A Crab Is Not a Fish: Unique Aspects of the Crustacean Endocrine System and Considerations for Endocrine Toxicology.

Crustaceans-and arthropods in general-exhibit many unique aspects to their physiology. These include the requirement to moult (ecdysis) in order to grow and reproduce, the ability to change color, and multiple strategies for sexual differentiation. Accordingly, the endocrine regulation of these processes involves hormones, receptors, and enzymes that differ from those utilized by vertebrates and other non-arthropod invertebrates. As a result, environmental chemicals known to disrupt endocrine processes in vertebrates are often not endocrine disruptors in crustaceans; while, chemicals that disrupt endocrine processes in crustaceans are often not endocrine disruptors in vertebrates. In this review, we present an overview of the evolution of the endocrine system of crustaceans, highlight endocrine endpoints known to be a target of disruption by chemicals, and identify other components of endocrine signaling that may prove to be targets of disruption. This review highlights that crustaceans need to be evaluated for endocrine disruption with consideration of their unique endocrine system and not with consideration of the endocrine system of vertebrates.

Sex Determination and Differentiation in Decapod and Cladoceran Crustaceans: An Overview of Endocrine Regulation.

Mechanisms underlying sex determination and differentiation in animals are known to encompass a diverse array of molecular clues. Recent innovations in high-throughput sequencing and mass spectrometry technologies have been widely applied in non-model organisms without reference genomes. Crustaceans are no exception. They are particularly diverse among the Arthropoda and contain a wide variety of commercially important fishery species such as shrimps, lobsters and crabs (Order Decapoda), and keystone species of aquatic ecosystems such as water fleas (Order Branchiopoda). In terms of decapod sex determination and differentiation, previous approaches have attempted to elucidate their molecular components, to establish mono-sex breeding technology. Here, we overview reports describing the physiological functions of sex hormones regulating masculinization and feminization, and gene discovery by transcriptomics in decapod species. Moreover, this review summarizes the recent progresses of studies on the juvenile hormone-driven sex determination system of the branchiopod genus Daphnia, and then compares sex determination and endocrine systems between decapods and branchiopods. This review provides not only substantial insights for aquaculture research, but also the opportunity to re-organize the current and future trends of this field.

Prenatal over- and undernutrition differentially program small intestinal growth, angiogenesis, absorptive capacity, and endocrine function in sheep.

The aim was to test the hypothesis that prenatal under- and overnutrition in late gestation can program small intestinal (SI) growth, angiogenesis, and endocrine function to predispose for a hyperabsorptive state, thereby increasing the susceptibility to the adverse effects of an early postnatal obesogenic diet. Twin-pregnant ewes were exposed to adequate (NORM), LOW (50% of NORM), or HIGH (150% energy and 110% protein of NORM) diets through the last trimester (term ~147 days). From 3 days to 6 months of age, their lambs were fed either a moderate (CONV) or a high-carbohydrate high-fat (HCHF) diet. At 6 months of age, responses in plasma metabolites and insulin to refeeding after fasting were determined and then different segments of the SI were sampled at autopsy. Prenatal overnutrition impacts were most abundant in the duodenum where HIGH had increased villus amplification factor and lowered villi thickness with increased IRS-1 and reduced GH-R expressions. In jejunum, HIGH lambs had an increased expression of Lactate gene and amplified when exposed to HCHF postnatally. Specifically, in LOW, sensitivity to HCHF was affected in ileum. Thus, the mismatching LOW-HCHF nutrition increased expressions of angiogenic genes (VEGF, VEGF-R1, ANGPT1, RTK) and increased mucosa layer (tunica mucosa) thickness but reduced muscle layer (Tunica muscularis) thickness. The SI is a target of prenatal nutritional programming, where late gestation overnutrition increased and shifted digestive capacity for carbohydrates toward the jejunum, whereas late gestation undernutrition predisposed for ileal angiogenesis and carbohydrate and fat hyperabsorptive capacity upon subsequent exposure to postnatal obesogenic diet.

