The role of growth hormone in fetal development

Aging, longevity, and the role of environmental stressors: a focus on wildfire smoke and air quality

Aging is a complex biological process involving multiple interacting mechanisms and is being increasingly linked to environmental exposures such as wildfire smoke. In this review, we detail the hallmarks of aging, emphasizing the role of telomere attrition, cellular senescence, epigenetic alterations, proteostasis, genomic instability, and mitochondrial dysfunction, while also exploring integrative hallmarks - altered intercellular communication and stem cell exhaustion. Within each hallmark of aging, our review explores how environmental disasters like wildfires, and their resultant inhaled toxicants, interact with these aging mechanisms. The intersection between aging and environmental exposures, especially high-concentration insults from wildfires, remains under-studied. Preliminary evidence, from our group and others, suggests that inhaled wildfire smoke can accelerate markers of neurological aging and reduce learning capabilities. This is likely mediated by the augmentation of circulatory factors that compromise vascular and blood-brain barrier integrity, induce chronic neuroinflammation, and promote age-associated proteinopathy-related outcomes. Moreover, wildfire smoke may induce a reduced metabolic, senescent cellular phenotype. Future interventions could potentially leverage combined anti-inflammatory and NAD + boosting compounds to counter these effects. This review underscores the critical need to study the intricate interplay between environmental factors and the biological mechanisms of aging to pave the way for effective interventions.

Reproductive and neurobehavioral effects of dinotefuran in an F1 -generation toxicity study in mice

BACKGROUND

Few studies were found for neurobehavioral toxicity of dinotefuran in mammals. This study was designed to evaluate the reproductive and neurobehavioral effects of dinotefuran exposure in mice.

METHODS

Dinotefuran was given in the diet to provide levels of 0% (control), 0.015%, 0.03%, and 0.06% from 5 weeks of age of the F0 generation to 11 weeks of age of the F1 generation in mice. Selected reproductive and neurobehavioral parameters were measured.

RESULTS

Movement time increased with a significant dose-related trend, and the related variables of rearing time decreased in significant dose-related trends in adult males in the F0 generation. Litter size and weight increased in significant dose-related trends, and sex ratio decreased in a significant dose-related trend. The average body weight of offspring increased in a significant dose-related trend on postnatal day (PND) 21 in both sexes. In the olfactory orientation on PND 14 in female offspring, the time required lengthened in a significant dose-related trend. In male offspring, total distance and the average speed decreased in significant dose-related trends, and the average time of rearing, number of defecations, and frequencies of mice with urination increased in a significant dose-related trend. In female offspring, the related variables of rearing increased in significant dose-related trends. In spontaneous behavior of males, the parallel lines during the control and treatment groups indicated a significant distance in the number of horizontal activities.

CONCLUSIONS

The dose levels of dinotefuran in the present study produced several adverse effects on reproductive and neurobehavioral parameters in mice.

Flexible conservatism in the skull modularity of convergently evolved myrmecophagous placental mammals

Background

The skull of placental mammals constitutes one of the best studied systems for phenotypic modularity. Several studies have found strong evidence for the conserved presence of two- and six-module architectures, while the strength of trait correlations (integration) has been associated with major developmental processes such as somatic growth, muscle-bone interactions, and tooth eruption. Among placentals, ant- and termite-eating (myrmecophagy) represents an exemplar case of dietary convergence, accompanied by the selection of several cranial morphofunctional traits such as rostrum elongation, tooth loss, and mastication loss. Despite such drastic functional modifications, the covariance patterns of the skull of convergently evolved myrmecophagous placentals are yet to be studied in order to assess the potential consequences of this dietary shift on cranial modularity.

Results

Here, we performed a landmark-based morphometric analysis of cranial covariance patterns in 13 species of myrmecophagous placentals. Our analyses reveal that most myrmecophagous species present skulls divided into six to seven modules (depending on the confirmatory method used), with architectures similar to those of non-myrmecophagous placentals (therian six modules). Within-module integration is also similar to what was previously described for other placentals, suggesting that most covariance-generating processes are conserved across the clade. Nevertheless, we show that extreme rostrum elongation and tooth loss in myrmecophagid anteaters have resulted in a shift in intermodule correlations in the proximal region of the rostrum. Namely, the naso-frontal and maxillo-palatine regions are strongly correlated with the oro-nasal module, suggesting an integrated rostrum conserved from pre-natal developmental processes. In contrast, the similarly toothless pangolins show a weaker correlation between the anterior rostral modules, resembling the pattern of toothed placentals.

Conclusions

These results reveal that despite some integration shifts related to extreme functional and morphological features of myrmecophagous skulls, cranial modular architectures have conserved the typical mammalian scheme.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-022-02030-9.

Genes and Longevity of Lifespan

Aging is a complex process indicated by low energy levels, declined physiological activity, stress induced loss of homeostasis leading to the risk of diseases and mortality. Recent developments in medical sciences and an increased availability of nutritional requirements has significantly increased the average human lifespan worldwide. Several environmental and physiological factors contribute to the aging process. However, about 40% human life expectancy is inherited among generations, many lifespan associated genes, genetic mechanisms and pathways have been demonstrated during last decades. In the present review, we have evaluated many human genes and their non-human orthologs established for their role in the regulation of lifespan. The study has included more than fifty genes reported in the literature for their contributions to the longevity of life. Intact genomic DNA is essential for the life activities at the level of cell, tissue, and organ. Nucleic acids are vulnerable to oxidative stress, chemotherapies, and exposure to radiations. Efficient DNA repair mechanisms are essential for the maintenance of genomic integrity, damaged DNA is not replicated and transferred to next generations rather the presence of deleterious DNA initiates signaling cascades leading to the cell cycle arrest or apoptosis. DNA modifications, DNA methylation, histone methylation, histone acetylation and DNA damage can eventually lead towards apoptosis. The importance of calorie restriction therapy in the extension of lifespan has also been discussed. The role of pathways involved in the regulation of lifespan such as DAF-16/FOXO (forkhead box protein O1), TOR and JNK pathways has also been particularized. The study provides an updated account of genetic factors associated with the extended lifespan and their interactive contributory role with cellular pathways.

Selection for increased tibia length in mice alters skull shape through parallel changes in developmental mechanisms

Bones in the vertebrate cranial base and limb skeleton grow by endochondral ossification, under the control of growth plates. Mechanisms of endochondral ossification are conserved across growth plates, which increases covariation in size and shape among bones, and in turn may lead to correlated changes in skeletal traits not under direct selection. We used micro-CT and geometric morphometrics to characterize shape changes in the cranium of the Longshanks mouse, which was selectively bred for longer tibiae. We show that Longshanks skulls became longer, flatter, and narrower in a stepwise process. Moreover, we show that these morphological changes likely resulted from developmental changes in the growth plates of the Longshanks cranial base, mirroring changes observed in its tibia. Thus, indirect and non-adaptive morphological changes can occur due to developmental overlap among distant skeletal elements, with important implications for interpreting the evolutionary history of vertebrate skeletal form.

Attenuation of growth hormone production at the fetal stage is critical for dioxin-induced developmental disorder in rat offspring

Although dioxins and related chemicals have been suspected to disrupt child development, their toxic mechanism remains poorly understood. Our previous studies in rat fetuses revealed that maternal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a highly-toxic dioxin, suppresses fetal synthesis of pituitary growth hormone (GH) that is essential for development. This study examined the hypothesis that attenuating GH expression in fetuses triggers developmental disorders. Treating pregnant rats with 1 μg/kg TCDD reduced the circulating level of GH and its downstream factor, insulin-like growth factor-1 (IGF-1), in the offspring only during the fetal and early neonatal stages. Although maternal TCDD exposure resulted in low body weight and length at babyhood and defects in the learning and memory ability at adulthood, GH supplementation in TCDD-exposed fetuses restored or tended to restore the defects including IGF-1 downregulation. Moreover, maternal TCDD exposure decreased the number of GH-positive cells during the fetal/neonatal stage. A microarray analysis showed that TCDD reduced the expression of death-associated protein-like 1 (DAPL1), a cell cycle-dependent proliferation regulator, in the fetal pituitary gland. In addition, TCDD treatment attenuated proliferating cells and cyclin mRNA expression in the fetal pituitary gland. Aryl hydrocarbon receptor (AHR)-knockout fetuses were insensitive to TCDD treatment, indicating that the TCDD-induced reduction in DAPL1 and GH mRNAs expression was due to AHR activation. Finally, DAPL1 knockdown suppressed GH and cyclin D2 expression in fetal pituitary cells. These results provide a novel evidence that dioxin suppresses GH-producing cell proliferation and GH synthesis due to partly targeting DAPL1, thereby impairing offspring development.

