Effect of the nitric oxide donor, glyceryl trinitrate, on human gall bladder motility

Background—Nitric oxide is a majorneurotransmitter in non-adrenergic, non-cholinergic (NANC) pathways.NANC inhibitory innervation has been shown in human gall bladder musclein vitro; the role of nitric oxide in human gall bladder emptyinghowever is undefined.
Aims—To study the effect of glyceryltrinitrate, a nitric oxide donor, on gall bladder emptying in healthysubjects using a randomised, double blind, crossover, placebocontrolled design.
Methods—Ultrasonographic gall bladdervolume was measured in the fasting state in eight healthy volunteersafter randomised administration of either glyceryl trinitrate 1200 µgbuccal spray or placebo spray. On two further occasions, afterrandomised administration of either glyceryl trinitrate 1200 µgbuccal spray or placebo spray, gall bladder volumes were also measuredafter a liquid test meal.
Results—Glyceryl trinitrate significantlyincreased fasting gall bladder volume to a mean of 114% (SEM 5%) ofpretreatment volume (p=0.039). Glyceryl trinitrate also significantlyimpaired gall bladder emptying between five and 40 minutespostprandially. Gall bladder ejection fraction was also reduced afterglyceryl trinitrate compared with placebo (43 (6.9)% versus 68.4 (6.5)%, p=0.016).
Conclusions—This study shows that glyceryltrinitrate produces gall bladder dilatation in the fasting state andreduces postprandial gall bladder emptying, suggesting that nitricoxide mechanisms may be operative in the human gall bladder in vivo.

Keywords:gall bladder motility; nitric oxide; glyceryltrinitrate

     

Biliary pain in postcholecystectomy patients without biliary obstruction

Biliary pain without obvious biliary obstruction is common in postcholecystectomy patients. We studied 20 symptomatic patients with episodes of biliary-type pain after cholecystectomy (all having undergone endoscopic retrograde cholangiography), and in 18 asymptomatic postcholecystectomy controls. We performed quantitative hepatobiliary radionuclide analysis with dimethyl-imidodiacetic acid. From a series of 90 dynamic images at 1-min intervals using a gamma camera coupled to a computer, time-activity curves were produced in regions of interest in the liver, intrahepatic biliary tree, common duct, and heart, from which quantitative biliary excretion indexes were obtained. The results demonstrate a biliary kinetic dysfunction in patients with postcholecystectomy pain without morphological abnormalities.     

Gallbladder ejection fraction and symptom outcome in patients with acalculous biliary-like pain

Patients with acalculous biliary-like pain present a difficult clinical challenge. Our aim was to evaluate the outcome of patients with recurrent biliary-like pain without gallstones who underwent testing of gallbladder ejection fraction (GBEF) by cholecystokinin-cholescintigraphy (CCK-CS) in order to determine clinical factors that may predict symptom resolution. We reviewed the records of patients with recurrent acalculous biliary-like pain who underwent CCK-CS from January 1995 to December 1999. For comparison, we also studied an age- and sex-matched group of patients who underwent cholecystectomy for symptomatic cholelithiasis. Outcome was obtained by telephone interview, using a scale from 0 to 3 where 0 = no improvement and 3 = clinical remission. Patient demographics, predominant symptom(s), method of management, gallbladder pathology, and response to treatment were recorded. One hundred twenty-nine patients underwent CCK-CS. Of 69 with an abnormal GBEF, 48 (70%) were available for interview. Forty patients underwent cholecystectomy. Twenty-seven patients reported symptom resolution after surgery while 4 nonsurgical patients reported the same (P = NS). Univariate analysis revealed no association between symptom outcome and presence of gastrointestinal symptom(s), severity and duration of abdominal pain, management, or gallbladder pathology. In addition, no GBEF cutoff level predicted symptom outcome. Of the remaining 60 patients with a normal GBEF, 30 (50%) were available for interview. Twenty-eight patients in this group were managed medically and 2 patients underwent cholecystectomy. Eighteen patients managed medically were asymptomatic, as were the 2 who underwent cholecystectomy. There was no difference in symptom outcome between patients who had GBEF >35% vs <35%. In conclusion, in a group of patients with recurrent acalculous biliary-like pain who underwent CCK-CS, we found a high rate of symptom resolution following cholecystectomy; however, this was not statistically different from a smaller cohort who did not undergo surgery. We were unable to determine any variable predictive of symptom resolution.     

