Thesis (M.Sc.) (Honours) -- University of Western Sydney, Hawkesbury, 2001. / A thesis submitted in fulfilment of the requirements for the degree of Masters of Science (Honours) in the Centre for Advance [sic.] Food Research, University of Western Sydney, Hawkesbury Campus, July 2001. Bibliography : leaves 98-110.

The aim of this study was to quantify the density of taste pores on the anterior region of the tongue, in adult males and 8 to 9 year old boys. Earlier studies had shown that, although 8 to 9 year olds were poorer than adults at sensing the tastant sucrose using a whole mouth procedure, localised regions of the tongue in male children were more sensitive than equivalent regions in adults. This study aims to detemine whether the age differences in sensitivity is related to a difference in taste pore density. Two areas of the tongue, for which children had previously been shown to have higher sensitivity than adults, were examined using a videomicrosocpy technique and the number and diameter of taste pores were measured. Children were found to have a greater density of taste pores, however the number of taste pores per papilla were similar in children and adults. It was found to be likely that the greater sensitivity of localised areas on the children's tongue is due to a greater taste pore density. The reduced sensitivity reported using whole mouth stimulation may be due to a reduced capacity to assimilate taste input from the whole mouth or due to different relative contributions to whole-mouth taste from the various receptive fields in the mouth. / Master of Science (Hons)

Among humans, the density of lingual fungiform papillae (DFP) is correlated with taste sensitivity. The purpose of this dissertation was to investigate the evolution of the primate gustatory system through a comparative analysis of DFP. This investigation was conducted in three separate studies. The first study took a broad perspective incorporating data from 37 primate species to assess the relationships among DFP, body mass, taste sensitivity, and diet. Among the major findings of this first study: (1) Sucrose sensitivity was negatively correlated with DFP and positively correlated with papilla area. (2) Sucrose sensitivity was not correlated with the percent of leaves or fruit in the diet. (3) DFP and papilla area were correlated with diet. (4) The relationships between fungiform papillae and diet differed among different taxonomic groups. The second study of DFP investigated whether there are sex differences in the DFP of non-human primates, as there are in humans. In all five primate species investigated, females had higher mean DFPs than males. These sex differences were significant in Pan troglodytes and Cebus apella, and not significant in Alouatta palliata, Cercopithecus aethiops, or Varecia variegata. Pan, Cebus, and Homo share large relative brain sizes with associated life history parameters making each offspring very costly. Accordingly it was suggested that sex differences in DFP may be due to the particularly high risk of lacking nutrients or ingesting toxins for females of these three species. The third study was a comparison of phenylthiocarbamide (PTC) taste ability and DFP in humans and chimpanzees. The major questions addressed in this study were (1) Is DFP correlated with PTC phenotype in chimpanzees as it is in humans? (2) Are there sex differences in PTC genotype and phenotype as there are in DFP? Although females had greater DFPs than males, and significantly more females had the genotype for higher PTC taste sensitivity, there was no correlation between DFP and PTC phenotype. Several explanations for the differences between human and chimpanzee results were offered, including small sample sizes for chimpanzees and greater accuracy in determining PTC sensitivity among humans. / text

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The amiloride-sensitive epithelial Na+ channel, ENaC, is the Na+-specific salt taste receptor in rodents. Compared to rodents, human salt taste perception is amiloride-insensitive. In rodents the ENaC is composed of aβg-subunits. Whereas humans express an additional subunit, the d-ENaC subunit. ENaC in human taste cells is composed of aβg-subunits or dβg-subunits, with the latter being amiloride-insensitive. Currently, it is not known if dβg-ENaC expression and trafficking is regulated by hormones and their downstream intracellular signaling effectors. The aim of this study is to investigate if arginine vasopressin (AVP), aldosterone, and cAMP regulate d-ENaC expression and trafficking in cultured fungiform human taste cells (HBO cells). Secondly, we want to demonstrate the expression of downstream signaling effectors involved in the trafficking of d-ENaC in HBO cells. Using molecular and immunocytochemical techniques, our results demonstrate that AVP, cAMP, and aldosterone increase expression of d-ENaC mRNA and protein in HBO cells. Furthermore, AVP, cAMP and aldosterone increased trafficking of the d-ENaC subunit from the cytosolic compartment to the apical pole of the HBO cells. Our results further demonstrate that HBO cells express several components of signaling cascade involved in ENaC translocation from cytosol to apical pole in HBO cells. The components of this signaling cascade include AVPR2, PKA, CREB, SGK-1, Nedd4-2, and GILZ-1. These hormones in mice and rats upregulate ENaC. Currently, we are not sure if these hormones affect ENaC this way in humans. By studying d-ENaC with these hormones, we are able to see how human ENaC is regulated in the tongue.