Biomedical subjects

C Zhu

Publications and source records attributed to C Zhu.

At least 91 records · Page 5Linked to original sources

PubMed2000

Double labeling immunoelectron microscopic study on the synaptic connections between glutamic acid neurons and GABA neurons in the hippocampus of rats.

In order to explore the roles of different neurotransmitters in epileptic pathogenesis, the synaptic connections between glutamic acid (Glu) neurons and GABA neurons in normal rat hippocampus were studied by pre-embedding double labeling immunoelectron microscopy. The GABA immunoreaction was first demonstrated by chromogen DAB, then the Glu immunoreaction was demonstrated by molybdic acid-TMB method. After being stabilized by DAB-cobalt chloride, the sections were processed for electron microscopic embedding. Under electron microscope, there were many Glu immunoreaction-positive neurons in the pyramidal layer of hippocampal CA1 area and some GABA immunoreaction-positive neurons with pyramidal or polygonal perikarya in the pyramidal, polymorphic and radiant layer of CA1 area. There were also symmetric dendro-axonic synapses formed by GABA-positive dendrites and Glu-positive axons in the polymorphic layer and symmetric axo-dendrites synapses formed by GABA-positive axons and Glu-positive dendritic in the radiant layer. In addition, there were symmetric autoregulatory axo-dendritic synapses between Glu-positive axons and dendrites and autoregulatory axo-axonic synapses (both symmetric and asymmetric) between GABA-positive axons. Above mentioned results, for the first time, showed that there were complex synaptic regulatory relationships between excitatory Glu neurons and inhibitory GABA neurons in the hippocampal CA1 area, thereby, providing ultrastructural evidence for different neurotransmitters participating in epileptic pathogenesis.

Animals↗

PubMed2000

The effect of coriaria lactone on NMDA receptor mediated currents in rat hippocampal CA1 neurons.

To investigate the exact mechanism of epileptogenesis induced by coriaria lactone (CL), the effect of CL on NMDA receptor mediated current (IAsp) in rat hippocampal CA1 neurons was investigated by using nystatin perforated whole-cell patch clamp. 10(-6)-10(-4) mol/L Asp acted on NMDA receptors and elicited an inward current (IAsp) at a holding potential (VH) of -40 mV in presence of 10(-6) mol/L glycine and absence of Mg2+ extracellularly. CL enhanced NMDA receptor mediated current induced by Asp, but had no effect on threshold concentration, EC50, Hill coefficient as well as maximal-effect concentration and reversal potential of IAsp. The effect had no relationship with holding potential. These results showed that CL could enhance NMDA receptor mediated current to increase [Ca2+]i of neurons by acting on Gly site, thereby inducing epilepsy.

Animals↗

PubMed2000

Screening of novel epilepsy-related genes and isolation and identification of cDNAs.

Twenty cDNA differential fragments were isolated from the hippocampus of rats in epileptic state using mRNA differential display technique. Four fragments were sequenced and compared with the known sequences in the Genebank, which showed that ERG8, ERG11, ERG12 had no significant identity to any known sequences; ERG14 had 64%-69% identity to microtubulin-associated protein of the rat. Because the differential expression of these genes was caused by epilepsy inducer coriaria lactone (CL) and anti-epilepsy drug MK-801 and ERG8 might be a novel candidate epilepsy gene; ERG11 and ERG12 might be novel candidate anti-epilepsy genes. Since the microtubulin-associated protein is closely associated with the collateral sprouting of mossy fibers in the hippocampus of seizured rat, the high expression of ERG14 in the early stage of epilepsy might predict the growth of axon and formation of synapse.

Animals↗

PubMed2000

Glomerulosclerosis in adriamycin-induced nephrosis is accelerated by a lipid-rich diet.

