Biomedical subjects

Y Zhang

Publications and source records attributed to Y Zhang.

At least 289 records · Page 16Linked to original sources

PubMed2003

A comparative map of bovine chromosome 19 based on a combination of mapping on a bacterial artificial chromosome scaffold map, a whole genome radiation hybrid panel and the human draft sequence.

We have constructed a medium density physical map of bovine chromosome 19 using a combination of mapping loci on both a bovine bacterial artificial chromosome (BAC) scaffold map and a whole genome radiation hybrid (WGRH) panel. The resulting map contains 70 loci spanning the length of bovine chromosome 19. Three contiguous groups of BACs were identified on the basis of multiple loci mapping to individual BAC clones. Bovine chromosome 19 was found in this study to be comprised almost entirely from regions of human chromosome 17, with a small region putatively assigned to human chromosome 10. Fourteen breakpoints between the bovine and human chromosomes were detected, with a possibility of five more based on ordering of the WGRH map.

Animals↗

PubMed2003

Biological treatment of printing ink wastewater.

Printing ink wastewater is usually very difficult to treat biologically and its chemical oxygen demand (COD) far exceeds standards of discharge. The COD in wastewater is usually 3,000 to 8,000 mg/L after flocculation and sedimentation. Herein, a strain of bacterium was isolated from the sludge and identified as Bacillus sp. and utilized to treat printing ink wastewater. The application of bacteria to degrade printing ink in wastewater is discussed in this paper. The influence of N and P sources on COD removal, and COD removal in combination with glucose was also discussed. More than 85 per cent of the COD could be removed using the proposed biological process. A novel internal airlift loop bioreactor with bacteria immobilized onto ceramic honeycomb support was used for the wastewater treatment.

Bacteria↗

PubMed2003

The dual pathway electrophysiology of the atrioventricular conduction. A new look at an old phenomenon.

Although we soon will be marking the 100th anniversary of the discovery of the atrioventricular (AV) node, the mysteries of this most complex of all parts of the conduction system of the heart remain. We are still battling controversies related to the precise morphology of the AV node and its atrial approaches. We are still debating the exact reentrant pathways of the AV nodal reentrant tachycardia. We are still uncertain if the so-called dual AV nodal electrophysiology encompasses two or more pathways, and what exactly makes these pathways in the absence of distinct insulated cables between the atrium and the AV node. It may be just surprising, in view of the above limitations, that current level of knowledge has nevertheless made possible some of the most spectacular successes in the modern cardiac electrophysiology. Thus, the cases of typical AVNRT are cured with a very high rate of success by radiofrequency ablations, increasing the quality of life of thousands of patients. AV nodal modifications are being performed to slow the ventricular rate during atrial fibrillation, although more progress is needed in this endeavor. The goal of the present review is to outline the major anatomic and electrophysiologic efforts in understanding the mechanisms underlying the dual pathway AV nodal propagation and to trace some novel approaches that promise to widen the horizon of the experimental and clinical fields.

Animals↗

PubMed2003

The curious characteristics of pyrazinamide: a review.

Pyrazinamide (PZA) is an important sterilising tuberculosis drug that helps to shorten the duration of current chemotherapy regimens for tuberculosis. When first discovered, it had activity in murine tuberculosis but no apparent in vitro activity, and its subsequent use in treatment depended largely on classic experiments at Cornell University, which showed its requirement for an acid pH for activity and its sterilising activity in the mouse. Recent studies have shown that PZA enters Mycobacterium tuberculosis by passive diffusion, is converted to pyrazinoic acid (POA) by nicotinamidase/pyrazinamidase (PZase) and is then excreted by a weak efflux pump. Protonated POA (HPOA) is reabsorbed into the bacilli under acid conditions and accumulates because the efflux pump is inefficient, causing cellular damage. Unlike other antibacterials, PZA has no defined target of action. PZA is more active against old than against actively growing cultures, probably because the energy production and efflux pump would be slowed down by low bacterial metabolism. This review deals with the activity of PZA in vitro, in macrophages and in animal models. It describes the evidence from clinical trials that it is an effective sterilising drug that acts synergistically with rifampicin. The highly diverse mutations in the PZase gene (pncA) that lead to loss of PZase activity cause PZA resistance. Methods for susceptibility determination either as tests against PZA or nicotinamide in liquid and solid media, as tests for PZase activity or for mutations in pncA, are reviewed.

