鲨鱼软骨粘多糖对辐照损伤雄性小鼠的保护作用

目的观察鲨鱼软骨粘多糖的抗辐照作用,为进一步临床应用提供资料。方法将50只ICR雄性小鼠随机分为正常对照组、模型组及鲨鱼软骨粘多糖低〔0.5 g/(kg·d)〕、中〔1.0 g/(kg·d)〕、高〔2.0 g/(kg·d)〕3个剂量组,灌胃给药,每天1次,2周后,除正常对照组外,各组均以0.83 Gy/h60Coγ射线一次性全身辐照6 h,辐照剂量为5.0 Gy。结果辐照后3 d,中、高剂量组白细胞计数均为(1.0±0.4)×109/ml,明显高于模型组〔(0.7±0.2)×109/ml,P0.05〕;辐照后14 d,中、高剂量组白细胞计数仍明显高于模型组(P0.05)。辐照后,各组红细胞计数和血小板数计数无明显变化(P0.05)。辐照后14 d,中、高剂量组的胸腺指数分别为(1.99±0.39)mg/g和(2.05±0.23)mg/g,明显高于模型组〔(1.58±0.58)mg/g,P0.05〕;高剂量组脾指数也明显高于模型组(P0.05)。中、高剂量组的骨髓有核细胞计数分别为(2.75±0.60)×107和(2.68±0.35)×107,明显高于模型组〔(2.16±0.44)×107,P0.05〕;中、高剂量组SOD活性分别为(203±12)U/ml和(216±10)U/ml,明显高于模型组〔(187±17)U/ml,P0.05,P0.01〕;低、中剂量组MAD含量明显低于模型组(P0.01)。结论鲨鱼软骨粘多糖对辐照损伤小鼠具有明显的保护作用。     

运动型乳饮料的抗疲劳作用

目的观察运动型乳饮料对小鼠的抗疲劳作用,为研制新型抗疲劳功能乳饮料提供科学依据。方法小鼠随机分成对照组、牛奶组和饮料低、中、高3个剂量组。对照组给予纯净水,牛奶组给予市售某品牌牛奶,低、中、高剂量组分别按小鼠每公斤体质量2.5、5、10 g剂量灌胃。每鼠日灌胃量每10 g体质量0.2 mL,共30 d。测定负重游泳时间、尿素氮(BUN)、血乳酸(LAC)和肝糖原(LG)。结果低、中剂量饮料组小鼠负重游泳时间分别为(425±117)s和(410±89)s,明显长于对照组〔(243±60)s,P<0.05〕;并且运动后血清尿素氮水平分别为(7.41±1.11)mmol/L和(7.44±1.80)mmol/L,显著低于对照组〔(9.01±1.29)mmol/L,P<0.05〕;低、中和高剂量饮料组肝糖原分别为(0.37±0.07)mg/g(、0.40±0.14)mg/g和(0.35±0.11)mg/g,明显高于对照组〔(0.17±0.07)mg/g,P<0.05〕;低剂量饮料组运动后血乳酸水平为(2.90±1.02)mmol/L,显著低于对照组〔(3.71±1.51)mmol/L,P<0.05〕。结论此运动型乳饮料对增强运动耐力和消除疲劳具有一定的的作用。     

鲨鱼软骨粘多糖对雄性小鼠免疫及生殖器官的辐射防护作用

目的 观察鲨鱼软骨粘多糖对γ射线损伤雄性小鼠免疫器官及生殖器官的保护作用。方法 将50只雄性小鼠随机分为正常对照组、模型组及低(0.5g/kg·d)、中(1.0g/kg·d)、高(2.0g/kg·d)三个剂量鲨鱼软骨粘多糖组,每天一次灌胃给药,给药体积为0.4ml/20g,灌胃2周后,除正常对照组外,各组均以剂量率为0.83Gy/h的⁶⁰Coγ射线进行一次全身照射,照射剂量为5Gy。于辐照前1d,辐照后3d、14d测定小鼠体重、外周血白细胞数,辐照后14d测定小鼠胸腺指数,脾指数,骨髓有核细胞计数、睾丸重量指数,精子总数及精子畸形率。结果 鲨鱼软骨粘多糖可使辐照后3d中、高剂量组小鼠外周血白细胞数明显高于模型组(P<0.05),辐照后14d,中、高剂量组小鼠的胸腺指数、骨髓有核细胞数及精子总数明显高于模型组(P<0.05),高剂量组小鼠的脾指数及睾丸重量指数显著高于模型组(P<0.05),中、高剂量组的精子畸形率显著低于模型组(P<0.01)。结论 鲨鱼软骨粘多糖对辐射损伤小鼠的免疫器官及生殖器官具有一定的保护作用。     

