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1.
Water Sci Technol ; 63(1): 80-7, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21245557

RESUMO

It takes a few millimetres of rainfall to cause the 34 most polluting combined sewer overflows (CSOs) to discharge into the River Thames. Currently, in a typical year, spillages to the tidal reaches of the River Thames occur about 60 times, with an estimated spill volume of 39 million cubic metres. Both the UK Government and the European Union have determined that the CSO discharges have an adverse environmental impact on fish species, introduce unacceptable aesthetics and elevate the health risks for recreational users of the Thames, with a frequency of discharge which is in breach of the Urban Wastewater Treatment Directive. Studies have established that the environmental objectives can be fully met on the most cost-effective basis by completing both quality improvements to treatment works and by the provision of a storage and transfer tunnel to intercept unsatisfactory CSOs. Extensive modelling has been undertaken to develop an optimised solution. In parallel with the design development a rigorous and comprehensive site selection methodology has been established to select sites and consult stakeholders and the public on the preferred sites and scheme, with the first stage of public consultation planned for later in 2010. The London Tideway Tunnels are an essential part of the delivery of improvements to the water quality of the tidal River Thames, and this ambitious, historic scheme represents a vital strategic investment in London's infrastructure.


Assuntos
Esgotos , Poluentes da Água , Londres
2.
J Neuroendocrinol ; 17(3): 186-94, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15796771

RESUMO

Signal transducers and activators of transcription (STATs) are a family of transcription factors linked to class I cytokine receptors. In the present study, we investigated whether their distribution in the hypothalamus reflects the feedback regulation by growth hormone and what role they might play in the functioning of target neurones. We demonstrate that each of the seven known STATs has a distinct distribution in the hypothalamus. Notably, the STAT5 proteins, that are important in growth hormone (GH) and prolactin signalling in peripheral tissues, were expressed in somatostatin neurones of the periventricular nucleus and dopamine neurones of the arcuate nucleus. Because somatostatin neurones are regulated by feedback from circulating GH, we investigated the importance of STAT5 in these neurones. We demonstrate that STAT5b protein expression, similar to somatostatin mRNA, is sexually dimorphic in the periventricular nucleus of rats and mice. Furthermore, chronic infusion of male dwarf rats with GH increased the expression of STAT5b, while a single injection of GH into similar rats induced the phosphorylation of STAT5 proteins. The cellular abundance of somatostatin mRNA in STAT5b-deficient mice was significantly reduced in the periventricular nucleus, effectively reducing the sexually dimorphic expression. These results are consistent with the hypothesis that STAT5 proteins are involved in the feedback regulation of somatostatin neurones by GH, and that these neurones may respond to patterned GH secretion to reinforce sexual dimorphism in the GH axis.


Assuntos
Proteínas de Ligação a DNA/fisiologia , Hormônio do Crescimento/fisiologia , Hipotálamo/metabolismo , Neurônios/metabolismo , Somatostatina/metabolismo , Transativadores/fisiologia , Animais , Proteínas de Ligação a DNA/deficiência , Proteínas de Ligação a DNA/genética , Modelos Animais de Doenças , Nanismo Hipofisário/metabolismo , Retroalimentação Fisiológica/fisiologia , Feminino , Hormônio do Crescimento/deficiência , Hipotálamo/citologia , Masculino , Camundongos , Camundongos Knockout , Núcleos da Linha Média do Tálamo/citologia , Núcleos da Linha Média do Tálamo/metabolismo , Proteínas do Leite/genética , Ratos , Ratos Mutantes , Fator de Transcrição STAT5 , Caracteres Sexuais , Transdução de Sinais/genética , Transdução de Sinais/fisiologia , Transativadores/deficiência , Transativadores/genética
3.
Neuropeptides ; 39(2): 81-7, 2005 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15752541

RESUMO

Insulin-like growth factor-I is a neurotrophic factor and can prevent neurons from ischemic brain injury. However, the large molecular weight and metabolic effects can be problematic in its central delivery. Glycine-proline-glutamate (GPE) is the N-terminal tripeptide of insulin-like growth factor-I, which is naturally cleaved in the plasma and brain tissues. GPE reduces neuronal loss from hypoxic-ischemic brain injury following central administration. Central penetration and the stability of GPE in the plasma and central nervous system were examined in rats using radioimmunoassay and HPLC. GPE was rapidly metabolised in the plasma (8 min) after intraperitoneal administration. Despite having a short half-life in plasma, GPE was detected in the cerebrospinal fluid up to 40 min after intraperitoneal administration. With present of peptidase inhibitors, GPE existed in the brain tissue up to 3 h after intracerebroventricular administration, suggesting a role for peptolysis in its stability. The endopeptidase inhibitors 4- (2-aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF) reduced GPE metabolism in the brain tissue while acid peptidase inhibitor pepstatin-A decreased GPE metabolism in the plasma. GPE reduced neuronal loss in the CA1-2 sub-region of the hippocampus given (intraperitoneally) after 30 min of hypoxic-ischemic injury in adult rats, further suggested the effectiveness of GPE central uptake. These results indicated that GPE crosses the blood-CSF and the functional CSF-brain barriers. The longer half-life of GPE in the CNS may be due to its unique enzymatic stability.


