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Biomedical subjects

C Montecucco

Publications and source records attributed to C Montecucco.

At least 235 records · Page 13Linked to original sources
PubMed1985

Transmembrane topology of acetylcholine receptor subunits probed with photoreactive phospholipids.

The domains of the acetylcholine receptor subunits that contact the lipid phase were investigated by hydrophobic photolabeling of receptor-rich membrane fragments prepared from Torpedo marmorata and Torpedo californica electric organs. The radioactive arylazido phospholipids used carry a photoreactive group, either at the level of the lipid polar head group (PCI) or at the tip of the aliphatic chain (PCII), and thus probe respectively the "superficial" and "deep" regions of the lipid bilayer. The four subunits of T. marmorata and T. californica acetylcholine receptor reacted with both the PCI and PCII probes and thus are all exposed to the lipid phase. Ligands known to stabilize different conformations of the acetylcholine receptor (nicotinic agonists, snake alpha-toxin, and noncompetitive blockers) did not cause any significant change in the labeling pattern. The acetylcholine receptor associated 43 000-dalton v1 protein did not react with any of the probes. A striking difference in labeling between T. marmorata and T. californica acetylcholine receptors occurred at the level of the alpha-subunit when the superficial PCI probe was used. An approximately 5-fold higher labeling of the alpha-subunit as compared to the beta-, gamma-, and delta-subunits was observed by using receptor-rich membranes from T. marmorata but not from T. californica. The same difference persisted after purification of the labeled receptors from the two species and was restricted to an 8000-dalton C-terminal tryptic peptide. The only mutation observed in this region of the complete alpha-subunit sequence of the two species is the substitution of cysteine-424 in T. marmorata by serine-424 in T. californica.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Cytokinetic studies in acute leukemia during early induction therapy.

The proliferative activity of bone marrow blasts was determined in 19 patients with acute leukemia during early induction therapy using in vitro tritiated thymidine (3H-TdR) cytoautoradiography and propidium iodide DNA flow cytofluorometry. Following 1-3 causes of treatment, the aliquot of bone marrow blasts in 9 patients, who later achieved remission or marrow aplasia, was reduced to a greater extent that of the remaining 10 patients who failed to respond. In the first group of patients, the 3H-TdR labeling index was increased by 259-653% over the pretreatment value, whereas it was lower than 104% of the pretreatment value in all but one unresponsive patient. Leukemic blast recruitment is conceivable. It might have facilitated remission by increasing the effectiveness of the antileukemic agents administered later.

Adolescent↗
PubMed1985

Hydrophobic photolabelling of sarcoplasmic reticulum with [125I]TID.

[125I]TID, a small photoreactive lipophylic reagent, was used to label intrinsic proteins of rabbit and rat sarcoplasmic reticulum membranes. A 160,000 glycoprotein, the Ca2+-ATPase and polypeptides of mol. wt 53-55,000, 30,000, 20,000 and 6000 dalton were labelled suggesting that these proteins are integral membrane components.

Animals↗
PubMed1985

DNA content analysis of peripheral blood B-lymphocytes in plasma cell malignancies.

A double fluorescence assay has been employed for the detection of cell surface and/or cytoplasmic immunoglobulins (Ig) and the measurement of nuclear DNA content in the same cell. Following staining for Ig by means of FITC conjugated antibodies directed against heavy or light chains, cell suspensions or cytospin preparations were ethanol fixed and stained with a propidium iodide-RNAse solution. In this way, the cytometric DNA content of circulating B-lymphocytes was analyzed in three patients suffering from plasma cell malignancies with an excess of peripheral blood B-lymphocytes and evidence of aneuploid bone marrow plasma cells. Aneuploid circulating B-lymphocytes with the same DNA stem-line as bone marrow plasma cells were found in two patients with advanced disease but not in the only one we studied at presentation. Aneuploid lymphocytes had surface immunoglobulins bearing the same light chain as the M-protein. In addition, a significant percentage (23%) of cells lacking either surface or cytoplasmic immunoglobulins proved to be aneuploid in plasma cell leukemia. Nuclear DNA measurement combined with surface or cytoplasmic marker analysis appears to be a reliable method for studying neoplastic lymphoid precursor cells in plasma cell malignancies.

