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1.
Modulation of rat skeletal muscle chloride channels by activators and inhibitors of protein kinase C
D. Tricarico D. Conte Camerino S. Govoni S. H. Bryant 《Pflügers Archiv : European journal of physiology》1991,418(5):500-503
The membrane electrical parameters and component conductances of rat extensor digitorum longus muscle fibres were studied in vitro at 30 °C with standard two microelectrode square pulse cable analysis in the presence of protein kinase C (PKC) activators and inhibitors. The PKC activator, 4--phorbol-12,13 dibutyrate (4--PDB), (2–90nM) blocked up to 67% chloride conductance (G
Cl) in rat skeletal muscle fibres and induced myotonic hyperexcitability. The concentration necessary to produce a 50% block of the membrane G
Cl was 23 nM. The inactive 4--phorbol-12,13 dibutyrate had no effect at 2 M. The blocking effect of 4--PDB on G
Cl was prevented by preincubation of the preparations with the PKC inhibitors, staurosporine (1–5 M) and tetrahydropapaverolone (50–100 M). The blocking effects on membrane G
Cl of 4--PDB and its antagonism by the inhibitors used support the concept of the involvement of PKC in regulating Cl channels of mammalian skeletal muscle fibres. 相似文献
2.
Domenico Tricarico Diana Conte Camerino 《Pflügers Archiv : European journal of physiology》1994,426(1-2):44-50
Electrical parameters of extensor digitorum longus (EDL) muscles and their contralaterals were measured in vitro at 30°C by a computerized two intracellular microelectrode technique after ischaemia and postischaemic reflow. In some muscles the adenosine triphosphate (ATP) levels are also measured. Ischaemia led to a 39% reduction of Cl– conductance (G
Cl), whereas reperfusion increase G
Cl by 18% with respect to contralateral control muscles. Ischaemia and reperfusion increased K+ conductance (G
K) by 21% and 68%, respectively; this increased was reversed by 50 M glybenclamide, suggesting an involvement of ATP-sensitive K+ channels. A statistically significant hyperpolarization and increase in excitability was observed after ischaemia, whereas after the reflow period the fibres were depolarized and less excitable. Ischaemia and reperfusion lowered the intracellular ATP content by 18% and 64%, respectively. 相似文献
3.
Kenji Kitamura Zhiling Xiong Noriyoshi Teramoto Hirosi Kuriyama 《Pflügers Archiv : European journal of physiology》1992,421(6):539-551
We examined the effects of heparin, guanosine nucleotides, protein kinase C (PKC) modulators, such as phorbol 12,13-dibutylate (PDBu) and H-7 on Ca2+-dependent K+ currents in smooth muscle cells of the rabbit portal vein using the whole-cell patch-clamp technique, to explore the effects of PKC on the oscillatory outward current (I
oo). Neomycin (30 M), an inhibitor of phospholipase C, and intracellular applications of heparin (10 g/ml) and guanosine 5-O-(2-thiodiphosphate) (GDP[S]; 1 mM) partly but consistently inhibited the generation of I
oo, whereas a higher concentration of heparin (100 g/ml) transiently enhanced then suppressed the generation of I
oo. Inhibition of I
oo generation by heparin was more powerful at the holding potential of + 20 mV than at –20 mV. Inositol 1,4,5-trisphosphate (InsP
3; 30 M) continuously generated I
oo at holding potentials more positive than –60 mV. Noradrenaline (10 M) and caffeine (3–20 mM) transiently augmented, then reduced the generation of I
oo. Heparin (10 g/ml) completely inhibited responses induced by InsP
3 and noradrenaline, but not those induced by caffeine. Intracellular application of guanosine 5-triphosphate (GTP; 200 M) or low concentrations of guanosine 5-O-(3-thiotriphosphate) (GTP[S]; 3 M) continuously augmented the generation of I
oo. High concentrations of GTP[S] (10 M) transiently augmented, then inhibited I
oo. Neither GTP[S] nor noradrenaline induced the transient augmentation or the subsequent inhibition of I
oo when applied in the presence of GDP[S] (1 mM), neomycin (30 M) or heparin (10 g/ml). PDBu (0.1 M) reduced the generation of I
oo but failed to produce an outward current following application of caffeine (3–5 mM). This action of PDBu was inhibited by pretreatment with H-7 (20 M). In the presence of H-7, GTP[S] continuously enhanced the generation of I
oo. The suppression of the generation of I
oo during application of noradrenaline (10 M) was reduced by pretreatment with H-7. Thus both InsP3 and protein kinase C contribute to the generation of I
oo in smooth muscle cells of the rabbit portal vein and heparin is not a specific InsP
3 antagonist on the InsP
3-induced Ca2+-release channel (PIRC). InsP
3 opens PIRC and protein kinase C may deplete the stored Ca2+ by either inhibiting the reuptake of Ca2+ or by enhancement of the releasing actions of InsP
3. 相似文献
4.