Assuntos
Encéfalo/metabolismo , Fator de Crescimento Insulin-Like I/metabolismo , Leucina/análogos & derivados , Oligopeptídeos/metabolismo , Oligopeptídeos/farmacocinética , Animais , Líquido Cefalorraquidiano/química , Estabilidade de Medicamentos , Hipocampo/efeitos dos fármacos , Hipóxia-Isquemia Encefálica/tratamento farmacológico , Cinética , Leucina/farmacologia , Masculino , Oligopeptídeos/administração & dosagem , Pepstatinas/farmacologia , Peritônio/efeitos dos fármacos , Inibidores de Proteases/farmacologia , Ratos , Ratos Wistar
4.
Neuropharmacology ; 47(6): 892-903, 2004 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-15527823

RESUMO

The N-terminal tripeptide of insulin-like growth factor-1, GPE is neuroprotective when given intracerebroventricularly 2 h after hypoxic-ischemic (HI) brain injury in rats. We have now examined whether GPE can cross the blood-brain barrier and exert neuroprotective actions following intravenous administration. Following a single bolus intravenous injection, GPE was rapidly metabolized and cleared from the circulation. The short half-life (<2 min) in blood was subsequently associated with modest and inconsistent neuroprotection. In contrast, potent neuroprotection of GPE was consistently observed in all brain regions examined following 4 h intravenous infusion (12 mg/kg). The neuroprotective effects of GPE after infusion showed a broad effective dose range (1.2-120 mg/kg) and an extended window of treatment to 7-11 h after injury. The central penetration of GPE after intravenous infusion was injury-dependent. GPE also improved long-term somatofunction with a comparable neuronal outcome. GPE reduced both caspase-3-dependent and -independent apoptosis in the hippocampus. Treatment with GPE also inhibited microglial proliferation and prevented the injury-induced loss of astrocytes. In conclusion, the neuroprotective actions of GPE infusion were global, robust and displayed a broad effective dose range and treatment window. GPE's activity included the prevention of neuronal apoptosis, promotion of astrocyte survival and inhibition of microglial proliferation. With injury specific central penetration, GPE has considerable promise as a systemic neuroprotective treatment after acute encephalopathies.


Assuntos
Hipóxia-Isquemia Encefálica/patologia , Hipóxia-Isquemia Encefálica/prevenção & controle , Fator de Crescimento Insulin-Like I/farmacologia , Fármacos Neuroprotetores , Oligopeptídeos/farmacologia , Animais , Química Encefálica/efeitos dos fármacos , Química Encefálica/fisiologia , Relação Dose-Resposta a Droga , Lateralidade Funcional/fisiologia , Meia-Vida , Hipocampo/patologia , Imuno-Histoquímica , Marcação In Situ das Extremidades Cortadas , Infusões Intravenosas , Fator de Crescimento Insulin-Like I/administração & dosagem , Fator de Crescimento Insulin-Like I/farmacocinética , Masculino , Peso Molecular , Neurônios/patologia , Oligopeptídeos/administração & dosagem , Oligopeptídeos/farmacocinética , Radioimunoensaio , Ratos , Ratos Wistar
5.
Int J Nurs Stud ; 41(7): 721-33, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15288795

RESUMO

Research has identified a number of negative societal perceptions of nursing related to gendered stereotyping, subordination to doctors, low academic standards, limited career opportunities and poor pay and conditions, and importantly how these perceptions may affect levels of recruitment into nursing. Focusing specifically on nurses, research has also considered the extent to which these societal perceptions are realities in their workplaces, and the direct experiences that contribute to attrition from both nursing courses and jobs. However, to date, few research has actually bridged the above approaches and considered the perceptions that nursing students hold as they first enter their education and how these change, or are confirmed, as a result of their experiences. In this context, the current study uses a combined questionnaire (n = 650), interview (n = 30) and focus group (n = 7) methodology to investigate the experiences of students based at two British Universities. The findings suggest that many students were surprised, yet not overwhelmed, by the high academic standards required of them and came to recognize and value the tremendous knowledge, skills set and responsibilities of nurses as they acquired them. However, their experiences reinforced both society's and their own image of an underpaid, overworked profession that lacks respect and has low morale. The findings support media initiatives that emphasize nurses' skills in order to influence public opinion. They also support a range of subtle changes in nurse education at the institutional level to make student life easier. Nevertheless, it is acknowledged that these may have a limited impact unless pay and conditions are adequately addressed at the national level.


Assuntos
Atitude do Pessoal de Saúde , Escolha da Profissão , Papel do Profissional de Enfermagem , Percepção Social , Estudantes de Enfermagem/psicologia , Mobilidade Ocupacional , Bacharelado em Enfermagem/organização & administração , Feminino , Grupos Focais , Humanos , Masculino , Moral , Negativismo , Pesquisa Metodológica em Enfermagem , Inovação Organizacional , Pesquisa Qualitativa , Salários e Benefícios , Evasão Escolar/psicologia , Evasão Escolar/estatística & dados numéricos , Inquéritos e Questionários , Reino Unido
6.
Anal Biochem ; 323(2): 156-63, 2003 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-14656520

RESUMO

Glycine-proline-glutamate (GPE) is the N-terminal tripeptide of insulin-like growth factor-1 and has been shown to be neuroprotective following ischemia-induced brain injury. The pharmacokinetics of GPE were studied in adult rats since GPE is a candidate for use in neuroprotection therapies. To measure plasma concentrations of GPE a novel radioimmunoassay was developed whereby GPE was initially derivatized with Bolton and Hunter reagent before use in a standard homologous assay against the Bolton and Hunter iodinated form. The derivatized GPE radioimmunoassay showed a 83% recovery of unlabeled GPE and complete parallel displacement with rat plasma. The simplicity and speed of the assay described here indicate an exciting new use for a previously described technology. The pharmacokinetic studies were conducted in adult rats using a single bolus intravenous injection of GPE at 30 or 100 mg/kg and showed that GPE was rapidly cleared from the circulation. In addition, evidence of the route of the metabolic degradation of GPE is presented. The findings presented here are the first description of the pharmacokinetics of GPE and suggest that, because of its very short half-life in plasma, continuous intravenous infusion of GPE may be the preferred route of administration for use in future neuroprotection therapies.


