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1.
Movement ofMimosa pudica L. pulvinules was investigated by using excised ones which were placed on a moist filter paper. The pulvinules excised in
the morning opened at the addition of IAA (10−7 M to 10−4M) in the dark. The lag period for the onset of the opening was about 15 min. Na-acetate buffer (pH 4) also induced the opening
of pulvinules in the dark, and the buffer-induced opening was inhibited by the uncouplers of oxidative phosphorylation. Na-MES
and Na-citrate buffers (pH 4) did not induce the opening.
Pulvinules taken from closed leaves in the evening were less responsive to IAA than those taken from open leaves in the morning.
The pulvinules taken in the evening slightly opened with incandescent light (4000 lux), but those preincubated with IAA (10−7M and 10−6M) opened distinctly upon the illumination. 相似文献
2.
M. A. Breygina A. V. Smirnova N. P. Matveeva I. P. Yermakov 《Cell and Tissue Biology》2009,3(6):573-582
Using methods of quantitative fluorescent microscopy, we studied membrane potential changes during pollen germination and
in growing pollen tubes. Two voltage-sensitive dyes were used, i.e., DiBAC4(3), to determine the mean membrane potential values in pollen grains and isolated protoplasts, and Di-4-ANEPPS, to map the
membrane potential distribution on the surfaces of the pollen protoplast and pollen tube. We have shown that the activation
of the tobacco pollen grain is accompanied by the hyperpolarization of the vegetative cell plasma membrane by about 8 mV.
Lily pollen protoplasts were significantly hyperpolarized (−108 mV) with respect to the pollen grains (−23 mV) from which
they were isolated. We have found the polar distribution of the membrane potential along the protoplast surface and the longitudinal
potential gradient along the pollen tube. In the presence of plasma membrane H+-ATPase inhibitor sodium orthovanadate (1 mM) or its activator fusicoccin (1 μM), the longitudinal voltage gradient was modified,
but did not disappear. Anion channel blocker NPPB (40 μM) fully discarded the gradient in pollen tubes. The obtained results
indicate the hyperpolarization of the plasma membrane during pollen germination and uneven potential distribution on the pollen
grain and tube surfaces. An inhibitory analysis of the distribution of the potential in the tube has revealed the involvement
of the plasma membrane H+-ATPase and anion channels in the regulation of its value. 相似文献
3.
Elongation growth of plant cells occurs by stretching of cell walls under turgor pressure when intermolecular bonds in the
walls are temporarily loosened. The acid-growth theory predicts that wall loosening is the result of wall acidification because
treatments (including IAA and fusicoccin) that cause lowered wall pH cause elongation. However, conclusive evidence that IAA
primarily reduces wall pH has been lacking. Calcium has been reported to stiffen the cell walls. We have used a microelectrode
ion-flux measuring technique to observe directly, and non-invasively, the net fluxes of protons and calcium from split coleoptiles
of oats (Avena sativa L.) in unbuffered solution. Normal net fluxes are 10 nmol · m−2 · s−1 proton efflux and zero calcium flux. The toxin fusicoccin (1 μM) causes immediate efflux from tissue not only of protons,
but also of calcium, about 110 nmol · m−2 · s−1 in each case. The data fit the “weak acid Donnan Manning” model for ion exchange in the cell wall. Thus we associate the
known “acid-growth” effect of fusicoccin with the displacement of calcium from the wall by exchange for protons extruded from
the cytoplasm. Application of 10 μM IAA causes proton efflux to increase transiently by about 15 nmol · m−2 · s−1 with a lag of about 10 min. The calcium influx decreases immediately to an efflux of about 20 nmol · m−2 · s−1. It appears that auxin too causes an “acid-growth” effect, with extruded protons exchanging for calcium in the cell walls.
I. Arif is currently recieving an AIDAB scholarship. This work was supported by an Australian Research Council grant to I.A.
Newman. 相似文献
4.
