Telomeric small RNAs related to PIWI-interacting RNAs (piRNAs) have been described in various eukaryotes; however, their role in germline-specific telomere function remains poorly understood. Using a Drosophila model, we performed an in-depth study of the biogenesis of telomeric piRNAs and their function in telomere homeostasis in the germline. To fully characterize telomeric piRNA clusters, we integrated the data obtained from analysis of endogenous telomeric repeats, as well as transgenes inserted into different telomeric and subtelomeric regions. The small RNA-seq data from strains carrying telomeric transgenes demonstrated that all transgenes belong to a class of dual-strand piRNA clusters; however, their capacity to produce piRNAs varies significantly. Rhino, a paralog of heterochromatic protein 1 (HP1) expressed exclusively in the germline, is associated with all telomeric transgenes, but its enrichment correlates with the abundance of transgenic piRNAs. It is likely that this heterogeneity is determined by the sequence peculiarities of telomeric retrotransposons. In contrast to the heterochromatic non-telomeric germline piRNA clusters, piRNA loss leads to a dramatic decrease in HP1, Rhino, and trimethylated histone H3 lysine 9 in telomeric regions. Therefore, the presence of piRNAs is required for the maintenance of telomere chromatin in the germline. Moreover, piRNA loss causes telomere translocation from the nuclear periphery toward the nuclear interior but does not affect telomere end capping. Analysis of the telomere-associated sequences (TASs) chromatin revealed strong tissue specificity. In the germline, TASs are enriched with HP1 and Rhino, in contrast to somatic tissues, where they are repressed by Polycomb group proteins. piRNAs play an essential role in the assembly of telomeric chromatin, as well as in nuclear telomere positioning in the germline. Telomeric arrays and TASs belong to a unique type of Rhino-dependent piRNA clusters with transcripts that serve simultaneously as piRNA precursors and as their only targets. Telomeric chromatin is highly sensitive to piRNA loss, implying the existence of a novel developmental checkpoint that depends on telomere integrity in the germline.

Furaneol is an aroma compound which occurs naturally in foods and is used as an artificial flavor. Detection of furaneol is required in food science and food processing industry. Capture- Systematic Evolution of Ligands by EXponential enrichment (SELEX) protocol was applied for the isolation of an aptamer binding to furaneol, a small volatile organic substance contributing to the flavor of various products. Thirteen cycles of selection were performed. The resulting DNA pool was cloned, using blunt-end cloning, and ninety-six plasmids were sequenced and analyzed. Eight oligonucleotides were selected as aptamer candidates and screened for the ability to bind to furaneol, using three different methods—magnetic-beads associated elution assay, SYBR Green I assay, and exonuclease protection assay. One of the candidates was further characterized as an aptamer. The apparent equilibrium constant was determined to be (1.1 ± 0.4) µM, by the fluorescent method. The reported aptamer was applied for development of the ion-sensitive field-effect transistor (ISFET)-based biosensor, for the analysis of furaneol, in the concentration range of 0.1–10 µM.

In order to study the FLASH effect using live models, this work compared proton-induced damage to embryos (nine days after fertilization) and one-day-old chicks (18 days after fertilization) from irradiated at different dose rates eggs of Japanese quail (Coturnix coturnix japónica). Eggs were irradiated with protons in different modes depending on the dose rate: in a conventional mode (<1 Gy/s, CONV), in a flash mode (∼100 Gy/s, FLASH) and in a single-pulse flash mode (∼10⁵ Gy/s SPLASH). By the criteria of body weight and length, as well as the number of erythrocytes with micronuclei in nine-day-old embryos from eggs irradiated in the spread-out Bragg peak (SOBP) (8.5 Gy), FLASH and SPLASH modes were found to be less traumatic compared with the CONV mode. Among all irradiated embryos, the maximum body weight and length were observed in the SPLASH mode. The lowest death incidence and the smallest number of abnormal erythrocytes were recorded after FLASH and SPLASH irradiation. In chicks that hatched from eggs irradiated in the CONV mode, a tendency for an increase in the number of abnormal erythrocytes was observed. The speed of movement of chicks from FLASH- and SPLASH-irradiated eggs was comparable with that from unirradiated eggs, while chicks from eggs irradiated in the CONV mode were less active than all others. The proton irradiation of eggs in SOBP using high dose-rate modes is less damaging for healthy tissues and for the development of embryos and chicks on the cellular, anatomical, and physiological levels.

