早产儿听神经通路的发育神经生物学特性

系统地观察了不同周龄正常早产儿脑干听觉诱发反应的特性,结果表明①刺激强度80、60dBnHL时Ⅰ波35周前,Ⅲ、Ⅴ波36周前明显长于足月新生儿(P<0.05,P<0.01),刺激强度30dBnHL时Ⅰ波35周前,Ⅲ、Ⅴ波至37周仍明显长于足月新生儿(P<0.05,P<0.01);②≤32周Ⅰ—Ⅲ、Ⅰ—ⅤIPL与足月新生儿比较分别延长0.40和0.55ms,33—35周平均延长0.31和0.29ms,36周接近足月新生儿;③Ⅰ、Ⅲ、Ⅴ波潜伏期—成熟函数曲线的斜率≤32—33周时分别为0.62、0.66和0.80ms/week,33—35周时分别为0.09、0.03和0.06ms/week,35—36周时分别为0.00、0.33和0.38ms/week。     

诱发性耳声发射向40-Hz听觉相关电位及行为反应间的相关分析

以500-Hz短纯音作为刺激声,分别测定了20位受试者(9例正常者,11例耳病患者,共40耳)的诱发性耳声发射(EOAE),40-Hz听觉相关电位(40-Hz AERP)和行为反应三项指标的阈值。结果如下:EOAE阈值的主要分布范围在〔20,60〕dB nHL,该范围耳数是其阈值总范围〔15,70)dB nHL耳数的93％;40-Hz AERP阈值主要在〔20,60〕dB nHL,耳数是其阈值范围〔20,90〕dB nHL耳数的95％;行为阈主要在〔20,40〕dB nHL,耳数是其阈值范围〔15,80〕dB nHL耳数的91％,全部受试者有13耳EOAE未引出(正常者3耳,耳病患者10耳),占总测试耳数的33％。三项指标的相关分析表明:EOAE—40Hz AERP,EOAE—行为反应,40Hz AERP一行为反应的r值分别为0.609(0.002相似文献   

诱发性耳声发射向40-Hz听觉相关电位及行为反应间的相关分析

以500-Hz短纯音作为刺激声,分别测定了20位受试者(9例正常者,11例耳病患者,共40耳)的诱发性耳声发射(EOAE),40-Hz听觉相关电位(40-Hz AERP)和行为反应三项指标的阈值。结果如下:EOAE阈值的主要分布范围在〔20,60〕dB nHL,该范围耳数是其阈值总范围〔15,70)dB nHL耳数的93％;40-Hz AERP阈值主要在〔20,60〕dB nHL,耳数是其阈值范围〔20,90〕dB nHL耳数的95％;行为阈主要在〔20,40〕dB nHL,耳数是其阈值范围〔15,80〕dB nHL耳数的91％,全部受试者有13耳EOAE未引出(正常者3耳,耳病患者10耳),占总测试耳数的33％。三项指标的相关分析表明:EOAE—40Hz AERP,EOAE—行为反应,40Hz AERP一行为反应的r值分别为0.609(0.002相似文献   

足月新生儿听觉脑干电反应的特性

本文工作根据北京市儿童医院临床的需要,在临床实验条件下对足月新生儿的ABR进行了测量,以期分析足月新生儿ABR的电反应特征。 新生儿听觉脑干反应(ABR)的波形是Ⅰ、Ⅲ、Ⅴ波为主的连续波复合体;新生儿在声强80dB(HL)刺激频率20次/秒的短声刺激条件下,I、Ⅲ、Ⅴ波潜伏期大体为2.50,5.00和7.00ms;新生儿ABR潜伏期—刺激强度函数的斜率是30—60μsec/dB(声刺激强度从80到50dB(HL),声刺激频率20次/秒);新生儿ABR Ⅴ波对Ⅰ波的比率大于1.0(短声强度80dB(HL),刺激频率20次/秒);在80dB(HL)短声条件下,改变声刺激频率(从20次/秒增止100次/秒),Ⅴ波潜伏期约延长0.6—1.0ms;新生儿ABR阈值在30—60dB(HL)的范围。综上所述新生儿ABR电反应特性,可以为其听力和脑干功能的临床诊断提供可靠的指标和依据。     

