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Biomedical subjects

M A Miranda

Publications and source records attributed to M A Miranda.

At least 37 records · Page 2Linked to original sources
PubMed2000

Synthesis and biological evaluation of new analogues of the active fungal metabolites N-(2-methyl-3-oxodecanoyl)-2-pyrroline and N-(2-methyl-3-oxodec-8-enoyl)-2-pyrroline (II).

New analogues of the bioactive enamides isolated from P. brevicompactum (2 and 3) have been synthesized to improve the biological activities. Two different structural modifications have been introduced: substitution of the aliphatic side chain present in the natural products (1-4) by other groups frequently found in other active compounds and use of other nitrogen-containing five-membered rings with different degrees of oxidation. In this way, the insecticidal and fungicidal activities have been improved. Thus, compound 9, which possess a 3-pyrroline ring, exhibited important insecticidal activity against third-instar nymphs of Oncopeltus fasciatus Dallas (100% mortality at 7.5 microg/cm(2)). Remarkable fungicidal activity was also found, and preliminary structure-activity relationships could be established.

Animals↗
PubMed2000

A photophysical and photochemical study of 6-methoxy-2-naphthylacetic acid, the major metabolite of the phototoxic nonsteroidal antiinflammatory drug nabumetone.

Nabumetone is a phototoxic nonsteroidal antiinflammatory drug used for the treatment of osteoarthritis. However, nabumetone is considered a prodrug with its metabolite 6-methoxy-2-naphthylacetic acid the active form. Photophysical and photochemical studies on this metabolite have been undertaken. It undergoes photodecarboxylation in aerated aqueous and organic solvents. In addition to the accepted photodegradation pathway for related molecules, a new mechanism that implies generation of the naphthalene radical cation from the excited singlet and addition of O2 prior to the decarboxylation process has been demonstrated. Evidence for the involvement of the excited singlet state in this mechanism have been obtained by steady-state and time-resolved fluorescence experiments. The fluorescence quenching by O2 and the shorter singlet lifetime in aerated solvents support this assignment. Laser flash photolysis also supports this mechanism by showing the noninvolvement of the triplet in the formation of the naphthalene radical cation. Finally, the well-known electron acceptor CCl4 acts as an efficient singlet quencher, enhancing the route leading to the radical cation, preventing intersystem crossing to the triplet and thus resulting in a dramatic increase in the yield of 6-methoxy-2-naphthaldehyde, the major oxidative decarboxylation product; this constitutes unambiguous proof in favor of the new mechanistic proposals.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Tiaprofenic acid-photosensitized damage to nucleic acids: a mechanistic study using complementary in vitro approaches.

In order to determine whether or not tiaprofenic acid (TPA) could cause cellular DNA damage, human fibroblasts were irradiated in the presence of the drug and subsequently examined by means of the comet assay. This led to the observation that TPA actually sensitizes cellular DNA to the subsequent irradiation. When TPA was irradiated in the presence of supercoiled plasmid DNA, it produced large amounts of single-strand breaks (SSB); this is consistent with the effects observed on cellular genomic DNA by the comet assay. More importantly, low concentrations of TPA, unable to produce direct SSB, caused photo-oxidative damage to DNA as revealed by the use of excision-repair enzymes. The fact that TPA-irradiated DNA was a substrate of formamidopyrimidine glycosylase as well as endonuclease III revealed that both purine and pyrimidine bases were oxidized. This was further supported by the TPA-photosensitized oxidation of 2'-deoxyguanosine which led to a product mixture characteristic of mixed type-I/II mechanisms. Thymidine was less reactive under similar conditions, but it also decomposed to give a typical type-I product pattern. Accordingly, the TPA triplet was quenched by the two nucleosides with clearly different rate constants (10(8) vs 10(7) M-1 s-1, respectively). As cellular RNA also contains oxidizable bases, it could be the target of similar processes, thus interfering with the biosynthesis of proteins by the cells. Extraction of total RNA from TPA-irradiated human fibroblasts, followed by gel electrophoresis and PCR analysis, confirmed this hypothesis. Finally, photosensitization experiments with Saccharomyces cerevisiae showed that, in spite of an efficient drug-yeast interaction leading to cytotoxicity, neither intergenic recombination nor gene conversion took place. Thus, while TPA-photosensitized damage to nucleic acids can result in genotoxicity, the risk of mutagenicity does not appear to be significant.

