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Find video protocols related to scientific articles indexed in Pubmed.
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Identification of the linkage group of the Z sex chromosomes of the sand lizard (Lacerta agilis, Lacertidae) and elucidation of karyotype evolution in lacertid lizards.
Chromosoma
PUBLISHED: 02-05-2014
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The sand lizard (Lacerta agilis, Lacertidae) has a chromosome number of 2n?=?38, with 17 pairs of acrocentric chromosomes, one pair of microchromosomes, a large acrocentric Z chromosome, and a micro-W chromosome. To investigate the process of karyotype evolution in L. agilis, we performed chromosome banding and fluorescent in situ hybridization for gene mapping and constructed a cytogenetic map with 86 functional genes. Chromosome banding revealed that the Z chromosome is the fifth largest chromosome. The cytogenetic map revealed homology of the L. agilis Z chromosome with chicken chromosomes 6 and 9. Comparison of the L. agilis cytogenetic map with those of four Toxicofera species with many microchromosomes (Elaphe quadrivirgata, Varanus salvator macromaculatus, Leiolepis reevesii rubritaeniata, and Anolis carolinensis) showed highly conserved linkage homology of L. agilis chromosomes (LAG) 1, 2, 3, 4, 5(Z), 7, 8, 9, and 10 with macrochromosomes and/or macrochromosome segments of the four Toxicofera species. Most of the genes located on the microchromosomes of Toxicofera were localized to LAG6, small acrocentric chromosomes (LAG11-18), and a microchromosome (LAG19) in L. agilis. These results suggest that the L. agilis karyotype resulted from frequent fusions of microchromosomes, which occurred in the ancestral karyotype of Toxicofera and led to the disappearance of microchromosomes and the appearance of many small macrochromosomes.
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The scent of disease: human body odor contains an early chemosensory cue of sickness.
Psychol Sci
PUBLISHED: 01-22-2014
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Observational studies have suggested that with time, some diseases result in a characteristic odor emanating from different sources on the body of a sick individual. Evolutionarily, however, it would be more advantageous if the innate immune response were detectable by healthy individuals as a first line of defense against infection by various pathogens, to optimize avoidance of contagion. We activated the innate immune system in healthy individuals by injecting them with endotoxin (lipopolysaccharide). Within just a few hours, endotoxin-exposed individuals had a more aversive body odor relative to when they were exposed to a placebo. Moreover, this effect was statistically mediated by the individuals' level of immune activation. This chemosensory detection of the early innate immune response in humans represents the first experimental evidence that disease smells and supports the notion of a "behavioral immune response" that protects healthy individuals from sick ones by altering patterns of interpersonal contact.
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Telomeric attrition with age and temperature in Eastern mosquitofish (Gambusia holbrooki).
Naturwissenschaften
PUBLISHED: 01-02-2014
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Telomeric attrition has repeatedly been found to correlate with the ageing of organisms; however, recent research is increasingly showing that the determinants of attrition dynamics are not well understood. This study examined the relative telomere lengths in Eastern mosquitofish, Gambusia holbrooki, kept at different temperatures and at different ages. Newly born fry were randomly selected for one of four treatment groups: 20, 30, 20-30, and 30-20 °C, where the third and fourth treatment groups were gradually changed from their starting temperature to their final temperature between days 10 and 14. Telomere length was measured, and it was found that length decreased with age and that fish exposed to the 20 °C treatment had significantly shorter telomeres than those that received the 30-20 °C treatment. Telomeric attrition with age agrees with results previously found in studies of telomeres; however, the variation in attrition with temperature was not simply predictable and may be the synergistic effects of temperature and some other factor.
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The impact of length and location of positive margins in predicting biochemical recurrence after robotic-assisted radical prostatectomy with a minimum follow-up time of five years.
BJU Int.
PUBLISHED: 09-11-2013
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To evaluate the role of positive surgical margin (PSM) size/ focality and location in relation to risk of biochemical recurrence (BCR) after robotic-assisted radical prostatectomy (RARP).
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Genetics and evolution of colour patterns in reptiles.
Semin. Cell Dev. Biol.
PUBLISHED: 03-08-2013
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The study of coloration in the polyphyletic reptilians has flourished in the last two decades, in particular with respect to the underlying genetics of colour traits, the function of colours in social interactions, and ongoing selection on these traits in the wild. The taxonomic bias, however, is profound: at this level of resolution almost all available information is for diurnal lizards. Therefore, we focus on case studies, for which there are as complete causal sequences of colour evolution as possible, from phenotypic expression of variation in colour, to ongoing selection in the wild. For work prior to 1992 and for a broader coverage of reptilian coloration we refer the readers to Cooper and Greenburgs (Biology of the Reptilia, 1992) review. There are seven major conclusions we would like to emphasise: (a) visual systems in diurnal lizards are broadly conserved but among the wider range of reptiles in general, there is functionally important variation in the number and type of photoreceptors, spectral tuning of photopigments and optical properties of the eye; (b) coloration in reptiles is a function of complex interactions between structural and pigmentary components, with implications for both proximate control and condition dependence of colour expression; (c) studies of colour-variable species have enabled estimates of heritability of colour and colour patterns, which often show a simple Mendelian pattern of inheritance; (d) colour-polymorphic lizard species sometimes, but not always, show striking differences in genetically encoded reproductive tactics and provide useful models for studying the evolution and maintenance of polymorphism; (e) both male and female colours are sometimes, but not always, a significant component of socio-sexual signalling, often based on multiple traits; (f) evidence for effects of hormones and condition on colour expression, and trade-offs with immunocompetence and parasite load, is variable; (g) lizards show fading of colours in response to physiological stress and ageing and are hence likely to be appropriate models for work on the interactions between handicaps, indicator traits, parasitology and immunoecology.
