Detecting menarcheal status through dental mineralization stages?

Menarche is an indicator frequently used to study variation in growth, development, and related health conditions among members of living populations. As a life event, menarche is often associated with changes in an individual's social identity. The reproductive lifespan, which for females starts with menarche, is a paramount feature of palaeodemographic studies. Determination of menarche status from the skeletal remains of individuals of past populations can be obtained by assessing the developmental status of the iliac crest, as well as the hand and wrist bones, which are, unlike teeth, often poorly recovered in bioarchaeological contexts. The present study seeks to evaluate the link between dental mineralization and menarche in a population of known menarche status. The relationship between permanent teeth mineralization and menarche status was investigated by using data of developing permanent teeth (167 radiographs) rated in accordance with the well‐known standards of Demirjian et al. and Moorrees et al. collected among 73 living French females of known menarcheal status. Using correlation ratios, GLMM and CART algorithm, menarcheal status is correlated with mineralization of the premolars. Menarcheal status is predicted correctly for 92 and 77% of radiographs of the learning and validation samples, respectively. Although promising, the results require caution prior to generalization to other populations. The age of menarche in this particular sample may simply coincide with the development of the premolars in this particular sample. Therefore, further investigation applied to populations with various mean ages of menarche is required in order to provide new evidence of variation in human growth and development from the correspondence between the mineralization of the permanent teeth and menarche.     

Genetic architecture of growth and early life‐history transitions in anadromous and derived freshwater populations of steelhead

Heritabilities of growth, precocious maturation and smolting were measured in 75 families of juvenile steelhead or rainbow trout Oncorhynchus mykiss , progeny of within and between line matings (crosses) of wild, anadromous steelhead and wild, resident (lake) rainbow trout originally derived from the same anadromous stock 70 years earlier. The tagged yearling progeny were combined by line in common freshwater rearing containers and graded into three categories: mature, smolt or rearing (undifferentiated) at age 2 years. Heritabilities of precocious male maturity, smolting and growth were moderate to high, and the genetic correlation between growth and smolting was low. Smolting and precocious male maturity were highly variable among families within lines and significantly different between lines. Each of the four lines produced significant numbers of smolts at age two. Smolting and maturation were negatively genetically correlated, which may explain the persistence of smolting in the lake population despite strong selection against lake smolts; balancing selection on male maturation age may help to maintain variation for smolting. The high heritability of smolting, coupled with the inability of smolts that leave the lake to return to it indicates that the genetic potential for smolting can lie dormant or be maintained through a dynamic interaction between smolting and early maturation for decades despite complete selection against the phenotype. The results have significant implications for the preservation of threatened anadromous stocks in fresh water and the inclusion of resident fish of formerly anadromous populations, currently trapped behind long‐standing barriers to migration, as one component of the same population.     

Probabilistic reaction norm reveals family-related variation in the association between size,condition, and sexual maturation onset in Atlantic salmon (Salmo salar)

This study investigated the relationship between the size, condition, year class, family, and sexual maturity of Atlantic salmon (Salmo salar) using data collected in an aquaculture selective breeding programme. Males that were sexually mature at 2 years of age (maiden spawn) have, on average, greater fork length and condition factor (K) at 1 year of age than their immature counterparts. For every 10-mm increase in fork length or 0.1 increase in K at 1 year of age, the odds of sexual maturity at 2 years of age increased by 1.48 or 1.22 times, respectively. Females that were sexually mature at 3 years of age (maiden spawn) have, on average, greater fork length and K at 2 years of age than their immature counterparts. For every 10-mm increase in fork length or 0.1 increase in K at 2 years of age, the odds of sexual maturity at 3 years of age increased by 1.06 or 1.44 times, respectively. The family explained 34.93% of the variation in sexual maturity among 2-year-old males that was not attributable to the average effects of fork length and K at 1 year of age and year class. The proportion of variation in sexual maturity among 3-year-old females explained by the family could not be investigated. These findings suggest that the onset of sexual maturation in Atlantic salmon is conditional on performance (with respect to energy availability) surpassing a threshold, the magnitude of which can vary between families and is determined by a genetic component. This could support the application of genetic selection to promote or inhibit the onset of sexual maturation in farmed stocks.     