Cells, Cultured↗
PubMed2000

A laser flash photolysis and pulse radiolysis study of primary photochemical processes of flumequine.

The 355 nm laser flash photolysis of argon-saturated pH 8 phosphate buffer solutions of the fluoroquinolone antibiotic flumequine produces a transient triplet state with a maximum absorbance at 575 nm where the molar absorptivity is 14,000 M(-1) cm(-1). The quantum yield of triplet formation is 0.9. The transient triplet state is quenched by various Type-1 photodynamic substrates such as tryptophan (TrpH), tyrosine, N-acetylcysteine and 2-deoxyguanosine leading to the formation of the semireduced flumequine species. This semireduced form has been readily identified by pulse radiolysis of argon-saturated pH 8 buffered aqueous solutions by reaction of the hydrated electrons and the CO2*- radicals with flumequine. The absorption maximum of the transient semireduced species is found at 570 nm with a molar absorptivity of 2,500 M(-1) cm(-1). In argon-saturated buffered solutions, the semireduced flumequine species formed by the reaction of the flumequine triplet with TrpH stoichiometrically reduces ferricytochrome C (Cyt Fe3+) under steady state irradiation with ultraviolet-A light. In the presence of oxygen, O2*- is formed but the photoreduction of Cyt Fe3+ by O2*- competes with an oxidizing pathway which involves photo-oxidation products of TrpH.

Anti-Infective Agents↗
PubMed1999

Cerebral tumor-like American trypanosomiasis in acquired immunodeficiency syndrome.

Cerebral tumor-like American trypanosomiasis (CTLAT) is an uncommon complication of Chagas' disease, observed only in immunosuppressed patients. We assessed 10 human immunodeficiency virus-positive patients with Chagas' disease who presented with CTLAT. All patients had neurological involvement and 6 developed intracranial hypertension. Neuroimaging studies showed supratentorial lesions in 9 patients, being single in 8. One case had infratentorial and supratentorial lesions. Low CD4+ cell counts were observed in all the cases and in 6 of them CTLAT was the first manifestation of acquired immunodeficiency syndrome. Serological tests for Chagas' disease were positive in 6 of 8 patients. Trypanosoma cruzi was identified in all brain specimens and in three cerebrospinal fluid samples. CTLAT should be considered in the differential diagnosis of intracranial mass lesions in human immunodeficiency virus-positive patients and should be added to the list of acquired immunodeficiency syndrome-defining illnesses.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Evaluation of IgG, IgM, and IgA antibodies to mycoplasma penetrans detected by ELISA and immunoblot in HIV-1-infected and STD patients, in São Paulo, Prazil.

The aim of the present study was to determine the frequency of IgG, IgA, and IgM antibodies to Mycoplasma penetrans in HIV-1-infected patients and in patients with sexually transmitted diseases. We tested serum samples from 106 HIV-1-positive patients and 110 individuals with clinical symptoms of urethritis. ELISA and the immunoblot test were performed using M. penetrans lipid associated membrane proteins as antigen. By ELISA, we found a higher frequency (P < 0.05) of IgG against M. penetrans in HIV-1-infected and STD patients (25.5 and 17.3%) than in controls (1.2%), as well as a higher frequency of IgA (P < 0.05) (15.1 and 17.3% compared to 1.2%). For IgM, no differences were observed (P >/= 0.05) (3.8, 9.1, and 5. 8%, respectively). When the frequencies of IgG, IgM, and IgA antibodies of the HIV-1-infected patients were compared taking into account the CD4/CD8 cell ratios < 0.3 and >/= 0.3, no significant differences were observed between the two groups (13.3, 10, and 20%, compared to 20, 0, and 5%, respectively) (P > 0.05), possibly due to the low number of samples on which we could perform T-cell counts (53/106). The M. penetrans peptide of 38 kDa, considered immunodominant, was recognized in immunoblot by 51.8% of positive sera by ELISA for IgG, 50.0% for IgM, and 75% for IgA in the AIDS patients group, and by 47.4, 60.0, and 75.0%, respectively, in the sexually transmitted disease group. Cross-reactions in immunoblot for IgG were observed in sera from individuals infected with Mycoplasma pneumoniae and Mycoplasma hominis, and cross-reactions in immunoblot for IgA were observed in sera from individuals infected with M. hominis; all of them were ELISA negative to M. penetrans.