Three lactation-related hormones: Regulation of hypothalamus-pituitary axis and function on lactation

The endocrine system plays a central role in many aspects of lactation, including mammogenesis (mammary gland development), lactogenesis (onset of lactation), and galactopoiesis (maintenance of milk secretion). Many hormones of the endocrine system directly or indirectly regulate lactation process. The secretion of prolactin (PRL), one of the most important lactation-related hormones, is inhibited by hypothalamus-pituitary dopaminergic system and stimulated by hypothalamus-pituitary oxytocinergic system. This hormone is essential in all stages of lactation. The growth hormone (GH) regulates metabolism and the distribution of nutrients between tissues mammary glands, and stimulates the production of IGF-I from the liver which binds to IGF-IR of mammary epithelial cells (MECs) to indirectly promote lactation. The synthesis and secretion of estrogen (E) are affected by the hypothalamus-pituitary axis. The hormone regulates duct morphogenesis and MECs proliferation. It also modulates the synthesis and secretion of PRL and GH, which together regulate the lactation in female animals. In this article, we reviewed the three main lactation-related hormones (PRL, GH, and E), summarize their regulation by the hypothalamus-pituitary axis and how they influence lactation.

Chlormequat chloride promotes rat embryonic growth and GH-IGF-1 axis

Chlormequat chloride, a plant growth regulator, is widely applied in agriculture because it can promote sturdier growth of the crops. In this research, we found that rat embryo growth on GD11 was inhibited in vitro at 50 μg/ml but promoted in vivo at 75 mg/kg.bw by maternal oral exposure. Therefore, the concentrations of chlormequat chloride in the sera of the pregnant rats on gestation day (GD)11 were determined by a high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) test to be 1.94 ± 0.023 μg/ml, 3.84 ± 0.080 μg/ml, and 7.08 ± 0.11 μg/ml, respectively, when the pregnant rats were orally exposed to chlormequat chloride at 75, 137.5, and 200 mg/kg.bw. Hence, we performed WEC tests again and confirmed that the rat embryo growth in vitro was promoted by chlormequat chloride at 5 μg/mL. The embryonic growth hormone (GH) and insulin-like growth factor 1 (IGF-1) levels were increased by chlormequat chloride both in vitro and in vivo compared with the control ones. We concluded that chlormequat chloride could elevate GH and IGF-1 levels in embryos and promote embryonic growth both in vitro and in vivo.

Neonatal Morbidities of Fetal Growth Restriction: Pathophysiology and Impact

Being born small lays the foundation for short-term and long-term implications for life. Intrauterine or fetal growth restriction describes the pregnancy complication of pathological reduced fetal growth, leading to significant perinatal mortality and morbidity, and subsequent long-term deficits. Placental insufficiency is the principal cause of FGR, which in turn underlies a chronic undersupply of oxygen and nutrients to the fetus. The neonatal morbidities associated with FGR depend on the timing of onset of placental dysfunction and growth restriction, its severity, and the gestation at birth of the infant. In this review, we explore the pathophysiological mechanisms involved in the development of major neonatal morbidities in FGR, and their impact on the health of the infant. Fetal cardiovascular adaptation and altered organ development during gestation are principal contributors to postnatal consequences of FGR. Clinical presentation, diagnostic tools and management strategies of neonatal morbidities are presented. We also present information on the current status of targeted therapies. A better understanding of neonatal morbidities associated with FGR will enable early neonatal detection, monitoring and management of potential adverse outcomes in the newborn period and beyond.

Growth hormone facilitates 5'-azacytidine-induced myogenic but inhibits 5'-azacytidine-induced adipogenic commitment in C3H10T1/2 mesenchymal stem cells

The C3H10T1/2 cells are considered mesenchymal stem cells (MSCs) because they can be induced to become the progenitor cells for myocytes, adipocytes, osteoblasts, and chondrocytes by the DNA methyltransferase inhibitor 5'-azacytidine. In this study, we determined the effect of growth hormone (GH) on the myogenic and adipogenic lineage commitment in C3H10T1/2 cells. The C3H10T1/2 cells were treated with recombinant bovine GH in the presence or absence of 5'-azacytidine for 4 days. The myogenic commitment in C3H10T1/2 cells was assessed by immunostaining them for MyoD, the marker for myoblasts, and by determining their capacity to differentiate into the multinucleated myotubes. The adipogenic commitment in C3H10T1/2 cells was assessed by determining their ability to differentiate into adipocytes. Myotubes and adipocyteswere identified by immunocytochemistry and Oil Red O staining, respectively. C3H10T1/2 cells treated with 5'-azacytidine and GH for 4 days contained a greater percentage of MyoD-positive cells than those treated with 5'-axacytidine alone (P < 0.05). The former generated more myotubes than the latter upon induced myoblast differentiation (P < 0.05). However, C3H10T1/2 cells treated with GH alone did not form any myotubes. C3H10T1/2 cells treated with 5'-azacytidine formed adipocytes upon adipocyte differentiation induction, whereas C3H10T1/2 cells treated with GH alone did not form any adipocytes. C3H10T1/2 cells treated with both 5'-azacytidine and GH formed fewer adipocytes than those treated with 5'-azacytidine alone (P < 0.05). Both GHR and IGF-I mRNA expression in C3H10T1/2 cells were increased by 5'-azacytidine (P < 0.05), but neither was affected by GH. Overall, this study showed that GH enhanced 5'-azacytidine-induced commitment in C3H10T1/2 cells to myoblasts but inhibited 5'-azacytidine-induced commitment to preadipocytes. These results support the possibility that GH stimulates skeletal muscle growth and inhibits adipose tissue growth in part by stimulating the myogenic commitment and inhibiting the adipogenic commitment, respectively, in mesenchymal stem cells.

Growth Hormone Secretion Patterns in German Landrace (DL) Fetuses and Piglets Compared to DL Piglets with Inherited 1,25-Dihydroxyvitamin D3 Deficiency

The regulation of growth hormone (GH) release during prenatal development and during early postnatal life is not entirely clarified. In this study plasma GH concentrations in pigs with inherited pseudo vitamin D deficiency type I (PDDR-I), which regularly show growth retardation, were compared during ontogeny with unaffected pigs of the same breed (German Landrace, DL) as control. Plasma GH concentrations were measured in plasma of chronically catheterized fetuses (beginning on day 101 after mating or after artificial insemination) and in piglets (day 37 postpartum (p.p.)—day 42 p.p.) of both lines. A growth curve beginning at day 7 p.p. was recorded for both lines. The relative amount of GH receptor (GHR) mRNA in liver was quantified by competitive reverse transcription polymerase chain reaction in piglets at day 42 p.p. A trend for higher GH concentrations was observed in PDDR-I fetuses (p < 0.1). In PDDR-I piglets compared to DL piglets higher plasma GH values (p < 0.01), were observed despite lower body weight. The relative quantity of GHR mRNA in liver was not significantly different between the two lines. Piglets with an inherited defect of vitamin D synthesis showed higher GH concentrations. A hormonal imprinting by low 1,25(OH)₂D₃ could be one reason for our observations and should be analysed in detail in future.