Aneuploidy↗
PubMed1985

Rate of M-component changes and plasma cell labeling index in 25 patients with multiple myeloma treated with peptichemio.

Twenty-five consecutive patients with previously untreated multiple myeloma were studied for bone marrow plasma cell labeling index, response to peptichemio induction therapy, and rate of M-component (MC) changes during the course of the disease. They received intermittent melphalan or cyclophosphamide as maintenance therapy and peptichemio associated with vincristine at first relapse. The response rate (76%) was independent of clinical stage, evaluated according to Merlini et al and to Durie and Salmon. Among responsive patients, rapid responders (half-life of MC decrease less than 47 days for IgA and IgG and less than 29 days for light chain myelomas) had a bone marrow plasma cell labeling index significantly higher (P less than 0.01) than that of slow responders. Rapid responders had a median survival of 15 months, while slow responders had a median survival of 42 months (P less than 0.05). The difference in survival between the two groups was accounted for mainly by the difference in duration of first response and the different rates of MC increase following it. Both of these parameters were directly related to the half-life of MC decrease at response in IgA and IgG myelomas. The duration of second response and the half-life of MC increase following it were shorter than the duration of first response and than the half-life of MC increase at first relapse.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1984

Labelling of the integral proteins of sarcoplasmic-reticulum membranes.

Photoreactive lipids were introduced into rabbit and rat sarcoplasmic-reticulum membranes to label specifically integral proteins. Evidence was obtained that, in addition to the Ca2+-dependent ATPase, the 160 000-Mr glycoprotein, the 53 000-56 000-Mr components and polypeptides of Mr 30 000, 20 000 and 6000 are integral components of sarcoplasmic-reticulum membranes.

Animals↗
PubMed1984

Plasma cell DNA content in multiple myeloma and related paraproteinemic disorders. Relationship with clinical and cytokinetic features.

In 62 patients with multiple myeloma (MM) and related disorders, the nuclear DNA content distribution of bone marrow plasma cells was assessed by flow and conventional cytofluorometry. Abnormal distributions, suggesting the presence of aneuploid populations, were observed in 53% of MM at diagnosis, in 50% of benign monoclonal gammopathies and in 12% of Waldenström's macroglobulinemias. Eighty-six percent of aneuploid cases had DNA stem-lines falling between the diploid and triploid value. In advanced and relapsing MM, abnormal distributions were found in 75% of cases. In 4 out of 14 patients with MM serially studied during the course of disease, emergence of new abnormal clones was documented. The abnormal DNA content of bone marrow plasma cells was not correlated with any clinical and laboratory characteristic and it affected neither response to therapy nor survival in patients studied at diagnosis. In advanced phases of MM, the presence of abnormal clones was correlated with high plasma cell proliferation rates (studied by tritiated thymidine incorporation) and poor response to chemotherapy. Seven out of 8 patients in acute terminal phase of MM had abnormal clones. Among these, five had DNA stem-lines over triploid value.

Adult↗
PubMed1983

Proliferative activity of bone marrow cells in primary dysmyelopoietic (preleukemic) syndromes.

The proliferative activity of bone marrow cells was studied in 24 patients with primary dysmyelopoiesis by means of flow cytometry and 3H-TdR autoradiography. Abnormal DNA content was found in two cases with aneuploid karyotypes. DNA content typical of a diploid population was observed in all patients with normal karyotype and in three patients with chromosomal aberrations. The fraction of bone marrow cells in S- and G2-phase was higher in primary acquired sideroblastic anemia and refractory anemia (without excess of blasts) than in refractory anemia with excess of blasts and chronic myelomonocytic leukemia. Regardless to the diagnosis, the patients with low fraction of cells in S- and G2-phase had short survival time and showed high rate of evolution into acute nonlymphoblastic leukemia. The labeling (LI) and mitotic (MI) indexes of both erythroblasts and granulocytic cells were decreased in nearly all patients. The lowest values of LI and MI of the granulocytic compartment were found in the patients who subsequently developed acute leukemia. These data suggest that cytokinetic analysis allows investigators to achieve useful information on the stage of disease in the dysmyelopoietic syndromes.

