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Biomedical subjects

Z Lou

Publications and source records attributed to Z Lou.

At least 19 recordsLinked to original sources
PubMed2001

A role for a RhoA/ROCK/LIM-kinase pathway in the regulation of cytotoxic lymphocytes.

Polarization of lipid rafts and granules to the site of target contact is required for the development of cell-mediated killing by cytotoxic lymphocytes. We have previously shown that these events require the activation of proximal protein tyrosine kinases. However, the downstream intracellular signaling molecules involved in the development of cell-mediated cytotoxicity remain poorly defined. We report here that a RhoA/ROCK/LIM-kinase axis couples the receptor-initiated protein tyrosine kinase activation to the reorganization of the actin cytoskeleton required for the polarization of lipid rafts and the subsequent generation of cell-mediated cytotoxicity. Pharmacologic and genetic interruption of any element of this RhoA/ROCK/LIM-kinase pathway inhibits both the accumulation of F-actin and lipid raft polarization to the site of target contact and the subsequent delivery of the lethal hit. These data define a specialized role for a RhoA-->ROCK-->LIM-kinase pathway in cytotoxic lymphocyte activation.

Actins↗
PubMed2001

[Extraction of MUAP from NEMG signal using self-organization competing NN].

The pattern classification of motor unit action potential (MUAP) of needle electrode electromyogram (NEMG) signal by means of self-organization competing Neural Network(NN) has been accomplished in this paper. The parameters and the power of excited white-noise of auto-regressive (AR) model are taken as the feature of MUAP. The results of simulated NEMG and real NEMG all show that this method of classification is very effective and correct, and thus it presents a new approach to the extraction of MUAP template in the study of decomposition of NEMG.

Action Potentials↗
PubMed2001

Automatic analysis of image of surface structure of cell wall-deficient EVC.

Some computer applications for cell characterization in medicine and biology, such as analysis of surface structure of cell wall-deficient EVC (El Tor Vibrio of Cholera), operate with cell samples taken from very small areas of interest. In order to perform texture characterization in such an application, only a few texture operators can be employed: the operators should be insensitive to noise and image distortion and be reliable in order to estimate texture quality from images. Therefore, we introduce wavelet theory and mathematical morphology to analyse the cellular surface micro-area image obtained by SEM (Scanning Electron Microscope). In order to describe the quality of surface structure of cell wall-deficient EVC, we propose a fully automatic computerized method. The image analysis process is carried out in two steps. In the first, we decompose the given image by dyadic wavelet transform and form an image approximation with higher resolution, by doing so, we perform edge detection of given images efficiently. In the second, we introduce many operations of mathematical morphology to obtain morphological quantitative parameters of surface structure of cell wall-deficient EVC. The obtained results prove that the method can eliminate noise, detect the edge and extract the feature parameters validly. In this work, we have built automatic analytic software named "EVC.CELL".

Cell Membrane↗
PubMed2000

A balance between positive and negative signals in cytotoxic lymphocytes regulates the polarization of lipid rafts during the development of cell-mediated killing.

Plasma membrane microdomains containing sphingolipids and cholesterol (lipid rafts) are enriched in signaling molecules. The cross-linking of certain types of cell surface receptors initiates the redistribution of these lipid rafts, resulting in the formation of signaling complexes. However, little is known about the regulation of the initial raft redistribution and whether negative regulatory signaling pathways target this phase of cellular activation. We used natural killer (NK) cells as a model to investigate the regulation of raft redistribution, as both positive and negative signals have been implicated in the development of their cellular function. Here we show that after NK cells form conjugates with sensitive tumor cells, rafts become polarized to the site of target recognition. This redistribution of lipid rafts requires the activation of both Src and Syk family protein tyrosine kinases. In contrast, engagement of major histocompatibility complex (MHC)-recognizing killer cell inhibitory receptors (KIRs) on NK cells by resistant, MHC-bearing tumor targets blocks raft redistribution. This inhibition is dependent on the catalytic activity of KIR-associated SHP-1, a Src homology 2 (SH2) domain containing tyrosine phosphatase. These results suggest that the influence of integrated positive and negative signals on raft redistribution critically influences the development of cell-mediated cytotoxicity.

Animals↗
PubMed2000

Effect of micelle fatty acid composition and 3,4,3', 4'-tetrachlorobiphenyl (TCB) exposure on intestinal [(14)C]-TCB bioavailability and biotransformation in channel catfish in situ preparations.

