A sensitive radioimmunoassay for somatomedin-C/insulin-like growth-factor I based on synthetic insulin-like growth factor 57-70

We have developed a region-specific radioimmunoassay for somatomedin-C/insulin-like growth factor-I (IGF-I) directed against IGF-I 57-70. This sequence includes part of the A region and all of the carboxyterminal D region. In addition to being highly specific, this immunoassay is sensitive to as little as 1 ng/ml of IGF-I, and has half-maximum displacement by 10 ng/ml of IGF-I. Comparison to other existent immunoassays for IGF-I shows correlation coefficients of greater than 0.95. This immunoassay has the advantage of being directed against a known region of the IGF-I molecule which is on the exterior of the 3-dimensional structure, and can use a readily available synthetic peptide as both radioligand and standard.

High molecular weight forms of insulin-like growth factor II and its binding protein identified by protein immunoblotting

Insulin-like growth factor (IGF)II is a mitogenic polypeptide which circulates in association with a binding protein(s). Immunoblotting studies were performed in human serum and indicate that:(1)a approximately 200 kDa covalently-linked IGF-II/binding protein complex is antigenically related to the 30 kDa binding protein, (2)IGF-II prohormone is associated with this complex, and (3)a major portion of the IGF-II prohormone immunoreactivity in human serum is present in fractions which would not be detected by standard radioimmunoassay methods. Our data provide insight regarding the inter-relationships of IGF-II and its binding protein, and direct evidence for the presence of IGF-II prohormone in human serum.

Purification and characterization of fructose-1,6-bisphosphatase from bovine brain

Fructose-1,6-bisphosphatase from bovine brain tissue has been purified to near homogeneity. This enzyme is similar to other mammalian fructose-1,6-bisphosphatases in many respects, and its properties are distinctly different from those reported for the enzyme from rat brain [A. L. Majumder and F. Eisenberg (1977) Proc. Natl. Acad. Sci. USA 74, 3222-3225; S. Chattoraj and A. L. Majumder (1986) Biochem. Biophys. Res. Commun. 139, 571-580]. The bovine enzyme (sp act 4, pH ratio (7.5/9.6) = 3.6) has a pH optimum of 7.5. The Km is 2 microM. Divalent metal ion is required for activity, and Vmax is obtained at either 4 mM Mg2+ or 0.3 mM Mn2+. Fructose 2,6-bisphosphate is a competitive inhibitor (Ki = 0.07 microM), and AMP a noncompetitive inhibitor (kis = 24 microM, Kii = 10 microM) of bovine brain fructose-1,6-bisphosphatase. The enzyme activity is enhanced by small amounts of EDTA relative to metal, and AMP inhibits fructose-1,6-bisphosphatase in either the presence or absence of the metal chelator; however, AMP is more effective in the absence of EDTA.

Antiserum developed for the E peptide region of insulin-like growth factor IA prohormone recognizes a serum protein by both immunoblot and radioimmunoassay

Nucleotide sequencing of the two known cDNAs encoding human insulin-like growth factor I (IGF-I) predicts two different prohormone forms of IGF-I. The predicted prohormone amino acid sequences (E peptide regions) extend the carboxy-terminus of IGF-I by either an additional 35 (IGF-IA) or 77 (IGF-IB) amino acids. We developed an antiserum directed against a synthetic peptide which is unique to the E peptide region of IGF-IA prohormone. In a RIA using this antiserum, synthetic E peptide immunoreactivity was found in the serum of patients with chronic renal failure. The protein recognized by this antiserum has a mol wt of about 13,000 by neutral gel filtration and about 19,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. These data suggest that the E peptide region of the IGF-IA prohormone is expressed and circulates as part of the prohormone.

The influence of proglumide, a putative CCK antagonist, on cerebral ischemia in gerbil

Studies were conducted to clarify the possible role of CCK in cerebral ischemia and to evaluate the effects of proglumide, a competitive and reversible CCK antagonist, as a potential therapeutic or prophylactic tool in the treatment of cerebral ischemia. Proglumide at the doses of 10, 50 and 150 mg/kg was administered to gerbils before unilateral carotid ligation, and its effect on stroke index score, incidence and mortality rate was observed. Our results show that proglumide injected prior to carotid ligation at the dose of 150 mg/kg significantly reduces both incidence and mortality rate and changes the distribution of the stroke index score in gerbils. There was a significant inverse relationship between the dose of proglumide and both incidence and mortality: the greater the injection dose of proglumide, the lower the incidence and mortality. These results suggest that CCK may be involved in the pathological processes of cerebral ischemia and proglumide or related compounds prove to be effective in the pharmacological prophylaxis of ischemic brain damage.

Serum somatomedin levels in adults with chronic renal failure: the importance of measuring insulin-like growth factor I (IGF-I) and IGF-II in acid-chromatographed uremic serum

