Sexual signalling in Propithecus verreauxi: male "chest badge" and female mate choice

Communication, an essential prerequisite for sociality, involves the transmission of signals. A signal can be defined as any action or trait produced by one animal, the sender, that produces a change in the behaviour of another animal, the receiver. Secondary sexual signals are often used for mate choice because they may inform on a potential partner's quality. Verreaux's sifaka (Propithecus verreauxi) is characterized by the presence of two different morphs of males (bimorphism), which can show either a stained or clean chest. The chest becomes stained by secretions of the sternal gland during throat marking (rubbing throat and chest on a vertical substrate while smearing the scent deposition). The role of the chest staining in guiding female mate choice was previously hypothesized but never demonstrated probably due to the difficulty of observing sifaka copulations in the wild. Here we report that stained-chested males had a higher throat marking activity than clean-chested males during the mating season, but not during the birth season. We found that females copulated more frequently with stained-chested males than the clean-chested males. Finally, in agreement with the biological market theory, we found that clean-chested males, with a lower scent-releasing potential, offered more grooming to females. This "grooming for sex" tactic was not completely unsuccessful; in fact, half of the clean-chested males copulated with females, even though at low frequency. In conclusion, the chest stain, possibly correlated with different cues targeted by females, could be one of the parameters which help females in selecting mates.     

Oxidative damage to plant DNA in relation to growth conditions.

In this study we investigated the level of 8-oxo-2'-deoxyguanosine (8-oxodG) in DNA of Cardamine pratensis plants subjected to different growth conditions trying to answer the question whether factors like light and water accessibility or low temperature may have an impact on the total DNA oxidative damage. The level of this modified nucleoside was determined using HPLC coupled to UV absorbance and electrochemical detection (HPLC-UV-EC). We did not observe any statistically significant differences in 8-oxodG level between DNA of etiolated and light exposed plants as well as between DNA of regularly watered and drought-subjected plants. In contrast, we have shown that chilling (1 degree C for 28 h) brings about the increase of 8-oxodG level in DNA.     

Oxidative stress and DNA damage in relation to transition metals overload in Abu-Qir Bay,Egypt

The aim of the present study is to evaluate the transition metals overload in Abu-Qir Bay in Egypt, as compared to a less polluted area (reference area) through some biomarkers of oxidative stress. Catalase enzyme activity, malondialdehyde (MDA) concentration and DNA damage (number of apurinic/apyrimidinic sites) were the tested biomarkers. The levels of iron and copper in Mugil cephalus liver tissues were significantly higher in samples from the polluted area as compared to the reference area: Fe: 407 ± 38 vs. 216 ± 21 μg/g wet wt; p = 0.008, Cu: 54 ± 6 vs. 17.7 ± 4 μg/g wet wt; p = 0.0001. This could account for the observed increase in MDA concentration (15.7 ± 5.7 vs. 2.5 ± 0.5 U/g; p = 0.035), and the elevated number of AP sites (13.9 ± 2.6 vs. 0.37 ± 0.2 AP site/1 × 10⁵ bp; p = 0.0001). Similarly, the activity of catalase enzyme responsible for the cellular defense was significantly high (58.3 ± 12.2 vs. 28.4 ± 4.0 U/mg; p = 0.032). The present data indicated a clear relationship between the pollution degree of the above marine environment and both biochemical and molecular responses of the piscine system.     

Adenosine-induced cell death: evidence for receptor-mediated signalling

Adenosine modulates the proliferation, survival and apoptosis of many different cell types, ranging from epithelial, endothelial and smooth muscle cells, to cells of the immune and neural lineages. In this review, we critically discuss the available in vitro and in vivo data which support a role for adenosine in both development-associated apoptosis, and in diseases characterized by either pathologically increased cell death (e.g., ischemia, trauma and aging-associated neurodegeneration) or abnormally reduced spontaneous apoptosis (e.g., cancer). Particular emphasis is given to the possible role of extracellular adenosine receptors, since these may represent novel and attractive molecular targets for the pharmacological modulation of apoptosis. In some instances, adenosine-induced cell death has been demonstrated to require entry of the nucleoside inside cells; however, in many other cases, activation of specific adenosine extracellular receptors has been demonstrated. Of the four G protein-coupled adenosine receptors so far identified, the A_2A and the A₃ receptors have been specifically implicated in modulation of cell death. For the A₃ receptor, results obtained by exposing both cardiomyocytes and brain astrocytes to graded concentrations of selective agonists suggest induction of both cell protection and cell death. Such opposite effects, which likely depend on the degree of receptor activation, may have important therapeutic implications in the pharmacological modulation of cardiac and brain ischemia. For the A_2A receptor, recent intriguing data suggest a specific role in immune cell death and immunosuppression, which may be relevant to both adenosine-deaminase-immunodeficiency syndrome (a pathology characterized by accumulation of adenosine to toxic levels) and in tumors where induction of apoptosis via activation of specific extracellular receptors may be desirable. Finally, preliminary data suggest that, in a similar way to the adenosine-deaminase-immunodeficiency syndrome, the abnormal accumulation of adenosine in degenerative muscular diseases may contribute to muscle cell death. Although the role of adenosine receptors in this effect still remains to be determined, these data suggest that adenosine-induced apoptosis may also represent a novel pathogenic pathway in muscular dystrophies.     

