part) and RITg (Reticulotegmental Nu of the Pons) of 17 days SF, while they were detected in posterior brain at Pyx (Pyramidal Decussation), Rob (Raphe Obscurus Nucleus) and RPA (Raphe Pallidus Nucleus) in SF of 19 days. They also increased in number (p<0.05) in DPGI (Dorsal Paragigantocellular Nu), CGPn (Central Gray of Pons) and PrH (Prepositus Hypoglossal Nucleus) of 17 days SF. Finally, any statistical differences were found among CF and SF in the following nuclei: anterior brain, AH (Anterior Hypothalamic Nucleus), DM (Dorsomedia L Hypothalamic Nucleus) of 17 days; ME (Median Eminence)., VMH (Ventromedial Hypothalamic Nucleus) of 19 days; medium brain in CG (Central Periaqueductal Gray), DR (Dorsal Raphe Nucleus) of 17 days and posterior brain in PnC (Pontine Reticular Nu, Caudal Part), PrH (Prepositus Hypoglossal Nucleus), RMgG (Raphe Magnus Nucleus), IO (Inferior Olive) of 17 days. The increase number of NPY neurons found in the stressed rat fetuses in all periods studied would indicate the participation of the NPY System in...

El propósito del presente estudio fue determinar los efectos del estrés crónico en la población de neuronas NPY encefálicas durante el desarrollo del S.N.C. fetal mediante técnicas inmunocitoquímicas. Se demostró que las neuronas NPY presentan un morfología similar en los días de gestación estudiados, pero su distribución varía en el cerebro anterior, medio y posterior. Se comprobaron diferencias altamente significativas entre el cerebro anterior, medio y posterior (p<0,01) de fetos estresados (FE), variando dicha significación dependiendo del día de la gestación y del área estudiada. En los diferentes núcleos cerebrales del cerebro anterior se detectaron aumentos en ARC (Arcuate Hypothalamic Nucleus), PH (Posterior Hypothalamic Area) de 17 días y DM (Dorsomedia L Hypothalamic Nucleus) y en ARC (Arcuate Hypothalamic Nucleus) de 19días (p<0,01) de F.E. En el cerebro medio se detectaron aumentos en DR (Dorsal Raphe Nucleus) (p<0,01) y PN (Pontine Nucleus) (p<0,05) de 19 F.E. En el cerebro posterior se detectaron aumentos en PnO (Pontine Reticular Nu, Oral Part) y RITg (Reticulotegmental Nu of the Pons) de 17 F. E. y Pyx, (Pyramidal Decussation), Rob (Raphe Obscurus Nucleus) y RPA (Raphe Pallidus Nucleus) de 19 F.E. Asimismo se comprobaron aumentos (p<0,05) en DPGI (Dorsal Paragigantocellular Nu.) de 17 F.E, CGPn (Central Gray of Pons) y PrH (Prepositus Hypoglossal Nucleus), de 19 F.E. Finalmente, no se comprobaron diferencias entre F. C. (fetos controles) y F. E. en los siguientes núcleos del cerebro anterior: AH (Anterior Hypothalamic Nucleus), DM (Dorsomedia L Hypothalamic Nucleus), de 17 días; y EM, (Median Eminence), VMH (Ventromedial Hypothalamic Nucleus) de 19 días. En el cerebro medio CG, (Central Periaqueductal Gray), DR (Dorsal Raphe Nucleus) de 17 días. En el cerebro posterior el PnC, (Pontine Reticular Nu, Caudal Part), PrH (Prepositus Hypoglossal Nucleus), RMgG (Raphe Magnus Nucleus), IO (Inferior Olive) de 17 días del cerebro posterior...

Dinámica de la córticoangiogénesis en el sistema nervioso central / Dinamics of the cortico-angiogenesis in the central nervous system

This study analyzes the temporal-spatial correlation between angio-and corticogenesis in the developing chick optic tectum (OT) by means of NADPH-diaphorase and immunolabeling methods. Qualitative and quantitative parameters were used to analyze a new vessels formation and growth of preexisting ones as a function of time and space...

