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PubMed1990

Sex differences and thyroid hormone sensitivity of hippocampal pyramidal cells.

In an effort to determine if sex differences exist in the morphologic characteristics of pyramidal cells and granule cells of the hippocampal formation and whether sex plays a role in determining thyroid hormone sensitivity of these neuronal populations, we used single-section Golgi impregnation to examine the effects of neonatal thyroid hormone administration on hippocampal cells from the brains of adult rats of both sexes. Quantitative analyses of control brains revealed sex differences in the number of primary dendrites and the number of spines on the apical dendritic shaft of CA3 pyramidal cells. These differences showed opposite trends; females possessed more primary dendrites, whereas males showed more apical excrescences. Neonatal treatment with thyroid hormone resulted in long-lasting and dramatic changes of the entire CA3 pyramidal cell. CA3 pyramidal cells from thyroid hormone-treated animals showed significantly larger cell body areas, greater numbers of dendritic branchpoints, and longer dendrites. In addition, CA3 pyramidal cells from thyroid hormone-treated animals showed changes in the morphological characteristics which were shown to be sexually dimorphic; treatment resulted in significantly greater numbers of both primary dendrites and apical excrescences. These treatment differences occurred in both sexes and were of equal magnitude, regardless of sex. On the other hand, no sex differences in the morphologic parameters examined were detected for pyramidal cells in the CA1 region. Moreover, neonatal thyroid hormone treatment did not affect the cell body area, dendritic branch points, or the length of dendrites of these cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Sex differences in beliefs about aggression: opponent's sex and the form of aggression.

Previous studies show that men endorse instrumental beliefs about aggression to a greater extent than women, whereas women endorse expressive beliefs to a greater extent than men. However, men and women indicate that they have different opponents in mind when thinking about aggression, and existing measures may emphasize physical forms of aggression. Therefore, beliefs about aggression were examined when the type of aggression (physical or verbal) and the sex of the opponent (same sex or opposite-sex partner) were specified, among a sample of 200 students. Expressive beliefs were higher and instrumental beliefs lower for an opposite-sex partner and for physical aggression. The characteristic sex difference applied across all manipulations for expressive beliefs, but not for instrumental ones: men showed higher scores than women only for same-sex physical aggression. Higher instrumental (but not lower expressive) scores were also found among those who based their responses on real rather than hypothetical events. The sex difference in instrumental beliefs for same-sex physical aggression was largely confined to respondents using a hypothetical event. As in previous studies, instrumental and expressive beliefs were relatively independent of one another. The position that the beliefs represent rhetorical devices is assessed in the light of these findings.

Adolescent↗
PubMed2006

Sex differences in the basolateral amygdala: the extracellular levels of serotonin and dopamine, and their responses to restraint stress in rats.

The sex difference in the emotional response to stress suggests a sex-specific stress response in the amygdala. To examine the sex difference in extracellular levels of serotonin (5HT) and dopamine (DA) in the basolateral amygdala (BLA) and their responses to restraint stress, in vivo microdialysis studies were performed in male and female rats. In experiment I, dialysates were collected from the BLA at 15-min intervals under the freely moving condition. Mean extracellular levels of 5HT or DA in the BLA were higher in male rats than in female rats. In experiment II, rats were subjected to restraint stress for 60 min to examine the stress response of 5HT or DA levels. Although restraint stress significantly increased extracellular 5HT levels in both sexes of rats, female rats showed a greater response than male rats. Moreover, restraint stress significantly increased extracellular DA levels in female rats, but not in male rats. In experiment III, rats were subjected to restraint stress for 30 min to examine behavioral responses to restraint stress. Although no sex difference was observed in the number of audible vocalizations, male rats defecated a larger number of fecal pellets than female rats. In experiment IV, rats were tested for freezing behavior to examine contextual fear responses. Conditioned male rats showed a longer freezing time than conditioned female rats. We found sex differences in the extracellular levels of 5HT and DA in the BLA and their responses to restraint stress, which may be involved in the sex-specific emotional response to stress in rats.

Aggression↗
PubMed1991

Sex differences in finger temperature response to music.

A finding of significant sex differences in finger temperature responses to stimuli would have implications for a variety of situations in which finger temperature changes in combination with other psychophysiological measures are employed as indicators of psychological and/or physiological states. In the present study, each subject listened to one of two distinct musical selections for 3-minutes and 40-seconds after being allowed to adapt for one of five durations ranging from 4 to 20 minutes. Females' finger temperatures decreased more or increased less than did males' finger temperatures. This finding held no matter which music was played and was true for all but the shortest adaptation duration. Control data indicated that the sex difference would not have occurred in the absence of the music, and thus the results suggest that females' finger temperatures decrease more than males' only when stimulation occurs. Possible causes of the sex difference are discussed as well as possible implications for studies in which finger temperature is employed as a dependent variable.

