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Biomedical subjects

Liang Zhang

Publications and source records attributed to Liang Zhang.

At least 91 records · Page 5Linked to original sources
PubMed2003

3,4-methylenedioxymethamphetamine (MDMA) abuse markedly inhibits acetylcholinesterase activity and induces severe oxidative damage and liperoxidative damage.

OBJECTIVE: To investigate whether 3,4-methylenedioxymethamphetamine (MDMA) abuse produces another neurotoxicity which may significantly inhibit the acetylcholinesterase activity and result in severe oxidative damage and liperoxidative damage to MDMA abusers. METHODS: 120 MDMA abusers (MA) and 120 healthy volunteers (HV) were enrolled in an independent sample control design, in which the levels of lipoperoxide (LPO) in plasma and erythrocytes as well as the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and acetylcholinesterase (AChE) in erythrocytes were determined by spectrophotometric methods. RESULTS: Compared with the average values of biochemical parameters in the HV group, those of LPO in plasma and erythrocytes in the MA group were significantly increased (P < 0.0001), while those of SOD, CAT, GPX and AChE in erythrocytes in the MA group were significantly decreased (P < 0.0001). The Pearson product-moment correlation analysis between the values of AChE and biochemical parameters in 120 MDMA abusers showed that significant linear negative correlation was present between the activity of AChE and the levels of LPO in plasma and erythrocytes (P < 0.0005-0.0001), while significant linear positive correlation was observed between the activity of AchE and the activities of SOD, CAT and GPX (P < 0.0001). The reliability analysis for the above biochemical parameters reflecting oxidative and lipoperoxidative damages in MDMA abusers suggested that the reliability coefficient (alpha) was 0.8124, and that the standardized item alpha was 0.9453. CONCLUSION: The findings in the present study suggest that MDMA abuse can induce another neurotoxicity that significantly inhibits acetylcholinesterase activity and aggravates a series of free radical chain reactions and oxidative stress in the bodies of MDMA abusers, thereby resulting in severe neural, oxidative and lipoperoxidative damages in MDMA abusers.

Acetylcholinesterase↗
PubMed2003

[Alterations of G proteins in heart diseases].

Guanine nucleotide binding proteins (G proteins), known as an important signal transduction molecular, can physiologically couple extracellular signals identified by G protein-coupled receptors (GPCRs) to a series of intracellular effector to cause changes of gene transcription and protein's structure and function. Members of G protein family including Gs, Gi/o, Gq/11, and G12/13 express in the myocardium. In the heart G protein-mediated signal transduction generates diverse effects on myocardiac contractility, heart rate, heart rhythm, and myocyte growth. This review focuses on alterations of G protein in cardiac hypertrophy, heart failure, acute myocardial ischemia, and arrhythmia to help us to understand the pathogenesis and pathophysiology in heart diseases.

Animals↗
PubMed2003

[Comparison of endoscopic irsection and vaporization for superficial bladder cancer].

OBJECTIVE: To evaluate the method and clinical value of endoscopic surgery by comparing endoscopic resection and vaporization for superficial bladder tumor. METHODS: 396 patients with superficial bladder papillary transitional cell carcinoma were treated by endoscopic therapy. 180 patients (Group A) were treated by transurethral resection of bladder tumor (TURBT) and 216 (Group B) by transurethral vaporization of bladder tumor (TVBT). Periodic postoperative intra-vascular instillation of chemotherapy was given to both groups. Operating time, amount of bleeding during operation, complications and recurrence rate were compared. RESULTS: In group B, the amount of bleeding and complications during operation were lower than those in group A, but TVBT rated better by clearer view and simplicity in maneuver. The operating time, recurrence rate in group B were similar to those in group A. CONCLUSION: Transurethral vaporization of bladder cancer, with simplicity in maneuver, less bleeding and fewer complications, rates better in effectiveness and clinical value than resection.

Adult↗
PubMed2003

[In vitro differentiation of embryonic stem cells mediated by the supernatant of retinal cells and retinoid acid].