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Sperm storage and sperm competition across ovarian cycles in the dragon lizard, Ctenophorus fordi.
J Exp Zool A Ecol Genet Physiol
PUBLISHED: 01-23-2013
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Female sperm storage can influence male reproductive success and may favour males that produce sperm that remain viable across several ovarian cycles. Here we show that sperm are viable in the female reproductive tract across ovarian cycles in the mallee dragon, Ctenophorus fordi. Based on experimental mating trials, we show that stored sperm were generally less likely to fertilize eggs than recently inseminated sperm. The fertilization success of stored sperm increased with male body size relative to rivals. This may be due to differences in ejaculate volume or sperm number transferred by males of different sizes. However, there was no evidence that copulation time, which is correlated with ejaculate volume, contributed to fertilization success. We suggest that sperm storage across ovarian cycles may be common in small, multi-clutched lizards and that its impact on selection on male phenotypes could contribute to the evolution of lizard mating systems.
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Progress in the prediction of pKa values in proteins.
Proteins
PUBLISHED: 09-10-2011
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The pK(a) -cooperative aims to provide a forum for experimental and theoretical researchers interested in protein pK(a) values and protein electrostatics in general. The first round of the pK(a) -cooperative, which challenged computational labs to carry out blind predictions against pK(a) s experimentally determined in the laboratory of Bertrand Garcia-Moreno, was completed and results discussed at the Telluride meeting (July 6-10, 2009). This article serves as an introduction to the reports submitted by the blind prediction participants that will be published in a special issue of PROTEINS: Structure, Function and Bioinformatics. Here, we briefly outline existing approaches for pK(a) calculations, emphasizing methods that were used by the participants in calculating the blind pK(a) values in the first round of the cooperative. We then point out some of the difficulties encountered by the participating groups in making their blind predictions, and finally try to provide some insights for future developments aimed at improving the accuracy of pK(a) calculations.
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Oxidative stress physiology in relation to life history traits of a free-living vertebrate: the spotted snow skink, Niveoscincus ocellatus.
Integr Zool
PUBLISHED: 06-08-2011
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Recent research suggests that oxidative stress, via its links to metabolism and senescence, is a key mechanism linking life history traits such as fecundity and growth with survival; however, this has rarely been put under empirical scrutiny within free-living populations. Using a wild population of live-bearing skinks, we explored how plasma antioxidant activity (OXY), reactive oxidative metabolites (ROM), and the estimated oxidative stress index are associated with female and male life history. We found that male skinks have a significantly higher ROM and estimated oxidative stress index than female skinks, but this was not accompanied by a sex difference in mortality. Both sexes showed a non-linear association between OXY and age, indicating that the oldest and youngest individuals had the lowest OXY. Interestingly, female skinks with high OXY showed a decreased probability of survival to the following season. However, we found no significant associations between female reproductive investment (litter size or litter mass) or parturition date (i.e. metabolism) and oxidative status. Combined, our results offer mixed support for a role of oxidative stress in mediating life history traits and suggest that future studies need to explore oxidative stress during vitellogenesis in addition to using an intra-individual approach to understand the cost of reproduction and patterns of aging.
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Basal superoxide as a sex-specific immune constraint.
Biol. Lett.
PUBLISHED: 06-01-2011
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There is increasing evidence that reactive oxygen species (ROS), a group of unstable and highly reactive chemical molecules, play a key role in regulating and maintaining life-history trade-offs. Upregulation of ROS in association with immune activation is costly because it may result in an imbalance between pro- and antioxidants and, hence, oxidative damage. Previous research aimed at quantifying this cost has mostly focused on changes in the pro-/antioxidant balance subsequent to an immune response. Here, we test the hypothesis that systemic ROS may constrain immune activation. We show that systemic, pre-challenge superoxide (SO) levels are negatively related to the strength of the subsequent immune response towards the mitogen phytohaemagglutinin in male, but not female painted dragon lizards (Ctenophorus pictus). We therefore suggest that systemic SO constrains immune activation in painted dragon males. We speculate that this may be due to sex-specific selection pressures on immune investment.
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Sexual differences in telomere selection in the wild.
Mol. Ecol.
PUBLISHED: 04-12-2011
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Telomere length is restored primarily through the action of the reverse transcriptase telomerase, which may contribute to a prolonged lifespan in some but not all species and may result in longer telomeres in one sex than the other. To what extent this is an effect of proximate mechanisms (e.g. higher stress in males, higher oestradiol/oestrogen levels in females), or is an evolved adaptation (stronger selection for telomere length in one sex), usually remains unknown. Sand lizard (Lacerta agilis) females have longer telomeres than males and better maintain telomere length through life than males do. We also show that telomere length more strongly contributes to life span and lifetime reproductive success in females than males and that telomere length is under sexually diversifying selection in the wild. Finally, we performed a selection analysis with number of recruited offspring into the adult population as a response variable with telomere length, life span and body size as predictor variables. This showed significant differences in selection pressures between the sexes with strong ongoing selection in females, with these three predictors explaining 63% of the variation in recruitment. Thus, the sexually dimorphic telomere dynamics with longer telomeres in females is a result of past and ongoing selection in sand lizards. Finally, we compared the results from our selection analyses based on Telometric-derived data to the results based on data generated by the software ImageJ. ImageJ resulted in shorter average telomere length, but this difference had virtually no qualitative effect on the patterns of ongoing selection.
