Renewal versus Retention: Isotopic Composition of Intestinal Epithelium and Eye Lens

Aims: To compare isotopic signatures of contrasting (due to the structure and metabolism) organs in mice of two contrasting ages. Study Design: Cross-sectional study. Place and Duration of Study: Biology Department of Moscow State University; Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences; 2007–2011. Methodology: Mass spectrometric measurements of carbon and nitrogen isotopic ratios of jejunal epithelium and lens in 1- and 22-mo mice fed a monotonous diet. Results: The lenses are enriched in carbon and nitrogen as compared with intestinal epithelium (by 5.5% and 4.5% in 1-mo mice and 8.3% and 6% in 22-mo mice, respectively). The 15N content is also higher in lenses than in intestinal epithelium (8.97‰ vs. 7.62‰ in 1-mo mice, and 7.40‰ vs. 6.58‰ in 22-mo mice). The 13C content of lenses exceeds that of intestinal epithelium in 1-mo mice (-20.27‰ vs. -21.69‰), although 13C content is equal in 22-mo mice (-22.56‰ vs. -22.67‰). 15N content is depleted in the intestinal epithelium of 22-mo mice (-1.04‰), whereas 13C depletion (-0.98‰) is non-significant. 13C and 15N content in lenses is also significantly decreased in 22-mo mice (-2.29‰ and -1.57‰). Conclusion: The intestinal epithelium represents a structure with short-term isotopic memory lasting a few days, whereas the events of the organism’s entire lifetime are retained in lens isotopic memory. The difference of the parameters measured is evidently determined by structural contrast, metabolic rate, and rejuvenation modes of the tissues. The 15N depletion in both the intestinal epithelium and lenses, as well as 13C depletion in lenses of 22-mo mice might be considered as a sign of ageing. In contrast, the depletion of 15N in lenses of 22-mo mice should be considered primarily as a result of dilution of breastmilk isotopic signature that probably obscures age-related alterations of the organ. Comparison of isotopic compositions of these contrasting organs may be useful for physiological and ecological determinations

Maternal - Fetal Interaction: An Insight through the Stable Isotope Fractionation Prism

Aims: To compare carbon and nitrogen isotopic composition of maternal and fetal organs. Study Design: Cross-sectional study. Place and Duration of Study: Biology Department of Lomonosov Moscow State University; Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences; 2008 – 2011. Methodology: Mass spectrometric measurements of carbon and nitrogen isotopic ratios of corresponding maternal and fetal organs of gravid mice fed a monotonous diet. Results: Both the maternal and fetal organs (kidney, muscles, liver, myocardium, brain) of mice at the last term of gestation are enriched in 13C and 15N relative to food consumed. Isotopic composition of organs strongly depends on the number of bearing fetuses. The increase of fetuses’ number results in coordinated 13C depletion and 15N enrichment in both the maternal and fetal organs. Conclusion: The alteration of the δ13C and δ15N values reflects solely the metabolic restructuring during a pregnancy, since mice were fed the monotonous diet prior to conception and during gestation. Isotopic alterations develop as a reaction to the nutritional stress of the maternal organism under the trophic demands of fetuses. The protein replenishment is the most probable cause of isotope ratio changes. Under the controlled experimental condition the stable Isotope composition of biogenic elements can be used as integral indicators of metabolic efforts of the particular organismic structures. The predictive role of such integral indicators consists at least in limitation of possible biochemical conversions underlying the metabolism change

Registration of the transition radiation with GaAs detector: Data/MC comparison

New developments of pixel detectors based on GaAs sensors offer effective registration of the transition radiation (TR) X-rays and perform simultaneous measurements of their energies and emission angles. This unique feature opens new possibilities for particle identification on the basis of maximum available information about generated TR photons. Results of studies of TR energy-angular distributions using a 500 um thick GaAs sensor attached to a Timepix3 chip are presented. Measurements, analysis techniques and a comparison with Monte Carlo (MC) simulations are described and discussed