Biomedical subjects

G Cilento

Publications and source records attributed to G Cilento.

At least 19 recordsLinked to original sources

PubMed1998

Prognostic significance of c-erbB-2 oncoprotein expression in intestinal-type adenocarcinoma of the sinonasal tract.

BACKGROUND: The c-erbB-2 gene codes for a putative transmembrane protein, similar in structure to the epidermal growth factor receptor. Amplification and/or overexpression of the gene has been recently described with a prognostic significance in a variety of human adenocarcinomas. METHODS: A monoclonal antibody against the c-erbB-2 oncoprotein has been used immunocytochemically in a retrospective study of formalin-fixed, paraffin-embedded samples from 28 consecutive intestinal-type adenocarcinomas (ITACs) of the nose and paranasal sinuses. RESULTS: Nine out of 28 primary adenocarcinomas (32%) showed positive staining. Clinical follow-up data, available for all patients, suggested in a univariate analysis a correlation between c-erbB-2 expression and poor prognosis, as measured by 5-year disease-free (p = .02) and overall survival curves (p = .07) as well as by recurrence of disease and the appearance of regional and distant metastases (p = .08). In multivariate analysis, c-erbB-2 expression was statistically significant in terms of disease-free survival (p = .046) but not of overall survival (p = .091) in our series. CONCLUSIONS: These data indicate that c-erbB-2 oncogene activation could be involved in sinonasal tract oncogenesis, with possible prognostic implications.

Adenocarcinoma↗

PubMed1997

Peroxidase activity may play a role in the cytotoxic effect of indole acetic acid.

Peroxidase activity in neutrophils is higher than in thioglycollate macrophages, while in lymphocytes this enzyme activity is very low. Indole-3-acetic acid is oxidized by peroxidase and the role of this enzyme in the cytotoxic effect of the compound was evaluated by measuring oxygen consumption, light emission and cell death in neutrophils, macrophages and lymphocytes. The increase in light emission, oxygen consumption and rate of cell death in cells cultured in the presence of indole-3-acetic acid presented a direct correlation with the peroxidase activity of the cells as follows: neutrophils > thioglycollate macrophages > resident macrophages > lymphocytes. Indeed, in lymphocytes that possess very low peroxidase activity, indole-3-acetic acid did not result in an increase in light emission or oxygen consumption and it was not cytotoxic.

Animals↗

PubMed1995

From free radicals to electronically excited species.

Biologically/medically important compounds, when metabolized, can generate free radicals from which electrically excited products--often in the triplet state--are generated. Peroxidases are particularly apt to catalyze such processes, which usually entail oxidations by electron transfer. In the latter case, the chemiluminescence may derive from peroxyl and alkoxyl radicals or excited states derived from dioxetanes. Besides peroxidases, prostaglandin-H synthase and lipoxygenase may catalyze the formation of excited carbonyls. The pronounced similarity in the chemical behavior and reactivity of radicals and excited species derives in part from the biradical nature of the latter. Usually in analyzing the biological effects of xenobiotics, only radicals and/or reactive ground state products have been considered. However, in such processes the generation of excited species is possible, which should be tested for by direct and/or sensitized emission or by photochemical transformation.

Animals↗

PubMed1994

Plant hormone ethylene is a Norrish type II product from enzymically generated triplet 1-butanal.

The peroxidase-catalyzed aerobic oxidation of a linear aldehyde, leading to the next lower homologue in the triplet state, is accompanied by Norrish type II product ethylene when the substrate is pentanal. This system appears to provide an example of "photobiochemistry without light" because ethylene is a plant hormone and is formed in lipid peroxidation when the recurrent oxidation of linear aldehydes occurs.

Journal Article↗

PubMed1994

Chemiexcitation in the peroxidative metabolism of N-methylcarbazole: mechanistic implications.

The peroxidative metabolism of N-methylcarbazole emits light independently of the presence of oxygen. It is likely that two chemiexcited transients are formed by electron transfer to the activated peroxidase, the cation radical by one electron transfer and a cation biradical by two electron transfer consistent with the failure to observe horseradish peroxidase-II in the steady state of the reaction. In the spectral range investigated (390-700 nm) the observed emission (570-700 nm) is ascribed to the biradical, as the latter is equivalent to an excited state of the postulated iminium cation. While lipoxygenase has no effect upon N-methylcarbazole, it markedly enhances the emission if peroxidase is present. This effect requires oxygen and is ascribed to an excited product formed by lipoxygenase acting upon an intermediate hydroperoxide of the aerobic process promoted by peroxidase. Our results are of importance on two counts. First they extend to N-methylcarbazole the formation of excited species in the peroxidative metabolism of important xenobiotics. Second, the mechanistic information they provide supports the scheme of metabolism postulated by Kedderis et al. (1986, J. Biol. Chem. 261, 15910-15914).