姜黄素对高原缺氧大鼠认知功能障碍的预防作用

目的:探讨姜黄素(curcumin)对高原缺氧大鼠认知功能障碍的预防作用。方法:将30只成年雄性SD大鼠随机分为健康对照组、模型组(Model组)、姜黄素[按体重60mg/(kg.d)]治疗组(curcumin组)。采用Morris水迷宫实验方法检测缺氧后大鼠学习记忆功能变化,同时检测脑片水平的LTP变化。结果:(1)模型组大鼠寻找平台的潜伏期明显长于对照组,具有统计学意义(P<0.05),姜黄素组寻找平台的潜伏期相对于模型组显著缩短(P<0.05)。撤离平台后,模型组大鼠在平台所在象限的停留时间明显短于对照组(P<0.05),姜黄素干预后大鼠在平台所在象限的停留时间较模型组显著延长(P<0.05)。(2)给予HFS刺激后各组兴奋性突出后电位(fEPSP)斜率较前明显增加,均可持续1h以上,与模型组比较缺氧组HFS刺激后fEPSP斜率明显减小(P<0.05),姜黄素可减轻缺氧所致的fEPSP斜率减小(P<0.05)。结论:姜黄素可改善慢性缺氧大鼠认知功能障碍,但其具体机制尚有待于进一步研究。     

脊髓运动神经元突触传递长时程增强的受体动力学分析

本文旨在观察下行通路激活在脊髓运动神经元(motoneuron,MN)诱发兴奋性突触后电位(excitatory postsynaptic potential,EPSP)的长时程增强现象(long-term potentiation,LTP)之受体动力学性质。应用8～14日龄新生大鼠离体脊髓MN细胞内记录技术,观察同侧腹外侧索(ipsilateral ventrolateral funiculus,iVLF)电刺激诱发的iVLF-EPSP的变化,进行EPSP受体动力学分析。结果显示,EPSP的幅度、曲线下面积和最大上升斜率与刺激强度呈正相关(P0.05或P0.01);而EPSP表观受体动力学分析的参数中表观解离速率常数K2和表观平衡解离常数KT与刺激强度呈负相关(P0.01或P0.05)。给予iVLF强直刺激(100 Hz,50脉冲/串,波宽0.4～1.0 ms,共6串,串间隔10 s,10～100 V),在11个记录的MNs中有5个MNs的EPSP幅度增大到基础值的120%以上,且至少维持30 min,可以被判为iVLF-LTP,同时EPSP的曲线下面积和最大上升斜率也增大到基础值的120%以上。选择iVLF-LTP过程中的EPSP进行表观受体动力学分析,结果显示有3个MNs的K2和KT在强直刺激后10 min内减小到基础值的80%以下,后逐渐有所恢复。以上受体动力学分析结果提示,部分MNs的iVLF-LTP早期可能涉及突触后受体亲和力增强的机制。     

姜黄素对癫痫大鼠认知功能障碍的预防作用及其可能机制

目的:探讨姜黄素(curcumin)对癫痫大鼠认知功能障碍的预防作用及其可能机制。方法:将30只成年雄性SD大鼠分为正常对照组、单纯致痫组(SE组)、姜黄素[60mg/(kg.d)]干预组(curcumin组)。采用Morris水迷宫方法检测大鼠学习记忆功能变化,并检测脑片水平的长时程增强(LTP)变化,处死大鼠后取脑组织并匀浆,测超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-PX)、谷胱甘肽(GSH)、丙二醛(MDA)的水平。结果:(1)SE组大鼠寻找平台的潜伏期明显长于对照组,具有统计学意义(P<0.05),姜黄素组寻找平台的潜伏期相对于SE组显著缩短(P<0.05)。撤离平台后,SE组大鼠在平台所在象限的停留时间明显短于对照组(P<0.05),姜黄素治疗后大鼠在平台所在象限的停留时间较SE组显著延长(P<0.05)。(2)给予HFS刺激后各组兴奋性突出后电位(fEPSP)斜率较前明显增加,均可持续1h以上,与对照组比较SE组HFS刺激后fEPSP斜率明显减小(P<0.05),姜黄素可减轻SE所致的fEPSP斜率减小(P<0.05)。(3)SE组SOD、GSH-PX、GSH显著下降,MDA明显增高,姜黄素可逆转上述现象,有统计学意义(P<0.05)。结论:姜黄素可显著减轻癫痫持续状态所致的大鼠认知功能障碍,减轻海马区的氧化应激反应从而保护海马海马是其可能机制之一。     

