Dopamine receptor D4 allele distribution in Amerindians: A reflection of past behavior differences?

The DRD4 variable number of tandem repeats (VNTR) allele distribution of 172 Guarani (Kaiowá and Ñandeva subgroups) and Kaingang Brazilian Amerindians is reported. These results are integrated with those previously obtained for this ethnic group. Allele frequencies for the three populations are within the interval observed for 15 other Native American populations and show intermediate values between those observed in Amazonia and Patagonia. Significant differences in allele distribution between recent past hunter–gatherer and agriculturalist populations are observed, with an increase of the 7R allele among hunter–gatherers (P < 0.001). Analysis of molecular variance (AMOVA) and pairwise F_ST data suggest three distinct sectors for the genetic landscape of Native South America: Andes, Center/Southeast region, and Amazonia. Common traits among hunter–gatherers such as novelty‐seeking temperament, hyperactivity, and impulsivity could have been important and advantageous in new environments during America's prehistoric colonization. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

Are age differences in sleep due to phase differences in the output of the circadian timing system?

Our aim was to evaluate whether age-related changes in the phase of the output of the circadian timing system (CTS) can explain age differences in habitual bedtime/wake time and in sleep consolidation parameters. Analyses focused on a group of healthy elderly people (older than 70 years) with no sleep problems and with similar subjective sleep quality as a young control group. The 2-week sleep diary data and 24h laboratory temperature recordings were examined for 70 subjects (22 young men [YM], 19 old men [OM], 29 old women [OW]). Polysomnographic (PSG) sleep data recorded during temperature data acquisition were also available for 62 subjects. These analyses made use of our recently developed technique to demask temperature rhythm data. As expected, compared to the young subjects, older subjects showed earlier habitual bedtime and wake time, more disturbed sleep, and a tendency for an earlier minimum of the circadian temperature rhythm. Despite sleep consolidation differences, the groups showed very similar habitual phase-angle differences (interval between the time occurrence of the fitted temperature minimum and habitual wake time). Both elderly and young subjects woke up on average 3h after the temperature minimum. After controlling for the effects of age group, habitual bedtime and wake time were related to clock time phase of the circadian temperature rhythm, with an earlier phase associated with earlier habitual bedtime and wake time. None of the sleep consolidation parameters were linked to the temperature phase angle. In conclusion, sleep consolidation changes associated with healthy aging do not appear to be related to changes in the phase-angle difference between the output signal from the CTS and sleep.     

Sex differences in insect immune function: a consequence of diet choice?

Males often have reduced immune function compared to females but the proximate mechanisms underlying this taxonomically widespread pattern are unclear. Because immune function is resource-dependent and sexes may have different nutritional requirements, we hypothesized that sexual dimorphism in immune function may arise from differential nutrient intake (acquisition hypothesis). To test this hypothesis, we examined patterns of phenoloxidase (PO) activity in relation to nutrient consumption in Queensland fruit flies (Q-flies). In the first experiment, flies were allowed to choose their preferred nutrient intake. Compared with males, female Q-flies had higher PO activity, consumed more calories, and preferred a higher protein:carbohydrate (P:C) diet, suggesting that differential acquisition could explain sex differences. In the second experiment, we restricted flies to one of 12 diets varying in protein and carbohydrate concentrations and mapped PO activity for each sex onto a nutritional landscape. Counter to our hypothesis, females had higher PO activity than males at any given level of nutrient intake. Both carbohydrate and protein intake affected PO activity in females but only protein affected PO activity in males. Our results indicate that sex differences in Q-fly immune function are not solely explained by sex differences in nutrient intake, although nutrition does contribute to the magnitude of these sex differences.     

Sex in the PAC: A hidden affair in dark septate endophytes?

Background

Fungi are asexually and sexually reproducing organisms that can combine the evolutionary advantages of the two reproductive modes. However, for many fungi the sexual cycle has never been observed in the field or in vitro and it remains unclear whether sexual reproduction is absent or cryptic. Nevertheless, there are indirect approaches to assess the occurrence of sex in a species, such as population studies, expression analysis of genes involved in mating processes and analysis of their selective constraints. The members of the Phialocephala fortinii s. l. - Acephala applanata species complex (PAC) are ascomycetes and the predominant dark septate endophytes that colonize woody plant roots. Despite their abundance in many ecosystems of the northern hemisphere, no sexual state has been identified to date and little is known about their reproductive biology, and how it shaped their evolutionary history and contributes to their ecological role in forest ecosystems. We therefore aimed at assessing the importance of sexual reproduction by indirect approaches that included molecular analyses of the mating type (MAT) genes involved in reproductive processes.

