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Biomedical subjects

S D Lu

Publications and source records attributed to S D Lu.

17 recordsLinked to original sources
PubMed2001

Role of excitatory amino acid transporter 1 in neonatal rat neuronal damage induced by hypoxia-ischemia.

The role of excitatory amino acid transporter 1 in neonatal rat neuronal damage was studied following hypoxia-ischemia. To induce hypoxia-ischemia injury, rats on postnatal day 7 were exposed to 8 % oxygen for 2 h following unilateral common carotid artery ligation. According to brain damage scoring based on Cresyl Violet staining, the neuronal damage time-dependently changed in the ischemic regions following hypoxia-ischemia. Immunohistochemical studies showed that excitatory amino acid transporter 1 expression was mainly observed in the cerebral cortex ipsilateral to common carotid artery ligation and markedly increased at 24 h and 48 h following hypoxia-ischemia. Combined with confocal laser scanning microscopic analysis, double staining showed that excitatory amino acid transporter 1 positive staining appeared in neurons as well as astrocytes after hypoxia-ischemia. Most excitatory amino acid transporter 1 positive staining cells exhibited regular morphological characteristics and only a few were double-stained by terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick-end labeling. Down-regulation of excitatory amino acid transporter 1 expression by intraventricular administration of specific antisense oligonucleotide exacerbated neuronal damage in hypoxia-ischemia brain. These results suggest that the increase of excitatory amino acid transporter 1 expression may be involved in a pathophysiological process of hypoxia-ischemia brain damage and may reflect a self-compensative mechanism for protecting neurons from further injury.

ATP-Binding Cassette Transporters↗
PubMed2001

[High level expression of human atrial natriuretic peptide in fusion form in E. coli system].

OBJECTIVE: To construct recombinant plasmid with human atrial natriuretic peptide (ANP) gene in fusion form for stable and high level expression of genetic engineering product ANP in E. coli system. METHODS: Plasmids with ANP fusion gene were constructed by PCR and sub-cloning and fusion protein was expressed in E. coli system. High level expression of the fusion genes was enhanced by linking operons in tandem. ANP was released from the fusion protein with thrombin treatment and purified by chromatography. Genetic-engineered ANP was evaluated with the drug production requirement, and produced ANP was tested for its effects of lowering blood pressure and diuresis in vivo and vasodilation in vitro. RESULTS: A series of 4 plasmid pCW111-114, containing 1 to 4 gene operons respectively, were constructed, and the yields of fusion protein were 46%, 54.8%, 56.1% and 60.1% of total cell protein. Fusion protein in the form of inclusion body was isolated and purified, and then treated with thrombin to release ANP. After purification using chromatography columns, at least 3 mg/L culture of ANP with the purity higher than 96% was produced in shaking flask. Primary pharmacological evaluation showed the produced ANP had the effects of blood pressure lowering in vivo and diuresis in vivo and vasodilation in vitro, which was similar to the activity of standard ANP. CONCLUSIONS: By the protocol of fusion gene cloning and expression, the human ANP was produced successfully in E. coli system.

Animals↗
PubMed1999

Intraventricular vascular endothelial growth factor antibody increases infarct volume following transient cerebral ischemia.

AIM: To clarify the role of vascular endothelial growth factor (VEGF) in neuronal damage induced by cerebral ischemia. METHODS: Expression of VEGF in adult rat brain was measured by immunohistochemistry. Transient middle cerebral artery occlusion (MCAO) model was induced by placing a nylon thread in the lumen of the internal carotid artery. The infarct volume was shown with 2,3,5-triphenyltetrazolium chloride (TTC) staining and quantitated by computer image analyzer with and without VEGF antibody treatment. RESULTS: VEGF expression was widely distributed in neuronal cells besides vascular endothelial cells, and the neuronal distribution of VEGF was specific. After intraventricular treatment with VEGF antibody (0.1 g.L-1 daily, for 7 d following the ischemia), infarct volume in the antibody treatment was increased versus vehicle-treated rats [(21.6 +/- 2.7 vs 16 +/- 6) mm3, P < 0.05] respectively. CONCLUSION: Intraventricular injection of VEGF antibody increased the infarct volume after focal cerebral ischemia in rats, suggesting that expression of neuronal VEGF may be one of neuronal protective mechanisms.

Animals↗
PubMed1999

Protective effect of melatonin on injuried cerebral neurons is associated with bcl-2 protein over-expression.