慈菇多糖对免疫功能低下小鼠免疫调节作用

目的探讨慈菇多糖对免疫功能低下小鼠免疫功能影响。方法清洁级ICR雌性小鼠50只,按体重随机分为5组:对照组,模型组,慈菇多糖高、中、低剂量组(300、200、100 mg/kg),连续灌胃慈菇多糖28 d,对照组和模型组灌胃等量蒸馏水;第21 d,对照组皮下注射等量生理盐水,其余4组小鼠皮下注射氢化可的松25 mg/kg,连续6 d(制备免疫功能低下模型),观察各组小鼠体重变化、脏器(胸腺、脾脏、肝脏)指数、巨噬细胞吞噬功能等指标。结果与对照组比较,模型组小鼠胸腺、脾和肝指数[分别为(1.255±0.319)、(2.380±0.574)、(40.442±1.882)mg/g]明显降低,巨噬细胞吞噬指数(1.794±0.514)降低(P<0.05);与模型组比较,低、中、高剂量慈菇多糖组小鼠胸腺指数[分别为(1.848±0.130)、(1.835±0.243)、(1.708±0.441)mg/g]、脾指数[分别为(3.433±0.250)、(3.386±0.577)、(2.602±0.609)mg/g]和肝指数[分别为(45.478±2.683)、(45.423±2.109)、(44.934±2.337)mg/g]均明显升高(均P<0.05),巨噬细胞吞噬指数[分别为(2.274±0.590)、(2.406±0.246)、(2.462±0.444)]升高(P<0.05)。结论慈菇多糖在一定程度上能够提高小鼠非特异性免疫力。     

纳豆菌糖肽对免疫功能低下小鼠的免疫调节作用

目的探讨纳豆菌糖肽(Bacillus natto glycopeptide,BNGP)对免疫功能低下小鼠的免疫调节作用。方法KM小鼠80只随机分成BNGP低、中、高(6.25、12.5、25 mg/ml)剂量、空白、模型、5组。试验组连续灌胃BNGP 30 d,空白组与模型组以等量生理盐水代替,除空白对照组外,其余各级于24,25,26 d按80 mg/(kg·bw)腹腔注射环磷酰胺(CTX)。灌胃结束后,测定小鼠脾脏、胸腺指数,血清溶血素水平,脾细胞转化能力,细胞因子分泌以及体外脾细胞增殖作用的测定,研究BNGP对免疫低下小鼠体外免疫活性的影响。结果 BNGP中、高剂量组小鼠脾脏指数、HC50均显著高于模型组(P<0.05,P<0.01),高剂量组胸腺指数显著高于模型组(P<0.05);低、中、高剂量组ConA诱导的脾细胞增殖活性均显著高于模型组(P<0.05,P<0.01);中、高剂量组IL-2水平、高剂量组IFN-γ水平显著高于模型组(均P<0.05),而IL-10水平显著低于模型组(P<0.05,P<0.01);100²00μg/ml BNGP-1-b和12.5200μg/ml BNGP-1-b和12.5²00μg/ml BNGP-2-a可显著增强体外脾淋巴细胞增殖活性(P<0.05,P<0.01),50μg/ml BNGP-1-b和50200μg/ml BNGP-2-a可显著增强体外脾淋巴细胞增殖活性(P<0.05,P<0.01),50μg/ml BNGP-1-b和50²00μg/ml BNGP-2-a对ConA诱导的体外脾淋巴细胞增殖活性也具有显著增强作用(P<0.05,P<0.01)。结论 BNGP具有增强免疫功能低下小鼠体液和细胞免疫的作用。     