Amidohydrolases↗

PubMed2003

Analysis of lewis antigens on cell surface and alpha1,3 fucosyltransferase subtypes in H7721 human hepatocarcinoma cells.

The expressions of Lewis antigens on H7721 human hepatocarcinoma cells were detected with monoclonal antibodies and flow-cytometry. It was found that H7721 mainly expressed SLex, and a small amount of SDLex, but Lex and SLea was negligible. The monoclonal antibody of SLex (KM93) significantly blocked the adhesion of H7721 cells to human umbilical vein epithelial cells, as well as cell migration and invasion, but the blocking effect of SDLex antibody (FH6) was not statistically significant. The expressions of five subtypes of alpha1,3fucosyltransferases (alpha1,3FucTs), the enzyme responsible for the fucosylation step in Lewis antigen synthesis, were also studied using real-time RT-PCR. The expression of FucT mRNAs were FucT-IV > FucT-III > FucT-VI > or = FucT-VII > FucT-IX. FucT-VI is supposed to be the main enzyme responsible for the synthesis SLex and SDLex. FucT-VII and III may also participate in SLex synthesis. The absence of FucT-IX expression and FucT-III not being the rate-limiting enzyme for SLea synthesis may be the reasons for the negligible expressions of Lex and SLea on the cell surface, respectively.

Antibodies, Monoclonal↗

PubMed2002

KChIP1 and frequenin modify shal-evoked potassium currents in pyloric neurons in the lobster stomatogastric ganglion.

The transient potassium current (I(A)) plays an important role in shaping the firing properties of pyloric neurons in the stomatogastric ganglion (STG) of the spiny lobster, Panulirus interruptus. The shal gene encodes I(A) in pyloric neurons. However, when we over-expressed the lobster Shal protein by shal RNA injection into the pyloric dilator (PD) neuron, the increased I(A) had somewhat different properties from the endogenous I(A). The recently cloned K-channel interacting proteins (KChIPs) can modify vertebrate Kv4 channels in cloned cell lines. When we co-expressed hKChIP1 with lobster shal in Xenopus oocytes or lobster PD neurons, they produced A-currents resembling the endogenous I(A) in PD neurons; compared with currents evoked by shal alone, their voltage for half inactivation was depolarized, their kinetics of inactivation were slowed, and their recovery from inactivation was accelerated. We also co-expressed shal in PD neurons with lobster frequenin, which encodes a protein belonging to the same EF-hand family of Ca(2+) sensing proteins as hKChIP. Frequenin also restored most of properties of the shal-evoked currents to those of the endogenous A-currents, but the time course of recovery from inactivation was not corrected. These results suggest that lobster shal proteins normally interact with proteins in the KChIP/frequenin family to produce the transient potassium current in pyloric neurons.

Animals↗

PubMed2002

Power propagation in homogeneous isotropic frequency-dispersive left-handed media.

We study transmission at a boundary between a right-handed medium (RHM: epsilon>0, mu>0) and a frequency dispersive left-handed medium [LHM: epsilon(omega)<0, mu(omega)<0 for some omega], both homogeneous and isotropic. In order to account for the dispersion, two types of signal spectra are considered. The first consists of two discrete frequencies, while the second is Gaussian. Explicit expressions for the time-domain fields are obtained, from which the time-averaged Poynting vectors and hence power flow vectors are calculated. In both cases, we find that waves refract at negative angles at a RHM-LHM interface.

Journal Article↗

PubMed2002

Stretching single stranded DNA, a model polyelectrolyte.

The elastic properties of single stranded (ss)DNA, studied by pulling on an isolated molecule, are shown to agree with a recent model of ssDNA that takes into account base pairings and screened electrostatic repulsion of the phosphodiester backbone. By an appropriate physicochemical treatment, the pairing interactions were suppressed and ssDNA used as an experimental model for a generic polyelectrolyte. The elastic behavior of such an altered ssDNA deviates strongly from the behavior of an ideal polymer. This deviation is shown to result from the elasticity of the chain and its electrostatic self-avoiding interactions.

DNA, Single-Stranded↗

PubMed2002

Insulating behavior of lambda-DNA on the micron scale.