The present study was performed to determine quantitatively the effect of hypercholesterolemia induced by a lipid-rich diet on glomerulosclerosis in an animal model of nephrotic syndrome (NS) induced by Adriamycin (ADR). Twenty NS Wistar rats administered ADR with a single intravenous dose of 5 mg/kg body weight were divided into standard and lipid-rich chow groups. Another 20 weight-matched non-NS rats that received a vehicle alone were grouped as controls. Quantitative analyses of renal histological changes were performed with determination of blood and urine biochemical parameters. It was found that serum cholesterol was markedly higher in rats with lipid-rich chow in both NS and non-NS rats. Urinary protein was significantly higher in rats on the lipid-rich diet in the NS group. The mesangial matrix and cell indices were significantly increased in rats with the lipid-rich diet and the most obvious changes were found in the NS group. Lipid deposits and foam cells were observed in mesangial areas, and some glomeruli had progressed to form focal and segmental glomerulosclerosis in the NS group. Findings indicated that diet-induced hyperlipidemia can lead to proliferation of mesangial cells and accumulation of mesangial matrices, and further aggravate glomerulosclerosis in Adriamycin-induced nephrosis.

Animals↗

PubMed2000

Modeling concurrent binding of multiple molecular species in cell adhesion.

Cell adhesion provides not only physical linkage but also communication between the cell and its environment. As such, it is important to many cellular functions. Recently, the probability distribution of forming a low number of specific adhesive bonds in a short-duration contact has been described (Chesla et al., Biophys. J. , 1998, 75:1553-1572). This model assumes that binding occurs between a single receptor species and a single ligand species. However, cell adhesion molecules rarely work alone in physiological settings. To account for these in vivo situations, we extended the previous model to include concurrent interactions of multiple receptor-ligand species, introducing the concept of independent binding. Closed-form solutions have been obtained for cases where competition is absent or can be neglected. In two companion papers (Williams et al., Biophys. J., 2000, 79:1858-1866; 2000, 79:1867-1875), the model developed herein has been applied to analyze two sets of experiments designed such that the validity of the theory was also tested.

Animals↗

PubMed2000

Concurrent binding to multiple ligands: kinetic rates of CD16b for membrane-bound IgG1 and IgG2.

CD16b (FcgammaRIIIb) is the most common receptor for the Fc domain of IgG on leukocytes. The binding of Fc receptors to immunoglobulin triggers a wide array of immune responses. In published assays measuring the reaction of CD16b with isotypes of soluble IgG, the affinity for IgG1 was low and that for IgG2 was undetectable. Here we report the first measurement of kinetic rates of CD16b binding to membrane-bound IgG isotypes-a physically distinct and physiologically more relevant presentation-using a recently developed micropipette method. In contrast to the soluble data, we found clearly measurable IgG2 binding, with a forward kinetic rate six-fold lower than that of IgG1 but with an equilibrium affinity only threefold lower. This suggests a nonnegligible role for IgG2 in Fc-mediated immune responses, particularly in longer duration contacts. The binding constants were measured from two sets of experiments. Single-isotype experiments were analyzed by an existing model (, Biophys. J. 75:1553-1572). The resulting kinetic rates were used as input to an extended model (, Biophys. J. 79:1850-1857.) to predict the results of mixed-isotype experiments. This design enabled rigorous validation of the concurrent binding model through a test of its predictive ability.

Animals↗

PubMed2000

Concurrent and independent binding of Fcgamma receptors IIa and IIIb to surface-bound IgG.

Fc receptor-antibody interactions are key mechanisms through which antibody effector functions are mediated. Neutrophils coexpress two low-affinity Fcgamma receptors, CD16b (FcgammaRIIIb) and CD32a (FcgammaRIIa), possessing overlapping ligand binding specificities but distinct membrane anchor and signaling capacities. Using K562 cell transfectants as a model, the kinetics of both separate and concurrent binding of CD16b and CD32a to surface-bound IgG ligands were studied. CD16b bound human IgG with 2-3 times higher affinity than did CD32a (A(c)K(a) = 4.1 and 1.6 x 10(-7) microm(4), respectively) and both FcgammaRs had similar reverse kinetic rates (k(r) = 0.5 and 0.4 s(-1), respectively). Because CD16b is expressed on neutrophils at a 4-5 times higher density than CD32a, our results suggest that CD16b plays the dominant role in binding of neutrophils to immobilized IgG. The question of possible cross-regulation of binding affinity between CD16b and CD32a was investigated using our multispecies concurrent binding model (Zhu and Williams, Biophys. J. 79:1850-1857, 2000). Because the model assumes independent binding (no cooperation among different species), the excellent agreement between the model predictions and the experimental data suggests that, when coexpressed on K562 cells, these two FcgammaRs do not interact in a manner that alters the kinetic rates of either molecule.

