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1.
Public Health ; 227: 194-201, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38237315

RESUMO

OBJECTIVES: The aim of this study was to analyse the trends of avoidable mortality in Brazil from 1990 to 2019 and its correlation with sociodemographic indexes (SDIs). STUDY DESIGN: Epidemiological mortality trends. METHODS: This study analysed data from the Global Burden of Disease database. The list of causes of avoidable death, as proposed by Nolte and McKee, was applied and included 32 causes. The current study used age-standardised mortality rates and the rates of change, in addition to a correlation analysis between avoidable death and the SDI. RESULTS: Mortality rates decreased from 343.90/100,000 inhabitants in 1990 to 155.80/100,000 inhabitants in 2019. Infectious diseases showed the largest decline in mortality rates, but notable decreases were also found for diarrhoeal diseases (-94.9%), maternal conditions (-66.5%) and neonatal conditions (-60.5%). Mortality rates for non-communicable diseases (NCDs) also decreased (-48%) but maintained a similar absolute number of deaths in 2019 compared with 1990. Decreased mortality rates were also found for ischaemic heart disease (-49.1%), stroke (-61.4%) and deaths due to adverse effects caused by medical treatments (-26.2%). Avoidable mortality rates declined in all of the 27 Brazilian states, and a high correlation was found between deaths and SDI (R = -0.74; P < 0.000001). CONCLUSIONS: A reduction in avoidable deaths was found throughout Brazil over the study period, although major regional inequalities were revealed. Richer states presented the best overall reduction in mortality rates. The biggest decreases in mortality were seen in maternal and paediatric infectious diseases in the poorest states due to the expansion of the Primary Health System and improvements in sanitation. Today, NCDs predominate and efforts should be made to formulate public policies for the prevention and control of NCDs.


Assuntos
Doenças Transmissíveis , Doenças não Transmissíveis , Criança , Recém-Nascido , Humanos , Causas de Morte , Brasil/epidemiologia , Carga Global da Doença , Saúde Global , Mortalidade
2.
New Phytol ; 189(3): 751-764, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21039570

RESUMO

• Primary carbohydrate metabolism plays a special role related to carbon/nitrogen exchange, as well as metabolic support of fruiting body development, in ectomycorrhizal macrofungi. In this study, we used information retrieved from the recently sequenced Tuber melanosporum genome, together with transcriptome analysis data and targeted validation experiments, to construct the first genome-wide catalogue of the proteins supporting carbohydrate metabolism in a plant-symbiotic ascomycete. • More than 100 genes coding for enzymes of the glycolysis, pentose phosphate, tricarboxylic acid, glyoxylate and methylcitrate pathways, glycogen, trehalose and mannitol metabolism and cell wall precursor were annotated. Transcriptional regulation of these pathways in different stages of the T. melanosporum lifecycle was investigated using whole-genome oligoarray expression data together with real-time reverse transcription-polymerase chain reaction analysis of selected genes. • The most significant results were the identification of methylcitrate cycle genes and of an acid invertase, the first enzyme of this kind to be described in a plant-symbiotic filamentous fungus. • A subset of transcripts coding for trehalose, glyoxylate and methylcitrate enzymes was up-regulated in fruiting bodies, whereas genes involved in mannitol and glycogen metabolism were preferentially expressed in mycelia and ectomycorrhizas, respectively. These data indicate a high degree of lifecycle stage specialization for particular branches of carbohydrate metabolism in T. melanosporum.


