Papillae

Taste-active chemicals react with receptors on the surface of sensory cells in the papillae causing electrical depolarization, ie, drop in the voltage across the sensory cell membrane. The collection of biochemical events that are involved in this process is called transduction (15,16). Not all the chemical steps involved in transduction are known however, it is clear that different transduction mechanisms are involved in different taste quaUties different transduction mechanisms exist for the same chemical in different species (15). Thus the specificity of chemosensory processes, ie, taste and smell, to different chemicals is caused by differences in the sensory cell membrane, the transduction mechanisms, and the central nervous system (14). 

The possible involvement of polygalacturonic acid-containing molecules in the defence reactions of tomato root cells against Fusarium oxysporum was suggested about 20 years ago by their accumulation at penetration sites. Since papillae are held to serve as a resistance mechanism to fungal penetration, it was assumed that the interrelation between pectin and other polymers - such as lignin - may contribute to enhancing the hardness of these newly formed structures (Benhamou et al., 1990). 

Lasareff put forward a chemical theory in which each receptor was responsive to only a single taste, and that applied stimuli caused the decomposition of a material within the cell. This decomposition produced ions which then excited the nerve endings in the papillae, the concentration of the ionized products determining the magnitude of the neural activity. 

The importance of lipophilicity to bitterness has been well established, both directly and indirectly. The importance of partitioning effects in bitterness perception has been stressed by Rubin and coworkers, and Gardner demonstrated that the threshold concentration of bitter amino acids and peptides correlates very well with molecular connectivity (which is generally regarded as a steric parameter, but is correlated with the octanol-water partition coefficient ). Studies on the surface pressure in monolayers of lipids from bovine, circumvallate papillae also indicated that there is a very good correlation between the concentration of a bitter compound that is necessary in order to give an increase in the surface pressure with the taste threshold in humans. These results and the observations of others suggested that the ability of bitter compounds to penetrate cell membranes is an important factor in bitterness perception. 

Fig. 39.—Binding of Sugars to Taste Papillae versus Behavioral Taste-preferences of Bovines. ° ...

The binding specificity of d-[ C]glucose by the taste-papillae membranes, compared to that of control membranes isolated from epithelial tissue, has been confirmed in two studies. One inherent problem in the approach is that the stimuli, primarily carbohydrate sweeteners, are not ideal model compounds to use, as they are not active at low concentrations and do not show sufficiently high binding-constants. The use of other stimulus compounds that are at least several hundred times sweeter than sucrose, such as saccharin, dihydrochalcone sweeteners, dipeptide sweeteners, stevioside, perillartine and other sweet oximes, the 2-substituted 5-nitroanilines, and... 

Fig. 40.—Inactivation of Binding of [ C]Sucrose to Taste Papillae by Heating in Boiling...

PI. 2.2 (A) Oral aperture of Prosimian AOS Naso-Palatine Papilla (Median Sulcus), without incisor-gap, in Aye-Aye (Dauhentania), (B) Rhinarium and Sulcus, with incisor-gap, in Angwantibo (Arctocebus). Arrow —> = Papillary Sulcus P = Naso-Palatine Papilla and RS = Rhinarial Sulcus (courtesy of Alain Schilling3). 

Fig. 2.6 Rostral nasal anatomy of Honey Possum (Tarsipes rostratus) showing (a) section levels and (b) TS at level 4 naso-palatine papilla with taste-buds (TB), gustatory chemoreceptors facing lumen of N-Pd (incisive duct, Id) (from Kratzing, 1987).

In the squamous/stratified epithelium covering, the palatal aperture of the N-P canals and the dorso-lateral surfaces of the papilla, there are occasional clusters of taste buds. These non-olfactory chemosensory elements are positioned at or near to the entrance to the AOS, suggesting that some initial chemosensation may arise from the sampling of material... 

Hofer H.O. (1978). The ductus nasopalatinus and the ductus vomeronasalis, and the occurrence of taste buds in the papilla palatina in Nycticebus coucang (Primates, Prosimiae). VerhAnat Ges 72, 649-650. 

Wohrmann-Repenning A. (1978). Geschmacksknospen an der papilla palatina von Tupaia glis (Diard 1820), ihr Vorkommen und ihre Beziehungen zum Jacobsonschen Organ. Morphol Jb 124, 375-384. 

Nodule Papilla Psoriasis Small node that is solid to the touch Small, nipple-shaped elevation A skin disease characterized by the formation of scaly red patches, particularly on the extensor surfaces of the body (elbows, knees)... 

Kaufmann H et al. Influence of low temperature on productivity, proteome and protein phosphorylation of CHO cells. Biotechnol Bioeng 1999 63 573-682. Kristensen DB et al. Analysis of the rat dermal papilla cell proteome. Exp Dermatol 1999 8 339-340. 

FIGURE 50-7 Rattongue, taste papillae and taste buds. (A) Surface of the rat tongue showing location of the taste papillae. (B) Cross-section of the three main types of taste papillae fungiform, foliate and vallate. (C) The taste bud contains 50-100 taste cells, including receptor cells and basal cells. 

Ramalho-Santos M, Pissarra J, Verissimo P, Pereira S, Salema R, Pires E, Faro CJ. Cardosin A, an abundant aspartic proteinase, accumulates in protein storage vacuoles in the stigmatic papillae of Cynara cardunculus I. Planta 1997 203 204-212. 

After peroral intake of nickel sulphate in mice, kidney damage appeared at the corticomedullary junction [296]. There was loss of renal tubular epithelial cells and protein loss, giving numerous hyaline casts in the renal tubules and collecting ducts, especially prominent in the renal papillae. 

Thordal-Christensen H, Zhang Z, Wei Y, Collinge DB (1997) Subcellular localization of H202 in plants. H202 accumulation in papillae and hypersensitive response during the barley-powdery mildew interaction. Plant J 11 1187-1194... 

Hairy Leukoplakia. This is an abnormal condition of the mouth in which white plaques appear on the surfaces of the tongue. These plaques are not due to the overgrowth of a fungus or bacterium. They are due to the abnormal growth of the papillae cells of the tongue. These plaques cannot be scraped off they resemble cancer cells and appear as a result of infection with Epstein-Barr virus, which is a member of the herpes virus family. 

Fig. 9.14 SEM images of lotus-like and honeycomb-like aligned CNT films (a) top view of lotus-like aligned CNT films (b) enlarged view of single micro-papilla of the lotus-like aligned CNT films and (c) top view of honeycomb-like aligned CNT films (Kashi wagi et al. 2002. With permission from all authors and Wiley)...

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