SPAM1 (PH-20) protein and mRNA expression in the epididymides of humans and macaques: utilizing laser microdissection/RT-PCR

Background  

The Sperm Adhesion Molecule 1 (SPAM1) is an important sperm surface hyaluronidase with at least three functions in mammalian fertilization. Previously our laboratory reported that in the mouse, in addition to its expression in the testis, Spam1 is synthesized in the epididymis where it is found in membranous vesicles in the principal cells of the epithelium in all three regions. Since SPAM1 is widely conserved among mammals the aim of the study was to determine if its expression pattern in the epididymis is conserved in rodents and primates.     

Breast symmetry,but not size or volume,predicts salivary immunoglobulin-A (sIgA) in women

Human breasts are larger and more enduring than reproductively necessary. It is thus unclear why this costly, yet conspicuous phenotype has been selected for, or what information they might convey about the underlying quality of the female. Following previous research on fluctuating asymmetry, we postulated that breast symmetry would predict a marker of mucosal immunity (salivary immunoglobulin-A; sIgA). Anthropometric breast measurements were provided by 97 young women. Controlling for Body Mass Index (BMI), breast size, and volume, results demonstrated that breast asymmetry predicted lower sIgA, whereas size and volume did not. Results support the hypothesis that symmetrical female breasts are a cue to underlying immunocompetence.     

Sexual size dimorphism decreases with temperature in a blowfly,Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae)

1. There is wide intra‐specific variation in sexual size dimorphism (SSD). Much of this variation is probably as a result of sexual differences in the selective pressure on body size. However, environmental variables could affect males and females differently, causing variation in SSD. 2. We examined the effects of two temperatures (20 and 30 °C) on SSD in six populations of the blowfly, Chrysomya megacephala. 3. We found that body size increased with temperature in all the populations studied, and the sexes differed in phenotypic plasticity of body size in response to rearing temperature. This created substantial temperature‐induced variation in SSD (i.e. sex × temperature interaction). Males were often smaller than females, but the degree of dimorphism was smaller at the higher temperature (30 °C) and larger at the lower temperature (20 °C). This change in SSD was not because of a gender difference in the effect of temperature on development time. Further studies should address whether this variation can be produced by adaptive canalisation of one sex against variation in temperature, or whether it may be a consequence of non‐adaptive developmental differences between the sexes. 4. Although most studies assume that the magnitude of SSD is fixed within a species, the present study demonstrates that rearing temperature can generate considerable intra‐specific variation in the degree of SSD.     

Sexual cannibalism, competition, and size dimorphism in the orb-weaving spider Nephila plumipes Latreille (Araneae: Araneoidea)

The degree and direction of sexual dimorphism varies widely,but in several taxa of orb-weaving spiders, including Nephila,males may be less than one-tenth the size of females. This differenceis commonly attributed to selection through precopulation sexualcannibalism: females may either fail to detect very small males,or ignore them as potential prey items. However, there is oftenthe potential for male-male competition in these species becauseseveral males can be found on the web of a single female. Weinvestigated experimentally the effects of sexual cannibalismand male-male competition on male body size and hence sexualdimorphism in the Australian golden orb-weaver (Nephila plumipes).Small males were less likely to be detected and cannibalizedthan larger males. However, larger males excluded small malesfrom the central hub of the web, where mating takes place. Theconflicting effects of sexual cannibalism and male-male competitionmay be responsible for the relatively large variation in malebody size in this species.     

