Systemic organization of functional interhemisphere asymmetry. Mirror asymmetry

The systemic organization of hemispherical asymmetry at the behavioral, neurophysiological, and biochemical levels was studied. An interconnection and hierarchic coordination of the parameters of different levels were revealed, which are confirmed by multiple correlations between them. An interrelation between the processes of peroxidation of brain membrane lipids, the level of direct current potential, and the behavior of animals was shown. A significant difference in correlations between right-hander and left-hander animals was found.     

Easter Islander palmar dermatoglyphics: sexual dimorphism, bilateral asymmetry, and family polymorphism

The palmar prints of 297 male and female Easter Islanders were analyzed according to the Penrose and Loesch topological classification system. While the frequencies of most pattern elements were not found to differ significantly between the sexes, the placement of the axial triradius was found to be highly significant (P less than 0.01). Both males and females were found to exhibit considerable bilateral asymmetry in the a-b count and in the atd angle, but there was no significant difference between the sexes in the amount of asymmetry expressed. Family data for a small subset of the sample (51 individuals) were subjected to further statistical analysis, from which significant results (P less than 0.05) were obtained both on chi-square tests for frequency of pattern elements and ANOVA tests for a-b counts, atd angle, and A-line exit. The implications of these results are considered from a developmental perspective. It is suggested that a particular pattern combination (termed a formula) could be used to represent a default value and that other formulae might then be considered as deviations from this default value. Such variation, theoretically at least, might be traced to genetic influences or to the embryological environment present during the time of dermatoglyphic formation.     

Physical criteria of pathological processes. II. Modulating role of functional interhemisphere asymmetry in forming and immune response in rheumatic diseases

The level of the brain permanent potential as a physiological criterion of the functional interhemisphere asymmetry, as well as immunological and biochemical characteristics of peripheral blood in patients with systemic rheumatic diseases were studied. It was found that the distribution of the characteristics of immune response in patients with different types of interhemisphere asymmetry. Significant differences were observed for average values of biochemical and immunological characteristics, their dispersions, as well as for the structure of relationships between the type of the interhemisphere asymmetry and immunobiochemical characteristics.     

Socio-bioenergetics and sexual dimorphism in primates

Socio-bioenergetics is presented as a practical method of estimating energy budgets of primates in a social context. Energy budgets are estimated on the basis of behavioral observations and a series of empirical formulae, which consider body weight, activity, and reproductive status. Data on a captive colony of Sykes' monkeys and baboons are incorporated as illustrations of the possible effects of group composition, body size, reproductive status, and activity patterns on energy requirements.Supported by the Wenner-Gren Foundation for Anthropological Research Incorporated and the National Science Foundation Grant GU-1598.     

Harderianization is another sexual dimorphism of rat exorbital lacrimal gland

The exorbital lacrimal glands (ELG) of rats were examined for both sexes to determine what degree of harderianization occurred as a function of age and after castration, and to investigate its time course and origin in ELG. Light microscopically, very small Harderian foci were seen in the ELG of both sexes at 3 weeks of age. As the male rats became older, the relative volume of the Harderian gland (HG) cells in the ELG increased. At age 6 months, the value was 1.25 +/- 0.31% in males and 0.13 +/- 0.05% in females (p less than 0.05). After castration, a significant decrease (0.21 +/- 0.01%, p less than 0.05) was observed in that of male ELG. In contrast, in female ELG, HG cells were inconspicuous and the relative volume of those did not vary during this experimental period or after castration. It appeared that the HG cells had developed from undifferentiated basal cells of the acini and the intercalated ducts in the ELG at age 2-6 months. Then, at age 22 months, they also probably developed from those of the excretory ducts of the ELG.     