We have investigated the electrical conductivity of lambda-DNA using DNA covalently bonded to Au electrodes. Thiol-modified dTTP was incorporated into the "sticky" ends of bacteriophage lambda-DNA using DNA polymerase. Two-probe measurements on such molecules provide a hard lower bound for the resistivity rho>10(6)Omega cm at bias potentials up to 20 V, in conflict with recent claims of moderate to high conductivity. By direct imaging, we show that the molecules are present after the measurements. We stress the importance of eliminating salt residues in these measurements.

Bacteriophage lambda↗

PubMed2002

The roles of terminal sugar residues of surface glycans in the metastatic potential of human hepatocarcinoma.

PURPOSE: The roles of terminal sialyl and fucosyl residues in cell surface glycans in the metastatic potential of H7721 cells, a human hepatocarcinoma cell line, were studied. METHODS: Neuraminidase and alpha-L-fucosidase were used to remove the sialyl and fucosyl residues, respectively. Cell adhesion to fibronectin (Fn), laminin (Ln), and human umbilical vein epithelial cell (HUVEC), as well as chemotactic cell migration and invasion, were selected as the parameters of metastatic potential ex vivo. RESULTS: Sialyl residue is not essential for cell adhesion to Fn, but is important in cell adhesion to Ln and invasion, and is crucial in cell adhesion to HUVEC and migration. In contrast, fucosyl residue contributes more than sialyl residue to cell adhesion to Fn and Ln, but less to adhesion to HUVEC, and is not essential in chemotactic cell migration and invasion. Cell adhesion to HUVEC, migration, and invasion were inhibited by the monoclonal antibody of sialyl Lewis X, but not by the antibody of non-sialyl Lewis X. CONCLUSION: Terminal sialyl residues on cell surface glycans are more important than fucosyl residues in mediating cell adhesion to HUVEC and cell migration/invasion, but the reverse is true in cell adhesion to Fn and Ln.

Antigens, Tumor-Associated, Carbohydrate↗

PubMed2002

Destruction of serotonergic nerve terminals prevents fluoxetine-induced desensitization of hypothalamic 5-HT(1A) receptors.

RATIONALE: Selective serotonin (5-HT, 5-hydroxytryptamine) reuptake inhibitors (SSRIs) such as fluoxetine produce a gradual desensitization of hypothalamic post-synaptic 5-HT(1A) receptor systems. It is assumed that the effects of SSRIs on post-synaptic 5-HT(1A) receptors are mediated by 5-HT reuptake inhibition, leading to an increase of 5-HT in the synapse. However, there is no direct evidence to support this hypothesis. OBJECTIVES: The present study determined whether 5-HT(1A) receptor desensitization was mediated by fluoxetine's effects on serotonergic nerve terminals. METHODS: Serotonergic nerve terminals were destroyed by intracerebroventricular (i.c.v.) injection of the serotonin neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) combined with injection of the norepinephrine/dopamine reuptake inhibitor nomifensine. 5,7-DHT-induced loss of serotonergic terminals was confirmed by a 95% reduction in the density of [(3)H]paroxetine-labeled 5-HT transporters in the hypothalamus and a 97% reduction in the levels of 5-HT and 5-hydroxyindoleacetic acid in the cortex. Two weeks after the 5,7-DHT injections, rats were injected daily with fluoxetine (5 mg/kg or 10 mg/kg, i.p.) or saline for 14 days. RESULTS: Injections of 10 mg/kg fluoxetine produced a significant decrease in body weight gain. Destruction of serotonergic nerve terminals reduced body weight and potentiated the ability of fluoxetine to further inhibit body weight gain. Increases in plasma levels of adrenal corticotrophic hormone (ACTH, corticotropin), corticosterone, and oxytocin after injection of the 5-HT(1A) agonist 8-hydroxy-2-dipropylaminotetralin [(+/-)8-OH-DPAT] were used as peripheral markers of 5-HT(1A) receptor function in the hypothalamus. In vehicle-pretreated rats, fluoxetine produced a dose-dependent reduction in the (+/-)8-OH-DPAT-induced increase in plasma ACTH and oxytocin levels. Destruction of serotonergic nerve terminals blocked the ability of fluoxetine to produce a desensitization in the ACTH, corticosterone, and oxytocin responses to (+/-)8-OH-DPAT. CONCLUSIONS: The ability of fluoxetine to induce a desensitization of hypothalamic post-synaptic 5-HT(1A) receptor systems is dependent on the integrity of serotonergic nerve terminals in the hypothalamus, while its effect on body weight is not mediated by serotonergic nerve terminals in the hypothalamus.