S. H. Bryant D. Conte-Camerino 《Pflügers Archiv : European journal of physiology》1991,417(6):605-610
External intercostal muscle biopsies from normal and congenitally myotonic goats were studied in vitro at 30° C using a two-microelectrode square-pulse cable analysis assisted by computer. The resting chloride conductance (G
cl) was estimated from the difference between the mean membrane conductance in chloride-containing and chloride-free bathing media. The protein kinase C (PKC) activator, 4--phorbol-12,13-dibutyrate, (0.1–2.0 M) blocks a maximum of 76% of G
cl in normal goat fibers and induces myotonic hyperexcitability similar to that of congenitally myotonic goat fibers. The G
cl block was partially antagonized by pretreatment with the PKC inhibitor, staurosporine (10 M). The inactive 4-phorbol-12, 13,didecanoate had no effect at 50 M, whereas the active 4- isomer blocked 41% G
cl at 1 M. The nearly absent G
cl of congenitally myotonic goat fibers was not restored by treatment with high concentrations of the PKC inhibitors staurosporine, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7), or tetrahydropapaveralone (THP). Also, forskolin and cholera toxin, which may increase cyclic adenosine monophosphate (cAMP) levels, or the R(+) clofibric acid enantiomers and taurine, which increase G
cl in normal fibers, were also unable to restore G
cl in myotonic goat fibers. The data suggest that PKC may be a chloride channel regulator in normal goat skeletal muscle fibers, however the molecular defect of congenitally myotonic fibers does not appear to be due to excessive activity of PKC. 相似文献
5.
Sil'kis IG 《Neuroscience and behavioral physiology》2003,33(4):379-386
A possible mechanism is proposed for the enhancement/weakening of those cortical signals in the cortex-basal ganglia-thalamus-cortex neural network which induce/do not induce opening of NMDA channels in the spiny neurons of the striatum and which can be regarded as strong/weak in terms of this measure. The mechanism is based on the modulatory influences of dopamine on changes in the efficiency of corticostriatal inputs. In the absence of dopamine, relative increases in the intensity of strong (weak) cortical signals can lead to the induction of long-term potentiation (depression) of corticostriatal synapses. In this case, because of the differently directed influences on thalamic cells of signals passing via strionigral and striopallidal cells, strong signals at the output of the thalamus are weakened, while weak signals are strengthened. Activation of dopamine D1 (D2) receptors on strionigral (striopallidal) neurons may facilitate increases in the extent of long-term potentiation/depression (decreases in the extent of long-term potentiation/depression or induction of long-term potentiation/depression). The consequence of this is that strong signals at the output of the thalamus can be strengthened synergistically, while weak signals cab be weakened synergistically. Background cortical signals evoking tonic release of dopamine in the striatum can decrease strengthening because of weakening of the modulatory influence of dopamine on the modification of corticostriatal synapses. 相似文献
6.