Polychlorinated biphenyls are transferred in the diet along aquatic food chains. This study investigated the effect of dietary micelle composition and 3,4,3',4'-tetrachlorobiphenyl (TCB) exposure upon the subsequent systemic bioavailability and intestinal metabolism of [(14)C]-TCB in a catfish in situ intestinal preparation. Initial in vitro experiments examined the solubility of [(14)C]-TCB in micelles of varying fatty acid composition. Micelles composed of single fatty acids demonstrated greater [(14)C]-TCB solubility with those fatty acids of longer chain length. Similarly, micelles of the long-chain fatty acid, linoleic acid, solubilized more [(14)C]-TCB than mixed micelles formulated from equal amounts of myristic (14:0), palmitic (16:0), stearic (18:0), or linoleic (18:2) acids. Systemic bioavailability of [(14)C]-TCB (60 microM) from an in situ perfused intestinal preparation was 2.2-fold greater when delivered to the intestine in linoleic acid micelles as compared to the mixed micelle preparation. Catfish exposed in vivo to either 0.5 or 5.0 mg TCB/kg feed for 10 days resulted in a 45 to 47% decrease in the subsequent systemic bioavailability of [(14)C]-TCB in the in situ intestinal preparation. Total intestinal cytochrome P450 content was not significantly affected by TCB preexposure. Immunodetectable CYP1A was found only in the 5.0 mg TCB/kg diet treatment. Corresponding intestinal aryl hydrocarbon hydroxylase (AHH) activities were 2.46 +/- 1.16, 2.43 +/- 1.58, and 11.35 +/- 10.25 pmol/min/mg protein for the control, 0.5, and 5 mg TCB/kg diet groups, respectively. [(14)C]-TCB in the in situ preparation was metabolized to only a small degree upon a single pass through the intestinal mucosa of the catfish. High variability and low rates of metabolism precluded the association of the magnitude of metabolism with dietary TCB pretreatment. Analysis of tissue sample extracts demonstrated 4 minor peaks, 3 of which were tentatively identified by co-elution with standards as 2-OH-3,4,3',4'-TCB, 4-OH-3,5,3',4'-TCB, and 5-OH-3, 4,3',4'-TCB. A fourth remains unidentified. Histological changes in the intestine such as thinning of the submucosa and increased numbers of goblet cells were evident at the 5.0 mg TCB/kg diet dose. These results suggest that TCB intestinal bioavailability may be linked to micelle composition as well as TCB exposure history. Furthermore, single pass intestinal metabolism appears to be a minor contributor to the biotransformational modification of dietary TCB.

Animals↗
PubMed2000

Effects of eating space and availability of water in feeders on productivity and eating behavior of grower/finisher pigs.

Three experiments were conducted to determine the effects of eating space and availability of water within feeders on the productivity and behavior of growing/finishing pigs. In Exp. 1, 12 commercial feeders were classified as being either single-space (SS) or multiple-space (MS), and either as dry (D) or wet/dry (WD), resulting in two SS-D, four MS-D, three SS-WD and three MS-WD models. Each model was evaluated using four pens of 12 pigs, which were fed a mash diet throughout the growing/finishing period (25 to 106 kg). Pigs were videotaped when they were approximately 40 and 80 kg in weight to determine eating behavior. The number of feeding spaces did not affect the productivity of the pigs, but the presence of water within the feeder resulted in increases in ADFI (P < .05) and ADG (P < .05) and a reduction in carcass lean (P < .05). Pigs eating from SS feeders spent 15% less time eating than those fed from two-space feeders (P < .05), and occupancy rate for feeding spaces was increased by 75% (P < .05). The WD feeders also resulted in a reduction (17%) in eatingtime compared to D models (P < .01), and occupancy rate for WD feeders was similarly reduced (P < .05). Pigs spent 16% less time eating when they weighed approximately 80 kg than when they weighed 40 kg (P < .01). In Exp. 2, rate of eating was determined during a short test on the same 12 feeder models for both small (48 kg) and large (90 kg) pigs. Large pigs ate faster than small pigs, but eating rate was not affected by feeding space or presence of water in the feeder. In Exp. 3, eating rate was determined for small amounts of dry or wet feed. Premixing water with the feed (1:1 ratio by weight) increased eating speed (P < .01). We concluded that 12 pigs can be fed from a single-space feeder without affecting productivity. The inclusion of water within a feeder decreases time spent eating, but it increases ADFI and ADG. When pigs are small, they spend more time eating, and feeder occupancy rates are higher than when they are large.

