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1.
To define sites of prostaglandin action of renal tubules, the distribution of adenylate cyclase sensitive to prostaglandin E2 (PGE2) was examined in single nephron segments dissected from rat kidney. Further, the interaction between PGE2 and vasopressin on adenylate cyclase activity in nephron segments sensitive to vasopressin was evaluated. Procedures involved in isolating nephron segments were without effects on adenylate cyclase stimulation by PGE2. PGE2 stimulated adenylate cyclase activity of the thin descending limb of Henle (tDL), cortical collecting tubules (CCT), and medullary collecting tubules (MCT) at concentrations of 1.4 × 10?5 to 2.8 × 10?5 M. PGE2 was without effects in other nephron segments tested including proximal convoluated tubules, proximal pars recta, the thin and thick ascending limb of Henle's loop, and distal and connecting tubules. PGE2, at both high (2.8 × 10?5 M) and low (2.8 × 10?8 M) concentrations, did not inhibit adenylate cyclase activity stimulated by submaximal doses of vasopressin in medullary thick ascending limb of Henle (MTAL), CCT, and MCT. These data define the distribution of PGE2-sensitive adenylate cyclase in the rat nephron, i.e., tDL, CCT, and MCT, and show the lack of direct inhibitory actions of PGE2 on vasopressin sensitive adenylate cyclase in MTAL, CCT, and MCT. 相似文献
2.
Evgeny Weinberg Ella Zeldich Max M. Weinreb Ofer Moses Carlos Nemcovsky Miron Weinreb 《Journal of cellular biochemistry》2009,108(1):207-215
Elevated levels of prostaglandins such as PGE2 in inflamed gingiva play a significant role in the tissue destruction caused by periodontitis, partly by targeting local fibroblasts. Only very few studies have shown that PGE2 inhibits the proliferation of a gingival fibroblast (GF) cell line, and we expanded this research by using primary human GFs (hGFs) and looking into the mechanisms of the PGE2 effect. GFs derived from healthy human gingiva were treated with PGE2 and proliferation was assessed by measuring cell number and DNA synthesis and potential signaling pathways were investigated using selective activators or inhibitors. PGE2 inhibited the proliferation of hGFs dose‐dependently. The effect was mimicked by forskolin (adenylate cyclase stimulator) and augmented by IBMX (a cAMP‐breakdown inhibitor), pointing to involvement of cAMP. Indeed, PGE2 and forskolin induced cAMP generation in these cells. Using selective EP receptor agonists we found that the anti‐proliferative effect of PGE2 is mediated via the EP2 receptor (which is coupled to adenylate cyclase activation). We also found that the effect of PGE2 involved activation of Epac (exchange protein directly activated by cAMP), an intracellular cAMP sensor, and not PKA. While serum increased the amount of phospho‐ERK in hGFs by ~300%, PGE2 decreased it by ~50%. Finally, the PGE2 effect does not require endogenous production of prostaglandins since it was not abrogated by two COX‐inhibitors. In conclusion, in human gingival fibroblasts PGE2 activates the EP2—cAMP—Epac pathway, reducing ERK phosphorylation and inhibiting proliferation. This effect could hamper periodontal healing and provide further insights into the pathogenesis of inflammatory periodontal disease. J. Cell. Biochem. 108: 207–215, 2009. © 2009 Wiley‐Liss, Inc. 相似文献
3.
Concentrations of cyclic AMP (cAMP) were increased in isolated renal cortical tubules from hamsters by both parathyroid hormone (PTH) and prostaglandin E1 (PGE1) with maximal effects of PGE1 being 6–8 fold greater than those of PTH during a 10 min period. However, cAMP concentrations in cells treated with 1-methyl-3-isobutylxanthine (MIX) were increased with maximal concentrations of either hormone to the same degree. Similar effects of both hormones were observed on adenylate cyclase activity in renal homogenates. Simultaneous addition of hormones produced changes in both cAMP concentrations in intact tubules as well as adenylate cyclase activity of homogenates which were not completely additive. Degradation of cAMP, estimated in intact tubules as the difference in cAMP levels in the presence and absence of MIX, was increased by both hormones, however, changes were 2–3 fold greater in tubules exposed to PTH than to PGE1. Neither hormone directly altered cAMP phosphodiesterase (PDE) activity in either 30,000 x g supernatant or pellets from renal cortical homogenates.The results suggest that both hormones increase the production of cAMP in renal cortical tubules and may share a common target cell type in this response. Degradation of cAMP, however, is differentially effected by the two hormones, probably reflecting differences exerted on intracellular mechanisms regulating the enzymatic hydrolysis of cAMP. 相似文献
4.
