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1.
Rolf Borchert 《Planta》1985,165(3):301-310
For experimental induction of crystal cells (=crystal idioblasts) containing calcium-oxalate crystals, the lower epidermis was peeled from seedling leaflets of Gleditsia triacanthos L., exposing the crystal-free mesophyll and minor veins to the experimental solutions on which leaflets were floated for up to 10 d under continous light. On 0.3–2.0 mM Ca-acetate, increasing numbers of crystals, appearing 96 h after peeling, were induced. The pattern of crystal distribution changed with Ca2+-concentration ([Ca2+]): at low [Ca2+], crystals formed only in the non-green bundlesheath cells surrounding the veins, believed to have a relatively low Ca2+-extrusion capacity; at higher [Ca2+], crystals developed in up to 90% of the mesophyll cells, and at supraoptimal [Ca2+], large extracellular crystals formed on the tissue surface. By sequential treatments with solutions of different [Ca2+], the following three phases were identified in the induction of crystal cells: (1) during the initial 24-h period (adaptive aging), Ca2+ is not required and crystal induction is not possible; (2) during the following 48 h (induction period), exposure to 1–2 mM Ca-acetate induces the differentiation of mesophyll cells into crystal cells; (3) crystal growth begins 72 h after the start of induction. In intact leaflets of Albizia julibrissin Durazz., calcium-oxalate crystals are found exclusively in the bundle-sheath cells of the veins, but crystals were induced in the mesophyll of peeled leaflets floating on 1 mM Ca-acetate. Exposure to inductive [Ca2+] will thus trigger the differentiation of mature leaf cells into crystal cells; the spatial distribution of crystals is determined by the external [Ca2+] and by the structural and functional properties of the cells in the tissue. 相似文献
2.
Rolf Borchert 《Planta》1990,182(3):339-347
Changes in the spacing patterns of Ca-oxalate crystals during enlargement ofCarya ovata Mill. leaves were quantified by computerized image-analysis. Single Ca-oxalate crystals form in the vacuoles of young mesophyll
cells transformed into crystal cells Crystals are very small in newly induced crystal cells and increase in size throughout
leaf development. Crystal patterns thus reflect both induction and relative age of crystal cells. Shortly after the emergence
of young leaves from the bud, very small crystals are formed in the mesophyll at high density. As leaves expand, these crystals
grow larger and become separated by increasing distances. New small crystals appear in the gaps between the older, larger
crystals. Later crystal patterns consist of widely spaced, larger crystals only. Finally, clusters of small crystals are formed
again in the gaps between large crystals. No crystals were observed in young leaves expanding in a moist chamber, but large
numbers of crystal cells were induced experimentally in sections of immature leaves floating on 4 mM Ca-acetate. The observations
support the following mechanism of crystal-pattern formation: Ca2+ carried into leaves with the transpiration stream acts as the developmental signal inducing transdifferentiation of a few
mesophyll cells into crystal cells when apoplastic [Ca2+] rises. Crystal cells precipitate absorbed Ca2+ as oxalate and, acting as Ca2+ sinks, inhibit crystal-cell induction in their vicinity by depleting apoplastic Ca2+. This prevents close spacing of crystal cells. New crystal cells form in the gaps between the depletion zones of older crystal
cells when these move apart during leaf expansion. Later changes in crystal patterns result from increasing sink strength
of crystal cells, lowered inducibility of mesophyll cells, and increased Ca2+ influx into leaves during intensive transpiration. Throughout leaf development, spacing of crystal cells permits rapid secretion
of apoplastic Ca2+ as Ca-oxalate.
Dedicated to Professor Erwin Bünning, University of Tübingen, Germany, who pioneered the analysis of spacing patterns 相似文献
3.
E. A. C. MacRobbie 《Planta》1989,178(2):231-241
The influx of 45Ca into isolated guard cells of Commelina communis L. has been measured, using short uptake times, and washing in ice-cold La3+-containing solutions to remove extracellular tracer after the loading period. Over 0.5–4 min the uptake was linear with time, through the origin. Over 20–200M external Ca2+ the influx measured with 10–20 mM external KCl was in the range 0.3–2.3 pmol·cm-2·s-1 (on the basis of estimated guard-cell area); with only 1 mM KCl externally the 45Ca influx was significantly reduced, in the range 0.3–1.1 pmol·cm-2·s-1 for external Ca2+ of 50–100 M. The results indicate that the Ca-channel is voltage-sensitive, opening with depolarisation. No consistent effect of the addition of abscisic acid could be found. In different experiments, on the addition of 0.1 mM abscisic acid the Ca2+ influx was sometimes stimulated by 28–79%, was sometimes unaffected, and was sometimes inhibited by 16–29%. The results rule out a long-lasting stimulation of 45Ca influx by ABA, but they do not rule out a transient stimulation followed by inhibition, perphaps as a consequence of down-regulation of Ca2+ influx by increasing cytoplasmic Ca2+. The hypothesis that ABA may act via an action on Ca2+ influx, increasing cytoplasmic Ca2+, with consequent effects on voltage-dependent and Ca2+-dependent ion channels in both plasmalemma and tonoplast, is neither proved nor disproved by these results.Abbreviations ABA
abscisic acid
- Cao, Ko
external Ca and K concentrations 相似文献
4.