Effect of auxin on mesocotyl elongation of dark-grown maize under different seeding depths 总被引:1,自引:0,他引:1
In order to elucidate the physiological mechanism of maize mesocotyl elongation induced by auxin under different seeding depths,
seeds of five maize inbred lines, including 3681-4 line tolerant to deep seeding, were treated with IAA and triiodobenzoic
acid (TIBA) under seeding depths of 20 or 2 cm. Under deep seeding conditions, maize mesocotyls grew by 1.5–2.0 times faster
than under shallow seeding conditions. IAA (10−6 to 10−4 M) applied to roots stimulated mesocotyl elongation only of 3681-4 line and only under deep seeding conditions. TIBA (10−5 and 10−4 M) applied to roots inhibited mesocotyl elongation in all lines, but only 3681-4 was sensitive to 10−6 M TIBA. IAA promoted only cell elongation, and TIBA inhibited both cell elongation and cell division. After IAA and TIBA
treatments, endogenous IAA content changed in parallel with the mesocotyl growth rate under different seeding depths. Furthermore,
ABP1 gene expression changed in parallel with the mesocotyl growth rate under deep seeding conditions. Therefore, deep seeding
tolerance of 3681-4 line was achieved due to auxin-regulated rapid mesocotyl elongation. 相似文献
5.
The membrane potential ofMycoplasma mycoides subsp.capri has been determined to beE
M=−48 mV±10%, inside negative. In this study we investigated the influence of cell membrane-active antimicrobial agents, viz.,
valinomycin, gramicidin, polymyxin, and clotrimazole, on membrane potential and viability ofM. mycoides subsp.capri. Valinomycin, an ionophore with extreme potassium selectivity, induced a membrane hyperpolarization,E
M=−110 mV. Valinomycin was not cidal, but static to mycoplasmas. Obviously the potassium drain induced by valinomycin can be
compensated for by the organisms. Gramicidin is an antibiotic forming cation conduction channels across membranes. It induced
a rapid depolarization,E
M=+23 mV, of mycoplasma membranes. At low concentrations, gramicidin had a static effect, whereas at high concentrations it
was cidal to mycoplasmas. The rapid permeation of cations through the stationary ion channels formed by gramicidin obviously
exerts an inhibitory or even lethal effect on mycoplasma metabolism and growth. Polymyxin B induced a depolarization,E
M=−35 mV, of mycoplasma membranes only when the organisms had been pretreated and hyperpolarized with valinomycin. After treatment
with both valinomycin and polymyxin B, a slight inhibition of mycoplasma growth was observed. Clotrimazole, a synthetic imidazole
antimycotic, hyperpolarized mycoplasma membranes (E
M=−80 mV). At high concentrations clotrimazole was cidal, whereas at low concentrations it was static to mycoplasmas. 相似文献
6.
Tomoki Kai Kazumi Nimura Hajime Yasui Hiroyuki Mizuta 《Journal of applied phycology》2006,18(1):95-101
Young sporophytes of Laminaria japonica Areshoug were cultured in six indole-acetic acid (IAA) concentrations (0, 10−8, 10−7, 10−6, 10−5, 10−4 M) to examine the effect of auxin on growth. The effects of auxin on sorus formation were also examined by using discs taken from the adult sporophyte. The auxin contents and IAA oxidase activities in the thallus and sorus parts of the sporophyte were determined with the blade and sporophyll of other Laminariales plants, Undaria pinnatifida (Harvey) Suringar and Alaria crassifolia Kjellman. The young sporophytes of L. japonica showed highest elongation rate in 10−5 M IAA. In contrast, the sorus formation on the discs cultured in 10−5 M IAA was markedly delayed in comparison with other concentrations, indicating that sorus formation was suppressed by IAA. Free and conjugated auxin contents were lower in the reproductive parts than in the vegetative parts. In three Laminariales sporophytes, IAA oxidase activity was about 3–9 times higher in the reproductive parts than in the vegetative parts. Taken together these results suggest that the growth and reproduction of Laminariales sporophytes are regulated by internal auxin levels. Elucidating the regulation mechanism is likely to provide information that is important for the management of plant production and the assessment of the physiological status of plants in the field. 相似文献
7.
