Biomedical subjects

M Bernardo-Filho

Publications and source records attributed to M Bernardo-Filho.

At least 55 records · Page 3Linked to original sources

PubMed1998

Shark cartilage-containing preparation: protection against reactive oxygen species.

There is overwhelming evidence to indicate that free radicals cause oxidative damage to lipids, proteins and nucleic acids and are involved in the pathogenesis of several degenerative diseases. Therefore, antioxidants, which can neutralize free radicals, may be of central importance in the prevention of these disease states. The protection that fruits and vegetables provide against disease has been attributed to the various antioxidants contained in them. Recently, an anti-inflammatory and analgesic activity of a water-soluble fraction from shark cartilage has been described. Using electrophoretical assays, bacteria survival and transformation and the Salmonella/mammalian-microsome assay, we investigated the putative role of shark cartilage-containing preparation in protecting cells against reactive oxygen species induced DNA damage and mutagenesis. If antimutagens are to have any impact on human disease, it is essential that they are specifically directed against the most common mutagens in daily life. Our data suggest that shark cartilage-containing preparation can play a scavenger role for reactive oxygen species and protects cells against inactivation and mutagenesis.

4-Nitroquinoline-1-oxide↗

PubMed1998

The effect of mitomycin-C on the biodistribution of 99Tcm-MDP in Balb/c mice.

Drug therapy can alter the biodistribution of radiopharmaceuticals. We studied the effect of mitomycin-C, a drug used in oncology, on the biodistribution in mice of 99Tcm-methylene diphosphonic acid (99Tcm-MDP). Three doses of mitomycin-C were administered. After the last dose, 99Tcm-MDP was injected and the animals were killed. The organs were isolated, their weight determined and the percent per gram injected dose (%ID/g) calculated. The %ID/g had increased in the pancreas, ovary, stomach, uterus, kidneys, spleen, thymus, heart, liver and lungs, but did not change significantly in thyroid, bone or brain. As a change in 99Tcm-MDP uptake by bone is not observed, a modification to bone scintigraphy is not required. As mitomycin-C treatment altered 99Tcm-MDP uptake in some organs, any hot spots should be evaluated carefully to avoid a misdiagnosis.

Animals↗

PubMed1998

In vitro radioautographic studies of the biodistribution of radiopharmaceuticals on blood elements.

In the present study we evaluated the binding of the radiopharmaceuticals sodium pertechnetate (Na 99mTcO4), methylenediphosphonic acid (99mTc-MDP) and glucoheptonate acid (99mTc-GHA) to blood elements using centrifugation and radioautographic techniques. Heparinized blood was incubated with the labelled compounds for 0, 1, 2, 3, 4, 6 and 24 h. Plasma (P) and blood cells (BC) were isolated and precipitated with 5% trichloroacetic acid (TCA), and soluble (SF) and insoluble fractions (IF) were separated. Blood samples were prepared (0 and 24 h) and coated with LM-1 radioautographic emulsions and percent radioactivity (%rad) in P and BC was determined. The binding of Na 99mTcO4 (%rad) to P was 61.2% (0 h) and 46.0% (24 h), and radioautography showed 63.7% (0 h) and 43.3% (24 h). The binding to BC was 38.8% (0 h) and 54.0% (24 h), and radioautography showed 36.3% (0 h) and 56.7% (24 h). 99mTc-MDP study presented 91.1% (0 h) to P and 87.2% (24 h), and radioautography showed 67.9% (0 h) and 67.4% (24 h). The binding to BC was 8.9% (0 h) and 12.8% (24 h), and radioautography showed 32.1% (0 h) and 32.6% (24 h). 99mTc-GHA study was 90.1% (0 h) to P and 79.9% (24 h), and radioautography showed 67.2% (0 h) and 60.1% (24 h). The binding to BC was 9.9% (0 h) and 20.1% (24 h), and radioautography showed 32.8% (0 h) and 39.9% (24 h). The comparison of the obtained results suggests that the binding to plasma and blood cells in the two techniques used (radioautography and centrifugation) is qualitatively in accordance.

