6-Thioguanine resistant T-lymphocyte determination as a possible indicator of human ionizing radiation exposure

We used the autoradiographic assay to assess human in vivo somatic cell gene mutation at the hypoxanthine guanine phosphoribosyl transferase (hgprt) locus in T-lymphocytes. Cells able to incorporate tritiated thymidine in vitro in 6-thioguanine containing shot-term cultures were enumerated in order to determine 6-thioguanine resistant (TGr) variant frequencies in cryopreserved lymphocytes from control indivuals and 3 persons suspected of 60Co exposure from an accident in Cd. Juárez, México. The data indicate that the lymphocyte TGr variant frequency assay may be potencially usefull for human population monitoring following accidental to ionizing radiation

Ambient 60-Hz magnetic flux density in an urban neighborhood.

A residential neighborhood in Buffalo, NY, was surveyed with a magnetic field meter to evaluate whether or not spot measurements are reliable predictors of the 60-Hz fields at street corners and residences. The results of repeated measurements over 7 days at 33 street corners in this neighborhood indicate that day-to-day variation in power line magnetic fields is negligible (intraclass correlation coefficient = 0.94). Multivariate linear regression analysis of the data indicates that transmission lines and thick, three-phase primary wires near the field measurement site are strong predictors and account for the majority of the ambient magnetic field variance between locations (multiple correlation coefficient squared = 0.60; F ratio = 22.2, P less than .001). Magnetic fields measured at the front sidewalk were highly correlated with fields at the front doorsteps of 45 homes in this neighborhood (gamma = 0.81). These results suggest that ambient power line magnetic field levels at urban residences can be reliably characterized on a one-time site inspection using a hand-held magnetic field meter and a simple wiring classification system.

Cataracts induced by microwave and ionizing radiation.

Microwaves most commonly cause anterior and/or posterior subcapsular lenticular opacities in experimental animals and, as shown in epidemiologic studies and case reports, in human subjects. The formation of cataracts seems to be related directly to the power of the microwave and the duration of exposure. The mechanism of cataractogenesis includes deformation of heat-labile enzymes, such as glutathione peroxide, that ordinarily protect lens cell proteins and membrane lipids from oxidative damage. Oxidation of protein sulfhydryl groups and the formation of high-molecular-weight aggregates cause local variations in the orderly structure of the lens cells. An alternative mechanism is thermoelastic expansion through which pressure waves in the aqueous humor cause direct physical damage to the lens cells. Cataracts induced by ionizing radiation (e.g., X-rays and gamma rays) usually are observed in the posterior region of the lens, often in the form of a posterior subcapsular cataract. Increasing the dose of ionizing radiation causes increasing opacification of the lens, which appears after a decreasing latency period. Like cataract formation by microwaves, cataractogenesis induced by ionizing radiation is associated with damage to the lens cell membrane. Another possible mechanism is damage to lens cell DNA, with decreases in the production of protective enzymes and in sulfur-sulfur bond formation, and with altered protein concentrations. Until further definitive conclusions about the mechanisms of microwaves and ionizing radiation induced cataracts are reached, and alternative protective measures are found, one can only recommend mechanical shielding from these radiations to minimize the possibility of development of radiation-induced cataracts.

The combined effects of mixtures of ionizing radiations.

Ionizing radiation is a special group of toxic agents whose general interaction can be calculated. This was demonstrated using a radiation interaction model previously published. In this paper, this model is refined and mathematically reformulated using a unified set of assumptions. It postulates the existence of a common intermediate lesion and the relative action of lesions before, at and after this common stage. General quantitative dose-effect relationships of mixed radiations can be derived from the dose-effect relationships of the components in the mixture.

Recuperaçäo de fontes hospitalares seladas de 137 Cs / Recovery of lost medical 137 Cs sources

Existe uma grande probabilidade de perda de fontes de braquiterapia devido a falta de atençäo dos encarregados e/ou de um comportamento inesperado do paciente que a ela é submetido. Considerando os últimos acontecimentos envolvendo fontes de radiaçäo ionizante, achamos oportuno nos reportarmos ao trabalho por nós desenvolvido há alguns anos sobre a recuperaçäo de três fontes equivalentes a 10 mCi ou 37 x 10**7 Bq cada uma, extraviadas de um aplicador intrauterino do tipo Henscke por uma paciente com problema mental e jogadas no ralo do banheiro e no lixo. Um protocolo para fontes perdidas também é sugerido

[Cytogenetic research on micropopulations of the root vole (Microtus oeconomus Pall.) living under various radioecological habitat conditions]. / Tsitogeneticheskoe issledovanie mikropopuliatsii polevki-ékonomki (Microtus oeconomus Pall.), obitaiushchikh v razlichnykh radioékologicheskikh usloviiakh.

Percentage of aneuploid cells and that of cell with chromosome aberrations in Microtus oeconomus Pall. living in areas with the enhanced radiation background (the dose of external radiation is 50 times and that of internal irradiation of bone marrow by incorporated 226Ra 10 times higher than the controls) exceeds significantly (p less than 0.05) the control values. It is concluded that mutations occur in the experimental animals more frequently than in the controls.