Monica Lupu-Meiri Hagit Shapira Yoram Oron 《Pflügers Archiv : European journal of physiology》1989,413(5):498-504
Muscarinic stimulation of follicle-enclosed oocytes ofXenopus laevis results in a complex response that involves both depolarizing and hyperpolarizing currents (Dascal and Landau 1980). We studied the involvement of protein kinase C (PK-C1) in the regulation of the acetylcholine-evoked rapid (D1) and of the slow (D2) depolarizing chloride (Cl–) currents. In oocytes maintained at –100 mV [the reversal potential of potassium (K+) ions] under two electrode voltage clamp, the PK-C activator 4--phorbol 12-myristate 13-acetate (-PMA, 0.1 M) stimulated D1 by 99±17% and inhibited D2 by 67±6%, vs. untreated controls. The inactive isomer (-PMA) or phorbol alone had no significant effect on the components of the muscarinic response. In order to identify the site of the regulation, we have microinjected the intracellular second messenger of calcium mobilization, inositol 1,4,5-trisphosphate (IP3). -PMA or the diacylglycerol analog, oleoylacetylglycerol (OAG) stimulated the rapid depolarizing current evoked by IP3 by 220±26% and 394±102%, respectively. -PMA had little if any effect. The calcium-evoked Cl– current in oocytes pre-treated with the divalent cation ionophore A23187 was, on the other hand, inhibited by -PMA and OAG (by 82±6% and 54±6%, respectively). -PMA and phorbol had a limited inhibitory effect. -PMA, but not -PMA, also mildly inhibited the IP3-evoked increase in45Ca efflux. The intracellular metabolism of IP3 was not affected by exposure to either -PMA or OAG. In conclusion, PK-C appears to regulate the acetylcholine-evoked Cl– response in a complex pattern: inhibition of the slow (D2) Cl– current (possibly directly on the Cl– channel) and stimulation of the rapid (D1) Cl– current. Both sites of regulation seem to be distal to IP3 metabolism and to IP3-evoked calcium mobilization. Our results are consistent with the possibility that the complex muscarinic response in Xenopus oocyte is mediated by two populations of Cl– channels.Abbreviations used ACh
Acetylcholine
- DG
diacylglycerol
- EGTA
ethyleneglycol bis-(aminoethyl ether) N,N,N,N-tetraacetic acid
- Hepes
N-2-hydroxyethylpiperazine-N-2-hydroxypropanesulfonic acid
- IP3
inositol 1,4,5-trisphosphate
- OAG
oleoylacetylglycerol
- PD Bu
4--phorbol 12,13-dibutyrate
- -PMA
4--phorbol 12-myristate 13-acetate
- -PMA
4--phorbol 12-myristate 13-acetate
- PIP2
phosphatidylinositol 4,5-bisphosphate
- PK-C
protein kinase C 相似文献
7.
B. Nürnberg T. Gudermann G. Schultz 《Journal of molecular medicine (Berlin, Germany)》1995,73(3):123-132
Seven-transmembrane receptors signal through nucleotide-binding proteins (G proteins) into the cell. G proteins are membrane-associated proteins composed of three subunits termed , and , of which the G subunit classifies the heterotrimer. So far, 23 different mammalian G subunits are known, which are grouped in four subfamilies (Gs, Gi, Gq, G12) on the basis of their amino acid similarity. They carry an endogenous GTPase activity allowing reversible functional coupling between ligand-bound receptors and effectors such as enzymes and ion channels. In addition, five G and seven G subunits have been identified which form tightly associated heterodimers. Upon activation by a ligand-bound receptor the G protein dissociates into G and G, which both transmit signal by interacting with effectors. On the G protein level, specificity and selectivity of the incoming signal is accomplished by G protein trimers composed of distinct subunits. On the other hand, many receptors have been shown to activate different G proteins, thereby regulating diverse signal transduction pathways.Abbreviations
CT
Cholera toxin
-
PT
Pertussis toxin 相似文献
8.
E. Bruch Igartua R. Domecq J. Findor 《Journal of molecular medicine (Berlin, Germany)》1973,51(6):272-274
Summary A new method for the separation of isoenzymes of-glutamyl-transpeptidase is described, using electrophoresis on acetate cellulose gel and a developing solution composed by-glutamyl-naphthylamide, and a colored diazonium compound.The method permits the separation of up to four different isoenzymes, which we called-GT1,-GT2,-GT3,-GT4, the first two showing an electrophoretic migration similar to that of
1- and
2-globulins and the other two to that of-globulins.The present technique has proved its usefulness in detecting isoenzymes in serum with values of total-glutamyl-transpeptidase higher than 80 U/L.The application of this method in 52 patients with different types of biliary obstruction and hepatocellular damage has shown that it provides new possibilities in differential diagnosis. 相似文献
9.
