Gender Differences in Post-Operative Human Skin.

Although the impact of age, gender, and obesity on the skin wound healing process has been extensively studied, the data related to gender differences in aspects of skin scarring are limited. The present study performed on abdominal human intact and scar skin focused on determining gender differences in extracellular matrix (ECM) composition, dermal white adipose tissue (dWAT) accumulation, and Foxn1 expression as a part of the skin response to injury. Scar skin of men showed highly increased levels of COLLAGEN 1A1, COLLAGEN 6A3, and ELASTIN mRNA expression, the accumulation of thick collagen I-positive fibers, and the accumulation of α-SMA-positive cells in comparison to the scar skin of women. However, post-injured skin of women displayed an increase (in comparison to post-injured men's skin) in collagen III accumulation in the scar area. On the contrary, women's skin samples showed a tendency towards higher levels of adipogenic-related genes (PPARγ, FABP4, LEPTIN) than men, regardless of intact or scar skin. Intact skin of women showed six times higher levels of LEPTIN mRNA expression in comparison to men intact (p < 0.05), men post-injured (p < 0.05), or women post-injured scar (p < 0.05) skin. Higher levels of FOXN1 mRNA and protein were also detected in women than in men's skin. In conclusion, the present data confirm and extend (dWAT layer) the data related to the presence of differences between men and women in the skin, particularly in scar tissues, which may contribute to the more effective and gender-tailored improvement of skin care interventions.

A Systematic Review on Quiescent State Research Approaches in S. cerevisiae.

Quiescence, the temporary and reversible arrest of cell growth, is a fundamental biological process. However, the lack of standardization in terms of reporting the experimental details of quiescent cells and populations can cause confusion and hinder knowledge transfer. We employ the systematic review methodology to comprehensively analyze the diversity of approaches used to study the quiescent state, focusing on all published research addressing the budding yeast Saccharomyces cerevisiae. We group research articles into those that consider all cells comprising the stationary-phase (SP) population as quiescent and those that recognize heterogeneity within the SP by distinguishing phenotypically distinct subpopulations. Furthermore, we investigate the chronological age of the quiescent populations under study and the methods used to induce the quiescent state, such as gradual starvation or abrupt environmental change. We also assess whether the strains used in research are prototrophic or auxotrophic. By combining the above features, we identify 48 possible experimental setups that can be used to study quiescence, which can be misleading when drawing general conclusions. We therefore summarize our review by proposing guidelines and recommendations pertaining to the information included in research articles. We believe that more rigorous reporting on the features of quiescent populations will facilitate knowledge transfer within and between disciplines, thereby stimulating valuable scientific discussion.

What do zebra finches learn besides singing? Systematic mapping of the literature and presentation of an efficient associative learning test.

The process of learning in birds has been extensively studied, with a focus on species such as pigeons, parrots, chickens, and crows. In recent years, the zebra finch has emerged as a model species in avian cognition, particularly in song learning. However, other cognitive domains such as spatial memory and associative learning could also be critical to fitness and survival, particularly during the intensive juvenile period. In this systematic review, we provide an overview of cognitive studies on zebra finches, with a focus on domains other than song learning. Our findings indicate that spatial, associative, and social learning are the most frequently studied domains, while motoric learning and inhibitory control have been examined less frequently over 30 years of research. All of the 60 studies included in this review were conducted on captive birds, limiting the generalizability of the findings to wild populations. Moreover, only two of the studies were conducted on juveniles, highlighting the need for more research on this critical period of learning. To address this research gap, we propose a high-throughput method for testing associative learning performance in a large number of both juvenile and adult zebra finches. Our results demonstrate that learning can occur in both age groups, thus encouraging researchers to also perform cognitive tests on juveniles. We also note the heterogeneity of methodologies, protocols, and subject exclusion criteria applied by different researchers, which makes it difficult to compare results across studies. Therefore, we call for better communication among researchers to develop standardised methodologies for studying each cognitive domain at different life stages and also in their natural conditions.

Variable ambient temperature promotes song learning and production in zebra finches.

