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Biomedical subjects

R Lauro

Publications and source records attributed to R Lauro.

At least 55 records · Page 3Linked to original sources
PubMed1989

Beta-endorphin receptors on cultured and freshly isolated lymphocytes from normal subjects.

[125I]-[D-Ala2]-beta EP*) binding to Epstein-Barr Virus (EBV) transformed B lymphocytes or to freshly isolated lymphocytes was characterized. The binding was time-, temperature- and pH-dependent; furthermore, it was reversible and cell concentration dependent. Maximum binding appeared at 15C in Tris buffer (pH 7.6) containing both BSA 0.5% and Bacitracin 0.1 mg/ml. beta EP inhibited BEP* binding to transformed lymphocytes and to freshly isolated lymphocytes by 50% at approximately 4 x 10(-8) M and 8 x 10(-9) M, respectively. Peptides representing amino-acid sequences 1-5, 1-16 and 1-17 of beta EP did not inhibit beta EP binding, neither did the opiates compounds Naloxone, Morphine, Bremazocine and Ethylketocyclazocine. On the contrary, beta EPd (6-31) inhibited beta EP* binding as effectively as beta EP, thus indicating that beta EP* binding to lymphocytes does not involve the N-terminal region of beta EP. 2 x 10(7)/ml freshly isolated lymphocytes bound 1.53 +/- 75%, whereas 2 x 10(6)/ml transformed lymphocytes bound 1.64 +/- 0.75% (mean +/- SD) beta EP* at tracer concentration. EBV transformed lymphocytes and freshly isolated lymphocytes may be useful to study beta EP receptors in humans.

Adrenocorticotropic Hormone↗
PubMed1989

An extracellular domain of the insulin receptor beta-subunit with regulatory function on protein-tyrosine kinase.

Anti-insulin receptor monoclonal antibody MA-10 inhibits insulin receptor autophosphorylation of purified rat liver insulin receptors without affecting insulin binding (Cordera, R., Andraghetti, G., Gherzi, R., Adezati, L., Montemurro, A., Lauro, R., Goldfine, I. D., and De Pirro, R. (1987) Endocrinology 121, 2007-2010). The effect of MA-10 on insulin receptor autophosphorylation and on two insulin actions (thymidine incorporation into DNA and receptor down-regulation) was investigated in rat hepatoma Fao cells. MA-10 inhibits insulin-stimulated receptor autophosphorylation, thymidine incorporation into DNA, and insulin-induced receptor down-regulation without affecting insulin receptor binding. We show that MA-10 binds to a site of rat insulin receptors different from the insulin binding site in intact Fao cells. Insulin does not inhibit MA-10 binding, and MA-10 does not inhibit insulin binding to rat Fao cells. Moreover, MA-10 binding to down-regulated cells is reduced to the same extent as insulin binding. In rat insulin receptors the MA-10 binding site has been tentatively localized in the extracellular part of the insulin receptor beta-subunit based on the following evidence: (i) MA-10 binds to insulin receptor in intact rat cells; (ii) MA-10 immunoprecipitates isolated insulin receptor beta-subunits labeled with both [35S]methionine and 32P; (iii) MA-10 reacts with rat insulin receptor beta-subunits by the method of immunoblotting, similar to an antipeptide antibody directed against the carboxyl terminus of the insulin receptor beta-subunit. Moreover, MA-10 inhibits autophosphorylation and protein-tyrosine kinase activity of reduced and purified insulin receptor beta-subunits. The finding that MA-10 inhibits insulin-stimulated receptor autophosphorylation and reduces insulin-stimulated thymidine incorporation into DNA and receptor down-regulation suggests that the extracellular part of the insulin receptor beta-subunit plays a role in the regulation of insulin receptor protein-tyrosine kinase activity.

Animals↗
PubMed1988

[Preparation of 125I-labelled monoclonal antibodies of the insulin receptor].

Three monoclonal anti-insulin receptor antibodies have been labelled with 125I according to various methods (Cloramine T, Lactoperoxidase and IODO-GEN). The effect of labelling on antibody structure and function has been characterized using the following parameters: a) specific activity obtained in four different labelling procedures, at least; b) TCA labelled antibody precipitable 90 days after labelling; c) interaction between labelled antibodies and the insulin receptor; d) ability of antibodies to inhibit insulin-stimulated receptor auto-phosphorylation. Cloramine T method produced labelled antibody with constant specific activity; however, some preparations were unstable and showed reduced capacity to recognize the insulin receptor. Lactoperoxidase method produced stable antibodies; however, specific activity was highly variable and antibodies had low capacity to interact with the insulin receptor. The IODO-GEN method produced antibodies with constant specific activity, stable, high capacity to interact with the insulin receptor, and, moreover, maintaining in full the capacity to inhibit the insulin-stimulated auto-phosphorylation of the insulin receptor, since it does not induce antibody alterations which in turn affect antibody-receptor interaction biological action.

