Biomedical subjects

Z Li

Publications and source records attributed to Z Li.

At least 55 records · Page 3Linked to original sources

PubMed2006

Inhibitory effects on HLA-DR1-specific T-cell activation by influenza virus haemagglutinin-derived peptides.

Collagen (CII) 263-272 peptide, an autoantigen in rheumatoid arthritis, is a specific human leukocyte antigen (HLA)-DR1/4-binding peptide recognized by T-cell receptors (TCR). The affinity of influenza virus haemagglutinin (HA) 306-318 peptide for the antigen-binding groove of HLA-DR1/4 molecules is higher than that of CII263-272. The HLA-DR1/4-binding residues of HA306-318 are located in the region 308-317. Altered HA308-317 peptides with substitutions of TCR-contact residues may inhibit HLA-DR1/4-specific T-cell activation by blocking the antigen-binding site of HLA-DR1/4 molecules. To evaluate the role of altered HA308-317 peptides in HLA-DR1-restricted T-cell activation, we synthesized three altered HA308-317 peptides. The specific binding of altered HA308-317 peptides to HLA-DR1 molecules was examined using flow cytometry. Effects of altered HA308-317 peptides on HLA-DR1-specific T-cell hybridoma were studied by measuring T-cell proliferation and surface expression of CD69 or CD25. The results showed that altered HA308-317 peptides were able to bind to HLA-DR1 molecules and competed with CII263-272 or wildtype HA308-317 peptide. Compared with wildtype CII263-272 or HA308-317, altered HA308-317 peptides did not stimulate significant T-cell proliferation and CD69 or CD25 expression. Furthermore, the altered HA308-317 peptides inhibited HLA-DR1-specific T-cell activation induced by CII263-272 or wildtype HA308-317 peptide, which may suggest an effective therapeutic strategy in inhibition of HLA-DR1-specific T-cell responses in autoimmunity.

Amino Acid Substitution↗

PubMed2006

Extreme rank selections for linkage analysis of quantitative trait loci using selected sib-pairs.

It is well known that linkage analysis using simple random sib-pairs has relatively low power for detecting quantitative trait loci with small genetic effects. The power can be substantially increased by using samples selected based on their trait values. Usually, samples that are obtained by truncation selection consist of random samples from a truncated trait distribution. In this article we propose an alternative method using extreme ranks for linkage analysis with selected sib-pairs. This approach approximates the truncation selection. With similar screening sizes and the same sample size of selected sib-pairs, the extreme rank selection and truncation method have similar power performance, both of which are substantially more powerful than when using random sib-pairs. Simulation results on the comparison of powers between the truncation selection and the extreme rank selection and/or random selection for linkage analysis are reported.

Genetic Linkage↗

PubMed2006

A frequent partial AZFc deletion does not render an increased risk of spermatogenic impairment in East Asians.

The gene families in the AZFc region of the Y chromosome have been shown to be functionally important in human spermatogenesis. The gr/gr deletion, a partial AZFc deletion that reduces the copy numbers of all the AZFc gene families, was identified as a significant risk factor for spermatogenic impairment in Dutch, Spanish and Italians. However, the presence of this deletion in healthy French and Germans questioned its importance in male infertility. In this study, we have shown that the gr/gr deletion does not render an increased risk in Han Chinese. In fact, the gr/gr deletion is frequent (about 8%) in our survey of 886 East Asians from 8 ethnic groups. Furthermore, the DAZ1/DAZ2 deletion has been detected as the primary subtype of the gr/gr deletion in East Asians, though this doublet has been considered as crucial for normal spermatogenesis in Europeans. The different spermatogenic effects of various types of the partial AZFc deletion suggest that the functional difference between AZFc gene copies is a likely cause of inconsistent associations of the gr/gr deletion with spermatogenic impairment across populations.

Base Sequence↗

PubMed2006

Statistical analysis for haplotype-based matched case-control studies.

Using unphased genotype data, we studied statistical inference for association between a disease and a haplotype in matched case-control studies. Statistical inference for haplotype data is complicated due to ambiguity of genotype phases. An estimating equation-based method is developed for estimating odds ratios and testing disease-haplotype association. The method potentially can also be applied to testing haplotype-environment interaction. Simulation studies show that the proposed method has good performance. The performance of the method in the presence of departures from Hardy-Weinberg equilibrium is also studied.

Biometry↗

PubMed2006

Effects of major endoleaks on a stented abdominal aortic aneurysm.

