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M J Waters

Publications and source records attributed to M J Waters.

At least 55 records · Page 3Linked to original sources
PubMed1997

Functional growth hormone (GH) receptors and GH are expressed by preimplantation mouse embryos: a role for GH in early embryogenesis?

The results of this study challenge the widely held view that growth hormone (GH) acts only during the postnatal period. RNA phenotyping shows transcripts for the GH receptor and GH-binding protein in mouse preimplantation embryos of all stages from fertilized eggs (day 1) to blastocysts (day 4). An antibody specific to the cytoplasmic region of the GH receptor revealed receptor protein expression, first in two-cell embryos, the stage of activation of the embryonic genome (day 2), and in all subsequent stages. In cleavage-stage embryos this immunoreactivity was localized mainly to the nucleus, but clear evidence of membrane labeling was apparent in blastocysts. GH receptor immunoreactivity was also observed in cumulus cells associated with unfertilized oocytes but not in the unfertilized oocytes. The blastocyst receptor was demonstrated to be functional, exhibiting the classic bell-shaped dose-response curves for GH stimulation of both 3-O-methyl glucose transport and protein synthesis. Maximal stimulation of 40-50% was seen for both responses at less than 1 ng/ml recombinant GH, suggesting a role for maternal GH. However mRNA transcripts for GH were also detected from the morula stage (day 3) by using reverse transcription-PCR, and GH immunoreactivity was seen in blastocysts. These observations raise the possibility of a paracrine/autocrine GH loop regulating embryonic development in its earliest stages.

3-O-Methylglucose↗
PubMed1997

The role of receptor dimerization domain residues in growth hormone signaling.

While there is a considerable amount of evidence that signal transduction by the growth hormone (GH) receptor requires receptor homodimerization, there has been no systematic study of the role of receptor dimerization domain residues in this process. In conjunction with the distances derived from the crystal structure of the hGH-hGH receptor (extracellular domain) complex, we have used a luciferase-based c-fos promoter reporter assay in transiently transfected Chinese hamster ovary (CHO) cells, and stable receptor expressing CHO cell populations to define the dimerization domain residues needed for effective signaling. In addition to alanine substitution, we have used both aspartate and lysine substitutions to allow us to provide evidence for proximity relations through charge complementation. Introduced cysteine substitutions were also used, but unlike the erythropoietin receptor, these were unable to generate constitutively active receptor. We conclude that serine 145, histidine 150, aspartate 152, tyrosine 200, and serine 201, but not leucine 146 or threonine 147 are required for effective signal transduction through the dimerization domain. This information may be valuable in designing small molecule antagonists of GH and other cytokines that block dimerization by binding to the dimerization domain.

Animals↗
PubMed1997

Expression of growth hormone receptor by peripheral blood lymphocytes in children: evaluation in clinical conditions of impaired growth.

OBJECTIVE: It is widely accepted that the haematopoietic system is a target of growth hormone action and that GH may act as a lymphokine. The expression of GH receptors (GHR) on human peripheral blood lymphocytes (PBL) has been reported previously in adult donors by dual fluorochrome flow cytometry. The aim of this study was to apply the cytofluorimetric method to the analysis of GHR expression on PBL in various human conditions characterized by different patterns of growth due to age or physiopathological conditions. SUBJECTS AND DESIGN: PBL from 38 normal (control) subjects (7 newborns, 18 prepubertal children, 13 adults) were studied in order to provide age-related physiological data. Twenty-two short children (18 with idiopathic short stature, 4 with Ullrich-Turner syndrome) were studied to determine the expression of GHR in conditions of impaired longitudinal growth which may or may not require GH treatment. METHODS: Analysis was performed using a fluorescein isothiocyanate (FITC)-conjugated antibody specific for the GHR (mAb263) and phycoerythrin (PE)-anti CD2 (T and natural killer cells) or PE-anti CD2 (B cells) in dual fluorochrome flow cytometric assays. Results were expressed as mean fluorescent intensity (MFI). RESULTS: Adult CD2+ coils exhibited a significantly higher GHR expression (MFI 347 +/- 40) than that expressed in children and newborns (MFI 285 +/- 36 and 299 +/- 41, respectively, P < 0.001). A significantly increased expression of GHR on CD2+ cells was also found in short children (MFI 330 +/- 42 vs 285 42- 36, respectively; P < 0.002), whereas Ullrich-Turner syndrome patients did not show any difference from their age and gender matched controls (254 +/- 52 and 288 +/- 40, respectively). A negative relationship was found between GHR expression on CD2+ cells and height-SDS (r - 0.54, P < 0.0001) or BMI (r - 0.4, P < 0.015) in controls and short children, independent of their GH secretory status. Expression of GHR and CD20+ cells was higher than that expressed on CD2+ cells in all subjects. No appreciable differences were found in the MFI levels of GHR expression on CD20+ cells either among the different age group controls or between short children or Ullrich-Turner syndrome patients. A significant downregulation of expression was shown in CD20+ (P < 0.008) but not CD2+ cells after 6 months of GH treatment in 6 short children who had a poor response to GH provocative tests. CONCLUSIONS: GH receptor expression on immune cells in non-syndromic short children appears to be inversely related to the linear growth expression and BMI of the subjects, contrary to findings with hepatic derived serum GHBP. This finding may reflect alternate exon usage in lymphoid cells, and indicates that GH has a distinctive role in the immune system.