Assuntos
Fator de Crescimento Insulin-Like I/farmacocinética , Oligopeptídeos/farmacocinética , Animais , Cromatografia Líquida de Alta Pressão , Fator de Crescimento Insulin-Like I/química , Masculino , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/farmacocinética , Radioimunoensaio , Ratos , Ratos Wistar , Sensibilidade e Especificidade
7.
J Endocrinol ; 171(1): 173-81, 2001 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-11572801

RESUMO

GH treatment can increase the mortality and morbidity of critically ill patients. The mechanisms of these harmful effects of GH are unknown but have been, in part, ascribed to interactions between GH and the immune system. Because GH has pattern-dependent actions we have now compared the dose-related effects of continuous and intermittent GH treatment given with or without an endotoxin (lipopolysaccharide; LPS) challenge. Male Wistar rats (n=6 per group) were treated for 5 days with recombinant human GH (0, 10, 100 or 1000 microg/kg per day) using either continuous s.c. infusion by osmotic minipump or intermittent twice daily s.c. injections. On day 4, endotoxin (5 mg/kg, i.p.) was injected and the animals monitored for a further 16 h. LPS administration alone led to neutrophilia and lymphopoenia, with increased plasma concentrations of urea, cholesterol, triglyceride, insulin and leptin, and decreased levels of IGF-I. High dose GH infusion (1000 microg/kg per day) followed by LPS caused greater increases in plasma urea, cholesterol, triglyceride, sodium and magnesium, but lower plasma glucose and insulin levels, than treatment with LPS alone. In contrast, twice daily injections of GH did not enhance these effects of endotoxin. In conclusion, the effects of endotoxin on plasma electrolytes, lipids, urea, glucose and insulin are differentially affected by the pattern of GH administration in the rat.


Assuntos
Infecções Bacterianas/sangue , Eletrólitos/sangue , Hormônio do Crescimento Humano/farmacologia , Lipopolissacarídeos/metabolismo , Linfopenia/sangue , Animais , Glicemia/metabolismo , Colesterol/sangue , Relação Dose-Resposta a Droga , Bombas de Infusão Implantáveis , Injeções Subcutâneas , Insulina/sangue , Fator de Crescimento Insulin-Like I/análise , Leptina/sangue , Lipopolissacarídeos/farmacologia , Magnésio/sangue , Masculino , Modelos Animais , Ratos , Ratos Wistar , Sódio/sangue , Triglicerídeos/sangue , Ureia/sangue
8.
Am J Ther ; 8(4): 231-6, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11441321

RESUMO

A retrospective analysis compared the coefficients of variation associated with the maximum plasma concentration (Cmax) and the extent of absorption (area under the curve [AUC] from 0 hour to the last observation) for oral, controlled-release tablet formulations of oxycodone (OxyContin) and morphine (MS Contin). Data from fasting, male subjects aged 18 to 45 years were taken from five controlled-release oxycodone (N = 82) and seven controlled-release morphine (N = 101) single-dose, bioequivalence studies. The coefficients of variation of Cmax and AUC were approximately 33% less for controlled-release oxycodone than for controlled-release morphine (P =.005). The variation from the minimum to maximum value was two to three times less for controlled-release oxycodone than for controlled-release morphine. Among healthy male subjects, the absorption of oxycodone from oral controlled-release oxycodone was significantly more consistent than the absorption of morphine from oral controlled-release morphine in terms of both maximum absorption and extent of absorption.


Assuntos
Morfina/farmacocinética , Oxicodona/farmacocinética , Adolescente , Adulto , Área Sob a Curva , Disponibilidade Biológica , Preparações de Ação Retardada/farmacocinética , Humanos , Masculino , Pessoa de Meia-Idade , Morfina/sangue , Oxicodona/sangue , Valores de Referência , Estudos Retrospectivos , Equivalência Terapêutica
9.
Growth Horm IGF Res ; 10(1): 45-52, 2000 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-10753592