Body size, male combat and the evolution of sexual dimorphism in eublepharid geckos (Squamata: Eublepharidae)

Lizards of the family Eublepharidae exhibit interspecific diversity in body size, sexual size dimorphism (SSD), head size dimorphism (HSD), occurrence of male combat, and presence of male precloacal pores. Hence, they offer an opportunity for testing hypotheses for the evolution and maintenance of sexual dimorphism. Historical analysis of male agonistic behaviour indicates that territoriality is ancestral in eublepharid geckos. Within Eublepharidae, male combat disappeared twice. In keeping with predictions from sexual selection theory, both events were associated with parallel loss of male-biased HSD and ventral scent glands. Eublepharids therefore provide new evidence that male-biased dimorphic heads are weapons used in aggressive encounters and that the ventral glands probably function in territory marking rather than in intersexual communication. Male-biased SSD is a plesiomorphic characteristic and was affected by at least three inversions. Shifts in SSD and male combat were not historically correlated. Therefore, other factors than male rivalry appear responsible for SSD inversions. Eublepharids demonstrate the full scope of Rensch's rule (small species tend to be female-larger, larger species male-larger). Most plausibly, SSD pattern hence seems to reflect body size variation. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 303–314.     

Floral symmetry is associated with flower size and pollen production but not insect visitation rates in Geranium robertianum (Geraniaceae)

The degree to which fine‐scaled variation in floral symmetry is associated with variation in plant fitness remains unresolved, as does the question of whether floral symmetry is in itself a target of pollinator‐mediated selection. Geranium robertianum (Geraniaceae) is a broadly distributed species whose five‐petaled flowers vary widely with respect to their degree of rotational asymmetry. In this study, we used a naturally occurring population of plants to investigate whether floral rotational asymmetry and leaf bilateral symmetry were phenotypically correlated with a series of fitness‐related traits, and also used an experimental array with model flowers to investigate the preference of insect visitors for varying degrees of floral size and symmetry. We found that leaf asymmetry was not associated with any of the phenotypic traits measured, and that the degree of floral rotational asymmetry was strongly associated with decreased flower size and decreased pollen production. Our experimental arrays showed that insect visitors did not discriminate among model flowers on the basis of size or symmetry alone; however, insect visitors preferentially visited smaller, symmetric model flowers over larger, severely asymmetric model flowers. Taken together, our results suggest that floral and leaf symmetry in G. robertianum are not likely strong indicators of phenotypic quality, and that floral symmetry is unlikely to be a target of pollinator‐mediated selection. However, the relationship between floral asymmetry and pollen production may provide a role for fecundity selection on symmetry in this species. These data importantly add to the growing literature on the adaptive nature of floral symmetry in the wild.     

Sexual selection accounts for the geographic reversal of sexual size dimorphism in the dung fly, sepsis punctum (Diptera: Sepsidae)

Sexual size dimorphism (SSD) varies widely across and within species. The differential equilibrium model of SSD explains dimorphism as the evolutionary outcome of consistent differences in natural and sexual selection between the sexes. Here, we comprehensively examine a unique cross-continental reversal in SSD in the dung fly, Sepsis punctum. Using common garden laboratory experiments, we establish that SSD is male-biased in Europe and female-biased in North America. When estimating sexual (pairing success) and fecundity selection (clutch size of female partner) on males under three operational sex ratios (OSRs), we find that the intensity of sexual selection is significantly stronger in European versus North American populations, increasing with male body size and OSR in the former only. Fecundity selection on female body size also increases strongly with egg number and weakly with egg volume, however, equally on both continents. Finally, viability selection on body size in terms of intrinsic (physiological) adult life span in the laboratory is overall nil and does not vary significantly across all seven populations. Although it is impossible to prove causality, our results confirm the differential equilibrium model of SSD in that differences in sexual selection intensity account for the reversal in SSD in European versus North American populations, presumably mediating the ongoing speciation process in S. punctum.     

