Biomedical subjects

Qun Shen

Publications and source records attributed to Qun Shen.

15 recordsLinked to original sources

PubMed2006

Crystal optics as guard apertures for coherent x-ray diffraction imaging.

A crucial issue in coherent x-ray diffraction imaging experiments is how to increase the signal-to-noise ratio when measuring relatively weak diffraction intensities from a nonperiodic object. A novel crystal guard aperture is described that makes use of a pair of multiple-bounce crystal optics to eliminate unwanted parasitic scattering background. This background is often produced by upstream optical elements such as a coherent-beam defining aperture. Recent experimental observation and theoretical analysis confirm the effectiveness of the crystal guard aperture method with coherence-preserved wave propagation through the crystal guard aperture and dramatically reduced scattering background in coherent x-ray diffraction images.

Journal Article↗

PubMed2006

Resonant scattering and multiple Bragg X-ray diffraction in LaMnO3; a classical view.

The mechanism for resonant scattering in LaMnO(3) has been the subject of some controversy between two models. Model (A) is based on orbital ordering, whereas model (B) invokes the Jahn-Teller distortion. From the structural point of view, the two models lead to different d-electron densities. The forbidden reflection 300 is turned on by resonance, leading to a well defined scheme for the lobes of the Mn d electrons [model (A)]. It turns out that the same experimental results could have been interpreted according to model (B). The only difference is that this alternative interpretation would have required a structure factor F(300) of opposite sign. This is a typical example of a phase problem. An experimental technique has been applied for phase determination based on multiple Bragg scattering. This shows that the multiple-beam results are in agreement with model (B), not with model (A), laying to rest a long overdue controversy.

Journal Article↗

PubMed2006

Functional variations in the JWA gene are associated with increased odds of leukemias.

The association between the -76G>C in the 5'-flanking region and 723T>G in JWA exon three variants were examined for risk of leukemia development in a hospital-based case-control study of 201 leukemia patients and 243 cancer-free controls in a Chinese population. Studies showed that the -76C allele was associated with significantly increased odds of leukemia but the 723G allele was correlated with marked decreased odds of leukemia. Variation in the -76C allele resulted in almost complete loss of oxidative stress stimulated transcription activities of the promoter fragment.

Adult↗

PubMed2006

Multilayer X-ray optics at CHESS.

Almost half of the X-ray beamlines at the Cornell High Energy Synchrotron Source (CHESS) are based on multilayer optics. ;Traditional' multilayers with an energy resolution of DeltaE/E approximately 2% are routinely used to deliver X-ray flux enhanced by a factor of 10(2) in comparison with standard Si(111) optics. Sagittal-focusing multilayers with fixed radius provide an additional factor of 10 gain in flux density. High-resolution multilayer optics with DeltaE/E approximately 0.2% are now routinely used by MacCHESS crystallographers. New wide-bandpass multilayers with DeltaE/E = 5% and 10% have been designed and tested for potential applications in macromolecular crystallography. Small d-spacing multilayers with d < or = 20 A have been successfully used to extend the energy range of multilayer optics. Analysis of the main characteristics of the Mo/B4C and W/B4C small d-spacing multilayer optics shows enhancement in their performance at higher energies. Chemical vapour deposited SiC, with a bulk thermal conductivity of a factor of two higher than that of silicon, has been successfully introduced as a substrate material for multilayer optics. Characteristics of different types of multilayer optics at CHESS beamlines and their applications in a variety of scattering, diffraction and imaging techniques are discussed.

Crystallography, X-Ray↗

PubMed2006

JWA, a novel signaling molecule, involved in all-trans retinoic acid induced differentiation of HL-60 cells.