Animals↗

PubMed1998

Influence of tobacco on the labelling of red blood cells and plasma proteins with technetium-99m.

Technetium-99m-labelled red blood cells (RBC) have been used as radiopharmaceutical in nuclear medicine. The influence of drug interaction in this labelling process has been described along with the biological effects of tobacco on the labelling of blood elements with technetium-99m. The labelling of RBC and plasma proteins can be decreased in presence of tobacco. This can be due to either a direct or indirect effect (reactive oxygen species) of tobacco by (i) oxidation of the stannous ion, (ii) possible damages caused in plasma membrane and/or (iii) possible chelating action on the stannous and/or pertechnetate ions.

Animals↗

PubMed1996

Lethality induced by stannous chloride on Escherichia coli AB1157: participation of reactive oxygen species.

Stannous chloride (SnCl2) has been widely used in nuclear medicine as a reducing agent of pharmaceutical products radiolabelled with technetium-99m. To verify whether the lethality induced by this salt could be mediated by reactive oxygen species (ROS), Escherichia coli cultures were treated with SnCl2 in the presence of catalase, ROS scavengers or metal-ion chelators. The inactivation effect, as measured by survival determination, was abolished by thiourea, sodium benzoate, dipyridyl or catalase. The results suggest the participation of ROS, generated by a Fenton-like reaction, in the lethal effect induced by SnCl2.

2,2'-Dipyridyl↗

PubMed1995

Effect of cyclophosphamide on the binding of 99mTcO-4 and 99mTc-MDP to blood cells and plasma proteins.

Since the introduction of technetium-99m (99mTc) and its rapid acceptance as a tool in nuclear medicine, very little information is available about its biological action as 99mTc-radiopharmaceuticals. We have determined if cyclophosphamide, an alkylating agent, used in oncology as a chemotherapeutic drug, modifies the binding of 99mTcO-4 and 99mTc-MDP (99mTc-methylenediphosphonic acid) to blood cells and to plasma proteins. The radiopharmaceuticals were injected intravenously (iv) into SW-55 mice (male and female, weight 25 g) and samples of plasma and blood cells were separated. Cyclophosphamide (50 micrograms) was injected iv 1 h before the radiopharmaceuticals. Samples of plasma and blood cells were also precipitated with 5% trichloroacetic acid and soluble and insoluble fractions were isolated. The following results were obtained: 1) cyclophosphamide did not alter (0.25 to 8 h) percent radioactivity of 99mTcO-4 in plasma or blood cells but increased the binding of 99mTc-MDP to blood cells; 2) cyclophosphamide did not alter (0.25 to 8 h) the binding of 99mTcO-4 in insoluble fraction of plasma and decreased (1 to 4 h) percent radioactivity of 99mTc-MDP in the insoluble fraction of plasma; 3) cyclophosphamide increased (0.25 to 4 h) percent radioactivity of 99mTcO-4 in the insoluble fraction of blood cells but did not alter the binding of 99mTc-MDP. Cyclophosphamide and/or its metabolites modified the effective half-life of these radiopharmaceuticals (to 99mTcO-4 was increased 2.3 to 3.4 h and to 99mTc-MDP was decreased 3.3 to 2.1 h) and possibly increased the permeability of blood cells to 99mTcO-4.

Alkylating Agents↗

PubMed1995

In vitro effect of cyclophosphamide on the binding of radiopharmaceuticals (99mTcO4- and 99mTc-MDP) to blood elements.

