Sex-dependent Patterns Research Articles

Supported liquid extraction coupled to gas chromatography-selective mass spectrometric scan modes for serum steroid profiling

Although, steroid profiling is being applied in clinical and biochemical studies, improvement of the technique is still needed for accurate quantification of steroids in case of limited biological sample volumes. To improve analytical sensitivity and selectivity in comparison to that of conventional methods, a method that comprises supported liquid extraction (SLE) and gas chromatography-mass spectrometry with a combination of selected-reaction and selected-ion monitoring modes (GC-SRM/SIM-MS) was developed. Here, this combination of SLE purification with GC-MS method was optimized with 37 different types of steroids and the results were compared to a solid-phase extraction (SPE) method. The devised assay led to an increase in extraction efficiency with the good chromatographic selectivity through a single extraction step. The limits of quantification of the serum steroids, ranged from 0.2 to 5 ng mL−1, except for cholesterol (0.2 μg mL−1), and the correlation coefficients for calibration curves were higher than 0.99. The precision and accuracy were 1.4%–10.5% and 82.7%–115.3%, respectively. The overall recoveries of 30 steroids ranged from 62.1% to 104.3%, while that of 7 sterols was 44.7%–75.7%. Then, this validated method was applied to monitor the serum steroid levels of mice, which showed significant sex and age dependent metabolic patterns. This technique can be used to evaluate the metabolic changes occurring in animal models as well as in clinical patients.

Sex- and age-dependent patterns of survival and breeding success in a long-lived endangered avian scavenger

In long-lived species, the age-, stage- and/or sex-dependent patterns of survival and reproduction determine the evolution of life history strategies, the shape of the reproductive value, and ultimately population dynamics. We evaluate the combined effects of age and sex in recruitment, breeder survival and breeding success of the globally endangered Egyptian vulture (Neophron percnopterus), using 31-years of exhaustive data on marked individuals in Spain. Mean age of first reproduction was 7-yrs for both sexes, but females showed an earlier median and a larger variance than males. We found an age-related improvement in breeding success at the population level responding to the selective appearance and disappearance of phenotypes of different quality but unrelated to within-individual aging effects. Old males (≥8 yrs) showed a higher survival than both young males (≤7 yrs) and females, these later in turn not showing aging effects. Evolutionary trade-offs between age of recruitment and fitness (probably related to costs of territory acquisition and defense) as well as human-related mortality may explain these findings. Sex- and age-related differences in foraging strategies and susceptibility to toxics could be behind the relatively low survival of females and young males, adding a new concern for the conservation of this endangered species.

Sex and age dependent migration phenology of the Pied Flycatcher in a stopover site in the Carpathian Basin

Abstract Very little is known about Pied Flycatchers crossing the Carpathian Basin. We give a comprehensive picture about its migration based on the data collected during the past 26 years (1989–2014) at a stopover site in Hungary: (1) sex and age related phenological changes over the years, (2) sex, age and size dependent migration patterns during and (3) between migration periods, (4) sex and age composition in spring and in autumn and their change over years. The timing of spring migration shifted to earlier dates in the case of males, while that of females did not change implying an increasing rate of protandry. In autumn the timing did not change, but juveniles leave the area earlier than adults. The average wing length increased during the past decades in spring in the case of both sexes. In autumn, wing length did not change significantly during the years, but it increased during the seasons in all age and gender groups. The proportion of males is about 60% in spring and among juveniles in autumn, and it is around 39% in the adult group in autumn. The male ratio diminishes during spring, but it does not change during the autumn season. The average wing of adults is shorter in spring than in autumn. Based on this fact and the different sex ratios in the two seasons we may hypothesize that Pied Flycatchers are loop migrants on this area, and even the sexes of the same population take different routes.

Sex differences in flea infections among rodent hosts: is there a male bias?

Recognizing patterns of parasite distribution among wildlife hosts is of major importance due to growing risk of transmission of zoonotic diseases to humans. Thus, sex-dependent parasite distribution in higher vertebrates is extensively studied, and males are often found more parasitized than females. Male-biased parasitism may be the result of weaker immunocompetence of male hosts owing to the immunosuppressive effect of androgens. Moreover, larger hosts (males) may demonstrate higher parasite infestation levels than smaller individuals (females), as they constitute a better nutritional resource for parasites and provide them with a greater variety of niches. In the present work, we investigated sex-dependent patterns of flea distribution among three common rodent species (Apodemus agrarius, Apodemus flavicollis, and Myodes glareolus). We hypothesized that males have a higher flea infestation than females. We confirm male-biased parasitism in A. agrarius and M. glareolus, but not in A. flavicollis. Additionally, flea infestation increased with body mass in A. agrarius, but not in A. flavicollis and M. glareolus. The detected differences in parasite distribution among sexes are probably the result of immunosuppressive effects of androgens and spatial behavior of males.