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UV-deprived coloration reduces success in mate acquisition in male sand lizards (Lacerta agilis).
PLoS ONE
PUBLISHED: 04-04-2011
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Recent work on animal signals has revealed a wide occurrence of UV signals in tetrapods, in particular birds, but also in lizards (and perhaps other Squamate reptiles). Our previous work on the Swedish sand lizard (Lacerta agilis) has verified, both in correlative selection analyses in the wild and with laboratory and field experiments, the importance of the green badge on the body sides of adult males for securing mating opportunities, probably mostly through deterring rival males rather than attracting females. The role of UV in communication has, however, never been examined.
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Olfactory working memory: effects of verbalization on the 2-back task.
Mem Cognit
PUBLISHED: 03-04-2011
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Working memory for odors, which has received almost no attention in the literature, was investigated in two experiments. We show that performance in a 2-back task with odor stimuli is well above chance. This is true not only for highly familiar odors, as has been shown by Dade, Zatorre, Evans, and Jones-Gotman, NeuroImage, 14, 650-660, (2001), but also for unfamiliar ones that are notoriously difficult to name. We can conclude that information about an olfactory stimulus can be retained in the short term and can continuously be updated for comparison with new olfactory probes along the lines of a functional odor working memory. However, the performance in the working memory task is highly dependent on participants verbalization of the odor. In addition, results indicated that odor working memory performance is dependent on the ability to discriminate among the odor stimuli (Experiment 2). The results are discussed in relation to recent ideas of a separate olfactory working memory slave system.
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Sex differences in sand lizard telomere inheritance: paternal epigenetic effects increases telomere heritability and offspring survival.
PLoS ONE
PUBLISHED: 02-04-2011
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To date, the only estimate of the heritability of telomere length in wild populations comes from humans. Thus, there is a need for analysis of natural populations with respect to how telomeres evolve.
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Graphical analysis of pH-dependent properties of proteins predicted using PROPKA.
BMC Struct. Biol.
PUBLISHED: 01-26-2011
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Charge states of ionizable residues in proteins determine their pH-dependent properties through their pKa values. Thus, various theoretical methods to determine ionization constants of residues in biological systems have been developed. One of the more widely used approaches for predicting pKa values in proteins is the PROPKA program, which provides convenient structural rationalization of the predicted pKa values without any additional calculations.
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Digit ratio, color polymorphism and egg testosterone in the Australian painted dragon.
PLoS ONE
PUBLISHED: 01-25-2011
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Variation in exposure to sex hormones during early development contributes to phenotypic plasticity in vertebrate offspring. As a proposed marker for prenatal sex hormone exposure and because of their association with various physiological and behavioral characteristics, digit ratio and/or digit length have received notable interest within the field of evolutionary ecology. However, the validity of digit measures as a proxy of prenatal sex hormone exposure is controversial and only few studies have provided direct evidence for the link between digit development and prenatal sex hormones. Here, we report morph- and sex-specific variation in digit ratio in wild painted dragon lizards (Ctenophorus pictus). Lizards expressing a yellow bib have significantly larger third-to-fourth toe ratios (3D:4D) than lizards without a bib. Males have significantly smaller 3D:4D than females. Furthermore, we show that experimental elevation of yolk testosterone significantly increases 3D:4D in hatchling painted dragon lizards, but has no influence on hatchling size. Our results provide direct and indirect evidence for the involvement of prenatal sex steroids in digit development and it is suggested that digit ratio may be used as a biomarker for prenatal steroid exposure in this reptilian species. As such, digit ratio may provide a useful tool to study temporal or spatial differences in the proximate hormonal mechanisms modulating physiological and behavioural phenotypes.
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Improving the desolvation penalty in empirical protein pKa modeling.
J Mol Model
PUBLISHED: 01-13-2011
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Unlike atomistic and continuum models, empirical pk(a) predicting methods need to include desolvation contributions explicitly. This study describes a new empirical desolvation method based on the Born solvation model. The new desolvation model was evaluated by high-level Poisson-Boltzmann calculations, and discussed and compared with the current desolvation model in PROPKA-one of the most widely used empirical protein pK(a) predictors. The new desolvation model was found to remove artificial erratic behavior due to discontinuous jumps from man-made first-shell cutoffs, and thus improves the desolvation description significantly.
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Protein electrostatics and pKa blind predictions; contribution from empirical predictions of internal ionizable residues.
Proteins
PUBLISHED: 01-10-2011
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In this study, we validate and probe the description of electrostatic interactions within proteins by predicting and comparing pK(a) values of ionizable groups in a series of mutated staphylococcal nuclease variants with experiments. This set of pK(a) values is found to be the most challenging pK(a) data to date, because ionizable residues have been introduced in hydrophobic patches in the protein interior and are therefore significantly shifted from their reference solvated values. We find that using PROPKA2 (Li et al., Proteins 2005;61:704-721) results in an rmsd value close to 2 for true blind predictions (1.6 if we reassign the tightly coupled Asp19/21 pair) and close to 1 for postpredictions with the newly developed PROPKA3 (Olsson et al., J. Chem. Theor. Comp. 2011;7:525-537). We also use the performance of the Null-model, predictions made with the reference value only, to provide a better description of the expected errors in pK(a) predictions and to compare submissions made using different subsets of the pK(a) data more consistently.
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In hot pursuit: fluctuating mating system and sexual selection in sand lizards.
