Neural growth hormone: an update

Response to growth hormone therapy in ring chromosome 15: Review and evidence from a new case on possible beneficial effect in neurodevelopment

Type 1 Insulin-like Growth Factor Receptor(IGF1R) plays a fundamental role in normal growth and development. Its disruption is usually characterized by severe intrauterine and postnatal growth retardation, microcephaly and neurodevelopmental delay.The efficacy of recombinant human growth hormone treatment remains a challenge for children with IGF1 resistance and pathogenic mutations of IGF1R, with limited data in patients carrying the most severe form of IGF1R defect, the ring chromosome 15.

SUBJECT AND METHOD

We tested a high dose of rhGH in a new patient with ring chromosome 15, as confirmed by karyotype and CGH array. We performed a systematic review, and all published r(15) syndrome cases treated by growth hormone(GH) up to April 2023 were searched, and their response to GH therapy was recorded and summarized.

RESULTS

Twelve patients with ring chromosome 15 received GH therapy according to a literature review. We expand the spectrum by the 13th case treated by GH, and we report an impressive improvement in intellectual performance and progressive catch-up growth after 5 and 20 months of follow-up. By introducing our new case in the analysis, the sex ratio was 3:10, and GH therapy was started at the age of 5.5 (3/9.4) (years) for an age of diagnosis of 4.75 (1.3/9.5) (years). The height before GH therapy was -5.1(-5.9/-4.1) SDS. The median duration of treatment was 1.7(0.9/2) (years), with a median height gain of 1(0.3/1.8) SDS and an improvement in growth velocity of 4.1(2.8/5.3) (cm/year).

CONCLUSION

GH seems to be effective for r(15) syndrome patients with short stature.

Gonadotropin-releasing hormone and growth hormone act as anti-inflammatory factors improving sensory recovery in female rats with thoracic spinal cord injury

The potential for novel applications of classical hormones, such as gonadotropin-releasing hormone (GnRH) and growth hormone (GH), to counteract neural harm is based on their demonstrated neurotrophic effects in both in vitro and in vivo experimental models and a growing number of clinical trials. This study aimed to investigate the effects of chronic administration of GnRH and/or GH on the expression of several proinflammatory and glial activity markers in damaged neural tissues, as well as on sensory recovery, in animals submitted to thoracic spinal cord injury (SCI). Additionally, the effect of a combined GnRH + GH treatment was examined in comparison with single hormone administration. Spinal cord damage was induced by compression using catheter insufflation at thoracic vertebrae 10 (T10), resulting in significant motor and sensory deficits in the hindlimbs. Following SCI, treatments (GnRH, 60 μg/kg/12 h, IM; GH, 150 μg/kg/24 h, SC; the combination of both; or vehicle) were administered during either 3 or 5 weeks, beginning 24 h after injury onset and ending 24 h before sample collection. Our results indicate that a chronic treatment with GH and/or GnRH significantly reduced the expression of proinflammatory (IL6, IL1B, and iNOS) and glial activity (Iba1, CD86, CD206, vimentin, and GFAP) markers in the spinal cord tissue and improved sensory recovery in the lesioned animals. Furthermore, we found that the caudal section of the spinal cord was particularly responsive to GnRH or GH treatment, as well as to their combination. These findings provide evidence of an anti-inflammatory and glial-modulatory effect of GnRH and GH in an experimental model of SCI and suggest that these hormones can modulate the response of microglia, astrocytes, and infiltrated immune cells in the spinal cord tissue following injury.

Therapeutic effects of growth hormone in a rat model of total sleep deprivation: Evaluating behavioral, hormonal, biochemical and electrophysiological parameters

OBJECTIVE

Total sleep deprivation (TSD) causes several harmful changes in the brain, including memory impairment, increased stress and depression levels, as well as reduced antioxidant activity. Growth hormone (GH) has been shown to boost antioxidant levels while improving memory and depression. The present study was conducted to explain the possible effects of exogenous GH against behavioral and biochemical disorders caused by TSD and the possible mechanisms involved.

MAIN METHODS

To induce TSD, rats were housed in homemade special cages equipped with stainless steel wire conductors to induce general and inconsistent TSD. They received a mild repetitive electric shock to their paws every 10 min for 21 days. GH (1 ml/kg, sc) was administered to rats during induction of TSD for 21 days. Memory retrieval, anxiety, depression-like behaviors, pain behaviors, antioxidant activity, hippocampal level of BDNF, and simultaneously brain electrical activity were measured at scheduled times after TSD.

KEY FINDINGS

The results showed that GH treatment improved memory (p < 0.001) in the PAT test of rats exposed to TSD. These beneficial effects were associated with lowering the level of anxiety and depression-like behavior (p < 0.001), rising the pain threshold (p < 0.01), increasing the activity of antioxidants (p < 0.01), hippocampal BDNF (p < 0.001), and regular brain electrical activity.

SIGNIFICANCE

Our findings show that GH plays a key role in modulating memory, anxiety and depression behaviors, as well as reducing oxidative stress and improve hippocampal single-unit activity in the brain during TSD.

Growth Hormone and the Auditory Pathway: Neuromodulation and Neuroregeneration

Growth hormone (GH) plays an important role in auditory development during the embryonic stage. Exogenous agents such as sound, noise, drugs or trauma, can induce the release of this hormone to perform a protective function and stimulate other mediators that protect the auditory pathway. In addition, GH deficiency conditions hearing loss or central auditory processing disorders. There are promising animal studies that reflect a possible regenerative role when exogenous GH is used in hearing impairments, demonstrated in in vivo and in vitro studies, and also, even a few studies show beneficial effects in humans presented and substantiated in the main text, although they should not exaggerate the main conclusions.

Growth hormone (GH) and synaptogenesis

Growth hormone (GH) is known to exert several roles during development and function of the nervous system. Initially, GH was exclusively considered a pituitary hormone that regulates body growth and metabolism, but now its alternative extrapituitary production and pleiotropic functions are widely accepted. Through excess and deficit models, the critical role of GH in nervous system development and adult brain function has been extensively demonstrated. Moreover, neurotrophic actions of GH in neural tissues include pro-survival effects, neuroprotection, axonal growth, synaptogenesis, neurogenesis and neuroregeneration. The positive effects of GH upon memory, behavior, mood, sensorimotor function and quality of life, clearly implicate a beneficial action in synaptic physiology. Experimental and clinical evidence about GH actions in synaptic function modulation, protection and restoration are revised in this chapter.

Therapeutic approaches of trophic factors in animal models and in patients with spinal cord injury

Trophic factors are naturally produced by different tissues that participate in several functions such as the intercellular communication, in the development, stability, differentiation and regeneration at the cellular level. Specifically, in the case of spinal injuries, these factors can stimulate neuronal recovery. They are applied both in experimental models and in clinical trials in patients. The trophic factors analysed in this review include gonadotropin-releasing hormone (GnRH), thyrotropin-releasing hormone (TRH), growth hormone (GH), melatonin, oestrogens, the family of fibroblast growth factors (FGFs), the family of neurotrophins and the glial cell-derived neurotrophic factor (GDNF). There are some trophic (neurotrophic) factors that already been tested in patients with spinal cord injury (SCI), but only shown partial recovery effect. It is possible that, the administration of these trophic factors together with physical rehabilitation, act synergistically and, therefore, significantly improve the quality of life of patients with SCI.