Nonautosomal genetic variation in carotenoid coloration.

Carotenoid-based coloration plays an important role in signaling, is often sexually dimorphic, and is potentially subject to directional and/or sex-specific selection. To understand the evolutionary dynamics of such color traits, it is essential to quantify patterns of inheritance, yet nonautosomal sources of genetic variation are easily overlooked by classical heritability analyses. Carotenoid metabolism has recently been linked to mitochondria, highlighting the potential for color variation to be explained by cytoplasmically inherited factors. In this study, we used quantitative genetic animal models to estimate the importance of mitochondrial and sex chromosome-linked sources of genetic variation in coloration in two songbird populations in which dietary carotenoids are either unmodified (great tit plumage) or metabolized into alternative color forms (zebra finch beak). We found no significant Z-linked genetic variance in great tit plumage coloration, while zebra finch beak coloration exhibited significant W linkage and cytoplasmic inheritance. Our results support cytoplasmic inheritance of color in the zebra finch, a trait based on endogenously metabolized carotenoids, and demonstrate the potential for nonautosomal sources to account for a considerable share of genetic variation in coloration. Although often overlooked, such nonautosomal genetic variation exhibits sex-dependent patterns of inheritance and potentially influences the evolution of sexual dichromatism.

Population density and phenotypic attributes influence the level of nematode parasitism in roe deer

The impact of parasites on population dynamics is well documented, but less is known on how host population density affects parasite spread. This relationship is difficult to assess because of confounding effects of social structure, population density, and environmental conditions that lead to biased among-population comparisons. Here, we analyzed the infestation by two groups of nematodes (gastro-intestinal (GI) strongyles and Trichuris) in the roe deer (Capreolus capreolus) population of Trois Fontaines (France) between 1997 and 2007. During this period, we experimentally manipulated population density through changes in removals. Using measures collected on 297 individuals, we quantified the impact of density on parasite spread after taking into account possible influences of date, age, sex, body mass, and weather conditions. The prevalence and abundance of eggs of both parasites in females were positively related to roe deer density, except Trichuris in adult females. We also found a negative relationship between parasitism and body mass, and strong age and sex-dependent patterns of parasitism. Prime-age adults were less often parasitized and had lower fecal egg counts than fawns or old individuals, and males were more heavily and more often infected than females. Trichuris parasites were not affected by weather, whereas GI strongyles were less present after dry and hot summers. In the range of observed densities, the observed effect of density likely involves a variation of the exposure rate, as opposed to variation in host susceptibility.

The relationships between EEG θ and β oscillations and the level of creativity

The interrelations between the level of creativity and both the baseline power and event-related desynchronization/synchronization (ED/ES) of θ and β rhythms during a figural creative task (Torrance’s “Incomplete Figures” test) were studied under the conditions of different motivations. A higher motivation was caused by instruction “to create most unique images” as opposed to the instruction “to create images.” The subjects, right-handed students (14 males and 14 females), were divided into two groups with high and low originality scores (OSs). The baseline power and the ED/ES of the θ2 and β rhythms of the subjects were found to depend on the level of creativity and person’s sex only in response to the instruction “to create images.” Male subjects with higher OSs differed from those with lower OSs in a stronger ED of the θ2 rhythm in temporal-parietal-occipital brain regions, whereas these differences were absent in female subjects. Task performance was accompanied by ED of β1 rhythm in men with higher OSs, whereas in women with higher OSs, ES was recorded in the same band. Only in women with high OSs did analysis of β1, 2 reference power show a higher β1 power in the caudal hemispheric regions as compared to the frontal ones. High-OS subjects of different genders also differed in the lateral patterns of activity in the electrode loci Fp1/2 (β1) and Fp1/2, F7/8 (β2). Our results suggest that a high level of creativity in men and women is related to sex-dependent specific patterns of frontal-occipital and lateral activities of θ and β rhythm oscillators in the brain cortex.

