[Properties and mechanisms of marine polysaccharidases].
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Agar↗
Biomedical subjects
X Jiang
Publications and source records attributed to X Jiang.
[Analysis of MRI for tumor of the sellar region].
PURPOSE: To introduce the characteristics of magnetic resonance imaging(MRI) for the tumors of the sellar region. METHODS: A retrospective analysis of 86 cases with the tumors of the sellar region was carried out. RESULTS: The pituitary tumor including the pituitary micro-adenoma and pituitary macro-adenoma was a common tumor of the sellar region. The pituitary micro-adenoma usually does not affect visual function; but the pituitary macro-adenoma often damages the optic pathway and reduces the visual function. The rest of the sellar region appears special feature on MRI. CONCLUSION: MRI is a useful method in diagnosing the tumors of the sellar region.
Adenoma↗
[Gene cloning, construction and expression of single-chain Fv (scFv) against the membrane protein of Schistosoma japonicum].
OBJECTIVE: To construct single chain antibody specific to membrane protein of Schistosoma japonicum by genetic engineering technique. METHODS: The VH (heavy-chain variable region) and VL(light-chain variable region) genes were amplified by PCR from the genomic DNA of NP11-4 cell line, and sequenced by Sanger's method. The ScFv was constructed in pTHA90 vector using VH and VL genes, then expressed by IPTG. RESULTS: The VH and VL genes were obtained through PCR. The DNA sequences showed that VH and VL were new variable region genes of antibody. They were registered by GenBank. A ScFv gene with (Gly4Ser) 3 intralinker in the pTHA90 vector was successfully constructed. The ScFv was expressed as thioredoxin-fused proteins about 36.2 kDa. CONCLUSION: A specific ScFv against the membrane protein of Schistosoma japonicum was constructed and expressed.
Amino Acid Sequence↗
[Expression of apoptosis of the skin lesion and muscle from patients with dermatomyositis].
OBJECTIVE: This study inquired into the relationship between the influence of corticosteroid and the expression of apoptosis, Fas and Bcl-2 in muscle from patients with dermatomyositis (DM). METHODS: Corticosteroid was given to group A (10 DM cases) but not given to group B (12 DM cases). RESULTS: Apoptotic cells were detected in situ by terminal deoxynucleotidyl transferase-mediated-dUTP nick end labeling (TUNEL). Fas and Bcl-2 expressions was determined with the use of immunohistochemical staining in DM. The results showed that more expression of apoptosis in keratinocytes, muscle cells and lymphocytes were observed in group A. The apoptotic index (AI) of muscle cells and that of lymphocytes were more marked in group A than in group B (P < 0.05). Less apoptosis cells were observed in two weeks of treatment, and no correlation was found between apoptosis and the lesion of skin and muscle. CONCLUSION: The authors suggest that corticosteroid may play a role in inducing the apoptosis of keratinocytes, muscle cells and lymphocytes, which may be one of the therapeutic mechanisms of corticosteroid. The length of administering corticosteroid to the patients seems related to apoptosis.
Adult↗
[The clinical characteristics of adhesive type cholesteatoma].
OBJECTIVE: To study the clinical characteristics of adhesive type cholesteatoma. METHODS: Fifty-two cases (52 ears) of adhesive type cholesteatomas were reviewed. Of the 52 cases there were 30 males and 22 females; 24 left ears and 28 right ears. The age of the patients ranged from 8 to 70 years. All of the patients were treated by tympanoplasty, and the open and close methods were performed in 37 ears and 10 ears, respectively. Other methods were employed in the remaining 5 cases. Nine ears underwent tympanoplasty type "O" without ossicular re-construction for an increase in the threshold of the bone conduction. Types I, III and IV tympanoplasties were performed in 1, 16 and 26 ears, respectively. RESULTS: The structures of the upper parts of the stapes had disappeared in 25 ears, which was significantly higher in this series than that in the attic type cholesteatoma. The over-all recovery rate of hearing was 69.8%, while 75.9% and 55.6% in the open and closed tympanoplasties, respectively. Postoperative complications of perforations and re-adhesions of the tense part of the tympanic membrane were observed in 3 and 4 ears, respectively. CONCLUSIONS: Adhesive type cholesteatoma is not uncommon. The cause of this disease may be the functional defects in the pharynotympanic tube. A thorough and effective treatment for the secretory otitis media is crucial for the prevention of adhesive type cholesteatomas. The open method tympanoplasty was considered as the first choice for adhesive type cholesteatoma while the closed method must be great careful.
