Comet assay to determine DNA damage induced by food deprivation in rats.

The aim of this work was to evaluate, by comet assay, the possible inducing of DNA lesions in peripheral blood mononuclear cells of rats subjected to acute or chronic food deprivation. Wistar male rats were subjected to 72 h of partial (50%), or total acute food deprivation, and then allowed to recover for different time periods (24, 48 and 72 h). In other experiments, comet scores were determined in peripheral blood mononuclear cells of rats subjected to chronic food deprivation (25% and 50%) for 50 days. Blood aliquots were obtained before, during and after food deprivation. Comet assay was carried out, the comet units photographed and scored (class 0 up to 3). Acute and chronic food-deprived rats presented peripheral blood mononuclear cells with DNA lesions (comet classes 1, 2 and 3) and a significant increase (p<0.05) in the number of comet units compared with its basal level. The increase was proportional to acute food deprivation time, but after being taken off, it progressively returned to basal level after 48 h (partial group) or 72 h (total group). Chronic food-deprived rats presented a progressive increase of comet score up to 5 days, and a decrease thereafter to reach a basal level. Possible mechanisms of DNA lesions are discussed.

Analysis of genotoxic potentiality of stevioside by comet assay.

Stevioside is a natural non-caloric sweetener extracted from Stevia rebaudiana (Bertoni) leaves. It has been widely used in many countries, including Japan, Korea, China, Brazil and Paraguay, either as a substitute for sucrose in beverages and foods or as a household sweetener. The aim of this work was to study its genotoxic potentiality in eukaryotic cells. Wistar rats were treated with stevioside solution (4mg/mL) through oral administration (ad libitum) and the DNA-induced damage was evaluated using the single cell gel electrophoresis (comet assay). The results showed that treatment with stevioside generates lesions in peripheral blood, liver, brain and spleen cells in different levels, the largest effect being in liver. Therefore, these undesired effects must be better understood, once the data present here point to possible stevioside mutagenic properties.

Adaptive response to H(2)O(2) protects against SnCl(2) damage: the OxyR system involvement.

The stannous ion, mainly the stannous chloride (SnCl(2)) salt form, is widely used as a reducing agent to label radiotracers with technetium-99m ((99m)Tc). These radiotracers can be employed as radiopharmaceuticals in nuclear medicine procedures. In this case, there is no doubt about absorption of this complex, because it is intravenously administered in humans, although biological effects of these agents have not been fully understood. In this work we used a bacterial system to study the cytotoxic potential of stannous chloride. It is known that SnCl(2) induces lesions that could be mediated by reactive oxygen species (ROS). We, thus, investigated the existence of cross-adaptive response between hydrogen peroxide (H(2)O(2)) and SnCl(2) and the role of the OxyR system known to promote cellular protection against oxidative damages. Here we describe the results obtained with prior treatment of different Escherichia coli strains with sub-lethal doses of H(2)O(2), followed by incubation with SnCl(2). Our data show that H(2)O(2) is capable of inducing cross-adaptive response against the lethality promoted by SnCl(2), suggesting the OxyR system participation through catalase, alkyl hydroperoxide reductase and superoxide dismutase enzymes

Biological effects of stannous chloride, a substance that can produce stimulation or depression of the central nervous system.