Carbazoles↗

PubMed1993

Generation of electronically excited triplet species at the cellular level: a potential source of genotoxicity.

Selected enzymatic systems can efficiently produce a product in the electronically excited triplet state. Earlier, only the formation of electronically excited singlet species was known. The formation of triplet species has been demonstrated with both normal substrates/metabolites and with xenobiotics, even at the cellular level. Triplet excited species have intrinsically much longer lifetimes than excited singlets, whereby they can be potentially important agents for normal and/or deleterious processes, including mutagenesis. Enzymically generated triplet species can damage DNA, even when protein coated, as in the case of the lambda-phage of Escherichia coli. Some evidence of damage by triplet species has also been reported for intact cells. Triplet excited species may produce their effects through type I and/or type II dark photosensitization, that is, the events may be started by H abstraction and/or singlet oxygen/superoxide ion production. The induction of lipid peroxidation, with concomitant clastogenic effects, appears to be of special importance.

Acetaldehyde↗

PubMed1993

The peroxidative metabolism of tenoxicam produces excited species.

The peroxidative metabolism of the nonsteroid anti-inflammatory oxicams generates metabolites of the type expected from a dioxetane intermediate. Therefore, electronically excited metabolites may be expected. Consistent with this possibility, both direct and sensitized light emission are observed when tenoxicam is exposed to horseradish peroxidase or when added to leukocytes, where it undergoes a myeloperoxidase-catalyzed aerobic oxidation. The similarity between peroxidative metabolism with concomitant oxygen uptake and photodegradation brought about by singlet oxygen addition to the substrate is pointed out. As a whole, the results strengthen the view that electronically excited species should also be considered when analyzing the effect(s) of xenobiotics.

Animals↗

PubMed1993

Photon emission by bacteria challenged with phenylacetaldehyde. A possible distinction between gram-positive and gram-negative bacteria.

With all bacteria tested, addition of phenylacetaldehyde leads to light emission. The latter is markedly stronger with gram-negative bacteria, presumably because they possess a thinner wall and an extra external lipophilic membrane. Consistent with this explanation, the bactericidal effect of phenylacetaldehyde is also stronger with gram-negative bacteria. The spectrum of the emitted light shows maximal emission in the 500 nm region and is very similar to that observed when a protein (bovine serum albumin), free amino acids or isopropylamine reacts with phenylacetaldehyde.

Acetaldehyde↗

PubMed1993

Light emission accompanies oxygen uptake during the peroxidative metabolism of tetracyclines.

Tetracycline molecules offer several sites for peroxidative metabolism of the type known to lead to oxygen consumption and electronic excitation. Accordingly, when tetracycline and chlortetracycline were exposed to horseradish peroxidase in the presence of hydrogen peroxide, oxygen was taken up and light emission was observed. The overall quantum yield of chemiluminescence is on the order of 10(-6), but that of chemiexcitation may be orders of magnitude higher as suggested by studies of sensitized emission. Given the widespread distribution of peroxidases, the formation of highly reactive metabolites of tetracycline may have biological importance.

Chlortetracycline↗

PubMed1993

Characterization of myeloid or lymphoid acute leukemia by a chemiluminescence assay. Comparison with immunocytochemistry using an antimyeloperoxidase antibody.

A simple and sensitive chemiluminescence assay for the demonstration of the activity of intracellular myeloperoxidase (MPO) is described, which is useful for the distinction between myeloid and lymphoid commitment in blasts from acute leukemia patients. When the cut-off point was settled at 13 mV of chemiluminescence all cases of acute myeloid leukemia (AML) were distinguished from those of acute lymphoid leukemia. In addition, this technique was able to demonstrate MPO activity in AML poorly differentiated (FAB-M0) which usually does not stain for MPO in classical cytochemistry preparations and could be negative also by immunocytochemistry with anti-MPO monoclonal antibody. Therefore the method here described presented a higher sensitivity than the immunocytochemistry procedure with anti-MPO.