肝硬化患者胆囊运动功能与Child-Pugh分级的相关性研究

探讨肝硬化患者胆囊运动功能与Child-Pugh分级之间的关系。研究对象分为正常对照组14例和肝硬化组62例,并行Child—Pugh分级。全部受试者均行mTc—EHIDA肝胆动态显像得到:①潜伏期(LP);②排胆期(EP);计算③排胆分数(GBEF);④排胆率(ER)。比较正常对照组与肝硬化组GBEF、LP、ER,可见肝硬化患者GBEF和ER明显低于正常对照组(P<0．01),LP高于正常对照组(P<0．05)。Child-Pugh A级、B级、C级三组的胆石发生率和胆囊运动异常发生率分别为:7．7％和15．4％,19．0％和19．0％,35．7%和46．4％。Child-Pugh分级越高,胆囊运动异常发生率越高(P<0．05),胆结石发生率也越高(但P>0．05),同时胆囊壁厚度越厚(P<0．05)。肝硬化患者的胆囊运动功能减弱,且与肝功能损害程度有一定的关系。     

Effect of aspirin on gallbladder motility in patients with gallstone disease

Patients with gallstone disease have impaired gallbladder motility. Prostaglandins are thought to be important mediators of gallbladder hypomotility. We assessed the effect of aspirin, a prostaglandin inhibitor on gallbladder resting volume and ejection fraction according to a double-blind study protocol in 20 healthy volunteers and 30 patients with gallstone disease. Healthy volunteers had a higher ejection fraction compared to patients with gallstone disease (73.9±0.9% vs 60.4±1.0%,P<0.05). Aspirin in a dose of 350 mg/day for two weeks did not alter gallbladder motility in the healthy volunteers. Thirty patients with gallstone disease were randomized into three treatment groups: group I (placebo), group II (aspirin 350 mg/day), and group III (aspirin 1400 mg/day). After two weeks of treatment, gallbladder ejection fraction was improved in group II (74.0±1.7% vs 62.0±1.7%,P<0.01) and group III (69.8±3.8% vs 61.2±1.3%,P<0.01) but not in group I (60.4±2.6% vs 59.0±1.9%,P=NS). The higher dose of aspirin did not induce a greater increase in gallbladder emptying. It is concluded that impaired gallbladder motility in patients with gallstone disease is corrected by short-term oral aspirin even in low dosage. This may be clinically useful in secondary prophylaxis after nonsurgical therapy for gallstone disease.     

一氧化氮在胃食管反流病发病机制中的作用

目的探讨一氧化氮(NO)在胃食管反流病(GERD)发病机制中的作用.方法应用PC polygraf HR高分辨多通道测压系统检测GERD患者的食管下括约肌压力(LESP)、食管下括约肌长度(LESL)及食管远端蠕动幅度等动力参数;应用Digitrapper MKⅢ动态食管pH监测仪检测其24 h食管内pH各项参数;应用硝酸还原酶法测定血清NO含量.结果与对照组比较,Savary Mller Ⅰ,Ⅱ,Ⅲ级GERD患者的LESP均显著降低(分别为1.1kPa±0.11kPa,1.1kPa±0.06kPa,1.0kPa±0.08kPa,P均＜0.01);Savary Miller Ⅰ,Ⅱ,Ⅲ级GERD患者的食管下段蠕动幅度也均显著降低(分别为7.7kPa±1.1kPa,7.2kPa±1.3kPa,6.9kPa±1.2kPa,P均＜0.01);GERD患者的食管内24 h pH值明显高于对照组;其血清NO含量也显著高于对照组.结论内源性NO可能参与GERD的致病机制.     