W. S. Marshall S. E. Bryson J. S. Burghardt P. M. Verbost 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(4):268-277
We examined transepithelial transport of Ca2+ across the isolated opercular epithelium of the euryhaline killifish adapted to fresh water. The opercular epithelium, mounted in vitro with saline on the serosal side and fresh water (0.1 mmol·l–1 Ca2+) bathing the mucosal side, actively transported Ca2+ in the uptake direction; net flux averaged 20–30 nmol·cm–2·h–1. The rate of Ca2+ uptake varied linearly with the density of mitochondria-rich cells in the preparations. Ca2+ uptake was saturable, apparent K
1/2 of 0.348 mmol·l–1, indicative of a multistep transcellular pathway. Ca2+ uptake was inhibited partially by apically added 0.1 mmol·l–1 La3+ and 1.0 mmol·l–1 Mg2+. Addition of dibutyryl-cyclic adenosine monophosphate (0.5 mmol·l–1)+0.1 mmol·l–1 3-isobutyl-l-methylxanthine inhibited Ca2+ uptake by 54%, but epinephrine, clonidine and isoproterenol were without effect. Agents that increase intracellular Ca2+, thapsigargin (1.0 mol·l–1, serosal side), ionomycin (1.0 mol·l–1, serosal side) and the calmodulin blocker trifluoperazine (50 mol·l–1, mucosal side) all partially inhibited Ca2+ uptake. In contrast, apically added ionomycin increased mucosal to serosal unidirectional Ca2+ flux, indicating Ca2+ entry across the apical membrane is rate limiting in the transport. Verapamil (10–100 mol·l–1, mucosal side), a Ca2+ channel blocker, had no effect. Results are consistent with a model of Ca2+ uptake by mitochondria rich cells that involves passive Ca2+ entry across the apical membrane via verapamil-insensitive Ca2+ channels, intracellular complexing of Ca2+ by calmodulin and basolateral exit via an active transport process. Increases in intracellular Ca2+ invoke a downregulation of transcellular Ca2+ transport, implicating Ca2+ as a homeostatic mediator of its own transport.Abbreviations
DASPEI
2-(4-dimethylaminostyryl)-N-ethylpyridinium iodide
-
db-cAMP
dibutyryl-cyclic adenosine monophosphate
-
FW
fresh water
-
G
t
transepithelial conductance
-
I
sc
short-circuit current
-
IBMX
3-isobutyl-1-methylxanthine
-
SW
sea water
-
TFP
trifluoperazine
-
V
t
transepithelial potential 相似文献
5.
L. Oliveira 《Planta》1992,188(3):279-288
Germination of aplanospores in Vaucheria longicaulis Hoppaugh var. macounii Blum proceeds through three stages of development. Stage I begins with the initiation of germination and lasts approx. 2 h. During this stage germinating filaments grow at an accelerated rate (266 ± 12 m · h–1). Stage II is characterized by a sharp decline in the growth rate of germinating filaments (96 ± 4 m · h–1) and lasts 4 h. This is followed, during the next 4 h, by a recovery in the growth rate (168 ± 8 m · h–1) of germinating filaments, stage III. Growth rates stabilize and remain unchanged during subsequent development (Oliveira and Fitch, 1988, J. Submicrosc. Cytol. Pathol. 20, 397–406). The Ca2+-influx modulators LaCl3, nifedipine and methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4 (2-trifluoromethylphenyl)-pyridine-5-carboxylate (Bay K-8644), the ionophore calcimycin (A23187), the intracellular Ca2+-release antagonist 8-N-N'-(diethylamino)-octyl-3,4, 5-trimethoxybenzoate (TMB-8), the Ca2+-uptake inhibitor ruthenium red and the phosphoinositide-cycle modulators LiCl and myo-inositol show that the events required for the initiation are distinct from those required for the completion of each stage of germination. These studies in conjunction with microinjection of germinating filaments with inositol 1,4,5-trisphosphate, the natural ligand for Ca2+ release from Ca-storing organelles (endoplasmic reticulum, vacuole), and treatment with chlorotetracycline (CTC), to visualize the distribution of membrane-bound Ca2+ reveal that both the initiation and completion of each stage of germination are controlled by Ca2+ signals which are restricted to well-defined time intervals and are modulated by the origin (source) of Ca2+.Abbreviations BAPTA
1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid
- Bay K-8644
methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4(2-trifluoromethylphenyl)-pyridine-5-carboxylate
- CTC
chlorotetracycline
- InsP3
inositol 1,4,5-trisphosphate
- RR
ruthenium red
- TMB-8
8-N-N-(diethylamino)-octyl-3,4,5-trimethoxybenzoate
The author wishes to express his gratitude to the technical group of the Immunocytochemistry Unit for their help with the microinjection studies. This work was supported by a grant from the Natural Sciences and Engineering Research Council of Canada (grant A-7844). 相似文献
6.
