J.M. Xue

Biological effects of protons targeted to different ranges in Arabidopsis seeds

Purpose: To investigate the biological effects of radiation damage induced at different depths of a plant seed and to investigate the difference in radiation response between dry seeds and water-imbibed seeds to the same type of radiation. Materials and methods: Arabidopsis seeds of the wild-type Columbia ecotype were used in our experiments. Dry or water-imbibed Arabidopsis seeds were irradiated with 1.1 MeV, 2.6 MeV or 6.5 MeV protons (H+). For comparison, 30 keV nitrogen ions (N+) were also used to irradiate dry Arabidopsis seeds. The germination and survival rates of the seeds were measured after each irradiation. Results: After irradiation with 2.6 MeV H+ and 6.5 MeV H+, the fluence-response curves for germination and survival had distinct shoulders and then survival was reduced rapidly with increasing fluence. 2.6 MeV H+ was more effective than 6.5 MeV H+ in inhibiting germination and survival and water-imbibed seeds were more sensitive to the 6.5 MeV H+ irradiation than dry seeds. For 1.1 MeV H+ the germination and survival rates were reduced gradually and an intermediate plateau emerged for germination, which was similar to that observed for survival following 30 keV N+ irradiation. One of the key morphologic malformations, the multi-SAM (shoot apical meristem), was observed both for dry and water-imbibed seeds after all proton irradiations and for the dry seeds after 30 keV N+ irradiation. Conclusions: Radiation-induced damage produced at different ranges in Arabidopsis seeds results in different fluence-response curves with water-imbibed seeds being more sensitive to proton irradiation than dry seeds. As well as the shoot apical meristem (SAM) being the primary target for irradiation, there exists a secondary target around the SAM that also contributes to the radiation response.

Molecular dynamics simulations on the ionic current through charged nanopores

Molecular dynamics (MD) simulation was performed to investigate the ionic current through charged nanopores, and the results were compared with the calculation of Poisson-Nernst-Planck (PNP) equations based on the continuum theory. Results show that the current obtained by MD simulation is lower than the current calculated by PNP equations, and the discrepancy depends on the surface charge density of the nanopores. Also, MD simulation shows that the contribution of the electro-osmotic flow effect on ionic current could be 10% higher than the results obtained by solving PNP equations. Since the PNP equations do not take the effect of the pore wall into consideration, we suggest that adjusting the diffusion coefficient in the PNP equations can obtain more accurate results when calculating the ionic current through charged nanopores.

Study of tribological properties of high-speed steel implanted by high-dose carbon ions

Abstract The changes in tribological behaviour of high-speed steel (M2) samples implanted with carbon ions at high fluences (5×10 17 ∼3×10 18 xa0cm −2 ) have been studied. The ion energies used were 50 and 100xa0keV leading to a modified layer of 200 and 400xa0nm, respectively. Obviously, the samples show an improved tribological behaviour, although the microhardness of the surface decreased after implantation. Tribological measurements, microhardness measurements, RBS, SEM and EDX analyses were performed before and after ion implantation. The experimental results are discussed, and it is concluded that the improvement of wear behaviour can be correlated to an improved toughness of the near surface layer modified by the ion implantation.

The surface microstructure of high-dose, carbon-implanted high-speed steel

Abstract Carbon ions generated by MEVVA ion facility with 70-keV energy were implanted into high-speed steel(HSS) samples at doses of 5×10 17 ∼3×10 18 xa0cm −2 . RBS, TEM, XRD, SEM and EDX were used to analyze the surface microstructure of implanted samples. It has been found that the dose reached saturation as the fluence reached 1×10 18 xa0cm −2 . The W, V concentration on the surface became much higher after implantation. An amorphous layer embedding some nano-size carbide particles was formed on the surface of high-dose carbon-implanted samples. There are also some unclear nano-structures appearing in the tungsten-rich area under the TEM.

Mutation effects of C2+ ion irradiation on the greasy Nitzschia sp.

Screening and nurturing algae with high productivity, high lipid content and strong stress resistance are very important in algae industry. In order to increase the lipid content, the Nitzschia sp. was irradiated with a 3MeV C(2+) beam. The sample pretreatment method was optimized to obtain the best mutagenic condition and the survival ratio curve. The positive mutants with a significant improvement in lipid content were screened and their C(2+) mutagenic effects were analyzed by comparing the greasiness and growth characteristics with the wild type algae. Results showed that when the Nitzschia sp. was cultivated in nutritious medium containing 10% glycerol solution, and dried on the filter for 5 min after centrifugation, the realization of the microalgae heavy ion mutagenesis could be done. The survival ratio curve caused by C(2+) irradiation was proved to be saddle-shaped. A positive mutant was screened among 20 survivals after irradiation, the average lipid content of the mutation increased by 9.8% than the wild type after 4 generations. But the growth rate of the screened mutation didnt change after the heavy ion implantation compared to the wild type algae.

Study on the desorption yield for natural botanic sample induced by energetic heavy ions

The dependence of desorption yield for the natural botanic sample bombarded with heavy ion on the electronic stopping power ðSeÞ and dose has been measured by weighing sample mass before and after irradiation. Primary ions including 50 keV N þ , 1.5 MeV F þ , 3.0 MeV F 2þ , 4.0 MeV F 2þ and 3.0 MeV Si 2þ were used in the experiment. Three megaelectron volts of F 2þ with doses ranging from 4 � 10 15 to 4 � 10 16 ions/cm 2 were used in order to investigate the influence of ion dose. A mass spectrum from the sample bombarded with 3 MeV Si 2þ was also taken for a better understanding of the desorption process. Results show that the natural botanic sample is very easily to be desorpted. The yield of MeV heavy ions can be as high as thousands CH2O/ion, and significantly depends on both the Se and dose. The measured yields increase quickly with Se, but drop down with increasing ion dose. These results fit roughly with the prediction of the pressure pulse model. 2002 Elsevier Science B.V. All rights reserved.

