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  • 1990-1994  (3)
  • Calliphora vicina  (1)
  • Immersion diuresis  (1)
  • Sodium channel  (1)
  • 1
    ISSN: 1432-1351
    Keywords: Calliphora vicina ; Circadian rhythms ; Phase response curve ; RH 5849 ; Ecdysteroids ; Computer modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract RH 5849, a non-steroidal ecdysteroid mimic, was found to cause consistent phase shifts in the circadian rhythm of locomotor activity of the blowfly, Calliphora vicina. This compound causes phase advances in the early subjective night and phase delays in the late subjective night. This effect is the opposite, but not the mirror image of the phase response curve obtained for 1 h light pulses. This suggests that ecdysteroids might act as entraining agents via the output pathway by feedback to “clock” neurons in the brain. A computer model based on 12 pacemaker neurons with circadian periods (τ values) from short to long without simulated feedback from the ecdysteroid system becomes arrhythmic; with feedback, the oscillators become synchronized to a common period. The possible role of ecdysteroids as endogenous synchronizing agents in the insect circadian system is discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biomedical science 1 (1994), S. 172-178 
    ISSN: 1423-0127
    Keywords: SK&F 96365 ; Crotamine ; Calcium channel blocker ; Local anesthetic ; Sodium channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effects of SK&F 96365, a blocker of the receptor-operated Ca2+ channel, on contractilities and the Na+ channel of mouse diaphragm were studied. SK&F 96365 (10–50 µM) reversibly inhibited twitches, tetanic contractions and muscle and nerve action potentials. The IC50 was 17–24 µM. The inward Na+ current was suppressed and its recovery from inactivations delayed. Crotamine, a peptide toxin that binds to neurotoxin receptor site 3 of the muscle Na+ channel, enhanced the inhibitory effects of SK&F 96365 and reduced the IC50 to about 4 µM. Veratridine had similar effects, although it was less effective than crotamine. On the other hand, the crotamine-induced membrane depolarizations and spontaneous discharges of muscle action potentials were inhibited by SK&F 96365 noncompetitively. The inhibitory effects of tetrodotoxin and tetracaine were additive with those of SK&F 96365 but were enhanced slightly by crotamine. The results suggested that SK&F 96365 acts on a distinct site and blocks the Na+ channel of excitable membranes at a concentration range that inhibits the receptor-operated calcium channel.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 67 (1993), S. 523-527 
    ISSN: 1439-6327
    Keywords: Breath-hold diver ; Ama ; Immersion diuresis ; Immersion natriuresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Head-out water immersion (HOI) induces a profound diuresis and natriuresis, which may endanger the body fluid balance of breath-hold divers during prolonged diving work. To investigate if adaptation is acquired by professional breath-hold divers, we have evaluated renal responses to 3-h HOI in 5 Korean women divers (Amas) and 11 nondiving housewives (controls). In both control and diver groups, the average urine flow during 3-h immersion was four times greater and Na+ excretion was 70%–80% greater than the pre-immersion value [urine flow: 3.7 (SD 1.0) ml·min−1 vs 0.9 (SD 0.4), P〈0.001, in controls; 4.3 (SD 0.9) vs 1.1 (SD 0.4), P〈0.001, in divers; Na+ excretion: 270 (SD 176) μmol· min−1 vs 161 (SD 84), P〈0.025, in controls; 303 (SD 31) vs 164 (SD 62), P〈0.005, in divers]. In all cases, the values for a given period were not significantly different between the two groups. The plasma concentrations of Na+ and osmolality, and renal clearance of creatinine did not change significantly. However, the osmolal clearance increased [from 2.0 (SD 0.8) ml·min−1 to 2.8 (SD 0.7), P〈0.05, in the controls; from 2.2 (SD 0.4) to 2.6 (SD 0.4), P〈0.05, in the divers] and free water clearance changed from negative to positive values [from -1.1 (SD 0.5) ml·min−1 to 1.2 (SD 0.3), P〈0.005, in the controls; from -1.2 (SD 0.4) to 1.6 (SD 1.1), P〈0.01, in the divers] during immersion, again the pattern of change being similar in the two groups. It was, therefore, concluded from our study that the renal response to HOI was unchanged in the Korean women professional breath-hold divers compared to the nondiving women.
    Type of Medium: Electronic Resource
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