Vitamin D-deficiency and sex-specific dysregulation of placental inflammation

To investigate an immunomodulatory role for vitamin D in pregnancy we used mice raised on vitamin D-sufficient (SUFF), or -deficient (DEF) diets. At embryonic day 14, pregnant mice received intraperitoneal injection of lipopolysaccharide (LPS) or vehicle for 24h, with age-matched non-pregnant mice as controls. In non-pregnant mice, 6 serum analytes (IL-1β, IL-18, MDC/CCL22, MIP-1α/CCL3, EGF, IgA) were lower in DEF mice. In pregnant DEF mice only GH was higher. In non-pregnant mice LPS induced 28 analytes, with 5 (IL-18, IP-10/CXCL10, MCP-1/CCL2, MIP-1β/CCL4, MIP-3β/CCL19) being highest in DEF mice. In pregnant SUFF mice 16 serum analytes increased with LPS, and 6 of these (IP-10/CXCL10, MCP-1/CCL2, SAP, TIMP-1, VCAM-1, vWF) were higher and 1 (GCP-2/CXCL6) lower in DEF mice. Parallel analysis of placental mRNAs showed elevated mRNA for Il-6, Ccl2 and Cxcl10 in placentae from male and female fetuses in LPS-DEF mice. However, LPS-induced expression of Ifnγ, Tnfα, and Cxcl6 was only observed in female placentae from DEF mice. LPS-DEF mice also showed smaller litter sizes relative to control SUFF mice. Numbers of female fetuses per dam were significantly lower for DEF mice with or without LPS challenge. LPS had no effect on numbers of male fetuses from DEF mothers, but significantly decreased male fetuses from SUFF mothers. These data indicate that vitamin D is an important component of anti-inflammatory immune responses during pregnancy, with the placenta and fetal sex playing pivotal roles in this process.

Nutrition, infection and stunting: the roles of deficiencies of individual nutrients and foods, and of inflammation, as determinants of reduced linear growth of children

The regulation of linear growth by nutritional and inflammatory influences is examined in terms of growth-plate endochondral ossification, in order to better understand stunted growth in children. Linear growth is controlled by complex genetic, physiological, and nutrient-sensitive endocrine/paracrine/autocrine mediated molecular signalling mechanisms, possibly including sleep adequacy through its influence on growth hormone secretion. Inflammation, which accompanies most infections and environmental enteric dysfunction, inhibits endochondral ossification through the action of mediators including proinflammatory cytokines, the activin A-follistatin system, glucocorticoids and fibroblast growth factor 21 (FGF21). In animal models linear growth is particularly sensitive to dietary protein as well as Zn intake, which act through insulin, insulin-like growth factor-1 (IGF-1) and its binding proteins, triiodothyronine, amino acids and Zn2+ to stimulate growth-plate protein and proteoglycan synthesis and cell cycle progression, actions which are blocked by corticosteroids and inflammatory cytokines. Observational human studies indicate stunting to be associated with nutritionally poor, mainly plant-based diets. Intervention studies provide some support for deficiencies of energy, protein, Zn and iodine and for multiple micronutrient deficiencies, at least during pregnancy. Of the animal-source foods, only milk has been specifically and repeatedly shown to exert an important influence on linear growth in both undernourished and well-nourished children. However, inflammation, caused by infections, environmental enteric dysfunction, which may be widespread in the absence of clean water, adequate sanitation and hygiene (WASH), and endogenous inflammation associated with excess adiposity, in each case contributes to stunting, and may explain why nutritional interventions are often unsuccessful. Current interventions to reduce stunting are targeting WASH as well as nutrition.

Increased linear bone growth by GH in the absence of SOCS2 is independent of IGF-1

Growth hormone (GH) signaling is essential for postnatal linear bone growth, but the relative importance of GHs actions on the liver and/or growth plate cartilage remains unclear. The importance of liver derived insulin like‐growth factor‐1 (IGF‐1) for endochondral growth has recently been challenged. Here, we investigate linear growth in Suppressor of Cytokine Signaling‐2 (SOCS2) knockout mice, which have enhanced growth despite normal systemic GH/IGF‐1 levels. Wild‐type embryonic ex vivo metatarsals failed to exhibit increased linear growth in response to GH, but displayed increased Socs2 transcript levels (P < 0.01). In the absence of SOCS2, GH treatment enhanced metatarsal linear growth over a 12 day period. Despite this increase, IGF‐1 transcript and protein levels were not increased in response to GH. In accordance with these data, IGF‐1 levels were unchanged in GH‐challenged postnatal Socs2^‐/‐ conditioned medium despite metatarsals showing enhanced linear growth. Growth‐plate Igf1 mRNA levels were not elevated in juvenile Socs2^‐/‐ mice. GH did however elevate IGF‐binding protein 3 levels in conditioned medium from GH challenged metatarsals and this was more apparent in Socs2^‐/‐ metatarsals. GH did not enhance the growth of Socs2^‐/‐ metatarsals when the IGF receptor was inhibited, suggesting that IGF receptor mediated mechanisms are required. IGF‐2 may be responsible as IGF‐2 promoted metatarsal growth and Igf2 expression was elevated in Socs2^‐/‐ (but not WT) metatarsals in response to GH. These studies emphasise the critical importance of SOCS2 in regulating GHs ability to promote bone growth. Also, GH appears to act directly on the metatarsals of Socs2^‐/‐ mice, promoting growth via a mechanism that is independent of IGF‐1. J. Cell. Physiol. 9999: 2796–2806, 2015. © 2015 Wiley Periodicals, Inc.

Rapid method for growth hormone receptor exon 3 delete (GHRd3) SNP genotyping from archival human placental samples

Analysis of archival samples from cohorts of pregnant women may be key to discovering prognosticators of stillbirth and pregnancy/perinatal complications. Growth hormone (GH) and its receptor (GHR) are pivotal in feto-placental development and pregnancy maintenance. We report a rapid, optimized method for genotyping the GHR full-length versus exon 3-deleted isoform (GHRd3). TaqMan single nucleotide polymorphism (SNP) genotyping proved superior to standard multiplex polymerase chain reaction (PCR) in allele detection and GHR genotyping from archived samples, including those with poor genomic deoxyribonucleic acid quality/quantity such as formalin fixed, paraffin embedded, blood, and serum. Furthermore, this assay is suitable for high through put 96 or 384-well plate quantitative PCR machines with automated genotype calling software. The TaqMan genotyping assay can increase the data obtained from precious archival human samples.

Mind the gap: genetic manipulation of basicranial growth within synchondroses modulates calvarial and facial shape in mice through epigenetic interactions

Phenotypic integration patterns in the mammalian skull have long been a focus of intense interest as a result of their suspected influence on the trajectory of hominid evolution. Here we test the hypothesis that perturbation of cartilage growth, which directly affects only the chondrocranium during development, will produce coordinated shape changes in the adult calvarium and face regardless of mechanism. Using two murine models of cartilage undergrowth that target two very different mechanisms, we show that strong reduction in cartilage growth produces a short, wide, and more flexed cranial base. This in turn produces a short, wide face in both models. Cranial base and face are already correlated early in ontogeny, and the relationship between these modules gains structure through postnatal growth and development. These results provide further evidence that there exist physical interactions between developing parts of the phenotype that produce variation at a distance from the actual locus upon which a particular selective pressure is acting. Phenotypic changes observed over the course of evolution may not all require adaptationist explanations; rather, it is likely that a substantial portion of observed phenotypic variation over the history of a clade is not directly adaptive but rather a secondary consequence of some local response to selection.