Leaf size in three generations of a dioecious tropical tree, Ocotea tenera (Lauraceae): Sexual dimorphism and changes with age

? Premise of the study: In dioecious species, selection should favor different leaf sizes in males and females whenever the sexes experience distinct environments or constraints such as different costs of reproduction. We took advantage of a long-term experimental study of Ocotea tenera (Lauraceae), a dioecious understory tree in Monteverde, Costa Rica, to explore leaf size differences between genders and age classes across generations. ? Methods: We measured leaf size in adult trees in a natural population, in their adult F(1) offspring in two experimental populations, and in their F(2) offspring at the seedling stage. Individual trees were measured at various times over 20 yr. ? Results: Leaves of female trees averaged 8% longer and 12% greater in area than those of males. Leaves were sexually dimorphic at reproductive maturity. Leaf size declined during the lifetime of most trees. Heritability estimates for leaf length were positive although not statistically significant (h(2) = 0.63, SE = 0.48, P = 0.095). ? Conclusions: We ruled out the ecological causation hypothesis for sexual dimorphism in leaf size because male and female trees co-occurred in the same habitats. Sexual dimorphism appeared not to result from genetic or phenotypic correlations with other traits such as height or flower size. Rather, females appear to compensate for higher costs of reproduction and diminished photosynthetic capacity by producing larger leaves. Additive genetic variance in leaf size, a prerequisite for an evolutionary response to selection for sexual dimorphism, was suggested by positive (although only marginally significant) heritability estimates.     

Swift laboratory thermal evolution of wing shape (but not size) in Drosophila subobscura and its relationship with chromosomal inversion polymorphism

Latitudinal clinal variation in wing size and shape has evolved in North American populations of Drosophila subobscura within about 20 years since colonization. While the size cline is consistent to that found in original European populations (and globally in other Drosophila species), different parts of the wing have evolved on the two continents. This clearly suggests that 'chance and necessity' are simultaneously playing their roles in the process of adaptation. We report here rapid and consistent thermal evolution of wing shape (but not size) that apparently is at odds with that suggestion. Three replicated populations of D. subobscura derived from an outbred stock at Puerto Montt (Chile) were kept at each of three temperatures (13, 18 and 22 degrees C) for 1 year and have diverged for 27 generations at most. We used the methods of geometric morphometrics to study wing shape variation in both females and males from the thermal stocks, and rates of genetic divergence for wing shape were found to be as fast or even faster than those previously estimated for wing size on a continental scale. These shape changes did not follow a neat linear trend with temperature, and are associated with localized shifts of particular landmarks with some differences between sexes. Wing shape variables were found to differ in response to male genetic constitution for polymorphic chromosomal inversions, which strongly suggests that changes in gene arrangement frequencies as a response to temperature underlie the correlated changes in wing shape because of gene-inversion linkage disequilibria. In fact, we also suggest that the shape cline in North America likely predated the size cline and is consistent with the quite different evolutionary rates between inversion and size clines. These findings cast strong doubts on the supposed 'unpredictability' of the geographical cline for wing traits in D. subobscura North American colonizing populations.     

H3K27me1 is E(z) in animals,but not in plants

Post-translational modifications of histones play key roles in the regulation of gene expression and chromatin structure in eukaryotes. Methylation of histone 3 on lysine 27 (H3K27) is one of the most common and well-studied histone post-translational modifications. The vast majority of research on this histone residue, however, has focused on the trimethylated form (H3K27me3). Despite occurring at higher levels than H3K27me3 in animals and plants, the monomethylated form of H3K27 (H3K27me1) remains relatively poorly characterized. The absence of information concerning H3K27me1 is due in large part to the fact that the enzymes catalyzing this epigenetic mark were only recently identified. In this article, we highlight new findings concerning H3K27me1, including the identification of two plant-specific H3K27 monomethyltransferases that are required for gene silencing and heterochromatin condensation. We also discuss the emerging similarities and differences in H3K27 methylation in plant and animal systems.     

Rhesus monkeys (Macaca mulatta) show robust primacy and recency in memory for lists from small, but not large, image sets

The combination of primacy and recency produces a U-shaped serial position curve typical of memory for lists. In humans, primacy is often thought to result from rehearsal, but there is little evidence for rehearsal in nonhumans. To further evaluate the possibility that rehearsal contributes to primacy in monkeys, we compared memory for lists of familiar stimuli (which may be easier to rehearse) to memory for unfamiliar stimuli (which are likely difficult to rehearse). Six rhesus monkeys saw lists of five images drawn from either large, medium, or small image sets. After presentation of each list, memory for one item was assessed using a serial probe recognition test. Across four experiments, we found robust primacy and recency with lists drawn from small and medium, but not large, image sets. This finding is consistent with the idea that familiar items are easier to rehearse and that rehearsal contributes to primacy, warranting further study of the possibility of rehearsal in monkeys. However, alternative interpretations are also viable and are discussed.     