Somatomedin levels measured by radioreceptor assay (RRA) or RIA on acid-ethanol-extracted or unextracted serum from patients with uremia are quite variable relative to normal values. We have investigated whether compounds accumulating in uremic serum were interfering with these RRA and RIA measurements. Insulin-like growth factor I (IGF-I) and IGF-II were separated from carrier proteins by either Sephadex G-50 acid chromatography or acid-ethanol extraction. IGF-I was measured by RIA, and IGF-II was determined by rat placental membrane RRA. IGF-I levels in the acid-ethanol extracts of serum from eight uremic adults were only 50% of the levels found in seven normal subjects, and IGF-II levels in these uremic patients were 350% of normal values. However, these significant differences were not found when comparable serum samples were acid chromatographed rather than acid-ethanol extracted; instead, IGF-I levels were 343 +/- 168 (mean +/- SD) ng/ml in uremic patients and 325 +/- 54 ng/ml in normal subjects, while IGF-II levels were 780 +/- 215 ng/ml in uremic patients and 588 +/- 46 ng/ml in normal subjects. To determine whether compounds that interfere with somatomedin assays were present in the acid-ethanol extracts of uremic serum, we acid chromatographed these extracts and found that a compound eluting in the carrier protein fraction of the uremic extract artifactually decreased IGF-I levels measured by RIA and increased IGF-II levels measured by RRA. We also found that unsaturated carrier protein binding of IGF-I and IGF-II was significantly increased in the carrier protein fraction of uremic acid-ethanol extracts at the dilutions used for somatomedin assays. We conclude that acid chromatography of unextracted or acid-ethanol-extracted uremic serum is necessary to remove a compound, probably unsaturated carrier protein, which interferes with RIA of IGF-I and RRA of IGF-II. Once this compound is removed, serum IGF-I levels (RIA) in uremic patients are not different from normal, and serum IGF-II levels (RRA) are not lower than normal.

The effect of partial gastrectomy on lipoproteins and other characteristics

Among 6860 50-77 year old men of Japanese ancestry examined in Honolulu 291 were known to have had a gastrectomy for benign gastric (189) or duodenal (102) ulcer, and 132 had documented peptic ulcer disease treated medically. Total serum cholesterol averaged 12 mg% lower in the surgical group than in the general population (p less than 0.01) while the medically treated men had intermediate values. Fasting lipoprotein determinations done in a sub-sample showed that the lower total cholesterol in the surgical group was due to depressed LDL, while HDL was higher in the operated men than in either the general population or the medically treated patients (p less than 0.01). The surgical patients were heavier users of cigarettes, beer and coffee and averaged about 10 lb. lighter than either the medically treated patients or the rest of the population. However, in multivariate analysis these differences did not not account for the differences in lipoproteins. A small decrement in blood pressure in the surgical patients as compared to the rest of the population became non-significant when weight and others factors were taken into account.

Gram stain in Legionnaires' disease

A case of Legionnaires' disease is presented in which gram staining of impression smears from lung biopsy specimens showed Legionella pneumophila while other laboratory findings remained negative. This case illustrates the usefulness of gram staining in this disease and in the management of therapy.

Somatomedins and insulin in diabetic pregnancies: effects on fetal macrosomia in the human and rhesus monkey

The concentrations of the somatomedins (SMs) insulin-like growth factors I and II (SM-C/IGF-I and IGF-II) were measured by RIA in six normal and seven insulin-dependent diabetic pregnant women and their infants at delivery. SM-C/IGF-I and IGF-II levels in the two groups of women were similar. Maternal IGF-II concentrations correlated with maternal hemoglobin AIc levels (r = 0.68) and infant birth weight ratios (actual birth weight/expected 50th percentile sex-corrected birth weight for gestation age; r = 0.54). SMC/IGF-I and IGF-II levels in umbilical plasma in infants of diabetic mothers did not differ from those in control infants, but were lower than the corresponding maternal values. In contrast, umbilical plasma levels of C-peptide immunoreactivity were significantly elevated in the infants of diabetic mothers (2.25 +/- 1.85 (+/-SD) vs. 0.34 +/- 0.15 pmol/ml; P less than 0.01). The infant birth weight ratio was logarithmically correlated with the umbilical plasma C-peptide immunoreactivity (r = 0.78). SM levels were also measured by radioreceptor assay in five normal and five hyperinsulinemic rhesus monkey fetuses. When chronic hyperinsulinemia was produced by continuous SC infusion of insulin in the fetal rhesus monkey, the fetal birth weight ratio was also found to be logarithmically correlated with the fetal plasma insulin concentration (r = 0.81). The fetal SM peptide content was elevated only in the fetuses with plasma insulin levels greater than 3000 microU/ml. The fetal weight gains in response to hyperinsulinemia in the human and rhesus are similar. Since fetal SM levels in the humans and monkeys were not significantly different in the two groups, our data suggest that insulin plays the predominant role in stimulating human and subhuman primate excess fetal weight gain of the infant of the diabetic mother during the latter part of gestation.

Mycobacterium thermoresistibile infection in an immunocompromised host

This is the second report of Mycobacterium thermoresistibile as the etiological agent of a pulmonary granuloma and the first occurrence of this organism in a patient who has not been outside the continental United States. The organism is susceptible to rifampin, ethambutol, and streptomycin but resistant to isoniazid and p-aminosalicylic acid.

Levels of insulin-like growth factors I and II in human cord blood

Levels of insulin-like growth factors I and II (IGF-I and IGF-II) and somatomedin peptide content (SMPC) were measured in 32 normal term and 11 preterm infants. After acid chromatography to remove somatomedin-binding protein, SMPC was measured by placental membrane radioreceptor assay, while plasma IGF-I and II concentrations were measured by specific RIAs. SMPC levels in term infants were significantly below normal adult levels [0.49 +/- 0.13 (+/- SD) U/ml for infants compared to 1.30 +/- 0.25 U/ml for adult males]. IGF-I levels in term infants were also low, averaging 113 +/- 35 ng/ml for infants; the normal adult levels is 184 +/- 32 ng/ml. The IGF-II level was 282 +/- 84 ng/ml for infants and 687 +/- 169 ng/ml for adults. Both IGF-I and II levels in preterm infants were lower than those in term infants. IGF-I, and IGF-II, and SMPC levels showed a positive correlation with birth weight in term infants. Both IGF-I and IGF-II levels showed a strong positive correlation with gestational age in all infants.