AIM: To study the protective effect of melatonin against neuronal injury and the possible roles of alteration in the expression of bcl-2 and bax following brain ischemia. METHODS: Brain ischemia was induced by left middle cerebral artery occlusion (MCAO) for 60 min in rats. Brain damage was evaluated by the infarct area and the neuronal cell counting. The expression of bcl-2 and bax was analyzed by immunohistochemical method. RESULTS: Melatonin decreased the infarct area and prevented the neuronal death after 24-h reperfusion following 1-h MCAO. Melatonin given before the ischemia enhanced the expression of bcl-2 in the penumbra area and had no significant effect on the expression of bax. CONCLUSION: Melatonin effectively attenuated ischemic brain injury and increased the expression of neuronal bcl-2 in the ischemic brain, indicating that the protective effect of melatonin was associated with up-regulation of bcl-2 in ischemia-induced neuronal death.

Animals↗
PubMed1998

Laboratory markers of antiviral activity.

Quantitative assays for viral nucleic acids have been instrumental in monitoring the response of patients to various antiviral therapies. The level of viraemia is predictive of clinical outcome in that a reduced risk of progression to AIDS or death was observed with lower plasma human immunodeficiency virus (HIV) RNA levels. Rebound in viral levels often signals therapeutic failures, some of which are associated with the development of drug resistance. Quantitative plasma assays for HIV, hepatitis C virus (HCV), cytomegalovirus (CMV) and hepatitis B virus (HBV) have been developed. Over time, modifications to these assays have been required to meet new demands. For example, as antiviral therapies have become more effective, HIV and HCV assays of greater sensitivity are required in order to follow patients for longer periods of time and to fully assess the extent of viral suppression. For HIV-1, a large percentage of patients treated with combination therapies had viral loads that were below the detection limit of the ultrasensitive assay (50 copies/ml). To assess the residual viral burden in this patient population an assay to quantify HIV-1 proviral DNA in peripheral blood mononuclear cells was developed. Studies to date indicate that proviral DNA remains easily detectable despite undetectable plasma RNA and may be useful in monitoring this patient population. To increase assay throughput, a new generation of quantitative assays that will provide real-time detection and a 6 log10 detection range from a single amplification is under development.

Antiviral Agents↗
PubMed1998

[Expression of opioid-receptor-like receptor (ORL1) gene in rat brain].

In situ hybridization with a digoxigenin-labeled oligonucleotide probe was used to investigate the expression of opioid-receptor-like receptor (ORL1) gene in rat brain. It was observed that ORL1 mRNA is widely expressed in many regions of rat brain, particularly in cerebral cortex, thalamus, hypothalamus, amygdala, hippocampus, septum, habenula, periaqueducted gray, raphe nuclei and locus coeruleus structure. These findings suggest that ORL1 receptor may participate in modulating a number of physiological functions in the brain in addition to pain.

Animals↗
PubMed1996

Inhibitory effects of dextromethorphan on c-fos protein expression during focal cerebral ischemia in rats.

AIM: To study the effect of dextromethorphan (DM) in focal cerebral ischemia. METHODS: The c-fos protein was detected immunohistochemically in the brain of rats after focal cerebral ischemia (induced by placing a nylon thread in the lumen of the internal carotid artery) with and without treatment with DM. RESULTS: Focal cerebral ischemia induced c-fos protein expression outside the core territory of the middle cerebral artery (MCA) and neuronal damage in the core territory of the MCA. There was an evident expression of c-fos protein in the ipsilateral regions outside the MCA territory (e.g. cingulate cortices, piriform cortices and entorhinal cortices), and in the contralateral regions of hippocampus after 4-h reperfusion following 1-h MCA occlusion. But morphological results showed severe edema and neuronal damage in the core territory and the ipsilateral hippocampus. DM blocked both the c-fos protein induction and neuronal damage in all regions. CONCLUSION: DM reduced c-fos protein expression and blocked the neuronal damage after focal cerebral ischemia.

Animals↗
PubMed1992

Molecular evolution of the fungi: relationship of the Basidiomycetes, Ascomycetes, and Chytridiomycetes.