Impact of early weaning on small intestine, metabolic, immune and endocrine system development, growth and body composition in artificially reared lambs.

AbstractThis study evaluated the effect of early weaning (EW) of artificially reared lambs using a restricted milk replacer (MR) feeding and step-down weaning system on the short- and long-term effects on growth, feed intake, selected blood metabolites and hormones, body composition, and small intestine development. Mixed-sex twin-born 2 to 5 d old lambs were randomly allocated to individual pens and fed MR at 20% of initial individual BW in week 1 and 15% in week 2 followed by weaning off MR by the end of week 4 (EW; n = 16) or week 6 (Control; Ctrl, n = 16) using a step-down procedure. Concentrate starter and fiber diets were offered ad libitum to week 9, then gradually removed over a 10-d period. All lambs were managed as a single group on pasture from weeks 6 to 16 of the trial. Feed intake was recorded daily in the first 6 wk, and BWs recorded weekly. At weeks 2, 4, 6, and 8, and pre- and postclostridial vaccination at week 8, blood samples were collected for analysis of selected blood metabolites, IGF-1, and immune function. Body composition was evaluated in eight animals per group at weeks 4 and 16 after euthanasia, and duodenal samples collected for histomorphometric evaluation. Early weaned lambs had lower DM, ME, CP, and NDF intake than Ctrl lambs at 21, 15, 21, and 36 d of rearing, respectively (P < 0.001), driven by lower intakes of MR from day 15 (P < 0.001) as per the experimental design, and lower total DMI of fiber (P = 0.001) from 21 to 42 d of rearing. Lamb BW tended (P = 0.097) to be lower in EW than Ctrl lambs from 5 to 10 wk of rearing, with lower ADG in EW lambs from weeks 3 to 6 (P = 0.041). Early weaning had negligible effects on duodenal morphology, organ, and carcass weights at weeks 4 and 16. Plasma metabolites (urea nitrogen, triglycerides, NEFA, glucose, and total protein) were similar between groups, while ß-hydroxybutyrate was greater in EW than Ctrl lambs at weeks 4 and 6 (P = 0.018) but not week 8 indicative of early rumen development. Serum IGF-1 tended to be lower in EW than Ctrl lambs from weeks 2 to 6 only (P = 0.065). All lambs developed antibody responses postvaccination and there was no effect of treatment (P = 0.528). The results of this study illustrate that artificially reared lambs can be weaned off MR by 4 or 6 wk of rearing without compromising growth, small intestine morphology, major organ development, and body composition, nor immune function at either 4 (preweaning) or 16 (postweaning) wk of age.

Sub-lethal effects of a neonicotinoid, clothianidin, on wild early life stage sockeye salmon (Oncorhynchus nerka).

One of the categories of environmental contaminants possibly contributing to declining sockeye salmon (Oncorhynchus nerka) in the Fraser River, British Columbia, Canada is pesticides. In this 4-month study, the effects of environmentally relevant concentrations of a waterborne neonicotinoid, clothianidin (0.15, 1.5, 15 and 150 µg/L), on embryonic, alevin and early swim-up fry sockeye salmon derived from four unique genetic crosses of the Pitt River, BC stock were investigated. There were no significant effects of clothianidin on survival, hatching, growth or deformities, although genetic variation significantly affected these endpoints. Clothianidin caused a significant 4.7-fold increase in whole body 17ß-estradiol levels in swim-up fry after exposure to 0.15 µg/L, but no effects were observed on testosterone levels. In addition, hepatic expression of the gene encoding glucocorticoid receptor 2 was also impacted at the highest concentration of clothianidin tested, and was found to be ∼4-fold lower compared to the sockeye reared in control water. These results indicate additional examination of clothianidin and its effects on salmonid gonad development and the reproductive and stress endocrine axes in general, is warranted.

Atrazine induced transgenerational reproductive effects in medaka (Oryzias latipes).