Pelvic growth: ontogeny of size and shape sexual dimorphism in rat pelves

The mammalian pelvis is sexually dimorphic with respect to both size and shape. Yet little is known about the differences in postnatal growth and bone remodeling that generate adult sexual dimorphism in pelvic bones. We used Sprague-Dawley laboratory rats (Rattus norvegicus), a species that exhibits gross pelvic size and shape dimorphism, as a model to quantify pelvic morphology throughout ontogeny. We employed landmark-based geometric morphometrics methodology on digitized landmarks from radiographs to test for sexual dimorphism in size and shape, and to examine differences in the rates, magnitudes, and directional patterns of shape change during growth. On the basis of statistical significance testing, the sexes became different with respect to pelvic shape by 36 days of age, earlier than the onset of size dimorphism (45 days), although visible shape differences were observed as early as at 22 days. Males achieved larger pelvic sizes by growing faster throughout ontogeny. However, the rates of shape change in the pelvis were greater in females for nearly all time intervals scrutinized. We found that trajectories of shape change were parallel in the two sexes until age of 45 days, suggesting that both sexes underwent similar bone remodeling until puberty. After 45 days, but before reproductive maturity, shape change trajectories diverged because of specific changes in the female pelvic shape, possibly due to the influence of estrogens. Pattern of male pelvic bone remodeling remained the same throughout ontogeny, suggesting that androgen effects on male pelvic morphology were constant and did not contribute to specific shape changes at puberty. These results could be used to direct additional research on the mechanisms that generate skeletal dimorphisms at different levels of biological organization.     

Ontogeny and sexual dimorphism of estradiol-2-hydroxylase activity in rat liver microsomes

A radio-enzymatic method was used to measure the activity of estradiol-2-hydroxylase in liver microsomes of male and female Wistar rats, ranging in age from 10 to 63 days. In pre-pubertal rats (10-30 days) the Vmax increased, but revealed no sex differences. After 30 days of age, however, it decreased in females. In males, on the other hand, it increased still further, reaching a maximum in adulthood. The apparent Km showed no significant sex differences in pre-pubertal rats, but appeared to decline after puberty in females. In females puberty was also associated with the appearance of important changes in the kinetic properties of estradiol-2-hydroxylase. These changes were reflected in hyperbolic Lineweaver-Burk plots. Hill plots of this data gave straight lines with slopes significantly less than one--indicating negative cooperativity. Alternatively the hyperbolic Lineweaver-Burk plots could mean that the enzyme consists of more than one form, which act on the same substrate, but with different affinities. It is concluded that development in female Wistar rats is associated with important qualitative changes in the kinetic properties of estradiol-2-hydroxylase and that factors which become operative during puberty play a key role in initiating these changes.     

Statistics of sexual size dimorphism

In comparative studies of sexual size dimorphism (SSD), the methods used to quantify dimorphism are controversial. SSD is commonly expressed as a ratio between species mean values of males and females, such as M/F or (M-F)/([M+F]/2), but a number of investigators have suggested that ratios should not be used, mainly because their distributions usually violate the assumptions of parametric statistical tests, or because they lead to spurious relationships that invalidate the interpretation and statistical significance of regressions and correlations. As an alternative to ratios, the comparative study of SSD can be conducted by a combination of regression with sex-specific data and residuals from this regression. Twenty-five data sets were selected from the literature and used to duplicate a variety of statistical procedures commonly employed in studies of SSD. All analyses were repeated with five different ratios and with methods that avoid the calculation of any ratios. These data and a review of the statistical properties of ratios and residuals indicate that: (1) most of the ratios used in the SSD literature are unnecessary, and several commonly used ratios are statistically inferior to others. Only two ratios are needed, one on a logarithmic scale and one on a linear scale; (2) there is no problem with spurious correlation or non-normality when ratios are used in several types of statistical procedures commonly employed in studies of SSD; (3) residuals cannot replace ratios for the evaluation of many questions regarding the pattern of SSD among species; and (4) residuals usually are used incorrectly, leading to misspecified regression equations. Most of the questions for which residuals are used should be addressed by multiple regression. These results apply to studies using comparative methods with or without adjustments for phylogenetic effects.     

