PubMed Health⌕ Search

Biomedical subjects

E Monti

Publications and source records attributed to E Monti.

At least 73 records · Page 4Linked to original sources
PubMed1989

Rapid preparation of a distinct lysosomal population from myelinating mouse brain using Percoll gradients.

To study the vesicular lysosome-associated transport and the metabolism of some brain macromolecules (in particular, sialoglycoconjugates), we developed a rapid procedure to obtain a distinct lysosomal population starting from myelinating mouse brain. This procedure is based on an initial differential centrifugation step producing a 1,000-17,500-g fraction (P2), followed by isopycnic centrifugation of fraction P2 on a self-generated colloidal silica gel (Percoll) gradient. The heaviest subfraction thus obtained is very rich in acid hydrolase activities like beta-galactosidase, arylsulfatase A, and acid phosphatase. The enrichment of these enzymes is approximately 100-fold as compared with the starting homogenate, whereas the markers of other subcellular organelles, such as mitochondria, plasma membranes, or the Golgi apparatus, are virtually absent. The lysosomal preparation contains approximately 12-14% of the total acid hydrolase activities, with a protein yield of approximately 0.12%. Electron microscopy shows that the lysosomal fraction is composed of an approximately 90% pure population of lysosomes. Therefore, the procedure described here is suitable for obtaining a highly purified lysosome preparation from myelinating mouse brain.

Animals↗
PubMed1989

Occurrence in brain lysosomes of a sialidase active on ganglioside.

A lysosomal preparation, obtained from brain homogenate of 17-day-old C57BL mice by centrifugation on a self-generating Percoll linear density gradient, showed relative specific activity (RSA) values for typical lysosomal enzymes of 40-120 and for mitochondria, plasma membrane, and cytosol markers of much lower than 1, a result indicating a high degree of homogeneity. The lysosomal preparation contained a sialidase activity that was assayed radiometrically with ganglioside [3H]GD1a and fluorimetrically with 4-methylumbelliferyl-1-alpha-D-N-acetylneuraminic acid (MUB-NeuAc). The properties of the lysosomal enzyme were compared with those of the plasma membrane-bound sialidase contained in a purified synaptosomal plasma membrane fraction that was prepared from the same homogenate and assayed with the same substrates. The optimal pH was 4.2 for the lysosomal and 5.1 for the plasma membrane-bound enzyme. The apparent Km values for GD1a and MUB-NeuAc were 1.5 X 10(-5) and 4.2 X 10(-5) M, respectively, for the lysosomal enzyme and 2.7 X 10(-4) and 6.3 X 10(-5) M for the plasma membrane-bound one. Triton X-100 had a predominantly inhibitory effect on the lysosomal enzyme, whereas it strongly activated the plasma membrane-bound one. The lysosomal enzyme was highly unstable on storage and freezing and thawing cycles, whereas the plasma membrane-bound one was substantially stable. The RSA value of the lysosomal sialidase in the lysosomal fraction closely resembled that of authentic lysosomal enzymes, whereas the RSA value of plasma membrane-bound sialidase in the plasma membrane fraction was very similar to that of typical plasma membrane markers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Direct detection of paramagnetic species in adriamycin perfused rat hearts.

Direct detection of paramagnetic species in control and adriamycin-perfused rat hearts has been carried out. Depending on the flow rate of the perfusion solution (8,4,2 and 1 ml/min) different paramagnetic species were observed: Fe(III)(g = 2.12) at 4 ml/min; three types of oxygen centered radicals of which two in control hearts (g = 2.05 g = 2.038 g = g = 2.008) and the third one (g = 2.03 g = 2.005) in adriamycin perfused hearts, at 2 ml/min. The latter radical was the only one observed at perfusion rate of 1 ml/min both in control and adriamycin treated systems. A relationship between the intracellular enzymatic reductive activation of the anthracycline and the occurrence of ischemic conditions (4,2 and 1 ml/min) in myocardial tissues is proposed basing on the relative amounts of the paramagnetic species above mentioned.

Animals↗
PubMed1988

Effect of calcium inhibitors and calcium mobilizers on doxorubicin accumulation in rat myocardial tissue.