Atrazine is presently one of the most abundantly used herbicides in the United States, and a common contaminant of natural water bodies and drinking waters in high-use areas. Dysregulation of reproductive processes has been demonstrated in atrazine exposed fish, including alteration of key endocrine pathways on hypothalamic-pituitary-gonadal (HPG) axis. However, the potential for atrazine-induced transgenerational inheritance of reproductive effects in fish has not been investigated. The present study examined the effects of early developmental atrazine exposure on transgenerational reproductive dysregulation in Japanese medaka (Oryzias latipes). F0 medaka were exposed to atrazine (ATZ, 5 or 50 µg/L), 17α-ethinylestradiol (EE2, 0.002 or 0.05 µg/L), or solvent control during the first twelve days of development with no subsequent exposure over three generations. This exposure overlapped with the critical developmental window for embryonic germ cell development, gonadogenesis, and sex determination. Exposed males and females of the F0 generation were bred to produce an F1 generation, and this was continued until the F2 generation. Sperm count and motility were not affected in F0 males; however, both parameters were significantly reduced in the males from F2 Low EE2 (0.002 µg/L), Low ATZ (5 µg/L), and High ATZ (50 µg/L) lineages. Fecundity was unaffected by atrazine or EE2 in F0 through F2 generations; however, fertilization rate was decreased in low atrazine and EE2 exposure lineages in the F2 generation. There were significant transgenerational differences in expression of the genes involved in steroidogenesis and DNA methylation. These results suggest that although early life exposure to atrazine did not cause significant phenotypes in the directly exposed F0 generation, subsequent generations of fish were at greater risk of reproductive dysfunction.

Copper caused reproductive endocrine disruption in zebrafish (Danio rerio).

Cu in surface waters has been demonstrated to affect aquatic animals at ecologically relevant concentrations. However, its effects on reproductive endocrine system and the underlying toxicological mechanisms are largely unknown. In this study, zebrafish (Danio rerio) were exposed to 0, 10, 20, 40 µg/L of Cu for 30 days. Growth, gonad histopathology, the hormone levels and the transcriptional profiles of genes in the hypothalamic-pituitary-gonadal (HPG) axis in both sexes were examined. The results indicated that body weight was significantly reduced, the gonadal development was affected, and the levels of E2, T and 11-KT were remarkably disturbed in Cu-exposed fish. Moreover, the expression profiles of steroidogenesis-related genes in gonad (3ßhsd, 17ßhsd, cyp11a1, cyp17, cyp19a, lhr, fshr, hmgra and star) and in brains (ar, cyp19b, erα, er2ß, lhß, fshß, gnrh2, gnrh3, gnrhr1, gnrh2 and gnrh4) displayed alterations after exposure to Cu. These results demonstrated that Cu could suppress the growth of zebrafish and significantly affect the reproductive biology in both sexes by damaging the structure of the gonads, altering the steroid hormone levels and the expressions of endocrine-related genes in HPG of zebrafish. This study suggests that Cu adversely affects the reproductive endocrine system in zebrafish and could pose a potential threat to fish populations inhabiting Cu-contaminated waters.

Endocrine system in supernumerary molting of the flour beetle, Tribolium freemani, under crowded conditions.

In the flour beetle, Tribolium freemani, a crowded environment in the last larval instar delays the development into a pupa, but the beetle continues to engage in larval-larval molting, which is an adaptive response to avoid being the victim of cannibalism as an immobile pupa. To understand the endocrine mechanism involved in this developmental process, we investigated the components of the juvenile hormone and ecdysone signaling systems. We examined whether elevated juvenile hormone levels in the crowded condition is the sole causal factor for the supernumerary molting. RNA interference (RNAi) of the JH acid methyltransferase (TfMT3) for lowering juvenile hormone titer in the crowded condition could not rescue pupation and instead resulted in lethality with developmental arrest at the prepupal stage. Kruppel-homolog 1 (TfKr-h1), the immediate downstream JH signal, was highly upregulated even in the RNAi of TfMT3 in a crowded condition. RNAi of TfKr-h1 resulted in a phenocopy of the lethal TfMT3 RNAi in a crowded condition. In addition, RNAi of TfMT3 in a crowded condition resulted in lack of the major ecdysone peak in the prepupal stage. We conclude that while a crowded condition induces supernumerary molts by elevating juvenile hormone levels, it can also inhibit metamorphosis by disrupting additional endocrine processes. The current study suggests that crowded conditions affect multiple independent factors in the endocrine and the downstream signaling systems.