Vieira LB Pimenta AM Richardson M Bemquerer MP Reis HJ Cruz JS Gomez MV Santoro MM Ferreira-de-Oliveira R Figueiredo SG Snutch TP Cordeiro MN 《Cellular and molecular neurobiology》2007,27(1):129-146
Summary Various neurotoxins have been described from the venom of the Brazilian spider Phoneutria nigriventer, but little is known about the venoms of the other species of this genus. In the present work, we describe the purification
and some structural and pharmacological features of a new toxin (PRTx3-7) from Phoneutria reidyi that causes flaccid paralysis in mice. The observed molecular mass (4627.26 Da) was in accordance with the calculated mass
for the amidated form of the amino acid sequence (4627.08 Da). The presence of an α-amidated C-terminus was confirmed by MS/MS
analysis of the C-terminal peptide, isolated after enzymatic digestion of the native protein with Glu-C endoproteinase. The
purified protein was injected (intracerebro-ventricular) into mice at dose levels of 5 μg/mouse causing immediate agitation
and clockwise gyration, followed by the gradual development of general flaccid paralysis. PRTx3-7 at 1 μM inhibited by 20%
the KCl-induced increase on [Ca2+]i in rat brain synaptosomes. The HEK cells permanently expressing L, N, P/Q and R HVA Ca2+ channels were also used to better characterize the pharmacological features of PRTx3-7. To our surprise, PRTx3-7 shifted
the voltage-dependence for activation towards hyperpolarized membrane potentials for L (−4 mV), P/Q (−8 mV) and R (−5 mV)
type Ca2+ currents. In addition, the new toxin also affected the steady state of inactivation of L-, N- and P/Q-type Ca2+ currents.
L. B. Vieira and A. M. C. Pimenta contributed equally to this work. 相似文献
8.
Lithospermum officinale callus produces shikalkin 总被引:1,自引:0,他引:1
Kamahldin Haghbeen Valiolah Mozaffarian Fatemeh Ghaffari Elahe Pourazeezi Mohammad Saraji Morteza Daliri Joupari 《Biologia》2006,61(4):463-467
To study biosynthetic abilities of Lithospermum officinale, callus formation from young leaves and stems of the plant was induced on Linsmaier-Skoog medium supplemented with 2,4-D
(10−6 M) and kinetin (10−5 M). Maintaining the calli on this medium resulted in polyphenolic compounds production. Their transfer onto White medium
containing IAA (10−7 M) and kinetin (10−5 M) resulted in the production of a red naphthoquinonic pigment named shikalkin. Shikalkin production from callus cultures
was suppressed on the White medium containing NAA instead of IAA. This observation indicates that both shikalkin and polyphenolic
acids biosynthetic pathways exist in the L. officinale callus cells and a regulatory system counterbalances the ratio of shikalkin to polyphenolic acids. 相似文献
9.
M. M. Reddy J. R. Riordan P. M. Quinton 《In vitro cellular & developmental biology. Plant》1988,24(9):905-910
Summary The present investigation was undertaken to examine the usefulness of cultured human sweat duct cells for ion transport and
related studies in the genetic disease, cystic fibrosis. Electrical properties of cultured duct (CD) cells were compared with
electrical properties of microperfused duct (MPD) cells. The resting apical membrane potential (V
a
) of the CD cells was −26.4±0.9 mV,n=158 cells as compared to −24.3±0.6 mV,n=105 of MPD cells. The Na+−K+ pump inhibitor ouabain, when applied to the apical surface of the CD cells and basolateral surface of MPD cells, depolarized
both CD cells (from −28.6±3.6 to −16.8±2.4 mV,n=5) and MPD cells (from −23.8±0.5 mV to −19.5±1.8 mV,n=6). The Na+ conductance inhibitor amiloride applied to the apical surface hyperpolarized the apical membrane potentials (Va) of CD cells and MPD cells by −13.2±1.4 mV,n=43 and −34.3±3.1 mV,n=19), respectively, indicating the presence of amiloride sensitive Na+ channels in both groups of cells. However, the amiloride sensitivity of CD cells was dependent on the age of the culture.