Beta-adrenergic receptors and catecholamine-sensitive adenylate cyclase activity were studied in erythrocytes obtained from rats 6 weeks, 6 months, and 15 months of age. Intact erythrocytes from 6 week old rats contained significantly more beta receptors (411 ± 31 sites/cell) than 6 month (328 ± 21) or 15 month old rats (335 ± 16), as determined by binding of [125I] iodohydroxybenzylpindolol. Erythrocytes from 6 week old rats also contained significantly greater isoproterenol-sensitive adenylate cyclase activity (95.0 ± 9.4pmoles/109 cells) than erythrocytes from 6 month (27.9 ± 3.3) or 15 month old rats (23.7 ± 3.6). The erythrocyte population of 6 week old rats was bigger (mean corpuscular volume = 62 ± 2μ3/cell) than the older rat erythrocytes (47 ± 1μ3 and 48 ± 1μ3). When the data were expressed relative to a unit of cell volume, there was no difference in the density of beta receptors among all three populations but a progressive and significant fall in hormone-sensitive adenylate cyclase activity. In the rat erythrocyte, the age-related loss of adenylate cyclase activity is not accompanied by changes in β-receptor density. 相似文献
5.
A Constantopoulos V A Najjar 《Biochemical and biophysical research communications》1973,53(3):794-799
Membrane adenylate cyclase (AC) from polymorphonuclear (PMN) leucocytes and platelet membranes are activated several fold by fluoride and prostaglandin E1 (PGE1) respectively. Incubation of such activated membranes in a phosphorylating system inhibits cyclase activity. The inhibition can now be relieved by further treatment with fluoride and PGE1 respectively. These findings suggest that AC exists in an inhibited phospho- and activated dephospho-form. This is supported by the finding that membrane preparations from both sources contain a cyclic adenylate (cAMP) stimulated protein kinase and points to the existence of an adequate membrane phosphorylating system. 相似文献
6.
Preparations of small and large steroidogenic cells from enzymatically dispersed ovine corpora lutea were utilized to study the effects of luteinizing hormone (LH) and prostaglandins (PG) E1, E2 and I2. Cells were allowed to attach to culture dishes overnight and were incubated with either LH (100 ng/ml), PGE2, PGE2, or PGI2 (250 ng/ml each). The secretion of progesterone by large cells was stimulated by all prostaglandins tested (P < 0.05) while the moderate stimulation observed after LH treatment was attributable to contamination of the large cell population with small cells. Prostaglandins E1 and E2 had no effect on progesterone secretion by small cells, while LH was stimulatory at all times (0.5 to 4 hr) and PGI2 was stimulatory by 4 hr. Additional studies were conducted to determine if the effects of PGE2 upon steroidogenesis in large cells were correlated with stimulated activity of adenylate cyclase. In both plated and suspended cells PGE2 caused an increase (P < 0.05) in the rate of progesterone secretion but had no effect upon the activity of adenylate cyclase or cAMP concentrations within cells or in the incubation media. Exposure of luteal cells to forskolin, a nonhormonal stimulator of adenylate cyclase, resulted in marked increases in all parameters of cyclase activity but had no effect on progesterone secretion. These data suggest that the actions of prostaglandins E1, E2 and I2 are directed primarily toward the large cells of the ovine corpus luteum and cast doubt upon the role of adenylate cyclase as the sole intermediary in regulation of progesterone secretion in this cell type. 相似文献
7.
