共查询到20条相似文献,搜索用时 62 毫秒
1.
Pramod K. Sinha Kedar N. Prasad 《In vitro cellular & developmental biology. Plant》1977,13(8):497-501
Summary Adenosine 3′,5′-cyclic monophosphate (cyclic AMP) phosphodiesterase activity in mouse neuroblastoma cells in culture markedly
increased during exponential growth and reached a maximal level at confluency; whereas guanosine 3′, 5′-cyclic monophosphate
(cyclic GMP) phosphodiesterase activity only slightly but significantly increased under a similar experimental condition.
The increase in cyclic AMP phosphodiesterase activity was blocked by both cycloheximide and dactinomycin, whereas the increase
in cyclic GMP phosphodiesterase was blocked by only cycloheximide. When the confluent cells were replated at low density,
the cyclic nucleotide phosphodiesterase activity decreased; however, when they were plated at high cell density which equaled
confluency, the enzyme activity did not decrease. Unlike cyclic AMP phosphodiesterase activity, cyclic GMP phosphodiesterase
activity did not change significantly in prostaglandin E1-treated cells, but decreased in cells treated with the inhibitor of phosphodiesterase. Like cyclic AMP phosphodiesterase
activity, cyclic GMP phosphodiesterase activity also did not change in cells treated with serum-free medium, X-irradiation,
sodium butyrate and 6-thioguanine.
This work was supported by USPHS NS-09230, and DRG-1273 from Damon Runyon-Walter Winchell Cancer Fund. 相似文献
2.
To investigate whether cyclic GMP (cGMP) would mediate, in an intracellular Ca2+ -dependent manner, coupling of auxin to stomatal opening, the stomatal opening responses to the auxin indolyl-3-butyric acid
(IBA) and to the cGMP membrane-permeable derivative 8-bromoguanosine 3′,5′-cyclic monophosphate (8-Br-cGMP) were compared in epidermal strips of Commelina communis. In this comparison were studied possible effects of intracellular Ca2+ modulators, GTP-binding protein (G-protein) modulators and selective inhibitors of enzymatic reactions which use or generate
cGMP. The stomatal response to IBA was almost similarly reversed by the Ca2+ buffer 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA), the intracellular Ca2+-release inhibitors ruthenium red and procaine, the inactive cGMP analog Rp-8-bromoguanosine 3′,5′-cyclic monophosphorothioate (Rp-8-Br-cGMPS), the inhibitor of cGMP-producing guanylyl cyclase LY 83583, the G-protein inhibitor
mas17 and the G-protein antagonist pGlu-Gln-D-Trp-Phe-D-Trp-D-Trp-Met-NH2. Comparison with stomatal opening in response to 8-Br-cGMP, which was almost completely suppressed by either BAPTA, ruthenium
red, procaine or Rp-8-Br-cGMPS, strongly suggests that cGMP acts downstream of G-protein activation as a second messenger
for IBA signal transduction and that the cGMP pathway likely depends on cytosolic Ca2+signaling.
Received: 8 November 1997 / Accepted: 6 March 1998 相似文献
3.
R. T. Dell'Orco T. J. Martin W. H. J. Douglas 《In vitro cellular & developmental biology. Plant》1977,13(1):55-62
Summary Mitotic activity in confluent cultures of human diploid fibroblasts was arrested by the reduction of the serum concentration
of the incubation medium to 0.5% or by the addition of 0.5mm 6-N, 2′-O-dibutyryl-adenosine 3′:5′-cyclic monophosphate (db cAMP). Under either of these conditions, cultures maintained
a constant cell number for 14 days; cultures continuously exposed to medium containing 10% serum doubled their cell number
during this 14-day period. The protein content per cell decreased by 20% when cells were maintained with 0.5% serum whereas
that of cells exposed to db cAMP remained constant. Ultrastructural studies revealed that cells exposed to db cAMP exhibited
a morphology typical of cells cultured with 10% serum alone, whereas cells incubated with 0.5% serum showed the ultrastructural
changes in mitochondria, endoplasmic reticulum and Golgi complex previously identified with low-serum arrest. Cellular adenosine
3′:5′-cyclic monophosphate (cAMP) levels remained constant during the 7-day growth period in which confluency was attained,
as well as during the 14-day arrested period with 0.5% serum. These results indicated that the mitotic inhibition induced
by reducing the serum concentration of the incubation medium was not mediated by increased intracellular levels of cAMP and
differed from that induced by the addition of exogenous db cAMP. 相似文献
4.