Adaptation, Physiological↗
PubMed1999

Sex differences in the clinical care and outcomes of congestive heart failure in the elderly.

BACKGROUND: There is evidence for sex differences in treatment and outcome of ischemic heart disease. However, little and conflicting data exist about sex differences in the care and outcome of elderly patients with heart failure. METHODS: We compared mortality rate, readmission, and use of selected treatments and procedures between women and men in a database of 2445 patients (1426 women) aged >/=65 admitted for heart failure to 18 Connecticut hospitals in 1994 and 1995. Demographic and clinical data were abstracted from the medical records. RESULTS: Women were older and more likely to have a history of hypertension whereas men more often had previous coronary heart disease. Women had more preserved left ventricular systolic function and higher systolic blood pressure on presentation than men. Treatments on day 1 (aspirin, angiotensin-converting enzyme [ACE] inhibitors, and diuretics), procedures during admission (assessment of left ventricular function, coronary angiography, and revascularization), and use of ACE inhibitors among ideal candidates at discharge were similar in men and women. Six-month rehospitalization rates were also similar. Although 30-day mortality rate did not differ between men and women, 6-month and 1-year mortality rates were lower in women after age adjustment (relative risk for 6-month death 0.81, 95% confidence interval, 0.68-0.95). In multivariable analysis, sex differences in mortality rate were reduced (relative risk 0.90, 95% confidence intervals, 0.75-1.08). History of hypertension, systolic blood pressure on admission, and left ventricular function mostly explained the observed sex differences in mortality rate. CONCLUSIONS: Female and male patients hospitalized for heart failure have a similar hospital course, treatment pattern, and readmission rates, but women live longer than men. When baseline differences are accounted for, the mortality risk of women and men becomes very similar.

Aged↗
PubMed2000

The evolution of sex differences in language, sexuality, and visual-spatial skills.

The evolutionary neurological and physical foundations for human sex differences in language, sexuality, and visual spatial skills are detailed and primate and human studies are reviewed. Trends in the division of labor were established early in evolution and became amplified with the emergence of the "big brained" Homo erectus. A bigger brain necessitated a size increase in the birth canal and female pelvis. These and other physical changes, e.g., the swelling of the breasts and buttocks, may have paralleled the evolution of full-time sexual receptivity, the establishment of the home base, and exaggerated sex differences in the division of labor (hunting vs. gathering), which in turn promoted innate sex differences in visual spatial vs. language skills. For example, female primates produce more social and emotional vocalizations and engage in more tool use and gathering activities, whereas males tend to hunt and kill. Similar labor divisions are evident over the course of human evolution. "Woman's work" such as child rearing, gathering, and domestic tool construction and manipulation contributed to the functional evolution of Broca's speech area and the angular gyrus--which injects temporal sequences and complex concepts into the stream of language and thought. These activities gave rise, therefore, to a female superiority in grammatical (temporal sequential) vocabulary-rich language. Hunting as a way of life does not require speech but requires excellent visual-spatial skills and, thus, contributed to a male visual-spatial superiority and sex difference in the brain. Over the course of evolution males acquired modern human speech through genetic inheritance and because they had mothers who taught them language.

Affect↗
PubMed1993

Sex differences in the risks of hormone-dependent cancers.

There are marked variations in the risk of hormone-dependent cancers between males and females, and these are likely to reflect sex differences in endogenous hormone profiles. The authors examined sex differences in the risk of hormone-dependent cancers of sex-shared sites by using data from the England and Wales national cancer registry for 1962-1984. Both breast and thyroid cancers showed marked excesses in risk for women, but the female: male ratio peaked around menopause for breast cancer and a puberty for thyroid cancer, suggesting that although female sex hormones may influence the risk of these two cancers, the mechanisms involved are probably different. In the descending colon, the risk of cancer was greater in females than in males at ages under 60 years, but greatest in males at ages above this, whereas in the ascending colon there were no age-specific differences in risk between the sexes. This is consistent with the hypothesis that female reproductive events may decrease a woman's risk of cancer in the descending but not in the ascending colon. Sex differences in bone cancer risk at puberty, particularly for osteosarcomas and Ewing's sarcomas, paralleled known sex differences in skeletal growth; there was a peak in age-specific rates earlier and lower in girls than in boys. Rhabdomyosarcoma, a soft tissue cancer, also showed a rise in risk at puberty with age differences between boys and girls that correlated with sex differences in muscle growth patterns; this suggests that its etiology may be hormonally related as well.