Effects of growth hormone on the ontogenetic allometry of craniofacial bones

Organism size is controlled by interactions between genetic and environmental factors mediated by hormones with systemic and local effects. As changes in size are usually not isometric, a considerable diversity in shape can be generated through modifications in the patterns of ontogenetic allometry. In this study we evaluated the role of timing and dose of growth hormone (GH) release on growth and correlated shape changes in craniofacial bones. Using a longitudinal study design, we analyzed GH deficient mice treated with GH supplementation commencing pre- and post-puberty. We obtained 3D in vivo micro-CT images of the skull between 21 and 60 days of age and used geometric morphometrics to analyze size and shape changes among control and GH deficient treated and non-treated mice. The variable levels of circulating GH altered the size and shape of the adult skull, and influenced the cranial base, vault, and face differently. While cranial base synchondroses and facial sutures were susceptible to either the direct or indirect effect of GH supplementation, its effect was negligible on the vault. Such different responses support the role of intrinsic growth trajectories of skeletal components in controlling the modifications induced by systemic factors. Contrary to the expected, the timing of GH treatment did not have an effect on catch-up growth. GH levels also altered the ontogenetic trajectories by inducing changes in their location and extension in the shape space, indicating that differences arose before 21 days and were further accentuated by a truncation of the ontogenetic trajectories in GHD groups.

Extrapituitary growth hormone and growth?

While growth hormone (GH) is obligatory for postnatal growth, it is not required for a number of growth-without-GH syndromes, such as early embryonic or fetal growth. Instead, these syndromes are thought to be dependent upon local growth factors, rather than pituitary GH. The GH gene is, however, also expressed in many extrapituitary tissues, particularly during early development and extrapituitary GH may be one of the local growth factors responsible for embryonic or fetal growth. Moreover, as the expression of the GH receptor (GHR) gene mirrors that of GH in extrapituitary tissues the actions of GH in early development are likely to be mediated by local autocrine or paracrine mechanisms, especially as extrapituitary GH expression occurs prior to the ontogeny of pituitary somatotrophs or the appearance of GH in the circulation. The extrapituitary expression of pituitary somatotrophs or the appearance of GH in the circulation. The extrapituitary expression of GH in embryos has also been shown to be of functional relevance in a number of species, since the immunoneutralization of endogenous GH or the blockade of GH production is accompanied by growth impairment or cellular apoptosis. The extrapituitary expression of the GH gene also persists in some central and peripheral tissues postnatally, which may reflect its continued functional importance and physiological or pathophysiological significance. The expression and functional relevance of extrapituitary GH, particularly during embryonic growth, is the focus of this brief review.

Mild reproductive effects of the Tityus bahiensis scorpion venom in rats

Background

Scorpion envenoming is a public health problem in Brazil, where Tityus serrulatus and T. bahiensis are considered the most dangerous scorpions. They are well adapted to urbanized environments, and there is an increasing probability of human exposure to these venoms, including during pregnancy. Not much is known about the effects of prenatal exposure to the venom, and no information is available to aid in the rational treatment of victims stung during pregnancy. Thus, this study aimed to investigate whether venom from the scorpion T. bahiensis administered once to pregnant female rats at a dose that causes a moderate envenomation may lead to deleterious effects on the reproductive performance of the dams and on the development of their offspring. This is the first work demonstrating that T. bahiensis venom, when administered experimentally to rats, alters maternal reproductive performance and the morphological development of fetuses. The venom was given to dams on the 5th (GD5) or on the 10th (GD10) gestational day. After laparotomy, on GD21, fetuses and placentas were counted, weighed and externally analyzed. The corpora lutea were counted. The sex and vitality of fetuses were evaluated, and each litter was then randomly divided for visceral or skeletal analyses. Data were analyzed by ANOVA followed by the Tukey-Kramer test and Fisher’s exact test. The significance level for all tests was set at p < 0.05.

Results

GD5 group presented an increased number of pre-implantation losses. Weight gains in fetuses and placentas were observed in the GD5 and GD10 groups. Weights of the heart and lungs were elevated in GD5 and GD10 and liver weight in GD10.

Conclusions

Moderate envenomation by T. bahiensis scorpion venom alters maternal reproductive performance and fetal development. However, these are preliminary results whose causes should be investigated more carefully in future studies.

Pituitary tumors and pregnancy: the interplay between a pathologic condition and a physiologic status

Pregnancy is becoming a relatively common event in patients with pituitary tumors (PT), due to the increasing availability of medical treatments, which control pituitary diseases associated with the development of PT. However, the presence of PT and its treatment may be a disturbing factor for pregnancy, and pregnancy significantly influences the course and the management of PT. This review summarizes the knowledge about the management of PT during pregnancy and the occurrence of pregnancy in patients with pre-existent PT, focusing on secreting PT characterized by hormonal excess and on clinically non-functioning PT often associated to hormone deficiency, which configure the hypopituitaric syndrome.

The Developmental Basis of Quantitative Craniofacial Variation in Humans and Mice

The human skull is a complex and highly integrated structure that has long held the fascination of anthropologists and evolutionary biologists. Recent studies of the genetics of craniofacial variation reveal a very complex and multifactorial picture. These findings contrast with older ideas that posit much simpler developmental bases for variation in cranial morphology such as the growth of the brain or the growth of the chondrocranium relative to the dermatocranium. Such processes have been shown to have major effects on cranial morphology in mice. It is not known, however, whether they are relevant to explaining normal phenotypic variation in humans. To answer this question, we obtained vectors of shape change from mutant mouse models in which the developmental basis for the craniofacial phenotype is known to varying degrees, and compared these to a homologous dataset constructed from human crania obtained from a single population with a known genealogy. Our results show that the shape vectors associated with perturbations to chondrocranial growth, brain growth, and body size in mice do largely correspond to axes of covariation in humans. This finding supports the view that the developmental basis for craniofacial variation funnels down to a relatively small number of key developmental processes that are similar across mice and humans. Understanding these processes and how they influence craniofacial shape provides fundamental insights into the developmental basis for evolutionary change in the human skull as well as the developmental-genetic basis for normal phenotypic variation in craniofacial form.

Early developmental influences on hepatic organogenesis

The liver is the largest of the body's organs, with the greatest number of functions, playing a central role in coordinating metabolic homeostasis, nutrient processing and detoxification. The fetal liver forms during early gestation in response to a sequential array of distinct biological events, regulated by intrinsically programmed mechanisms and extracellular signals which instruct hepatic cells to either proliferate, differentiate or undergo apoptosis. A vast number of genes are involved in the initiation and control of liver development, many of which are sensitive to nutritional and hormonal regulation in utero. Moreover, liver mass is influenced by the gestational environment. Therefore, during periods of hepatic cell proliferation and differentiation, the developing fetal liver is sensitive to damage from both internal and external sources including teratogens, infection and nutritional deficiencies. For example, fetuses exposed to decreased materno-fetal nutrition during late gestation have a reduced liver mass, and/or perturbed liver function, which includes increased plasma LDL cholesterol and fibrinogen concentrations. These occur in conjunction with other risk factors present in the early stages of cardiovascular disease i.e. decreased glucose tolerance and insulin insensitivity in later life. Taken together, these findings suggest that liver mass, and later function, are essentially set in utero during fetal development-a process that is ultimately regulated by the intrauterine environment.

The effect of growth hormone (GH) and insulin-like growth factor-I (IGF-I) on in vitro maturation of equine oocytes

The objective of this study was to test the hypothesis that equine growth hormone (eGH), in combination with insulin growth factor-I (IGF-I), influences positively in vitro nuclear and cytoplasmic maturation of equine oocytes. Cumulus–oocyte complexes were recovered from follicles that were < 25 mm in diameter, characterized by morphology and were allocated randomly as follow: (a) control (no additives); (b) 400 ng/ml eGH; (c) 200 ng/ml IGF-I; (d) eGH + IGF-I; and (e) eGH + IGF-I + 400 ng/ml anti-IGF-I antibody. Oocytes were matured for 30 h at 38.5°C in air with 5% CO2 and then stained with 10 μg/ml propidium iodide (PI) to evaluate nuclear status and 10 μg/ml Lens culinaris agglutinin-fluorescein complex (FITC-LCA) to assess cortical granule migration by confocal microscopy. The proportion of immature oocytes that developed to the metaphase II (MII) stage in the eGH + IGF-I group (15 of 45) was greater than in the groups that were treated only with IGF-I (7 of 36, p = 0.03). Oocytes that reached MII in the control group (20 of 56; 35.7%) showed a tendency to be different when compared with eGH + IGF-I group (15 of 45; 33.3%, p = 0.08). The treated group that contained anti-IGF-I (15 of 33; 45.4%) decreased the number of oocytes reaching any stage of development when compared with eGH (47 of 72; 65.3%) and eGH + IGF-I (33 of 45; 73.3%) groups (p = 0.05) when data from MI and MII were combined. We concluded that the addition of eGH to in vitro maturation (IVM) medium influenced the in vitro nuclear and cytoplasmic maturation of equine oocytes. The use of GH and IGF-I in vitro may represent a potential alternative for IVM of equine oocytes.

