Evolución histogenética de las células bipolares de la retina un estudio en el embrión de pollo

La estructura retiniana representa, aún hoy día, uno de los problemas del sistema nervioso que sigue ofreciendo lagunas y planteando incógnitas. Ramón y Cajal en 1933 decía en Madrid dirigiéndose a los miembros del XIV Congreso Internacional de Oftalmol ... ogía que todavía quedaban en la retina tantos puntos oscuros que su esclarecimiento supondría trabajo para varias generaciones. Bien es verdad, que desde Ramón y Cajal hasta el presente se han estudiado y discutido repetidas veces los problemas estructurales de la retina de los vertebrados, siendo realmente excelentes muchos de estos trabajos. Sin embargo, a pesar de las interesantes contribuciones de muchos investigadores, poco se ha hecho a nivel morfológico desde el trabajo de Ramón y Cajal publicado en La Cellule en el año 1892, que pueda representar un paso decisivo.Al ser el pollo un animal de fácil adquisición, el conocimiento de la organización óptica de su retina resulta sumamente importante dentro de la disciplina de neurohistología al existir una correlación estructural entre las distintas clases de vertebrados.En particular, el estudio de la neurogénesis de la célula bipolar retiniana es sumamente importante, debido a que es dicha neurona la encargada de conectar entre sí las dos capas sinápticas, sirviendo de puente para el paso de la información visual, desde los fotorreceptores que captan la energía lumínica hasta las células ganglionares que envían dicha información al lóbulo óptico.El objetivo concreto del presente trabajo es el análisis con técnicas lumínicas y electrónicas del desarrollo histogénico de la células bipolar en la retina de pollo a lo largo del periodo embriológico que va desde el 7º día de incubación hasta el momento de la eclosión.En el terreno estrictamente morfol

Effect of ethanol on the cerebellar cortex of the chick embryo

The effect of ethanol on the cerebellar cortex of chick embryos was studied in semi-thin sections of material prepared for electron microscopy. The embryos were injected with ethanol on the 3rd or 6th day of incubation and observed until days 13, 15, 17 and 21 of development. A decrease was seen in the number of germinal cells generated, together with defects in neuronal migration and the existence of a lower quantity of cells due to a generalised process of cell death. At the same time, a progressive neuronal degeneration was observed until the 15th day of incubation, the tissue recovering progressively on days 17 and 21. On the other hand, the embryos treated with ethanol on the 3rd day were less affected than those injected on the 6th day

Alcohol-Induced Lipid and Morphological Changes in Chick Retinal Development

BACKGROUND: Alcohol exposure causes alterations in the lipid content of different organs and a reduction of long-chain fatty acids. During embryo development, the central nervous system is extremely vulnerable to the teratogenic effects of alcohol, and the visual system is particularly sensitive. METHODS: White Leghorn chick embryos were injected with 10- and 20-microl alcohol doses into the yolk sac at day 6 of incubation. The lipid composition of the retina was analyzed in embryos at day 7 of incubation (E7), E11, E15, and E18. The percentages of phospholipids, free cholesterol, esterified cholesterol, diacylglycerides, and free fatty acids were estimated by using an Iatroscan thin layer chromatography flame ionization detector. Gas chromatography and mass spectrometry were used to determine fatty acid composition. The morphological study was performed at E7, E11, and E19 by means of semithin and immunohistochemical techniques. RESULTS: In the retina, alcohol causes the total lipid content to change, with a remarkable increase in free cholesterol and a dramatic decrease in esterified cholesterol. Diacylglycerides and free fatty acids tend to increase. Phosphatidylcholine and phosphatidylethanolamine decrease, whereas phosphatidylserine, sphingomyelin, and phosphatidylinositol increase. The main fatty acids of the retina also undergo changes. At E7, myriotic acid increases, and oleic acid and polyunsaturated fatty acids such as arachidonic acid and docosahexaenoic acid decrease. From E18 onward, there is some recovery, except for fatty acids, which recover earlier. From a morphological point of view, alcohol effects on retinal development are various: increase of intercellular spaces in all cell layers, pyknosis with loss of cellularity in the inner nuclear cell layer and ganglion cell layer, retarded or disorderly cell migration, early cell differentiation, and loss of immunoreactivity for myelin oligodendrocyte-specific protein. CONCLUSIONS: Acute alcohol exposure during embryo development causes the lipid composition of the retina to change, with a trend to recovery in the last stages. These alterations are in line with the changes observed at a morphological level.Peer reviewe

The protective role of squalene in alcohol damage in the chick embryo retina

This work has received the prize ‘II Premio Nacional de la Asociación Española de Municipios del Olivo a la Investigación sobre Aceite y Salud 2003’.The developing CNS, and in particular the visual system, is very sensitive to the effects of alcohol. Alcohol causes lipid peroxidation. Squalene, the major olive oil hydrocarbon, is a quencher of singlet oxygen and prevents the corresponding lipid peroxidation. We presumed that squalene can protect against the alcohol-induced damage already observed during the development of the chick retina. Alcohol+squalene was administered directly into the yolk sac of the egg of White Leghorn chicks at day 6 of incubation. The lipid composition of the retina was analyzed in embryos at E7, E11, E15 and E18. The proportions of phospholipids, free and esterified cholesterol, diacylglycerides and free fatty acids were estimated using the Iatroscan TLC/FID procedure. Gas chromatography and mass spectrometry were used to determine the fatty acid composition. The morphological study was carried out at E11 using semithin sections, and by means of immunohistochemical techniques at E19. Comparing the results obtained in control embryos, the administration of alcohol+squalene reduces the effects of alcohol on the total lipid composition of the retina during development. The effects were, in fact, of less magnitude than in embryos treated only with alcohol. The major phospholipid species of alcohol+squalene-treated embryos exhibited total recuperation at E15. As far as fatty acids are concerned, no significant changes were observed with regard to control embryos during development. From a morphological point of view, the retinas of alcohol+squalene-treated embryos show at E11 fewer cellular alterations than the retinas of alcohol-treated embryos. In this respect, the retinas of alcohol+squalene-treated embryos exhibited: a columnar cell arrangement similar to that observed in control retinas; few pycnotic cells and very few alterations in ganglion cell layers and in the optic nerve fibers layer. At E19 the recuperation of the expression of myelin oligodendrocyte specific protein (MOSP) in alcohol+squalene-treated embryos was recorded. Since squalene reduces the deleterious effects caused by alcohol on the lipid composition and the structure of the retina, squalene could act as a naturally occurring agent for the prevention of damage caused by abusive alcohol ingestion during pregnancy.This work was supported by funds from the Comisión Interministerial de Ciencia y Tecnología (CICYT) (AGL2002-00495) and (BFI2002-04481-C02-01); Consejería de Agricultura y Pesca (CAO01-002) and Red FIS.S de investigatión cooperativa G03-140 (PREDIMED).Peer reviewe