Adolescent↗
[Determination of enantiomeric purity of (S)-(-)-alpha-phenylethylamine by NMR].
It was reported the determination of enantiomeric purities of (S)-(-)-alpha-phenylethylamine by 1H NMR, using (2R, 3R)-dibenzoyl-tartaric acid as chiral solvating agent. 1H NMR chemical shift non-equivalence of the methyl doublet of alpha-phenylethylamine was 0.08 ppm(base-line separation) in solvent CDCl3, when the concentration of the sample was 0.051 mol.L-1, the molar ratio between chiral solvating agent and the sample was 0.33. The enantiomeric purities could be determined by the peak areas of the methyl doublet of alpha-phenylethylamine. The relative standard deviation depended upon the enantiomeric purities of sample. With enantiomeric purities as high as 99.1% ee, the RSD was 0.3% (n = 4).
Magnetic Resonance Spectroscopy↗
Calreticulin modulates capacitative Ca2+ influx by controlling the extent of inositol 1,4,5-trisphosphate-induced Ca2+ store depletion.
Calreticulin (CRT) is a highly conserved Ca(2+)-binding protein that resides in the lumen of the endoplasmic reticulum (ER). We overexpressed CRT in Xenopus oocytes to determine how it could modulate inositol 1,4,5-trisphosphate (InsP(3))-induced Ca(2+) influx. Under conditions where it did not affect the spatially complex elevations in free cytosolic Ca(2+) concentration ([Ca(2+)](i)) due to InsP(3)-induced Ca(2+) release, overexpressed CRT decreased by 46% the Ca(2+)-gated Cl(-) current due to Ca(2+) influx. Deletion mutants revealed that CRT requires its high capacity Ca(2+)-binding domain to reduce the elevations of [Ca(2+)](i) due to Ca(2+) influx. This functional domain was also required for CRT to attenuate the InsP(3)-induced decline in the free Ca(2+) concentration within the ER lumen ([Ca(2+)](ER)), as monitored with a "chameleon" indicator. Our data suggest that by buffering [Ca(2+)](ER) near resting levels, CRT may prevent InsP(3) from depleting the intracellular stores sufficiently to activate Ca(2+) influx.
Animals↗
Human caliciviruses are a significant pathogen of acute sporadic diarrhea in children of Santiago, Chile.
Human caliciviruses (HuCVs) are increasingly recognized as common pathogens that cause acute sporadic diarrhea in children; however, regional antigenic and genetic diversity complicate detection techniques. Stool samples from children seeking medical attention in 2 outpatient clinics, a large emergency department, and 2 hospital wards were evaluated for HuCVs by reverse transcription-polymerase chain reaction, using primers based on a conserved sequence of the polymerase region of a previously sequenced Chilean strain. HuCVs were detected in 53 (8%) of 684 children 1 month to 5 years of age (mean, 13 months). Detection occurred year-round without a clear seasonal peak, and detection frequency declined from 16% in 1997 to 2% in 1999. The decline may have been due to a change in virus genotype. HuCVs are a significant pathogen of acute sporadic diarrhea in Chilean children, and continuous characterization of genetic diversity will be crucial for appropriate detection.
Acute Disease↗
Cytochrome c promotes caspase-9 activation by inducing nucleotide binding to Apaf-1.
