Sexual dimorphism in the face of Australopithecus africanus

Recently discovered crania of Australopithecus africanus from Sterkfontein Member 4 and Makapansgat enlarge the size range of the species and encourage a reappraisal of both the degree and pattern of sexual dimorphism. Resampling methodology (bootstrapping) is used here to establish that A. africanus has a greater craniofacial size range than chimpanzees or modern humans, a range which is best attributed to a moderately high degree of sexual dimorphism. Compared to other fossil hominins, this variation is similar to that of Homo habilis (sensu lato) but less than that of A. boisei. The finding of moderately high dimorphism is corroborated by a CV-based estimate and ratios between those specimens considered to be male and those considered to be female. Inferences about the pattern of craniofacial dimorphism in the A. africanus face currently rely on the relationship of morphology and size. Larger specimens, particularly Stw 505, show prominent superciliary eminences and glabellar regions, but in features related in part to canine size, such as the curvature of the infraorbital surface, large and small specimens of A. africanus are similar. In this respect, the pattern resembles that of modern humans more so than chimpanzees or lowland gorillas. A. africanus may also show novel patterns of sexual dimorphism when compared to extant hominines, such as in the form of the anterior pillar. However, males of the species do not exhibit characteristics of more derived hominins, such as A. robustus.     

Sexual dimorphism in the physiques of World Championship divers

The aim of this study was to evaluate sexual dimorphism in male (n = 43) and female (n = 39) springboard and platform divers at the 1991 World Diving Championships in Perth, Western Australia. In addition to recording the age, height and body mass of each diver, measurements were taken of 8 skinfolds, 13 girths, 8 breadths and depths, and 11 lengths. The derived variables were somatotype, sum of 6 skinfolds (SUM6) and height-adjusted proportional z-scores. The mean (+/- s) values for the males were: age, 22.2 +/- 4.6 years; height, 171 +/- 9 cm; body mass, 66.7 +/- 10.2 kg; somatotype, 2.0-5.3-2.4 +/- 0.5-1.0-0.8; SUM6, 45.9 +/- 11.4 mm. For the females, these values were: age, 20.9 +/- 3.8 years; height, 161 +/- 6 cm; body mass, 53.7 +/- 5.5 kg; somatotype, 2.8-3.8-2.8 +/- 0.7-1.0-0.9; SUM6, 65.6 +/- 17.0 mm. The males were taller, heavier, more mesomorphic, less endomorphic and had a smaller SUM6 than the females (P < 0.01). A series of discriminant function analyses were applied to groups of variables. Wilks' lambda and the overall F-ratio were highly significant (P < 0.001), with correct classification of sex reaching 84-99%. The best combinations of variables were as follows: (1) absolute size, 3 girths + SUM6, or body mass + SUM6 + height (Wilks' lambda = 0.17-0.35); (2) relative size, 2 girths + SUM6 + body mass. Combinations of breadths and lengths, skinfolds, or somatotype components, were less successful, with 84-87% classified correctly (Wilks' lambda = 0.40-0.48). We conclude that, in addition to the expected absolute size differences, sexual dimorphism between male and female divers can be explained by differences in relative size, skinfolds and somatotype, and that these differences may have implications for coaching and selection in diving.     

Sex differences in the relationship between visual memory and MRI hippocampal volumes.

This study investigated sex differences in the relationships between visual memory and MRI-determined hippocampal volume data before and after right and left temporal lobectomy (TL). Preoperative visual memory and postoperative visual memory change were evaluated by the Wechsler Memory Scale-Revised, and MRI hippocampal volumes were obtained in 54 right (28 men and 26 women) and 75 left (33 men, 42 women) TL patients. Preoperative visual memory and postoperative visual memory change were significantly related to the difference between hippocampal volumes (DHV) in right TL women but not right TL men. That is, extirpation of a large right hippocampus was significantly associated with a visual memory decline, but only in women. These findings support the presence of sexually dimorphic brain function and suggest that visual memory ability in women may be less plastic after a developmentally early right mesial temporal insult. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual arousal to rape depictions: Individual differences.

