A strategic research alliance: Turner syndrome and sex differences

Sex chromosome constitution varies in the human population, both between the sexes (46,XX females and 46,XY males), and within the sexes (e.g., 45,X and 46,XX females, and 47,XXY and 46,XY males). Coincident with this genetic variation are numerous phenotypic differences between males and females, and individuals with sex chromosome aneuploidy. However, the molecular mechanisms by which sex chromosome constitution impacts phenotypes at the cellular, tissue, and organismal levels remain largely unexplored. Thus, emerges a fundamental question connecting the study of sex differences and sex chromosome aneuploidy syndromes: How does sex chromosome constitution influence phenotype? Here, we focus on Turner syndrome (TS), associated with the 45,X karyotype, and its synergies with the study of sex differences. We review findings from evolutionary studies of the sex chromosomes, which identified genes that are most likely to contribute to phenotypes as a result of variation in sex chromosome constitution. We then explore strategies for investigating the direct effects of the sex chromosomes, and the evidence for specific sex chromosome genes impacting phenotypes. In sum, we argue that integrating the study of TS with sex differences offers a mutually beneficial alliance to identify contributions of the sex chromosomes to human development, health, and disease.     

Stability of individual differences in cardiovascular reactivity: A thirteen month follow-up

This study concerns the stability of individual differences in cardiovascular reactivity among nineteen male subjects who had participated in a similar investigation thirteen months earlier. In the previous study (Year I), subjects were presented a frustrating task in concept formation to perform at each of two experimental sessions, scheduled one week apart, and recordings of heart rate (HR) and systolic and diastolic blood pressure (SBP, DBP) obtained during periods of rest and task performance on each occasion of testing. Under the current procedure (Year II), subjects were exposed to the same experimental stressor as on year I, as well as a second cognitive task involving a difficult problem in “mental arithmetic”; HR, SBP and DBP were again recorded both at rest and while subjects performed the instructed tasks. Measures of task-related cardiovascular arousal across the two years of observation revealed reproducible individual differences with respect to the magnitude of subjects' HR and SBP, but not DBP, reactivity. Although individual differences in HR and SBP responses correlated positively, neither HR nor SBP reactivity covaried reliably with DBP changes. It was suggested that concomitant response differences in HR and SBP, as observed under these experimental conditions, may reflect an underlying dimension of individual differences in beta-adrenergic reactivity.     

Comorbidity of Mathematics and Reading Deficits: Evidence for a Genetic Etiology

In order to assess the genetic etiology of the comorbidity of reading and mathematics difficulties, data were ascertained from two samples: (1) 102 identical and 77 same-sex fraternal twin pairs in which at least one member of each pair is reading disabled and (2) 42 identical and 23 same-sex fraternal twin pairs in which at least one member is math disabled. Composite reading and mathematics performance data from each sample were fitted to the basic multiple regression model for the analysis of selected twin data and its bivariate extension. Resulting estimates of bivariate heritability and the genetic correlation between the reading and the mathematics performance measures suggest that the comorbidity between mathematics and reading difficulties is due in part to genetic influences.     

Stability of individual differences in cardiovascular reactivity

Examining the stability of individual differences in cardiovascular reactivity, 42 male subjects were presented a difficult cognitive task to perform at each of two experimental sessions, scheduled 1 week apart, and recordings of hear rate and systolic and diastolic blood pressure obtained during periods of rest and task performance on each occasion of testing. Measures of task-related arousal (reactivity) across the two experimental sessions revealed substantial and reliable individual differences on all three response variables, as evidenced by (1) subsets of subjects representing clearly differentiated groups of Reactors and NonReactors on each measure and (2) correlation of reactivity scores of all subjects between the first and second sessions. While individual differences in systolic blood pressure and heart rate reactivity correlated positively, magnitude of systolic and diastolic blood pressure responses did not covary reliably among subjects. It was concluded that the present data demonstrate consistency, or reproducibility, of idiosyncratic cardiovascular reactivity and suggested that the variability of relationships among response measures may reflect more basic dimensions of individual differences involving neuroregulatory mechanisms underlying cardiovascular adjustments.     

Neural correlates of individual differences related to appetite

Using neuroimaging technologies to compare normal weight and obese individuals can reveal much about the pathophysiological state of obesity but such comparisons tell us little about what makes some normal weight individuals susceptible to obesity or about important individual differences amongst obese individuals. The current review therefore reviews neuroimaging research on individual difference measures that can illuminate these important topics. After introducing three neuropsychological models of the nature of motivation to approach rewarding stimuli, neuroimaging research on measures of impulsivity, craving, binge eating, restrained eating and disinhibited eating is reviewed. Although neuroimaging research on individual differences measures of brain activity related to appetite is in its infancy, existing studies suggest that such research could enrich the understanding, prevention and treatment of disordered eating and obesity.     