稳态白噪声对豚鼠听觉脑干诱发反应(ABR)功率谱的影响

本文对豚鼠125和131dBSPL稳态白噪声暴露后听觉脑干诱发反应(ABR)功率谱进行了研究.研究结果表明:125dBSPL噪声暴露组0—200、210—500Hz频段谱能量比对照组相应频段谱能量增多(P<0.05),而510—900Hz频段谱能量却显著下降(P<0.01);131dBSPL噪声暴露组0-200Hz频段谱能量显著下降(P<0.01),但210-500Hz、910-1400Hz频段谱能量却明显增多(P<0.01).     

我国正常成人脑干听觉电反应各波潜伏期的测定

在10名正常被试者的20只耳,用不同强度的短声测定了脑干听觉电反应(BSR)的7个波的潜伏期(数值见表1),结果表明,各波的潜伏期都随刺激声强的减弱(80到0 dB)而延长,且呈直线函数关系,并且这种延长主要来自1波。由每个被试者两耳所诱发的 BSR 各波的潜伏期及其与刺激声强的变化关系都较为恒定和对称。V 波振幅较大,出现率较高,接近主观听觉阈值,是 BSR 中的主波,其潜伏期(声强80 dB 时为5.7±0.6毫秒)如明显超出此范围(6.3毫秒)或两侧不对称时,应考虑为异常。我们还在半数测试例中记录到Ⅷ波,关于它的生理意义,尚不清楚。     

促红细胞生成素对脑损伤早产儿NBNA评分、肝肾功能以及脑干听觉诱发电位的影响

目的:探讨促红细胞生成素(EPO)对脑损伤早产儿新生儿神经行为测定(NBNA)评分、肝肾功能以及脑干听觉诱发电位的影响。方法:选取2015年2月~2018年7月期间我院收治的脑损伤早产儿117例,将上述研究对象根据随机数字表法将其分为对照组(n=58)和观察组(n=59),对照组患儿给予常规对症治疗,观察组在对照组的基础上联合EPO治疗,比较两组NBNA评分、肝肾功能以及脑干听觉诱发电位,记录两组患儿治疗期间并发症发生情况。结果:观察组纠正胎龄40周时NBNA评分高于对照组(P<0.05)。两组患儿治疗后峰间期(Ⅰ~Ⅲ波、Ⅲ~Ⅳ波、Ⅰ~Ⅳ波)、潜伏期(Ⅰ波、Ⅲ波、Ⅳ波)均较治疗前降低,且观察组低于对照组(P<0.05)。两组患儿治疗前、后尿素氮(BUN)、肌酐(Cr)、血清谷丙转氨酶(SGPT)、总胆红素(TBIL)比较差异均无统计学意义(P>0.05)。两组患儿动脉导管未闭、新生儿败血症发生率比较差异无统计学意义(P>0.05),而观察组支气管肺发育不良、颅内出血、脑干听觉诱发电位异常等发生率低于对照组(P<0.05)。结论:EPO对脑损伤早产儿具有一定的神经保护作用,能够有效保护受损神经细胞与听觉神经通路,降低脑损伤并发症的发生率,且不影响患儿的肝肾功能。     

Dynamics of potentials evoked in the auditory pathway and reticular formation of the cat. Studies during waking and sleep stages