软肝冲剂对四氯化碳致小鼠肝损伤的保护作用

目的观察软肝冲剂对四氯化碳(CCl4)诱导的小鼠肝纤维化模型的保护作用。方法将60只C57B/L小鼠随机分为空白对照组、模型组、秋水仙碱对照组、软肝冲剂低剂量组和软肝冲剂高剂量组,每组12只。空白对照组腹腔注射100%花生油1 ml/kg,每周2次,共10周;其余各组均给予腹腔注射含20%CCl4的花生油1 ml/kg,每周2次,共10周造模;第3周起秋水仙碱对照组予秋水仙碱0.1 mg/(kg·d)灌胃,软肝冲剂低、高剂量组分别予软肝冲剂1 g/(kg·d)、5 g/(kg·d)灌胃。在第10周通过摘除眼球取血,检测小鼠血清中透明质酸(HA)、层粘连蛋白(LN)、三型前胶原(PCⅢ)、四型胶原(Ⅳ-C)、丙氨酸转氨酶(ALT)、天门冬氨酸转氨酶(AST)含量,检测肝脏组织中超氧化物歧化酶(SOD)和丙二醛(MDA)的含量,计算肝脏指数,观察小鼠肝脏的HE染色病理组织学改变。结果模型组小鼠血清中HA、LN、PCⅢ、Ⅳ-C、ALT和AST含量分别为(480.11±62.12)μg/L、(411.65±30.63)μg/L、(454.12±41.81)μg/L、(311.15±31.61)μg/L、(140.4±9.8)U/L和(198.2±9.7)U/L,均明显高于其它各组(P0.05);肝脏组织中SOD[(122.53±7.68)U/mg]低于空白对照组(P0.05);MDA[(5.59±0.33)nmol/mg]高于空白对照组(P0.05);肝脏指数[(4.7±1.5)%]高于空白对照组(P0.05)。病理切片显示肝细胞坏死并出现脂肪空泡、纤维组织增生和炎细胞浸润。软肝冲剂低剂量组与秋水仙碱组治疗效果相似。软肝冲剂高剂量组效果较好,小鼠血清中HA、LN、PCⅢ、Ⅳ-C、ALT和AST含量分别为(143.21±21.53)μg/L、(139.11±35.23)μg/L、(134.45±24.77)μg/L、(119.32±29.34)μg/L、(45.4±6.3)U/L和(53.6±7.1)U/L,均明显低于模型组(P0.05);肝脏组织中SOD[(189.5±7.5)U/mg]高于模型组(P0.05),MDA[(2.45±0.33)nmol/mg]低于模型组(P0.05);肝脏指数[(3.4±0.4)%]低于模型组(P0.05);病理检查显示肝脏组织中无炎性浸润、脂肪空泡和无纤维组织沉积。结论软肝冲剂可以改善肝脏功能,保护肝细胞和抑制肝纤维化,减轻CCl4诱导小鼠肝纤维化程度。     

枳实对糖尿病小鼠肾脏抗氧化能力及胰岛影响

目的 研究枳实提取物对实验性糖尿病小鼠肾脏抗氧化能力及胰岛形态的影响.方法 将枳实提取物分成高、中、低剂量[5.1,3.4,1.7 g/(kg·bw)]治疗糖尿病小鼠4周后,观察其一般状况、肾脏的抗氧化能力及胰岛形态变化.结果 枳实高剂量组小鼠末期血糖为(20.37±5.25)mmol/L,明显低于糖尿病组的(25.74±2.99)mmol/L(P<0.05);枳实高剂量组谷胱甘肽(GSH)含量为[(34.40±8.54)mg/(g·prot)],明显高于糖尿病组的[(21.38±3.91)mg/(g·prot)](P<0.01);枳实高剂量组丙二醛(MDA)和NO含量分别为[(0.89±0.37)nmol/(mg·prot)],[(1.27±0.56)μmol/(g·prot)],明显低于糖尿病组的[(1.46±0.39)nmol/(mg·prot)],[(2.15±0.85)μmol/(g·prot)](P<0.01或P<0.05),光镜下枳实提取物治疗组胰岛细胞损伤程度较糖尿病组轻.结论 枳实提取物能增强肾脏的抗氧化能力;保护胰岛组织细胞并降低胰岛细胞损伤.     