Sodium pertechnetate (99mTcO4-) and many 99mTc-products are the radiopharmaceuticals most frequently used in nuclear medicine. Using an in vitro model, we evaluated the effect of cyclophosphamide on percent radioactivity of 99mTcO4- and methylenediphosphonic acid (99mTc-MDP) bound to isolated blood elements. Blood samples were incubated with the two radiopharmaceuticals, plasma and blood cells were separated and precipitated, and soluble and insoluble fractions were separated. To evaluate the effect of cyclophosphamide, blood was incubated with this drug 1 h prior to the addition of the radiopharmaceuticals. The fraction of 99mTcO4- radioactivity was slightly higher in plasma (61.2 to 53.8%) than in blood cells (38.8 to 46.2%) up to 6 h and cyclophosphamide did not interfere with this distribution. The amount of 99mTc-MDP radioactivity was higher in plasma (91.1 to 87.2%) than in blood cells (8.9 to 12.8%) up to 24 h and cyclophosphamide did not modify it. The binding of 99mTcO4- to the insoluble fraction of plasma (4.9 to 6.1%) was low and cyclophosphamide did not interfere with it up to 6 h, but a small blockade (9.8 to 4.8%) was observed at 24 h. From 3 h on, cyclophosphamide slightly inhibited 99mTcO4- binding to blood cells (23.1 to 16.6%) and increased it at 24 h (31.2 to 14.3%). Cyclophosphamide did not alter 99mTc-MDP binding to the insoluble fraction of blood cells and slightly decreased 99mTc-MDP binding to the insoluble fraction of plasma (29.8 to 23.6%) up to 6 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkylating Agents↗

PubMed1994

99mTc labeling white blood cells with a simple technique: clinical application.

Several radionuclides and different methods have been employed as cellular labels to study inflammatory sites in man. Here we present the results obtained with white blood cells (WBC) labeled with 99mTc using a simple and low cost new technique (SnTec). WBC were incubated with 12 micrograms/ml of stannous chloride for 10 min at room temperature. Then 99mTc was added. After 10 min, the 99mTc-labeled WBC were washed and injected into the patient. Comparison studies with 99mTc-labeled WBC using the HMPAO technique were carried out in patients with suspected osteomyelitis. Since the results are similar with both methods, we suggest the use of SnTec to label WBC, in cases of inflammatory diseases.

Adolescent↗

PubMed1994

Evaluation of potential genotoxicity of stannous chloride: inactivation, filamentation and lysogenic induction of Escherichia coli.

Because of the importance of stannous chloride in various fields of human endeavour, the potential genotoxicity of this reducing agent was evaluated by measurement of either the inactivation or the induction of SOS responses in bacteria. Escherichia coli strains used in this work (wild type, uvrA, recA, lexA and uvrA recA) were treated with stannous chloride; the wild type was found to be the most resistant and the double mutant, the most sensitive strain. As these strains present mutations on specific genes for the repair of DNA, stannous chloride would appear to be capable of inducing and/or producing lesions in DNA and, thus, can be considered to be a potential genotoxic agent. This capability was confirmed by the lysogenic induction of E. coli K12 (lambda) (Inductest) and by microscopic observation of E. coli B filamentation.

DNA Repair↗

PubMed1994

Effect of different anticoagulants on the labelling of red blood cells and plasma proteins with 99Tcm.

There are controversies about the effect of different anticoagulants on the labelling of blood elements with 99Tcm. Our results show that the type of anticoagulant employed to withdraw the whole blood can modify the 99Tcm labelling of red blood cells (RBC) and plasma proteins (PP). The anticoagulants ACD (citric acid, sodium citrate and dextrose solution), heparin and sodium oxalate present similar results for the 99Tcm labelling of RBC with the exception of 0.13 microM stannous chloride. In this assay oxalate provides the best RBC labelling. In addition, with ethylenediaminetetraacetic acid (EDTA) the labelling of RBC is almost always lower than with the other anticoagulants, probably due to its high chelating capacity. The anticoagulants ACD, oxalate and heparin show the same results as expected with 99Tcm labelling of PP. The lowest labelling at 13.00 microM stannous chloride in the presence of oxalate is probably due to its low chelating capacity. The results also reinforce the idea that the erythrocyte membrane exerts an important role in the regulation of stannous ion transport into RBCs.

Anticoagulants↗

PubMed1994

Oxamniquine: a labeling procedure with technetium-99m and a biodistribution study in mice.