Endocrine and metabolic profile of peripubertal Standardbred colts.

The objectives of this study were to determine the concentrations of reproductive and metabolic hormones during the peripubertal period and to assess their relationship with testicular development and body fat deposition. Blood samples were collected from 23 healthy Standardbred colts every four weeks for twelve months. Colts were weighed monthly, and percent of body fat and testicular volume estimated by ultrasound. Onset of puberty was determined as the month when testosterone was two standard deviations above the previous mean. Plasma FSH, LH, leptin, estradiol-17ß, androstenedione, IGF-1, insulin, inhibin-A, and inhibin-B were analyzed for a seven month peripubertal period. Spring born Standardbred colts underwent puberty at 13 months of age; onset of puberty coincided with exponential testicular growth but did not coincide with an increase in cutaneous body fat deposition or leptin (p > 0.05). Plasma inhibin-B concentrations were significantly increased in the postpubertal period (p < 0.05), but no increase was seen in inhibin-A, androstenedione, FSH, LH, or estradiol-17ß. In conclusion, the rise in testosterone and subsequent onset of puberty coincides with rapid testicular growth but is not correlated with an increase in gonadotropins, IGF-1, cutaneous body fat or leptin in the horse.

Dynamic modulation of sociality and aggression: an examination of plasticity within endocrine and neuroendocrine systems.

Endocrine and neuroendocrine systems are key mediators of behavioural plasticity and allow for the ability to shift social behaviour across dynamic contexts. These systems operate across timescales, modulating both rapid responses to environmental changes and developmental plasticity in behavioural phenotypes. Thus, not only do endocrine systems mediate behavioural plasticity, but also the systems themselves exhibit plasticity in functional capabilities. This flexibility at both the mechanistic and behavioural levels can be crucial for reproduction and survival. Here, we discuss how plasticity in nonapeptide and steroid actions may influence the expression of, and allow rapid shifts between, sociality and aggression-behavioural shifts that can be particularly important for social interactions. Recent findings of overlap in the mechanisms that modulate social and aggressive behaviour suggest the potential for a mechanistic continuum between these behaviours. We briefly discuss the potential for a sociality-aggression continuum and novel techniques that will enable probing of the functional connectivity of social behaviours. From an evolutionary perspective, we suggest that plasticity in endocrine and neuroendocrine mechanisms of behaviour may be important targets of selection, and discuss the conditions under which we would predict selection to have resulted in differences in endocrine plasticity across species that differ in social organization.This article is part of the themed issue 'Physiological determinants of social behaviour in animals'.

The Lipocalin LPR-1 Cooperates with LIN-3/EGF Signaling To Maintain Narrow Tube Integrity in Caenorhabditis elegans.

Lipocalins are secreted cup-shaped glycoproteins that bind sterols, fatty acids, and other lipophilic molecules. Lipocalins have been implicated in a wide array of processes related to lipophilic cargo transport, sequestration, and signaling, and several are used as biomarkers for human disease, but the functions of most lipocalins remain poorly understood. Here we show that the Caenorhabditis elegans lipocalin LPR-1 is required to maintain apical membrane integrity and a continuous lumen in two narrow unicellular tubes, the excretory duct and pore, during a period of rapid lumen elongation. LPR-1 fusion protein is expressed by the duct and pore and accumulates both intracellularly and in apical extracellular compartments, but it can also function cell nonautonomously when provided from outside of the excretory system. lpr-1 mutant defects can be rescued by increased signaling through the epidermal growth factor (EGF)-Ras-extracellular signal regulated kinase (ERK) pathway, which promotes the more elongated duct vs. less elongated pore tube fate. Spatial and temporal rescue experiments indicate that Ras signaling acts within the duct and pore tubes during or prior to cell fate determination to bypass the requirement for LPR-1 lpr-1 mutations did not disrupt LIN-3/EGF-dependent duct-fate specification, prevent functioning of any specific LIN-3/EGF isoform, or alter LET-23/EGFR localization, and reduced signaling did not phenocopy or enhance lpr-1 mutant defects. These data suggest that LPR-1 protects lumen integrity through a LIN-3/EGF-independent mechanism, but that increased signaling upregulates some target(s) that can compensate for lpr-1 absence.