Adult↗
PubMed1997

Subpopulations of stromal cells from long-term human bone marrow cultures: ontogeny of progenitor cells and expression of growth hormone receptors.

Long-term culture of bone marrow derived stromal colony forming cells (S-CFC) in matrix and nutrient defined agar medium resulted in stromal cell colonies that pass sequentially through three distinct morphological stages: firstly, aggregated loose syncytium of round to avoid cells (stage I), a second developmental stage of large branching colonies in which the cells become enlarged, elongated with cytoplasmic projections forming a loosely anastomized network with adjacent cells (stage II), and finally cells become dissociated, loosing their long, thin cytoplasmic filaments and breaking their contacts with one another, but remain large and retain a bi-polar nature (stage III). Cells were also grown in liquid medium in a culture microenvironment closely resembling conditions of haemopoiesis in vitro. Using a panel of well defined monoclonal antibodies reactive against the rat, rabbit and human growth hormone receptors, this study found immunochemical evidence of the presence and localization of binding sites of growth hormone (GH) in the cell membrane and extra-nuclear Golgi area of long-term bone marrow derived human stromal cells in liquid and semi-solid nutrient agar mediums. GH-receptor immunoreactivity was present in small proliferating progenitor cells, myofibroblast-like cells, large reticular fibroblast cells, adipocytes and endothelial cells. Only MAb known to be reactive against human tissue resulted in strong immunoreactivity. The expression of GH-receptors not only on small proliferating, but also on the well differentiated cells, indicates a role for growth hormone on non-progenitor cells. GH-receptor immunoreactivity on differentiating and/or differentiated cells suggests that GH is also necessary for, or has a trophic function in differentiation. We propose that direct GH action is necessary not only for differentiation of progenitor cells as implied by the dual effector hypothesis, but also their subsequent clonal expansion, differentiation and maintenance.

Animals↗
PubMed1997

Growth hormone (GH) regulation of submandibular gland structure and function in the GH-deficient rat: upregulation of haptocorrin.

Based on localization studies of the GH receptor/binding protein (BP) in the gastrointestinal tract, we have recently demonstrated growth hormone regulation of gastric intrinsic factor. In order to define the role of GH in the submandibular gland (SMG) we have investigated the effect of GH on SMG structure and function with particular reference to haptocorrin. Bovine GH (65 micrograms/100 g body weight) was administered twice daily to adult male dwarf rats for 6 days (DW+) while control animals received vehicle (DW-). Administration of GH produced a significant increase in body weight (P < 0.001) and allometric increase in SMG weight (P = 0). There was no change in RNA or protein content per g SMG and GH administration produced a small decrease in DNA content normalized to SMG weight. Morphometric analysis of the SMG revealed a significant increase in the percentage area of the gland occupied by tubular (GH receptor/BP expressing) structures and a significant increase in the diameter of both the intralobular striated and granular convoluted tubules. The effect of GH on cellular proliferation in the ductular and acinar components was determined by the immunohistochemical detection of nuclear 5'-bromo-2'-deoxyuridine (BrdU) incorporated during a 2-h pulse of BrdU. GH treatment induced a 5.5-fold increase in the labelling index of tubular cells whereas the acinar cell labelling index increased only 3.3-fold. Soluble extracts of SMG were prepared for estimation of 57Co-cyanocobalamin (vitamin B12) binding. GH administration resulted in an increase in total 57Co-cyanocobalamin (CBL) binding per mg SMG protein. To determine the contribution of haptocorrin (R-protein) the amount of cobinamide dicyanide (CD) displaceable binding was calculated. GH administration produced a 70% increase in CD displaceable CBL binding per mg SMG indicating GH regulation of haptocorrin. A comparison of total SMG CBL binding and CD displaceable CBL binding between male and female rats detected no sex difference. Therefore sex-specific GH secretory profiles are unlikely to be of importance in the regulation of haptocorrin. In conclusion we have demonstrated that GH stimulates hypertrophy and hyperplasia of components of the SMG in the dwarf rat. The observed upregulation of haptocorrin may synergize with the GH-stimulated increase in intrinsic factor to facilitate absorption of CBL during the anabolic state.