Results

The study included 19 PAC species and > 3, 000 strains that represented populations from different hosts, continents and ecosystems. Whereas A. applanata had a homothallic (self-fertile) MAT locus structure, all other species were structurally heterothallic (self-sterile). Compatible mating types were observed to co-occur more frequently than expected by chance. Moreover, in > 80% of the populations a 1:1 mating type ratio and gametic equilibrium were found. MAT genes were shown to evolve under strong purifying selection.

Conclusions

The signature of sex was found in worldwide populations of PAC species and functionality of MAT genes is likely preserved by purifying selection. We hypothesize that cryptic sex regularely occurs in the PAC and that further field studies and in vitro crosses will lead to the discovery of the sexual state. Although structurally heterothallic species prevail, it cannot be excluded that homothallism represents the ancestral breeding system in the PAC.     

Sex differences in human adipose tissues – the biology of pear shape

Women have more body fat than men, but in contrast to the deleterious metabolic consequences of the central obesity typical of men, the pear-shaped body fat distribution of many women is associated with lower cardiometabolic risk. To understand the mechanisms regulating adiposity and adipose tissue distribution in men and women, significant research attention has focused on comparing adipocyte morphological and metabolic properties, as well as the capacity of preadipocytes derived from different depots for proliferation and differentiation. Available evidence points to possible intrinsic, cell autonomous differences in preadipocytes and adipocytes, as well as modulatory roles for sex steroids, the microenvironment within each adipose tissue, and developmental factors. Gluteal-femoral adipose tissues of women may simply provide a safe lipid reservoir for excess energy, or they may directly regulate systemic metabolism via release of metabolic products or adipokines. We provide a brief overview of the relationship of fat distribution to metabolic health in men and women, and then focus on mechanisms underlying sex differences in adipose tissue biology.     

Crosstalk between the M1 muscarinic acetylcholine receptor and the endocannabinoid system: A relevance for Alzheimer's disease?

Alzheimer's disease (AD) is a neurodegenerative disorder which accounts for 60–70% of the 50 million worldwide cases of dementia and is characterised by cognitive impairments, many of which have long been associated with dysfunction of the cholinergic system. Although the M₁ muscarinic acetylcholine receptor (mAChR) is considered a promising drug target for AD, ligands targeting this receptor have so far been unsuccessful in clinical trials. As modulatory receptors to cholinergic transmission, the endocannabinoid system may be a promising drug target to allow fine tuning of the cholinergic system. Furthermore, disease-related changes have been found in the endocannabinoid system during AD progression and indeed targeting the endocannabinoid system at specific disease stages alleviates cognitive symptoms in numerous mouse models of AD. Here we review the role of the endocannabinoid system in AD, and its crosstalk with mAChRs as a potential drug target for cholinergic dysfunction.     

A role for the interferon system in the pathogenesis of multiple sclerosis?

MS may be caused by an as yet unidentified virus whose life-long persistence in the body may deregulate the immune system so as to make it react against central nervous system tissue. Interferon are endogenous, hormone-like proteins with antiviral and immunomodulatory properties. This paper analyses current knowledge on the production and action of these proteins in the perspective of their possible involvement in the pathogenesis of MS. It also reviews observations made sofar on interferon production and action in MS patients.     

Are there differences between proseriates and lower flatworms in ultrastructure of the nervous system?

The ultrastructure of the CNS (central nervous system) in three species of the Proseriata — Archiloa unipunctata (O. Fabricius), Bothriomolus balticus (Meixner), and Promonotus schultzei (Meixner) — was studied and compared to that of the lower flatworms Stenostomum leucops (Catenulida) and Microstomum lineare (Macrostomida) in material available from our previous studies. Conventional electron microscopical fixation was used for A. unipunctata and B. balticus; the tannic-acid-incubation method (TARI), a method that reveals especially nonsynaptic exocytotic release of neuronal substances, was applied in study of P. schultzei.In general, the ultrastructural features of neurons and nerve fibers were similar in proseriates and lower flatworms. A striking feature common to both groups was the secretory appearance of all neurons. A significant difference between them is the occurrence, in the proseriates, of wrapping of neurons by glial cells. Heterogeneity in the population of neuronal vesicles and in structure of synapses in the proseriates are probably advanced characters; by contrast, S. leucops has relatively homogeneous vesicles and simple synapses. A gradual advancement from the state in the catenulids through that in the macrostomids to the proseriates seems to be reflected in the differentiation of synapses and the variability of neuronal vesicles. This probably reflects differences in functional demands but also evolutionary advancement.     