Skeletal muscle as a gene regulatory endocrine organ.

PURPOSE OF REVIEW: Skeletal muscle is gaining increased attention as an endocrine organ. Recently, novel myokines and new effects of already established myokines have been identified. The objective of this review is to give an update on the recent advances in the field. RECENT FINDINGS: Several hundred putative myokines have been described, some of which are induced by contraction and differentially regulated between healthy and metabolically diseased individuals. Interleukin-6 (IL-6) is the prototype myokine, which was identified as a muscle-derived cytokine 15 years ago. Recently, IL-6 has been linked to ß-cell survival and inhibition of cancer-cell growth. Moreover, trans-signaling appears to determine whether IL-6 acts as a proinflammatory or an anti-inflammatory cytokine. Irisin has been shown to be a secreted myokine, which contribute to circulating concentrations dependent on training status. IL-15 has been established as a cytokine mediating cross-talk between skeletal muscle and skin tissue, and decorin has been characterized as a contraction-induced myokine which apparently is differentially regulated between healthy and dysglycemic individuals. SUMMARY: Skeletal muscle is an endocrine organ which, by the release of myokines, may influence metabolism in virtually all organs in the body. This knowledge may potentially open up for the possibility of designing new drugs that mimic the effects of myokine signaling.

Contribution of the Endocrine Perspective in the Evaluation of Endocrine Disrupting Chemical Effects: The Case Study of Pubertal Timing.

Debate makes science progress. In the field of endocrine disruption, endocrinology has brought up findings that substantiate a specific perspective on the definition of endocrine disrupting chemicals (EDCs), the role of the endocrine system and the endpoints of hormone and EDC actions among other issues. This paper aims at discussing the relevance of the endocrine perspective with regard to EDC effects on pubertal timing. Puberty involves particular sensitivity to environmental conditions. Reports about the advancing onset of puberty in several countries have led to the hypothesis that the increasing burden of EDCs could be an explanation. In fact, pubertal timing currently shows complex changes since advancement of some manifestations of puberty (e.g. breast development) and no change or delay of others (e.g. menarche, pubic hair development) can be observed. In a human setting with exposure to low doses of tenths or hundreds of chemicals since prenatal life, causation is most difficult to demonstrate and justifies a translational approach using animal models. Studies in rodents indicate an exquisite sensitivity of neuroendocrine endpoints to EDCs. Altogether, the data from both human and animal studies support the importance of concepts derived from endocrinology in the evaluation of EDC effects on puberty.

Maternal stress and plural breeding with communal care affect development of the endocrine stress response in a wild rodent.

Maternal stress can significantly affect offspring fitness. In laboratory rodents, chronically stressed mothers provide poor maternal care, resulting in pups with hyperactive stress responses. These hyperactive stress responses are characterized by high glucocorticoid levels in response to stressors plus poor negative feedback, which can ultimately lead to decreased fitness. In degus (Octodon degus) and other plural breeding rodents that exhibit communal care, however, maternal care from multiple females may buffer the negative impact on pups born to less parental mothers. We used wild, free-living degus to test this hypothesis. After parturition, we manipulated maternal stress by implanting cortisol pellets in 0%, 50-75%, or 100% of adult females within each social group. We then sampled pups for baseline and stress-induced cortisol, negative feedback efficacy, and adrenal sensitivity. From groups where all mothers were implanted with cortisol, pups had lower baseline cortisol levels and male pups additionally had weaker negative feedback compared to 0% or 50-75% implanted groups. Contrary to expectations, stress-induced cortisol did not differ between treatment groups. These data suggest that maternal stress impacts some aspects of the pup stress response, potentially through decreased maternal care, but that presence of unstressed mothers may mitigate some of these effects. Therefore, one benefit of plural breeding with communal care may be to buffer post-natal stress.

