遗传与家庭环境对儿童个性影响的双生子研究

目的:探索遗传和家庭环境对儿童个性的影响.方法:采用横断面设计,以学籍登记为线索募集6-16岁的双生子56对,采集颊黏膜标本提取DNA,进行卵型鉴定.用儿童版艾森克个性测验(EPQ)作为儿童个性测缝工具,用一般健康问卷(GHQ-12)、父母的养育方式和维度问卷(PSDQ)、家庭活动计划一般功能量表(FAD-GFS)、应激生活事件问卷等向其父母收集家庭环境信息.结果:(1)50对双生子成功提取DNA,卵型鉴定结果显示:同卵双生子24对,异卵双生予26对;(2)同卵双生(MZ)组的EPQ内外向、稳定性、掩饰度三个因子分每对双生子个体之间均正相关(r=0.75,0.73,0.56;P＜0.05),而异卵双生(DZ)组仅有稳定性因子分在每对双生子个体之间有相关性,且相关系数小于MZ组(r=0.47,P＜0.05;MZ组:Z值呵信区间为(0.94±0.44);DZ组:Z=0.51);(3)110位双生子个体的EPQ内外倾向性(E分)与FAD-GFS分值呈负相关(r=-0.20,P＜0.05),精神质(P分)与母亲GHQ-12分值呈正相关(r=0.22,P＜0.05),稳定性(N分)与父亲的专制养育分呈正相关(r=0.24,P＜0.05).结论:本研究提示儿童个性主要受遗传因素决定,但家庭环境中母亲的心理健康状况、父亲的养育方式、健康的家庭功能等对儿童个性的形成也可能有不可忽视的作用.     

威斯康星卡片分类测验作为双生子基因功能稳定性指标的初探

目的：探索威斯康星卡片分类测验测试各指标中更稳定、更精确的指标（内表型）。方法：在重庆市主城区募集6—16岁的双生子。签写知情同意书后，用威斯康星卡片分类测验对59对6—16岁的双生子测试（同卵双生28对，异卵双生31对），比较双生子两个体之间的六个常用指标（正确数、错误数、持续错误数、非持续错误数、总分类数、完成第一个分类所需个数）得分的相关系数，采取双生子的颊黏膜标本以提取DNA并进行卵型鉴定。结果：MZ组和DZ组的年龄、性别、受教育年限具有可比性（P〉0．05），MZ组的持续错误数指标在双生子对个体之间的相关系数有显著相关（r=0．65，P=0．001），其余五个指标和DZ组的六个指标在双生子对个体之间的得分无显著性相关（P〉0．05）。结论：在威斯康星卡片分类测验常用的六个指标中，持续错误数受遗传的影响更大，作为内表型指标可能优于威斯康星卡片分类测验中的其他指标。     

应用双生子法计算遗传度

双生子法(twin method)是人类和医学遗传学的重要方法之一。所谓双生子法,主要是通过调查,利用同卵双生子(mono-zygotic twins,MZ)完全相同的遗传性和异卵双牛子(dizygotic twins,DZ)部分相同的遗传性,来研究某些疾病(或性状)中遗传因素和环境因素相互作用的程度。最早提出并应用双生子法的是达尔文的表弟F.Galton(1876)(?),他曾应用这种方法研究遗传与人类智力和才能的关系。随后,许多学者都开始应用双生子法来研究遗传和环境因素对某些疾病(或性状)所产生的影响。但由于当时还没有较精确的卵性鉴定     

遗传对人血清高密度脂蛋白(HDL)水平的影响

血清高密度脂蛋白(HDL)水平已经可以用人高密度脂蛋白的两种主要多肽——脱辅基脂蛋白A—Ⅰ和脱辅基脂蛋白A—Ⅱ的抗血清进行免疫测定。对同卵双生子和异卵双生子的一系列观察表明,至少脱辅基脂蛋白A—Ⅰ的浓度变化,在某种程度上决定于遗传。同卵双生子和异卵双生子的脱辅基脂蛋白A—Ⅰ的组内相关。γ=对间方差-对内方差/对间方差+对内方差分别是0.58和0.29;脱辅基脂蛋白A—Ⅱ分别是0.30和0.17。A—Ⅰ和A—Ⅱ总计的相     

年龄、性别和遗传对姊妹染色单体交换的影响

对21对性别相同的双生进行了淋巴细胞培养以研究姊妹染色单体交换(SCE),即11对同卵双生(MZ),10对异卵双生(DZ)。取血时,没有任何人患有病毒疾病或癌症,9个年老的和5个年轻的受检者服用抗     

