Sexual selection is not the origin of long necks in giraffes

The evolutionary origin of the long neck of giraffes is enigmatic. One theory (the 'sexual selection' theory) is that their shape evolved because males use their necks and heads to achieve sexual dominance. Support for this theory would be that males invest more in neck and head growth than do females. We have investigated this hypothesis in 17 male and 21 female giraffes with body masses ranging from juvenile to mature animals, by measuring head mass, neck mass, neck and leg length and the neck length to leg length ratio. We found no significant differences in any of these dimensions between males and females of the same mass, although mature males, whose body mass is significantly (50%) greater than that of mature females, do have significantly heavier (but not longer) necks and heavier heads than mature females. We conclude that morphological differences between males and females are minimal, that differences that do exist can be accounted for by the larger final mass of males and that sexual selection is not the origin of a long neck in giraffes.     

Vanished Gender Differences of Cardiometabolic Risk Factors After Matching the Apnea Hypopnea Index at Postmenopausal Age

BackgroundSleep-disordered breathing (SDB) and cardiometabolic risk factors are male prevalent.ObjectiveThis study investigated whether gender differences remained prominent after matching for the apnea hypopnea index (AHI) and postmenopause.MethodsIn a retrospective analysis of 350 eligible SDB patients, female patients were matched with male patients of the same age and body mass index (BMI) (age-BMI-matched [nAHImt]; n = 102 pairs) or were matched with male patients of the same age, BMI, and AHI (age-BMI-AHI-matched [AHImt]; n = 66 pairs). The nAHImt or AHImt patients were further separated into junior and senior subgroups.ResultsIn the nAHImt/junior group, women had shorter neck circumferences, better sleep architecture, and lower AHI, Epworth Sleepiness Scale (ESS) score, blood pressure (BP), total cholesterol (TC), triglyceride (TG), and uric acid (UA) than nAHImt/junior men. In the AHImt/junior group, women had shorter neck circumferences, lower waist/hip ratios, ESS, BP, TG, and UA than AHImt junior men. In the nAHImt/senior group, women had lower AHI, neck circumferences, waist/hip ratios, diastolic BP, and UA than men. In contrast, in the AHImt/senior group, most cardiometabolic parameters were similar between women and men. After further matching for the AHI, many elements of gender differences disappeared.ConclusionsCompared with AHImt men, women had lower UA, TG, BP, and daytime sleepiness before menopause, but gender differences became indistinguishable postmenopause. We suggested that matching sleep quality or adjusting AHI would be noteworthy and required for studying gender differences.     

Some implications of relative biomechanical neck length in hominid femora

Demonstration of a size-based influence on relative biomechanical neck length of the femur predicts relatively longer necks for smaller femurs. Fossil hominids through the middle Pleistocene appear to have relatively longer femur necks than expected from this relation, excepting the two small australopithecine females. It is suggested that this variation results from smaller crania at birth in the fossils, and the possibility is raised that australopithecine populations were characterized by marked brain size differences at birth.     

Central and noncentral blood volumes in cirrhosis: relationship to anthropometrics and gender

The size of the central and arterial blood volume (CBV) is essential in the understanding of fluid retention in cirrhosis. Previously, it has been reported decreased, normal, or increased, but no reports have analyzed CBV with respect to gender and lean body mass. The aim of the present study was by means of an optimized technique to reassess it in a large group of patients with cirrhosis compared with healthy controls and matched controls in relationship to their body dimensions and gender. Eighty-three patients with cirrhosis (male/female, 60:23), 67 patients without liver disease (male/female, 22:45), and 14 young healthy controls (male/female, 6:8) underwent a hemodynamic investigation with determination of cardiac output, central circulation time, and CBV determined according to kinetic principles. Related to gender, CBV was lower in male cirrhotics (1.48 +/- 0.30 liter) than in matched and young controls (1.68 +/- 0.33 and 1.72 +/- 0.33 liter, respectively; P < 0.05-0.01). No significant differences in CBV were seen between female cirrhotics and controls. Absolute and adjusted CBVs were lower in the females than in men with cirrhosis (P < 0.001), and men with cirrhosis had lower absolute and body weight-adjusted CBVs than matched controls (P < 0.01). Normalized values of CBV (%total blood volume) were significantly lower in patients with cirrhosis (25 +/- 4%) than in matched controls (31 +/- 7%) and young controls (28 +/- 4%; P < 0.02). CBV correlated significantly with anthropometrics, including lean body mass (r = 0.68-0.82; P < 0.0001). In conclusion, the CBV of patients with cirrhosis was lower than that of controls when adjusted for body dimensions and gender. There are significant gender differences, and signs of underfilling are more pronounced in male than in female patients. The results emphasize the importance of adjustments of blood volumes for anthropometrics and gender.     