RESUMO

Synthetic GH-releasing peptides such as GHRP-6 are potent GH secretagogues (GHSs) in several species, but attempts to stimulate growth by continuous GHS exposure have had limited success. GHSs also release ACTH and adrenal steroids. Since glucocorticoid excess is associated with poor linear growth, stimulation of the hypothalamo-pituitary-adrenal (HPA) axis by continuous GHS administration may compromise their growth-promoting effects. We have now examined the effects of continuous GHRP-6 infusion (100 mg/day, s.c. for 14 days) in normal 150-day-old female rats, and in adrenalectomized (Adx) rats with or without dexamethasone (Dex) replacement. Infusion of GHRP-6 did not significantly affect body weight gain compared with excipient-treated controls in either intact rats (controls, 9.0 +/- 1.6 vs GHRP-6, 11.8 +/- 0.9 g) or Adx rats (4.4 +/- 1.5 vs 7.9 +/- 2.7 g). However, GHRP-6 significantly increased weight gain in Adx rats treated with Dex (controls, 3.5 +/- 1.4 vs GHRP-6, 15.4 +/- 1.6 g;P<0.01). Adrenalectomy decreased plasma triglycerides (P<0.01), and Dex treatment increased plasma cholesterol (P<0.001), GHRP-6 treatment did not affect these plasma lipids. Dex treatment also reduced plasma GH-binding protein levels and hepatic GH binding (P<0.05). Pituitary GH content was decreased in Adx rats (P<0.05) but not in Dex-treated Adx rats. Adrenalectomy markedly decreased GHS-receptor mRNA expression in the arcuate (P<0. 001) and ventromedial nuclei (P<0.01), whilst Dex treatment normalized GHS-receptor expression. These results suggest that adrenal steroids are necessary for normal GHS-receptor expression and GHRP-6-induced weight gain, but long-term stimulation of the HPA axis by continuous GHS exposure may be detrimental to the growth response.


Assuntos
Peso Corporal/efeitos dos fármacos , Glucocorticoides/fisiologia , Hormônio do Crescimento/metabolismo , Receptores da Somatotropina/metabolismo , Glândulas Suprarrenais/fisiologia , Adrenalectomia , Animais , Glicemia/metabolismo , Colesterol/sangue , Dexametasona/farmacologia , Feminino , Hormônio do Crescimento/sangue , Hipotálamo/efeitos dos fármacos , Hibridização In Situ , Insulina/sangue , Fígado/efeitos dos fármacos , Ratos , Receptores da Somatotropina/sangue , Fatores de Tempo , Triglicerídeos/sangue
10.
J Neuroendocrinol ; 11(3): 229-36, 1999 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10201819

RESUMO

In transgenic growth-retarded (Tgr) rats, expression of human growth hormone (hGH) is targeted to hypothalamic GH-releasing hormone (GHRH) neurones. In these rats, GHRH is reduced and somatostatin expression is increased, resulting in secondary GH deficiency and dwarfism. Tgr rats also show reduced pituitary prolactin (PRL), which may reflect an additional lactogenic feedback action of the hGH transgene, analogous to that in mice transgenic for peripheral hGH which show enhanced dopamine (DA) and tyrosine hydroxylase (TH) expression in the hypothalamic tuberoinfundibular dopaminergic (TIDA) neurones that inhibit PRL secretion. The present study examined DA histofluorescence and TH immunoreactivity in Tgr rats, and also in dw/dw rats, a dwarf strain with primary pituitary GH but not PRL deficiency. Radioimmunoassay confirmed a significant decrease in total pituitary PRL content in Tgr rats, but showed a marked increase in total pituitary PRL in dw/dw rats. Despite their PRL deficiency, Tgr rats showed qualitatively increased TIDA histofluorescence and TH immunoreactivity compared with AS control rats, though the total number of detectable TH-positive TIDA neurones was similar for Tgr and AS. In contrast, dw/dw rats showed increased numbers of TH-immunoreactive TIDA neurones whilst TIDA fluorescence was unchanged, and these findings were not affected in dw/dw rats given bovine GH (200 microg/d s.c. for 7 d). These results suggest that reduced PRL in Tgr rats is due to a local lactogenic feedback effect of hGH to stimulate TIDA neurones. The complex changes in TIDA neurones probably reflect a combination of increased lactogenic feedback in Tgr rats, with an increased (Tgr) or decreased (dw/dw) somatogenic feedback on GHRH neurones, some of which coexpress TH. Thus, the unchanged number of TIDA neurones in Tgr rats may result from hGH stimulation of TH and DA, but a reduction in GHRH-producing cells, whereas increased TIDA neurones in dw/dw rats suggests a stimulation by endogenous PRL with an increased GHRH cell complement due to GH deficiency. These findings therefore indicate that differences in lactogenic feedback in these dwarf rat models are reflected in marked differences in their hypothalamic TIDA neurones.


Assuntos
Dopamina/metabolismo , Hipotálamo/metabolismo , Neurônios/metabolismo , Hipófise/metabolismo , Prolactina/metabolismo , Animais , Animais Geneticamente Modificados , Hormônio do Crescimento/genética , Hipotálamo/citologia , Masculino , Modelos Biológicos , Radioimunoensaio , Ratos , Ratos Mutantes
11.
Endocrinology ; 138(11): 4552-7, 1997 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-9348177

RESUMO

Synthetic GH secretagogues (GHSs) act via a receptor (GHS-R) distinct from that for GH-releasing hormone (GHRH). We have studied the hypothalamic expression and regulation of this receptor by in situ hybridization using a homologous riboprobe for rat GHS-R. GHS-R mRNA is prominently expressed in arcuate (ARC) and ventromedial nuclei (VMN) and in hippocampus, but not in the periventricular nucleus. Little or no specific hybridization could be observed in the pituitary under the conditions that gave strong signals in the hypothalamus. No sex difference in GHS-R expression was found in ARC or hippocampus, though expression in VMN was lower in males than in females. Compared with GHRH and neuropeptide Y (NPY), GHS-R was expressed in a distinct region of ventral ARC, and in regions of VMN not expressing GHRH or NPY. GHS-R expression was highly sensitive to GH, being markedly increased in GH-deficient dw/dw dwarf rats, and decreased in dw/dw rats treated with bovine GH (200 microg/day) for 6 days. Similar changes were observed in GHRH expression, whereas NPY expression was reduced in dw/dw rats and increased by bGH treatment. Continuous sc infusion of GHRP-6 in normal female rats did not alter ARC or VMN GHS-R expression. Our data implicate ARC and VMN cells as major hypothalamic targets for direct GHS action. The sensitivity of ARC GHS-R expression to modulation by GH suggests that GHS-Rs may be involved in feedback regulation of GH.