Adolescent↗
PubMed1999

Insecticidal, anti-juvenile hormone, and fungicidal activities of organic extracts from different Penicillium species and their isolated active components.

Organic extracts from mycelium and culture broth of 21 Penicillium isolates have been tested for insecticidal, insect anti-juvenile hormone (anti-JH), and antifungal activities. Culture broth extracts were the most active, mainly against insects; nearly 25% of them have shown high entomotoxicity (100% mortality at 100 microg/cm(2)). A strong in vivo anti-JH activity against Oncopeltus fasciatus Dallas was detected in the culture broth extracts from P. brevicompactum P79 and P88 isolates. The two new natural products isolated from P79, N-(2-methyl-3-oxodec-8-enoyl)-2-pyrroline (1) and 2-hept-5-enyl-3-methyl-4-oxo-6,7,8,8a-tetrahydro-4H-pyrrolo[2,1-b]-1, 3-oxazine (2), possessed anti-JH and insecticidal activity, respectively, against O. fasciatus. Synthesized natural compound 1 has shown an ED(50) of 0.7 microg/nymph when assayed on newly molted fourth-instar nymphs of O. fasciatus. Promising biological activities have also been detected in the synthetic precursors.

Animals↗
PubMed1999

Synthesis and biological evaluation of new analogues of the active fungal metabolites N-(2-methyl-3-oxodecanoyl)-2-pyrroline and N-(2-methyl-3-oxodec-8-enoyl)-2-pyrroline.

To evaluate the effect of simplifying the beta-ketoamide system present in active isolated metabolites from Penicillium brevicompactum (2 and 3) on the activity, new analogues with a monocarbonylic amide functionality have been obtained. In this way, the insecticidal and fungicidal activities have been improved in relation to the natural products taken as lead molecules. Thus, two of the synthetic analogues (5a and 5b) showed very important insecticidal activities against third-instar nymphs of Oncopeltus fasciatus Dallas, with acute LD(50) values of 3.0 and 1.5 microg/cm(2), respectively. Moreover, some analogues showed good levels of fungicidal activity against a wide range of commercially important and taxonomically diverse fungi; remarkably, compound 7c has proved to be highly active against Colletotrichum gloesporoides and Colletotrichum coccodes, with ED(50) values of 2.04 and 11.7 microg/mL, respectively.

Animals↗
PubMed1999

Vertical shear injuries: is there a relationship between residual displacement and functional outcome?

BACKGROUND: Residual vertical displacement is often cited as being related to poor outcome in patients with pelvic injuries. This study attempts to clarify the relationship between residual vertical displacement and functional outcome. METHODS: From 1982 to 1989, over 500 patients with pelvic ring injuries were treated at two Level I trauma centers. Thirty-three patients with vertical shear (Tile C) fractures and residual displacement (2-52 mm) were evaluated. Outcomes were quantified by using SF-36 Short-Form Health Survey (SF-36) and the Iowa Pelvic Score (IPS). RESULTS: There was no correlation between IPS or SF-36 scales and residual vertical displacement. The IPS correlated (p<0.05) with seven of eight SF-36 categories, excluding mental health. Patients reporting limp and leg length discrepancy also correlated with the IPS and select SF-36. CONCLUSION: Pelvic injuries showed no correlation between functional outcome and residual vertical displacement suggesting other factors. The degree of residual vertical displacement does not affect functional outcome.

Adolescent↗
PubMed1999

Lysosomes are sites of fluoroquinolone photosensitization in human skin fibroblasts: a microspectrofluorometric approach.