Influx of 45Ca into internodal cells of Chara corallina has been measured, using short uptake times, and a wash in ice-cold La3+-containing pondwater after the labelling period to overcome the difficulty of distinguishing extracellular tracer from that in the cell. Over 5–15 min the uptake was linear with time, through the origin. The basal influx from 0.1 mM Ca2+ externally was 0.25–0.5 pmol·cm-2·s-1, but some batches of cells showed higher fluxes. The influx was markedly stimulated by depolarisation in pondwater containing 20 mM K+. In cells in which the control flux was less than about 0.5 pmol·cm-2·s-1 there was no effect of 50 M nifedipine. In cells in which the control flux was greater than about 0.5 pmol·cm-2·s-1 (whether by natural variability, pretreatment, or by depolarisation in 20 mM K+), the flux was reduced by 50 M nifedipine to a value in the range 0.25–0.59 pmol·cm-2·s-1. It is suggested that two types of Ca-channel are probably involved, both opening on depolarisation, but only one sensitive to nifedipine. The flux was inhibited by 10 M BAY K 8644, which in animal cells more commonly opens Ca-channels. The apparent influx measured over long uptake times was much reduced, and the kinetics indicated filling a pool of apparent size about 1.45 nmol·cm-2 with a halftime of about 38 min, probably representing cytoplasmic stores. It is argued that in spite of the very small pool of (free+bound) cytoplasmic Ca2+ the measured influx is a reasonable estimate of the influx at the plasmalemma.Abbreviations 0.4K-APW6
artificial pondwater, pH 6, containing 0.4 mM KCl
- 20 K-APW6
artificial pondwater, pH 6, containing 20 mM KCl
- Cao
external Ca2+ 相似文献
7.
Enhanced elongation of coleoptile cells has been proposed to be related to a rise in secretory activity. Therefore, to obtain a direct measurement of exocytotic events in maize (Zea mays L.) coleoptile protoplasts we used the patch-clamp method to record changes in membrane capacitance (Cm) as a parameter proportional to fluctuations of the membrane surface area. The secretory activity of protoplasts was correlated with the cytosolic free Ca2+ concentration ([Ca2+]cyt): dialyzing protoplasts with 1 M [Ca2+]cyt caused a steady rise in Cm of 3.3 ± pF·s–1. In contrast, dialysis with a solution containing <20 nM Ca2+ produced a small and persistent decrease in Cm. This demonstrates that secretory activity in coleoptile cells can be controlled by factors which modulate [Ca2+]cyt.Abbreviation Cm
membrane capacitance
This work was made possible by a visiting grant from the Research Council of Slovenia and financial support of the Deutsche Forschungsgemeinschaft to G.T. We are grateful to Dr. W. Diekmann (University of Göttingen) for teaching us the preparation of coleoptile protoplasts. 相似文献
8.
Summary The actin-activated ATPase activityPhysarum myosin was shown to be inhibited of M levels of Ca2+. To determine if Ca2+ regulates ATP-dependent movement ofPhysarum myosin on actin, latex beads coated withPhysarum myosin were introduced intoChara cells by intracellular perfusion. In perfusion solution containing EGTA, the beads moved along the parallel arrays ofChara actin filaments at a rate of 1.0–1.8 m/sec; however, in perfusion solution containing Ca2+, the rate reduced to 0.0–0.7 m/sec. The movement of beads coated with scallop myosin, whose actin-activated ATPase activity is activated by Ca2+, was observed only in the perfusion solution containing Ca2+, indicating that myosin is responsible for the inhibitory effect of Ca2+ onPhysarum myosin movement. The involvement of this myosin-linked regulation in the inhibitory effect of Ca2+ on the cytoplasmic streaming observed inChara internodal cell andPhysarum plasmodium was discussed.Abbreviations ATP
adenosine 5-triphosphate
- DTT
dithiothreitol
- EDTA
ethylenediaminetetraacetic acid
- EGTA
ethyleneglycolbis(-aminoethylether) N,N,N,N-tetraacetic acid
- PIPES
piperazine-N,N-bis(2-ethanesulfonic acid) 相似文献
9.
