Search results for " Dizygotic"
showing 10 items of 71 documents
Unpredicted ovulations and conceptions during early pregnancy: an explanatory mechanism of human superfetation
2012
In this bioessay, a literature review on human superfetation was performed in order to find epidemiological variables associated with this phenomenon. Thereafter, an explanatory mechanism of superfetation compatible with the endocrinological, histological and physiological changes undergone by women during early pregnancy is proposed. Superfetation can be defined as the ovulation, fertilisation and implantation of a second or additional embryo(s) during pregnancy. The literature review evidences a small discordance in gestational age between dizygotic twins in humans (range: 2–4 weeks; mean ± s.e.m.: 3.3 ± 0.3 weeks). This difference is compatible with a luteal out-of-phase (LOOP; i.e. atyp…
Muscle Cross-Sectional Area and Structural Bone Strength Share Genetic and Environmental Effects in Older Women
2009
The purpose of this study was to estimate to what extent muscle cross-sectional area of the lower leg (mCSA) and tibial structural strength are influenced by common and trait-specific genetic and environmental factors. pQCT scans were obtained from both members of 102 monozygotic (MZ) and 113 dizygotic (DZ) 63- to 76-yr-old female twin pairs to estimate the mCSA of the lower leg, structural bending strength of the tibial shaft (BSIbend), and compressive strength of the distal tibia (BSIcomp). Quantitative genetic models were used to decompose the phenotypic variances into common and trait-specific additive genetic (A), shared environmental (C), and individual environmental (E) effects. The …
Twins. Similarities, differences and individuality
2015
This study aims to investigate the self-differentiating perceptions and the separation-individuation’s process in emerging adulthood twins. A group of 40 Italian pairs of twins (21 couples dizygotic-DZ and 19 monozygotic-MZ) aged 20-30 years, were evaluated using the test of graphic projection Family Life Space (DSSVF) and thought a specific questionnaire ad hoc constructed for this research. The research hypothesis focus on Zazzo’s test of parallel testimony and provide to give empirical evidence about the capacity of MZ Twins to use more internal resources of the couple than DZ Twins, causing the split slowdown on identification. The data show that there are no difference between not bise…
Genetics of maximal walking speed and skeletal muscle characteristics in older women.
2008
AbstractThe aim of this study was to examine whether maximal walking speed, maximal isometric muscle strength, leg extensor power and lower leg muscle cross-sectional area (CSA) shared a genetic effect in common. In addition, we wanted to identify the chromosomal areas linked to maximal walking speed and these muscle characteristics and also investigate whether maximal walking speed and these three skeletal muscle characteristics are regulated by the same chromosomal areas. We studied 217 monozygotic (MZ) and dizygotic (DZ) female twin pairs aged 66 to 75 years in the Finnish Twin Study on Aging study. The DZ pairs (94) were genotyped for 397 microsatellite markers in 22 autosomes and X-chr…
Genetic influences on resting electrocardiographic variables in older women: a twin study.
2009
Background: Previous studies in young and middle-aged men and women have shown that resting electrocardiographic (ECG) variables are influenced by genetic factors. However, the extent to which resting ECG variables are influenced by genetic factors in older women is unknown. Thus, the aim of this study was to estimate the relative contribution of genetic and environmental influences to individual differences in resting ECG variables among older female twins without overt cardiac diseases. Methods: Resting ECG recordings were obtained from 186 monozygotic and 203 dizygotic twin individuals, aged 63–76 years. Quantitative genetic modeling was used to decompose the phenotypic variance in each …
Heritability of maximal isometric muscle strength in older female twins.
2003
The purpose of the present study was to examine genetic and environmental effects on maximal isometric handgrip, knee extension, and ankle plantar flexion strength. In addition, we wanted to investigate whether the strength of these three muscle groups shares a genetic component or whether the genetic effect is specific for each muscle group. Muscle strength was measured as part of the Finnish Twin Study on Aging in 97 monozygotic (MZ) and 102 dizygotic (DZ) female twin pairs, aged 63-76 yr. The MZ and DZ individuals did not differ from each other in age, body height, weight, or self-related health. The age-adjusted pairwise (intraclass) correlations of the MZ and DZ twins were, respective…
Heredity of interocular similarities in components of refraction: a population-based twin study among 66- to 79-year-old female twins.
2019
Purpose: To examine genetic influences on interocular similarities in ocular refraction and components of refraction among elderly female twins. Methods: Refraction was assessed in 94 monozygotic (MZ) and 74 dizygotic (DZ) female twins aged 66–78 years. Absolute values of interocular differences (Aniso variables) in spherical refraction (SR), refractive astigmatism (AST), spherical equivalent (SE), corneal refractive power (CR), corneal astigmatism (CAST), anterior chamber depth (ACD) and axial length (AL) were calculated. The differences between sisters in each of the Aniso variables were calculated and graded into two categories, best differentiating the groups, here isometropic and aniso…
Heritability of corneal refraction and corneal astigmatism: a population-based twin study among 66- to 79-year-old female twins.
2012
. Purpose: To examine the heritability of corneal refraction power (CR) and corneal astigmatism (AST) in older women. Methods: Corneal refraction and AST were measured by IOL master in 52 monozygotic (MZ) and 47 dizygotic (DZ) female twin pairs aged 66–79 years. The relative contribution of genetic and environmental factors to individual differences in CR was estimated by applying an independent pathway model to the twin data and AST by intraclass correlations (ICC). Results: For the right eye, mean CR was 44.58 dioptres (D) (standard deviation (SD) ±1.28) When comparing CR of the right and left eye between MZ and DZ, no significant difference was found. Mean AST was 0.77 D (SD ±0.44) wi…
The world of twins: an update
2010
In last years, owing to the widespread availability of assisted-reproduction technology, multiple pregnancy rates in Western countries have increased. In twin pregnancies, an increased rate of gestational complications, intrauterine growth restriction (IUGR), preterm birth and severe perinatal conditions is present. These complications are more frequent in monozygotic twins compared to dizygotic twins as well as an increased relative risk of chromosomal abnormalities and congenital malformation. Monochorionic twins are at higher risk for complications, since they share a common placenta where an imbalance in unidirectional arteriovenous anastomoses can lead to twin#x2013;twin transfusion sy…
Shared Genetic and Environmental Effects on Strength and Power in Older Female Twins
2005
Purpose: This study examined the relative contribution of genetic and environmental effects on maximal leg extensor power and also investigated whether leg extensor power and maximum voluntary isometric knee extensor strength share a genetic component. Methods: Muscle functions were measured as part of the Finnish Twin Study on Aging in 101 monozygotic (MZ) and 116 dizygotic (DZ) female twin pairs aged 63–76 yr. Leg extensor power was measured using the Nottingham Leg Extensor Power Rig and maximum voluntary isometric knee extensor strength using an adjustable dynamometer chair. The analyses were carried out using the maximum likelihood method in Mx-program on the raw data set. Results: A b…