健康双生子外周血CD4^＋和CD8^＋ T细胞亚群相对计数遗传度研究

目的分析围生期及生命早期环境因素与外周血CD4＋、CD8＋T细胞相对计数的关系,估计CD4＋和CD8＋T细胞亚群的遗传度。方法采用双生子研究设计,经纳入与排除标准选取在新疆医科大学第一附属医院、乌鲁木齐市妇幼保健医院、新疆维吾尔自治区人民医院、中国人民解放军乌鲁木齐总医院和乌鲁木齐市第一人民医院出生的健康双生子。收集研究对象一般家庭状况、母亲孕期及分娩状况、出生时状况等信息,在双生子满1周岁时进行体检。体重和身高等体格发育指标依照＂1995年中国九市7岁以下儿童体格发育调查研究＂标准进行测量。测定外周血CD4＋和CD8＋T细胞亚群相对计数,并通过微卫星DNA基因分型技术进行卵型鉴定。CD4＋和CD8＋T细胞亚群的遗传度估计应用Mx软件进行分析。结果研究期间共有172对双生子进入分析,其中82对为（47.7%）同卵双生子（MZ）,90对为异卵双生子（DZ）。Apgar评分与MZ、DZ组CD4＋T细胞相对计数呈弱正相关（rMZ=0.16,rDZ=0.14,P〈0.05）。最终选择AE模型得到1岁幼儿外周血CD4＋和CD8＋T细胞的遗传度分别为61.8%（95%CI：38.3%-74.8%）与57.3%（95%CI：34.5%-70.2%）。结论 1岁幼儿外周血CD4＋和CD8＋T细胞亚群遗传度高于成人水平,Apgar评分或与CD4＋和CD8＋T细胞亚群相对计数相关。     

遗传与环境因素对儿童内向行为影响的双生子研究

目的 利用双生子设计的定量遗传分析方法探讨遗传因素与环境因素对于儿童内向行为的影响.方法 使用Achenbach儿童行为评定量表家长版本调查了189对成都地区6～16岁双生子的内向行为,采用Holzinger公式计算遗传度,家长评定家庭亲密度和适应性量表、一般健康问卷调查特定环境因素.结果 (1)儿童内向行为遗传度为0.54,年龄、性别与其相关.(2)家庭实际适应性、父母心理健康情况与儿童的内向行为显著相关(r=-0.213,0.250,0.309;Ps＜0.001),母亲心理健康状况为其危险因素(OR=2.483,P=0.008).结论 遗传因素和环境因素对儿童的内向行为均有影响,年龄和性别与遗传度相关,影响儿童内向行为的环境因素包括家庭功能和父母的心理健康水平.     

肾脏疾病时血与尿中的瘦素水平

目的探讨人瘦素 ( leptin,L EP)在肾脏疾病中的作用机制及其表达特征。方法采用放射免疫分析法对慢性肾功能衰竭等 10组肾脏疾病患者进行血清和尿液中瘦素水平检测。观察其浓度变化与 Cr、BU N的关系 ,并与 3 0例正常人比较。结果 15 2例患者中 ,除肾积水组外 ,其它各组瘦素水平均不同程度高于对照组 ,差异显著 ( P<0 .0 1)慢性肾衰组瘦素含量随 Cr、BU N增高而增高 ,呈正相关关系 ( r=0 .4 0 ,P<0 .0 1,r=0 .3 8,P<0 .0 5 )。尿液中瘦素在慢性肾炎和肾病综合症组含量增高 ,慢性肾衰和肾肿瘤组则较正常人降低。结论瘦素增高与多种因素有关 ,并与肾脏功能受损程度成正比。     

瘦素、RAAS与高血压的关系

目的 探讨瘦素和肾素-血管紧张素-醛固酮系统（RAAS）与高血压的相互关系及病理生理机制.方法 采用放射免疫方法测定91例高血压患者及67名健康志愿者的血清瘦素、血浆肾素活性（PRA）、血管紧张素Ⅱ（AngⅡ）和醛固酮（ALD））水平;同时测量身高、体重,计算体质指数（BMI）.结果 ①同组内女性瘦素水平均显著高于男性（P＜0.01）;高血压组女性瘦素水平显著高于正常组女性（P＜0.01）;高血压组男性瘦素水平也显著高于对照组男性（P＜0.05）.②高血压患者血清瘦素、PRA、收缩压（SBP）和舒张压（DBP）均显著高于对照组（P＜0.01）; AngⅡ水平也明显高于对照组（P＜0.05）,而BMI和ALD水平与对照组比较无明显变化.③直线相关统计分析显示,高血压组患者血清瘦素的升高与PRA、AngⅡ、BMI和SBP呈正相关（PRA：r =0.52,P＜0.01;AngⅡ：r=0.43,P＜0.01;BMI：r =0.55,P＜0.01;SBP：r=0.33,P＜0.05）,而与ALD和DBP无相关性;对照组瘦素仅与BMI呈高度正相关（r=0.54,P＜0.01）,其它指标均无相关性.结论 血清瘦素水平对血压的影响与性别有关,高血压患者存在瘦素抵抗,瘦素可通过影响RAAS的活性使血压升高,主要为收缩压（SBP）的增高.     