The effect of four calcium-modulating agents on myocardial doxorubicin (DXR) accumulation was studied: the calcium-inhibitors verapamil (0.1 microM), trifluoperazine (5 microM) and flunarizine (0.05 microM) and the calcium-mobilizer taurine (50 mM). Myocardial cells of isolated Langendorff rat hearts receiving the drugs showed a significantly enhanced 14C-DXR uptake. These observations are in contrast with the hypothesis that DXR accumulation processes may be related to a decrease in calcium influx and suggest that a combined therapy with DXR and calcium-modulating agents might enhance the drug-induced cardiotoxicity.

Animals↗
PubMed1987

Identification of a phosphorylated form of phosphoenolpyruvate carboxykinase from the yeast Saccharomyces cerevisiae.

A phosphoprotein of 65 kDa, as determined by SDS-gel electrophoresis, has been isolated from yeast crude extracts. This phospho form copurifies with phosphoenolpyruvate carboxykinase in the enzyme purification procedure worked out in our laboratory (Tortora, P., Hanozet, G.M. and Guerritore, A. (1985) Anal. Biochem. 144, 179-185). Moreover, both proteins bind strongly to 5'AMP-Sepharose 4B in the presence of Mn2+, whereas a substantially lower binding occurs if Mn2+ is replaced by Mg2+. This binding pattern is consistent with the well-known Mn2+-dependence of yeast phosphoenolpyruvate carboxykinase. These data suggest that the 65-kDa protein might be a phosphorylation product of the native enzyme. Furthermore, although the phospho form is not immunoprecipitated by anti-phosphoenolpyruvate carboxykinase antibodies, addition of Protein A-Sepharose CL-4B to crude extracts preincubated with the antibodies results in the binding to the resin of the phospho form, thus providing immunological evidence for its identification as a modified form of native enzyme. The same 65-kDa phosphoprotein is detectable in extracts from cells grown in the presence of [32P]Pi, as well as in cell extracts incubated with [gamma-32P]ATP. Moreover, digestion of the phosphoprotein with BrCN or with Staphylococcus aureus V8 proteinase, yields two and three fragments, respectively, which appear parallel to digestion products of phosphoenolpyruvate carboxykinase, again supporting the proposed identification. Finally, analysis of the phosphorylated amino acids in the 65-kDa protein shows that phosphoserine is the only labelled phosphoamino acid.

Adenosine Triphosphate↗
PubMed1986

Relationship between doxorubicin-induced ECG changes and myocardial alterations in rats.

The aim of the present study was to evaluate the dose- and time-dependence of the effect displayed by doxorubicin (DXR) on the electrocardiogram (ECG) and to establish the relationship between structural alterations of the myocardium and ECG changes in rats administered DXR, at a dose of 1.5 or 3.0 mg/kg, every 3 days for a total of three administrations. The most interesting findings consisted of a dose-dependent, but reversible prolongation of the QRS complex, and in a dose-dependent and progressive irreversible increase in QaT and, in particular, in SaT duration. Furthermore, animals treated with the higher DXR dose showed a slight increase in serum K+ concentration and a significant decrease in serum Ca2+ levels. A good correlation was found between the morphologic score indicating the degree of observed tissue damage and SaT prolongation. These results therefore support the usefulness of measuring this ECG parameter for monitoring the development of DXR-induced cardiotoxicity in rats.

Animals↗
PubMed1986

Determination of doxorubicin and doxorubicin-3-ol in rat heart.

The discovery of a delayed form of DXR-induced cardiotoxicity raises the question whether the presence of the drug or of metabolites in myocardial cells is necessary for the development of cardiotoxicity. The present investigations deal with a new method for the determination of DXR and of its main metabolite, DXR-3-ol, in cardiac cells. Rat hearts "ex-vivo", isolated 24 h after i.v. administration of 6 mg/kg DXR and 20 micro C of DXR-14C, were perfused with ice-cold Tyrode solution, which releases anthracyclines from extracellular spaces. After homogenization DXR and DXR-3-ol were extracted from the cell at room temperature. The separation was carried out by HPLC; the recovery was about 95%, measured by the extracted radioactivity compared with that of the pellet residue.

Animals↗
PubMed1986

Myocardial contractility and heart pharmacokinetics of adriamycin following a single administration in rat.

