Searching for the Advantages of Virus Sex

Origins of Life and Evolution of Biospheres - Sex (genetic exchange) is a nearly universal phenomenon in biological populations. But this is surprising given the costs associated with sex. For...     

Vomeronasal receptors in Turtles

Summary The functional similarities observed with electrophysiological techniques between olfactory and vomeronasal receptors allow speculation that morphological details essential to the common function should be observed in both cases. Both mucosae have primary receptors within the epithelium which are surrounded, but not completely isolated, by so-called supporting cells. These last secrete a granular product. In both epithelia receptor cells contact each other at the axonal, perikaryal, dendritic and junctional complex levels. The axons of the two types of receptors are unmyelinated and their diameter ranges from 0.1 to 0.4 micron. The most interesting difference between the two types of receptors lies at the level of their exposed endings. The olfactory vesicle, as it is classically represented in olfactory receptors and is common in those of turtles in the form of a ball-like protrusion above the epithelial surface, is usually missing in the vomeronasal receptors. These have a tapering cone-shaped irregular projection always complicated by a set of branched microvilli. They do, furthermore, consistently lack cilia. This observation is in agreement with recent TEM observations. The assumption that cilia are essential in the mechanism of olfactory transduction is discussed on the basis of these anatomical findings.     

Biogenic Amines in the Vomeronasal Organ

The vomeronasal organ of frog and mouse was investigated forthe presence and content of serotonin and catecholamines bymeans of high-performance liquid chromatography. Measurableamounts of serotonin, adrenaline and noradrenaline were foundin the vomeronasal organ of adult individuals of both species.The amine content varied with sex of adult frogs and mice andsexual maturity of mice. In preliminary experiments, acute exposureto male urine containing pheromone affected the amine contentin the vomeronasal organ of adult female mice. These data suggestthat functional sex dimorphism is present in the vomeronasalorgan, and biochemical changes therein take place accordingto stage of sexual maturity. The role of biogenic amines inthe vomeronasal organ deserves further study. Chem. Senses 22:439–445, 1997.     

Molecular Sex Differences in Human Serum

Background

Sex is an important factor in the prevalence, incidence, progression, and response to treatment of many medical conditions, including autoimmune and cardiovascular diseases and psychiatric conditions. Identification of molecular differences between typical males and females can provide a valuable basis for exploring conditions differentially affected by sex.

Methodology/Principal Findings

Using multiplexed immunoassays, we analyzed 174 serum molecules in 9 independent cohorts of typical individuals, comprising 196 males and 196 females. Sex differences in analyte levels were quantified using a meta-analysis approach and put into biological context using k-means to generate clusters of analytes with distinct biological functions. Natural sex differences were established in these analyte groups and these were applied to illustrate sexually dimorphic analyte expression in a cohort of 22 males and 22 females with Asperger syndrome. Reproducible sex differences were found in the levels of 77 analytes in serum of typical controls, and these comprised clusters of molecules enriched with distinct biological functions. Analytes involved in fatty acid oxidation/hormone regulation, immune cell growth and activation, and cell death were found at higher levels in females, and analytes involved in immune cell chemotaxis and other indistinct functions were higher in males. Comparison of these naturally occurring sex differences against a cohort of people with Asperger syndrome indicated that a cluster of analytes that had functions related to fatty acid oxidation/hormone regulation was associated with sex and the occurrence of this condition.

Conclusions/Significance

Sex-specific molecular differences were detected in serum of typical controls and these were reproducible across independent cohorts. This study extends current knowledge of sex differences in biological functions involved in metabolism and immune function. Deviations from typical sex differences were found in a cluster of molecules in Asperger syndrome. These findings illustrate the importance of investigating the influence of sex on medical conditions.     

Sex Differences in Detecting Sexual Infidelity

Despite the importance of extrapair copulation (EPC) in human evolution, almost nothing is known about the design features of EPC detection mechanisms. We tested for sex differences in EPC inference-making mechanisms in a sample of 203 young couples. Men made more accurate inferences (φ_men = 0.66, φ_women = 0.46), and the ratio of positive errors to negative errors was higher for men than for women (1.22 vs. 0.18). Since some may have been reluctant to admit EPC behavior, we modeled how underreporting could have influenced these results. These analyses indicated that it would take highly sex-differentiated levels of underreporting by subjects with trusting partners for there to be no real sex difference. Further analyses indicated that men may be less willing to harbor unresolved suspicions about their partners’ EPC behavior, which may explain the sex difference in accuracy. Finally, we estimated that women underreported their own EPC behavior (10%) more than men (0%).     