Manual therapy as a conservative treatment for adolescent idiopathic scoliosis: a systematic review

Background

Studies on adolescent idiopathic scoliosis have well documented the differences between natural history of male and female patients. There are also differences in responses to nonoperative treatment, but the results of operative treatment in male patients compared with females have not been widely reported. Only few studies had compared the outcomes of operative treatment between male and female patients with different results.

Methods

We retrospectively reviewed the outcome of 150 (112 girls and 38 boys) consecutive patients with diagnosis of adolescent idiopathic scoliosis who were managed surgically between May 1996 and September 2005. Next, male radiographic parameters were compared with female ones pre- and postoperatively. Then, a subgroup of 38 matched girls was compared regarding the age, curve type, curve magnitude, and the instrumentation we used.

Results

In comparing male patients with unmatched girls, the boys had greater mean age (17.3 ± 2.3 vs. 16.3 ± 2.9; p = 0.049), greater primary curve (71.4 ± 21.3° vs. 62.7 ± 17.5°; p = 0.013), less flexibility (30.1 ± 13.5% vs. 40.3 ± 17.8%; p = 0.01), and less correction percentage (51.3 ± 12.9% vs. 58.8 ± 16.5%; p = 0/013). The loss of correction was comparable between the two groups. In the matched comparison, the flexibility in boys was less than girls (30.1 ± 13.5% vs. 38.1 ± 17.5%; p = 0.027). Also, the boys had a smaller correction percentage compared to the girls, but this finding was not statistically significant.

Conclusion

There was similar distribution curve pattern between male and female patients with AIS. Males had more rigid primary curves compared to females but a similar degree of postoperative scoliosis correction. Male AIS patients were older at the time of surgery. These preoperative gender differences, however; did not compromise the radiological outcomes of surgical treatment and the results were comparable between the genders.     

Revisiting Gender Differences in Somatic Symptoms of Depression: Much Ado about Nothing?

Background

Women have a higher prevalence of Major Depressive Disorder (MDD) and report more severe depressive symptoms than men. Several studies have suggested that gender differences in depression may occur because women report higher levels of somatic symptoms than men. Those studies, however, have not controlled or matched for non-somatic symptoms. The objective of this study was to examine if women report relatively more somatic symptoms than men matched on cognitive/affective symptoms.

Methods

Male and female patients receiving treatment for MDD in outpatient psychiatric clinics in New Jersey and Pennsylvania, USA were matched on Beck Depression Inventory-II (BDI-II) cognitive/affective symptom scores. Male and female BDI-II somatic symptom scores were compared using independent samples 2-tailed t-tests.

Results

Of 472 male and 1,026 female patients, there were 470 male patients (mean age = 40.1 years, SD = 15.1) and 470 female patients (mean age = 43.1 years, SD = 17.2) successfully matched on BDI-II cognitive/affective symptom scores. Somatic symptoms accounted for 35% of total BDI-II scores for male patients versus 38% for matched female patients. Female patients had somatic symptom scores on average 1.3 points higher than males (p<.001), equivalent to 4% of the total BDI-II scores of female patients. Only 5% of male patients and 7% of female patients scored 2 or higher on all BDI-II somatic symptom items.