JWA (AF070523) was originally identified as a novel all-trans retinoic acid (ATRA) responsible gene in primary human tracheal bronchial epithelial cells. For the notable performance achieved by ATRA in the differentiation induction therapy, we investigated the role of JWA in ATRA-mediated differentiation of the human myeloid leukemia HL-60 cells. We found that concomitant with the progressive cell differentiation, JWA expression was up-regulated by ATRA in a dose- and time-dependent manner. Inhibition of JWA expression by RNA interference partially blocked ATRA-induced differentiation and growth inhibition of HL-60 cells. Pre-treatment of phorbol-12-myristate-13-acetate (TPA), a PKC activator, decreased ATRA-mediated differentiation, companied with the down-regulation of JWA expression. Arsenic trioxide (As(2)O(3), 0.5 microM) enhanced the cellular differentiation induced by 0.01 microM ATRA, but had no noticeable effect on the differentiation induced by 0.1 microM ATRA. Concurrent with the enhancement, JWA expression was up-regulated. All the data suggest that up-regulation of JWA expression is essential for ATRA-induced differentiation of HL-60 cells. And JWA, associated with PKC, is involved in its signal pathways. Ideal therapeutic efficacy with low toxicity may be obtained if low doses of ATRA (0.01 microM) and As(2)O(3) (0.5 microM) are combined. These findings may present a novel mechanism that cellular differentiation and growth inhibition induced by ATRA are mediated at least in part through regulation of JWA expression. JWA may be a novel molecular marker for ATRA-induced HL-60 cell differentiation. ATRA up-regulates JWA expression by stimulating the transcriptional activity of JWA gene promoter.

Cell Differentiation↗

PubMed2006

JWA, a novel signaling molecule, involved in the induction of differentiation of human myeloid leukemia cells.

Dysregulation of hematopoietic cellular differentiation contributes to leukemogenesis. Unfortunately, relatively little is known about how cell differentiation is regulated. JWA (AF070523) is a novel all-trans retinoic acid (ATRA) responsible gene that initially isolated from ATRA-treated primary human tracheal bronchial epithelial cells. For the notable performance achieved by ATRA in the differentiation induction therapy, we investigated the role of JWA in the induction of differentiation of human myeloid leukemia cells. Our results showed that JWA was not only regulated by ATRA but also by several other differentiation inducers such as phorbol-12-myristate-13-acetate (TPA), arabinoside (Ara-C), and hemin, involved in the mechanisms of differentiation along different lineages of myeloid leukemia cells arrested at different stages of development. Generally, JWA was up-regulated by these inducers in a time-dependent manner. Inhibition of JWA by RNA interference decreased the induced cellular differentiation. However, in NB4 cells treated with ATRA, dissimilar with others, the expression of JWA was down-regulated, and the induced cellular differentiation could be enhanced by silencing of JWA. Collectively, JWA works as a potential critical molecule, associated with multi-directional differentiation of human myeloid leukemia cells. In NB4 cells, JWA may function as a lineage-restricted gene during differentiation along the monocyte/macrophage-like or granulocytic pathway.

Blotting, Western↗

PubMed2006

[Chronic myeloid leukemia onset with marked thrombocythemia].

This study was aimed to investigate the clinical, pathological and biological features of a special case of chronic myeloid leukemia (CML) with marked thrombocythemic onset. The morphological changes of cells were analyzed by using bone marrow smear and biopsy; Ph chromosome, a specific marker of CML, was assayed by conventional chromosomal analysis and fluorescence in situ hybridization, bcr/abl fusion gene was detected by reverse transcription-polymerase chain reaction. The results indicated that CML mimicked essential thrombocythemia (ET) at presentation was relatively rare and might be misdiagnosed as ET, bone marrow smear and biopsy revealed, marked thrombocytosis and moderate leukocytosis; RT-PCR, FISH and conventional chromosomal analysis demonstrated the existence of Ph chromosome and bcr/abl fusion gene. This special CML could progress into accelerated phase or blast crisis. The megakaryocytes in Ph+ ET were smaller than normal ones and had typically hypolobulated round nuclei. Patients diagnosed as Ph+ ET might progress into CML and showed a high tendency to myelofibrosis and blastic transformation. It is concluded that the value of routine cytogenetical and molecular biological analysis in diagnosis for potential CML cases, which mimicked ET as in this presentation, is very distinctive, and the importance is magnified by the recent availability of imatinib, a specific inhibitor of the bcr/abl tyrosine kinase produced by the Philadelphia chromosome. Every case of "ET" should be tested for the Philadelphia chromosome and bcr/abl transcript.