Current climate change is leading to increasingly unpredictable environmental conditions and is imposing new challenges to wildlife. For example, ambient conditions fluctuating during critical developmental periods could potentially impair the development of cognitive systems and may therefore have a long-term influence on an individual's life. We studied the impact of temperature variability on zebra finch cognition, focusing on song learning and song quality (N = 76 males). We used a 2 × 2 factorial experiment with two temperature conditions (stable and variable). Half of the juveniles were cross-fostered at hatching to create a mismatch between pre- and posthatching conditions, the latter matching this species' critical period for song learning. We found that temperature variability did not affect repertoire size, syllable consistency, or the proportion of syllables copied from a tutor. However, birds that experienced variable temperatures in their posthatching environment were more likely to sing during recordings. In addition, birds that experienced variable prenatal conditions had higher learning accuracy than birds in stable prenatal environments. These findings are the first documented evidence that variable ambient temperatures can influence song learning in zebra finches. Moreover, they indicate that temperature variability can act as a form of environmental enrichment with net positive effects on cognition.

Little transparency and equity in scientific awards for early- and mid-career researchers in ecology and evolution.

Scientific awards can shape scientific careers, helping to secure jobs and grants, but can also contribute to the lack of diversity at senior levels and in the elite networks of scientists. To assess the status quo and historical trends, we evaluated 'best researcher' awards and 'best paper' early- and mid-career awards from broad-scope international journals and societies in ecology and evolution. Specifically, we collated information on eligibility rules, assessment criteria and potential gender bias. Our results reveal that, overall, few awards foster equitable access and assessment. Although many awards now explicitly allow extensions of the eligibility period for substantial career interruptions, there is a general lack of transparency in terms of assessment and consideration of other differences in access to opportunities and resources among junior researchers. Strikingly, open science practices were mentioned and valued in only one award. By highlighting instances of desirable award characteristics, we hope this work will nudge award committees to shift from simple but non-equitable award policies and practices towards strategies enhancing inclusivity and diversity. Such a shift would benefit not only those at the early- and mid-career stages but the whole research community. It is also an untapped opportunity to reward open science practices, promoting transparent and robust science.

The role of antioxidant response and nonphotochemical quenching of chlorophyll fluorescence in long-term adaptation to Cu-induced stress in Chlamydomonas reinhardtii.

Copper is an essential micronutrient, but at supraoptimal concentrations it is also highly toxic, inducing oxidative stress and disrupting photosynthesis. The aim of the present study was to analyze selected protective mechanisms in strains of Chlamydomonas reinhardtii adapted and not adapted for growth in the presence of elevated copper concentrations. Two algal lines (tolerant and non-tolerant to high Cu2+ concentrations) were used in experiments to study photosynthetic pigment content, peroxidase activity, and non-photochemical quenching. The content of prenyllipids was studied in four different algal lines (two of the same as above and two new ones). The copper-adapted strains contained about 2.6 times more α-tocopherol and plastoquinol and about 1.7 times more total plastoquinone than non-tolerant strains. Exposure to excess copper led to oxidation of the plastoquinone pool in non-tolerant strains, whereas this effect was less pronounced or did not occur in copper-tolerant strains. Peroxidase activity was approximately 1.75 times higher in the tolerant strain than in the non-tolerant one. The increase in peroxidase activity in the tolerant strain was less pronounced when the algae were grown in dim light. In the tolerant line nonphotochemical quenching was induced faster and was usually about 20-30% more efficient than in the non-tolerant line. The improvement of antioxidant defense and photoprotection may be important factors in the evolutionary processes leading to tolerance to heavy metals.

Will GLP-1 Analogues and SGLT-2 Inhibitors Become New Game Changers for Diabetic Retinopathy?

Diabetic retinopathy (DR) is the most frequent microvascular complication of diabetes mellitus (DM), estimated to affect approximately one-third of the diabetic population, and the most common cause of preventable vision loss. The available treatment options focus on the late stages of this complication, while in the early stages there is no dedicated treatment besides optimizing blood pressure, lipid and glycemic control; DR is still lacking effective preventive methods. glucagon-like peptide 1 receptor agonists (GLP-1 Ras) and sodium-glucose cotransporter 2 (SGLT-2) inhibitors have a proven effect in reducing risk factors of DR and numerous experimental and animal studies have strongly established its retinoprotective potential. Both drug groups have the evident potential to become a new therapeutic option for the prevention and treatment of diabetic retinopathy and there is an urgent need for further comprehensive clinical trials to verify whether these findings are translatable to humans.

Adults Do Not Distinguish Action Intentions Based on Movement Kinematics Presented in Naturalistic Settings.