Conclusions

Gender differences in somatic scores were very small. Thus, differences in the experience and reporting of somatic symptoms would not likely explain gender differences in depression rates and symptom severity.     

Differential infant carrying in captive and wild common marmosets (Callithrix jacchus)

Callitrichids are communal breeders that lack sexual dimorphism, and only a few studies have examined behavioral gender differences among them. The purpose of this study was to investigate gender differences in infant carrying in 16 captive and seven wild common marmoset groups. Our results showed that female–female twin pairs were carried significantly more often by fathers than were male–male and male–female pairs both in the wild and in captivity. We suggest these differences may be related to different reproductive potentials of male and female Callithrix jacchus and possibly to future breeding competition among females.     

Communication of gender from human breath odors: Relationship to perceived intensity and pleasantness

During five consecutive daily test sessions, 10 men and women rated the relative intensity and pleasantness of breath odors from 14 males and 19 females on a no-oral-hygiene regimen. In addition, the likely gender of the donor of each odor was also estimated. The breath odors of males were rated, on the average, as more intense and less pleasant than the breath odors of females. Women consistently gave lower pleasantness ratings to the odors than did men. Both the male and female judges assigned the breath odors to the correct gender classes at a frequency unlikely due to chance, although the females were more accurate in this regard. An inverse relation between breath odor intensity and pleasantness was noted. Systematic changes in the rated intensity and pleasantness of the odors were present across the 5 days of the study period. These data suggest that differences exist between the breath odors of men and women, and that humans, like many other mammals, may be capable of assessing gender from oral odors. However, such assignments conceivably reflect the strategy of assigning stronger and less pleasant odors to the male category, and weaker and less unpleasant odors to the female category, regardless of the true sex of the odor donor.     

The effects of induced masculinization on reproductive and aggressive behaviors of the female mosquitofish,Gambusia affinis affinis

Synopsis FemaleGambusia affinis affinis were masculinized with the degraded products of 65% stigmastanol-30% B-sitosterol, a phytosterol. The masculinized females were paired with non-treated males, non-treated females, and other masculinized females. The pairs were analyzed for reproductive and aggressive behaviors exhibited. The behavioral patterns of these pairs were compared statistically to the behavior patterns of the following non-treated pairs: male with male, female with female, and male with female. The masculinized females behaved like males in that they followed, swung, and thrust their gonopodia at non-treated females and larger masculinized females. However, the male-like behavior of the masculinized females was not as intense as that of normal males. Also, the effect of masculinization on the behavior of the treated female was context-dependent as seen when placed with a male or a smaller masculinized female. Under these conditions the masculinized females behaved like typical females and exhibited no masculinized behaviors. The effects of anal spots and size differences are discussed as possible explanations for the variability in behaviors exhibited. The masculinized females displayed no change in aggressive behaviors.     

Gender difference in baroreflex-mediated bradycardia in young rats: role of cardiac sympathetic and parasympathetic components.

In a previous clinical study we have demonstrated a significantly lower baroreflex-mediated bradycardic response in young women compared with men. The present study determined whether sexual dimorphism in baroreflex sensitivity in young rats also covers the reflex tachycardic response. The study was then extended to test the hypothesis that an attenuated cardiac cholinergic component of the baroreflex heart rate response in females may account for the gender difference. Baroreflex sensitivity (BRS) was expressed as the regression coefficient of the reciprocal relationship between evoked changes in blood pressure and heart rate. BRS measured in conscious rats with phenylephrine (BRS(PE)) and nitroprusside (BRS(NP)) represented the reflex bradycardic and tachycardic responses, respectively. Female rats exhibited significantly lower BRS(PE) compared with male rats (-1.53+/-0.1 vs. -2.36+/-0.13 beats x min(-1) x mmHg(-1); p < 0.05) but similar BRS(NP) (-2.60+/-0.20 vs. -2.29+/-0.17 beats x min(-1) x mmHg(-1)). Blockade of cardiac muscarinic receptors with atropine methyl bromide elicited greater attenuation of BRS(PE) in male than in female rats (72+/-4.6 vs. 53+/-6.7% inhibition; p < 0.01) and abolished the gender difference. In male rats cardiac muscarinic blockade attenuated BRS(PE) significantly more than did cardiac beta-adrenergic receptor blockade with propranolol (72+/-4.6 vs. 43+/-2.7; p < 0.01), which suggests greater dependence of BRS(PE) on the parasympathetic component. In females, muscarinic and beta-adrenergic blockade elicited similar attenuation of BRS(PE). The findings suggest that (i) BRS is differentially influenced by gender; female rats exhibit substantially lower BRS(PE) but similar BRS(NP) compared with age-matched male rats and (ii) the sexual dimorphism in BRS(PE) results, at least partly, from a smaller increase in vagal outflow to the heart in response to baroreceptor activation.     