Evolution
PUBLISHED: 11-05-2010
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A changing climate is expected to have profound effects on many aspects of ectotherm biology. We report on a decade-long study of free-ranging sand lizards (Lacerta agilis), exposed to an increasing mean mating season temperature and with known operational sex ratios. We assessed year-to-year variation in sexual selection on body size and postcopulatory sperm competition and cryptic female choice. Higher temperature was not linked to strength of sexual selection on body mass, but operational sex ratio (more males) did increase the strength of sexual selection on body size. Elevated temperature increased mating rate and number of sires per clutch with positive effects on offspring fitness. In years when the "quality" of a females partners was more variable (in standard errors of a male sexual ornament), clutches showed less multiple paternity. This agrees with prior laboratory trials in which females exercised stronger cryptic female choice when male quality varied more. An increased number of sires contributing to within-clutch paternity decreased the risk of having malformed offspring. Ultimately, such variation may contribute to highly dynamic and shifting selection mosaics in the wild, with potential implications for the evolutionary ecology of mating systems and population responses to rapidly changing environmental conditions.
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Functional neuronal processing of human body odors.
Vitam. Horm.
PUBLISHED: 09-14-2010
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Body odors carry informational cues of great importance for individuals across a wide range of species, and signals hidden within the body odor cocktail are known to regulate several key behaviors in animals. For a long time, the notion that humans may be among these species has been dismissed. We now know, however, that each human has a unique odor signature that carries information related to his or her genetic makeup, as well as information about personal environmental variables, such as diet and hygiene. Although a substantial number of studies have investigated the behavioral effects of body odors, only a handful have studied central processing. Recent studies have, however, demonstrated that the human brain responds to fear signals hidden within the body odor cocktail, is able to extract kin specific signals, and processes body odors differently than other perceptually similar odors. In this chapter, we provide an overview of the current knowledge of how the human brain processes body odors and the potential importance these signals have for us in everyday life.
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Ultrasound transducer function: annual testing is not sufficient.
Eur J Echocardiogr
PUBLISHED: 06-08-2010
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The objective was to follow-up the study High incidence of defective ultrasound transducers in use in routine clinical practice and evaluate if annual testing is good enough to reduce the incidence of defective ultrasound transducers in routine clinical practice to an acceptable level.
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Correlation between circulatory, local prostatic, and intra-prostatic androgen levels.
Prostate
PUBLISHED: 06-01-2010
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Testosterone is converted to the more potent androgen dihydrotestosterone (DHT) in the prostate. DHT and androgen metabolites are inactivated by uridine diphospho (UDP)-glucuronosyl transferase (UGT) enzymes. Here we have studied the influence of the prostate gland on the systemic levels of DHT. Moreover, genetic variation in androgen metabolizing UGT enzymes and the intra-prostatic levels of glucuronidated DHT metabolites were investigated.
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Female choice for males with greater fertilization success in the Swedish Moor frog, Rana arvalis.
PLoS ONE
PUBLISHED: 04-01-2010
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Studies of mate choice in anuran amphibians have shown female preference for a wide range of male traits despite females gaining no direct resources from males (i.e. non-resource based mating system). Nevertheless, theoretical and empirical studies have shown that females may still gain indirect genetic benefits from choosing males of higher genetic quality and thereby increase their reproductive success.
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Proximate determinants of telomere length in sand lizards (Lacerta agilis).
Biol. Lett.
PUBLISHED: 03-31-2010
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Telomeres are repeat sequences of non-coding DNA that cap the ends of chromosomes and contribute to their stability and the genomic integrity of cells. In evolutionary ecology, the main research target regarding these genomic structures has been their role in ageing and as a potential index of age. However, research on humans shows that a number of traits contribute to among-individual differences in telomere length, in particular traits enhancing cell division and genetic erosion, such as levels of free radicals and stress. In lizards, tail loss owing to predation attempts results in a stress-induced shift to a more cryptic lifestyle. In sand lizard (Lacerta agilis) males, telomere length was compromised by tail regrowth in a body size-related manner, so that small males, which already exhibit more cryptic mating tactics, were less affected than larger males. Tail regrowth just fell short of having a significant relationship with telomere length in females, and so did age in males. In females, there was a significant positive relationship between age and telomere length. We conclude that the proximate effect of compromised antipredation and its associated stress seems to have a more pronounced effect in males than in females and that age-associated telomere dynamics differ between the sexes.
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Carbon chain length and the stimulus problem in olfaction.
Behav. Brain Res.
PUBLISHED: 02-03-2010
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Understanding how odour quality perception is encoded in its molecular properties arguably poses one of the most significant problems in olfaction. Determining the odour structure-quality relationships of structurally similar odorants could provide a key tool to this problem. We tentatively explored whether a mixture of two molecules, differing only in carbon chain length (C), would yield the same percept as a single odorant with an intermediate carbon chain length, akin to colour vision, or be perceived as a different quality. Ability to discriminate between pairs of iso-intense solutions of n-butanol (4C), n-propanol (3C), n-pentanol (5C), and an intermediate 50/50 molecular weight mixture of n-propanol and n-pentanol (3C/5C) was assessed in 20 healthy young adults. We found that participants were able to discriminate 4C from the 50/50 molecular weight mixture of n-propanol and n-pentanol (3C/5C), and also from the other alcohols. In conclusion, we successfully replicated previous data demonstrating that participants are able to discriminate between structurally similar alcohols, and, more importantly, the present study shows that an odour mixture of two molecules differing only in carbon chain length is clearly distinguishable from a single odorant with an intermediate carbon chain length. These findings suggest that although carbon chain length matters to odour quality, carbon chain length is not a physical continuum within homologous series of substances that corresponds to a single qualitative dimension akin to the wavelength-hue relation for monochromatic light.