Assuntos
Ascomicetos/genética , Metabolismo dos Carboidratos/genética , Regulação Fúngica da Expressão Gênica , Genes Fúngicos , Genoma Fúngico , Micorrizas/genética , Ascomicetos/enzimologia , Ascomicetos/metabolismo , Citratos/metabolismo , Carpóforos , Perfilação da Expressão Gênica , Micélio , Micorrizas/enzimologia , Micorrizas/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Regulação para Cima , beta-Frutofuranosidase/metabolismo
3.
Ann Oncol ; 22(1): 86-92, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20603432

RESUMO

BACKGROUND: the expression of ATP-binding cassette transporters on circulating tumor cells (CTCs) is predictive of response to chemotherapy in cancer patients. We tested the hypothesis that drug-resistant CTCs might have predictive value in metastatic breast cancer (MBC) and possibly retain stem-like properties. PATIENTS AND METHODS: CTCs obtained from 42 MBC patients were evaluated for multidrug-resistance-related proteins (MRPs), aldehyde dehydrogenase 1 (ALDH1), estrogen receptor α (ERα) and human epidermal growth factor receptor 2 (HER2/neu). Primary objective was to evaluate the prognostic and predictive value of CTCs profile. Secondary end points were the level of concordance in ERα and HER2/neu status between primary tumors and CTCs and the correlation in CTCs between ALDH1, drug resistance profile and number of MRPs. RESULTS: A difference in progression-free survival (PFS) was found between CTCs-positive and CTCs-negative patients. PFS was shorter in patients with a 'drug resistance' CTCs profile and in patients whose CTCs expressed two or more MRPs. No correlation was found between tumor characteristics and ALDH1. ALDH1 correlated to negative ERα and positive HER2/neu status in CTCs. The correlation between the number of MRPs expressed in CTCs and ALDH1 was statistically significant. CONCLUSION: in MBC, the presence of CTCs expressing MRPs and ALDH1 is predictive of response to chemotherapy.


Assuntos
Neoplasias da Mama/sangue , Neoplasias da Mama/patologia , Células Neoplásicas Circulantes/metabolismo , Células Neoplásicas Circulantes/patologia , Adulto , Idoso , Aldeído Desidrogenase/metabolismo , Família Aldeído Desidrogenase 1 , Resistencia a Medicamentos Antineoplásicos , Receptor alfa de Estrogênio/metabolismo , Feminino , Humanos , Isoenzimas/metabolismo , Pessoa de Meia-Idade , Metástase Neoplásica , Fenótipo , Prognóstico , Receptor ErbB-2/metabolismo , Retinal Desidrogenase
4.
Curr Genet ; 56(2): 109-19, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-20039042

RESUMO

The homocysteine synthase (tbhos) and putative sulfate transporter (tbsul1) genes have been characterized in order to understand the sulfate metabolism and regulation in the ectomycorrhizal fungus Tuber borchii. The analyses of tbsul1 and tbhos nucleotide and deduced amino acid sequences led to the identification of the typical domains shown in homologous proteins. Sulfate starvation condition upregulates both genes. The real-time PCR assay of tbsul1 revealed that gene expression was about threefold higher in mycelia grown under sulfate starvation for 2 days than in the mycelial control and in the same starvation condition, the sulfate uptake increased. Real-time PCR and enzymatic assays showed regulation of tbhos when sulfur sources were lacking, suggesting that a transcriptional regulation of this gene rather than a post-transcriptional one occurred. Furthermore, the tbsul1 and tbhos expression patterns were evaluated during the truffle life cycle, revealing an over-expression in the mature ascomata for both genes. In the ectomycorrhizal tissue, only tbhos was upregulated suggesting its substantial role in T. borchii cysteine synthesis. The regulation of tbsul1 and tbhos occurs primarily at the transcriptional level both during vegetative and fruiting phases and these genes could be directly involved in VOCs production.


