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Biomedical subjects

Q Niu

Publications and source records attributed to Q Niu.

At least 19 recordsLinked to original sources
PubMed2001

An evaluation of the colorimetric assays based on enzymatic reactions used in the measurement of human natural cytotoxicity.

In recent years colorimetric assays based on an enzymatic reaction such as the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay have been used in an attempt to replace the conventional isotopic assay for cell-mediated cytotoxicity. To clarify the problems in the colorimetric assays for natural cytotoxicity, K562 cells were employed as target cells and peripheral mononuclear cells (PBMCs) from cancer patients were used as effector cells. No correlation was found between the 51Cr assay and the MTT assay (P>0.05) or the N-acetyl-beta-D-glycosaminidase (NAG) release assay (P>0.05) in 16 cancer patients. Labeling effector cells showed that the 51Cr release levels of such cells in 19 chemotherapy patients were significantly higher than the levels from target cells in this group (P<0.01) and from effector cells in the control group (P<0.01). There was no correlation between the positive and negative 51Cr assays (P>0.05). The sensitivity of the MTT assay was greatly decreased by washing K562 cells prior to loading MTT solution. Enzyme release occurs as a result of cell metabolism and elevated enzyme release is associated with freezing. These findings indicate that the colorimetric assays based on an enzymatic reaction are not suitable for the detection of natural cytotoxicity in all populations, and are especially not suitable for the assay of natural cytotoxicity in chemotherapy patients.

Chromium Radioisotopes↗
PubMed2001

Shape of the quantum diffusion front.

We show that quantum diffusion has well-defined front shape. After an initial transient, the wave packet front (tails) is described by a stretched exponential P(x,t) = A(t)exp(-absolute value of [x/w](gamma)), with 1 < gamma < infinity, where w(t) is the spreading width which scales as w(t) approximately t(beta), with 0 < beta < or = 1. The two exponents satisfy the universal relation gamma = 1/(1-beta). We demonstrate these results through numerical work on one-dimensional quasiperiodic systems and the three-dimensional Anderson model of disorder. We provide an analytical derivation of these relations by using the memory function formalism of quantum dynamics. Furthermore, we present an application to experimental results for the quantum kicked rotor.

Journal Article↗
PubMed2001

Trichloroethylene in urine as biological exposure index.

Occupational exposure to trichloroethylene (TRI) was studied by analysis of environmental air and urine from 49 workers operating in a special printing house on glass. For the measurement of environmental concentration of TRI (Cenv), the ambient air was sampled using personal passive dosimeters. The activated charcoal was desorbed with carbon disulfide and injected into a gas-cromatograph - mass spectrometer (GC-MSD). The biological monitoring of exposed workers was conducted by determining the concentration of TRI in urine (Curine) Urine concentration of TRI was determined by headspace analysis using GC-MSD. Significant correlation was found between the environmental TRI concentration and urinary TRI concentration. The use of a regression equation between Curine (microg/l) and Cenv (mg/m3) (Curine = 0.081 x Cenv + 4.27) resulted in a value of Curine corresponding to Threshold Limit Value-Time Weighted Average (TLV-TWA) exposure value (269 mg/m3) of 26.0 microg/L.

Adult↗
PubMed2001

[Effect on manganese exposure on blood prolactin and plasma renin activity].

In order to study the adverse effects of manganese on neuro-endocrine and cardiovascular system, radioimmunoassay (RIA) was used to test the blood prolactin concentration and plasma renin activity among manganese-exposed workers. The result showed that the blood prolactin concentration and Plasma renin activity in manganese exposed workers were significantly higher than those of control group. It suggested that manganese exposure might affect the function at tubero-infundibular area and renin-angiotensin aldosterone system.

Adult↗
PubMed2001

[Relationship between serum matrix metalloproteinase-2 and metastasis and recurrence following radical hepatic resection in hepatocellular carcinoma].

OBJECTIVE: To study the relationship between serum matrix metalloproteinase-2 (MMP-2) and metastasis and recurrence following radical hepatic resection in hepatocellular carcinoma (HCC). METHODS: Cox's proportional hazard model was used to determine the significant clinical factor of prognosis. Meanwhile, enzyme linked immunoadsordent assay (ELISA) and northern blot analysis were adopted to detect serum and tumor tissue levels of MMP-2 respectively in HCC patients. RESULTS: Cox's proportional hazard model showed that tumor size and tumor number were significant prognostic factors of HCC patients following hepatic resection (P=0.022 and P=0.040). According to this result, we divided HCC patients into high-tendency to metastasis recurrence and low-tendency to metastasis recurrence groups. Serum levels of MMP-2 in high-tendency to metastasis recurrence following radical hepatic resection group were significantly higher than those in low-tendency group (26.39ng/m+/-2.64ng/ml vs 24.86ng+/-1.95ng/ml, P<0.05). Serum levels of MMP-2 in HCC patients performed non-radical hepatic resection group were also significantly higher than those in HCC patients performed radical hepatic resection group (29.43ng+/-3.12 ng/ml vs 25.72ng+/-2.45ng/ml, P<0.01). Northern blot analysis revealed that the changes of MMP-2 level in the serum were consistent with those of its mRNA level in the tumor tissue of HCC patients. CONCLUSIONS: Serum MMP-2 level is an indicator for metastatic recurrence following radical hepatic resection in HCC. The high levels of MMP-2 in the serum are due to high MMP-2 mRNA expression in the tumor tissue of HCC patients.

Carcinoma, Hepatocellular↗
PubMed2000

Steering an eigenstate to a destination

The control of time evolution of a quantum state under various physical constraints is investigated and solved in the context of a two-level system. We have discovered a general scheme of steering an eigenenergy state to a destination without net nonadiabatic transitions, and we discuss how the result may be tested and utilized in practice.