PURPOSE: To analyse the differentiation features of embryonic stem cells which were induced by the supernatant of retinal cells and retinoid acid (RA). METHODS: Embryonic bodies (EB) were gained when embryonic stem cells (ESC) were propagated 1 generation after anabiosis. 3.5d EB without digestion were induced at four conditions sorted as condition A, B, C and D. A contains only retinoid acid (RA) in medium; B contains RA and the supernatant from retinal neurons and glia of mouse; C contains RA and the supernatant from retinal pigment epithelium of human; D contains RA and the supernatant of fetal retinal glia. The changes of embryonic stem cells were observed and the immune cytochemistry was adopted to detect the nestin, glial fibrillary acid protein (GFAP), cytokeratin, microtubule-associated protein 2 (MAP-2) and rhodopsin in induced cells. RESULTS: (1) The changes of differentiation features of EB: The characteristics for early stage were almost same at the four conditions. The cells with various shapes could be seen around EB. EB were dispersed 3 weeks later. Additionally, the cells which were no more abounded and not clear boundary appeared at condition A, the round cells with high transparency at condition B, EB and the cells around EB with apparent pigment at condition C, the large cells with simplex shape and glia-like appearance at condition D. (2) Immune cytochemistry showed that the most induced cells were MAP-2 (+) cells, no nestin (+) cells appeared at the four conditions. There were no GFAP, cytokeratin or rhodopsin positive cells in condition A; However, GFAP (+), cytokeratin (+) and rhodopsin(+) cells could be seen at condition B, cytokeratin positive cells at condition C, GFAP positive cells at condition D. CONCLUSION: RA can induce embryonic stem cells into neurons in second induction. Several kinds of the supernatant from retinal cells have an effect on induction of ESC. ESC can be differentiated into cells associated with the origin of the supernatant.

Animals↗
PubMed2003

[Cloning, expressing and functional analysis of SjMF4, a novel Schistosoma japonicum gene].

Based on the phenomenon of the natural anti-schistosomiasis in Microtus fortis, the sera from normal Microtus fortis were employed to immunoscreen the cDNA library of adult Schistosoma japonicum (Chinese strain), two positive clones were obtained, RACE technique was further applied to amplify one of the clones, and a cDNA fragment with an ORF was identified. Sequencing revealed that it was a novel gene of Schistosoma japonicum, and it was named SjMF4 (Schistosoma japonicum Microtus fortis 4). Then the structure and functional motifs of SjMF4 were analysed. The gene was subcloned into pET-28a(+) vector; the recombinant protein showed good antigenicity in Western blotting. The gene was further subcloned into eukaryotic expression vector pcDNA3 to construct the DNA vaccine containing SjMF4. Immune experiments in mice showed significant protection that the recombinant plasmid did induce 28.64%+/-3.82% worm reduction and 21.73%+/-3.98% egg reduction than controls against the Schistosoma japonicum cercaria challenge.

Amino Acid Sequence↗
PubMed2002

Increased neonatal mortality in mice lacking cellular retinol-binding protein II.

Cellular retinol-binding protein II (CRBP II) is a member of the cellular retinol-binding protein family, which is expressed primarily in the small intestine. To investigate the physiological role of CRBP II, the gene encoding CRBP II was inactivated. The saturable component of intestinal retinol uptake is impaired in CRBP II(-/-) mice. The knockout mice, while maintained on a vitamin A-enriched diet, have reduced (40%) hepatic vitamin A stores but grow and reproduce normally. However, reducing maternal dietary vitamin A to marginal levels during the latter half of gestation results in 100% mortality/litter within 24 h after birth in the CRBP II(-/-) line but no mortality in the wild type line. The neonatal mortality in heterozygote offspring of CRBP II(-/-) dams (79 +/- 21% deaths/litter) was increased as compared with the neonatal mortality in heterozygote offspring of wild type dams (29 +/- 25% deaths per litter, p < 0.05). Maternal CRBP II was localized by immunostaining in the placenta at 18 days postcoitum as well as in the small intestine. These studies suggest that both fetal as well as maternal CRBP II are required to ensure adequate delivery of vitamin A to the developing fetus when dietary vitamin A is limiting.

Animals↗
PubMed2002

Patch-clamp recordings from white matter glia in thin longitudinal slices of adult rat spinal cord.

