Biomedical subjects

D S Schalch

Publications and source records attributed to D S Schalch.

At least 19 recordsLinked to original sources

PubMed1998

Serum insulin-like growth factors and their binding proteins in patients with hepatic failure and after liver transplantation.

The liver is the major source of circulating insulin-like growth factor-I and -II (IGF-I and IGF-II) and several of their binding proteins (BPs). This study examined the effects of end-stage liver disease (ESLD) and subsequent liver transplantation (LT) on serum levels of these growth factors and their BPs in four children and six adults for up to 2 years. Serum IGF-I and IGF-II were quantified by radioimmunoassay (RIA), IGFBP-3 by immunoradiometric assay (IRMA), and changes in IGFBP-1, -2, -3, and -4 were estimated by Western ligand blotting (WLB). In severe hepatic disease, serum concentrations of IGF-I (10 +/- 5 ng/mL) and IGF-II (126 +/- 32 ng/mL) were significantly (P < .01) less than in normal controls (170 +/- 37 and 590 +/- 41 ng/mL, respectively). One year following LT, the mean levels of IGF-I (344 +/- 55 ng/mL) and IGF-II (627 +/- 38 ng/mL) were within normal limits and remained so for the duration of the study. Patients exhibited considerable variation not only in the rate of achieving normal IGF-I and IGF-II concentrations, but also in the ultimate height and stability of these peptide levels. Serum IGFBP-3 in hepatic failure (580 +/- 140 ng/mL) was significantly (P < .05) lower than in controls (2,900 +/- 220 ng/mL) and increased to normal levels (3,650 +/- 360 ng/mL) 2 to 14 weeks after LT. Serum levels of IGFBP-1, -2, and -4 before and after LT were variable but usually remained within normal limits compared with control sera. The decreases observed in IGF-I, IGF-II, and IGFBP-3 in patients with hepatic failure and their subsequent restoration after LT probably result primarily from the reduced number of functional hepatocytes in ESLD and their subsequent replacement by healthy hepatic tissue. These changes may also result from hormonal alterations and nutritional deficiencies known to exist in patients with severe liver dysfunction, which are corrected by LT. We conclude that LT in patients with severe hepatic insufficiency enhances the potential for normal cell growth and replication by restoring serum IGF-I, IGF-II, and IGFBP-3 concentrations to normal concomitantly with the improvement in hormonal and nutritional status.

Adolescent↗

PubMed1997

Hypocalcemia and skeletal disease as presenting features of celiac disease.

OBJECTIVE: To describe 15 patients examined for hypocalcemia, skeletal disease, or both in whom the diagnosis of celiac disease was subsequently made. DESIGN: Observational case series. PATIENTS: Fifteen patients (7 women and 8 men) were examined for hypocalcemia (n = 11), skeletal disease (n = 3), or both (n = 1). The diagnosis of celiac disease was subsequently made. The mean age of the patients was 62 years, and 11 patients were 60 years of age or older. RESULTS: Four patients had no gastrointestinal symptoms, 7 patients had mild or intermittent gastrointestinal symptoms, and 4 patients had persistent diarrhea. Ten patients had experienced weight loss. The serum total alkaline phosphatase level was elevated in 10 of 15 patients, the parathyroid hormone level was elevated in all patients, and the urinary calcium level was low in all 6 of the patients tested. The level of 25-hydroxyvitamin D was frankly low in 4 patients, marginal in 8 patients, and normal in 3 patients. Bone mineral density was reduced in all 8 patients in whom it was measured. CONCLUSIONS: Celiac disease should be considered in patients with unexplained metabolic bone disease or hypocalcemia, especially because gastrointestinal symptoms may be absent or mild. Advanced age does not exclude the diagnosis of celiac disease.

Adult↗

PubMed1994

Anabolic effect of IGF-I coinfused with total parenteral nutrition in dexamethasone-treated rats.

