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Biomedical subjects

D Cavallini

Publications and source records attributed to D Cavallini.

At least 19 recordsLinked to original sources
PubMed2001

Formation of nitrotyrosine by methylene blue photosensitized oxidation of tyrosine in the presence of nitrite.

Methylene blue photosensitized oxidation of tyrosine in the presence of nitrite produces 3-nitrotyrosine, with maximum yield at pH 6. The formation of 3-nitrotyrosine requires oxygen and increases using deuterium oxide as solvent, suggesting the involvement of singlet oxygen in the reaction. The detection of dityrosine as an additional reaction product suggests that the first step in the interaction of tyrosine with singlet oxygen generates tyrosyl radicals which can dimerize to form dityrosine or react with a nitrite-derived species to produce 3-nitrotyrosine. Although the chemical identity of the nitrating species has not been established, the possible generation of nitrogen dioxide (*NO(2)) by indirect oxidation of nitrite by intermediately produced tyrosyl radical, via electron transfer, is proposed. One important implication of the results of this study is that the oxidation of tyrosine by singlet oxygen in the presence of nitrite may represent an alternative or additional pathway of 3-nitrotyrosine formation of potential importance in oxidative injures such as during inflammatory processes.

Animals↗
PubMed2000

Methylene blue photosensitized oxidation of cysteine sulfinic acid and other sulfinates: the involvement of singlet oxygen and the azide paradox.

The methylene blue photosensitized oxidation of cysteine sulfinic acid is investigated. Enhancement of the oxygen consumption rate in deuterium oxide suggests the involvement of singlet oxygen ((1)O(2)) in oxidation. Addition of the (1)O(2) quencher azide produced an unusual enhancement of the oxidation rate of all the sulfinates assayed. It is assumed that azide works as a one-electron carrier between (1)O(2) and the sulfur compounds. Analyses of the products indicate that the photochemical oxidation of cysteine sulfinic acid proceeds through two simultaneous mechanisms. The Type II (singlet oxygen) mechanism is responsible for oxidation of the sulfinic group to the sulfonic group with production of cysteic acid, stable to the photooxidation system, whereas the Type I (electron transfer) mechanism is involved in the degradation of cysteine sulfinic acid to acetaldehyde. Other products detected were ammonia, sulfate, and hydrogen peroxide which account for the degradation of cysteine sulfinic acid and for the excess of oxygen consumption detected during the oxidative reaction.

Aerobiosis↗
PubMed2000

Hypotaurine and superoxide dismutase: protection of the enzyme against inactivation by hydrogen peroxide and peroxidation to taurine.

Hypotaurine is able to prevent the inactivation of SOD by H2O2. The protection is concentration-dependent: at 20 mM hypotaurine the inactivation of SOD is completely prevented. It is likely that hypotaurine exerts this effect by reacting with hydroxyl radicals, generated during the inactivation process, in competition with the sensitive group on the active site of the enzyme. According to this, spectral studies indicate that in presence of hypotaurine the integrity of the active site of SOD is preserved by the disruptive action of H2O2. An interesting outcome of the SOD/H2O2/hypotaurine interaction is that SOD catalyzes the peroxidation of hypotaurine to taurine. Indeed, the formation of taurine increases with the reaction time and with the enzyme concentration. Although the peroxidase activity of SOD is not specific and relatively slow compared to the dismutation of superoxide, it might represent another valuable mechanism of production of taurine.

Animals↗
PubMed2000

Identification of an oxidation product of aminoethylcysteine ketimine dimer.

In continuation of our previous work dedicated to the detection of the oxidation products of aminoethylcysteine ketimine dimer by oxygen reactive species, we give here data for the identification of the alpha, beta unsaturated sulfoxide as the main product of interaction of the dimer with H2O2. Identification has been done on the basis of mass spectrometry and NMR analyses of the product isolated by preparative chromatography.

Amino Acids, Sulfur↗
PubMed1999

Oxidation of hypotaurine to taurine with photochemically generated singlet oxygen: the effect of azide.

Hypotaurine is oxidized to taurine by singlet oxygen (1O2) generated with methylene blue used as a photosensitizer. The oxidation rate increases in the presence of deuterium oxide as expected for the involvement of 1O2. Addition of the 1O2 quencher azide also produced an activating effect in contrast with the expected inhibition. Azidyl radicals produced by the oxidation of azide by the horseradish peroxidase/hydrogen peroxide system stimulate the oxidation of the added hypotaurine. It is concluded that azide competes with hypotaurine for 1O2 generating the azidyl radical which is a strong one-electron oxidant transfer of the radical to hypotaurine. The hypotaurine radical is then converted into taurine, possibly through the disulfone intermediate. Formation of the sulfonic hydroperoxide is the possible intermediate in the absence of azide. The finding that the azidyl radical efficiently oxidizes hypotaurine to its metabolic product taurine raises the expectation of hypotaurine being a valuable scavenger of endogenous and exogenous radicals.