A E Kitabchi D B Wilson R K Sharma 《Biochemical and biophysical research communications》1971,44(4):898-904
Corticosterone production in isolated adrenal cells (IAC) of rat has been measured in response to ACTH or ribonucleoside 3′,5′-cyclic phosphate of adenosine (c-AMP), guanosine (c-GMP), inosine (c-IMP) and N6-2′-0 dibutyryl adenosine monophosphate (dc-AMP) in the presence and absence of caffeine. Caffeine inhibited ACTH-induced steroidogenesis in a manner independent of its effect on PDE. Study of PDE in whole adrenal homogenate showed hydrolysis of c-AMP, c-GMP and c-IMP but not of dc-AMP and other cyclic nucleotides. No PDE activity was demonstrable in IAC. High sensitivity of IAC to minute quantities of ACTH and various cyclic nucleotides may be due in part to lack of PDE activity in these preparations. 相似文献
5.
Plant Cyclic Nucleotide Signalling: Facts and Fiction 总被引:1,自引:0,他引:1
Juliana Martinez-Atienza Carl Van Ingelgem Luc Roef Frans JM Maathuis 《Plant signaling & behavior》2007,2(6):540-543
6.
The calcium-dependent modulation of the affinity of the cyclic nucleotide-gated (CNG) channels for adenosine 3′,5′-cyclic
monophosphate (cAMP) was studied in enzymatically dissociated rat olfactory receptor neurons, by recording macroscopic cAMP-activated
currents from inside-out patches excised from their dendritic knobs. Upon intracellular addition of 0.2 mm Ca2+ (0.2 Ca) the concentration of cAMP required for the activation of half-maximal current (EC50) was reversibly increased from 3 μm to about 30 μm. This Ca2+-induced affinity shift was insensitive to the calmodulin antagonist, mastoparan, was abolished irreversibly by a 2-min exposure
to 3 mm Mg2++ 2 mm EGTA (Mg + EGTA), and was not restored by the application of calmodulin (CAM). Addition of CAM plus 0.2 mm Ca2+ (0.2 Ca + CAM), further reversibly shifted the cAMP affinity from 30 μm to about 200 μm. This affinity shift was not affected by Mg + EGTA exposure, but was reversed by mastoparan. Thus, the former Ca2+-only effect must be mediated by an unknown endogenous factor, distinct from CAM. Removal of this factor also increased the
affinity of the channel for CAM. The affinity shift induced by Ca2+-only was maintained in the presence of the nonhydrolyzable cAMP analogue, 8-bromo-cAMP and the phosphatase inhibitor, microcystin-LR,
ruling out modulation by phosphodiesterases or phosphatases. Our results indicate that the olfactory CNG channels are modulated
by an as yet unidentified factor distinct from CAM.
Received: 26 December 1995/Revised: 14 March 1996 相似文献
7.
The dependence of currents through the cyclic nucleotide-gated (CNG) channels of mammalian olfactory receptor neurons (ORNs)
on the concentration of NaCl was studied in excised inside-out patches from their dendritic knobs using the patch-clamp technique.
With a saturating concentration (100 μm) of adenosine 3′, 5′-cyclic monophosphate (cAMP), the changes in the reversal potential of macroscopic currents were studied
at NaCl concentrations from 25 to 300 mm. In symmetrical NaCl solutions without the addition of divalent cations, the current-voltage relations were almost linear,
reversing close to 0 mV. When the external NaCl concentration was maintained at 150 mm and the internal concentrations were varied, the reversal potentials of the cAMP-activated currents closely followed the
Na+ equilibrium potential indicating that P
Cl/P
Na≈ 0. However, at low external NaCl concentrations (≤100 mm) there was some significant chloride permeability. Our results further indicated that Na+ currents through these channels: (i) did not obey the independence principle; (ii) showed saturation kinetics with K
ms in the range of 100–150 mm and (iii) displayed a lack of voltage dependence of conductance in asymmetric solutions that suggested that ion-binding sites
were situated midway along the channel. Together, these characteristics indicate that the permeation properties of the olfactory
CNG channels are significantly different from those of photoreceptor CNG channels.
Received: 7 November 1996/Revised: 24 March 1997 相似文献
8.
Cholera enterotoxin (CT) increased the concentration of adenosine 3′-5′-cyclic monophosphate (cAMP) in monolayer cultures of adrenal tumor cells after a 60 min lag phase in contrast to the rapid effect of adrenocorticotropin (ACTH). The change in intracellular cAMP was accompanied by the release of steroids into the culture medium and a reversible alteration of monolayer morphology. 相似文献
9.
