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Sex differences in valgus knee angle during a single-leg drop jump.

CONTEXT: Sex differences in lower extremity landing mechanics and muscle activation have been identified as potential causative factors leading to the increased incidence of anterior cruciate ligament injuries in female athletes. Valgus knee alignment places greater strain on the anterior cruciate ligament than a more neutral alignment. Gluteus medius (GM) activation may stabilize the leg and pelvis during landing, limiting valgus knee motion and potentially preventing anterior cruciate ligament injury. OBJECTIVE: To determine if frontal-plane knee angle and GM activation differ between the sexes at initial contact and maximal knee flexion during a single-leg drop landing. DESIGN: Between-groups design. SETTING: Motion analysis laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty-two healthy subjects between the ages of 18 and 30 years. INTERVENTION(S): The independent variables were sex (male or female) and position (initial contact or maximal knee flexion). MAIN OUTCOME MEASURE(S): Frontal-plane knee angle and GM average root mean square (aRMS) amplitude. RESULTS: At initial contact, women landed in knee valgus and men landed in knee varus (P < .025). At maximal knee flexion, both men and women were in a position of knee varus, but the magnitude of varus was less in women than in men (P < .025). The GM aRMS amplitude was greater at maximal knee flexion than at initial contact (P < .025); however, male GM aRMS did not differ from female GM aRMS amplitude at either position (P > .025). CONCLUSIONS: Women tended to land in more knee valgus before and at impact than men. The GM muscle activation did not differ between the sexes and, thus, does not appear to be responsible for the sex differences in knee valgus. The excessive valgus knee angles displayed in women may help to explain the sex disparity in anterior cruciate ligament injury.

Journal Article↗

PubMed2006

Sex differences in the effects of amiloride on formalin test nociception in mice.

Amiloride is a nonspecific blocker of acid-sensing ion channels (ASICs) that have been recently implicated in the mediation of mechanical and chemical/inflammatory nociception. Preliminary data using a transgenic model are suggestive of sex differences in the role of ASICs. We report here that systemic administration of amiloride (10-70 mg/kg ip) produces a robust, dose-dependent blockade of late/tonic phase nociceptive behavior on the mouse formalin test (5%; 20 microl) in female but not male mice, completely abolishing the known sex difference in formalin test response. Adult gonadectomy produced a "switching" of sex differences in amiloride efficacy, with castrated males displaying an amiloride blockade and ovariectomized females rendered less sensitive to amiloride. Gonadectomized mice could be switched back to their intact status using chronic estrogen benzoate or testosterone propionate replacement via osmotic minipump (6 microg/day or 250 microg/day, respectively). It is unclear whether this striking sex difference is due to sex-specific involvement of ASICs in pain processing, but the present data represent one of the first demonstrations of pain-related sex differences with no obvious opioid involvement.

Amiloride↗

PubMed2006

PAG mu opioid receptor activation underlies sex differences in morphine antinociception.

Given the findings that (1) systemic opioid antinociception varies by estrous stage in females and (2) the magnitude of sex differences in opioid antinociception is negatively correlated with opioid agonist efficacy, we hypothesized that sex differences in the function of the descending pain modulatory system are likely influenced by estrous stage in females and by the number of available opioid receptors therein. The present study tested these hypotheses by (1) comparing antinociception produced by morphine microinjection to the ventral periaqueductal gray (vPAG) in females at different stages of the estrous cycle and (2) examining systemic morphine antinociception in males versus females under conditions of reduced vPAG mu opioid receptor availability. When estrous stage of females was not controlled for (Experiment 1), there was no significant sex difference in tail withdrawal antinociception following morphine microinjection (0.3-10microg), although morphine was more potent in males than females in producing immobility. Experiment 2 showed that intra-vPAG morphine produced less antinociception and immobility in estrus than in diestrus females; that is, only estrus females' response to morphine was lower than that of males. Experiment 3 showed that microinjection of the irreversible mu opioid antagonist beta-funaltrexamine (beta-FNA) into the vPAG shifted the systemic morphine dose-effect curve farther to the right in females than in males. That is, a reduction in available vPAG mu opioid receptors had a greater impact on opioid antinociception in females than in males, suggesting that females have fewer vPAG mu opioid receptors than males. Overall, these data suggest that ovarian hormones and PAG mu opioid receptor density contribute to sex differences in antinociception produced by morphine.