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Poor relief, taxes and the first Universal Pension Reform: the origin of the Swedish welfare state reconsidered.
Scand J Hist
PUBLISHED: 01-06-2010
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In the year 1900, Sweden probably had the oldest population in the contemporary world. It was also the first nation to implement a universal pension system in 1913. The universal character in early social legislation has certainly been decisive for the development of the Swedish welfare state. This alternative has not been self-evident. Why did the reforms turn universal, when the continental model, the Bismarck social security system, was exclusively directed at industrial workers? Research has concentrated on demographic factors and growing demands for social security, or on the fact that Sweden was still a predominantly rural society with about 2,400 local authorities. This article examines the development of social legislation in the light of local government expenditures and incomes, and suggests an overlooked possibility: the formulation of the first universal national social security reform was a redistributional response to uneven distribution of incomes and general expenditures among the rural districts in Sweden.
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High incidence of defective ultrasound transducers in use in routine clinical practice.
Eur J Echocardiogr
PUBLISHED: 09-01-2009
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The objective was to evaluate the function of ultrasound transducers in use in routine clinical practice and thereby estimating the incidence of defective transducers.
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Consistent paternity skew through ontogeny in Perons tree frog (Litoria peronii).
PLoS ONE
PUBLISHED: 08-18-2009
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A large number of studies in postcopulatory sexual selection use paternity success as a proxy for fertilization success. However, selective mortality during embryonic development can lead to skews in paternity in situations of polyandry and sperm competition. Thus, when assessment of paternity fails to incorporate mortality skews during early ontogeny, this may interfere with correct interpretation of results and subsequent evolutionary inference. In a previous series of in vitro sperm competition experiments with amphibians (Litoria peronii), we showed skewed paternity patterns towards males more genetically similar to the female.
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Odor interaction between Bourgeonal and its antagonist undecanal.
Chem. Senses
PUBLISHED: 07-20-2009
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The perceived quality of a binary mixture will, as a rule of thumb, be dominated by the quality of the stronger unmixed component. On the other hand, there are mechanisms that, in theory, suggest that this will not always be true; one example being receptor antagonism. Undecanal has been indicated as an antagonist for bourgeonal-sensitive receptors in the human olfactory epithelium. Therefore, we investigated mixtures of isointense concentrations of bourgeonal and undecanal and, as a control, mixtures of isointense concentrations of bourgeonal and n-butanol. Both mixture types were investigated at 2 levels of concentration. The particular aim was to see if the bourgeonal-undecanal mixtures would exhibit asymmetric odor quality favoring the perception of the antagonist and the control mixture would not. For the control mixture, indeed odor quality tended to be dominated by the strongest component before mixing as would be suggested from previous studies. In line with the hypothesis, the bourgeonal-undecanal mixture was dominated by the antagonists quality, but only when mixed at higher concentrations, altogether suggesting the effects of a low-affinity receptor antagonism. This is, to our knowledge, the first demonstration of how antagonistic interaction at the level of the receptor can affect the perception of odor mixtures in humans.
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Variation in levels of reactive oxygen species is explained by maternal identity, sex and body-size-corrected clutch size in a lizard.
Naturwissenschaften
PUBLISHED: 04-28-2009
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Many organisms show differences between males and females in growth rate and crucial life history parameters, such as longevity. Considering this, we may expect levels of toxic metabolic by-products of the respiratory chain, such as reactive oxygen species (ROS), to vary with age and sex. Here, we analyse ROS levels in female Australian painted dragon lizards (Ctenophorus pictus) and their offspring using fluorescent probes and flow cytometry. Basal level of four ROS species (singlet oxygen, peroxynitrite, superoxide and H(2)O(2)) measured with a combined marker, and superoxide measured specifically, varied significantly among families but not between the sexes. When blood cells from offspring were chemically encouraged to accelerate the electron transport chain by mitochondrial uncoupling, net superoxide levels were three times higher in daughters than sons (resulting in levels outside of the normal ROS range) and varied among mothers depending on offspring sex (significant interaction between maternal identity and offspring sex). In offspring, there were depressive effects on ROS of size-controlled relative clutch size, which relies directly on circulating levels of vitellogenin, a confirmed antioxidant in some species. Thus, levels of reactive oxygen species varies among females, offspring and in relation to reproductive investment in a manner that makes its regulatory processes likely targets of selection.
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Learning features in computer simulation skills training.
Nurse Educ Pract
PUBLISHED: 04-03-2009
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New simulation tools imply new opportunities to teach skills and train health care professionals. The aim of this study was to investigate the learning gained from computer simulation skills training. The study was designed for optimal educational settings, which benefit student-centred learning. Twenty-four second year undergraduate nursing students practised intravenous catheterization with the computer simulation program CathSim. Questionnaires were answered before and after the skills training, and after the skills examination. When using CathSim, the students appreciated the variation in patient cases, the immediate feedback, and a better understanding of anatomy, but they missed having an arm model to hold. We concluded that CathSim was useful in the students learning process and skills training when appropriately integrated into the curriculum. Learning features to be aware of when organizing curricula with simulators are motivation, realism, variation, meaningfulness and feedback.
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Sex-specific developmental plasticity in response to yolk corticosterone in an oviparous lizard.