The fluoroquinolone antibiotics are widely used despite their strong phototoxicity under solar UV irradiation. Although they are known as good photodynamic photosensitizers, other factors than production of activated oxygen species may play a role in the effectiveness of the phototoxic effect. Subcellular localization is one of the important parameters that may determine this strength. Using microspectrofluorometry, it is shown that norfloxacin, ofloxacin, lomefloxacin, ciproflaxin and BAYy3118 are readily incorporated into lysosomes of HS68 human skin fibroblasts although weak staining of the whole cytoplasm also occurs especially with norfloxacin. Consistent with their photoinstability in solutions, the fluoroquinolones under study are readily photobleached by UVA in the HS68 fibroblasts. The BAYy3118 derivative that has the fastest bleaching rate also shows the strongest phototoxicity toward HS68 fibroblasts. Photosensitization with these fluoroquinolones induces lysosomal membrane damage as shown by the increased rate of leakage of the lysosomal probe lucifer yellow as compared to that observed with untreated cells.

Anti-Infective Agents↗
PubMed1998

Photosensitizing drugs containing the benzophenone chromophore.

The nonsteroidal anti-inflammatory agents ketoprofen, tiaprofenic acid, suprofen and tolmetin, together with the anti-hyperlipoproteinemic drug fenofibrate and the anti-arrhythmic amiodarone can be included in the group of benzophenone-derived photosensitizing drugs. They contain a diaryl ketone chromophore and mediate the development of phototoxic reactions. In some cases, photoallergic responses have been reported. These properties have been substantiated in clinical reports, as well as by means of in vivo and in vitro assays. Tolmetin is phototoxic in vitro, however there are no reports on photosensitization by this drug in humans. In general, photochemical and photobiological studies strongly suggest that photosensitization involves formal hydrogen abstraction (either in a single step or via electron transfer followed by proton transfer) by the benzophenone-like chromophore from the excited triplet state. In the case of amiodarone, the radicals generated by photodehalogenation from the triplet are responsible for the photosensitivity side-effects.

Animals↗
PubMed1998

Drug-photosensitized protein modification: identification of the reactive sites and elucidation of the reaction mechanisms with tiaprofenic acid/albumin as model system.

Certain drugs can photosensitive the formation of protein modifications, which are thought to be responsible for the occurrence of photoallergy. In the present work, the UV irradiation of serum albumin in the presence of tiaprofenic acid has been studied as a model system for drug-photosensitized protein modifications. The photolysates evidenced that His, Tyr, and Trp are the reactive sites of the protein. The experimental results strongly suggest that formal hydrogen abstraction from the OH or NH groups of Tyr or Trp by the excited drug is the key photochemical process. Competition between cage escape and in cage recombination of the resulting radical pairs governs the final outcome: protein photo-cross-linking versus drug-protein adduct formation. These findings are highly relevant to understand the process of photohapten formation, the first event in the onset of photoallergy.

Amino Acids↗
PubMed1998

Phototoxicity associated with diclofenac: a photophysical, photochemical, and photobiological study on the drug and its photoproducts.

Diclofenac (1) is a photosensitizing nonsteroidal antiinflammatory drug. Its photodecomposition gives rise to chlorocarbazole 2a. This product undergoes photodehalogenation to 3a in a subsequent step. When the photobiological activities of 1, 2a, and 3a are compared by means of the photohemolysis test, it is clearly observed that chlorocarbazole 2a causes cell lysis with a markedly higher efficiency than the parent drug or the secondary photoproduct 3a. Laser flash photolysis studies suggest that photodehalogenation of 2a occurs from its excited triplet state via quenching by ground-state 2a and formation of an excimer. As a consequence, an aryl radical plus an N-centered carbazolyl radical are formed. These radical intermediates appear to be responsible for the observed photobiological effects of diclofenac, via hydrogen abstraction from the target biomolecules, which initiates a type-I photodynamic effect. The efficient peroxidation of model lipids, such as linoleic acid, photosensitized by 2a are in favor of this proposal. Thus, the photosensitizing properties of diclofenac appear to be associated with the photochemical and photobiological activity of its major photoproduct.

Animals↗
PubMed1998

Triplet photoreactivity of the diaryl ketone tiaprofenic acid and its decarboxylated photoproduct. Photobiological implications.