We report here the biochemical analysis of the reconstituted de novo procaspase-9 activation using highly purified cytochrome c, recombinant apoptotic protease-activating factor-1 (Apaf-1), and recombinant procaspase-9. Using a nucleotide binding assay, we found that Apaf-1 alone bound dATP poorly and the nucleotide binding to Apaf-1 was significantly stimulated by cytochrome c. The binding of dATP to Apaf-1 induces the formation of a multimeric Apaf-1. cytochrome c complex, apoptosome. Procaspase-9 also synergistically promotes dATP binding to Apaf-1 in a cytochrome c-dependent manner. The dATP bound to apoptosome remained as dATP, not dADP. A nonhydrolyzable ATP analog, ADPCP (beta,gamma-methylene adenosine 5'-triphosphate), was able to support apoptosome formation and caspase activation in place of dATP or ATP. These data indicate that the key event in Apaf-1-mediated caspase-9 activation is cytochrome c-induced dATP binding to Apaf-1.
Adenosine Triphosphate↗
Transverse asymmetry AT' from the quasielastic 3He(e,e') process and the neutron magnetic form factor.
We have measured the transverse asymmetry A(T') in 3He(e,e(')) quasielastic scattering in Hall A at Jefferson Laboratory with high precision for Q2 values from 0.1 to 0.6 (GeV/c)(2). The neutron magnetic form factor G(n)(M) was extracted based on Faddeev calculations for Q2 = 0.1 and 0.2 (GeV/c)(2) with an experimental uncertainty of less than 2%.
Journal Article↗
Pharmacological profiles of selective non-peptidic delta opioid receptor ligands.
Several non-peptidic opioids have been synthesized recently as part of a program to develop selective delta receptor agonists. In this study, the affinities of a set of compounds for cloned delta and mu opioid receptors expressed in HEK 293 cell lines were determined by competition analysis of [3H]bremazocine binding to membrane preparations. All compounds studied exhibited high affinity and selectivity, with apparent dissociation constants in the range of 0.6-1.7 nM for the delta opioid receptor and 240-1165 nM for the mu opioid receptor. We next sought to determine which domain of the delta receptor was critical for mediating the highly selective binding by analysis of ligand affinities for mu/delta receptor chimeras. Receptor binding profiles suggested that a critical site of receptor/ligand interaction was located between transmembrane domain 5 (TM5) and TM7 of the delta receptor. Substitution of tryptophan 284, located at the extracellular surface of TM6, with lysine, which is found at the equivalent position in the mu opioid receptor, led to a spectrum of effects on affinities, depending on the ligand tested. Affinities of SB 219825 and SB 222941 were particularly sensitive to the substitution, displaying a 50-fold and 70-fold decrease in affinity, respectively. Activities of the delta receptor-selective agonists were tested in two functional assays. Brief exposure of HEK 293 cells expressing delta opioid receptors with selective ligands induced phosphorylation of MAP kinase, although the non-peptidic ligands were less efficacious than the enkephalin derivative DADL (Tyr-D-Ala-Gly-Phe-D-Leu). Similarly, chronic exposure of HEK 293 cells expressing delta opioid receptors with selective, non-peptidic ligands, with the exception of SB 206848, caused receptor down-regulation, however, the SB compounds were less efficacious than DADL.
Amino Acid Sequence↗
Cell-based screen for antimitotic agents and identification of analogues of rhizoxin, eleutherobin, and paclitaxel in natural extracts.
We describe a cell-based assay for antimitotic compounds that is suitable for drug discovery and for quantitative determination of antimitotic activity. In the assay, cells arrested in mitosis as a result of exposure to antimitotic agents in pure form or in crude natural extracts are detected by ELISA using the monoclonal antibody TG-3. The assay was used to screen >24,000 extracts of marine microorganisms and invertebrates and terrestrial plants and to guide the purification of active compounds from 5 of 119 positive extracts. A new rhizoxin analogue was found in a Pseudomonas species, six new eleutherobin analogues were identified from the octocoral Erythropodium caribaeorum, and two paclitaxel analogues were found in the stem bark of the tree Ilex macrophylla. The assay was also used for quantitative comparison of the antimitotic activity of different analogues. It revealed the importance of the C-11 to C-13 segment of the diterpene core of eleutherobin for its antimitotic activity. The identification of antimitotic compounds in very low abundance and their high (0.5%) occurrence in natural extracts indicates that drug discovery efforts using this cell-based assay may lead to the identification of structurally novel antimitotic agents.