[D-cells of the gastroenteropancreatic system: development, structure, function and regeneration (history and current state of the problem)].

The present review summarizes the literature data and the results of authors' own research on the development, structure, function and regeneration of D-endocrinocytes of gastroenteropancreatic (GEP) system. The history of the research of these cells is reviewed and its current state of the problem is discussed. The information on the difference of somatostatin-producing D-endocrinocytes from other types of endocrine cells of GAP system is presented, namely, the prevalence of these cells in all the organs of the digestive system (stomach, small and large intestine, pancreas) and other systems of the body, the peculiarities of their structure and regeneration in various species of vertebrate animals and humans in embryonic development, under conditions of normal functioning and in various types of pathology. On the basis of the data on the early differentiation of D-endocrinocytes and their secretion of hormones during embryonic development, structure, cytophysiology and relationships within the general endocrinocyte population, it is suggested that D-endocrinocytes play an important role in the morpho-functional state of GEP system.

More similar than you think: Frog metamorphosis as a model of human perinatal endocrinology.

Hormonal control of development during the human perinatal period is critically important and complex with multiple hormones regulating fetal growth, brain development, and organ maturation in preparation for birth. Genetic and environmental perturbations of such hormonal control may cause irreversible morphological and physiological impairments and may also predispose individuals to diseases of adulthood, including diabetes and cardiovascular disease. Endocrine and molecular mechanisms that regulate perinatal development and that underlie the connections between early life events and adult diseases are not well elucidated. Such mechanisms are difficult to study in uterus-enclosed mammalian embryos because of confounding maternal effects. To elucidate mechanisms of developmental endocrinology in the perinatal period, Xenopus laevis the African clawed frog is a valuable vertebrate model. Frogs and humans have identical hormones which peak at birth and metamorphosis, have conserved hormone receptors and mechanisms of gene regulation, and have comparable roles for hormones in many target organs. Study of molecular and endocrine mechanisms of hormone-dependent development in frogs is advantageous because an extended free-living larval period followed by metamorphosis (1) is independent of maternal endocrine influence, (2) exhibits dramatic yet conserved developmental effects induced by thyroid and glucocorticoid hormones, and (3) begins at a developmental stage with naturally undetectable hormone levels, thereby facilitating endocrine manipulation and interpretation of results. This review highlights the utility of frog metamorphosis to elucidate molecular and endocrine actions, hormone interactions, and endocrine disruption, especially with respect to thyroid hormone. Knowledge from the frog model is expected to provide fundamental insights to aid medical understanding of endocrine disease, stress, and endocrine disruption affecting the perinatal period in humans.

Establishment of hormone reference intervals for infants born < 30 weeks' gestation.

OBJECTIVE: Preterm infants, especially those born very preterm (<32 weeks' gestation), suffer a number of morbidities. Immaturity of the endocrine system and its potential impact on morbidity is the subject of numerous studies. Hormone concentrations are sometimes measured in very preterm infants, however there are little normative data available to be able to interpret the results. The aim of this study was to describe age appropriate hormone reference intervals for babies born less than 30 weeks' gestation. STUDY DESIGN: Samples were collected at 1, 4, 7, 14, 21, 28 and 42 days after birth from babies born 23-29 weeks' gestation. The serum was analyzed for seven hormones by automated chemiluminescent immunoassay (Siemens Immulite 2000). Results from the 107 infants who survived beyond 40 weeks' corrected gestational age were included in the data analysis. RESULTS: Cortisol, dehydroepiandrosterone sulfate, growth hormone and progesterone levels were highest during the first seven days with levels up to 10,801nmol/L; 26.6µmol/L; 343mU/L; and >63.6nmol/L respectively. Free thyroxine levels were as low as <2.6pmol/L for the first 28 days with the nadir at 7days. Estradiol levels ranged from <73 to 1626pmol/L over the six weeks. Reference intervals for IGF-1 could not be established as the levels were below the analyzer's sensitivity. There were no differences in reference intervals between male and female infants. CONCLUSIONS: We describe gestation appropriate reference intervals for six hormones measured in babies born <30 weeks' gestation. Utilization of these reference intervals permits the correct and timely interpretation of results to the clinician.