Predicting others' actions is an essential part of acting in the social world. Action kinematics have been proposed to be a cue about others' intentions. It is still an open question as to whether adults can use kinematic information in naturalistic settings when presented as a part of a richer visual scene than previously examined. We investigated adults' intention perceptions from kinematics using naturalistic stimuli in two experiments. In experiment 1, thirty participants watched grasp-to-drink and grasp-to-place movements and identified the movement intention (to drink or to place), whilst their mouth-opening muscle activity was measured with electromyography (EMG) to examine participants' motor simulation of the observed actions. We found anecdotal evidence that participants could correctly identify the intentions from the action kinematics, although we found no evidence for increased activation of their mylohyoid muscle during the observation of grasp-to-drink compared to grasp-to-place actions. In pre-registered experiment 2, fifty participants completed the same task online. With the increased statistical power, we found strong evidence that participants were not able to discriminate intentions based on movement kinematics. Together, our findings suggest that the role of action kinematics in intention perception is more complex than previously assumed. Although previous research indicates that under certain circumstances observers can perceive and act upon intention-specific kinematic information, perceptual differences in everyday scenes or the observers' ability to use kinematic information in more naturalistic scenes seems limited.

The orchard plot: Cultivating a forest plot for use in ecology, evolution, and beyond.

"Classic" forest plots show the effect sizes from individual studies and the aggregate effect from a meta-analysis. However, in ecology and evolution, meta-analyses routinely contain over 100 effect sizes, making the classic forest plot of limited use. We surveyed 102 meta-analyses in ecology and evolution, finding that only 11% use the classic forest plot. Instead, most used a "forest-like plot," showing point estimates (with 95% confidence intervals [CIs]) from a series of subgroups or categories in a meta-regression. We propose a modification of the forest-like plot, which we name the "orchard plot." Orchard plots, in addition to showing overall mean effects and CIs from meta-analyses/regressions, also include 95% prediction intervals (PIs), and the individual effect sizes scaled by their precision. The PI allows the user and reader to see the range in which an effect size from a future study may be expected to fall. The PI, therefore, provides an intuitive interpretation of any heterogeneity in the data. Supplementing the PI, the inclusion of underlying effect sizes also allows the user to see any influential or outlying effect sizes. We showcase the orchard plot with example datasets from ecology and evolution, using the R package, orchard, including several functions for visualizing meta-analytic data using forest-plot derivatives. We consider the orchard plot as a variant on the classic forest plot, cultivated to the needs of meta-analysts in ecology and evolution. Hopefully, the orchard plot will prove fruitful for visualizing large collections of heterogeneous effect sizes regardless of the field of study.

Mapping the past, present and future research landscape of paternal effects.

BACKGROUND: Although in all sexually reproducing organisms an individual has a mother and a father, non-genetic inheritance has been predominantly studied in mothers. Paternal effects have been far less frequently studied, until recently. In the last 5 years, research on environmentally induced paternal effects has grown rapidly in the number of publications and diversity of topics. Here, we provide an overview of this field using synthesis of evidence (systematic map) and influence (bibliometric analyses). RESULTS: We find that motivations for studies into paternal effects are diverse. For example, from the ecological and evolutionary perspective, paternal effects are of interest as facilitators of response to environmental change and mediators of extended heredity. Medical researchers track how paternal pre-fertilization exposures to factors, such as diet or trauma, influence offspring health. Toxicologists look at the effects of toxins. We compare how these three research guilds design experiments in relation to objects of their studies: fathers, mothers and offspring. We highlight examples of research gaps, which, in turn, lead to future avenues of research. CONCLUSIONS: The literature on paternal effects is large and disparate. Our study helps in fostering connections between areas of knowledge that develop in parallel, but which could benefit from the lateral transfer of concepts and methods.

Proximate Causes of Infertility and Embryo Mortality in Captive Zebra Finches.

