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PubMed1990

Design of molecules labeled with beta+ emitters for use in multitracer investigations using positron emission tomography.

The development of positron emission tomography (PET) in the past few years reflects the improvements in sensitivity and resolution of detector systems and the increasing access to useful positron emitting tracer molecules. Today, synthetic methods for routine production of compounds labeled with 15O, 13N, 11C and 18F with half-lives of 2, 10, 20.4 and 110 min, respectively, are available. This has a great impact on the use of positron emitting tracers in investigations in clinical studies as well as in research. In the beginning of the PET era studies on blood flow, blood volume and energy metabolism were the main targets for investigation. Today, these are only a few of the many important areas of PET. In the future, the main progress of PET as a general tracer method will be in monitoring in vivo biochemistry in normal as well as pathologic states. The use of multitracer investigations and multivariable statistical analysis will then be a most interesting approach. In this paper some aspects on this matter will be discussed.

Beta Particles↗
PubMed1991

Threshold-like dose of local beta irradiation repeated throughout the life span of mice for induction of skin and bone tumors.

The backs of female ICR mice were irradiated with beta rays from 90Sr-90Y three times a week throughout life. Previously we observed 100% tumor incidence at five different dose levels ranging from 1.5 to 11.8 Gy per exposure, but no tumor on repeated irradiation with 1.35 Gy for 300 days (Radiat. Res. 115, 488, 1988). In the present study, delay of tumor development was again seen at a dose of 1.5 Gy per exposure, with further delay at 1.0 Gy. The final tumor incidence was 100% with these two doses. At 0.75 Gy per exposure, no tumor appeared within 790 days after the start of irradiation, but one osteosarcoma and one squamous cell carcinoma did finally appear. These findings indicate a threshold-like response of tumor induction in this repeated irradiation system and further suggest that the apparent threshold may be somewhat less than 0.75 Gy per exposure.

Animals↗
PubMed1991

Estimates of beta absorbed fractions in small tissue volumes for selected radionuclides.

Energy deposition patterns are dependent upon the size and geometry of the source region, distribution of radioactive material, types of radiations and energies emitted by the radionuclide, as well as interfaces between different materials which may exist within the region. Commonly, in absorbed dose calculations for internally deposited beta-emitting radionuclides, it is assumed that the absorbed fraction of energy for the mean beta energy is a sufficient representation of the beta spectrum. The accuracy of this assumption was tested by comparing absorbed fractions calculated using actual beta spectral energies with those obtained using the mean beta energy for several radionuclides commonly used in nuclear medicine. A sphere composed of tissue was chosen as the preferred geometry. Spheres of 0.1, 0.5, 1.0, and 2.0 cm radius were used, and absorbed fractions were calculated as a function of surface-to-volume ratios. This allows the assessment of absorbed fraction in spheres where there is a uniform distribution of a radionuclide.

Beta Particles↗
PubMed1991

Radiation absorbed dose calculations for samarium-153-EDTMP localized in bone.

Calculations have been undertaken to estimate the likely radiation dose received by patients undergoing treatment with samarium-153-EDTMP. Previously known bone structure parameters have been employed to partition correctly the energy absorbed in the bone matrix between red bone marrow, yellow marrow, and various types of mineral bone. Both uniform surface and volume distribution of the radioactivity are considered. The key findings of the calculations can be stated in terms of the MIRD "S-factors" for red bone marrow and the endosteal layer of cells on bone surfaces. In particular, the S-factor for red bone marrow is either 0.0276 mGy/MBq.h or 0.0077 mGy/MBq.h for surface and volume distributed radioactivity, respectively. For the endosteal layer of thickness (10 microns) on bone surfaces, the corresponding values are 0.0723 mGy/MBq.h and 0.0213 mGy/MBq.h, respectively.

Beta Particles↗
PubMed1991

[Nervous system function in persons receiving irradiation at different dose ranges during the cleanup after the accident at the Chernobyl Atomic Electric Power Station].

The paper is concerned with the results of neurological examination of 113 patients who developed acute radiation sickness of various degrees of severity during the elimination of the effects of the accident at the Chernobyl Nuclear Power Station. A clinical picture of neurological disorders at different periods of ARS was described. CNS specific and nonspecific lesions were defined.

Accidents↗
PubMed1991

Effects of low energy beta-irradiation from tritiated water on the morphology of 3T3 fibroblasts.

Cellular alterations of cultured 3T3 cells irradiated with beta-rays from tritiated water were studied by scanning and transmission electron microscopy. We observed decreased negative surface charges, vacuolization of rough endoplasmic reticulum and Golgi-complex, degeneration of mitochondria, increase of lysosomal activity and changes in distribution and amount of microfilaments in the irradiated cells, that parallelled changes in cell shape.