J. Exp. Biol.
PUBLISHED: 03-31-2009
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Corticosterone exposure during prenatal development as a result of maternal upregulation of circulating hormone levels has been shown to have effects on offspring development in mammals. Corticosterone has also been documented in egg yolk in oviparous vertebrates, but the extent to which this influences phenotypic development is less studied. We show that maternal corticosterone is transferred to egg yolk in an oviparous lizard (the mallee dragon, Ctenophorus fordi Storr), with significant variation among clutches in hormone levels. Experimental elevation of yolk corticosterone did not affect hatching success, incubation period or offspring sex ratio. However, corticosterone did have a sex-specific effect on skeletal growth during embryonic development. Male embryos exposed to relatively high levels of corticosterone were smaller on average than control males at hatching whereas females from hormone-treated eggs were larger on average than control females. The data thus suggest that males are not just more sensitive to the detrimental effects of corticosterone but rather that the sexes may have opposite responses to corticosterone during development. Positive selection on body size at hatching for both sexes in this species further suggests that increased corticosterone in egg yolk may have sex-specific fitness consequences, with potential implications for sex allocation and the evolution of hormone-mediated maternal effects.
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Climate effects on offspring sex ratio in a viviparous lizard.
J Anim Ecol
PUBLISHED: 03-25-2009
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1. Understanding individual and population responses to climate change is emerging as an important challenge. Because many phenotypic traits are sensitive to environmental conditions, directional climate change could significantly alter trait distribution within populations and may generate an evolutionary response. 2. In species with environment-dependent sex determination, climate change may lead to skewed sex ratios at hatching or birth. However, there are virtually no empirical data on the putative link between climatic parameters and sex ratios from natural populations. 3. We monitored a natural population of viviparous lizards with temperature-dependent sex determination (Niveoscincus ocellatus) over seven field seasons. Sex ratios at birth fluctuated significantly among years and closely tracked thermal conditions in the field, with the proportion of male offspring increasing in colder years. 4. This is the first study to demonstrate the effect of local climatic conditions (e.g. temperature) on offspring sex ratio fluctuations in a free-living population of a viviparous ectotherm. A succession of warmer-than-usual years (as predicted under many climate-change scenarios) likely would generate female-biased sex ratios at birth, while an increase in interannual variation (as also predicted under climate change scenarios) could lead to significant fluctuations in cohort sex ratios. If cohort sex ratio bias at birth leads to adult sex ratio bias, long-term directional changes in thermal conditions may have important effects on population dynamics in this species.
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The human brain distinguishes between single odorants and binary mixtures.
Cereb. Cortex
PUBLISHED: 03-10-2009
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Single odors are processed differently from odor mixtures in the cortex of rodents. We investigated whether single and binary odor mixtures activate different regions also in the human brain. We analyzed data from positron emission tomography scans using pyridine, citral, and 5 mixtures of pyridine and citral in proportions varying from 10/90 to 90/10, with 50/50 being the most impure. Comparing mixtures with single odorants gave activation in the left cingulate and right parietal and superior frontal cortices and bilateral activation in the anterior and lateral orbitofrontal cortices. We also found that brain activity in the lateral orbitofrontal cortex (OFC) increased with odorant impurity, whereas the anterior OFC was activated for binary odor mixtures and deactivated for single components. We conclude that binary odor mixtures and their individual components are processed differently by the human brain. The lateral portion of the OFC responds to mixture impurity in a graded fashion, whereas the anterior portion acts like an on-off detector of odor mixtures.
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Consistent male-male paternity differences across female genotypes.
Biol. Lett.
PUBLISHED: 02-25-2009
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In a recent paper, we demonstrated that male-female genetic relatedness determines male probability of paternity in experimental sperm competition in the Perons tree frog (Litoria peronii), with a more closely related male outcompeting his rival. Here, we test the hypothesis that a male-male difference in siring success with one female significantly predicts the corresponding difference in siring success with another female. With male sperm concentration held constant, and the proportion of viable sperm controlled statistically, the male-male difference in siring success with one female strongly predicted the corresponding difference in siring success with another female, and alone explained more than 62 per cent of the variance in male-male siring differences. This study demonstrates that male siring success is primarily dictated by among-male differences in innate siring success with less influence of male-female relatedness.
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Testing the quality of a carrier: a field experiment on lizard signalers.
Evolution
PUBLISHED: 01-22-2009
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In the Australian painted dragon lizard (Ctenophorus pictus), males occur in two different morphs with respect to gular color, with or without a yellow bib. Males without a bib lost within-clutch paternity significantly more often to rivals than bibbed males. Thus, it appears that bibs identify some phenotypic advantage linked to competitive ability. To test whether this could be related to whole-organism capacity to withstand an increased workload (due to better health and vigor, or evolved differences in self-maintenance), we implanted males with a lead pellet (loaded), Styrofoam pellet (controls), or sham-operated males without implants (shams), and compared male categories with respect to how they maintained body mass during the mating season. Somewhat unexpectedly, bibbed males consistently lost more body weight across all treatments and controls, although we could not verify that this translated into higher mortality in this short-lived animal (about 80% survive for one year only). However, bibbed males may invest more into "mating success" than nonbibbed males, which agrees with our experimental results and paternity data.
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Polymorphic ROS scavenging revealed by CCCP in a lizard.
