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The Ultrastructure Of Visual Cells, Visual Pathways, And FMRI Studies Of Visual And Somatosensory Stimulation-related Cortical Activation

Posted on:2006-10-13Degree:DoctorType:Dissertation
Country:ChinaCandidate:M R FangFull Text:PDF
GTID:1100360152993135Subject:Cell biology
Abstract/Summary:PDF Full Text Request
The diversities between actinopterygians and the teleosts and other higher vertebrates are evolutionarily significant. As an archaic fish, an living fossil among the actinopterygians , sturgeon attracts most attention because of its economic value. There has been a very limited number of studies conducted on the visual cells in the retina of the sturgeon. In present study, the ultrastructure of visual cells in the retinae of the sturgeon were studied by the scanning electron microscope (SEM), and transmission electron microscope (TEM). Dil labeled fibers of the visual pathways following uniocular injection were examined and recorded with a laser scanning confocal microscope.Despite that rods have been frequently studied, the different types of cones in the fish have not received adequate attention. The difference between twin and double cones in morphology probably hinted at a difference in function. The aim of this study was therefore to demonstrate if there were twin cones or non-identical double cones in the fish morphologically or both , and if so, were they present in different subgroups of fish. For this purpose, the retinae of three subgroups of fishes:the actinopterygi, the elasmobranch and the teleost were employed for studies.Hypoxia is a frequent challenge to aquatic vertebrates as compared to their terrestrial counterpart. When fish experience aquatic hypoxia on regular basis, they may have ways in counteracting such environmentalchanges. In spite of some works on hypoxia in goldfish, the effect of hypoxia on cellular apoptosis in the sturgeon has not been adequately studied. For this purpose, this study is also to find out the effects of hypoxia on apoptosis in the central nervous system of sturgeon, an archaic fish.Nothing is known concerning the visual centers of mammals in postnatal development. In the eyes of mammals, for example the pig, the retinae mature by the early postnatal days. In order to link the initial functioning of the visual system with the eye, a study on the activation of the visual cortex is badly needed. Using fMRI, the current study aims to decipher functional activation in the brains of the minipig upon visual stimulation and its alterations from early postnatal period to 6 months.The pig' s brain lends itself as a useful model in medical research, due to its similarities with the human brain, its size and activity, can be relatively easily examined by MRI. During development, the pig CNS also shows striking parallels to that of the human. Up to now, there is remarkable scarcity in information on functional MRI responses in conscious pigs, allowing to relate structure to function. In addition, a systematic analysis of fMRI responses in the developing pig brain is lacking. There are no data correlating maturation parameters during the postnatal development of the pig brain with its functional activity. We have therefore evaluated the fMRI responses of the brains of un-anes-thetized young pigs ,2 months to 6 months postnatal age upon pain stimulation and initiation of passive movement. We have then correlated these data with the cytochemical brain development of these animals, i. e. immunoreaction for synaptophysin, and for GABA, the most prominent inhibitory neurotransmitter in the brain, which plays a major role in neuronal plasticity .Part IThe complexity of the visual cells and visual pathways of the sturgeonAIM: To investigate the ultrastructure of the visual cells, and the visual pathways of the sturgeon. METHODS : The ultrastructure of visual cells in the retinae of the sturgeon were studied by the scanning electron microscope (SEM), and transmission electron microscope (TEM). Dil labeled fibers of the visual pathways following uniocular injection were examined and recorded with a laser scanning confocal microscope. RESULTS: (l)Similarly to other vertebrates, our investigations revealed the presence of two types of the photoreceptors (or visual cells) in theretina of the sturgeon , rods and cones. The cones were much shorter than the rods, with most half the height of the ro...
Keywords/Search Tags:sturgeon, visual cell, apoptosis, fMRI, cortical activation development
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