Sugar sensitive cells

Receptor cells sensitive to host plant compounds that stimulate feeding have also been identified in several species of Yponomeuta moths. Y. cagnagellus feeding on Euonymus has one dulcitol (sugar)-sensitive cell in the medial and one in the lateral sensillum styloconicum (van Drongelen, 1979,1980). Another species, Y. evonymellus, is also stimulated by dulcitol at the sensory and behavioral level even though the compound does not occur in its host plant. This contradictory result may be explained by the possible presence of dulcitol in an ancestral host plant (van Drongelen, 1979,1980). 

Mitchell, B. K. and Gregory, P. (1979) Physiology of the maxillary sugar sensitive cell in the red turnip beetle, Entomoscelis americana, J, comp. Physiol, 132, 167-78. 

A shift of phosphate from extracellular fluid to intracellular fluid is a common cause of hypophosphatemia. A major etiology of low serum phosphate is carbohydrate-induced stimulation of insuhn secretion, which increases the transport of glucose and phosphate into insulin-sensitive cells, where it is incorporated into sugar phosphates and ATP. Oral or intravenous carbohydrate and injected insuhn decrease serum phosphate. Refeeding of malnourished individuals creates an anabohc state, causing an intracellular shift of phosphate. Respiratory alkalosis leads to an increase in intracellular pH, which activates phosphoffuctokinase and accelerates glycolysis, causing a shift of phosphate into the cell. 

Hansen (1978) and Hansen and Wieczorek (1981) compared the sugar receptor cells of various insect species in detail. Most cells were found to be sensitive to glucose and sucrose (with the exception of lepidopteran larvae), and seem to have at least two receptor sites for pyranoses and furanoses. A closer examination of the sugar cells reveals remarkable differences between cells of different insects and even closely related species (Hansen and Wieczorek, 1981 Jakinovich etal., 1981 Mitchell and Gregory, 1979). An explanation for these differences could lie in the adaptations to specific food sources and feeding behaviors. However, this is not evident in Pieris rapae when stimulatory activity and nutritive values are compared (Kusano and Sato, 1980 Mitchell, 1981). The classical blowfly water receptor also reacts to sugars. The receptor site in this cell is similar to the furanose site of the sugar receptor cell (Wieczorek, 1980). 

In addition to the mechanoreceptor and the sugar-, water- and salt-sensitive cells, the chemoreceptive sensilla of the blowfly labellum contain a fifth or anion cell. The sensitivity spectrum of this cell is not well defined. Dethier and Hanson (1968) foimd that this cell responds to salts of fatty acids of Cj to chain length. Since natural foods like honey and apple also strongly stimulated this cell (Dethier, 1974a), it is evident that more investigation is required to characterize its sensitivity spectrum. 

An ECD measures the current generated by electroactive analytes in the HPLC eluent between electrodes in the flow cell. It offers sensitive detection (pg levels) of catecholamines, neurotransmitters, sugars, glycoproteins, and compounds containing phenolic, hydroxyl, amino, diazo, or nitro functional groups. The detector can be the amperometric, pulsed-amperometric, or coulometric type, with the electrodes made from vitreous or glassy carbon, silver, gold, or platinum, operated in the oxidative or reductive mode. Manufacturers include BSA, ESA, and Shimadzu. 

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