Parent-of-origin effects on voluntary exercise levels and body composition in mice

Despite the health-related benefits of exercise, many people do not engage in enough activity to realize the rewards, and little is known regarding the genetic or environmental components that account for this individual variation. We created and phenotyped a large G(4) advanced intercross line originating from reciprocal crosses between mice with genetic propensity for increased voluntary exercise (HR line) and the inbred strain C57BL/6J. G(4) females (compared to males) ran significantly more when provided access to a running wheel and were smaller with a greater percentage of body fat pre- and postwheel access. Change in body composition resulting from a 6-day exposure to wheels varied between the sexes with females generally regulating energy balance more precisely in the presence of exercise. We observed parent-of-origin effects on most voluntary wheel running and body composition traits, which accounted for 3-13% of the total phenotypic variance pooled across sexes. G(4) individuals descended from progenitor (F(0)) crosses of HRfemale symbol and C57BL/6Jmale symbol ran greater distances, spent more time running, ran at higher maximum speeds/day, and had lower percent body fat and higher percent lean mass than mice descended from reciprocal progenitor crosses (C57BL/6Jfemale symbol x HRmale symbol). For some traits, significant interactions between parent of origin and sex were observed. We discuss these results in the context of sex dependent activity and weight loss patterns, the contribution of parent-of-origin effects to predisposition for voluntary exercise, and the genetic (i.e., X-linked or mtDNA variations), epigenetic (i.e., genomic imprinting), and environmental (i.e., in utero environment or maternal care) phenomena potentially modulating these effects.

Current comorbidity among consecutive adolescent psychiatric outpatients with DSM-IV mood disorders

To compare selected characteristics (age, sex, age of onset for depression, impairment, severity of depression, somatic comorbidity, and treatment status) of adolescents with currently comorbid and non-comorbid depression. A sample of 218 consecutive adolescent (13-19 years) psychiatric outpatients with depressive disorders, and 200 age- and sex-matched school-attending controls were interviewed for DSM-IV Axis I and Axis II diagnoses. Current comorbidity, most commonly with anxiety disorders, was equally frequent (>70%) in outpatients and depressed controls. Younger age (OR 0.20; 95% CI 0.08, 0.51) and male gender (OR 0.02; 95% CI 0.09, 0.55) were associated with concurrent disruptive disorders. Current comorbidity with substance use disorders (SUD) was independent of age (OR 1.13; 95% CI 0.51, 2.49) and sex (OR 0.51; 95% CI 0.22, 1.17). Personality disorders associated with older age (OR 2.06; 95% CI 1.10, 3.86). In multivariable logistic regression analysis, impairment (GAF <or=60) was associated with current comorbidity (OR 3.13; 95% CI 1.53, 6.45), while severity of depression and lifetime age of onset for depression were not. Adolescent depression presents with age- and sex-dependent patterns of multiple co-occurring problem areas. While many clinical characteristics of adolescent depression are not affected by comorbidity, comorbidity associates with increased impairment.

Sexual dimorphism of hepatic gene expression: novel biological role of KRAB zinc finger repressors revealed.

Significant physiological differences between the sexes exist, and underlying these differences are sex-dependent genetic regulatory events that are ultimately dictated by the sex chromosome genotype of the organism. For example, it has been known for many decades that the mammalian liver is a sexually dimorphic organ, exhibiting major sex differences in the profile of steroid and drug metabolism (Yates et al. 1958; Colby 1980). The physiological requirements for steroid hydroxylation differ between the sexes, and accordingly, many enzymes involved in steroid metabolism, most notably steroid hydroxylases belonging to the cytochrome P450 superfamily (Nelson 1999, 2003), are expressed in the liver in unique, sex-dependent patterns during postnatal and pubertal development (Waxman 1988; Shapiro et al. 1995). These sex differences are most dramatic in rodents, but may occur in humans as well, where they have an impact on cytochrome P450-catalyzed drug metabolism and pharmacokinetics (Jaffe et al. 2002; Meibohm et al. 2002). Early studies established that growth hormone (GH), acting via its sex-dependent patterns of pituitary hormone secretion, is a major player in establishing and maintaining the sexual dimorphism of hepatic gene transcription that emerges in rodents at puberty (Gustafsson et al. 1983; Norstedt and Palmiter 1984). These patterns are ultimately determined by neonatal exposure to testosterone, which imprints on the hypothalamus the male program of neuroendocrine control of pulsatile pituitary GH secretion that is first seen at puberty and continues through adulthood (Jansson et al. 1985). The underlying molecular mechanisms that govern the sexdependent expression of hepatic cytochromes P450 and other enzymes, and their regulation by plasma GH profiles, are proposed to involve the stimulatory action of the signal transducer and transcriptional activator STAT5b, but are only partially understood (Waxman 2000; Schwartz 2001). Major new insight is provided by the discovery, reported in this issue of Genes & Development, of a pair of KRAB (Kruppel-associated box) zinc finger genes, termed Rsl1 and Rsl2, that can exert strong repression of male-specific hepatic gene expression in both males and females (Krebs et al. 2003). This repression is partially relieved in males at puberty in response to pulsatile GH signaling, greatly accentuating adult sex differences in gene expression.

