Alleviation of pre-exposure of mouse brain with low-dose C-12(6+) ion or Co-60 gamma-ray on male reproductive endocrine damages induced by subsequent high-dose irradiation

Irradiation has been widely reported to damage organisms by attacking on proteins, nucleic acid and lipids in cells. However, radiation hormesis after low-dose irradiation has become the focus of research in radiobiology in recent years. To investigate the effects of pre-exposure of mouse brain with low-dose C-12(6+) ion or Co-60 gamma (gamma)-ray on male reproductive endocrine capacity induced by subsequent high-dose irradiation, the brains of the B6C3F(1) hybrid strain male mice were irradiated with 0.05 Gy of C-12(6+) ion or Co-60 gamma-ray as the pre-exposure dose, and were then irradiated with 2 Gy as challenging irradiation dose at 4 h after pre-exposure. Serum pituitary gonadotropin hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), testosterone, testis weight, sperm count and shape were measured on the 35th day after irradiation. The results showed that there was a significant reduction in the levels of serum FSH, LH, testosterone, testis weight and sperm count, and a significant increase in sperm abnormalities by irradiation of the mouse brain with 2 Gy of C-12(6+) ion or Co-60 gamma-ray. Moreover, the effects were more obvious in the group irradiated by C-12(6+) ion than in that irradiated by Co-60 gamma-ray. Pre-exposure with low-dose C-12(6+) ion or Co-60 gamma-ray significantly alleviated the harmful effects induced by a subsequent high-dose irradiation.

Adaptive hormetic response of pre-exposure of mouse brain with low-dose C-12(6+) ion or Co-60 gamma-ray on growth hormone (GH) and body weight induced by subsequent high-dose irradiation

The brain of the Kun-Ming strain mice were irradiated with 0.05 Gy of C-12(6+) ion or Co-60 gamma-ray as the pre-exposure dose, and were then irradiated with 2 Gy of 12C6+ ion or Co-60 gamma-ray as challenging irradiation dose at 4 h after per-exposure. Body weight and serum growth hormone (GH) concentration were measured at 35th day after irradiation. The results showed that irradiation of mouse brain with 2 Gy of C-12(6+) ion or Co-60 gamma-ray significantly diminished mouse body weight and level of serum GH. The relative biological effectiveness values of a 2 Gy dose of C-12(6+) ion calculated with respect to Co-60 gamma-ray were 1.47 and 1.34 for body weight and serum GH concentration, respectively. Pre-exposure with a low-dose (0.05 Gy) of C-12(6+) ion or Co-60 gamma-ray significantly alleviated reductions of mouse body weight and level of serum GH induced by a subsequent high-dose (2 Gy) irradiation. The data suggested that low-dose ionizing irradiation can induce adaptive hormetic responses to the harmful effects of pituitary by subsequent high-dose exposure.

Control led/living free-radical copolymerization of 4-(azidocarbonyl) phenyl methacrylate with methyl acrylate under Co-60 gamma-ray irradiation

A new vinyl acyl azide monomer, 4-(azidocarbonyl) phenyl methacrylate, has been synthesized and characterized by NMR and FTIR spectroscopy. The thermal stability of the new monomer has been investigated with FTIR and thermal gravimetry/differential thermal analysis (TG/DTA), and the monomer has been demonstrated to be stable below 50 degrees C in the solid state. The copolymerizations of the new monomer with methyl acrylate have been carried out at room temperature under Co-60 gamma-ray irradiation in the presence of benzyl 1-H-imidazole-1-carbodithioate. The results show that the polymerizations bear all the characteristics of controlled/living free-radical polymerizations, such as the molecular weight increasing linearly with the monomer conversion, the molecular weight distribution being narrow (< 1.20), and a linear relationship existing between In([M](0)/[M]) and the polymerization time. The data from H-1 NMR and FTIR confirm that no change in the acyl azide groups has occurred in the polymerization process and that acyl azide copolymers have been obtained. The thermal stability of the polymers has also been investigated with TG/DTA and FTIR.

Chromosomal aberrations induced by C-12(6+) ions and Co-60 gamma-rays in mouse immature oocytes

The ovaries of Kun-Ming strain mice (3 weeks) were irradiated with different doses of C-12(6+) ion or Co-60 gamma-ray. Chromosomal aberrations were analyzed in metaphase II oocytes at 7 weeks after irradiation. The relative biological effectiveness (RBE) of C C-12(6+) ion was calculated with respect to Co-60 gamma-ray for the induction of chromosornal aberrations. The C-12(6+) ion and Co-60 gamma-ray dose-response relationships for chromosomal aberrations were plotted by linear quadratic models. The data showed that there was a dose-related increase in frequency of chromosomal aberrations in all the treated groups compared to controls. The RBE values for C-12(6+) ions relative to (CO)-C-60 gamma-rays were 2.49, 2.29, 1.57, 1.42 or 1.32 for the doses of 0.5, 1.0, 2.07 4.0 or 6.0 Gy, respectively. Moreover, a different distribution of the various types of aberrations has been found for C-12(6+) ion and Co-60 gamma-ray irradiations. The dose-response relationships for C-12(6+) ion and (CO)-C-60 gamma-ray exhibited positive correlations. The results from the present study may be helpful for assessing genetic damage following exposure of immature oocytes to ionizing radiation.

The effect of Co-60 gamma-rays on the crystal structure, melting and crystallization behavior of poly(butylene succinate)

The results obtained for poly(butylene succinate) (PBS) after Co-60 gamma-ray irradiation, studied by wide-angle X-ray diffraction (WAXD), differential scanning calorimeter (DSC) and polarizing optical microscopy (POM), revealed that the degree of crystallinity, melting temperature and enthalpy decreased with increasing irradiation dose, but that the crystal structure of PBS did not vary when compared to non-irradiated PBS. By using Scherrer equation, small changes occurred in the crystal sizes of L-020, L-110 and L-111. The spherulitic morphology of PBS was strongly dependent on irradiation dose and changed significantly at higher irradiation dosages. The crystallization kinetics of PBS indicated that the Avrami exponent (n) for irradiated PBS was reduced to 2.3, when compared to non-irradiated PBS (3.3).

