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Biomedical subjects

H Xie

Publications and source records attributed to H Xie.

At least 253 records · Page 14Linked to original sources
PubMed1994

[Improvement of memory function of fornix-fimbria transected rats by transplantation of the superior cervical ganglion into hippocampus].

Memory impairments of passive avoidance response were observed in 38 Wistar rats with bilateral fornix-fimbria transection. After fornix-fimbria lesions the degree of performance decreased from 65.3% to 13.6% (P < 0.01). Autotransplantation of superior cervical ganglion (SCG) into bilateral dorsal hippocampi improved memory function to a considerable extent. In the end of the behavioral experiments, implanted rats were sacrificed for histofluorescence study of grafts and measurement of norepinephrine (NA) content in the hippocampus. These experiments showed that the hippocampal NA content in implanted rats was considerably higher than that in untransplanted fornix-fimbria transected rats and consequently suggested that improvement of memory function was to some extent due to supplement of monoamine transmitter by the transplanted SCG.

Animals↗
PubMed1993

Deregulation by zinc of the sodium efflux in barnacle muscle fibers.

Single muscle fibers from the barnacle Balanus nubilus were employed to study the behavior of the resting Na+ efflux toward external and internal application of zinc (Zn2+). This involved both unpoisoned and ouabain-poisoned fibers. The results obtained are as follows: (i) External application of Zn2+, e.g., 2 mM (a maximal dosage) in 10 mM Hepes-ASW (pH 7.3) causes a fall in the resting Na+ efflux which exceeds that caused by 10(-4) M ouabain in companion controls. (ii) The buffer of choice is found to be Hepes, rather than HCO3- or imidazole. (iii) The observed fall in the resting Na+ efflux caused by external application of Zn2+ is concentration-dependent, the IC50 being 10 microM. (iv) The inhibitory effect of Zn2+ is partially reversible; occasionally, however, reversibility is not seen. (v) The Zn(2+)-insensitive component of the Na+ efflux is reduced by 10(-4) M ouabain. (vi) The ouabain-insensitive component of the Na+ efflux is reduced by external application of Zn2+. This response is concentration-dependent. (vii) Preinjection of EGTA reduces the sensitivity of the Na+ efflux to external application of Zn2+. This is true of both unpoisoned and ouabain-poisoned fibers. (viii) (a) The resting Na+ efflux is reduced by injecting Zn2+. Ouabain application reduces the remaining Na+ efflux. (b) Injection of Zn2+ reduces the ouabain-insensitive component of the Na+ efflux. (c) External application of Zn2+ following the injection of Zn2+ reduces the remaining Na+ efflux. Ouabain is ineffective when applied after both maneuvers. (d) Injection of Zn2+ after its external application is without effect. Subsequent application of ouabain is also without effect. (e) Injection or external application of Zn2+ reduces the ouabain-insensitive Na+ efflux. Whereas in the former case subsequent external application of Zn2+ reduces the remaining Na+ efflux, in the latter case Zn2+ injection after external application of Zn2+ is ineffective. Collectively, these results provide evidence in support of the hypothesis that Zn2+ is a potent inhibitor of the ouabain-sensitive and ouabain-insensitive components of the Na+ efflux, and that the inhibitory effect is partly due to the entry of Zn2+ into the myoplasm. They also raise the possibility that the inhibitory effect caused by Zn2+ injection may be the result of Zn2+ leakage from the fiber interior.

Animals↗
PubMed1993

Induction of CREB activity via the surface Ig receptor of B cells.

The regulation and function of CREB was examined in B cells to begin to elucidate the role of cAMP-derived signals in B cell activation. CRE-binding activity detected by the electrophoretic mobility shift assay was found to be constitutively expressed in nuclear extracts of primary murine splenic B cells and was unchanged in nuclear extracts obtained from B cells stimulated in a variety of ways. This activity was shown to be specific by competition analysis and to represent CREB or a closely related molecule on the basis of a "supershift" in the mobility of the nucleoprotein complex induced by anti-CREB antiserum. The function of B cell CREB was assessed by transient transfection of the murine B lymphoma cell line, BAL-17, with a CRE-dependent chloramphenicol acetyl-transferase (CAT) construct that contains a portion of the somatostatin promoter. Cross-linking of the surface Ig receptors of transfected BAL-17 B cells produced a threefold induction of CAT activity. Forskolin, which markedly induced CAT expression in PC12 cells transfected with the CRE-dependent construct, failed to stimulate CAT activity in transfected BAL-17 B cells despite an increase in cAMP. However, anti-Ig was found to act in synergy with forskolin to produce enhanced CAT activity. A phosphoprotein of appropriate molecular size for CREB was immunoprecipitated from anti-Ig plus forskolin treated BAL-17 B cells. These results suggest that CREB is present in primary B cells and that CRE-dependent gene expression is regulated by surface Ig either alone or in synergy with cAMP; the latter implies cross-talk between intracellular signaling pathways acting at the level of CREB.