We determined the anabolic effects of recombinant human insulin-like growth factor I (rhIGF-I, 800 micrograms/day) coinfused with total parenteral nutrition (TPN) in male Sprague-Dawley rats (230-250 g), with and without dexamethasone (Dex, 70 micrograms/day)-induced catabolism for 6 days. Dex without IGF-I increased serum insulin concentrations 300% and glucose concentrations 20%; IGF-I plus Dex significantly reduced serum insulin and glucose concentrations to TPN control levels. Animals given Dex without IGF-I lost 30 +/- 3 g; IGF-I plus Dex reduced the weight loss to 9 +/- 3 g, P < 0.001. IGF-I without Dex resulted in a weight gain of 14 +/- 2 g compared with a gain of 4 +/- 1 g in TPN controls, P < 0.01. Determination of nitrogen balance and body composition confirmed that changes in body weight were due to corresponding changes in nitrogen excretion and total body protein content. IGF-I significantly reduced TPN-induced intestinal atrophy, resulting in a 30% increase in weight of the small intestine plus colon compared with TPN without IGF-I. These results indicate that coinfusion of rhIGF-I with TPN counteracts Dex-induced insulin resistance and has a significant net anabolic effect when given with or without Dex in rats.

Analysis of Variance↗

PubMed1994

Adverse effects of recombinant human insulin-like growth factor I in obese insulin-resistant type II diabetic patients.

Data from studies in diabetic rodents and evidence from clinical situations of severe resistance to insulin suggest that insulin-like growth factor I (IGF-I) is able to at least partly overcome insulin resistance. To assess the efficacy of recombinant human IGF-I in subjects with the most common form of insulin resistance, e.g., obese, type II diabetic patients, we administered recombinant human IGF-I (rhIGF) in doses of 120 and 160 micrograms/kg twice daily for 4-52 days to seven such individuals who had been treated previously with high doses of insulin (> 0.7 U.kg-1 x day-1). Four patients exhibited comparable or enhanced, whereas three had diminished, blood glucose control on rhIGF-I relative to that while on twice daily NPH insulin during the six-week control period. The occurrence of adverse effects in all patients compelled us to discontinue rhIGF-I administration before completing the 8-week treatment period. These adverse effects included edema primarily on the face and hands, mild weight gain, occasional dyspnea, bilateral jaw tenderness, arthralgias and myalgias, fatigue, tachycardia, flushing, orthostatic hypotension, and local burning at the injection site. We conclude that the frequency and severity of side effects associated with administering high-dose subcutaneous rhIGF-I to obese insulin-resistant diabetic patients make it an unacceptable therapeutic agent for these patients despite its ability to produce reasonable blood glucose control in approximately 50% of them.

Adult↗

PubMed1993

Short-term effects of recombinant human insulin-like growth factor I on metabolic control of patients with type II diabetes mellitus.

Recombinant human insulin-like growth factor I (rhIGF-I) lowers blood glucose, serum insulin, C-peptide, and lipid levels in healthy and diabetic animals and humans. We hypothesized that rhIGF-I might control blood glucose levels and concomitantly reduce pancreatic insulin secretion in patients with type II diabetes. If true, rhIGF-I might serve as a therapeutic agent that could mitigate some of the detrimental effects of hyperinsulinemia secondary to insulin resistance in these patients. In this study, we treated 12 patients with type II diabetes mellitus twice daily for 5 days with sc rhIGF-I in doses of 90, 120, or 160 micrograms/kg body weight. Metabolic parameters in the fasting and postprandial states were assessed during a 3-day baseline period, the rhIGF-I treatment period, and a 3-day follow-up period, respectively. Administration of rhIGF-I significantly reduced mean (+/- SD) concentrations of fasting blood glucose (12.3 +/- 4.5 to 9.1 +/- 2.6 mmol/L), serum insulin (98 +/- 52 to 56 +/- 27 pmol/L), and C-peptide (993 +/- 298 to 728 +/- 232 pmol/L). It also decreased postprandial (area under the curve) blood glucose (32.5 +/- 12.7 to 23.9 +/- 8.1 mmol/L.h), serum insulin (1102 +/- 707 to 467 +/- 332 pmol/L.h), and C-peptide (5958 +/- 2747 to 3442 +/- 1523 pmol/L.h). The administration of rhIGF-I was also associated with a small but significant reduction in serum triglycerides (6.76 +/- 3.45 to 5.32 +/- 2.59 mmol/L) and total cholesterol (6.13 +/- 1.25 to 5.66 +/- 1.20 mmol/L), 24-h creatinine clearance increased significantly (85 +/- 30 to 133 +/- 51 mL/min), and microalbuminuria was unchanged. Although rhIGF-I was reasonably well tolerated, side effects included low-grade edema, mild and mainly asymptomatic orthostatic hypotension, and bilateral temporomandibular tenderness. We conclude that short-term treatment of type II diabetic patients with rhIGF-I favorably affects metabolic control and enhances kidney function. An assessment of the risk/benefit ratio of rhIGF-I administration to this group of patients awaits extended experiments.