保健食品耐缺氧功能体外评价方法建立

目的将小鼠大脑皮质神经元的缺糖/缺氧模型用于耐缺氧保健食品的体外评价。方法采用血清药理学方法制备含牛磺酸复合制剂的小鼠血清,观察其对缺糖缺氧损伤神经元的乳酸脱氢酶(LDH)、超氧化物歧化酶(SOD)活力及细胞生存率的影响,并与小鼠急性脑缺血性缺氧实验结果比较。结果中、高剂量含牛磺酸复合制剂小鼠血清组LDH活力分别为(5.97±0.85)、(5.68±1.55)U/(g.prot),低于空白血清对照组的(8.27±1.54)U/(g.prot)(P<0.05);低、中、高剂量含牛磺酸复合制剂小鼠血清组SOD活力分别为(6.83±0.65)、(6.95±0.68)、(7.55±0.82)U/(mg.prot),高于空白血清对照组的(5.57±0.89)U/(mg.prot),细胞生存率分别为90.06%、89.04%、91.92%,高于空白血清对照组的75.74%(P<0.05);牛磺酸复合制剂低、中、高剂量组小鼠急性脑缺血性缺氧存活时间分别为17.3、19.5、18.2 s,比纯水对照组的15.5 s长(P<0.05)。结论含有某保健食品的小鼠血清对神经元缺糖/缺氧损伤具有保护作用;小鼠大脑皮质神经元的缺糖/缺...     

敌敌畏、乐果和马拉硫磷混合染毒对雄性小鼠生殖功能的影响

目的 研究敌敌畏、乐果和马拉硫磷混合染毒后对雄性小鼠生殖功能影响的特点和可能机制。方法 将105只雄性ICR小鼠按体重分层随机分成7组,每组15只,即对照组(0 mg/kg),敌敌畏、乐果和马拉硫磷混合低( 10.8 mg/kg)、中(21.5mg/kg)、高剂量组(43.0 mg/kg),以及敌敌畏组(5.1 mg/kg)、乐果组(12.6 mg/kg)和马拉硫磷组(25.3 mg/kg),经口连续灌胃染毒35 d,每天1次。染毒第36天后处死动物。测量小鼠体重、精子活力,观察精子数量及精子畸形率,检测血清中性激素[包括睾酮(T)、卵泡刺激素(FSH)、黄体生成素(LH)、雌二醇(E2)等]的水平,并观察睾丸及附睾的病理及电镜下改变。结果 染毒后第14天,混合高剂量组小鼠体重[(22.40±3.07)g]低于对照组[(26.73±2.82)g](P＜0.05);染毒后第28天,混合中剂量组小鼠体重[(30.00±4.93)g]亦低于对照组[(33.13±3.29)g](P ＜0.05)。混合中、高剂量组精子数[分别为(321.17±18.19)×106/g附睾重、(225.00±19.67)×106/g附睾重]和精子活力[分别为(64.67±9.91)％、(57.83±9.66)％]均低于对照组[分别为( 373.33±14.65)× 106/g附睾重、(75.17±7.68)％](P值均＜0.05);精子畸形率[分别为(43.33 ±8.66)‰、(55.00±13.80)‰]高于对照组[(32.67±8.17)‰]（P值均＜0.05）;与对照组相比[FSH、E2、LH、T分别为(1.41±0.20)、(17.32±2.72)、(8.75±1.32)、（3.45±0.80）nmol/L],混合中、高剂量组小鼠血清中FSH[分别为(3.14±0.62)、(3.85±0.37) nmol/L]、E2[分别为(36.81±6.68)、（43.76±9.82）nmol/L]水平升高（P值均＜0.01）,LH[分别为(5.21 ±1.23)、(4.27±1.09) nmol/L]、T[分别为(1.37±0.38)、(0.73±0.18)nmol/L]水平降低（P值均＜0.01）。混合高剂量组小鼠睾丸成熟精子数减少,并可见结构异常的精子头、精子尾。结论 敌敌畏、乐果和马拉硫磷混合联合染毒可直接损害小鼠睾丸及附睾的结构和功能,而导致生殖细胞生成过程异常;并导致下丘脑-垂体-性腺轴性激素的分泌紊乱。     