Foraging costs drive female resistance to a sensory trap

Male ornaments can evolve through the exploitation of female perceptual biases such as those involved in responding to cues from food. This type of sensory exploitation may lead to confusion between the male signals and the cues that females use to find/recognize food. Such interference would be costly to females and may be one reason why females evolve resistance to the male ornaments. Using a group of species of viviparous fish where resistance to a sensory trap has evolved, we demonstrate that females exposed to an ornament that resembles food have a diminished foraging efficiency, that this effect is apparent when foraging on a food item with which the ornament shares visual attributes, and that not all species are equally affected by such confusion. Our results lend support to the model of ornamental evolution through chase-away sexual conflict.     

Reversed plumage ontogeny in a female hummingbird: implications for the evolution of iridescent colours and sexual dichromatism

In polygynous birds, bright plumage is typically more extensive in the sexually competitive males and develops at or after sexual maturity. These patterns, coupled with the importance of male plumage in sexual displays, fostered the traditional hypothesis that bright plumages and sexual dichromatism develop through the actions of sexual selection on males. This view remains problematic for hummingbirds, all of which are polygynous, because their bright iridescent plumages are also important non-sexual signals associated with dominance at floral nectar sources. Here I show that female amethyst-throated sunangels [ Heliangelus amethysticollis (d'Orbigny & Lafresnaye)], moult from an immature plumage with an iridescent gorget to an adult plumage with a non-iridescent gorget. This 'reversed' ontogeny contradicts the notion that iridescent plumage has a sexual function because sexual selection in polygynous birds should be lowest among non-reproductive immature females. Moreover, loss of iridescent plumage in adult females indicates that adult sexual dichromatism in H. amethysticollis is due in large part to changes in female ontogeny. I suggest that both the ontogeny and sexual dichromatism evolved in response to competition for nectar.     

Oxidative stress: damage to intact cells and organs

Oxidative cell damage can be monitored by detection of (a) photoemission of singlet molecular oxygen formed from radical interactions (so-called low-chemical chemiluminescence), (b) end products of lipid peroxidation, such as ethane, and (c) glutathione disulphide release. These methods, preferably used in a complementary fashion, provide insight into the pro-oxidant-antioxidant balance in the intact cell or organ. Recent work from this laboratory on the metabolism of hydroperoxides and aldehydes as well as on redox cycling of the quinone menadione is presented. The comparison of GSSG transport systems in liver and heart reveals a limitation of capacity in the latter, thus making GSSG export potentially critical in the heart. As part of an inter-organ feedback system between extrahepatic tissues and liver, the newly described hormone stimulation of GSH release from liver is also presented.     

Oxidative and nitrative DNA damage in animals and patients with inflammatory diseases in relation to inflammation-related carcinogenesis

Infection and chronic inflammation are proposed to contribute to carcinogenesis through inflammation-related mechanisms. Infection with hepatitis C virus, Helicobacter pylori and the liver fluke, Opisthorchis viverrini (OV), are important risk factors for hepatocellular carcinoma (HCC), gastric cancer and cholangiocarcinoma, respectively. Inflammatory bowel diseases (IBDs) and oral diseases, such as oral lichen planus (OLP) and leukoplakia, are associated with colon carcinogenesis and oral squamous cell carcinoma (OSCC), respectively. We performed a double immunofluorescence labeling study and found that nitrative and oxidative DNA lesion products, 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), were formed and inducible nitric oxide synthase (iNOS) was expressed in epithelial cells and inflammatory cells at the site of carcinogenesis in humans and animal models. Antibacterial, antiviral and antiparasitic drugs dramatically diminished the formation of these DNA lesion markers and iNOS expression. These results suggest that oxidative and nitrative DNA damage occurs at the sites of carcinogenesis, regardless of etiology. Therefore, it is considered that excessive amounts of reactive nitrogen species produced via iNOS during chronic inflammation may play a key role in carcinogenesis by causing DNA damage. On the basis of our results, we propose that 8-nitroguanine is a promising biomarker to evaluate the potential risk of inflammation-mediated carcinogenesis.     

Oxidative damage to DNA in mammalian chromatin.