Adolescent↗
PubMed2000

Sex differences in mathematical reasoning ability at age 13: their status 20 years later.

Reported is the 20-year follow-up of 1,975 mathematically gifted adolescents (top 1%) whose assessments at age 12 to 14 revealed robust gender differences in mathematical reasoning ability. Both sexes became exceptional achievers and perceived themselves as such; they reported uniformly high levels of degree attainment and satisfaction with both their career direction and their overall success. The earlier sex differences in mathematical reasoning ability did predict differential educational and occupational outcomes. The observed differences also appeared to be a function of sex differences in preferences for (a) inorganic versus organic disciplines and (b) a career-focused versus more-balanced life. Because profile differences in abilities and preferences are longitudinally stable, males probably will remain more represented in some disciplines, whereas females are likely to remain more represented in others. These data have policy implications for higher education and the world of work.

Adolescent↗
PubMed2007

Sex differences in the potency of kappa opioids and mixed-action opioids administered systemically and at the site of inflammation against capsaicin-induced hyperalgesia in rats.

RATIONALE: Sex differences in the potency of the antinociceptive effects of kappa opioids have been reported in various acute pain models with evidence suggesting that these sex differences are mediated by activity in the N-methyl-D: -aspartate (NMDA) system. OBJECTIVES: The purpose of the present study was to evaluate sex differences in the antihyperalgesic actions of selected kappa and mixed-action opioids in a persistent pain model and determine if the NMDA system modulates these effects in a sexually dimorphic manner. METHODS: Using gonadally intact male and female F344 rats, hyperalgesia was induced by local administration of capsaicin in the tail, after which the tail was immersed in a mildly noxious thermal stimulus (45 degrees C water), and tail-withdrawal latency measured. Opioids were then administered systemically (s.c.) and locally (in the tail) alone, and in selected combinations with the noncompetitive NMDA antagonist dextromethorphan. RESULTS: When administered systemically and locally, the kappa opioids spiradoline, U69,593 and U50,488, and the mixed-action opioids butorphanol and nalbuphine, produced dose-dependent antihyperalgesic effects. Whereas the kappa opioids were generally more potent in males, sex differences were not observed with the mixed-action opioids. Peripheral receptor activity was confirmed for local administration of kappa opioids by the antagonism observed after local, but not intracerebroventricular (i.c.v.), administration of the kappa antagonist nor-binaltorphamine (nor-BNI). Dextromethorphan was equally potent in attenuating the antihyperalgesia induced by kappa opioids in both males and females. CONCLUSIONS: These findings demonstrate sex differences in kappa opioid activity in a persistent pain model. Although an NMDA antagonist blocked the effects of kappa opioids in this model, these effects were not sexually dimorphic as reported in most acute pain models.

Analgesics, Opioid↗
PubMed1982

Gender and energy balance: sex differences in adaptations for feast and famine.

According to this theory/review, the cross-culturally common finding of more women than men among the obese is at least in part a consequence of sex differences in evolutionary selection pressure. James and Trayhurn claim that the propensity to obesity is linked to th ability to survive a fast and both may involve reduced heat production. The present theory extends this relationship to sex differences in energy balance. According to the theory proposed here, mammalian females were subjected to more severe selection pressures during times of short food supply than males were and hence females were under more pressure to evolve mechanisms to facilitate survival during famine, which led to sex differences in obesity. The data relevant to sex differences in starvation survival, obesity and heat production, and the possible evolutionary roles and implications of sex differences in chromosomes and in organizational and activational sex hormones are reviewed. The conclusion is that evolution has created a linkage between sex chromosomes, hormones and energy balance, and this linkage is at least in part responsible for the greater resistance of the female to famine and for her greater tendency to become obese in times of feast.

Adaptation, Physiological↗
PubMed2002

Sex differences in repolarization homogeneity and its circadian pattern.