Cl− substitution at the apical side by the impermeant anion gluconate depolarized the V
a
of CD cells and MPD cells by 12.2±0.9 mV,n=32 and 37.9±4.3 mV,n=12, respectively. The effect of β-adrenergic agonist isoproterenol (IPR), was inconsistent. In CD cells, IPR either hyperpolarized
(ΔV
a
=−8.3±1.2mV,n=5) or depolarized (ΔV
a
=8.2±2.3 mV,n=4) or had no effect,n=2. In contrast, most of the MPD cells did not respond to IPR, but three cells had a varied response to IPR. Our results suggest
that CD cells, like MPD cells, retain significant Na+ and Cl− conductances. CD cells seem to have developed a higher sensitivity to β-adrenergic stimulation in tissue culture as compared
to MPD cells.
This work was supported by grants from the National Institutes of Health, Bethesda, MD, DK26547, Getty Oil Co., the Gillette
Co., Cystic Fibrosis Research Inc., and the U.S. National Cystic Fibrosis Foundation. 相似文献
10.
Single-channel properties of a delayed rectifier voltage-gated K+ channel (I-type) were investigated in peripheral myelinated axons from Xenopus laevis. Channels activated between −60 and −40 mV with a potential of half-maximal activation, E50, at −47.5 mV. Averaged single-channel currents activated with a time delay at all membrane potentials tested. Time to half-maximal
activation decreased from 80 to 1.6 msec between −60 and +40 mV. The channel inactivated monoexponentially with a time constant
of 10.9 sec at −40 mV. The time constant of deactivation was 126 msec at −80 mV and 16.9 msec at −110 mV. In symmetrical 105
mm K+, the single-channel conductance (γ) was 22 and 13 pS at negative and positive membrane potentials, respectively, at 13–15°C.
In Na+-rich solution with 2.5 mm extracellular K+γ was 7 pS and the reversal potential was negative to −80 mV, indicating a high selectivity for K+ over Na+. γ depended on extracellular K+ concentration (K
D
= 19.6 mm) and temperature (Q
10= 1.45). External tetraethylammonium (TEA) reduced the apparent single-channel current amplitude at all potentials tested
with a half-maximal inhibiting concentration (IC50) of 0.6 mm. Open probability of the channel, but not single-channel current amplitude was decreased by extracellular dendrotoxin (DTX,
IC50= 6.8 nm) and mast cell degranulating peptide (MCDP, IC50= 41.9 nm). In Ringer solution the membrane potential of macroscopic I-channel patches was about −65 mV and depolarized under TEA and
DTX. It is concluded that besides their activation during action potentials, I-channels may also stabilize the resting membrane
potential.
Received: 2 June 1995/Revised: 13 October 1995 相似文献
11.
The plants of mung bean (Vigna radiata L. Wilczek) were raised from the seeds soaked in water (control), IAA or 4-C-IAA (10−6, 10−8 or 10−10 M) for 8 or 12 h. The plants were allowed to grow in a net house and were sampled at 30 and 45 days after sowing (DAS). Both
IAA and 4-Cl-IAA significantly affected the growth (length, fresh and dry mass of roots and shoots), the number of nodules,
their fresh and dry mass and the activity of nitrogenase. However, the contents of nitrogen and carbohydrate exhibited a decrease
in response to both the auxins. 4-Cl-IAA, at a concentration of 10−8 M, generated the best response. Moreover, 4-Cl-IAA at other two concentrations (10−6 and 10−10 M) was much more active than any of the IAA concentration used. 相似文献
12.