Marie -Christine Broillet Anouk Berger Jean -Daniel Horisberger 《Pflügers Archiv : European journal of physiology》1993,424(1):91-93
Summary Aldosterone increases the basolateral conductance in target epithelia. The basolateral membrane of tight epithelia contains two different types of K+ conductances (GK), a resting and a volume-activated GK. We have studied the early effects (at 4 hours) of 500 nmol/l aldosterone on the basolateral membrane Gk of A6 cells (a Xenopus laevis kidney cell line), after the permeabilization of the apical membrane with amphotericin B. In the presence of a 97 to 3 mmol/l apical to basolateral K+ gradient, the resting, inward rectifying GK was similar in control and aldosterone treated cells. In contrast, aldosterone induced a 2-fold increase of the volume-activated quinidine sensitive GK. 相似文献
10.
Summary Embryogenic and non-embryogenic long-term callus cultures of hexaploid wheat exhibit differences in the organization of their mitochondrial genome. Embryogenic and non-embryogenic fractions of callus cultures initiated from immature embryos of the wheat cultivar Chinese Spring have been isolated and subsequently subcultured. DNA-DNA hybridization experiments using labelled cloned wheat mitochondrial DNA fragments have shown that the mitochondrial DNA organization of embryogenic subcultures derived from embryogenic parts of Chinese Spring calli is closely related to that of the initial Chinese Spring calli, while non-embryogenic subcultures derived from non-embryogenic fragments of Chinese Spring calli exhibit a mitochondrial DNA organization similar to that found in non-embryogenic calli derived from cultivar Aquila. In addition, somatic tissue cultures initiated from three other non-embryogenic wheat cultivars (Talent, Thésée and Capitole) display mitochondrial DNA arrangements similar to those found in cultivar Aquila. These results strongly suggest that, in wheat callus cultures, a particular mitochondrial genome organization is correlated with the ability of cultured cells to regenerate whole plants.Abbreviations
mtDNA
mitochondrial DNA
-
ctDNA
chloroplast DNA
-
rRNA
ribosomal RNA
-
kb
kilobase pair
-
cv
cultivar
-
2,4-D
2,4-dichlorophenoxyacetic acid 相似文献
11.
O. Wetter und K. Jahnke 《Journal of molecular medicine (Berlin, Germany)》1966,44(14):807-813
Zusammenfassung Die aus dem optischen Drehungsvermögen abgeleiteten Konstanten elektrophoretisch isolierterA-Paraproteine werden mitgeteilt. Die Dispersionskonstante
c
weist keine Unterschiede zwischen den 3 ParaproteingruppenG,A undM auf. Der nach dem Verfahren vonMoffitt undYang ermittelte Parameterb
0 wurde zu Schätzung des-Helixgehaltes benutzt. Er betrug in den 7 untersuchten Paraproteinen 0. Für den Parameter —a
0 ergab sich ein Mittelwert von 276,0±35,1. FürG-Paraprotein wurde in früheren Untersuchungen ein solcher von 312,8±20,8, fürM-Paraprotein 217,9±26,7 gefunden. Der Mittelwertsvergleich zeigte Signifikanz der Konstantea
0 für jede der 3 Paraproteingruppen.a
0 beschreibt demnach gruppenspezifische Eigenschaften von Paraproteinen. Die für den Wert vona
0 maßgeblichen strukturellen Voraussetzungen sind kaum bekannt. Sie werden am ehesten die die spezifischen Antigendeterminanten tragenden H-Ketten des Paraproteinmoleküls betreffen.
