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L Berti

Publications and source records attributed to L Berti.

At least 37 records · Page 2Linked to original sources
PubMed1994

Glucose-induced translocation of protein kinase C isoforms in rat-1 fibroblasts is paralleled by inhibition of the insulin receptor tyrosine kinase.

Rat-1 fibroblasts stably overexpressing high levels of human insulin receptor were used as a model system to study the effects of hyperglycemia on insulin receptor tyrosine kinase (IRK) activity and protein kinase C (PKC) translocation in parallel in the intact cell. Glucose (10-25 mM) induced a significant reduction of IRK activity (tyrosine phosphorylation of IR-beta-subunit and IR-substrate-1) within 10 min. This effect was paralleled by a rapid translocation of several PKC isoforms (cPKC alpha, nPKC delta, nPKC epsilon, nPKC zeta) to the plasma membrane within 1 min. Kinetics of IRK inhibition and PKC translocation are consistent with the idea that the glucose effect on IRK is mediated by PKC activation. This hypothesis is supported by further observations. Addition of the protein kinase C inhibitor H-7 can prevent the effect of glucose on IRK. Inhibition of IRK is also observed after stimulation of the cells with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate, which can substitute for a physiological activator of PKC. Glucose (25 mM) increases the 32P incorporation in serine residues of the beta-subunit of IRK. We conclude that high levels of glucose induce inhibition of IRK in vivo. There is indirect evidence that this effect is mediated by a glucose-induced PKC translocation/activation and serine phosphorylation of the insulin receptor.

3-O-Methylglucose↗
PubMed1994

Troglitazone prevents glucose-induced insulin resistance of insulin receptor in rat-1 fibroblasts.

Troglitazone (CS045), a compound belonging to the thiazolidine diones, is being tested as a new oral antidiabetic agent. Evidence exists from animal studies and clinical trials with non-insulin-dependent diabetes mellitus patients that Troglitazone might reduce insulin resistance. The molecular mechanism of this effect is not understood. In this study, we investigated whether Troglitazone might interfere with the mechanism of glucose-induced insulin resistance. Several studies indicate that hyperglycemia reduces the kinase activity of the insulin receptor in different cell types. This effect is paralleled by translocation of several protein kinase C (PKC) isoforms, and it can be prevented by PKC inhibitors, which suggests that glucose-induced receptor desensitization is mediated by activation of PKC. We studied the effect of hyperglycemia on the insulin receptor kinase activity and its modulation by Troglitazone in rat-1 fibroblasts that stably overexpress the human insulin receptor. Before stimulation with insulin (10(-7) M), cells were acutely exposed to hyperglycemic conditions in the absence or presence of Troglitazone (0.01-2 micrograms/ml). The insulin receptor was solubilized from a plasma membrane fraction or whole cell lysates, and proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotted against antiphosphotyrosine and anti-insulin receptor beta-subunit (CT 104) antibodies. Acute hyperglycemia (25 mM glucose) induced a significant inhibition of the insulin receptor kinase (IRK) activity within 30 min (inhibition to 30 +/- 12.5% of maximal insulin-stimulated beta-subunit phosphorylation, n = 9, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

Inositol phospho-oligosaccharides from rat fibroblasts and adipocytes stimulate 3-O-methylglucose transport.

Inositol phospho-oligosaccharides (IPOs), which are released from liver membranes upon stimulation by insulin, mimic a wide spectrum of insulin effects in different cells, but not the stimulation of glucose transport. We investigated whether other insulin-sensitive tissues release glucose transport-stimulating IPOs and whether this is related to the human insulin receptor isoform-A or -B (HIR-A or HIR-B). Rat1 fibroblasts overexpressing HIR-A or -B (rat1-HIR cells) were labelled with [3H]glucosamine, [3H]mannose or myo-[3H]inositol. IPOs from the cell supernatant were partially purified by an AG1X2 anion-exchange column, and fractions were eluted at different pH values (pH 3, pH 2 and pH 1.3). The label from glucosamine, mannose and myo-inositol appeared predominantly in the pH 2 fraction. The biological activity of the fractions was determined by measuring 3-O-methylglucose transport and lipogenesis in fat cells. Using the pH 2 fraction from the supernatant of rat1-HIR fibroblasts, insulin increased the release of 3-O-methylglucose-transport-stimulating activity (HIR-A: without insulin, 22.4 +/- 5.4%; with insulin 54.0 +/- 8.4%; HIR-B: without insulin 21.6 +/- 7.5%, with insulin, 44.7 +/- 10.6%, given as a percentage of equilibrium glucose transport reached after 4 s) and lipogenesis-stimulating activity (HIR-A: without insulin, 1.24 +/- 0.17; with insulin, 4.69 +/- 0.2; HIR-B: without insulin, 1.34 +/- 0.18; with insulin, 4.98 +/- 0.31, given as nmol of [3H]glucose converted into lipids/min per 10(6) cells). Analogous experiments were performed with isolated rat fat cells expressing the physiological level of insulin receptors. Upon insulin stimulation of fat cells in the presence of 2.5 mM mannose, the release of 3-O-methylglucose-transport-stimulating activity was detected (for purified supernatant of adipocytes without insulin, 6.9 +/- 1.12%; with insulin, 41.0 +/- 3.6%) and lipogenesis-stimulating activity (without insulin, 0.93 +/- 0.17, with insulin 2.96 +/- 0.31 nmol/min per mg). These data suggest (1) that adipocytes and rat1-HIR fibroblasts release IPOs that are able to stimulate glucose transport, (2) that both insulin receptor isoforms (HIR-A and HIR-B) mediate the effect of insulin on IPO release, and (3) that overexpression of insulin receptors increases the basal release of IPOs.