Summary We used an extracellular vibrating probe to investigate local transmembrane ion currents that occur just before and during localized cytoplasmic movement associated with feeding initiation in the marine dinoflagellateNoctiluca, Our results indicates that the currents flow only through a specialized cellular region, the sulcus, suggesting a heterogeneous distribution of an ion channel in the cell membrane. A current enters into the middle of the sulcus where the cytostome exists and leaves from both ends of the sulcus. The mean inward and outward current densities were approx. + 11 and — 1 A·cm–2, respectively. The cytoplasm began to stream toward the cytostome in association with the currents and then aggregated around it. Removal of Ca2+, Na+, or Mg2+ ions from the external medium diminished the inward current. Ca2+ ions were proved to carry only 5% of the inward current. The Ca2+ current appears to be enough to raise Ca2+ concentration in a localized region of the cytoplasm, causing the cytostome-directed cytoplasmic movement. Rest of the current seems to be carried by Na+ ions. Most of the outward current was inhibited by an ion pump inhibitor, but the current-carrying ion species could not be identified. 相似文献
10.
Summary Dantrolene-Na is a muscular relaxant which binds to sarcoplasmic reticulum (SR) with high affinity and decreases the availability of Ca2+ channels. The binding of fluorescent compounds, dantrolene-Na, nifedipine and chlortetracycline to the ciliary membrane ofParamecium aurelia has been studied. Dantrolene at the concentrations of 1.9 · 10–5, 3.8 · 10–5 and 7.9 · 10–5 M manifested a punctuated binding pattern to the cell membrane. Isolated cilia also bound dantrolene at their basal portion, whereas deciliated cell bodies lost their dotted binding pattern. Chlortetracycline showed a similar but weaker fluorescent staining. Nifedipine treated cells revealed no sign of fluorescent binding to the membrane and was only taken up in food vacuoles.Based on these observations we propose that dantrolene binding regular arrays ofParamecium cell membrane could be identical to granular plaques observed by electron microscope. The possible functioning of these structures as Ca2+ reservoirs is also discussed. 相似文献
11.
Effects of changes in environmental calcium on prolactin secretion in Japanese eel,Anguilla japonica
E. Arakawa S. Hasegawa T. Kaneko T. Hirano 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(2):99-106
Effects of changes in environmental Ca2+ on the secretion of prolactin, a possible hypercalcemic hormone, were examined both in vivo and in vitro in the Japanese ecl, Anguilla japonica. Transfer of seawater- or freshwater-adapted fish to fresh water, fresh water containing 10 mmol Ca2+ · 1-1 sea water, Ca2+-free sea water, or deionized water was accompanied by significant changes in plasma Ca2+ levels after 7 days, except for the fish transferred from fresh water to fresh water and from sea water to sea water. Changes in external Ca2+ concentrations did not affect plasma prolactin levels, although plasma prolactin levels as well as pituitary prolactin contents were significantly greater in fish in a hypotonic environment than those in a hypertonic environment, regardless of the external Ca2+ concentration. Hypercalcemia, induced by removal of the corpuscles of Stannius, did not alter plasma prolactin levles. Incubation of the pituitary in the medium with different Ca2+ concentrations (up to 2.9 mmol·l-1) did not affect the basal release of prolactin, except at an extremely low Ca2+ concentration (less than 0.1 mmol·l-1) where prolactin release was inhibited. Addition of Ca2+ ionophore (A23187) to the medium led to a marked and significant increase in prolactin release, indicating that an increase in intracellular Ca2+ stimulates prolactin release. However, the effect was not specific to prolactin cells; a similar increase was seen in growth hormone release. These results indicate that changes in environmental Ca2+ concentration may not be the primary factor influencing prolactin secretion in the eel; changes in environmental osmolality or Na+ levels seem to be more critical for the regulation of prolactin secretion.Abbreviations CSX
stanniectomy
- DMSO
dimethylsulphoxide
- DW
deionized water
- FW
fresh water
- GH
growth hormone
- PRL
prolactin
- SW
sea water 相似文献
12.