Summary The constants of the optical rotatory dispersion of electrophoretically isolatedA-paraproteins are communicated. There is no difference between theG,A andM-paraprotein group with respect to the dispersion constant c . The parameterb 0 was measured according toMoffitt andYang. The-Helix-content calculated fromb 0 of 7A-paraproteins was sero (0).The mean value of the parameter —a 0 was 276±35,1. In earlier experiments it was found that —a 0 forG-paraproteins is 312,8±20,8 and forM-paraproteins 217,9±26,7. The parametera 0 of each group differs significantly from the others; in other words,a 0 is group specific. The structural implications of these findings are discussed.相似文献
12.
Dietrich Mack Mathias Pulz Jürgen Heesemann 《Medical microbiology and immunology》1991,180(4):205-211
The structural relation of YOP-1 of european and american Yersinia enterocolitica serotypes O3, O9, O5, 27, and O8 and O20, respectively, and Y. pseudotuberculosis serotypes I, II, and III was compared by sodium dodecyl sulfate polyacrylamide gel electrophoresis and peptide mapping using Staphylococcus aureus protease V8. Apparent molecular weights of YOP-1 ranged from 206,000 (O3) to approx. 180,000 (O8). According to their respective peptide maps YOP-1 of the european and american Y. enterocolitica serotypes and Y. pseudotuberculosis serotypes could be assigned to three different groups. Evaluation of several isolates of Y. enterocolitica serotypes O3, O9, and O8 by peptide mapping indicated that YOP-1 is conserved within a serotype. However, one serotype O8 isolate differed from the consensus peptide pattern of the other serotype O8 and O20 isolates. The similarity of the peptide patterns of Yersinia serotypes which predominate in certain geographical locations, i. e., european and american Y. enterocolitica serotypes, suggest common evolution of YOP-1 of these serotypes independent of the evolution of the other serotypes. 相似文献
13.
Frédéric Becq Etienne Hollande Maurice Gola 《Pflügers Archiv : European journal of physiology》1993,425(1-2):1-8
A low-conductance Cl– channel has been identified in the apical membrane of the human pancreatic duct cell Capan-1 using patch-clamp techniques. Cell-attached channels were activated by the vasoactive intestinal polypeptide (VIP, 0.1 mol/l), dibutyryl-adenosine 3,5-cyclic monophosphate (db-cAMP, 1 mmol/l), 8-bromo adenosine 3,5-cyclic monophosphate (8-BrcAMP, 1 mmol/l), 3-isobutyl-1-methyl-xanthine (IBMX, 100 mol/l) and forskolin (10 mol/l). No channel activity was observed in non-stimulated control cells. In both cell-attached and excised inside-out patches, the channel had a linear current/voltage relationship and a unitary conductance of 9 pS at 23°C and 12 pS at 37°C. Its opening probability was not voltage dependent although pronounced flickering was induced at negative potentials. Anionic substitution led to the selectivity sequence Cl–>I–>HCO3
–>gluconate. In insideout excised patches, the channel activity declined spontaneously within a few minutes. Reactivation of silent excised channels was achieved by adding protein kinase A (PKA, in the presence of ATP, cAMP and Mg2+). Conversely, active channels were silenced in the presence of alkaline phosphatase. The PKA-activated Cl– channel was 4,4-diisothiocyanatostilbene-2,2-disulphonic acid (DIDS, 100 mol/l) and 4-acetamido-4-isothiocyanatostilbene-2, 2-disulphonic acid (SITS, 100 mol/l) insensitive, but was blocked by diphenylamine-2-carboxylic acid (DPC, 100 mol/l). These results demonstrate that the apical low-conductance Cl– channel in Capan-1 is regulated on-cell by VIP receptors via cAMP and off-cell by PKA and phosphatases. They provide evidence that this channel is closely related to the cystic fibrosis transmembrane conductance regulator (CFTR) Cl– channel. 相似文献
14.
