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Biomedical subjects

L Xia

Publications and source records attributed to L Xia.

At least 91 records · Page 5Linked to original sources
PubMed1997

[Experiences in management of acute necrotic pancreatitis].

To establish a treatment program for patients with acute necrotic pancreatits (ANP), we treated 211 patients with ANP from 1973 to 1995. 122 patients in group A were treated mainly by early operation before 1992 and 75 in group B, by early nonoperativemethod. The results showed that the occurrance of complications (ARDS, renal failure, heart failure, pancreatic abscess, intestinal fistula) was lower than that in the group B (P < 0.01). Also the mortality in the group B (10.67%) was decreased as compared with that (22.95%) in the group A. We suggested that the nonoperative treatment with rigid criterion for ANP might be recommended first. An intensive nonsurgical management of ANP, surgical indications during nonoperative period and complete program of management for ANP were discussed.

Adult↗
PubMed1997

[Construction and expression of a functional chimeric murine-human antibody directing against human cross-linked fibrin].

OBJECTIVE: In order to reduce the immunogenicity of the murine antifibrin monoclonal antibody (MAb) SZ-63 to human beings. METHODS: First of all, the cDNA sequences encoding the constant regions of the murine kappa light chain and gamma 1 heavy chain in the SZ-63 MAb were substituted with the corresponding human genomic sequences. Then the constructed MAb was cloned separately into two selectable expression vectors, and the latter were transfected into mouse myeloma cells (SP2/0) one by one. RESULTS: ELISA, Western blot and competition experiment results showed that there was 0.8 approximately 1.0 mg/L of chimeric 63 IgG in the conditioned medium of selected cell lines, and the expressed IgG had higher antifibrin D-Dimer capability than that of the original MAb. CONCLUSION: The expressed chimeric antibody can be used as a targeting agent for thrombus imaging and treatment.

Animals↗
PubMed1997

Identification of specific nucleotide sequences and structural elements required for intronic U14 snoRNA processing.

Vertebrate U14 snoRNAs are encoded within hsc70 pre-mRNA introns and U14 biosynthesis occurs via an intron-processing pathway. We have shown previously that essential processing signals are located in the termini of the mature U14 molecule and replacement of included boxes C or D with oligo C disrupts snoRNA synthesis. The experiments detailed here now define the specific nucleotide sequences and structures of the U14 termini that are essential for intronic snoRNA processing. Mutagenesis studies demonstrated that a 5', 3'-terminal stem of at least three contiguous base pairs is required. A specific helix sequence is not necessary and this stem may be extended to as many as 15 base pairs without affecting U14 processing. The spatial positioning of boxes C and D with respect to the terminal stem is also important. Detailed analysis of boxes C and D revealed that both consensus sequences possess essential nucleotides. Some, but not all, of these critical nucleotides correspond to those required for the stable accumulation of nonintronic yeast U14 snoRNA. The presence of box C and D consensus sequences flanking a terminal stem in many snoRNA species indicates the importance of this "terminal core motif" for snoRNA processing.

Animal Population Groups↗
PubMed1997

Construction and expression of mouse-human chimeric antibody SZ-51 specific for activated platelet P-selectin.

A murine monoclonal (mAb) SZ-51 specific for human P-selectin may be used for in vivo thrombus imaging and for the targeting of fibrinolytic agents to thrombi. In order to reduce the immunogenicity of the murine mAb SZ-51 in humans, we cloned and sequenced the cDNAs encoding the variable region of mAb SZ-51 in order to develop mouse/human chimeric reagents. The E. coli expression vector pHEN1-SZ51Fab/Hu was constructed by fusing the variable regions of mAb SZ-51 with human IgG gamma 1CH1 and C kappa genes. The constructs were introduced into E. coli HB2151 for expression of soluble chimeric Fab fragment. We also constructed two fusion products by joining the variable regions of mouse antibody to the appropriate constant regions of human Ig gamma 1 and kappa. These chimeras were cloned into two eukaryotic selectable expression vectors separately, which were then contransfected into a non-Ig secreting murine myeloma line SP2/0 with lipofectin reagent. Six cell lines remained positive for Ig secretion. The highest producing cell line, which showed stable integration and expression at 5 mg/l of culture, was selected for the large scale production of chimeric antibody. Immunoblotting analysis demonstrated that both of the chimeric antibodies (SZ51Fab/Hu, SZ51/Hu) in the culture supernatants, like the native mAb SZ-51, bind P-selectin. In addition, the whole chimeric antibody can compete for binding to activated platelets with murine SZ-51. Therefore, the SZ-51 chimeric antibody may be a potential agent for diagnosis and treatment of thrombotic diseases in the future.