Genetics of educational attainment in Australian twins: Sex differences and secular changes

The relative effects of genetic and environmental factors in producing individual differences in educational achievement are compared across women and men and over birth cohorts. In a large sample of Australian twin pairs, the heritability of self-reported educational attainment did not vary among women and men born before and after 1950. In a “psychometric” model of twin resemblance, based on separate self-reports in 1981 and 1989, genetic factors explained 57% of the stable variance in educational achievement, while environmental factors shared by twins accounted for 24% of the variance. Corrections for phenotypic assortative mating for educational level, however, suggested that estimated common-environmental effects could be entirely explained by the correlation between additive genetic values for mates. Taking this into account, heritability of “true” educational attainment in Australia may be as high as 82% with the remaining variation being due to individual environments or experiences. Unlike previous studies in Scandinavian countries, results in Australia suggest that factors influencing educational success are comparable between women and men and for individuals born at different points during this century.     

Individual differences in task-related activation and performance

Previous studies from this laboratory have explored the relationships between physiological response magnitudes, behavioural performance measures, current arousal level, and activation (defined as task-related change in arousal) during a continuous performance task. We have reported larger physiological responses with increased arousal, and performance improvement with higher levels of activation. Performance results have been consistent at the level of averaged data, whether obtained from between-participant studies using across-trials averaging (yielding one data point per person), or using across-subject within-trials averaging (yielding 1 data point per trial). The present study was designed to explore this relationship at the individual level. A repeated continuous performance task (CPT) was used with normal adults. Reaction time performance at each target in the first block was considered relative to the corresponding target in the second block. Skin conductance level (SCL) was recorded during the task as an index of arousal at each target. Activation at each target in the first block was calculated by subtracting the level of arousal at the corresponding target in the second block. The relationship between first-block performance enhancement and activation in different participants followed different trends. Some participants showed the traditional inverted-U relationship, and some showed the opposite trend. In line with our previous studies, the average linear relationship over all participants was positive. The importance of these findings is discussed in relation to sport performance enhancement.     

Contextualizing individual differences in error monitoring: Links with impulsivity,negative affect,and conscientiousness

The error‐related negativity (ERN) is a neural measure of error processing that has been implicated as a neurobehavioral trait and has transdiagnostic links with psychopathology. Few studies, however, have contextualized this traitlike component with regard to dimensions of personality that, as intermediate constructs, may aid in contextualizing links with psychopathology. Accordingly, the aim of this study was to examine the interrelationships between error monitoring and dimensions of personality within a large adult sample (N = 208). Building on previous research, we found that the ERN relates to a combination of negative affect, impulsivity, and conscientiousness. At low levels of conscientiousness, negative urgency (i.e., impulsivity in the context of negative affect) predicted an increased ERN; at high levels of conscientiousness, the effect of negative urgency was not significant. This relationship was driven specifically by the conscientiousness facets of competence, order, and deliberation. Links between personality measures and error positivity amplitude were weaker and nonsignificant. Post‐error slowing was also related to conscientiousness, as well as a different facet of impulsivity: lack of perseverance. These findings suggest that, in the general population, error processing is modulated by the joint combination of negative affect, impulsivity, and conscientiousness (i.e., the profile across traits), perhaps more so than any one dimension alone. This work may inform future research concerning aberrant error processing in clinical populations.     

Sex differences in frequencies of dermatoglyphic patterns by individual fingers

Background: The size of sex differences in dermatoglyphic features and their inter-population differences remains a subject of debate. Combining fingers in traditional dermatoglyphic methodology and omitting finger-specific variations might be a cause for uncertainty.

Aim: To compare sex differences in whorl frequencies between fingers.

Subjects and methods: Using meta-analytical methods, the authors studied sex differences in frequencies of whorls (log Odd Ratios) for each finger separately, including their heterogeneities (between-samples variance). The dataset of 204 population samples was extracted from published dermatoglyphic studies.

Results: Aggregated effects of sex differences were significant in all fingers, except for the left 1st finger. Sex differences were higher in the right hand and increased from radial to ulnar fingers. Apart from the right 1st and 3rd fingers, heterogeneities were small and literally zero in the right 4th finger.