Dr. John A. Williams 《Cell and tissue research》1978,186(2):287-295
Summary The effects of the Ca2+ ionophore A 2317 on pancreatic amylase and lactate dehydrogenase (LDH) release, cellular electrolyte balance and ultra-structure were studied with the use of incubated pancreatic fragments. A 23187 (0.3 M) in the presence of Ca2+, increased amylase release but at higher concentrations (1–10 M) also increased LDH release and increased uptake of 14C-sucrose with concomitant loss of tissue K+ and gain in Na +. The ultrastructure of the majority of acini appeared normal and showed depletion of zymogen granules. Microtubules and microfilaments which have been implicated in the release process were normal or increased in number. In the absence of Ca+ the ionophore had no effect on secretion, cellular integrity or ultrastructure. It is concluded that A 23187 in the presence of Ca2+ increases amylase release by a mechanism comparable to the terminal steps in stimulussecretion coupling induced by physiological secretagogues. This provides further evidence that amylase release is mediated by a rise in cell Ca2+ although the mechanisms of the ionophore- and physiological secretagogue-induced rise in Ca+ are probably different. High concentrations of ionophore (> 1 M) also induce Ca2+ dependent damage in a fraction of the cells.Supported by grants from the NIH (GM 19998) and the Cystic Fibrosis FoundationI am indebted to Drs. Douglas Chandler and John Heuser for discussion and advice and to M. Lee and E. Roach for technical assistance 相似文献
13.
Ca2+ is proposed to function as a messenger in such phytochrome-mediated responses as localized cell growth, intracellular movements, and control of plasma membrane properties. To test this hypothesis, the uptake of Ca2+ in irradiated and non-irradiated regions of individual threads of the green alga Mougeotia was studied with the aid of 45Ca2+ and low temperature autoradiography: 10–20 cells within 40–60 cell-long threads were irradiated for up to 1 min, transferred to darkness for 3 to 10 min, submersed in a radioactive medium for 1 min, washed in an unlabelled medium for 30 min, and then autoradiographed at-80° C for several days.The autoradiographs show that those cells which had been pre-irradiated with red light did take up 2–10 times more Ca2+ than the adjacent non-irradiated cells of the same thread. Cells pre-irradiated with farred light or red light followed by far-red light showed no enhanced uptake of Ca2+. These results might be interpreted to indicate, firstly, that phytochrome-Pfr is involved in the enhanced uptake of Ca2+ and secondly, that the accumulation of radioactive Ca2+ in red light irradiated cells is an expression of an increased intracellular concentration of Ca2+. This interpretation is based on the data that (i) the dark interval between irradiation and labelling precluded the involvement of photosynthesis, (ii) the effect of red light was reversible with far-red light, and (iii) the accumulation of Ca2+ persisted during the long wash-out period. We speculate, that the red light-enhanced accumulation of Ca2+ in Mougeotia cells is caused by a Pfr-mediated increase of the Ca-permeability of the plasma membrane, and perhaps by a Pfr-impeding of an active Ca2+-extrusion.Abbreviations APW
artificial pond water
- EGTA
ethylene glycol-bis-(-amino ethyle ether) N,N-tetraacetic acid
- R
red irradiation
- D
darkness
- FR
far-red irradiation
- Pfr
physiologicallyactive form of phytochrome
- Pr
physiologically inactive form of phytochrome
This paper is part of a Ph. D. Thesis submitted to the University of Erlangen-Nürnberg by E.M. Dreyer 相似文献
14.
Otto Baumann Bernd Walz 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1989,165(5):627-636
Summary The photoreceptor cells in the honeybee drone contain an elaborate Ca2+-sequestering endoplasmic reticulum (ER). We measured Ca-oxalate formation within the ER of permeabilized retinal slices with a microphotometer and studied the kinetics of Ca2+-uptake into the ER and the properties of Ins(1,4,5)P3-induced Ca2+-release.The ATP-dependent Ca2+-uptake mechanism has a high affinity for Ca2+: Uptake rate was half maximal at Ca2+
free 0.6 M.Addition of Ins(1,4,5)P3 caused a persistent depression of Ca-oxalate formation due to Ca2+ -release from the ER. The Ins(1,4,5)P3-dependent Ca2+-release mechanism has a high affinity (half maximal rate with 0.2 M Ins(1,4,5)P3) and a high specificity for Ins(1,4,5)P3: Ins(2,4,5)P3 was 6 times, Ins(1,3,4,5)P4 was 15 times less potent in inducing Ca2+-release. 3 M Ins(1,4)P2 had no detectable effect. The sensitivity for Ins(1,4,5)P3 was maximal between 280 nM and 1.6 M Ca2+
free and decreased at higher and lower Ca2+-concentrations.Our data show that the ER in invertebrate photoreceptor cells is an effective Ca2+ -sink and an Ins(1,4,5)P3-sensitive Ca2+-source. We support the idea (Payne et al. 1988) that the ER-network close to the photoreceptive membrane, the submicrovillar cisternae (SMC), are the light- and Ins(1,4,5)P3-sensitive Ca2+-stores.Abbreviations
ER
endoplasmic reticulum
-
Ins(1,4,5)P
3
D-inositol 1,4,5-trisphosphate
-
Ins(1,3,4)P
3
D-inositol 1,3,4-trisphosphate
-
Ins(2,4,5)P
3
D-inositol 2,4,5-trisphosphate
-
Ins(1,4)P
2
D-inositol 1,4-bisphosphate
-
Ins(1,3,4,5)P
4
D-inositol 1,3,4,5-tetrakisphosphate
-
SMC
submicrovillar cisternae
-
[Ca
2+]i
intracellular free Ca2+-concentration 相似文献
15.