Derivatives of cyclic-3′,5′-adenosine monophosphate, N6,2′-O-dibutyryl-cAMP, 8-(chlorophenylthio)-cAMP and 8-bromoadenosine-cAMP added at 0.1–10 μmol/L concentrations into the growth
medium have markedly stimulated conidiation inTrichoderma viride. Their stimulatory effect on conidiation was best observed in colonies that were constantly kept in the dark but was also
marked in colonies illuminated by sub-saturating doses of light. The relative stimulation of conidiation depended not only
on the concentration of exogenous cyclic nucleotides but also on the concentration of glucose in the medium. It was more pronounced
in glucose-rich media than in media where the concentration of the sugar was low. Concentrations of cAMP analogues equal to
50 μmol/L and higher inhibited the conidiation. 相似文献
10.
Costanzo G Pino S Botta G Saladino R Di Mauro E 《Origins of life and evolution of the biosphere》2011,41(6):559-562
Nucleic bases are obtained by heating formamide in the presence of various catalysts. Formamide chemistry also allows the
formation of acyclonucleosides and the phosphorylation of nucleosides in every possible position, also affording 2′,3′ and
3′,5′ cyclic forms. We have reported that 3′,5′ cyclic GMP and 3′,5′ cyclic AMP polymerize in abiotic conditions yielding
short oligonucleotides. The characterization of this reaction is being pursued, several of its parameters have been determined
and experimental caveats are reported. The yield of non-enzymatic polymerization of cyclic purine nucleotides is very low.
Polymerization is strongly enhanced by the presence of base-complementary RNA sequences. 相似文献
11.
Broken cells ofEscherichia coli contain an enzyme system breaking down cyclic 3′,5′-adenosine monophosphate (Ado-3′,5′-P). The enzyme splitting this nucleotide
is located in the supernatant fraction at 20,000 ×g. Some characteristics of the enzyme were studied. In contrast with the animal enzyme theEscherichia coli enzyme is not inhibited by caffeine. 相似文献
12.
Infrared spectra of neutral aqueous solutions of nucleoside 3′,5′-cyclic monophosphates indicate an increase in the antisymmetric phosphoryl stretching frequency to 1236 cm?1 from 1215 cm?1 in trimethylene cyclic phosphates. A further increase to 1242 cm?1 accompanies esterification of the 2′-ribose hydroxyl. The O2′-esterified and 2′-deoxy cyclic nucleotides examined display both reduced kinase binding and altered phosphoryl stretching frequencies, suggesting that modification of the phosphate ring represents a common feature in decreased kinase activation. Reversible inhibition of mitosis in thymidine-synchronized human lymphocytes by 2 mmN6,O2′-dibutyryladenosine 3′,5′-cyclic monophosphate and N6-monobutyryladenosine 3′,5′-cyclic monophosphate was observed. However, adenosine 3′,5′-cyclic monophosphate, O2′-monobutyryladenosine 3′,5′-cyclic monophosphate, butyric acid, and ethyl butyrate had no effect on mitosis when present at 2 mm concentrations during S and G2. These results are consistent with hydrolysis of O2′-monobutyryladenosine 3′,5′-cyclic monophosphate and adenosine 3′,5′-cyclic monophosphate by esterase and phosphodiesterase enzymes and suggest that modification of the N6 amino group is necessary for the antimitotic activity of N6,O2′-dibutyryladenosine 3′, 5′-cyclic monophosphate. 相似文献
13.
The role of 3′,5′-cyclic adenosine monophosphate (cAMP), protein kinase A (PKA), protein kinase C (PKC) and phosphatases
in the regulation of the taurine influx via the β-system in Ehrlich ascites tumor cells has been investigated. The taurine
uptake by the β-system in Ehrlich cells is inhibited when PKC is activated by phorbol 12-myristate 13-acetate (PMA) and when
protein phosphatases are inhibited by calyculin A (CLA). On the other hand, taurine uptake by the β-system is stimulated by
an increased level of cAMP or following addition of N6,2′-O-dibutyryl-3′,5′-cyclic adenosine monophosphate (dbcAMP). The effect of dbcAMP is partially blocked by addition of the
protein kinase inhibitor H-89, and suppressed in the presence of CLA. It is proposed that the β-system in the Ehrlich cells
exists in three states of activity: State I, where a PKC phosphorylation site on the transporter or on a regulator is phosphorylated and transport activity is low. State II, where the PKC phosphorylation site is dephosphorylated and transport activity is normal. State III, representing a state with high transport activity, induced by an elevated cellular cAMP level. Apparently, cAMP preferentially
stimulates taurine transport when the β-system is in State II.