Analysis of Variance↗

PubMed1997

Sex differences in immunocompetence differ between two Peromyscus species.

Males generally exhibit reduced immunocompetence and greater susceptibility to disease than females. The explanations for why males may be more susceptible to disease than females fall into two categories: 1) the proximate mechanisms mediating immunity, such as hormonal mechanisms, and 2) variation in reproductive success between the sexes. The present study examined the extent to which these factors contribute to sex differences in cell-mediated immune function in polygynous Peromyscus maniculatus and monogamous Peromyscus californicus. Prevailing hypotheses suggest that, because variation in male and female reproductive success is greater among polygynous than monogamous species, sex differences in immunocompetence should be greater among polygynous than monogamous species as well. In contrast to these predictions, sex differences in cell-mediated immunity and body mass were only observed among monogamous P. californicus, in which females exhibited higher splenocyte proliferation in response to the T cell mitogen, concanavalin A, and weighed less than male conspecifics. Male P. maniculatus had higher serum testosterone concentrations than male P. californicus, but females of the two species did not differ in circulating estradiol concentrations. Sex steroid concentrations were not correlated with either immunocompetence or body mass; however, large P. californicus males exhibited reduced immune responses. Taken together, these results do not support the hypothesis that sex differences in immunocompetence are more pronounced among polygynous compared with monogamous species. Furthermore, these data suggest that circulating testosterone does not mediate sex differences in immuno-competence or body mass in P. californicus.

Animals↗

PubMed1991

Sex differences, social desirability, masculinity, and the tendency to worry.

Relationships between worry and sex differences, social desirability, masculinity, and femininity were explored in this study. Data were obtained from 141 undergraduates who answered a questionnaire containing a worry scale, the Crowne-Marlowe (1964) Social Desirability Scale, the Bem (1974) Sex Role Inventory, the Trait Anxiety scale of the State-Trait Anxiety Inventory (Spielberger, Gorsuch, & Lushene, 1970), and several demographic items. Women reported significantly higher levels of worry than men did, and worry was significantly correlated with lower social desirability and with lower masculinity but not with femininity. However, multiple regression strategies revealed that sex differences in reported worry cannot be accounted for solely by variations in social desirability and masculinity. Also, sex differences in the tendency to worry were not eliminated by statistically controlling for trait anxiety, social desirability, and masculinity simultaneously.

Adult↗

PubMed1997

Sex differences in the nervous system of reptiles.

1. The study of sex differences in the brain and behavior of reptiles presents an excellent opportunity both to discern general principles of sexual differentiation in the nervous system and to explore the evolutionary history of this process in amniote vertebrates. 2. Findings in several reptiles suggest that some sex differences found in mammals and birds are conserved while others are not. Conserved features include areas in the limbic forebrain involved in the regulation of social and sexual behaviors. As in mammals and birds, it is rare to find differences in the distribution of sex steroid concentrating neurons in reptiles but common to find differences in the distribution of the various steroid hormone receptors and in their regulation. 3. This research has revealed that differences in social and sexual behavior are reflected better by the activity, not by the size, of hormone-sensitive limbic areas. 4. Finally, species differences in plasma levels of sex hormones are paralleled by differences in behavioral sensitivity to these hormones as well as by differences in the regulation of genes coding for steroid hormone receptors.

Animals↗

PubMed2001

[Gender perspective can result in better research on sex differences and revascularization].

This article focuses on how sex differences in revascularization, PTCA and CABG, are discussed in medical research. We selected and analyzed 10 articles identified through Medline, for the purpose of studying such discussions. Three explanatory models were identified by qualitative analysis: biological, psychosocial and discriminatory. Although the articles focused on sex differences in revascularization, the discussions in the articles on this issue were sparse. We demonstrate how a gender perspective can generate new questions and theories and contribute to a better prognosis for women and men with heart disease.

Angioplasty, Balloon, Coronary↗

PubMed1997

Sex differences in the cardiovascular and renal actions of vasopressin in conscious rats.

