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PubMed1985

Protein microcrystal diffraction and the effects of radiation damage with ultra-high-flux synchrotron radiation.

By using ultra-high-flux synchrotron x-radiation from a wiggler source, good Laue diffraction data have been obtained from protein microcrystals of size 30 X 35 X 10 microns3, mounted wet in glass capillaries. At the flux level of 10(13)-10(14) photons per sec/mm2, the radiation damage is still low enough to allow a large survey of reciprocal space for a microcrystal and a complete survey for a normal-sized protein crystal. The development of sources for ultra-high-intensity synchrotron radiation is thus an important improvement in the technique for determination of structure through protein crystallography as well as in other cases where crystal size is often a limiting factor.

Gramicidin↗
PubMed1998

Ultraviolet radiation, but not gamma radiation or etoposide-induced DNA damage, results in the phosphorylation of the murine p53 protein at serine-389.

Polyclonal antibodies were produced and purified that selectively react with a p53 epitope containing the murine phosphoserine-389 or the human phosphoserine-392 residue, but not the unphosphorylated epitope. These antibodies, termed alpha-392, were employed to demonstrate that the phosphorylation of this serine-389 residue in the p53 protein occurs in vivo in response to ultraviolet radiation of cells containing the p53 protein. After ultraviolet radiation of cells in culture, p53 levels increase and concomitantly serine-389 is phosphorylated in these cells. By contrast, the serine-389 phosphorylation of the p53 protein was not detected by these antibodies in the increased levels of p53 protein made in response to gamma radiation or the treatment of cells with etoposide. These results demonstrate an ultraviolet responsive and specific phosphorylation site at serine-389 of the mouse or serine-392 of the human p53 protein. Previous studies have demonstrated that this phosphorylation of p53 activates the protein for specific DNA binding. This study demonstrates in vivo a unique phosphorylation site in the p53 protein that responds to a specific type of DNA damage.

Animals↗
PubMed1987

Effect of ionizing radiation on artificial (planar) lipid membranes. II. The ion carriers valinomycin and nonactin as probes for radiation induced structural changes of the membrane.

Planar lipid membranes in the presence of the ion carriers valinomycin or nonactin were irradiated with 14 MeV electrons from a linear accelerator. A large increase of the membrane conductance by up to more than two orders of magnitude was found. The effect is virtually abolished either at high pH, or in the absence of oxygen, or in the presence of the radical scavenger ethanol. A further prerequisite for the effect is the presence of unsaturated fatty acid residues. A kinetic analysis of the carrier transport model based on current-voltage curves and on voltage-jump relaxation experiments was performed as a function of radiation dose. Only the translocation rate constant, kMS, of the charged carrier-ion complex was found to be influenced by irradiation. The effect is interpreted as an increase of the polarity (dielectric constant) of the membrane interior induced by the presence of polar products of lipid peroxidation. A combined action of OH- and HO2-radicals seems to be responsible for the phenomena. At large radiation doses (greater than or equal to 10(3) Gy) a reduction of the membrane conductance was observed. This is interpreted as an increased microviscosity, possibly caused by cross-linking of fatty acid residues. Ion carriers represent sensitive probes of radiation induced membrane damage.

Anti-Bacterial Agents↗
PubMed1988

The effect of modulators of radiation-induced G2 arrest on the repair of radiation-induced DNA damage detectable by neutral filter elution.

It has been suggested that radiation-induced G2-arrest is an extension of interphase to allow repair of DNA double-strand breaks (dsb) prior to mitosis. Cycloheximide blocks the repair of the lesions which result in radiation-induced G2 arrest. Caffeine and cordycepin reduce the duration of G2 arrest. All of these agents should therefore reduce the cell's ability to repair dsb. The influence of cycloheximide (50 micrograms/ml), caffeine (5 mM) and cordycepin (0.15 mM) on the repair of the damage detectable in DNA by neutral filter elution was determined. Chinese hamster ovary cells (CHO) were irradiated with X-ray doses of 20, 60 and 100 Gy then allowed to repair without drug treatment or in the presence of each drug for intervals up to 6 h. DNA damage repair proceeded in two phases. The fast component of the repair process (t1/2 approx. 7 min) was not modified by drug treatment; the slow component (t1/2 approx. 170 min) was unaffected by cycloheximide or cordycepin, but appeared to be inhibited by caffeine. It was concluded that: (a) the lesion which results in radiation-induced G2 arrest is not the lesion which is detectable by neutral filter elution, and (b) the influence of caffeine on dsb repair is specific to caffeine and is not mediated by a reduction in the duration of G2 arrest.