Assuntos
Ascomicetos/enzimologia , Carbono-Oxigênio Liases/genética , Genes , Micorrizas/metabolismo , Sulfatos/metabolismo , Sequência de Aminoácidos , Ascomicetos/genética , Ascomicetos/metabolismo , Ensaios Enzimáticos , Expressão Gênica , Regulação Fúngica da Expressão Gênica , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/metabolismo , Micélio/genética , Micélio/metabolismo , Micorrizas/genética , Reação em Cadeia da Polimerase , Enxofre/metabolismo
5.
Curr Genet ; 55(1): 59-68, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19115055

RESUMO

This study focuses on the cloning and characterization of the major nitrogen regulator element from the ectomycorrhizal fungus Tuber borchii, TbNre1. Sequence analysis of the predicted protein and complementation experiments in Neurospora crassa demonstrated that the cloned gene is orthologous to areA/nit-2 gene. Transcriptional expression investigations by real-time RT-PCR showed TbNre1 up-regulation in the presence of nitrate or in the absence of nitrogen during free-living mycelium growth. On the contrary, TbNre1 mRNA levels remained at basal values in the presence of preferred nitrogen sources like ammonium and glutamine. Furthermore, TbNre1 mRNA was found to be up-regulated during T. borchii and T. platyphyllos interaction. All these data suggest that the regulatory protein TBNRE1 could play a major role in regulating N metabolism genes of T. borchii in the free living mycelium and in T. borchii-T. platyphyllos interaction. Finally, the possible role of the transcription factor TBNRE1 in the induction of proteases and virulence-like genes, necessary in ectomycorrhizal establishment, was also discussed.


Assuntos
Ascomicetos/genética , Proteínas Fúngicas/genética , Regulação Fúngica da Expressão Gênica/fisiologia , Micorrizas/genética , Proteínas PII Reguladoras de Nitrogênio/genética , RNA Mensageiro/metabolismo , Sequência de Aminoácidos , Ascomicetos/crescimento & desenvolvimento , Ascomicetos/metabolismo , Southern Blotting , Clonagem Molecular , DNA Fúngico , Perfilação da Expressão Gênica , Dados de Sequência Molecular , Micélio/citologia , Micélio/metabolismo , Nitrogênio/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de Aminoácidos , Regulação para Cima
6.
J Chemother ; 16(4): 392-9, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15332716

RESUMO

Docetaxel was proven to be effective as second-line therapy for patients with advanced NSCLC after failure of platinum-based front-line chemotherapy. We designed this phase I/II study to define the Maximum Tolerated Dose of weekly docetaxel combined with weekly vinorelbine, and subsequently evaluate tolerability and activity of this schedule in NSCLC patients who were progressive after treatment with either cisplatin and gemcitabine or carboplatin and paclitaxel regimens. To be eligible for the study, patients were required to have a WHO performance status < or =2, failure after at least two cycles of first platinum-based chemotherapy, and no prior treatment with docetaxel and vinorelbine. A total of 27 patients were enrolled in this phase I/II study. A weekly docetaxel dose of 25 mg/m2 was recommended in combination with fixed vinorelbine dose of 20 mg/m2, and 24 patients were treated at this dose level. Severe neutropenia (62%) and febrile neutropenia (29%) were the most frequent toxicities, with 83% of patients requiring dose modification or delay. In the phase II study, 5 (21%) patients obtained a partial response, 8 (33%) patients had stable disease, whereas 10 (42%) patients progressed. After a median follow-up of 18.7 months, median survival was 8 months, with 30% surviving at 1 year. Regardless of the use of weekly docetaxel schedule, this regimen was highly myelosuppressive, and did not seem to improve response rate and survival compared to single-agent docetaxel. No further developments of this schedule are warranted.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Neoplasias Pulmonares/tratamento farmacológico , Terapia de Salvação , Taxoides/administração & dosagem , Vimblastina/análogos & derivados , Vimblastina/administração & dosagem , Adolescente , Adulto , Idoso , Carcinoma Pulmonar de Células não Pequenas/mortalidade , Carcinoma Pulmonar de Células não Pequenas/patologia , Docetaxel , Relação Dose-Resposta a Droga , Esquema de Medicação , Humanos , Neoplasias Pulmonares/mortalidade , Neoplasias Pulmonares/patologia , Dose Máxima Tolerável , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Medição de Risco , Análise de Sobrevida , Taxoides/efeitos adversos , Vimblastina/efeitos adversos , Vinorelbina
7.
J Exp Clin Cancer Res ; 23(1): 25-32, 2004 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15149147

