ABSTRACT
Different from most mammalian species, the optic nerve of the rabbit eye is initially formed inside the retina where myelination of the axons of the ganglion cells starts and vascularization occurs. Astrocytes are confined to these regions. The aforementioned nerve fibers known as medullated nerve fibers form two bundles that may be identified with the naked eye. The blood vessels run on the inner surface of these nerve fiber bundles (epivascularization) and, accordingly, the accompanying astrocytes lie mostly facing the vitreous body from which they are separated only by the inner limiting membrane of the retina. The arrangement of the astrocytes around blood vessels leads to the formation of structures known as glial tufts. Fragments (N = 3) or whole pieces (N = 3) of the medullated nerve fiber region of three-month-old male rabbits (Orictolagus cuniculus) were fixed in glutaraldehyde followed by osmium tetroxide, and their thin sections were examined with a transmission electron microscope. Randomly located discontinuities (up to a few micrometers long) of the basement membrane of the inner limiting membrane of the retina were observed in the glial tufts. As a consequence, a direct contact between the astrocyte plasma membrane and vitreous elements was demonstrated, making possible functional interactions such as macromolecular exchanges between this glial cell type and the components of the vitreous body
Subject(s)
Animals , Male , Rabbits , Astrocytes , Retina , Vitreous Body , Astrocytes , Basement Membrane , Cell Communication , Microscopy, Electron , Nerve Fibers , Vitreous BodyABSTRACT
Se estudió la concentración de nitrito residual en 507 muestras de cecinas comercializadas en la Región Metropolitana durante el período junio-septiembre de 1987, empleando la técnica de la AOAC. Se encontró que el 21% de las muestras analizadas presentó niveles de residuos de nitrito superiores a lo establecido en el Reglamento Sanitario de Alimentos. Los altos niveles detectados son el resultado del uso incorrecto de este aditivo en la industria cecinera
Subject(s)
Meat Products/standards , Food Additives/standards , Legislation as Topic , Sodium Nitrite/analysisABSTRACT
Se realizó un estudio de residuos de plaguicidas fosforados en 180 muestras de frutas y hortalizas de consumo interno, encontrando residuos de clorpirifos, bromofos, malatión, etilparatión, fentión como los más frecuentes. El 78% de las muestras presentaron residuos de plaguicidas fosforados. Entre un 10% y 17% de las muestras estuvieron no conformes de acuerdo al Reglamento Sanitario de los Alimentos (5)