Aged↗

PubMed1992

Ethanol-fed Sprague-Dawley rats maintain normal levels of insulin-like growth factor I.

Ethanol-fed rats do not gain weight as fast as their isoenergetically pair-fed controls; the reasons for this slower rate of growth remain uncertain. Insulin-like growth factor I (IGF-I) is a major component of the growth-promoting endocrine system. To determine whether ethanol impairs growth by interfering with this component of the endocrine system, rats were pair-fed ethanol-containing and control liquid diets. When rats were meal-fed on the day before the experiment there were no differences in serum IGF-I concentrations or hepatic IGF-I mRNA levels between ethanol-fed and control animals after 2, 3 or 4 wk. These results indicate that ethanol consumption per se does not interfere with IGF-I production and that energy derived from ethanol sustains this component of the growth-promoting endocrine system as well as carbohydrate energy. The schedule used to administer the diets, however, did have a significant effect on hepatic IGF-I mRNA levels. When after 4 wk of dietary treatment rats were not meal-fed but received their entire dietary ration in a single morning feeding on the day before the experiment, the ethanol-fed animals had significantly higher hepatic IGF-I mRNA levels than their pair-fed controls. This finding indicates that these animals are nutritionally dissimilar despite isoenergetic pair-feeding.

Animals↗

PubMed1990

Effects of streptozotocin-induced diabetes mellitus on growth and hepatic insulin-like growth factor I gene expression in the rat.

Poorly controlled diabetes mellitus in humans and animals is often accompanied by impaired growth. We undertook this study in young rats to determine whether the reduction in growth rate associated with streptozotocin (STZ)-induced diabetes might be related to changes in both serum insulin-like growth factor I (IGF-I) and IGF-II levels, and, if so, whether these changes reflect alterations in serum growth hormone (GH) and in hepatic IGF-I and IGF-II gene expression. Serum rat GH (rGH) levels were variable during the first 4 days after STZ administration, but during the subsequent 5- to 11-day period the mean (+/- SEM) levels in insulin-treated (DI) (21.4 +/- 4.9 ng/mL) and untreated (D) (8.5 +/- 1.5 ng/ml) diabetic rats were significantly (P less than .001) lower than in controls (C) (117.8 +/- 22.9 ng/mL). Multiple transcripts of IGF-I (7.0, 4.0, 1.9, 1.0 kb), but barely detectable amounts of IGF-II mRNA, were found in the livers of normal and diabetic rats by Northern blot analysis. Using dot blot analysis, we have shown that the abundance of total hepatic IGF-I mRNA in untreated, growth-retarded diabetic animals decreases rapidly over a period of 3 days after STZ administration. Both serum IGF-I and IGF-II levels are also diminished during this interval in these markedly hyperglycemic rats. Insulin treatment for 3 to 4 days, started either immediately (6 hours) or within 3 days after administering STZ, blunts diabetes-induced impairment of growth and restores mean hepatic IGF-I mRNA abundance to control levels, but does not normalize serum IGF-I and IGF-II concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Infusion of human insulin-like growth factor I (IGF-I) into malnourished rats reduces hepatic IGF-I mRNA abundance.

To determine whether the serum level of IGF-I influences its hepatic synthesis through negative feedback regulation, we infused 200 micrograms/d of human IGF-I subcutaneously into young male rats eating either an energy-restricted or ad lib diet. In energy-restricted rats, a two-fold increase in serum IGF-I concentration produced a 41% increase in growth rate at the end of one week, and a 30% decrease in steady state hepatic IGF-I mRNA and 56% drop in serum GH at the end of two weeks. In ad lib fed rats, the increased serum IGF-I concentration neither enhanced growth rate nor significantly reduced hepatic IGF-I mRNA abundance or serum GH levels. These data suggest that the abundance of hepatic IGF-I mRNA in energy-restricted rats is controlled, in part, by serum IGF-I levels via negative feedback regulation.

Animals↗

PubMed1987

Effect of a carbohydrate-restricted, calorie-reduced diet on the growth of young rats and on serum growth hormone, somatomedins, total thyroxine and triiodothyronine, free T4 index, and total corticosterone.