Preparations of small and large steroidogenic cells from enzymatically dispersed ovine corpora lutea were utilized to study the
effects of luteinizing hormone (LH) and prostaglandins (PG) E1, E2 and I2. Cells were allowed to attach to culture dishes overnight and were incubated with either LH (100 ng/ml), PGE2, PGE2, or PGI2 (250 ng/ml each). The secretion of progesterone by large cells was stimulated by all prostaglandins tested (P < 0.05) while the moderate stimulation observed after LH treatment was attributable to contamination of the large cell population with small cells. Prostaglandins E1 and E2 had no effect on progesterone secretion by small cells, while LH was stimulatory at all times (0.5 to 4 hr) and PGI2 was stimulatory by 4 hr. Additional studies were conducted to determine if the effects of PGE2 upon steroidogenesis in large cells were correlated with stimulated activity of adenylate cyclase. In both plated and suspended cells PGE2 caused an increase (P < 0.05) in the rate of progesterone secretion but had no effect upon the activity of adenylate cyclase or cAMP concentrations within cells or in the incubation media. Exposure of luteal cells to forskolin, a nonhormonal stimulator of adenylate cyclase, resulted in marked increases in all parameters of cyclase activity but had no effect on progesterone secretion. These data suggest that the actions of prostaglandins E1, E2 and I2 are directed primarily toward the large cells of the ovine corpus luteum and cast doubt upon the role of adenylate cyclase as the sole intermediary in regulation of progesterone secretion in this cell type. 相似文献
8.
Serum LH levels were determined by radioimmunoassay at the normal time of the proestrous LH peak (17.30 – 18.00) and ovulatory performance was examined on the morning of estrus in rats treated with indomethacin, an inhibitor of prostaglandin synthesis. When the drug was administered at 14.30 on the day of proestrus, only 21% of the rats ovulated and the total number of ova shed was reduced to 4% of that found in the untreated control group, but there was no significant change in peak serum LH level (1122 ± 184 vs. 975 ± 240 ng/ml ± S.E., treated vs. control). Prostaglandin E2 (PGE2) given late on the day of proestrus (25 to 750 μ g/rat at 24.00) was effective in overcoming this antiovulatory action of indomethacin: 71–90% of the rats ovulated, though the number of eggs shed was low (24–55% of control value). Indomethacin was still effective in blocking ovulation when given at 20.00, that is after completion of the proestrous LH surge, but not at 24.00. Administration of PGE2 (2 × 750 μ g/rat) in the early afternoon of proestrus elicited a rise in serum LH levels in rats in which the cyclic LH surge had been blocked with Nembutal (470 ± 87 vs. 106 ± 17 ng/ml ± S.E.) and induced ovulation in two-thirds of these animals.The results confirm, by direct measurement, that indomethacin does not block LH release but interferes with a late phase of the ovulatory process. PGE2 reverses this action of indomethacin on the ovary. In addition, PGE2 has a central effect causing LH release. 相似文献
9.
The effects of ethanol on the gastric mucosal adenosine 3′, 5′-monophosphate (cAMP) system were evaluated. The activity of adenylate cyclase (AC), phosphodiesterase (PDE), and tissue content of cAMP were determined in the presence of ethanol. NaF stimulated AC in rat gastric mucosa was inhibited in vitro and in vivo by 20% ethanol. Basal AC activity was so low (0.05 ± 0.10 pmoles cAMP formed/min/mg protein) that consistent results without NaF could not be obtained. The PDE activity (172 ± 11 pmoles cAMP consumed/min/mg protein) was approximately 350 fold greater than the basal AC activity. All levels of ethanol tested (2.0–20.0%) significantly inhibited (p<0.05) PDE in vitro. Gastric mucosal levels of cAMP are not measurably altered by ethanol in vivo (5–20%). 相似文献
10.
《Journal of receptor and signal transduction research》2013,33(6):451-463
AbstractProlonged (16 h) preexposure to prostaglandin E1 (PGE1) of cells from a murine virus-induced T lymphoma cell line BL/VL3 provoked, in their membranes, a dose-dependent reduction of PGE1-mediated adenylate cyclase stimulation. Smaller (but significant) decreases of helodermin- and isoproterenol-mediated stimulations were also observed. After a 16 h incubation of these cells with 1 µM PGE1, that reduced by 85%, the PGE1-mediated adenylate cyclase stimulation in membranes, 50% of the PGE1 response recovered after 2 h of PGE1 withdrawal from the incubation medium. Over the following 2 - 24 h time interval, further recovery was limited. Protein synthesis was required for this resensitization mechanism of functional PGE1 receptors coupled to adenylate cyclase, as judged by the inhibitory effects of cycloheximide. 相似文献
11.
