Altered affinity of insulin-like growth factor II (IGF-II) for receptors and IGF-binding proteins, resulting from limited modifications of the IGF-II molecule

The binding affinities of seven analogues of recombinant human insulin-like growth factor II (hIGF-II) were characterized for the IGF type-I and type-II receptors and insulin receptors, as well as for IGF-binding protein (IGFBP)-1, IGFBP-2, IGFPB-3 and human serum IGFBPs. A switch of two of the three cysteine bridges in hIGF-II, 9-47 and 46-51 to 9-46 and 47-51, severely impaired the binding of this analogue to all receptors and to the IGFBPs. The affinities for the IGF type-I receptor and the IGFBPs were decreased over 100-fold, while the binding to the insulin receptor and the IGF type-II receptor was less affected, with a 6-10-fold decrease in affinity. Slight modifications of the N-terminus had only minor effects upon the binding of hIGF-II to the IGFBPs or to the receptors. Deletion of both the N-terminal amino acid and the two C-terminal amino acids resulted in moderate decreases in affinity, with a 60% decrease in affinity for IGFBP-1 and the IGF type-I receptor. Acetylation of the N-terminus of Ala1 and the epsilon-nitrogen of Lys65 decreased the affinity, by 60-90%, of hIGF-II for all of the IGFBPs and receptors. The experiments involving acetylation of IGF-II or switching of its cysteine bridges indicated that these modifications (no substitution, deletion or addition of any of the 67 amino acids of hIGF-II) may lead to a severe impairment of the binding affinity of IGF-II for both the IGFBPs and the receptors. Acetylation of the epsilon-nitrogen of Lys65, which causes a charge change, or alteration of the three-dimensional structure, as shown by the cysteine bridge switch, lead to a severe impairment of the binding affinity for the binding proteins and for the receptors. In general, care should be taken with the synthesis of analogues and the interpretation of resulting binding data, since affinity alterations ascribed to amino acid changes may instead be caused by alterations of the charge or the three-dimensional structure of the protein.

[Leu27] insulin-like growth factor II is highly selective for the type-II IGF receptor in binding, cross-linking and thymidine incorporation experiments

Insulin-like growth factor-II (IGF-II) is able to interact with three different receptors: the type-I and type-II IGF receptors, and the insulin receptor, although with a lower affinity. This cross reactivity obscures the mechanisms via which the biological activities of IGF-II are mediated. We have synthesized an IGF-II analog, [Leu27]IGF-II, that is highly selective for the type-II IGF receptor. Receptor binding experiments demonstrate a high affinity for the type-II IGF receptor, analogous to synthetic (syn) and recombinant (rec) IGF-II, but no affinity for the type-I IGF and the insulin receptor at concentrations up to 50 and 200 ng/ml, respectively. The lack of affinity for these two receptors is confirmed by biological studies which demonstrated that this analog, in contrast with synIGF-II, did not stimulate [3H]thymidine incorporation in Balb/c 3T3 cells. [Leu27]IGF-II opens new ways to identify which actions of IGF-II are mediated via the type-II receptor and which are due to cross reactivity with the type-I IGF or the insulin receptor.

Dose dependency of germanium-dioxide-induced nephrotoxicity in rats

The dose dependency of germanium dioxide(GeO2)-induced nephrotoxicity was investigated experimentally in rat groups orally treated with high (150 mg/kg/day), moderate (75 mg/kg/day), or low (37.5 mg/kg/day) doses of GeO2, and in an untreated group. Renal dysfunction, indicated by the increase of blood urea nitrogen and the decrease of creatinine clearance, and systemic toxicity by weight loss, anemia, and hypoproteinemia were more apparent in rats treated with higher dose of GeO2. Urinalysis including daily urinary protein excretion did not reveal any abnormalities in any of the groups. Urinary excretion and renal-tissue content of Ge were significantly elevated in the group of the higher dose of GeO2. Light microscopically, vacuolar degeneration and depositions of granules positive for periodic acid-Schiff in distal tubules were predominant in the higher-dose group of GeO2. The present study demonstrates that GeO2-induced nephrotoxicity develops dose dependently.