Methanospirillum hungatei strains GP1 and JF1 when cultivated at 37°C in JMA medium grew as motile single cells or short chains of cells (typically 10–30 m long). When M. hungatei was grown in low Ca2+ concentrations or with the divalent cation chelator EDTA, the organism grew as long non-flagellated filaments (up to 900 m long). The two strains had different thresholds of calcium concentrations for long filament formation (<0.25 mM for GP1 and <0.15 mM for JF1) as well as different minimal Ca2+ requirements for growth. Both strains produced long, almost straight, filaments at Ca2+ concentrations near the minimum required for growth. At suboptimal growth temperatures the organisms still grew as short filaments but no longer possessed flagella. Western blot analysis indicated that flagellin monomer was present in cultures of long non-flagellated filaments and short non-flagellated cultures grown at suboptimal temperatures. The amount of flagellin present appeared to be equal in both non-flagellated and flagellated cultures. When cells were grown as long non-flagellated filaments and switched to growth conditions inducing short, flagellated forms, flagella were first observed at 2.5 h after this switch.Portions of this work were previously presented at the 91st General Meeting of the American Society for Microbiology, May 5–9 1991, Dallas, Texas (abstract I-81) and at the 41st Annual Meeting of the Canadian Society of Microbiologists, June 3–6 1991, London, Ontario (Abstract MP-1) 相似文献
16.
M. Heinz R. Krattenmacher B. Hoffmann W. Clauss 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(4):363-370
Summary Transepithelial electrogenic Na+ transport (INa) was investigated in the coprodeum of 20-days-old chicken embryos in Ussing chambers. Short circuit current (Isc) and transepithelial resistance (Rt) were 14.7±4.8 A · cm-2 (n=12) and 0.53±0.09 k · cm-2 (n=12), respectively. INa was calculated from changes in Isc by substitution of mucosal Na+ by (N-methyl-d-glucamine) (NMDG). Isc inversed during Na+ removal, and INa was found to be 27.8±4.7 A · cm-2 (n=12). Amiloride (100 mol · l-1) inhibited only about 60% of INa. Analysis of Isc fluctuations revealed a Lorentzian component in the power density spectrum with a corner frequency of about 57 Hz. This component was not correlated to INa, and its origin is still unclear. Removal of mucosal Ca2+ increased INa about 2.5-fold due to an increase of the amiloride-insensitive component of INa in additionally investigated adult tissues. The results clearly show that this is due to a non-selective cation channel with an apparent order of selectivity Cs+>Na+=K+>Rb+>Li+. The Ca2+ concentration required to block 50% of the Isc was about 18 mol · l-1. The I
sc
Ca
could also be supressed by other divalent cations such as Mg2+ and Ba2+. Additionally, an INa-linked Lorentzian component occurred which dominated the control spectrum with a significantly higher corner frequency (about 88 Hz). The results indicate that Na+ absorption in the coprodeum of the chicken embryo is more complex than in adult hens. However, the Ca2+ sensitivity of INa is similar to comparable effects described for other epithelia. This possibly reflects the existence of two types of amiloride-insensitive apical cation channels as pathways for Na+ absorption, which may be involved to differing degrees in ontogenetic developments of nonselective channels to Na+-specific ion channels.Abbreviations
DPL
direct-linear-plot method
-
slope of the back-ground noise component
-
EGTA
ethylene glycol-bi(2-amino-ethylether)-N,N,N,N-tetraacetic acid
-
f
frequency
-
f
c
corner frequency of the Lorentzian noise component
-
G
t
transepithelial conductance
-
HEPES
N-hydroxyethylpiperazine-N-ethanesulfonic acid
-
I
sc
short-circuit current
-
I
Na
transepithelial sodium current
-
I
sc
Ca
Ca2+-sensitive short-circuit current
-
K
m
Ca
Michaelis-Menten constant for Ca2+
-
K
B
power density of the background noise component at f=1Hz
-
m
mucosal
-
NMDG
N-methyl-D-glucamine
-
R
t
transepithelial resistance
-
s
serosal
-
SEM
standard error of mean
-
S(f)
power density of the Lorentzian noise component
-
S
o
plateau value of the Lorentzian noise component 相似文献
17.