Growth hormone promotes synaptogenesis and protects neuroretinal dendrites against kainic acid (KA) induced damage

There is increasing evidence that suggests a possible role for GH in retinal development and synaptogenesis. While our previous studies have focused largely on embryonic retinal ganglion cells (RGCs), our current study demonstrates that GH has a synaptogenic effect in retinal primary cell cultures, increasing the abundance of both pre- (SNAP25) and post- (PSD95) synaptic proteins. In the neonatal chick, kainate (KA) treatment was found to damage retinal synapses and abrogate GH expression. In response to damage, an increase in Cy3-GH internalization into RGCs was observed when administered shortly before or after damage. This increase in internalization also correlated with increase in PSD95 expression, suggesting a neuroprotective effect on the dendritic trees of RGCs and the inner plexiform layer (IPL). In addition, we observed the presence of PSD95 positive Müller glia, which may suggest GH is having a neuroregenerative effect in the kainate-damaged retina. This work puts forth further evidence that GH acts as a synaptogenic modulator in the chick retina and opens a new possibility for the use of GH in retinal regeneration research.

Growth Hormone (GH) and Gonadotropin-Releasing Hormone (GnRH) in the Central Nervous System: A Potential Neurological Combinatory Therapy?

This brief review of the neurological effects of growth hormone (GH) and gonadotropin-releasing hormone (GnRH) in the brain, particularly in the cerebral cortex, hypothalamus, hippocampus, cerebellum, spinal cord, neural retina, and brain tumors, summarizes recent information about their therapeutic potential as treatments for different neuropathologies and neurodegenerative processes. The effect of GH and GnRH (by independent administration) has been associated with beneficial impacts in patients with brain trauma and spinal cord injuries. Both GH and GnRH have demonstrated potent neurotrophic, neuroprotective, and neuroregenerative action. Positive behavioral and cognitive effects are also associated with GH and GnRH administration. Increasing evidence suggests the possibility of a multifactorial therapy that includes both GH and GnRH.

Growth Hormone (GH) and Rehabilitation Promoted Distal Innervation in a Child Affected by Caudal Regression Syndrome

Caudal regression syndrome (CRS) is a malformation occurring during the fetal period and mainly characterized by an incomplete development of the spinal cord (SC), which is often accompanied by other developmental anomalies. We studied a 9-month old child with CRS who presented interruption of the SC at the L2–L3 level, sacral agenesis, a lack of innervation of the inferior limbs (flaccid paraplegia), and neurogenic bladder and bowel. Given the known positive effects of growth hormone (GH) on neural stem cells (NSCs), we treated him with GH and rehabilitation, trying to induce recovery from the aforementioned sequelae. The Gross Motor Function Test (GMFM)-88 test score was 12.31%. After a blood analysis, GH treatment (0.3 mg/day, 5 days/week, during 3 months and then 15 days without GH) and rehabilitation commenced. This protocol was followed for 5 years, the last GH dose being 1 mg/day. Blood analysis and physical exams were performed every 3 months initially and then every 6 months. Six months after commencing the treatment the GMFM-88 score increased to 39.48%. Responses to sensitive stimuli appeared in most of the territories explored; 18 months later sensitive innervation was complete and the patient moved all muscles over the knees and controlled his sphincters. Three years later he began to walk with crutches, there was plantar flexion, and the GMFM-88 score was 78.48%. In summary, GH plus rehabilitation may be useful for innervating distal areas below the level of the incomplete spinal cord in CRS. It is likely that GH acted on the ependymal SC NSCs, as the hormone does in the neurogenic niches of the brain, and rehabilitation helped to achieve practically full functionality.

Growth hormone/IGF-1 axis longitudinal evaluation in clinically isolated syndrome patients on interferon β-1b therapy: stimulation tests and correlations with clinical and radiological conversion to multiple sclerosis

BACKGROUND AND PURPOSE

Growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis abnormalities in multiple sclerosis (MS) suggest their role in its pathogenesis. Interferon β (IFN-β) efficacy could be mediated also by an increase of IGF-1 levels. A 2-year longitudinal study was performed to estimate the prevalence of GH and/or IGF-1 deficiency in clinically isolated syndrome (CIS) patients and their correlation with conversion to MS in IFN treated patients.

METHODS

Clinical and demographic features of CIS patients were collected before the start of IFN-β-1b. IGF-1 levels and GH response after arginine and GH releasing hormone + arginine stimulation tests were assessed. Clinical and magnetic resonance imaging evaluations were performed at baseline, 1 year and 2 years.

RESULTS

Thirty CIS patients (24 female) were enrolled. At baseline, four patients (13%) showed a hypothalamic GH deficiency (GHD), whilst no one had a pituitary GHD. Baseline demographic, clinical and radiological data were not related to GHD, whilst IGF-1 levels were inversely related to age (P < 0.001) and GH levels (P = 0.03). GH and IGF-1 serum mean levels were not significantly modified after 1 and 2 years of treatment in the whole group, although 3/4 GHD patients experienced a normalization of GH levels, whilst one dropped out. After 2 years of treatment 13/28 (46%) patients converted to MS. The presence of GHD and GH and IGF-1 levels were not predictive of relapses, new T2 lesions or conversion occurrence.

CONCLUSIONS

Growth hormone/IGF-1 axis function was found to be frequently altered in CIS patients, but this was not related to MS conversion. Patients experienced an improvement of GHD during IFN therapy. Longer follow-up is necessary to assess its impact on disease progression.

A Common Phenotype Polymorphism in Mammalian Brains Defined by Concomitant Production of Prolactin and Growth Hormone

Pituitary Prolactin (PRL) and Growth Hormone (GH) are separately controlled and sub-serve different purposes. Surprisingly, we demonstrate that extra-pituitary expression in the adult mammalian central nervous system (CNS) is coordinated at mRNA and protein levels. However this was not a uniform effect within populations, such that wide inter-individual variation was superimposed on coordinate PRL/GH expression. Up to 44% of individuals in healthy cohorts of mice and rats showed protein levels above the norm and coordinated expression of PRL and GH transcripts above baseline occurred in the amygdala, frontal lobe and hippocampus of 10% of human subjects. High levels of PRL and GH present in post mortem tissue were often presaged by altered responses in fear conditioning and stress induced hyperthermia behavioral tests. Our data define a common phenotype polymorphism in healthy mammalian brains, and, given the pleiotropic effects known for circulating PRL and GH, further consequences of coordinated CNS over-expression may await discovery.

Astaxanthin supplementation enhances adult hippocampal neurogenesis and spatial memory in mice

SCOPE

There is a growing necessity for efficacious natural supplements with antioxidant effects on the brain, in particular, hippocampal function. One such compound, which also has a neuroprotective effect, is the carotenoid astaxanthin (ASX). Despite ASX's potential benefit to the brain, very little is known about its effect on hippocampal plasticity and cognition. Thus, we investigated the effect of ASX on adult hippocampal neurogenesis (AHN) and spatial memory using a mouse model.

METHODS AND RESULTS

Dose-response was examined in mice fed ASX-supplemented diets (0, 0.02, 0.1, and 0.5%) to define the effect of ASX on AHN. In conjunction with AHN results, hippocampus-dependent cognitive function was assessed. We delineated molecular mechanisms associated with ASX-enhanced AHN using DNA microarray analysis. Results revealed that ASX enhanced cell proliferation and survival at 0.1% and 0.5% doses. Newborn mature neurons were higher only with 0.5% ASX, which also enhanced spatial memory. Transcriptomic profiling revealed potential AHN-associated molecules (Prl, Itga4, and Il4) that were ASX induced. Their downstream factors, identified through Ingenuity Pathway Analysis, were positively correlated with ASX-induced increases in spatial memory.

CONCLUSION

ASX supplementation enhanced AHN and spatial memory, and a DNA microarray approach provided, for the first time, novel molecular insights into ASX action.

Growth hormone and cancer: GH production and action in glioma?