Adult↗
PubMed1983

Membrane topology of ATP synthase from bovine heart mitochondria and Escherichia coli.

The polypeptides exposed to lipids in the membranous F0 sector of the mitochondrial and Escherichia coli ATP synthases were labelled with radioactive photoreactive lipids. Highly resolving gel electrophoretic conditions were used in order to separate all the eighteen components forming the bovine heart mitochondrial enzyme. The hydrophobic labelling was performed on fully active and inhibitor-sensitive ATP synthases. In the mitochondrial enzyme prepared according to Serrano et al. (1976) [J. Biol. Chem. 251, 2453-2461] seven polypeptides of Mr 30500; 11500; 10500; 10000; 9500; 8500 and 4500 were labelled. The major amount of radioactivity was associated with the 30500-Mr component, which is thought to be the adenine nucleotide carrier. In the preparation of Galante et al., (1979) which almost completely lacks this component [J. Biol. Chem. 254, 12372-12378] nine polypeptides of Mr 25000; 21000; 11500; 10500; 10000; 9500; 9200; 8500 and 4500 were labelled. In the ATPase synthase from E. coli the major amount of labelling was associated with subunit b and only a minor portion with subunit c.

ATP Synthetase Complexes↗
PubMed1983

Labeling of subunit b of the ATP synthase from Escherichia coli with a photoreactive phospholipid analogue.

Purified ATP synthase (F1F0) from Escherichia coli K12 was labeled with the hydrophobic photoreactive label 1-palmitoyl 2-(2-azido-4-nitro)benzoyl sn-glycero-3-[3H]phosphocholine in reconstituted proteoliposomes. The F0-subunit b was predominantly labeled. A very low amount of label was detected on the other F0-subunits a and c. The label in subunit b could be traced back by proteolytic digestion to the NH2-terminal fragment 1 to 53 which contains the stretch of hydrophobic amino acid residues 1 to 32. By sequencing the intact protein, the distribution of label among the amino acids in this segment was determined. Cysteine 21 was predominantly labeled. Other labeled amino acids occurred at the NH2-terminal (Asn-2) and at position 26 (tryptophan). Due to the restricted mobility of the label in the lipid bilayer, these residues are suggested to be located in or close to the polar head of the lipid bilayer. These results will be compared with predictions for the arrangement of the polypeptide b derived from the hydrophobicity profile.

ATP Synthetase Complexes↗
PubMed1983

Flow cytometric DNA content in myelodysplastic syndromes.

DNA flow cytometric analysis of unfixed bone marrow cells stained with propidium iodide was carried out in 33 patients with untreated primary myelodysplastic syndromes. Patients with stable clinical course for up to 3 years had higher fractions of cells in S and G2 phases (22.7 +/- 12.4% and 12 +/- 3.6%) than those who developed acute leukemia and/or died early in the course of disease (14.4 +/- 8.5% and 6.6 +/- 4%). Median survival was more than 36 mo in patients with S + G2 cell fraction higher than 24%, and 14 mo in the remaining 16 patients with lower values (P less than 0.01). Analyses repeated after 3-24 mo showed no major changes in cell proliferation pattern in ten out of 11 patients. The remaining patient had sharp decrease in S and G2 cell fraction 3 mo before the transition into acute leukemia. The DNA index (DI) of bone marrow cells was calculated to assess ploidy. However, comparative evaluation of cytologic, cytogenetic, and flow cytometric data suggest that, under our experimental conditions, the DI may be influenced by factors such as the degree of chromatin compactness.

Adolescent↗
PubMed1982

Different polypeptides of bovine heart cytochrome c oxidase are in contact with cytochrome c.

Two water-soluble carbodiimides, differing in molecular dimensions, have been used to characterize the cytochrome c binding site of bovine heart cytochrome c oxidase. Several polypeptide components of the enzyme contain acidic residues which are modified by these reagents. Carboxyl groups present in subunit II, VII and polypeptide c, are protected from modification when cytochrome c, equimolar to oxidase, is added and they can cross-link to the substrate once activated by the carbodiimide. Comparison of the modification patterns suggest that the most reactive residues are located on subunit II and VII, the former being also more exposed. The data obtained indicate that even though subunit II plays the major role in binding cytochrome c, at least two other lower Mr polypeptides contribute to the cytochrome c binding domain.