The reason for sex differences in arrhythmic risk remains unclear. Heterogeneity of ventricular repolarization is directly linked to arrhythmogenesis; thus we investigated repolarization homogeneity and its circadian pattern in men and women. During 24-h Holter recordings in 60 healthy subjects (27 males), a 12-lead electrocardiogram (ECG) was obtained every 30 s. RR and QT intervals, and, after singular-value decomposition, two characteristics of repolarization homogeneity were calculated in each ECG. Corrected QT (QTc) values were obtained using an individually optimized heart rate (HR) correction formula. All values were averaged over 10-min time bands from 0000 to 2400. There were substantial sex differences in both global repolarization homogeneity (measured by the total cosine of the angle between QRS and T wave vectors) and regional homogeneity of repolarization (quantified independently by the relative T wave residuum). Whereas women throughout the 24 h followed more closely the pattern of inverse sequence between depolarization and repolarization, they also showed much higher localized repolarization heterogeneity than men. In both women and men, repolarization irregularity was greatest during morning hours. A sex difference was also observed for HR and QTc interval; however, the circadian patterns of the repolarization homogeneity descriptors were different from those of HR and QTc intervals.

Adolescent↗
PubMed2003

Sex differences in management and outcome after stroke: a Swedish national perspective.

BACKGROUND AND PURPOSE: It is disputed whether there are sex differences in management and outcome after stroke; early studies have shown inconsistent results. The objective of this study was to verify and explain differences between men and women in management and outcome after stroke in a national perspective. METHODS: In 2001, 20 761 stroke patients were registered in Riks-Stroke, the national quality register for stroke care in Sweden in which all 84 hospitals participate. Data from 9 hospitals that had reported <70% of the estimated stroke events were excluded from analyses, leaving 19 547 patients (9666 women, 9881 men) at 75 hospitals for the present analyses. RESULTS: Women were older than men (77.8 versus 73.2 years). After age adjustment, female patients were more often disabled, living at home with community support, or in institutions before the stroke. They also had a different cardiovascular risk factor profile. Case fatality ratios during the first 3 months were similar in men and women. After 3 months, more women were physically and mentally impaired and dependent on other persons. Female patients with atrial fibrillation received oral anticoagulants less often than men. Even after multiple adjustments for differences between sexes, female sex was independently associated with institutional living 3 months after the stroke (odds ratio, 1.2; 95% confidence interval, 1.0 to 1.4). CONCLUSIONS: Women have a worse prestroke condition. Except for case fatality ratios, they also have a worse outcome after stroke after adjustment for other prognostic factors. There are also sex differences in the medical management of stroke that need to be rectified.

Aged↗
PubMed2003

Overexpression of bcl-2 reduces sex differences in neuron number in the brain and spinal cord.

Several sex differences in the nervous system depend on differential cell death during development in males and females. The anti-apoptotic protein, Bcl-2, promotes the survival of many types of neurons during development and in response to injury. To determine whether Bcl-2 might similarly control cell death in sexually dimorphic regions, we compared neuron number in wild-type mice and transgenic mice overexpressing Bcl-2 under the control of a neuron-specific promoter. Three neural areas were examined: the spinal nucleus of the bulbocavernosus (SNB), in which neuron number is greater in males; the retrodorsolateral nucleus (RDLN) of the spinal cord, which exhibits no sex difference in neuron number; and the anteroventral periventricular nucleus (AVPV) of the hypothalamus, in which both overall cell density and the number of tyrosine hydroxylase immunoreactive (TH-ir) neurons are greater in females. Bcl-2 overexpression significantly increased SNB cell number in females, overall cell density of AVPV in males, and RDLN cell number in both sexes. Bcl-2 overexpression did not alter the number of TH-ir neurons in AVPV of males or females. These findings indicate that Bcl-2 can regulate sexually dimorphic cell number in the brain and spinal cord and suggest that Bcl-2 may mediate effects of testosterone on cell survival during neural development. In contrast to the regulation of overall cell density in AVPV, the sex difference in TH cell number apparently is not caused by a Bcl-2-dependent mechanism.

Animals↗
PubMed1979

Sex differences in patterns of career mobility.

Using the 1970 Census data, this paper examines differences by sex in patterns of intragenerational occupational mobility over a five year period (1965-1970) for two cohorts of white, U.S. men and women. The observed mobility patterns are separated into that part due to structural factors (i.e., the different distributions over occupational origins and destinations by sex) and that due to sex-related individual and group characteristics. Most of the observed differences in mobility patterns are found to be the result of occupational sex segregation.

Career Mobility↗
PubMed1996

Sex differences in performance in the Morris water maze and the effects of initial nonstationary hidden platform training.