The hypersecretion of pituitary growth hormone (GH) is associated with an increased risk of cancer, while reducing pituitary GH signaling reduces this risk. Roles for pituitary GH in cancer are therefore well established. The expression of the GH gene is, however, not confined to the pituitary gland and it is now known to occur in many extrapituitary tissues, in which it has local autocrine or paracrine actions, rather than endocrine function. It is, for instance, expressed in cancers of the prostate, lung, skin, endometrium and colon. The oncogenicity of autocrine GH may also be greater than that induced by endocrine or exogenous GH, as higher concentrations of GHR antagonists are required to inhibit its actions. This may reflect the fact that autocrine GH is thought to act at intracellular receptors directly after synthesis, in compartments not readily accessible to endocrine (or exogenous) GH. The roles and actions of extrapituitary GH in cancer may therefore differ from those of pituitary GH. The possibility that GH may be expressed and act in glioma tumors was therefore examined by immunohistochemistry. These results demonstrate, for the first time, the presence of abundant GH- and GH receptor (GHR-) immunoreactivity in glioma, in which they were co-localized in cytoplasmic but not nuclear compartments. These results demonstrate that glioma differs from most cancers in lacking nuclear GHRs, but GH is nevertheless likely to have autocrine or paracrine actions in the induction and progression of glioma.

High Postnatal Growth Hormone Levels Are Related to Cognitive Deficits in a Group of Children Born Very Preterm

CONTEXT AND OBJECTIVES

Little is known regarding the influence of GH on brain development, especially in infants born very preterm (VP; <30 weeks' gestation). Preterm infants are thought to have higher levels of GH in the first days of life compared with full-term infants. VP infants experience cognitive difficulties in childhood and have a diffuse pattern of structural brain abnormalities. This study aimed to explore the relationship between postnatal GH concentrations following VP birth and its association with cognitive functioning and brain volumes at age 7 years.

METHODS

Eighty-three infants born VP had GH concentrations measured at eight time points postnatally, and 2- and 6-week area under the curve (AUC) summary measures were calculated. Followup at age 7 years included neuropsychological assessment and brain magnetic resonance imaging. Univariable and multivariable regression modeling were used where AUC for GH was the main predictor of neurodevelopmental outcome at age 7 years.

RESULTS

Univariable modeling revealed that higher GH levels (2-week AUC) were related to poorer performance on a verbal working memory (P = .04) and shifting attention task (P = .01). These relationships persisted on multivariable modeling and when the 6-week AUC was analyzed; working memory (P = .03), immediate spatial memory (P = .02), and delayed spatial memory (P = .03) deficits were found. Higher GH levels were also associated with larger amygdala volumes after adjustment for potential confounders (P = .002, 2-week AUC; P = .03, 6-week AUC).

CONCLUSIONS

Higher postnatal GH levels may potentially contribute to the documented neurodevelopmental abnormalities seen in children born VP at school age.

Neural growth hormone: regional regulation by estradiol and/or sex chromosome complement in male and female mice

BACKGROUND

Sex differences in pituitary growth hormone (GH) are well documented and coordinate maturation and growth. GH and its receptor are also produced in the brain where they may impact cognitive function and synaptic plasticity, and estradiol produces Gh sex differences in rat hippocampus. In mice, circulating estradiol increases Gh mRNA in female but not in male medial preoptic area (mPOA); therefore, additional factors regulate sexually dimorphic Gh expression in the brain. Thus, we hypothesized that sex chromosomes interact with estradiol to promote sex differences in GH. Here, we assessed the contributions of both estradiol and sex chromosome complement on Gh mRNA levels in three large brain regions: the hippocampus, hypothalamus, and cerebellum.

METHODS

We used the four core genotypes (FCG) mice, which uncouple effects of sex chromosomes and gonadal sex. The FCG model has a deletion of the sex-determining region on the Y chromosome (Sry) and transgenic insertion of Sry on an autosome. Adult FCG mice were gonadectomized and given either a blank Silastic implant or an implant containing 17β-estradiol. Significant differences in GH protein and mRNA were attributed to estradiol replacement, gonadal sex, sex chromosome complement, and their interactions, which were assessed by ANOVA and planned comparisons.

RESULTS

Estradiol increased Gh mRNA in the cerebellum and hippocampus, regardless of sex chromosome complement or gonadal sex. In contrast, in the hypothalamus, females had higher Gh mRNA than males, and XY females had more Gh mRNA than XY males and XX females. This same pattern was observed for GH protein. Because the differences in Gh mRNA in the hypothalamus did not replicate prior studies using other mouse models and tissue from mPOA or arcuate nucleus, we examined GH protein in the arcuate, a subdivision of the hypothalamus. Like the previous reports, and in contrast to the entire hypothalamus, a sex chromosome complement effect showed that XX mice had more GH than XY in the arcuate.

CONCLUSIONS

Sex chromosome complement regulates GH in some but not all brain areas, and within the hypothalamus, sex chromosomes have cell-specific actions on GH. Thus, sex chromosome complement and estradiol both contribute to GH sex differences in the brain.

Secreted ectodomain of sialic acid-binding Ig-like lectin-9 and monocyte chemoattractant protein-1 promote recovery after rat spinal cord injury by altering macrophage polarity

Engrafted mesenchymal stem cells from human deciduous dental pulp (SHEDs) support recovery from neural insults via paracrine mechanisms that are poorly understood. Here we show that the conditioned serum-free medium (CM) from SHEDs, administered intrathecally into rat injured spinal cord during the acute postinjury period, caused remarkable functional recovery. The ability of SHED-CM to induce recovery was associated with an immunoregulatory activity that induced anti-inflammatory M2-like macrophages. Secretome analysis of the SHED-CM revealed a previously unrecognized set of inducers for anti-inflammatory M2-like macrophages: monocyte chemoattractant protein-1 (MCP-1) and the secreted ectodomain of sialic acid-binding Ig-like lectin-9 (ED-Siglec-9). Depleting MCP-1 and ED-Siglec-9 from the SHED-CM prominently reduced its ability to induce M2-like macrophages and to promote functional recovery after spinal cord injury (SCI). The combination of MCP-1 and ED-Siglec-9 synergistically promoted the M2-like differentiation of bone marrow-derived macrophages in vitro, and this effect was abolished by a selective antagonist for CC chemokine receptor 2 (CCR2) or by the genetic knock-out of CCR2. Furthermore, MCP-1 and ED-Siglec-9 administration into the injured spinal cord induced M2-like macrophages and led to a marked recovery of hindlimb locomotor function after SCI. The inhibition of this M2 induction through the inactivation of CCR2 function abolished the therapeutic effects of both SHED-CM and MCP-1/ED-Siglec-9. Macrophages activated by MCP-1 and ED-Siglec-9 extended neurite and suppressed apoptosis of primary cerebellar granule neurons against the neurotoxic effects of chondroitin sulfate proteoglycans. Our data suggest that the unique combination of MCP-1 and ED-Siglec-9 repairs the SCI through anti-inflammatory M2-like macrophage induction.

Expression and function of growth hormone in the nervous system: a brief review

There is increasing evidence that growth hormone (GH) expression is not confined exclusively to the pituitary somatotrophs as it is synthesized in many extrapituitary locations. The nervous system is one of those extrapituitary sites. In this brief review we summarize data that substantiate the expression, distribution and characterization of neural GH and detail its roles in neural function, including cellular growth, proliferation, differentiation, neuroprotection and survival, as well as its functional roles in behavior, cognition and neurotransmission. Although systemic GH may exert some of these effects, it is increasingly evident that locally expressed neural GH, acting through intracrine, autocrine or paracrine mechanisms, may also be causally involved as a neurotrophic factor.