The present study was carried out to investigate whether prostaglandins (PG) are involved in the mechanism that contributes to the sex difference in the antidiuretic and pressor actions of vasopressin. The experiments were performed in conscious male and nonestrous female rats. In hydrated rats, the graded infusion of vasopressin (10-1,000 pg.min 1.kg body wt-1) resulted in a dose-dependent antidiuresis: decreases in urine flow and free water clearance and an increase in urine osmolality. These responses were significantly greater in male than in nonestrous female rats. Pretreatment with a cyclooxygenase inhibitor, indomethacin (10 mg/kg body wt iv), significantly enhanced the antidiuretic response to vasopressin in both sexes. However, the magnitude of this enhancement was greater in female than in male rats. Thus indomethacin abolished the sex difference in the antidiuretic response to vasopressin. In a separate experiment in rats without water hydration and urine collection, infusion of pressor doses of vasopressin (1,000-6,000 pg.min-1.kg body wt-1) resulted in a greater increase in blood pressure in male than in nonestrous female rats. Treatment with indomethacin enhanced this response equivalently in both sexes and thus did not affect the sex difference in the pressor action of vasopressin. These data indicate that renal PG may mediate, at least in part, the sex difference in the antidiuretic action of vasopressin, whereas vascular PG seem not to play an important role in the sex difference in the pressor action of vasopressin.

Animals↗

PubMed2006

Sex differences and role of gonadal hormones on glutamate level in the nucleus accumbens in morphine tolerant rats: a microdialysis study.

Sex differences are observed in the development of tolerance to the antinociceptive effect of opioid drugs such as morphine, but the precise underlying mechanism remains unclear. There are evidences about the interaction between gonadal hormones and neuromodulatory systems including opioidergic and glutamatergic systems. We examined the sex differences and the role of gonadal hormones on the glutamate level in the nucleus accumbens in morphine tolerant rats using in vivo microdialysis. A microdialysis probe was implanted into the left nucleus accumbens core of rats and CSF (cerebrospinal fluid) dialysates were collected. The concentration of glutamate was measured by high-performance liquid chromatography with a fluorescence detector. The results showed that after chronic morphine administration, tolerance to antinociceptive effects of morphine was significantly greater in male rats (P<0.001). Sex differences in tolerance to morphine disappeared with gonadectomy of animals. There was also a significant sex difference in the glutamate level in the nucleus accumbens of morphine tolerant rats (P<0.001), ovariectomy of female rats decreased the glutamate level significantly (P<0.001), while gonadectomy did not change the glutamate level in males significantly. In conclusion, these experiments demonstrate that the excitatory amino acid release in the nucleus accumbens may be modulated by an estrogen-sensitive mechanism and play a role in the morphine analgesia and tolerance.

Analgesics, Opioid↗

PubMed2002

Evolution and development of sex differences in cooperative behavior in meerkats.

In cooperatively breeding birds, where helpers of both sexes assist with the provisioning and upbringing of offspring who are not their own, males tend to contribute more than females to rearing young. This sex difference has been attributed to paternity uncertainty, but could also occur because males contribute more where they are likely to remain and breed in their group of origin. In contrast to most birds, female meerkats (Suricata suricatta) are more likely to breed in their natal group than males. We show that female meerkat helpers contribute more to rearing young than males and that female helpers feed female pups more frequently than males. Our results suggest that sex differences in cooperative behavior are generated by sex differences in philopatry and occur because females derive greater direct benefits than males from raising recruits to their natal group. These findings support the view that direct, mutualistic benefits are important in the evolution of specialized cooperative behavior.

Aging↗

PubMed1995

Beyond sex differences in visuo-spatial processing: the impact of gender trait possession.

Much research has emphasized the presence of sex differences in visuo-spatial processes while neglecting individual differences in performance within the two sexes (Archer, 1987). The present study looks beyond sex differences and considers the association of self-perceived gender trait possession with performance in two visuo-spatial tasks. The findings indicate that, in a 3-D mental rotation task, where a substantial sex difference occurred, gender trait possession adds significantly to the overall explanation of performance, the important gender trait variable being a measure of androgyny. With the Group Embedded Figures Task, gender trait measures were the only significant variables in differentiating performance, in this case masculinity was the important gender trait variable. The implication of such results for conventional explanations of individual differences in visuo-spatial processing is discussed.

Adolescent↗

PubMed2004

Absence of sex differences in pharmacotherapy for acute myocardial infarction.