Infant toxicology: state of the science and considerations in evaluation of safety.

Differences in the physiology and biological susceptibilities of adults and infants have led to growing interest in safety evaluation methods for exposures from infant formula packaging. In addition to potential physiological differences, infants aged 0-6 months may consume a sole source of food, infant formula or breast milk, and consume higher amounts of food relative to body weight compared to adults. While the duration of the exposure is short compared to the expected lifespan of the individual, it occurs during a period of important developmental processes. The purpose of this document is to (1) review key biological and exposure elements that may impact the evaluation of safety for food contact products intended for use by infants, (2) summarize the current reproductive and developmental toxicity testing protocols available, and (3) identify potential data gaps concerning this period of development.

Development of the human pancreas from foregut to endocrine commitment.

Knowledge of human pancreas development underpins our interpretation and exploitation of human pluripotent stem cell (PSC) differentiation toward a ß-cell fate. However, almost no information exists on the early events of human pancreatic specification in the distal foregut, bud formation, and early development. Here, we have studied the expression profiles of key lineage-specific markers to understand differentiation and morphogenetic events during human pancreas development. The notochord was adjacent to the dorsal foregut endoderm during the fourth week of development before pancreatic duodenal homeobox-1 detection. In contrast to the published data from mouse embryos, during human pancreas development, we detected only a single-phase of Neurogenin 3 (NEUROG3) expression and endocrine differentiation from approximately 8 weeks, before which Nirenberg and Kim homeobox 2.2 (NKX2.2) was not observed in the pancreatic progenitor cell population. In addition to revealing a number of disparities in timing between human and mouse development, these data, directly assembled from human tissue, allow combinations of transcription factors to define sequential stages and differentiating pancreatic cell types. The data are anticipated to provide a useful reference point for stem cell researchers looking to differentiate human PSCs in vitro toward the pancreatic ß-cell so as to model human development or enable drug discovery and potential cell therapy.

Longitudinal study of hormonal and physical development in young twins.

CONTEXT AND OBJECTIVE: Information on the correlation of normative reproductive hormone levels with physical development (Tanner stages) during puberty and on the influences of genes and environment on variation in these hormones and Tanner stages is limited. DESIGN, SETTING, AND PARTICIPANTS: One hundred twelve healthy 9-year-old twin pairs (n = 224) took part in a longitudinal study, of which 89 pairs participated again at age 12 years (n = 178). MAIN OUTCOME MEASURES: Morning urinary LH, FSH, estradiol, and salivary testosterone levels, determined by competitive immunoassays, were measured. Tanner stages were determined through physical examination. RESULTS: Over the 3-year interval, all hormone levels showed a 2- to 9-fold increase. LH and FSH at age 9 years predicted sex-specific Tanner stages at age 12 years in both boys and girls. Most of the associations between hormone levels at age 9 years and physical development at 12 years were explained by genetic influences. FSH in 9-year-old boys correlated with all hormone levels and Tanner stages at age 12 years. Moderate to high heritability estimates were found for hormone levels at both ages and in both sexes. In girls a shift from environmental (age 9 years) to genetic influences (age 12 years) was found for estradiol and pubic hair development, and for breast development a shift in the opposite direction was seen. CONCLUSIONS: During development LH and FSH (and testosterone in boys) levels predict secondary sexual characteristics in boys and girls 3 years later. These correlations are largely due to genes that are involved in both early pubertal hormone levels and subsequent physical development.