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  • Lobster  (3)
  • Springer  (3)
  • American Chemical Society
  • American Physical Society
  • International Union of Crystallography
  • PANGAEA
  • 1
    ISSN: 1432-1351
    Keywords: Lobster ; Antenna ; Chemoreceptor organs ; Amino acids ; Concentration dependent tuning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. We determined the spectral tuning properties of 47 chemoreceptor cells of the antenna of Homarus americanus to amino acids and other compounds. Tests with 17 single compounds at 10-4 M showed 40 of 47 cells responded best to hydroxyproline, 4 cells to taurine and 3 cells to betaine. Mean tuning breadth (H-metric) doubled with 10 fold increase in concentration. 2. In hydroxyproline-best cells the mean threshold for hydroxyproline (Hyp) was found between 10-7 M and 10-8 M. An equimolar mixture of the 17 compounds generated a shallower stimulus-response function with thresholds similar to Hyp function (mixture suppression). Hyp-best cells were relatively narrowly tuned, often with arginine or leucine as second best stimuli. 3. Thus, physiologically the second antenna of H. americanus is a major chemoreceptor organ. It is more than any of the 5 chemoreceptor organs studied so far dominated by a single best-cell type (Hyp). Receptor cell composition of antennae resembles that of antennules more than legs or maxillipeds. Hyp-best cells in antennae and lateral antennules have similar tuning spectra. 4. Our cell tuning studies argue for independent receptors for all amino acids tested. We conclude that diversity of receptor cell tuning is created by cell-specific blends of receptors. At the organ level, differences in organ tuning result from different blends of receptor cells.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 175 (1994), S. 95-105 
    ISSN: 1432-1351
    Keywords: Chemoreceptor ; Response reliability ; Intensity coding ; Hydroxy-L-proline ; Lobster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 1. To determine reliability of stimulus intensity coding we measured the response variability of 30 hydroxy-L-proline sensitive chemoreceptor cells from antennules of Homarus americanus. First, cells were tested with 5 repeated presentations of 10-5 M and l0-4 M hydroxy-L-proline. Then a stimulus response function was determined in each cell from l0-6to 5 × l0-4 M in half log steps. 2. Population mean responses to repetitive stimulation showed little variability and mean stimulus response functions increased monotonically. In contrast, most individual cells showed a high response variability and no single cell stimulus-response function increased monotonically. The greatest response variability occurred between different cells. 3. Mean response magnitude of a 30 cell population allowed reliable discrimination between 10-5 M and l0-4 M hydroxy-L-proline for each of the 5 repetitions. It also allowed discrimination of all concentrations of hydroxy-L-proline tested. Across-fiber response patterns also differed significantly with concentration while they remained relatively stable with repetition of the same stimulus. 4. We applied different analytical methods to test the reliability of response magnitude and across-fiber pattern as possible codes for intensity discrimination. We demonstrated that a random population of rather unreliable receptor cells could provide remarkably reliable intensity information to the CNS based on response magnitude or across-fiber pattern.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 166 (1990), S. 865-874 
    ISSN: 1432-1351
    Keywords: Chemoreceptor ; Sensory adaptation ; Lobster ; Glutamate receptor cell ; Signal-to-background ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary and conclusion 1. We determined the time course of cumulative adaptation, e.g. the recovery from the effects of prior stimulation, in 127 glutamate-sensitive chemoreceptor cells in extracellular recordings from the walking legs of the lobster, Homarus americanus. 2. Interstimulus intervals of 5 s, 10 s, or 20 s did not affect the degree of cumulative adaptation of glutamate sensitive cells as a population. Cumulative adaptation represents a change in state rather than a gradual process. Individual cells revealed great diversity in the time course of cumulative adaptation, regardless of interstimulus interval. 3. Various combinations of high and low glutamate backgrounds and stimulus intensities showed that the stimulus-to-background ratio did not determine the time course of cumulative adaptation. 4. Low response magnitudes, regardless of what caused them, resulted in less cumulative adaptation. 5. Since cumulative adaptation was independent from background adaptation, underlying cellular mechanisms may be different. 6. Cumulative adaptation reduces the cell's response variability and might therefore enhance the temporal resolving power of single cells. 7. The rates of adaptation and disadaptation determine the temporal filter properties of a cell. Background adaptation keeps a cell in a working range where instantaneous (chemical) contrast can be measured.
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