The biological effect of low-level radiation doses on the morphological composition of the peripheral blood in children]

Examination of 339 children at the age of 2 to 12 years, living in the caesium contaminated region (from 2 to 5 Ci/km2) has revealed that total radioactivity of their urine is, on the average, twice as high as that of children living in "pure" regions. Quantitative and qualitative changes were observed in the erythroid series, neutrophilic leukocytes, eosinophils and B-lymphocytes of the peripheral blood of children subjected to long-term low-level irradiation. It should be noted that the character and direction of these changes were a function of the children's age and the level of total radioactivity of their urine.     

Mechanism of the stimulating action of penetrating radiation on biological matter

In this work, the author attributes the stimulatory effect of super-low doses of penetrating radiation to cell division. In terms of the proposed model, the calculation results permit to associate the value of a change in the rate of division of cells, depending on the dose rate, with their sizes. The experimental evidence favors the model proposed.     

The grounds of interspices difference in radiation-genetic effects of low-level radiation

Radiation-genetic effects are characterized by large quantitative difference. After the low dose radiation appearance of mutation is the largest in Drosophila, substantially lower in mice, especially if irradiation was protracted, and practically absent in humans. As the possible grounds of this difference the author consider the existence of non-specific repair mechanism, which has arouse during evolution for diminution of different detrimental impacts, including ionizing radiation. The efficacy of such mechanism of natural protection is determined by the efficacy of the repair mechanisms, which is elevated in compliance with specific life span, which is of necessity for its maintenance. The evolution has led to maximal development of this mechanism in human beings, and it is proved in particular in prevention of the hereditary effect of low-level radiation.     

Hypothesis regarding a membrane-associated mechanism of biological action due to low-dose ionizing radiation

A novel theory is proposed regarding the action of ionizing radiation in the range of very low doses. The basic premise of the theory presented is that the low-dose effect cannot be explained by direct damage to the DNA (as has generally been assumed) and that effects on cellular membranes should be considered instead. Low-dose radiation damaging the plasma membrane decreases the concentration of low-molecular weight compounds (LMWC) inside the cell, which through an unspecific mechanism induces an activation of all enzymes. The mechanism described here has been well substantiated. The changes in the intracellular contents of LMWC and the increase of pH_in cause chromatin rearrangements, alterations in DNA folding and finally, if the latter are strong enough, expression of various ”silent” genes including repair enzyme genes. Received: 2 February 1999 / Accepted: 15 May 2000     

The biological action of Yersinia pseudotuberculosis endotoxin

Experimental studies on guinea pigs have shown that Y. pseudotuberculosis lipopolysaccharide is capable of inducing endotoxinemia accompanied by the development of the thrombohemorrhagic syndrome. In cases of pseudotuberculosis the importance of the increased synthesis of prostaglandins and cyclic nucleotides with the prevalence of PGF2 alpha and cGMP in the genesis of toxico-allergic manifestations of pathologic processes has been established. The pathomorphological picture of pseudotuberculosis endotoxinemia is characterized by sludge, the vascular thrombosis of the microcirculatory bed, diapedetic hemorrhages, delymphatization of the immunogenetic organs. The moderately pronounced action of indomethacin, a prostaglandin inhibitor, on the manifestations of pseudotuberculosis endotoxinemia has been revealed.     

Mechanism of low-level microwave radiation effect on nervous system

The aim of this study is to explain the mechanism of the effect of low-level modulated microwave radiation on brain bioelectrical oscillations. The proposed model of excitation by low-level microwave radiation bases on the influence of water polarization on hydrogen bonding forces between water molecules, caused by this the enhancement of diffusion and consequences on neurotransmitters transit time and neuron resting potential. Modulated microwave radiation causes periodic alteration of the neurophysiologic parameters and parametric excitation of brain bioelectric oscillations. The experiments to detect logical outcome of the mechanism on physiological level were carried out on 15 human volunteers. The 450-MHz microwave radiation modulated at 7, 40 and 1000 Hz frequencies was applied at the field power density of 0.16 mW/cm². A relative change in the EEG power with and without radiation during 10 cycles was used as a quantitative measure. Experimental data demonstrated that modulated at 40 Hz microwave radiation enhanced EEG power in EEG alpha and beta frequency bands. No significant alterations were detected at 7 and 1000 Hz modulation frequencies. These results are in good agreement with the theory of parametric excitation of the brain bioelectric oscillations caused by the periodic alteration of neurophysiologic parameters and support the proposed mechanism. The proposed theoretical framework has been shown to predict the results of experimental study. The suggested mechanism, free of the restrictions related to field strength or time constant, is the first one providing explanation of low-level microwave radiation effects.     