RESUMO

The combination of carboplatin and paclitaxel given every three weeks is a tolerated and reasonably active regimen in advanced non-small cell lung cancer (NSCLC). This study was designed to evaluate the maximum tolerated dose (MTD) of a fixed dose of carboplatin with an area under the curve (AUC) of 6 and escalating doses of weekly paclitaxel with an initial dose of 50 mg/m2 with 10 mg/m2 increments at each level in untreated NSCLC patients (phase I study). The study continued with a phase II study. Thirty patients entered the phase I study. The MTD was: carboplatin AUC = 6 on days 1 and 28 plus paclitaxel 100 mg/m2 (1 hour) on days 1, 8,15, 28. The dose-limiting toxicity (DLT) was severe neutropenia and cardiological toxicity. Subsequently, 42 patients entered the phase II study with the same treatment schedule. The 2-drug combination was globally well tolerated. The overall response rate (RR) was 42% [CI 95%: 26.3-57.7], stable disease (SD) 29% and progression (PD) 29%. The median duration of response was 8.0 mos (range: 1.0-19.0). The median time to progression was 8.0 mos (range: 7.0-19.0) and the median survival was 14.0 months (range: 9.0-19.0). The association of carboplatin AUC = 6 and weekly paclitaxel 100 mg/m2 proved to be manageable, active and extremely safe even in elderly patients (one third of all patients in our cohort). The survival results were interesting: the median survival time was 14 months (9-19 months) and the 1- and 2-year survival was 59% and 16%, respectively.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Carboplatina/administração & dosagem , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Neoplasias Pulmonares/tratamento farmacológico , Paclitaxel/administração & dosagem , Adulto , Idoso , Área Sob a Curva , Carcinoma Pulmonar de Células não Pequenas/mortalidade , Estudos de Coortes , Progressão da Doença , Feminino , Humanos , Neoplasias Pulmonares/mortalidade , Masculino , Dose Máxima Tolerável , Pessoa de Meia-Idade , Metástase Neoplásica , Fatores de Tempo , Resultado do Tratamento
8.
Fungal Genet Biol ; 33(1): 15-23, 2001 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-11407882

RESUMO

Recent biochemical investigations of Tuber borchii Vittad. mycelium have demonstrated the presence of three distinct forms of hexokinase (HK(M1), HK(M2), and HKM3). In the investigation described here, a gene coding for hexokinase (hxk-1) from T. borchii was isolated and characterized. The hxk-1 gene is characterized by an ORF of 1494 nucleotides and codes for a polypeptide of 497 aa. The gene was overexpressed in Escherichia coli, and the recombinant protein was kinetically characterized. The K(cat) value for fructose is in agreement with the data reported for the hexokinase of Yarrowia lipolytica, the Km for ATP is not dependent on the sugar used, and the enzyme is not inhibited by trehalose 6-phosphate or glucose 6-phosphate. The biochemical characteristics confirm that this enzyme is a hexokinase, as suggested by the Pileup results, and it corresponds to the HKM1 isoform. This work represents the first characterization of the key enzyme of the glycolytic pathway and the related gene in a Tuber species.


Assuntos
Ascomicetos/enzimologia , Hexoquinase/genética , Sequência de Aminoácidos , Animais , Ascomicetos/genética , Ascomicetos/crescimento & desenvolvimento , Sequência de Bases , Metabolismo dos Carboidratos , Clonagem Molecular , DNA Fúngico , Escherichia coli , Genes Fúngicos , Hexoquinase/isolamento & purificação , Hexoquinase/metabolismo , Humanos , Isoenzimas/genética , Isoenzimas/isolamento & purificação , Isoenzimas/metabolismo , Cinética , Dados de Sequência Molecular , Filogenia , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência
9.
Mol Cell Biochem ; 218(1-2): 65-70, 2001 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-11330839