Animals↗
PubMed1997

Evidence for a local action of growth hormone in embryonic tooth development in the rat.

Studies in non-dental embryonic tissues have suggested that an interaction between growth hormone and its receptor may play a role in growth and development before the foetal pituitary gland is competent. This study reports the distribution of growth hormone, its receptor and binding protein in developing rat tooth germs from embryonic day 17 to 21 and postnatal day 0 using antibodies specific for each of these proteins. Four foetal rats were processed at each time point (E17, E18, E20/21 and postnatal day 0). Following routine fixation and paraffin embedding, sections were treated with antisera to rat growth hormone, rat growth hormone binding protein and growth hormone receptor. Localization of antibody/antigen complexes was subsequently visualized by addition of biotinylated IgG and reaction with streptavidin peroxidase and diaminobenzidine. Assessment of the level of staining was qualitative and based on a subjective rankings ranging from equivocal to very strong staining. Overall, growth hormone and its binding protein were located both in the cellular elements and throughout the extracellular matrix, whereas the growth hormone receptor showed an exclusively intra-cellular location. All three proteins were detectable in cells of the dental epithelium and mesenchyme at the primordial bud stage (E17) which occurs prior to expression of pituitary growth hormone. At the cap stage of odontogenesis (E18-19), numerous cells in both the dental epithelium and mesenchyme were intensely immunoreactive for growth hormone, its binding protein and receptor. In the succeeding early bell stage (E20-21), most of the mesenchymal cells in the dental pulp were mildly positive for these proteins, while the dental epithelium and adjacent mesenchyme were more immunoreactive. At the late bell stage (postnatal day 0), all three proteins were localized in dental epithelium, differentiating mesenchymal cells the cuspal surface facing the epithelial-mesenchymal interface, preodontoblasts, and odontoblasts forming dentine. From these observations, immunoreactive growth hormone, its receptor and binding protein appear to be expressed in odontogenic cells undergoing histodifferentiation, morphodifferentiation and dentinogenesis in a cell-type and stage-specific pattern throughout embryonic tooth development. This suggests the possibility that growth hormone, or a growth hormone-like protein, plays a paracrine/autocrine role in tooth development in utero.

Animals↗
PubMed1996

Involvement of a subset of tyrosine kinases and phosphatases in regulation of the beta-lactoglobulin gene promoter by prolactin.

This study used pharmacological intervention to provide support for a role of kinases and phosphatases in prolactin transactivation of a milk protein gene. It was based on transient cotransfection using a rabbit prolactin receptor expression plasmid and a beta-lactoglobulin promoter/CAT reporter construct. In cotransfected CHO cells, herbimycin A and tyrphostin, two tyrosine kinase inhibitors, were able to decrease the CAT response by over 50%, along with tyrosine phosphorylation of cellular proteins, whereas genistein and lavendustine were without effect on lactoglobulin transactivation. Orthovanadate, an inactivator of tyrosine phosphatases, was able to substitute for prolactin in inducing the CAT response. Staurosporine, a non-specific kinase inhibitor, was able, when used at low concentrations (10 nM), to augment the prolactin response strikingly. Threonine/serine kinases do not appear to be involved early in beta-lactoglobulin promoter transactivation, since four C-kinase inhibitors and okadaic acid a threonine/serine phosphatase inhibitor, were without substantive effect. We conclude that specific tyrosine kinases are responsible for most of the signal transduction from the prolactin receptor to the beta-lactoglobulin gene promoter.