Genetic variants of endothelial nitric oxide synthase in patients with primary biliary cirrhosis: association with disease severity

BACKGROUND AND AIMS: Primary biliary cirrhosis (PBC) presents a wide spectrum of clinical manifestations. In experimental models of liver cirrhosis and cholestasis it has been suggested that altered nitric oxide production is involved in liver injury and portal hypertension development. The present study investigated endothelial nitric oxide synthase (eNOS) genetic polymorphisms (894G/T, -786T/C) in patients with PBC and in controls to verify whether disease susceptibility and progression are associated with a particular genotype. METHODS: Genomic DNA from 109 Italian PBC patients (65 with advanced disease, i.e. liver transplantation or histological stage III-IV) was obtained and polymorphisms determined by fluorescent probe analysis. Healthy subjects (n = 242) were used as a control group. RESULTS: The allelic frequencies of both polymorphisms did not differ significantly between PBC patients and controls. When the association between genotypes and disease severity was addressed, both the 894T and the -786T alleles were more frequently found in the 22 patients with progressing disease (894T, frequency 0.455 compared with 0.240; P = 0.032; -786T, frequency 0.682 compared with 0.460; P = 0.038). Patients with 894TT presented higher Mayo score values (6.1 +/- 1.2 compared with 5.4 +/- 1.3 in 894G/G patients; P = 0.030) but similar age and disease duration values. CONCLUSIONS: The authors suggest that genetic variants of eNOS are not associated with susceptibility to PBC, although the genotypes may lead to differences in disease severity and progression.     

胃节律紊乱综合征的胆囊运动研究

目的：为了研究胃节律紊乱综合征患者的胆囊运动。方法：用99mTc放射性核素序列显像法对29例胃节律紊乱综合征（GastricdysrhythmasyndormeGDS）患者检测胃排空的同时对其空腹和餐后胆囊排空运动进行了前瞻性研究．并与15例正常人进行比较。在口服多潘立酮治疗之后，23例胃节律紊乱纠正的患者，重复上述检查．结果：GDS患者的胃、空腹和餐后胆囊排空分数明显低于正常对照组（P均＜0．01）。多潘立酮治疗后胃节律紊乱纠正的患者，在其胃运动障碍纠正的同时，空腹和餐后胆囊排空分数显著性提高（P均＜0．01），而与正常人比较，差异无显著性（P均＞0．05）。结论：GDS患者在男运动障碍的同时存在着胆囊运动障碍。     

Effect of oral protease inhibitor administration on gallbladder motility in patients with mild chronic pancreatitis

Oral administration of a protease inhibitor (camostat) induces pancreatic hypersecretion via hormonal and neural systems in humans. Camostat may also affect gallbladder motility via these systems. The aim of this study was to evaluate the effect of camostat on gallbladder function. Gallbladder emptying in response to caerulein administration and to egg yolk ingestion was examined ultrasonographically in 15 patients with mild chronic pancreatitis before and after 6 months of camostat treatment, and in 10 control subjects. The plasma cholecystokinin concentration after yolk ingestion was measured by radioimmunoassay. Fasting gallbladder volume and contractile function, whether stimulated by caerulein or yolk, did not differ between pancreatitis patients before camostat treatment and controls. Plasma cholecystokinin levels, basal and yolk-stimulated, did not differ between nontreated pancreatitis patients and control subjects. Fasting volume had decreased significantly by 1, 3, and 6 months of camostat treatment, while contractile function was not affected. Camostat did not influence plasma cholecystokinin levels. Oral administration of a protease inhibitor appears to decrease fasting gallbladder volume via a mechanism other than cholecystokinin release.     

Detection of serum nitrite and nitrate in primary biliary cirrhosis: possible role of nitric oxide in bile duct injury

BACKGROUND: The role of nitric oxide synthase (NOS) in autoimmune disease is gaining increased attention because of the relationships between NOS activity and T-lymphocyte subpopulations and, in particular, the influence of NO on cytokine production by Th1 versus Th2 cells. In addition, there is evidence that both the liver and infiltrating hepatic T cells have inducible NOS-2 activity. METHODS: We studied serum levels of nitrite (NO2-) and nitrate (NO3-) in groups of patients with liver disease secondary to hepatitis B, hepatitis C, autoimmune hepatitis and primary biliary cirrhosis (PBC). Simultaneously, in a nested subpopulation, we studied the liver expression of NOS-2. RESULTS: Interestingly, there was a significant elevation both of nitrite and of nitrate in patients with PBC but not other liver diseases. Despite such increments, there was no correlation of the levels of nitrite and nitrate with sera levels of tumor necrosis factor-alpha, interferon-gamma, alanine aminotransferase, total bilirubin, alkaline phosphatase, gamma-glutamyl transpeptidase, platelet count, IgG, IgM, antimitochondrial antibodies or prothrombin time. These data were extended by demonstrating the expression of NOS-2 by immunohistochemistry in 13/14 patients with PBC, including in 9/14 patient hepatocyte populations and 4/14 bile duct cells. In contrast, NOS-2 expression was noted in hepatitis B and hepatitis C, but only found within mononuclear cells. CONCLUSION: Our data suggest that NO produced through NOS-2 may play a role in the pathogenesis of bile duct injury in some PBC patients.     