Animals↗
PubMed1980

Free radical initiation in proteins and amino acids by ionizing and ultraviolet radiations and lipid oxidation--Part 22: ultraviolet radiation and photolysis.

Parallels and similarities in chemical and functional damage to proteins by ionizing and UV radiations and oxidizing lipids have been recognized for some time. However, only recently have oxidizing lipids been shown directly by electron spin resonance to be radiomimetic also in their capacity for protein free radical production. Free radicals play a key role in the transformation of energy to molecular and cellular damage. It is thus of critical importance to elucidate the general mechanisms of free radical formation and reactions in proteins in order to understand protein involvement in various pathological conditions and in food deterioration. Accordingly, this review is a detailed comparison of gamma radiation, UV radiation, and lipid oxidation for what is presently known concerning (1) the specific modes of energy deposition and free radical formation, (2) the free radicals formed in proteins and amino acids, and (3) the typical damage correlating with these radicals.

Amino Acids↗
PubMed1981

Microdosimetric investigations on collimated fast neutron beams for radiation therapy: II. The problem of radiation quality and RBE.

The correlation between radiation quality and cellular RBE of a mixed n-gamma field produced by a collimated fast-neutron beam produced by the bombardment of 14 MeV deuterons on Be in a water phantom is investigated. The microdosimetric parameters yF and YD are used for a physical description of the local distribution of radiation components. On the basis of the dose fractions of these components, the dependence of RBE on depth is calculated and is compared with experimental RBE data. Outside the beam centre, it is shown that the microdosimetric parameter y can be used for estimates of local changes of RBE, if particular conditions for the absorbed dose and for the range of neutron energies are met. The spatial distributions of y for the mixed radiation changes in RBE for equal absorbed doses of 1 Gy are at maximum 10% and thus perhaps negligible.

Cells, Cultured↗
PubMed2003

The direct measurement using an imaging plate for coincidence of radiation centre and laser position in external radiation therapy.

A new method of quality assurance has been studied to measure coincidence of the radiation centre and a patient-setup laser position on a transverse plane to the beam at the isocentre. This measurement is achieved by using an imaging plate (IP). When radiation is applied to an IP, the energy is stored as trapped electrons. The number of electrons is decreased by local laser exposure. As a result, the radiation field produced by external beam irradiation is recorded as 'positive' information and the position of the patient-setup laser is recorded as 'negative' on an IP. The advantages of this method are the direct measurement, short time and high resolution. These are required for daily and monthly quality checks. We confirmed the advantage of this method by an experiment using a proton beam.

Calibration↗
PubMed2002

Correlation of red marrow radiation dosimetry with myelotoxicity: empirical factors influencing the radiation-induced myelotoxicity of radiolabeled antibodies, fragments and peptides in pre-clinical and clinical settings.