AbstractSome species show high rates of reproductive failure, which is puzzling because natural selection works against such failure in every generation. Hatching failure is common in both captive and wild zebra finches (Taeniopygia guttata), yet little is known about its proximate causes. Here we analyze data on reproductive performance (the fate of >23,000 eggs) based on up to 14 years of breeding of four captive zebra finch populations. We find that virtually all aspects of reproductive performance are negatively affected by inbreeding (mean r=-0.117); by an early-starting, age-related decline (mean r=-0.132); and by poor early-life nutrition (mean r=-0.058). However, these effects together explain only about 3% of the variance in infertility, offspring mortality, fecundity, and fitness. In contrast, individual repeatability of different fitness components varied between 15% and 50%. As expected, we found relatively low heritability in fitness components (median: 7% of phenotypic variation and 29% of individually repeatable variation). Yet some of the heritable variation in fitness appears to be maintained by antagonistic pleiotropy (negative genetic correlations) between male fitness traits and female and offspring fitness traits. The large amount of unexplained variation suggests a potentially important role of local dominance and epistasis, including the possibility of segregating genetic incompatibilities.

Monitoring of fungal root colonisation, arbuscular mycorrhizal fungi diversity and soil microbial processes to assess the success of ecosystem translocation.

To compensate for an airport expansion, including construction on valuable wet meadows of a Natura 2000 system, 1.3 ha of turf, cut into blocks, were transferred to artificial basins in a habitat garden. To evaluate the impact of translocation on this ecosystem, and thus the success of its preservation, we monitored fungal root colonisation of Molinia caerulea, the diagnostic plant species for wet meadows, along with arbuscular mycorrhizal fungi (AMF) species richness and composition in soils and soil microbial processes for three seasons: prior to the transfer (2013) and the two following years (2014-15). We observed few changes in the fungal colonisation of M. caerulea, suggesting that the fungal associations of this species were unaffected. The number of AMF species declined directly after the translocation; however, in 2015, an increased number of species was recorded. There were no differences in AMF species composition, nor did soil basal respiration rate, substrate-induced respiration (SIR), or substrate-active biomass (Cmic) change over the years. Only metabolic coefficient (qCO2) decreased after the transfer. The small number of effects in fungal root colonisation, AMF diversity, and microbial processes following the translocation of the ecosystem prove its success. This can be attributed to the deep turf translocation that kept the relevant microbial communities almost unaffected.

Chicken or egg? Outcomes of experimental manipulations of maternally transmitted hormones depend on administration method - a meta-analysis.

Steroid hormones are important mediators of prenatal maternal effects in animals. Despite a growing number of studies involving experimental manipulation of these hormones, little is known about the impact of methodological differences among experiments on the final results expressed as offspring traits. Using a meta-analytical approach and a representative sample of experimental studies performed on birds, we tested the effect of two types of direct hormonal manipulations: manipulation of females (either by implantation of hormone pellets or injection of hormonal solutions) and manipulation of eggs by injection. In both types of manipulation we looked at the effects of two groups of hormones: corticosterone and androgens in the form of testosterone and androstenedione. We found that the average effect on offspring traits differed between the manipulation types, with a well-supported positive effect of egg manipulation and lack of a significant effect of maternal manipulation. The observed average positive effect for egg manipulation was driven mainly by androgen manipulations, while corticosterone manipulations exerted no overall effect, regardless of manipulation type. Detailed analyses revealed effects of varying size and direction depending on the specific offspring traits; e.g., egg manipulation positively affected physiology and behaviour (androgens), and negatively affected future reproduction (corticosterone). Effect size was negatively related to the dose of androgen injected into the eggs, but unrelated to timing of manipulation, offspring developmental stage at the time of measuring their traits, solvent type, the site of egg injection and maternal hormone delivery method. Despite the generally acknowledged importance of maternal hormones for offspring development in birds, the overall effect of their experimental elevation is rather weak, significantly heterogeneous and dependent on the hormone and type of manipulation. We conclude by providing general recommendations as to how hormonal manipulations should be performed in order to standardize their impact and the results achieved. We also emphasize the need for research on free-living birds with a focus on fitness-related and other long-term effects of maternal hormones.

[Application of Brain-Boy Universal Professional in preliminary assessment of auditory processing disorder]. / Zastosowanie Brain-Boy Universal Professional we wstepnej ocenie zaburzen przetwarzania sluchowego.