Animals↗
PubMed1996

Cellular trafficking of exogenous growth hormone in dwarf rat pituitary.

In order to determine the processing of growth hormone (GH) by its pituitary target cells, male rats were injected intracardially with 125I-bGH and their pituitaries removed at specific time intervals (2-120 min). Autoradiographic analysis performed at the electron-microscopic level showed that only three cell populations specifically took up 125I-bGH: somatotropes, lactotropes and gonadotropes. Specificity was demonstrated by concomitant injection with an excess of unlabeled bGH. A time course study indicated that eight compartments had distinct labeling patterns. The plasma membrane was highly labeled after as little as 2 min, and showed biphasic labeling 2 and 60 min after injection. The secretory granules of the somatotropes were more intensely labeled than those of the other cell populations. The rough endoplasmic reticulum was more intensely labeled in the gonadotropes. The Golgi apparatus was specifically labeled only in the gonadotropes. The mitochondria showed the highest degree of labeling at 15 and 120 min after injection. The lysosome compartment showed triphasic labeling, with maxima at 2, 30 and 120 min after injection. The labeling of the nuclear membrane showed a biphasic pattern, firstly at 15 min, then at 120 min after injection, except in the gonadotropes, and the labeling in the nuclear matrix showed similar biphasic pattern and maxima. These results show that GH is specifically taken up in the anterior pituitary by the somatotropes, lactotropes and gonadotropes, where, after binding to the plasma membrane, it is internalized into several cellular compartments, including the nucleus. The differences in cellular localization and processing between these cell types may reflect different paracrine and autocrine roles for GH.

Animals↗
PubMed1996

Human growth hormone fragments 1-43 and 44-191: in vitro somatogenic activity and receptor binding characteristics in human and nonprimate systems.

Human GH (hGH) fragments 1-43 and 44-191 have potent in vivo effects on glucose homeostasis in rodents but cannot stimulate body growth. To assess the in vitro bioactivity of these hGH fragments we tested their activity against GH-responsive FDC-P1 cell lines expressing full-length human (h), mouse (m), or rabbit (r) GH receptors (GHR). Binding specificity and affinity was tested using GHR-containing membrane preparations from three species and recombinant hGH binding protein (hGHBP). Recombinant hGH 1-43 and recombinant 44-191 stimulated proliferation of FDC-P1-hGHR cells with half-maximal effect at approximately 2000 and 100 nM, respectively, whereas intact hGH stimulates proliferation of FDC-P1-hGHR cells with ED50 of 0.02-0.03 nM. However, these fragments had minimal effect on cells expressing mGHR or rGHR. Although 44-191 did not stimulate proliferation of FDC-P1-rGHR cells, when added to these cells in the presence of 0.23 nM hGH, it antagonized hGH action in a dose-dependent manner (ED50 at 230 nM). Binding of these GH fragments was compared using membrane preparations from rabbit liver, rabbit and mouse adipose tissue, and recombinant hGHBP. Binding competition curves were consistent, with 44-191 having at least a 10-fold lower affinity for rabbit liver GHR and rabbit adipose GHR than bovine GH and a 61-fold lower affinity for hGHBP than hGH. Binding of hGH 1-43 could not be demonstrated to GHRs in rabbit liver microsomes, adipose microsomes, or to hGHBP. HGH 1-43 did not compete for insulin binding sites in adipose microsomes. In conclusion, hGH 44-191 binds with low affinity to the GHR and at supraphysiologic levels stimulates proliferation of FDC-P1-hGHR cells. At high doses, 44-191 can also antagonize GH action in FDC-P1-rGHR cells, presumably by blocking receptor dimerization. Binding of 1-43 to GHR could not be detected, and the basis for its weak in vitro mitogenic effect remains to be elucidated. The low affinity of the fragments for cloned GHRs and low biopotency in these systems suggests that the metabolic actions of these fragments are unlikely to be mediated by the cloned GHR. This raises the possibility of a separate receptor mediating metabolic effects of these fragments.

Adipose Tissue↗
PubMed1996

Decreased growth hormone receptor expression in long bones from toothless (osteopetrotic) rats and restoration by treatment with colony-stimulating factor-1.

