Ionizing radiation induced degradation of poly (2-methoxy-5-(2 '-ethyl-hexyloxy)-1,4-phenylene vinylene) in solution

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Poly [1,1'-bis(ethynyl)-4,4'-biphenyl(bis-tributylphosphine)Pt(II)] solutions used as low dose ionizing radiation dosimeter

In this work, the effect of gamma radiation on the optical properties of polymetallayne poly[1,1'-bis(ethynyl)-4,4'-biphenyl(bis-tributylphosphine)Pt(II) ] (Pt-DEBP) in chloroform solution is studied. The samples were irradiated at room temperature with doses from 0.01 Gy to 1 Gy using a 60Co gamma ray source. A new band at 420 nm is observed in the emission spectra, in superposition to the emission maximum at 398 nm, linearly dependent on dose. We propose to use the ratio of the emission amplitude bands as the dosimetric parameter. This method proved to be robust, accurate, and can be used as a dosimeter in medical applications. © 2013 AIP Publishing LLC.

Effects of ionizing radiation and preservation on biomechanical properties of human costal cartilage

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of 60Co gamma radiation on crotamine

Ionizing radiation can change the molecular structure and affect the biological properties of biomolecules. This has been employed to attenuate animal toxins. Crotamine is a strongly basic polypeptide (pI 10.3) from Crotalus durissus terrificus venom composed of 42 amino acid residues. It induces skeletal muscle spasms leading to a spastic paralysis of hind limbs in mice. The objective of the present study was to carry out a biochemical study and a toxic activity assay on native and irradiated crotamine. Crotamine was purified from C.d. terrificus venom by Sephadex G-100 gel filtration followed by ion-exchange chromatography, and irradiated at 2 mg/ml in 0.15 M NaCl with 2.0 kGy gamma radiation emitted by a 60Co source. The native and irradiated toxins were evaluated in terms of structure and toxic activity (LD50). Irradiation did not change the protein concentration, the electrophoretic profile or the primary structure of the protein although differences were shown by spectroscopic techniques. Gamma radiation reduced crotamine toxicity by 48.3%, but did not eliminate it.

Abortion and background radiation in Brazil

It is well known that radiation causes mutation, and that mutations are generally deleterious. They can lead to disease, malformation and death. It is further known that we live in a radioactive world. The air, the soil, the water, the food, all are somewhat radioactive. Natural radiation is not uniformly distributed throughout the earth's crust. There are some areas, especially in Brazil and India, where the levels of background radiation are several times higher than generally obtains. We have undertaken a specially prepared house-to-house genetic-epidemiologic, retrospective survey in a large Brazilian area with levels of natural radiation ranging from 7 (normal) to 133 (high) micro-roentgens per hour. In all, 24 different localities were surveyed during a period of 10 months by a trained team of nurses and social assistants. Our total sample consists of more than 8,000 couples who have had almost 44,000 pregnancy terminations. Our results do not disprove that natural radiation is one of the causes of socalled spontaneous mutations. They only show that, under the conditions of this study, no detectable effect on abortion was found. Our results also attest to the importance of extraneous variables in the analysis of morbidity and mortality data.