Contaminación por radiaciones ionizantes / Contamination by ionizing radiations

El personal que trabaja en el Departamento de Radiología, recibe una sobrecarga de radiación mucho mayor que cada uno de los pacientes, que por regla general se exploran unas pocas veces en su vida. Los autores demuestran la importancia de las medidas preventivas en el manejo de los equipos, la disciplina en el trabajo, la impecable técnica, la permanencia del operador en la zona de sombra, el empleo de protectores plomados, el control médico, las ausencias periódicas legales y el uso de dosímetros que minimizan el riesgo de sobre irradiación en el personal del Departamento de Radiologia del Hospital Naval "Dr Raúl Perdomo Hurtado", donde se disparan más de cuarenta mil placas al año

Irradiation of the embryo and fetus.

The human evidence on radiation damage to the individual developing in utero is confined to mental impairment and carcinogenesis. New evidence is becoming available about levels of mental impairment of direct interest to radiological protection, but as yet no framework of understanding exists to allow quantitative predictions for the purposes of radiological protection. There is general agreement that malignant disease has been increased following antenatal radiography but no unanimity yet in concluding that irradiation was the main causal factor: reasons are given for accepting that radiography was the cause. Recent increases in biological understanding suggest why maldevelopment is not to be expected after irradiation of the conceptus. A clonal hypothesis for organogenesis provides a reasonable explanation for quantitative aspects of experimental observations on teratogenesis by ionising radiation, including the commonly found highly curvilinear dose-response relationship, the occurrence of so-called critical stages of sensitivity after exposures of a few hundred roentgens, and the reduction in frequency of induced abnormality with protraction of exposure. Clonal hypotheses predict that there will be a virtual threshold for polycystic (non-stochastic) forms of radiation damage. It may be misguided to adopt a linear dose-response relationship for deriving risk estimates for the practical purposes of radiological protection unless some mechanism for production of clinically evident harm can be advanced which provides a plausible reason for expecting linearity.

Radiation risks in perspective.

The main difficulty in presenting radiation risks in their proper perspective is that they must, in most cases, be estimated predictively. This contrasts with most other occupational and public risks, of which the magnitude and severity are known from past records and experience. The problem is greater at the low effective dose rates now observed in the majority of all forms of exposure, usually of less than 3 mSv per year from natural causes, from occupational exposure, and from exposure of "critical groups" of the general public. For most of these populations there are particular problems also in epidemiological studies at low dose, in addition to those due to the very large numbers of person-years that need to be studied and the long latencies of most radiation effects. Adequate estimates can, however, now be made of the carcinogenic risk of exposure at higher dose of various organs selectively and of the whole body uniformly, and of modes of inference to the risk at lower dose. Estimates can also be made of the risks of inducing major types of inheritable and developmental abnormality. An essential step in viewing the sum of all such radiation risks in the perspective of other occupational and public risks must now be to develop an informed consensus on the relative weight that is regarded as attaching to hazards of different kind and severity.

[Embryonic mortality of the root vole as an index of the effect of small doses of natural radioactivity on genetic processes in populations]. / Embrional'naia smertnost' polevki-ékonomki kak pokazatel' vliianiia malykh doz estestvennoi radioaktivnosti na geneticheskie protsessy v populiatsiiakh.

A study was made of the pre- and post-implantation death of (F2--F4) Microtus oeconomus progeny whose parents lived in territories where natural radiation background was increased (an exposition dose-rate of 3.6-144.0 pC/kg X s). The spontaneous rate of pre- and post-implantation death of progeny of irradiated (experimental) animals was higher than that of intact ones (control). The animals kept in conditions of chronic irradiation (46.2 pC/kg X s) exhibited a more pronounced discrepancy in embryonal death rate. It is suggested that genetic differences in the populations were responsible for different rate of embryonal death of the control and experimental animals.

Exámen médico preempleo en trabajadores expuestos a radiaciones ionizantes / Pre-employment medical examination in workers exposed to ionizing radiations

Se realiza un estudio a 119 alumnos de primer año del curso básico de técnicos de rayos X del Instituto Politécnico de la Salud "Dr. Carlos J. Finlay" en la Ciudad de la Habana, con el fin de detectar posibles afecciones en estos casos, las cuales pudieran ser invalidantes para ocupar puestos de trabajo expuestos a radiaciones ionizantes. Se informa que el estudio estuvo basado a la aplicación de una encuesta elaborada al efecto, la cual brindó los datos necesarios para la elaboración del mismo. Se hace un análisis y una discusión de las tablas. Se llega a la conclusión de que la única afección incapacitante en el grupo de estudio correspondió a 1 caso que padecía de epilepsia

Exámen médico preempleo en trabajadores expuestos a radiaciones ionizantes / Pre-eployment medical examination in workers exposed to ionizing radiations

Se realiza un estudio a 119 alumnos de primer año del curso básico de técnicos de rayos X del Instituto Politécnico de la Salud "Dr. Carlos J. Finlay" en la Ciudad de la Habana, con el fin de detectar posibles afecciones en estos casos, las cuales pudieran ser invalidantes para ocupar puestos de trabajo expuestos a radiaciones ionizantes. Se informa que el estudio estuvo basado a la aplicación de una encuesta elaborada al efecto, la cual brindó los datos necesarios para la elaboración del mismo. Se hace un análisis y una discusión de las tablas. Se llega a la conclusión de que la única afección incapacitante en el grupo de estudio correspondió a 1 caso que padecía de epilepsia