Impaired Function of Bone Marrow Mesenchymal Stem Cells from Immune Thrombocytopenia Patients in Inducing Regulatory Dendritic Cell Differentiation Through the Notch-1/Jagged-1 Signaling Pathway

Immune thrombocytopenia (ITP) is an autoimmune disease in which dendritic cells (DCs) play a crucial role in the breakdown of self-tolerance. Studies have identified the function of mesenchymal stem cells (MSCs) in promoting the development of regulatory DCs (regDCs). Our previous work revealed that MSCs in ITP exerted senescence, apoptosis, and impaired immunosuppressive effects on T and B cells. However, it is unclear whether the effects of MSCs on regDC induction are altered in ITP. Our data demonstrated that MSCs in ITP were impaired in inhibiting CD1a+ DC and CD14+ DC differentiation from CD34+ hematopoietic progenitor cells (CD34+ HPCs). DCs differentiated with MSCs in ITP exhibited an increased expression of costimulatory molecules CD80/CD86 and secretion of proinflammatory interleukin-12 (IL-12). Accordingly, the tolerogenic characteristics were deficient in DCs induced by MSCs in ITP. DCs differentiated with MSCs in ITP exhibited an impaired ability to inhibit CD3+ T cell proliferation, to suppress T helper (Th)1 cell differentiation, and to induce anergic and regulatory T cells (Tregs). The expression of Notch signaling components was measured in MSCs in ITP. Reduced expression of the ligand Jagged-1, the receptor Notch-1 intracellular domain (NICD-1), and the target gene Hes-1 was identified in MSCs in ITP. The addition of biologically active Jagged-1 to CD34+ HPCs was observed to promote regDC differentiation. When cultured on Jagged-1-coated plates, MSCs in ITP showed an enhancement of the Notch-1 pathway activation, Jagged-1 expression, and the function in inducing regDCs. Pretreatment with all-trans retinoic acid (ATRA) was found to partially restore the capacity of MSCs in both ITP patients and healthy controls in inducing CD34+-derived regDCs. Our data elucidated that MSCs in ITP were impaired in inducing CD34+-regDCs, associated with the Notch-1/Jagged-1 signaling pathway. ATRA could partially correct the impairment of MSCs, suggesting that ATRA could serve as a potential therapeutic alternative for ITP.

Combined prednisone and levothyroxine improve treatment of severe thrombocytopenia in hepatitis B with compensatory cirrhosis accompanied by subclinical and overt hypothyroidism

The aim of the present study was to investigate the relationship between hypothyroidism and thrombocytopenia in hepatitis B-related compensatory liver cirrhosis and to determine whether treatment with levothyroxine and prednisone is superior in a multicenter, open-label, observational study in China. In total, 125 consecutive hepatitis B-related compensated liver cirrhosis patients with severe thrombocytopenia accompanied by hypothyroidism were included. The patients were divided into four groups according to treatment strategy: a control group (n=29), a prednisone group (n=25), a levothyroxine group (n=32) and a prednisone plus levothyroxine group (n=39). Severe thrombocytopenia was more prevalent in hepatitis B-associated compensatory liver cirrhosis patients with hypothyroidism than in euthyroid patients (29.6% vs. 14.7%, P<0.05). Combination treatment with prednisone and levothyroxine decreased the risk of bleeding and improved platelet recovery compared to control treatment and treatment with either prednisone or levothyroxine alone. The platelet count before therapy, serum thyroid stimulating hormone and combination treatment with prednisone and levothyroxine were associated with bleeding events. Therefore, the present study suggests that hypothyroidism is associated with severe thrombocytopenia in hepatitis B-associated compensatory liver cirrhosis. Treatment with prednisone plus levothyroxine may present a novel approach in these patients.

Integrated mRNA and miRNA profiling revealed deregulation of cellular stress response in bone marrow mesenchymal stem cells derived from patients with immune thrombocytopenia

Our understanding of the pathogenesis of immune thrombocytopenia (ITP) remains limited due to the complexity and heterogeneity of the disease. Recently, we observed that bone marrow mesenchymal stem cells (MSCs) derived from ITP patients exhibited growth defects and functional abnormalities that might be involved in the breakdown of self-tolerance. However, the underlying mechanism remains unclear. In this study, we profiled the expression of both mRNAs and miRNAs by utilizing the microarray technique and deciphered the mechanism underlying the impairment of MSCs derived from ITP patients (MSC-ITP). In total, we identified 740 genes and 32 miRNAs that were differentially expressed between ITP patients and controls. A compromised unfolded protein response (UPR) and decreased DNA transcription were shown to be significantly related to MSC-ITP. The interaction of miRNA with mRNA suggested that the cellular stress response, the UPR, and DNA transcription may be involved in the defects observed in MSC-ITP. Key differentially expressed genes were further validated by RT-PCR. Our results highlight that defects in the cellular stress response, as shown by a compromised UPR and differential DNA transcription, play key roles in causing the abnormalities observed in MSC-ITP. These data might contribute to a better understanding of the abnormal bone marrow niche and provide new insights into the pathogenesis of ITP.