Animal Husbandry↗
PubMed2000

[Experiments on elimination of the noise in NEMG by adopting wavelet transform].

Wavelet transform (WT) is a promising technique for time-frequency analysis. By decomposing signals into elementary building blocks that are well localized both in time and frequency, the WT can characterize the local regularity of signal. In this paper, we process the needle electrode electromyography (NEMG) signal with noise by adopting WT and have completed the contrast experiments. The results show that WT is an effective method by which high frequency noise and baseline drift in NEMG can successfully be eliminated by selecting proper transform scales of WT.

Electromyography↗
PubMed1999

Properties of excitatory amino acid transport in the human U373 astrocytoma cell line.

In this study, we describe the presence of Na(+)-dependent high-affinity L-glutamate transport activity in the human U373 astrocytoma cell line. U373 cells exhibited a robust accumulation of L-glutamate which was predominantly (85%) extracellular Na(+)-dependent. Kinetic analysis of this transport activity revealed that the uptake followed first-order Michaelis-Menten kinetics and was high-affinity in nature. The kinetic parameters estimated by Eadie-Hofstee transformation of the saturable uptake were 37.3 +/- 5.1 microM for K(m) and 0.13 +/- 0.02 nmol min-1 mg-1 protein for Vmax. A total of 14 known inhibitors of high-affinity L-glutamate transport were examined for their abilities to inhibit L-glutamate uptake by U373 cells. Three compounds, kainate (KA), dihydrokainate (DHK) and alpha-aminoadipic acid produced less than 30% inhibition at 1 mM. The lack of effect of both KA and DHK indicates that the predominant astroglial L-glutamate transporter EAAT2 (excitatory amino acid transporter 2) does not contribute to the uptake activity present in these cells. The rank order of inhibitory potency for the remaining 11 compounds tested was L-cysteine sulphinate = L-CCG-III = L-cysteate = L-aspartate = threo-beta-hydroxyaspartate > trans-PDC > D-aspartate = MPDC > beta-glutamate > L-CCG-IV = L-aspartate-beta-hydroxamate. Pre-treatment of U373 cells with phorbol ester for 30 min resulted in a 56% decrease in L-glutamate uptake and this effect was blocked in a concentration-dependent manner by the PKC inhibitor bisindolylmaleimide I. Expression of L-glutamate transporters by U373 cells was examined by reverse transcriptase polymerase chain reaction (RT-PCR) and Western analysis. Transcripts for both the EAAT1 and EAAT3 transporter subtypes were detected but not for EAATs 2, 4, and 5. Immunoblot analysis confirmed the presence of EAAT3 protein, however, we were unable to detect EAAT1 protein. In conclusion, the Na(+)-dependent high-affinity L-glutamate transport into human U373 astrocytoma cells appears to be mediated predominantly by the EAAT3 subtype.

ATP-Binding Cassette Transporters↗
PubMed1999

Steroid hormone-inducible expression of the GLT-1 subtype of high-affinity l-glutamate transporter in human embryonic kidney cells.

The cDNA encoding the predominant rat brain high-affinity l-glutamate transporter GLT-1 was isolated and subcloned into the pIND expression vector for the establishment of steroid hormone inducible expression in vitro using the ecdysone-inducible mammalian expression system. Steroid hormone-inducible expression was demonstrable in a stable cell line designated HEK/GLT-1. Treatment of HEK/GLT-1 cells with 10 microM ponasterone A for 24 hincreased the maximum velocity (V(max)) of Na(+)-dependent l-glutamate uptake by greater than 10-fold, as compared with the uninduced cells. Equivalent levels of l-glutamate transport capacity were observed in the uninduced GLT-1 cell line and the host cell line indicating that the expression of GLT-1 was tightly regulated. To confirm that the increased l-glutamate uptake observed in HEK/GLT-1 cells following induction was attributable to the expression of GLT-1, rather than the up-regulation of the endogenously expressed EAAT3 subtype present in the host cells, we evaluated the effects of the selective GLT-1 inhibitors dihydrokainate (DHK) and kainate. Both DHK and kainate produced concentration-dependent inhibition of the l-glutamate uptake into HEK/GLT-1 cells, and the estimated IC(50) values were consistent with those described for the cloned GLT-1. These results demonstrate that the expression of GLT-1 can be tightly regulated in vitro using the ecdysone system.