Assuntos
Hormônio do Crescimento/fisiologia , Hipotálamo/metabolismo , Receptores de Superfície Celular/metabolismo , Receptores Acoplados a Proteínas G , Animais , Bovinos , Feminino , Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/fisiologia , Hormônio Liberador de Hormônio do Crescimento/genética , Masculino , Neuropeptídeo Y/genética , Oligopeptídeos/farmacologia , RNA Mensageiro/metabolismo , Ratos , Ratos Endogâmicos , Receptores de Superfície Celular/genética , Receptores de Grelina , Distribuição Tecidual
12.
Endocrinology ; 138(10): 4316-23, 1997 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-9322945

RESUMO

Besides stimulating GH release, some GH secretagogues also release ACTH and adrenal steroids. Several novel classes of potent GH secretagogues have recently been described, and we have now tested their ability to release corticosterone in conscious normal rats. All analogs that released GH also stimulated corticosterone release to some degree, though the relative effects on GH and corticosterone varied somewhat. The corticosterone responses for some analogs were in the range of those obtained with CRF (2 microg, iv), whereas closely related analogs inactive for GH release failed to release corticosterone. Activation of the hypothalamic-pituitary-adrenal axis with GH release by GHRPs could be a highly diabetogenic combination in susceptible individuals. Therefore, a potent GHRP pentapeptide analog (G7039, 100 microg/day, sc, bid) was given to young obese male Zucker diabetic fatty rats (ZDF, n = 8/group) for 24 days. Other groups received hGH (500 microg/day, sc, bid), recombinant human insulin-like growth factor (rhIGF)-1 (750 microg/day, sc, infusion) or excipient, alone or in combination. Both G7039 and hGH increased weight gain, markedly raised serum glucose (G7039, 542 +/- 37; hGH, 725 +/- 30; excipient, 330 +/- 57 mg/dl) and doubled insulin levels but had opposite effects on serum triglycerides (G7039, 1412 +/- 44; hGH 501 +/- 46; excipient 1058 +/- 73 mg/dl) and fat depot weights. In contrast, treatment with IGF-1, alone or in combination with hGH or G7039, improved the diabetic state and stimulated growth. Thus, both G7039 and hGH treatment stimulated growth in ZDF rats, but greatly worsened diabetes, unless IGF-1 was coadministered. Some of the effects ofG7039 could be explained by GH release, but the effects on blood lipids and body fat were not seen with hGH and may reflect the additional activation of the hypothalamic-pituitary-adrenal axis by the secretagogue. The magnitude of these adverse effects in the ZDF animals suggest that chronic administration of GHRP analogs with cortisol-releasing activity to obese or diabetes-prone individuals warrants careful evaluation.


Assuntos
Diabetes Mellitus Experimental/etiologia , Hormônio Liberador de Hormônio do Crescimento/farmacologia , Hormônio do Crescimento/farmacologia , Hormônios/farmacologia , Sistema Hipotálamo-Hipofisário/efeitos dos fármacos , Fator de Crescimento Insulin-Like I/farmacologia , Oligopeptídeos/farmacologia , Sistema Hipófise-Suprarrenal/efeitos dos fármacos , Animais , Glicemia/análise , Glicemia/metabolismo , Peso Corporal/efeitos dos fármacos , Peso Corporal/fisiologia , Colesterol/sangue , Colesterol/metabolismo , Corticosterona/sangue , Corticosterona/metabolismo , Diabetes Mellitus Experimental/sangue , Diabetes Mellitus Experimental/metabolismo , Hormônio do Crescimento/sangue , Hormônio do Crescimento/metabolismo , Hormônio Liberador de Hormônio do Crescimento/análogos & derivados , Humanos , Hidrocortisona/sangue , Hidrocortisona/metabolismo , Sistema Hipotálamo-Hipofisário/fisiologia , Insulina/sangue , Insulina/metabolismo , Masculino , Sistema Hipófise-Suprarrenal/fisiologia , Ratos , Ratos Zucker , Proteínas Recombinantes/farmacologia , Triglicerídeos/farmacologia
13.
J Endocrinol ; 153(3): 385-91, 1997 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-9203992