DNA microarray profiling identified a new role of growth hormone in vascular remodeling of rat ductus arteriosus

The ductus arteriosus (DA), a fetal arterial connection between the pulmonary artery and the aorta, has a character distinct from the adjacent arteries. We compared the transcriptional profiles of the DA and the aorta of Wistar rat fetuses on embryonic day 19 (preterm) and day 21 (near-term) using DNA microarray analyses. We found that 39 genes were expressed 2.5-fold greater in the DA than in the aorta. Growth hormone (GH) receptor (GHR) exhibited the most significant difference in expression. Then, we found that GH significantly promoted migration of DA smooth muscle cells (SMCs), thus enhancing the intimal cushion formation of the DA explants. GH also regulated the expression of cytoskeletal genes in DA SMCs, which may retain a synthetic phenotype in the smooth muscle-specific cytoskeletal genes. Thus, the present study revealed that GH-GHR signal played a role in the vascular remodeling of the DA.

Genetic regulation of the growth plate

The epiphyseal growth plate consists of a layer of cartilage present only during the growth period and vanishes soon after puberty in long bones. It is divided to three well-defined zones, from epiphyses; resting, proliferative, and hypertrophic zones. Chondrocyte proliferation and differentiation and subsequent bone formation in this cartilage are controlled by various endocrine, autocrine, and paracrine factors which finally results into elimination of the cartilaginous tissue and promotion of the epiphyseal fusion. As chondrocytes differentiate from round, quiescent, and single structure to flatten and proliferative and then large and terminally differentiated, they experience changes in their gene expression pattern which allow them to transform from cartilaginous tissue to bone. This review summarizes the literature in this area and shortly describes different factors that affect growth plate cartilage both at the local and systemic levels. This may eventually help us to develop new treatment strategies of different growth disorders.

Maternal undernutrition and endocrine development

Maternal undernutrition, whether it occurs before conception, throughout gestation or during lactation, may lead to physiological adaptations in the fetus that will affect the health of the offspring in adult life. The timing, severity, duration and nature of the maternal nutritional insult may affect the offspring differently. Other factors determining outcome following maternal undernutrition are fetal number and gender. Importantly, effects of maternal undernutrition may be carried over into subsequent generations. This review examines the endocrine pathways disrupted by maternal undernutrition that affect the long-term postnatal health of the offspring. Maternal and childhood undernutrition are highly prevalent in low- and middle-income countries, and, in developed countries, unintentional undernutrition may arise from maternal dieting. It is, therefore, important that we better understand the mechanisms driving the long-term effects of maternal undernutrition, as well as identifying treatments to ameliorate the associated mortality and morbidity.

Signaling mechanisms mediating local GH action in the neural retina of the chick embryo

Growth hormone (GH) is found in the retina and vitreous of the chick embryo, where it appears to act as a growth and differentiation factor, having neuroprotective effects on retinal ganglion cells (RGCs). Here, we review the molecular mechanisms of the anti-apoptotic effect of GH in chick RGCs. GH treatment of RGCs reduces Akt levels, while raising Akt-phos levels, consistent with a role for Akt signaling pathways in the GH neuroprotective action. The induction of apoptosis by immunoneutralization with GH antiserum is accompanied by an increase in caspase-3 and caspase-9 activation, and also PARP-1 cleavage. Calpain activation also appears to be a major caspase-independent pathway to PARP-1 cleavage and apoptosis in these cells, supporting the view that caspase and calpain inhibitors are major neuroprotective agents for RGCs, and that pathways that activate both caspases and calpains are important for the anti-apoptotic actions of GH in these cells. These pathways involve the activation of cytosolic tyrosine kinases (Trks) and extracellular-signal-related kinases (ERKs). Occupation of the GH receptor by GH involves downstream intracellular Trk pathways. The Akt and Trk pathways appear to converge on the activation of cAMP response element binding protein (CREB), which is able to initiate transcription of pro- or anti-apoptotic genes. These results indicate that the action of GH in the neuroprotection of embryonic RGCs involves pathways common to with other neurotrophins, and that GH can be considered to be a growth and differentiation factor in the development of the embryonic retina. We have also investigated the relationship between the overlapping anti-apoptotic effects of GH and insulin-like growth factor-1 (IGF-1), two functionally closely related factors. We find that simultaneous immunoneutralization of GH and IGF-1 does not increase the level of apoptosis in the cultures above that achieved by immunoneutralization of GH alone. We therefore conclude that the neuroprotective actions of GH in the developing retina are likely mediated in large part through the action of IGF-1.

Growth hormone-dependent changes in the rat lung proteome during alveorization

Growth hormone (GH) mRNA and protein have recently been demonstrated in the rat lung throughout the period of alveolarization (day 4-14 postnatally). The functional significance of this finding was therefore assessed, by determining the effects of GH mRNA knockout using aerosolized antisense oligodeoxynucleotides (ODN) directed against the GH gene. In a preliminary experiment, the effectiveness of the antisense GH ODN was demonstrated in a lung Type II epithelial cell line (L2 cells), in which constitutive GH mRNA expression was completely abolished by GH ODN transfection. Administration of the aerosolized GH ODN to 4-day-old rats for 10 days was accompanied by a widespread presence of its delivery liposomes within lung cells. Aerosolized GH ODN treatment decreased lung concentrations of IGF (insulin-like growth factor)-1 and increased concentrations of albumin, calcyclin binding protein, superoxide dismutase, RNA binding protein motif 3, and the alpha- and beta-subunits of ATP synthase and electron transfer flavoprotein. At least 32 other proteins (identified by 2D gel electrophoresis) were also significantly affected by the antisense GH ODN treatment. By changing the lung proteome, these results indicate hitherto unsuspected autocrine/paracrine actions of GH in developmental lung function.

Prolactin-dependent modulation of organogenesis in the vertebrate: Recent discoveries in zebrafish

The scientific literature is replete with evidence of the multifarious functions of the prolactin (PRL)/growth hormone (GH) superfamily in adult vertebrates. However, little information is available on the roles of PRL and related hormones prior to the adult stage of development. A limited number of studies suggest that GH functions to stimulate glucose transport and protein synthesis in mouse blastocytes and may be involved during mammalian embryogenesis. In contrast, the evidence for a role of PRL during vertebrate embryogenesis is limited and controversial. Genes encoding GH/PRL hormones and their respective receptors are actively transcribed and translated in various animal models at different time points, particularly during tissue remodeling. We have addressed the potential function of GH/PRL hormones during embryonic development in zebrafish by the temporary inhibition of in vivo PRL translation. This treatment caused multiple morphological defects consistent with a role of PRL in embryonic-stage organogenesis. The affected organs and tissues are known targets of PRL activity in fish and homologous structures in mammalian species. Traditionally, the GH/PRL hormones are viewed as classical endocrine hormones, mediating functions through the circulatory system. More recent evidence points to cytokine-like actions of these hormones through either an autocrine or a paracrine mechanism. In some situations they could mimic actions of developmentally regulated genes as suggested by experiments in multiple organisms. In this review, we present similarities and disparities between zebrafish and mammalian models in relation to PRL and PRLR activity. We conclude that the zebrafish could serve as a suitable alternative to the rodent model to study PRL functions in development, especially in relation to organogenesis.