The response of endothelial adenylate cyclase (AC) to prostaglandins (PGE1, PGE2, PGF1α, PGF2α, PGD2 and PGI2) and the relationship of PGE2 to adrenergic systems were investigated in cerebrovascular endothelial cultures. E-type prostaglandins and PGI2 were more effective in stimulating endothelial AC (EC50 = 3 × 10?7M, and 3 × 10?7M, respectively) than prostaglandins of the F-series and PGD2 which activated AC at high doses only. A modulation of endothelial AC response to either PGE2 or norepinephrine (NE) was observed in the presence of both agents in the system. It was manifested by a dose-dependent NE inhibition of the PGE2-stimulated formation of cAMP, which was partially restored by phentolamine. Alpha and β-adrenergic agonists (α, clonidine and 6-fluoronorepinephrine; β, isoproterenol) also partly blocked while forskolin and PGE2 synergistically stimulated the production of cAMP in the endothelial cultures. These findings strongly suggest that the interaction of prostaglandins and α- and β-adrenergic agonists with the AC system in cerebrovascular endothelium may play a role in the regulation of the cerebral microcirculation and/or blood pressure. 相似文献
12.
E Pick 《Cellular immunology》1977,32(2):329-339
Intracellular levels of cyclic 3′,5′-adenosine monophosphate (cAMP) in purified guinea pig peritoneal macrophages were elevated following incubation with the adenylate cyclase stimulators prostaglandins E1 and E2 (PGE1, PGE2), isoproterenol, and cholera toxin. Exposure of macrophages to antigen-stimulated lymphocyte culture supernatants, containing migration inhibitory factor (MIF), resulted in a moderate but consistent decrease in the cAMP level, which was best expressed after 1–2 hr of incubation. Incubation of macrophages with MIF-containing supernatants or partially purified MIF for 1–2 hr resulted in reduced cAMP accumulation in response to PGE1, PGE2, isoproterenol, and cholera toxin (nonspecific refractoriness). These findings indicate that MIF-induced inhibition of macrophage migration is not due to an increase in the cellular level of cAMP and that the reduction in cAMP concentration, caused by MIF, is probably a secondary phenomenon unrelated to the inhibition of cellular motility. 相似文献
13.
Y.H. Lee W.D. Cheng R.G. Bianchi K. Mollison J. Hansen 《Prostaglandins & other lipid mediators》1973,3(1):29-45
The anti-secretory and anti-ulcer effects of prostaglandin E2 (PGE2) using iso-osmotic buffer as a vehicle have been investigated in several types of laboratory animals. Orally administered PGE2 was found to be highly effective in preventing formation of ulcers in several experimental models -- pylorus ligated induced ulcers in rats, histamine induced ulcers in guinea pigs, reserpine induced ulcers in rats and pentagastrin induced ulcers in guinea pigs and cats. PGE2 also suppressed acid secretion but not pepsin activity. It was concluded that the anti-ulcer effects of PGE2 were due to its anti-secretory activity rather than antipepsin activity. In view of PGE2's activity in preventing ulceration induced by histamine and reserpine in addition to pentagastrin, it is suggested that the anti-pentagastrin activity of PGE2 is not specific. 相似文献
14.
《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1988,970(3):343-354
Nucleotides such as GTP and GDP appear to be involved in signal transduction via G protein modulation of adenylate cyclase activity. Studies on direct binding of [3H]GDP to membranes prepared from cultured immature rat Sertoli cells indicated that this process was reversible, approached steady state within 10 min, had a Ka of 4.5 ·106M−1 and was specific for guanine nucleotides. The non-hydrolyzable analog, guanosine 5′-O-[3-thio]triphosphate (GPPP[S]), was most effective as an inhibitor of [3H]GDP binding (ED50 = 4.8·10−8M), whereas guanosine 5′-O-[2-thio]diphosphate (Gpp[S]) was less potent (ED50 = 3.4·10−7M). Release of bound GDP was enhanced by follitropin (FSH) in the presence of Gppp[S], although not by FSH alone. Sertoli cell membranes possess guanine nucleotide hydrolase activity, where 95% of added nucleotide was rapidly degraded to guanosine. Binding kinetics were significantly influenced by nucleotide metabolism, which was prevented by controlling the Mg2+ concentration with EDTA and including App[NH]p to reduce nonspecific hydrolysis. Kinetic studies indicated that Gpp[S] inhibited (P < 0.05) Gppp[S]-stimulated adenylate cyclase activity (Ki = 1.8·10−7M), whereas basal activity remained unaffected. Addition of Gpp[S] to pre-activated enzyme (FSH plus GTP) resulted in a time-dependent decay of adenylate cyclase activity with a Koff value of 6 ± 1·min−1. Using a two-stage pre-inculbation technique, adenylate cyclase activity was demonstrated to be sensitive to the nucleotide bound. When FSH was included, catalytic activity was not altered by the order of pre-incubation with the nucleotides. This suggested that the exchange of bound Gpp[S] for Gppp[S] was enhance by FSH. Activation and attenuation of FSH-sensitive adenylate cyclase activity is dependent on a nucleotide exchange mechanism which is driven by (1) the higher affinity of G for GTP than GDP, (2) enhanced release of GD when FSH is present and (3) GTP hydrolysis coupled to rapid metabolism of guanine nucleotides. 相似文献
15.