RESUMO

The fetal hypothalamo-pituitary-gonadal axis reaches a peak in activity at mid-gestation and this is followed by a period of suppression which persists until the onset of puberty. The decline in gonadotrophic activity during late gestation is thought to reflect the maturation of central and peripheral feedback signals. In order to establish if sustained pituitary responsiveness is rate limiting to the reinstatement of reproductive function, we have examined the endocrine consequences of repeated pulsatile GnRH administration to male and fetal sheep during late gestation. Beginning on day 121 of gestation (term = 145 days) chronically catheterized fetal sheep were given i.v. pulses of either 500 ng GnRH or saline every 2 h for 14 days. Pituitary and gonadal responses were assessed by measuring changes in plasma concentrations of LH, FSH, inhibin and testosterone (in male fetuses) in response to the first pulse of GnRH on day 1 and to the corresponding pulse on days 4, 7, 10 and 14. In response to the first pulse of GnRH there was an immediate release of LH, with the peak response being significantly (P < 0.01) greater than on subsequent days. In male fetuses each pulse of LH was followed by a rise in plasma testosterone concentrations within 40-60 min. The amplitude of these testosterone responses increased significantly (P < 0.01) after 9 days of treatment despite a decline in the plasma LH response. Basal FSH concentrations increased progressively (P < 0.05) during pituitary stimulation with GnRH in both male and female fetuses. Immunoreactive inhibin concentrations were significantly (P < 0.05) higher in males than in females, and there was a gradual increase throughout the experimental period irrespective of treatment. We observed no inverse correlation between inhibin and FSH concentrations. These data show that pulsatile administration of GnRH to fetal sheep during late gestation results in sustained re-activation of pituitary-gonadal function. The decline in fetal gonadotrophins, which is a characteristic feature of late gestation, is therefore likely to result from inadequate GnRH secretion from the fetal hypothalamus rather than an inhibition of pituitary function by peripheral feedback signals.


Assuntos
Hormônio Liberador de Gonadotropina/farmacologia , Gonadotropinas Hipofisárias/metabolismo , Ovário/efeitos dos fármacos , Hipófise/efeitos dos fármacos , Ovinos/embriologia , Testículo/efeitos dos fármacos , Animais , Esquema de Medicação , Feminino , Sangue Fetal/química , Hormônio Foliculoestimulante/sangue , Hormônio Foliculoestimulante/metabolismo , Idade Gestacional , Hormônio Liberador de Gonadotropina/administração & dosagem , Gonadotropinas Hipofisárias/sangue , Inibinas/sangue , Hormônio Luteinizante/sangue , Hormônio Luteinizante/metabolismo , Masculino , Ovário/embriologia , Ovário/metabolismo , Hipófise/embriologia , Hipófise/metabolismo , Estimulação Química , Testículo/embriologia , Testículo/metabolismo , Testosterona/sangue , Fatores de Tempo
14.
Endocrinology ; 138(4): 1585-91, 1997 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-9075719

RESUMO

GH-releasing hexapeptide (GHRP-6) is a synthetic secretagogue that stimulates the release of GH by acting at both hypothalamic and pituitary sites. GHRPs also consistently elicit small, but significant, increases in plasma concentrations of ACTH and adrenal steroids. As these secretagogues do not release ACTH directly, they probably interact with the hypothalamic peptidergic systems controlling ACTH release, such as CRH and arginine vasopressin (AVP). We have now examined the activation of the hypothalamo-pituitary-adrenal axis by GHRP-6 in conscious rats. In a series of experiments, rats were injected i.v. with 10 microg GHRP-6, 2 microg CRH, 0.5 microg AVP, or saline, alone or in combination, and serial plasma samples withdrawn and assayed for ACTH, corticosterone, and GH. CRH and AVP increased plasma ACTH levels in all rats, whereas ACTH and corticosterone responses to GHRP-6 were variable and were dependent on the prevailing activity of the hypothalamo-pituitary-adrenal axis. GHRP-6 stimulated the largest ACTH responses in rats that had the lowest basal plasma ACTH and corticosterone levels before GHRP-6 administration. GHRP-6 given in combination with CRH did not increase ACTH levels beyond the response to CRH alone (change in ACTH, 1570 +/- 207 vs. 1714 +/- 245 pg/ml), whereas the combination of GHRP-6 and AVP markedly increased ACTH levels compared with the effects of AVP alone (change in ACTH, 5587 +/- 669 vs. 2338 +/- 451 pg/ml; P < 0.05). The GH responses to GHRP-6 were significantly greater in rats with low basal plasma ACTH and corticosterone levels than in rats with elevated ACTH and corticosterone levels (change in GH response, 119 +/- 27 vs. 29 +/- 7 ng/ml; P < 0.01). CRH alone significantly inhibited GH release (pre- vs. 40 min post-CRH, 11.9 +/- 3.8 vs. 1.7 +/- 0.4 ng/ml; P < 0.05), whereas AVP alone had no effect on GH levels. Neither CRH nor AVP had any effect on the GH response to GHRP-6. We suggest that GHRP-6 acts via the hypothalamus to mediate the release of ACTH, and that these effects are probably mediated at least in part via the release of endogenous CRH and are subject to regulation by circulating glucocorticoids.