It was demonstrated that tin, as stannous chloride (SnCl(2)), can facilitate the neuromuscular transmission by accelerating the transmitter release from the nerve terminals in the mouse. When this salt is injected into laboratory animals, it can produce stimulation or depression of the central nervous system. Because calcium (Ca(2+)) influx into the cytoplasm is indispensable to release the transmitter, it would be possible that SnCl(2) increases the Ca(2+) influx at the nerve terminals but not by blocking the K(+) channels. SnCl(2) is known to inhibit the immune response in rodents and to induce tumor generation in thyroid gland. There is no general agreement regarding its genotoxicity and it was discussed that the effects of this salt might depend on the physicochemical conditions and the route of its administration. SnCl(2) has been used in many sectors of human interest, such as food industry and nuclear medicine. This salt is directly administered to human beings endovenously, when it is used as a reducing agent to prepare 99mTc-radiopharmaceuticals which are also used for cerebral studies. SnCl(2) is capable to promote the generation of reactive oxygen species (ROS) that are responsible for the oxidative stress. Oxidative stress has been related with aging and other neurological diseases. So, it is relevant to evaluate other biological effects of SnCl(2). We decided to study these effects using Escherichia coli mutant strains, deficient in DNA repair genes, and supercoiled plasmid DNA. We evaluated the influence of medicinal plants, metal chelating agents, and ROS scavengers against the SnCl(2) deleterious effects. Our results show that SnCl(2) produced lesions in vitro as well as in vivo. This inactivation may be due to the production of ROS. We observed that the genotoxic effect of SnCl(2) was partly inhibited or disappeared, when the treatments were done in the presence of medicinal plants, metal chelating agents, and ROS scavengers. In conclusion, these findings suggest that the SnCl(2) biological effects may be associated with the generation of ROS. Moreover, we can speculate that ROS could be associated with the detrimental effects in the brain due to exogenous or endogenous metals.

Ocular health myths among a hospital staff.

In order to evaluate their common beliefs in the field of ocular health, an exploratory survey was carried out among 122 professionals belonging to different ranks and specialty areas of the University of Campinas Clinical Hospital (UNICAMP-CH), São Paulo, Brazil. The non-structured questionnaire used asked about common ophthalmologic problems as well as the presence of popular myths about ocular health, such as: 'cure' of visual problems by the use of glasses; reading under insufficient lighting or watching TV too much close to the apparatus is harmful; consequences from the intensive use of the eyes; or special food being needed for better vision. The results indicated the existence of various misconceptions, even among health professionals, such as: belief in the cure of refractive problems by the use of glasses (40.0%); or damage to vision due to insufficient lighting, watching TV too much close to the apparatus or from the intensive use of the eyes (86.7%). Among the professionals performing activities within the ophthalmology department, 62.5% admitted believing in visual damage as a result of conditions such as those mentioned above and 37.5% stated that reading in a moving vehicle is detrimental to vision. From these data, one is entitled to conclude that misconceptions continue to be present, even among professionals in the health area; this indicates that educational programs in ocular health should be provided, especially for individuals working within a hospital ophthalmological service.

Stannous chloride mediates single strand breaks in plasmid DNA through reactive oxygen species formation.

Stannous ion (Sn) has been employed in nuclear medicine and in food industry. We described that Stannous Chloride (SnCl2) inactivation effect in Escherichia coli is mediated by a Fenton-like reaction. The effect of SnCl2 was studied through: (i) the alteration of plasmid topology in neutral and acidic pH by gel electrophoresis; and (ii) the transformation efficiency of an wild type E. coli strain. Treatment of plasmid DNA pUC 9.1 with SnCl2, at pH 7.4, results in DNA single-strand breaks (SSB), in a dose-dependent manner. Addition of sodium benzoate partly inhibited the DNA damage, while EDTA completely abolishes DNA-SSB. Furthermore, the ability of the plasmid to transform E. coli was reduced. At pH 1.3, SnCl2 exerts a protective effect on plasmid against HCI depurination. Our results suggest the generation of ROS, such as *OH by a Fenton-like reaction, close to the site of the lesions due to a possible complexation of stannous ion to DNA.

Damage induced by stannous chloride in plasmid DNA.

Stannous chloride (SnCl(2)) is widely used in daily human life, for example, to conserve soft drinks, in food manufacturing and biocidal preparations. In nuclear medicine, stannous chloride is used as a reducing agent of Technetium-99m, a radionuclide used to label different cells and molecules. In spite of this, stannous chloride is able to generate reactive oxygen species (ROS) which can damage DNA. In this work, plasmid DNA (pUC 9.1) was incubated with SnCl(2) under different conditions and the results analyzed through DNA migration in agarose gel electrophoresis. Our data reinforce the powerful damaging effect induced by stannous ion and suggest that this salt can play a direct role in inducing DNA lesions.

Genotoxic potentiality of aqueous extract prepared from Chrysobalanus icaco L. leaves.

