9 research outputs found
Free radicals properties of gamma-irradiated penicillin-derived antibiotics : piperacillin, ampicillin, and crystalline penicillin
The aim of this work was to determine the concentrations and properties of free radicals in piperacillin, ampicillin, and crystalline penicillin after gamma irradiation. The radicals were studied by electron paramagnetic resonance (EPR) spectroscopy using an X-band spectrometer (9.3 GHz). Gamma irradiation was performed at a dose of 25 kGy. One- and two-exponential functions were fitted to the experimental data, in order to assess the influence of the antibiotics’ storage time on the measured EPR lines. After gamma irradiation, complex EPR lines were recorded confirming the presence of a large number of free radicals formed during the irradiation. For all tested antibiotics, concentrations of free radicals and parameters of EPR spectra changed with storage time. The results obtained demonstrate that concentration of free radicals and other spectroscopic parameters can be used to select the optimal parameters of radiation sterilization of β-lactam antibiotics. The most important parameters are the constants τ (τ 1(A),(I) and τ 2(A),(I)) and K (K 0(A),(I), K 1(A),(I), K 2(A),(I)) of the exponential functions that describe free radicals decay during samples storage
Metastasis inhibition after proton beam, β- and γ-irradiation of melanoma growing in the hamster eye
Standard ocular tumor treatment includes brachytherapy, as well as proton therapy, particularly for large melanoma tumors. However, the effects of different radiation
types on the metastatic spread is not clear. We aimed at
comparing ruthenium (106 Ru, emitting β electrons) and
iodine (125I, γ-radiation) brachytherapy and proton beam
therapy of melanoma implanted into the hamster eye on
development of spontaneous lung metastases. Tumors
of Bomirski Hamster Melanoma (BHM) implanted into
the anterior chamber of the hamster eye grew aggressively and completely filled the anterior chamber within
8–10 days. Metastases, mainly in the lung, were found
in 100% of untreated animals 30 days after enucleation.
Tumors were irradiated at a dose of 3–10 Gy with a 106Ru
plaque and at a dose of 6–14 Gy using a 125I plaque. The
protons were accelerated using the AIC-144 isochronous
cyclotron operating at 60 MeV. BHM tumors located in
the anterior chamber of the eye were irradiated with 10
Gy, for the depth of 3.88 mm. All radiation types caused
inhibition of tumor growth by about 10 days. An increase in the number of metastases was observed for
3 Gy of β-irradiation, whereas at 10 Gy an inhibition of
metastasis was found. γ-radiation reduced the metastatic
mass at all applied doses, and proton beam therapy at
10 Gy also inhibited the metastastic spread. These results are discussed in the context of recent clinical and
molecular data on radiation effects on metastasis
Metastasis inhibition after proton beam, \beta - and \gamma -irradiation of melanoma growing in the hamster eye
Free radicals properties of gamma-irradiated penicillin-derived antibiotics: piperacillin, ampicillin, and crystalline penicillin
The aim of this work was to determine the concentrations and properties of free radicals in piperacillin, ampicillin, and crystalline penicillin after gamma irradiation. The radicals were studied by electron paramagnetic resonance (EPR) spectroscopy using an X-band spectrometer (9.3 GHz). Gamma irradiation was performed at a dose of 25 kGy. One- and two-exponential functions were fitted to the experimental data, in order to assess the influence of the antibiotics’ storage time on the measured EPR lines. After gamma irradiation, complex EPR lines were recorded confirming the presence of a large number of free radicals formed during the irradiation. For all tested antibiotics, concentrations of free radicals and parameters of EPR spectra changed with storage time. The results obtained demonstrate that concentration of free radicals and other spectroscopic parameters can be used to select the optimal parameters of radiation sterilization of β-lactam antibiotics. The most important parameters are the constants τ (τ(1(A),(I)) and τ(2(A),(I))) and K (K(0(A),(I)), K(1(A),(I)), K(2(A),(I))) of the exponential functions that describe free radicals decay during samples storage
Astronaut's Organ Doses Inferred from Measurements in a Human Phantom Outside the International Space Station
Astronaut's organ doses inferred from measurements in a human phantom outside the international space station
Astronaut’s Organ Doses Inferred from Measurements in a Human Phantom Outside the International Space Station
Space radiation hazards are recognized as a key concern for human space flight. For long-term interplanetary missions, they constitute a potentially limiting factor since current protection limits for low-Earth orbit missions may be approached or even exceeded. In such a situation, an accurate risk assessment requires knowledge of equivalent doses in critical radiosensitive organs rather than only skin doses or ambient doses from area monitoring. To achieve this, the MATROSHKA experiment uses a human phantom torso equipped with dedicated detector systems. We measured for the first time the doses from the diverse components of ionizing space radiation at the surface and at different locations inside the phantom positioned outside the International Space Station, thereby simulating an extravehicular activity of an astronaut. The relationships between the skin and organ absorbed doses obtained in such an exposure show a steep gradient between the doses in the uppermost layer of the skin and the deep organs with a ratio close to 20. This decrease due to the body self-shielding and a concomitant increase of the radiation quality factor by 1.7 highlight the complexities of an adequate dosimetry of space radiation. The depth-dose distributions established by MATROSHKA serve as benchmarks for space radiation models and radiation transport calculations that are needed for mission planning