Bond strenght of dental adhesive systems irradiated with ionizing irradiation

The aim of the present paper was to determine the effect of different types of ionizing radiation on the bond strength of three different dentin adhesive systems. Materials and Methods: One hundred twenty specimens of 60 human teeth (protocol number: 032/2007) sectioned mesiodistally were divided into 3 groups according to the adhesives systems used: SB (Adper Single Bond Plus), CB (Clearfil SE Bond) and AP (Adper Prompt Self-Etch). The adhesives were applied on dentin and photo-activated using LED (Lec 1000, MMoptics, 1000 mW/cm2). Customized elastomer molds (0.5 mm thickness) with three orifices of 1.2 mm diameter were placed onto the bonding areas and filled with composite resin (Filtek Z-250), which was photoactivated for 20 s. Each group was subdivided into 4 subgroups for application of the different types of ionizing radiation: ultraviolet radiation (UV), diagnostic x-ray radiation (DX), therapeutic x-ray radiation (TX) and without irradiation (control group, CG). Microshear tests were carried out (Instron, model 4411), and afterwards the modes of failure were evaluated by optical and scanning electron microscope and classified using 5 scores: adhesive failure, mixed failures with 3 significance levels, and cohesive failure. The results of the shear bond strength test were submitted to ANOVA with Tukey's test and Dunnett's test, and the data from the failure pattern evaluation were analyzed with the Mann Whitney test (p = 0.05). Results: No change in bond strength of CB and AP was observed after application of the different radiation types, only SB showed increase in bond strength after UV (p = 0.0267) irradiation. The UV also changed the failure patterns of SB (p = 0.0001). Conclusion: The radio-induced changes did not cause degradation of the restorations, which means that they can be exposed to these types of ionizing radiation without weakening the bond strength.

ESR dating of pleistocene mammal teeth and its implications for the biostratigraphy and geological evolution of the coastal plain, Rio Grande do Sul, southern Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Occupational exposure of physical therapists to electric and magnetic fields and the efficacy of Faraday cages

Objective. Measure physical therapists' exposure to the electric and magnetic fields produced by 17 shortwave diathermy devices in physical therapy clinics in the city of Presidente Prudente, São Paulo State, Brazil. Compare the observed values with the exposure levels recommended by the International Commission on Non-ionizing Radiation Protection (ICNIRP). Observe the efficacy of Faraday cages as a means of protecting physical therapists from exposure to oscillating electric and magnetic fields.Methods. Electric and magnetic field measurements were taken at four points during actual physical therapy sessions: in proximity to the operator's pelvis and head, the devices' electrical cables, and the electrodes. The measuring equipment was a Wandel & Goltermann EMR-200.Results. The values obtained in proximity to the electrodes and cables were 10 to 30 times higher than ICNIRP's recommended occupational reference levels. In the shortwave diathermy treatment rooms with Faraday cages, the fields were even higher than in treatment rooms not so equipped-principally the magnetic field, where the values were more than 100 times higher than the ICNIRP exposure limit.Conclusions. The electric and magnetic field intensities obtained in this study are generally above the exposure levels recommend in ICNIRP standards. It was also observed that the Faraday cage offers physical therapists no protection, and instead, increases their level of exposure.

Pharmaceutical applications of AC Biosusceptometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Measurement of gastric contraction activity in dogs by means of AC biosusceptometry

The mechanical nature of gastric contraction activity (GCA) plays an important role in gastrointestinal motility. The aim of this study was to detect GCA in anaesthetized dogs, using simultaneously the techniques of AC biosusceptometry (ACB) and manometry, analysing the characteristics of frequency and amplitude (motility index) of GCA, modified by drugs such as prostigmine and N-butyl-scopolamine. The ACB method is based on a differential transformer of magnetic flux and the magnetic tracer works as a changeable external nucleus. This magnetic tracer causes a modification in the magnetic flux, which is detected by the coils. The results obtained from the ACB showed a performance comparable to the manometry in measuring the modifications in the frequency and amplitude of the GCA. We concluded that this ACB technique, non-invasive and free of ionizing radiation, is an option for evaluating GCA and can be employed in future clinical studies.

Cytostatic in vitro Effects of DTCM-Glutarimide on Bladder Carcinoma Cells

Bladder cancer is a common malignancy worldwide. Despite the increased use of cisplatin-based combination therapy, the outcomes for patients with advanced disease remain poor. Recently, altered activation of the PI3K/Akt/mTOR pathway has been associated with reduced patient survival and advanced stage of bladder cancer, making its upstream or downstream components attractive targets for therapeutic intervention. In the present study, we showed that treatment with DTCM-glutaramide, a piperidine that targets PDK1, results in reduced proliferation, diminished cell migration and G1 arrest in 5637 and T24 bladder carcinoma cells. Conversely, no apoptosis, necrosis or autophagy were detected after treatment, suggesting that reduced cell numbers in vitro are a result of diminished proliferation rather than cell death. Furthermore previous exposure to 10 mu g/ml DTCM-glutarimide sensitized both cell lines to ionizing radiation. Although more studies are needed to corroborate our findings, our results indicate that PDK1 may be useful as a therapeutic target to prevent progression and abnormal tissue dissemination of urothelial carcinomas.