BACKGROUND: Previous studies have indicated that sex differences may exist in the pharmacological management of acute myocardial infarction (AMI), with female patients being treated less aggressively. OBJECTIVES: To determine if previously reported sex differences in AMI medication use were also evident among all AMI patients treated at hospitals in an urban Canadian city. METHODS: All patients who had a primary discharge diagnosis of AMI from all three adult care hospitals in Calgary, Alberta, in the 1998/1999 fiscal year were identified from hospital administrative records (n=914). A standardized, detailed chart review was conducted. Information collected from the medical charts included sociodemographic and clinical characteristics, comorbid conditions, and cardiovascular medication use during hospitalization and at discharge. RESULTS: Similar proportions of female and male patients were treated with thrombolytics, beta-blockers, angiotensin-converting enzyme inhibitors, nitrate, heparin, diuretics and digoxin. Among patients aged 75 years and over, a smaller proportion of female patients received acetylsalicylic acid in hospital than did male patients (87% versus 95%; P=0.026). Multivariable logistic regression analysis revealed that, after correction for age, use of other anticoagulants/antiplatelets and death within 24 h of admission, sex was no longer an independent predictor for receipt of acetylsalicylic acid in hospital. Medications prescribed at discharge were similar between male and female patients. CONCLUSION: The results from this Canadian chart review study, derived from detailed clinical data, indicate that the pattern of pharmacological treatment of female and male AMI patients during hospitalization and at discharge was very similar. No sex differences were evident in the treatment of AMI among patients treated in an urban Canadian centre.

Adrenergic beta-Antagonists↗

PubMed2001

Increased frontal [(18)F]fluorodopa uptake in early Parkinson's disease: sex differences in the prefrontal cortex.

Previous imaging studies in Parkinson's disease have focused mainly on the striatum, a region with very high dopaminergic activity. Using modern high-sensitivity 3D [(18)F]fluorodopa (Fdopa)-PET, mesocortical monoamine projections can be studied. To study the frontal monoaminergic system in unmedicated early Parkinson's disease in vivo, we examined 20 early Parkinson's disease patients (10 women, 10 men) and 16 healthy subjects (nine women, seven men) with 3D Fdopa-PET, using standard region-of-interest-based analysis with MRI co-registration. Women with Parkinson's disease had 87% higher Fdopa uptake in the right dorsolateral prefrontal cortex (area 46) compared with men with Parkinson's disease, whereas there was no sex difference in the control group (sex x disease interaction, P = 0.03). The uptake in the right dorsolateral prefrontal cortex was 82% higher in men with Parkinson's disease and 219% higher in women with Parkinson's disease compared with control groups (effect of disease, P < 0.0001). Also in the left dorsolateral prefrontal cortex and in the medial frontal cortex, early Parkinson's disease patients had significantly (18-94%) higher Fdopa uptake compared with healthy controls. In the putamen, both men and women with Parkinson's disease had a significantly lower (27-46%) uptake compared with healthy controls. These results indicate that frontal monoaminergic activity is increased and that there is a sex difference in the prefrontal monoaminergic system in early Parkinson's disease. The reported sex difference may be linked to clinical sex differences in the symptoms and treatment response in Parkinson's disease.

Aged↗

PubMed1984

Sex differences in human circadian rhythms: intrinsic periods and sleep fractions.

The period of freerunning circadian rhythms is significantly shorter and the fraction of sleep is significantly larger in human females than in males, as long as the rhythms run internally synchronized. The sex difference in the period could be a property either of the whole circadian system or of only one of the oscillators in a multi-oscillator system. The sex difference in the sleep fraction could be a fixed property of the sleep-wake rhythm or could depend on interactions in the multi-oscillator system. To investigate these questions, a sample of 33 long-term experiments, in which the rhythms ran internally synchronized in one section and internally desynchronized in another section, were analyzed. The periods of rhythms in rectal temperature were different in females and males during internal synchronization, but became identical during internal desynchronization. In contrast, sex differences in sleep-wake periods were more pronounced when the rhythms were desynchronized than when they were internally synchronized. This result provides evidence that the sex difference in periodicity is a property only of the sleep-wake rhythm; the intrinsic periods of temperature rhythms are identical in females and males, whereas those of sleep-wake rhythms are distinctly shorter in females than in males. In the state of internal synchronization, the joint period is a compromise between the intrinsic periods of the rhythms involved, and therefore it shows a small but significant sex difference. Moreover, the transition from internally synchronized to desynchronized rhythms is combined with a highly significant reduction in the sleep fraction, which is considerably greater in females than in males. These results suggest that the occurrence of internal desynchronization strongly affects the sleep-wake rhythm, and that the influence of rhythm disorders is considerably greater in females than in males.

