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PubMed2001

Sex differences in sensitivity to seizures elicited by pentylenetetrazol in mice.

Sex differences in sensitivity to seizures elicited by intraperitoneally injected pentylenetetrazol (PTZ) were studied in 240 (120 males and 120 females) adult Swiss mice. Animals were separated into four groups according to the dose that was injected: 40, 50, 60 and 70 mg/kg. Seizure severity was expressed by the following scoring scale: (0) no abnormal behavior; (1) myoclonus; (2) running bouncing (RB) clonus; (3) tonic hind limb extension (THE). The analyses of the dose-response curves indicated that females were more susceptible than males when the 50- and 60-mg/kg doses were used. Specifically, females often displayed RB clonus, while males frequently displayed only myoclonus or no abnormal behavior. No significant sex differences were demonstrated when either the 40- or the 70-mg/kg doses were used. These data indicate that, for a specific range of doses, sex differences in seizure susceptibility can be clearly demonstrated with the use of intraperitoneally injected PTZ. In this sense, this method could be used as a tool to investigate the role played by sexual hormones in regulating the sensitivity of the gamma-aminobutiric acid (GABA(A)) receptor complex (GRC).

Animals↗
PubMed1985

Urine and kidney epidermal growth factor: ontogeny and sex difference in the mouse.

We have explored the physiology of urinary epidermal growth factor (EGF) in the mouse by studying its ontogeny, and the effects of testosterone therapy on immunoreactive EGF (IR-EGF) concentrations in urine, kidney, serum and submandibular gland (SMG). Urine IR-EGF (U-EGF) increased about 100-fold relative to urea concentration and about 1000-fold relative to urine volume from the 1st day of life to adulthood. Most of this increase occurred between days 6 and 18, which is the known period of steep rise in plasma thyroid hormone concentration in the mouse. A small F greater than M sex difference was present in the adult. This difference was opposite in direction to the large M greater than F sex difference in adult SMG-EGF concentration. On day 26 (age of appearance of morphological sex difference in SMG) the sex difference was not yet present in urine, although in SMG it was even larger than in the adult. Kidney EGF concentration was low relative to U-EGF: 1 ml of adult urine contained approximately as much IR-EGF as 100 pairs of adult kidneys. In the adult, but not on day 26, there was a sex difference in kidney EGF concentration parallel to the sex difference in urine: female levels were about 30% higher than male levels. Ten days of testosterone treatment of adult female mice evoked an increase in IR-EGF concentration which was 1.7-fold for serum and 5-fold for SMG. In contrast, this treatment did not increase kidney or urine IR-EGF concentrations although kidney weight increased 1.3-fold.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2007

Sex differences in judging self-orientation: the morphological horizon and body pitch.

BACKGROUND: Sex differences exist for many spatial tasks. This is true for circular vection, field dependence, and perception of veridical vertical with body tilt. However, explanations for these sex differences is lacking in the literature. In this study, we investigated the nature of individual differences in the perception of self-orientation in humans. Male and female participants were asked to identify their Morphological Horizon (i.e., line perpendicular to saggital plane at eye-level) in different body orientations relative to gravity (i.e., 45 deg and 135 deg body pitch) with and without prior whole body rotation. RESULTS: Sex explained the observed differences in the perception of self-orientation only when blood distribution was least altered (i.e., 45 deg body pitch) and without prior whole body rotation. Specifically, females presented a more footward bias than males in these conditions. CONCLUSION: These results add to the literature on sex differences for spatial orientation tasks. As the differences were only observed with static conditions and when blood distribution was least affected, we concluded that sex differences in the perception of self-orientation are associated with gravireceptors (e.g., otoliths).

Adult↗
PubMed1995

Is there a sex difference in human laterality? II. An exhaustive survey of visual laterality studies from six neuropsychology journals.