Sex differences in rats' performance on a stationary hidden-platform task (spatial task) in the Morris water maze and the effects of initial nonstationary hidden platform training (NSP training) were examined. The NSP training was designed to familiarize rats with the general requirements of the water-maze task without providing spatial information. NSP training led to faster acquisition and improved retention of the subsequent spatial task in both males and females. There was a sex difference favoring males on acquisition and retention of the spatial task only in rats that had not received previous NSP training. Moreover, there was an apparent reversed sex difference favoring females on some measures of spatial performance in NSP-trained rats. These results suggest that performance on the water-maze task, including the expression of sex differences, can be altered by previous familiarization with nonspatial aspects of the task.

Animals↗
PubMed2001

Is there a sex difference in human laterality? IV. An exhaustive survey of dual-task interference studies from six neuropsychology journals.

The entire contents of six neuropsychology journals (161 volumes, 612 issues) were screened to identify dual-task laterality experiments. Of 112 experiments thus identified, 45.5% provided information about sex differences. Although 23 experiments yielded at least one significant main effect or interaction involving the sex factor, only 5 outcomes represented an unambiguous sex difference in laterality. All 5 of those sex differences support the hypothesis of greater hemispheric specialization in males. The confirmatory outcomes constitute less than 10% of the informative experiments and less than 5% of the total population of experiments. These data alone do not rule out the possibility that sex differences are chance findings (Type I errors). However, when considered along with similar results from perceptual laterality data previously examined, the dual-task data fit the pattern of a small but reliable population-level sex difference in human laterality.

Adult↗
PubMed1985

Thiazide-induced hypercholesterolemia: sex differences.

Thiazide diuretics are used commonly to treat hypertension. Unfortunately, they also are known to elevate serum cholesterol levels. Because serum lipid fraction levels differ between the sexes, possible sex-related differences in thiazide-induced changes in serum total cholesterol (TC), triglycerides (TG) and high density lipoprotein cholesterol (HDL-C) levels were examined. Four groups of male and female hamsters were treated for a minimum of 3 months with hydrochlorothiazide (HCTZ) at zero, 1, 2 or 4 mg/kg/day. At zero dose, there was no difference in TG levels between the sexes; however, females had significantly higher TG concentrations than did males at 1, 2 and 4 mg HCTZ (all p less than 0.05). Females demonstrate a significant dose response with HCL-C levels increasing with increasing doses of HCTZ, (r = 0.983; p less than 0.02); in contrast males had a similar increase in HDL-C at all dose levels (all p less than 0.05) thus there was no demonstrable dose response (r = 0.539). Total cholesterol concentrations were significantly higher in the females than in males (p less than 0.05) at all 3 dose levels as well as at zero dose. Further, the females demonstrated a direct dose response in TC levels (r = 0.986; p less than 0.02) while the males showed no such dose response (r = 0.824; p less than 0.01). Based on these findings we conclude that: 1) HCTZ increases TG, TC and HDL-C levels in both male and female hamsters; 2) TC levels are higher in females than in males regardless of HCTZ dose; 3) only females show a dose-dependent increase in HCL-C and TC in response to HCTZ. These sex-related changes in lipid fractions occurring with HCTZ treatment, if they occur in humans, may contribute to sex-related differences in rates and severity of atherosclerosis in HCTZ-treated populations.

Animals↗
PubMed2001

Sex differences in songbirds 25 years later: what have we learned and where do we go?

About 25 years ago, Nottebohm and Arnold reported that there are profound male-biased sex differences in volume in selected nuclei in telencephalic portions of the song control system. This review focuses on issues related to the cellular bases of these sex differences in volume and comparative studies that might elucidate the function of this variation between the sexes. Studies utilizing a variety of neurohistological methods in several different species to define the boundaries of two key telencephalic song nuclei HVc and the robust nucleus of the archistriatum (RA) all tend to find a sex difference in volume in agreement with Nissl-defined boundaries. Sex differences in volume in nuclei such as HVc and RA are associated with differences in cell size and cell number. Other attributes of the phenotype of cells in these nuclei are also different in males and females such as the number of cells expressing androgen receptors. Comparative studies have been employed to understand the function of these sex differences in the brain. In some songbird species, females sing rarely or not at all, and the brain nuclei that control song are many times larger volume in males than females. In other species, males and females sing approximately equally, and the brain nuclei that control song are approximately equal between the sexes. Recently, statistical methods have been employed to control for phylogenetic effects while comparing the co-evolution of traits. This analysis indicates that the evolution of sex differences in song has co-evolved with the evolution of sex differences in singing behavior in songbird species. Future studies should focus on the function of the smaller song control nuclei of females and investigate the role these nuclei might play in perception as well as in production.

Animals↗