5,7-Dihydroxytryptamine↗

PubMed2002

Absolute structure-factor measurements of an Al-Pd-Mn quasicrystal.

A number of X-ray reflections from an icosahedral quasicrystal Al-Pd-Mn have been measured with great accuracy on an absolute basis by making use of Bragg-case diffraction. Since the specimen had high crystal quality, the dynamical theory was used for analyzing the results and to extract structure factors from measured integrated intensities. Good agreement was found between theory and experiment for strong reflections. Anomalous transmission was found to be strong in the 'good' regions of the quasicrystalline specimen and it was measured on an absolute basis, but the small residual strains present in the specimen prevented an accurate comparison between theory and experiment. A detailed discussion is presented on the parameters that mostly affect anomalous transmission in relationship to the adopted structural model.

Journal Article↗

PubMed2002

Thyroid-beta2 and the retinoid RAR-alpha, RXR-gamma and ROR-beta2 receptor mRNAs; expression profiles in mouse retina, retinal explants and neocortex.

In neonatal retinal explants cultured long-term green cones are missing. Recently it was reported that thyroid hormone beta2 receptors (TR-beta2) are essential for these green cones to differentiate. Therefore transcript level of these receptors was investigated in our mouse retinal explants. However, thyroid receptors function as heterodimers with retinoid receptors (RR); so the fate of selected RRs was similarly analyzed using semi-quantitative RT-PCR. Loss of TR-beta2 and RR (RXR-gamma and ROR-beta2) mRNAs was observed after culturing the neonatal retina for 12 days. This indicates that these proteins are involved in determination of green cone identity. In addition, levels of the selected RR transcripts are differentially affected by short- or long-term culture. In the latter case an attached retinal pigment epithelium seems to play a protective role. Furthermore, divergent diurnal peaks of RR mRNAs are present in young as well as aged mouse retina and neocortex. This data might be relevant in the context of human ageing disorders.

Aging↗

PubMed2002

A high statistics measurement of the Lambda(+)(c) lifetime.

A high statistics measurement of the Lambda(+)(c) lifetime from the Fermilab fixed-target FOCUS photoproduction experiment is presented. We describe the analysis technique with particular attention to the determination of the systematic uncertainty. The measured value of 204.6 +/- 3.4 (stat) +/- 2.5 (syst) fs from 8034 +/- 122 Lambda(+)(c)-->pK(-)pi(+) decays represents a significant improvement over the present world average.

Journal Article↗

PubMed2002

Cognitive impairment in Parkinson's disease revealed by event-related potential N270.

Disturbed cognitive function is a well-recognized feature of idiopathic Parkinson's disease (PD). The aim of this study was to find a susceptive index to reveal the minor cognitive impairment in PD patients. Thirty PD patients without clinical dementia and thirty-four age-matched normal controls performed a matching task while event-related potentials (ERPs) were recorded from their scalp. There were two kinds of stimulus pairs in this study: match condition, the second stimulus (S2) in a pair was identical to the first one (S1); conflict condition, S2 conflicted with S1 in the color attribute. Subjects were required to press a button in the match condition and another button in the conflict condition. A negative ERP component, N270, which was considered to reflect the conflict processing activity in human brain, was evoked by the S2 of the conflict condition. The patient group showed a delayed and smaller N270 than the control group. The prolongation of its peak latency was significant at P3 and P4 electrodes and the reduction of its mean amplitude was significant at P3 electrode. The amplitude of P300 elicited in the match condition was decreased in the patient group at P4 electrode but its latency did not differ from the control group. These results indicate that PD patients as a group showed cognitive decline even in the absence of clinical dementia. N270 is a sensitive index in revealing this minor cognitive impairment.

Adult↗

PubMed2002

Transfection of the nm23-H1 gene into human hepatocarcinoma cell line inhibits the expression of sialyl Lewis X, alpha1,3 fucosyltransferase VII, and metastatic potential.