ATP-Binding Cassette Transporters↗
PubMed1999

Inducible expression and pharmacology of the human excitatory amino acid transporter 2 subtype of L-glutamate transporter.

1. In this study we have examined the use of the ecdysone-inducible mammalian expression system (Invitrogen) for the regulation of expression of the predominant L-glutamate transporter EAAT2 (Excitatory Amino Acid Transporter) in HEK 293 cells. 2. HEK 293 cells which were stably transformed with the regulatory vector pVgRXR (EcR 293 cells) were used for transfection of the human EAAT2 cDNA using the inducible vector pIND and a clone designated HEK/EAAT2 was selected for further characterization. 3. Na+-dependent L-glutamate uptake activity (3.2 pmol min-1 mg-1) was observed in EcR 293 cells and this was increased approximately 2 fold in the uninduced HEK/EAAT2 cells, indicating a low level of basal EAAT2 activity in the absence of exogenous inducing agent. Exposure of HEK/EAAT2 cells to the ecdysone analogue Ponasterone A (10 microM for 24 h) resulted in a > or = 10 fold increase in the Na+-dependent activity. 4. L-glutamate uptake into induced HEK/EAAT2 cells followed first-order Michaelis-Menten kinetics and Eadie-Hofstee transformation of the saturable uptake data produced estimates of kinetic parameters as follows; Km 52.7+/-7.5 microM, Vmax 3.8+/-0.9 nmol min-1 mg-1 protein. 5. The pharmacological profile of the EAAT2 subtype was characterized using a series of L-glutamate transport inhibitors and the rank order of inhibitory potency was similar to that described previously for the rat homologue GLT-1 and in synaptosomal preparations from rat cortex. 6. Addition of the EAAT2 modulator arachidonic acid resulted in an enhancement (155+/-5% control in the presence of 30 microM) of the L-glutamate transport capacity in the induced HEK/EAAT2 cells. 7. This study demonstrates that the expression of EAAT2 can be regulated in a mammalian cell line using the ecdysone-inducible mammalian expression system.

ATP-Binding Cassette Transporters↗
PubMed1999

[Changes of glutamate and GABA in cerebrospinal fluid of patients with pneumonia complicated with central nervous system damage].

Glutamate(Glu), gamma-aminobutyric acid(GABA), and malondialdehyde(MDA) in cerebrospinal fluid (CSF) were measured in 18 children with pneumonia complicated with central nervous system(CNS) damage, 14 children with pneumonia without CNS damage, and 7 children with hypocalcemic tetany. The concentration of Glu and MDA and the ratio of Glu/GABA in CSF of pneumonia without CNS damage were significantly higher than the others. The ratio of Glu/GABA in CSF of the children with pneumonia with consciousness obstacle after convulsion was higher than that without consciousness obstacle after convulsion. These results suggest that Glu and free radicals may play a critical role in the CNS damage caused by pneumonia, however GABA may reduce the CNS damage caused by pneumonia.

Brain Diseases↗
PubMed1999

[Studies on identification of yinchaihu by UV and IR].

OBJECTIVE: To study the identification of nine species of Yinchaihu derived from four genera of Caryophyllaceae, namely, Stellaria dichotoma var. lanceolata, St. dichotoma var. dichotoma, Arenaria juncea, A. capillaris var. glandulifera, Silene fortunei, Si. jenisseensis, Gypsophila pacifica, G. oldhamiana and G. licentiana. METHOD: UV and IR of alcohol extraction. RESULTS: The UV and IR spectra of these 9 plant roots have some difference. CONCLUSION: St. dichotoma var. lanceolata specified in the Chinese Pharmacopoeia can be distinguished from the other plants and all these 4 genera can be differentiated from one another by both UV and first derivative spectra. The genus Stellaria can be identified from the other 3 genera by IR.

Caryophyllaceae↗
PubMed1998

The pharmacological profile of L-glutamate transport in human NT2 neurones is consistent with excitatory amino acid transporter 2.