Antibodies, Blocking↗

PubMed2000

Kinetics and mechanics of cell adhesion.

Cell adhesion is mediated by specific interaction between receptors and ligands. Such interaction provides not only physical linkage but also communication between the cell and its environment. The kinetics and mechanics of cell adhesion are coupled, because force can influence the formation and dissociation of receptor-ligand bonds. The kinetic rates and their force dependence determine how likely, how rapidly and how strongly cells bind as well as how long they remain bound. Since adhesion molecules are linked to apposing cellular membranes, their interaction is governed by two-dimensional (2D) kinetics. This is in contrast to the three-dimensional (3D) binding of soluble ligands to cell surface receptors. Unlike the 3D case in which many methods are available for measuring kinetic rates, not until recently have the 2D kinetic rates become experimentally measurable. In this review, I will discuss the recent progress in the experimental methods that enable quantification of the relevant kinetic and mechanical parameters, the fundamental concepts that underlie the physics of the biological phenomena, and the mathematical models that relate functions to the intrinsic properties of the adhesion molecules.

Animals↗

PubMed2000

Photocatalytic degradation of AZO dyes by supported TiO2 + UV in aqueous solution.

The photocatalytic degradation performance of photocatalysts TiO2 supported on 13-X, Na-Y, 4A zeolites with different loading content was evaluated using the photocatalytic oxidation of dyes direct fast scarlet 4BS and acid red 3B in aqueous medium. The results showed that the best reaction dosage of TiO2-zeolite catalysts is about 2 g/l and the photocatalytic kinetics follows first order for all supported catalysts. The photocatalytic activity order of the three series catalysts is 13X type >Y type >4A type. The physical state of titanium dioxide on the supports is evaluated by X-ray photoelectron spectra (XPS), powder X-ray diffraction (XRD), BET, and FTIR.

Azo Compounds↗

PubMed2000

A study on producing monoclonal antibody with one diagnostic marker screened electrophoretically from the urine of individuals infected with Schistosoma japonicum.

One diagnostic marker (a glycoprotein with 30kDa) from the urine of individuals infected with S. japonicum was screened with electrophoresis, and used as antigen to produce McAbs. Two lines of McAbs, named NP56 and NP54,were obtained. McAb NP56 was of better immunoreactivity and its immunoglobulin isotype was IgG(2b.) McAb NP56 could react with SEA (soluble egg antigen) and AWA (adult worm antigen) and express on miracidia in eggs of S. japonicum. When determined with NP56 as a probe in indirect ELISA, the sensitivity and specificity of positive urine samples (EPG median 69) was 50% and 80% in original urine samples, and 90% and 100% in concentrated urine samples, respectively. The results above indicated that with established means it is feasible to produce McAb with the diagnostic marker screened electrophoretically from the metabolic product of the individuals infected with this pathogen, and that McAb-NP56 is of potential value in the diagnosis of chronic cases and individuals with light infection with S. japonicum.

Animals↗

PubMed2000

3Beta-hydroxy-6-aza-cholestane and related analogues as phosphatidylinositol specific phospholipase C (PI-PLC) inhibitors with antitumor activity.

6-Aza steroid analogues were synthesized as PI-PLC inhibitors. The most active compound, 3beta-hydroxy-6-aza-cholestane (1) showed potent PI-PLC inhibition (IC50 = 1.8 microM), similar to that of the commercially available steroid analogue U73122 (IC50 = 1-2.1 microM). Compound 1 exhibited significant growth inhibition effects (IC50 = 1.3 microM in each case) against MCF-7 and HT-29 cancer cells in in vitro cell culture. Compound 1 also inhibited the in vitro adhesion and transmigration of HT-1080 fibrosarcoma cells at 2.5 and 5.0 microM, respectively. In vivo, compound 1, at 1 mg/kg/day, reduced the volume of MCF-7 tumors in xenograft models, without weight loss in mice. Structure activity relationships of this series of compounds revealed that a hydrophobic cholesteryl side chain, 3beta-hydroxy group and a C-6 nitrogen containing a hydrogen atom at position-6 are crucial for activity. N-Maleic amidoacid derivative 11 also exhibited weak inhibition (IC50 = 16.2 microM).

Animals↗

PubMed2000

DNA ligase IV deficiency in mice leads to defective neurogenesis and embryonic lethality via the p53 pathway.