We developed a technique of whole cell patch-clamp recordings from white matter oligodendrocytes and astrocytes in 200-250 microm-thick horizontal slices of adult (>2 months, 240-260 g) rat thoracic spinal cord. The viability of the white matter, sectioned in Na(+)-free, low Ca(2+) media, and the function of axons were preserved for >8 h, as demonstrated by the propagation of TTX-sensitive compound action potentials (CAPs) and the sensitivity of their refractory period to K(+) channel blocker 4-aminopyridine (1 microM). Glial cells were visually identified within the slices with a 40 x water immersion objective using infra-red differential interference contrast (IR-DIC) video microscopy, and the details of their morphology were further elucidated after filling the cells with Lucifer Yellow or Alexa 350 fluorescent dyes during whole-cell recording. Using voltage steps and ramps, we revealed pronounced non-linearity of I-V relationships in both oligodendrocytes and astrocytes. Both types of cells expressed TEA-sensitive outward delayed rectifier-type currents activated at positive voltages but showed little, if any, signs of inward rectification at voltages up to -140 mV. At -70 mV holding voltage, bath-applied kainic acid (100 microM) activated inward currents in both types of cells. This novel horizontal slice preparation of adult rat thoracic cord will facilitate the examination of mature glial cell physiology, glial-axonal signaling and the pathophysiology of spinal cord trauma and ischemia.

4-Aminopyridine↗
PubMed2002

"Fleximers". Design and synthesis of a new class of novel shape-modified nucleosides(1).

A new class of shape-modified nucleosides is introduced. These novel "fleximers" feature the purine ring systems of adenosine, inosine, and guanosine split into their individual imidazole and pyrimidine components (as in 1-3). This structural modification serves to introduce flexibility into the nucleoside while still retaining the elements essential for recognition. As a consequence, these novel fleximers should find use as bioprobes for investigating enzyme-coenzyme binding sites as well as nucleic acid and protein interactions. Their design and synthesis are described.

Adenosine↗
PubMed2002

A fundamental oscillatory state of isolated rodent hippocampus.

Population neuronal rhythms of various frequencies are observed in the rodent hippocampus during distinct behavioural states. However, the question of whether the hippocampus exhibits properties of spontaneous rhythms and population synchrony in isolation has not been definitively answered. To address this, we developed a novel preparation for studying neuronal rhythms in a relatively large hippocampal tissue in vitro. We isolated the whole hippocampus from mice up to 28 days postnatal age, removing the dentate gyrus while preserving the functional CA3-to-CA1 connections. Placing the hippocampal isolate in a perfusion chamber for electrophysiological assessment extracellular recordings from the CA1 revealed rhythmic field potential of 0.5 to </= 4 Hz that occurred spontaneously and propagated along the ventro-dorsal hippocampal axis. We provide convergent evidence, via measurements of extracellular pH and K(+), recordings of synaptic and intracellular activities and morphological assessments, verifying that these rhythms were not the consequence of hypoxia. Data obtained via simultaneous extracellular and patch clamp recordings suggest that the spontaneous rhythms represent a summation of GABAergic IPSPs originating from pyramidal neurons, which result from synchronous discharges of GABAergic inhibitory interneurons. Similar spontaneous field rhythms were also observed in the hippocampal isolate prepared from young gerbils and rats. Based on these data, we postulate that the spontaneous rhythms represent a fundamental oscillatory state of the hippocampal circuitry isolated from extra-hippocampal inputs.

Animals↗
PubMed2002

Expression profiling of the response of Saccharomyces cerevisiae to 5-fluorocytosine using a DNA microarray.

5-Fluorocytosine is a commonly used antifungal agent. It acts by inhibiting the synthesis of fungal DNA and protein. In order to understand the global response of Saccharomyces cerevisiae to changes in DNA and protein synthesis caused by 5-fluorocytosine, genome-wide transcript profiling following 5-fluorocytosine exposure was obtained. A total of 96 genes were identified as responsive to 25 microg/ml fluorocytosine treatment for 90 min, which caused approximately 17% specific growth inhibition. The transcript levels of 57 genes were increased more than 2-fold, while it was found that the transcript levels of the other 39 genes decreased to a similar extent. Genes involved in DNA repair, synthesis and replication represented the highest proportion of induced genes identified, which may account for the easily acquired resistance to 5-fluorocytosine. Two enzyme encoding genes CTS1 and EGT2, which function in the separation of daughter cells from their mother cells, were down-regulated by a factor of 3.7 and 10.2, respectively, indicating that 5-fluorocytosine may also inhibit the separation of fungal cells.