Body size,but not age-at-maturation or context,affects the expression of predator-induced behavioural plasticity in female green swordtails (Xiphophorus hellerii)

Behavioural plasticity is a form of reversible phenotypic plasticity in which a genotype can express different behavioural phenotypes under different environmental conditions. Though an interest in among-individual differences in behavioural plasticity has flourished in recent decades, few studies have considered the effects of intrinsic factors, such as life-history or morphological traits, in tandem with extrinsic factors, such as presence of conspecifics in different social contexts, on predator-induced behavioural plasticity. Here, we present a study conducted with female green swordtail fishes, Xiphophorus hellerii, designed to assess the effects of age-at-maturation and body size on the expression of predator-induced behavioural plasticity in two social contexts: (a) female-only (two females) and (b) female-and-male (two females and a male). We further examined the extent to which individual expression of behavioural plasticity is consistent across these two social contexts. We found that in the presence of a predator, focal females were more timid in response to the stimulus and more tolerant of the non-focal female, and small females expressed this change from bold/less tolerant to timid/more tolerant to a greater degree than large females, regardless of age-at-maturation. However, individuals were not consistent in the degree or direction of plasticity expressed in the behaviours of interest between the female-only and the female-and-male context. Here, we show that within- and among-individual differences in behavioural expression are common but inconsistent. How intrinsic and extrinsic factors independently or together drive expression of plasticity in antipredator and agonistic behaviours is varied and warrants further study.     

Wing morphology and migration status,but not body size,habitat or Rapoport's rule predict range size in North‐American dragonflies (Odonata: Libellulidae)

Understanding why species range sizes vary is important for predicting the impact of environmental change on biodiversity. Here we use a multi‐variable approach in a phylogenetic comparative context to understand how four morphological, two ecological, and two eco‐geographical variables are associated with range size, latitudinal range and longitudinal range in 81 species of North‐American libellulid dragonflies. Our results show that: 1) migratory species and species with a more expanded basal hindwing lobe have a larger range size; 2) opposite to Rapoport's rule, latitudinal range is negatively correlated with mid‐range latitude; 3) longitudinal range is predicted by wing morphology and migration; 4) body size and larval habitat are not correlated with range size, latitudinal range or longitudinal range. These results suggest that dispersal‐related traits, such as wing shape and migratory status, are important factors in predicting the range size of libellulid dragonflies. In addition, the reverse Rapoport's rule suggests that more northern‐centred species might be more specialized than more southern‐centred species. We suggest that the variables predicting range size are likely imposed by taxon‐specific morphological, ecological, physiological and behavioural traits. Taxon‐specific knowledge is thus necessary to understand the dynamics of range sizes and is important to implement successful restoration and conservation plans of threatened species.     

Chronic, but not acute, administration of morphine alters antiopiate (Tyr-MIF-1) binding sites in rat brain

Opiate addiction could involve a change in the binding of endogenous antiopiates. A candidate for such a role is Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2), a brain peptide that can antagonize exogenous and endogenous opiates and bind to opiate receptors. Its primary action, however, may be through its own binding site in brain, which we now report is altered by chronic administration of morphine. Rats given morphine pellets had reduced binding of both iodinated and tritiated Tyr-MIF-1 on day 5, when substantial tolerance is evident. In contrast, mu and delta opiate receptors were increased. Acute injection of an analgesic dose of morphine did not reduce Tyr-MIF-1 binding, indicating that chronic administration is required for the change. These findings open new approaches to the study of addiction by focusing on antiopiate activity.     