PURPOSE: The expressions of Lewis antigens, alpha1,3 fucosyltransferase (alpha1,3 FucT)-VII, and the metastatic potential of the 7721 human hepatocarcinoma cell line after the transfection of the cDNA of nm23-H1, a known metastasis-suppressive gene, were studied using mock cells as the control, which were transfected with the pcDNA3 vectors. METHODS: Cell adhesion to human umbilical vein epithelial cells (HUVEC), chemotaxic cell migration through transwells, and invasion through matrigel were selected as the metastasis-related phenotypes to assess the metastatic potential at the cell level. RESULTS: The results showed that the expression of SLe(x) was high, while the expression of Le(x), SDLe(x), and SLe(a) were very low on the surface of the mock cells. After transfection of nm23-H1, the expressions of SLe(x), alpha1,3 FucT-VII, and the cell adhesion to HUVEC, as well as cell migration and invasion were simultaneously decreased in all three clones of nm23-H1-transfected cells. Among different clones, the decreased expressions of SLe(x) and alpha1,3 FucT-VII were roughly correlated to each other, and also, in general, proportional to the ability of cell adhesion to HUVEC, cell migration, and invasion. The expressions of these metastasis-related phenotypes were lowest in clone 3 and highest in clone 4. Only the specific monoclonal antibody to SLe(x) (KM93) significantly abolished the cell adhesion, migration, and invasion, while other monoclonal antibodies against SDLe(x) or Le(x) and SLe(a) only slightly inhibited or entirely failed to inhibit the above-mentioned phenotypes. However, the rate of cell growth was not changed after the transfection of nm23-H1, and the ability of colony formation on the soft agar was only decreased in one clone. CONCLUSIONS: These findings reveal that the down-regulation of alpha1,3 FucT-VII and its product, SLe(x), is one of the mechanisms to explain the metastasis-suppressive effect of the nm23-H1 gene.

Blotting, Northern↗

PubMed2002

Search for CP violation in the decays D+--> K(S)pi+ and D+-->K(S)K+.

A high-statistics sample of photoproduced charm from the FOCUS experiment has been used to search for direct CP violation in the decay rates for D+-->K(S)pi+ and D+-->K(S)K+. We have measured the following asymmetry parameters relative to D+-->K-pi+pi+: A(CP)(K(S)pi+) = (-1.6+/-1.5+/-0.9)%, A(CP)(K(S)K+) = (+6.9+/-6.0+/-1.5)%, and A(CP)(K(S)K+) = (+7.1+/-6.1+/-1.2)% relative to D+-->K(S)pi+. We have also measured the relative branching ratios and found Gamma(D+-->K(0)pi+)/Gamma(D+-->K-pi+pi+) = (30.60+/-0.46+/-0.32)%, Gamma(D+-->K(0)K+)/Gamma(D+-->K-pi+pi+) = (6.04+/-0.35+/-0.30)%, and Gamma(D+-->K(0)K+)/Gamma(D+-->K(0)pi+) = (19.96+/-1.19+/-0.96)%.

Journal Article↗

PubMed2002

Impaired apoptosis, extended duration of immune responses, and a lupus-like autoimmune disease in IEX-1-transgenic mice.

Susceptibility of activated T cells to apoptosis must be tightly regulated to ensure sufficient T cell progeny for an effective response, while allowing a rapid depletion of them at the end of the immune response. We show here that a previously isolated, NF-kappa B/rel target gene IEX-1 (Immediate Early response gene X-1) is highly expressed in T cells at early stages of activation, but declines with a prolonged period of activation time, coincident with an increased susceptibility of T cells to apoptosis during the late phases of an immune response. Transgenic expression of IEX-1 specifically in lymphocytes impaired apoptosis in activated T cells, extended a duration of an effector-phase of a specific immune response, and increased the accumulation of effector/memory-like T cells and the susceptibility to a lupus-like autoimmune disease. Our study demonstrated an antiapoptotic effect of IEX-1 on T cell apoptosis triggered by ligation of Fas and T cell receptor (TCR)/CD3 complex. The ability of extending life expectancy of T effectors, in line with a decrease in its expression following prolonged T cell activation, suggests a key role for IEX-1 in regulating T cell homeostasis during immune responses.

Animals↗