Tonometer utilization, accuracy, and calibration under field conditions

A field survey conducted in 94 ophthalmologists' offices in our immediate area assessed the accuracy of tonometers in daily use. One hundred eighty-five instruments were examined: 127 were slit lamp mounted, 48 were hand held, and 10 were noncontact devices. Nineteen percent of applanation tonometers were outside the manufacturers' specifications (1 mm Hg of the calibration) and 4.5% were more than 2 mm Hg in error. The error was constant across the scale. Hand-held applanators were less accurate than those on slit lamps (P less than .02); the latter demonstrated an association between accuracy and age (P less than .05) and heavier use (P less than .01). Annual recalibration was performed in 86% of instruments. Those practitioners who themselves performed the calibration had the most accurate instruments. Less than 15% knew how to perform the calibration check.

Identification of insulin-like growth factor-binding protein-2 (IGF-BP-2) and a low molecular weight IGF-BP in human seminal plasma

Three distinct binding proteins for the insulin-like growth factors (IGF-BPs) have recently had their cDNAs cloned and sequenced. We have evaluated IGF-BP expression in normal, oligospermic and azospermic human seminal plasma (SP), and have identified IGF-BP-2 in all samples. Additionally, SP contains a non-glycosylated low molecular weight IGF-BP (24K), which does not appear to be structurally or immunologically related to IGF-BP-1, -2 or -3.

Germanium dioxide-induced nephropathy: a new type of renal disease

Chronic renal failure developed in 5 patients who were taking germanium dioxide (GeO2)-containing compounds. Renal functional deterioration was slow but progressive and dialysis treatment was necessitated temporarily in 2 patients. After the discontinuation of GeO2, the impaired renal function tended to improve but remained abnormal for an observation period of 10-40 months. The lack of proteinuria and hematuria was characterized as the clinical manifestations. Renal biopsy specimens revealed the tubular epithelial cell degeneration containing hematoxylin-positive fine granules on light microscopy, and electron-dense inclusions in the swollen mitochondria on electron microscopy. These findings localized mainly in distal segment of the tubules. In the rats given GeO2 orally for 10 weeks, similar histological lesions were evident, as manifested by marked weight loss, anemia, azotemia, and negative proteinuria. In the rats given carboxyethylgermanium sesquioxide, these changes were not observed and Ge concentration of kidney was significantly lower than in the rats given GeO2. The present study indicates that chronic GeO2 intake causes progressive renal dysfunction characterized by the degeneration of distal tubules.

Digital respirosonography. New images of lung sounds

We used tape recordings from normal subjects and from patients with lung disease to generate spectrographic images of respiratory sounds on a personal computer. These digital respirosonograms presented timing and frequency content of lung sounds, with the sound intensities displayed on a color scale. Respiratory sounds during inspiration and expiration could be recognized by their association with concurrent respiration curves. Contributions of low-frequency cardiac sounds were visually identified by their relationship to simultaneously recorded ECGs. Typical characteristics of normal and adventitious lung sounds were documented and displayed both in the time and the frequency domain. Digital respirosonography provides an easy way to assess lung sound amplitudes, frequencies and timing over several breaths.