Received: 8 September/Revised: 9 November 1995 相似文献
14.
Chloride (Cl−) conductances were studied in primary cultures of the bright part of rabbit distal convoluted tubule (DCTb) by the whole
cell patch clamp technique. The bath solution (33°C) contained (in mm): 140 NaCl, 1 CaCl2, 10 N-2-hydroxy-ethylpiperazine-N′-2-ethanesulfonic acid (HEPES), pH 7.4 and the pipette solution 140 N-methyl-d-glucamine (NMDG)-Cl, 5 MgATP, 1 ethylene-glycol-bis(b-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), 10 HEPES, pH 7.4. We identified a Cl− current activated by 10−5
m forskolin, 10−3
m 8-bromo adenosine 3′,5′-cyclic monophophosphate (8 Br-cAMP), 10−6
m phorbol 12-myristate 13-acetate (PMA), 10−3
m intracellular adenosine 3′,5′-cyclic monophophosphate (cAMP) and 10−7
m calcitonin. The current-voltage relationship was linear and the relative ion selectivity was Br− > Cl−≫ I− > glutamate. This current was inhibited by 10−3
m diphenylamine-2-carboxylate (DPC) and 10−4
m 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) and was insensitive to 10−3
m 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS). These characteristics are similar to those described for the cystic
fibrosis transmembrane conductance regulator (CFTR) Cl− conductance. In a few cases, forskolin and calcitonin induced an outwardly rectifying Cl− current blocked by DIDS. To determine the exact location of the Cl− conductance 6-methoxy-1-(3-sulfonatopropyl) quinolinium (SPQ) fluorescence experiments were carried out. Cultures seeded
on collagen-coated permeable filters were loaded overnight with 5 mm SPQ and the emitted fluorescence analyzed by laser-scan cytometry. Cl− removal from the apical solution induced a Cl− efflux which was stimulated by 10−5
m forskolin, 10−7 calcitonin and inhibited by 10−5
m NPPB. In 140 mm NaBr, forskolin stimulated an apical Br− influx through the Cl− pathway. Forskolin and calcitonin had no effect on the basolateral Cl− permeability. Thus in DCTb cultured cells, exposure to calcitonin activates a Cl− conductance in the apical membrane through a cAMP-dependent mechanism.
Received: 5 July 1995/Revised: 21 December 1995 相似文献
15.
Polysphondylium violaceum is shown to produce and excrete cyclic nucleotides and to produce a cell-associated cyclic nucleotide phosphodiesterase(s). The amount of adenosine 3′,5′-cyclic monophosphate (cAMP) excreted by the amebae reaches a maximum during development when aggregation centers are just forming and then falls off rapidly. Measurements of total cAMP show that the amount synthesized increases more than 15-fold throughout development with the majority of the increase coming during the culmination stages. Guanosine 3′,5′-cyclic monophosphate (cGMP) is either not excreted or is excreted at levels below our limits of detection. An increase in the total cGMP synthesized occurs at mid-aggregation when two or three sharp peaks of synthesis are observed. However, development of P. violaceum is not affected by the addition of high concentrations of either cAMP or cGMP (or their dibutyryl derivatives) to the medium despite the fact that the cells produce these nucleotides. Cell-associated cyclic nucleotide phosphodiesterase activity, which hydrolyses both cAMP and cGMP, is greatest at the onset of starvation with a second increase in activity during aggregation. 相似文献
16.
Phosphate esters play a central role in cellular energetics, biochemical activation, signal transduction and conformational
switching. The structural homology of the borate anion with phosphate, combined with its ability to spontaneously esterify
hydroxyl groups, suggested that phosphate ester recognition sites on proteins might exhibit significant affinity for nonenzymatically
formed borate esters. 11B NMR studies and activity measurements on ribonuclease A (RNase A) in the presence of borate and several cytidine analogs
demonstrate the formation of a stable ternary RNase A·3′-deoxycytidine–2′-borate ternary complex that mimics the complex formed
between RNase A and a 2′-cytidine monophosphate (2′-CMP) inhibitor. Alternatively, no slowly exchanging borate resonance is
observed for a ternary RNase A, borate, 2′-deoxycytidine mixture, demonstrating the critical importance of the 2′-hydroxyl
group for complex formation. Titration of the ternary complex with 2′-CMP shows that it can displace the bound borate ester
with a binding constant that is close to the reported inhibition constant of RNase A by 2′-CMP. RNase A binding of a cyclic
cytidine-2′,3′-borate ester, which is a structural homolog of the cytidine-2′,3′-cyclic phosphate substrate, could also be
demonstrated. The apparent dissociation constant for the cytidine-2′,3′-borate·RNase A complex is 0.8 mM, which compares with
a Michaelis constant of 11 mM for cytidine-2′,3′-cyclic phosphate at pH 7, indicating considerably stronger binding. However,
the value is 1,000-fold larger than the reported dissociation constant of the RNase A complex with uridine–vanadate. These
results are consistent with recent reports suggesting that in situ formation of borate esters that mimic the corresponding
phosphate esters supports enzyme catalysis. 相似文献
17.