Acute Disease↗

PubMed1992

Horseradish peroxidase-catalyzed aerobic oxidation and peroxidation of indole-3-acetic acid. I. Optical spectra.

A study of the indole-3-acetate reaction with horse-radish peroxidase, in the absence or presence of hydrogen peroxide, has been performed, employing rapid scan and conventional spectrophotometry. We present here the first clear spectral evidence, obtained on the millisecond time scale, indicating that at pH 5.0 and for high [enzyme/substrate] ratios peroxidase compound III is formed. Most, if not all, of the compound III is formed by oxygenation of the ferrous peroxidase. There is an inhibitory effect of superoxide dismutase and histidine on compound III formation which indicates the involvement of the active oxygen species superoxide and singlet oxygen. It is concluded that the oxidation of indole-3-acetate by horseradish peroxidase at pH 5.0 proceeds through compound III formation to the catalytically inactive forms P-670 and P-630. A reaction path in which the enzyme is directly reduced by indole-3-acetate might be involved as an initiation step. Rapid scan spectral data, which indicate differences in the formation and decay of enzyme intermediate compounds at pH 7.0, in comparison with those observed at pH 5.0, are also presented. At pH 7.0 compound II is a key intermediate in oxidation--peroxidation of substrate. Mechanisms of reactions consistent with the experimental data are proposed and discussed.

Aerobiosis↗

PubMed1992

Horseradish peroxidase-catalyzed aerobic oxidation of indole-3-acetic acid. II. Oxygen uptake and chemiexcitation.

Light emission from the horseradish peroxidase-catalyzed aerobic or anaerobic oxidation of indole-3-acetic acid has been investigated under opposite extreme conditions of enzyme/substrate ratio. The O2-dependent chemiluminescent processes represent a minor part of the total oxygen consumption. Superoxide is involved in chemiexcitation as is evident from the observed inhibitory effect of superoxide dismutase. At high enzyme/substrate ratio, only a part of the emission is dependent on superoxide ion; at low ratio the dependence is extensive. At high ratio, some of the emission is independent of superoxide and O2. The identical quenching effects of D- and L-tryptophan are consistent with the formation of the quenching species only in bulk solution. The similarity of the emission spectra under extreme conditions indicates that the same main emitters are formed. This is also supported by the effect of quenchers. Possibly some of the emitters originate in the oxidative cleavage of the 2,3-double bond of the indole ring.

Aerobiosis↗

PubMed1992

Chemiexcitation in the peroxidative metabolism of diethylstilbestrol. Metabolic products.

In the presence of the surfactant hexadecyltrimethyl ammonium bromide (CTAB) a cascade of electronically excited states accompanies the successive steps in the peroxidative metabolization of the strong estrogenic and tumourogenic diethylstilbestrol. Reversing the order by necessity, we report in this first paper results with the metabolites. Exposure of 4-hydroxypropiophenone, Z,Z-dienestrol or E,E-dienestrol to horseradish peroxidase and H2O2 promotes oxygen uptake and spectral alterations. Light emission is observed provided that the surfactant CTAB is present. With the three substrates, 4-hydroxybenzoic acid and a new metabolite, p-benzoquinone, have been identified. With both dienestrol isomers, 1-(4'-hydroxyphenyl)-propan-1-on-2-ol has been identified. In all cases the emission spectrum indicates the presence of several emitters. Possible chemiexcitation routes are pointed out. From the dramatic increase of the emission by enhancers, values as high as 1 x 10(-5) are inferred for the product of the quantum yields of chemiexcitation and energy transfer.

Dienestrol↗

PubMed1992

Chemiexcitation in the peroxidative metabolism of diethylstilbestrol.

When the synthetic estrogen and tumourogenic compound diethylstilbestrol is exposed to horseradish peroxidase (HRP) and H2O2 in the presence of the cationic surfactant hexadecyltrimethylammonium bromide (CTAB), a burst of oxygen consumption and concomitant light emission are observed. The quinone form of the product is not seen in the absorption spectrum because CTAB strongly catalyses its conversion to Z,Z-dienestrol. The emission spectrum shows several peaks. Total emission is dramatically enhanced by chlorophyll and by xanthene dyes. A key intermediate in chemiexcitation is 4-hydroxypropiophenone. The ability to promote chemiexcitation is retained through various generations of metabolites, giving origin to a cascade of excited states. Since the biological effects of diethylstilbestrol appear to be connected with its peroxidative metabolism, chemiexcitation may eventually prove to be of importance in, for example, toxicity of the drug.