Electrophysiological and neuroanatomical evidence of sexual dimorphism in aortic baroreceptor and vagal afferents in rat

Evidence for sexual dimorphism in autonomic control of cardiovascular function is both compelling and confounding. Across healthy and disease populations sex-associated differences in neurocirculatory hemodynamics are far too complex to be entirely related to sex hormones. As an initial step toward identifying additional physiological mechanisms, we investigated whether there is a sex bias in the relative expression of low-threshold-myelinated and high-threshold-unmyelinated aortic baroreceptor afferents in rats. These two types of afferent fibers have markedly different reflexogenic effects upon heart rate and blood pressure and thus the potential impact upon baroreflex dynamics could be substantial. Our results, using a combination of a patch-clamp study of fluorescently identified aortic baroreceptor neurons (ABN) and morphometric analysis of aortic baroreceptor nerve fibers, demonstrate that females exhibit a greater percentage of myelinated baroreceptor fibers (24.8% vs. 18.7% of total baroreceptor fiber population, P < 0.01) and express a functional subtype of myelinated ABN rarely found in age-matched males (11% vs. 2.3%, n = 107, P < 0.01). Interestingly, this neuronal phenotype is more prevalent in the general population of female vagal afferent neurons (17.7% vs. 3.8%, n = 169, P < 0.01), and ovariectomy does not alter its expression but does lessen neuronal excitability. These data suggest there are fundamental neuroanatomical and electrophysiological differences between aortic baroreceptor afferents of female and male rats. Possible explanations are presented as to how such a greater prevalence of low-threshold myelinated afferents could be a contributing factor to the altered baroreflex sensitivity and vagal tone of females compared with males.     

On sexual dimorphism in immune function

Sexual dimorphism in immune function is a common pattern in vertebrates and also in a number of invertebrates. Most often, females are more 'immunocompetent' than males. The underlying causes are explained by either the role of immunosuppressive substances, such as testosterone, or by fundamental differences in male and female life histories. Here, we investigate some of the main predictions of the immunocompetence handicap hypothesis (ICHH) in a comparative framework using mammals. We focus specifically on the prediction that measures of sexual competition across species explain the observed patterns of variation in sex-specific immunocompetence within species. Our results are not consistent with the ICHH, but we do find that female mammals tend to have higher white blood cell counts (WBC), with some further associations between cell counts and longevity in females. We also document positive covariance between sexual dimorphism in immunity, as measured by a subset of WBC, and dimorphism in the duration of effective breeding. This is consistent with the application of 'Bateman's principle' to immunity, with females maximizing fitness by lengthening lifespan through greater investment in immune defences. Moreover, we present a meta-analysis of insect immunity, as the lack of testosterone in insects provides a means to investigate Bateman's principle for immunity independently of the ICHH. Here, we also find a systematic female bias in the expression of one of the two components of insect immune function that we investigated (phenoloxidase). From these analyses, we conclude that the mechanistic explanations of the ICHH lack empirical support. Instead, fitness-related differences between the sexes are potentially sufficient to explain many natural patterns in immunocompetence.     

Host sexual dimorphism and parasite adaptation

In species with separate sexes, parasite prevalence and disease expression is often different between males and females. This effect has mainly been attributed to sex differences in host traits, such as immune response. Here, we make the case for how properties of the parasites themselves can also matter. Specifically, we suggest that differences between host sexes in many different traits, such as morphology and hormone levels, can impose selection on parasites. This selection can eventually lead to parasite adaptations specific to the host sex more commonly encountered, or to differential expression of parasite traits depending on which host sex they find themselves in. Parasites adapted to the sex of the host in this way can contribute to differences between males and females in disease prevalence and expression. Considering those possibilities can help shed light on host-parasite interactions, and impact epidemiological and medical science.     

Visualizing sexual dimorphism in the brain

Sexually dimorphic behaviors are likely to involve neural pathways that express the androgen receptor (AR). We have genetically modified the AR locus to visualize dimorphisms in neuronal populations that express AR. Analysis of AR-positive neurons reveals both known dimorphisms in the preoptic area of the hypothalamus and the bed nucleus of the stria terminalis as well as novel dimorphic islands in the basal forebrain with a clarity unencumbered by the vast population of AR-negative neurons. This genetic approach allows the visualization of dimorphic subpopulations of AR-positive neurons along with their projections and may ultimately permit an association between neural circuits and specific dimorphic behaviors.     