145 male undergraduates participated (a) in an orientation session in which personality variables, sexual motivations, sexual experience, and self-reported likelihood of raping were assessed and (b) in a laboratory session in which they listened to 1 of 8 audiotaped depictions of an interaction involving sexual acts between a man and a woman. The content of these depictions was systematically manipulated along the dimensions of consent, pain, and outcome. Later in the 2nd session, Ss listened to a 2nd audiotaped portrayal of either nonconsenting or consenting sex. Their sexual arousal was assessed throughout this 2nd session by penile tumescence and self-reports. Results highlight the importance of the interaction between individual differences variables and manipulations in the content of the portrayals in affecting sexual arousal to rape depictions. Support was obtained for the prediction that such arousal is not an isolated response but is associated with other measures of sexually aggressive tendencies. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual dimorphism in physiological performance of whiptail lizards (genus Cnemidophorus)

Numerous studies have examined sexual dimorphism in the morphology and behavior of vertebrates; very few, however, have explicitly investigated the possibility of gender differences in physiological performance, despite the observations of such differences in humans. In this study, I investigated physiological sexual dimorphism in the lizard genus Cnemidophorus by measuring five whole-animal traits, all of which are likely to influence fitness in these species: burst speed, endurance, maximal exertion capacity, standard metabolic rate, and evaporative water loss rate. Because at least some of these traits are known to be strongly influenced by body size, I tested for dimorphism using both absolute and size-corrected trait values. An examination of six Cnemidophorus species and subspecies revealed a strong trend toward higher absolute trait values in males for all variables except endurance. Most of the dimorphism in standard metabolic rate and evaporative water loss rate could be explained by differences in body mass between males and females; for the locomotor traits, however, body size explained only a small fraction of the overall sexual dimorphism. The portion of trait differences not explained by body size was likely due to gender differences in physiology, such as differences in relative muscularity and fat content.     

Sexual dimorphism in the pelvic midplane and its relationship to Neandertal reproductive patterns

The fragmentary nature of the fossil record has limited the analysis of the Neandertal pelvis to the superior pubic ramus and the pelvic inlet. From an obstetric viewpoint, the pelvic midplane or "plane of least dimensions," defined by the distance between the ischial spines, must be considered in the analysis of hominid reproduction. We examined the relationship between BSD and weight in a mixed sex hospital population undergoing diagnostic computed tomography (CT) scans (41 females and 40 males). Because femoral head diameter squared (FH(2)) has been used as a proxy for weight in skeletal populations, it was also analyzed with respect to BSD and weight. Bivariate regression analysis of BSD with other body dimensions indicates the presence of significant sex differences. In females, but not in males, weight is a statistically significant predictor of BSD. FH(2) is an even better predictor of BSD in females while nonsignificant in males. Although weight and FH(2) are significantly correlated with BSD in females, FH(2) does not predict weight in females as well as it does in males. The positive correlation between skeletal frame size and BSD in females is indicative of an evolutionary pattern that must take into account the pressures of reproduction. Our results indicate that critical dimensions of the pelvis must increase as the maternal skeleton becomes larger. These results provide a context for the interpretation of the reproductive patterns of a relatively robust hominid population like the Neandertals.     

Sexual orientation-related differences in prepulse inhibition of the human startle response.

Prepulse inhibition (PPI) refers to a reduction in the startle response to a strong sensory stimulus when this stimulus is preceded by a weaker stimulus--the prepulse. PPI reflects a nonlearned sensorimotor gating mechanism and also shows a robust gender difference, with women exhibiting lower PPI than men. The present study examined the eyeblink startle responses to acoustic stimuli of 59 healthy heterosexual and homosexual men and women. Homosexual women showed significantly masculinized PPI compared with heterosexual women, whereas no difference was observed in PPI between homosexual and heterosexual men. These data provide the first evidence for within-gender differences in basic sensorimotor gating mechanisms and implicate the known neural substrates of PPI in human sexual orientation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual dimorphism in ultrasonic vocalizations of mice (Mus musculus): Gonadal hormone regulation.

