Implications of Control Theory for Homeostasis and Phosphorylation of Transport Molecules*

Hansen, Ulf‐Peter

doi:10.1111/j.1438-8677.1990.tb00120.x

Cited by 14 publications

(4 citation statements)

References 25 publications

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“…The control loop involved is very slow (% = 2220 s). This is reasonable from the biological point of view, because control mechanisms need energy (Hansen 1990). Consequently, fast control mechanisms would be more expensive for the organism.…”

Section: Discussionmentioning

confidence: 99%

Light dependence of protoplasmic streaming in Nitella flexilis L. as measured by means of laser-velocimetry

Plieth

Hansen

1992

Planta

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Laser-velocimetry was applied in order to study the effect of light on the velocity of protoplasmic streaming (pps) in Characean cells. A change from dark to light (= 6 W · m(-2)) leads to an acceleration of streaming by about 15-30% with a time-constant of approx. 300 s. The transition from light to dark causes a transient decrease of velocity below the original dark level. This response occurs with a time constant of about 500 s. It returns to its initial value with a time-constant of about 2000 s. This may indicate that a control loop of cytosolic homeostasis takes a decrease in pCa more seriously than an increase. A possible involvement of temperature effects caused by illumination was excluded by measuring the influence of temperature. Steady-state velocity of streaming changed by 5% per 1° C. Irradiation with infra-red light (λ > 780 nm) did not cause a change in velocity. The absence of a light effect on streaming velocity in the presence of 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU) shows that photosynthesis and not phytochrome is involved. The role of light-induced changes of pCa is discussed, especially with respect to the hypothesis of Vanselow and Hansen (1989, J. Membr. Biol. 110, 175-187) that photosynthesis acts on the plasmalemma K(+)-channel via light-induced uptake of Ca(2+) into the chloroplasts.

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Section: Discussionmentioning

confidence: 99%

Light dependence of protoplasmic streaming in Nitella flexilis L. as measured by means of laser-velocimetry

Plieth

Hansen

1992

Planta

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“…The detailed mechanism used for this task may be complicated. A minimum scheme for such a homeostatic controller was suggested by Hansen (1990). The reaction there was furnished for homeostasis in a compartment by mean of transmembrane transport, however, the same equations hold for homeostasis by chemical reactions.…”

Section: The Modelmentioning

confidence: 99%

Electrically Triggered All-or-None Ca2+-Liberation during Action Potential in the Giant Alga Chara

Wacke¹,

Thiel

2001

The Journal of General Physiology

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Electrically triggered action potentials in the giant alga Chara corallina are associated with a transient rise in the concentration of free Ca2+ in the cytoplasm (Ca2+cyt). The present measurements of Ca2+cyt during membrane excitation show that stimulating pulses of low magnitude (subthreshold pulse) had no perceivable effect on Ca2+cyt. When the strength of a pulse exceeded a narrow threshold (suprathreshold pulse) it evoked the full extent of the Ca2+cyt elevation. This suggests an all-or-none mechanism for Ca2+ mobilization. A transient calcium rise could also be induced by one subthreshold pulse if it was after another subthreshold pulse of the same kind after a suitable interval, i.e., not closer than a few 100 ms and not longer than a few seconds. This dependency of Ca2+ mobilization on single and double pulses can be simulated by a model in which a second messenger is produced in a voltage-dependent manner. This second messenger liberates Ca2+ from internal stores in an all-or-none manner once a critical concentration (threshold) of the second messenger is exceeded in the cytoplasm. The positive effect of a single suprathreshold pulse and two optimally spaced subthreshold pulses on Ca2+ mobilization can be explained on the basis of relative velocity for second messenger production and decomposition as well as the availability of the precursor for the second messenger production. Assuming that inositol-1,4,5,-trisphosphate (IP3) is the second messenger in question, the present data provide the major rate constants for IP3 metabolism.

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“…All processes which lead to a disturbance of the cytosolic pH (one of them being the light-induced uptake of H + into the chloroplasts) initiate the activity of a pH-controlling system which causes oscillations of membrane potential (Fisahn et al 1986;Hansen 1990).…”

Section: Introductionmentioning

confidence: 99%

Light-induced cytosolic calcium transients in green plant cells. ll. The effect on a K + channel as studied by a kinetic analysis in Chara corallina

Plieth

Sattelmacher

Hansen

1998

Planta

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The¯uorescent dye chlorotetracycline was used to study the relationship between the light-induced decrease in cytosolic free calcium concentration, [Ca 2+ ] c , and its eect on ion transport at the plasma membrane in the giant cells of Chara corallina Klein ex Willd. A kinetic analysis of the simultaneously measured lightinduced changes in membrane potential and in [Ca 2+ ] c led to the same time constant of about 40 s. The reversal potential of the light eect on membrane potential was in agreement with the dominant role of a K + channel in the plasma membrane. Thus, the experiments reported here provide evidence for the following light-driven signal transduction chain from the chloroplasts to K + transport of the plasma membrane: (i) light causes an uptake of Ca 2+ into the chloroplasts, (ii) this causes a decrease in cytosolic [Ca 2+ ] c , (iii) this leads to a decrease in the activity of a K + channel. The results also initiated a re-analysis of previously published data of the light eect on the velocity of cytosolic streaming and supported the hypothesis that Ca 2+¯u xes coming out of the chloroplasts upon darkening cause a Ca 2+ -induced phosphorylation of myosin, which slows down cytoplasmic streaming.

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Implications of Control Theory for Homeostasis and Phosphorylation of Transport Molecules*

Cited by 14 publications

References 25 publications

Light dependence of protoplasmic streaming in Nitella flexilis L. as measured by means of laser-velocimetry

Light dependence of protoplasmic streaming in Nitella flexilis L. as measured by means of laser-velocimetry

Electrically Triggered All-or-None Ca2+-Liberation during Action Potential in the Giant Alga Chara

Light-induced cytosolic calcium transients in green plant cells. ll. The effect on a K + channel as studied by a kinetic analysis in Chara corallina

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