Animals↗
PubMed1997

Extraction of implicit information in biosignals.

The first part of this paper explains the meaning of implicit information in biosignals. Image reconstruction from projections and ECG inverse problem are two typical examples. In the second part the limitation of conventional ECG inverse problem study is discussed, that is, the excitation propagation process that was not included in inverse study. In the third part a new approach to ECG inverse problem studies is introduced. To verify the new method, we used this method to localize the ventricular preexcitation site with simulated body surface potentials of WPW syndrome. The experimental results show that the inversely recovered preexcitation sites are in close agreement with the true preexcitation site.

Computer Simulation↗
PubMed1997

[Mitomycin C concentrations in rabbit ocular tissues after topical administration during glaucoma filtration surgery].

Using high-performance liquid chromatography, we measured Mitomycin C (MMC) concentrations in conjunctiva, sclera and aqueous of 22 rabbit eyes after single topical administration of 0.2 mg.ml-1 MMC during glaucoma filtration surgery. The peaks of MMC concentrations in conjunctiva, sclera, aqueous were 2.01 micrograms.g-1, 2.95 micrograms.g-1 and 0.16 microgram.ml-1 with half life of 0.63, 0.35 and 0.84 hours respectively. Irrigating the ocular surface with 20 ml of normal saline after MMC application reduced the peak drug concentration to 1/8 in conjunctiva, to 1/5 in sclera and to 1/3 in aqueous. The results showed that the MMC concentrations in conjunctiva and sclera were well above the ID50 of rabbit subconjunctival fibroblast (0.1 microgram.ml-1), and the concentration in aqueous was well below the level known to cause endothelium toxicity (approximately 0.2 mg.ml-1) and retinal toxicity (> 1.3 micrograms.ml-1). Therefore, 0.2 mg.ml-1 MMC can inhibit subconjunctival fibroblast effectively and has no side effect on visual function.

Administration, Topical↗
PubMed1996

A truncated hMSH2 transcript occurs as a common variant in the population: implications for genetic diagnosis.

Germline mutations of the hMSH2 gene are responsible for many cases of hereditary nonpolyposis colorectal cancer. While screening for hMSH2 gene mutations in hereditary nonpolyposis colorectal cancer kindreds, we observed that a previously reported germline mutation is in fact a common, alternatively spliced variant in the population. Using RT-PCR and the protein truncation test, the hMSH2 exon 13 deletion variant was found in more than 90% of individuals. The exon 13 deletion transcript was only present in lymphocyte RNA, no abnormalities were detected in genomic DNA flanking exon 13, and the deletion transcript is apparently not translated. These findings highlight further that caution should be exercised in providing genetic risk assessment on the basis of currently used germline mutation detection strategies.

Colorectal Neoplasms↗
PubMed1996

Site-directed mutagenesis of Cys324 and Cys331 in human cytosolic phospholipase A2: locus of action of thiol modification reagents leading to inactiviation of cPLA2.

