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Articles by G. Xu
Total Records ( 5 ) for G. Xu
  C Xia , Q Tong , Q Wang , Z Tang , L Qi , S Chi , M Zhang , X Wang , H Li and G. Xu
  Background

The in vitro directive of the European Union requires traceability to the international recommended reference procedures. The application of the reference procedures is necessary in order to evaluate the accuracy of -glutamyltransferase (GGT) assays of routine measurement systems in China.

Methods

Five frozen patient-pooled serum samples were assigned values by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference procedure in order to evaluate the traceability of the results of GGT catalytic activity from six homogeneous systems. One of the serum samples was used to calibrate seven non-homogeneous systems.

Results

All of the homogeneous systems, except the Dade system (Dade Bering Inc, IL, USA), achieved traceability within the measurement range. The Roche and Hitachi systems were better than the other systems. After calibration, the variance of the non-homogeneous systems decreased dramatically from between 14.50% and 25.23% to between 1.25% and 3.09% and the bias decreased from between –11.4% and –4.1% to between 0.5% and 3.5%.

Conclusion

Manufacturers in China should ensure that their calibration systems correspond to the IFCC reference procedures. Fresh frozen pooled patient serum assigned by reference laboratories can be used to calibrate non-homogeneous systems in order to achieve traceability.

  C. Chang , L. Gao , H. Kou , X. Liu , Z. Qin and G. Xu
  An integrity batch report protocol based on the waiting stack is proposed, which aims at solving the bottleneck problem of the Trusted Platform Module (TPM) signature of integrity report. In the protocol, integrity attestation requests are placed sequentially in a waiting stack with constant head part and varying length. The TPM processes the integrity batch report one after another and thus the flexibility problem of trusted gateway can be solved efficiently. This study also proposes a data compressing method based on the Merkle tree to reduce the communication complexity in processing integrity batch report. The length of fresh number connection string transferred to the challenger can be compressed from mx20 bytes to log2mx20 bytes. The laboratory result indicates that the responding capacity of gateway adopting integrity batch report protocol is prior to adopting TCG integrity report protocol and the processing capacity of gateway can be improved from 1~3.3 to 32~256 times per second.
  C Xu , J He , H Jiang , L Zu , W Zhai , S Pu and G. Xu
 

Hypercortisolemia and glucocorticoid treatment cause elevated level of circulating free fatty acids (FFAs). The basis of this phenomenon has long been linked to the effect of glucocorticoids permitting and enhancing the adipose lipolysis response to various hormones. In this study, we demonstrate that glucocorticoids directly stimulate lipolysis in rat primary adipocytes in a dose- and time-responsive manner; this lipolytic action was attenuated by treatment with the glucocorticoid antagonist RU486. Dexamethasone down-regulates mRNA and protein levels of cyclic-nucleotide phosphodiesterase 3B, thereby elevating cellular cAMP production and activating protein kinase A (PKA). On inhibition of PKA but not other kinases, the lipolysis response ceases. Furthermore, dexamethasone induces phosphorylation and down-regulation of perilipin, a lipid droplet-associating protein that modulates lipolysis; this effect is restored by RU486 or PKA inhibitor H89. Dexamethasone up-regulates mRNA and protein levels of hormone-sensitive lipase (HSL) and adipose triglyceride lipase; these effects, parallel to increased lipolysis, are attenuated by RU486 or actinomycin D. Phosphorylation at Ser-563 and Ser-660 residues of HSL and activity of cellular lipases are elevated on dexamethasone stimulation but abrogated by the coaddition of H89. However, dexamethasone does not induce HSL translocation to the lipid droplet surface in differentiated adipocytes. We show that elevated FFA concentration in plasma is associated with increased lipase activity and lipolysis in vivo in adipose tissues of dexamethasone-treated rats. Therefore, the lipolytic action of glucocorticoids liberates FFA efflux from adipocytes to the bloodstream, which could be a cellular basis of systemic FFA elevation in response to glucocorticoid challenge.

  R. Yang , T. Xia , G. Xu , Z. Li , Z. Ying and X. Xu
  Our study sought to investigate the immune response of cytotoxic T lymphocytes to human cytomegalovirus (HCMV) in kidney transplant recipients with virus reactivation. Nine kidney transplant recipients with serum HCMV immunoglobulin G and HLA-A*0201 genotype displayed HCMV pp65 antigenemia and were compared with 29 control recipients who were free of antigenemia. The frequency of total HCMV-specific cytotoxic T cells was determined using HLA-A2-NLVPMVATV-pentamer staining. The frequency of HCMV specific interferon (INF)-γ secreting CD8+ T cells was determined using intracellular INF-γ staining after NLVPMVATV pulsing in vitro. The proportion of IFN-γ secreting pentamer-stained CD8+ T cells was calculated, representing the capacity for INF-γ secretion among HCMV-specific CD8+ T cells. We observed that the frequency of HCMV-specific pentamer-stained CD8+ T cells and HCMV-specific IFN-γ secreting CD8+ T cells both remained unchanged, yet the proportion of IFN-γ secreting CD8+ T cells showed a significant difference between the 2 groups (39.2% ± 17.2% vs 20.0% ± 13.3% respectively; P = .004), reflecting impaired IFN-γ secreting capacity of HCMV-specific CD8+ T cells among kidney transplant recipients displaying antigenemia, which may be a crucial reason for HCMV reactivation in immunosuppressed patients.
 
 
 
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