Peptide hormones as developmental growth and differentiation factors

Peptide hormones, usually considered to be endocrine factors responsible for communication between tissues remotely located from each other, are increasingly being found to be synthesized in developing tissues, where they act locally. Several hormones are now known to be produced in developing tissues that are unrelated to the endocrine gland of origin in the adult. These hormones are synthesized locally, and are active as differentiation and survival factors, before the developing adult endocrine tissue becomes functional. There is increasing evidence for paracrine and/or autocrine actions for these factors during development, thus, placing them among the conventional growth and differentiation factors. We review the evidence for the view that thyroid hormones, growth hormone, prolactin, insulin, and parathyroid hormone-related protein are developmental growth and differentiation factors.

Immunohistochemical distribution of regulatory peptides in the human fetal adenohypophysis

We have studied here the cellular distribution of several regulatory peptides in hormone-producing cells of the human pituitary during the fetal period. Immunohistochemistry was used to show the expression of several regulatory peptides, namely Angiotensin-II, Neurotensin and Galanin, at successive gestational stages and their co-localization with hormones in the human fetal adenohypophysis. Somatotrophs, gonadotrophs and thyrotrophs were differentiated earliest. At gestational week 9, Angiotensin-II immunoreactivity was co-localized only with growth hormone immunoreactivity in somatotrophs, one of the first hormone-producing cells to differentiate. This co-localization remained until week 37. Neurotensin immunoreactivity was present in gonadotrophs and thyrotrophs in week 23, after FSH and TSH hormone differentiation. Galanin immunoreactivity was present in all hormone-producing cell types except corticotrophs. The different pro-opiomelanocortin-derived peptides were detected at different stages of gestation and adrenocorticotrophic hormone immunoreaction was the last to be detected. Our results show an interesting relationship between regulatory peptides and hormones during human fetal development, which could imply that these peptides play a regulatory role in the development of pituitary function.

Transmission ratio distortion at the growth hormone gene (GH1) in bovine preimplantation embryos: An in vitro culture-induced phenomenon?

The growth hormone gene (GH1) and its polypeptide product (GH) have a crucial role in reproduction, embryogenesis and general development. A polymorphism present in the fifth exon of the bovine GH1 gene (GH1 p.Leu127Val) has been associated with GH release and milk production in cattle. The objective of the present study was to examine the genotype frequencies of the GH1 p.Leu127Val polymorphism in bovine blastocysts produced in vitro and in vivo to determine if allelic variation of the GH1 gene affects embryo development and survival. A heterozygous (p.Leu127/Val127) sire was used for in vitro fertilization of oocytes of unknown maternal genotype (n = 104) and known maternal genotype (n = 115). PCR amplification and genotyping of the GH1 gene from Day 8 blastocysts derived from these fertilized oocytes demonstrated that there was significant over-representation from the expected Mendelian ratio of GH1 p.Leu127/Leu127 homozygotes from oocytes of known maternal genotype (P = 0.006). Contrary to this, analysis of in vivo-produced bovine blastocysts of known parental GH1 genotype (n = 69) did not reveal an overrepresentation of GH1 p.Leu127/Leu127 homozygotes. These results suggest that developing in vitro-produced embryos are exposed to a selection process, probably due to a less favorable culture environment, that acts to increase the number of GH1 p.Leu127/Leu127 homozygotes, thereby giving rise to the observed transmission ratio distortion (TRD) of GH1 genotypes when compared to in vivo produced embryos.

Sexual dimorphism in relations of blood growth-hormone levels to body and brain weights in newborn rats

The growth promoting effects of growth hormone (GH) are well-known. However, the studies in this respect did not consider the sexual dimorphism. The adverse--growth limiting--GH effects were also reported in human newborns (see Tan, 1992, 1995; Tan et al., 1998). A similar study was replicated in the newborn rat pups in the present work. The serum GH level, body weight, body height, right- and left-brain weights were measured just after birth in rat pups. The relations of the serum GH levels to the bodily measurements were found to be sexually dimorphic. Namely, there were no significant correlations between the serum GH levels and the body size (weight and height) in males, whereas there were inverse relations between these parameters in females. The GH level negatively linearly related to the right-, left-, and right- minus left-brain weights in females, whereas only the right-brain weight positively linearly correlated with the serum GH level, the right- minus left-brain weight being also positively linearly correlated with the serum GH level in males. The results suggested that the sexual dimorphism should be taken into consideration in studies concerning the global GH effects. The relation of the serum GH level to the right-left brain asymmetry, also sexually dimorphic, suggests a role of GH in cerebral lateralization.

Ontogeny and nutritional programming of the hepatic growth hormone-insulin-like growth factor-prolactin axis in the sheep

The liver is an important metabolic and endocrine organ in the fetus, but the extent to which its hormone receptor sensitivity is developmentally regulated in early life is not fully established. Therefore, we examined developmental changes in mRNA abundance for the GH receptor (GHR) and prolactin receptor (PRLR) plus IGF-I and -II and their receptors. Fetal and postnatal sheep were sampled at either 80 or 140 d gestation, 1 or 30 d, or 6 months of age. The effect of maternal nutrient restriction between early gestation to midgestation (i.e. 28-80 d gestation, the time of early liver growth) on gene expression was also examined in the fetus and juvenile offspring. Gene expression for the GHR, PRLR, and IGF-I receptor increased through gestation peaking at birth, whereas IGF-I was maximal near to term. In contrast, IGF-II mRNA decreased between midgestation and late gestation to increase after birth, whereas IGF-II receptor remained unchanged. A substantial decline in mRNA abundance for GHR, PRLR, and IGF-I receptor then occurred up to 6 months. Maternal nutrient restriction reduced GHR and IGF-II receptor mRNA abundance in the fetus, but caused a precocious increase in the PRLR. Gene expression for IGF-I and -II were increased in juvenile offspring born to nutrient-restricted mothers. In conclusion, there are marked differences in the ontogeny and nutritional programming of specific hormones and their receptors involved in hepatic growth and development in the fetus. These could contribute to changes in liver function during adult life.

Effects of maternal parity and late gestational nutrition on mRNA abundance for growth factors in the liver of postnatal sheep

The liver is a major metabolic and endocrine organ in growing neonates, but the extent to which its hormone receptor (R) sensitivity is potentially determined by maternal parity and the mother's nutritional environment is unknown. This was therefore investigated by sampling livers from postnatal sheep born to nulliparous or multiparous mothers. Offspring were sampled 1 or 30 days after birth from mothers consuming either 100 or 50% [i.e., nutrient-restricted (NR) group] of total metabolizable energy requirements from 110 days gestation to term (∼147 days). Regardless of maternal diet, offspring of nulliparous mothers were lighter at birth and had smaller livers. By 1 mo of age, they exhibited catch-up growth, an adaptation not seen when mothers were NR, but they retained their lighter livers. At both sampling ages, livers from offspring born to nulliparous mothers exhibited increased mRNA abundance for growth hormone (GH) receptor, IGF-IR, plus hepatocyte growth factor (HGF); and at day 1 only IGF-I, but not IGF-IIR mRNA was decreased. In addition, mRNA for IGF-II, the HGFR, c-Met, and Bax were persistently reduced in these offspring. Effects of parity were largely unaffected by maternal nutrient restriction. Maternal parity therefore has a substantial effect on liver size during postnatal development and its receptor population that is not dependent on maternal diet. First-born offspring appear to exhibit a resetting of the endocrine control of hepatic growth within the HGF and GH-IGF axis, which could have later consequences after their growth has caught up.

The effects of the members of growth hormone family knockdown in zebrafish development

Growth hormone (GH), prolactin (PRL), and somatolactin (SL) are members of GH/PRL superfamily. These hormones are involved in the regulation of an array of physiological processes, including growth, lactation, and osmoregulation. While recent evidence has shown the GH, PRL, and SL gene transcripts and protein products are expressed during early zebrafish development, their functions at this time of embryogenesis remain unknown. In the current study, antisense morpholino oligonucleotide (MO) inhibition of gh, prl, and sl gene translation was used to examine the effects of gene knockdown on hormone function in zebrafish development. We observed that PRL, SLalpha and SLbeta MO treatment all affected development. PRL MO-treated embryos showed defects in gas bladder inflation, reduced head and eye size, shorter body length and fewer melanophores than untreated controls, whereas SLalpha and SLbeta MO-treated embryos were only defective in gas bladder inflation, GH MO-inhibition of GH specific translation did not lead to any discernable morphological changes within 10 days post fertilization (dpf). The effects of PRL knockdown were further verified using a second PRL morpholino antisense and by a rescue experiment with in vitro transcribed prl mRNA containing 5 nucleotide mismatch within the PRL-MO binding region. These results provide the first evidence that members of the GH/PRL superfamily play a role in proper development of various structures including the head, eyes, melanophores and the gas bladder in zebrafish.