Cetrimonium↗

PubMed1992

Free radicals and excited species in the metabolism of indole-3-acetic acid and its ethyl ester by horseradish peroxidase and by neutrophils.

The peroxidative metabolization of indole-3-acetic acid, a biologically important process, has been followed by EPR spectroscopy with the aim of obtaining information on the mechanism of generation of electronically excited species. The skatole-3-methylene radical detected during oxidation by horseradish peroxidase, does not appear to be involved in a major oxygen consuming process or in the generation of singlet oxygen. The chemiluminescence spectrum exhibits several maxima, which are also observed when the ethyl ester of indole-3-acetic acid is metabolized by horseradish peroxidase or by myeloperoxidase in neutrophils. When the ester is metabolically activated in either of these systems, the EPR spectrum indicates a tertiary carbon-centered radical. This radical centered on the carbon in the 3-position participates in a chemiexcitation/emissive route. Within the cell, this emissive process is responsible for a large part of the oxygen consumed. Some of the emitters originate in the cleavage of the 2,3 double bond. The ester, which is capable of penetrating into the cells, also emits with other myeloperoxidase-containing cells. This compound may have useful applications as an intracellular chemiluminescent probe for the presence of myeloperoxidase.

Animals↗

PubMed1991

Chemiexcitation in the arachidonic acid cascade.

As investigated in neutrophils, the very weak luminescence accompanying the arachidonic acid cascade is associated with the lipoxygenase pathway. The emission is dramatically enhanced by energy transfer to chlorophyll a. The number of chlorophyll molecules excited to the fluorescent state per oxygen consumed, (the S1/O2 ratio), equal to the product of the quantum yields of chemiexcitation and of energy transfer, is 5.4 x 10(-6). The quantum yield of chemiexcitation is inferred to be higher than 1 x 10(-3). The two most likely chemiexcitation routes point to triplet conjugated carbonyls as the most likely candidates for the excited species that transfer to chlorophyll. As such the emission intensity may reflect the level of hydroperoxyeicosatetraenoic acid. This is the first case where addition of a biotic substrate to a cellular system results in substantial generation of electronic excited states without any drastic loss of cell viability. Whether the formation of excited states in the arachidonic acid cascade in neutrophils is accidental or has a biological role is an open question.

Animals↗

PubMed1990

Effects induced in neutrophils by a precursor of triplet acetone.

The addition of a precursor of the enol form of isobutanal to neutrophils results in formation of triplet acetone, as attested to by emission from appropriate acceptors and cell damage (Nascimento et al., 1986 Biochim. Biophys. Acta 888, 337-342). The present study confirms the formation of triplet acetone by detection of the direct emission (lambda max 430 nm) and differentiates between effects produced by triplet acetone and by the enol substrate itself. Thus, triplet acetone: (1) enhances the release of ribonucleic acid; (2) promotes lipid peroxidation (N3(-)-inhibitable formation of thiobarbituric acid reactive products and concomitant light emission peaking at 480-500 nm); (3) increases myeloperoxidase activity, presumable as a result of damage and consequent increased exposure of the enzyme. On the other hand, the enol greatly enhances the release of protein(s) into the medium. These results confirm the utility of the neutrophil as a model system for the study of chemiexcitation processes induced at the cellular level. They also provide the first demonstration that an excited species formed at the cellular level may induce release of nucleic acids, thus reflecting the occurrence of deleterious processes in situ.

1-Propanol↗

PubMed1990

The peroxidase-promoted metabolic activation of acetaminophen produces electronically excited species.

When the analgesic and antipyretic drug acetaminophen is exposed to the horseradish peroxidase/hydrogen peroxide system, light emission is observed. Both the rate of reaction and the emission intensity are increased in the presence of the cationic detergent CTAB. The emission spectrum indicates the presence of at least three emitters. The peak at 445 nm is close to the position of the only band observed in the fluorescence spectrum of the spent reaction mixture and is ascribed to excited N-acetyl-p-benzoquinoneimine. The other two emission bands (505 and 580 nm) must be due to transients. Total emission from the system increases in the presence of Triton X-100 solubilized-chlorophyll; the main donor to chlorophyll is the 445 nm emitter. The generation of excited species in this model system of acetaminophen peroxidative metabolization expands the number of candidates responsible for the deleterious effects of the drug in high doses.

Acetaminophen↗