Plants have been related to our lives, being used as medicine, regardless of scientific evidence of side effects. This work analyses the toxicological effects of Chrysobalanus icaco L. aqueous extract, used in different pathologies. It was studied through: (i) alteration of plasmid pUC 9.1 topology; (ii) survival of bacterial strains submitted, or not, to previous treatment with SnCl2; (iii) transformation efficiency of E. coli strain by the treatment with the plasmid pUC 9.1. In (i), the treatment of the plasmid resulted in DNA single-strand breaks (SSB). A decrease of the lethal effect induced by SnCl2 in presence of the extract was found, while no C. icaco bacterial survival reduction was observed. The transformation efficiency of the plasmid was also reduced. Results suggest that the extract could present a potential genotoxic effect, as demonstrated either by the induction of SSB in plasmid or in transformation efficiency experiments. Finally, it presents an antioxidant action.

Mutational potentiality of stannous chloride: an important reducing agent in the Tc-99m-radiopharmaceuticals.

Stannous chloride (SnCl2) is frequently used in nuclear medicine as a reducing agent to label many radiopharmaceutical products with technetium-99m (99mTc). The aim of the present paper was to study the role of DNA repair genes in the repair of SnCl2-induced damage, using mutant strains of Escherichia coli lacking one or more DNA repair genes. Our results suggest that the product of the xthA gene, exonuclease III, is required for the repair of lesions induced by SnCl2. We further investigated the mutagenic properties of SnCl2 to a molecular level by using the supF tRNA gene as target in a forward mutational system. We have found that the survival of E. coli cells was strongly reduced with increasing concentrations of SnCl2. Moreover, when the shuttle vector pAC189 carrying the supF gene was treated with SnCl2, and then transfected to E. coli, we observed that its transformation efficiency dropped when compared to the non-treated control, with a parallel increase in mutation frequency after the damaged plasmids have replicated in bacterial cells. The mutation spectrum induced by SnCl2 reveals a high frequency of base substitutions, involving guanines. Sequence analysis of 41 independent supF mutant plasmids revealed that 39 mutants contained base substitutions, with 21 G:C to T:A and 17 G:C to C:G transversions. G to T transversions presumably resulted from 8-oxoG. However, the G to C one may be due to a yet unidentified lesion.

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.

Genotoxic effects of stannous chloride (SnCl2) in K562 cell line.

The toxic effects of SnCl2 in K562 cells were analyzed in this study. This cell line is resistant to reactive oxygen species (ROS) making it suitable to evaluate the impact of SnCl2 in culture either through ROS or by direct toxicity using Trypan blue dye exclusion, comet and flow cytometry assays. An important loss of viability induced by SnCl2 in a dose-response manner was observed in cells treated in Tris-buffered saline (TBS). This necrotic cell death was further confirmed by flow cytometry. On the other hand, there was no loss of viability when cells were treated in rich medium (RPMI). DNA damage was visualized in SnCl2-treated K562 cells in both tested conditions. The data indicate that SnCl2 induces DNA damage and reduces K562 viability. Both actions seem to be correlated with ROS formation and direct linkage to DNA.

Boldine action against the stannous chloride effect.

Peumus boldus extract has been used in popular medicine in the treatment of biliar litiase, hepatic insufficiency and liver congestion. Its effects are associated to the substance boldine that is present in its extract. In the present work, we evaluated the influence of boldine both in: (i) the structural conformation of a plasmid pUC 9.1 through gel electrophoresis analysis; and in (ii) the survival of the strain of Escherichia coli AB1157 submitted to reactive oxygen species (ROS), generated by a Fenton like reaction, induced by stannous chloride. Our results show a reduction of the lethal effect induced by stannous chloride on the survival of the E. coli culture in the presence of boldine. The supercoiled form of the plasmid is not modified by stannous chloride in the presence of boldine. We suggest that the protection induced by boldine could be explained by its anti-oxidant mechanism. In this way, the boldine could be reacting with stannous ions, protecting them against the oxidation and, consequently, avoiding the generation of ROS.