Summary Primary cultures of human reabsorptive sweat duct cells were grown in MCDB 170 medium buffered with either HEPES, bicarbonate,
or a mixture of HEPES and bicarbonate buffers. Cultures grown in MCDB media containing bicarbonate seemed to differentiate
into a multilayered, keratinized epithelium and began senescing after 1 wk in culture. In contrast, cultures grown in media
containing HEPES as the only buffer seemed to undergo a selection process, resulting in the outgrowth of cells that did not
multilayer or keratinize extensively for up to 3 or 4 wk in culture. Despite marked differences in growth, cells grown in
both bicarbonate and HEPES-buffered media retained electrophysiologic characteristics appropriate to the progenitor. Mean
resting potentials were −21.8±0.8 mV (n=82), −23.3±1.3 mV (n=70) and −18.2±0.8 mV (n=82) for duct cells grown in HEPES, bicarbonate, and HEPES-bicarbonate media, respectively. Substitution of Cl− with the impermeant anion gluconate in the bathing medium caused membrane potential depolarization in all media, revealing
the presence of a Cl− conductance. Administration of the Na+ conductance inhibitor amiloride hyperpolarized the mean resting potential of cells grown in HEPES medium (−6.8±0.6 mV,n=68), bicarbonate medium (−6.9±0.5 mV,n=60), and HEPES-bicarbonate medium (−5.9±0.6 mV,n=69), demonstrating expression of a Na+ conductance. We observed some but minimal variation with age in any of these conditions.
This work was supported by grant DK41329-02 from the National Institute of Health, Bethesda, MD, and a Postdoctoral Fellowship
to Dr. Bell from the National Cystic Fibrosis Foundation. 相似文献
13.
The dose-response curves for IAA and 4-Cl-IAA-induced growth of Zea mays L. coleoptile segments were studied as a function of time. Moreover, some characteristic growth parameters for both auxins
were compared. The dose-response curve of growth rate measured after IAA or 4-Cl-IAA application was bell-shaped in all experiments.
The optimum concentration was 10−6 M for 4-Cl-IAA and was found not to depend on the time of the growth measurement. However, in the case of IAA the optimum
shifted from 10−6 M at the time of maximal growth rate to 10−5 M or even 10−4 M, when growth measured 3–4 hours after auxin application was analysed. The relative activity of 4-Cl-IAA-induced growth
rate (as compared to IAA) increased significantly with increasing time from addition of this auxin to the medium. For both
auxins the time needed to reach the maximal growth rate was clearly related to their concentrations. These data provided further
evidence that 4-Cl-IAA is much more active auxin than IAA and can also suggest that IAA is more rapidly metabolized in comparison
to 4-Cl-IAA. 相似文献
14.
In this study, the effects of Cd on root growth, respiration, and transmembrane electric potential (E
m) of the outer cortical cells in maize roots treated with various Cd concentrations (from 1 μM to 1 mM) for several hours
to one week were studied. The E
m values of root cells ranged between −120 and −140 mV and after addition of Cd they were depolarized immediately. The depolarization
was concentration-dependent reaching the value of diffusion potential (E
D) when the Cd concentration exceeded 100 μM. The values of E
D ranged between −65 to −68 mV (−66 ± 1.42 mV). The maximum depolarization of E
m was registered approx. 2.5 h after addition of Cd to the perfusion solution and in some cases, partial (Cd > 100 μM) or complete
repolarization (Cd < 100 μM) was observed within 8–10 h of Cd treatment. In the time-dependent experiments (0 to 168 h) shortly
after the maximum repolarization of E
m a continuous concentration-dependent decrease of E
m followed at all Cd concentrations. Depolarization of E
m was accompanied by both increased electrolyte leakage and inhibition of respiration, especially in the range of 50 μM to
1 mM Cd, with the exception of root cells treated with 1 and 10 μM Cd for 24 and 48 h. Time course analysis of Cd impact on
root respiration revealed that at higher Cd concentrations (> 50 μM) the respiration gradually declined (∼ 6 h) and then remained
at this lowest level for up to 24 h.
All the Cd concentrations used in this experiment induced significant inhibition of root elongation and concentrations higher
than 100 μM stopped the root growth within the first day of Cd treatment. Our results suggest that Cd does not cause irreversible
changes in the electrogenic plasma membrane H+ ATPase because fusicoccin, an H+ ATPase activator diminished the depolarizing effect of Cd on the E
m. The depolarization of E
m in the outer cortical cells of maize roots was the result of a cumulative effect of Cd on ATP supply, plasmalemma permeability,
and activity of H+ ATPase. 相似文献
15.