Conclusion: Higher sex differences in ulnar fingers and the lack of interpopulation differences all over the world in the 4th finger might be caused by a stronger influence of genetic and/or hormonal factors on dermatoglyphic development of the ulnar side of the hand. It is suggested that future studies, when applying dermatoglyphic traits as markers of prenatal environment, use traits by individual fingers or their relationships within the hand.     

Sex differences in cardiovascular reactivity to physical appearance and performance challenges

We examined sex differences in cardiovascular reactivity to a novel body image speech task and to three performance-oriented challenges: serial subtraction, handgrip, and mirror tracing tasks. Forty-nine men and 64 women completed the four tasks while heart rate, systolic blood pressure, diastolic blood pressure, and mean arterial pressure were measured. The speech was perceived as requiring more emotionality and empathy for success, whereas the performance tasks were perceived as requiring greater competitiveness. As predicted, women showed greater heart rate reactivity to the body image speech, but men showed greater blood pressure reactivity to the subtraction, grip, and mirror tracing tasks. Results underscore the importance of contextual factors in influencing sex differences in stress responses; women may be more physiologically vulnerable to challenges in the domain of physical appearance, whereas men may react to competitive, performance-oriented challenges.     

A comment on Jensen's note on sex linkage and race differences in spatial ability

Several criticisms of Jensen's hypothesis on sex linkage and race differences in spatial ability are raised. Data on whether blacks have a deficit in spatial ability are inconsistent. Whether there are X-linked influences on spatial ability has been questioned recently. Two studies provide data inconsistent with Jensen's hypothesis.     

Relative left frontal activation to appetitive stimuli: considering the role of individual differences

Experiments examining asymmetrical frontal activity in response to affective pictures have produced inconsistent results. These inconsistencies may have occurred because the pictorial stimuli may not have evoked strong emotional or motivational tendencies for all individuals. In the current study, participants were asked to indicate their liking for dessert and the time since they had last eaten to assess individual differences in emotion and motivation. Then, they were shown dessert pictures or neutral pictures while EEG activity was recorded. Results indicated that the individual differences predicted greater left than right frontal activity (inverse of the alpha power) within the first second as well as all 12 s of viewing of the dessert pictures.     

Assessment of sex differences in children's and adolescents' self-reported pain from venipuncture.

Examined venipuncture pain and anxiety among 90 male and 90 female children and adolescents (5 to 17 years) who were attending a hospital laboratory. The purpose of the study was to assess sex differences in pain. Ss reported state anxiety and expected pain prior to having venipuncture and sensory and affective pain following venipuncture. Analysis of data determined that male and female were alike regarding age, state anxiety, expected pain, and perceived sensory and affective venipuncture pain. From analysis of pain estimation errors, it was found that males were significantly more likely to underestimate pain and females were significantly more likely to overestimate pain. These findings were discussed in terms of implications for coping research and for clinical practice.     

腹主动脉瘤性别差异性的生物力学研究进展

腹主动脉瘤具有性别差异性,男性发病率较高,而女性的破裂发生率与术后死亡率均较高,这一性别差异性现象会影响到腹主动脉瘤患者的诊断、治疗及术后康复。本文综述了腹主动脉瘤性别差异性的研究现状,从阈值判定及生物力学、力学生物学等方面探究了腹主动脉瘤性别差异性这一现象,并指出男女腹主动脉尺寸差异、解剖结构及血管结构成分不同而导致的生物力学以及力生物学的差异,可能是导致两性腹主动脉瘤呈现出差异性的重要原因。针对腹主动脉瘤性别差异性的生物力学研究,将会为腹主动脉瘤诊断、治疗及器械设计、患者护理和康复提出基于性别差异的改进建议。     

Sleepiness phenomics: Modeling individual differences in subjective sleepiness profiles