Advancing avian behavioral neuroendocrinology through genomics

Genome technologies are transforming all areas of biology, including the study of hormones, brain and behavior. Annotated reference genome assemblies are rapidly being produced for many avian species. Here we briefly review the basic concepts and tools used in genomics. We then consider how these are informing the study of avian behavioral neuroendocrinology, focusing in particular on lessons from the study of songbirds. We discuss the impact of having a complete "parts list" for an organism; the transformational potential of studying large sets of genes at once instead one gene at a time; the growing recognition that environmental and behavioral signals trigger massive shifts in gene expression in the brain; and the prospects for using comparative genomics to uncover the genetic roots of behavioral variation. Throughout, we identify promising new directions for bolstering the application of genomic information to further advance the study of avian brain and behavior.

Cognitive improvement by acute growth hormone is mediated by NMDA and AMPA receptors and MEK pathway

It has been reported that Growth hormone (GH) has an immediate effect enhancing excitatory postsynaptic potentials mediated by AMPA and NMDA receptors in hippocampal area CA1. As GH plays a role in adult memory processing, this work aims to study the acute effects of GH on working memory tasks in rodents and the possible involvement of NMDA and AMPA receptors and also the MEK/ERK signalling pathway. To evaluate memory processes, two different tests were used, the spatial working memory 8-arm radial maze, and the novel object recognition as a form of non-spatial working memory test. Acute GH treatment (1mg/kg i.p., 1h) improved spatial learning in the radial maze respect to the control group either in young rats (reduction of 46% in the performance trial time and 61% in the number of errors), old rats (reduction of 38% in trial time and 48% in the number of errors), and adult mice (reduction of 32% in the performance time and 34% in the number of errors). GH treatment also increased the time spent exploring the novel object respect to the familiar object compared to the control group in young rats (from 63% to 79%), old rats (from 53% to 70%), and adult mice (from 61 to 68%). The improving effects of GH on working memory tests were blocked by the NMDA antagonist MK801 dizocilpine (0.025 mg/kg i.p.) injected 10 min before the administration of GH, in both young and old rats. In addition, the AMPA antagonist DNQX (1mg/kg i.p.) injected 10 min before the administration of GH to young rats, blocked the positive effect of GH. Moreover, in mice, the MEK inhibitor SL 327 (20mg/kg i.p.) injected 30 min before the administration of GH, blocked the positive effect of GH on radial maze and the novel object recognition. In conclusion, GH improved working memory processes through both glutamatergic receptors NMDA and AMPA and it required the activation of extracellular MEK/ERK signalling pathway. These effects could be related to the enhancement of excitatory synaptic transmission in the hippocampus reported by GH.

Somatotropic signaling: trade-offs between growth, reproductive development, and longevity

Growth hormone (GH) is a key determinant of postnatal growth and plays an important role in the control of metabolism and body composition. Surprisingly, deficiency in GH signaling delays aging and remarkably extends longevity in laboratory mice. In GH-deficient and GH-resistant animals, the "healthspan" is also extended with delays in cognitive decline and in the onset of age-related disease. The role of hormones homologous to insulin-like growth factor (IGF, an important mediator of GH actions) in the control of aging and lifespan is evolutionarily conserved from worms to mammals with some homologies extending to unicellular yeast. The combination of reduced GH, IGF-I, and insulin signaling likely contributes to extended longevity in GH or GH receptor-deficient organisms. Diminutive body size and reduced fecundity of GH-deficient and GH-resistant mice can be viewed as trade-offs for extended longevity. Mechanisms responsible for delayed aging of GH-related mutants include enhanced stress resistance and xenobiotic metabolism, reduced inflammation, improved insulin signaling, and various metabolic adjustments. Pathological excess of GH reduces life expectancy in men as well as in mice, and GH resistance or deficiency provides protection from major age-related diseases, including diabetes and cancer, in both species. However, there is yet no evidence of increased longevity in GH-resistant or GH-deficient humans, possibly due to non-age-related deaths. Results obtained in GH-related mutant mice provide striking examples of mutations of a single gene delaying aging, reducing age-related disease, and extending lifespan in a mammal and providing novel experimental systems for the study of mechanisms of aging.

Neuro-protective effects of growth hormone (GH) after hypoxia-ischemia injury in embryonic chicken cerebellum

Neuroprotection is a mechanism within the central nervous system (CNS) that protects neurons from damage as a result of a severe insult. It is known that growth hormone (GH) is involved in cell survival and may inhibit apoptosis in several cell types, including those of the CNS. Both GH and GH-receptor (GHR) genes are expressed in the cerebellum. Thus, we investigated the possible neuroprotective role of GH in this organ, which is very sensitive to hypoxic/ischemic conditions. Endogenous GH levels increased in the brain and cerebellum (30% and 74%, respectively) of 15-day-old chicken embryos exposed to hypoxia during 24h compared to normoxia. In primary embryonic cerebellar neuron cultures treated under hypoxia (0.5% O(2)) and low glucose (1g/L) conditions (HLG) for 1h, GH levels increased 1.16-fold compared to the control. The addition of 1nM recombinant chicken GH (rcGH) to cultures during HLG increased cell viability (1.7-fold) and the expression of Bcl-2 (1.67-fold); in contrast the caspase-3 activity and the proportion of apoptotic cells decreased (37% and 54.2%, respectively) compared to HLG. rcGH activated the PI3K/Akt pathway both under normoxic and HLG conditions, increasing the proportion of phosphorylated Akt (1.7- and 1.4-fold, respectively). These effects were abolished by wortmannin and by immunoneutralization, indicating that GH acts through this signaling pathway. Furthermore, the 15-kDa GH variant (10nM) significantly increased cell viability and decreased caspase-3 activity during HLG condition. Thus GH may act as a paracrine/autocrine neuroprotective factor that preserves cellular viability and inhibits apoptotic cell death.

Postnatal growth hormone deficiency in growing rats causes marked decline in the activity of spinal cord acetylcholinesterase but not butyrylcholinesterase

The effects of growth hormone (GH) deficiency on the developmental changes in the abundance and activity of cholinesterase enzymes were studied in the developing spinal cord (SC) of postnatal rats by measuring the specific activity of acetylcholinesterase (AChE), a marker for cholinergic neurons and their synaptic compartments, and butyrylcholinesterase (BuChE), a marker for glial cells and neurovascular cells. Specific activities of these two enzymes were measured in SC tissue of 21- and 90 day-old (P21, weaning age; P90, young adulthood) GH deficient spontaneous dwarf (SpDwf) mutant rats which lack anterior pituitary and circulating plasma GH, and were compared with SC tissue of normal age-matched control animals. Assays were carried out for AChE and BuChE activity in the presence of their specific chemical inhibitors, BW284C51 and iso-OMPA, respectively. Results revealed that mean AChE activity was markedly and significantly reduced [28% at P21, 49% at P90, (p<0.01)] in the SC of GH deficient rats compared to age-matched controls. GH deficiency had a higher and more significant effect on AChE activity of the older (P90) rats than the younger ones (P21) ones. In contrast, BuChE activity in SC showed no significant changes in GH deficient rats at either of the two ages studied. Results imply that, in the absence of pituitary GH, the postnatal proliferation of cholinergic synapses in the rat SC, a CNS structure, where AChE activity is abundant, is markedly reduced during both the pre- and postweaning periods; more so in the postweaning than preweaning ages. In contrast, the absence of any effects on BuChE activity implies that GH does not affect the development of non-neuronal elements, e.g., glia, as much as the neuronal and synaptic compartments of the developing rat SC.