血清瘦素水平与缺血性脑血管病关系的研究

目的 :探讨瘦素、胰岛素抵抗与血脂的相互关系 ,评价瘦素在缺血性脑血管病 (ICVD)发病中的作用。方法 :选 1 31例不同类型ICVD患者和 36例正常人 ,采用放射免疫分析测定空腹血清瘦素、血脂、胰岛素水平 ,并进行相关分析。结果 :ICVD患者瘦素水平明显高于对照组 ;血脂与胰岛素水平类似瘦素变化。相关实验显示 ,瘦素水平与CH及TG呈正相关 (r=0 .4 5 ,P <0 .0 5 ;r=0 .31 ,P <0 .0 5 ) ,与INS呈显著正相关 (r=0 .5 5 ,P<0 .0 1 ) ,与HDL -C呈显著负相关 (r=- 0 .38,P <0 .0 5 )。结论 :ICVD患者的瘦素水平与血脂代谢、高胰岛素血症 /胰岛素抵抗以及代谢综合征的其他成分密切相关 ,提示高瘦素血症 /瘦素抵抗可能是ICVD的又一特征 ,并可能在其发病中起重要作用     

Heritability and risk factors of uterine fibroids--the Finnish Twin Cohort study

OBJECTIVES: Our aim was to study heritability, risk factors and hospitalization for uterine fibroids. METHODS: A random sample of 80 MZ and 80 DZ twins from the Finnish Twin Cohort were invited and 51% of the eligible women (n=82, 17 MZ and 16 DZ pairs, 40-47 years, mean age 43.0), underwent a transvaginal ultrasound. The entire cohort of 13872 women was linked to the national hospital discharge registry 1972-1990. RESULTS: Prevalence of fibroids was 66% and the average number of fibroids 1.7. The casewise concordance for being hospitalized for uterine fibroids was higher in MZ (0.31, 95% CI 0.24-0.37) than in DZ pairs (0.18, 95% CI 0.14-0.22). The proportion of variance in liability to fibroid hospitalization accounted for by genetic factors was 54.8% (95% CI 46.2-62.7%). Women with fibroids had higher body mass index (23.7 vs 21.7, P=0.0086), lower age at first birth (25.7 vs 29.3, P=0.012) and higher parity (3+ children 48.2 vs 29.6%, P=0.009) than women without fibroids. Risk ratio (RR) for fibroids in a MZ twin whose sister had been diagnosed with fibroids was 1.1 (95% CI 0.08;15), for a DZ twin 1.1 (95% CI 0.16;8.8) and for all twins 1.3 (95% CI 0.3; 6.1). Intraclass correlation for the number of fibroids was 0.24 for MZ and 0.11 for DZ twins, yielding an heritability estimate of 0.26. CONCLUSION: Reproductive and anthropometric factors may have at least as large role in pathogenesis of fibroids than genetic factors.     

A genetic analysis of the Epworth Sleepiness Scale in 1560 World War II male veteran twins in the NAS-NRC Twin Registry

Responses to the eight-item Epworth Sleepiness Scale (ESS) obtained from 1560 World War II male veteran twin pairs [818 monozygotic (MZ), 742 dizygotic (DZ)] were analysed to determine the extent to which genetic influences are involved in self-reported daytime sleepiness in the elderly. Average ESS score (+/- SD) in this sample was 7.1 +/- 3.9, range 0--24. More than half of the twins (65%--67%) reported a moderate to high chance of falling asleep while lying down to rest; fewer than 3% admitted that this would occur while sitting and talking to someone or while stopped in traffic. Daytime sleepiness was not associated with age but was significantly and positively associated with obesity. The intraclass twin correlation on ESS scores was 0.39 in MZ pairs and 0.21 in DZ pairs (both P < 0.001). Structural equation modeling of the observed variance-covariance matrices for MZ and DZ twins estimated the heritability of ESS to be 38% (95% confidence interval 33%--44%). Environmental influences not shared by twin brothers accounted for the remaining variance in daytime sleepiness. A reasonable interpretation of the heritability of ESS in this healthy cohort of elderly male twins is a genetic susceptibility for disordered breathing during sleep.     