Journal Article↗
PubMed2000

Morphological symmetry breaking during epitaxial growth at grazing incidence

It is shown that, in submonolayer growth at off-normal incidence, even much less than 1% of transfer from the condensation energy of the deposited atoms into adatom motion is sufficient to induce a net adatom current from the illuminated edge of a two-dimensional island to the other edges, thereby breaking the island symmetry. Such a symmetry breaking phenomenon is most pronounced for deposition at grazing incidence. Comparison between our theoretical predictions and existing experimental results confirms the general validity of the model.

Journal Article↗
PubMed2000

Nonlinear effects in interference of bose-einstein condensates

Nonlinear effects in the interference of Bose-Einstein condensates are studied using exact solutions of the one-dimensional nonlinear Schrodinger equation, which is applicable when the lateral motion is confined or negligible. With the inverse scattering method, the interference pattern is studied as a scattering problem with the linear Schrodinger equation, whose potential is profiled by the initial density distribution of the condensates. Our theory not only provides an analytical framework for quantitative predictions for the one-dimensional case, it also gives an intuitive understanding of some mysterious features of the interference patterns observed in experiments and numerical simulations.

Journal Article↗
PubMed1998

Proto-oncogene PML controls genes devoted to MHC class I antigen presentation.

Fragments of foreign antigens associated with class I molecules of the major histocompatibility complex (MHC) are presented at the cell surface to elicit an immune response. This presentation requires the coordinated expression of several genes contained in the MHC, including those encoding the MHC class I heavy chain, the proteins LMP-2 and LMP-7, which are involved in the proteasomal degradation of cytosolic antigens into peptide fragments that are destined for association with MHC class I molecules, and TAP-1 and TAP-2, which transport these fragments across the membrane of the endoplasmic reticulum at the start of their journey to the cell surface. In many virus-transformed cell lines and spontaneous tumours, these genes are simultaneously repressed. However, the key factor(s) that are essential for their expression and repression have not been identified. Here we report that the proto-oncogene product PML induces expression of LMP-2, LMP-7, TAP-1 and TAP-2 in an MHC-class I-negative, recurrent tumour, leading to the re-expression of cell-surface MHC in tumours and to rejection of the tumours. PML also regulates MHC expression in untransformed fibroblasts. We conclude that malfunction of PML may enable a tumour to evade the immune defence of its host.

3T3 Cells↗
PubMed1998

Expression and cytogenetic localization of the human SM22 gene (TAGLN).

SM22 is a 22-kDa protein identified variously as SM22, transgelin, WS3-10, or mouse p27. Though its precise function is unknown, it is abundant in smooth muscle and so may contribute to the physiology of this widespread tissue. We found that cosmid 16b6 contains the entire 5.4-kb, five-exon human SM22 gene (HGMW-approved symbol, TAGLN), and we cytogenetically localized the gene to chromosome 11q23.2. Northern analysis of human adult tissues showed that SM22 mRNA is most prevalent in smooth muscle-containing tissues, but is also found at lower levels in heart. The human SM22 promoter contains nuclear factor-binding motifs known to regulate transcription in smooth muscle, and human SM22 promoter-luciferase reporter constructs exhibited high transcriptional activity in A7r5 or primary canine aortic smooth muscle cells, but show little activity in nonmuscle COS7 cells. In addition, human SM22 promoter activity increased by two- to threefold upon serum stimulation of nonmuscle cells.

Adult↗
PubMed1998

[Study on the changes of heart-rate in lead-exposed workers].

ECG examination and questionnaires survey were performed among lead-exposed workers in order to assess whether moderate occupational lead exposure may cause autonomic nervous system (ANS) dysfunction. The tests included; 1. heart-rate response to Valsalva manoeuvre (HR-V); 2. heart-rate variation during deep breathing (HR-DB); 3. immediate heart-rate response to immediate stand up (30:15 or Max:Min). The results did not show any evidence that lead exposure is related to ANS dysfunction. There was no significant difference between the exposed workers and controls who were with the same ages (P > 0.05). The important cause for ANS dysfunction was aging.

Adult↗
PubMed1996

CD40L is important for induction of, but not response to, costimulatory activity. ICAM-1 as the second costimulatory molecule rapidly up-regulated by CD40L.

The CD40 ligand (CD40L):CD40 interaction plays an important role in the activation of both T and B cells. However, the mechanisms by which this interaction is involved in activation of T cells is still unclear. Here we show that CD40L is not essential for T cell response to TCR engagement if the APC have costimulatory activity, although it is essential for T cell-mediated induction of such costimulatory activity. To determine the molecular basis of this activity, we have produced three mAbs that appear to recognize the costimulatory molecules rapidly induced by CD40L. Two of them recognize CD44H, which we showed to have CD28-independent costimulatory activity for T cells. The molecule recognized by the remaining mAb is hereby identified as ICAM-1. Furthermore, ICAM-1-mediated costimulation is likely to serve for a function similar to that mediated by the B7:CD28 interaction, as targeted mutation of CD28 renders T cell responses to Con A more dependent on ICAM-1.

Animals↗
PubMed1996

Formation of Atomically Flat Silver Films on GaAs with a "Silver Mean" Quasi Periodicity

A flat epitaxial silver film on a gallium arsenide [GaAs(110)] surface was synthesized in a two-step process. Deposition of a critical thickness of silver at low temperature led to the formation of a dense nanocluster film. Upon annealing, all atoms rearranged themselves into an atomically flat film. This silver film has a close-packed (111) structure modulated by a "silver mean" quasi-periodic sequence. The ability to grow such epitaxial overlayers of metals on semiconductors enables the testing of theoretical models and provides a connection between metal and semiconductor technologies.

Journal Article↗