Vulcanization of polybutadiene latex induced by Co-60 gamma radiation

Polybutadiene latex (PBL) vulcanization induced by Co-60 radiation and the influence of dose on crosslinking were investigated. Morphology and particle size distribution were examined by AFM and a particle size analyzer. The casting films were characterized for their swelling and mechanical properties as a function of dose.

Co-60 gamma irradiation prevents Bothrops jararacussu venom neurotoxicity and myotoxicity in isolated mouse neuromuscular junction

The ability of gamma radiation from Co-60 (2000 Gy) to attenuate the toxic effects of Bothrops jararacussu venom was investigated on mouse neuromuscular preparations in vitro. A comparative study between the effects of native and irradiated venoms was performed on both phrenic-diaphragm (PD) and extensor digitorum longus (EDL) preparations by means of myographic, biochemical and morphological techniques. Native venom (10 and 20 mug/ml) induced a concentration-dependent paralysis of both directly and indirectly evoked contractions on PD preparations. At 20 mug/ml, it also caused a pronounced myotoxic effect on the EDL muscle preparation that was characterized by an increase of creatine kinase release and by several morphological changes of this preparation. By contrast, irradiated venom, even at concentrations as high as 40 mug/ml, induced neither paralyzing nor myotoxic effects. It was concluded that Co-60 gamma radiation is able to abolish both the paralyzing and the myotoxic effects of B. jararacussu venom on the mouse neuromuscular junction. These findings support the hypothesis that gamma radiation could be an important toot to improve antisera production by reducing toxicity while preserving immunogenicity. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Structural Changes of Conjugated Pt-Containing Polymetallaynes Exposed to Gamma Ray Radiation Doses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Medicated wound dressings based on poly(vinyl alcohol)/poly(N-vinyl pyrrolidone)/chitosan hydrogels

Poly(vinyl alcohol) /poly(N-vinyl pyrrolidone) (PVP)/chitosan hydrogels were prepared by a low-temperature treatment and subsequent Co-60 -gamma-ray irradiation and then were medicated with ciprofloxacin lactate (an antibiotic) and chitosan oligomer (molecular weight = 3000 g/mol). The gel content, swelling ratio, tensile strength, and crystallinity of the hydrogels were determined. The effects of the chitosan molecular weight, the low-temperature treatment procedure, and the radiation dosage on the hydrogel properties were examined. The molecular weight of chitosan was lowered by the irradiation, but its basic polysaccharide structure was not destroyed. Repeating the low-temperature treatment and gamma-ray irradiation caused effective physical crosslinking and chemical crosslinking, respectively, and contributed to the mechanical strength of the final hydrogels. The incorporation of PVP and chitosan resulted in a significant improvement in the equilibrium swelling ratio. and elongation ratio of the prepared hydrogels. The ciprofloxacin lactate and chitosan oligomer were soaked into the hydrogels. Their in vitro release behaviors were examined, and they were found to follow diffusion-controlled kinetics.

Electrochemical characteristic of LaNi-based hydrogen storage alloys

Effect of purity of alloy components on the electrode performance of LaNi2 alloys was investigated. The results showed the purity of components had less effect on discharge capacity and self-discharge of LaNi2 alloys. Partial substitution of Al or Mn for Ni greatly improved discharge properties of LaNi2-xAlx, or LaNi2-yMny alloys as negative electrodes in MFl-Ni battery, 0.15less than or equal toxless than or equal to0.25; 0.15less than or equal toyless than or equal to0.25. In addition, surface treatment of LaNi1.8Al0.2 alloy electrode was performed by polymerizing cis-butenedioate with Co-60- gamma -ray radiation, which. had better affect on self-discharge and cycle life of the alloy electrodes at low temperature(-28 C-degrees).

Test experiments of gamma-ray linear polarization using a Clover detector

We have investigated the performance of a EXOGAM-Segmented-Clover with 16 segments as a Compton polarimeter to measure the linear polarization of gamma rays. The polarization sensitivity of the Clover detector has been measured at the energy of 1332keV through the coincidence measurements of cascade gamma-rays from Co-60. Experimental values were in good accord with our expectation.We have investigated the performance of a EXOGAM-Segmented-Clover with 16 segments as a Compton polarimeter to measure the linear polarization of gamma rays. The polarization sensitivity of the Clover detector has been measured at the energy of 1332keV through the coincidence measurements of cascade gamma-rays from Co-60. Experimental values were in good accord with our expectation.

Optical Behavior of Conjugated Pt-Containing Polymetallaynes Exposed to Gamma-Ray Radiation Doses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Cs-137 and Co-60 isotopes and sedimentation rates in Late Holcene sediments from the Northwestern Black Sea

Results of measurements of Cs-137 and Co-60 concentrations in bottom sediments of the Northwestern Black Sea indicate inhomogenity of their distribution both over the studied area and along sediment cores. Intermittency of sediment layers with different concentration of radionuclides in the cores reflects active horizontal movements and redistribution of sediments on the shelf and continental slope. As a result sediment layers dated by the Chernobyl mark as seven years old were found in the 5-7 cm depth layer. Maximum Cs-137 concentration in the surface sedimentary layer on the shelf was 42 mBq/g. Maximum Co-60 concentration of 1320 mBq/g was measured due to a hot particle. No correlation was found between Cs-137 and the Co-60 contents.