Male mice, during courtship and sexual behavior, vocalize substantially more 70-kHz ultrasounds than do females. Four experiments conducted with 109 male and female DBA/2J and ADK2F? mice demonstrated that testosterone propionate (TP) substantially increased ultrasonic emissions and mounting by ovariectomized females and that long-term gonadectomized males and females increased their amount of ultrasound production in response to TP to approximately the same levels. From these results it is suggested that the sexual dimorphism normally seen in ultrasonic vocalizations can be accounted for by the activational effects of androgen in adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual dimorphism in facial shapes and their discrimination in Japanese monkeys (Macaca fuscata).

The authors examined the ability of Japanese monkeys (Macaca fuscata) to discriminate between sexes based on facial features. The shape and position of facial features (facial morphology) were measured to quantify the differences between sexes. The distance between the chin and nose was longer in males than females, and the outline of the face around the upper jaw and upper face differed between sexes. Using operant conditioning, 2 monkeys succeeded in discriminating sex based on facial pictures. Furthermore, they successfully generalized the discrimination to novel pictures of faces. Tests with morphed pictures of faces revealed that the monkeys used facial morphology to discriminate between males and females. Our results suggest that Japanese monkeys have sexual dimorphism in facial shape and they can use the morphological differences to discriminate conspecific sex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in the effects of captivity on hippocampus size in brown-headed cowbirds (Molothrus ater obscurus).

In brood parasitic cowbirds, hippocampus (Hp) size is correlated with environmental spatial memory demands. Searching for host nests is the presumed causal factor influencing cowbird Hp size, because Hp volumes vary across species, sexes, and seasons according to nest-searching participation. Brown-headed cowbirds have female-only nest searching and, at least in the eastern subspecies, a larger Hp in females than in males, suggesting that nest searching influences cowbird Hp size. We predicted that female brown-headed cowbirds housed in aviaries lacking host nests would have a smaller Hp than wild-caught females whereas males would be unaffected. We found that the Hp was smaller in captive females, but not males, compared to their wild-caught counterparts. This did not appear to be due to general effects of an impoverished environment on all brain regions. Our results imply that interruption of nest searching in cowbirds prevents seasonal increase in Hp size in females. Future studies should isolate which behavioral differences between wild and captive birds contributed to captivity-induced changes in Hp volume in females while not affecting males. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual dimorphism in the tooth crown dimensions of the second deciduous and first permanent molars of Taiwan Chinese

Corticosteroids such as prednisone are commonly prescribed for a variety of illnesses mediated by the immune system. This paper reviews the available literature on mood symptoms during corticosteroid treatment. Few studies have used well-recognized measures of symptoms or clearly defined diagnostic criteria to characterize such mood changes. The limited data available suggest that symptoms of hypomania, mania, depression, and psychosis are common during therapy. Symptoms appear to be dose dependent and generally begin during the first few weeks of treatment. Risk factors for the development of mood instability or psychosis are not known. The similarities of the psychiatric symptoms resulting from corticosteroid treatment to the symptoms of bipolar disorder are discussed.     

拜格诺理论在悬振锥面选矿机分选中的应用

根据拜格诺剪切理论,对悬振锥面选矿机分选机理进行阐述。结合微细粒矿物特征,通过简化假设和理论计算,对分选锥面上矿浆固有剪切分散压与设备运转附加剪切分散压进行了分析,探讨了矿粒悬浮分层的理论条件。研究结果表明:在使用悬振锥面选矿机分选时,分选锥面上矿浆流膜主要呈层流流态,矿浆中颗粒群受设备回旋振动产生的附加剪切分散压是矿粒悬浮分层的关键因素,证明了悬振锥面选矿机分选矿物的可行性,为论证细粒矿物重选设备的分选理论提供参考。     