A female head–neck model for rear impact simulations

Several mathematical cervical models of the 50th percentile male have been developed and used for impact biomechanics research. However, for the 50th percentile female no similar modelling efforts have been made, despite females being subject to a higher risk of soft tissue neck injuries. This is a limitation for the development of automotive protective systems addressing Whiplash Associated Disorders (WADs), most commonly caused in rear impacts, as the risk for females sustaining WAD symptoms is double that of males.In this study, a finite element head and neck model of a 50th percentile female was validated in rear impacts. A previously validated ligamentous cervical spine model was complemented with a rigid body head, soft tissues and muscles. In both physiological flexion-extension motions and simulated rear impacts, the kinematic response at segment level was comparable to that of human subjects. Evaluation of ligament stress levels in simulations with varied initial cervical curvature revealed that if an individual assumes a more lordotic posture than the neutral, a higher risk of WAD might occur in rear impact.The female head and neck model, together with a kinematical whole body model which is under development, addresses a need for tools for assessment of automotive protection systems for the group which is at the highest risk to sustain WAD.     

Gender Differences in Histamine-Induced Depolarization and Inward Currents in Vagal Ganglion Neurons in Rats

Evidence has shown gender differences regarding the critical roles of histamine in the prevalence of asthma, anaphylaxis, and angina pectoris. Histamine depolarizes unmyelinated C-type neurons without any effects on myelinated A-type vagal ganglion neurons (VGNs) in male rats. However, little is known if VGNs from females react to histamine in a similar manner. Membrane depolarization and inward currents were tested in VGNs isolated from adult rats using a whole-cell patch technique. Results from males were consistent with the literature. Surprisingly, histamine-induced depolarization and inward currents were observed in both unmyelinated C-type and myelinated A- and Ah-type VGNs from female rats. In Ah-type neurons, responses to 1.0 μM histamine were stronger in intact females than in males and significantly reduced in ovariectomized (OVX) females. In C-type neurons, histamine-induced events were significantly smaller (pA/pF) in intact females compared with males and this histamine-induced activity was dramatically increased by OVX. Female A-types responded to histamine, which was further increased following ovariectomy. Histamine at 300 nM depolarized Ah-types in females, but not Ah-types in OVX females. In contrast, the sensitivity of A- and C-types to histamine was upregulated by OVX. These data demonstrate gender differences in VGN chemosensitivity to histamine for the first time. Myelinated Ah-types showed the highest sensitivity to histamine across female populations, which was changed by OVX. These novel findings improve the understanding of gender differences in the prevalence of asthma, anaphylaxis, and pain. Changes in sensitivity to histamine by OVX may explain alterations in the prevalence of certain pathophysiological conditions when women reach a postmenopausal age.     