Retinal ganglion cell survival in development: mechanisms of retinal growth hormone action

Several variants of growth hormone (GH) are found in the retina and vitreous of the chick embryo, where they appear to act as cell survival factors, having neuroprotective effects on retinal ganglion cells (RGCs). Here, we investigate the molecular mechanisms of the anti-apoptotic effect of GH in cultured RGCs. GH treatment increased Akt phosphorylation in these cells, which is an anti-apoptotic event. Whereas unphosphorylated Akt was detected in both nucleus and cytoplasm of RGCs by immunocytochemistry, the phosphorylated form of Akt (Akt-phos) was located primarily in the cytoplasm of both normal and apoptotic cells, although levels were markedly lower in the latter. It was found that GH treatment of RGCs reduced Akt levels, while concomitantly raising Akt-phos levels, consistent with a role for Akt signaling pathways in GH neuroprotective action. This was substantiated using Wortmannin, which, like GH antiserum, inhibited Akt phosphorylation and initiated apoptosis. The addition of Wortmannin to RGC cultures simultaneously with GH significantly reduced the anti-apoptotic effect of GH. The induction of apoptosis by GH antiserum was clearly accompanied by an increase in caspase-3 activation and PARP-1 cleavage, both of which were significantly reduced in the presence of the broad spectrum caspase inhibitor, Q-VD-OPh, which itself had a dramatic neuroprotective effect on cultured RGCs. Calpain activation appeared to be a major caspase-independent pathway to PARP-1 cleavage and apoptosis in these cells. Calpain inhibitor III (MDL 28170) was able to reduce PARP-1 cleavage and abrogate the apoptogenic effect of GH antiserum. The results support the view that caspase and calpain inhibitors are major neuroprotective agents for RGCs, and that pathways that activate both caspases and calpains are important for the anti-apoptotic actions of GH in these cells.

Maternal ghrelin plays an important role in rat fetal development during pregnancy

Ghrelin, an acylated peptide serving as an endogenous ligand for GH secretagogue receptor (GHS-R), was originally isolated from rat and human stomach. In this study, we report the critical role of maternal ghrelin in fetal development. High levels of ghrelin receptor (GHS-R) mRNA were detected in various peripheral fetal tissues beginning at embryonic d 14 and lasting until birth. Fetal GHS-R expression was also confirmed in fetal tissues by immunohistochemistry. Autoradiography revealed that both des-acyl ghrelin and acyl ghrelin bind to fetal tissues. Chronic treatment of mothers with ghrelin resulted in a significant increase in birth weight in comparison to newborns from saline-treated mothers. Even when maternal food intake after ghrelin treatment was restricted through paired feeding, significant stimulation of fetal development still occurred. Conversely, active immunization of mothers against ghrelin decreased fetal body weight during pregnancy. A single ghrelin injection into the mother increased circulating ghrelin levels in the fetus within 5 min of injection, suggesting that maternal ghrelin transits easily to the fetal circulation. High levels of des-acyl ghrelin were detected in fetal blood and amniotic fluid. Both acylated and des-acyl ghrelin increased [3H]thymidine and 5-bromo-2'-deoxyuridine incorporation of cultured fetal skin cells in a dose-dependent manner, and calcium-imaging analysis revealed that acyl and des-acyl ghrelin increased the Ca2+ influx in discrete cultured fetal skin cells, respectively. These results indicate that maternal ghrelin regulates fetal development during the late stages of pregnancy.

Retinal growth hormone is an anti-apoptotic factor in embryonic retinal ganglion cell differentiation

Cells of the neural retina in the chick embryo undergo several waves of apoptosis during development, including peaks at approximately embryonic day (ED) 7 and 12. Prominent among the cells involved in these phases of cell death are the retinal ganglion cells (RGCs). We have previously shown that growth hormone (GH) is expressed in the neural retina, and particularly, in the RGCs. Here we study the ability of GH to rescue retinal cells from apoptosis, both in vitro and in vivo. When retinas from embryos at ED 6-8 are explanted on collagen gels, the application of recombinant GH, at 10(-6)m, significantly reduced the incidence of apoptotic cells in the cultures as judged by terminal deoxynucleotide transferase-mediated dUTP-biotin nick end labelling (TUNEL). GH was delivered to neural retinas in ovo, by microinjection into the eye cup at ED 2. When these embryos were examined at ED 6-8, no reduction in cell death was observed below the normal low control levels. However, when antibodies to GH were microinjected, the incidence of cell death increased significantly at ED 6, providing evidence that in vivo immunoneutralization of endogenous GH results in triggering of apoptotic signaling pathways. Evidence that RGCs are a particular target of this neuroprotective effect of GH was provided by examination of cultures enriched for RGCs by immunopanning. In serum-free culture, RGCs, identified by anti-Islet 1 immunolabelling, were found to be susceptible to the effect of GH immunoneutralization, which approximately quadrupled the incidence of apoptosis in the cultures. We propose that GH is a naturally occurring autocrine and/or paracrine neuroprotective agent in the developing retina which is involved in the regulation of retinal cell numbers during early embryogenesis.

Heterozygote effects in mice with partial truncations in the growth hormone receptor cytoplasmic domain: assessment of growth parameters and phenotype

The GH receptor (GHR) is essential for normal postnatal growth and development, and the molecular basis of GHR action has been studied intensively. Clinical case studies and more recently mouse models have revealed the extensive phenotype of impaired GH action. We recently reported two new mouse models, possessing cytoplasmic truncations at position 569 (plus Y539/545-F) and 391, which were created to identify functional subdomains within the cytoplasmic signaling domain. In the homozygous state, these animals show progressively impaired postnatal growth coupled with complex changes in gene expression. We describe here an extended phenotype analysis encompassing the heterozygote state to identify whether single copies of these mutant receptors bring about partial or dominant-negative phenotypes. It appears that the retention of the ubiquitin-dependent endocytosis motif in the N-terminal cytoplasmic domain permits turnover of these mutant receptors because no dominant-negative phenotype is seen. Nonetheless, we do observe partial impairment of postnatal growth in heterozygotes supporting limited haploinsufficiency. Reproductive function is impaired in these models in a progressive manner, in parallel with loss of signal transducer and activator of transcription-5 activation ability. In summary, we describe a more comprehensive phenotypic analysis of these mouse models, encompassing overall and longitudinal body growth, reproductive function, and hormonal status in both the heterozygote and homozygote state. Our results suggest that patients expressing single copies of similarly mutated GHRs would not display an obvious clinical phenotype.

Expression of growth hormone and its receptor in the lungs of embryonic chicks

The lung is well established as being a postnatal target site for growth hormone (GH) action, since pathophysiological states of GH excess and deficiency are both associated with impaired pulmonary function. Pituitary GH is therefore probably involved in normal lung growth or development, although perinatal lung development occurs prior to the differentiation of pituitary somatotrophs and the ontogeny of pituitary GH secretion. The lung itself may, however, be a site of GH production during prenatal development, since a specific GH-response gene (a marker of GH activity) is expressed in the lungs of early chick embryos, in which GH immunoreactivity is widespread in many other peripheral tissues. We have assessed this possibility in embryonic chicks. A 690-bp cDNA, identical in size and nucleotide sequence to the full-length pituitary GH transcript, was amplified by reverse transcription/polymerase chain reaction from total RNA extracted from the lungs of embryos at 11, 13, 15, and 18 days of the 21-day incubation period. This transcript was localized by in situ hybridization to mesenchymal and epithelial cells of the developing lungs, in which specific GH immunoreactivity was similarly located. Intense GH immunoreactivity was also present after embryonic day 15 (ED15) in the smooth muscle surrounding blood vessels in the lung and surrounding the bronchioles. Lung GH immunoreactivity was primarily associated with a 15-kDa protein, rather than the 26-kDa protein in the pituitary gland. After the onset of pituitary GH secretion (at ED17), GH mRNA was barely detectable in the lungs of ED20 embryos, at the start of lung breathing. GH immunoreactivity was, however, still present in some cells in the lungs of ED20 embryos. GH-receptor mRNA and immunoreactivity were also widespread and abundant within the embryonic lung. Lung GH may thus have autocrine or paracrine roles in lung development or in pulmonary function prior to the ontogeny of the pituitary gland and the appearance of GH in peripheral plasma.