Ontogeny of serum insulin-like growth factor binding proteins in the rat

Insulin-like growth factors (IGF-I and -II) are peptide growth factors that may be important for neonatal development. Specific high affinity IGF binding proteins (BPs) have been characterized in serum and extracellular fluids. The major serum binding complex in the adult has an apparent Mr of 150 K, while the predominant BP in the neonate is approximately 30 K. In the rat, the transition from the neonatal BP to the adult form occurs during the third postnatal week, concomitant with an increase in serum IGF-I and a decrease in serum IGF-II concentrations. Using specific RIAs and Western ligand blot analyses we have characterized the changes in serum IGF and IGF BPs, respectively, during the early postnatal period. Seven BPs were identified in serum with apparent Mr values of 42, 41, 40, 38, 28, 26, and 22 K. After deglycosylation, the 42, 41, 40, and 38 K BPs were reduced to two bands with apparent Mr values of 35 and 32 K, while the 28, 26, and 22 K BP were unchanged. In the neonate, the 28, 26, and 22 K BPs were present, with the 28 K BP in highest concentration. With increasing age, the 28 K BP decreased and the 42, 41, 40, and 38 K BPs appeared at approximately 19 days of age. Comparison of Western ligand blots of neonatal serum, BRL-3A conditioned media, rat amniotic fluid, and rat cerebrospinal fluid (CSF) demonstrated that all contained a prominent 28 K BP. A polyclonal antibody (alpha Hec 1) developed against the 31 K human IGF-BP (hBP-31) immunoprecipitated the 28 K BP from neonatal rat serum, BRL-3A media, rat amniotic fluid, and rat CSF, but did not react with adult rat serum. These findings suggest that, in the rat, the predominant neonatal serum BP is structurally and immunologically similar to the major BRL-3A, amniotic fluid, and CSF BPs, but distinct from the predominant adult serum BP.

[Cholesterol atheroembolic renal failure after arteriography. Report of a case diagnosed by renal biopsy]

A case of atheroembolic renal failure diagnosed by renal biopsy was presented. A 69-year-old man was referred because of progressive renal failure two months after major angiography for occlusive arterial disease of lower limbs. The physical examination on admission revealed an uncontrollable hypertension. The laboratory findings showed elevated serum creatinine (7.5 mg/dl) and eosinophilia (1022/mm3) with normal urinalysis findings. Renal biopsy disclosed a occlusive lesion of the arcuate artery which contained cholesterol clefts and foam cells, and showed ischemic renal parenchymal changes. These findings were compatible with cholesterol atheroembolic renal disease. In spite of the aggressive medical treatment, renal function had deteriorated progressively and the patient has been on regular hemodialysis. Atheroembolic renal failure after arteriography have been reported recently, but the case diagnosed by renal biopsy has been rare. Since there is no therapeutic way to reverse this type of renal failure, strict selection of patients for the angiographic examination and use of flexible catheter might be mandatory. Subacute course of renal failure after angiography and eosinophilia seem to be the important diagnostic clues for this disorder.

Expression of two insulin-like growth factor-binding proteins in a human endometrial cancer cell line: structural, immunological, and genetic characterization

Insulin-like growth factors (IGFs) bind with high affinity to specific proteins in human serum, cerebrospinal fluid (CSF), and amniotic fluid. In serum, IGFs are bound to a complex with an apparent mol wt of 150K in which an acidstable binding protein of 53K, termed BP-53, is found. In amniotic fluid, a different binding protein with an apparent mol wt of 25K, termed hBP-25, has been identified. This binding protein is secreted by endometrial cells and has been shown to block the binding of IGFs to their membrane receptors and inhibit the mitogenic action of the IGFs on human choriocarcinoma cells. It has been proposed that hBP-25 modulates the action of IGFs on endometrial tissue, especially during pregnancy. We have identified two binding proteins produced by an endometrial adenocarcinoma, HEC 1A, neither of which is related structurally or genetically to hBP-25. One is present in two glycosylated forms with apparent mol wt of 37K and 40K, both of which are immunoprecipitated with an antiserum made to BP-53. Both forms are reduced to a core protein of 30K upon digestion with endoglycosidase-F. Furthermore, BP-53-specific RNA was detected in HEC 1A cells. A second binding protein with an apparent mol wt of 32K was also detected and did not increase in size upon treatment with endo glycosidase F. These two binding proteins were partially purified by a combination of wheat germ agglutinin and IGF affinity chromatography, and polyclonal antibodies were generated. The polyclonal antiserum specifically recognizes a 32K protein in human CSF, suggesting that the HEC 1A cells produce the same binding protein that is predominant in CSF. The findings suggest that IGF action in the endometrium may be modulated by more than a single binding protein, and that at least three structurally distinct human IGF binding proteins exist.