Oxamniquine (OXY), a tetrahydroquinoline derivative, is used as an antischistosomal drug and generally has been labeled with carbon-14 and tritium. We decided instead to label it with technetium-99 (99mTc). In order to determine the optimal conditions, different concentrations of this drug were incubated with various stannous chloride solutions. We then added 99mTc, and chromatography was performed using 0.9% NaCl solution, acetone and 1.2N HCl as the mobile phase. Using a solution of 1.0 mg/mL stannous chloride and 0.5 mg/mL oxamniquine, over 94% of the radioactivity bound to oxamniquine (99mTc-OXY). In the biodistribution study, 99mTc-OXY was administered in mice intramuscularly, orally and intravenously. When the intramuscular route was used, the main uptake (after 30 minutes) of the labeled drug was in the kidneys, liver and intestines; after 240 minutes the labeled drug was still found in the liver and kidneys, but at increased levels in the intestines. It was also present in the faeces. When the oral route was employed, labeled OXY was mainly found in the stomach after 30 minutes, but there was a decrease after 240 minutes. During this period radioactivity increased in the intestines. When the intravenous route was employed the labeled OXY was found in the liver and spleen. The radioactivity decreased with time in these organs. Using infected animals, radioactivity was found in isolated worms.

Animals↗

PubMed1994

Near-UV light protection effect against lethality induced by stannous chloride in Escherichia coli.

Stannous chloride (SnCl2) is a reducing agent largely employed in industry and in medical procedures. To evaluate its potential genotoxicity, several Escherichia coli strains were treated with SnCl2 and their survival rates determined. Results showed that the double mutant on specific genes for the repair of deoxyribonucleic acid damage was the most sensitive strain. Simultaneous near-UV illumination inhibited the lethal effect of SnCl2 in the wild type strain. Although the nature of the induced lesions are not known these results indicate the potential genotoxicity of SnCl2.

DNA Repair↗

PubMed1992

Neighbour restoration: a possible explanation for some "broken" survival curves of UV-irradiated Escherichia coli K12 cells.

Survival curves for UV irradiation of five non-filamenting strains of E. coli K12 decrease exponentially at moderate levels of radiation but are broken at high levels of radiation. That is, it appears a change in the slope of survival curves, featuring a tail. As this phenomenon was observed with strains bearing uvrA and recA mutations it must be independent of the products of these genes. Experiments with isolated surviving colonies and synchronized cultures eliminated genetic and phenotypic heterogeneity as reasons for the tails in the survival curves. UV survival increased 10- to 15-fold when UV-irradiated cells were plated either with cells unable to grow in the plating medium or with bacterial cell-free extracts. We suggest that factors related to the high cell densities used to obtain survival curves at high radiation levels (neighbour restoration) could be responsible for the survival increases, generating the tailed survival curves.

Escherichia coli↗

PubMed1989

Adherence of Pseudomonas aeruginosa to respiratory epithelium and the effect of leucocyte elastase.

The tracheobronchial secretions from patients with cystic fibrosis often contain high amounts of free proteases. To evaluate whether human leucocyte elastase (HLE) can favour the persistence of bacterial airways infection, we exposed the frog palate mucosa to HLE and then to radiolabelled Pseudomonas aeruginosa and followed the sequence of events by scanning electronmicroscopy. In response to HLE there was a marked outpouring of mucus and a desquamation of the epithelium. P. aeruginosa was shown to adhere to recently secreted granules of mucus and to the exposed submucosal underlying connective tissues. For the eight different bacterial strains studied, a significative adherence to HLE-injured mucosa was observed only in strains that possessed internal haemagglutinating activity. Neither the presence of fimbriae, nor of the mucoid exopolysaccharide, nor of the bacterial surface haemagglutinating activity could be related to adherence of P. aeruginosa to the injured mucosa. These results support the hypothesis that HLE enhances bacterial infection of the respiratory mucosa both by inducing mucus hypersecretion and by exposing receptors to the microbial adhesins. It is also suggested that P. aeruginosa internal lectins may be implicated in adherence to host tissues.

Animals↗

PubMed1989

Labelling of the platyhelminth Dugesia tigrina with 99mtechnetium.