Defecto del cierre del tubo neural: acrania: a propósito de un caso / Neural tube defect closing: acrania: a purpose of a case

Las malformaciones congénitas son un problema poco frecuente; considerando todas las malformaciones en conjunto, éstas se presentan en menos del 2 por ciento de los recién nacidos. Los defectos del cierre del tubo neural: anencefalia, espina bifida, acrania y meningocele, al igual que la mayoría de las malformaciones congénitas, son un grupo de afecciones de etiología multifactorial, producto de la interacción de factores genéticos y ambientales. Los factores genéticos actúan en un sistema poligenético, en el que se tienen que considerar los riesgos de recurrencia, cálculos de heredabilidad, la frecuencia de consanguineidad y las variaciones raciales, los factores ambientales, las infecciones virales, agentes físicos como la hipertemia (fiebre), deficiencia o alteraciones del metabolismo del ácido fólico, así como la exposición a diversas substancias químicas.

Considerações sobre a evolução filogenética do sistema nervoso, o comportamento e a emergência da consciência / Considerations about the nervous system phylogenetic evolution, behavior, and the emergence of consciousness

Tendo como base dados de literatura, esta revisão trata dos aspectos genéricos da evolução filogenética do sistema nervoso central, ressaltando em particular o desenvolvimento evolutivo das estruturas encefálicas relacionadas com o comportamento e com as funções cognitivas que vieram caracterizar o ser humano. Sobre as estruturas límbicas, que por ocasião do advento dos mamíferos evolutivamente se desenvolveram sobre o topo do sistema nervoso mais primitivo dos seus ancestrais, o ulterior desenvolvimento cortical com neurônios dispostos em camadas constituiu a base estrutural que viabilizou a discriminação fina das funções sensitivas e sensoriais, a maior complexidade das funções motoras e o desenvolvimento das funções cognitivas e intelectuais que acabaram caracterizando o ser humano. O conhecimento da evolução filogenética do sistema nervoso central nos permite inferir possíveis correlações entre as estruturas encefálicas que se desenvolveram ao longo do processo evolutivo e o comportamento dos seus respectivos seres. Nesta direção, sem se deter em questões de ordem conceitual, a presente revisão termina discutindo possíveis paralelos entre a evolução do sistema nervoso central e a emergência da consciência, à luz das recentes contribuições sobre o assunto.

This text reviews the generic aspects of the central nervous system evolutionary development, emphasizing the developmental features of the brain structures related with behavior and with the cognitive functions that finally characterized the human being. Over the limbic structures that with the advent of mammals were developed on the top of the primitive nervous system of their ancestrals, the ultimate cortical development with neurons arranged in layers constituted the structural base for an enhanced sensory discrimination, for more complex motor activities, and for the development of cognitive and intellectual functions that finally characterized the human being. The knowledge of the central nervous system phylogeny allow us particularly to infer possible correlations between the brain structures that were developed along phylogeny and the behavior of their related beings. In this direction, without discussing its conceptual aspects, this review ends with a discussion about the central nervous system evolutionary development and the emergence of consciousness, in the light of its most recent contributions.

Expression of dorsal-ventral genes during early development of Rhynchosciara americana embryos