Expression of the BRL-3A insulin-like growth factor binding protein (rBP-30) in the rat central nervous system

The expression of the BRL 3A insulin-like growth factor binding protein (rBP-30) was characterized in rat brain, hypothalamus, and pituitary tissue and cultured neuronal and astroglial cells. The 27K BP expressed by BRL 3A cells (rBP-30) was found to also be expressed in conditioned media from newborn rat astrocytes and fetal neurons, but not in the medium from the neuroblastoma cell line, B104. Moreover, a polyclonal antibody, anti HEC1, specifically immunoprecipitated the BRL 3A BP from the same conditioned media, as well as from rat cerebrospinal and amniotic fluid and from conditioned medium of cells isolated from the neurointermediate lobe of adult rat pituitary. The same antibody also immunoprecipitated hBP-31 from human CSF. Northern blot analyses showed that rBP-30 mRNA was expressed in adult rat brain and pituitary, fetal brain and liver, and in fetal neurons and newborn astrocytes maintained in culture. We conclude that the BRL 3A BP (rBP-30) is the major insulin-like growth factor binding protein in the rat CNS and may be the rat analog of hBP-31, the predominant BP in human CSF.

Characterization of insulin-like growth factor-binding proteins in cultured rat pituitary cells

Binding proteins (BPs) for the insulin-like growth factors (IGFs) produced by cultured rat anterior pituitary (AP) and neurointermediate lobe (NI) cells were studied by competitive binding, affinity cross-linking, and Western ligand blot techniques. Conditioned medium from AP cultures contained specific high affinity IGF BPs with apparent mol wt of 35K, 27K, and 24K, while the 27K BP predominated in NI conditioned medium. Treatment of AP and NI conditioned media with endoglycosidase-F did not alter the 27K BP, but significantly reduced the apparent mol wt of the 35K BP into the 27-29K range, suggesting that the 35K BP may be a glycosylated form of the 27K BP. This 27K pituitary BP appeared similar to the BP produced by BRL-3A cells in both size and apparent lack of glycosylation. Although type 2 IGF receptors could be identified in conditioned medium from NI and GH3 pituitary cells, binding of [125I]IGF to pituitary BPs could not be inhibited, nor could the cross-linked BPs be immunoprecipitated, by antibody against the type 2 receptor. We conclude that cultured AP and NI cells produce a variety of related IGF BPs that are structurally distinct from the type 2 IGF receptor.

Characterization of insulin-like growth factor binding proteins of cultured rat astroglial and neuronal cells

Insulin-like growth factor binding proteins produced by cultured rat neurons, astrocytes, and rat cell lines BRL-3A and B104 were compared to binding proteins found in rat serum, using affinity labeling, deglycosylation, and Western ligand blotting studies. Each source elaborated an unique pattern of heterogeneous binding proteins. Some of the binding proteins from different sources behaved similarly in each experimental system suggesting that subsets of these binding proteins may be structurally related. In particular, our data suggest that cultured astrocytes and neurons make the major binding protein produced by BRL-3A cells.

Acquired renal cysts in five-sixths nephrectomized rats: the roles of oxalate deposits in renal tubules and a renotropic factor

The present study was undertaken to see if the oxalate deposits seen in renal tubules are a causative factor in the development of acquired renal cysts in chronic renal failure. Thirty 5/6 nephrectomized rats had free access to water containing 8 mg/ml of vitamin C (oxalate precursor) and 20 5/6 nephrectomized rats were given tap water without vitamin C. Oxalate deposits were found on microscopy in the renal tubules of vitamin C-treated rats in the 11th and 12th postnephrectomy months; however, acquired renal cysts were noted far in advance of the appearance of oxalate crystals. It has been suggested that the tubular dilatation seen in 5/6 nephrectomized rats is caused by an abrupt decrease in the functioning renal mass, leading to the production of a so-called 'renotropic factor'. However, oxalate deposits and renal tubular dilatation in oxalate-treated 5/6 nephrectomized rats preceded the renal tubular dilatation of untreated partially nephrectomized rats. In addition, these histological changes in the kidney were also seen in healthy rats which were given oxalate orally and subcutaneously. The present study suggested that the pathogenesis of acquired renal cysts is multifactorial. Renotropic factor may play an important role leading to nephron hyperplasia, but oxalate deposits in the renal tubules seem to be an important factor in the formation of these cysts.