Sexual dimorphism of the weight of internal organs in fetal ontogenesis

The paper contains results of the investigation on the sexual differentiation of the weight of brain, heart, lungs, liver, spleen, kidneys, adrenal glands and thymus. The studies were carried out on a total of 632 fetuses (349 males and 283 females) and 1276 newborns (795 males and 481 females) in the age from 17 to 43 weeks of life. The study of sexual dimorphism of internal organs concludes that in the period of fetal development of man this dimorphism is weakly developed.     

Evolution of mating preference and sexual dimorphism

A quantitative genetic model of the joint evolution of female mating preferences and sexual dimorphism in homologous characters of the sexes is described for polygamous species with no male parental effort, such that mating preferences are selectively neutral and evolve only by indirect selection on genetically correlated characters. The male character and the homologous female character are each under stabilizing natural selection toward an optimum phenotype. At an evolutionary equilibrium the female character under natural selection is at its optimum, whereas there is a line of possible equilibria between female mating preferences and the male character. The line of equilibria may be stable or unstable, depending on the intensity of natural selection, the type of mating preferences, and the inheritance of the characters. Various mechanisms for maladaptive evolution of mating preferences and sexual dimorphism are discussed.     

Hormonal and meta-hormonal determinants of sexual dimorphism

The role of hormones in the determination of sexual characteristics has been known for several decades. It has been shown, for example, that several products, including sex steroids, may influence the body development pattern, metabolic pathways, fat and muscle distribution and vocal cord anatomy, thus producing an overall outcome consistent with a masculine or feminine phenotypic pattern. These qualities are usually described as secondary sexual traits, so as to be distinguished from primary sex traits, usually referring to the gonads and external genitalia. However, it must be noted that hormonal regulation may not explain the full range of the sexual phenotype, since the central nervous system retains a significant role in the establishment of sexual identity, thus giving rise to a higher sex determination stage exclusively described in humans, namely behavioral or psychological sex. Recently, it has been suggested that differences among the sexes are not limited to brain function but they may also refer to anatomical differences and different biochemical profiles, including a distinct pattern of AR and ER distribution. This new aspect of sexual dimorphism suggests a whole system of meta-hormonal regulation, recently described as the sexual brain model. The role of local androgen and/or estrogen concentrations in the initial establishment of brain sexual dimorphism is still under evaluation, since the first results are relatively inconclusive and no direct cause and effect relationship has been proven so far. On the other hand, sex hormones have recently been found to participate in processes well beyond their initially suggested spectrum of action. For instance, ER interacts with EGFR in a number of ways, affecting development of a number of epithelial structures. Estrogen receptors have also been detected in a number of non-classic targets of steroids, such as the brain and the lungs. This observation may imply that sexual dimorphism goes a lot deeper than previously estimated, affecting virtually every organic system, suggesting, in essence, the existence of two different functional models for the whole human body, formulated and conserved throughout the evolutionary progress.     

Leucine aminopeptidase (LAP) activity and sexual dimorphism in rat exorbital lacrimal gland

Leucine amonopeptidase (LAP) activity was histochemically studied in the rat exorbital lacrimal gland. The enzyme is present in the secreting cells of both male and female prepuberal rats, in vivo and in monolayer cultures, while in the adult rat it is demonstrable only in the female. Furthermore, LAP is influenced by the sex hormones, disappearing in the female gland after testosterone treatment and appearing in the adult male gland after administration of estradiol or cyproterone acetate. These results show that the behaviour of LAP can be considered as another character of sexual dimorphism of the rat exorbital gland. Furthermore, our findings, showing an inverse relationship between LAP activity and the PAS positivity of the secretion products, suggest the hypothesis that the presence of this exopeptidase could induce qualitative modifications of one or more secreted glycoprotein.