A. Cavalié T. J. A. Allen W. Trautwein 《Pflügers Archiv : European journal of physiology》1991,419(5):433-443
In the heart, the guanosine 5-triphosphate (GTP)-binding protein Gs is activated by hormone binding to -adrenergic receptors and stimulates the intracellular cyclic adenosine 3,5-monophosphate (cAMP) pathway that leads to phosphorylation of L-type Ca channels by the cAMP-dependent protein kinase A [28]. Additionally, Gs can modulate cardiac Ca channels directly in cell-free systems [57]. In order to examine the question of whether these pathways could be separated functionally and whether they act independently or synergistically on L-type Ca channels in intact cells, the whole-cell Ca current (I
Ca) and the respective current density were measured in guinea-pig ventricular myocytes at 0 mV. The following results were obtained.First, typically, the I
Ca density increased from 12 to 40 A/cm2 following application of 1 M isoproterenol (ISP) to myocytes bathed in solutions containing 1.8 mM CaCl2. However, 1 M ISP enhanced I
Ca only from 9 to 17 A/cm2 after inhibition of the protein kinase A by dialysis of 0.5 mM Rp-cAMPS (the Rp-isomer of adenosine 3,5-monophosphorothioate) in the presence of 0.5 mM GTP. Withdrawal of GTP from the dialysate attenuated the effects of ISP on I
Ca. Thus, Rpc-AMPS unmasks a GTP-dependent component of the -adrenergic stimulation of I
Ca, which probably reflects the direct stimulation of Ca channels by Gs under block of cAMP-dependent phosphorylation.Second, in cells under dialysis with 100 or 200 M cAMP, bath application of 20–40 M 3-isobutyl-1-methylxanthine (IBMX) enhanced the I
Ca density to about 41 A/cm2 indicating saturation of the cAMP pathway. Under this condition, 1 M ISP was without significant effect on I
Ca. This result may suggests that direct Gs stimulation is rather ineffective on Ca channels after maximal cAMP-dependent phosphorylation. Alternatively, maximal stimulation of the cAMP pathway may also interfere with the activation of the Gs pathway in intact myocytes.Third, simultaneous application of 1 M ISP and 40 M IBMX enhanced I
Ca up to densities of around 75 A/cm2 during cell dialysis with 100 M cAMP, an effect much stronger than that exerted by IBMX alone under similar conditions. Since it seems likely that Gs is activated more quickly, than the cAMP pathway during application of the ISP/IBMX mixture, the latter result suggests that a direct effect of Gs may act to prime L-type Ca channels for cAMP-dependent phosphorylation during -adrenergic stimulation of cardiac myocytes. 相似文献
15.
Selected ester- (AL-5898 and AL-8417) and amide-linked benzopyran analogues (AL-7538 and AL-12615) were evaluated in vitro for their ability to inhibit key enzymes/processes of the inflammatory response. AL-7538 and AL-12615 exhibited weak intrinsic cyclooxygenase inhibitory activity (IC50 = 13 M, 37 M). In contrast, 5-HETE and LTB4 synthesis in A23187-stimulated neutrophils was effectively inhibited by both ester and amide analogs (IC50 = 2–3 M). While there was some indication for differing sensitivities among benzopyran esters and amides in the suppression of cytokine synthesis in stimulated U-937 cells, there appeared to be no great discrimination when assessing their effect on U-937 cell adhesion to IL-1 activated HMVEC-L cells. Inhibition of cell adhesion was concentration-dependent, with IC50 values ranging between 18 M and 30 M for AL-5898. Concentration-dependent inhibition of inflammatory cytokine production (i.e., IL-1, TNF-, GM-CSF and IL-6) was also apparent in LPS-stimulated, cultured PBMC as well as in PMA/A23187 activated U-937 cells monitoring the synthesis of IL-1, IL-8, TNF-, and MCP-1. Notably, the hydrolysis products of the benzopyranyl ester, AL-5692 and (S)-6-methoxy--methyl-2-naphthaleneacetic acid, were devoid of pharmacological activity when assessed for inhibition of monocyte adhesion or IL-1 synthesis. Collectively, our data demonstrate the unique in vitro polypharmacology of a novel series of benzopyran analogs that suppress pivotal enzymes and processes in the inflammatory response. 相似文献
16.