Sex difference in the effect of puberty on the relationship between fat mass and bone mass in 926 healthy subjects, 6 to 18 years old

Objective: Understanding factors influencing bone mineral accrual is critical to optimize peak bone mass during childhood. The epidemic of pediatric obesity and reported higher incident of fracture risk in obese children led us to study the influence of fat mass on bone mineral content (BMC) in children. Research Methods and Procedures: Height; weight; pubertal stage; and BMC, non‐bone fat‐free mass (nbFFM), and fat mass (FM) by DXA were obtained in a multiethnic group of healthy children (444 girls/482 boys; 6 to 18 years old) recruited in the New York metropolitan area. Regression techniques were used to explore the relationship between BMC and FM, with age, height, nbFFM, pubertal stage, sex, and ethnicity as covariates. Results: Because there were significant sex interactions, separate regression analyses were performed for girls and boys. Although ln(nbFFM) was the greatest predictor of ln(BMC), ln(FM) was also a significant predictor in prepubertal boys and all girls but not in pubertal boys. This effect was independent of ethnicity. Discussion: FM was a determinant of BMC in all girls but in only prepubertal boys. Our study confirms nbFFM as the greatest predictor of BMC but is the first to find a sex difference in the effect of puberty on the relationship of FM to BMC. Our results suggest that, in two individuals of the same sex and weight, the one with greater fat mass will have lower BMC, especially pubertal boys. The implications of these findings for achievement of optimal peak bone mass in a pediatric population with an unprecedented incidence of overweight and “overfat” status remain to be seen.     

Lin28 gene and mammalian puberty

Lin28a and Lin28b, homologs of the Caenorhabditis elegans Lin28 gene, play important roles in cell pluripotency, reprogramming, and tumorigenicity. Recently, genome‐wide association and transgenic studies showed that Lin28a and/or Lin28b gene were involved in the onset of mammalian puberty, the stage representing the attainment of reproduction capacity; however, the detailed mechanism of these genes in mammalian puberty remains largely unknown. The present paper reviews the research progress on the roles of Lin28a/b genes in the onset of mammalian puberty by analyzing the results coming from gene expression patterns, mutations, and transgenic studies, and put forward possible pathways for further studies on their roles in animal reproduction.     

Maternal care of heterozygous dopamine receptor D4 knockout mice: Differential susceptibility to early‐life rearing conditions

The differential susceptibility hypothesis proposes that individuals who are more susceptible to the negative effects of adverse rearing conditions may also benefit more from enriched environments. Evidence derived from human experiments suggests the lower efficacy dopamine receptor D4 (DRD4) 7‐repeat as a main factor in exhibiting these for better and for worse characteristics. However, human studies lack the genetic and environmental control offered by animal experiments, complicating assessment of causal relations. To study differential susceptibility in an animal model, we exposed Drd4^+/? mice and control litter mates to a limited nesting/bedding (LN), standard nesting (SN) or communal nesting (CN) rearing environment from postnatal day (P) 2‐14. Puberty onset was examined from P24 to P36 and adult females were assessed on maternal care towards their own offspring. In both males and females, LN reared mice showed a delay in puberty onset that was partly mediated by a reduction in body weight at weaning, irrespective of Drd4 genotype. During adulthood, LN reared females exhibited characteristics of poor maternal care, whereas dams reared in CN environments showed lower rates of unpredictability towards their own offspring. Differential susceptibility was observed only for licking/grooming levels of female offspring towards their litter; LN reared Drd4^+/? mice exhibited the lowest and CN reared Drd4^+/? mice the highest levels of licking/grooming. These results indicate that both genetic and early‐environmental factors play an important role in shaping maternal care of the offspring for better and for worse.     