刺五加多糖对60Co γ射线辐照大鼠胃肠道及生殖系统的保护作用

目的 探讨刺五加多糖对⁶⁰Co γ射线辐照大鼠的胃肠道及生殖系统的影响。方法 68只雄性Wistar大鼠随机分成正常对照组、模型对照组、WR-2721组、523片组和刺五加多糖高(200 mg/kg·d)、中(100 mg/kg·d)、低(50 mg/kg·d)剂量组。5 Gy ⁶⁰Co γ射线(吸收剂量率为0.388 Gy/h)全身照射一次。分别于照前5d、照后第3、10、14天测定大鼠体重及外周血白细胞数;照后第14天断颈处死大鼠,测定大鼠肝、脾、胸腺指数、肠道长度,睾丸、附睾指数及精子相对计数。结果 照后模型对照组较正常对照组体重、脾脏、胸腺指数及肠道长度、睾丸、附睾指数及精子相对计数均明显下降,刺五加多糖各给药组各项指数相对模型对照组均升高;照前刺五加多糖各给药组WBC明显或非常明显高于正常对照组,且随给药剂量的增大,WBC值增高,提示刺五加多糖在动物正常情况下可以升高白细胞,照后模型对照组WBC明显低于正常对照组,而刺五加多糖给药组相对于模型对照组升高,刺五加多糖可以促进辐射大鼠外周血WBC的升高;照后模型对照组肝指数较正常对照组升高,辐射造成大鼠肝损伤,引起肝肿大,此时刺五加多糖中、低剂量组较模型对照组降低,提示药物对辐射大鼠肝脏有保护作用。结论 刺五加多糖对辐射大鼠的胃肠道及生殖系统有保护作用。     

国际卫生改革中权力下放的主要形式

从世界范围看,当前的卫生改革往往伴随着明显的权力下放。根据不同国家卫生改革的潮流,世界卫生组织以五种形式对以下权力下放作了分类总结:其中两种形式是加强下一级的卫生系统和地方政府,这是传统的权力下放形式;其他三种则是较新的形式,这些形式大体情况是:发展自治机构;发展执行机构;发展非政府提供者。     

Incentivizing Organ Donor Registrations with Organ Allocation Priority

How donor organs are allocated for transplant can affect their scarcity. In 2008, Israel's Parliament passed an Organ Transplantation Law granting priority on organ donor waiting lists to individuals who had previously registered as organ donors. Beginning in November 2010, public awareness campaigns advertised the priority policy to the public. Since April 2012, priority has been added to the routine medical criteria in organ allocation decisions. We evaluate the introduction of priority for registered organ donors using Israeli data on organ donor registration from 1992 to 2013. We find that registrations increased when information about the priority law was made widely available. We find an even larger increase in registration rates in the 2 months leading up to a program deadline, after which priority would only be granted with a 3‐year delay. We also find that the registration rate responds positively to public awareness campaigns, to the ease of registration (i.e. allowing for registering online and by phone) and to an election drive that included placing registration opportunities in central voting locations. Copyright © 2016 John Wiley & Sons, Ltd.     

Organ donation agency: A discourse analysis of correspondence between donor and organ recipient families

Studies about the psychosocial issues concerning organ donation and transplantation tend to focus on the experiences of donor or recipient families. Little is known about the part played by correspondence exchanged between these two groups; in particular how they perceive the agency of organ donation. This is the first analysis to address the representation of the act of donation from the viewpoint of both donor and recipient families through interrogation of archived correspondence data, using linguistic techniques. The data was drawn from a collection of letters, from four USA organ procurement organisations, exchanged between donor and transplant recipient families. Donor families consistently linguistically ascribed agency and accountability for donation to the person who died, the donor. For the recipient families, on the other hand, the ‘giver’ was mainly implied, ambiguous or ascribed to the donor family.     

An expedient and ethical alternative to xenotransplantation

The current voluntary posthumous organ donation policy fails to provide sufficient organs to meet the demand. In these circumstances xenografts have been regarded as an expedient solution. The public perception seems to be that the only impediments to this technology are technical and biological. There are, however, important ethical issues raised by xenotransplantation that need to be considered as a matter of urgency. When the ethical issues raised by using non-human animals to provide replacement organs for human beings are considered in a wider context and the possible alternatives to xenotransplantation are taken into account, a new dimension is added to the debate. In this broader context it is argued that a less ethically problematic solution is to adopt a presumed consent or opt-out organ procurement policy to regulate posthumous organ harvesting from humans. If there are still too few organs available, then the whole question of transplantation must be reassessed.This revised version was published online in October 2005 with corrections to the Cover Date.     

