Radiation Induces Distinct Changes in Defined Subpopulations of Neural Stem and Progenitor Cells in the Adult Hippocampus

While irradiation can effectively treat brain tumors, this therapy also causes cognitive impairments, some of which may stem from the disruption of hippocampal neurogenesis. To study how radiation affects neurogenesis, we combine phenotyping of subpopulations of hippocampal neural stem and progenitor cells with double- and triple S-phase labeling paradigms. Using this approach, we reveal new features of division, survival, and differentiation of neural stem and progenitor cells after exposure to gamma radiation. We show that dividing neural stem cells, while susceptible to damage induced by gamma rays, are less vulnerable than their rapidly amplifying progeny. We also show that dividing stem and progenitor cells that survive irradiation are suppressed in their ability to replicate 0.5–1 day after the radiation exposure. Suppression of division is also observed for cells that entered the cell cycle after irradiation or were not in the S phase at the time of exposure. Determining the longer term effects of irradiation, we found that 2 months after exposure, radiation-induced suppression of division is partially relieved for both stem and progenitor cells, without evidence for compensatory symmetric divisions as a means to restore the normal level of neurogenesis. By that time, most mature young neurons, born 2–4 weeks after the irradiation, still bear the consequences of radiation exposure, unlike younger neurons undergoing early stages of differentiation without overt signs of deficient maturation. Later, 6 months after an exposure to 5 Gy, cell proliferation and neurogenesis are further impaired, though neural stem cells are still available in the niche, and their pool is preserved. Our results indicate that various subpopulations of stem and progenitor cells in the adult hippocampus have different susceptibility to gamma radiation, and that neurogenesis, even after a temporary restoration, is impaired in the long term after exposure to gamma rays. Our study provides a framework for investigating critical issues of neural stem cell maintenance, aging, interaction with their microenvironment, and post-irradiation therapy

Spatiotemporal 3D image registration for mesoscale studies of brain development

Comparison of brain samples representing different developmental stages often necessitates registering the samples to common coordinates. Although the available software tools are successful in registering 3D images of adult brains, registration of perinatal brains remains challenging due to rapid growth-dependent morphological changes and variations in developmental pace between animals. To address these challenges, we introduce CORGI (Customizable Object Registration for Groups of Images), an algorithm for the registration of perinatal brains. First, we optimized image preprocessing to increase the algorithm's sensitivity to mismatches in registered images. Second, we developed an attention-gated simulated annealing procedure capable of focusing on the differences between perinatal brains. Third, we applied classical multidimensional scaling (CMDS) to align ("synchronize") brain samples in time, accounting for individual development paces. We tested CORGI on 28 samples of whole-mounted perinatal mouse brains (P0-P9) and compared its accuracy with other registration algorithms. Our algorithm offers a runtime of several minutes per brain on a laptop and automates such brain registration tasks as mapping brain data to atlases, comparing experimental groups, and monitoring brain development dynamics

DALMATIAN: An Algorithm for Automatic Cell Detection and Counting in 3D

Current 3D imaging methods, including optical projection tomography, light-sheet microscopy, block-face imaging, and serial two photon tomography enable visualization of large samples of biological tissue. Large volumes of data obtained at high resolution require development of automatic image processing techniques, such as algorithms for automatic cell detection or, more generally, point-like object detection. Current approaches to automated cell detection suffer from difficulties originating from detection of particular cell types, cell populations of different brightness, non-uniformly stained, and overlapping cells. In this study, we present a set of algorithms for robust automatic cell detection in 3D. Our algorithms are suitable for, but not limited to, whole brain regions and individual brain sections. We used watershed procedure to split regional maxima representing overlapping cells. We developed a bootstrap Gaussian fit procedure to evaluate the statistical significance of detected cells. We compared cell detection quality of our algorithm and other software using 42 samples, representing 6 staining and imaging techniques. The results provided by our algorithm matched manual expert quantification with signal-to-noise dependent confidence, including samples with cells of different brightness, non-uniformly stained, and overlapping cells for whole brain regions and individual tissue sections. Our algorithm provided the best cell detection quality among tested free and commercial software

Synthetic Thymidine Analog Labeling without Misconceptions

Tagging proliferating cells with thymidine analogs is an indispensable research tool; however, the issue of the potential in vivo cytotoxicity of these compounds remains unresolved. Here, we address these concerns by examining the effects of BrdU and EdU on adult hippocampal neurogenesis and EdU on the perinatal somatic development of mice. We show that, in a wide range of doses, EdU and BrdU label similar numbers of cells in the dentate gyrus shortly after administration. Furthermore, whereas the administration of EdU does not affect the division and survival of neural progenitor within 48 h after injection, it does affect cell survival, as evaluated 6 weeks later. We also show that a single injection of various doses of EdU on the first postnatal day does not lead to noticeable changes in a panel of morphometric criteria within the first week; however, higher doses of EdU adversely affect the subsequent somatic maturation and brain growth of the mouse pups. Our results indicate the potential caveats in labeling the replicating DNA using thymidine analogs and suggest guidelines for applying this approach

Выявление особенностей фазовых и структурных превращений при углеродотермии молибденового концентрата