Animals↗
PubMed1982

Micellar gangliosides mediate the lipid insertion of cholera toxin protomer A.

The topology of the interaction of cholera toxin with ganglioside and detergent micelles was studied with the technique of hydrophobic photolabelling. Cholera toxin alpha and gamma polypeptide chains appear to penetrate into the hydrophobic core of ganglioside micelles. Micelles of SDS cause the labelling also of the beta polypeptide chains, while Triton X-100 micelles have little ability to mediate the labelling of the toxin. The specific reduction of the alpha-gamma disulfide bond allows the penetration of the alpha polypeptide chain into Triton X-100 micelles, but does not affect the interaction of cholera toxin with either ganglioside or SDS micelles. Thus, ganglioside micelles appear to cause a conformational change of the native toxin, such as to induce the penetration of the alpha chain into the micelle hydrophobic core.

Cholera Toxin↗
PubMed1982

Sequential vincristine, arabinosylcytosine and adriamycin in acute leukemia: cytologic and cytokinetic studies.

Cytokinetic and cytocidal effects exerted on peripheral blood blasts by sequential administration of vincristine (VCR) 2 mg on day 1, arabinosylcytosine (Ara-c) 50-60 mg/m2/12 hr from day 2-4), and Adriamycin (ADM, Farmitalia, Milan, Italy, 40-60 mg/m2 on day 5) have been examined in 22 courses of treatment performed on 12 patients with nonlymphoblastic and in 4 with lymphoblastic acute leukemia. In 4 patients, the bone marrow blasts wee examined before and also after VCR-Ara-c administration. In vitro tritiated thymidine autoradiography and propidium iodide-DNA flow cytometry were employed for kinetic studies. Blasts disappeared from blood with a median half time of 35 hr. After VCR-Ara-c administration, a significant increase in labeling index (LI) and in the aliquot of cells with DNA content between the diploid (2n) and the tetraploid (4n) values was observed in 80% of the courses in peripheral blood blasts and in all courses in bone marrow blasts. The median grain count over the labeled nuclei was decreased, and the 4n cell percentage and the bone marrow blast mitotic index did not increase. These findings suggest that the increase in the S phase fraction of blast population is due to cell synchronization. Increase in the S phase appears to heighten the cytocidal effect of ADM. The aliquot of the blasts cleared from blood after ADM were in fact related directly to the degree of labeling index increase observed during the previous administration of VCR and Ara-c.

Acute Disease↗
PubMed1982

Effect of ionophores on lymphocyte cellular metabolism.

The effect of valinomycin, nigericin, gramicidin S and D, A23187 and X537A on respiration and cellular ATP content of rat spleen lymphocytes is presented. It has been found that while valinomycin and nigericin interfere with mitochondrial functions gramicidin D does not show an appreciable effect. These results are explained in terms of different ability of ionophores to re-distribute among intracellular membranes. A23187 and X537A, added with Ca2+, strongly enhanced O2 consumption and reduced cellular ATP content.

Animals↗
PubMed1981

Membrane topology of beef-heart ubiquinone-cytochrome c reductase (complex III).

The membrane topology of ubiquinone-cytochrome c reductase (EC 1.10.2.2.) has been investigated with photoreactive lipid analogs (Bisson, R., and Montecucco, C. (1981) Biochem. J. 193, 757-763), both in its isolated form and when part of succinate-cytochrome c reductase (Complex II + III). These probes react specifically with those polypeptide chains exposed to lipids, thereby labeling them radioactively. Highly resolving gel electrophoretic conditions have been used to determine the patterns of labeling. Core protein I, cytochrome b, cytochrome c1, and polypeptides VI, VII, VIII, and IX contribute to the lipid-protein boundary of Complex III. Evidence that the interaction between Complex II and Complex III involves their hydrophobic domains is also presented.

Animals↗