Insertion of a stent-graft into an aneurysm, especially abdominal aortic aneurysms (AAAs), is a very attractive surgical intervention; however, it is not without major postoperative complications, such as endoleaks. An endoleak is the transient accumulation of blood in the AAA cavity, which is formed by the stent-graft and AAA walls. Of the four blood pathways, a type I endoleak constitutes the major one. Thus, focusing on both proximal and distal type I endoleaks, i.e., the minute net influx of blood past the attachment points of a stent-graft into the AAA cavity, the transient three-dimensional interactions between luminal blood flow stent-graft wall, leakage flow, and AAA wall are computationally simulated. For different type I endoleak scenarios and inlet pressure wave forms, the impact of type I endoleaks on cavity pressure, wall stress, and stent-graft migration force is analyzed. The results indicate that both proximal type I-a and distal type I-b endoleaks may cause cavity pressures close to a patient's systemic pressure; however, with reduced pulsatility. As a result, the AAA-wall stress is elevated up to the level of a nonstented AAA and, hence, such endoleaks render the implant useless in protecting the AAA from possible rupture. Interestingly enough, the net downward force acting on the implant is significantly reduced; thus, in the presence of endoleaks, the risk of stent-graft migration may be mitigated.

Aorta, Abdominal↗

PubMed2006

Microdialysis for monitoring the process of functional tissue culture.

Continuous monitoring is important during tissue culture. However, there are still technical difficulties in monitoring the internal status of cells or tissues. In this paper, microdialysis is adopted to monitor functional tissue growth in a bioreactor. Explanted bovine caudal intervertebral disc (IVD) was used as the test tissue. A microdialysis membrane probe of 100 kDa molecular weight cut-off was employed and in situ calibration methods with phenol red and fluorescent 40 kDa dextran were developed to measure the relative recovery of the solute of interest, and membrane fouling, respectively. Tissue metabolism was monitored successfully. At the same time soluble macromolecules were picked up by the probe and were detected and quantified by Fast Protein Liquid Chromatography (FPLC) and/or Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis (SDS-PAGE). These proteins were believed to be associated with biofunction of engineered tissue. Monitoring of phenol red content in the dialysate indicated that there was no significant fouling of the membrane probe during a 7-day culture period and the Relative Recovery of macromolecules of interests remained roughly 9%. We concluded that microdialysis could be used to sample a wide range of molecular species released during cell metabolism and extracellular matrix turnover, which were direct or indirect indications of cell and tissue functions. The application of the developed system could be extended to monitor tissue repair in vivo, and the development of the engineered tissue.

Animals↗

PubMed2006

Application of in vivo cryotechnique to the examination of cells and tissues in living animal organs.

When all biological materials in cells and tissues of living animal organs are quickly and promptly frozen, immunolocalization of their components and structural features in situ is necessary to understand their in vivo functioning states. However, these direct morphological analyses were difficult to achieve by conventional chemical fixation methods during the last century. A new cryofixation method, named the "in vivo cryotechnique", in which the normal blood circulation in living animals is always retained at the moment of freezing, has become a powerful tool to visualize the real native morphology of cells and tissues with functional meaning. The "in vivo cryotechnique" can usually be combined with a wide range of subsequent preparation techniques, and can thereby enable us to perform various direct analyses on biological samples, reflecting the physiological functions of living animal organs.

Animals↗

PubMed2006

Immunohistochemical study of serum albumin in normal and cadmium-treated mouse testis organs by "in vivo cryotechnique".

The in vivo injection of cadmium (Cd) was reported to induce blood-testis barrier disruption, and assumed to be an experimental model to examine junctional structures in seminiferous tubules. The purpose of this study is to investigate time-dependent changes of albumin permeability in the normal or Cd-treated mouse testis by our "in vivo cryotechnique" with immunohistochemistry, reflecting tight junctional (TJ) barriers of Sertoli cells. The albumin in the seminiferous tubules was firstly immobilized by the cryotechnique, in which normal blood circulation was always kept. The cryofixed testicular tissues were then processed for freeze-substitution, and embedded in the paraffin wax. Serial sections were immunostained by anti-mouse albumin antibody with peroxidase immunostaining, and also stained with hematoxylin-eosine (HE) for morphological observation. In normal seminiferous tubules, the immunoreaction products were localized around peritubular myoid cells and between Leydig cells, as well as in blood vessels. They were also localized as arch-like patterns around some spermatogonia in basal compartments of seminiferous tubules. Twenty-four and 48 hrs after Cd-treatment, some enlarged spaces and vesicular formations in the seminiferous epithelium were observed on the HE-stained sections. The albumin immunolocalization was detected not only in the basal compartments, but also in the adluminal compartments between Sertoli cells and germ cells. Thus, the structural disruptions of inter-Sertoli TJ barriers could be clearly demonstrated by the "in vivo cryotechnique".

