Programmed cell death occurs in browning explants of Fraxinus mandshurica during somatic embryogenesis, but the underlying mechanism is unclear. In this study, single cotyledons of zygotic embryos of F. mandshurica we...Programmed cell death occurs in browning explants of Fraxinus mandshurica during somatic embryogenesis, but the underlying mechanism is unclear. In this study, single cotyledons of zygotic embryos of F. mandshurica were used as explants. Mitochondrial structure and function, caspase-3-like protease activity, hydrogen peroxide metabolism, and nitric oxide accumulation induced by high concentrations of sucrose and plant growth regulators were studied. The results show that plant growth regulators induced somatic embryogenesis and also promoted explant browning. High sucrose concentrations had similar effects. High concentrations of sucrose and plant growth regulators led to the accumulation of hydrogen peroxide and nitric oxide which induced changes in mitochondrial structure and function such as modifications in mitochondrial morphology, increased membrane permeability, decreased membrane potential, and the release of cytochrome c into the cytoplasm. An increase in caspase-3-like protease activity triggered programmed cell death in some browning explant cells. During somatic embryogenesis there were increased activities of superoxide dismutase, peroxidase, and catalase, which are associated with hydrogen peroxide metabolism and jointly maintain reactive oxygen species levels. Intracellular nitric oxide synthase and nitrate reductase activities were not significantly correlated with nitric oxide content. Instead, intracellular nitric oxide may be derived from non-enzymatic reactions. Our results indicate that hydrogen peroxide and nitric oxide may function as signals, playing key roles in somatic embryogenesis and programmed cell death of explant cells of F. mandshurica. The interaction between nitric oxide and reactive oxygen species determines the occurrence of programmed cell death in explant cells;somatic embryogenesis and programmed cell death are positively regulated by hydrogen peroxide. However, the regulation of nitric oxide is complex.展开更多
Experiments on stratification discussed here have revealed the mechanical nature of lamination as well as the role of turbulent current as agent of stratification. They challenge Steno’s principle that superposed str...Experiments on stratification discussed here have revealed the mechanical nature of lamination as well as the role of turbulent current as agent of stratification. They challenge Steno’s principle that superposed strata are successive sedimentary layers. They show that relative chronology should not be referred to as “stages” but as “sequences” of series. The rock formation studied by Lalomov shows that the duration of sedimentation could be considerably shorter than indicated by the Geological Time Scale. The latter scale corresponds to large marine transgressions and regressions that can result from the shift of polar axis following such major orogeneses as the Caledonian, Hercynian and Alpine.展开更多
Correction to:J.For.Res.https://doi.org/10.1007/s11676-021-01392-y In this article Ling Yang should have been denoted as a corresponding author.The original article has been corrected.Publisher’s Note Springer Nature...Correction to:J.For.Res.https://doi.org/10.1007/s11676-021-01392-y In this article Ling Yang should have been denoted as a corresponding author.The original article has been corrected.Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affi liations.展开更多
This study aimed to explore the optimal invisible orthodontic force system during the en-mass distalization of two maxillary molars to minimize the side effect of anchorage loss by changing the direction of the applic...This study aimed to explore the optimal invisible orthodontic force system during the en-mass distalization of two maxillary molars to minimize the side effect of anchorage loss by changing the direction of the application of the orthodontic force system.A high bio-fidelity 3D finite element model including maxilla,periodontal ligament,dentition,clear aligner,3D anchorage attachment and mini-implant was established.Different lengths of lateral hooks of 3D-printed anchorage attachments and mini-implant positions into the palatal alveolus were considered.A 200 g distal force was applied to the lateral hooks of different horizontal lengths(3.26 mm,6.52 mm and 9.78 mm)with the mini-implant as the application point.Using ABAQUS software,orthodontic tooth movements under 12 different clinical treatment designs were analyzed and calculated.The 3D anchorage attachment enhanced the anchorage of anterior teeth and alleviated the tipping/extrusion of premolars.In contrast to without clear aligners,length of the lateral hook had a negligible effect on both mesial tipping and buccal tipping with clear aligners,which could then be ignored.The change in mesial tipping was less and nearly remained constant despite of the different heights of the mini-implant.The 3D anchorage attachment assisted clear aligner can avoid the side effects of anterior tooth proclination caused by insufficient anchorage.The length of the lateral hook,and height of the mini-implant in this invisible orthodontic force system hardly affects the tooth movement of anchorage units.Clear aligners can effectively control the rotation and tipping of anchorage units caused by 3D anchorage attachment.展开更多
基金This work was supported by the Fundamental Research Funds for the Central Universities(2572018BW02)the Innovation Project of State Key Laboratory of Tree Genetics and Breeding(2016C01)+1 种基金the National Key R&D Program of China(2017YFD0600600)the National Natural Science Foundation of China(31400535 and 31570596).