Growth hormone (GH) is known to regulate growth and development of skeletal tissues. This study examined the distribution of growth hormone receptor (GHR) expression in tibias from normal and osteopetrotic tl/tl rats. For normal 2 week-old rats, GHR expression was detected immunocytochemically in cells of the articular and epiphyseal cartilage, primary and secondary ossification centres, zone of resting cartilage and bone marrow. Within the marrow, GHR immunopositive cells were concentrated in the central cone and largely excluded from the zone of immature progenitors at the periphery. For the marrow haemopoietic compartment, GHR expression was almost restricted to the nucleus in large mononuclear cells, adipocytes and megakaryocytes. A population of small lymphocytelike cells in the marrow periphery expressed GHR on the plasma membrane. GHR was not detected in mature erythroid cells, macrophages, granulocytes, or osteoclasts. The expression of GHR was significantly reduced in bone marrow cells of the tl/tl rat (p < 0.001) compared with normal animals. Injection of recombinant CSF-1 into tl/tl rats every 48 hours for 2 weeks from birth restored GHR-positive cells to the central core of the marrow space. The most striking change was the appearance of substantial numbers of mononuclear cells expressing abundant GHR on the cell surface. We infer that these cells are a novel subset of CSF-1 responsive cells involved in bone resorption. The differences in relative expression of GHR by bone marrow cells in untreated and CSF-1-treated tl/tl rats suggests a CSF-1-dependent recruitment of cells bearing surface GHRs.

Animals↗
PubMed1995

A growth hormone agonist produced by targeted mutagenesis at binding site 1. Evidence that site 1 regulates bioactivity.

Growth hormone (GH) is believed to signal by dimerizing its receptor through two binding sites on the hormone. Previous attempts to increase the biopotency of GH by increasing its site 1 affinity have been unsuccessful, which has led to a bias toward engineering site 2 interactions in the quest for creation of super agonists. Here we report that increasing site 1 affinity can markedly increase proliferative bioactivity in FDC-P1 cells expressing full-length GHR. In contrast, we find three site 1 mutants with affinities for site one similar to or greater than wild type GH, which have markedly decreased bioactivity. Through crystal structure analysis of the receptor interactive regions of these GH analogues, we are able to suggest why previous mutagenesis on human GH failed to improve biopotency, and thus provide a new avenue for GH and cytokine agonist design.

Animals↗
PubMed1995

The rabbit mammary gland prolactin receptor is tyrosine-phosphorylated in response to prolactin in vivo and in vitro.

We report the first in vivo study demonstrating tyrosine phosphorylation of mammary gland proteins including the prolactin receptor, in response to the injection of prolactin. Immunoblotting of mammary gland membrane extracts revealed that subunits of 200, 130, 115, 100, 90, 70, and 45 kDa display increased tyrosine phosphorylation within 5 min of prolactin administration. The 100-kDa component was identified as the full-length prolactin receptor by a variety of means including immunoprecipitation and immunoblotting with monoclonal (U5, 917, 110, and 82) and polyclonal (46) antibodies to the prolactin receptor. Maximal receptor phosphorylation was seen within 1 min of hormone injection, and to obtain a strong response it was necessary to deprive rabbits of their endogenous prolactin for 36 h. Rapid tyrosine phosphorylation of the full-length receptor was verified by its demonstration in Chinese hamster ovary cells stably transfected with rabbit prolactin receptor cDNA. Both in vivo and in vitro, the phosphorylation signal was transient, being markedly reduced within 10 min of exposure to prolactin. Tyrosine-phosphorylated receptor was shown to be associated with JAK 2 by immunoblotting of receptor immunoprecipitated from transfected Chinese hamster ovary cells with polyclonal 46. A 48-kDa ATP-binding protein was also shown to be associated with the mammary gland receptor by U5 or polyclonal 46 immunoprecipitation of receptor complexes following covalent labeling with [alpha-32P]azido-ATP. Our demonstration of prolactin receptor tyrosine phosphorylation raises the possibility of signaling pathways regulated by receptor/SH2 protein interaction, which would facilitate prolactin specific responses. The fact that a period of hormone deprivation is needed for significant hormone triggered receptor phosphorylation indicates that the mammary gland receptor exists in a largely desensitized state in vivo, analogous to the related growth hormone receptor.

Adenosine Triphosphate↗
PubMed1995

Vinculin localization and actin stress fibers differ in thyroid cells organized as monolayers or follicles.