Animals↗
PubMed1993

Methyl esterification of C-terminal leucine residues in cytosolic 36-kDa polypeptides of bovine brain. A novel eucaryotic protein carboxyl methylation reaction.

Incubation of cytosolic extracts of bovine brain with S-adenosyl[methyl-3H]methionine results in the predominant [3H]methyl esterification of a 36-kDa polypeptide. This reaction appears to be distinct from any of the three known types of protein carboxyl methylation reactions previously established. We show here that the methylated 36-kDa polypeptide is a component of a cytosolic protein with a native molecular mass estimated at 178 kDa by gel filtration chromatography. The methyl group is not stable on the protein and is lost as [3H]methanol with a half-life of about 180 min at pH 7.0, 37 degrees C. The methyltransferase responsible for this reaction is a cytosolic protein with a native molecular mass of about 40 kDa that is readily separated from the well described protein-L-isoaspartate (D-aspartate) O-methyltransferase (EC 2.1.1.77). The methyl ester linkage is cleaved by carboxypeptidase Y, suggesting that the 36-kDa polypeptide is methylated on its C-terminal carboxyl group. Extensive digestion of gel-purified 3H-methylated 36-kDa polypeptide with trypsin and leucine aminopeptidase results in a radioactive product that co-chromatographs with authentic L-leucine methyl ester in reverse phase high performance liquid chromatography (HPLC), thin layer chromatography, thin layer electrophoresis, and high resolution-sulfonated polystyrene cation-exchange chromatography. Additionally, the o-phthalaldehyde/beta-mercaptoethanol-derived isoindole derivative of the 3H digestion product co-migrates on HPLC with the corresponding isoindole for L-leucine methyl ester. We demonstrate that a similar methylation system is present in yeast Saccharomyces cerevisiae but not in the bacterium Escherichia coli. These results provide evidence for a new type of reversible posttranslational modification reaction that may function to modulate the activities of its methyl-accepting substrates.

Amino Acid Sequence↗
PubMed1993

Radioimmunotherapy for unresectable hepatocellular carcinoma using 131I-Hepama-1 mAb: preliminary results.

Twenty-three patients with surgically verified unresectable hepatocellular carcinoma (HCC) have been treated by intrahepatic arterial administration of 131I-labeled anti-HCC monoclonal antibody (Hepama-1) combined with hepatic artery ligation. Radioimmunoimaging demonstrated that the median tumor/liver ratio was 2.1 (1.1-3.6) at day 5. A decline in alpha-fetoprotein level and shrinkage of tumor were observed in 75% (12/16) and 78% (18/23) of patients respectively. Sequential resection was done in 11 patients (48%) after treatment. The surgical specimens revealed massive necrosis of tumor, but residual cancer cells were found at the edge of the specimens. Anti-antibody was determined in 43% (10/23) of patients 2-4 weeks after the administration of 131I-Hepama-1 mAb. No marked toxic effects were noted. It is suggested that 131I-Hepama-1 mAb might be of value as one of the multimodality treatments for unresectable HCC.

Animals↗
PubMed1993

Targeting of saporin to CD25-positive normal and neoplastic lymphocytes by an anti-saporin/anti-CD25 bispecific monoclonal antibody: in vitro evaluation.