The establishment of dorsal-ventral polarity in Drosophila is a complex process which involves the action of maternal and zygotically expressed genes. Interspecific differences in the expression pattern of some of these genes have been described in other species. Here we present the expression of dorsal-ventral genes during early embryogenesis in the lower dipteran Rhynchosciara americana. The expression of four genes, the ventralizing genes snail (sna) and twist (twi) and the dorsalizing genes decapentaplegic (dpp) and zerknüllt (zen), was investigated by whole-mount in situ hybridization. Sense and antisense mRNA were transcribed in vitro using UTP-digoxigenin and hybridized at 55°C with dechorionated fixed embryos. Staining was obtained with anti-digoxigenin alkaline phosphatase-conjugated antibody revealed with NBT-BCIP solution. The results showed that, in general, the spatial-temporal expression of R. americana dorsal-ventral genes is similar to that observed in Drosophila, where twi and sna are restricted to the ventral region, while dpp and zen are expressed in the dorsal side. The differences encountered were subtle and probably represent a particular aspect of dorsal-ventral axis determination in R. americana. In this lower dipteran sna is expressed slightly later than twi and dpp expression is expanded over the lateral ectoderm during cellular blastoderm stage. These data suggest that the establishment of dorsal-ventral polarity in R. americana embryos follows a program similar to that observed in Drosophila melanogaster.

[Quantitative and qualitative study of dermatoglyphic patterns of schizophrenia in Khorasan Province]

Finger and hand prints are formed during the late first and second trimester of fetal development, and then remain unchanged. Schizophrenia is a psychotic disease that coexists with structural and biochemical changes of CNS. It is probably under the influence of environmental and/or genetic factors. There are some suggestions that disturbance in the dermatoglyphic patterns are probably in relationship with the appearance of schizophrenia. It seems that this disturbance appears in the first and second trimesters of fetal development, which is a critical period for CNS growth. We have studied the dermatoglyphic changes in 91 schizophrenic patients [49M, 42F] in Ebne Sina Psychosis Hospital of Mashhad, and have compared them with those of 72 healthy controls [42M, 30F]. The x2 test was used for quantitative and T-test for qualitative data analysis. The results showed a significant reduction of TABRC between healthy and patient. The forms of Loop and Arch are heterogeneous and compared to the control group were significant [P=.0/04,P=0/036]. In conclusion, these results provide further evidence that abnormal dermatoglyphic patterns exist in some patients with schizophrenia, and that, the a-b ridge count can be used as a marker of this psychotic disease, and support the idea that the incidence of schizophrenia maybe due to the adverse intrauterine events. Because these events probably affect the brain, behavior and finger print patterns, dermatoglyphics would be a proper method for prognosis of some cases of schizophrenia

Anencefalia: presentación de un caso clínico / Anencephaly: a clinical case

La anencefalia es una malformación del sistema nervioso, causado por la falla del cierre del neuroporo anterior durante la embriogénesis. Su incidencia es de 1 en 1.000 embarazos en Estados Unidos. Los recién nacidos con anencefalia generalmente sobreviven sólo pocas horas o días, y excepcionalmente se han descrito casos de sobrevida de algunas semanas. Existen numeroso estudios que sugieren la existencia de factores genéticos y ambientales en la génesis de este trastorno, por ejemplo, mutaciones en el gen que codifica la enzima metilentetrahidrofolato reductasa, elevados niveles plasmáticos de homocisteína y bajos de folato en madres de niños con defectos del tubo neural y factores ambientales diversos. La mayoria de los casos son diagnosticados mediante ultrasonografía precozmente durante el embarazo (antes de las 20 semanas). Se presenta un caso clínico de recién nacido con anencefalia, en el Hospital de Salamanca, que tuvo una sobrevida excepcionalmente prolongada y se revisa el tema

Extracellular matrix molecules play diverse roles in the growth and guidance of central nervous system axons

Axon growth and guidance represent complex biological processes in which probably intervene diverse sets of molecular cues that allow for the appropriate wiring of the central nervous system (CNS). The extracellular matrix (ECM) represents a major contributor of molecular signals either diffusible or membrane-bound that may regulate different stages of neural development. Some of the brain ECM molecules form tridimensional structures (tunnels and boundaries) that appear during time- and space-regulated events, possibly playing relevant roles in the control of axon elongation and pathfinding. This short review focuses mainly on the recognized roles played by proteoglycans, laminin, fibronectin and tenascin in axonal development during ontogenesis