Establishing the phylogeny of fungi and protists often has proved difficult owing to the simple morphologies and convergent characters in these organisms. We used DNA sequences of nuclear small-subunit ribosomal RNA genes to determine phylogenetic relationships among three major classes of organisms considered to be fungi--Basidiomycetes, Ascomycetes and Chytridiomycetes--and to assess the taxonomic position of Neocallimastix, an economically important anaerobic rumen microorganism whose classification is controversial. The Basidiomycetes and Ascomycetes, two classes of nonflagellated fungi, are the most closely related taxa. Chytridiomycetes, though bearing flagella, group with these higher fungi rather than with the protists. Neocallimastix, a eukaryote lacking mitochondria and variously classified as a protist or as a fungus, shows closest molecular affinities with the Chytridiomycete fungi in the order Spizellomycetales.

Ascomycota↗
PubMed1989

Stimulation of IS1 excision by bacteriophage P1 ref function.

Lysogenization by a c1ts variant of coliphage P1, P1c1.100, markedly increased the frequency of reversion of a galT::IS1 mutation. The formation of Gal+ colonies presumably occurs by microhomologous recombination between the 9-base-pair repeats in galT (CGCCGCTAC) generated by the transposition of IS1. The responsible P1 gene, ref, has been cloned and sequenced. ref encodes a 22.8-kilodalton protein and is located near the P1 site-specific recombination function, cre. Expression of ref was repressed by P1 c+. The absence of a distinctive ribosome-binding site is consistent with a poor translation of ref from an expression vector in vivo. Placement of a ribosome-binding site before ref resulted in the extensive synthesis of the Ref protein. Ref stimulated precise excision in recB or himA cells, but not in recA mutants. Ref was active in lexA3 mutants, suggesting that the recombination activity of RecA was directly involved in the reaction. We have constructed a P1c1.100 ref::Tn10 mutant. The absence of Ref did not appear to restrict dramatically the ability of P1 to grow lytically or to form lysogens. Thus, the role of ref in the physiology of P1 remains to be determined.

Amino Acid Sequence↗
PubMed1988

A novel form of TNF/cachectin is a cell surface cytotoxic transmembrane protein: ramifications for the complex physiology of TNF.

Tumor necrosis factor (TNF) is a monocyte-derived cytotoxin that has been implicated in tumor regression, septic shock, and cachexia. The mechanism by which TNF induces these different disease states is unclear. We have identified and characterized a novel, rapidly inducible cell surface cytotoxic integral transmembrane form of TNF. The existence and behavior of this novel form of TNF may explain the complex physiology of this molecule. We suggest that activated monocytes synthesize transmembrane TNF at the site of inflammation and kill their targets by either cell-to-cell contact or local release of the TNF secretory component. In contrast, septic shock and cachexia may result from either acute or chronic systemic activation of monocytes, resulting in the widespread release of TNF secretory component into the circulation of the affected individual. We further suggest that cell borne cytokines and cytotoxins may be the primary mediators of directed inflammatory responses.

Cells, Cultured↗
PubMed1984

Site-specific mutagenesis of the human interleukin-2 gene: structure-function analysis of the cysteine residues.

The gene encoding human interleukin-2 (IL-2) has been cloned from human spleen cells, peripheral blood lymphocytes, and the Jurkat cell line. Nucleotide sequence analysis of the gene revealed that the encoded IL-2 protein has three cysteines located at amino acid residues 58, 105, and 125 of the mature protein. Site-specific mutagenesis procedures were used to modify the IL-2 gene by changing each of the cysteine codons individually to serine codons. Substitution of serine for cysteine residues at either position 58 or 105 of the IL-2 protein substantially reduced biological activity, indicating that the cysteines at these positions are necessary for maintenance of the biologically active conformation and may therefore be linked by a disulfide bridge. The modified IL-2 protein containing a substitution at position 125 retained full biological activity, suggesting that the cysteine at this position is not involved in a disulfide bond and that a free sulfhydryl group at that position is not necessary for receptor binding.

Amino Acid Sequence↗
PubMed1984

Site-specific mutagenesis of the human fibroblast interferon gene.

Human fibroblast interferon has three cysteine residues, located at amino acid positions 17, 31, and 141. Using the technique of site-specific mutagenesis with a synthetic oligonucleotide primer, we changed the codon for cysteine-17 to a codon for serine. The resulting interferon, IFN-beta Ser-17, retains the antiviral, natural killer cell activation, and antiproliferative activities of native fibroblast interferon. The purified IFN-beta Ser-17 protein has an antiviral specific activity of 2 X 10(8) units/mg, similar to that of purified native fibroblast interferon. In addition, the purified protein is stable to long-term storage at -70 degrees C.

Amino Acid Sequence↗