Averaged evoked potentials in the inferior colliculus (IC), medial geniculate nucleus (MG) and reticular formation (RF) of chronically implanted and freely moving cats were measured using auditory step functions in the form of tone bursts of 2000 Hz. The most prominent components of the AEP of the inferior colliculus were a positive wave of 13 msec and a negative wave of 40–55 msec latency. The AEP of the medial geniculate nucleus was characterized by a large negative wave peaking at 35–40 msec. During spindle sleep and slow wave sleep stages changes in the AEPs of both nuclei occured.Transient evoked responses of the inferior colliculus, medial geniculate nucleus and reticular formation were transformed to the frequency domain using the Laplace transform (one sided Fourier transform) in order to obtain frequency characteristics of the systems under study. The amplitude characteristics of IC, MG. and RF obtained in this way revealed maxima in alpha (8–13 Hz), beta (18–35 Hz) and higher frequency (50–80 Hz) ranges. During spindle sleep stage a maximum in the theta frequency range (3–8 Hz) and during slow wave sleep maximum in the delta (1–3 Hz) frequency range appeared in the amplitude characteristics of these nuclei.The amplitude characteristics of the inferior colliculus and medial geniculate nucleus were compared with the amplitude characteristics of other brain structures. The comparison of AEPs and amplitude frequency characteristics obtained using these AEPs reveals that the existence of a number of peaks (waves) with different latencies in the time course does not necessarily indicate the existence of different functional structures or neural groups giving rise to these waves. The entire time course of evoked potentials and not the number and latencies of the waves, carries, the whole information concerning different activities and frequency selectivities of brain structures.Supported by Turkish Scientific and Technical Research Council Grant TAG-266.Presented in Part at the VIIIth International Congress of Electroencephalography and Clinical Neurophysiology in Marseilles, September 1–7, 1973.     

Stochastic Properties of Discrete Waves of the Limulus Photoreceptor

In the dark-adapted photoreceptor of the horseshoe crab, Limulus, transient discrete depolarizations of the cell membrane, discrete waves, occur in total darkness and their rate of occurrence is increased by illumination. The individual latencies of the discrete waves evoked by a light stimulus often cannot be resolved because the discrete waves overlap in time. The latency of the first discrete wave that follows a stimulus can be determined with reasonable accuracy. We propose a model which allows us to make an estimate of the distribution of the latencies of the individual light-evoked discrete waves, and to predict the latency distribution of the first discrete wave that follows a stimulus of arbitrary intensity-time course from the latency distribution of the first discrete wave that follows a brief flash of light. For low intensity stimuli, the predictions agree well with the observations. We define a response as the occurrence of one or more discrete waves following a stimulus. The distribution of the peak amplitudes of responses suggests that the peak amplitude of individual discrete waves sometimes has a bimodal distribution. The latencies of the two types of discrete waves, however, follow similar distributions. The area under the voltage-time curve of responses that follow equal energy long (1.25 sec) and short (10 msec) light stimuli follows similar distributions, and this suggests that discrete waves summate linearly.     

早产儿支气管肺发育不良的影响因素及血清MMP-16、NF-κB检测的临床意义

目的:探讨早产儿支气管肺发育不良(BPD)的影响因素及血清基质金属蛋白酶-16(MMP-16)、核因子κB(NF-κB)检测的临床意义。方法:前瞻性选取2014年8月~2019年2月期间我院收治的早产儿196例,将早产儿根据是否发生BPD分为无BPD组(n=109)和BPD组(n=87)。将BPD组根据校正胎龄36周或出院时是否需氧分为轻度BPD组(n=28)、中度BPD组(n=30)、重度BPD组(n=29)。采用酶联免疫吸附法检测血清MMP-16、NF-κB水平,采用Pearson相关性分析MMP-16与NF-κB的关系,采用多因素Logistic回归分析早产儿BPD的影响因素。结果:随着BPD病情严重程度的增加,血清MMP-16、NF-κB水平呈不断升高趋势(P<0.05)。Pearson相关性分析可得,MMP-16与NF-κB呈正相关(P<0.05)。单因素分析结果显示,早产儿BPD的发生与出生体质量、胎龄、有无羊水污染、孕母有无妊娠期高血压、有无早产儿呼吸窘迫综合征、使用或未使用肺表面活性物质、有无肺出血、闭合或未闭合动脉导管、有无机械通气、是否吸入氧浓度>40%有关(P<0.05),而与性别、胎膜早破史无关(P>0.05)。多因素Logistic回归分析显示,胎龄为28~31周、动脉导管未闭合、使用肺表面活性物质、机械通气、羊水污染、出生体质量为1000~1500 g均是早产儿BPD发生的独立危险因素(P<0.05)。结论:早产儿BPD体内血清MMP-16、NF-κB水平呈异常升高,可能参与着疾病的发生、发展,BPD与多种因素息息相关,可采取积极的预防措施以减少BPD的发生。     

ELF magnetic fields increase amino acid uptake into Vicia faba L. roots and alter ion movement across the plasma membrane