An ATP-Sensitive K+ Current that Regulates Progression Through Early G1 Phase of the Cell Cycle in MCF-7 Human Breast Cancer Cells 总被引:4,自引:0,他引:4
Whole-cell recordings were used to identify in MCF-7 human breast cancer cells the ion current(s) required for progression
through G1 phase of the cell cycle. Macroscopic current-voltage curves were fitted by the sum of three currents, including
linear hyperpolarized, linear depolarized and outwardly rectifying currents. Both linear currents, but not the outwardly rectifying
current, were increased by 1 μm intracellular Ca2+ and blocked by 2 mm intracellular ATP. When tested at concentrations previously shown to inhibit proliferation by 50%, linogliride, glibenclamide
and quinidine inhibited the linear hyperpolarized current, and quinidine and linogliride inhibited the linear depolarized
current; none of these agents affected the outwardly rectifying current. In contrast, tetraethylammonium completely inhibited
the outwardly rectifying current, but did not inhibit either linear current. Changing the bath solution to symmetric K+ shifted the reversal potential of the linear hyperpolarized current from near the K+ equilibrium potential (−84 mV) to −4 mV. Arrest of the cell cycle in early G1 by quinidine was associated with significantly
smaller linear hyperpolarized currents, without a change in the linear depolarized or outwardly rectifying currents, but this
reduction was not observed with arrest by lovastatin at a site ≈6 hr later in G1. The linear hyperpolarized current was significantly
larger in ras-transformed than in untransformed cells. We conclude that the linear hyperpolarized current is an ATP-sensitive K+ current required for progression of MCF-7 cells through G1 phase.
Received: 22 January 1999/Revised: 11 May 1999 相似文献
16.
V. Z. Podolnyi Ivana Macháčková Zuzana Josefusová-Vondráková J. Eder J. Krekule M. Kh. Chailakhyan 《Biologia Plantarum》1991,33(1):26-31
Cotyledons ofXanthium strumarium, organs with low sensitivity to photoperiodic treatment show a higher free indol-3-ylacetic acid level (by about 35 %) than
the first pair leaves, organs with high sensitivity to photoperiodic treatment. This was seen in plants of three different
age groups : A. with the first pair of leaves of 15–20 mm in length; B. with the first pair of leaves having finished their
growth and C. with the third leaf of 30–40 mm in length.
Changes in free IAA level during the inductive dark period were similar in both cotyledons and leaves of the first pair. The
level of IAA rose in the first half of the dark period, began to decrease in the latter half, reaching nearly initial level
at its end.
Application of IAA (10−4 – 10−2M) to the cotyledons reduced their already low photoperiodic sensitivity resulting in inhibition of flowering (almost 70 %
using 10−4M IAA).
Elevated free IAA level is assumed to be one of the causal factors of low photoperiodic sensitivity of cotyledons. 相似文献
17.
Romuald Czerpak Andrzej Bajguz Marta Gromek Grażyna Kozłowska Izabela Nowak 《Acta Physiologiae Plantarum》2002,24(1):45-52
This study was conducted to investigate the influence of salicylic acid (SA) on the growth and changes of nucleic acids, protein,
photosynthetic pigments, sugar content and photosynthesis levels in the green alga Chlorella vulgaris Beijerinck (Chlorophyceae). The most significant changes in the content of nucleic acids and proteins was observed at the concentration 10−4 M SA between 8 and 12 day of cultivation. This concentration of SA increased the number of cells (about 40 %) and content
of proteins (about 60 %) and its secretion to the medium. The slight stimulation of protein secretion occurred on the 12th
day of cultivation at concentration 10−4 M, while in the range of 10−5 M to 10−6 M the protein secretion was inhibited. SA also stimulated the content of nucleic acids, especially RNA by 20–60 %, compared
with the control. The most stimulating influence upon the contents of chlorophylls a and b (50–70 %), total carotenoids (25–57 %), sugar (27–41 %) and intensity of net photosynthesis (18–33 %) was found at 10−4 M of SA. At the concentration of 10−6 M SA the slight inhibition of growth and biochemical activity of the algae was recorded at the first days of cultivation. 相似文献
18.