多疣狭口蛙昆明种群雌雄配对行为及形态适应选择

测量和比较采自昆明东北郊的24对抱对多疣狭口蛙(Kaloulaverrucosa)标本,同时野外观察其繁殖行为。配对雌雄蛙的体长、体重和头宽3个形态特征的Pearson相关系数大于0·5;择体长和体重作回归分析,结果表明,雌雄蛙体长选择和雌雄蛙体重配对都呈良好的线性关系。雌蛙选择雄蛙体长为自身体长的(81·8±5·7)%、体重为自身体重的(53·1±10·7)%的个体为最适配偶。雌蛙选择体长较长而体重较轻的雄蛙作为配偶,这样有利于形成较好的空间(雄性胸腹部皮肤腺长度,雌雄抱对时泄殖孔位置等)配对关系。多疣狭口蛙属于雌性选择模式,即雄蛙鸣叫,雌蛙受吸引,主动接近雄蛙,如果雄蛙条件适合则形成配对。     

中国汉族人的身体围度

2009~2013年在中国22个省、自治区测量了26695例(乡村男性8174例,城市男性4791例,乡村女性8327例,城市女性5403例)的头围、颈围、平静胸围、吸气时胸围、呼气时胸围、腹围、臀围、大腿围、小腿围、上臂围、前臂围、上臂最大围值,进行了围度与纬度、经度、年龄的相关分析,城市与乡村汉族、北方与南方汉族身体围度均数的比较。结果发现,男性的上臂围、上臂最大围与纬度无显著相关,其余10项围度均与纬度呈显著正相关。女性12项围度均与纬度呈显著正相关。男性、女性12项围度均与经度呈显著正相关,男性四肢围度多与年龄呈显著负相关。女性下肢围度也与年龄呈显著负相关,但上肢3项围度与年龄呈显著正相关。男性、女性躯干5项围度、颈围随年龄增加而增大。北方男性除头围、上臂围值与南方男性接近外,其余10项围度值均大于南方男性。北方女性12项围度值均大于南方女性。城市、乡村汉族12项围度的差异均具有统计学意义。城市汉族的各项围度均大于乡村汉族。     

Gender differences between hypocretin/orexin knockout and wild type mice: age,body weight,body composition,metabolic markers,leptin and insulin resistance

Female hypocretin knockout (Hcrt KO) mice have increased body weight despite decreased food intake compared to wild type (WT) mice. In order to understand the nature of the increased body weight, we carried out a detailed study of Hcrt KO and WT, male, and female mice. Female KO mice showed consistently higher body weight than WT mice, from 4 to 20 months (20–60%). Fat, muscle, and free fluid levels were all significantly higher in adult (7–9 months) as well as old (18–20 months) female KO mice compared to age‐matched WT mice. Old male KO mice showed significantly higher fat content (150%) compared to age‐matched WT mice, but no significant change in body weight. Respiratory quotient (?19%) and metabolic rates (?14%) were significantly lower in KO mice compared to WT mice, regardless of gender or age. Female KO mice had significantly higher serum leptin levels (191%) than WT mice at 18–20 months, but no difference between male mice were observed. Conversely, insulin resistance was significantly higher in both male (73%) and female (93%) KO mice compared to age‐ and sex‐matched WT mice. We conclude that absence of the Hcrt peptide has gender‐specific effects. In contrast, Hcrt‐ataxin mice and human narcoleptics, with loss of the whole Hcrt cell, show weight gain in both sexes.

     

Sex differences in energy expenditure in non-human primates

Female mammals bear the energetic costs of gestation and lactation. Therefore, it is often assumed that the overall energetic costs are greater for females than they are for males. However, the energetic costs to males of intrasex competition may also be considerable, particularly if males maintain a much larger body size than females. Using data from 19 non-human primates, this paper examines the relationship between male and female energetic costs both in the short term (daily energy expenditure) and the long term (the energetic cost of producing a single offspring). It is shown that the major determinant of sex differences in energetic costs is body size dimorphism. In the long term, the energetic costs are often greater for females, but, when male body size exceeds female body size by 60% or more, male energetic costs are greater than those for females. That is, in highly sexually dimorphic species the energetic costs of gestation and lactation for the females are matched by the energetic costs to the males of maintaining a large body size.     