Sexual dimorphism of growth hormone in the hypothalamus: regulation by estradiol

GH is best known as an anterior pituitary hormone fundamental in regulating growth, differentiation, and metabolism. GH peptide and mRNA are also present in brain, in which their functions are less well known. Here we describe the distribution of GH neurons and fibers and sex differences in Gh mRNA in adult mouse brain. Cell bodies exhibiting GH immunoreactivity are distributed in many brain regions, particularly in the hypothalamus in which retrograde labeling suggests that some of these cells project to the median eminence. To determine whether Gh mRNA is sexual dimorphic, we carried out quantitative RT-PCR on microdissected brain nuclei. Ovary-intact mice had elevated Gh mRNA in the arcuate nucleus and medial preoptic area (MPOA) compared with gonad-intact males. In males, castration increased Gh mRNA in the MPOA, whereas ovariectomy decreased Gh mRNA in both regions. When gonadectomized adults of both sexes were treated with estradiol Gh mRNA increased in females but had no effect in castrated males. Tamoxifen was able to blunt the rise in Gh mRNA in response to estradiol in females. In addition, we found that estrogen receptor-α is coexpressed in GH neurons in the MPOA and arcuate nucleus. In summary, the findings reveal sexual dimorphisms in Gh gene expression in areas of the brain associated with reproduction and behavior. Interestingly, estradiol enhances Gh mRNA in females only, suggesting that multiple factors orchestrate this sexual dimorphism.

Selective inner retinal dysfunction in growth hormone transgenic mice

OBJECTIVE

The discovery of locally produced growth hormone (GH) and its receptor in the retina of rodents raises the possibility that GH might modulate retinal function. To test this hypothesis, we determined the retinal electroretinogram (ERG) of bovine GH (bGH) transgenic mice.

DESIGN

ERGs were recorded from 11 wild type (WT) and 9 bGH mice, at 2 months of age in response to a series of light flashes at increasing intensity. Three ERG components were assessed for their amplitude and timing: a-wave, b-wave and oscillatory potentials (OPs). OPs were isolated with a 75-300 Hz digital filter. Retina layer sizes, nuclei number and vascularization were assessed by respectively staining cross sections with DAPI and Bandeiraea simplicifolia.

RESULTS

OPs were selectively affected in the bGH mouse compared to WT. When OP amplitude values were normalized to the a-wave amplitude (to account for inter-animal variability in WT and bGH groups), OP2, OP3, and OP4 showed amplitude reductions (of 65%, 72%, and 68%, respectively) in the bGH mouse compared to the WT. This was accompanied by a prolongation of the implicit time for the peak of OP3 (28.1 vs 31.1 ms, WT vs bGH) and OP4 (37.8 vs 41.6 ms), while the implicit time of a- and b-waves were unaffected. Fast Fourier transform analysis revealed that the OPs' dominant frequency was significantly reduced (P<0.05) in the bGH mice (100 Hz) compared to WT (108Hz). There was no significant change in retinal histology except for a significant increase in the axial length of the eye in bGH mice.

CONCLUSIONS

Mice expressing bGH display a selective inner retinal defect as demonstrated using ERG recordings. The specific OP defect observed in these mice is similar to the ERG results obtained in patients with diabetic retinopathy and in related animal models.

Expression, cellular distribution, and heterogeneity of growth hormone in the chicken cerebellum during development

Although growth hormone (GH) is mainly synthesized and secreted by pituitary somatotrophs, it is now well established that the GH gene can be expressed in many extrapituitary tissues, including the central nervous system (CNS). Here we studied the expression of GH in the chicken cerebellum. Cerebellar GH expression was analyzed by in situ hybridization and cDNA sequencing, as well as by immunohistochemistry and confocal microscopy. GH heterogeneity was studied by Western blotting. We demonstrated that the GH gene was expressed in the chicken cerebellum and that its nucleotide sequence is closely homologous to pituitary GH cDNA. Within the cerebellum, GH mRNA is mainly expressed in Purkinje cells and in cells of the granular layer. GH-immunoreactivity (IR) is also widespread in the cerebellum and is similarly most abundant in the Purkinje and granular cells as identified by specific neuronal markers and histochemical techniques. The GH concentration in the cerebellum is age-related and higher in adult birds than in embryos and juveniles. Cerebellar GH-IR, as determined by Western blot under reducing conditions, is associated with several size variants (of 15, 23, 26, 29, 35, 45, 50, 55, 80 kDa), of which the 15 kDa isoform predominates (>30% among all developmental stages). GH receptor (GHR) mRNA and protein are also present in the cerebellum and are similarly mainly present in Purkinje and granular cells. Together, these data suggest that GH and GHR are locally expressed within the cerebellum and that this hormone may act as a local autocrine/paracrine factor during development of this neural tissue.

Extrapituitary growth hormone

Pituitary somatotrophs secrete growth hormone (GH) into the bloodstream, to act as a hormone at receptor sites in most, if not all, tissues. These endocrine actions of circulating GH are abolished after pituitary ablation or hypophysectomy, indicating its pituitary source. GH gene expression is, however, not confined to the pituitary gland, as it occurs in neural, immune, reproductive, alimentary, and respiratory tissues and in the integumentary, muscular, skeletal, and cardiovascular systems, in which GH may act locally rather than as an endocrine. These actions are likely to be involved in the proliferation and differentiation of cells and tissues prior to the ontogeny of the pituitary gland. They are also likely to complement the endocrine actions of GH and are likely to maintain them after pituitary senescence and the somatopause. Autocrine or paracrine actions of GH are, however, sometimes mediated through different signaling mechanisms to those mediating its endocrine actions and these may promote oncogenesis. Extrapituitary GH may thus be of physiological and pathophysiological significance.

Growth hormone promotes proliferation of adult neurosphere cultures

OBJECTIVES

Growth hormone (GH) and its receptor (GHR) are widely expressed in the CNS. During development, GH signaling regulates both proliferation of neural progenitor cells as well as their differentiation into neurons and glia. Here we have examined the effect of GH signaling on adult subventricular zone derived neural progenitor cells cultured as neurospheres.

DESIGN

GH was added to adult wild-type (WT) neurosphere cultures and neurosphere growth measured using the MTT cell proliferation assay. To examine the influence of endogenous GH production on neural progenitors, neurospheres derived from GH receptor knockout (GHRKO) mice were examined by measuring neurosphere sizes and Ki67 and TUNEL immunoreactivity. In addition, neurosphere growth curves were compared following long term culture. Finally, the differentiation of WT vs. GHRKO neurospheres was compared using immunocytochemistry for betaIII-tubulin and GFAP.

RESULTS

While GH alone was insufficient to support neurosphere formation, it enhanced neurosphere growth by 20% in the presence of epidermal growth factor and fibroblast growth factor-2. Compared to wildtype neurospheres, GHRKO neurospheres were smaller, contained fewer proliferating cells and exhibited reduced self-renewal in long term culture. Addition of GH increased STAT5 phosphorylation levels in neurosphere cells. Upon differentiation, GHRKO neurospheres showed accelerated neurogenesis, although over time similar numbers of betaIII-tubulin positive neurons were generated by cells of both genotypes.

CONCLUSIONS

GH functions as an autocrine mitogen in adult neurosphere cultures and promotes proliferation of neural progenitor cells as well as self-renewal of neurosphere cultures. In addition, signaling through the GHR appeared to delay neuronal differentiation in adult neurospheres.