We have studied the effect of a carbohydrate-restricted, calorie-reduced diet on the growth of young rats and on serum levels of GH, somatomedins [insulin-like growth factors (IGFs) I and II], total T4 and T3, free T4 index, and total corticosterone. Experimental animals consumed the same quantities of protein and fat as controls, but only 50.3% as much carbohydrate and 76% as many calories. While the experimental group grew at 69.4% of the control rate, their mean (+/- SEM) GH level (175.7 +/- 36.9 ng/mL) was not significantly different from that in the control group (180 +/- 30 ng/mL). In contrast, serum total IGF and IGF-I, while not correlated with serum GH levels, were significantly correlated in all animals with body weight (r = .87 and r = .82, respectively, P less than .01) and tail length (r = .61 and r = .62, respectively, P less than .01). The somatomedin levels of the carbohydrate-restricted rats were significantly lower than those of their age-matched, but not weight-matched, controls by the eighth day of study. Serum T4, T3, and free T4 index were not significantly different in these two groups, while total corticosterone in the experimental group (245 +/- 73 ng/mL) was slightly lower than in controls (292 +/- 80 ng/mL, P less than .05). These data indicate that by restricting carbohydrate intake we have compromised the anabolic use of dietary protein by growing rats, resulting in a retardation of growth and a reduction in serum total IGF and IGF-I levels.

Animals↗

PubMed1987

Nutritionally-induced changes in hepatic insulin-like growth factor I (IGF-I) gene expression in rats.

We have used [32P]-labeled human and mouse IGF-I cDNA probes to identify three hepatic IGF-I transcripts (8.0, 1.8 and 1.1 kilobase) in rats and to quantify nutritionally-induced changes. During fasting, the major (8.0 kilobase) transcript decreased progressively after 6 h, and at 30 h was only 39% as abundant as in the nonfasted control. Refeeding animals fasted 24 h caused a marked rise in the 8.0-kb mRNA by 6 h, and an 18-fold increase at 30 h. The two minor transcripts also appeared to behave in a similar manner. Serum IGF-I concentrations paralleled levels of the major hepatic transcript during periods of both fasting and refeeding, verifying the central role of nutrition in growth regulation.

Animals↗

PubMed1987

Interaction of insulin-like growth factor II with rat chondrocytes: receptor binding, internalization, and degradation.

We have characterized the interaction of insulin-like growth factor II (IGF-II) with its plasma membrane receptor(s) on cultured rat chondrocytes. Our studies, paralleling those already reported for IGF-I, demonstrate that [125I]IGF-II binds to these receptors with a high degree of affinity and that this process is reversible, specific, and time, temperature, and concentration dependent. At 4 C, unlabeled IGF-II causes half-maximal displacement of the labeled ligand at a concentration of 22 ng/ml, whereas IGF-I is approximately 1/200th as potent, and insulin does not displace [125I]IGF-II even at a concentration of 10 micrograms/ml. Maximum binding to chondrocytes (44% of added radioactivity) occurred after 4-5 h of incubation at 15 C. Compared to [125I]IGF-I binding, this value is 7-fold higher and is consistent with an affinity constant (Ka = 3.8 X 10(8) M-1) approximately 1 order of magnitude greater. Photoaffinity labeling studies disclose that IGF-II binds primarily to the type II IGF receptor, which has an apparent mol wt of 220K when electrophoresed under nonreducing conditions and 270K under reducing conditions. Nanomolar concentrations of IGF-II stimulated the synthesis of DNA and RNA in a dose-related manner, and micromolar concentrations of insulin demonstrated an additive effect with respect to the incorporation of [3H]thymidine into DNA, but not [3H]uridine into RNA. Preincubation of rat chondrocytes with increasing concentrations of insulin caused a marked dose-related increase in [125I]IGF-II binding, a phenomenon previously reported in several other cell types. In addition to defining the binding characteristics of IGF-II, we used the lysosomotropic agents chloroquine and ammonium chloride to demonstrate that its ligand-receptor complex, like that of IGF-I, is internalized and degraded partially via the lysosomal pathway.

Affinity Labels↗

PubMed1986

Interaction of insulin-like growth factor I/somatomedin-C with cultured rat chondrocytes: receptor binding and internalization.

We have characterized the interaction of insulin-like growth factor I/somatomedin C (IGF-I/Sm-C) with its plasma membrane receptors on cultured rat chondrocytes. Our studies have demonstrated that [125I]IGF-I/Sm-C binding to these receptors is a relatively specific, reversible, and time-, temperature-, pH-, and concentration-dependent process. Insulin displaces [125I]IGF-I/Sm-C from its receptors on rat chondrocytes, but with a potency only 10(-4) that of IGF (I and II). Using the known lysosomotropic agents chloroquine and ammonium chloride as well as the substituted diamine monodansylcadaverine, we have shown that this 125I-labeled Sm is internalized and partially degraded via the lysosomal pathway. These conclusions have been further supported by photoaffinity labeling studies which, surprisingly, demonstrate that the predominant IGF receptor on chondrocytes is the type II receptor, and that [125I]IGF-I/Sm-C is bound primarily in this ligand-receptor complex which is internalized and degraded, in part, by lysosomes.