The Ca2+ indicator 7-chlorotetracycline has been shown to bind to a pore complex on both outer surfaces of all non-meristematic cells in the unistratose thallus of Riella (chlorotetracycline-binding surface region=CSR; Grotha, 1983, Planta 158, 473–481). Prolonged treatment of the thallus with 7-chlorotetracycline, 5-hydroxytetracycline, verapamil and desmethoxyverapamil induces the deposition of callose at the same region. The influence of various treatments on verapamil-induced CSR-callose was measured in situ by microfluorometry of aniline-blue-stained material. Callose deposition is maximal at 10-4M verapamil or 5·10-5M desmethoxyverapamil with 2·10-4M Ca2+ or Mg2+ in the medium. The reaction is completely inhibited at pH 5.5 and is optimal between pH 6.5 and 7.5. The production of CSR-callose is absolutely light-dependent with callose being first visible after 30 min of light. La3+, ethylene glycol-bis(-aminoethylether)-N,N,N,N-tetraacetic acid and amiprophosmethyl, antagonists of Ca2+ functions, and 2-deoxy-D-glucose suppress the verapamil induction of CSR-callose. Furthermore the ionophores A 23187, valinomycin and monensin effectively block the reaction. The deposition of CSR-callose is diminished at increasing external osmolarity and is abolished at osmotic values that stimulate plasmolysis-callose. Wounding causes the formation of wound-callose but inhibits the induction of CSR-callose in cells of the wound edge. Nifedipine increases or prolongs callose synthesis in cell plates. The Ca2+-channel blocker diltiazem is completely ineffective. It is suggested as a working hypothesis that verapamil-induced CSR-callose synthesis is caused by a local change in membrane permeability, possibly as a consequence of the opening of Ca2+ channels being involved in Golgi-vesicle mediated exocytosis (A. Kramer and H. Lehmann, 1986, Ber. Dtsch. Bot. Ges. 99, 111–121).Abbreviations APM
amiprophosmethyl
- APW
artificial pond water
- CSR
chlorotetracycline-binding surface region
- CTC
7-chlorotetracycline
- DDG
2-deoxy-D-glucose
- EGTA
ethylone glycol-bis(2-aminoethylether)-N,N,N,N-tetraacetic acid
- OTC
5-hydroxytetracycline
- Pipes
1,4-piperazinediethane sulfonic acid
Dedicated to Professor Luise Stange on the occasion of her 60th birthday 相似文献
18.
This paper deals with the effect of calcium binding in the cell wall on the measured 45Ca influx in Chara corallina Klein ex Will. esk. R.D. Wood. Calcium in the cell wall was in the range 687–1197 (mol · m–2 compared to the sap which contained only 144–256 mol · m–2. In dilute culture solutions the calcium content of the cell wall was relatively independent of external calcium at concentrations above about 0.1 mol · m–3. The half-times for exchange of calcium from 45Ca-labelled cell walls varied from 45 min at 0.05 mol · m–3 to less than 2 min at 2 mol · m–3. The effectiveness of other cations in displacing calcium from cell walls was in the order La > Zn > Co > Ni > Mg. Rinsing of 45Ca-labelled cell walls in 2 mol · m–3 LaCl3 for 20 min removed more than 99% of the bound 45Ca. However, the residual 45Ca activity in isolated cell walls following La3+ rinsing was similar to that in whole cells. It is concluded that in whole cells 45Ca influx cannot normally be distinguished from extracellular binding of calcium. Methods are described for the measurement of 45Ca fluxes in charophyte cells by isolation of intracellular 45Ca after the uptake period using techniques which avoid contamination from the large amount of tracer bound in the cell wall. At an external calcium concentration of 1 mol · m–3, the plasmalemma influx was approx. 0.2 nmol · m–2 · s–1 of which about half entered the vacuole and half was effluxed back into the external solution. The cytoplasm filled with calcium with a half-time of 40–50 min with an apparent pool size of 50 mmol · m–3. After 2 h the net flux to the cell was almost the same as the vacuolar flux. The fluxes reported are an order of magnitude lower than previously reported calcium fluxes in plants.Abbreviations APW
artificial pond water
This work was supported by the Australian Research Council. The authors wish to thank Patrick Kee for his skilful technical assistance and Professor E.A.C. MacRobbie, University of Cambridge, UK, and Dr. M. Tester for helpful discussions. 相似文献
19.