We have studied patterns in the influence of O/C in the charge on the content of C, O2, and Mo in metallized molybdenum concentrate after different temperatures of thermal treatment. it was determined that O/C at 1.75‒2.00 in the charge after treatment at 1,223–1,423 K provides for the content of Mo in metallized molybdenum concentrate at 74.6–78.0 % by weight. The content of C and O2 was 0.5–2.0 % by weight, and 0.6–5.5 % by weight, respectively. At O/C in the charge at 2.50, the products of reduction after heat treatment at 1,323 K consisted of Mo and MoO2. The residual molybdenum-containing oxide component is due to the insufficient amount of a reducing agent. The presence in the phase composition of carbide Mo2C together with Mo was found at O/C in the charge at 1.33, indicating a certain excess of the carbon reducing agent. The most favorable conditions for reduction were ensured at O/C in the charge at the level of 1.83 with a transition of most of the oxides to the metal phase of Mo. We have obtained a spongy structure of the metallized product, which ensures an increased rate of dissolving the obtained molybdenum-containing additive in a liquid metal at alloying. We did not identify in the phase composition any compounds susceptible to sublimation, which predetermines a reduction in the losses of Mo when using an alloying additive.Определено влияние O/C шихты на состав металлизованного молибденового концентрата после обработки при 1223–1423 K. Наиболее выгодным является O/C в пределах 1,75–2,00, обеспечивая относительно низкие остаточные C, O2 и преобладание Mo в фазовом составе. Структура неоднородная из спеченных микрочастиц. Не выявлено соединений, склонных к сублимации. Это обуславливает снижение потерь Mo при использовании легирующей добавки, что подтверждено в опытно-промышленных условияхВизначено вплив O/C шихти на склад металізованого молібденового концентрату після обробки при 1223–1423 K. Найбільш вигідним є O/C в межах 1,75–2,00, забезпечуючи відносно низькі залишкові C, O2 і переважання Mo у фазовому складі. Структура неоднорідна із спечених мікрочасток. Не виявлено з’єднань, схильних до сублімації. Це обумовлює зниження втрат Mo при використанні легуючої добавки, що підтверджено в дослідно-промислових умова

Выявление особенностей фазовых и структурных превращений при углеродотермии молибденового концентрата

We have studied patterns in the influence of O/C in the charge on the content of C, O2, and Mo in metallized molybdenum concentrate after different temperatures of thermal treatment. it was determined that O/C at 1.75‒2.00 in the charge after treatment at 1,223–1,423 K provides for the content of Mo in metallized molybdenum concentrate at 74.6–78.0 % by weight. The content of C and O2 was 0.5–2.0 % by weight, and 0.6–5.5 % by weight, respectively. At O/C in the charge at 2.50, the products of reduction after heat treatment at 1,323 K consisted of Mo and MoO2. The residual molybdenum-containing oxide component is due to the insufficient amount of a reducing agent. The presence in the phase composition of carbide Mo2C together with Mo was found at O/C in the charge at 1.33, indicating a certain excess of the carbon reducing agent. The most favorable conditions for reduction were ensured at O/C in the charge at the level of 1.83 with a transition of most of the oxides to the metal phase of Mo. We have obtained a spongy structure of the metallized product, which ensures an increased rate of dissolving the obtained molybdenum-containing additive in a liquid metal at alloying. We did not identify in the phase composition any compounds susceptible to sublimation, which predetermines a reduction in the losses of Mo when using an alloying additive.Определено влияние O/C шихты на состав металлизованного молибденового концентрата после обработки при 1223–1423 K. Наиболее выгодным является O/C в пределах 1,75–2,00, обеспечивая относительно низкие остаточные C, O2 и преобладание Mo в фазовом составе. Структура неоднородная из спеченных микрочастиц. Не выявлено соединений, склонных к сублимации. Это обуславливает снижение потерь Mo при использовании легирующей добавки, что подтверждено в опытно-промышленных условияхВизначено вплив O/C шихти на склад металізованого молібденового концентрату після обробки при 1223–1423 K. Найбільш вигідним є O/C в межах 1,75–2,00, забезпечуючи відносно низькі залишкові C, O2 і переважання Mo у фазовому складі. Структура неоднорідна із спечених мікрочасток. Не виявлено з’єднань, схильних до сублімації. Це обумовлює зниження втрат Mo при використанні легуючої добавки, що підтверджено в дослідно-промислових умова

Suppressed neurogenesis without cognitive deficits: effects of fast neutron irradiation in mice.

This study assessed the effects of combined low-dose neutron and γ-ray irradiation on hippocampal neurogenesis and hippocampal-dependent memory. Neural progenitor cell division and survival were evaluated in brain sections and whole hippocampal preparations following head irradiation at a dose of 0.34 Gy for neutron radiation and 0.36 Gy for γ-ray radiation. Hippocampal-dependent memory formation was tested in a contextual fear conditioning task following irradiation at doses of 0.4 Gy for neutron radiation and 0.42 Gy for γ-ray radiation. Cell division was suppressed consistently along the entire dorsoventral axis of the hippocampus 24 h after the irradiation, but quiescent stem cells remained unaffected. The control and irradiated mice showed no differences in terms of exploratory behavior or anxiety 6 weeks after the irradiation. The ability to form hippocampus-dependent memory was also unaffected. The data may be indicative of a negligible effect of the low-dose of fast neutron irradiation and the neurogenesis suppression on animal behavior at 6 weeks after irradiation