Lipid rafts: A nexus for endocannabinoid signaling?

The endocannabinoids are endogenous agonists of the cannabinoid receptors and some members of the transient receptor potential, vanilloid type (TRPV), family of cation channels. Endocannabinoids along with their target receptors comprise a signaling system that is not well characterized. There have been many advances in our collective understanding of endocannabinoid signaling in the last decade and experimental evidence is mounting that pharmacological augmentation of endocannabinoid tone might have a significant therapeutic benefit in several disease states. However, the mechanisms responsible for the biosynthesis, cellular uptake, and intracellular processing of endocannabinoids are not well understood and have been the source of much debate. Recent studies have revealed a role for detergent insoluble membrane domains called lipid rafts in various aspects of signaling associated with the endocannabinoid anandamide. Intact detergent insoluble membrane domains appear to play a role in an anandamide-induced signaling cascade that is independent of G protein-coupled cannabinoid receptors or TRPV channels. Furthermore, detergent insoluble membrane domain-related endocytosis and recycling to lipid rafts appear to regulate the organization and localization of anandamide metabolites. We will discuss the implications that these findings have on the way we view endocannabinoid signaling, trafficking, and processing.     

Extreme Sexual Brain Size Dimorphism in Sticklebacks: A Consequence of the Cognitive Challenges of Sex and Parenting?

Selection pressures that act differently on males and females produce numerous differences between the sexes in morphology and behaviour. However, apart from the controversial report that males have slightly heavier brains than females in humans, evidence for substantial sexual dimorphism in brain size is scarce. This apparent sexual uniformity is surprising given that sexually distinct selection pressures are ubiquitous and that brains are one of the most plastic vertebrate organs. Here we demonstrate the highest level of sexual brain size dimorphism ever reported in any vertebrate: male three-spined stickleback of two morphs in an Icelandic lake have 23% heavier brains than females. We suggest that this dramatic sexual size dimorphism is generated by the many cognitively demanding challenges that males are faced in this species, such as an elaborate courtship display, the construction of an ornate nest and a male-only parental care system. However, we consider also alternative explanations for smaller brains in females, such as life-history trade-offs. Our demonstration of unprecedented levels of sexual dimorphism in brain size in the three-spined stickleback implies that behavioural and life-history differences among the sexes can have strong effects also on neural development and proposes new fields of research for understanding brain evolution.     

The pharmacology of curcumin: is it the degradation products?

The natural product curcumin has gained considerable attention in recent years for its multiple pharmacological activities, but more efforts are needed to understand how curcumin can have these pharmacological effects considering its low bioavailability. In addition, it is unclear how curcumin exerts inhibitory effects against numerous enzymes, especially those that cannot accommodate curcumin within recognized binding pockets. By analyzing the similarities between the biological activities of curcumin and its degradation products against diseases such as Alzheimer's disease and cancer, as well as the preferential inhibition of some enzymes by degradation products, it appears that the bioactive degradation products may contribute to the pharmacological effects of curcumin. This possibility should be given full attention when elucidating the pharmacology of this promising natural product for various diseases.     

Sex: Is Giardia Doing It in the Dark?

The protist Giardia has long been considered strictly asexual. Now genes specific for meiotic recombination have been found in the Giardia genome, but their consequences for genetics, epidemiology and evolution remain unknown.     

A single origin of the central nervous system?

As Denes et al. (2007) reveal in this issue, the expression profile and roles of genes that pattern the nervous system in embryos of chordates and annelids are surprisingly similar. This extraordinary conservation suggests that the patterning mechanism has been inherited largely unchanged from the bilaterian common ancestor and that the central nervous system, although dorsal in fish and ventral in worms, is an ancient characteristic of animals.     

Sex differences in scent‐marking in sifaka: Mating conflict or male services?