Animals↗
PubMed1990

[The photosensitization of uveal melanoma cells by ionizing radiation].

A study of the character of changes in melanoma cells "in vitro" subjected to successive beta-radiation and light energy of low intensity has revealed a more expressed loss of cells as compared with a "pure" ionizing action. Essential differences in the cells density in the monolayer appear already by the 3d-8th day and reach the maximum 2-3 weeks later. The dynamics of changes in the cells density isn't connected with the cellular type of the tumor and initial density isn't connected with the cellular type of the tumor and initial density of their distribution in the monolayer. The duration of the culture existence becomes shorter. If monolayers not subjected to the action perished after 54.0 +/- 6.2 days, after beta-radiation 35.2 +/- 2.4 days later, then after combined action they perished 17.2 +/- 2.6 days later. Thus, the effect was revealed that is actually opposite to a recently discovered phenomenon of photoreactivation of ionizing injury. Despite difficulty of interpreting possible mechanisms of the discovered phenomenon, it is already possible to suggest about its possibility to be used in treatment of pigmentary new formations.

Beta Particles↗
PubMed1990

Low-dose-rate effect of tritium beta-rays on transfection activity of phage DNA related to an oxidative species different from .OH, HO2. O2-., and H2O2.

In order to study the low-dose-rate effect of tritium beta-irradiation, we exposed single-stranded DNA of M13 mp10 phage to purified tritiated water. The beta-irradiated DNA was then transfected to E. coli K12 JM101. The lower the radiation dose rate, the more the transfection activity decreased. After the low-dose-rate effect was confirmed, the characteristics of tritiated water were also studied. The formation of an active oxidative species different from .OH, HO2., O2-., and H2O2 was found in the tritiated water by using UV spectrometry and luminescence measurement. Attributing it to nescent oxygen by reason of the production of the epoxide from mesityl oxide, we discussed the low-dose-rate effect from the viewpoint that the yield of the DNA modification could be relatively higher than that of the O2 formation in a competition reaction when the dose rate was lower.

Bacteriophages↗
PubMed1990

[Hygienic regulation of static electric field generated by devices with electron-ray tube].

When detecting and hygienically assessing the static electric field generated by the devices with a half-tone storage tube it is necessary to take account of the impact of a number of characteristics of field intensity ranging on the obtained results. Taking into consideration the above characteristics during the research permits to lower error in the derived values and approximate them to the characteristics affecting the organisms of those using devices with a half-tone storage tube.

Beta Particles↗
PubMed1990

A comparison of the radiation response of the epidermis in two strains of pig.

The response of the epidermis was compared in two strains of pig, the English Large White and the Göttinger Miniature, after irradiation with 90Sr beta rays. The effects of two types of anesthesia were also tested in pigs of each strain, a volatile gas mixture of approximately 70% oxygen, approximately 30% nitrous oxide, and 2% halothane, and an intravenously administered narcotic azaperon/etimodat with the animals breathing air. Strain- and anesthetic-related changes were compared on the basis of dose-effect curves for the incidence of moist desquamation from which ED50 values (+/- SE) were determined, i.e., the dose required to produce this effect in 50% of the fields irradiated. For English Large White pigs anesthetized with the volatile gas mixture, an ED50 of 27.32 +/- 0.52 Gy was obtained for moist desquamation. Irradiation with the azaperon/etomidat anesthesia in this strain of pig produced a significantly higher ED50 of 33.36 +/- 0.76 Gy (P less than 0.001). This appeared to be related to the fact that the animals were breathing air, i.e., a lower oxygen concentration (approximately 21%), at the time of irradiation. For the Göttinger Miniature pig the ED50 values for moist desquamation were 38.93 +/- 3.12 Gy and 43.36 +/- 1.34 Gy while using the gaseous anesthetic mixture and the azaperon/etomidat anesthesia with the animals breathing air, respectively. These ED50 values are 10-11 Gy higher than those obtained for the English Large White pig under identical conditions of anesthesia, which resulted in a strain difference ratio of approximately 1.35. Radiation under the volatile gas mixture anesthesia resulted in a uniform irradiation response over the skin of the flank in both strains of pig. Radiation under azaperon/etomidat anesthesia resulted in a nonuniform skin response over the flank. The ED50 for moist desquamation was significantly higher in dorsal sites on the flank compared with the ventral area of English Large White pigs; a similar trend was seen in Göttinger Miniature pigs. This difference in the radiosensitivity over the flank skin while the animals are under azaperon/etomidat anesthesia at the time of irradiation was associated with the animals breathing air and is in agreement with findings published previously for animals under halothane anesthesia and breathing air.