Capuchin monkeys (Sapajus [Cebus] apella) play Nash equilibria in dynamic games,but their decisions are likely not influenced by oxytocin

Comparative approaches to experimental economics have shed light on the evolution of social decision‐making across a range of primate species, including humans. Here we replicate our previous work looking at six pairs of capuchin monkeys' (Sapajus [Cebus] apella) responses to scenarios requiring both coordination (Assurance Game) and anti‐coordination (Hawk‐Dove Game). This then provides a foundation for assessing their responses to two additional games, one with a scenario of beneficial cooperation with a temptation to defect (Prisoner's Dilemma) and one with an environment requiring changing strategies within short temporal proximity (Alternating Economic Game). We additionally explored the effects of exogenous oxytocin on decision‐making. Oxytocin did not affect decisions in any of our games. Results from the first two games largely replicated our previous findings. Responses to the Prisoner's Dilemma were more varied than was seen in previous games, with pairs respectively cooperating, defecting, and failing to establish stable strategies. Such variability indicates that this game may be a good assay for individual differences in social decision‐making. Finally, capuchins were able to flexibly switch between their previously established strategies within each of the different games, even when the games were presented within the same session, requiring strategy adjustments within short temporal proximity. These results build on earlier findings showing that capuchins can alter decision‐making strategies as the context demands, which is likely essential for decision‐making in naturally occurring contexts.     

Thioredoxin peroxidase-1 (peroxiredoxin-1) is increased in thioredoxin-1 transfected cells and results in enhanced protection against apoptosis caused by hydrogen peroxide but not by other agents including dexamethasone, etoposide, and doxorubicin

Thioredoxin-1 (Trx-1) is a small redox oncoprotein whose expression is increased in a number of human primary cancers where it is associated with aggressive tumor growth, inhibition of apoptosis and decreased patient survival. We report that Trx-1-transfected MCF-7 human breast cancer cells have increased expression of thioredoxin peroxidase-1 (TrxP-1) a peroxiredoxin family member that scavenges H(2)O(2) using Trx-1 as a source of reducing equivalents. Our work shows that TrxP-1 is more effective than selenium-dependent glutathione peroxidase in protecting cells against H(2)O(2) damage. Transfection of mouse WEHI7.2 lymphoma cells with human TrxP-1 or TrxP-2, but not TrxP-4, protects the cells against H(2)O(2) induced apoptosis but does not protect against apoptosis induced by dexamethasone, etoposide, or doxorubicin. The results show that an increase in TrxP-1 expression contributes to the protection against H(2)O(2) induced apoptosis caused by Trx-1, but does not protect against apoptosis induced by other agents.     

Estradiol stimulates Akt, AMP-activated protein kinase (AMPK) and TBC1D1/4, but not glucose uptake in rat soleus

Post-menopausal women exhibit decreases in circulating estrogen levels and whole body insulin sensitivity, suggesting that estrogen regulates skeletal muscle glucose disposal. Thus, we assessed whether estrogen stimulates glucose uptake or enhances insulin sensitivity in skeletal muscle. Ex vivo muscle stimulation with 17β-estradiol (10 nM) resulted in a rapid (?10 min) increase in the phosphorylation of Akt, AMP-activated protein kinase (AMPK), and TBC1D1/4, key signaling proteins that regulate glucose uptake in muscle. Treatment with the estrogen receptor antagonist, ICI 182,780, only partly inhibited signaling, suggesting both an estrogen receptor-dependent and independent mechanism of estradiol action. 17β-Estradiol did not stimulate ex vivo muscle [³H]-2-deoxyglucose uptake or enhance insulin-induced glucose uptake, demonstrating discordance between the estradiol-induced stimulation of signaling proteins and muscle glucose uptake. This study is the first to demonstrate that estradiol stimulates Akt, AMPK, and TBC1D1/4 in intact skeletal muscle, but surprisingly, estradiol does not stimulate muscle glucose uptake.