Antifungal Agents↗
PubMed2002

Response of gene expression in Saccharomyces cerevisiae to amphotericin B and nystatin measured by microarrays.

The response of the yeast Saccharomyces cerevisiae to two polyene antibiotics, amphotericin B and nystatin, was studied by genomic expression profiling. The two agents produced highly similar expression pattern changes, which was consistent with their known identical mechanisms of action on cell membranes. Detailed analysis was focused on the amphotericin B-treated sample in this study. Our data showed that genes involved in mitochondrial ribosomal protein synthesis were more severely repressed than those in the cytoplasm, which might contribute to the cytotoxicity of amphotericin B. To counteract the leakage of intracellular nutrients and ions from the pores in the cell membrane caused by amphotericin B, c. 17 genes involved in transport facilitation were induced, presumably to allow more efficient uptake of nutrients and ions. The expression level of five genes involved in ergosterol synthesis dropped and three genes related to cell wall biogenesis were induced, indicating that the cell membrane and cell wall were also affected by the presence of polyene antibiotics. It was observed that the pleiotropic drug resistance network in yeast cells was activated after exposure to amphotericin B, possibly contributing to the acquisition of amphotericin B resistance. Part of the gene expression alteration measured by microarray was confirmed by quantitative RT-PCR.

Amphotericin B↗
PubMed2002

Analysis of human cellular retinol-binding protein II promoter during enterocyte differentiation.

Cellular retinol binding protein II (CRBP II) is a vitamin A-binding protein that is expressed specifically in small intestinal villus absorptive cells. Previous studies have shown that retinoic acid upregulates endogenous human CRBP II gene expression in differentiated Caco-2 cells. To better characterize the regulation of human CRBP II expression, we analyzed the ability of receptor-selective agonists to enhance transcription from the 5'-upstream flanking region of the human CRBP II gene. Stable transfection experiments showed that the proximal 2.8-kb region of the human CRBP II gene is sufficient for retinoic acid inducibility in differentiated Caco-2 cells. However, direct sequence analysis and transient transfection experiments indicate that, unlike the rat CRBP II promoter, the human CRBP II promoter is not a direct retinoid X receptor target. The results indicate that the retinoic acid responsiveness of the human CRBP II promoter is mediated by an indirect mechanism and that this mechanism is associated with enterocyte differentiation.

5' Flanking Region↗
PubMed2002

Analysis of amlodipine in human plasma by liquid chromatography-mass spectrometry.

A simple, sensitive, and specific liquid chromatographic method coupled with electrospray ionization (ESI)-mass spectrometry for the determination of amlodipine is developed. After extraction by ethyl acetate using nicardipine as the internal standard, solutes are separated on a C18 column with a mobile phase of methanol-1% HAc (65:35). Detection is performed on an air pressure ionization single quadruple mass spectrometer equipped with an ESI interface and operated in positive-ionization mode. Amlodipine quantitation is realized by computing the peak-area ratio (amlodipine-nicardipine) of the extracts analyzed in single ion monitoring mode (m/z 431 and m/z 480 for amlodipine and nicardipine, respectively) and comparing them with the calibration curve (r = 0.9991).

Amlodipine↗
PubMed2002

Effects of antisense glutamic acid decarboxylase oligodeoxynucleotide on epileptic rats induced by pentylenetetrazol.

