Development of a heterologous radioimmunoassay for somatomedin C in sheep blood

Underwood, Louis E.; D’Ercole, A. Joseph; Copeland, Kenneth C.; Wyk, Judson J. Van; Hurley, Thomas W.; Handwerger, Stuart

doi:10.1677/joe.0.0930031

Cited by 65 publications

(21 citation statements)

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“…This would indicate a molecular mass of approximately 65 kDa, much lower than the 150 kDa reported when the separation of plasma or serum from several species was carried out by Sephadex G-200 or Superóse chromatography at neutral pH (Kaufmann étal. 1978;Furlanetto, 1980;Underwood, D'Ercole, Copeland et al 1982;Wilkins & D'Ercole, 1985;Hodgkinson et al 1987). However, the measured difference in molecular mass is not real but a property ofthe Fractogel column.…”

Section: Discussionmentioning

confidence: 99%

Plasma half-lives of native and modified insulin-like growth factor-I in lambs

Francis

McNamara²,

Filsell³

et al. 1988

Journal of Endocrinology

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The clearance of labelled insulin-like growth factor-I (IGF-I) has been measured in lambs following acid gel-permeation chromatography and immunoprecipitation of plasma samples. The half-lives obtained in three experiments were between 5 and 7h. Chromatography at neutral pH on a Fractogel HW55(S) column demonstrated that all the radioactivity associated with undegraded peptide in plasma was bound to a carrier protein. Similar studies with IGF-I that had been reduced by prior dithiothreitol treatment showed that two-thirds of the initial radioactivity in plasma decayed with a much shorter half-life and represented material that did not bind to carrier proteins in plasma. The remaining radioactivity was both associated with a binding protein and exhibited the characteristically long half-life of the native growth factor. Analysis of plasma samples using reversed-phase chromatography demonstrated that the radioactive component with a long half-life was IGF-I while that with a short half-life had been reoxidized to an incorrect form of the growth factor. When reoxidation of reduced IGF-I was blocked by S-carboxymethylation before injection of the radioactive peptide into lambs, it remained unbound in plasma and had a 0.8-0.9 h half-life. We suggest that reduced IGF-I only associates with the binding protein upon oxidation and correct folding and that this association is necessary in order for IGF-I to have a relatively long half-life.

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Section: Discussionmentioning

confidence: 99%

Plasma half-lives of native and modified insulin-like growth factor-I in lambs

Francis

McNamara²,

Filsell³

et al. 1988

Journal of Endocrinology

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“…SM-C was measured with RIA kits (Nichols Institute Diagnostics, Los Angeles, CA). Before assay, serum samples were acidified by the method of Underwood et al (13). Equal volumes of serum and 0.1 M glycineglycine HC1 buffer, with a final pH of 3.8 ± 0.1, were mixed and incubated at 37 C for 48 h. Samples were neutralized with a volume of 1 N NaOH equal to 3% of the original incubation volume.…”

Section: Methodsmentioning

confidence: 99%

Purified Chicken Growth Hormone (GH) and a Human Pancreatic GH-Releasing Hormone Increase Body Weight Gain in Chickens

et al. 1986

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Purified chicken GH (cGH) and a synthetic human GH-releasing hormone (hpGRF) were tested for the ability to improve growth performance in chickens. Purified cGH was given to 4-week-old cockerels at 5, 10, and 50 micrograms/day for 14 days via daily iv injection. Body weights of chickens receiving 5 and 10 micrograms/day cGH were significantly increased at 6 days by 13.5% and 11.2%, respectively, relative to control values. At 14 days, body weights averaged 8.1% and 7.7% greater than controls, but these values were not statistically significant. There was a slight stimulation of body weight gain in chickens receiving 50 micrograms/day cGH. In general, cGH produces a transient stimulation of body weight gain in chickens. hpGRF was also given to 4-week-old cockerels for 14 days via daily iv injection at 0.1, 1.0, and 10.0 micrograms/day. hpGRF at 0.1 microgram/bird daily increased body weight on day 14 (9.1% over the control value). The stimulating effects of hpGRF on body weight are also transient. The effects of cGH on serum somatomedin-C (SM-C) were examined. Serum SM-C concentrations were significantly elevated 24 and 36 h after injection of cGH. In conclusion, purified cGH and hpGRF appear to have some growth-promoting activity. The stimulatory effect of hpGRF on weight gain may be mediated via GH, and the stimulatory effect of cGH could be mediated through SM-C.