The contents of six neuropsychology journals (98 volumes, 368 issues) were screened to identify visual half-field (VHF) experiments. Of the 516 experiments identified, 42% provided information about sex differences. Sixty-eight experiments yielded a total of 92 sex differences, 23 of which met stringent criteria for sex differences in laterality. Of the 20 sex differences satisfying stringent criteria and lending themselves to interpretation in terms of the differential lateralization hypothesis, 17 supported the hypothesis of greater hemispheric specialization in males than in females. The 17 confirmatory outcomes represent 7.8% of the informative experiments. When less stringent criteria were invoked, 27 outcomes (12.3% of the informative experiments) were found to be consistent with the differential lateralization hypothesis. Six findings were contrary to the hypothesis. The results, which closely resemble results for auditory laterality studies, are compatible with a population-level sex difference that accounts for 1 to 2% of the variance in laterality.

Adult↗
PubMed2001

Stereotypes and steroids: using a psychobiosocial model to understand cognitive sex differences.

To further our understanding of cognitive sex differences, we studied the relationship between menstrual phase (via serum estradiol and progesterone levels) and cognitive abilities and cognitive performance in a sample of medical students in eastern Turkey. As expected, we found no sex differences on the Cattell "Culture Fair Intelligence Test" (a figural reasoning test), with females scoring significantly higher on a Turkish version of the Finding A's Test (rapid word knowledge) and males scoring significantly higher on a paper-and-pencil mental rotation test. The women showed a slight enhancement on the Finding A's Test and a slight decrement in Cattell scores during the preovulatory phase of their cycle that (probably) coincided with a rise in estrogen. There were also small cycle-related enhancements in performance for these women on the mental rotation test that may reflect cyclical increases in estrogen and progesterone. Additional analyses showed an inverted U-shaped function in level of estradiol and the Cattell Test. Finally, for women who were tested on Day 10 of their menstrual cycle, there was a negative linear relationship between their Cattell scores and level of progesterone. Stereotypes about the cognitive abilities of males and females did not correspond to performance on the mental rotation or Finding A's Test, so the sex-typical results could not be attributed to either stereotype threat or stereotype activation. For practical purposes, hormone-related effects were generally small. Variations over the menstrual cycle do not provide evidence for a "smarter" sex, but they do further our understanding of steroidal action on human cognitive performance.

Adolescent↗
PubMed1987

Sex differences in sexuality among medical students: effects of increasing socioeconomic status.

Research has consistently shown that, compared to men, women are more cautious and selective and maintain greater marital aspirations in entering and maintaining sexual relationships. One explanation of this sex difference is that women have traditionally had inferior access to earning power and social status and consequently were forced to acquire socioeconomic status (SES) through their choice of marriage partners. A contrasting view is that this difference is a component of the basic sex difference identified in the Kinsey studies: Men are more likely than women to dissociate coitus from emotional attachment and to desire and seek coitus with a variety of partners. These two explanations were explored in open-ended interviews with matched samples of 20 male and 20 female medical students. The results were more consistent with the perspective of basic sex differences than with the differential resources explanation. Increasing female SES does not appear to eliminate or even substantially reduce this sex difference. Increasing SES tends to enlarge the pool of acceptable, available sexual and marital partners for men while it tends to reduce the pool for women. Increasing SES thus tends to have different effects on men and women and may cause sex differences in the tendency to associate coitus with emotional attachments and marital aspirations to be more, rather than less, apparent. Extensive case data with verbatim quotations are presented to reveal the emotions and desires underlying subjects' overt behavior.

Adult↗
PubMed2005

Adolescent sex differences in adiponectin are conditional on pubertal development and adiposity.