Usually, the red marrow (RM) is the first dose-limiting organ in systemic radionuclide therapy, e.g., radioimmuno-or radiopeptide therapy. However, several studies have obtained rather poor correlations between the marrow doses and the resulting toxicities. Red marrow doses are mostly not determined directly, but are derived from blood or whole-body doses. The aim of our recent work was to analyze, in a nude mouse model in more detail, additional factors than just total dose, such as dose rate or relative biological effectiveness (RBE) factors, that may influence the resulting myelotoxicity. Furthermore, we wanted to analyze, whether correlations between the red marrow doses and the resulting myelotoxicities can be found in clinical metabolic endo-radiotherapy. The maximum tolerated activities (MTAs) and doses (MTDs) of several murine, chimeric and humanized immunoconjugates as complete IgG or fragments (F(ab)(2), Fab), as well as peptides, labeled with beta(-)- (such as (131)I or (90)Y), Auger electron- (such as (125)I or (111)In), or alpha-emitters (such as (213)Bi) were determined in nude mice. Blood counts were monitored at weekly intervals; bone marrow transplantation (BMT) was performed in order to support the assumption of the RM as dose-limiting. The radiation dosimetry was derived from biodistribution data of the various conjugates, accounting for cross-organ radiation; the activities in the blood, bone, bone marrow, and major organs were determined over time. Dosimetry and myelotoxicity data of three clinical radioimmunotherapy trials, involving a total of 82 colorectal cancer patients, treated with (131)I-labeled anti-CEA IgG, and twelve non-Hodgkin's lymphoma patients, treated with (131)I-labeled anti-CD20 IgG, were analyzed. In the preclinical model, at the respective MTAs, the RM doses differed significantly between the three conjugates: e.g., with (131)I-labeled conjugates, the maximum tolerated activities were#10; 260 microCi for IgG, 1200 microCi for F(ab)(2), and 3 mCi for Fab, corresponding to blood doses of 17 Gy, 9 Gy, and 4 Gy, respectively. However, initial dose rates were 10 times higher with Fab as compared to IgG, and still 3 times higher as compared to F(ab)(2); interestingly, all 3 deliver approximately 4 Gy within the first 24 h. The MTDs of all three conjugates were increased by BMT by approximately 30%. Similar observations were made for the (90)Y-labeled conjugates. Higher blood-based RM doses were tolerated with Auger-emitters than with conventional beta(-)-emitters, whereas the MTDs were similar between alpha- and beta(-)-emitters. In accordance to dose rates never exceeding those occurring at the single injection MTA, re-injections of (131)I-, (90)Y-, or (213)Bi-labeled Fab' were tolerated without increased lethality, if administered 24-48 h apart, whereas reinjection of bivalent conjugates was not possible. Clinically, a sigmoidally shaped dose-effect correlation was found in colorectal cancer patients treated with (131)I-anti-CEA IgG. Previous mitomycin chemotherapy was identified as additional myelosensitizing factor leading to enhanced myelotoxicity. At comparable doses, non-Hodgkin's lymphoma patients developed higher degrees of myelotoxicity with a less clearly pronounced predictability from red marrow doses. In summary, results in the murine model suggest a strong influence of the dose rate (or better: dose per unit time), not only total dose on the resulting myelotoxicity, whereas the influence of high- (alpha, Auger/conversion electrons) versus low-LET (beta,gamma) type radiation seems to be much lower than expected from previous in vitro data. The lower myelotoxicity of Auger e(-) emitters is probably due to the short path length of their low-energy electrons, which cannot reach the nuclear DNA if the antibody is not internalized into the stem cells of the red marrow. Clinically, additional factors than just marrow dose (e.g., previous myelotoxic therapy, bone marrow involvement by metastatic malignancy) seem to a, bone marrow involvement by metastatic malignancy) seem to affect the resulting myelotoxicity.

Animals↗
PubMed1985

Radiation therapy alone or in combination with chemotherapy in the treatment of residual or inoperable carcinoma of the rectum and rectosigmoid or pelvic recurrence following colorectal surgery. Radiation Therapy Oncology Group study (76-16).

