[Disproportionate eruption of maxillary and mandibular incisors in the long-tailed ground squirrel].

Abstract-The surface of the maxillary and mandibular incisors of Spermophilus undulatus long-tailed ground squirrels, including those born in the current year and those that have hibernated (trapped one month or later after hibernation) is studied. The presence of daily growth on the incisors' surface allows the evaluation of their eruption rate; a specific change in the character of the incisors' eruption corresponds to winter hibernation (hibernation zone), which serves as the time mark. Correlation between the eruption rates of the maxillary and mandibular incisors typical for rodents is found in yearlings and some animals after hibernation.

Dynamics of radionuclide concentrations in calcified tissues of reindeer in the western Russian Arctic.

The specific activities of artificial and natural nuclides were determined in bone and teeth of reindeer that had lived before, during, and after nuclear tests on the Archipelago Novaya Zemlya and of reindeer from the nearby mainland region. In bone of reindeer from Novaya Zemlya, 90Sr and 210Pb are the main source of beta-activity, the 210Po is the main source of the alpha activity. In bone of reindeer that lived on Novaya Zemlya during underground tests, the 90Sr activity was relatively high (0.

Relationships between ESR-evaluated doses estimated from enamel and activity of radionuclides in bone and teeth of reindeer.

Doses of radiation estimated from ESR analysis of tooth enamel were compared with activities of alpha- and beta-emitters in enamel and in bone tissue of mandibles of 77 reindeer from populations with different levels of radiation contamination. Contribution of the radionuclides incorporated into bone (or bone-seeking radionuclides in food) to ESR-evaluated doses was substantial and the contribution of the radionuclides incorporated into enamel itself proved to be relatively small.

[The dynamics of the radiation load on reindeer on Novaya Zemlya].

The ESR analysis was carried out aiming at studying the activity of radionuclides in the dental enamel, dentin, and mandible bone tissues of reindeer of Novaya Zemlya. Doses of absorbed ionizing radiation were assessed. It was determined that the doses obtained by reindeer during underground nuclear tests were ten times higher and the activity of 90Sr was greater than those for reindeer living after the nuclear tests were suspended.

Estimation of accumulated dose of radiation by the method of ESR-spectrometry of dental enamel of mammals.

ESR-spectrometry was used to investigate radiation-induced paramagnetic centers in enamel of mammals: carnivores (polar bear and fox), ungulates (reindeer, European bison, moose), and man. Values at half the microwave power saturation of the radiation signal, P1/2, evaluated at room temperature, was found to range from 16 to 26 mW for animals and man. A new approach to discrimination of the radiation induced signal from the total ESR spectrum of reindeer enamel is proposed.

Radiation dosage accumulated by reindeer from Novaya Zemlya.

ESR spectrometry of tooth enamel revealed a significant difference in accumulated radiation dose between reindeer which lived on Novaya Zemlya when underground nuclear tests were performed there and those which lived there after the tests were stopped.

[New prospects in assessing the absorbed radiation dose by electron paramagnetic resonance].

Spin-lattice relaxation rates of radiation induced and background centers in dental enamel have been investigated by electron spin resonance techniques. It has been found that these centers differ in the value of the saturation half-power and the saturation process. Based on these experimental results a new approach to discrimination of the radiation induced signal from the total ESR spectrum of dental enamel is proposed.

[Cumulative radiation dosage and epidemiological research in the Chernobyl region].

Individual biological dosimetry covering chromosomal analysis and electronic paramagnetic resonance spectrometry has been performed in 1300 subjects exposed to ionizing radiation after the Chernobyl accident. Cumulative radiation doses above 40 ImC were registered in 5%, about 100 ImC in 1% of the examinees. In 1% of cytogenetic investigations there appeared multiaberrant cells indicative of hot particle incorporation.

[Determining the accumulated dose of gamma radiation in the tooth enamel].

Following ideas of Japanese and Canadian scientists the authors tried to develop practical application of dental enamel for dosimetry of gamma-radiation accumulated by an individual. Human teeth were irradiated in vitro with gamma-rays of 60Co and with x-rays, and the amount of free radicals in ++non-caries enamel was measured on an ESR spectrometer. Linear regression ESR signals on dose of radiation within an interval of 0.

[Diurnal layer formation in the incisor dentin of rodents].

The growth of dentin of the constantly growing lower incisors in rodents was studied using tetracycline as a vital marker of the growing parts of bones and teeth. In the common vole in nature the incisors grow in length at a rate of 490 micrometers per day; a basal-apical gradient of growth of the tooth walls in thickness was found: the minimal daily increment at the tooth base and the maximal in the apical third, it decreases again at the very apex. In the peripulp part of dentin of the apical incisor half there are diurnal layers seen both on polished sections and stained slides the formation of which correlates with the diurnal rhythm of skeleton growth.