Agarose gel electrophoresis system in the classroom: Detection of DNA strand breaks through the alteration of plasmid topology.

Good quality scientific teaching depends on the ability of researchers to translate laboratory experiments into high school and undergraduate classes, bridging the advanced and basic science with common knowledge. A fast-growing field in biomedical sciences is oxidative stress, which has been associated to several diseases, including cancer and neurodegenerative disorders. We suggest herein a simple methodology for exploring DNA damage as an introductory pathway to these themes. The potential of natural or artificial products to induce DNA strand breaks can be easily tested in supercoiled plasmids incubated with selected products followed by agarose gel electrophoresis. This is designed to detect single and double strand breaks caused by reactive oxygen species generated by the products being tested. The altered topology of the damaged plasmid migrates slowly in the gel, creating a new band. We further introduce the quantitation of supercoiled DNA forms using densitometry of the gel with a digital camera; the values can then be used to estimate the number of breaks per genome using Poisson distribution. The system is inexpensive, rapid, and does not need high-cost equipment and supplies and can be performed in high schools and undergraduate classes with a minimal structure.

Quantification (grading) of inferior oblique muscle recession for V-pattern strabismus.

PURPOSE: To determine the effectiveness of grading such surgery according to the magnitude of the V pattern and inferior oblique muscle overaction (IOOA). METHODS: We retrospectively reviewed all 53 cases we operated since 1984 for V pattern with IOOA, who had undergone graded inferior oblique recession, recessed according to the anatomical recession table of Apt and Call, ranging from 8mm for V pattern of 12 PD with +1 IOOA to 12mm for 30+ PD with +3 IOOA. RESULTS: A "satisfactory outcome" (defined as = V pattern of 8 PD or less) was observed in 75% of the cases with a preoperative V pattern less than 20 PD, in 70% of those with a preop' V pattern between 20 PD and 29 PD, and in 57% of those with a preop' V pattern greater than 29 PD. There were no overcorrections. All unsatisfactory outcomes were undercorrections. CONCLUSIONS: The principle of grading this surgery is supported and affirmed by these results. However, the results also suggest a need to increase the amount of surgery for all categories and add anterior transposition for larger V patterns.

Biological effects of stevioside on the survival of Escherichia coli strains and plasmid DNA.

Stevioside is widely used daily in many countries as a non-caloric sugar substitute. Its sweetening power is higher than that of sucrose by approximately 250-300 times, being extensively employed as a household sweetener, or added to beverages and food products. The purpose of this study was to ascertain stevioside genotoxic and cytotoxic potentiality in different biological systems, as its use continues to increase. Agarose gel electrophoresis and bacterial transformation were employed to observe the occurrence of DNA lesions. In addition to these assays, Escherichia coli strains were incubated with stevioside so that their survival fractions could be obtained. Results show absence of genotoxic activity through electrophoresis and bacterial transformation assays and drop of survival fraction of E. coli strains deficient in rec A and nth genes, suggesting that stevioside (i) is cytotoxic; (ii) could need metabolization to present deleterious effects on cells; (iii) is capable of generating lesions in DNA and pathways as base excision repair, recombination and SOS system would be important to recover these lesions.

Dna damage in peripheral blood nuclear cells assessed by comet assay from individuals submitted to scintigraphic examinations.

Stannous chloride (SnCl2) is employed as a reducing agent to obtain Technetium-99m-labelled radiophamaceuticals in nuclear medicine kits, being injected endovenously in humans. Toxic effects of these kits were not studied, thus making it important to evaluate their impact in humans. In this study, the toxic effects were evaluated from peripheral blood nuclear cells (PBNC) from patients who received radiopharmaceuticals obtained using such kits. The analyses included results performed by comet assay. DNA damage was visualized in PBNC samples collected within a time up to 2 hr, and 24 hr after radiopharmaceutical injection in the patients. Initially we observed an increase of comet signals, which subsequently were reduced to zero after 24 hr. The diminishing of comet amounts probably is associated with DNA repair of damaged cells or with the elimination by apoptosis of cells whose DNA are not repaired.