OBJECTIVE: Adiponectin is an adipose tissue protein with important insulin-sensitizing, anti-inflammatory, and cardioprotective properties but is paradoxically lower in obese individuals. Sex differences in adiponectin have been reported in adults and adolescents but not in prepubertal children. In this study, we hypothesized that sex differences in adiponectin would develop during puberty and would be influenced by level of adiposity. RESEARCH METHODS AND PROCEDURES: Adiponectin levels were measured in 1196 white and African-American adolescents. Insulin resistance was estimated using the homeostasis model (HOMA-IR). Demographic, developmental, and metabolic variables, including interactions with adiposity measurements, were evaluated for independent relationships with adiponectin levels. RESULTS: Overall, adiponectin levels varied significantly by sex, race, adiposity, and puberty stage. Significant sex differences in adiponectin developed after the onset of puberty, particularly in lean adolescents. Adolescent boys had lower adiponectin levels in post-puberty compared with pre-puberty (p = 0.01) and had lower levels than girls in both puberty and post-puberty (both p < 0.001), after adjusting for race, BMI z-score, and natural logarithm-(HOMA-IR). Sex differences were also conditional on adiposity level, with significant sex differences among lean (p < 0.001) but not among non-lean (p = 0.16) adolescents. Adiponectin levels in girls decreased more with increasing adiposity than in boys (p = 0.004), but only marginally so after standardizing for girls' higher mean adiponectin level (p = 0.11). DISCUSSION: Sex differences in adiponectin are dependent on both puberty stage and adiposity in adolescents, such that by post-puberty, non-lean boys exhibit the lowest levels of adiponectin.

Adiponectin↗
PubMed2006

Sex differences in the level of Bcl-2 family proteins and caspase-3 activation in the sexually dimorphic nuclei of the preoptic area in postnatal rats.

In developing rats, sex differences in the number of apoptotic cells are found in the central division of the medial preoptic nucleus (MPNc), which is a significant component of the sexually dimorphic nucleus of the preoptic area, and in the anteroventral periventricular nucleus (AVPV). Specifically, male rats have more apoptotic cells in the developing AVPV, whereas females have more apoptotic cells in the developing MPNc. To determine the mechanisms for the sex differences in apoptosis in these nuclei, we compared the expression of the Bcl-2 family members and active caspase-3 in postnatal female and male rats. Western blot analyses for the Bcl-2 family proteins were performed using preoptic tissues isolated from the brain on postnatal day (PD) 1 (day of birth) or on PD8. In the AVPV-containing tissues of PD1 rats, there were significant sex differences in the level of Bcl-2 (female > male) and Bax (female < male) proteins, but not of Bcl-xL or Bad proteins. In the MPNc-containing tissues of PD8 rats, there were significant sex differences in the protein levels for Bcl-2 (female < male), Bax (female > male), and Bad (female < male), but not for Bcl-xL. Immunohistochemical analyses showed significant sex differences in the number of active caspase-3-immunoreactive cells in the AVPV on PD1 (female < male) and in the MPNc on PD8 (female > male). We further found that active caspase-3-immunoreactive cells of the AVPV and MPNc were immunoreactive for NeuN, a neuronal marker. These results suggest that there are sex differences in the induction of apoptosis via the mitochondrial pathway during development of the AVPV and MPNc.

Animals↗
PubMed1991

Sex differences in the corpus callosum of the living human being.

The sexual dimorphism of the corpus callosum has remained controversial since the original report by de Lacoste-Utamsing and Holloway in 1982, for several reasons: (1) measurements have been performed in a variety of ways in different laboratories, in part because published reports frequently do not describe the methodology in detail; (2) despite known age-related changes during both childhood and adulthood, no investigators have explicitly age-matched subjects; and (3) the size and shape of corpora callosa vary considerably among individuals, requiring large sample sizes to demonstrate significant sex differences. Therefore, we have examined magnetic resonance images for 24 age-matched children and 122 age-matched adults for possible sex differences in the corpus callosum. While we observed a dramatic sex difference in the shape of the corpus callosum, there was no conclusive evidence of sexual dimorphism in the area of the corpus callosum or its subdivisions. Utilizing several criteria, there were significant sex differences in shape: subjective evaluation indicated that the posterior region of the corpus callosum, the splenium, was more bulbous shaped in females as a group and in women, and more tubular-shaped in males as a group and in men; mathematical evaluation confirmed this observation in that the maximum width of the splenium was significantly greater in women than in men, and that the percentage by which the average width of the splenium was greater than that of the adjacent corpus callosum was significantly greater in females than in males. However, sex differences in bulbosity did not reach significance in children (aged 2-16 yr). In contrast, among the area measurements of the corpus callosum and 22 subdivisions, only 1 exhibited a significant sex difference, which would be expected by chance. The area of the corpora callosa increased significantly with age in children and decreased significantly with age in adults. In adults, the midsagittal surface area of the cerebral cortex decreased significantly with age in women but not in men. These anatomical sex differences could, in part, underlie gender-related differences in behavior and neuropsychological function.