Alkaloids↗
Structure of the active core of human stem cell factor and analysis of binding to its receptor kit.
Stem cell factor (SCF) is an early-acting hematopoietic cytokine that elicits multiple biological effects. SCF is dimeric and occurs in soluble and membrane-bound forms. It transduces signals by ligand- mediated dimerization of its receptor, Kit, which is a receptor tyrosine kinase related to the receptors for platelet-derived growth factor (PDGF), macrophage colony-stimulating factor, Flt-3 ligand and vascular endothelial growth factor (VEGF). All of these have extracellular ligand-binding portions composed of immunoglobulin-like repeats. We have determined the crystal structure of selenomethionyl soluble human SCF at 2.2 A resolution by multiwavelength anomalous diffraction phasing. SCF has the characteristic helical cytokine topology, but the structure is unique apart from core portions. The SCF dimer has a symmetric 'head-to-head' association. Using various prior observations, we have located potential Kit-binding sites on the SCF dimer. A superimposition of this dimer onto VEGF in its complex with the receptor Flt-1 places the binding sites on SCF in positions of topographical and electrostatic complementarity with the Kit counterparts of Flt-1, and a similar model can be made for the complex of PDGF with its receptor.
Amino Acid Sequence↗
Time dependent theory for random lasers
A model to simulate the phenomenon of random lasing is presented. It couples Maxwell's equations with the rate equations of electronic population in a disordered system. Finite difference time domain methods are used to obtain the field pattern and the spectra of localized lasing modes inside the system. A critical pumping rate P(c)(r) exists for the appearance of the lasing peaks. The number of lasing modes increases with the pumping rate and the length of the system. There is a lasing mode repulsion. This property leads to a saturation of the number of modes for a given size system and a relation between the localization length xi and average mode length L(m).
Journal Article↗
A rat model for human T lymphocyte virus type I-associated myeloneuropathy. down-regulation of bcl-2 expression and increase in sensitivity to TNF-alpha of the spinal oligodendrocytes.
We reported that the tumor necrosis factor-alpha (TNF-alpha) expression and apoptotic death of oligodendrocytes appeared to be a major pathogenesis of the demyelination of spinal cords of Wistar-King-Aptekman-Hokudai (WKAH) rats with human T lymphocyte virus type I (HTLV-I) infection, HAM rats. In the present study, we examined the sensitivity to TNF-alpha-induced cell death of in vitro-separated oligodendrocytes from HTLV-I-infected WKAH rats. Although the number of non-viable oligodendrocytes increased by adding recombinant TNF-alpha, in a dose-dependent manner, in both HTLV-I-infected and uninfected control rats, oligodendrocytes from the infected rats were more susceptible to TNF-alpha. In situ detection of DNA fragmentation showed apoptotic death of oligodendrocytes. The expression of bcl-2, an anti-apoptotic gene, was strongly down-regulated in oligodendrocytes of the infected rats but not in the control rats. We suggest that the down-regulation of bcl-2 expression in the oligodendrocytes of the HTLV-I-infected rats may increase the susceptibility to TNF-alpha-induced apoptosis of oligodendrocytes, the result being development of HTLV-I-induced myeloneuropathy in rats.
Animals↗
Antioxidant enzyme expression and reactive oxygen species damage in prostatic intraepithelial neoplasia and cancer.