Naturwissenschaften
PUBLISHED: 01-07-2009
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Ingestion of antioxidants has been argued to scavenge circulating reactive molecules (e.g., free radicals), play a part in mate choice (by mediating access to this important resource), and perhaps increase life span. However, recent work has come to question these relationships. We have shown elsewhere in the polychromatic lizard, Ctenophorus pictus, that diet supplementation of carotenoids as antioxidants does not depress circulating natural reactive oxygen species (ROS) levels and leads to no corresponding improvement of color traits. However, a much stronger test would be to experimentally manipulate the ROS levels themselves and assess carotenoid-induced ROS depression. Here, we achieve this by using carbonyl cyanide 3-chlorophenylhydrazone, which elevates superoxide (SO) formation approximately threefold at 10 microM in this model system. We then look for depressing effects on ROS of the carotenoids in order to assess whether super-production of SO makes carotenoid effects on elevated ROS levels detectable. The rationale for this treatment was that if not even such elevated levels of SO are reduced by carotenoid supplementation, the putative link carotenoids, ROS depression, and mate quality (in terms of antioxidant capacity) is highly questionable. We conclude that there is no significant effect of carotenoids on mean SO levels even at the induced ROS levels. However, our results showed a significant interaction effect between carotenoid treatment and male color, with red males having higher ROS levels than yellow males. We suggest that this may be because different pigments are differently involved in the generation of the integumental colors in the two morphs with concomitant effects on ROS depletion depending on carotenoid uptake or allocation to coloration and antioxidation.
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Pre-hatching exposure to water mold reduces size at metamorphosis in the moor frog.
Oecologia
PUBLISHED: 01-07-2009
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Developmental plasticity is increasingly recognized as important for ecological and evolutionary processes. However, few studies consider the potential for delayed effects of early environments. Here, we show that tadpoles hatching from clutches exposed to water mold (Saprolegnia) have 20% decreased mass at metamorphosis, despite no further exposure subsequent to hatching. The effects were consistent across four populations that have previously been shown to vary in their resistance to infection during embryonic development. Contrary to expectations, time to hatching or metamorphosis was not affected, suggesting that the results do not reflect an evolved escape strategy from infected waters triggered by embryonic conditions. Instead, decreased mass at metamorphosis may arise from carry-over effects of impaired embryo development. Such strong links across developmental stages have potential consequences for the evolution of plasticity and the responses of populations to emergent infections.
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Mind over age--stereotype activation and olfactory function.
Chem. Senses
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Given that context affects olfaction and the elderly exhibit olfactory deficits, the current study tested whether a subtle change in internal context, evoked by priming the elderly stereotype, would affect performance in a variety of olfactory tasks including odor sensitivity, discrimination, and identification (Experiment 1), as well as perceived odor intensity, pleasantness and familiarity, and an odor reaction time task (Experiment 2). Such internalization of the elderly stereotype has been demonstrated with slower walking speeds and fewer words recalled in a memory task. In the current study, 76 participants first listened to a presentation about age-related declines in olfaction and then participated in 3 language tasks which, unbeknownst to them, served as the elderly stereotype priming manipulation. This priming manipulation was effective at decreasing walking speed and word recall, confirming the findings of previous researchers; however, olfaction was not affected. Whether olfaction is resistant to stereotype priming is discussed.
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A significant component of ageing (DNA damage) is reflected in fading breeding colors: an experimental test using innate antioxidant mimetics in painted dragon lizards.
Evolution
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A decade ahead of their time, von Schantz et al. united sexual selection and free radical biology by identifying causal links between deep-rooted physiological processes that dictate resistance to toxic waste from oxidative metabolism (reactive oxygen species, ROS), and phenotypic traits, such as ornaments. Ten years later, these ideas have still only been tested with indirect estimates of free radical levels (oxidative stress) subsequent to the action of innate and dietary antioxidants. Here, we measure net superoxide (a selection pressure for antioxidant production) and experimentally manipulate superoxide antioxidation using a synthetic mimetic of superoxide dismutase (SOD), Eukarion 134 (EUK). We then measure the toxic effect of superoxide in terms of DNA erosion and concomitant loss of male breeding coloration in the lizard, Ctenophorus pictus. Control males suffered more DNA damage than EUK males. Spectroradiometry showed that male coloration is lost in relation to superoxide and covaries with DNA erosion; in control males, these variables explained loss of color, whereas in EUK males, the fading of coloration was unaffected by superoxide and unrelated to DNA damage. Thus, EUKs powerful antioxidation removes the erosion effect of superoxide on coloration and experimentally verifies the prediction that colors reflect innate capacity for antioxidation.
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Predictors of telomere content in dragon lizards.
Naturwissenschaften
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Telomeres shorten as a consequence of DNA replication, in particular in cells with low production of telomerase and perhaps in response to physiological stress from exposure to reactive oxygen species, such as superoxide. This process of telomere attrition is countered by innate antioxidation, such as via the production of superoxide dismutase. We studied the inheritance of telomere length in the Australian painted dragon lizard (Ctenophorus pictus) and the extent to which telomere length covaries with mass-corrected maternal reproductive investment, which reflects the level of circulating yolk precursor and antioxidant, vitellogenin. Our predictors of offspring telomere length explained 72 % of telomere variation (including interstitial telomeres if such are present). Maternal telomere length and reproductive investment were positively influencing offspring telomere length in our analyses, whereas flow cytometry-estimated superoxide level was negatively impacting offspring telomere length. We suggest that the effects of superoxide on hatchling telomere shortening may be partly balanced by transgenerational effects of vitellogenin antioxidation.
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Sex-specific SOD levels and DNA damage in painted dragon lizards (Ctenophorus pictus).