Growth hormone as an early embryonic growth and differentiation factor

In this review we consider the evidence that growth hormone (GH) acts in the embryo as a local growth, differentiation, and cell survival factor. Because both GH and its receptors are present in the early embryo before the functional differentiation of pituitary somatotrophs and before the establishment of a functioning circulatory system, the conditions are such that GH may be a member of the large battery of autocrine/paracrine growth factors that control embryonic development. It has been clearly established that GH is able to exert direct effects, independent of insulin-like growth factor-I (IGF-I), on the differentiation, proliferation, and survival of cells in a wide variety of tissues in the embryo, fetus, and adult. The signaling pathways behind these effects of GH are now beginning to be determined, establishing early extrapituitary GH as a bona fide developmental growth factor.

Extraordinarily stable disulfide-linked homodimer of human growth hormone

Although a 22-kDa human growth hormone (hGH) is the predicted protein product of the hGH-N gene, a pleiotropic collection of uncharacterized molecular weight and charge isoforms is also produced. Using chromatography and preparative SDS-PAGE under reducing conditions we isolated an unusually stable mercaptoethanol-resistant (MER) 45-kDa hGH. A 5-h incubation at 100 degrees C in the presence of 2-mercaptoethanol was required to convert approximately 90% of MER-45-kDa hGH into a 22-kDa hGH. Other reductants were not as effective in splitting MER-45-kDa hGH. After fracturing MER-45-kDa hGH, the 22-kDa hGH fragments would spontaneously reassociate if the reductant was removed; however, alkylation of cysteine residues prevented their reassociation. Identical amino acid sequences for the first six N-terminal residues were obtained for MER-45-kDa hGH and its 22-kDa hGH cleavage product. Structural identity of MER-45-kDa hGH and 22-kDa hGH was demonstrated by MALDI-TOF mass spectrometry of tryptic digests. MER-45-kDa hGH did not break up upon incubation with EDTA and EGTA. The significance of this work to our understanding of the structure of hGH isoforms is that it demonstrates that MER-45-kDa hGH is not a single chain polypeptide but is instead a homodimer of 22-kDa hGH monomers. The MER-45-kDa hGH dimer is held together by interchain disulfide bonds and not by divalent metal cation bridges. Additionally, MER-45-kDa hGH's interchain disulfide links are exceptionally resistant to reducing agents and thus confer extreme stability to the homodimer.

Alterations of protein metabolism in acromegaly

PURPOSE OF REVIEW

Growth hormone is a powerful anabolic hormone necessary for normal growth, but its importance in maintaining the cellular and protein mass in adult life is still unclear. However, it is viewed as a drug capable of combating the tissue loss and some metabolic derangements of aging. Growth hormone excess causes acromegaly, a disease characterized by overgrowth of some tissues and multiple metabolic abnormalities. The purpose of this article is to review recent knowledge in acromegaly considering it as a model for clarifying aspects of growth hormone action on body composition, protein dynamics and molecular mechanisms in adult life.

RECENT FINDINGS

Acromegaly induces well-documented changes in body fat (decreased), and bone density and water retention (increased), but there are less-clear changes in protein and body cell-mass accretion. Recent studies related insulin resistance to glucose metabolism to accelerated fat oxidation and described the reversibility of such alterations after surgical or pharmacologic therapy. Less attention was paid to changes in protein metabolism. Acromegalics are profoundly insulin-resistant to the antiproteolytic action of insulin, but amino acids are channelled towards protein synthesis because they are still normally spared from oxidation by insulin. This insulin resistance persists months after the surgical cure of acromegaly when glucose metabolism is already normalized. Recent studies suggested that increased use of fat for fuel by growth hormone may also promote protein anabolism and reduce amino acid oxidation.

SUMMARY

Despite important advances in understanding molecular mechanisms in acromegaly, the specific effects on body cell and protein mass and the specific modulation of local protein dynamics remain poorly defined.

Corpus Luteum Development: Lessons from Genetic Models in Mice

The corpus luteum is a transient endocrine gland that produces essentially progesterone, a required product for the establishment and maintenance of early pregnancy. In the absence of pregnancy, the corpus luteum will cease to produce progesterone, and the structure itself will regress in size over time. The life span and function of the corpus luteum is regulated by complex interactions between stimulatory (luteotrophic) and inhibitory (luteolytic) mediators. Although the process of luteal formation and regression has been studied for several decades, many of the regulatory mechanisms involved in loss of function and involution of the structure are incompletely understood. In rodents, prolactin is the major luteotrophic hormone by maintaining the structural and functional integrity of the corpus luteum for several days after mating. Other factors involved in steroidogenesis, control of cell cycle, apoptosis, and tissue remodeling have been shown to play a role in corpus luteum development and maintenance. Especially, PGF2alpha seems to be the most potent luteolytic hormone. One of the most important advances in the study of mammalian genes has been the development of techniques to obtain defined mutations in mice. These tools enable us to target specific genes and to analyze the impact of their loss on cell fate and function. With these approaches, several receptors, transcription factors, enzymes, and other factors have been linked to corpus luteum development and maintenance. These models are helping to define mechanisms of reproductive function and to identify potential new contraceptive targets and genes involved in the pathophysiology of reproductive disorders.

Novel mutations of the growth hormone 1 (GH1) gene disclosed by modulation of the clinical selection criteria for individuals with short stature

Subtle mutations in the growth hormone 1 (GH1) gene have been regarded as a comparatively rare cause of short stature. Such lesions were sought in a group of 41 individuals selected for short stature, reduced height velocity, and bone age delay; a group of 11 individuals with short stature and idiopathic growth hormone deficiency (IGHD); and a group of 154 controls. Heterozygous mutations were identified in all three groups but disproportionately in the individuals with short stature, both with (odds ratio 25.2; 95% CI, 5.1-132.2) and without (odds ratio 3.6; 95% CI, 1.0-12.9) IGHD. Twenty-four novel GH1 gene lesions were found. Thirteen novel missense mutations were characterized by assaying the signal transduction activity of in vitro expressed variants; six (T27I, K41R, N47D, S71F, S108R, and T175A) exhibited a reduced ability to activate the JAK/STAT pathway. Molecular modeling suggested that both K41R and T175A might compromise GH receptor binding. Seven GH variants (R16C, K41R, S71F, E74K, Q91L, S108C, and a functional polymorphism, V110I) manifested reduced secretion in rat pituitary cells after allowance had been made for the level of expression attributable to the associated GH1 proximal promoter haplotype. A further leader peptide variant (L-11P) was not secreted. Eleven novel mutations in the GH1 gene promoter were assessed by reporter gene assay but only two, including a GH2 gene-templated gene conversion, were found to be associated with a significantly reduced level of expression. Finally, a novel intron 2 acceptor splice-site mutation, detected in a family with autosomal dominant type II IGHD, was shown to lead to the skipping of exon 3 from the GH1 transcript. A total of 15 novel GH1 gene mutations were thus considered to be of probable phenotypic significance. Such lesions are more prevalent than previously recognized and although most may be insufficient on their own to account for the observed clinical phenotype, they are nevertheless likely to play a contributory role in the etiology of short stature.