Between 1976 and 1981, 147 patients with residual, inoperable, or locally recurrent carcinoma of the rectum were randomized to receive either radiation (XRT) alone or XRT plus chemotherapy (concomitant 5-FU during XRT and maintenance 5-FU + MeCCNU). An initial field received 4,500-5,100 rad in 5-6 weeks, with a boost field dose to a maximum of 7000 rad/8 weeks (maximum 6,000 rad/7 weeks with chemotherapy), dependent on findings of special small bowel films. One hundred twenty-nine patients were evaluable (65 XRT, 64 XRT + chemo). There were no statistically significant differences between treatments with respect to overall survival, complete remission rate, time to disease progression, local failure rate, or radiation dose distribution. Median survival was 17 months for XRT, 18 months for XRT + chemo; the 2-year survival probability was 36% for XRT, 44% for XRT + chemo. Initial performance status was a significant prognostic factor for both survival and time to disease progression. A trend was observed favoring the combination treatment for patients with residual disease. Treatment complications were greater for the combined modality arm than for radiation alone. Twenty-seven patients (22%) were alive at last data analysis, with no evidence of disease (NED) from 2-51 months (30 months median). Patients with resection of gross disease before or after irradiation had a much better result than those with gross residual or without any resection, but the relative influence of patient selection versus impact of surgery remains unclear.

Abscess↗
PubMed1993

Collagen gene expression and wound strength in normal and radiation-impaired wounds. A model of radiation-impaired wound healing.

BACKGROUND: Poorly healing wounds result in significant morbidity postoperatively. Numerous attempts have been made to study wound healing in vivo to understand better the normal healing process and factors that impair healing. Animal models of wound healing have been developed to evaluate wound healing in a systematic and controlled setting. Incisional wounds are created in animals to mimic the surgical patient. They may then be evaluated by a variety of methods for degree of healing. OBJECTIVE: To give insight into the mechanisms of wound healing impairment, we developed a model of impaired wound healing in guinea pigs using radiation applied to the skin surfaces only. METHODS: Wound bursting strength, a direct measure of the force required to burst apart healing linear incisions, was measured. Collagen content, measured indirectly as collagen gene expression, was measured. RESULTS: Significant reductions in wound bursting strength were noted after radiation administration. Collagen gene expression was decreased in wounds 7 days after radiation, but recovered to control levels 14 days after irradiation. Our model enables the inclusion of irradiated and unirradiated skin flaps within the same animal, thus eliminating intra-animal variation when comparing impaired and normal wounds. CONCLUSION: Wound bursting strength analysis, combined with techniques aimed at elucidating changes at the molecular level, provides a useful tool for the study of factors that impair healing and potential treatments for resulting healing deficits.

Animals↗
PubMed2002

On the role of intensity-modulated radiation therapy in radiation oncology.

Physicists are critical members of the radiation therapy team, and rightfully so. Therefore, it is not unreasonable that they be acquainted with the broader aspects of the management of patients who receive radiation treatments, as well as the roles played by surgeons, medical oncologists and other members of the treatment team. The spate of recent technical developments openly embraced by medical physicists, many of whom appear unconcerned by questionable benefits and very high costs, leads the authors to believe that this acquaintance is not as widespread as it should be. The present paper provides a brief review of clinical considerations in radiation oncology, statistics for the most prevalent cancers, and how those cancers that account for over 90% of mortality are currently treated. With these data as background, it then considers the extent to which one of the more widely promoted new technologies is likely to impact upon survival. By providing this modicum of perspective, physicists will be in a better position to evaluate these new technologies in more fundamental clinical terms, and thereby enhance their contributions to the overall care of the cancer patient.

Disease-Free Survival↗
PubMed2004

An implantable radiation dosimeter for use in external beam radiation therapy.

An implantable radiation dosimeter for use with external beam therapy has been developed and tested both in vitro and in canines. The device uses a MOSFET dosimeter and is polled telemetrically every day during the course of therapy. The device is designed for permanent implantation and also acts as a radiographic fiducial marker. Ten dogs (companion animals) that presented with spontaneous, malignant tumors were enrolled in the study and received an implant in the tumor CTV. Three dogs received an additional implant in collateral normal tissue. Radiation therapy plans were created for the animals and they were treated with roughly 300 cGy daily fractions until completion of the prescribed cumulative dose. The primary endpoints of the study were to record any adverse events due to sensor placement and to monitor any movement away from the point of placement. No adverse events were recorded. Unacceptable device migration was experienced in two subjects and a retention mechanism was developed to prevent movement in the future. Daily dose readings were successfully acquired in all subjects. A rigorous in vitro calibration methodology has been developed to ensure that the implanted devices maintain an accuracy of +/-3.5% relative to an ionization chamber standard. The authors believe that an implantable radiation dosimeter is a practical and powerful tool that fosters individualized patient QA on a daily basis.