OBJECTIVE: To investigate the effects of antisense glutamic acid decarboxylase (GAD(67)) oligodeoxynucleo-tide (ODN) on behavior, seizure threshold and EEG of hippocampus in the epileptic rats induced by pentylenetetrazol (PTZ). METHODS: A model of chronic epilepsy in rats was established by PTZ. The inhibition of GAD(67) mRNA expression in hippocampus was selectively induced by antisense oligodeoxynucleotide of GAD(67). The effect of antisense GAD(67) ODN on behavior, seizure threshold and EEG recording of kindled rats was examined. RESULTS: Antisense GAD(67) ODN could inhibit the expression of GAD(67) mRNA and the concentration of GABA. It also could significantly shorten the latencies of seizure and increase the level of seizure and the frequency of epileptiform discharges. CONCLUSION: The gene of GAD(67) may be an anti-seizure gene, which might inhibit epileptiform discharge. The treatment of epilepsy by GAD(67) gene will have a bright future.

Animals↗
PubMed2002

[Protective effect induced by vaccination with a partial cDNA expression library of Schistosoma japonicum in mice].

The cDNA fragments of interest were amplified using Sj lambda ZipLox library as the templates by PCR and then cloned into a eukaryotic expression vector p-CMV-GH; A small number of DNA fragments inserted in the recombinants was identified by restriction cleavage, EST sequencing and bioinformatical analysis; mice were injected intramuscularly with the expression library (L-CMV-SjR) or sublibraries(L-CMV-SjR1, L-CMV-SjR2 and L-CMV-SjR3), immunized mice were challenged with Schistosoma japonicum cercariae on day 35, the levels of IgG antibodies in sera from the immunized mice were detected by ELISA. The results demonstrated that a partial cDNA expression library of S.j, with approximately 10(5) transformants, was constructed, most of the recombinants contained the insert DNA fragments of interest, and these fragments had the features of protein-coding sequences for Schistosome. There were no significant differences for the levels of IgG antibodies in sera from all of the immunized groups. Mice immunized with L-CMV-SjR, L-CMV-SjR1 and L-CMV-SjR2 developed significant protective effect against Sj infection compared to control mice injected with the empty plasmid, the rate of worm reduction was about 30%.

Animals↗
PubMed2002

Effect of pore size of D, L-polylactic acid as bone repair material on bone regeneration.

OBJECTIVE: To study the bone regeneration behavior in porous D,L-polylactic acid (D,L-PLA) with different pore sizes. METHOD: A particulate-leaching method was employed to prepare porous biodegradable D,L-PLA with different pore sizes (75, 250, 400, 750 micrometer) and with porosity of 75% as the materials to repair bone defects in rabbits. The materials were then implanted at random into 40 rabbits with bilateral radius bone defect, leaving another 10 rabbits without implantation as blank control. Gross observation and X-ray and histomorphological examination as well as assessment of the biomechanics of the implants were performed in 2, 4, 8 and 12 weeks respectively after the operation. RESULTS: New bone tissue occurred around the implanted materials with pore sizes of 250, 400 or 750 micrometer 12 weeks after the operation. In the control group and in the rabbits with implants with pore size of 75 micrometer, the bone defect was filled with connective tissues. The implants with 250-micrometer pores had the strongest biomechanical strengths of all the materials (P<0.01) at 8 weeks and 12 weeks after the operation. CONCLUSION: The pore size of the porous implants decides the behavior of bone regeneration, and D, L-PLA polymer with 250-micrometer pores produces the most desired effects.

Animals↗
PubMed2002

[Cloning and expression of 21.7 kD protein gene of Schistosoma japonicum (Chinese strain)].

A 558 bp cDNA fragment was amplified by RT-PCR from adult Schistosoma japonicum(Chinese strain) mRNA with a pair of primers that were designed according to published Sj21.7p gene encoding 21.7 kD protein of Schistosoma japonicum(Philippines strain). Sequence analysis indicated that this frame, named Sj21.7 (Ch), with 99% homology to Sj21.7 p, contained a complete open reading fragment (ORF) of 21.7 kD protein gene of Schistosoma japonicum(Chinese strain). The amino acid sequence shared 98% homology with 21.7 kD protein of Schistosoma japonicum. This fragment was cloned into the expression vector pET28a (+) and subsequently expressed in Escherichia coli with IPTG induction. SDS-PAGE analysis revealed that the molecular weight of this expressed product was 25.4 kD. Western blotting showed that the recombinant protein reacted well with the rabbit serum immunized with Sj worm antigen, indicating that this expressed product had good antigenicity.

Amino Acid Sequence↗