The human teratocarcinoma cell line NTera2/D1 can be differentiated to produce post-mitotic neurones (NT2-N cells) by prolonged (> 3 week) exposure to retinoic acid. In this study, we describe the characterisation of high-affinity Na+-dependent L-glutamate transport activity in post-mitotic differentiated NT2-N cells. NT2-N cells, but not the undifferentiated precursor cells, transported L-glutamate in a Na+-dependent manner, as determined by equimolar replacement of Na+ with choline. L-glutamate uptake was saturable and Eadie-Hofstee transformation of the saturation data revealed a Km of 10.6+/-0.8 microM, and a maximum transport capacity (Vmax) of 100.3+/-12.3 pmol min(-1) mg(-1) protein. Pharmacological characterisation of the transport activity in NT2-N cells produced a rank order of inhibitory activity which was identical to that determined for the human excitatory amino acid transporter 2 which we have analysed in a stable mammalian cell line (Madin Darby Canine Kidney (MDCK) cells). Of particular note, L-glutamate transport by NT2-N cells was sensitive to both dihydrokainate and kainate. The expression of human excitatory amino acid transporter mRNAs was studied using reverse transcriptase polymerase chain reaction. NT2-N cells expressed transcripts for excitatory amino acid transporters 2 and 3, but not for the subtypes 1, 4 and 5. We conclude that although the mRNA expression studies suggest the presence of transcripts for both excitatory amino acid transporter 2 and 3 in NT2-N cells, the sensitivity to dihydrokainate and kainate determined in the pharmacological analysis indicates that, of the known transporter subtypes, excitatory amino acid transporter 2 contributes to the bulk of the L-glutamate transport activity present in these cells.

Animals↗
PubMed1998

[The development of a myocardial infarction monitoring system].

In this paper, the author will discuss the system design of one portable myocardial infarction monitoring system which possesses the functions of the general arrhythmia monitoring and the alarm & emergency of acute myocardial infarction (AMI). This system also can provide accurate real time ECG signal parameters for clinic diagnosis.

Equipment Design↗
PubMed1996

[Restricting effects of geologic background system on genuine crude drugs in Sichuan].

The distribution, growth, output and quality of genuine crude drugs are restricted by geologic background system (GBS), whose extensional vector system "rock-->soil-->medicinal plants" accomplishes the unity of geological grand cycle and biological pulmonary circulation. This article describes how genuine crude drugs in Sichuan, such as Coptis chinensis, etc. for example, are restricted by GBS.

Animals↗
PubMed1996

[Botanical origin of commercial samples of traditional Chinese drug xixin (Herba Aasari)].

It has been found out that amony the 158 samples of commercial drug. Xixin (Herba Asari) collected from 28 provinces/cities of China, only three guarters are derived from the species specified in the Chinese Pharmacopoeia and the rest are not. One hundred and eleven samples are derived from Asarum heterotropoides var. mandshuricum and are presently used in 26 provinces/cities, 25 samples are derived from A. himalaicum and used in 10 provinces, the other 22 samples are derived from 9 species such as A. sieboldii, A. forbesii, etc.

China↗
PubMed1995

Characterization of the receptor protein tyrosine phosphatase gene product PTP gamma: binding and activation by triphosphorylated nucleosides.

A full-length cDNA for a novel isoform of the human receptor tyrosine phosphatase gamma gene (PTPRG) was overexpressed in Sf9 insect cells, and the gene product, PTP gamma, was purified and characterized. The protein was expressed as a M(r) approximately 185,000 protein accompanied by a M(r) approximately 120,000 putative cleavage product on SDS-PAGE analysis. The protein undergoes N-linked glycosylation and constitutive phosphorylation of serine residues. When assayed for tyrosine-specific phosphatase activity, PTP gamma dephosphorylated myelin basic protein at a pH optimum of 7.5 and a Km of 12.6 microM; reduced carboxyamidomethylated and maleylated lysozyme (RCM-lysozyme) at a pH optimum of 6.0 and a Km of 12 microM; and p-nitrophenylphosphate with a pH optimum of 5.5 and a Km of 3.5 mM. Phosphatase activity was inhibited by ZnCl2 and sodium orthovanadate; Mg2+, Mn2+, and Ca2+ ions were ineffective. The partially purified form of the enzyme was allosterically activated by triphosphorylated nucleosides, with a preference for purines. This activation was prevented by Mg2+ addition and did not occur when a purified form of the enzyme was utilized, suggesting that its activation depends on specific activating factors or conformational constraints. Interestingly, PTP gamma protein was specifically bound by an ATP-agarose matrix through its intracellular domain, suggesting a link between binding of nucleotides and activation of the phosphatase.

Adenosine Triphosphate↗