Growth hormone production and action in N1E-115 neuroblastoma cells

Neuroblastoma cells are undifferentiated cells derived from the neural crest and are commonly used as models for studying neural function. Mouse N1E-115 neuroblastoma cells are derived from cancerous tissue and provide a model for studying the oncogenesis of neural cells. As growth hormone (GH) has been implicated as an autocrine or paracrine involved in neural regulation and in the induction or progression of cancer, the possibility that N1E-115 cells are sites of GH production and GH action was assessed. Using RT-PCR, cultured N1E-115 cells were found to express the mouse GH and GH receptor (GHR) genes. Immunocytochemistry demonstrated that both of the translated proteins (GH and its receptor) were abundantly present in the cytoplasm of these cells and their co-localization was established by confocal cytochemistry. GH action in these cells was determined in cells cultured for 72 h in the presence or absence of 10(-6) M or 10(-9) M mouse GH, which induced neurite sprouting and increased axon growth. In summary, the expression of GH and its receptor in GH responsive tumor-derived N1E-115 neuroblastoma cells suggests they provide a useful experimental model to assess GH actions in neural function or neural oncogenesis.

Growth hormone signaling and hippocampal neurogenesis: insights from genetic models

Adult hippocampal neurogenesis (AHN) is modulated by a variety of factors through effects on the proliferation-differentiation-survival regulatory axis. We have employed growth hormone receptor knockout (GH-R-/-) and suppressor of cytokine signaling-2 transgenic (SOCS-2 Tg) mice as models of altered GH-signaling to assess their affects on basal and exercised-induced hippocampal neurogenesis. Assessment of proliferation 24-h after 7-days of bromodeoxyuridine (BrdU) labeling with or without voluntary running showed that the density of BrdU(+) cells in the subgranular zone remained unchanged between genotypes in control housing, while running induced significant increases in BrdU-labeled cells in WT, GH-R-/-, and SOCS-2 Tg mice. The proportion of BrdU/doublecortin and BrdU/S100beta cells did not vary between genotype or running conditions at this time-point. Assessment of cell survival 28-days after BrdU labeling showed that SOCS-2 Tg animals had significantly higher BrdU(+) cell densities in the granule cell layer compared to WT and GH-R-/- animals in control housing and after voluntary running. There were no differences in cell survival between WT and GH-R-/- mice with or without running. Mature phenotype analysis showed similar proportions of BrdU/NeuN and BrdU/S100beta in all groups. While SOCS-2 Tg mice had similar social interaction behaviors and sensorimotor gating, they appeared to be less anxious with heightened basal locomotor activity and showed enhanced performance in the Morris watermaze test. Overall, our data indicated that mice over-expressing SOCS-2 showed increased survival of neurons generated during AHN, which correlated with improved performance in a hippocampal-dependent cognitive task. Furthermore, voluntary running increased AHN in WT, SOCS-2 Tg, and serum-IGF-1-deficient GH-R-/- mice.

Prion disease induced alterations in gene expression in spleen and brain prior to clinical symptoms

Prion diseases are fatal neurodegenerative disorders that affect animals and humans. There is a need to gain understanding of prion disease pathogenesis and to develop diagnostic assays to detect prion diseases prior to the onset of clinical symptoms. The goal of this study was to identify genes that show altered expression early in the disease process in the spleen and brain of prion disease-infected mice. Using Affymetrix microarrays, we identified 67 genes that showed increased expression in the brains of prion disease-infected mice prior to the onset of clinical symptoms. These genes function in many cellular processes including immunity, the endosome/lysosome system, hormone activity, and the cytoskeleton. We confirmed a subset of these gene expression alterations using other methods and determined the time course in which these changes occur. We also identified 14 genes showing altered expression prior to the onset of clinical symptoms in spleens of prion disease infected mice. Interestingly, four genes, Atp1b1, Gh, Anp32a, and Grn, were altered at the very early time of 46 days post-infection. These gene expression alterations provide insights into the molecular mechanisms underlying prion disease pathogenesis and may serve as surrogate markers for the early detection and diagnosis of prion disease.

Small chicken growth hormone (scGH) variant in the neural retina

A novel variant of chicken growth hormone (cGH) that is severely truncated has recently been discovered in the neural retina. It is, however, unknown whether this protein binds to GH receptors (GHRs) and has biological activity. This possibility has therefore been addressed by homology modeling, using human (h)GH as a template because it is the only GH molecule with a crystal structure and because hGH binds to cGH receptors (cGHRs). Most of the residues of the small (s)cGH model fitted the hGH template, apart from two restricted regions from Ser 12 to Gln 20 and from Ser 55 to Val 58. The scGH model differs, however, from hGH in structure: hGH is composed of a four-helix bundle, whereas scGH has three main helices. Helices 2, 3, and 4 of hGH correspond to helices 1, 2, and 3 of scGH, but they are longer by one, four, and one residues, respectively. The secondary structure of the C-terminus of scGH is therefore similar to C-terminal hGH. The N-terminus of scGH is, however, severely truncated, lacking the residues of the full-length molecule derived from exons 1, 2, and 3. The N-terminus of scGH also includes 20 residues derived from intron C of full-length cGH. The predicted structure of its N-terminus has no classical secondary structure (alpha-helix or beta-sheet), whereas the N-terminus of hGH is composed of helix 1 and two mini-helices located between helix 1 and 2. This difference in ribbon structure results in a difference in the overall shape of the scGH model and hGH. The possibility that scGH could bind to a GHR dimer was assessed by examining the primary and hypothetical tertiary structure of scGH. hGH binds the extracellular domain (ECD) of two GHRs sequentially at its binding site 1 (or high affinity site) then at its binding site 2 (or low affinity site). Sequence alignment of scGH with hGH demonstrates that scGH lacks three key residues (of 14) at site 1 and nine residues (of 15) at site 2. It is therefore unlikely that tight binding of ECD1 to the site 1 of scGH could occur. scGH also lacks most of the site 2 residues, suggesting that it is unlikely that ECD2 would bind to the scGH model. In summary, we have developed a novel, structural model of scGH, with implications for its putative actions through classical GHRs.

Growth hormone in the visual system: comparative endocrinology

Growth hormone (GH) is rarely considered to be involved in ocular development or vision or to be present in the visual system. Basic and clinical studies nevertheless support roles for GH in the ocular function of most vertebrate groups and for its extrapituitary production in ocular tissues. The comparative endocrinology of endocrine, autocrine or paracrine GH in the visual system of vertebrates is the focus of this brief review.

Neuroendocrine control of growth hormone in fish

The biological actions of growth hormone (GH) are pleiotropic, including growth promotion, energy mobilization, gonadal development, appetite, and social behavior. Accordingly, the regulatory network for GH is complex and includes many endocrine and environmental factors. In fish, the neuroendocrine control of GH is multifactorial with multiple inhibitors and stimulators of pituitary GH secretion. In fish, GH release is under a tonic negative control exerted mainly by somatostatin. Sex steroid hormones and nutritional status influence the level of brain expression and effectiveness of some of these GH neuroendocrine regulatory factors, suggesting that their relative importance differs under different physiological conditions. At the pituitary level, some, if not all, somatotropes can respond to multiple regulators. Therefore, ligand- and function-specificity, as well as the integrative responses to multiple signals must be achieved at the level of signal transduction mechanisms. Results from investigations on a limited number of stimulatory and inhibitory GH-release regulators indicate that activation of different but convergent intracellular pathways and the utilization of specific intracellular Ca(2+) stores are some of the strategies utilized. However, more work remains to be done in order to better understand the integrative mechanisms of signal transduction at the somatotrope level and the relevance of various GH regulators in different physiological circumstances.