RESUMO

The influence of carbohydrate utilisation on the growth of three strains of Tuber borchii Vittad. mycelium (1BO, 17BO and 10RA) in culture was assessed using culture media containing glucose (control), mannose or mannitol. Mannose was the best substrate for growth of the strains and this was particularly evident for strain 17BO. Mannitol instead was metabolized only by 10RA and 1BO. In order to explain the different growth trends, analyses of enzyme levels, kinetic parameters, protein patterns and the morphology of the three strains were carried out. Our results show that these strains of T. borchii mycelium were affected by the substrates used in the media. The aim of the present work was to optimise the in vitro production of T. borchii mycelium for use in experiments which require the fungus in precise and reproducible conditions, such as mycorrhizal synthesis or protein and nucleic acid extractions.


Assuntos
Ascomicetos/crescimento & desenvolvimento , Ascomicetos/genética , Glucose/metabolismo , Hexoquinase/metabolismo , Manitol/metabolismo , Manose/metabolismo , Biomassa , Meios de Cultura/química , Eletroforese em Gel de Poliacrilamida , Técnicas In Vitro , Cinética , Fatores de Tempo
10.
Can J Microbiol ; 47(3): 264-8, 2001 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-11315117

RESUMO

Previous studies on Tuber borchii fruit bodies in early maturation stages suggested a role of bacteria in sporocarp structural modifications. In order to verify this hypothesis, in the present study we investigated by means of microbial and ultrastructural approaches, the bacterial population of T. borchii sporocarps from intermediate maturation phases to advanced decomposition stages, paying particular attention to chitinolytic and cellulolytic bacteria and to their relationships with ascii and ascospores. We found that Pseudomonas fluorescens and spore-forming Bacillaceae, both able to degrade cellulose and chitin, are present inside the sporocarps in all maturation stages investigated. Moreover, rod-shaped bacteria seem able to erode ascus walls and colonize the interior of ascii containing mature spores. These results suggest a possible role of these bacteria in the process of ascus opening. Moreover, the presence of P. fluorescens and Bacillaceae on isolated mature spores after decontamination suggests an intimate association between these bacteria and the ascospores.


Assuntos
Ascomicetos/crescimento & desenvolvimento , Bacillaceae , Bacillaceae/isolamento & purificação , Pseudomonas fluorescens/isolamento & purificação , Simbiose , Ascomicetos/ultraestrutura , Bacillaceae/ultraestrutura , Pseudomonas fluorescens/ultraestrutura
11.
Tumori ; 86(6): 475-9, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-11218190

RESUMO

BACKGROUND: Malignant insulinoma is a rare tumor. Metastatic disease confined to the liver can be treated with various locoregional treatments. CASE REPORT: We report a case of a young woman who developed liver metastases twelve years following resection of a pancreatic insulinoma positive to anti-insulin antibodies. With five cycles of intra-arterial locoregional chemotherapy (fluorouracil and epirubicin) to the liver and monthly hormone therapy (octreotide) the patient obtained a clinical complete response. After twelve months she is still disease free. CONCLUSION: Locoregional therapy for insulinoma metastatic to the liver might represent the treatment of choice; hepatic intra-arterial chemotherapy is an interesting therapeutic approach which deserves attention. The role of somatostatin analogs is limited to symptom control.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Insulinoma/tratamento farmacológico , Insulinoma/secundário , Neoplasias Hepáticas/tratamento farmacológico , Neoplasias Hepáticas/secundário , Neoplasias Pancreáticas/patologia , Adulto , Anticorpos Antineoplásicos/análise , Epirubicina/administração & dosagem , Feminino , Fluoruracila/administração & dosagem , Humanos , Infusões Intra-Arteriais , Insulina/imunologia , Insulinoma/diagnóstico por imagem , Insulinoma/imunologia , Neoplasias Hepáticas/diagnóstico por imagem , Neoplasias Hepáticas/imunologia , Octreotida/administração & dosagem , Neoplasias Pancreáticas/imunologia , Tomografia Computadorizada por Raios X , Resultado do Tratamento
12.
Mol Cell Biochem ; 194(1-2): 71-7, 1999 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-10391126

