During exposure to hypoxia, many vertebrates undergo behavioural, biochemical, and physiological changes in an attempt to overcome the lack of oxygen and thus maintain a constant metabolic rate. Numerous genes are known to be influenced by hypoxia in mammalian systems. Many of the genes that have been identified are similar to those found in fish. Two such genes are adrenomedullin and neuroglobin. Adrenomedullin is a multifunctional peptide that has shown to be expressed in a number of tissues. Neuroglobin is a recently discovered member of the globin family that is predominantly found in neuronal tissues and has a high affinity for oxygen. While the effects of hypoxia on these two genes are relatively well known in mammalian systems, they have not yet been examined in fish. To characterize the expression of both neuroglobin and adrenomedullin in different tissues and measure expressional changes during hypoxic exposure, adult zebrafish (Danio rerio) were exposed to hypoxic conditions (pO2 ∼23 torr or 3.07 kPa) for up to 24 hours. A variety of techniques were used, including in situ hybridization, immunohistochemistry, and real time PCR. Adrenomedullin was found to be present in all tissues examined except blood, the highest of which was found in the kidney and eye. Expression of neuroglobin was highest in the brain and eye; however, low levels of expression were also found in the gill, stomach and kidney. No significant changes in expression of either gene were observed following hypoxic exposure. In the brain, eye and gill, in situ hybridization and immunohistochemistry techniques were used to characterize expression of both genes at the protein and mRNA levels. Adrenomedullin mRNA staining was observed in the inner plexiform layer, outer nuclear layer and pigment epithelium of the eye, the chloride cells on the lamellae and in the interlamellar regions of the gill, and throughout all regions of the brain. Immunostaining revealed the presence of adrenomedullin protein in inner plexiform layer, outer plexiform layer and the pigment epithelium of the eye, apical membrane of lamellar epithelial cells of the gills and throughout all regions of the brain. Neuroglobin mRNA staining was observed in the ganglion cell layer as and the outer and inner nuclear layers of the eye, the chloride cells of the gill, and throughout all regions of the brain. Immunostaining revealed the presence of neuroglobin protein in the ganglion cell layer, pigment epithelium and photoreceptor cells as well as in the inner and outer plexiform layers of the eye, specific cells found throughout the gill filament, and in large neuronal cells as well as surrounding blood vessels of the brain.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/27498 |
| Date | January 2007 |
| Creators | Yorston, Jennifer K |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 87 p. |
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