Animals↗

PubMed2006

[Distribution of hepatitis B virus genotypes in Guizhou and analysis of clinical significance.].

BACKGROUND: To investigate the distribution of HBV genotypes in Guizhou and study the relationship between the genotype and the progression of liver disease. METHOD: Totally 693 patients with chronic HBV infection, from 4 areas of Guizhou, including 292 asymptomatic HBV carriers (ASC), 276 cases with chronic hepatitis (CH), 76 liver cirrhosis (LC), 49 hepatocellular carcinoma (HCC) were examined. The HBV genotype was determined by restriction fragment length polymorphism analysis and the relationship between HBV genotype and the progression of liver disease was studied by multifactor analysis such as HBsAg positivity, HBV DNA load and ALT level. RESULTS: Of the 693 patients, 6 (0.87%), 449 (64.79%), 233 (33.62%), and 5 (0.72%) belonged to genotype A, B, C and D, respectively. There was a statistically siganificant difference in the distribution of genotype B among Kaili (96.4%), Zunye (78.79%), Duyun (76.19%) and Guiyang (53.66%) areas (P less than 0.01). Genotype C was more prevalent in Guiyang than in other three areas (45.68% vs. 23.8%, 45.68% vs. 13.13%, 45.68% vs. 3.96%, P less than 0.01, respectively). There were also statistically significant difference in distribution of genotype B and C in various stages of liver disease (P less than 0.01). Genotype B showed a decreasing trend from ASC, CH, LC to HCC and genotype C was more frequent in patients with CH (45.92%) than in those with ASC (20.6%), LC (17.17%) and HCC (16.31%). The ALT levels and the mean ages were significantly higher and older in patients with genotype C than those in genotype B. The HBeAg positivity was significantly lower in genotype C than that in genotype B (48.07% vs 61.90%, P less than 0.01). CONCLUSION: Genotype A, B, C and D exist in Guizhou. Genotype B predominates and genotype C was the second common. The geographic distribution of genotype B and C are different in some areas of Guizhou. Compared with genotype B, genotype C is associated with the development of more severe liver damage.

China↗

PubMed2005

Precision measurements of the timelike electromagnetic form factors of pion, kaon, and proton.

Using 20.7 pb(-1) of e(+)e(-) annihilation data taken at sq.rt(r) = 3.671 GeV with the CLEO-c detector, precision measurements of the electromagnetic form factors of the charged pion, charged kaon, and proton have been made for timelike momentum transfer of |Q(2)| = 13.48 GeV(2) by the reaction e(+)e(-) --> h(+)h(-). The measurements are the first ever with identified pions and kaons of |Q(2)| > 4 GeV(2), with the results F(13.48 GeV(2)) = 0.075 +/- 0.008(stat) +/- 0.005(syst) and F(K)(13.48 GeV(2)) = 0.063 +/- 0.004(stat) +/- 0.001(syst). The result for the proton, assuming G(p)(E) = G(p)(M), is G(p)(M)(13.48 GeV(2)) = 0.014 +/- 0.002(stat) +/- 0.001(syst), which is in agreement with earlier results.

Journal Article↗

PubMed2005

Effects of environmental and pharmacological stressors on c-fos and corticotropin-releasing factor mRNA in rat brain: Relationship to the reinstatement of alcohol seeking.

We have observed marked heterogeneity among different stressors in their ability to reinstate alcohol seeking in rats. Of the stressors we have tested, only the environmental stressor footshock and the pharmacological stressor yohimbine induce reinstatement. The reasons for such differences among stressors are not known. The purpose of the experiments presented here is to determine the neuroanatomical substrates that underlie these behavioral differences. To this end, we assessed whether stressors effective in inducing reinstatement of alcohol seeking activate a different set of neuronal pathways than do those that are ineffective, using the technique of in situ hybridization of the mRNAs for c-fos, a marker of neuronal activation, and corticotropin-releasing factor (CRF), a stress-related peptide we have shown to be critical to footshock-induced reinstatement of alcohol seeking. Exposure of rats to the environmental stressors footshock, restraint or social defeat, or the pharmacological stressors yohimbine or FG-7142 increased levels of the mRNAs for c-fos and CRF in the brain in a number of areas previously shown to be responsive to stressors. We found regionally specific effects of the stressors on c-fos and CRF mRNA in brain regions associated with the rewarding effects of alcohol and other abused drugs. The two stressors we have previously shown to be effective in inducing reinstatement of alcohol seeking, footshock and yohimbine, induced c-fos mRNA in the shell of the nucleus accumbens, and the basolateral and central amygdalar nuclei. These two stressors also induced CRF mRNA in the dorsal region of the bed nucleus of the stria terminalis. Taken together, these results provide evidence that activity in these regions may be involved in the reinstatement of alcohol seeking induced by these stressors. These results are also in keeping with the previously demonstrated role of CRF neurons in the dorsal bed nucleus of the stria terminalis in the reinstatement of alcohol seeking induced by stress.