Among the methods for increasing the specificity of tumor radiotherapy, FLASH radiotherapy (FLASH-RT) stands out, having recently entered clinical trials. A distinctive feature of this treatment method is the delivery of a therapeutic dose in a fraction of a second with a typical mean dose rate greater than 40 Gy/s. In addition to improved patient comfort and a shorter hospital stay, this therapy potentially carries a lower risk of radiation-related side effects due to reduced damage to normal tissues. Numerous preclinical and in vivo laboratory trials of FLASH-RT have demonstrated that, in addition to reducing the severity of radiation-related complications, FLASH radiotherapy has antitumor efficacy similar to conventional radiotherapy. Partly reduced radiotoxicity after such a dose rate delivery obtained, in a broader radiobiological sense, an eponymous term FLASH effect. Although the first clinical trials aimed to evaluate the safety and efficiency of FLASH-RT against bone metastases (FAST-01/02), melanoma skin metastases (IMPulse, Flash-Skin I), Squamous Cell Carcinoma, or Basal Cell Carcinoma (LANCE) have already started or even finished and showed promising results (FAST-01), the radiobiological basis of the FLASH effect is far from a complete explanation. The fundamental factors explaining the nature of the FLASH effect are mainly considered to be the following: (1) changes in the balance of water radiolysis products and a decrease in the generation of stable reactive oxygen species (ROS), (2) differential oxygen depletion, depending on the initial oxygen concentration in tissues, and (3) physiological and metabolic, gene expression and probably epigenetic shifts in response to irradiation in normal and tumor cells. The main purpose of this review is the systematization of the radiobiological manifestations of the FLASH effect together with a consideration of the elementary processes laying in the basis of the FLASH effect in order to actualize rationale and future application developments of FLASH-RT.

The study of biological effects of high-dose-rate ionizing radiation using animal models remains an urgent problem. In the work, a comparison of proton-induced damage to embryos (the 9 ^th post-fertilization day) and 1-day-old baby chicks (the 18 ^th post-fertilization day) from irradiated eggs of Japanese quail ( Coturnix coturnix japónica ) irradiated in and outside the Bragg peak with the conventional and ultra-high dose rate D (CONV D < 1 Gy/s, FLASH D ∼100 Gy/s and single-pulse flash - SPLASH D ∼10 ⁶ Gy/s, respectively) was carried out. The following criteria were used: survival, body weight and body length of embryos, weight of chicks, percentage of erythrocytes with anomalies (with micronuclei, without nuclei, with two nuclei), and the speed of movement of 1-day-old chicks in the open field test. The largest number of dead embryos was recorded after irradiation with 7 and 14 Gy in the plateau region of the proton trajectory. By the criteria of body weight and length, as well as the number of erythrocytes with micronuclei in 9-day-old embryos from eggs irradiated with a dose of 8.5 Gy in the Bragg peak, FLASH and SPLASH modes were found to be the least traumatic compared with the CONV mode. The weight of chicks from eggs irradiated with a dose of 4 Gy in the Bragg peak did not differ from the control and did not depend on the irradiation mode. The lowest death incidence and the smallest number of abnormal erythrocytes were recorded after FLASH and SPLASH irradiation; in chicks that hatched from eggs irradiated in the CONV mode, a tendency for an increase in the number of abnormal erythrocytes was observed. The speed of movement of chicks from FLASH- and SPLASH-irradiated eggs was comparable with that from unirradiated eggs, and chicks from eggs irradiated in the CONV mode were less active than chicks from unirradiated eggs and eggs irradiated in the other regimes. Thus, the irradiation of eggs with a beam of accelerated protons in the Bragg peak in the FLASH/SPLASH modes is less damaging for healthy tissues and for the development of embryos and chicks on the cellular, anatomical, and physiological levels.

The use of ultra-high dose-rate ionizing radiation, termed FLASH irradiation (≥40 Gy/s), contributes to healthy tissue sparing while maintaining tumor control compared to conventional dose rate irradiation. This review summarizes current knowledge dedicated to studies of tumor and normal cell lines, animals including tumor-bearing ones irradiated in conventional and FLASH dose rate irradiation modes. As a comparison, data on FLASH irradiation with photons, electrons, protons, helium and carbon ions are also presented. The biophysical, molecular biological and immunological aspects of FLASH effect which are essential for understanding the radiation-induced processes in cells and tissues in order to improve radiotherapy of tumors are discussed.