Mechanisms for species differences in receptor-mediated carcinogenesis

Species differences resulting from a number of mechanisms are common in receptor-mediated chemical carcinogenesis. In this review, examples of possible mechanisms underlying these differences are discussed, including ligand metabolism, receptor polymorphisms, receptor isoforms, receptor levels, and crosstalk between signal transduction pathways. In addition, a number of other mechanisms also are likely to be important. The developmental state of the animal will determine the expression of receptors in different tissues. The regulatory pathways for cell proliferation and cell death and cell cycle check point controls can vary among species and tissues. Adaptation or potentiation of responses during chronic exposures to chemicals can greatly influence species differences. The mechanisms of adaptive processes are poorly understood but probably highly important for chronic toxicities such as cancer. Finally, different species may have different stem cell populations that are the targets for neoplastic transformation, and this will influence receptor-mediated carcinogenic responses. The implications of species differences in receptor-mediated responses for risk assessment are discussed.     

Sexual dimorphism in the social proximity behavior of Japanese quail (Coturnix coturnix japonica).

Previous research by the present authors (see record 1986-16367-001) showed that after opportunity for copulation, male Japanese quail spent about 75% of their time throughout daylight hours near a window that provided visual access to a female conspecific. In Exp I of the present study, 8 female Japanese quail typically spent less than 20% of their time near a window that provided visual access to 1 of 8 male conspecifics under comparable conditions. In Exp II, using the same Ss, a small clear plastic cage was placed in a large test arena, and Ss were observed when the cage was either empty or contained a sexual partner. Males tended to remain much closer to the cage when it contained a female conspecific than when it was empty. In contrast, the presence of a male did not significantly attract females to the cage area. These findings demonstrate strong sexual dimorphism in the social proximity behavior of Japanese quail. Results are discussed in terms of implications concerning the social structure of Japanese quail and implications for studies of sexual classical conditioning. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impact of differences in ultrasound and computed tomography volumes on treatment planning of permanent prostate implants

PURPOSE: Both ultrasound (US) and computerized tomography (CT) images have been used in the planning of prostate interstitial therapy. Ultrasound images more clearly define the apex and capsule of the prostate, while CT images define seed positions for postimplant dosimetry. Proper registration of the US volume with the CT volume is critical to the assessment of dosimetry. We therefore compared US and CT prostate volumes to determine if differences were significant. METHODS AND MATERIALS: Ten consecutive patients entered in an interstitial implant program were studied by pretreatment US. In addition, pretreatment CT scans were obtained and three physicians independently outlined the dimensions of the prostate on these images. The patients subsequently underwent placement of radioactive 125I or 103Pd. Postimplant CT images were obtained the next day and the postimplant prostate volumes were outlined by the same three physicians. Seven of 10 patients underwent late CT scans 9-14 months postimplant for comparison of preimplant and immediate postimplant CT studies. RESULTS: There were differences between US and CT volumes. Although the physician-to-physician variation was significant, the trends were consistent, with US prostate volume typically smaller (47%) than the preimplant CT volume and markedly smaller (120%) than the postimplant CT volume. Prostate volumes derived from late CT images did not consistently return to preimplant levels. CONCLUSIONS: Significant differences in volume of the prostate structure were found between US and CT images. The data suggests that: (a) Implants planned on CT tend to overestimate the size of the prostate and may lead to unnecessary implantation of the urogenital diaphragm and penile urethra. (b) Registration of initial US and postimplant CT prostate volumes required for accurate dosimetry is difficult due to the increased volume of prostate secondary to trauma. (c) Further study to determine the optimal time for the postimplant CT is necessary.     

高职院校学生能力培养的误区与现代转型

高职院校大学生能力的培养是新形势下高等职业教育改革与发展面临的一个全新课题.重新梳理与认识长期以来高职院校学生能力培养过程中的误区与缺失,对于确立高职院校学生能力培养的目标与定位,探究人才培养模式,促进高职大学生能力培养的现代转型.适应时代发展有着重要的价值导向和现实意义.