Antibodies, Monoclonal↗
PubMed1987

Characterization of differences in insulin receptors from young and old red blood cells.

It has been demonstrated that young RBCs (reticulocytes and early mature erythrocytes) possess more insulin receptors than old RBCs (late mature erythrocytes) but it is not yet known whether insulin receptors on young and old RBCs are regulated similarly. In the present investigation insulin receptors on young and old RBCs have, therefore, been studied in five normal male subjects before and after 2 days dexamethasone ingestion (0.5 mg tablet every 6 h) and, in the same subjects, before and 5 h after ingestion of 75 g glucose. The results obtained clearly demonstrate that dexamethasone increases insulin receptor concentration while glucose ingestion increases both insulin receptor affinity and concentration on young RBCs. By contrast, neither stimuli modify insulin receptors on old RBCs. Studies on RBCs are usually performed on the whole RBC population not taking into account this differential responsiveness of receptors on young versus old RBCs; consequently, this phenomenon might be responsible of the fact that some data reported on RBCs are not in agreement with those reported on monocytes or adipocytes and it should be taken into consideration when using RBCs to evaluate insulin receptor regulation.

Adult↗
PubMed1987

Regulation of insulin receptor-associated tyrosine kinase by a polyclonal IgG.

The effect of a polyclonal anti-insulin receptor antibody (pIgG) on the insulin receptor tyrosine kinase (IRTK) activity toward poly-(Glu-Tyr) was examined using wheat germ agglutinin agarose-purified insulin receptors from rat liver membranes. The main effect of pIgG was a reduction of Vmax (from 60.8 to 31.8 pmol/min/mg), without changes of Km, when IRTK was activated by insulin. In contrast, when IRTK was activated by ATP preincubation, pIgG was unable to affect the reaction, suggesting that IRTK possesses at least two regulatory mechanisms, one of which can be affected by pIgG.

Animals↗
PubMed1987

Species specificity of insulin binding and insulin receptor protein tyrosine kinase activity.

The effect of monoclonal anti-insulin receptor antibody MA 10 on [125I]insulin binding and on insulin receptor protein tyrosine kinase activity was investigated in human and rat tissues. It was observed that MA 10 inhibits insulin binding to human, but not rat, tissues while inhibiting insulin-stimulated receptor autophosphorylation and protein tyrosine kinase activity in both human and rat tissues. These data suggest that MA 10 is directed against a region of the insulin receptor that is in between the insulin-binding domain and the beta-subunit and that in human, but not rat, tissues, this region is involved in insulin binding.

Adipose Tissue↗
PubMed1986

Insulin-like growth factor I (IGF I) receptor autophosphorylation and kinase activity. Effect of a human polyclonal antibody (pIgG)

IGF I receptor is a tyrosine kinase capable of phosphorylating the receptor itself and other substrates. A high degree of homology does exist in tyrosine kinase domain among receptors for several polypeptide growth factor receptors and this enzymic activity has been indicated as a possible mediator of biological action. Nevertheless growth factor receptors possess peculiar specificities both in their functions and tissue distribution. A human polyclonal IgG (pIgG), previously characterized as anti insulin receptor antibody, able to inhibit insulin receptor kinase activity, was used to further investigate subunit homologies and differences in antigenicity and functional regulation between IGF I and insulin receptors, IGF I receptor tyrosine kinase was stimulated by a IGF I analog (aIGF I), produced by DNA recombinant technology, pIgG was able to inhibit IGF I receptor kinase activity, thus revealing antigenic homologies between the kinase domains of insulin and IGF I receptors. However the more pronounced inhibition of IGF I receptor-compared with insulin receptor kinase activity by pIgG suggests the existence of different regulatory mechanisms.

Antigen-Antibody Reactions↗
PubMed1985

Inhibition of insulin and epidermal growth factor (EGF) receptor autophosphorylation by a human polyclonal IgG.

The immunoglobulin G of a polyclonal antiserum (pIgG) from a patient with insulin resistance and hypoglycemia was tested for its ability to inhibit insulin binding and to affect the autophosphorylation of partially-purified insulin receptors extracted from rat liver membranes. pIgG, when added 4 hr prior to insulin, inhibited subsequent insulin binding by 50% at 30 micrograms added protein; however, insulin previously bound to the receptor could not be displaced by a 4 hr subsequent exposure of up to 70 micrograms pIgG. pIgG, independent of its effect on insulin binding, inhibited both basal and insulin-stimulated autophosphorylation of the insulin receptor in a dose-dependent manner with a half maximal effect at 3.3 to 7 micrograms protein. Furthermore, pIgG also reduced basal autophosphorylation of the EGF receptor. The effect of pIgG to inhibit basal autophosphorylation of insulin and EGF receptors, together with its ability to reduce autophosphorylation of insulin receptors fully occupied by insulin, imply that the effect of pIgG on receptor autophosphorylation is largely independent of its effect on ligand binding. Moreover, these findings suggest that pIgG may inhibit autophosphorylation by acting on domains which are similar in the insulin and EGF receptors.