Sex Differences in Hadza Dental Wear Patterns

Among hunter-gatherers, the sharing of male and female foods is often assumed to result in virtually the same diet for males and females. Although food sharing is widespread among the hunting and gathering Hadza of Tanzania, women were observed eating significantly more tubers than men. This study investigates the relationship between patterns of dental wear, diet, and extramasticatory use of teeth among the Hadza. Casts of the upper dentitions were made from molds taken from 126 adults and scored according to the Murphy dental attrition scoring system. Females had significantly greater anterior occlusal wear than males when we controlled for age. Males exhibited greater asymmetry in wear, with greater wear on the left side in canines, first premolars, and first molars. We suggest that these sex differences in wear patterns reflect the differences seen in the diet, as well as in the use of teeth as tools.     

Sex Differences in Mobility and Spatial Cognition

The fertility and parental care hypothesis interprets sex differences in some spatial-cognitive tasks as an adaptive mechanism to suppress women’s travel. In particular, the hypothesis argues that estrogens constrain travel during key reproductive periods by depressing women’s spatial-cognitive ability. Limiting travel reduces exposure to the dangers and caloric costs of navigating long distances into unfamiliar environments. Our study evaluates a collection of predictions drawn from the fertility and parental care hypothesis among the Twe and Himba people living in a remote region of Namibia. We find that nursing mothers travel more than women at any other stage of their reproductive career. This challenges the assumption that women limit travel during vulnerable and energetically demanding reproductive periods. In addition, we join previous studies in identifying a relationship between spatial ability and traveling among men, but not women. If spatial ability does not influence travel, hormonally induced changes in spatial ability cannot be used as a mechanism to reduce travel. Instead, it appears the fitness consequences of men’s travel is a more likely target for adaptive explanations of the sex differences in spatial ability, navigation, and range size.     

Sex Differences in Olfactory Communication in Saguinus labiatus

We assessed behaviors involved with depositing and receiving scent in three captive heterosexual pairs of red-bellied tamarins (Saguinus labiatus). The frequencies of scent deposition and scent investigatory behaviors differed between the sexes. Females scent marked exclusively by the anogenital gland. Males deposited 95.8% of scent marks via the anogenital gland and 4.2% via the sternal gland. Females scent marked at a significantly higher rate than that of males (0.9 ± 0.1 versus 0.3 ± 0.1 per 20 min, respectively). Males investigated the scent of their opposite-sex partners whereas females investigated no male scent. Mean ± SEM latency for males to investigate female scent was 208.7 ± 65.0 sec. Around 9% of all scent marks were overmarked within 8 min and there was a nonsignificant trend for males to overmark the scent of their female partners than vice versa. We discuss the sex differences in olfactory communication in red-bellied tamarins in terms of sexual selection theory.     

Structure of the Mouse Sex Peptide Pheromone ESP1 Reveals a Molecular Basis for Specific Binding to the Class C G-protein-coupled Vomeronasal Receptor

Exocrine gland-secreting peptide 1 (ESP1) is a sex pheromone that is released in male mouse tear fluids and enhances female sexual receptive behavior. ESP1 is selectively recognized by a specific class C G-protein-coupled receptor (GPCR), V2Rp5, among the hundreds of receptors expressed in vomeronasal sensory neurons (VSNs). The specific sensing mechanism of the mammalian peptide pheromone by the class C GPCR remains to be elucidated. Here we identified the minimal functional region needed to retain VSN-stimulating activity in ESP1 and determined its three-dimensional structure, which adopts a helical fold stabilized by an intramolecular disulfide bridge with extensive charged patches. We then identified the amino acids involved in the activation of VSNs by a structure-based mutational analysis, revealing that the highly charged surface is crucial for the ESP1 activity. We also demonstrated that ESP1 specifically bound to an extracellular region of V2Rp5 by an in vitro pulldown assay. Based on homology modeling of V2Rp5 using the structure of the metabotropic glutamate receptor, we constructed a docking model of the ESP1-V2Rp5 complex in which the binding interface exhibited good electrostatic complementarity. These experimental results, supported by the molecular docking simulations, reveal that charge-charge interactions determine the specificity of ESP1 binding to V2Rp5 in the large extracellular region characteristic of class C GPCRs. The present study provides insights into the structural basis for the narrowly tuned sensing of mammalian peptide pheromones by class C GPCRs.     

Sex Differences in the Rapid Detection of Emotional Facial Expressions

Background

Previous studies have shown that females and males differ in the processing of emotional facial expressions including the recognition of emotion, and that emotional facial expressions are detected more rapidly than are neutral expressions. However, whether the sexes differ in the rapid detection of emotional facial expressions remains unclear.

Methodology/Principal Findings

We measured reaction times (RTs) during a visual search task in which 44 females and 46 males detected normal facial expressions of anger and happiness or their anti-expressions within crowds of neutral expressions. Anti-expressions expressed neutral emotions with visual changes quantitatively comparable to normal expressions. We also obtained subjective emotional ratings in response to the facial expression stimuli. RT results showed that both females and males detected normal expressions more rapidly than anti-expressions and normal-angry expressions more rapidly than normal-happy expressions. However, females and males showed different patterns in their subjective ratings in response to the facial expressions. Furthermore, sex differences were found in the relationships between subjective ratings and RTs. High arousal was more strongly associated with rapid detection of facial expressions in females, whereas negatively valenced feelings were more clearly associated with the rapid detection of facial expressions in males.