Human cytosolic phospholipase A2 contains two cysteines, cyS324 and cyS331, chemical modification of which using thiol modifying reagents abolishes the activity of the enzyme [Li et al. (1994) Biochemistry 33, 8594-8603]. To verify the functional importance of the two cysteine residues, site-directed mutagenesis has been used to create six mutations at positions 324 and 331. The mutant enzymes include C324A, C331A, C324Q, C331Q, C324R, and C331S. Complete loss of activity is observed for C331Q, whereas the other mutants have retained varying degrees of activity. These results show that neither CyS324 nor CyS311 is catalytically essential for the enzyme activity. Further chemical modification studies of the mutant enzymes by thiol-specific reagents suggest that modification of Cys331 is responsible for the complete loss of the enzyme activity. The possible roles of Cys324 and Cys331 are discussed.

Amino Acid Sequence↗
PubMed1996

Preparation of an antifibrin thrombus-specific murine/human chimeric monoclonal antibody Fab fragment in Escherichia coli.

We have successfully developed a murine antifibrin monoclonal antibody designated SZ-63 with property of binding specifically with thrombus both in vitro and in vivo. In order to reduce its immunogenicity and molecular weight, a murine/human chimeric Fab fragment of the antibody was prepared. mRNA was selected on oligo (dT) cellulose from total RNA isolated from SZ-63 hybridoma cells. cDNAs coding for heavy and light variable regions were amplified by reverse transcriptase polymerase chain reaction. The amplified fragments were cloned and sequenced. The nucleotides of SZ-63 VH and VL are 354 and 321 respectively. The variable genes were then linked with human IgG gamma1 CH and kappa CL genes. Expression vector pHEN1-63 Fab/Hu was thereby constructed and chimeric Fab fragment was expressed in E. coli HB2151 cells in soluble form. Western blot and ELISA results showed that it remained the same capability of binding with cross-linked fibrin as the murine SZ-63 antibody, the content in culture is about 125 ug/L.

Animals↗
PubMed1996

Lineage-specific CaN19 expression in human skin: lack of expression in normal melanocytes.

Although expression of CaN19 is reduced in cell lines derived from tumors of diverse origin, its expression in their normal counterparts has not been studied in detail. We find that CaN19 mRNA is expressed at very low to undetectable levels in normal melanocytes as well as malignant melanoma cell lines, confirming that CaN19 expression in normal cells is lineage-dependent.

Cells, Cultured↗
PubMed1996

Effects of 2-deoxy-d-glucose on the functional state of the rat myoblast GLUT 1 transporter.

Based on the rationale that internalized 2-deoxy-D-glucose (dGlc) is toxic to cells, glucose transport (GLUT) defective myoblast mutants have been isolated by their ability to grow in glucose-free medium containing dGlc. Recent studies revealed that the GLUT 1 transport process was activated when GLUT 3-GLUT 4-mutants were grown in glucose-free medium. It was therefore puzzling why these GLUT3-GLUT4-myoblasts could survive in the presence of dGlc during the mutant selection process. The present study revealed that GLUT 1 transport affinity in dGlc-grown cells was at least four folds lower than that in control cells. This loss of GLUT 1 transport activity was apparent only after exposure to the toxic sugar analogues for more than 10 hrs. This dGlc-mediated effect was not due to competitive inhibition by the residual dGlc carried over from growth medium, changes in glycolytic enzymes, nor accumulation of the negatively charged dGlc-6-PO4. In fact, GLUT 1 transcript level was elevated in dGlc-treated cells. Both immunoprecipitation and immunoblotting studies indicated that the size of the GLUT 1 transporter in dGlc-grown myoblasts was reduced from 52 kDa to that of the unglycosylated form (38 kDa). These findings suggest that growth in the presence of dGlc inhibits glycosylation of the GLUT 1 transporter, thus reducing its transport affinity. This inability of the GLUT 1 transporter to take up dGlc may therefore explain why GLUT 3-GLUT 4-mutants are able to grow in the presence of the toxic dGlc during the mutant selection procedure.

3-O-Methylglucose↗
PubMed1996

Interleukin-1 stimulates the central release of corticotropin-releasing hormone in the primate.