功能性消化不良患者血清一氧化氮含量与食管动力变化特征研究

目的　探讨一氧化氮 (NO)在功能性消化不良 (FD)患者食管动力变化中的作用。方法　 5 8例FD患者和 19名健康受试者纳入本研究 ,应用PCPolygraphHR动力监测系统测定FD患者食管压力 ;应用硝酸还原酶法测定血清NO含量。结果　FD患者食管下段平均蠕动波幅显著低于对照组 (7 12± 1.35kPavs 13.2 6± 2 .36kPa ,P <0 .0 1) ,而双峰波的病理性蠕动发生率则显著高于正常对照组 (48.3%vs 10 .5 % ,P <0 .0 1)。FD组血清NO含量显著高于对照组 (99.7± 17.5 μmoL/Lvs 72 .4± 15 .2 3μmoL/L ,P <0 .0 1)。结论　功能性消化不良患者存在食管运动功能异常 ,NO可能参与FD消化道动力功能障碍的发病机制     

Suprahepatic gallbladder and right lobe anomaly of the liver in patients with biliary cancers

Summary The suprahepatic region is a rare ectopic location of the gallbladder. It usually combines with right lobe anomaly of the liver. Here we report two unusual cases of suprahepatic gallbladder with agenesis or hypogenesis of the right lobe of the liver and biliary cancer. A patient with a gallbladder tumor was admitted to our emergency room with acute cholecystitis and liver abscess. Imaging examinations and operation confirmed the suprahepatic position of gallbladder, agenesis of the right lobe, and dissemination of gallbladder cancer. In the patient with cholangiocarcinoma, CT scans and percutaneous transhepatic cholangiography documented the presence of a hilar tumor and hypogenesis of the right lobe. Both of these patients died from biliary tract cancer soon after operation.     

In vivo recording of colonic motility in conscious rats with deficiency of interstitial cells of Cajal, with special reference to the effects of nitric oxide on colonic motility

Background We recorded in vivo colonic motility in rats with a deficiency of interstitial cells of Cajal (ICC) (Ws/Ws rats) and in wild-type rats (+/+ rats), with special reference to the effects of nitric oxide (NO) on colonic motility in both types of rats, in order to ascertain the role of ICC in colonic motility, and the relationship between NO and ICC in regard to colonic motility. Methods Miniature strain-gauge force transducers were sutured on the surface of the ascending and sigmoid colon of Ws/Ws rats and +/+ rats as controls. After 1 week and a fasting period of 24 h, colonic motility in +/+ and Ws/Ws rats was recorded. We also studied the effect of NO on colonic motility in both types of rats, by means of the administration of N-nitro-l-arginine methyl ester (l-NAME) or l-arginine. Results In +/+ rats, there were contractions with high amplitude and long duration in both the ascending and sigmoid colon. The number, amplitude, and duration of contractions in the ascending colon were 9.9/20 min, 6.1 g, and 22.7 s, respectively. These findings in the sigmoid colon were 5.2/20 min, 5.2 g, and 23.0 s, respectively. The number of contractions in the ascending and sigmoid colon in Ws/Ws rats (2.3 and 1.0/20 min) was significantly lower than that in +/+ rats (P < 0.05). The number of contractions in the ascending and sigmoid colon in +/+ rats (9.7 and 5.1/20 min before treatment) was significantly increased by l-NAME administration (28.7 and 13.9/40–60 min after treatment; P < 0.05), but that in Ws/Ws rats was not influenced. The number of contractions in the ascending and sigmoid colon in +/+ rats (10.2 and 5.2/20 min before treatment) was significantly decreased by l-arginine administration (3.6 and 2.1/40–60 min after treatment; P < 0.05), but that in Ws/Ws rats was not influenced. Conclusions ICC must be related to the occurrence of a normal number of colonic contractions. NO may be involved in the inhibitory regulation of colonic motility, and the effect of NO on the occurrence of contractions appears to be mediated by ICC.     