Increasing numbers of hearing pathology is auditory processing disorders. Auditory Processing Disorders (APD) are defined as difficulty in using auditory information to communicate and learn in the presence of normal peripheral hearing. It may be recognized as a problem with understanding of speech in noise and perception disorder of distorted speech. APD may accompany to articulation disorders, language problems and difficulties in reading and writing. The diagnosis of auditory processing disorders causes many difficulties primarily due to the lack of common testing procedures, precise criteria for qualification to the group of norm and pathology. The Brain-Boy Universal Professional (BUP) is one of diagnostics tools. It enables to assess the higher auditory functions. AIM: The aim of the study was preliminary assessment of hearing difficulties that may suggest the occurrence of auditory processing disorders in children. The questionnaire of hearing difficulties and BUP was used. MATERIALS AND METHODS: Study includes 20 participants 2nd grade students of elementary school. The examination of the basic central functions was carried out with BUP. The parents and teacher complete the questionnaire to evaluate the hearing problems. RESULTS: Studies carried out indicate that the 40% schoolchild have hearing difficulties. The high percentage of deficits in auditory functions was confirmed with research results of medical device and the questionnaire for teacher. CONCLUSIONS: On the basis of the studies conducted may establish that the Warnke Method can serve as preliminary assessment of hearing difficulties that may suggest the occurrence of auditory processing disorders in children.

Higher growth rate and gene expression in male zebra finch embryos are independent of manipulation of maternal steroids in the eggs.

Sexual dimorphism in prenatal development is widespread among vertebrates, including birds. Its mechanism remains unclear, although it has been attributed to the effect of maternal steroid hormones. The aim of this study was to investigate how increased levels of steroid hormones in the eggs influence early embryonic development of male and female offspring. We also asked whether maternal hormones take part in the control of sex-specific expression of the genes involved in prenatal development. We experimentally manipulated hormones' concentrations in the egg yolk by injecting zebra finch females prior to ovulation with testosterone or corticosterone. We assessed growth rate and expression levels of CDK7, FBP1 and GHR genes in 37h-old embryos. We found faster growth and higher expression of two studied genes in male compared to female embryos. Hormonal treatment, despite clearly differentiating egg steroid levels, had no effect on the sex-specific pattern of the embryonic gene expression, even though we confirmed expression of receptors of androgens and glucocorticoids at such an early stage of development. Thus, our study shows high stability of the early sex differences in the embryonic development before the onset of sexual differentiation and indicates their independence of maternal hormones in the egg.

Elevated reproduction does not affect telomere dynamics and oxidative stress.

ABSTRACT: Oxidative stress and telomere dynamics are considered to be powerful biomarkers quantifying a potential trade-off between current reproduction and self-maintenance. Recent studies confirmed the negative impact of elevated reproduction on telomeres, but the evidence for the cost of reproduction in terms of oxidative stress remains equivocal. In order to induce reproductive costs, we experimentally manipulated reproductive effort by increasing brood size in captive zebra finches (Taeniopygia guttata) and additionally challenged all birds by a low ambient temperature to facilitate detection of these costs. We were not able to show any negative effects of elevated reproductive effort on telomere dynamics and oxidative stress among parents, although brood enlargement was effective in terms of total mass and number of fledged young. Interestingly, irrespective of brood size treatment, we found a significant increase in antioxidant capacity at peak breeding while oxidative damage did not change with time. Our results may suggest that reproduction, instead of generating costs, may stimulate physiological functions promoting self-maintenance in terms of higher protection against free radicals. Possibly, opportunistic breeders such as zebra finches may not impede their future performance for the sake of current reproduction. SIGNIFICANCE STATEMENT: This study interrogates a molecular background behind one of the most intriguing trade-offs that potentially occurs between self-maintenance and reproduction. We manipulated breeding effort in zebra finches to understand if the cost of reproduction can be mediated by telomere dynamics and oxidative stress. In our study system, we did not detect the direct reproductive costs in terms of parental oxidative damage and telomere loss; instead, these costs were paid by the offspring in terms of their inhibited growth rate. Moreover, we found that entering into the reproductive state strongly stimulated self-maintenance by increasing antioxidant capacity in parents. Our results emphasize that current reproductive success is not always prioritized over investment in body maintenance preventing the oxidative cost of reproduction.

Increased fat catabolism sustains water balance during fasting in zebra finches.