Retinal growth hormone in perinatal and adult rats

Growth hormone (GH) mRNA and protein have recently been localized in the neural retina of embryonic chicks, in which exogenous GH promotes cell survival. GH is also expressed in the rat CNS, in which it has neuroprotective roles, although its presence in the rat neural retina is unknown and is the focus of the present study. GH immunoreactivity, to a 22-kDa protein, was present in extracts of fetal (embryonic day [ED]17) eyes and in extracts from the neural retinas of newborn pups, comparable to GH immunoreactivity in pituitary extracts. The GH immunoreactivity in the neural retina was widespread but was most intense in large rounded cells in the retinal ganglion cell (RGC) layer and in the optic fiber layer derived from the axons of the RGCs. A 693-bp cDNA was also generated by the RT-PCR of RNA extracted from the eyes of ED17 rats and from the neural retinas and eyes of newborn rats, when amplified in the presence of oligonucleotide primers for the rat GH cDNA. Expression of the GH gene in the neural retina was also shown by specific in situ hybridization of an antisense GH riboprobe to cells in the neural retina, particularly those in the RGC layers of fetal and adult rat eyes. These results demonstrate GH expression in the neural retinas of fetal, newborn, and adult rats, in which retinal GH might have neuroprotective roles.

Expression, translation, and localization of a novel, small growth hormone variant

A novel transcript of the GH gene has been identified in ocular tissues of chick embryos. It is, however, unknown whether this transcript (small chicken GH, scGH) is translated. This possibility was therefore assessed. The expression of scGH mRNA was confirmed by RT-PCR, using primers that amplified a 426-bp cDNA of its coding sequence. This cDNA was inserted into an expression plasmid to transfect HEK 293 cells, and its translation was shown by specific scGH immunoreactivity in extracts of these cells. This immunoreactivity was directed against the unique N terminus of scGH and was associated with a protein of 16 kDa, comparable with its predicted size. Most of the immunoreactivity detected was, however, associated with a 31-kDa moiety, suggesting scGH is normally dimerized. Neither protein was, however, present in media of the transfected HEK cells, consistent with scGH's lack of a signal sequence. Similar moieties of 16 and 31 kDa were also found in proteins extracted from ocular tissues (neural retina, pigmented epithelium, lens, cornea, choroid) of embryos, although they were not consistently present in vitreous humor. Specific scGH immunoreactivity was also detected in these tissues by immunocytochemistry but not in axons in the optic fiber layer or the optic nerve head, which were immunoreactive for full-length GH. In summary, we have established that scGH expression and translation occurs in ocular tissues of chick embryos, in which its localization in the neural retina and the optic nerve head is distinct from that of the full-length protein.

Feedback regulation of growth hormone synthesis and secretion in fish and the emerging concept of intrapituitary feedback loop

Growth hormone (GH) is known to play a key role in the regulation of body growth and metabolism. Similar to mammals, GH secretion in fish is under the control of hypothalamic factors. Besides, signals generated within the pituitary and/or from peripheral tissues/organs can also exert a feedback control on GH release by effects acting on both the hypothalamus and/or anterior pituitary. Among these feedback signals, the functional role of IGF is well conserved from fish to mammals. In contrast, the effects of steroids and thyroid hormones are more variable and appear to be species-specific. Recently, a novel intrapituitary feedback loop regulating GH release and GH gene expression has been identified in fish. This feedback loop has three functional components: (i) LH induction of GH release from somatotrophs, (ii) amplification of GH secretion by GH autoregulation in somatotrophs, and (iii) GH feedback inhibition of LH release from neighboring gonadotrophs. In this article, the mechanisms for feedback control of GH synthesis and secretion are reviewed and functional implications of this local feedback loop are discussed. This intrapituitary feedback loop may represent a new facet of pituitary research with potential applications in aquaculture and clinical studies.

Growth hormone and insulin growth factor-I levels in plasma and cerebrospinal fluid of patients with multiple sclerosis

Multiple sclerosis (MS) has several clinically different forms. Whereas the illness progresses slowly in most of the patients, 10% have an aggressively progressive course with fatal outcome without signs of remyelination capability. The process of remyelination depends on numerous interactive factors, including the presence of various growth factors, the most important of which in the adult is insulin growth factor-I (IGF-I). On the other hand, the most powerful postnatal regulator of IGF-I is growth hormone (GH), which also acts as a neuroprotective and an antiapoptotic agent, and has direct influence on myelination. Levels of these growth factors have never been examined in the cerebrospinal fluid (CSF) of patients with MS. The levels of IGF-I and GH were measured in serum and CSF of 46 MS patients and compared with those of 49 patients with no evidence of demyelinating disease. The only positive finding was a deficiency of GH in the CSF of MS patients. The possible implications of those findings in the etiopathogenesis of MS will be discussed.

Growth hormone enhances excitatory synaptic transmission in area CA1 of rat hippocampus

The hippocampus produces growth hormone (GH) and contains GH receptors, suggesting a potential role for GH signaling in the regulation of hippocampal function. In agreement with this possibility, previous investigations have found altered hippocampal function and hippocampal-dependent learning and memory after chronic GH administration or deficiency. In this study we applied GH to in vitro rat hippocampal brain slices, to determine whether GH has short-term effects on hippocampal function in addition to previously documented chronic effects. We found that GH enhanced both AMPA- and NMDA-receptor-mediated excitatory postsynaptic potentials (EPSPs) in hippocampal area CA1, but did not alter GABA(A)-receptor-mediated inhibitory synaptic transmission. GH enhancement of excitatory synaptic transmission was gradual, requiring 60-70 min to reach maximum, and occurred without any change in paired-pulse facilitation, suggesting a possible postsynaptic site of action. In CA1 pyramidal neurons, GH enhancement of EPSPs was correlated with significant hyperpolarization and decreased input resistance. GH enhancement of EPSPs required Janus kinase 2 (JAK2), phosphatidylinositol-3 (PI3) kinase, mitogen-activated protein (MAP) kinase kinase (MEK), and synthesis of new proteins. Although PI3 kinase and MEK were required for initiation of GH effects on excitatory synaptic transmission, they were not required for maintained enhancement of EPSPs. GH treatment and tetanus-induced long-term potentiation were mutually occluding, suggesting a common mechanism or mechanisms in both forms of synaptic enhancement. Our results demonstrate that GH has powerful short-term effects on hippocampal function, and extend the timescale for potential roles of GH in regulating hippocampal function and hippocampal-dependent behaviors.

Sexually dimorphic gene expression in the hypothalamus, pituitary gland, and cortex

We examined sex differences in the transcriptomes of hypothalamus, pituitary gland, and cortex of male and female mice using serial analysis of gene expression. In total 940,669 tags were sequenced. In hypothalamus, 3 transcripts are differentially expressed by gender, including growth hormone (neuromodulation) and 3beta-hydroxysteroid dehydrogenase-1 (steroidogenesis). In pituitary gland, 43 transcripts are differentially expressed, including RAS guanyl-releasing protein 2 (cell signaling), ornithine transporter (mitochondrial transport), H3 histone family 3B (chromatin structure), heterogeneous nuclear ribonucleoprotein U (chromatin remodeling), NADH dehydrogenase (mitochondrial oxidative phosphorylation), neuronatin (cell differentiation), and ribosomal protein S27a (protein metabolism). EST X (inactive)-specific transcript antisense is expressed at a higher level in the three female organs, whereas growth hormone and NADH dehydrogenase are expressed at higher levels in female cortex. Thus, the current study has characterized key sexual dimorphisms in the transcriptomes of the hypothalamus, pituitary, and cortex.