Male and female interests can either be in conflict or serve as a basis for exchange. Communication is thus an important aspect of intersexual relationships. Verreaux's sifaka (Propithecus verreauxi verreauxi), like many prosimians, uses chemical signals as one form of communication. The goals of this study were to determine 1) if males and females exhibit sex differences in their scent-marking behavior, and 2) if scent-marking is an example of mating conflict or cooperation. All occurrences of scent-marks, scent-mark context, and scent-mark style were collected on 23 sifaka in the Kirindy Forest of western Madagascar for 7 months (September 2001-March 2002). Scent-mark rates were collected using continuous focal animal sampling from November 2000-March 2002. Home-range data were collected using monthly censuses and instantaneous focal sampling throughout those 17 months. The pressures of behavioral ecology seem to have shaped scent-marking in sifaka: the sexes exhibited significantly different scent-marking behavior. Results from this study are consistent with the hypotheses that 1) females scent-mark to advertise their presence and mark their resources, 2) clean-chested males use scent-marks as between-group communication to advertise their presence, and 3) stained-chested males use scent-marks as a form of olfactory mate-guarding. Scent-marking does not appear to be a \"service\" that males provide to females, because overmarking limits female communication rather than adding to the overall number of scent-marks. Scent-marking behavior is a crucial aspect of the mating conflict and for understanding intersexual relationships in sifaka.     

Sex differences and the effects of ovariectomy on the β-adrenergic contractile response

The presence of sex differences in myocardial β-adrenergic responsiveness is controversial, and limited studies have addressed the mechanism underlying these differences. Studies were performed using isolated perfused hearts from male, intact female and ovariectomized female mice to investigate sex differences and the effects of ovarian hormone withdrawal on β-adrenergic receptor function. Female hearts exhibited blunted contractile responses to the β-adrenergic receptor agonist isoproterenol (ISO) compared with males but not ovariectomized females. There were no sex differences in β(1)-adrenergic receptor gene or protein expression. To investigate the role of adenylyl cyclase, phosphodiesterase, and the cAMP-signaling cascade in generating sex differences in the β-adrenergic contractile response, dose-response studies were performed in isolated perfused male and female hearts using forskolin, 3-isobutyl-1-methylxanthine (IBMX), and 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (CPT-cAMP). Males showed a modestly enhanced contractile response to forskolin at 300 nM and 5 μM compared with females, but there were no sex differences in the response to IBMX or CPT-cAMP. The role of the A(1) adenosine receptor (A(1)AR) in antagonizing the β-adrenergic contractile response was investigated using both the A(1)AR agonist 2-chloro-N(6)-cyclopentyl-adenosine and A(1)AR knockout (KO) mice. Intact females showed an enhanced A(1)AR anti-adrenergic effect compared with males and ovariectomized females. The β-adrenergic contractile response was potentiated in both male and female A(1)ARKO hearts, with sex differences no longer present above 1 nM ISO. The β-adrenergic contractile response is greater in male hearts than females, and minor differences in the action of adenylyl cyclase or the A(1)AR may contribute to these sex differences.     

Sex and asymmetry in humans: what is the role of developmental instability?

Because asymmetric individuals are less attractive and may suffer from reduced fitness, bilateral asymmetry is widely believed to affect human sexual selection. Its evolutionary significance is based on the presumed relationship with developmental instability (DI). Yet, relationships between DI and bilateral asymmetry are often weak and possibly confounded by asymmetric mechanical loadings because of handedness. We related asymmetry in hands and faces to degrees of handedness and sexual behaviour in 100 humans. Handedness correlated to levels of asymmetry, thereby likely invalidating the use of asymmetry to estimate DI. For facial asymmetry, applying existing theoretical models refuted a link between asymmetry and DI. Explicit statistical modelling at the level of DI confirmed the absence of a link between DI and aspects of sexual behaviour. Nevertheless, asymmetries in both hands and face correlated significantly with sexual behaviour. We conclude that bilateral asymmetry per se, rather than its presumed link with DI, more likely relates to measures of human sexual behaviour. Because lateralization of behaviour appears widespread, evaluating the role of DI in evolution and ecology relies on a very critical selection of traits whose asymmetry can reliably reflect DI.     

Sex differences in children’s investment in peers

It is hypothesized from within an evolutionary framework that females should be less invested in peer relations than males. Investment was operationalized as enjoyment in Study 1 and as preference for interaction in Study 2. In the first study, four- and six-year-old children’s enjoyment of peer interaction was observed in 26 groups of same-sex peers. Girls were rated as enjoying their interactions significantly less than boys. In the second study, six- and nine-year-old children were interviewed about the individuals with whom they spend time in their homes and neighborhoods and about the individuals who participate in their favorite activities. The proportion of individuals named by children who were peers was significantly lower for girls than boys both in children’s neighborhoods and in children’s favorite activities. Results strongly support the hypothesis that females and males have evolved differential preferences for interaction with peers.