Summary A series of transposable element-induced mutations at the HIS4 locus in Saccharomyces cerevisiae have been attributed to the transposition of a Ty element into the 5 regulatory region of this gene. Various Ty-containing His+ revertants have been isolated and the HIS4/Ty junction region sequenced. The only difference found in this region between a His- and a weak His+ strain was a single point mutation, an AG transition. The position of Ty remained unaltered. Examination of lacZ fusion plasmids further implicated this AG transition as being reponsible for the altered phenotype, the bp transition representing an allele of a cis-acting regulatory element. Subsequent gel retardation and methylation interference experiments revealed that this AG mutation enabled the binding of a trans-acting factor (TyBf) in vitro. In this paper we show that the TyBf binding site is in a region of chromatin hypersensitive to digestion by DNase I. The binding site is protected in vivo from digestion with exonuclease III, suggesting the presence of a bound protein in His+ (on) but not His- (off) Ty-containing strains. We propose that a trans-acting factor binding in vivo, presumably TyBf, is responsible for the activation of HIS4 expression in these insertion mutants. 相似文献
17.
We have previously shown that trauma patients' monocytes which arein vivo activated by multiple injury-induced mediators have elevated transforming growth factor-beta (TGF) bioactivity. Interleukin-4 (IL-4), a Th2 and B lymphocyte stimulatory factor, has been shown to inhibit monocyte production of a number of mediators both after lipopolysaccharide stimulation and after trauma-induced stimulation. However, IL-4 inhibitory effects appears to vary, depending on the mixture of inducing stimuli. Here we describe thein vitro IL-4 inhibition of human monocyte TGF bioactivity using several stimulation induction protocols: muramyl dipeptide stimulation alone, or after FcRI (CD64) cross-linking induction, interferon-gamma (IFN) priming, or trauma-generatedin vivo mediator induction. IL-4 suppressed both muramyl dipeptide-induced TGF bioactivity and TGF mRNA in a dose-dependent fashion and was most effective when IL-4 was administered at initiation of normal monocyte stimulation. Muramyl dipeptide (MDP)-induced increases in trauma patients' monocyte TGF bioactivity were also inhibited by high doses of IL-4 (25 ng/ml). FcRI cross-linking increased MDP-induced normal monocyte TGF bioactivity, but this increase could be consistently inhibited only by very high IL-4 concentrations (50 ng/ml). IL-4 did not consistently downregulate MDP-induced TGF bioactivity in IFN-primed monocytes. IL-4 can suppress monocyte TGF production, as well as other monocyte mediators, but its efficiency depends on the stimuli combination present in the microenvironment. 相似文献
18.
Kohtaro Fujihashi Mi-Na Kweon Hiroshi Kiyono John L. VanCott Frederick W. van Ginkel Masafumi Yamamoto Jerry R. McGhee 《Springer Seminars in Immunopathology》1997,18(4):477-494
Conclusions Mucosal immune responses are strongly regulated by CD4+ T cells and their derived cytokines. In this regard, IFN-–/– mice (i.e., which lack Th1 and have elevated Th2 cells) showed strong mucosal Th2-type responses together with S-IgA production, while IL-4–/– (e.g., dominant Th1 and lack of Th2 cells) mice had impaired mucosal Th2 and IgA responses following oral delivery of TT and CT. However, when rSalmonella or radenovirus were used for antigen delivery, significant levels of mucosal IgA responses were induced in both IFN-–/– and IL-4–/– mice. The choice of the antigen delivery system which leads to optimal Th and B cell interactions are important for the induction of effective IgA responses, even in situations where the immune system is compromised. It is clear that Th2-type cytokines are important in mucosal IgA responses; however, other cytokine combinations can compensate for mucosal immunity in situations in which Th2 cell responses are absent. Mucosally induced tolerance may be one approach to prevent several systemic immune disorders; however, the mechanism of this phenomenon still needs to be elucidated. Our recent findings have suggested that IFN- may play an important role in induction of systemic unresponsiveness since oral tolerance was not induced in IFN-–/– mice.Our studies as well as those of others indicated that at least two phases of a triad of cell interactions are important for the mucosal immune system. First, it has been shown that epithelial cell-produced IL-7 and SCF and T cell-derived IL-2 are essential activation and growth signals for intestinal T cells. Second, our studies with TCR knockout mice have suggested that mucosal T cells also play a critical role in the regulation of mucosal IgA responses. Thus, a mucosal internet among T cells, T cells, and IgA B cells appear critical for mucosal homeostasis and for regulation of specific mucosal immune responses. 相似文献
19.