In epithelial cells interactions between the actin cytoskeleton and cell-cell junctions regulate paracellular permeability and participate in morphogenesis. We have studied the relationship between supracellular morphology and actin-junction interactions using primary cultures of porcine thyroid cells grown either as three-dimensional follicles or as open monolayers. Regardless of morphology, thyroid cells assembled occluding and adhesive junctions containing ZO-1 and E-cadherin, respectively, and showed F-actin staining in apical microvilli and a perijunctional ring. In monolayers, actin stress fibers were also observed in the apical and basal poles of cells, where they terminated in the vinculin-rich zonula adherens and in cell-substrate focal adhesions, respectively. Surprisingly, we were unable to detect vinculin localization in follicular cells, which also did not form stress fibers. Immunoblotting confirmed significantly greater vinculin in triton-insoluble fractions from monolayer cells compared with follicular cells. Incubation of monolayers with 8 chloro(phenylthio)-cyclic AMP decreased the level of immunodetectable vinculin in the zonula adherens, indicating that junctional incorporation of vinculin was regulated by cyclic AMP. In monolayer cultures, cytochalasin D (1 microM) cause actin filaments to aggregate associated with retraction of cells from one another and the disruption of cell junctions. Despite morphologically similar perturbations of actin organization in follicular cultures treated with cytochalasin D, junctional staining of ZO-1 and E-cadherin was preserved and cells remained adherent to one another. We conclude that in cultured thyroid cells structural and functional associations between actin filaments and cellular junctions differ depending upon the supracellular morphology in which cells are grown. One important underlying mechanism appears to be regulation of vinculin incorporation into adhesive junctions by cyclic AMP.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1995

Comparison of the effects of growth hormone, insulin-like growth factor-I and fetal calf serum on mouse molar odontogenesis in vitro.

The effects of growth hormone, its mediator insulin-like growth factor-I (IGF-I), and fetal calf serum on odontogenesis were compared to those of serum-free medium. Explanted, 16-day, fetal mouse first molar tooth germs in early bell stage were grown on semisolid, serum-free medium supplemented with ascorbic and retinoic acids. Recombinant human growth hormone at 50 or 100 ng/ml, IGF-I at 100 or 200 ng/ml, or fatal calf serum at 20% concentration were added to the media. Volumetric changes in serial sections of six tooth germs per treatment over 3 days of treatment (4, 5, 6 days in vitro) were compared by digitized morphometry. Mitotic indices were also compared and the cell densities of the dental papillae recorded. Qualitative ratings of differentiation were ascribed to each tooth germ by light microscopy. Differences in volume, mitotic activity and cell densities were found. The growth hormone-treated tooth germs were not larger than the serum-free ones but had increased mitotic indices and higher cell densities in the dental papillae. IGF-I-treated tooth germs had larger volumes than with all other treatments, e.g. germs treated with 200 ng/ml of IGF-I, after 6 days in culture, were significantly larger than with all other treatments (p<0.01-<0.001). Whilst IGF-I-treated germs displayed the greatest extent of differentiation, growth hormone-treated germs also showed advanced differentiation compared to those on serum-free medium. These results suggest that growth hormone and IGF-I are involved in odontogenesis of murine teeth in vitro by affecting mitotic activity, tissue volume and cell differentiation. In conjunction with previous immunohistochemical studies that show expression of growth hormone receptor and IGF-I in developing teeth, these results provide evidence that both growth hormones and its mediator play a part in odontogenesis.

Animals↗
PubMed1995

Altered endogenous growth hormone secretory kinetics and diurnal GH-binding protein profiles in adults with chronic liver disease.