Structural analysis of female and hermaphroditic flowers of a gynodioecious tree, Ocotea tenera (Lauraceae)

The evolution of gynodioecy from hermaphroditism involves modifications of floral structure such that male or female fitness is enhanced in hermaphrodites and females, respectively. We present an analysis of structural specialization of flowers of Ocotea tenera, in order to evaluate gender system evolution in this tropical tree species. Significant morphological and anatomical variation was found between high fruiting and low or nonfruiting trees. Female flowers were significantly smaller than hermaphroditic flowers, produced no viable pollen, and made relatively greater allocation to structures that increase female fitness. Hermaphroditic flowers were significantly larger than female flowers, produced copious quantities of pollen, and made relatively greater allocation to male structures. Analyses indicated that changes in allometries between whole-flower growth and growth of reproductive structures may have occurred, which enhance function of the flower and plant as a male or female. Efficiency of nutrient allocation for reproduction is argued to be a factor driving gender system evolution in Ocotea tenera.     

Virgin females compete for mates in the male lekking species Ceratitis capitata

Abstract. Aggressive behaviour occurring in intrasexual competition is an important trait for animal fitness. Although female intrasexual aggression is reported in several insect species, little is known about female competition and aggressive interactions in polygynous male lekking species. The interactions of female Mediterranean fruit flies, Ceratitis capitata (a male lekking species), with other females and mating pairs under laboratory conditions are investigated. Mature, unmated (virgin) females are aggressive against each other and against mating pairs, whereas immature females are not. Female aggression against other females decreases dramatically after mating; however, mated females maintain aggression against mating pairs. In addition, higher intrasexual aggression rates are observed for mature, virgin females than for virgin males of the same age. The results show that female aggressiveness is virginity related, suggesting female competition for mates. These findings have important implications for understanding the physiological aspects of a complex social behaviour such as aggression and should stimulate further research on female agonistic behaviour in male lekking mating systems.     

Metabolic response in type I and type II muscle fibers during a 30-s cycle sprint in men and women.

The acute metabolic response to sprint exercise was studied in 20 male and 19 female students. We hypothesized that the reduction of muscle glycogen content during sprint exercise would be smaller in women than in men and that a possible gender difference in glycogen reduction would be higher in type II than in type I fibers. The exercise-induced increase in blood lactate concentration was 22% smaller in women than in men. A considerable reduction of ATP (50%), phosphocreatine (83%), and glycogen (35%) was found in type II muscle fibers, and it did not differ between the genders. A smaller reduction of ATP (17%) and phosphocreatine (78%) was found in type I fibers, and it did not differ between the genders. However, the exercise-induced reduction in glycogen content in type I fibers was 50% smaller in women than in men. The hypothesis was indeed partly confirmed: the exercise-induced glycogen reduction was attenuated in women compared with men, but the gender difference was in type I rather than in type II fibers. Fiber-type-specific and gender-related differences in the metabolic response to sprint exercise might have implications for the design of training programs for men and women.     

Gender differences in upper airway compliance during NREM sleep: role of neck circumference.

It has been proposed that the gender difference in sleep apnea prevalence is related to gender differences in upper airway structure and function. We hypothesized that men would have smaller retropalatal cross-sectional area and higher compliance during sleep compared with women. Using upper airway imaging, we measured upper airway cross-sectional area and retropalatal compliance in wakefulness and non-rapid eye movement (NREM) sleep in 15 men and 15 women without sleep-disordered breathing. Cross-sectional area at the beginning of inspiration tended to be larger in men compared with women in both wakefulness [194.5 +/- 21.3 vs. 138.8 +/- 12.0 (SE) mm(2)] and NREM sleep (111.1 +/- 17.6 vs. 83.3 +/- 11.9 mm(2); P = 0.058). There was no significant difference, however, after correction for body surface area. Retropalatal compliance also tended to be higher in men during both wakefulness (5.9 +/- 1.4 vs. 3.1 +/- 1.4 mm(2)/cmH(2)O; P = 0.006) and NREM sleep (12.6 +/- 2.7 vs. 4.7 +/- 2.6 mm(2)/cmH(2)O; P = 0.055). However, compliance was similar in men relative to women after correction for neck circumference. We conclude that the gender difference in retropalatal compliance is more accurately attributed to differences in neck circumference between the genders.