Prenatal yolk corticosterone exposure promotes skeletal growth and induces oxidative imbalance in yellow-legged gull embryos

Maternally-derived hormones induce variation in offspring phenotype, with consequences that can carry-over into post-natal life and even into adulthood. In birds, maternal egg corticosterone (CORT) is known to exert contrasting effects on offspring morphology, physiology and behaviour after hatching. However, information on the effects of CORT exposure on pre-hatching embryonic development is limited. We experimentally increased yolk CORT levels in yellow-legged gull (Larus michahellis) eggs, and assessed the effects on embryo pre-hatching development and oxidative status of brain and liver. CORT-supplemented embryos reached a larger skeletal size and liver mass compared to controls. Embryos from CORT-injected last-laid eggs showed decreased activity of the hepatic antioxidant enzymes superoxide dismutase and catalase, while intermediate-laid eggs showed an increased levels of lipid peroxidation. However, elevated yolk CORT did not affect oxidative stress endpoints in the brain. Our results indicate that elevated yolk CORT levels affect prenatal embryo development by promoting skeletal growth, and induce laying sequence- and organ-specific oxidative imbalance, with potential adverse consequences during postnatal life especially for late-hatched offspring.

Social-Economic-Political-Emotional (SEPE) factors regulate human growth

Background There is a recurring and seamless interaction between the biology of human development and the social-economic-political-emotional (SEPE) environment. The SEPE environment influences the quality of the material conditions for human biology and, simultaneously, human growth in height and other dimensions provide social and moral signals that provide information to community networks. Objectives This article reviews the role of SEPE factors in human growth, especially skeletal growth. Sample and Methods The meaning of SEPE is defined and shown to be related to individual and group prestige, to social identity, and to ego and task motivation. These influence dominance or subordination of communities and the material and moral conditions of societies. Historical and contemporary examples of SEPE effects on skeletal size are presented. Results Membership in a SEPE community impacts skeletal size in height and breadth. Higher SEPE classes are taller, lower SEPE classes are broader. In elite level sport the winners have more growth stimulation via the hormone IGF-1 even before the contest. These findings are explained in terms of dominance versus subordination and the Community Effect in Height hypothesis. Conclusions SEPE factor regulation of human growth is shown to be a more comprehensive explanation for plasticity in height than traditional concepts such as socioeconomic status and simple-minded genetic determinism. People belonging to upper SEPE class communities, the elites, know that they are superior and are treated as such by the non-elites. The material and moral condition for life operating through these community social networks provide positive stimulation for the elites and negative stimulation for the lower SEPE classes. These differences maintain the gradients in height between SEPE communities in human societies.

Osteohistology and growth dynamics of the Brazilian noasaurid Vespersaurus paranaensis Langer et al., 2019 (Theropoda: Abelisauroidea)

Although the knowledge of bone histology of non-avian theropods has advanced considerably in recent decades, data about the bone tissue patterns, growth dynamics and ontogeny of some taxa such as abelisauroids are still limited. Here we describe the bone microstructure and growth dynamics of the Brazilian noasaurine Vespersaurus paranaensis using five femora and six tibiae and quantify the annual growth marks through retrocalculation of missing ones to estimate ontogenetic ages. The femoral series comprises four femoral histological classes (FHC I-IV), varying from two annuli or LAGs to seven LAGs. Femora show that sexual maturity was achieved around the seventh to tenth year of life, whereas the tibiae suggest it was earlier (around three to five years old). Tibiae represent three histological classes (THC I-III) displaying from three to nine LAGs. Two tibiae (THC III) exhibit an external fundamental system indicating that these specimens reached full skeletal size. The heterogeneous maturity observed in Vespersaurus hind limb bones could result from differential allometry scaling between femora and tibiae length with the body length. The predominant parallel-fibered bone matrix suggests that Vespersaurus grew more slowly than most theropods, including other abelisauroids, in a pattern shared with the noasaurines Masiakasaurus knopfleri from Madagascar and CPPLIP 1490 from Brazil. This deviation from the typical theropod growth pattern may be mainly correlated with small body size, but also may related to resource limitation imposed by the arid climate prevailing in southwestern Gondwana during Cretaceous. Moreover, given the ecological and phylogenetic similarities among these taxa, such features would probably be apomorphic within Noasauridae.