Conclusion

Our data suggest that females and males differ in their subjective emotional reactions to facial expressions and in the emotional processes that modulate the detection of facial expressions.     

Sex Differences in Retrieval Behavior by the Biparental Convict Cichlid

Biparental species occasionally demonstrate a division of roles in which parents perform sex-typical tasks, with females offering direct care and spending the majority of their time with the offspring while males are more indirect in their care, providing the majority of defense against potential brood predators. To examine the flexibility in the sex-typical roles shown by convict cichlids ( Amatitlania nigrofasciata ), we displaced non-swimming young at three different distances from the nest and then analyzed the retrieval behaviors of each parent. Retrieval of altricial young is a behavior commonly used to measure parental care in mammalian studies, but has rarely been used in other taxa. We found sex differences in retrieval behavior: on average, females retrieved young close to the nest and males retrieved young far from the nest. This difference in parental contribution suggests a division of labor with sex-specific roles. Sex differences may be due to proximity to young and/or apparent risk of offspring predation. Additionally, we found that latency to first retrieval and total time spent retrieving young remained consistent across the various displacement distances, suggesting that retrieval is an essential parental behavior. Additionally, we include observations of wriggler retrieval by parents in a natural population of Costa Rican convict cichlids.     

Sex Differences in the Play Behavior of Yearling Yellow-bellied Marmots

Play in yearling yellow-bellied marmots (Marmota flaviventris) was studied under non-manipulative field conditions in the Upper East River Valley of Colorado. The behavior patterns constituting play were described and illustrated and 12 specific hypotheses related to sex differences were tested. The results of these tests were used to evaluate the adaptive significance of play by comparing two major functional hypotheses: motor training and social cohesion.     

Morbid Jealousy and Sex Differences in Partner-Directed Violence

Previous research suggests that individuals diagnosed with morbid jealousy have jealousy mechanisms that are activated at lower thresholds than individuals with normal jealousy, but that these mechanisms produce behavior that is similar to individuals with normal jealousy. We extended previous research documenting these similarities by investigating sex differences in partner-directed violence committed by individuals diagnosed with morbid jealousy. The results support some of our predictions. For example, a greater percentage of men than women diagnosed with morbid jealousy used physical violence, attempted to kill, and actually killed their partners, and used their hands rather than an object to kill their partners. These results replicate results generated for individuals with normal jealousy. Discussion addresses implications of the current research and highlights directions for future research on the psychology of morbid jealousy.

Sex Differences in Reactivity of the Sympathoadrenal System in Rat Ontogenesis

Sex differences in reactivity of the sympathoadrenal system were studied in male and female Wistar rats of three age groups (22-day-old, 31-day-old, and adult). An essential increase of catecholamine excretion level in males between the 22nd and 31st day after the birth has been noted both after stress (immobilization water-immersion action) and after injection of ₂-adrenoblockator yohimbine. In females the response to stress and injection of yohimbine practically did not change at this age stage. The sex dimorphism revealed as a higher level of adrenaline excretion in the 22-day-old females, as compared with males, was characterized in older groups by a higher level of its excretion in males. It might be suggested that sex dimorphism in non-reproductive types of behavior can depend on two factors: on differences in the maturity rate between females and males and on direct or mediated effects of sex hormones on physiological processes and related behavioral reactions.     

Sex Differences in the Development of Estrogen Receptors in the Rat Brain

The mechanisms involved in sexual differentiation of the brain remain incompletely defined. In mammals, testosterone secretion by the male during early development permanently alters the capacity of the brain to respond to circulating estrogen. In rats, this change in estrogen responsiveness is associated with a reduction in estrogen receptor (ER) levels in the periventricular region of the preoptic area (PVP), the medial preoptic nucleus (MPO), and the hypothalamic ventromedial nucleus (VMN) of the male. To determine whether these differences represent a response to early testosterone exposure or a secondary consequence of gonadal secretions at puberty, ER levels were measured by quantitative in vitro autoradiography in the brains of rats killed at intervals between 1-10 and 28-49 days of age. As early as 24 hr after birth, ER sex differences in the MPO and PVP are already quantitatively similar to those observed in adulthood. A sex difference in the VMN emerges later, between 5 and 10 days of age. Differences between brain regions are also observed in the rate of ER development after the first week of life, ER concentrations in the PVP and MPO being close to adult levels within 1 day of birth, in contrast to the VMN where they increase markedly between Day 10 and adulthood in both sexes. These observations suggest that changes in ER concentrations may be one of the earliest hallmarks of brain sexual differentiation. Sex differences in ER in different brain regions may, however, be expressed asynchronously, providing a possible mechanism for variation in the duration of "critical periods" for testosterone-mediated organization of specific CNS functions.