MEH-PPV hypsochromic shifts in halogenated solvents induced by gamma-rays

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Assessment of Gastrointestinal Motility in Renal Transplant Recipients by Alternate Current Biosusceptometry

Background. Gastrointestinal (GI) complications are common after renal transplantation, mainly owing to immunosuppressive therapy. Assessment of GI transit time can facilitate rational management of these disorders.Objective. We evaluate the GI transit parameters in renal transplant recipients taking tacrolimus, azathioprine, and prednisone with the use of the alternate current biosusceptometry (ACB) technique and compared them with healthy volunteers.Methods. Ten renal transplant recipients and 10 healthy volunteers were enrolled in this study. After an overnight fast, patients and volunteers ingested a standard meal containing magnetic markers. The biomagnetic monitoring was performed at 10-minute intervals for at least 8 hours to obtain gastric emptying as well as the colonic arrival time-intensity curves. Mean gastric emptying time (MGET), mean colon arrival time (MCAT), and mean small intestinal transit time (MSITT) were quantified and compared between control and patient groups with results expressed as mean +/- SD.Results. The MGET measured by the ACB technique was 48 +/- 31 minutes and 197 +/- 50 minutes for patients and healthy subjects, respectively. MSITT and MCAT values calculated for patients versus volunteers were 171 +/- 71 minutes versus 197 +/- 71 minutes and 219 +/- 83 minutes versus 373 +/- 52 minutes, respectively. Renal transplant recipients showed significantly faster; gastric emptying and colon arrival times (P < .001) compared with normal volunteers; however, small intestinal transit time was not significantly different (P = .44).Conclusions. In stable renal transplant recipients, the GI transit parameters were significantly faster than in normal healthy volunteers. ACB sensors are versatile technologies that can be used for clinical research, because they offer an excellent opportunity to evaluate GI transit in a noninvasive manner without the use of ionizing radiation.

Chromosome sensitivity to bleomycin in G2 lymphocytes from Down syndrome patients

Several studies have demonstrated that lymphocytes from patients with Down syndrome (DS) exhibit an increased frequency of chromosome aberrations when they are exposed to ionizing radiation or to chemicals at the G0 or G1 phases of the cell cycle, but not at G2 when compared to normal subjects. To determine the susceptibility of DS lymphocytes at G2 phase, bleomycin, a radiomimetic agent, was used to induce DNA breaks in blood cultures from 24 Down syndrome patients. All the patients with DS showed free trisomy 21 (47,XX + 21 or 47,XY + 21). Individuals that showed an average number of chromatid breaks per cell higher than 0.8 were considered sensitive to the drug. No control child showed susceptibility to bleomycin, and among the 24 patients with DS, only one was sensitive to the drug. No significant difference was observed between the two groups, regarding chromatid break frequencies in treated G2 lymphocytes. The distribution of bleomycin-induced breaks in each group of chromosomes was similar for DS and controls. No significant difference was found in the response to bleomycin between male and female subjects. Probably, the main factor involved in chromosome sensitivity of lymphocytes from patients with DS is the phase of the cell cycle in which the cell is treated.

A novel biomagnetic instrumentation with four magnetoresistive sensors to evaluate gastric motility.

A novel instrumentation using anisotropic magnetoresistive (AMR) sensors associated with magnetic coils excitation was developed to evaluate gastrointestinal tract motility parameters. The susceptometer has four sensors that were used to measure the gastric activity contractions (GAC) in anaesthetized dogs, its performance was evaluated by manometry with good results.