Calcium-dependent membrane depolarisation activated by phytochrome in the moss Physcomitrella patens
In caulonemal filaments of Physcomitrella patens which had been preincubated in the dark for 24 h, irradiation with red light (640 nm, fluence rate 85 mol · m–2 · s–1) evoked (i) the development of side branch initials and (ii) a rapid, but transient, depolarisation of the plasma membrane by 90 ± 13 mV from a resting potential of -178 ± 13 mV. This was followed by a transient hyperpolarisation to a value 21± 8 mV more negative than the original membrane potential. The refractory period for the transient depolarisation was between 12 and 15 min. The fluence rate of red light required to evoke maximal depolarisation was about 80 mol · m–2 · s–1 for a 1-min pulse. At this fluence rate, a depolarising response could be recorded for pulse lengths as small as 7 s. The transient depolarisation was insensitive to 3-(3,4dichlorophenyl)-1,1-dimethyl urea (DCMU) and was unchanged in plants bleached by growth on norflurazon (SAN 9789). Furthermore, the electrical response could be blocked by simultaneous application of far-red light. These results suggest the involvement of the photoreceptor phytochrome in the response. Removing Ca2+ from the external medium or replacing Ca2+ with Mg2+ blocked the depolarisation. The depolarisation could also be blocked by the K+ channel-blocker tetraethylammonium (10 mM) and the Cl– channel-blocker niflumic acid (1 M). Conversely, although calcium channel-antagonists such as nifedipine and lanthanides, applied at a concentration of 100 M, also altered the response, they did not block it. A possible ionic mechanism for the membrane potential transient is advanced, and the physiological significance discussed in the context of early events in the phytochrome signalling pathway.Abbreviations [Ca2+]c
cytosolic Ca2+ concentration
- DCMU
3-(3,4-dichlorophenyt)-1,1-dimethylurea
- TEA
tetraethylammonium
We thank Prof. David Cove (Department of Genetics, University of Leeds) for fruitful discussions, providing plants and advice on culturing methods, Dr. Richard Firn (York) for stimulating discussions, Ian Jennings (York) for technical advice on the electrophysiological apparatus, and Anna Bate (York) for looking after the plant cultures. Financial support was received from the Biotechnology and Biological Sciences Research Council (Grant P87/4043 to D.S. and Grant PDF/14 to E.J.) and The New Phytologist Trust (studentship support to E.E.). 相似文献
20.
Germination of Dryopteris spores is mediated by the physiologically active, far-red-absorbing form of phytochrome, Pfr, and external Ca2+ is necessary for the transduction of the light signal. Because knowledge about the cytoplasmic calcium ion concentration, [Ca2+]i, is of great importance for understanding the role of calcium during signal transduction, this value was measured using fura-2 in fern spores undergoing the normal developmental progression into germination. Fura-2 was loaded into the spores by electroporation, which does not disrupt the normal process of germination. The intensity of the fluorescence emission of the loaded fura-2 was analysed by a microspectrophotometric assay of single spores, and successful loading could be obtained by the application of ten electrical pulses (field strength 7.5 kV · cm–1, half-life (time constant) 230 s). Fura-2 was alternately excited by light of wavelengths 355 and 385 nm through an inverted fluorescence microscope, and the emitted fura-2 fluorescence was collected by a silicon-intensified video camera. The cytoplasmic calcium ion concentration was calculated from the ratio of the camera output obtained for both wavelengths and displayed by a pseudo-color technique. Spores responded to changes of the extracellular Ca2+ concentration, and this observation is considered as evidence that fura-2 is loaded into the cytoplasm. The substitution of a low external [Ca2+] (1 mM ethyleneglycol-bis(2-aminoethyl-ether) {ie166-01},N-tetraacetic acid (EGTA)) by 1 mM CaCl2 caused a fast increase of [Ca2+]i from approx. 50 nM to above 500 nM. In contrast, the subsequent substitution of CaCl2 by EGTA decreased [Ca2+]i again below 100 nM within 0.5 h. Furthermore, the application of ionomycin could initiate a change in [Ca2+]i according to the Ca2+ gradient established between the extracellular medium and cytoplasm. In spores sown on a Ca2+-free medium, [Ca2+]i, analysed in a buffer containing EGTA, was found to be around 50 nM during the first days of cultivation, independent of the irradiation protocol. However, if spores were grown in darkness on a Ca2+-containing medium and analysed in EGTA, [Ca2+]i was significantly higher ( 500 nM). In red-light-irradiated spores, [Ca2+]i was found to decrease with increasing time after irradiation, and was determined to be less than 100 nM when analysis was done 44 h after germination was initiated by the light treatment.Dedicated to Professor H. Mohr on the occasion of his 60th birthday 相似文献