Efforts have been made to characterize and measure DNA modifications produced in mammalian chromatin in vitro and in vivo by a variety of free radical-producing systems. Methodologies incorporating the technique of gas chromatography/mass spectrometry have been used for this purpose. A number of products from all four DNA bases and several DNA-protein cross-links in isolated chromatin have been identified and quantitated. Product formation has been shown to depend on the free radical-producing system and the presence or absence of oxygen. A similar pattern of DNA modifications has also been observed in chromatin of cultured mammalian cells treated with ionizing radiation or H2O2 and in chromatin of organs of animals treated with carcinogenic metal salts.     

Oxidative damage to 5-methylcytosine in DNA.

Exposure of pyrimidines of DNA to ionizing radiation under aerobic conditions or oxidizing agents results in attack on the 5,6 double bond of the pyrimidine ring or on the exocyclic 5-methyl group. The primary product of oxidation of the 5,6 double bond of thymine is thymine glycol, while oxidation of the 5-methyl group yields 5-hydroxymethyluracil. Oxidation of the 5,6 double bond of cytosine yields cytosine glycol, which decomposes to 5-hydroxycytosine, 5-hydroxyuracil and uracil glycol, all of which are repaired in DNA by Escherichia coli endonuclease III. We now describe the products of oxidation of 5-methylcytosine in DNA. Poly(dG-[3H]dmC) was gamma-irradiated or oxidized with hydrogen peroxide in the presence of Fe3+ and ascorbic acid. The oxidized co-polymer was incubated with endonuclease III or 5-hydroxymethyluracil-DNA glycosylase, to determine whether repairable products were formed, or digested to 2'-deoxyribonucleosides, to determine the total complement of oxidative products. Oxidative attack on 5-methylcytosine resulted primarily in formation of thymine glycol. The radiogenic yield of thymine glycol in poly(dG-dmC) was the same as that in poly(dA-dT), demonstrating that 5-methylcytosine residues in DNA were equally susceptible to radiation-induced oxidation as were thymine residues.     

Female plumage colour influences seasonal oxidative damage and testosterone profiles in a songbird

Across diverse taxa, morphological traits mediate social interactions and mate selection. Physiological constraints on signal elaboration have been widely documented, but the potential for trait display to influence physiological state remains poorly understood. We tested for the presence of causal links between ventral plumage colour—a trait known to covary with reproductive performance—and physiological measures in female North American barn swallows, Hirundo rustica erythrogaster. Naturally darker swallows have lower levels of plasma oxidative damage. Females manipulated to display darker ventral plumage during reproduction rapidly decreased oxidative damage, adopting the physiological state of naturally darker individuals. These results support the presence of a social mechanism that links static plumage traits with the physiological state of their bearer during trait advertisement, long after the completion of signal development.     

No evidence for general condition-dependence of structural plumage colour in blue tits: an experiment

Condition-dependence is a central but contentious tenet of evolutionary theories on the maintenance of ornamental traits, and this is particularly true for structural plumage colour. By providing diets of different nutritional quality to moulting male and female blue tits, we experimentally manipulated general condition within the natural range, avoiding deprivation or stressful treatments. We measured reflectance of the structural-coloured UV/blue crown, a sexually selected trait in males, and the white cheek, a nonpigmented structural colour, directly after moult and again during the following spring mating season. We employed a variety of colour indices, based on spectral shape and avian visual models but, despite significant variation in condition and coloration, found no evidence for condition-dependence of UV/blue or white plumage colour during either season. These and previously published results suggest that structural colour might be sensitive to stress, rather than reduced body condition, during moult.     

Energetic costs of size and sexual signalling in a wolf spider

A prerequisite for honest handicaps is that there are significant condition-dependent costs in the expression of sexual traits. In the wolf spider Hygrolycosa rubrofasciata (Ohlert), sexual signalling (drumming) is costly in terms of increased mortality. Here we investigated whether this mortality may be caused by increased energy expenditure. During sexual signalling, metabolic rate was 22 times higher than at rest and four times higher than when males were actively moving. Metabolic rate per unit mass was positively related to absolute body mass during sexual signalling but not during other activities. This positive relationship is novel to any studies of metabolic rates. Indeed, it seems that the largest males can drum only 12 times per minute before reaching the maximum sustainable metabolic rate, whereas the smallest males may drum up to 39 times per minute. However, there is no relationship between body mass and drumming rate, indicating that larger males are able to compensate for the higher cost of drumming. There was a quadratic relationship between relative abdomen mass and overall body mass, which may provide a partial explanation for the increased energy expenditure of largest males while drumming. Altogether, our results indicate that sexual signalling is highly energetically demanding, which may be the main reason for the honesty of signalling in this species. In addition, the energetic costs are surprisingly strongly size dependent, which may compensate any disadvantage of small male size.     