Evolutionary origins of vertebrate placodes: insights from developmental studies and from comparisons with other deuterostomes

Ectodermal placodes comprise the adenohypophyseal, olfactory, lens, profundal, trigeminal, otic, lateral line, and epibranchial placodes. The first part of this review presents a brief overview of placode development. Placodes give rise to a variety of cell types and contribute to many sensory organs and ganglia of the vertebrate head. While different placodes differ with respect to location and derivative cell types, all appear to originate from a common panplacodal primordium, induced at the anterior neural plate border by a combination of mesodermal and neural signals and defined by the expression of Six1, Six4, and Eya genes. Evidence from mouse and zebrafish mutants suggests that these genes promote generic placodal properties such as cell proliferation, cell shape changes, and specification of neurons. The common developmental origin of placodes suggests that all placodes may have evolved in several steps from a common precursor. The second part of this review summarizes our current knowledge of placode evolution. Although placodes (like neural crest cells) have been proposed to be evolutionary novelties of vertebrates, recent studies in ascidians and amphioxus have proposed that some placodes originated earlier in the chordate lineage. However, while the origin of several cellular and molecular components of placodes (e.g., regionalized expression domains of transcription factors and some neuronal or neurosecretory cell types) clearly predates the origin of vertebrates, there is presently little evidence that these components are integrated into placodes in protochordates. A scenario is presented according to which all placodes evolved from an adenohypophyseal-olfactory protoplacode, which may have originated in the vertebrate ancestor from the anlage of a rostral neurosecretory organ (surviving as Hatschek's pit in present-day amphioxus).

Local expression of GH and IGF-1 in the hippocampus of GH-deficient long-lived mice

Beneficial effects of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) on the development and function of the central nervous system are well documented. In spite of primary deficiency of GH and secondary IGF-1 deficiency, Ames dwarf mice live considerably longer than normal animals, exhibit apparently normal cognitive functions and maintain them into advanced age. In an attempt to reconcile these findings, we have examined local expression of GH and IGF-1 in the hippocampus of normal and Ames dwarf mice. We found that both hippocampal GH and IGF-1 protein levels are increased and the corresponding mRNAs are normal in Ames dwarf as compared with normal mice. Increased phosphorylation of Akt and cyclic AMP responsive element-binding protein (CREB) were detected in the hippocampus of Ames dwarf mice. Our results suggest that increase in hippocampal GH and IGF-1 protein expression and subsequent activation of PI3K/Akt-CREB signal transduction cascade might contribute to the maintenance of cognitive function and is likely to be responsible for the integrity of neuronal structure, and maintenance of youthful levels of cognitive function in these long-lived mice during aging.

Selective cerebral overexpression of growth hormone alters cardiac function, morphology, energy metabolism and catecholamines in transgenic mice

BACKGROUND

Growth hormone (GH) has important regulatory effects on cardiac morphology and function both during normal development as well as in pathophysiological settings such as myocardial infarction (MI) and congestive heart failure (CHF). In order to investigate in more detail the interaction between GH and sympathetic nervous system (SNS) system we studied the effects of selective cerebral GH overexpression on myocardial content of catecholamines, myocardial and brain energy metabolism as well as on cardiac function during resting and stress conditions in a transgenic mouse model.

METHODS

Transgenic mice with selective bovine GH overexpression under control of glial fibrillary acidic protein promoter in the brain (GFAP-bGH, n=15) were created and compared to genetically matched non-transgenic mates (Control, n=15). Cardiac morphology and function were evaluated in vivo using transthoracic echocardiography during resting and stress conditions induced pharmacologically by dopamine (D) and isoprotenolol (ISO). Myocardial and brain energy metabolism were evaluated non-invasively using in vivo volume-selective phosphorus magnetic resonance spectroscopy ((31)P MRS). Myocardial content of catecholamines was analyzed by means of HPLC.

RESULTS

Compared to the C animals, the GFAP-bGH mice have showed several differences in the cardiac phenotype. Systolic (fractional shortening) and diastolic function (E/A wave ratio of mitral flow) was disturbed in the GFAP-bGH mice (both p<0.05). During the dopamine stress, there was chronotropic insufficiency in the GFAP-bGH group (p<0.01) while no difference was observed in response to isoprotenolol. Left ventricular dimensions were increased in GFAP-bGH mice (p<0.05). There was a tendency for higher body weight in GFAP-bGH compared to the control group (p=0.06) while no difference was observed in heart weight and brain weight when normalized for body weight. Myocardial content of noradrenaline was lower in the GFAP-bGH group (p<0.05). PCr/ATP ratio was higher (p<0.05) in the brain and lower in the heart (p<0.05) in the GFAP-bGH mice.

CONCLUSIONS

Selective cerebral overexpression of GH results in alterations of cardiac function, morphology and metabolism in transgenic mice. Decreased myocardial content of catecholamines in the GFAP-bGH mice suggests central interaction between GH and sympathetic nervous system.

Role of SOCS2 in growth hormone actions

Growth hormone (GH) has numerous effects in the body and is most commonly known for its role in regulating metabolism and body growth. Because GH is involved in many aspects of cell function, its signaling is tightly controlled by several pathways at both the extracellular and intracellular level. Suppressor of cytokine signaling-2 (SOCS2) is one such intracellular regulator of GH signal transduction. Expression of SOCS2 is tightly regulated and alteration of its levels leads to marked abnormalities in metabolism and growth. Unexpectedly, GH and SOCS2 have been recently shown to regulate neural development, neural stem cell differentiation and neuronal growth -- functions that might have important therapeutic implications for both repairing nervous system injuries and treating neurological disease.

Peripherally administered growth hormone increases brain dopaminergic activity and swimming in rainbow trout

There is increasing evidence that growth hormone (GH) has important behavioral effects in fish, but the underlying mechanisms are not well understood. To investigate if peripherally administered GH influences the monoaminergic activity of the brain, and how this is correlated to behavior, juvenile rainbow trout were implanted intraperitoneally with ovine GH. Fish were either kept isolated or in groups of five. The physical activity and food intake of the isolated fish were observed after 1 and 7 days, when brains were also sampled. The content of serotonin, dopamine, and noradrenaline and their metabolites in hypothalamus, telencephalon, optic tectum, and brain stem was then analyzed. For fish kept isolated for 7 days following implant, GH increased swimming activity and the levels of the dopamine metabolite 3, 4-hydroxy-phenylacetic acid (DOPAC) were higher in all brain parts examined. In the optic tectum, the levels of the dopamine metabolite homovanillic acid (HVA) were lowered by the GH treatment. One-day GH implant did not affect behavior or monoamine levels of isolated fish. In the fish kept in groups, a 7-day GH implant increased the hypothalamic levels of DOPAC, but not in the other brain parts examined, which may indicate an effect on the brain dopaminergic system from social interactions. It can be concluded that peripherally administered GH may function as a neuromodulator, affecting the dopaminergic activity of the rainbow trout brain, and this is associated with increased swimming activity.

Provision for children with developmental co-ordination disorder (DCD): audit of the service provider

BACKGROUND

The aim of this study was to conduct an audit of parent/carer satisfaction with the service provided for children presenting with movement difficulties [developmental co-ordination disorder (DCD)/dyspraxia] at the out-patient physiotherapy clinic of a specialist tertiary referral paediatric hospital.

METHOD

A postal questionnaire was used to obtain objective and subjective data on the service offered. Factual information on aspects such as waiting time for first appointment, type of intervention offered, etc. was checked against clinical records. Satisfaction with the service was assessed using ratings and open-ended comment.

RESULTS

Forty-five families completed the questionnaire. The results showed that the service was generally rated highly. The opportunity to discuss the child's problems and its implications was considered valuable. Among families offered 1 : 1 intervention, a statistically significant correlation emerged between the number of sessions attended and perceived effectiveness. Among families offered a home programme, perceived effectiveness was related to the number of times per week the child practised the programme.

CONCLUSIONS

This study showed that many children from mainstream schools with co-ordination problems continued to find it difficult to obtain a clear diagnosis. Once a referral and assessment had been achieved, however, parents/carers were shown to be satisfied with the package offered by this service provider.