彩色多普勒超声联合性激素对性早熟女童的诊断价值及其相关性分析

摘要 目的：探讨彩色多普勒超声联合性激素对性早熟女童的诊断价值及其相关性分析。方法：选择2017年10月至2019年10月我院收治的性早熟女童80例,根据促性腺激素释放激素（GnRH）激发试验结果将其分为中枢性性早熟（CPP）组（n=31）,外周性性早熟（PPP）组49例（n=49）。比较两组女童的彩色多普勒超声检查结果及性激素水平,分析卵巢容积、子宫容积与性激素的相关性,并分析子宫容积、卵巢容积及FSH峰值、LH峰值、LH峰值/ FSH峰值在性早熟女童中的鉴别诊断价值。结果：CPP组女童卵巢容积、卵泡个数、最大卵泡直径、子宫容积、子宫内膜厚度、乳腺低回声团厚度均显著高于PPP组女童（P<0.05）。CPP组女童促卵泡生成素（FSH）基础值、FSH峰值、促黄体生成素（LH）基础值、LH峰值、LH峰值/ FSH峰值均显著高于PPP组女童（P<0.05）。CPP组女童卵巢容积、子宫容积与LH峰值、LH峰值/FSH峰值呈正相关（P<0.05）,PPP组女童卵巢容积、子宫容积与性激素水平无相关性（P>0.05）,两组LH峰值与LH峰值/FSH峰值均呈正相关（P<0.05）。ROC曲线分析显示,子宫容积、卵巢容积、LH峰值、FSH峰值、LH峰值/ FSH峰值鉴别诊断性早熟女童的曲线下面积分别为0.834,0.804,0.753,0.802,0.873。结论：彩色多普勒超声和性激素能够为性早熟女童病情的鉴别提供重要的临床信息,两者结合应用有助于提高性早熟女童的诊断价值。     

Emergence of breeding tubercles and puberty onset in male zebrafish: evidence for a dependence on body growth

The presence of breeding tubercles (BTs) on the pectoral fins has been investigated as a typical male secondary sexual characteristic (SSC) that distinguish males from females in adult zebrafish. Nonetheless, the earliest occurrence of these tubercles and its association with puberty onset and body growth remain unclear. In this study, using morphological, histological and statistical analyses, the authors examined the first appearance of BTs and puberty onset in male zebrafish, with particular emphasis on the potential impact of body growth on them. The results of this study revealed that BTs distributed along the first five branched pectoral fin rays were the earliest manifestation of male SSCs, which is significantly strongly correlated with body weight (R² = 0.9609, P < 0.001), and could be used as a “gold standard” for the earliest sex distinction (<0.1 g in weight). Using the first appearance of BTs (<0.20 mm²) as a metric, the authors established that male puberty commenced at a body weight of c. 0.056 ± 0.015 g or a standard length of 10.99 ± 1.051 mm (mean ± S.D. ). In this study, the authors thus established a simple method that can be used to sex live zebrafish at the pubertal stage and provides the first evidence for the relationship of BTs and male puberty initiation with body growth. These findings will accordingly lay a foundation for exploring mechanisms of the SSCs and male puberty onset in zebrafish and other teleost fish.     

Evaluation of Hydroxyatrazine in the Endocrine Disruptor Screening and Testing Program's Male and Female Pubertal Protocols

Two critical components of the validation of any in vivo screening assay are to demonstrate sensitivity and specificity. Although the Endocrine Disruptor Screening Program's Tier 1 Male and Female Pubertal Protocols have been shown to be sensitive assays for the detection of weak endocrine disrupting chemicals (EDCs), there are concerns that the assays lack specificity for EDC effects when a chemical induces systemic toxicity. A lack of specificity, or the ability to correctly identify an inactive or “negative” chemical, would increase the probability of identifying false positives. Here, we orally exposed rats to hydroxyatrazine (OH‐ATR), a biotransformation by‐product of the chlorotriazine herbicides that produced nephrotoxicity following a 13‐week dietary exposure. Based on a previous study in our laboratory, males were dosed with 11.4 to 183.4 mg/kg OH‐ATR and females were dosed with 45.75 to 183.4 mg/kg OH‐ATR. Following exposure in both sexes, there was a dose–response increase in mean kidney weights and the incidence and severity of kidney lesions. These lesions included the deposition of mineralized renal tubule concretions, hydronephrosis, renal tubule dilatation, and pyelonephritis. However, no differences in body weight, liver weight, or reproductive tissue weights, reproductive or thyroid histology, hormone concentrations or the age of pubertal onset were observed. Therefore, the results demonstrate that the endpoints included in the pubertal assay are useful for nonendocrine (systemic) effects that define an no observable effect level (NOEL) or lowest observable effect level (LOEL) and provide one example where an impact on kidney function does not alter any of the endocrine‐specific endpoints of the assay.