Ammonium Chloride↗

PubMed1985

Protein utilization in growth: effect of lysine deficiency on serum growth hormone, somatomedins, insulin, total thyroxine (T4) and triiodothyronine, free T4 index, and total corticosterone.

We have studied the effect of a lysine-deficient diet on the growth of young rats and on serum levels of GH, somatomedins [insulin-like growth factors (IGFs) I and II], insulin, total T4 and T3, free T4 index, and total corticosterone. Rats eating a wheat gluten diet consumed about one third as much lysine as controls eating an isocaloric and isonitrogenous casein diet and grew at approximately 56% of the control rate. The mean (+/- SEM) GH level in the experimental group (68 +/- 9 ng/ml) was significantly lower (P less than 0.01) than that in the controls (106 +/- 17 ng/ml), but was not correlated with age or body weight and was only weakly correlated with total IGF. In contrast, total IGF and IGF-I were significantly correlated with age and body weight (r = 0.86 and r = 0.84, respectively; P less than 0.01). The levels of these somatomedins in the wheat gluten-fed animals were consistently and significantly lower than those in their age-matched controls, but not significantly different from those in their weight-matched controls, throughout the study. Serum total T4 and T3 (but not the free T4 index) and corticosterone were significantly elevated in the experimental rats, perhaps representing a serum binding globulin adaptation to lysine deficiency that is not clearly understood. In this study, we have compromised the ability of growing rats to use dietary protein anabolically to examine the nutritional effects of qualitative protein deficiency on growth and the growth-promoting endocrine system.

Aging↗

PubMed1985

Protein utilization in growth: effect of calorie deficiency on serum growth hormone, somatomedins, total thyroxine (T4) and triiodothyronine, free T4 index, and total corticosterone.

We have studied the effect of a calorie-restricted diet on the growth of young rats and on serum levels of GH, somatomedins (insulin-like growth factors I and II), total T4 and T3, free T4 index, and total corticosterone. Experimental rats consumed the same quantities of protein and carbohydrate as control animals, but less fat, so that their calorie intake was approximately 76% that of controls. The mean (+/- SEM) GH level in the experimental group (78 +/- 21 ng/ml) was not significantly different from that in the control group (89 +/- 31 ng/ml). In contrast, serum total insulin-like growth factor and insulin-like growth factor IGF-I, while not correlated with serum GH, were significantly correlated with age and body weight (r = 0.93 and r = 0.69, respectively; P less than 0.01). The levels of these somatomedins in the calorie-restricted rats were significantly lower than those in their age-matched, but not weight-matched, controls after approximately 2 weeks of study. Serum T4, T3, and free T4 index were all significantly reduced in the experimental animals and may represent an adaptive response to calorie restriction. Serum corticosterone levels in the experimental and control rats were essentially identical. In this study, by restricting calorie intake we have compromised the ability of growing rats to use dietary protein anabolically, creating a useful model to examine in some detail nutritional influences on growth and the growth-promoting endocrine system.

Animals↗

PubMed1985

Somatomedin synthesis by a subclone of Buffalo rat liver cells. Influence of divalent cations on rIGF-II release.

Previous studies have provided evidence that biosynthesis and secretion of somatomedin (SM) is not only hormone dependent, but also modulated by nutritional factors. Little is known, however, about the role of divalent cations in these processes. A subclone of Buffalo rat liver (BRL) cells, known to secrete rat insulin-like growth factor-II (rIGF-II) into serum-free medium, was used to define the influence of Ca2+, Mg2+ and Zn2+ on this function. The secretion of rIGF-II by subclone BRL-3SC appears to be quite stable in minimal essential medium (MEM) over a wide range in Ca2+ concentrations (0.18-3.0 mM) but is reduced to only 8% of controls in the absence of Ca2+ (P less than 0.01). Reducing, and even eliminating, the extracellular concentration of Mg2+ alone caused no change in basal rIGF-II release, while simultaneously decreasing Mg2+ and Ca2+ results in a marked drop in the secretion of this SM, reaching a nadir of 38% of controls in the absence of Mg2+ (P less than 0.001). A Mg2+ concentration of 10 mM, or 25 times 'normal', did not alter the basal secretion of rIGF-II. Eliminating the trace amount (0.8 nM) of Zn2+ in MEM by chelation with EDTA decreased rIGF-II secretion to 62% of control levels (P less than 0.01), while increasing the concentration of this cation to 3 mM did not alter the basal release of this SM. Decreased rIGF-II release in the presence of EGTA and EDTA is not due to irreversible cell damage since the secretion of this SM was restored to normal during subsequent reincubation in MEM alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1983