The present study investigates individual differences in subjective sleepiness profiles during 36 h of sustained wakefulness in a modified constant routine protocol. Twenty-three volunteers (11 females), aged between 18 and 47 yrs (M age = 30.41, SD = 10.26) enrolled in the study. Subjective sleepiness ratings were collected every 2 h by means of visual analogue scales. Circadian rhythmicity was assessed by means of salivary cortisol. Subjective sleepiness data were analyzed using functional principal component analysis (fPCA). Our results show that approximately 80% of the variance is accounted for by three functional components. The first component explains 50.28% of the variance and is characterized by a profile of exclusively positive loadings, representing vertical shifts from the mean sleepiness profile. Scores on this component are positively related to self-reported habitual sleep times and mean slow wave activity (SWA) during wake. Positive scores on the second component (18.40% of the variance) are characterized by a higher than average peak-to-trough amplitude in subjective sleepiness profiles. Participants with higher than average scores on this component show a significantly higher amplitude in salivary cortisol profiles as opposed to participants with lower than average scores. Participants with positive scores on the third component (10.09% of the variance) show higher than average levels of subjective sleepiness during morning hours, a buildup of wake effort occurring later and more afternoon sleepiness after sleep deprivation than negative scorers. Peak levels of salivary cortisol occur significantly later in these participants. Taken together, our results suggest that component 1 represents tonic differences in sleepiness profiles primarily related to mechanisms of sleep homeostasis, component 2 to circadian amplitude differences and component 3 to diurnal preference. However, since the components are additions to a mean profile, each of the three components is likely to correspond to a mixture of multiple physiological parameters, rather than to a single process. The approach shows interesting potential for (1) revealing unidentified physiological processes, (2) testing existing assumptions about regulatory mechanisms at the basis of interindividual variability in sleepiness profiles and (3) the specification of sleepiness phenotypes on a quantitative basis.     

Rat sex and strain differences in responses to stress

Sensitivity to stress has been linked to the development of a variety of physical and psychological disorders. Studies to-date have focused on extreme stress phenotypes, have studied mostly male responses, have used limited dependent variables, and have included a limited number of measurement time points. The present experiment was designed to address these limitations. Feeding, body weight, open-field activity, acoustic startle reflex (ASR), and prepulse inhibition (PPI) responses of adult male and female Sprague-Dawley and Long-Evans rats to daily immobilization stress (20 min/day) were evaluated for 3 weeks. Stress significantly decreased feeding and body weight of males but generally not of females. Effects were greatest in Long-Evans males. Stress decreased 15-min activity levels for males on Stress Day 1, but not on other days. Stress did not affect 15-min activity levels of Long-Evans females but decreased 15-min activity levels of Sprague-Dawley females on every measurement day. ASR responses to stress differed based on rat strain; percent PPI responses differed based on rat strain and sex. Stress increased startle responses of Sprague-Dawley males and females but not of Long-Evans males and females. Stress reduced PPI of Long-Evans females on every measurement day but not of other groups. These findings indicate that strain and sex of rat is important to consider in evaluating behavioral and physiological responses to stress.     

Sensation seeking in opposite-sex twins: An effect of prenatal hormones?

Intrauterine hormones and position with respect to male and female littermates influence sexually dimorphic adult behavior in litter-bearing animals. Opposite-sex dizygotic twins offer the opportunity to examine analogous effects on sex-related human behaviors. To illustrate this approach, Sensation Seeking Scale (SSS) scores from 422 British twin pairs, including 51 opposite-sex pairs (Zuckerman, M.,et al., J. Consult. Clin. Psychol. 46:139–149, 1978), were reanalyzed. Zuckermanet al. (1978) have shown that some aspects of sensation seeking are consistently increased in males relative to females. In comparing age-adjusted data for opposite and same-sex twins, our reanalysis demonstrated the predicted increase in sensation seeking in female members of opposite-sex pairs. Results were significant for measures of disinhibition, experience seeking, and overall sensation seeking. In contrast, male opposite-sex twins were not significantly different from male same-sex twins. Although psychosocial explanations of the increased sensation seeking in opposite-sex female twins cannot be excluded, these findings are consistent with hypothesizedin utero hormonal influences on later behavioral development.     

A new model of individual differences in hemodynamic profile and blood pressure reactivity

A quantitative, theory-driven model of hemodynamics was developed, relating reactivity in blood pressure to orthogonal dimensions of "hemodynamic profile" and "compensation deficit," which were derived from the (multiplicative) interaction of cardiac output and total peripheral resistance. A Finapres 2300e was used to estimate blood pressure, cardiac output, and total peripheral resistance in 100 healthy men and women during mental arithmetic and cold pressor tasks on two occasions. Results were consistent with model predictions. As predicted, cardiac output and peripheral resistance reactions were curvilinearly related, and blood pressure reactivity was strongly related to compensation deficit (r = .76-.89). Conversely, the orthogonally defined hemodynamic profile remained independent of blood pressure reactivity (r = .11 or less). The data show that the present model overcomes several difficulties and inconsistencies in previous attempts to obtain an independent measure of hemodynamic profile. The new model could help to elucidate sources of cardiovascular pathogenesis not suggested from the study of blood pressure reactivity alone.