Assuntos
Hormônios/farmacologia , Sistema Hipotálamo-Hipofisário/metabolismo , Oligopeptídeos/farmacologia , Sistema Hipófise-Suprarrenal/metabolismo , Hormônio Adrenocorticotrópico/sangue , Animais , Arginina Vasopressina/farmacologia , Corticosterona/sangue , Hormônio Liberador da Corticotropina/farmacologia , Hormônio do Crescimento/sangue , Sistema Hipotálamo-Hipofisário/efeitos dos fármacos , Masculino , Sistema Hipófise-Suprarrenal/efeitos dos fármacos , Radioimunoensaio , Ratos , Estereoisomerismo
15.
J Pain Symptom Manage ; 13(2): 75-82, 1997 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-9095564

RESUMO

A single-dose, analytically blinded, randomized, crossover study was conducted in 22 healthy male volunteers to compare the bioavailability of one 20 mg with two 10 mg controlled-release (CR) oxycodone tablets. In addition, pharmacodynamic effects were assessed using both objective and subjective measures for up to 48 hr after dosing. The two treatments were bioequivalent, with comparable rates (Cmax of one 20 mg tablet was 109% of two 10 mg tablets; 90% confidence limits: 98.4%-120%) and extents (AUC0-infinity: 107%; 100%-114%) of absorption. In addition, no significant differences between tablets were found for mean values of Tmax, T/12abs, or T/12elim. Correlations between plasma oxycodone concentrations and most pharmacodynamic measures were significant. The strongest correlations were observed for pupil size (r = -0.53) and subjects' assessment of drug effect (r = 0.53), with changes in plasma concentration accounting for more than 25% of the observed changes in these variables. This study demonstrated bioequivalence of two 10 mg and one 20 mg CR oxycodone tablet, with significant correlation between plasma oxycodone concentrations and pharmacodynamic effects in normal volunteers.


Assuntos
Analgésicos Opioides/farmacocinética , Oxicodona/farmacocinética , Adulto , Analgésicos Opioides/farmacologia , Disponibilidade Biológica , Preparações de Ação Retardada , Humanos , Masculino , Oxicodona/farmacologia , Valores de Referência
16.
EMBO J ; 15(15): 3871-9, 1996 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-8670892

RESUMO

Expression of human growth hormone (hGH) was targeted to growth hormone-releasing (GRF) neurons in the hypothalamus of transgenic rats. This induced dominant dwarfism by local feedback inhibition of GRF. One line, bearing a single copy of a GRF-hGH transgene, has been characterized in detail, and has been termed Tgr (for Transgenic growth-retarded). hGH was detected by immunocytochemistry in the brain, restricted to the median eminence of the hypothalamus. Low levels were also detected in the anterior pituitary gland by radioimmunoassay. Transgene expression in these sites was confirmed by RT-PCR. Tgr rats had reduced hypothalamic GRF and mRNA, in contrast to the increased GRF expression which accompanies GH deficiency in other dwarf rats. Endogenous GH mRNA, GH content, pituitary size and somatotroph cell number were also reduced significantly in Tgr rats. Pituitary adrenocorticotrophic hormone (ACTH) and thyroid-stimulating hormone (TSH) levels were normal, but prolactin content, mRNA levels and lactotroph cell numbers were also slightly reduced, probably due to feedback inhibition of prolactin by the lactogenic properties of the hGH transgene. This is the first dominant dwarf rat strain to be reported and will provide a valuable model for evaluating the effects of transgene expression on endogenous GH secretion, as well as the use of GH secretagogues for the treatment of dwarfism.


Assuntos
Nanismo/genética , Hormônio Liberador de Hormônio do Crescimento/biossíntese , Hormônio do Crescimento/metabolismo , Neurônios/metabolismo , Animais , Animais Geneticamente Modificados , Southern Blotting , Cosmídeos/química , Feminino , Genes Dominantes , Hormônio do Crescimento/genética , Humanos , Hipotálamo/citologia , Masculino , Hipófise/citologia , Reação em Cadeia da Polimerase , Prolactina/genética , RNA Mensageiro/metabolismo , Ratos , Mapeamento por Restrição , Transgenes , Regulação para Cima
17.
Domest Anim Endocrinol ; 13(3): 251-8, 1996 May.
Artigo em Inglês | MEDLINE | ID: mdl-8738866

RESUMO

The effects of growth hormone-releasing peptide-6 (GHRP-6) on peripheral plasma concentrations of growth hormone (GH) and hypophysial portal plasma concentrations of growth hormone-releasing hormone (GHRH) and somatostatin (SRIF) were investigated in conscious ewes. Paired blood samples were collected from the hypophysial portal vessels and from the jugular vein of nine ewes for at least 2 hr. The sheep were then given a bolus injection of 10 micrograms of GHRP-6 per kg followed by a 2-hr infusion of GHRP-6 (0.1 microgram/kg.hr). Blood sampling continued throughout the infusion and for 2 hr afterwards. An increase in plasma GH concentration was observed in the jugular samples of six of the nine ewes (1.4 +/- 0.3 vs 7.4 +/- 2.0 ng/ml, P < 0.05) 5-10 min after the GHRP-6 bolus injection, but in no case did we observe a significant coincident release of GHRH. During the infusion period, mean plasma GHRH levels were not significantly increased but there was a 50% increase (P < 0.05) in GHRH pulse frequency; GHRH pulse amplitude was not changed. Mean SRIF concentration, pulse frequency, and pulse amplitude were unchanged by GHRP-6 treatment. These data indicate that GHRP-6 causes a small, but significant effect on the pulsatile secretion of GHRH, indicating action at the hypothalamus or higher centers of the brain. The large initial GH secretory response to GHRP-6 injection does not appear to be the result of GHRP-6 action on GHRH or SRIF secretion.