RESUMO

Truffles are ectomycorrhizal fungi which have a great dependence on carbohydrates supplied by their host plants. The catabolism of hexoses in the mycobiont is important for the production of energy, and the first enzyme in the hexose assimilation pathways is hexokinase. This study reports differences in the expression of this enzyme during the growth of Tuber borchii Vittad. mycelium (strain ATCC 96540). Three hexokinase activities (HKM1, HKM2 and HKM3) were isolated by anion-exchange chromatography and partially purified. HKM1 and HKM2 were present in the linear phase at 15-50 days of growth. Two remarkable differences were found in the sugar-phosphorylating activity and stability of HKM1 and HKM2. HKM2 did not phosphorylate the fructose and it was present in the chromatographic profile only when substrates such as glucose, glucosamine or mannose were added to the extraction buffer. On the contrary, HKM1 utilized also fructose and was detected under all the experimental conditions used. HKM3 was the only molecular form observed after 70 days, when the fungus growth had reached a plateau. To our knowledge these results represent the first evidence for the presence in T. borchii mycelium of three distinct enzymatic forms of hexokinase which are differently expressed during growth of the fungus.


Assuntos
Ascomicetos/enzimologia , Hexoquinase/metabolismo , Isoenzimas/metabolismo , Ascomicetos/crescimento & desenvolvimento , Cromatografia em Gel , Cromatografia por Troca Iônica , Eletroforese em Gel de Poliacrilamida , Estabilidade Enzimática , Hexoquinase/isolamento & purificação , Isoenzimas/isolamento & purificação , Cinética
13.
Arch Biochem Biophys ; 342(2): 191-6, 1997 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-9186478

RESUMO

Recent studies performed in our laboratory demonstrated that rabbit red blood cell hexokinase was remarkably inhibited by the cocktail ascorbic acid/Fe(II) (Stocchi et al., 1994, Arch. Biochem. Biophys. 311, 160-167) and that the formation of dehydroascorbic acid was a key event in this process (Fiorani et al., 1996, Arch. Biochem. Biophys, 334, 357-361). The present study was undertaken to determine the final hexokinase-inactivating species using cell-free extract as a model. Our results demonstrate superimposable kinetics of hexokinase decay promoted by either ascorbic acid/Fe(II) or dehydroascorbic acid in erythrocyte lysates in which the reduced glutathione (GSH) levels were variously manipulated. In particular, neither removal nor addition of this tripeptide was able to significantly alter the rate or extent of hexokinase inhibition. Thus, GSH-reductive processes are dispensable events in the process of hexokinase inhibition promoted by ascorbic acid/Fe(II) in red blood cells. As a consequence, dehydroascorbic acid appears to be the species which directly inhibits hexokinase. This inference is further supported by the observation that addition of dehydroascorbic acid to the purified enzyme leads to a remarkable inhibition in its activity.


Assuntos
Ácido Ascórbico/farmacologia , Ácido Desidroascórbico/farmacologia , Eritrócitos/enzimologia , Compostos Ferrosos/farmacologia , Glutationa/metabolismo , Hexoquinase/antagonistas & inibidores , Animais , Ácido Desidroascórbico/metabolismo , Eritrócitos/efeitos dos fármacos , Glutationa/análogos & derivados , Dissulfeto de Glutationa , Hexoquinase/sangue , Peróxido de Hidrogênio/metabolismo , Oxirredução , Oxigênio/metabolismo , Coelhos
14.
Arch Biochem Biophys ; 334(2): 357-61, 1996 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-8900411