文摘Programmed cell death occurs in browning explants of Fraxinus mandshurica during somatic embryogenesis, but the underlying mechanism is unclear. In this study, single cotyledons of zygotic embryos of F. mandshurica were used as explants. Mitochondrial structure and function, caspase-3-like protease activity, hydrogen peroxide metabolism, and nitric oxide accumulation induced by high concentrations of sucrose and plant growth regulators were studied. The results show that plant growth regulators induced somatic embryogenesis and also promoted explant browning. High sucrose concentrations had similar effects. High concentrations of sucrose and plant growth regulators led to the accumulation of hydrogen peroxide and nitric oxide which induced changes in mitochondrial structure and function such as modifications in mitochondrial morphology, increased membrane permeability, decreased membrane potential, and the release of cytochrome c into the cytoplasm. An increase in caspase-3-like protease activity triggered programmed cell death in some browning explant cells. During somatic embryogenesis there were increased activities of superoxide dismutase, peroxidase, and catalase, which are associated with hydrogen peroxide metabolism and jointly maintain reactive oxygen species levels. Intracellular nitric oxide synthase and nitrate reductase activities were not significantly correlated with nitric oxide content. Instead, intracellular nitric oxide may be derived from non-enzymatic reactions. Our results indicate that hydrogen peroxide and nitric oxide may function as signals, playing key roles in somatic embryogenesis and programmed cell death of explant cells of F. mandshurica. The interaction between nitric oxide and reactive oxygen species determines the occurrence of programmed cell death in explant cells;somatic embryogenesis and programmed cell death are positively regulated by hydrogen peroxide. However, the regulation of nitric oxide is complex.
文摘Experiments on stratification discussed here have revealed the mechanical nature of lamination as well as the role of turbulent current as agent of stratification. They challenge Steno’s principle that superposed strata are successive sedimentary layers. They show that relative chronology should not be referred to as “stages” but as “sequences” of series. The rock formation studied by Lalomov shows that the duration of sedimentation could be considerably shorter than indicated by the Geological Time Scale. The latter scale corresponds to large marine transgressions and regressions that can result from the shift of polar axis following such major orogeneses as the Caledonian, Hercynian and Alpine.
文摘Correction to:J.For.Res.https://doi.org/10.1007/s11676-021-01392-y In this article Ling Yang should have been denoted as a corresponding author.The original article has been corrected.Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affi liations.
基金This work was supported by the National Natural Science Foundation of China(Grant No.12072055,11872135,U20A20390,U22A20314)Natural Science Foundation of Beijing(Grant No.L212063)+3 种基金the Fundamental Research Funds for the Central Universities,the 111 Project(No.B13003)the National Research Program of China(Grant No.2022YFC2504200)Orthodontic research project of youth clinical research fund of Chinese Stomatological Association(Grant No.CSA-O2020-07)Municipal graduate tutor team construction project(dstd201903).
文摘This study aimed to explore the optimal invisible orthodontic force system during the en-mass distalization of two maxillary molars to minimize the side effect of anchorage loss by changing the direction of the application of the orthodontic force system.A high bio-fidelity 3D finite element model including maxilla,periodontal ligament,dentition,clear aligner,3D anchorage attachment and mini-implant was established.Different lengths of lateral hooks of 3D-printed anchorage attachments and mini-implant positions into the palatal alveolus were considered.A 200 g distal force was applied to the lateral hooks of different horizontal lengths(3.26 mm,6.52 mm and 9.78 mm)with the mini-implant as the application point.Using ABAQUS software,orthodontic tooth movements under 12 different clinical treatment designs were analyzed and calculated.The 3D anchorage attachment enhanced the anchorage of anterior teeth and alleviated the tipping/extrusion of premolars.In contrast to without clear aligners,length of the lateral hook had a negligible effect on both mesial tipping and buccal tipping with clear aligners,which could then be ignored.The change in mesial tipping was less and nearly remained constant despite of the different heights of the mini-implant.The 3D anchorage attachment assisted clear aligner can avoid the side effects of anterior tooth proclination caused by insufficient anchorage.The length of the lateral hook,and height of the mini-implant in this invisible orthodontic force system hardly affects the tooth movement of anchorage units.Clear aligners can effectively control the rotation and tipping of anchorage units caused by 3D anchorage attachment.