Effects of nitric oxide synthase inhibitor to esophagus in a feline esophagitis model

The present study explores the effects of nitric oxide synthase inhibitor on esophageal motility in a feline model with esophagitis. Perfusion of the esophagus with acid produced inflammatory changes of esophageal mucosa. The esophageal motility was measured before and after the perfusion. One group of cats was given nitric oxide inhibitor orally at the same time as the perfusion of acid. The control group was given water instead. Esophagitis impairs the motility of the esophagus. However, the esophageal motility of the cats that were given nitric oxide synthase inhibitor decreased less than that of the control group. The results suggested that during esophagitis there is an alteration of the nitric oxide synthase/nitric oxide pathway in the esophagus, which may be one of the important mechanisms of esophageal motility dysfunction.     

Hypogenesis of intramural vascularity and perivascular plexuses of gallbladder in patients with congenital biliary dilatation

Background

We hypothesized neuronal disorders of the biliary tract as the cause of congenital biliary dilation (CBD).

Methods

Gallbladders were removed from a total of 15 patients who were categorized into two study groups: a CBD group (eight patients) and in a control group (neuroblastoma, acute myelogenous leukemia, wandering gallbladder, Wilms’ tumor, glycogen storage disease, familial amyloid polyneuropathy; seven patients). Whole-mount preparations of the gallbladders were made to immunostain the intramural nerves.

Results

The intramural vascularity in the gallbladders of the CBD group (5.5 ± 1.9/cm²) was significantly lower than that in the control group (27.6 ± 14.4/cm²). The rate of perivascular plexuses on the surface of intramural vessels was also significantly lower in the CBD group than in the controls (37.7 ± 18.1 vs. 80.2 ± 17.4%, respectively). The numbers of ganglion cells per visual field were 38.5 ± 24.0 and 42.3 ± 20.6, respectively, in the CBD and control groups; this difference was not statistically significant.

Conclusions

There may be a mechanism in CBD causing contractile failure and dilatation of the biliary tract as a result of decreased intramural blood flow that accompanies the diminished vascularity.     

Gastrobiliary motility is not coordinated in patients with non-ulcer dyspepsia of normal gastric emptying time: simultaneous sonographic study

BACKGROUND: Disorders of the motor function of the upper gastrointestinal tract have been implicated in the pathogenesis of non-ulcer dyspepsia. Approximately 50% of patients with abdominal symptoms (without ulcer) have normal gastric emptying. Apart from gastric emptying, other mechanisms are very important in the etiology of non-ulcer dyspepsia. METHODS: Gastric emptying and gallbladder motility were simultaneously investigated in 16 patients with non-ulcer dyspepsia and in 15 healthy controls. Fasting blood samples were taken, and pepsinogen levels were assayed. RESULTS: Gastric emptying time, fasting antral diameter, and post-prandial antral diameter were not significantly different between the patients with non-ulcer dyspepsia and the controls. Fasting gallbladder volume, the time required to reach minimal gallbladder residual volume, minimal gallbladder residual volume, and the serum levels of pepsinogen were not significantly different. Simple linear regression was used to summarize the relationship between gastric emptying time and time required to reach minimal gallbladder residual volume. In the controls, the gastric emptying time and time required to reach minimal gallbladder residual volume were linearly related. However, in the patients with non-ulcer dyspepsia, they were not related. CONCLUSIONS: These observations suggest that disturbance of coordination between gastric emptying and gallbladder emptying is a cause of the symptoms of non-ulcer dyspepsia.     

Nitrosation of melatonin by nitric oxide: a computational study

Melatonin is being increasingly promoted as a therapeutic agent for the treatment of jet lag and insomnia, and is an efficient free radical scavenger. We have recently characterized a product for the reaction of melatonin with nitric oxide (NO), N-nitrosomelatonin. In the present work, reaction pathways with N1, C2, C4, C6 and C7 as possible targets for its reaction with NO that yield the respective nitroso derivatives have been investigated using semiempirical AM1 computational tools, both in vacuo and aqueous solution. Specifically, two different pathways were studied: a radical mechanism involving the hydrogen atom abstraction to yield a neutral radical followed by NO addition, and an ionic mechanism involving addition of nitrosonium ion to the indolic moiety. Our results show that the indolic nitrogen is the most probable site for nitrosation by the radical mechanism, whereas different targets are probable considering the ionic pathway. These results are in good agreement with previous experimental findings and provide a coherent picture for the interaction of melatonin with NO.     