Adolescent↗
PubMed2001

Sex matters: secular and geographical trends in sex differences in coronary heart disease mortality.

OBJECTIVE: To examine secular trends and geographical variations in sex differences in mortality from coronary heart disease and investigate how these relate to distributions in risk factors. DESIGN: National and international data were used to examine secular trends and geographical variations in sex differences in mortality from coronary heart disease and risk factors. SETTING: England and Wales, 1921-98; Australia, France, Japan, Sweden, and the United States, 1947-97; 50 countries, 1992-6. DATA SOURCES: Office for National Statistics, World Health Organization, and Food and Agriculture Organization of the United Nations. RESULTS: The 20th century epidemic of coronary heart disease affected only men in most industrialised countries and had a very rapid onset in England and Wales, which has been examined in detail. If this male only epidemic had not occurred there would have been 1.2 million fewer deaths from coronary heart disease in men in England and Wales over the past 50 years. Secular trends in mean per capita fat consumption show a similar pattern to secular trends in coronary heart disease mortality in men. Fat consumption is positively correlated with coronary heart disease mortality in men (r(s)=0.79; 95% confidence interval 0.70 to 0.86) and inversely associated with coronary heart disease mortality in women (-0.30; -0.49 to -0.08) over this time. Although sex ratios for mortality from coronary heart disease show a clear period effect, those for lung cancer show a cohort effect. Sex ratios for stroke mortality were constant and close to unity for the entire period. Geographical variations in the sex ratio for coronary heart disease were associated with mean per capita fat consumption (0.64; 0.44 to 0.78) but were not associated with the sex ratio for smoking. CONCLUSION: Sex differences are largely the result of environmental factors and hence not inevitable. Understanding the factors that determine sex differences has important implications for public health, particularly for countries and parts of countries where the death rates for coronary heart disease are currently increasing.

Adult↗
PubMed1990

Sex differences in the effects of inescapable footshock on central catecholaminergic and serotonergic activity.

In two experiments sex differences in changes in central noradrenergic, dopaminergic and serotonergic activity were measured immediately after a 30-min session of inescapable footshocks. In Experiment 1 concentrations of noradrenaline, dopamine, serotonin and their major metabolites were determined in the frontal cortex, hypothalamus, amygdala, striatum, mesencephalon and the medulla-pons area. Inescapable shock increased the activity of all 3 transmitter systems, as evidence by increased metabolite concentrations in specific brain areas. Shock-induced increments in metabolite levels were larger in females than in males, especially for the serotonergic system. In addition, shock presentation resulted in a decrement in the noradrenaline content in most areas studied. In the frontal cortex, noradrenaline was reduced by inescapable shock in males but not in females. In Experiment 2, sex-dependent neurochemical consequences of predictable versus unpredictable shocks were studied in the frontal cortex and the medulla-pons area. Similar to Experiment 1, both brain parts showed large shock-induced increments in the activity of the catecholaminergic systems. Differential effects of predictable and unpredictable shock were not found (frontal cortex) or were rather small (medulla-pons) and appeared sex-dependent for serotonin in this area. The sex differences in neurochemical change found in the first experiment were largely replicated in the second experiment. The relevance of the observed sex differences in central neurotransmitter reactivity for sex differences in behavior is discussed.

3,4-Dihydroxyphenylacetic Acid↗
PubMedDate not supplied

Sex difference in daily water consumption of rats: effect of housing and hormones.