Bernd Grünewald Anna Wersing 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2008,194(4):329-340
GABAergic inhibitory transmission is very abundant within the insect brain. We, therefore, studied the functional properties
of the ionotropic GABA receptor of honeybee mushroom body Kenyon cells in vitro. GABA applications elicit rapidly activating
and desensitizing currents, which are concentration-dependent between 10 and 500 μM. The mean peak amplitude induced by 500 μM
GABA at a holding potential of −110 mV is −1.55 ± 0.23 nA (SEM, n = 29). The GABA-induced current is mediated by Cl− ions because (1) the reversal potential of the GABA-induced current of −40.6 mV is very close to the calculated Nernst potential
of chloride (−44.8 mV). (2) With equimolar chloride concentrations the reversal potential shifted to about 0 mV. GABA or muscimol
are equally efficient channel agonists, whereas CACA is a partial agonist. Picrotoxin or philanthotoxin (100 μM) completely
and reversibly block the GABA-induced current, bicuculline (100 μM) has no effect. Elevating the intracellular Ca2+ concentration increases the GABA current amplitude. This modualtory effect is blocked by the kinase blocker K 252a, but not
by blockers of CaMkinaseII (KN-93), PKC (bisindolylmaleimide) or PKA (KT 5720). We conclude that Kenyon cells express functional
GABA receptors whose properties support an inhibitory role of GABAergic transmission. 相似文献
19.
P. M. Paes de Sousa S. R. Pauleta M. L. Simões Gonçalves G. W. Pettigrew I. Moura M. M. Correia dos Santos J. J. G. Moura 《Journal of biological inorganic chemistry》2007,12(5):691-698
This work reports the direct electrochemistry of Paracoccus pantotrophus pseudoazurin and the mediated catalysis of cytochrome c peroxidase from the same organism. The voltammetric behaviour was examined at a gold membrane electrode, and the studies
were performed in the presence of calcium to enable the peroxidase activation. A formal reduction potential, E
0′, of 230 ± 5 mV was determined for pseudoazurin at pH 7.0. Its voltammetric signal presented a pH dependence, defined by
pK values of 6.5 and 10.5 in the oxidised state and 7.2 in the reduced state, and was constant up to 1 M NaCl. This small copper
protein was shown to be competent as an electron donor to cytochrome c peroxidase and the kinetics of intermolecular electron transfer was analysed. A second-order rate constant of 1.4 ± 0.2 × 105 M−1 s−1 was determined at 0 M NaCl. This parameter has a maximum at 0.3 M NaCl and is pH-independent between pH 5 and 9. 相似文献
20.
W. A. Stirk G. D. Arthur A. F. Lourens O. Novák M. Strnad J. van Staden 《Journal of applied phycology》2004,16(1):31-39
Two seaweed concentrates were made from the kelps Ecklonia maxima and Macrocystis pyrifera using a cell burst method. Cytokinin- and auxin-like activities were measured using the soybean callus and mungbean bioassays,
respectively. Cytokinin-like activity was detected in both seaweed concentrates, being equivalent to approximately 50 μg L−1 kinetin. Auxin-like activity was also detected in both concentrates with the E. maxima derived concentrate having higher biological activity, equivalent to 10−5–10−4 M indole-butyric acid. Two replicates of each concentrate were stored at 54 °C for 14 days to accelerate the effects of storage.
Both fresh and stored samples of the two seaweed concentrates were analysed for their endogenous cytokinin and auxin content.
The samples were purified using a combined DEAE-Sephadex octadecylsilica column and immunoaffinity chromatography based on
wide-range cytokinin and IAA specific monoclonal antibodies. These extracts were analysed by HPLC linked to a Micromass single
quadrupole mass spectrophotometer. Eighteen and nineteen different cytokinins were detected, respectively, in the two concentrates,
with trans-zeatin-O-glucoside being the main cytokinin present. Accelerated storage of the concentrates caused an increase in the total
cytokinin concentration with a large increase in the aromatic meta-topolin. Indole-3-acetic acid was the main auxin in both seaweed concentrates. Indole conjugates, including amino acid conjugates,
were also quantified. The total auxin concentration decreased with accelerated storage for both concentrates.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献