Adrenergic alpha-Antagonists↗

PubMed2005

Potential role of disc repositioning in preventing postsurgical recurrence of traumatogenic temporomandibular joint ankylosis: a retrospective review of 17 consecutive cases.

The potential role of disc repositioning in preventing postsurgical recurrence of traumatogenic temporomandibular joint (TMJ) ankylosis was investigated. Seventeen cases of traumatogenic TMJ ankylosis underwent disc repositioning during arthroplasty. During surgery, the dislocated disc was carefully dissected outside the ankylotic TMJ and repositioned over the top of the condylar stump, and then sutured to the soft tissue of the zygomatic root. In the 22 ankylotic TMJs of the 17 patients, dislocated discs were found in front of the ankylotic TMJ, behind the ankylotic TMJ or between the ramus and fossa. At the last follow-up (longer than 1 year) examination, interincisal opening distances ranged from 24 to 43 mm (mean 32.86 mm). No recurrence and TMJ symptoms were found during the period of follow-up. Disc repositioning in the treatment of traumatogenic TMJ ankylosis proves to be a feasible and effective method of preventing recurrence of this condition.

Adolescent↗

PubMed2005

Computational analysis of type II endoleaks in a stented abdominal aortic aneurysm model.

Insertion of a stent-graft into an aneurysm to form a new (synthetic) blood vessel and prevent the weakened artery wall from rupture is an attractive surgical intervention when compared to traditional open surgery. However, focusing on a stented abdominal aortic aneurysm (AAA), post-operative complications such as endoleaks may occur. An endoleak is the net influx of blood during the cardiac cycle into the cavity (or sac) formed by the stent-graft and the AAA wall. A natural endoleak source may stem from one or two secondary branches leading to and from the aneurysm, labeled types IIa and IIb endoleaks. Employing experimentally validated fluid-structure interaction solvers, the transient 3-D lumen and cavity blood flows, wall movements, pressure variations, maximum wall stresses and migration forces were computed for types IIa and IIb endoleaks. Simulation results indicate that the sac pressure caused by these endoleaks depends largely on the inlet branch pressure, where the branch inlet pressure increases, the sac pressure may reach the systemic level and AAA-rupture is possible. The maximum wall stress is typically located near the anterior-distal side in this model, while the maximum stent-graft stress occurs near the bifurcating point, in both cases, due to local stress concentrations. The time-varying leakage rate depends on the pressure difference between AAA sac and inlet branch. In contrast, the stent-graft migration force is reduced by type II endoleaks because it greatly depends on the pressure difference between the stent-graft and the aneurysm cavity.

Algorithms↗

PubMed2005

Analysis of biomechanical factors affecting stent-graft migration in an abdominal aortic aneurysm model.

Focusing on a representative abdominal aortic aneurysm (AAA) with a bifurcating stent-graft (SG), a fluid-structure interaction (FSI) solver with user-supplied programs has been employed to solve for blood flow, AAA/SG deformation, sac pressure and wall stresses, as well as the downward forces acting on the SG. Simulation results indicate that implanting a SG can significantly reduce sac pressure, mechanical stress, pulsatile wall motion, and maximum diameter change in AAAs; hence, it may restore normal blood flow and prevent AAA rupture effectively. The transient SG drag force is similar in trend as the cardiac pressure. Its magnitude depends on multi-factors including blood flow conditions, as well as SG and aneurysm geometries. Specifically, AAA neck angle, iliac bifurcation angle, neck aorta-to-iliac diameter ratio, SG size, and blood waveform play important roles in generating a fluid flow force potentially leading to SG migration. It was found that the drag force can exceed 5N for an AAA with a large neck or iliac angle, wide aortic neck and narrow iliac arteries, large SG size, and/or abnormal blood waveform. Thus, the fixation of self-expandable or balloon-expandable SG contact may be inadequate to withstand the forces of blood flowing through the implant and hence means of extra fixation should be considered. A comprehensive FSI analysis of the coupled SG-AAA dynamics provides physical insight for evaluating the luminal hemodynamics, and maximum AAA-stresses as well as biomechanical factors leading potentially to SG migration.