Females rats consume more water than males per day when consumption is indexed to body weight. We examined the developmental expression of this sex difference as well as the organizational and activational influences of testosterone (T). The amount of water consumed from weaning to adulthood exhibited a linear decrease with age in both sexes. The development of a sex difference in water consumption was evident immediately after weaning in singly housed animals, but did not emerge until about Day 42-45 in group-housed animals, when females began to consume greater amounts of water than males. Castration at weaning had minimal effects on the sex difference. Treating dams with testosterone propionate (TP; 0.3 mg/kg; E15-E20) resulted in a significant increase in adult water consumption in offspring of both sexes, but the sex difference remained. Overall, these data indicate that gonadal steroids are not the primary organizational influence on this sex difference. The greater water consumption in females is consistent with other studies demonstrating sex differences in plasma vasopressin levels, as well as differences in vasopressin sensitivity.

Animals↗
PubMed1985

Sex differences in minor psychiatric morbidity.

This monograph is concerned with some epidemiological observations of minor psychiatric morbidity. Differences in rates of specific disorders have historically formed a crucial part of epidemiological enquiry. Sex differences in the prevalence of minor affective disorders have been demonstrated in studies of populations in treatment and in community populations, and have been variously ascribed to constitutional or environmental factors. A review of the literature exposes the methodological problems of measurement and study design, and the conflicting nature of the findings. Efforts have recently concentrated on establishing the social factors important in the aetiology of minor affective disorder without adequate exclusion of constitutional factors. The importance of life events, chronic social stress and inadequate social supports in the aetiology of minor affective disorder has been demonstrated, but the variance explained by such factors is small, reinforcing the view that constitutional factors of some kind are likely to be of importance. The evidence for a genetic contribution to minor affective disorder is tenuous, but there is circumstantial evidence that changes in gonadal hormones are linked to mood changes in women. Until further evidence is available this must remain a powerful possibility in the genesis of sex differences in minor affective disorder. This investigation used epidemiological methods to assess whether there is a sex difference in the constitutional vulnerability of the male and female phenotype to minor psychiatric morbidity. In order to minimize the effects of environment and of sex roles and stereotypes as far as possible, a sample of relatively homogeneous employed men and women (drawn from a population of executive officers in the Home Office) was studied. The data obtained from this population of men and women of similar age, education, occupation and social environment were compatible with the null hypothesis that there is no sex difference in the prevalence of minor psychiatric morbidity, or its outcome in such a homogeneous group. However, women did report significantly more somatic symptoms than men. The second hypothesis, that there is a substantial sex difference in the self-perception of illness, illness behaviour and sickness absence in individuals with minor psychiatric morbidity among a homogeneous group of men and women of similar age, education and occupation, and subject to similar levels of social stress and support, received only partial support from the findings of the study.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1982

The sex difference on one test of spatial visualization: a nontrivial difference.

Plomin and Foch's conclusion that sex differences in cognition account for very little of the total variability is challenged by demonstrating that, on a complex test of spatial visualization, the difference between males and females accounts for a quite substantial portion of the variability of the test scores. 2 measures of spatial visualization--the ETS Card Rotations test and the Shepard/Metzler Mental Rotations test--were administered to a large sample of college students. The Card Rotations test requires identification of fairly simple abstract forms after rotation within the plane; the Mental Rotations test requires identification of representations of more complex 3-dimensional figures after rotation in 3-dimensional space. Males scored significantly higher than females on both tests. Sex accounted for only 2% of the variance on the Card Rotations test but for 16% of the variance on the Mental Rotations test. Comparable sex differences on the Shepard/Metzler Mental Rotations test have also been found by other investigators.

Adolescent↗
PubMed1999

Early sex differences in spatial skill.

This study investigated sex differences in young children's spatial skill. The authors developed a spatial transformation task, which showed a substantial male advantage by age 4 years 6 months. The size of this advantage was no more robust for rotation items than for translation items. This finding contrasts with studies of older children and adults, which report that sex differences are largest on mental rotation tasks. Comparable performance of boys and girls on a vocabulary task indicated that the male advantage on the spatial task was not attributable to an overall intellectual advantage of boys in the sample.