3-O-Methylglucose↗
PubMed1992

Evaluation of mitral stenosis by cine magnetic resonance imaging.

To evaluate the ability of cine magnetic resonance imaging (cine MRI) in the assessment of mitral stenosis (MS), we studied 20 patients (14 women and 6 men, mean age 60.6 +/- 8.5 years) with rheumatic mitral valve stenosis by using an 0.5 T magnet. Cine MRI showed several signs of MS. Mitral leaflet thickening, reduced diastolic opening, and abnormal valve motion toward the left ventricular outflow tract were all common features. MS was also characterized by an abnormal diastolic transmitral signal from blood. Both left atrial and left ventricular dimensions were similar to those obtained at two-dimensional echocardiography (2-DE) (r = 0.89 and r = 0.86, respectively; p less than 0.001). A significant relationship was also found between the maximum mitral leaflet separation measured by cine MRI in diastole and the mitral valve area as calculated using the pressure half-time method and continuous wave Doppler (r = 0.81; p less than 0.001). These data indicate the improved ability of MRI to detect and assess MS and also suggest that this technique may contribute to the noninvasive assessment of MS.

Aged↗
PubMed1991

An inositol phosphoglycan stimulates glycolysis in human platelets.

Upon hydrolysis of membrane glycosyl-phosphatidylinositol (gly-PtdIns), an inositol phosphoglycan (IPG) is generated, responsible for multiple biological activities and recently proposed as mediator of the action of a variety of hormones and growth factors. The present study shows that IPG is able to significantly stimulate platelet glycolysis, which represents the major energy producing pathway in this cell system. The activation of glycolytic flux induced by IPG appears to be specific and very rapid even though the molecular mechanism involved remains to be elucidated.

Blood Platelets↗
PubMedDate not supplied

Energy-transfer cassette labeling for capillary array electrophoresis short tandem repeat DNA fragment sizing.

Energy-transfer (ET) dye-labeled primers significantly improve fluorescent DNA detection because they permit excitation at a single common wavelength and they produce well separated and intense acceptor dye emission. Recently, a new ET cassette technology was developed [Berti, L. et al. (2001) Anal. Biochem. 292, 188-197] that can be used to label any PCR, sequencing, or other primer of interest. In this report we examine the utility of this ET cassette technology by labeling seven different short tandem repeat (STR) specific primers with each of the four ET cassettes and analyzing the PCR products generated on a MegaBACE-1000 capillary array electrophoresis system. More than 60 amplicons were generated and successfully analyzed with the ET cassette-labeled primers. Both forward and reverse primers were labeled for multiplex PCR amplification and analysis. Single base pair resolution was achieved with all four ET cassettes. This ET cassette-primer labeling procedure is ideally suited for creating four-color fluorescent ET primers for STR and other DNA assays where large numbers of different loci are analyzed including sequencing, genetic identification, gene mapping, loss of heterozygosity testing, and linkage analysis.

DNA↗
PubMedDate not supplied

[Chemotherapy of gestational chorionepithelioma].

The department of Gynecology and Obstetrics of Florence University reports the following findings for the chemotherapy of gestational choriocarcinoma during the period 1962-74. Sixteen cases, 11 of which were rated high risk cases, were given chemotherapy with MTX alone or in association with other cytotoxic agents. In the 12 surviving cases that may be considered the incidence of complete remission (from 4 to 13 years) is 67%. Of the 8 cases rated as cured 3 were high risk cases at the beginning of treatment. Intermittent chemotherapy with MTX only was given by slow intravenous injection at doses of 3 to 4 mg/kg for 24-48 h followed from the 48th h by folinic acid treatment for 1-2 days. This schedule is recommended because of its negligible toxicity as a replacemen for intramuscular MTX in 5-day courses, which carries a fairly high risk of toxicity.

Adult↗
PubMedDate not supplied

Circumscribed myositis ossificans of the iliopsoas muscle. Description of a case followed-up after 1 and 14 years.

The term myositis ossificans (MO) means a pathology characterized by the formation of heterotopic bone tissue within the connective tissue of the muscle. Two clearly differentiated forms of the disease are described: one is generalized and one is localized or circumscribed (CMO). It is the purpose of this study to describe a case of circumscribed myositis ossificans located in the iliopsoas muscle, clinically by CT scan and followed-up after 1 and 14 years.

Adult↗