Efficiency of bio-indicators for low-level radiation under field conditions

Relatively little is known about biological consequences of natural variation in background radiation, and variation in exposure due to nuclear accidents, or even the long term consequences to human health stemming from the over-use of nuclear medicine and imaging technologies (i.e. CAT scans). This realization emphasizes the need for assessment and quantification of biological effects of radiation on living organisms. Here we report the results of an environmental analysis based on extensive censuses of abundance of nine animal taxa (spiders, dragonflies, grasshoppers, bumblebees, butterflies, amphibians, reptiles, birds, mammals) around Chernobyl in Ukraine and Belarus during 2006–2009. Background levels of radiation explained 1.5–26.5% of the variance in abundance of these nine taxa, birds and mammals having the strongest effects, accounting for a difference of a factor 18 among taxa. These effects were retained in analyses that accounted for potentially confounding effects. Effect size estimated as the amount of variance in abundance explained by background level of radiation was highly consistent among years, with weaker effects in years with low density. Effect sizes were greater in taxa with longer natal dispersal distances and in taxa with higher population density. These results are consistent with the hypotheses that costs of dispersal (i.e. survival) were accentuated under conditions of radioactive contamination, or that high density allowed detection of radiation effects. This suggests that standard breeding bird censuses can be used as an informative bio-indicator for the effects of radiation on abundance of animals.     

The action of ultraviolet radiation on yeast catalase

The effect of prolonged UV irradiation (mostly 2537 A) on the catalase activity of an aqueous yeast suspension was divisible into 4 periods. First, the period during which the cells lost their ability to form colonies, but during which no change in catalase activity was noted. Second, the period during which a considerable rise in catalase activity (Euler effect) occurred. The Euler effect was accompanied by enzyme alteration as shown by the simultaneous decrease in the activation energy of the enzyme-substrate system. However, during the initial phase of this period, as the catalase activity of the suspension began to increase, the activation energy rose to a transient level higher even than that characterizing the unaltered enzyme. Heat accelerated the rate of alteration when applied either during or after the irradiation; the activation energy for the over-all alteration reaction was 24 kcal., a value close to that recorded previously for alteration induced by chemical agents. Nevertheless, the rate-limiting step appeared to be different in the two cases. A model of these events was presented in which the primary photochemical action was on the site at which catalase is located within the cell. Third, a rather long period during which irradiation led to no diminution in the catalase activity of the maximally active suspension. This protection effect was duplicated in intro by a model crystalline catalase-KNA system, or by adding either ribonuclease digestion products of RNA or adenine to a catalase solution prior to irradiation. Evidence was adduced that the protection effect was not a simple screening, but involved some sort of interaction between the enzyme and the nitrogenous components of RNA, an interaction which must likewise occur within the cell. Alteration induced by CHCl₃ did not eliminate the protection effect, but that by butanol did. The onset of photoinactivation was due to modification of protein structure, not of RNA. Fourth, the period of photoinactivation of the intracellular enzyme, which was quite similar to that of the crystalline enzyme in vitro.     

The effects of low-level radiofrequency and microwave radiation on brain tissue and animal behaviour

There has been much public interest and controversy about the effects of exposure to low levels of microwave and radiofrequency radiation. Of particular interest are reports of radiation-induced changes in brain tissue and animal behaviour. This review considers the evidence supporting some of these effects. The main conclusions of the review are: The levels of tracer substances in the brain tissue of conscious or anaesthetized animals can be altered by acute exposure to microwave radiation that is sufficient to raise the brain temperature by several degrees Celsius. However, the results of such experiments are difficult to interpret, being in some cases contradictory or influenced by various confounding factors, and the data cannot be considered sufficient to recommend a threshold for human tolerance. The evidence that calcium ion exchange in living nervous tissues is affected by amplitude-modulated radiofrequency and microwave radiation is inconclusive. Exposure sufficient to cause an increase in core temperature of about 1 degree C, corresponding to specific energy absorption rates of about 2-8 W kg-1 may adversely affect animal behaviour.     