Oxidative defence reactions in sunflower roots induced by methyl-jasmonate and methyl-salicylate and their relation with calcium signalling

Ca²⁺ plays a critical role as second messenger in the signal–response coupling of plant defence responses, and methyl-jasmonate and methyl-salicylate are important components of signal transduction cascades activating plant defences. When intact axenic non-induced seedling roots of sunflower were treated with different Ca²⁺ concentrations up to 1 mM, there was no significant increase in O ₂ ^.? generation or DMAB–MBTH peroxidase (extracellular, ECPOX) activities in the apoplast, probably because these roots had enough Ca²⁺ in their exo- and endocellular reservoirs. Both activities were strongly inhibited by the RBOH–NADPH oxidase inhibitor DPI and by the Ca²⁺ surrogate antagonist La³⁺, but the voltage-dependent Ca²⁺ channel blocker verapamil was only inhibitory at concentrations higher than those active on animal L-type Ca²⁺ channels. Concentrations >5 mM EGTA (chelating Ca²⁺ in the apoplast) and Li⁺ (inhibiting PI cycle dependent endogenous Ca²⁺ fluxes) also inhibited both activities. W7, inhibitor of binding of Ca–CaM to its target protein, enhanced both activities, but the inactive analogue W5 showed a similar effect. Our data suggest that Ca²⁺ from exocellular and, to a lesser extent, from endocellular stores is involved in oxidative activities, and that RBOH–NADPH oxidase is the main system supporting them. Ca²⁺ activation of the PM cytosolic side of RBOH–NADPH oxidase is probably the key to Ca²⁺ involvement in these processes. Roots induced by MeJA or MeSA showed significant enhancement of both oxidative activities, as corresponding to the oxidative burst evoked by the two phytohormones in the root apoplast. But while ECPOX activity showed a response to the effectors similar to that described above for non-induced roots, O ₂ ^.? generation activity in the apoplast of induced roots was insensitive to EGTA, verapamil and Li⁺, the inhibitors of exogenous and endogenous Ca²⁺ fluxes; only DPI and La³⁺ were inhibitory. As exogenously added 0.1 mM Ca²⁺ also increased O ₂ ^.? generation, we propose that, in these roots, activation of RBOH–NADPH oxidase by Ca²⁺ could be regulated by Ca²⁺ sensors in the apoplast.     

Oxidative damage to surfactant protein D in pulmonary diseases

Surfactant protein D is an important innate host defence molecule that has been shown to interact with a variety of pathogens and to play a role in surfactant homeostasis. The aim of this study was to examine the influence of oxidation on surfactant protein D in different lung diseases. Bronchoalveolar lavage fluids (BALFs) from patients with different grade of protein oxidation were examined for changes in the primary chain and the quaternary structure of surfactant protein D. Significant changes of quaternary surfactant protein-D (SP-D) structure were detected under oxidative conditions in vitro and in vivo. The functional capacity of surfactant protein D to agglutinate bacteria was impaired by oxidation. We conclude that surfactant protein D is an important target of free radicals generated in the lungs. Host defence may be impaired due to the oxidation of surfactant protein D and may contribute to the suppurative lung diseases like cystic fibrosis (CF).     

A label of health: a previous immune challenge is reflected in the expression of a female plumage trait

Studies of ornaments as indicators of individual quality have hitherto focused on males, while studies of female ornaments have been almost absent. However, females within the same species may show large variation in both outer appearance and individual quality. We experimentally examined the effect of an immune challenge on the size of white fringes in the wing feathers produced one to two months after the challenge in female common eiders (Somateria mollissima), a long-lived sea duck. Immune-challenged females produced feathers with smaller white fringes, showing that a previous immune challenge may affect the expression of a plumage trait. We also report an unexpected difference in the expression of this white plumage trait within the immune-challenged group, related to the specific immune response against one of the injected antigens.     

High costs of female choice in a lekking lizard

Although the cost of mate choice is an essential component of the evolution and maintenance of sexual selection, the energetic cost of female choice has not previously been assessed directly. Here we report that females can incur high energetic costs as a result of discriminating among potential mates. We used heart rate biologging to quantify energetic expenditure in lek-mating female Galápagos marine iguanas (Amblyrhynchus cristatus). Receptive females spent 78.9+/-23.2 kJ of energy on mate choice over a 30-day period, which is equivalent to approximately (3/4) of one day's energy budget. Females that spent more time on the territories of high-quality, high-activity males displayed greater energetic expenditure on mate choice, lost more mass, and showed a trend towards producing smaller follicles. Choosy females also appear to face a reduced probability of survival if El Ni?o conditions occur in the year following breeding. These findings indicate that female choice can carry significant costs, and suggest that the benefits that lek-mating females gain through mating with a preferred male may be higher than previously predicted.