Sexual dimorphism in skeletal shape in voles (Arvicolinae): disparate selection on male bodies and female heads

Sexual dimorphism evolves as a response to different selective pressures on males and females. In mammals, sexual selection on traits that improve a male’s ability to compete for access to mates is a common cause of sexual dimorphism. In addition to body mass, adaptations in specific components of the musculoskeletal system that increase strength, stability, and agility, may improve male fighting performance. Here we test the hypotheses that males, when compared to females, are more specialized for physical competition in their skeletal anatomy and that the degree of this sexual dimorphism increases with the intensity of male–male competition. In three species of voles (Cricetidae: Arvicolinae: Microtus), we found partial support for these hypotheses. Male-biased sexual dimorphism in a set of functional indices associated with improved fighting performance was identified in the postcranial anatomy. This dimorphism was greatest in the polygynous Microtus californicus, absent in the monogamous M. ochrogaster, and intermediate in the promiscuous or socially flexible M. oeconomus. However, in the skull, we found results opposite to our predictions. Females had larger skulls relative to overall skeletal size than did males. This may be associated with selection for increased food processing efficiency, which should be highly important because of the compounding effects of increased caloric requirements during gestation and lactation, and the generally low-quality diet of voles. In addition, larger heads in females may be associated with selection for greater digging ability or for defending offspring. These results suggest disparate selective pressures on the postcranial skeletons and skulls of male and female voles.

P3419Independent effects of visceral, subcutaneous and liver fat, and fat-free mass on cardiometabolic risk factors in teenagers

Cardiometabolic (CM) disorders begin earlier than previously thought. Better understanding of drivers of CM risk in the young is needed to address this. Adiposity is an established concern but studies largely rely on indirect markers eg. body mass index (BMI) to assess it. BMI is known to reflect both skeletal size & adiposity. This study aimed to compare effects of BMI with independent effects of liver fat percentage (LFP), fat-free mass (FFM), & subcutaneous (SAT) & visceral (SAT) adipose tissue on CM risk in teenagers. Healthy teens [N=82; Age 13–19y; 39 overwt/obese; 46F/36M] had volumetric magnetic resonance (MR) tissue mapping (neck-to-knee T2*-IDEAL). BMI z-score (WHO age/sex reference; zBMI), systolic BP (SBP), fasting blood (TRIGlyceride; CHOLesterol; HDL; IL6; CRP; white blood cells [WBC]; LEPTIN), & insulin & glucose response [0, 20, 40, 60, 90, 120 & 240 min] to a mixed meal (75g glucose + cream) were assessed. Indices of insulin resistance (HOMA-IR) and sensitivity (MATSUDA-IS) were derived from fasting measures & integrated meal responses, respectively. Independent effects of LFP, FFM, SAT & VAT were tested by conditional regression in a 4 compartment model (4CM). Higher zBMI was positively correlated with TRIG, IL6, CRP, WBC, HOMA-IR, LEPTIN & SBP, & inversely with HDL & MATSUDA-IS (Table). The 4CM showed that SAT was responsible for most of these links but VAT contributed to lower MATSUDA-IS, SAT was positively correlated with CHOL (zBMI was not), & FFM was a significant predictor of HDL, CRP & LEPTIN. It was solely responsible for the association of zBMI with SBP. There were no independent effects of LFP. zBMI was strongly driven by both FFM & SAT, limiting its ability to differentiate effects of skeletal size from those of adiposity. Correlation coefficients BMI TRIG (mmol/L) CHOL (mmol/L) HDL (mmol/L) IL6 (pg/mL) CRP (mg/L) WBC (x109/L) HOMA-IR MATSUDA-IS LEPTIN (ng/mL) SBP (mmHg) Median (IQR) 23.4 (20.3, 29.6) 0.64 (0.52, 1.00) 3.5 (3.2, 4.0) 1.2 (1.0, 1.3) 4.0 (2.6, 6.7) 0.67 (0.22, 1.80) 5.6 (4.7, 7.1) 1.5 (0.8, 2.2) 9.3 (5.5, 12.6) 11.1 (2.1, 24.6) 114 (108, 120) zBMI 0.33§ 0.16 −0.43‡ 0.27¶ 0.69‡ 0.51‡ 0.54‡ −0.48‡ 0.77‡ 0.27¶ LFP 0.18 −0.06 0.18 0.19 0.00 −0.06 0.11 0.23 −0.21 −0.00 0.13 VAT 0.07 0.18 0.08 −0.22 0.09 −0.00 0.12 0.19 −0.35§ −0.08 0.09 SAT 0.89‡ 0.37§ 0.33§ −0.25¶ 0.37§ 0.57‡ 0.45† 0.61‡ −0.44† 0.85‡ −0.10 FFM 0.86‡ 0.04 −0.16 −0.34§ −0.02 0.31¶ −0.01 0.25 −0.25 0.39§ 0.34§ ¶P<0.05; §P<0.01; †P<0.001; ‡P<0.0001. We found associations of zBMI with CM risk in teens that are usually interpreted as due to adiposity. Although SAT was largely responsible, FFM & VAT were important too & the link between BMI & SBP was due solely to FFM. Associations of CM risk factors with BMI may reflect non-adipose tissue effects & should be interpreted cautiously in the young. Acknowledgement/Funding Alexander Jones is funded by a British Heart Foundation Intermediate Clinical Research Fellowship (FS/18/22/33479)