Genetic influence on the serum levels of naturally occurring human IgG antibodies to dietary antigens. Quantitative assessment from a twin study

Serum IgG antibodies to ovalbumin (OA) and beta-lactoglobulin (BLG) were quantified by ELISA techniques in 22 monozygotic (MZ) and 24 dizygotic (DZ) healthy twin pairs. Antibody levels were comparable in the MZ and DZ groups both for anti-OA and anti-BLG antibodies. The genetic variance (GWT) was 0.167 for log IgG anti-OA antibodies, and 0.173 for log IgG anti-BLG antibodies, with heritability estimates of 0.44 and 0.37, respectively. No indication was observed of genotype-environmental interaction or differential environmental covariance for the log antibody levels in the MZ and DZ twins. The anti-OA and anti-BLG antibody levels in the same individual correlated only to a low degree. The levels of naturally occurring serum IgG antibodies are significantly influenced by genetic factors.     

Genetic variance of erythrocyte parameters in adult male twins

Erythrocyte count, hematocrit, mean corpuscular volume and reticulocyte counts were measured in 59 pairs of monozygotic (MZ) and 69 pairs of dizygotic (DZ) adult, Caucasian male twins. The means of MZ and DZ twins were not significantly different for any of the traits measured. Erythrocyte count and mean corpuscular volume had significant estimates of genetic variance (P less than 0.05).     

Heritability of reproductive hormones in adult male twins

BACKGROUND: Proper functioning of the male reproductive axis depends on complex feedback systems between several hormones. In this study, the genetic contribution of various endocrine components of the hypothalamic-pituitary-testicular axis is evaluated and previously observed differences in FSH and inhibin B levels between mono- (MZ) and dizygotic (DZ) twins are re-investigated. METHODS: Inhibin B, FSH, LH, sex hormone-binding globulin (SHBG) and testosterone levels were assayed in 128 adult males (20 MZ twin pairs, 7 single MZ twins, 10 DZ twin pairs, 27 single DZ twins and 34 siblings of twins, constituting 10 sibling pairs), aged 15.6-68.7 years. Hormone levels were compared across zygosity groups and heritability estimates were obtained using maximum likelihood variance component analysis. RESULTS: Heritability estimates ranged from 56% (testosterone) to 81% (inhibin B and SHBG). For LH and FSH, the heritability was estimated at 68% and 80% respectively. No mean differences in hormone levels were observed across groups. CONCLUSIONS: All measured hormones are highly heritable. A difference in the FSH-inhibin B feedback system between DZ twin males and MZ twin males could not be confirmed.     

Genetic variation in neuromuscular performance

Using a simple cumulative model of heredity plus environment, based on intrapair differences observed in monozygous (MZ) and dizygous (DZ) twins, the relative contribution of heredity to the interindividual variance in several neuromuscular parameters was determined with 15 pairs of male (8 MZ and 7 DZ) and 14 pairs of female (7 MZ and 7 DZ) twins ranging in age from 10 to 14 years. The data disclosed that in boys the variability in maximal mechanical (anaerobic) power was 99.2% genetically determined under the environmental conditions of the study. The corresponding heritability estimate values for the patellar reflex time and reaction time were 97.5% and 85.7%, respectively. In girls the heritability estimates could not be computed, because the MZ twins seemed to show almost as much diversity as the DZ twins in all of the variables studied. On the basis of the obtained data it is suggested that the variation observed in maximal mechanical power, patellar reflex time and reaction time may be more susceptible to environmental modifications in girls than in boys.This study was supported by research grants from the Ministery of Education of Finland (8551/79/70) and the Medical Research Council of Canada (MA-3905).     