The body distribution and biological action of xenobiotics

The authors explored the tissue and intracellular distribution in the body of xenobiotics (aniline-1-14C hydroclorate, dioxane-1,4-14C, toluol-1-14C, phenol-1-14C and 1,2-14C ethylene glycol) following their administration in single doses to white rats. The distribution of the tested substances in the body was correlated with their toxic effects. An analysis of distribution coefficients revealed a multifactorial nature of the distribution in the body of xenobiotics--environmental pollutants. A key role in the distribution of xenobiotics in the body is attributed to histohematic barriers which provide for the selective accumulation of xenobiotics in tissues by utilizing existing modes of active and passive membrane transport. The polytropic nature of the biological effects typical of most chemical environmental pollutants is accounted for by their multireceptor interactions in the body as well as by membrane damage resulting in the distortion of genetic information and, consequently, disorganization of metabolic processes.     

Discrimination between different types of low-level luminescence in mammalian cells: The biophysical radiation

Cellular low-level luminescence was measured after various disintegrative processes in brain cell preparations. In addition to known origins of low-level luminescence, e.g. oxygen radical reactions or enzymatic and non-enzymatic redox systems, a further source of photon emission is reported which is independent of external oxygen, oxygen radicals and enzyme activities. Vital cells from rat brain homogenates or pig oligodendrocytes could be kept for hours at 37 °C without any photon emission. Only after disintegrative processes a cellular photon emission could be induced. The maximal intensity of about 400 impulses/s/mg protein and a total radiation of about 6 × 10⁶ I/mg depended on the type of cells. The signal could be retained completely at 4 °C or in frozen samples. Heating (10 min, 90 °C) did not suppress the photon emission. Luminol and lucigenin did not amplify the signal as is usually observed in oxygen radical-producing cells. Non-specific radical scavengers as well as detergents suppressed the cellular photon emission completely. It is suggested that this cellular luminescence represents a biophysical radiation which originates from the interruption of an intermolecular radiationless energy transfer.     

Cytogenetic monitoring of hospital workers exposed to low-level ionizing radiation

In the present study the cytogenetic effects in hospital workers exposed to low-level radiation were evaluated. Samples of peripheral blood were collected from 63 subjects working in radiodiagnostics and from 30 subjects, working in the same hospitals, who were used as controls. A higher number of cells with chromosome-type aberrations (CA) was observed in the exposed workers vs. the controls and the difference was statistically significant (p less than 0.05). No correlation was, on the contrary, found between CA and years of exposure. A significant difference was observed in the incidence of cells with CA between smokers and non-smokers, but in the control group only. In contrast, in the workers exposed to ionizing radiation, the frequency of cells with CA was very similar in smokers and non-smokers.     

Protein synthesis modulates the biological effectiveness of the combined action of hyperthermia and high-LET radiation.

The combined effects of heavy-ion radiation and hyperthermia on the survival of CHO-SC1 cells and its temperature-sensitive (ts) mutant tsH1 cells were studied using accelerated neon ions followed by mild heating at 41.5 degrees C. The sequence of application of heat and high-LET radiation is significant to cell-killing effects. Heat applied to cells prior to irradiation with neon plateau ions (LET = 32 keV/microns) was less effective than heat applied immediately after irradiation. The ability of cells to synthesize new proteins plays a key role in this sequence-dependent thermal sensitization. When protein synthesis was shut down in tsH1 cells, the thermal enhancement of cell killing by high-LET radiation was the same regardless of the sequence. The thermal enhancement of radiation-induced cell killing was LET-dependent for the SC1 cells, but this was not clearly demonstrated in the tsH1 cells. Furthermore, the RBE of heated SC1 cells varied with LET and reached a maximum of greater than 3 at 80 keV/microns. In the absence of protein synthesis, the maximum RBE value was reduced to 2.6. These results suggest that the accumulation of cellular damage caused by exposure to densely ionizing particles with increasing LETs can be potentiated with active protein synthesis during postirradiation heat treatment.