PubMed Health⌕ Search

Biomedical subjects

H Martins

Publications and source records attributed to H Martins.

16 recordsLinked to original sources
PubMed2006

Vanadium distribution, lipid peroxidation and oxidative stress markers upon decavanadate in vivo administration.

The contribution of decameric vanadate species to vanadate toxic effects in cardiac muscle was studied following an intravenous administration of a decavanadate solution (1mM total vanadium) in Sparus aurata. Although decameric vanadate is unstable in the assay medium, it decomposes with a half-life time of 16 allowing studying its effects not only in vitro but also in vivo. After 1, 6 and 12h upon decavanadate administration the increase of vanadium in blood plasma, red blood cells and in cardiac mitochondria and cytosol is not affected in comparison to the administration of a metavanadate solution containing labile oxovanadates. Cardiac tissue lipid peroxidation increases up to 20%, 1, 6 and 12h after metavanadate administration, whilst for decavanadate no effects were observed except 1h after treatment (+20%). Metavanadate administration clearly differs from decavanadate by enhancing, 12h after exposure, mitochondrial superoxide dismutase (SOD) activity (+115%) and not affecting catalase (CAT) activity whereas decavanadate increases SOD activity by 20% and decreases (-55%) mitochondrial CAT activity. At early times of exposure, 1 and 6h, the only effect observed upon decavanadate administration was the increase by 20% of SOD activity. In conclusion, decavanadate has a different response pattern of lipid peroxidation and oxidative stress markers, in spite of the same vanadium distribution in cardiac cells observed after decavanadate and metavanadate administration. It is suggested that once formed decameric vanadate species has a different reactivity than vanadate, thus, pointing out that the differential contribution of vanadium oligomers should be taken into account to rationalize in vivo vanadate toxicity.

Animals↗
PubMed2005

Vanadium distribution following decavanadate administration.

An acute exposure of two vanadate solutions-metavanadate and decavanadate-containing different vanadate oligomers, induces different patterns of subcellular vanadium distribution in blood plasma, red blood cells (RBC), and cardiac muscle subcellular fractions of the fish Sparus aurata (gilthead seabream). The highest amount of vanadium was found in blood plasma 1 h after (5 mM) intravenous vanadate administration (295 +/- 64 and 383 +/- 104 microg V/g dry tissue, for metavanadate and decavanadate solutions, respectively), being 80-fold higher than in RBC. After 12 h of administration, the amount of vanadium in plasma, as well as in cardiac cytosol, decreased about 50%, for both vanadate solutions. During the period between 1 and 12 h, the ratio of vanadium in plasma/vanadium in RBC increased from 27 to 128 for metavanadate, whereas it remains constant (77) for decavanadate. Both vanadium solutions were primarily accumulated in the mitochondrial fraction (138 +/- 0 and 195 +/- 34 ng V/g dry tissue for metavanadate and decavanadate solutions, respectively, after 12 h exposure), rather than in cytosol. The amount of vanadium in cardiac mitochondria was twofold higher than in cytosol, earlier for metavanadate (6 h) than for decavanadate (12 h). It is concluded that, in fish cardiac muscle, the vanadium distribution is dependent on the administration of decameric vanadate, with vanadium being mainly distributed in plasma, before being accumulated into the mitochondrial fraction.

Animals↗
PubMed2005

Vanadate oligomers: in vivo effects in hepatic vanadium accumulation and stress markers.

The formation of vanadate oligomeric species is often disregarded in studies on vanadate effects in biological systems, particularly in vivo, even though they may interact with high affinity with many proteins. We report the effects in fish hepatic tissue of an acute intravenous exposure (12, 24 h and 7 days) to two vanadium(V) solutions, metavanadate and decavanadate, containing different vanadate oligomers administered at sub-lethal concentration (5 mM; 1 mg/kg). Decavanadate solution promotes a 5-fold increase (0.135 +/- 0.053 microg V(-1) dry tissues) in the vanadium content of the mitochondrial fraction 7 days after exposition, whereas no effects were observed after metavanadate solution administration. Reduced glutathione (GSH) levels did not change and the overall reactive oxygen species (ROS) production was decreased by 30% 24 h after decavanadate administration, while for metavanadate, GSH levels increased 35%, the overall ROS production was depressed by 40% and mitochondrial superoxide anion production decreased 45%. Decavanadate intoxication did not induce changes in the rate of lipid peroxidation till 12 h, but later increased 80%, which is similar to the increase observed for metavanadate after 24 h. Decameric vanadate administration clearly induces different effects than the other vanadate oligomeric species, pointing out the importance of taking into account the different vanadate oligomers in the evaluation of vanadium(V) effects in biological systems.