Anesthetics↗
PubMed1990

Beta-radiation-induced resistance to MNNG initiation of papilloma but not carcinoma formation in mouse skin.

We have shown previously that the risk of tumor initiation, promotion, and progression in animals initiated with alkylating agents can be drastically altered by hyperthermia treatments. We show here that ionizing radiation can also alter the risk of tumor initiation by alkylating agents. Using a two-step skin tumorigenesis protocol in female SENCAR mice (initiation by MNNG, promotion with TPA), we exposed the dorsal skin of the mice to various doses of 90Sr/90Y beta radiation near the time of initiation. The radiation produced a dose-dependent reduction in the number of papillomas which appeared after TPA promotion, with about a 20% reduction in animals receiving 0.5 Gy surface dose just before initiation, about 50% reduction after 2.5 Gy, and greater than 80% at doses above 5 Gy. A dose of 2.5 Gy in animals initiated with DMBA produced no significant reduction. One skin hyperthermia treatment (44 degrees C, 30 min) along with radiation in MNNG-initiated animals partially blocked the protective effect of radiation and increased the papilloma frequency. Radiation (2.5 Gy) given either 6 days before or after MNNG initiation was less effective but still reduced papilloma frequency about 20%. In sharp contrast to the marked reduction in papilloma formation, these same animals showed no change in carcinoma frequency with any of the doses or schedules of beta radiation. MNNG initiation alone produced three types of initiated cells. One type, produced in low yield, was promotion-independent with a high probability of progression to a carcinoma and appeared unaffected by the radiation. A second type, produced in intermediate yield, was promotion-dependent and also had a high progression probability, but was likewise unaffected by the radiation. The third and most abundant type was promotion-dependent with a very low progression probability. Radiation exposure resulted in a decrease in the risk of an MNNG initiation event which led only to the third type of cell. The data therefore indicate that the risk of some, but not all, tumor-initiating events caused by alkylating agents can be reduced by an exposure to ionizing radiation.

Animals↗
PubMed1990

The effect of topical dexamethasone and preoperative beta irradiation on a model of glaucoma fistulizing surgery in the rabbit.

We studied the effect of topical dexamethasone (1%) and preoperative beta irradiation on a model of glaucoma fistulizing surgery in the rabbit. Intraocular pressure and gross facility of aqueous outflow following surgery were not influenced by either treatment, although blebs persisted longer in the irradiated eyes. Steroids reduced clinically observable inflammation as well as the number of inflammatory cells identifiable by microscopy. Fibroblast production temporarily slowed, and ultra-structural examination demonstrated lipid-filled vacuoles and dilated mitochondria in these eyes. Also, the scar was thinner at 24 days. Beta irradiation delayed wound healing and the scar was thinner in the early postoperative stages, but the light microscopic appearance of the scar was unaltered at 59 days. Inflammation was more pronounced initially, with abundant fibrin in the wound. Recovery of the conjunctival epithelium was delayed. The delay in fibroblast recruitment and wound contraction, the thinner scar tissue, and the increased survival of the bleb are all factors that suggest that beta irradiation may be a useful adjunct to glaucoma surgery.

Analysis of Variance↗
PubMedDate not supplied

[The significance of immunity disorders in the development of tumorous effects during the long-term action of tritium in mice].

In experiments with CBA mice it was shown that the long-term influence of tritium oxide administered with drinking water daily during 180 days (370 kBq.g-1 of body mass, cumulative dose 8.7 Gy, dose rate 4.5 cGy.day-1) causes the development of immunity deficiency 90 days after the onset of the administration that persists for up to 270 days. There is a 34% decrease in the average life of irradiated animals and an increase in the number of malignant neoplasms (postmortem examination was performed after natural death or killing on days 250, 350 and 450). There is a direct relationship between the occurrence of malignant neoplasms and the immunity deficiency.

Animals↗
PubMed1990

[Invasion of poststyloid space and metastasis of deep upper cervical lymph node in nasopharyngeal carcinoma].

From March 1985 to September 1988, 38 out-patients with nasopharyngeal carcinoma (NPC), proven by pathology and examined by CT scan or MRI with involvement of deep upper cervical lymph nodes larger than 2 cm, were treated. The invasion of the poststyloid space is probably caused by metastases of the lymph nodes deep-seated in the neck and not by direct infiltration of the primary tumor. In TNM staging, it should be considered as N1, but not T3. As to the design of radiotherapy for these cases, the upper margin of the cervical field should be moved up to the level of the external auditory meatus in order to encompass the base of the skull. If lymph nodes in the mastoid cells on the same side are involved, beta-beams with energy not lower than 15 Mev should be used to ensure enough dose in the target volume.

Adult↗