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  • Cell cycle  (2)
  • healthy volunteers  (2)
  • Springer  (4)
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  • Springer  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Effects of light and acetate on the liberation of zoospores by a mutant strain ofChlamydomonas reinhardtii (1989)
    Springer
    Planta 178 (1989), S. 456-462 
    Details
    ISSN: 1432-2048
    Keywords: Cell cycle ; Chlamydomonas ; Cell wall ; Autolysin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In light-dark-synchronized cultures of the unicellular green algaChlamydomonas reinhardtii, release of zoospores from the wall of the mother cell normally takes place during the second half of the dark period. The recently isolated mutant ‘ls’, however, needs light for the liberation of zoospores when grown photoautotrophically under a 12 h light-12 h dark regime. The light-induced release of zoospores was found to be prevented by addition of the photosystem-II inhibitor 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea. Furthermore, light dependence of this process was shown to be abolished when the mutant ‘ls’ was grown either photoautotrophically under a 14 h light-10 h dark regime or in the presence of acetate. Our findings indicate that the light-dependency of zoospore liberation observed in cultures of this particular mutant during photoautotrophic growth under a 12 h light-12 h dark regime might be attributed to an altered energy metabolism. The light-induced release of zoospores was found to be prevented by addition of cycloheximide or chloramphenicol, antibiotics which inhibit protein biosynthesis by cytoplasmic and organellar ribosomes, respectively. Actinomycin D, an inhibitor of RNA synthesis, however, did not affect the light-induced liberation of zoospores. Sporangia accumulate in stationary cultures of the mutant ‘ls’. Release of zoospores was observed when these sporangia were collected by centrifugation and incubated in the light after resuspension in fresh culture medium. Since liberation of zoospores was not observed after dilution of the stationary cultures with fresh culture medium, we suppose that components which interfere with the action of the sporangial autolysin are accumulated in the culture medium of the mutant ‘ls’.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00963815
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  • 2
    Electronic Resource
    Electronic Resource
    The behaviorally active peptide ACTH 4-10: Measurement in plasma and pharmacokinetics in man (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 371-377 
    Details
    ISSN: 1432-1041
    Keywords: ACTH 4-10 ; radioimmunoassay ; plasma extraction ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A specific radioimmunoassay for the quantitative measurement of ACTH 4-10 and a procedure for its extraction from plasma have been developed. Its pharmacokinetics was studied in eight healthy male volunteers given ACTH 4-10 125 µg/kg body weight as a bolus i.v. injection, by infusion and intranasally. Following the i.v. bolus, plasma levels rapidly declined biexponentially, with half-lives of 0.39±0.05 min for the α-phase and 3.84 ± 1.5 min for the β-phase (mean±SD). The constant rate i.v. infusion yielded steady-state levels between 0.74 and 5.06 ng/ml plasma. Administered as intranasal spray, absorption of intact ACTH 4-10 was low and variable (maximal bioavailability 7.6%). The results are discussed in relation to the dose-dependent effects of ACTH 4-10 on the auditory evoked potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00561367
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  • 3
    Electronic Resource
    Electronic Resource
    Fluocortolone: Pharmacokinetics and effect on ACTH and cortisol secretion during daily and alternate-day administration (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 177-181 
    Details
    ISSN: 1432-1041
    Keywords: fluocortolone ; cortisol ; alternate day therapy ; plasma cortisol ACTH ; plasma level ; healthy volunteers ; circadian rhythm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of fluocortolone and its effect on the circadian rhythm of plasma cortisol and ACTH have been studied during different schedules of oral administration. Groups of 6 healthy male adults were given a single daily dose of fluocortolone 5, 10 and 20 mg, and another group received 20 mg every second day. Administration to all groups was continued for 8 days. Pharmacokinetic parameters of fluocortolone (half lives of absorption- t1/2a and elimination t1/2e, volume of distribution V and oral clearance (CL/f) were independent of the duration of treatment and dose. Areas under the plasma level curves, AUC and Cmax values increased in proportion to the dose, indicating dose linearity of fluocortolone pharmacokinetics. A normal morning cortisol peak occurred during all treatment schedules, which indicates that circadian cortisol secretion was not seriously affected by the glucocorticoid treatment. On the other hand, when the level of circulating fluocortolone was high the 12.00 a.m. and 4.00 p.m. cortisol levels were diminished compared to the pre and posttreatment values. There was no definite correlation between the ACTH and cortisol levels, either on treatment or on control days. ACTH levels were suppressed by daily treatment with the 20 mg dose. Thus, even during administration of a high dose of a glucocorticoid, the circadian secretion of cortisol can be preserved if the treatment is adjusted according to the half-life of the drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609249
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  • 4
    Electronic Resource
    Electronic Resource
    The Chlamydomonas cell cycle is regulated by a light/dark-responsive cell-cycle switch (1987)
    Springer
    Planta 172 (1987), S. 463-472 
    Details
    ISSN: 1432-2048
    Keywords: Cell cycle ; Chlamydomonas (cell cycle) ; Light/dark response (cell cycle)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cultures of the unicellular green alga Chlamydomonas reinhardii can be synchronized by light/dark cycling not only under photoautotrophic but also under mixotrophic growth conditions. We observed that cultures synchronized in the presence of acetate continue to divide synchronously for one cell-cycle period when transferred to heterotrophic growth conditions. This finding enabled us to investigate the differential effects of light on cell growth and cell division. When cells were exposed to continuous light at the beginning of the growth period they entered the division phase earlier than dark-grown cells as a consequence of an increased growth rate. Illumination at the end of the growth period, however, caused a considerable delay in cell division and an extended growth period. The light-induced delay in cell division was also observed in the presence of 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosystem II. This finding demonstrates that cell division is directly influenced by a light/dard-responsive cell-cycle switch rather than by light/dark-dependent changes in energy metabolism. The importance of this light/dark control to the regulation of the Chlamydomonas cell cycle was investigated in comparison with other control mechanisms (size control, time control). We found that the light/dard-responsive cell-cycle switch regulates the transition from G1-to S-phase. This control mechanism is effective in cells which have attained the commitment to at least one round of DNA replication and division but have not attained the maximal cell mass which initiates cell division in the light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393861
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