Azides↗
PubMed1999

Splenectomy induced complete remission in a patient with multicentric Castleman's disease and autoimmune hemolytic anemia.

Castleman's disease (CD) is a rare disorder of the lymphoid tissue in which the clinical manifestations often mimic a malignant lymphoma. Despite the absence of monoclonality of the lymphoid proliferation, the multicentric variant of the disease (MCD) is characterized by severe symptoms and poor prognosis. Etiologic, pathogenetic, and therapeutic aspects of MCD are still uncertain. We report the case of a 57-year-old patient affected by MCD complicated by severe immunohemolytic anemia. Whereas the clinical and laboratory response to steroids and chemotherapeutic agents was only partial, splenectomy induced a complete remission of hemolysis and disappearance of the constitutional symptoms and of all generalized lymphadenopathies.

Anemia, Hemolytic, Autoimmune↗
PubMed1998

Detection of a decarboxylated dimer of aminoethylcysteine ketimine in bovine cerebellum.

Aminoethylcysteine ketimine is a sulfur-containing cyclic compound produced by the enzymatic alpha-deamination of the parent aminoethylcysteine that has been detected in bovine brain and cerebellum. Aminoethylcysteine ketimine is known to dimerize spontaneously and easily lose one carboxyl group. This decarboxylated compound, simply named the dimer, has been recently detected in normal human urine. In this article we provide evidence on the occurrence of the dimer in the bovine cerebellum.

Animals↗
PubMed1998

Antioxidant properties of the decarboxylated dimer of aminoethylcysteine ketimine: assessment of its ability to scavenge peroxynitrite.

The natural sulfur compound aminoethylcysteine ketimine decarboxylated dimer (AECK dimer) has been investigated for its ability to act as peroxynitrite scavenger. It has been found that the product efficiently protects against the nitration of tyrosine and the inactivation of alpha1-antiproteinase by peroxynitrite. The tyrosine nitration can be completely prevented by 100 microM AECK dimer which appears as effective as the antioxidants glutathione and N-acetylcysteine. The AECK dimer was also found to limit surface charge alteration of low density lipoprotein induced by peroxynitrite. These findings indicate that the AECK dimer is a strong protective agent against peroxynitrite damage and that it could play an important role in the defence against oxidative stress in human diseases.

Amino Acids, Sulfur↗
PubMed1998

Antioxidant activity of aminoethylcysteine ketimine decarboxylated dimer on copper-induced LDL oxidation.

Aminoethylcysteine ketimine decarboxylated dimer (AECK-DD), a member of a family of natural cyclic sulfur-containing aminoacids, recently detected in biological samples, protects low density lipoprotein (LDL) against copper-mediated oxidation, as assessed by monitoring the kinetics of conjugated diene formation, thiobarbituric acid-reactive substances production and LDL-tryptophan fluorescence quenching. Moreover, AECK-DD exerts a protective effect also against metal-independent, peroxyl radical-induced lipoprotein oxidation. It is of note that the concentrations exerting a protective effect against LDL oxidation are similar to those found in biological samples.

Amino Acids, Sulfur↗
PubMed1997

Some new details of the copper-hydrogen peroxide interaction.

The addition of neocuproine (NC) or bathocuproinedisulphonate at the end of the autooxidation of Cu(I) in phosphate buffer, pH 7.4, regenerates almost entirely the O2 consumed. Other chelating agents assayed, including o-phenanthroline, cannot replace NC in promoting the O2 formation. O2 is also produced by adding NC to a mixture of Cu(II) and H2O2. Concomitant with the O2 evolution, the typical absorbance of the (NC)2Cu(I) complex appears to account for the complete reduction of Cu(II) to Cu(I). It is concluded that the addition of H2O2 with Cu(II) produces the equilibrium Cu(II)(O2H)(-)<--> Cu(I.)O2H. Addition of NC shifts the equilibrium to the right side by binding Cu(I). The released O2.- then reacts with the remaining Cu(II) yielding, in the presence of NC, the net reaction of 4 NC + 2 Cu(II) + H2O2 --> 2 (NC)2Cu(I) + O2 + 2 H+. O2 is also released in the absence of added NC provided the H2O2 concentration is increased. In these conditions the Cu(II)(O2H) complex undergoes other reactions leading to the copper-catalysed decomposition of H2O2.

Catalase↗
PubMed1996

Aminoethylcysteine ketimine decarboxylated dimer detected in normal human urine by gas-liquid chromatography, selected-ion monitoring and mass spectrometry.