The cytokine interleukin-1 (IL-1) is present in the brain and is known to cause a variety of neuroendocrine and immune effects in the rodent; the neuropeptide corticotropin-releasing hormone (CRH) plays a critical role in mediating many of these effects. Little is known about these neuropeptide interactions in the primate. We have therefore examined the effects of IL-1 alpha on the release of CRH in the ovariectomized rhesus monkey in vitro and in vivo. In 3 animals, the effect of IL-1 alpha on CRH release from the superfused hypothalamus was studied in vitro. The hypothalamus was divided in half and fragments from each half were superfused separately. Mean CRH release was 262 +/- (SE) 46 pg/20 min and increased to 1,340 +/- 470 pg/20 min after exposure to IL-1 alpha (p < 0.05). The effect of IL-1 alpha on CRH release into cerebrospinal fluid (CSF) in vivo was studied in 8 animals with chronic cannulas implanted in the lateral ventricle for IL-1 infusion; indwelling catheters were also placed via lumbar puncture and threaded into the cervical area for CSF collection. CSF was collected at a rate of 800 microliters/h during a 4-hour baseline period and for 4-8 h after intracerebroventricular infusion of 4.2 micrograms of IL-1 alpha. CRH increased significantly over time in CSF after IL-1 alpha infusion; the mean concentration of CRH increased from 83 +/- 17 pg/ml during the baseline period to 203 +/- 40 pg/ml after IL-1 alpha infusion (p < 0.01). We conclude that IL-1 stimulates central CRH release in the primate and that the effects of cytokines on the release of this important neuromodulator can be monitored in chronically cannulated animals in vivo.

Animals↗
PubMed1996

Elements essential for processing intronic U14 snoRNA are located at the termini of the mature snoRNA sequence and include conserved nucleotide boxes C and D.

Essential elements for intronic U14 processing have been analyzed by microinjecting various mutant hsc70/Ul4 pre-mRNA precursors into Xenopus oocyte nuclei. Initial truncation experiments revealed that elements sufficient for U14 processing are located within the mature snoRNA sequence itself. Subsequent deletions within the U14 coding region demonstrated that only the terminal regions of the folded U14 molecule containing con- served nucleotide boxes C and D are required for processing. Mutagenesis of either box C or box D completely blocked U14 processing. The importance of boxes C and D was confirmed with the excision of appropriately sized U3 and U8 fragments containing boxes C and D from an hsc7O pre-mRNA intron. Competition studies indicate that a trans-acting factor (protein?) is binding this terminal motif and is essential for U14 processing. Competition studies also revealed that this factor is common to both intronic and non-intronic snoRNAs possessing nucleotide boxes C and D. Immunoprecipitation of full-length and internally deleted U14 snoRNA molecules demonstrated that the terminal region containing boxes C and D does not bind fibrillarin. Collectively, our results indicate that a trans-acting factor (different from fibrillarin) binds to the box C- and D-containing terminal motif of U14 snoRNA, thereby stabilizing the intronic snoRNA sequence in an RNP complex during processing.

Animals↗
PubMed1996

[Three-dimensional recons-truction of lumbar-sacral canal and its contents: experimental study].

In order to suit the needs of studies in spinal column surgery on three-dimensional spatial structure and morphology of lumbar-sacral canal and the nervous tissue within it, an experimental model was applied by the authors using lumbosacral specimens from two fresh young adult cadavers. Successive 2mm thick CTM screening was carried out from L3 to S2 vertebral bodies with an interval of 1mm. The serial two-dimensional CT photographical pictures so obtained were inputted into a computer and the three-dimensional images were reconstructed through a VIDAS image analysis system. The experimental results indicated that the three-dimensional images of reconstructed vertebral canal and the nervous tissue within it were lifelike. These images could not only reveal their three-dimensional structure and morphology, but also be cut and composed together at any direction and section by turning and transpositioning along X, Y and Z axes. The authors hold that the visual effect expressed by three-dimensional images reconstructed from two-dimensional pictures can play important role in stereomorphologic, biomechanical, and other studies in fields of anatomy, image analysis, and clinical medicine.