Cord blood immunoglobulin E in like-sexed monozygotic and dizygotic twins

Genetic and environmental factors have been implicated in the etiology of atopy and of serum IgE levels. In order to eliminate post-natal environmental influences we measured IgE in cord blood (CB-IgE) from a cohort of unselected, like-sexed twins. IgE determination was performed with a sensitive radioimmunoassay with a detection limit of 0.01 kU/l. Samples with contamination by maternal blood were identified by IgA determination and excluded. CB-IgE was evaluated in 29 monozygotic (MZ) and 28 dizygotic (DZ) twin pairs. The means and variances for IgE values were comparable for MZ and DZ twins when sex was controlled for. Placental anatomy (MZ twins with mono-and dichorial placenta and DZ twins with one or two placentae) had no significant influence on the IgE levels. In an analysis of variance with subsampling the among-pair, within-pair and analytical variance components were calculated. The analytical variance was well below the biological variances. Biometrical analysis showed that the best model by Akaike Information Criteria was a model including only additive genetic and non-shared environmental factors. With this model the heritability estimate was 0.8. These data suggest that the majority of the variation in CB-IgE is accounted for by genetic factors, but a substantial effect of a common environment cannot be excluded with the present sample size.     

Toddler see,toddler do? Genetic and environmental influences on laboratory-assessed elicited imitation

The imitative performance of 311 pairs of 24-month old twins (143 MZ, 168 same-sex DZ) was assessed via three multi-step imitative sequences. Composite imitation score correlations suggested the presence of genetic influences on imitation, with MZ correlations significantly exceeding DZ correlations. Univariate model-fitting procedures supported this finding. Substantial broad heritability was found for imitative performance, with no evidence for shared environment. However, we are unable to say with certainty to what extent this heritability is represented by additive and nonadditive genetic variance. Estimates of heritability derived from both ACE and ADE model-fitting procedures accounted for approximately 50% of the total variance, with the remaining variance in imitative performance attributable to nonshared environmental factors. Edited by Dorret Boomsma & John K Hewitt     

Twin study of genetic and aging effects on X chromosome inactivation

To investigate the genetic influence on X chromosome inactivation and on age-related skewing of X inactivation, in particular, we analysed the X inactivation pattern (XIP) in peripheral blood cells from 118 young monozygotic (MZ) twin pairs (18-53 years), 82 elderly MZ twin pairs (55-94 years), 146 young dizygotic (DZ) twin pairs (20-54 years) and 112 elderly DZ twin pairs (64-95 years). Elderly twins had a higher frequency of skewed X inactivation (34%) than young twins (15%) (P<0.001). Our data suggest that the increase in skewing occurs after age 50-60 years. The intraclass correlation was 0.61 and 0.58 in young and elderly MZ twin pairs, and 0.08 and 0.09 in young and elderly DZ twin pairs. Biometric analysis showed that dominant genetic effects accounted for 63 and 58% of the variance of XIP in the young and elderly twin pairs, respectively. The dominant genetic effect and the shared environment for monochorionic MZ twins may explain the high intraclass correlation for the MZ twin pairs compared to the DZ twin pairs. We did not observe a significant decrease in the intraclass correlation in elderly MZ twins compared to young MZ twins, which would be expected if age-related skewing were due to stochastic factors. We conclude that the increased skewing with age implies that a genetically dependent selection of blood cells take place.     

Risk factors for asthma in young adults: a co-twin control study

Background: The liability to asthma is influenced both by genetic and environmental factors. The objective of this study was to identify risk factors for asthma in young adult twin pairs during an 8‐year period. Methods: From the birth cohorts 1953–1982 of the Danish Twin Registry, 6090 twin pairs who were initially unaffected with respect to asthma at a nationwide questionnaire‐based study in 1994 participated in a similar follow‐up study in 2002. Subjects were regarded incident asthma cases when responding affirmatively to the question ‘Do you have, or have you ever had asthma'? in 2002. Pairs in which only one twin developed asthma – discordant pairs – were identified and conditional logistic regression was applied to detect effects of risk factors. Results: A total of 126 monozygotic (MZ) and 273 dizygotic (DZ) discordant twin pairs were identified. In MZ twins hay fever (OR = 3.16, 95% CI: 1.29–7.73, P = 0.007) and exercise (OR for inactivity = 0.35, 95% CI: 0.13–0.91, P = 0.023) were significantly associated with asthma, whereas in DZ twins, hay fever (OR = 2.44, 95% CI: 1.44–4.13, P = 0.001), eczema (OR = 1.96, 95% CI: 1.02–3.78, P = 0.040), female sex (OR between males and females = 0.54, 95% CI: 0.36–0.80, P = 0.002), and increasing levels of body mass index (BMI; OR per unit = 1.11, 95% CI: 1.02–1.20, P = 0.009) were significant predictors of asthma. Conclusions: Hay fever, eczema, female sex, exercise and increasing levels of BMI were risk factors for asthma in young adults. The different risk profile observed in MZ twins compared with DZ twins may reflect an underlying genetic vulnerability shared between those risk factors and asthma.