Prostacyclin (PGX) ( has been found to be a potent stimulator of cAMP accumulation in human platelet rich plasma (PRP), and a direct stimulator of platelet microsome adenylate cyclase. Prostacyclin is, on a molar basis, at least 10 times more potent a stimulator of cAMP accumulation in platelets than PGE1. The prostacyclin stimulation of platelet cAMP accumulation can be antagonized by the prostaglandin endoperoxide PGH2, and a PGH2-induced platelet aggregation is antagonized by prostacyclin. A model of platelet homeostasis is proposed that suggests platelet aggregation is controlled by a balance between the adenylate cyclase stimulating activity of prostacyclin, and the cAMP lowering activity of PGH2. 相似文献
16.
An adenylate cyclase activity of 16.02±1.03 pmol cAMP produced min−1 (mg protein)−1 was detected in a cell homogenate ofDunaliella viridis, a unicellular halotolerant green alga. It was present in both the membrane fraction and soluble fraction separated from
the homogenate. Adenylate cyclase activity in the homogenate was activated by 1μM GTPγS but not by Ca2++calmodulin, suggesting this enzyme to be regulated by a G-protein. A phosphodiesterase activity of 23.12±15.03 pmol cAMP
decomposed min−1 (mg protein)−1 was found in the homogenate. These activities suggest the presence of a cAMP mediated signal transduction system inDunaliella. Cells, transferred from 1.7 M NaCl medium to 1 M NaCl, showed rapid increase in cAMP within 2 min to about 1.5 times the
original concentration (from 2.4±0.2 to 3.9±0.2 pmol per 108 cells) which was recovered in 30 min. 相似文献
17.
Effects of recombinant murine interferon-γ (rIFN-γ) on the membrane adenylate cyclase of a murine macrophage cell line (P388D1) were investigated in order to explore the nature of a signal transmitted by IFN-γ receptor. Following the incubation of P388D1 cells with 40 U/ml of rIFN-γ, the intracellular level of cAMP gradually increased about twofold over the control level within 60 min, and then began to gradually decline to about half the control level by 24 h incubation. The initial rise in cAMP level appeared to be due to the modest activation of adenylate cyclase and not due to the inhibition of cAMP-phosphodiesterase. Later decrease of intracellular cAMP may be due to quantitative down-regulation of the adenylate cyclase system. The basal enzymatic activity of the membrane prepared from P388D1 cells exposed to IFN-γ for 24 h was found to be reduced to about 20% of that of the control membrane. However, the quality of the adenylate cyclase system appeared unchanged, because the relative degree of the response of the down-regulated membrane adenylate cyclase to prostaglandin PGE2, NaF, guanylimidodiphosphate (GppNHp), cholera toxin (CT), or forskolin was found to remain unchanged. This quantitative down-regulation of adenylate cyclase must be due to the action of rIFN-γ, since the prior treatment of rIFN-γ with either acid (pH 2) or monoclonal anti-IFN-γ antibody inhibited the ability of IFN-γ to induce the down-regulation. The rIFN-γ-induced down-regulation is a reversible process, since the adenylate cyclase activity of the membrane was found to be restored when the rIFN-γ-exposed cells were cultured for 72 h in the absence of rIFN-γ. In addition, the 48 h-incubation of P388D1 cells with rIFN-β or IFN-α was found not to significantly affect the membrane adenylate cyclase system. 相似文献
18.