Patterns of physiological flexibility in response to fasting are well established, but much less is known about the contribution of water deprivation to the observed effects. We investigated body composition and energy and water budget in three groups of zebra finches: birds with access to food and water, food-deprived birds having access to drinking water and food-and-water-deprived birds. Animals were not stimulated by elevated energy expenditure and they were in thermoneutral conditions; thus, based on previous studies, water balance of fasting birds was expected to be maintained by increased catabolism of proteins. In contrast to this expectation, we found that access to water did not prevent reduction of proteinaceous tissue, but it saved fat reserves of the fasting birds. Thus, water balance of birds fasting without access to water seemed to be maintained by elevated fat catabolism, which generated 6 times more metabolic water compared with that in birds that had access to water. Therefore, we revise currently established views and propose fat to serve as the primary source for metabolic water production. Previously assumed increased protein breakdown for maintenance of water budget would occur if fat stores were depleted or if fat catabolism reached its upper limits due to high energy demands.

Bacteria of leg atheromatous arteries responsible for inflammation.

BACKGROUND: Ischaemia of the lower limbs is frequently followed by inflammation and, in advanced cases, necrosis of peripheral tissues. Whether this is caused by arterial hypoperfusion only or by the presence of bacteria in the arterial walI as well remains unclear. The aim of the study was to prove the presence and source of bacteria in arterial specimens and evaluate their chemotactic properties resulting in the formation of periarterial cellular infiltrates. MATERIALS AND METHODS: Bacterial culture and testing for 16sRNA were performed in fragments of popliteal artery harvested from amputated limbs. Carotid artery plaques served as controls. Fragments of arteries were transplanted into scid mice to evaluate their chemotactic activity for macrophages. RESULTS: a) higher prevalence of isolates and 16sRNA in atherosclerotic popliteal than carotid arteries, b) high density of plaque and periarterial infiltrates and mRNA level for pro-inflammatory cytokines in popliteal arteries, c) prevalent microbes were Staphylococcus aureus, S. epidermidis and Enterococci, d) foot skin and arterial bacterial phenotypes and DNA revealed evident similarities, and e) more intensive mouse macrophage accumulation in popliteal than carotid implants into scid mice. CONCLUSIONS: The presence of bacteria in the lower limb arterial wall was documented. They may predispose to inflammation secondary to ischaemic changes.

Primary hyperparathyroidism in pregnancy ­ a diagnostic and therapeutic challenge.

Hypercalcaemia during pregnancy is uncommon, and mostly associated with primary hyperparathyroidism (pHPT). If unrecognised, it poses a significant risk for the mother and the foetus. Maternal symptoms include: hyperemesis, muscle weakness, pancreatitis, nephrolithiasis, bone disease, mental status changes, and hypercalcaemic crisis. Untreated disease complicates foetal development and foetal death is a significant risk. Our case illustrates the difficulty in detecting pHPT during pregnancy, serious complications connected with severe hypercalcaemia, and difficulties in preparing the patient for surgical treatment. Our review of the medical literature did not identify any previous case of a pregnant woman with hypercalcaemic crisis (total calcium 17 mg/dL, parathyroid hormone 2302 pg/mL), acute pancreatitis caused by pHPT, and with hyperthyroidism, who had undergone a successful surgical treatment.

Sexual Dimorphism in the Early Embryogenesis in Zebra Finches.

Sex-specific gene expression before the onset of gonadogensis has been documented in embryos of mammals and chickens. In several mammalian species, differences in gene expression are accompanied by faster growth of pre-implantation male embryos. Here we asked whether avian embryos before gonadal differentiation are also sex-dimorphic in size and what genes regulate their growth. We used captive zebra finches (Taeniopygia guttata) whose freshly laid eggs were artificially incubated for 36-40 hours. Analyses controlling for the exact time of incubation of 81 embryos revealed that males were larger than females in terms of Hamburger and Hamilton stage and number of somites. Expression of 15 genes involved in cell cycle regulation, growth, metabolic activity, steroidogenic pathway and stress modulation were measured using RT-PCR in 5 male and 5 female embryos incubated for exactly 36 h. We found that in the presence of equal levels of the growth hormone itself, the faster growth of male embryos is most likely achieved by the overexpression of the growth hormone receptor gene and three other genes responsible for cell cycle regulation and metabolism, all of them located on the Z chromosome. Autosomal genes did not show sex-specific expression, except for the steroidogenic factor 1 which was expressed only in female embryos. To our knowledge this is the first report of sexual size dimorphism before gonadogenesis in birds. The finding suggests that faster growth of early male embryos is conserved through the mammalian and bird phyla, irrespective of their differential sex chromosome systems.