Growth hormone-releasing hormone receptor (GHRH-R) and growth hormone secretagogue receptor (GHS-R) mRNA levels during postnatal development in male and female rats.

Experimental evidence suggests that differential pituitary sensitivity to hypothalamic signals exerts a role in mediating both age and sex dependent patterns of growth hormone (GH) release and synthesis. One mechanism by which pituitary sensitivity to hypothalamic GH regulators could be modified is by the differential synthesis of their pituitary receptors. In the present report we therefore studied the age and sex dependency of the expression of receptors for two known stimulators of GH release, growth hormone-releasing hormone (GHRH) and the synthetic peptidyl and non-peptidyl GH secretagogues (GHSs). Pituitary GHRH receptor (GHRH-R) and GHS receptor (GHS-R) mRNA levels were measured by reverse transcriptase-polymerase chain reaction (RT-PCR) in male and female rats at postnatal day 1, 10, 30 and 75. We also examined the age- and sex-dependent expression of the GHS-R in whole hypothalamic extracts, since the GHS-R is also expressed in a variety of nuclei within the hypothalamus and has been linked to central regulation of the GH-axis. Pituitary GHRH-R mRNA concentrations were age-dependent; the highest levels were observed in d1 pituitaries and then declined with age, reaching a nadir by d30. These results are in concordance with the age-related decline in pituitary GHRH sensitivity. In contrast, the ontogenic pattern of GHS-R expression was bimodal; GHS-R mRNA concentrations in dl and d30 pituitaries were approximately twice those at d10 and d75. These results mirror the transient increase in GHS sensitivity observed around the onset of puberty, suggesting that gonadal steroids mediate GHS-R expression. GHRH-R mRNA levels were comparable in males and females within each age while GHS-R mRNA levels were gender dependent. At d30, male GHS-R mRNA levels were 30% greater than in their female counterparts. This was reversed at d75, when females had 89% more GHS-R mRNA per pituitary and 65% more per somatotrope than did age-matched males. These sexual differences further support a role for gonadal steroids in the modulation of pituitary GHS-R synthesis. The ontogenic and gender-specific pattern of hypothalamic GHS-R expression differed from that observed for the pituitary. Hypothalamic GHS-R mRNA levels increased with age but exhibited no significant sex difference at each age tested. Taken together, these data demonstrate that changes in the levels of pituitary GHS-R mRNA, but not GHRH-R mRNA, are associated with changes in the gonadal steroid environment, thereby implicating the GHS/GHS-R signalling system as a control point in the establishment and maintenance of sexually dimorphic patterns of GH secretion.

Effects of overweight on lung function.

Spirometric data from 1586 healthy children, who did not smoke, were analysed to examine the effects of overweight as measured by the body mass index (weight/height2) on lung function. Overweight (72 boys, 88 girls) was defined as on or above the 90th percentile weight for height. After having controlled for the confounding variables of height and age, there were positive partial correlations between body mass index and lung function in girls whose weight was normal, in overweight girls, and in boys whose weight was normal, but not in overweight boys. In contrast to adults, body mass index has a positive effect on lung function in girls, whatever their weight. No such correlation between body mass index and lung function was seen in overweight boys. The observations may be accounted for by distinct sex dependent patterns of fat distribution in children.

Effects of overweight on lung function.

Spirometric data from 1586 healthy children, who did not smoke, were analysed to examine the effects of overweight as measured by the body mass index (weight/height2) on lung function. Overweight (72 boys, 88 girls) was defined as on or above the 90th percentile weight for height. After having controlled for the confounding variables of height and age, there were positive partial correlations between body mass index and lung function in girls whose weight was normal, in overweight girls, and in boys whose weight was normal, but not in overweight boys. In contrast to adults, body mass index has a positive effect on lung function in girls, whatever their weight. No such correlation between body mass index and lung function was seen in overweight boys. The observations may be accounted for by distinct sex dependent patterns of fat distribution in children.