Animals↗
PubMed1985

Human autoantibodies directed against the human, but not the rat, insulin receptor.

Prior studies with monoclonal antibodies produced against the human insulin receptor in mice revealed that these antibodies may be species specific. Whether species-specific antibodies to the insulin receptor occur spontaneously in patients, however, has not been previously investigated. Recently, we found that the serum immunoglobulin G from a patient with lupus nephritis, insulin resistance, and hypoglycemia contained multiple subpopulations of antibodies directed at the human insulin receptor. We report herein that one such subpopulation has a high affinity for the human insulin receptor. This antibody subpopulation at 10 nM half-maximally inhibited [125I]insulin binding to human IM-9 lymphocytes, circulating erythrocytes and monocytes, isolated adipocytes, and placenta membranes. In contrast, this antibody subpopulation did not inhibit [125I]insulin binding to isolated rat adipocytes and hepatocytes, even at concentrations as high as 100 nM. These studies indicate that species-specific antibodies can occur spontaneously in patients with antiinsulin receptor antibodies.

Animals↗
PubMed1985

Tissue-specific antibodies against the fibroblast insulin receptor in a patient with lupus nephritis and hypoglycemia.

We recently reported that the serum from a patient with lupus nephritis, insulin resistance, and hypoglycemia contains multiple populations of antibodies directed at the human insulin receptor. In the present study, we found a subpopulation of antibodies (eluted from a protein A-Sepharose affinity column at pH 4.3) directed at the human fibroblast insulin receptor. When tested against human placental membranes, IM-9 lymphocytes, circulating monocytes and erythrocytes, and isolated adipocytes, the antibody subpopulation did not compete with 125I-insulin for binding to its receptor. In contrast, the antibody subpopulation competed with 125I-insulin for binding to the human fibroblast insulin receptor. This antibody subpopulation stimulated [3H]alpha-aminoisobutyric acid [( 3H]AIB) uptake to these cells. Unlike the effect of insulin, however, this regulation of transport was not antagonized by a mouse monoclonal antibody to the human insulin receptor that inhibits 125I-insulin binding. These studies indicate, therefore, that a tissue-specific antibody subpopulation can occur spontaneously in patients with antibodies to the human insulin receptor. Furthermore, they indicate the presence of anti-insulin receptor autoantibodies specifically directed against a tissue that is not primarily involved in glucose metabolism.

Animals↗
PubMed1984

Chronobiological approach to the treatment of essential hypertension: preliminary data.

The effect on bioperiodic parameters of hypertension elicited by the beta-blocking agent mepindolol, administered as a single dose of 10 mg at 8 a.m. vs 10 mg at 8 p.m., was evaluated in this study. Circadian blood pressure monitoring was performed in age-matched patients with essential hypertension after a two-week wash-out period with placebo and four weeks treatment. Patients were randomly allocated to one of the two treatment groups. Standard blood chemistry and electrocardiogram were performed at the beginning and end of the treatment period. Statistical analysis of blood pressure circadian rhythm characteristics (mesor, amplitude, acrophase) showed a significant decrease of mesor of systolic and diastolic blood pressure in both groups. Values of the mesor were not significantly different between the two groups. Interestingly, changes of acrophase and amplitude induced by the drug were different in regard to the time mepindolol was administered. Side effects were generally mild.

Adult↗
PubMed1983

Red blood cell age, pyruvate kinase activity, and insulin receptors. Evidence that monocytes and RBCs may behave differently.

