14102 studies
The purpose of this study was to evaluate the contribution of endogenous GH-releasing hormone (GHRH) to exogenous GH-releasing hexapeptide (GHRP-6) activity, and to determine whether TRH or GnRH are endogenous analogs of GHRP-6. The activity of GHRP-…
Forty-one primiparous beef heifers were used over 2 yr to evaluate the effect of prepartum administration of a growth hormone-releasing factor analog (GRF-A) or growth hormone-releasing factor (GRF(1-29)-NH2) on somatotropin (ST), insulin-like growth…
Four new growth hormone-releasing hormone (GHRH) analogs with C-terminal agmatine were compared with the parent human GHRH(1-29)NH2 fragment to assess their abilities to increase serum concentrations of growth hormone (GH) in the bovine. The four ana…
We have recently reported that pulsatile GH secretion is elevated 24 h after unilateral nephrectomy (UNX) in adult rats. In addition, suppression of the increase in GH with an antagonist to GH-releasing factor (GRF-AN) significantly attenuated compen…
Previous research on growth hormone-releasing factor analogues has used pituitary cell culture assay systems to evaluate in vitro their biological activity. However, binding assay systems in which receptor affinity and peptide stability can be assess…
Solution structures were determined for a linear analogue of growth hormone releasing factor (GRF), and cyclic and dicyclic analogues in which the side chains of aspartyl and lysyl residues spaced at positions i-(i + 4) were joined to form a lactam.…
In an attempt to establish the reference pattern and the plasma growth hormone (GH) response to growth hormone releasing factor (GRF) (1-29)NH2, 5 normal stature with single kidney children and 14 with idiopathic GH deficient dwarfism received intrav…
The shortened analogue of growth hormone releasing factor (GRF) Ro 23-7861 (1) has a molecular weight of 3929 daltons [equivalent to GRF (1-29)] and is more potent than the endogenous GRF (1-44). The in vitro hairless guinea pig model and vertical an…
Recombinant alpha-amidating enzyme was used in the semisynthesis (1-5 mg scale) of human growth hormone-releasing factor, GRF(1-44)-NH2, by in vitro enzymatic oxidation of the glycine-extended precursor, GRF(1-44)-Gly-OH, prepared by solid-phase synt…
Analogs of the 29-amino acid sequence of growth hormone-releasing hormone (GH-RH) with agmatine (Agm) or Lys-NH2 in position 29 have been synthesized by the solid-phase method, purified, and tested in vitro. Except for one peptide, all analogs contai…
Clinical and veterinary uses of growth hormone-releasing factor [GRF(1- 29)NH2] require the design of analogs that are resistant to proteolysis by serum and liver degrading enzymes. This study investigated rat GRF(1-29)NH2 processing in serum and liv…
The effects of aging and intake on growth hormone (GH) kinetics and GH-releasing factor (GRF)-induced GH concentrations were studied in two groups of 12 Holstein heifers each (80 d, 85 kg: young; and 273 d of age, 246 kg: old). Each group was then eq…
The kinetics and selectivity of proteolysis of synthetic human growth hormone-releasing factor and analogs by purified human placental dipeptidyl peptidase IV (DPP IV) were studied by HPLC. The initial rates of Ala2-Asp3 cleavage (pH 7.8, 37 degrees…
Aging is associated with decreased GH and insulin-like growth factor-I (IGF-I) levels and lean body mass, and increased body fat. Recombinant human GH treatment of old men partially reverses body composition changes. Administration of GH-releasing ho…
Fifty-two Yorkshire x Landrace gilts were equally allotted to four treatments: 1) controls, saline injections (CTL); 2) injections of 12 mg of growth hormone-releasing factor (GRF) (1-29)NH2 thrice daily (0700, 1500, and 2300) from d 100 of gestation…
Previous studies have demonstrated that glucagon-superfamily peptides stimulate insulin release from the pancreatic islets in a glucose dependent manner. In this study we have carried out a structure-activity study of their insulinotropic activity us…
A superpotent analog of human growth hormone-releasing factor, [desNH2Tyr1,D-Ala2,Ala15]-GRF(1-29)-NH2 (4), was prepared from the precursor, [Ala15,29]-GRF(4-29)-OH (1), by a two-step enzymatic semisynthesis. The amidated C-terminus, essential for hi…
Patients with hyperthyroidism have reduced spontaneous and stimulated growth hormone (GH) secretion. The aim of our study was to evaluate the effects of galanin, a novel neuropeptide which stimulates GH secretion in man, on the GH response to GHRH in…
Cholinergic neurotransmission exerts a physiological control on GH secretion. Pirenzepine (Pz), an antagonist of muscarinic receptors, by enhancing hypothalamic somatostatin release, inhibits stimulated GH secretion in normal subjects but not in acro…
An 18-kDa hemagglutinin which possesses the property of inducing both aggregation of amebocytes and agglutination of erythrocytes has been isolated from Limulus polyphemus amebocytes and purified by ion exchange chromatography. This nonglycosylated,…