Aminoethylcysteine ketimine is a biochemical product known to be converted spontaneously in the decarboxylated dimer. Since the ketimine has been detected in a mammalian brain, it was assumed that also the dimer could be present in the mammalian body and eventually excreted in the urine. Using human urine as the biological source, an extract was prepared which, submitted to gas-liquid chromatography, selected-ion monitoring and mass spectrometry, indicated the presence of the dimer.

Adult↗
PubMed1996

Effect of cystathionine and cystathionine metabolites on the phosphorylation of tyrosine residues in human neutrophils.

The effect of cystathionine and cystathionine metabolites found in the urine of patients with cystathioninuria on the phosphorylation of tyrosine residues was studied with human peripheral blood polymorphonuclear leukocytes. Among the cystathionine metabolites, cystathionine ketimine markedly increased phosphorylation of a 45 kDa protein with time and the phosphorylation depended on the concentration of cystathionine ketimine, while cystathionine and the reduced form of cystathionine ketimine (cyclothionine) did not increase the phosphorylation of the 45 kDa protein. The phosphorylation of the 45 kDa protein induced by cystathionine ketimine was inhibited by genistein and herbimycin A, inhibitors of tyrosine kinase, but was not inhibited by 1-(5-isoquinolinesulfonyl)-2-methylpiperazine and staurosporine, inhibitors of protein kinase C.

Benzoquinones↗
PubMed1996

[Alpha interferon in the therapy of polycythemia vera].

In previous researches recombinant interferon alpha (IFN-alpha) has been demonstrated to significantly control red cell mass and thrombocytemia in patients with polycythemia vera (PV). Further evaluation of drug effectiveness and of modalities of maintenance therapy is warranted. We treated four patients with PV according to PVSG criteria with IFN-alpha (3 MU subcutaneously three times a week) for five months. Thereafter the starting dose was reduced to 1.5 MU three times a week. Treatment with IFN-alpha at the higher dosage induced regression in sizes of the spleen and a return to normal levels of peripheral blood platelets and leukocytes. Phlebotomies, previously performed to keep under control hematocrit values, were no more needed. During maintenance treatment with IFN-alpha reduced dose platelet level remained in the normal range, spleen size did not show further variation but hematocrit slowly rose and phlebotomies had to be resumed. These results confirm IFN-alpha effectiveness in PV, but suggest the need of relatively high dosages of the drug and difficulties in switching to a maintenance treatment.

Aged↗
PubMed1995

Circulating hematopoietic progenitor cells in polycythemia vera: the in vivo effect of hydroxyurea.

The in vivo effects of hydroxyurea (HU) on circulating erythroid (BFU-E) and granulocyte-macrophage progenitors (CFU-GM) in patients with polycythemia vera (PV) have been evaluated. HU induced a strong decrease of both BFU-E and CFU-GM in the first month of treatment. During the following 4 months of treatment the level of circulating progenitors remained at very low values, until the end of the period of observation. HU activity involved both erythroid and myeloid committed progenitors and both erythropoietin-stimulated (normal) and endogenous (derived from the abnormal PV clone) BFU-E.

Aged↗
PubMed1995

Antioxidant properties of the decarboxylated dimer of aminoethylcysteine ketimine.

The decarboxylated dimer of aminoethylcysteine ketimine has been investigated for a possible general protective effect against oxyradical damage. It has been found that the dimer protects brain microsomes against lipid peroxidation induced by NADPH in the presence of Fe(III)-ADP chelate or by cumene hydroperoxide. The compound also inhibits lipid peroxidation stimulated by L-dopa and related compounds in the presence of Fe(III)-ADP complex. Furthermore the dimer is able to protect deoxyribose against hydroxyl radical induced degradation. These observations suggest that the dimer is a lipid peroxidation protective agent and a free radical scavenger.

Adenosine Diphosphate↗
PubMed1994

Aminoethylcysteine ketimine decarboxylated dimer protects submitochondrial particles from lipid peroxidation at a concentration not inhibitory of electron transport.

In contrast with other inhibitors of the NADH dehydrogenase of the respiratory chain, the decarboxylated dimer of aminoethylcysteine ketimine protects bovine heart submitochondrial particles (SMP) from the NADH-Fe(+3)-ADP-induced lipid peroxidation. This effect, measured as inhibition of malondialdehyde formation, is concentration-dependent in the range 0.02-0.2 mM. This range of concentration is not inhibitory on NADH-oxidase activity of SMP. Furthermore the dimer is able to counteract the malondialdehyde formation stimulated by the Complex I inhibitors rotenone and N-methyl-4-phenylpyridinium (MPP+).

Amino Acids, Sulfur↗