Oecologia
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When groups of individuals differ in activities that may influence the production of reactive molecules, such as superoxide, we expect selection to result in congruent upregulation of antioxidant production in the group(s) most at risk of suffering concomitant erosion of essential tissue and biomolecules, such as DNA. We investigate this in a (near) annual lizard species, the Australian painted dragon (Ctenophorus pictus), in which males and females have fundamentally different lifestyles, with males being overtly conspicuous and aggressive, whereas females are placid and camouflaged. When kept in identical conditions to females in captivity, males had higher levels of superoxide dismutase (SOD) through the activity season, which is consistent with selection for a higher capacity of superoxide antioxidation and a lower level of DNA damage than females. Males, however, lacked the clear negative, linear relationship between SOD and DNA erosion observed in females, suggesting that female upregulation of SOD results in a more predictable antioxidation and a more immediate target for selection. Lastly, we analysed aspects of female reproduction from a DNA erosion perspective. Females closer to ovulation, hence with less remaining, circulating vitellogenin, had higher superoxide levels. Furthermore, a multiple regression analysis showed that females that produced more clutches over time suffered more DNA erosion, whereas females with higher SOD levels suffered less DNA erosion.
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The smell of age: perception and discrimination of body odors of different ages.
PLoS ONE
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Our natural body odor goes through several stages of age-dependent changes in chemical composition as we grow older. Similar changes have been reported for several animal species and are thought to facilitate age discrimination of an individual based on body odors, alone. We sought to determine whether humans are able to discriminate between body odor of humans of different ages. Body odors were sampled from three distinct age groups: Young (20-30 years old), Middle-age (45-55), and Old-age (75-95) individuals. Perceptual ratings and age discrimination performance were assessed in 41 young participants. There were significant differences in ratings of both intensity and pleasantness, where body odors from the Old-age group were rated as less intense and less unpleasant than body odors originating from Young and Middle-age donors. Participants were able to discriminate between age categories, with body odor from Old-age donors mediating the effect also after removing variance explained by intensity differences. Similarly, participants were able to correctly assign age labels to body odors originating from Old-age donors but not to body odors originating from other age groups. This experiment suggests that, akin to other animals, humans are able to discriminate age based on body odor alone and that this effect is mediated mainly by body odors emitted by individuals of old age.
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The testing effect as a function of explicit testing instructions and judgments of learning.
Exp Psychol
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During study, people monitor their learning; the output of this monitoring is captured in so-called judgments of learning (JOLs). JOLs predict later recall better if they are made after a slight delay, instead of immediately after study (the delayed JOL effect). According to the self-fulfilling prophecy (SFP) hypothesis delayed JOLs are based on covert retrieval attempts from long-term memory, and successful retrieval attempts in themselves enhance learning (the testing effect). We compared memory for 40 Swahili-Swedish paired associates after a week as a function of three different learning conditions, namely study plus (i) explicitly instructed self-testing, (ii) delayed JOLs, or (iii) less self-testing. We showed that repeated delayed JOLs lead to a memory improvement that does not differ significantly from a comparable condition where the participants are explicitly testing memory, and both the latter groups performed reliably better than a group that self-tested less. The results suggest that delayed JOLs improve long-term retention as efficiently as explicit memory testing and lend support to the SFP hypothesis.
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Net superoxide levels: steeper increase with activity in cooler female and hotter male lizards.
J. Exp. Biol.
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Ectotherms increase their body temperature in response to ambient heat, thereby elevating their metabolic rate. An often inferred consequence of this is an overall upregulation of gene expression and energetic expenditure, and a concomitant increased production of reactive oxygen species (e.g. superoxide) and, perhaps, a shortened lifespan. However, recent work shows that this may be a superficial interpretation. For example, sometimes a reduced temperature may in fact trigger up-regulation of gene expression. We studied temperature and associated activity effects in male and female Australian painted dragon lizards (Ctenophorus pictus) by allowing the lizards to bask for 4 h versus 12 h, and scoring their associated activity (inactive versus active basking and foraging). As predicted, long-basking lizards (hereafter hot) showed heightened activity in both sexes, with a more pronounced effect in females. We then tested for sex-specific effects of basking treatment and activity levels on the increase in net levels of superoxide. In males, short-baskers (hereafter cold) had significantly more rapidly decreasing levels of superoxide per unit increasing activity than hot males. In females, however, superoxide levels increased faster with increasing activity in the cold than in the hot basking treatment, and females earlier in the ovarian cycle had lower superoxide levels than females closer to ovulation. In short, males and females differ in how their levels of reactive oxygen species change with temperature-triggered activity.
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Polymorphic male color morphs visualized with steroids in monomorphic females: a tool for designing analysis of sex-limited trait inheritance.
J. Exp. Biol.
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In diploid animals, males and females share most of the genome (except sex-specific elements, such as sex chromosome genes), yet despite sharing the underlying genes that hard-wire traits, males and females may differ in their phenotypes when traits are controlled by proximate mechanisms, such as hormones. In color polymorphic species where coloration is only expressed in one sex, the design of studies of the inheritance of color and coevolved morph-specific traits (e.g. territorial vs sneaker strategies, skewed energetic investment in territorial defense vs sperm production, etc.) is compromised as the expression of morph-coding genes is only visualized in one sex. Here, we circumvented this problem by first characterizing oxidative stress traits in both sexes and then using testosterone implants in females to expose their otherwise silent coloration. Males of our model species are highly territorial and exhibit morph-specific levels of aggression, whereas females are non-territorial and display very low levels of aggression. Interestingly, reactive oxygen species levels were found to be morph specific regardless of sex, despite considerable differences in lifestyle. Males and females did differ remarkably, however, in superoxide levels depending on whether they sported a colored throat bib or not, a trait also used in male sexual signaling. Females with throat bibs had significantly lower levels of superoxide than females without a bib, which was not the case for males.
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JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.