Animals↗

PubMed2005

Observation of the hc(1P1) state of charmonium.

The h(c)((1)P(1)) state of charmonium has been observed in the reaction psi(2S) --> pi(0)h(c) --> (gammagamma)(gammaeta(c)) using 3.08 x10(6) psi(2S) decays recorded in the CLEO detector. Data have been analyzed both for the inclusive reaction, where the decay products of the eta(c) are not identified, and for exclusive reactions, in which eta(c) decays are reconstructed in seven hadronic decay channels. We find M(h(c)) = 3524.4 +/- 0.6 +/- 0.4 MeV which corresponds to a hyperfine splitting DeltaM(hf)(1P) triple-bond pi(0)h(c)) x B(h(c) --> gammaeta(c)) = (4.0 +/- 0.8 +/- 0.7) x 10(-4).

Journal Article↗

PubMed2005

Observation of thirteen new exclusive multibody hadronic decays of the psi(2S).

Using data accumulated with the CLEO detector corresponding to an integrated luminosity of [symbol: see text] = 5.63 pb(-1) on the peak of the psi(2S) [3.08 x 10(6) psi(2S) decays] and 20.70 pb(-1) at square root of[s] = 3.67 GeV, we report first measurements of the branching fractions for the following 13 decay modes of the psi(2S): eta3pi, &eta'3pi, rhoK+K-, K+K-pi+pi-pi0, 2(K+K-), 2(K+K-)pi0, rhopp, pppi+pi-pi0, etapp, ppK+K-, lambdalambdapi+pi-, lambdapK+, and lambdapK+pi+pi-, and more precise measurements of 8 previously measured modes: 2(pi+pi-), rhopi+pi-, 2(pi+pi-)pi0, omegapi+pi-, K+K-pi+pi-, omegaK+K-, phiK+K-, and pppi+pi-. We also report new branching fraction measurements of phipi+pi- and omegapp and upper limits for etapi+pi-, etaK+K-, and phivpp. Results are compared, where possible, with the corresponding J/psi branching ratios to provide new tests of the 12% rule.

Journal Article↗

PubMed2005

Supramolecular nanostructures of 1,3,5-benzene-tricarboxylic acid at electrified Au(111)/0.05 M H2SO4 interfaces: an in situ scanning tunneling microscopy study.

The potential-induced adsorption and self-assembly of 1,3,5-benzene-tricarboxylic acid (TMA) was investigated at the electrified Au(111)/0.05 M H2SO4 interface by in-situ scanning tunneling microscopy (STM) and surface enhanced infrared reflection absorption spectroscopy (SEIRAS) in combination with electrochemical techniques. Depending on the applied electric field, TMA forms five distinctly different, highly ordered supramolecular adlayers on Au(111) surfaces. We have elucidated their real-space structures at the molecular scale. In the potential range -0.25 V < E < 0.20 V, planar-oriented TMA molecules form a hexagonal open-ring honeycomb structure, Ia, a hydrogen-bonded ribbon-type phase, Ib, and a herringbone-type phase, Ic, stabilized by directional hydrogen bonding and weak substrate-adsorbate interactions. Interfacial water molecules are being replaced. In 0.20 V < or = E < 0.40 V, e.g., around the potential of zero charge, and at slightly higher coverages, a close-packed physisorbed adlayer of hydrogen-bonded TMA dimers, II, was observed. Further increase of the electrode potential to positive charge densities causes an orientation change from planar to upright. An initially disordered phase, IIIa, transforms into an ordered, stripelike chemisorbed adlayer, IIIb, of perpendicularly oriented TMA molecules. One carboxylate group per molecule is bound to the electrode surface, while the two other protonated carboxyl groups are directed toward the electrolyte and act as structure-determining components of a hydrogen-bonded two-dimensional ladder-type network. Structural transitions between the various types of ordered molecular adlayers are attributed to (hole) nucleation and growth processes.

Journal Article↗

PubMed2005

Branching fractions for psi(2S)-to-J/psi transitions.

We describe new measurements of the inclusive and exclusive branching fractions for psi(2S) transitions to J/psi using e(+)e(-) collision data collected with the CLEO detector operating at CESR. All branching fractions and ratios of branching fractions reported here represent either the most precise measurements to date or the first direct measurements. Indirectly and in combination with other CLEO measurements, we determine B(chi(cJ) --> gamma(J/psi)) and B[psi(2S) --> light hadrons].

Journal Article↗