Assuntos
Hormônio Liberador de Hormônio do Crescimento/sangue , Oligopeptídeos/farmacologia , Hipófise/irrigação sanguínea , Ovinos/sangue , Somatostatina/sangue , Animais , Estado de Consciência/fisiologia , Feminino , Hormônio do Crescimento/sangue , Hormônios/administração & dosagem , Hormônios/farmacologia , Infusões Intravenosas/métodos , Infusões Intravenosas/veterinária , Oligopeptídeos/administração & dosagem , Sistema Porta/fisiologia , Ovinos/fisiologia
18.
J Endocrinol ; 145(1): 35-42, 1995 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-7798028

RESUMO

In order to investigate the ontogeny of gonadal inhibin production in the male fetal sheep, testes were collected from male fetuses at days 70, 100, 130 and 140 of gestation (term = 145 days). The expression and localization of inhibin alpha- and inhibin beta A-subunit mRNA and protein were evaluated using in situ hybridization and immunocytochemistry. The expression of inhibin alpha-subunit mRNA was localized within the seminiferous cords of the developing fetal testis and progressively increased with gestational age. Immunostaining corresponding to immunoreactive inhibin alpha-subunit was detected in Sertoli cells within the seminiferous cords at days 100, 130 and 140 of gestation. In addition, immunostaining was detectable in a small proportion of Leydig cells. No expression of inhibin beta A-subunit mRNA or immunoreactivity was detected in any testicular tissue at any stage of gestation. These data show that the Sertoli cells of the developing fetal sheep testis have the capacity to produce inhibin alpha-subunit by day 100 of gestation and that production increases during late gestation.


Assuntos
Inibinas/biossíntese , Biossíntese Peptídica , Proteínas Secretadas pela Próstata , Ovinos/embriologia , Testículo/embriologia , Animais , Idade Gestacional , Processamento de Imagem Assistida por Computador , Imuno-Histoquímica , Hibridização In Situ , Inibinas/análise , Inibinas/genética , Masculino , Peptídeos/análise , Peptídeos/genética , RNA Mensageiro/análise , Túbulos Seminíferos/química , Túbulos Seminíferos/embriologia , Células de Sertoli/química , Ovinos/metabolismo , Testículo/química , Testículo/metabolismo
19.
J Endocrinol ; 144(2): 323-31, 1995 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-7706985

RESUMO

The putative negative feedback effects of IGF-I and IGF-II on GH secretion were tested by intracerebroventricular (icv) and intrapituitary administration to sheep. Over two consecutive days, serial jugular blood samples were taken at 10 min intervals for 6 h from ewes (n = 3/group) fitted with indwelling stainless steel cannulae into the lateral or third cerebral ventricles. The sheep were injected (icv) with either vehicle or purified ovine IGF-I (2, 4 or 8 micrograms). IGF-I injection had no effect on plasma GH secretion. Serial blood samples were taken from a second group of nine ewes in which ovine or recombinant human (rh) IGF-I was infused (2.5 micrograms/h for 2 h) into the third ventricle; once again, IGF-I failed to affect the episodic pattern of GH secretion. Three ewes fitted with indwelling stainless steel cannulae placed in the anterior pituitary gland were consecutively infused with either ovine or rhIGF-I (2.5 micrograms/h for 2 h) or vehicle. Plasma GH concentrations were suppressed in 3/3 sheep from 1-1.5 h after the commencement of infusion and GH levels remained low for the remainder of the sampling period. In another group of five ewes synergistic effects of IGF-I and IGF-II on GH secretion were tested by icv infusion of rhIGF-I, rhIGF-II, or rhIGF-I+rhIGF-II (5 micrograms/h for 2 h) or vehicle (sterile 10 mM HCl/saline). Each sheep received each treatment in a randomised design. Infusion (icv) of IGF-I and IGF-II alone or in combination failed to alter GH secretion.(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Hormônio do Crescimento/metabolismo , Hipófise/metabolismo , Somatomedinas/metabolismo , Animais , Retroalimentação , Feminino , Hormônio do Crescimento/sangue , Hipotálamo/metabolismo , Fator de Crescimento Insulin-Like I/administração & dosagem , Fator de Crescimento Insulin-Like I/metabolismo , Fator de Crescimento Insulin-Like II/administração & dosagem , Fator de Crescimento Insulin-Like II/metabolismo , Hipófise/efeitos dos fármacos , Ovinos
20.
Mol Cell Endocrinol ; 107(2): 141-7, 1995 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-7768325

RESUMO

In adult sheep, inhibin expression in developing follicles appears to be associated with antrum formation. Our objective was to investigate using in situ hybridization and immunohistochemistry whether antral follicles present before birth in the sheep expressed mRNA or peptide for inhibin alpha- and beta A-subunits. At days 70 and 100 when only primordial and primary follicles were present, there was no detectable mRNA or peptide for either inhibin subunit. By days 130 and 140 (term = 145 days), many secondary follicles were present, a proportion of which (approximately 50%) expressed detectable levels of alpha-subunit mRNA but not peptide. A number of antral follicles were present by this stage, all of which expressed alpha-subunit mRNA and peptide. Expression of beta A-subunit mRNA and peptide was undetectable at all stages of gestation. Our results indicates that even in non-ovulatory follicles present before birth, expression of inhibin, at least the alpha-subunit, is developmentally linked with antrum formation.


Assuntos
Inibinas/genética , Ovário/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Animais , Feminino , Feto/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Idade Gestacional , Imuno-Histoquímica , Hibridização In Situ , Inibinas/química , Inibinas/metabolismo , Ovário/embriologia , Gravidez , Conformação Proteica , Ovinos
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