Adult↗
PubMed1996

Inhibitory effects of Acanthopanax gracilistylus saponins on human platelet aggregation and platelet factor 4 liberation in vitro.

AIM: To study the effects of Acanthopanax gracilistylus var pubescens Li saponins (AGVPS) on human platelet aggregation and platelet factor 4 (PF4) liberation in vitro. METHODS: Human platelet aggregations induced by ADP, adrenaline, and collagen were measured turbidimetrically. The aggregation curve was recorded on a platelet aggregometer and the maximal aggregation rate (ARmax), effective deaggregation rate in 5 min (DR5 min) and lag time (LT) were autocalculated by the built-in microcomputer; PF4 liberation from human platelets stimulated by ADP and collagen was determined by recording the heparin thrombin clotting time (HTCT). Thrombosis was tested by weighing the wet and dry thrombi formed in a siliconized revolving ring. RESULTS: AGVPS inhibited in vitro the ARmax with IC50 of 1.33 (95% confidence limits: 1.09-1.63, ADP-induced), 1.66 (1.54-1.79, adrenaline-induced), and 4.2 g.L-1 (0.6-29, collagen-induced). The DR5 min (on ADP-induced aggregation) and LT (collagen-induced) were also increased as well. Meanwhile, AGVPS 0.63-2.50 g.L-1 prolonged HTCT on ADP- and collagen-stimulated PF4 liberation. At 0.34-1.39 g.L-1, AGVPS reduced the wet and dry weight of thrombi formed in vitro. CONCLUSION: AGVPS inhibits human platelet aggregation, liberation, and thrombosis in vitro, suggesting its possible antithrombotic action in man.

Adult↗
PubMed1995

Intronic U14 snoRNAs of Xenopus laevis are located in two different parent genes and can be processed from their introns during early oogenesis.

U14 is a member of the rapidly growing family of intronic small nucleolar RNAs (snoRNAs) that are involved in pre-rRNA processing and ribosome biogenesis. These snoRNA species are encoded within introns of eukaryotic protein coding genes and are synthesized via an intron processing pathway. Characterization of Xenopus laevis U14 snoRNA genes has revealed that in addition to the anticipated location of U14 within introns of the amphibian hsc70 gene (introns 4, 5 and 7), additional intronic U14 snoRNAs are also found in the ribosomal protein S13 gene (introns 3 and 4). U14 is thus far a unique intronic snoRNA in that it is encoded within two different parent genes of a single organism. Northern blot analysis revealed that U14 snoRNAs accumulate during early oocyte development and are rapidly expressed after the mid-blastula transition of developing embryos. Microinjection of hsc70 pre-mRNAs into developing oocytes demonstrated that oocytes as early as stages II and III are capable of processing U14 snoRNA from the pre-mRNA precursor. The ability of immature oocytes to process intronic snoRNAs is consistent with the observed accumulation of U14 during oocyte maturation and the developmentally regulated synthesis of rRNA during oogenesis.

Animals↗
PubMed1995

Evidence for a novel exon in the coding region of the adenomatous polyposis coli (APC) gene.

Germline mutations of the tumor suppressor gene APC cause familial adenomatous polyposis. Somatic APC alterations are involved in several sporadic neoplasms, including colorectal, duodenal, gastric, and esophageal carcinoma. The APC mRNA is encoded by 15 exons. Additional transcripts have been reported, due to alternative splicing of coding as well as noncoding regions. Two mRNA isoforms occur due to a deletion of exon 7 or a partial deletion of exon 9. We have identified a novel exon, flanked by APC exons 10 and 11, which is expressed as an alternatively transcribed product of the gene. Further, we have shown that the novel exon consists of a heptad repeat motif and is conserved across species.

Adenomatous Polyposis Coli↗