P. G. Kostyuk E. A. Lukyanetz A. S. Ter-Markosyan 《Pflügers Archiv : European journal of physiology》1992,420(2):146-152
Effects of parathyroid hormone substance (PTH) on the voltage-activated calcium current (I
Ca) were studied on intracellularly perfused neurones of the snail, Helix pomatia, under voltage-clamp conditions. Application of 0.1 nM PTH produced a marked potentiation of the current. The effect developed slowly (60–70 min) and remained after removal of PTH. Potentiation could be observed in most neurones, but varied considerably from cell to cell; in some neurones I
Ca was increased 2- to 3-fold. Addition of ethylenebis(oxonitrilo)tetraacetate (EGTA, 10 mM) to, or removal of adenosine 5-triphosphate (ATP, 2 mM) from the intracellular perfusing solution resulted in a suppression or attenuation of the potentiating effect. The effect could be reproduced by the synthetic 1–34 amino acid fragment of PTH. Extracellularly applied protein kinase-C (PK-C) activator phorbol ester phorbol 12-myristate 13-acetate (PMA, 0.1–10 M) produced a similar slow increase in I
Ca (up to 1.5- to 2-fold), while its inactive analogue (4-phorbol ester) had no effect on ICa. The effects of PTH and PMA were not additive. PK-C inhibitors [1-(5-isoquinoline-sulphonyl)-2-methylpiperazine hydrochloride] (H-7, 100 M) and staurosporine (100 M) as well as calcium channel antagonists Cd2+, verapamil, nifedipine and nimodipine depressed the effect of PTH. The chloride channel blocker 4,4-diisothiocyanato-stilbene-2,2-disulphonic acid (DIDS, 1 mM) did not affect the potentiating action of PTH. Activation of the adelylate cyclase system also potentiated I
Ca in some neurones, but this effect had a different time course and was additive to the effect of PTH. A conclusion is made that activation of PK-C may mediate the slowly developing enhancement of I
Ca by PTH. 相似文献
20.
Ken Nakazawa 《Pflügers Archiv : European journal of physiology》1994,427(1-2):129-135
Modulation by protein phosphorylation of the relation between acetylcholine (ACh)-activated current (I
ACh) and adenosine triphosphate-(ATP)-activated current (I
ATP) was investigated with the whole-cell voltage-clamp technique in rat sympathetic neurons. During simultaneous activation by 100 M ATP of an inward current, the current evoked by 100 M ACh was reduced to 60–70% of that in the absence of ATP. Effects of compounds that are known to modulate protein phosphorylation were tested by including them in the intracellular solution. The reduction ofI
ACh by ATP was not observed when K252a (1 M), a non-selective protein kinase inhibitor, adenosine 5-O-(3-thiotriphosphate) (ATP[S], 1 mM) or,-methylene ATP (1 mM) were included in the intracellular solution. Activators of protein kinases, adenosine 3,5-cyclic monophosphate (cAMP, 100 M), guanosine 3,5-cyclic monophosphate (cGMP, 100 M), phorbol 12-myristate 13-acetate (PMA, 1 M), also abolished the reduction by ATP ofI
ACh. The effects of okadaic acid, a protein phosphatase inhibitor, were paradoxical: okadaic acid (2 M) itself abolished the reduction by ATP ofI
ACh but it antagonized the abolishment by cAMP or cGMP of the reduction ofI
ACh. Okadaic acid did not affect the disappearance of the reduction ofI
ACh by ATP in the presence of intracellular PMA. The results suggest that the interaction betweenI
ACh andI
ATP is regulated by protein phosphorylation/dephosphorylation. Possible mechanisms underlying the effects of these modulators of protein phosphorylation are discussed. 相似文献