Effect of vitamin C supplementation on renal oxalate deposits in five-sixths nephrectomized rats

We have previously reported that hyperoxalemia can be aggravated by vitamin C supplementation in regular hemodialysis patients. The present study was undertaken to examine the validity of this observation in an experimental setting. Fifty five-sixths nephrectomized rats were divided into two groups: 30 rats were allowed free access to water containing 8 mg/ml of vitamin C (100-160 mg/100 g/24 h) and the remainder given tap water without vitamin C. The serum creatinine increased and the Hct decreased gradually; however, there was no difference between the two groups. Plasma vitamin C, oxalate and urinary oxalate levels were higher in the vitamin -treated group than the nontreated rats. Histological examination revealed glomerular and interstitial fibrosis and round cell infiltration as well as tubular cyst formation. Oxalate deposits in renal tubules were found only in vitamin C-treated rats with advanced renal failure. Nontreated animals with equally advanced renal impairment showed no oxalate deposits. These results confirm our previous clinical findings that vitamin C supplementation aggravates the secondary oxalosis of chronic renal failure.

Pharmacokinetics of a new angiotensin I converting enzyme inhibitor (delapril) in patients with deteriorated kidney function and in normal control subjects

Pharmacokinetic properties of a new angiotensin-converting enzyme inhibitor, delapril (CV-3317), which converts to two active metabolites (M-1 and M-2) and one inactive metabolite (M-3) after oral administration, were investigated in six subjects with normal, 10 subjects with slight (SRF), and six subjects with markedly (MRF) deteriorated kidney function. The elimination half-life of M-1 was prolonged significantly in subjects with MRF and that of M-3 was also prolonged in subjects with SRF or MRF. The peak plasma drug concentration, time to reach peak concentration (tmax), and AUC were significantly larger in subjects with SRF and MRF than in normal subjects, except for Tmax in subjects with SRF. In M-2 and unchanged delapril, no difference was observed. The 24-hour cumulative urinary excretion of those metabolites was significantly lower in subjects with MRF than in normal subjects. Plasma angiotensin-converting enzyme activity, suppressed at 4 hours in all subjects, remained significantly low in patients with MRF at 24 hours. Blood pressure was reduced more in subjects with chronic renal failure. It was concluded that delapril is excreted mainly through the kidney and its pharmacodynamics and biologic effects are affected by the renal dysfunction.

Beneficial effect of aluminum hydroxide on progress of adriamycin-induced nephropathy in rats

To investigate the effect of phosphate binder on adriamycin (ADR)-induced nephropathy, serial changes in renal histology and renal hemodynamics were compared between ADR rats treated with aluminum hydroxide (ADR-AH group) and those without AH (ADR group) for 24 weeks. Urinary protein excretion was less marked in the ADR-AH group than in the ADR group. Serum creatinine in the ADR group increased progressively from week 20, while in the ADR-AH group the increase was less. There were no significant differences in glomerular filtration rate or renal plasma flow between the both groups until week 12 but these parameters decreased to the significantly lower levels at week 24 in the ADR group. Vacuolative degeneration in glomerular epithelium, which was determined as an initial renal lesion, was more marked in the ADR group compared to the ADR-AH group. Glomerular sclerosis and tubulointerstitial changes developed progressively in the ADR group at the later stages. These changes were lessened in the ADR-AH group. In conclusion, AH prevents the progress in ADR-induced nephropathy. The beneficial effects appeared as the preservation of glomerular epithelial cells.