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“…The effects of binding pro¬ teins were eliminated by acidification of plasma and immediate dilution before addition to the assay tubes, or chromatographing by gel permeation to separate liberated SM-C from binding proteins. For the acidifi¬ cation and dilution of samples, plasma was incubated with glycyl-glycyl-HCl (0-2 mol/1, pH 2-0) for 24 h at room temperature to achieve a final plasma pH of 3-5 (Underwood, D'Ercole, Copeland et al 1982). Plasma samples were further diluted 1:80 with Tris assay buffer (005 mol Tris/1, 001 mol EDTA/1, 0-25% bovine serum albumin (BSA), 005% (v/v) Tween 20, pH 8-0 at 4°C ) and 50 pi were used immediately as assay volume.…”

Section: Animalsmentioning

confidence: 99%

Influence of parasitism on plasma concentrations of growth hormone, somatomedin-C and somatomedin-binding proteins in calves

Elsasser¹,

Rumsey²,

Hammond³

et al. 1988

Journal of Endocrinology

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A parasitic disease model (sarcocystosis) was used to study the effects of infection and associated plane of nutrition on GH and somatomedin-C (SM-C) patterns in plasma, and SM-C binding protein patterns in plasma from 4-month-old male Holstein calves. Calves, matched by age and rate of growth before the experiment, were divided into three treatment groups (n = 7). In the first (control), animals were uninfected and food was available ad libitum; in the second, animals were infected with Sarcocystis cruzi and food was available ad libitum. The third group consisted of uninfected animals pair-fed to the level of feed intake of the infected animals. Blood samples were obtained at various times after infection for analysis of the secretory patterns of GH (day 27 after infection, samples every 10 min for 6 h), SM-C (days 27, 35 and 58 after infection) or binding protein (day 42 after infection). Samples were analysed for GH and SM-C by radioimmunoassay. Relative molecular weights of binding proteins were assessed by elution patterns from gel permeation columns. Clinical signs of infection were manifest abruptly on day 26 after infection. Voluntary feed intakes of infected calves as a per cent of control calves were 18, 46 and 78 on days 27, 35 and 58 after infection respectively. Plasma GH concentrations were lower in infected and pair-fed than in control calves (P less than 0.05). Plasma SM-C concentrations were reduced in calves with diminished feed intakes and lower still in infected calves (P less than 0.05). Plasma SM-C was positively correlated with nitrogen retention across treatment groups (r = 0.81). Two classes of binding proteins differing in molecular weight were identified. The relative amounts of each binding protein in plasma were reduced during low feed intake with some differences in the endogenous saturation affected by infection. These data suggest that altered growth and metabolism in parasitized calves may arise in part from both nutritional and infection-mediated effects on the regulation of GH, SM-C and SM-C binding proteins.

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Development of a heterologous radioimmunoassay for somatomedin C in sheep blood

Cited by 65 publications

References 0 publications

Plasma half-lives of native and modified insulin-like growth factor-I in lambs

Plasma half-lives of native and modified insulin-like growth factor-I in lambs

Purified Chicken Growth Hormone (GH) and a Human Pancreatic GH-Releasing Hormone Increase Body Weight Gain in Chickens

Influence of parasitism on plasma concentrations of growth hormone, somatomedin-C and somatomedin-binding proteins in calves

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