BACKGROUND: Oxidative stress results in damage to cellular structures and has been linked to many diseases, including cancer. The authors sought to determine whether the expression of three major antioxidant enzymes, copper-zinc superoxide dismutase (SOD1), manganese superoxide dismutase (SOD2), and catalase, was altered in human prostate carcinoma and its likely precursor, high grade prostatic intraepithelial neoplasia (PIN). The level of reactive oxygen species damage was evaluated by measuring the expression of the DNA adduct 8-hydroxydeoxyguanosine. METHODS: The authors evaluated the tissue expression of the antioxidant enzymes in prostate carcinoma by immunohistochemistry, immunogold electron microscopy, and enzymatic assay. The polymerase chain reaction was used to amplify and screen tissue specimens for the genes of SOD1, SOD2, and extracellular SOD (SOD3). Matched paraffin embedded tissue sections were evaluated by RNA in situ hybridization for expression of SOD1 and immunohistochemically for the DNA adduct 8-hydroxydeoxyguanosine. RESULTS: All prostatic tissues, including cancer, displayed immunoreactivity for the three antioxidant enzymes in epithelial cells, with no staining of the stroma, inflammatory cells, or endothelial cells. The number of immunoreactive cells was greater in benign epithelium than in PIN and cancer for each enzyme. The mean percentage and intensity of immunoreactive cells was greatest for SOD2, intermediate for SOD1, and lower for catalase. Staining in cancer was heterogeneous. Immunogold ultrasound studies revealed strong mitochondrial labeling for SOD2, which was greater in benign epithelium than in cancer; SOD1 labeling was invariably weaker, with nuclear labeling in benign epithelium and cytoplasmic labeling in cancer cells. There was no difference in enzyme activity for the three antioxidant enzymes between benign epithelium and cancer. No mutations were found in the 5 exons of SOD1, 5 exons of SOD2, and 3 exons of SOD3, except for 3 of 20 cases with polymorphisms for exon 3 of SOD1. Intense nuclear immunoreactivity for 8-hydroxydeoxyguanosine was present in fewer than 3% of epithelial cells, with no apparent differences among benign epithelium, PIN, and cancer. CONCLUSIONS: SOD1, SOD2, and catalase had lower expression in PIN and prostate carcinoma than in benign epithelium. The number of immunoreactive cells in PIN was similar to cancer, indicating that these are closely related. Enzyme activities were variable, with no difference between benign epithelial cells and cancer, although this lack of change in enzyme activity could have been due to the presence of contaminating benign cells within the cancer specimens. The results of reactive oxygen species damage were found only in the epithelium and not in the stroma. Expression of the DNA adduct 8-hydroxydeoxyguanosine was present in fewer than 3% of cells, with no apparent differences among benign epithelium, PIN, and cancer. These findings suggest that oxidative stress is an early event in carcinogenesis.
Aged↗
A practical and facile route for the preparation of 18-norandrostan-17-ones from androstan-17-ones using SmI(2)-promoted cyclization and dehydroxylation.
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Androstanes↗
Lactoferrin binding to the rat asialoglycoprotein receptor requires the receptor's lectin properties.
Lactoferrin binds to rat hepatic lectin 1 (RHL1), the major subunit of the asialoglycoprotein (ASGP) receptor, with high affinity, by a galactose-independent mechanism. To better understand the molecular basis of this novel interaction, we compared the binding of lactoferrin and asialo-orosomucoid (ASOR) to isolated rat hepatocytes and to purified ASGP receptors as a function of pH, Ca(2+) and receptor acylation. Binding of (125)I-lactoferrin and (125)I-ASOR to isolated rat hepatocytes at 4 degrees C decreased sharply at pH<6, following similar titration curves. Binding of (125)I-lactoferrin and (125)I-ASOR to hepatocytes was Ca(2+)-dependent. Binding increased progressively at > or =300 microM CaCl(2), in the presence of 1 mM EDTA. Monensin treatment of hepatocytes, which causes hepatocytes to accumulate inactive ASGP receptors, reduced surface binding of (125)I-lactoferrin and (125)I-ASOR by 46 and 49%, respectively, with only a 16% loss of immunodetectable receptor protein from the cell surface. Finally, deacylation of purified ASGP receptors in vitro with 1 M hydroxylamine abolished receptor lectin activity as reflected by the loss of (125)I-ASOR binding as well as the complete loss of specific (125)I-lactoferrin binding. Treatment with 1 M Tris had no effect on binding of either ligand. We conclude from these data that galactose-independent lactoferrin binding to the ASGP receptor requires the receptor's carbohydrate-recognition domain to be in an active configuration. An active configuration is promoted by neutral pH and Ca(2+), and also requires the receptor subunits to be acylated.
Animals↗