Animals↗
PubMed2002

Oxidative stress in toadfish (Halobactrachus didactylus) cardiac muscle. Acute exposure to vanadate oligomers.

Vanadate solutions as "metavanadate" (containing ortho and metavanadate species) and "decavanadate" (containing mainly decameric species) (5 mM; 1 mg/kg) were injected intraperitoneously in Halobatrachus didactylus (toadfish), in order to evaluate the contribution of decameric vanadate species to vanadium (V) intoxication on the cardiac tissue. Following short-term exposure (1 and 7 days), different changes on antioxidant enzyme activities-superoxide dismutase (SOD), catalase (CAT), selenium-glutathione peroxidase (Se-GPx), total glutathione peroxidase (GPx), lipid peroxidation and subcellular vanadium distribution were observed in mitochondrial and cytosolic fractions of heart ventricle toadfish. After 1 day of vanadium intoxication, SOD, CAT and Se-GPx activities were decreased up to 25%, by both vanadate solutions, except mitochondrial CAT activity that increased (+23%) upon decavanadate administration. After 7 days of exposure, decavanadate versus metavanadate solutions promoted different effects mainly on cytosolic CAT activity (-56% versus -5%), mitochondrial CAT activity (-10% versus +10%) and total GPx activity (+1% versus -35%), whereas lipid peroxidation products were significantly increased (+82%) upon 500 microM decavanadate intoxication. Accumulation of vanadium in total (0.137+/-0.011 microg/g) and mitochondrial (0.022+/-0.001 microg/g) fractions was observed upon 7 days of metavanadate exposure, whereas for decavanadate, the concentration of vanadium increased in cytosolic (0.020+/-0.005 microg/g) and mitochondrial (0.021+/-0.009 microg/g) fractions. It is concluded that decameric vanadate species are responsible for a strong increase on lipid peroxidation and a decrease in cytosolic catalase activity thus contributing to oxidative stress responses upon vanadate intoxication, in the toadfish heart.

Animals↗
PubMed1998

Enkephalin-processing oligopeptidases in cobra venom: inhibition by thiorphan and bestatin reveals co-operative actions.

The peptidase inhibitors thiorphan and bestatin were tested for their ability to inhibit the actions of the oligopeptidases contained in the venom of the Taiwan cobra (Naja naja atra). With methionine enkephalin (TyrGlyGlyPheMet) as substrate, thiorphan was an effective inhibitor of cleavage of the GlyPhe peptide bond while bestatin inhibited cleavage of the TyrGly peptide bond. Thiorphan and bestatin also inhibited subsequent cleavage of the fragments GlyGlyPheMet and TyrGlyGly respectively. These inhibitors reveal an interplay between the venom oligopeptidases in which the enzymes provide additional substrates for each other following their initial competitive attack on the neuropeptide. A possible explanation is that the system is intended to ensure a steady release of Tyr, GlyGly and PheMet over time. Significantly, Tyr is the favoured substrate of the L-amino acid oxidase present in the venom, which rapidly transforms this aromatic amino acid into phenolic derivatives. The efficacies of these inhibitors also suggest that there are similarities between the venom oligopeptidases and the peptidases associated with the processing of enkephalin in its normal contexts.

Aminopeptidases↗
PubMed1997

Mutation frequency and spectrum in lymphocytes of small cell lung cancer patients receiving etoposide chemotherapy.