Stopped-flow spectrophotometric studies of the reductive amination of L-ketoglutarate by L-glutamate dehydrogenase showed a biphase time course, which consisted of a rapid first phase lasting 60–100 msec and a slow final phase in which the rate of coenzyme oxidation increased until the coenzyme was depleted. The effects of 3,5-cyclic adenosine monophosphate (cAMP) and 3,5-cyclic guanosine monophosphate (cGMP) on the time course of both phases were established. The results showed that in the concentration ranges used the cyclic nucleotides accelerate the catalytic reaction. The effect of cAMP was more pronounced as compared to cGMP. In all cases this influence was most clearly expressed in the first phase. Using an Arrhenius plot the activation parameters were calculated. The experiments with cAMP and cGMP at different molar ratios showed that a specific cAMP binding may occur. 相似文献
18.
Myogenesis in vitro. Enhancement by dibutyryl cAMP 总被引:1,自引:0,他引:1
Cholera enterotoxin (CT) increased the concentration of adenosine 3′-5′-cyclic monophosphate (cAMP) in monolayer cultures of adrenal tumor cells after a 60 min lag phase in contrast to the rapid effect of adrenocorticotropin (ACTH). The change in intracellular cAMP was accompanied by the release of steroids into the culture medium and a reversible alteration of monolayer morphology. 相似文献
19.
Ulrike Beckert Wen Yih Aw Heike Burhenne Lisa F?rsterling Volkhard Kaever Lisa Timmons Roland Seifert 《PloS one》2013,8(8)
Adenosine 3′, 5′-cyclic monophosphate (cAMP) and guanosine 3′, 5′-cyclic monophosphate (cGMP) are well-studied second messengers that transmit extracellular signals into mammalian cells, with conserved functions in various other species such as Caenorhabditis elegans (C. elegans). cAMP is generated by adenylyl cyclases, and cGMP is generated by guanylyl cyclases, respectively. Studies using C. elegans have revealed additional roles for cGMP signaling in lifespan extension. For example, mutants lacking the function of a specific receptor-bound guanylyl cyclase, DAF-11, have an increased life expectancy. While the daf-11 phenotype has been attributed to reductions in intracellular cGMP concentrations, the actual content of cyclic nucleotides has not been biochemically determined in this system. Similar assumptions were made in studies using phosphodiesterase loss-of-function mutants or using adenylyl cyclase overexpressing mutants. In the present study, cyclic nucleotide regulation in C. elegans was studied by establishing a special nematode protocol for the simultaneous detection and quantitation of cyclic nucleotides. We also examined the influence of reactive oxygen species (ROS) on cyclic nucleotide metabolism and lifespan in C. elegans using highly specific HPLC-coupled tandem mass-spectrometry and behavioral assays. Here, we show that the relation between cGMP and survival is more complex than previously appreciated. 相似文献
20.
The effect of calcium concentration on ACTH stimulation of steroidogenesis in mouse adrenal tumor cells 总被引:1,自引:0,他引:1
Calcium is required for ACTH stimulated steroidogenesis in adrenal tumor cells in tissue culture. In the absence of calcium, the dose of ACTH required to induce half maximum steroidogenesis was increased 30 fold. In contrast to intact adrenal glands or isolated adrenal cells, high doses of ACTH (50 mU/ml) maximally stimulated steroidogenesis in the absence of calcium. Growth for up to six days in medium with low calcium did not affect basal or ACTH induced steroidogenesis. The addition of calcium to cells incubated with ACTH produced a maximum steroidogenic response in 15 minutes. In contrast to intact adrenal glands, calcium is not required for adenosine-3′,5′-cyclic monophosphate (cyclic AMP) stimulated steroidogenesis in adrenal tumor cells. These experiments support the concept that calcium is important at the level of ACTH-membrane receptor site interaction or activation of adenyl cyclase in adrenal tumor cells. 相似文献