Influence of age on deterioration of the remnant kidney in uninephrectomized rats

To investigate the influence of age on the remnant kidney, unilateral nephrectomy was performed in rats at 1 day (group N-0), 2 weeks (group N-2), 4 weeks (group N-4) or 8 weeks (group N-8) of age. Serial changes in urinary protein during 48 weeks after the uninephrectomy and blood chemistries and renal histology at week 48 were compared between the groups. The increase in proteinuria was significantly greater in groups N-0, N-2 and N-4 than in group N-8 from week 32 to week 48 after the uninephrectomy. There was no significant difference in urinary protein between groups N-0, N-2 and N-4. Hypoproteinaemia and hypoalbuminaemia were also more severe in groups N-0, N-2 and N-4 than in group N-8 at week 48. A compensatory renal growth in groups N-0 and N-4 was significantly greater than that in group N-8 at week 48 after the uninephrectomy. Focal and segmental glomerular sclerosis, a characteristic finding in the uninephrectomy groups, was significantly more marked in groups N-0, N-2 and N-4 than in group N-8 at week 48. We conclude that uninephrectomy at young ages leads to increased incidence of glomerular sclerosis in rats compared with uninephrectomy in the adult.

Cerebral hemorrhage in patients on maintenance hemodialysis. CT analysis of 25 cases

Site of hematoma and clinical outcome in cerebral hemorrhage were analyzed in 25 maintenance hemodialysis (HD) patients and compared with those in 27 non-HD patients. Ganglionic-thalamic hemorrhage was found in 56% of HD and 74% of non-HD patients, lobar hemorrhage in 36% and 11%, respectively. Size of hematoma, expressed as a ratio (%) of hematoma area to entire brain on CT slice, was 6.5 +/- 4.2% (mean +/- SD) in HD, being significantly larger than that of 4.7 +/- 3.5% in non-HD patients (p less than 0.05). Mortality rate was 60% in HD patients, nearly twice as much as the 33% in non-HD patients. The hematomas were significantly larger in the death cases (8.4 +/- 3.7%) than the survivors on HD (3.6 +/- 3.1%, p less than 0.005). Likewise, the fatal cases in the non-HD group had bigger hematomas (6.9 +/- 4.3%) than the non-fatal ones (3.6 +/- 2.4%, p less than 0.05). Intraventricular hemorrhage (IVH) was found in 40% of HD and 44% of non-HD patients. Hematomas were significantly larger in HD patients with IVH (9.3 +/- 3.3%) than in those without IVH (4.6 +/- 3.7, p less than 0.005). Ninety percent of the HD patients with IVH but only 42% of non-HD patients died of hemorrhage. Hypertension was equally seen in HD (76%) and non-HD patients (74%). It is concluded that in HD patients cerebral hemorrhage is more severe in terms of hematoma size, association of IVH and clinical outcome. Chronic systemic heparinization might be responsible to the severity in HD patients.

Effects of acute reduction in blood pressure on the renal function of rats with diseased kidneys

We studied the effect of an acute reduction in blood pressure, induced by diltiazem, on the renal hemodynamics of spontaneously hypertensive rats (SHR) with focal glomerular sclerosis, as induced by adriamycin (ADR). Renal plasma flow (RPF) and glomerular filtration rate (GRF) were determined before (first period) and during (second period) intravenous infusion of diltiazem in SHR 4-6 weeks after ADR treatment (group 1), 14-20 weeks after treatment (group 2), and in controls without treatment (group 3). Rats in group 1 had a normal renal function (RPF and GFR) in the first period, which was not significantly different from control rats (group 3). Rats in group 2 showed a reduced renal function, reflected by the lower levels of RPF and GFR, compared with groups 1 and 3. Mean blood pressure decreased equally in the 3 groups by about 50 mm Hg after the infusion of diltiazem. During the second period, 13.4 or 12.4% increase in RPF and a 29.0 or 23.2% elevation of GFR were evident in groups 1 or 3, respectively. In contrast, a 32.0% reduction of RPF was observed in group 2, accompanied by a 25.7% decline of GFR. A reduction in renal function (percent change of RPF or GFR) significantly correlated with the severity of renal dysfunction (RPF or GFR in the first period) in group 2. Thus, the renal function of rats with diseased kidneys is sensitive to an acute reduction in blood pressure by diltiazem, and the sensitivity depends on the degree of renal deterioration.