Vicia faba seedlings, subjected to a 10 microT 50 Hz square wave magnetic field for 40 min together with a radioactive pulse, showed a marked increase in amino acid uptake into intact roots. A more modest increase was observed with a 100 microT 50 Hz square wave. An increase in media conductivity at low field intensities from 10 microT 50 Hz square wave, 100 microT 50 Hz sine wave, and 100 microT 60 Hz square wave fields, indicated an alteration in the movement of ions across the plasma membrane, most likely due to an increase in net outflow of ions from the root cells. Similarly, marked elevation in media pH, indicating increased alkalinity, was observed at 10 and 100 microT for both square and sine waves at both 50 and 60 Hz. Our data would indicate that low magnetic field intensities of 10 and 100 microT at 50 or 60 Hz can alter membrane transport processes in root tips.     

Associations between FSH concentrations and major and minor follicular waves in pregnant mares

Follicular waves were detected in 19 pregnant mares (Days 11 to 40) by a significant increase followed by a significant decrease in diameters of follicles after removing large (>/=25 mm) follicles from the data sets. The waves were defined as major (largest follicle, >/=35 mm; n=18) or minor (largest follicle, <35 mm; n=17). Six mares (32%) had 2 successive major waves beginning on mean Days 15.2 and 26.8; 6 had a solitary major wave beginning on Days 11 to 20; and 6 had only minor waves occurring at irregular intervals. The mean interval between minor waves (7.8 days) was less (P<0.05) than for major waves (11.7 days). Mean divergence in diameters of the largest and second largest follicles of a wave began 4 days after the detected emergence of consecutive major waves, and was taken as the beginning of the expression of dominance by the largest follicle. The interval from emergence to divergence was several days longer (P<0.05) for solitary major waves than for consecutive waves. Dominance was not detected for the minor waves, using mean diameters of the 2 largest follicles, but was apparent on inspection of individual wave profiles in 5 of 17 (29%) minor waves. Minor waves, compared with major waves, had larger diameter of follicles on the day of wave emergence (15.0 versus 12.1 mm), and significantly greater variation in the day of attainment of maximal diameter of largest follicle and small follicles. A mean increase in FSH was temporally associated with the emergence of both major and minor waves. In mares with minor waves, concentrations of FSH were higher, on average, over Days 11 to 40, which seemed consistent with the origin of follicular waves from larger follicles in the basal populations. The lower overall FSH levels in mares with major waves seemed at least partly due to depression of FSH levels beginning at the time of divergence between the 2 largest follicles.     

The hippocampal EEG-activity and a systems analytical interpretation of averaged evoked potentials of the brain

Evoked Potentials in the hippocampus dorsalis are measured using chronically implanted and freely moving cats in applying auditory stimulations in the form of tone bursts of 3000 Hz. The hippocampal evoked potentials are characterized by 3 positive (I, III, V) and 3 negative peaks (II, IV, VI). Peaks I to VI have latencies of about 10, 28, 50, 75, 95 and 125 msec. These responses are then analyzed with a Laplace transform in order to obtain the hippocampal frequency characteristics. The amplitude frequency characteristic depicts resonance maxima of EEG-amplitude in theta (3–8 Hz) and beta (18–32 Hz) frequency ranges. A resonance in the frequencies of 3–8 Hz was expected because of the spontaneous hippocampal theta activity. Therefore this finding emphasize the reliability of the mathematical method used. On the other hand the existence of a hippocampal beta selectivity is highly remarkable and apparently the hippocampal activity is regulated at least by two different systems. The use of the mathematical method (Laplace transform) indicates that the simple knowledge of the latencies and the number of potential waves(usuallydenoted as P ₁, P ₂, ..., N ₁, N ₂ ...) cannot allow exact statements on mechanisms causing the formation of these peaks. Rather the slope and slope changes of the waves are determining. Different waves in the transient evoked response can be generated from a mechanism having only one resonant maximum in the frequency domain.Supported in part by Turkish Scientific and Technical Research Council Grant No. TAG-182.     