DNA ligase IV (LIG4) is a nonhomologous end-joining (NHEJ) protein used for V(D)J recombination and DNA repair. In mice, Lig4 deficiency causes embryonic lethality, massive neuronal apoptosis, arrested lymphogenesis, and various cellular defects. Herein, we assess potential roles in this phenotype for INK4a/ARF and p53, two proteins implicated in apoptosis and senescence. INK4a/ARF deficiency rescued proliferation/senescence defects of Lig4-deficient fibroblasts but not other phenotypic aspects. In contrast, p53 deficiency rescued embryonic lethality, neuronal apoptosis, and fibroblast proliferation/senescence defects but not lymphocyte development or radiosensitivity. Young Lig4/p53 double null mice routinely died from pro-B lymphomas. Thus, in the context of Lig4 deficiency, embryonic lethality and neuronal apoptosis likely result from a p53-dependent response to unrepaired DNA damage, and neuronal apoptosis and lymphocyte developmental defects can be mechanistically dissociated.

Animals↗

PubMed2000

Telomere dysfunction impairs DNA repair and enhances sensitivity to ionizing radiation.

Telomeres are specialized nucleoprotein complexes that serve as protective caps of linear eukaryotic chromosomes. Loss of telomere function is associated with rampant genetic instability and loss of cellular viability and renewal potential. The telomere also participates in processes of chromosomal repair, as evidenced by the 'capture' or de novo synthesis of telomere repeats at double-stranded breaks and by the capacity of yeast telomeres to serve as repositories of essential components of the DNA repair machinery, particularly those involved in non-homologous end-joining (NHEJ). Here we used the telomerase-deficient mouse, null for the essential telomerase RNA gene (Terc), to assess the role of telomerase and telomere function on the cellular and organismal response to ionizing radiation. Although the loss of telomerase activity per se had no discernable impact on the response to ionizing radiation, the emergence of telomere dysfunction in late-generation Terc-/- mice imparted a radiosensitivity syndrome associated with accelerated mortality. On the cellular level, the gastrointestinal crypt stem cells and primary thymocytes showed increased rates of apoptosis, and mouse embryonic fibroblasts (MEFs) showed diminished dose-dependent clonogenic survival. The radiosensitivity of telomere dysfunctional cells correlated with delayed DNA break repair kinetics, persistent chromosomal breaks and cytogenetic profiles characterized by complex chromosomal aberrations and massive fragmentation. Our findings establish a intimate relationship between functionally intact telomeres and the genomic, cellular and organismal response to ionizing radiation.

Animals↗

PubMed2000

Correlation between caspase-3 activation and three different markers of DNA damage in neonatal cerebral hypoxia-ischemia.

Caspase-3 has been identified as a key protease that, by targeting a limited number of proteins, can disrupt essential homeostatic processes and initiate an orderly disassembly of cells, including degradation of genomic DNA. We demonstrate the usefulness of an antibody specific for activated caspase-3 in a model of neonatal rat hypoxia-ischemia (Hl) and correlate the spatial and temporal activation of caspase-3 with three different markers of DNA damage and with the loss of a neuronal marker [microtubule-associated protein 2 (MAP 2)]. An oligonucleotide hairpin probe (HPP) with one base overhang in the 3' end displayed a close colocalization with caspase-3 activation at 3 h post-Hl, whereas terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) appeared later (24 h post-Hl). A monoclonal antibody against single-stranded DNA appeared to stain an entirely different population of cells, not positive for active caspase-3, HPP, or TUNEL at this time point. After 24 h of reperfusion, however, when cellular injury is extensive, all markers stained a large number of cells with a high degree of colocalization, and all markers delineated regions with loss of MAP 2. We conclude that the HPP shows the best correlation with pathological caspase-3 activation in this model.

Animals↗

PubMed2000

Inhibition of oxidative DNA damage in vitro by extracts of brussels sprouts.

