1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

481 Poster Developmental, Neurogenesis, and ConsumerResearchMICROGLIA IN THE ZEBRAFISH IMMUNE RESPONSE TOINJURYFuller C.L. 1 , Koenig J.J. 1 , Byrd C.A. 1 1 Biological Sciences, WesternMichigan University, Kalamazoo, MIThe zebrafish olfactory system is a good model for studies ofneuronal plasticity and recovery from brain injury or disease. This studyattempts to determine the immune response of the zebrafish brain toinjury, with particular interest in the role of microglia. Microglia arephagocytic cells that respond to neuronal death by removing cellulardebris and they can be identified using a variety of histochemical labelsincluding certain plant lectins. They play an important role in thedefense of the central nervous system and may increase at the site ofinjury as part of an inflammatory response. Here we establish thenormal microglial composition of the adult zebrafish brain and examinethe microglial response to damage. Normal and injured fish wereanalyzed at various time points for the presence of microglia using thelectin marker IsoB4. In normal animals, very few IsoB4 lectin-positiveprofiles were seen in the olfactory bulb and optic tract, although profileswere more prevalent around the ventricles. Injured animals underwenteither olfactory deafferentation or optic nerve crush. In deafferentedolfactory bulbs there were very few lectin-positive cells and noevidence of microglial proliferation. Following optic nerve crush,however, a large number of lectin-positive microglia were visualized inthe optic tract and diencephalon. Thus, we conclude that olfactorydeafferentation elicits a different type of wound response from otherperipheral injury; the olfactory damage response does not involve aproliferation of IsoB4 lectin-positive microglia. We will continue toinvestigate the mechanisms by which the olfactory bulb responds todamage by examining microglia following direct bulb injury. Supportedby NIH DC04262 to CAB482 Poster Developmental, Neurogenesis, and ConsumerResearchCOUMARIN PRODUCES SELECTIVE DEAFFERENTATIONOF THE OLFACTORY BULBSanguino A. 1 1 Psychology, University of South Florida, Tampa, FLCoumarin (1,2-benzopyrone), a compound found in the essential oilsof many plants, had been employed as a fixative and flavoring agent butis now banned in food products because of its potential hepatotoxicity.In rats, doses subthreshold for liver toxicity produce cytotoxicity in theolfactory epithelium, due, in part, to OE-specific P450 bioactivation ofthe toxicant (Gu et al., 1997; Zhuo et al., 1999). We assessed theeffects of ip injections of coumarin on projections from the OE to theolfactory bulb. Anterograde transport of HRP*WGA from OE to theOB was evaluated 7 or 21 days after treatment with 50 or 100 mg/kgcoumarin. Rats appeared normally active 24 hr after treatment. 50mg/kg had little effect on anterograde transport. Seven day 100 mg/kgsurvival cases (n = 5) had dense HRP*WGA reaction product inglomeruli of the AOB but no reaction product in the MOB or very lightreaction product in some glomeruli in the mid lateral and posteriorventral medial bulb. There was considerable recovery of input to all butglomeruli on the dorsal and medial wall of the MOB in 21 day survivalcases (n = 5). Surprisingly, patterns of deafferentation were notbilaterally symmetrical and, in most cases, one bulb had considerablyless input than the other. Higher doses (200–500 mg/kg) were notnecessarily more effective than the 100 mg/kg dose. A study of theeffects of coumarin on odor detection and discrimination is in progress.Supported in part by NIH grant DC04671.483 Poster Developmental, Neurogenesis, and ConsumerResearchMORPHOLOGICAL AND FUNCTIONAL REGENERATION OFTHE OLFACTORY EPITHELIUM DEPENDS UPON THEEXTENT OF THE ABLATIONPlibersek K. 1 , Valentincic T. 1 1 Biology, University of Ljubljana,Ljubljana, SloveniaRegeneration of olfactory lamellae occurs following partial ablationof the olfactory organ of black bullhead catfish (Ameiurus melas).Depending upon the size of the remaining tissue, the olfactoryepithelium regenerated into either small roseta, single lamellae orepithelial tissue. Four months post the ablation, large medial sections ofthe olfactory lamellae (1-3.6 mm x 2 mm x 0.3 mm) regenerated intoeither small rosetae with 14-22 lamellae or fan-like rosetae with 5-11lamellae. The regenerated rosetae contained ciliated and microvillousolfactory receptor neurons (ORNs). Axons of the ciliated ORNsconnected to the anterior area and axons of microvillus ORNsconnected to the lateral area of the ventral olfactory bulb whichindicated full functional regeneration. In a second experiment, smallmedial sections of the olfactory lamellae (0.6-1.4 mm x 1 mm x 0.3mm) regenerated into either flat or fingerlike lamellae or into smalldeformed epithelial tissues. Four months after the ablation there was nobehavioral evidence of olfactory discrimination. The small regeneratedlamellae did not contain ORNs and did not respond to amino acidselectrophysiologically. A year after the ablation, four of the catfish withthe small regenerated lamellae discriminated the conditioned L-norvaline from other amino acids, whereas three catfish with fewregenerated lamellae and four catfish with deformed epithelial tissuesdid not discriminate amino acids. Catfish with functionally regeneratedolfactory organs responded to olfactory stimulation, whereas anosmiccatfish responded to taste stimulation only (Valentincic et al., 1994).Supported by Slovenian Ministry of Higher Education and Sciencegrant P1-0184.484 Poster Developmental, Neurogenesis, and ConsumerResearchHEMOCYTE INFILTRATION OF OLFACTORY RECEPTORNEURON CLUSTERS AFTER AESTHETASC DAMAGE INTHE SPINY LOBSTERSchmidt M. 1 , Derby C. 1 1 Biology, Georgia State University, Atlanta,GAIn the spiny lobster, Panulirus argus, olfactory sensilla (aesthetascs)are comprised of large clusters of olfactory receptor neurons (ORNs)and ensheathing cells. Aesthetascs are continuously generated in adults,and after severe damage they degenerate and subsequently regenerate(Harrison et al. J. Neurobiol. 47:51-66, 2001; Harrison et al. J. Comp.Neurol. 471:72-84, 2004). To study cellular events underlying the localde- and regeneration of aesthetascs, we monitored the tissuecomposition in the olfactory organ with confocal microscopy afterfocally damaging aesthetascs in two ways: shaving off their entire setae,or clipping them at about 50 % of their length. Shortly after the damage(6 h–3 days), infiltration of damaged ORN clusters by granulocytes—aprominent type of circulating hemocytes containing large granules andf-actin—was observed in both treatments. However, this infiltration wasmuch more substantial after clipping the aesthetascs than after shavingthem. Later time points revealed radically different fates of the ORNclusters in both treatments: after clipping, ORN clusters remainedmassively infiltrated by granulocytes for several more days andappeared normal after 3 weeks; after shaving, ORN clusters completelydegenerated within ca. 2 weeks and then started to regenerate by mitoticactivity, without granulocytes being present. These findings indicatethat granulocytes are the main agents of an immune response inducedby physiological relevant damage to aesthetascs and that they contributeto repair mechanisms allowing the damaged ORNs to survive.Acknowledgments: Supported by NIH grant DC00312.121