La dieta como determinante del desarrollo del sistema nervioso central: rol de los ácidos grasos asenciales / Diet as a determinant of the central nervous system development: role of essential fatty acids

El sistema nervioso central es el segundo tejido más rico en lípidos del organismo, luego del adiposo. Los fosfolípidos constituyentes de las membranas cerebrales poseen un alto contenido de ácidos grasos poliisaturados de cadena larga (AGPICL) de las familias n-3 y n-6, derivados de los respectivos ácidos grasos esenciales. Las mayores concentraciones de AGPICL en tejido nervioso corresponden al ácido docosahexaenoico (22:6n-3), en membranas de materia gris de corteza cerebral y fotoreceptores de retina. La deficiencia de AGPICL n-3 en recién nacidos, especialmente de pretérmino, modifica la función nerviosa, provocando dificuldades de aprendizaje y alteraciones de la función visual. El período de mayor acumulación de estos lípidos en cerebro es perinatal. Por esta razón, es importante la alimentación adecuada de la embarazada, antes y durante la gestación, y de la mujer que amamanta, que transfieren los AGPICL al feto y recién nacido, respectivamente. En niños de pretérmino, que nacen con menores reservas de AGPICL, estos tienen la calidad de condicionalmente esenciales. La formulación de las preparaciones destinadas a la alimentación de lactantes, especialmente si son prematuros, debe incluir AGPICL n-3 y n-6 en proporciones adecuadas.

Ontogénia de la Función Cerebral / Ontogenesis of Brain Function

En tanto el encéfalo no pueda realizar cuando menos una de sus funciones básicas, el sistema sólo tendrá el potencial del funcionamiento encefálico del organismo humano. La definición tentaaativa del inicio de la vida encefálica humana es idéntica al inicio del aspecto operacional de éste sistema crítico. El uso del término "vida cerebral", es dificil de definir; sin embargo debe considerarse en el contexto de su capacidad estructural y funcional en su totalidad. La neurogénesis recapitula la ontogénia cerebral de la misma manera que la ontogénesis recapitula la filogénesis. En este trabajo se revisan los aspectos neurogenéticos y la ontogénesis del Sistema Nervioso.

Regional changes in central noradrenaline levels after X-irradiation at birth

La inyección neonatal de nerutóxicos a roedores produce cambios permanentes en los niveles centrales de noradrenalina (NA). Estos cambios se asocian a una hiperinervación del tallo encefálico (BS) y cerebelo (CE) y a una hipoinvervación de la corteza cerebral (CO) y médula espinal (SC). El sistema nervioso central en desarrollo de los mamíferos es sensible a los rayos-X. El objetivo de este trabajo fue estudiar los efectos de una dosis de radiación-X en ratas neonatas sobre los niveles centrales de NA, evaluados post-nacimiento. La cabeza de los animales fue expuesta a 200, 500 ó 700 rad (SC no irradiada) en las 24 h luego del nacimiento. Fueron sacrificados a los 30, 90, 185 ó 390 días de edad y se separon las siguientes regiones: BS, CO, CE, SC y el "resto del encéfalo" (RB). La NA se aisló por adsorción en columnas de alúnina y se determinó por métodos fluorométrico. A los 30 días, la NA del BS se incrementó luego de 200 (173 % del control), 500 (205.9%) y 700 rad (188.2%), retornando a los valores del control alrededor del día 90. Luego de 500 rad se produjo un aumento persistente en la concentración de NA tanto en CE como en RB, inclusive evaluada al día 390: 220% y 170.3%, respectivamente. Asimismo, 700 rad determinaron un incremento permanente en la concentración de NA del CE: 186.7%, determinada en el día 390. Una atrofia persistente del CE fue inducida tanto por 500 (78.4% del control) como por 700 rad (39.1%), pesado en el día 390. Las dos dois mayores produjeron una...