OBJECTIVE: Increased serum GH concentrations and GH responses to a variety of stimuli have been reported in patients with chronic liver disease (CLD). We investigated the pulsatile pattern of endogenous GH release and GH-binding protein (GHBP) and insulin-like growth factor-I (IGF-I) diurnal profiles in adults with cirrhosis, in comparison with healthy, matched control subjects. DESIGN: Case-control, cross-sectional. PATIENTS: Seven patients with biopsy proven cirrhosis, and sex, age, height, weight and oestrogen status matched controls. MEASUREMENTS: Serum immunoreactive GH concentrations in samples collected at 20-minute intervals for 24 hours were analysed using a multi-parameter deconvolution method to simultaneously resolve endogenous GH secretory and disappearance rates. Diurnal patterns of GHBP (specific immunoprecipitation method) and serum IGF-I (RIA after acid-ethanol extraction) were assessed. RESULTS: The mean daily GH secretion rate in patients with CLD was increased (210 +/- 93 vs 100 +/- 55 mU/I/day; P = 0.025), and GH disappearance half-time was prolonged (43 +/- 10 vs 24 +/- 9 min; P = 0.006) compared to controls. Detectable GH secretory bursts were more frequent in patients with CLD (10 +/- 1 vs 6 +/- 3/day; P = 0.038), but of similar mean mass (21 +/- 10 vs 17 +/- 8 mU/I) compared to controls. In patients with CLD, mean serum GHBP was slightly lower (63 +/- 36 vs 71 +/- 14% pooled control; P > 0.1). Fasting serum IGF-I concentrations (after size-exclusion HPLC) were lower in the patients with CLD (13 +/- 5 vs 21 +/- 2 nmol/l; P < 0.0001). Multiple regression analysis showed that GH secretion rate was increased in patients with CLD with higher Child's classifications (R2 = 0.86; P = 0.002) and with lower serum IGF-I concentrations measured after HPLC (R2 = 0.11; P = 0.044). CONCLUSIONS: Adults with chronic liver disease have (1) increased total daily GH secretion rates, which appear to be influenced by disease severity and diminished serum IGF-I-mediated negative feedback; (2) markedly impaired endogenous GH clearance, possibly reflecting changes in hepatic GH-receptor status; and (3) GHBP levels which do not correlate with GH kinetics or serum IGF-I concentrations.

Adult↗
PubMed1995

Effect of growth hormone on the distribution of decorin and biglycan during odontogenesis in the rat incisor.

Previous studies have shown that growth hormone can influence the expression of N-acetylgalactosamine-containing molecules in the extracellular matrix of developing rat incisors. N-acetylgalactosamine is a principal component of proteoglycans containing chondroitin sulfate and dermatan sulfate, as well as of some glycoproteins. Since chondroitin sulfate proteoglycans are identifiable components in enamel, dentin, and cementum, we have tested the hypothesis that growth hormone modulates their expression in developing rat incisors. The distribution of the chondroitin-sulfate-rich proteoglycans, decorin and biglycan, was investigated. We used the Lewis dwarf rat as a model because their circulating growth hormone levels are markedly reduced. Polyclonal antibodies against decorin and biglycan were used to localize these two proteoglycans. Semi-quantitative assessments of the staining patterns and intensities were made for each proteoglycan within compartments of the developing teeth. In normal Lewis rats, decorin and biglycan differentially expressed throughout the enamel organ, dental papilla, and dental follicle. Decorin displayed a wide distribution throughout all three regions and was closely associated with different cellular components. In contrast, biglycan showed little association with cells and was identified in the predentin and osteoid matrices. The expression of both proteoglycans was dramatically decreased in the growth-hormone-deficient animals. Administration of growth hormone to the dwarf rats markedly elevated the expression of both proteoglycans, approximating the distribution and intensity of staining seen in normal animals. These findings confirm that growth hormone status can modulate the expression of decorin and biglycan, and hence matrix deposition, in the rat tooth.

Animals↗
PubMed1995

Growth hormone and colony-stimulating factor 1 share multiple response elements in the c-fos promoter.

The c-fos protooncogene is induced by GH rapidly, but transiently. Induction requires C kinase activation and the serum response element, and recent binding studies have also implicated the sis-inducible element (SIE). However, no systematic study of the promoter elements responsible for transactivation by GH has been undertaken. Here we used Chinese hamster ovary K1 cells transiently cotransfected with rabbit GH receptor and c-fos promoter-luciferase constructs to demonstrate that the major region responsible for GH induction is located between 284-396 base pairs upstream of the transcription start site. Full induction by GH requires all of the known elements located in this region to be intact, including the SIE or signal transducer and activator of transcription binding element. We also report novel negative elements located around -216 upstream of the start site that reduce induction by GH and provide gel shift evidence for factors binding in this region. Cotransfection of Chinese hamster ovary K1 cells with c-fms and c-fos promoter constructs followed by the addition of CSF-1 revealed that these same c-fos elements contribute to transactivation by c-fms. Serum also uses the same elements to induce c-fos expression, except for the SIE. These results indicate that GH receptor and c-fms tyrosine kinase operate through multiple common response elements to regulate c-fos gene expression despite their structural differences.

Animals↗