Variation of long-lived free radicals responsible for the EPR native signal in bone of aged or diseased human females and ovariectomized adult rats.

The purpose of this study was to gain insights into the variations seen in the electron paramagnetic resonance (EPR) spectroscopy of the native signals of teeth and bones used for retrospective dosimetry measurements. We determined that changes occur in the long-lived free radicals responsible for the native signal of cortical bone in aging or diseased human females and aged ovariectomized rats. This was done by measuring the magnitude of the broad (BC) and narrow (NC) components of the native EPR signal of bone following chemical extraction, aging, crushing and thermal annealing. Bone from the upper midshaft of femora of young (17-34 years old, n=5) and elderly (70-92 years old, n=18) females was examined. The results showed that the elderly women had significantly higher BC than the younger women (P<0.01). A similar interpretation was made of the data from an aging female rat osteoporosis model. The results for the NC signals were similar. Finally, dramatic decreases in both NC and BC signals were seen in HIV positive and uncontrolled diabetic (one each) patients indicating the need for studying this signal for a broad spectrum of metabolic disorders. Experiments were performed which strongly indicate that iron liganded with organic molecules is the source of the BC signal. Finally, the accuracy achieved in this study indicates that resolving the dosimetric signal (g=2.0018) should be improved by subtraction of the deconvoluted NC and BC signals from the original spectrum.

New approaches for study of mechanisms of bone demineralization due to microgravity.

NASA: Changes in nano-scale subsystems of rat femurs due to the axial unloading of hindlimbs are studied by means of electron paramagnetic resonance (EPR). After irradiation by 60Co isotopes, the results indicate that weightlessness simulation leads to formation of free radicals in tropocollagen molecules and to a reduction in the amount of CO2 radicals, located on the surface of bioapatite nanocrystals.^ieng

Temperature stability of carbonate groups in tooth enamel.

The tooth enamel EPR signal at g = 1.9973 consists of several components, which correspond to different functions of the spatial orientation of the CO2- radicals, have different temperature stability and different saturation curves. Using a new technique described in this paper, we have detected and investigated two groups of CO2- radicals with different thermal stability and saturation characteristics.

[Minerals of biological origin: their structural formation and properties]. / Mineraly biologicheskogo proiskkhozhdeniia: formirovanie struktury i svoistv.

A study is presented of human tooth enamel and its changes during heating. The measurements were done by methods of electron paramagnetic resonance, roentgen structural analysis and gaseous chromatography. A new effect has been found related to changes of enamel structure during heating. It was established that at T 170 degrees C there occurs reorientation of the crystallites of hydrohylapatite that form the structure of tooth enamel as well as changes of the properties of organic layers between these crystallites. Discussed are the general principles determining the structure and properties of minerals of biological origin. It is shown that the organic structure of the biomineral effects the properties of inorganic crystallites by means of the spatial geometric factor. This factor is finally related to the fact, that superficial energy of the crystallite contributes essentially in its general energy. The authors discuss the obtained results from the viewpoint of diagnosis and new treatment methods of diseases related to the biomineral of the human body.