RESUMO

In this study we investigated the species involved in the process of hexokinase inactivation induced by ascorbic acid/Fe(II) in rabbit erythrocytes. Our results suggest a model in which divalent iron is first oxidized to the trivalent state and then triggers the oxidation of ascorbic acid. The H202 formed during this process accelerates the formation of dehydroascorbic acid, which appears to be necessary and sufficient to induce hexokinase inactivation. This model was validated by showing that: (a) H202-decomposing enzymes, unlike scavengers of the hydroxyl radicals, reduced the extent of hexokinase inactivation; (b) when H202 was used instead of ascorbate/Fe(II), it was unable, even at very high concentrations, to inhibit hexokinase activity; (c) replacing Fe(II) with either Fe(III) or H202 resulted in comparable levels of ascorbic acid-induced hexokinase inactivation; (d) expression of maximal hexokinase inhibiting activity was also triggered via enzyme-catalyzed oxidation of ascorbic acid or direct addition of dehydroascorbic acid; (e) the level of dehydroascorbic acid, which was actively generated in the external medium upon addition of ascorbic acid/Fe(II), increased as a function of time. Taken together, these results demonstrate that the process of hexokinase inactivation induced by ascorbic acid/Fe(II) is mediated by dehydroascorbate and that iron and H202 have the sole function of accelerating its formation.


Assuntos
Ácido Ascórbico/farmacologia , Ácido Desidroascórbico/farmacologia , Eritrócitos/enzimologia , Compostos Ferrosos/farmacologia , Hexoquinase/sangue , Animais , Catalase/farmacologia , Ácido Desidroascórbico/sangue , Glutationa Peroxidase/farmacologia , Hexoquinase/antagonistas & inibidores , Peróxido de Hidrogênio/sangue , Peróxido de Hidrogênio/farmacologia , Radical Hidroxila/sangue , Cinética , Coelhos
15.
Biochem Mol Biol Int ; 35(5): 1133-42, 1995 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-7549932

RESUMO

Exposure of rabbit reticulocytes to Fe(II)/ascorbate induced a pronounced decay in hexokinase activity. In reticulocytes, this enzyme is present in at least three different molecular forms, Ia, Ia* and Ib, sub-types of hexokinase type I, which show different intracellular distribution. Hexokinase Ia and Ib are soluble, whereas hexokinase Ia* is almost entirely bound to the mitochondria. Anion exchange chromatography of hexokinase from intact reticulocytes exposed to Fe(II)/ascorbate revealed a selective inactivation of forms Ia and Ib, whereas the form Ia* did not show any decay. Binding to the mitochondrial membrane seems to be responsible for the observed resistance of the form Ia* to the inactivation elicited by Fe(II)/ascorbate. Indeed, by using a cell-free system in which hexokinase Ia* was solubilized using Triton X-100, the decay in hexokinase activity induced by iron/ascorbate involved all three enzymatic forms.


Assuntos
Antineoplásicos/farmacologia , Ácido Ascórbico/farmacologia , Ativação Enzimática/efeitos dos fármacos , Compostos Ferrosos/farmacologia , Hexoquinase/efeitos dos fármacos , Hexoquinase/fisiologia , Mitocôndrias/metabolismo , Reticulócitos/enzimologia , Animais , Membrana Celular/metabolismo , Cromatografia por Troca Iônica , Hexoquinase/química , Isoenzimas/química , Octoxinol , Coelhos , Solubilidade , Fatores de Tempo
16.
Res Commun Chem Pathol Pharmacol ; 42(1): 135-43, 1983 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-6417743

RESUMO

A microbial bioassay for the detection of agents which induce increased lethal damage in DNA repair deficient strains of B. subtilis was modified and evaluated using six established mutagens. This modified procedure used a liquid pre-incubation technique with the plate incorporation assay allowing detection of mutagenic compounds which require metabolic activation and are sparingly soluble in water.


Assuntos
Bacillus subtilis/genética , Mutagênicos , Reparo do DNA , Testes de Mutagenicidade/métodos
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