Etoposide, a topoisomerase II inhibitor, is a chemotherapeutic agent that is used in the treatment of a wide variety of neoplasms, including small cell lung cancer, germ cell cancer, testicular cancer, acute leukemia, and lymphoma. Although it has proven valuable, etoposide is also a known mutagen and has been implicated as a causative agent of treatment-related secondary acute nonlymphocytic leukemia. We have investigated the induction of mutation following etoposide treatment in vivo using the hypoxanthine phosphoribosyltransferase (hprt) T-cell cloning assay in small cell lung cancer patients receiving single-drug etoposide chemotherapy. This report presents results on the monitoring of 12 patients (mean age, 74.8 +/- 6.0 years; range, 66-83 years) before, during, and after chemotherapy. The treatment regimen included up to six cycles of oral etoposide given in twice-daily 50-mg tablets for 10-14 days, separated by 2 weeks of rest. Peripheral blood samples were collected on the first day of each cycle prior to treatment. Patients received one to six etoposide cycles and were followed for 0.7-5.3 months after the start of chemotherapy (total etoposide dose, 1.4-8.4 g). Results from the pooled data show no significant increase in the hprt mutant frequency (pretreatment, 46 x 10(-6) +/- 38 x 10(-6), versus posttreatment, 55 x 10(-6) +/- 46 x 10(-6)), although considerable interpatient variability was observed. Of a total of 424 selected mutants, 228 were analyzed by sequencing hprt cDNA. Spectra of 56 pretreatment and 147 posttreatment mutations revealed significant enhancement of AT-->TA transversions and a concomitant decrease in the number of GC-->TA transversions in posttreatment spectra, when they were compared with pretreatment or control spectra. No evidence for the induction of gross deletions or rearrangements was found in the spectra of mutants that were recovered from patients after etoposide treatment. The lack of enhanced mutant frequency after treatment suggests that the etoposide chemotherapy was not particularly effective in inducing mutation, as measured by the hprt assay. It is proposed that mutated cells are eliminated through apoptosis due to accumulated DNA damage.

Age Factors↗
PubMed1996

Phase II study of docetaxel (taxotere) in patients with previously untreated extensive small cell lung cancer.

The objective of this multicenter phase II study was to evaluate the activity of docetaxel in previously untreated small cell lung cancer. Fourteen patients were treated at a dose of 75 mg/m2 intravenously every three weeks. Of the 12 patients evaluable for response, one had a partial response for a duration of 12 weeks for a response rate of 8.3%. Toxicity was mild. We conclude that docetaxel has, at the dose given in this study, little activity in previously untreated small cell lung cancer.

Aged↗
PubMed1996

[Evaluation of the protection received by a BC antimeningococcal vaccine in the State of Santa Catarina, Brazil, 1990/92].

Results of the evaluation of the anti-meningococcal BC Cuban vaccine based on routine epidemiological surveillance information of meningitis for the years 1990 to 1992, following mass-vaccination of 232,022 children aged between 3 months and 7 years in 1989/90 during an epidemic of serogroup B meningococcal disease in the State of Santa Catarina, Brazil, are presented. The protective efficacy of the vaccine was calculated from the incidence rates for the cohort of vaccinated and non-vaccinated children in 20 municipalities. Main results for cases confirmed by bacteriological tests were 59% (CI 95%: 23 to 78%) for children aged under 4 years and 78% (CI 95%: 54 to 90%) for children aged 4 to 7 years. Eighty-six percent of cases serogrouped (n = 29) were B, and in these cases efficacy increased to 66% (< 4 years) and 88% (4-7 years), but at 95% CI were wider. The protective efficacy based on death rates from the disease in children < 4 years was 76% (CI 95%: 41 to 91%). There was no evidence of decreasing protective efficacy in the three year follow-up, as shown by the yearly estimates. An interesting hypothesis arising from the findings is that the lower protective efficacy for children aged < 4 years, observed in studies in which only cases confirmed by laboratory tests are analysed, could be due to a selective effect of this procedure. More severe cases die shortly after the onset of the disease, often before medical care is provided. On the other hand, the attenuation of the disease by vaccination gives a better chance for medical intervention and collection of samples for laboratory analysis. Finally, the authors support the use of the vaccine in epidemics of serogroup B meningococcal disease. They also suggest that three, rather than two doses of vaccine should be tested in children under 2 years of age to further increase its efficacy.