Body Temperature↗

PubMed2005

Sex differences in the emotional brain.

In this issue, Schienle et al. use brain imaging to examine emotion-related activation differences between men and women. Are those differences related to the way the sexes feel emotions? Are they hardwired? In this commentary, we briefly review sex differences in feeling, perception of emotionally evocative cues, and expression of emotions, and we discuss how they may be related to sex differences in the emotional brain.

Brain↗

PubMed1988

Relationship between cigarette smoking and histologic type of lung cancer, with special reference to sex difference.

In order to clarify sex differences associated with the relationship between smoking and each histologic type of lung cancer, the smoking histories of 2,083 lung cancer patients (1,660 men and 423 women) diagnosed at the Center for Adult Diseases, Osaka, from 1965 to 1983 were analyzed. The rates expected of smokers among these cases were calculated from the sex and age specific rates of smokers in the general population, reported annually by the Japan Tobacco and Salt Public Corporation. The odds ratios for smoking were estimated to be 5.2, 3.1, 6.9, and 4.1 in men for squamous cell carcinoma, adenocarcinoma, small cell carcinoma and large cell carcinoma, and 7.2, 1.8, 14.4 and 3.8 in women respectively. Significant differences in the odds ratios for each histologic type between men and women were observed only for adenocarcinoma. In squamous cell carcinomas, the odds ratios were estimated by dividing them into two groups according to location. No difference was found between men and women in this respect.

Adenocarcinoma↗

PubMed2003

Substance use disorders: sex differences and psychiatric comorbidities.

OBJECTIVE: This article reviews sex differences in psychiatric comorbidity among individuals with substance use disorders and, in particular, the clinical significance of these differences for treatment outcome among women. METHOD: We undertook a computerized search of major health care databases. To enhance the search, we drew prior relevant articles from the reference list. RESULTS: Women with alcohol and other drug use disorders present higher rates of psychiatric comorbidity, particularly mood and anxiety disorders, than do men. Moreover, the comorbid diagnosis, particularly of depression, is more often primary in women, while in men the comorbidity is more often secondary to the substance abuse diagnosis. In addition, there is evidence that psychiatric comorbidity is associated with distinct, sex-specific outcomes for substance use treatment. CONCLUSIONS: Sex differences in the clinical presentation of substance-dependent individuals with psychiatric comorbidity present specific treatment challenges and opportunities.

Anxiety Disorders↗

PubMed1989

Lack of sex differences in antioxidant enzyme development in the fetal rabbit lung.

A sex difference characterized by a female advantage in the maturation of the fetal pulmonary surfactant system is well documented. Because the surfactant system and the antioxidant enzyme system of the fetal lung have chronologically similar developmental patterns and share some of the same hormonal regulators, such as glucocorticoids, we questioned whether a sex difference would be present in antioxidant enzyme maturation as it is in surfactant system maturation. We studied fetal rabbits at days 26 and 28 of a 31-day gestational period. Fetal sex was identified histologically. Fetal lung lavage was performed and lavage fluid assayed for phosphatidylcholine, disaturated phosphatidylcholine, and sphingomyelin. Lung tissue from separate fetuses was assayed for disaturated phosphatidylcholine content and total phospholipid content and for the activities of three antioxidant enzymes--superoxide dismutase, catalase, and glutathione peroxidase. No differences were present in antioxidant enzyme maturation between male and female fetal rabbits at the gestational days studied. A female advantage was observed in the lung lavage disaturated phosphatidylcholine/sphingomyelin ratio (at 26 days: female 1.38 +/- 0.42, male 0.99 +/- 0.26; and at 28 days: female 3.29 +/- 0.53; male 2.26 +/- 0.35, p less than 0.05). A female advantage in surfactant development was not reflected in lung tissue disaturated phosphatidylcholine or total phospholipid. We conclude that, unlike the development of the surfactant system, the development of the antioxidant enzyme system in the fetal rabbit lung does not demonstrate a sex difference.

Animals↗