Animals↗
PubMed1963

INACTIVATION OF THE RADIATION-RESISTANT SPOILAGE BACTERIUM MICROCOCCUS RADIODURANS. I. RADIATION INACTIVATION RATES IN THREE MEAT SUBSTRATES AND IN BUFFER.

A simplified technique permitting the pipetting of raw puréed meats for quantitative bacteriological study is described for use in determining survival of these non-sporing bacteria, which are exceptionally resistant to radiation. Survival curves, using gamma radiation as the sterilizing agent, were determined in raw beef with four strains of Micrococcus radiodurans. Survival curves of the R(1) strain in other meat substrates showed that survival was significantly greater in raw beef and raw chicken than in raw fish or in cooked beef. Resistance was lowest in the buffer. Cells grown in broth (an artificial growth medium) and resuspended in beef did not differ in resistance from cells that had been grown and irradiated in beef. Survival rate was statistically independent of the initial cell concentration, even though there appeared to be a correlation between lower death rate and lower initial cell concentrations. The initial viable count of this culture of the domesticated R(1) strain in beef was reduced by a factor of about 10(-5) by 3.0 megarad, and 4.0 megarad reduced the initial count by a factor of more than 10(-9). Data suggest that M. radiodurans R(1) is more resistant to radiation than spore-forming spoilage bacteria for which inactivation rates have been published.

Animals↗
PubMed1963

INACTIVATION OF THE RADIATION-RESISTANT SPOILAGE BACTERIUM MICROCOCCUS RADIODURANS. II. RADIATION INACTIVATION RATES AS INFLUENCED BY MENSTRUUM TEMPERATURE, PREIRRADIATION HEAT TREATMENT, AND CERTAIN REDUCING AGENTS.

The R(1) strain of Micrococcus radiodurans, previously determined to be more resistant than three other strains exposed to gamma radiation, was studied further to determine the influence of certain environmental factors on resistance to radiation inactivation. The frozen state offered insignificant protection to the organisms irradiated in raw puréed beef. Resistance was reduced by higher menstruum temperatures (40 and 50 C) during irradiation. Preirradiation heat treatment was found to lower resistance to subsequent irradiation. When the cells were irradiated in buffer at pH 5, 7, or 9, no differences in resistance were noted. Cell suspensions in buffer were protected to some extent by cysteine but not by thioglycolate. Ascorbate enhanced radiation inactivation.

Animals↗
PubMed1971

Radiation, Infection, and Macrophage Function IV. Effect of Radiation on the Proliferative Abilities of Mononuclear Phagocytes in Tuberculous Lesions of Rabbits.

Rabbits were irradiated with 400 to 600 rads 2 to 3 days before they were infected with BCG or with virulent tubercle bacilli. Biopsies were periodically removed from the resulting lesions and incubated for 1 hr with (3)H-thymidine in vitro under hyperbaric oxygen. Twelve to 16 days after radiation there was a reduction in the percentage of mononuclear cells (macrophages and some lymphocytes) that had incorporated (3)H-thymidine in the lesions. At this time, the lesions of the irradiated group were smaller than those of controls. These results can be explained by the reduction in the number of new mononuclear cells that entered the lesions of the irradiated group and support the tenet that local mononuclear cell division occurs mainly in cells that have recently emigrated from the blood stream. An alternate, but less likely, explanation of these results would be that radiation caused the bone marrow to release a higher percentage of "defective" mononuclear cells that were unable to divide, i.e., incorporate (3)H-thymidine, in the lesions. The reduction produced by radiation in both local cell infiltration and local cell division would decrease the number of macrophages available to control the tuberculous infection in the host.

Journal Article↗
PubMed1978

Specificity of cell surface virus receptors on radiation leukemia virus and radiation-induced thymic lymphomas.