Bacterial Vaccines↗
PubMed1996

Risk factors for left ventricular hypertrophy: role of Na(+)-Li+ countertransport.

Left ventricular hypertrophy (LVH) is associated with an increase in cardiovascular death in essential hypertension (EH). The factors involved in LVH are multiple and complex. We looked for risk factors of LVH in a group of 28 nonobese patients with EH (mean age = 45.3 years). We analyzed the activity of several erythrocyte ion transports (Vmax of NaLi countertransport, NaKCl cotransport and NaK-pump, and the Na-leak Kp Na), the intracellular Na and the insulin sensitivity index. All these parameters were used as independent variables whereas the left ventricular mass index (LVMI) was used as the dependent variable. Variables showing a significant univariate correlation (age, time of EH, mean blood pressure and Vmax of NaLi countertransport) were introduced in a stepwise multiple regression model. Only age (P = 0.014), time of EH (P = 0.038) and Vmax of NaLi countertransport (P = 0.032) were independently associated with LVMI (R2 = 0.581, P = 0.0001). The NaLi CT, an operating mode of the NaH exchanger that facilitates cellular growth, may be a marker of LVH, and consequently a marker of increased cardiovascular risk.

Adult↗
PubMed1995

Oral etoposide and carboplatin. Effective therapy for elderly patients with small cell lung cancer.

PURPOSE: Elderly patients with small cell lung cancer (SCLC) and/or those with comorbid conditions are frequently not considered candidates for standard combination chemotherapy. An active, but less toxic regimen is needed for this group of patients. PATIENTS AND METHODS: Forty-seven elderly (> 65 years) or medically unfit patients with SCLC were treated with oral etoposide 100 mg/m2 x 7 days and carboplatin 150 mg/m2 day 1. Treatment was given every 3-4 weeks for six cycles in responding patients. Patients responding to the chemotherapy regimen were also treated with prophylactic cranial irradiation, and limited-stage patients received thoracic radiotherapy. The study population included 36 extensive-stage patients and 11 limited-disease patients with renal or cardiac disease that precluded standard chemotherapy. The median age of the study population was 69 years (range: 47-84). RESULTS: Nine of 47 patients were inevaluable for response, including four patients who succumbed to sepsis. Of the 38 patients evaluable for response, 71% responded (95% CI: 56-86%) (88% LD; 67% ED) with a complete response in 29% of patients (50% LD; 23% ED). Based on an analysis of intent to treat, the overall response rate was 60% and the median survival time of the whole group was 46 weeks (LD, 59 weeks; ED, 45 weeks). Treatment was generally well tolerated. Neutropenia was the dose-limiting toxicity; the median nadir granulocyte count was 1.04 x 10(9)/L (range: 0-8.2). CONCLUSION: We conclude that this regimen can provide palliation to SCLC patients who might not otherwise be considered for systemic chemotherapy.

Aged↗
PubMed1983

Tick-bite fever in South Africa. The occurrence of severe cases on the Witwatersrand.

Tick-bite fever, the variety of tick typhus occurring in southern Africa, is caused by Rickettsia conori var. pijperi and is transmitted by hard or ixodid ticks. It is usually a mild disease, especially in children and young adults, but in middle-aged and elderly patients (and sometimes in young adults) it may assume a severe form. This is characterized by high fever, severe headache, delirium, stupor and occasionally coma, and a profuse maculopapular rash which becomes haemorrhagic and is associated with petechiae in the skin and later, but rarely, by the development of gangrene of the fingers and toes. During these severe attacks the central nervous system may be involved and marked disorders of liver and kidney function sometimes lead to kidney failure and the need for treatment and dialysis in an intensive care unit. Three illustrative cases are described in which diagnosis was delayed. One patient died; 2 patients responded to administration of tetracycline. The danger of allowing tick-infested dogs onto one's bed is stressed. Infections transmitted by dog ticks tend to be more severe than those acquired via ticks from the bushveld, possibly because they so often occur in middle-aged and elderly patients. Serological tests have recently indicated that there are antigenic differences between 'suburban' and 'bushveld' strains; these clearly require further study.

Adult↗