. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 380 H. G. TRAPIDO-ROSENTHAL ET AL •\: o CD 300 % 200 • 3 CL E • 100 () /,\ [ ] Control Saline HI Saline plus Taurine (100) 0) (1000) Mil 1 23456 Cell Number Figure 8. Mean responses (+SEM) of taurine-sensitive cells in the presence and absence of taurine in the perfusion saline. The micromolar concentrations of taunne in the perfusion medium are indicated in pa- rentheses. For each cell, a test-stimulus concentration close to the EC50 was presented via the carrier stream of ASW. boundary layer of seawater. This boundary l
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 380 H. G. TRAPIDO-ROSENTHAL ET AL •\: o CD 300 % 200 • 3 CL E • 100 () /,\ [ ] Control Saline HI Saline plus Taurine (100) 0) (1000) Mil 1 23456 Cell Number Figure 8. Mean responses (+SEM) of taurine-sensitive cells in the presence and absence of taurine in the perfusion saline. The micromolar concentrations of taunne in the perfusion medium are indicated in pa- rentheses. For each cell, a test-stimulus concentration close to the EC50 was presented via the carrier stream of ASW. boundary layer of seawater. This boundary layer can also limit the rate of amino acid efflux from aesthetascs by acting as a buffer between the sensilla and seawater outside the aesthetasc tuft. If it is assumed that a major fraction of the glycine and taurine leaking from the cells of an aesthetasc during the interflick interval remains within the sensillar lymph (volume = 200 pi), then only about 300 ms would be required for the sensillum to attain the equilibrium concentrations measured in the current study (Fig. 9). Hence, during a considerable portion of each interflick interval, the sensillar receptors are probably ex- posed to backgrounds ranging from low nanomolar in the case of taurine, to as high as micromolar in the case of glycine. When sensilla are immersed in seawater, the efflux of glycine and taurine from intracellular stores does not continue unabated until the concentration in the sensilla and medium are equal. Rather, at equilibrium the intra- cellular concentration is about 100,000-fold greater than the medium. Uptake systems in the sensilla are the most plausible mechanisms for regulating the amino acid efflux. The hypothesis that uptake systems might control the net efflux or loss of intracellular amino acids was proposed by Wright and Secomb (1986) based on studies with the gills of marine mussels. These workers noted that mussel gills contain intracellular taurine at a concentration of
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