The 2-benzoylthiophene chromophore of the photosensitizing drug tiaprofenic acid and of its decarboxylated derivative is characterized by a unusually high energy gap between the T1 (pi, pi*) and T2 (n, pi*) excited states, which makes this a unique system to study the intrinsic photoreactivity of the two states. Weak fluorescence and phosporescence emission were detected at room temperature. Tiaprofenic acid undergoes photodecarboxylation from the triplet manifold as the main reaction. The photoprocess is temperature dependent with activation energy of 7-10 kcal/mol, close to the energy gap between T1 and T2. The decarboxylated product abstracts hydrogen in type I reactions. The involvement of T2 in the above processes is proposed. Moreover the decarboxylated derivative exhibits reactivity toward phenols, consistent with a participation of the T1 state as electron acceptor. The observed photoprocesses can account for biological photosensitization reactions, like membrane damage and protein modification.

Decarboxylation↗
PubMed1998

Release of inflammatory mediators (PGE2, IL-6) by fenofibric acid-photosensitized human keratinocytes and fibroblasts.

Ultraviolet-A radiation has weak effects on the release of inflammatory mediators by skin cells due to the poor overlap between UVA wavelengths and the absorption spectra of the relevant chromophores of key biomolecules. However, this situation could be very different in the presence of a photosensitizing drug. To investigate this issue, we have irradiated human skin cells (keratinocytes and fibroblasts) in the presence of fenofibric acid (the active phototoxic metabolite of fenofibrate). The results of this research show a dual effect on the production/release of inflammatory mediators: the synthesis of the proinflammatory cytokine interleukin-6 becomes strongly inhibited at photosensitizer concentrations that clearly stimulate the production of prostaglandins (PGE2) by skin cells. We have found evidences showing that the de novo synthesis of cytokines is inhibited in photosensitized cells due to the fact that cellular mRNA is degraded. Interestingly, when the medium taken from irradiated cultures is added to nonexposed cells, a significant stimulation of cytokine synthesis is observed that can be inhibited by anti-PGE2 antibodies. These observations may be relevant in vivo, where prostaglandins released by photosensitized skin cells could stimulate cytokine synthesis by underlying, nonirradiated cells.

Cells, Cultured↗
PubMed1998

Photobinding of tiaprofenic acid and suprofen to proteins and cells: a combined study using radiolabeling, antibodies and laser flash photolysis of model bichromophores.

Drug photoallergy is a matter of current concern. It involves the formation of drug-protein photoadducts (photoantigens) that may ultimately trigger an immunological response. Tyrosine residues appear to be key binding sites in proteins. The present work has investigated the photobinding of tiaprofenic and (TPA) and the closely related isomer suprofen (SUP) to proteins and cells by means of radioactive labelling and drug-directed antibodies. To ascertain whether preassociation with the protein may play a role in photoreactivity, two model bichromophoric compounds (TPA-Tyr and SUP-Tyr) have been prepared and studied by laser flash photolysis. The results of this work show that (a) TPA and SUP photobind to proteins with similar efficiencies, (b) both drugs form photoadducts that share a basic common structure, as they are recognized by the same antibody and (c) drug-protein preassociation must play a key role in photoreactivity, as indicated by the dramatic decrease in the triplet state lifetimes of the model bichromophores compared to the parent drugs.

3T3 Cells↗
PubMed1997

Photophysical and photochemical characterization of a photosensitizing drug: a combined steady state photolysis and laser flash photolysis study on carprofen.

Carprofen (1a) is a photosensitizing nonsteroidal anti-inflammatory drug. It undergoes photodehalogenation from its triplet excited state. The resulting aryl radical (II) is able to abstract hydrogen atoms from model lipids, mediating their peroxidation by a type I mechanism. This aryl radical intermediate appears to be responsible for the observed photobiological effects of carprofen. The active involvement of the triplet state has been confirmed by direct detection of this species in laser flash photolysis and by quenching experiments with cyclohexadiene and naphthalene. Carprofen also photosensitizes singlet oxygen production with a quantum yield of 0.32. A minor reaction pathway is photodecarboxylation, which occurs from the excited singlet state and leads to an acetyl derivative (1b). In the case of the dehalogenated photoproduct (2a), photodecarboxylation to the ethyl (2d) and acetyl (2b) derivatives, together with singlet oxygen production (quantum yield = 0.18), is also possible. However, the biological activity of 2a in the linoleic acid photoperoxidation and photohemolysis tests is markedly lower than that of 1a, which constitutes further evidence in favor of the important role of photodehalogenation in the adverse photobiological effects of carprofen.

Carbazoles↗