Adult↗
PubMed1994

Sex differences of infant and child mortality in China.

The purpose of this paper was to study the sex differences in infant mortality and mortality before the age of 5 in China, and the differences between urban and rural areas on the one hand and urban areas of mainland China and Hong Kong on the other. Published data from the 1982 and 1990 national censuses, the mortality survey of 1976, and UN's publications were used to calculate sex differences and sex ratios of mortality. Infant mortality of both sexes decreased notably from the 1970's onwards, the sex ratios of mortality being 1.15 in 1973-75, 1.06 in 1981 and 0.86 in 1990. A remarkable decline of mortality before the age of 5 was also seen in both sexes, but the sex ratios of mortality were not greatly altered, remaining less than 1 from the 1970's on. In rural areas female infants and young children had a higher mortality compared with males than in urban areas. In Hong Kong, the sex differences of infant and early child mortality were much smaller than in urban areas of mainland China.

Child, Preschool↗
PubMed2005

[Sex differences in brain stem auditory evoked potentials and P300 examination in patients with mild cognitive impairment and Alzheimer's disease].

OBJECTIVE: To compare the sex differences on brain stem auditory evoked potentials (BAEP) and P300 in the elderly patients with mild cognitive impairment (MCI) and the patients with Alzheimer's disease (AD). METHODS: Thirty-eight elderly patients with MCI, 26 cases of AD and 20 health controls (HC) were examined with BAEP, P300 . Sex difference of the variables was compared inter-and intra-groups. RESULTS: Significant sex differences of BAEP were found in the latency period wave III, V of left side in the MCI group (P <0.01), in the latency period wave IV, V of left side in HC group (P<0.01), and no such differences were found in AD group. The females had longer latency period in P300 measurement than males in MCI group (P <0.01), but there were no significant differences within AD or HC groups. The males showed significant differences in wave I, II in left side between the MCI and AD groups. The males also showed significant difference in wave I, III approximate, equals V in left side, wave IV in right side between AD and HC groups, and so did the females in wave I approximate, equals V in both sides. The males had significant difference in the left wave III, IV and right wave I, IV, V between MCI and HC groups, and so did the females in right side wave I, II, V. In P300, longer latency waves were found in AD group than in MCI group. Both sexes showed significant differences in the latency of Fz, Cz, Pz between AD and HC groups, but no significant differences were found in the latency of Fz, Cz, Pz in the females between the MCI and HC groups. CONCLUSION: Sex differences were found in the examination of both BAEP and P300 in MCI group, but not in AD group. The people of same sex have different expression of BAEP and P300 among MCI, AD and HC groups, suggesting the sex difference should be considered in the differential diagnosis.

Aged↗
PubMed1994

Sex differences in the anticoagulant effects of warfarin.

Sex differences in the anticoagulant effects of warfarin were studied in rats. Warfarin was administered to rats from 7 days of gestation until 14 weeks of age. In male rats, the normal prothrombin level in the plasma was reduced, and the blood coagulation time was prolonged by treatment with warfarin at 4, 9 and 14 weeks of age. However, in female rats, the effects of warfarin on the prothrombin level and blood coagulation time were observed at 4 weeks to the same degree as in male rats, but these effects were reduced with aging, and at 14 weeks, no effect of warfarin was observed. Rats ovariectomized at 12 weeks of age and subsequently treated with warfarin for 2 weeks showed prolongation of blood coagulation time to the same level as in warfarin-treated male rats, which was inhibited by administration of 17 beta-estradiol (100 micrograms/kg/day for 4 days, i.m.). In male rats, treatment with 17 beta-estradiol also inhibited the anticoagulant effects of warfarin without changing the warfarin level in plasma. These results suggest that there is a sex difference in the anticoagulant effects of warfarin, and that this difference may be related to the estradiol level in plasma.

Animals↗