Winning Hearts and Minds: Using Psychology to Promote Voluntary Organ Donation

Recent psychological research concerning determinantsof and barriers to organ donation is reviewed with theintention of ascertaining acceptable and potentiallyeffective ways of improving organ retrieval. On thebasis of this review, five recommendations are made.(1) Individuals' donation wishes, where explicit,should be decisive. (2) Next of kin should witnessdonor decisions. (3) Mandated choice should replacevoluntary `opting-in'. (4) Initial donation choicesshould be repeatedly re-evaluated. (5) Those involvedin organ procurement should distance themselves frommodel of bodies as machines or gardens and embracemodels where bodies are viewed as sacred extensions ofself. In combination, these recommendations are arguedto be preferable in several ways to opt-out/presumedconsent procurement options.     

Incentivizing organ donation through a nonmonetary posthumous award

Since 2013, The Order of St John Award for Organ Donation has been offered to the families of deceased solid organ donors in the United Kingdom to honor the donors and inspire others to donate. We evaluate the effects of this award using a difference‐in‐differences approach that builds on the fact that solid organ donors are eligible for the award, whereas cornea‐only donors are not. We find that the introduction of the award led to an increase in the number of deceased solid organ donors.     

气相色谱-质谱法检测血液中15种农药残留

目的建立血液中15种农药的气相色谱-质谱检测方法(GC-MS)。方法取2ml全血,用二氯甲烷萃取浓缩,以古洛糖酸内酯甲醇溶液定容,供装有DB-35MS(30m×0.25mm×0.25μm)毛细管柱的GC-MS定性定量测定。结果二嗪农、阿特拉津、扑草净、丁草胺、联苯菊酯在4～80μg/L浓度范围内,甲拌磷、2,4-D丁酯、甲基对硫磷、马拉硫磷、氯丹、甲氰菊酯在10～200μg/L浓度范围内,α-硫丹、β-硫丹、三氟氯氰菊酯在20～400μg/L浓度范围内,乐果在40～800μg/L浓度范围内,具有良好的线性响应,相关系数(r2)在0.998～1.000之间,各待测物的方法加标回收率为51.3%～113.1%,方法的检出限为0.05～1.00μg/L,方法的定量限为0.20～3.00μg/L,批内精密度在3.17%～22.79%,批间精密度在5.58%～26.13%。结论该方法适用于血液样品中15种农药的含量检测。     

Absence of significant dissent should be sufficient for deceased donor organ procurement in New Zealand

Objective: New Zealand's organ donation rates are among the lowest in the OECD. In a bid to increase organ availability, the New Zealand Human Tissue Act 2008 introduces new consent arrangements for deceased donor organ procurement. This article assesses these new arrangements and presents the case for further reform.
Approach: Our assessment and arguments are based on philosophical analysis informed by empirical data on the effectiveness of alternative consent systems. We: 1) Identify widely held ethical judgments about policies and practices relevant to organ donation (e.g. those relating to coronial post-mortems), 2) Assess the implications of these judgments for the Human Tissue Act and the assumptions that underpin it, and 3) Derive policy recommendations that are consistent with the judgments.
Conclusion: The Human Tissue Act 2008 retains a strong consent requirement for organ procurement: organs may not be transplanted unless either the deceased or the family consents. We argue that organ availability could and should be increased by shifting from a model that requires consent to one that requires the absence of significant dissent.
Implications: We recommend that New Zealand adopt either 1) an organ donation system similar to the existing system for ordering coronial post-mortems, or 2) a variant of the 'opt-out' system already in place in several other countries.     

纳米二氧化硅毒性机制研究

随着纳米技术在世界范围内的迅速发展,纳米颗粒在生产生活中运用越来越普遍,其中纳米二氧化硅材料广泛运用于生物医学领域,特殊的理化特性导致其对机体的毒理作用也与常规材料不尽相同.国内外研究显示纳米二氧化硅对机体的毒作用机制主要有氧化损伤及炎症反应、影响细胞凋亡改变细胞周期、细胞膜毒性以及DNA损伤几个方面,本文将从以上几个...     

公开考评医院机关干部队伍的实践与思考

本文着眼提高机关干部的能力素质、激发创新活力,介绍了军队医院评估机关干部队伍建设的做法、取得的成效与经验体会,对各大型医院改进考核工作,加强机关干部队伍建设具有一定的参考价值。