Cruciferous vegetables have cancer preventive effects which may be due to reduction of oxidative DNA damage. We investigated the effect of an aqueous extract of cooked Brussels sprouts on formation of 7-hydro-8-oxo-2'-deoxyguanosine (8-oxodG) in calf thymus DNA in vitro. Damage was induced by a Fenton reaction, UVC (254 nm), UVA (365 nm), sunlamp light, and methylene blue with visible light. The extract inhibited 8-oxodG formation in all systems except visible light with methylene blue. The IC50 values were 6-20 microg/ml corresponding to the extract of 5-20 g of Brussels sprouts distributed in a volume of 50 L. The protective effect in the Fenton reaction was unaffected by addition of EDTA. After HPLC separation fractions were identified with similar DNA protective effects. Sinigrin, a glucosinolate abundant in Brussels sprouts, co-eluted with the most effective fraction and had DNA protective effects. In comparison with other antioxidants the patterns of effect of the extract in the five damage systems were more similar to that of sodium azide than to those of dimethylsulfoxide and vitamin C. Constituents of Brussels sprouts can protect DNA by direct scavenging, e.g. hydroxyl radical and other oxidants, without prooxidant effects at concentrations potentially achievable by modest intake of the vegetable.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2000

Fundamentals of biomechanics in tissue engineering of bone.

The objective of this review is to provide basic information pertaining to biomechanical aspects of bone as they relate to tissue engineering. The review is written for the general tissue engineering reader, who may not have a biomechanical engineering background. To this end, biomechanical characteristics and properties of normal and repair cortical and cancellous bone are presented. Also, this chapter intends to describe basic structure-function relationships of these two types of bone. Special emphasis is placed on salient classical and modern testing methods, with both material and structural properties described.

Animals↗

PubMed2000

A homolog of mammalian antizyme is present in fission yeast Schizosaccharomyces pombe but not detected in budding yeast Saccharomyces cerevisiae.

MOTIVATION: The antizymes (AZ) are proteins that regulate cellular polyamine pools in metazoa. To search for remote homologs in single-celled eukaryotes, we used computer software based on hidden Markov models. The most divergent homolog detected was that of the fission yeast Schizosaccharomyces pombe. Sequence identities between S.POMBE: AZ and known AZs are as low as 18-22% in the most conserved C-terminal regions. The authenticity of the S.POMBE: AZ is validated by the presence of a conserved nucleotide sequence that, in metazoa, promotes a +1 programmed ribosomal frameshift required for AZ expression. However, no homolog was detected in the completed genome of the budding yeast Saccharomyces cerevisiae. Procedural details and supplementary information can be found at http://itsa.ucsf.edu/ approximately czhu/AZ.

Amino Acid Sequence↗

PubMed2000

Comparison of isoflurane effects on motor evoked potential and F wave.

BACKGROUND: Volatile anesthetics produce surgical immobility by suppressing the motor system. The anesthetic action site in the motor pathway is unclear. Anesthetic effects on the whole and the lower portion of motor pathway can be studied by measuring the motor evoked potentials (MEP) and the F wave. This study measured the effect of isoflurane on the MEP and the F wave. METHODS: With institutional review board approval, we studied 12 adult patients with American Society of Anesthesiologists physical status I or II. After intubation, anesthesia was maintained with nitrous oxide/oxygen and propofol infusion. MEPs were elicited by transcranial electrical stimuli (train-of-five pulse; stimuli intensity 40-160 mA) through electrodes placed in the scalp at C3/C4 positions and recorded at the anterior tibialis muscle with an Axon Sentinel-4EP monitor. F waves were elicited by an electrode fixed over the posterior tibial nerve at the medial malleolus and recorded at the abductor hallucis muscle. After end-tidal concentration of isoflurane was maintained at 0.5% for 20 min, the MEP and F wave were measured again. MEP and F-wave changes before and after isoflurane were analyzed using paired Wilcoxon test with Bonferroni correction. The difference between the changes in MEP and F wave was analyzed using Friedman's test. RESULTS: Motor evoked potential amplitudes (median, 205 microV; 25th-75th percentiles, 120-338 microV), F-wave amplitude (median, 100 microV; 25th-75th percentiles, 64.2-137.5 microV), and F-wave persistence (59 +/- 29%) were decreased to 0 microV (0-15 microV), 49 microV (12.4-99.6 microV), and 30 +/- 31%, respectively, by 0.5% isoflurane. MEP amplitude suppression was different from the changes in F-wave amplitude and persistence (P < 0.02). CONCLUSIONS: Isoflurane 0.5% suppresses the motor pathway by decreasing both MEP and F wave. The MEP is suppressed more than the F wave.

Adult↗