早产儿超声心脏几何形态学与血流动力学的相关性分析

摘要 目的：探讨与分析早产儿超声心脏几何形态学与血流动力学的相关性。方法：研究时间为2018年8月到2020年6月,选择本院收治的早产儿150例(早产组)和足月儿150例(足月组)作为研究对象,两组新生儿都给予超声检查,记录、左心室舒张期内径(Left ventricular diastolic diameter,LVDd)、左心室收缩期内径(Left ventricular systolic diastolic,LVDs)、左房内径(Left atrial diameter,LAD)、左心室相对厚度(Left ventricular relative wall thickness,LVRWT)、左心室心肌质量(Left ventricular myocardial mass,LVM)、左室后壁舒张期厚度(Left ventricular posterior walldepth,LVPWd)、左心室舒张末期容积(Left ventricular end diastolic volume,LVDV)、左心室收缩末期容积(Left ventricular end systolic volume,LVSV)、每搏输出量(Stroke volume,SV)、左心室射血分数(Left ventricular ejection fraction,LVEF)、左心室缩短分数(Left ventricular fractional shortening,LVFS)等指标并进行相关性分析。结果：早产组的LVDd、LVDs、LAD、LVPWd、LVRWT、LVM值都显著低于足月组(P<0.05)。早产组的LVDV、LVSV、SV值低于足月组(P<0.05),两组LVEF、LVFS值对比差异无统计学意义(P>0.05)。在早产组中,Pearson相关性分析显示LVDd、LVDs、LAD、LVPWd、LVRWT、LVM值与LVDV、LVSV、SV值存在正相关性(P<0.05)。Cox比例风险回归模型显示早产儿的出生体重、身长为影响LVDd、LVDV值的主要因素(P<0.05)。结论：早产儿超声心脏几何形态学指标与血流动力学指标呈正相关,提示超声能准确记录和监测早产儿的心脏几何形态学与血流动力学,可作为评估早产儿心功能的一种可靠方法。     

新生儿凝血指标及部分生化指标检测参考区间调查

目的:调查分析新生儿凝血指标及部分生化指标检测参考区间。方法:以十所三甲医院2012年1月~2014年6月收治的新生儿2683例为研究对象,其中足月儿1700例,早产儿983例,选择同期十所医院职工健康体检1000例为对照组,通过全自动血凝仪、全自动生化分析仪测定所有对象凝血指标及12项生化指标,并建立相关指标参考区间。结果:足月新生儿PT、TT、APTT凝血指标较对照组延长,Fib较对照组降低,差异均有统计学意义(P=0.000);早产儿PT、TT、APTT较足月儿延长(P=0.000),Fib(P=0.001)降低;足月新生儿Glc水平较对照组低(P=0.000),早产儿Glc水平较足月新生儿更低(P=0.000);足月新生儿血钙水平低于对照组,血清TC、Cr、BUN、ALT含量均在对照组之下(P=0.000),早产儿相对更低(P均0.05);足月新生儿LDH、CK酶活性及K+水平均高于对照组(P均0.05),早产儿水平更高(P0.05);足月儿血清Alb、TP及Na+水平低于对照组(P0.05),早产儿更低(P均0.05)。结论:新生儿凝血表达与成人不同,凝血及部分生化指标参考区间的变化与年龄有联系,有必要为新生儿建立与年龄相关的凝血、生化指标参考区间。     

301例早产儿视网膜病变筛查结果及其高危因素分析

目的:调查早产儿视网膜病变(ROP)的发生情况并分析其高危因素。方法:选取2017年6月至2018年6月在我院进行眼底检查的301例早产儿,依据《早产儿治疗用氧和视网膜病变防治指南》和《中国早产儿视网膜病变筛查指南》对早产儿进行筛查和随诊,同时收集早产儿及其母亲的相应病历信息,采用多因素Logistic回归分析分析ROP的高危因素。结果:301例早产儿中,共检出ROP患儿43例,其中须接受治疗的患儿13例,所有患儿经过2-6个月的治疗和随诊后均好转。围产因素中,胎龄小、出生体重低、吸氧、输血、有急性呼吸窘迫综合征(ARDS)的早产儿ROP检出率更高(均P0.05);母体因素中,多胎分娩的早产儿ROP检出率高于单胎分娩的早产儿(P0.05)。Logistic回归分析显示,胎龄小、出生体重低、吸氧、输血和有ARDS为早产儿ROP的高危因素(P0.05)。结论:早产儿ROP发病率较高,胎龄小、出生体重低、吸氧、输血和有ARDS是其高危因素,在临床实践中应给予重视,及早发现ROP并规范治疗,以降低早产儿ROP的发病率。