We have developed a system for analysis of murine leukemic virus (MuLV) receptors on the surface of thymic lymphoma cells utilizing the fluorescence-activated cell sorter. The binding of fluoresceinated or rhodaminated MuLV to target cells showed saturation kinetics and was blocked by homologous MuLV, and bound MuLV had a polypeptide profile identical to that of input MuLV. Thymic lymphomas bound specifically the MuLV which induced them, whereas only 0.5 to 2% of normal thymocytes showed equivalent MuLV binding. Simultaneous binding of excess fluoresceinated RadLV and rhodaminated MCF-247 AKR virus to radiation leukemia virus-induced or spontaneous AKR thymic lymphomas demonstrated that even in the presence of both viruses the cells bound preferentially the inducing MuLV. Examination of the C57BL/Ka endogenous viruses showed that radiation leukemia virus-induced thymic lymphomas bind only thymotropic-leukemogenic radiation leukemia virus and not eco- or xenofibrotropic MuLV's. Thus, virus binding in this system involves only leukemogenic isolates of these retroviruses and implies a central role of this receptor-ligand interaction in the processes of leukemic transformation.

Cell Line↗
PubMed2005

[Radiation therapy with synchrotron radiation and cisplatin-based chemotherapy as a treatment of gliomas].

The application of synchrotron radiation in medicine dates back to more than one decade. In particular, a team of researchers led by Dr. F. Esteve has been working for several years in the Grenoble Synchrotron (ESRF) on radiotherapy treatments to heal brain tumors. The team has recently obtained a very promising new result. Gliomas the commonest brain tumor in the adult and the mean survival in advanced disease patients is lower than one year. Conventional radiation therapy is used palliatively since it is one of the most radiotherapy-resistant tumors. Moreover, chemotherapy and surgery have no utility in most cases. Experiments at the Grenoble Synchrotron have been carried out in mice with gliomas and they consist of injecting cysplatine into the tumors so that an intense monochromatic radiation is applied afterwards. Half-life of sick untreated mice is 28 days. With the use of cysplatine alone, it expands to 48 days. However, the association of two treatments supposes a half-life of 206 days (six times greater than in untreated mice). After one year of treatment, 34% of animals remain alive, which constitutes a result never seen before in this type of radio-resistant tumors.

Animals↗
PubMed2003

Beta radiation and inhibition of recanalization after coil embolization of canine arteries and experimental aneurysms: how should radiation be delivered?

BACKGROUND AND PURPOSE: Beta radiation prevents recanalization after coil embolization. We sought to determine the effects of varying coil caliber, length, activity of 32P per centimeter of coil or per volume, and spatial distribution of coils on recanalization. METHODS: We studied the angiographic evolution of 81 canine maxillary, cervical, and vertebral arteries implanted with a variety of nonradioactive (n=29 arteries) or radioactive (n=52) devices. We compared 1- or 2-caliber 0.015 or 0.010 coils ion-implanted or not with 3 different activity levels (0.05 to 0.08, 0.06 to 0.12, 0.18 to 0.32 microCi/cm) of 32P and totaling 4, 8, and 16 cm in length for the same arterial volume. We also compared inhibition of recanalization by beta radiation delivered by stents, after coil occlusion proximal to or within the stent, with that delivered by coils placed within nonradioactive stents. We finally studied the angiographic evolution of canine lateral wall carotid aneurysms treated with 1 or 2 stents of various activity levels positioned inside the parent artery across the neck. Animals were killed at 4 and 12 weeks for macroscopic photography and pathological examination. RESULTS: All arteries (29 of 29) occluded with nonradioactive devices were recanalized, while 49 of 52 arteries (94%) implanted with 32P devices were occluded at 4 weeks. All aneurysms treated with stents, radioactive or not, demonstrated residual filling of the sac or of channels leading to the aneurysms at follow-up angiography at 4 weeks. CONCLUSIONS: The recanalization process found in the canine arterial occlusion model is minimally affected by coil caliber, number, and length or packing density. Beta radiation reliably inhibits this process, but thrombosis is an essential condition for the efficacy of a radioactive coil strategy.

Aneurysm↗