A single administration of adriamycin (DXR) 6.0 mg/kg i.v. to rats brings about a biphasic impairment of the maximal myocardial contractile performance, measured as dF/dt of ex vivo isolated atria incubated in the presence of calcium concentrations varying up to 12 mM. The initial impairment of the contractile performance peaks 1 week after DXR administration and recovers within 3 weeks (acute phase of cardiotoxicity). After this time and up to the end of the observation period (8 weeks after treatment), delayed cardiotoxicity occurs, showing a progressive and irreversible impairment of the contractile performance of the atria. This behaviour parallels the previously shown ECG and morphological abnormalities. Tissue determinations of DXR showed that the drug is present in myocardium during the acute phase of cardiotoxicity, while the metabolite adriamycinol is not detectable 1 week after DXR administration. These data show that the presence of DXR and/or metabolites in heart muscle is not necessary for the delayed form of cardiotoxicity to become apparent and suggest that this form of cardiotoxicity is related to a mechanism different from that involved in acute cardiotoxicity.

Animals↗
PubMed1985

Preliminary evaluation of myocardial toxicity of 4'-deoxydoxorubicin: experimental and clinical results.

4'-deoxydoxorubicin (4'-deoxy-DXR), a new doxorubicin (DXR) analogue with interesting antineoplastic activity, was tested for its cardiotoxicity in guinea pigs and humans. In experiments on isolated guinea pig heart, which is considered a highly predictive model of acute anthracycline cardiotoxicity in humans, 4'-deoxy-DXR was found to be significantly less cardiotoxic than DXR. This effect was correlated with a lower degree of inhibition of the fast-exchanging calcium compartment and of the low affinity sarcolemmal calcium-binding sites. The preliminary study on 4'-deoxy-DXR in humans was conducted on 117 patients affected by advanced malignancies resistant to conventional chemotherapy. The drug was administered by bolus i.v. injection in doses ranging from 10 to 40 mg/m2 in the phase I study and in doses of 35 mg/m2 in the phase II study, which is still ongoing. Cardiologic evaluation consisted of recording of EKG, left ventricular systolic time intervals (STI), echocardiography and radionuclide ejection fraction. Preliminary data indicated a lower percentage of EKG abnormalities in comparison not only with DXR but also with other anthracycline analogues. Analysis of STI recorded 1 h after different doses of 4'-deoxy-DXR failed to show the dose-dependent effect on left ventricular function which has been described for DXR, thus confirming the lower acute cardiotoxic effect. Functional parameters serially measured to evaluate chronic cardiotoxicity in 15 patients who received more than 200 mg/m2 were not significantly different from basal values.

Adult↗
PubMed1983

Role of the fast-exchanging calcium compartment in the early cardiotoxicity of anthracycline analogs.

Two new anthracycline analogs, 4'-epi-doxorubicin and 4'-deoxydoxorubicin, were tested for their cardiotoxicity and their activity on calcium turnover in guinea pig heart. The df/dt was used as an index of contractile force; calcium turnover was studied by means of a radioisotopic technique. 4'-Epi-doxorubicin was found less cardiotoxic than doxorubicin, whereas 4'-deoxydoxorubicin was found almost completely devoid of cardiotoxicity. The different cardiotoxic activity was found to be linearly correlated with the relative capacity to inhibit the fast-exchanging calcium compartment in cardiac muscle: doxorubicin greater than 4'-epi-doxorubicin greater than 4'-deoxydoxorubicin. This result supports that the inhibition of calcium exchange is involved in development of the early cardiotoxicity of anthracyclines.

Animals↗
PubMed1983

Interaction between doxorubicin and mitomycin C on mortality and myocardial contractility in guinea pig.

The present investigations were carried out in guinea pig to ascertain whether mitomycin C has a direct cardiotoxic effect or interacts with doxorubicin-induced cardiotoxicity. I.p. administration of mitomycin C did not modify the survival rate up to 30 days, whereas the combined administration of doxorubicin and mitomycin C significantly decreased the survival time in comparison to the doxorubicin-treated group. On isolated atria, mitomycin C did not cause significant inhibition of the contractile force or an enhancement of the doxorubicin-induced negative inotropic effect. These results do not support the possibility that mitomycin C potentiates the acute cardiotoxic effects produced by doxorubicin.

Animals↗