Data emerging from insulin receptor studies performed on red blood cells (RBCs) and monocytes from the same subject are not always in agreement; dichotomy might occur since variations in mean RBC age are not taken into account or because insulin receptors on the two cell types behave differently. In the present investigation RBCs from normal male subjects were separated into five populations of different mean age by means of centrifugation of RBCs on a discontinuous gradient of buffered Percoll for 10 min at 1000 X g. Insulin binding varied significantly depending upon the RBC population tested and was closely correlated to the activity of pyruvate kinase (r2 = 0.86), a well-known marker of RBC age. These data suggested that pyruvate kinase assay might be helpful in studies of RBCs. To confirm this hypothesis, RBCs from 10 normal male subjects and 13 male patients with hemolytic anemia were studied; insulin binding was correlated to pyruvate kinase activity. By adjusting insulin binding to 2 X 10(9) RBCs/ml the range of data was abnormally high, but it became acceptable after adjusting insulin binding to pyruvate kinase activity (0.75 U/2 X 10(9) RBCs). The overall data indicated that insulin binding was highly correlated to pyruvate kinase activity (r2 = 0.82) but only slightly to reticulocyte number (r2 = 0.56) since not only reticulocytes but also erythrocytes lose receptors during maturation. Pyruvate kinase activity was measured in RBCs from normal men and from normally menstruating women at the seventh and twenty-fourth days of the cycle; results demonstrated that adjustment of data, according to mean RBC age, broadens dichotomy of monocyte and RBC data.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Circulating anti-insulin receptor antibodies in a patient suffering from lupus nephritis and hypoinsulinemic hypoglycaemia.

A 46-year-old female patient suffering from Lupus Nephritis came to our attention in 1981 for severe recurrent hypoglycaemia; she was obliged to eat every 5-7 hr to maintain glucose values not below 1.3-1.6 mM. All known causes of hypoglycaemia were excluded by performing selective angiography of the pancreas and skull, chest and abdominal computerized tomography, as well as stimulation and suppression tests. Oral glucose tolerance, tolbutamide and intravenous insulin (0.4 U/Kg b.w.) tests demonstrated that the patient was highly insulin resistant; furthermore, studies on the patient's red blood cells suggested that her insulin receptors were completely unable to bind insulin. Studies carried out to reveal the reason for this binding inhibition demonstrated that red blood cells from normal subjects as well as adipocytes from normal rats incubated with the patient's serum did not bind insulin (50% inhibition occurring at about 1:30 serum dilution). Insulin binding inhibitors were found in the fraction of the serum precipitated by ammonium sulphate. The serum cleared of IgG fraction was unable to affect insulin binding. These data demonstrate that the serum from the female patient investigated contained anti-insulin receptor antibodies blocking the binding of insulin to its receptors. Plasmapheresis improved the patient's metabolic status. The clinical picture would suggest that recurrent hypoglycaemia was caused by anti-insulin receptor antibodies acting as insulin on target cells.

Autoantibodies↗
PubMed1982

Decreased insulin receptors but normal glucose metabolism in Duchenne muscular dystrophy.

Compared to matched controls, 17 patients with Duchenne muscular dystrophy showed decreased insulin binding to monocytes due to decreased receptor concentration. These patients showed no signs of altered glucose metabolism and retrospective analysis of the clinical records of a further 56 such patients revealed no modification in carbohydrate metabolism. These data suggest that reduced insulin receptor number does not produce overt modifications of glucose metabolism in Duchenne muscular dystrophy.

Adolescent↗
PubMed1982

Factor VII in liver cirrhosis.

Factor VII activity and factor VII cross-reacting material (CRM) in plasma of patients with liver cirrhosis have been studied before and after vitamin K1 parenteral administration. Subjects were divided into two groups according to the absence (group I) or the presence (group II) of the following clinical findings: ascites, portal hypertension, encephalopathy. Factor VII activity and CRM show a statistically significant correlation (p less than 0.001) in all patients. In group II, significantly reduced levels of both activity and CRM were found as compared to the reference and the group I values. No variations were found after vitamin K administration. Different thromboplastins, investigated with respect to their sensitivity for factor VII, acted differently. Patients with normal albumin levels also showed normal levels of factor VII activity and antigen. No correlation was found in group II. The data discussed suggest that in liver cirrhosis with unknown aetiology no immunologically detectable precursor of factor VII is present.

Adult↗
PubMed1981

Transient effect of glucocorticoids on red blood cell insulin receptors.

The effect of oral administration of dexamethasone or cortisone on circulating red blood cell (RBC) insulin receptors was evaluated in normal males before treatment and 24 h (day 1), 48 h (day 2) and 72 h (day 3) after the commencement of steroid administration. Dexamethasone induced a slight significant decrease of insulin binding (p less than 0.05) on days 1 and 3, whereas cortisone did not. Cortisone, on the other hand, produced transient reduction (i.e. insulin binding lower than mean -2 SD of control values) in six subjects out of eight on days 1, 2 or 3 varying from subject to subject. Binding impairment was due mainly to reduced receptor affinity, even if slight reduction of receptor concentration was detectable. Qualitatively the present data agree that impaired insulin binding is due mainly to reduced receptor affinity; however, the effect of steroids on RBC is not significant and persistent as that on monocytes. The less marked effect of dexamethasone and cortisone on RBC versus monocytes indicates that receptor modifications may be tissue specific.

Cortisone↗