Growth hormone and thyrotropin secretory profiles and provocative testing in aged rats

The impact of aging on both basal and induced GH and TSH secretion in male and female rats was investigated. Analysis of the individual GH secretory profiles in young (3–4 month) and old (19–20 month) rats indicated that sex-dependent patterns of GH secretion was preserved in old animals. However, we observed a reduction of individual GH peak amplitudes of 66% in old males and 53% in old females when compared to their respective young animals. Further, the GH response to an intravenous bolus of GH-releasing factor (GRF), morphine and clonidine was dramatically blunted or absent in old male and female animals. In contrast to GH, basal TSH secretion was elevated, while the TSH response to thyrotropin-releasing hormone (TRH) was not significantly affected in old animals of either sex. The present data provide evidence that reduced pituitary sensitivity to GRF may be a possible cause for reduced GH secretion in old animals. Further, the elevation in plasma TSH observed in old animals is not the result of an increased pituitary sensitivity to TRH.

Somatostatin Inhibition of Growth Hormone Secretion by Somatotropes from Male, Female, and Androgen Receptor-Deficient Rats: Evidence for Differing Sensitivities*

To investigate the role of somatostatin (SRIF) in regulating sexually dimorphic GH secretion, we used a reverse hemolytic plaque assay and acutely dispersed somatotropes from age-matched normal male, normal female, and androgen receptor-deficient, testicular feminized (Tfm) rats. Hemolytic plaques were developed after a 90-min incubation in the presence of GH antiserum, 10 nM GH-releasing hormone (GHRH), and the following concentrations of SRIF: 0, 0.001, 0.003, 0.01, 0.03, 0.1, 0.3, 1, 3, 10, 30, and 100 nM. Additional studies were performed with 0 or 100 nM SRIF in the absence of GHRH. The absolute number of somatotropes (x10(6); mean +/- SEM) recovered from the pituitaries of Tfm rats (1.73 +/- 0.18) was significantly greater than that from the males (1.11 +/- 0.13; P = 0.01); the number from female rats (1.30 +/- 0.15) was not different from that of either male or Tfm animals. GHRH-stimulated GH secretion, as estimated by the mean GH plaque area (micron2 x 10(4); mean +/- SEM) in the absence of SRIF, was greater for somatotropes from male rats (3.36 +/- 0.41) than that for either Tfm (2.27 +/- 0.32; P = 0.02) or female (1.78 +/- 0.24; P = 0.001) rats; values for the latter two groups did not differ. However, mean GH plaque areas for each group during maximal SRIF inhibition in either the presence or absence of GHRH were indistinguishable from each other and from mean plaque areas obtained under basal conditions. As demonstrated by a lesser EC50 value (0.04 +/- 0.02 nM; mean +/- SEM), somatotropes from female rats were more sensitive to the inhibitory effect of SRIF than were those from either male (EC50 = 1.82 +/- 0.45; P = 0.0001) or Tfm (EC50 = 0.74 +/- 0.22, P = 0.0001) rats; values for the latter two groups were indistinguishable. These observed differences suggest that gender and/or the gonadal hormone environment may be important determinants of the inhibitory effects of SRIF on GH secretion by the somatotrope. While these gender-associated differences may represent effects of the gonadal hormones directly on the somatotrope, they could reflect modulation of the secretion of hypothalamic SRIF and/or GHRH by the prevailing gonadal hormone environment. Such gender-related differences may contribute to the overall sex-dependent patterns of GH secretion in the intact animal.

Age-and sex-dependent patterns of aggregation in the tropical gastropod Strombus luhuanus

The spatial dispersion of the tropical coral sand-dwelling mesogastropod Strombus luhuanus Linne, 1758 was studied at several sites in two localities (Australian Great Barrier Reef and southern Papua New Guinea), from September 1980 to February 1983. S. luhuanus usually occurred in local aggregations, many of which were relatively dense with discrete boundaries: Four types of aggregation are described: mixed age-class, juvenile, mating, and clusters. The former two are termed colonies, because they persisted over time and exhibited some coordinated movements. Mixed age-class colonies contain individuals of all ages, but within them the different ageclasses are frequently spatially segregated from each other. This was sometimes due to the younger age-classes' preference for shallower areas, but also occurred in areas of constant depth. Juvenile colonies are relatively smaller in area but higher in density, and are dominated by a single size-class. Mating aggregations are concentrations of copulating individuals, in which competition between males for access to females occurs. Clusters are concentrations of inactive individuals (juvenile and adult) piled together in close contact. All types of aggregation were concentrated in only a part of what appeared to be the suitable habitat. Most aggregations' boundaries shifted over time within the habitat. We conclude that intraspecific attraction must be an important factor which maintains the spatial structure of all aggregations, although habitat specificity sets the larger area in which they move. Processes which may underlie this pattern, and some of its implications, are discussed.