Adult↗

PubMed2005

Crystallographic data collection using a 0.22% bandwidth multilayer.

To bridge the gap between traditional multilayer and crystal optics a high-resolution multilayer monochromator with a bandwidth of 0.22% has been designed and installed on a bending-magnet beamline (F3) at the Cornell High Energy Synchrotron Source (CHESS) to provide an unfocused monochromatic X-ray beam for protein crystallography experiments. Crystallographic data of excellent quality from a medium-sized protein, Concanavalin A, were collected and processed using standard crystallographic programs. The data were successfully used for a structure solution and refinement. The flux from the multilayer monochromator is enhanced, relative to that from a flat Si(111) monochromator, by a factor of 5; consequently, data collection is faster and/or smaller samples may be used. At the same time, the bandwidth is narrow enough to avoid streaked spots. This experiment suggests that multilayer optics may play a valuable role in satisfying the demands of the structural biology community for rapid X-ray data collection, particularly at under-utilized bending-magnet beamlines.

Concanavalin A↗

PubMed2005

[JWA gene in regulating committed differentiation of HL-60 cells induced by ATRA, Ara-C and TPA].

The study was aimed to explore the role of gene JWA, a novel retinoic acid responsible and cytoskeleton associate gene, in regulating committed differentiation of HL-60 cell and the molecular mechanism in the course of differentiation and apoptosis of leukemic cells. By using FCM, the changes of CD13, CD14, CD15, CD11b and cell cycles were detected in HL-60 cells treated with ATRA (10(-6) mol/L), Ara-C (10 ng/ml) and TPA (10(-8) mol/L) respectively. The samples were determined by semi-quantitative reverse transcript-polymerase chain reaction (RT-PCR) and Western blot for the expression of JWA, Bcl-2, HSP27 and HSP70 at day 0, 2, 4, 6, 8. The results showed that HL-60 cells committedly differentiated into granulocyte-, monocyte-, macrophage-like cells. As a result, JWA was up-regulated in a time-dependent manner, while Bcl-2 was down- regulated at the same time. In ATRA and TPA group, the change of HSP70 had positive correlation with JWA, and negative correlation with Bcl-2. The expression of HSP27 was not detected. Contrast to the cells from APL patient, the expression of JWA need not be activated by ATRA in advance. In this study, we also exposed HL-60 cells in higher dose of Ara-C (20 ng/ml), and JWA expression underwent opposite trend comparing with in lower dose of Ara-C (10 ng/ml). It is concluded that JWA may play double important roles in regulating ATRA and TPA-induced differentiation and apoptosis in leukemic cells. The JWA expression had a negative correlation between induction and cytotoxic response. The difference of JWA expressions between HL-60 cell and ANLL patient cells would be involved in different leukemia pathogenesis.

Antineoplastic Agents↗

PubMed2005

[Influence of Qingdai compound on expression of bcr/abl and JWA in K562 cells].