支气管哮喘患者呼出气一氧化氮与外周血嗜酸性粒细胞的相关性

目的观察支气管哮喘患者呼出气一氧化氮(Fe NO)的表达水平,分析其与外周血嗜酸性粒细胞(EOS)之间的相关性。方法收集2013年2月-2014年12月期间贵州省人民医院支气管哮喘患者58例,其中支气管哮喘急性发作期40例(急性发作期组),支气管哮喘缓解期18例(缓解期组),健康对照组30例。采用Fe NO分析仪测定Fe NO水平,并检测各组外周血嗜酸粒细胞计数,采用SPSS 11.5统计软件进行统计学处理,组间差异性比较采用单因素方差分析,相关性分析采用Pearson相关性分析。P0.05为差异有统计学意义。结果支气管哮喘急性发作期组Fe NO为101.44±32.87ppb,EOS为5.0±2.62×10~9/L;缓解期组Fe NO为32.83±11.42 ppb,EOS为1.32±0.59×10~9/L;健康对照组Fe NO为8.43±3.02ppb,EOS为0.22±0.09×10~9/L。发作期组及缓解期组Fe NO及EOS水平均高于健康对照组(P0.05)。急性发作期组与缓解期组比较,Fe NO及EOS水平差异有统计学意义(P0.05)。支气管哮喘患者Fe NO水平与EOS呈正相关性(P0.05)。结论 Fe NO能够一定程度上反应气道嗜酸细胞炎症,Fe NO检测可能有助于评估支气管哮喘的控制水平。     

外源性一氧化氮抗日本血吸虫的实验研究

目的观察外源性一氧化氮(NO)抗日本血吸虫的效果。方法以蜂蜡为NO的吸收剂,在不同条件下用逆转乳化法制备NO乳状液,测定其中NO的含量,选择乳状液中NO含量最大的用于抗日本血吸虫试验。在小鼠感染日本血吸虫尾蚴后22天起灌服,剂量为0.5ml/d,连续灌服5d,心脏灌注法收集虫体计数,研究外源性NO抗日本血吸虫的效果。结果外源性NO中NO的最大含量为536.2μmol/L;对小鼠日本血吸虫有一定的杀虫效果,减虫率达45.0%,减卵率达42.7%。结论外源性NO对日本血吸虫有一定的抗虫作用。     

一氧化氮及一氧化氮合酶抑制剂对小鼠血吸虫病肝纤维化程度的影响

目的研究一氧化氮(NO)对小鼠日本血吸虫病肝纤维化程度的影响。方法昆明小鼠经腹部皮肤感染日本血吸虫,于感染后第4周末治疗组和抑制剂组分别给予NO前体-L-精氨酸(L-Arg)及一氧化氮合酶(NOS)抑制剂-NG-左旋-硝基精氨酸甲基乙酯(L-NAME),于第10周末处死小鼠,取血,分离血清,剖取肝脏。应用病理组织学方法及生物化学方法,观察各组小鼠血吸虫病肝纤维化程度,同时测定血清NO、层粘连蛋白(LN)、透明质酸(HA)、谷-草转氨酶(AST)及谷-丙转氨酶(ALT)活性和肝组织羟脯氨酸(Hyp)含量。结果小鼠感染血吸虫后,感染组肝脏有明显的纤维化,血清中HA、LN、AST、ALT等指标显著升高,肝组织内Hyp含量也明显增加。与感染组相比:L-Arg高、中剂量组肝纤维化程度评分降低显著,低剂量组虽有减轻但无统计学意义,同时,L-Arg高、中剂量组血清LN、HA、AST、ALT的水平和肝组织Hyp的含量有所降低;低剂量组HA、LN、AST、ALT的水平虽然降低,但无统计学意义,Hyp水平降低明显;抑制剂组血清LN、HA、AST、ALT含量和肝组织Hyp的水平均明显升高。血清NO的水平随着精氨酸剂量的增加而显著增加,而精氨酸抑制剂组NO的水平降低明显。结论NO能明显降低血吸虫病肝纤维化的程度和减轻肝纤维化所造成的损伤作用。