Somatomedin synthesis by a subclone of Buffalo rat liver cells: characterization and evidence for immediate secretion of de novo synthesized hormone.

Previous studies have reported that cultured Buffalo rat liver (BRL-3A) cells synthesize and release a somatomedin called multiplication-stimulating activity, a major component of which is rat insulin-like growth factor-II (rIGF-II). We have isolated a subclone of hepatocytes (BRL-3SC) from these cells, which release rIGF-II into serum-free medium at a similar but considerably more uniform rate than BRL-3A cells, and have described their morphology and defined some of the conditions regulating the rate of synthesis and secretion of rIGF-II. Time-course experiments indicate that after a 2-h lag, rIGF-II is released at a nearly constant rate of 70 microU insulin-like activity/ml . 24 h for 5 days. These cells demonstrate considerable resistance to variations in environmental pH, with extremes of pH 6.8-8.0 in the initial culture medium causing a negligible effect on rIGF-II release. We found no evidence for the existence of an appreciable amount of intracellular rIGF-II, consistent with the lack of secretion granules in these cells. Moreover, at concentrations not causing irreversible cell damage, inhibitors of protein synthesis, cycloheximide and actinomycin D, produced 87% and 76% reductions, respectively, in rIGF-II release in 24 h, and inhibitors of oxidative phosphorylation, dinitrophenol and sodium azide, reduced rIGF-II release by 72% and 78%, respectively. We conclude from these studies that BRL-3A cells, and particularly those of the subclone BRL-3SC herein described, may provide an excellent model for investigations of somatomedin synthesis and release and that such studies are facilitated by the fact that rIGF-II released into serum-free medium appears to be the immediate product of de novo peptide synthesis.

Animals↗

PubMed1983

Effect of hypophysectomy and hormonal replacement on the uptake of Tc-99m methylene diphosphonate in the metaphysis and shaft of the rat femur: concise communication.

We have investigated the uptake of Tc-99m methylene diphosphonate (Tc-MDP) in the metaphysis and shaft of the rat femur as affected by hypophysectomy and hormonal replacement with growth hormone and thyroxine. Two hours following injection of Tc-MDP, the metaphysis and a specimen of shaft were obtained and the metaphysis-to-shaft radioactivity ratio was measured. By five days after hypophysectomy the metaphysis-to-shaft ratio fell from a control value of 3.8 +/- 0.2 (mean +/- s.e.) to 2.4 +/- 0.2 (p less than 0.05) and remained significantly decreased throughout the 30-day study. When daily hormonal replacement with 0.5 mg of bovine growth hormone and 10 micrograms of thyroxine (both administered intraperitoneally) was given, beginning on the eighth day after hypophysectomy, the metaphysis-to-shaft ratio of Tc-MDP returned to control levels in twelve days. This model demonstrates the effect of growth hormone and thyroxine on the distribution of Tc-MDP, and may be useful as a radiobioassay of net circulating skeletal growth-promoting activity.

Animals↗

PubMed1982

Structure of somatomedin-binding protein: alkaline pH-induced dissociation of an acid-stable, 60,000 molecular weight complex into smaller components.

The association of somatomedin (Sm) peptides with their specific serum binding proteins (SmPBs) and the preservation of SmBP integrity are both pH dependent. Acid extracts of human plasma Cohn fraction IV-4 chromatographed at pH 5.0 after incubation with [125I]iodoinsulin-like growth factor I yield predominantly a 60,000 molecular weight complex of specifically bound radiolabeled peptide. Alkaline exposure (pH 8.0) of either the initial acid extract of Cohn fraction IV-4 or the isolated 60,000 molecular weight chromatographic peak shifts the recovery of bound [125I]iodoinsulin-like growth factor I on rechromatography to two smaller complexes of approximately 46,000 and 30,000 molecular weight. These results support the existence of two or more forms of human plasma SmBP that may possess a common 30,000 molecular weight component.

Animals↗