To study the effects of Qingdai compound on proliferation and apoptosis of K562 cells, as well as the expression of bcr/abl and JWA mRNA, K562 cells were treated in culture with different concentrations of Qingdai compound (2.5, 5, 7.5, 10 and 20 mg/ml) and harvested at 24 hours. Then morphological changes were observed by light microscopy (LM); expressions of bcr/abl and JWA were detected with semi-quantitative RT-PCR. The results showed that morphological changes were observed as the increment of the Qingdai compound concentration. Inhibition effects on proliferation and apoptosis in K562 cells were seen. A concentration-dependent decreases were found in bcr-abl and JWA mRNA expression of K562 cells. Qingdai compound partially inhibited proliferation and induced apoptosis of K562 cells. Expressions of both bcr/abl and JWA, which took part in cell proliferation and apoptosis, were down-regulated in a dose dependent manner. In conclusion, Qingdai compound can partially inhibit the expressions of bcr/abl and JWA genes in K562 cells, and the clinical effect of Qingdai compound on CML may be associated with apoptosis of leukemic cells.

Antineoplastic Agents, Phytogenic↗

PubMed2004

Diffractive imaging of nonperiodic materials with future coherent X-ray sources.

Coherent diffractive imaging using a coherent X-ray source promises to be a useful microscopic method for imaging noncrystalline objects at high spatial resolution. In this article a simple method to estimate the coherently scattered signal as a function of resolution is presented, and it is shown that the required X-ray flux or dose scales as the inverse third power of resolution for a specimen of constant volume and density. A simulated case study using the proposed energy-recovery linac source is also presented, which confirms the estimated flux requirement.

Journal Article↗

PubMed2003

Anomalous difference signal in protein crystals.

A scattering-angle-dependent formula is obtained for estimation of anomalous diffraction signals in Friedel pairs in protein crystals. In addition to the angle dependences of atomic form factor and temperature factor, a correlation form factor is introduced for the first time to take into account anomalous-scattering clusters such as disulfide bonds. Good agreements with experimental observations suggest that such correlated anomalous difference signals may be visible from measurements before a complete structural solution is obtained.

Crystallization↗

PubMed2003

Improving triplet-phase accuracy by symmetry observations in reference-beam diffraction measurements.

The reference-beam X-ray diffraction technique allows parallel measurements of many three-beam interference profiles in a modified rotating-crystal experiment. Because of the unique symmetry relations that exist in the reference-beam geometry, a complete 360 degrees rotation leads to a fourfold redundancy of any given triplet phase delta(H) involving primary reflection H, reference reflection G and coupling reflection H-G, measured in a data set. Two such redundant measurements correspond to simple duplications with the reciprocal node H going into and coming out of the Ewald sphere, while the other two correspond to the Friedel mate G-H of the coupling reflection H-G passing through the Ewald sphere in a similar fashion. It is shown that substantial differences may exist between the H and the G-H cases, with an enhanced triplet-phase interference effect in one of them. These symmetry-related observations, coupled with inverse-beam triplet measurements, would improve the phase measurement accuracy of the reference-beam diffraction technique.

Crystallography, X-Ray↗

PubMed2003

Recursive direct phasing with reference-beam diffraction.

The reference-beam diffraction technique provides a practical way to measure a large number of triplet phases in a standard oscillating-crystal diffraction experiment for protein crystals. The triplet-phase data set from such reference-beam measurements contains a unique phase-occurrence pattern that leads to a new recursive phasing algorithm for the individual structure-factor phases. Application of the new algorithm is demonstrated for tetragonal lysozyme using 7360 triplet phases measured in a reference-beam experiment with a median phase discrepancy of 45 degrees. An electron-density map obtained using this phasing algorithm and the measured triplet phases shows good agreement with the known protein structure.

Algorithms↗

PubMed2002

[Comparison studies on chemical constituents of essential oil from Ramulus Cinnamomi and Cortex Cinnamomi by GC-MS].

Essential oil from Ramulus Cinnamomi (Cinnamomum cassia Presl) and Cortex Cinnamomi were obtained by steam distillation. The chemical components of the oil were examined and compared by means of gas chromatography-mass spectrometry. 54 of the separated constitutents were identified. 10 components of these were not observed in the oil from Ramulus Cinnamomi, and 16 components of these were not observed in the oil from Cortex Cinnamomi.

Benzaldehydes↗