Prostaglandin E2 (PGE2) is well known to regulate cell functions through cAMP; however, the role of exchange protein directly activated by cAMP (Epac1) and protein kinase A (PKA) in modulating such functions is unknown in human umbilical cord blood‐derived mesenchymal stem cells (hUCB‐MSCs). Therefore, we investigated the relationship between Epac1 and PKA during PGE2‐induced hUCB‐MSC proliferation and its related signaling pathways. PGE2 increased cell proliferation, and E‐type prostaglandin (EP) 2 receptor mRNA expression level and activated cAMP generation, which were blocked by EP2 receptor selective antagonist AH 6809. PGE2 increased Epac1 expression, Ras‐related protein 1 (Rap1) activation level, and Akt phosphorylation, which were inhibited by AH 6809, adenylyl cyclase inhibitor SQ 22536, and Epac1/Rap1‐specific siRNA. Also, PGE2 increased PKA activity, which was inhibited by AH 6809, SQ 22536, and PKA inhibitor PKI. HUCB‐MSCs were incubated with the Epac agonist 8‐pCPT‐cAMP or the PKA agonist 6‐phe‐cAMP to examine whether Epac1/Rap1/Akt activation was independent of PKA activation. 8‐pCPT‐cAMP increased Akt phosphorylation but not PKA activity. 6‐Phe‐cAMP increased PKA activity, but not Akt phosphorylation. Additionally, an Akt inhibitor or PKA inhibitor (PKI) did not block the PGE2‐induced increase in PKA activity or Akt phosphorylation, respectively. Moreover, PGE2 increased glycogen synthase kinase (GSK)‐3β phosphorylation and nuclear translocation of active‐β‐catenin, which were inhibited by Akt inhibitor or/and PKI. PGE2 increased c‐Myc and vascular endothelial growth factor (VEGF) expression levels, which were blocked by β‐catenin siRNA. In conclusion, PGE2 stimulated hUCB‐MSC proliferation through β‐catenin‐mediated c‐Myc and VEGF expression via Epac/Rap1/Akt and PKA cooperation. J. Cell. Physiol. 227: 3756–3767, 2012. © 2012 Wiley Periodicals, Inc. 相似文献
19.
Synthetic human pancreatic growth hormone-releasing factor (hpGRF) (1–40)-NH2 stimulates adenylate cyclase activity in rat anterior pituitary particulate fraction at an ED50 value of approximately 150 nM. GTP more than doubles the stimulatory effect of hpGRF aand PGE2 on [32p] cyclic AMP formation. The present data show that hpGRF as well as PGE2, another potent stimulus of GH secretion, act at least partly, through GTP-dependent mechanisms in their coupling with adenylate cyclase. 相似文献
20.
Ovine luteal slices were used to study the effects of prostaglandins (PG) F2α on luteinizing hormone (LH)-stimulated secretion of progesterone and adenylate cyclase activity. The accumulation of progesterone in incubation medium and adenylate cyclase activity was similar after incubation of luteal slices with Medium 199 alone or Medium 199 containing PGF2α (250 ng/ml) for 3 hr. Addition of luteinizing hormone (LH; 100 ng/ml) resulted in a 2–3 fold increase in both the rate of progesterone accumulation and adenylate eyclase activity by 3 hr. When luteal slices were incubated in the presence of both LH and PGF2α the rates of progesterone accumulation and adenylate cyclase activity were identical to those in flasks containing LH alone after 1 hr; however, after 3 hr both LH stimulated progesterone accumulation and adenylate cyclase activity were inhibited to levels similar to those observed in control slices.In a second experiment, after 60–120 min of exposure to PGF2α the rate of progesterone accumulation in the medium was not different from that in untreated control slices. In addition, after this experiment the luteal slices were homogenized and the basal, sodium fluoride, LH, isoproterenol (ISO) and PGE2 sensitive adenylate cyclase activities were determined to evaluate the hormonal specificity of the negative effect of the pretreatment with PGF2α. Both LH and ISO stimulated adenylate cyclase activities were reduced after PGF2α pretreatment. However, fluoride ion stimulated adenylate cyclase activity was not significantly effected by PGF2α pretreatment and PGE2 sensitive adenylate cyclase was effected only slightly. 相似文献