Atoh8 acts as a regulator of chondrocyte proliferation and differentiation in endochondral bones

Atonal homolog 8 (Atoh8) is a transcription factor of the basic helix-loop-helix (bHLH) protein family, which is expressed in the cartilaginous elements of endochondral bones. To analyze its function during chondrogenesis we deleted Atoh8 in mice using a chondrocyte- (Atoh8flox/flox;Col2a1-Cre) and a germline- (Atoh8flox/flox;Prx1-Crefemale) specific Cre allele. In both strains, Atoh8 deletion leads to a reduced skeletal size of the axial and appendicular bones, but the stages of phenotypic manifestations differ. While we observed obviously shortened bones in Atoh8flox/flox;Col2a1-Cre mice only postnatally, the bones of Atoh8flox/flox;Prx1-Crefemale mice are characterized by a reduced bone length already at prenatal stages. Detailed histological and molecular investigations revealed reduced zones of proliferating and hypertrophic chondrocytes. In addition, Atoh8 deletion identified Atoh8 as a positive regulator of chondrocyte proliferation. As increased Atoh8 expression is found in the region of prehypertrophic chondrocytes where the expression of Ihh, a main regulator of chondrocyte proliferation and differentiation, is induced, we investigated a potential interaction of Atoh8 function and Ihh signaling. By activating Ihh signaling with Purmorphamine we demonstrate that Atoh8 regulates chondrocyte proliferation in parallel or downstream of Ihh signaling while it acts on the onset of hypertrophy upstream of Ihh likely by modulating Ihh expression levels.

A unified-models analysis of the development of sexual size dimorphism in Damaraland mole-rats, Fukomys damarensis

Individual variation in growth rates often generates variation in fitness. However, the ability to draw meaningful inferences from growth data depends on the use of growth models that allow for direct comparisons of growth between the sexes, between populations, and between species. Unlike traditional sigmoid functions, a recently parameterized family of unified growth models provides a reliable basis for comparisons since each parameter affects a single curve characteristic and parameters are directly comparable across the unified family. Here, we use the unified-models approach to examine the development of sexual size dimorphism in Damaraland mole-rats (Fukomys damarensis), where breeding males are larger than breeding females. Using skeletal measurements, we show here that the larger size of male Damaraland mole-rats arises from an increased growth rate across the entire period of development, rather than through sex differences in the duration or timing of growth. Male-biased skeletal size dimorphism is not unusual among rodents, and our measures of sex differences in size in captive mole-rats are close to sexual size differences in the wild, where size dimorphism = 1.04 (male:female). We hope our study will encourage the wide use of unified growth models by mammalogists.