The study of the labelling of planaria with 99mTc shows that the incorporation of radioactivity in this platyhelminth increases with an increase in SnCl2 concentration from 0.13 to 1.3 microM, reaching a plateau in the range of 1.3-130 microM then decreasing with 1300 microM. At concentrations of 1.3 and 13 microM SnCl2, a stronger binding of 99mTc was obtained. The biological viability of the labelled planaria was not altered when the described methodology was used. The advantage of this new labelling technique is that it is possible to obtain a platyhelminth preparation labelled with a radionuclide that is very cheap, is easily available and is a gamma emitter with a photon energy of 140 keV.

Animals↗

PubMed1987

The 99m technetium labeling effect on bacterial surface properties.

The present study was undertaken to determine whether labeling Pseudomonas aeruginosa with 99m Technetium would modify some of the bacterial physicochemical surface properties which play an important role in the interaction between bacteria and eukaryotic cells. No significant difference in electrophoretic mobility or distribution of cationized ferritin on the cell surface was observed between labeled and unlabeled bacteria. Also, the 99m Tc labeling process did not modify bacterial hydrophobicity or adhesiveness to human buccal epithelial cells. It is concluded that bacterial labeling with 99m Tc can be accepted as a useful method for biological research.

Bacterial Adhesion↗

PubMedDate not supplied

A model to evaluate the biological effect of natural products: vincristine action on the biodistribution of radiopharmaceuticals in BALB/c female mice.

Natural products have been widely used by human beings. However, sometimes the biological effects of these products are not fully known. We are trying to develop a model to evaluate the toxicity of compounds employed as therapeutic drugs. This model is based on the capability of natural products to alter the biodistribution of radiopharmaceuticals labelled with technetium-99m (99mTc). The acceptance of 99mTc-labelled radiopharmaceuticals is so rapid and its current use so diverse that it is not possible to study this radionuclide's behaviour in the body more deeply. There is evidence that the biodistribution or the pharmacokinetics of radiopharmaceuticals can be modified by some drugs, by pathological states, by irradiation and by surgical procedures. A lack of knowledge of such factors can induce a misvisualization of the scintigraphic images, leading to a misdiagnosis. Vincristine is a natural product that has been employed in various chemotherapeutic protocols in oncology. We have studied the effect of vincristine on the distribution of [99mTc]methylenediphosphonic acid ([99mTc]MDP) in female mice. After the last dose of vincristine, [99mTc]MDP was injected, the animals were sacrificed and the percentage of radioactivity (%ATI) was determined in the isolated organs. The %ATI was significantly decreased in the uterus, ovary, spleen, thymus, lymph nodes (inguinal and mesentheric), kidney, liver, pancreas, stomach, heart, brain and bone of the animals treated with the natural product. Several biological effects have been reported in patients treated with vincristine. These effects could justify the alterations in the uptake of the radiopharmaceutical in specific organs. Moreover, these results have shown that it is possible to employ this model to evaluate the toxicity of drugs.

Animals↗

PubMedDate not supplied

Technetium-99m distribution into Klebsiella pneumoniae.

Bacteria labelled with radionuclide has been the subject of much investigation and has been applied in microbiological research. Technetium-99m (99mTc) may be an alternative radionuclide for the labelling of bacteria employed in various microbiological procedures. This radionuclide is easily available, is not expensive and presents important physical and biological characteristics. 99mTc-labelled bacteria are stable and their cell viability and biological properties are not modified. Study of the distribution of radioactivity in 99mTc-labelled Klebsiella pneumoniae cultures, after homogenization and differential centrifugation of the cells fractions, showed that this radionuclide was present inside the cell, mainly in a ribosomal fraction. Treatment of these fractions with enzymes and detergent revealed a high sensitivity to pronase and Triton X-100. After phenol extraction, a large percentage of radioactivity was detected in the phenol phase. Treatment of the soluble fraction with trichloroacetic acid at different temperatures showed that the concentration of 99mTc in the precipitate was lower at 100 degrees than at 4 degrees C. These results suggest that 99mTc binds mainly to the proteins in Klebsiella pneumoniae.

Isotope Labeling↗