This study has been designed to verify the specific toxicity of saporin, a type 1 ribosome-inactivating protein (RIP), with the same activity as ricin A chain, targeted by a bispecific monoclonal antibody (bimAb) recognising both the CD25 antigen and the RIP. The CD25 antigen is expressed by lymphoid populations upon activation and by leukaemias and lymphomas with an activated membrane phenotype (Hodgkin's lymphoma, anaplastic large cell lymphoma, adult T cell leukaemia). The bimAb-saporin mixture was tested on CD25+ targets at different bimAb and saporin concentrations. Saporin, in the presence of a bimAb concentration of 10(-9) M, inhibited protein synthesis by CD25+ neoplastic lymphocytes (L540 and MT2 cell lines) with IC50S (concentrations giving 50% of inhibition) ranging from 8 x 10(-12) M to 3 x 10(-11) M. The saporin-bimAb mixture was also effective in blocking the phytohaemagglutinin-driven proliferation of normal lymphocytes, whereas it displayed the same level of toxicity exerted by saporin alone on an irrelevant CD25-negative cell line (EBV-infected B lymphoblastoid cell line). From these results it is possible to envisage a clinical use of this bimAb as a cytotoxic agent for CD25+ leukaemias and lymphomas, as well as an immunosuppressive agent for severe immune disorders such as graft-vs-host disease (GVHD) and transplanted organ rejection.

Animals↗
PubMed1993

Interactions of Porphyromonas gingivalis with epithelial cells.

The invasion of gingival epithelial cells by certain pathogenic periodontal bacteria may account for their presence within diseased gingival tissue. To dissect the initial steps of a potential invasion pathway for the periodontal pathogen Porphyromonas gingivalis, laboratory and clinical bacterial isolates were tested for their interactions with a human oral epithelial cell line (KB). Several P. gingivalis strains immobilized on filters could bind oral epithelial cells. Quantitative adherence assays supported these results. The invasion of epithelial cells by P. gingivalis 33277 was measured by assay and confirmed by transmission electron microscopy. These preliminary results demonstrate that certain P. gingivalis strains are capable of internalization by human oral epithelial cells in vitro.

Bacterial Adhesion↗
PubMed1993

Insulin resistance of glucose response produced by hepatic denervations.

This study investigated the glucose response to insulin infused after hepatic denervation. Hepatic denervations were performed on 13 anesthetized cats at different levels: (i) surgical hepatic anterior plexus denervation, (ii) chemical total hepatic denervation by painting phenol on the tissues around the portal vein, bile duct, common hepatic artery, and hepatic ligaments, and (iii) bilateral vagotomy. Sham denervations were performed on 9 animals. Before denervation and after each performance of denervations, insulin (100 mU/kg, i.v.) was infused. Plasma glucose concentrations were analyzed at 15, 30, 45, and 60 min after insulin infusion. Hepatic anterior plexus denervation produced a significant reduction in insulin effectiveness. Phenol denervation and bilateral vagotomy failed to further significantly alter the level of insulin resistance developed by hepatic anterior plexus denervation. These observations demonstrate that the effect of insulin on glucose regulation is markedly reduced in the absence of hepatic anterior plexus innervation, suggesting that hepatic nerve function is necessary for the normal glucose response to insulin. Furthermore, the hepatic nerves of relevance appear to reach the liver primarily, if not exclusively, by the anterior hepatic plexus.

Animals↗
PubMed1992

Targeting of "T" lymphocytes against human hepatoma cells by a bispecific monoclonal antibody: role of different lymphocyte subsets.

In an attempt to construct bispecific monoclonal antibodies (bimAbs) able to target cytotoxic T lymphocytes against human hepatoma cells, an HGPRT-deficient mutant of the Hepama-6 hybridoma, which produces an antihuman-hepatoma mAb, was directly fused with splenocytes from Balb/C mice immunized by a polyclonal cytotoxic T-cell line. Hybrid hybridomas were selected in HAT medium, and their supernatants were directly screened for the ability to induce IL-2-cultured cytotoxic T lymphocytes to kill hepatoma cells in a 51Cr-release assay. The selected hybrid hybridoma, termed DQ-33, secretes a bimAb, which reacts with a CD3-associated determinant. When resting peripheral-blood lymphocytes were used as effector cells, virtually no cytolytic activity could be induced by DQ-33, whereas phytohemagglutinin-activated lymphocytes that had been expanded in vitro in IL-2-containing medium could be efficiently targeted against hepatoma cells. Targeting by DQ-33 bimAb was analyzed on different subsets of IL-2-cultured lymphocytes. It was evident that CD+4-8+ TCR alpha/beta+ and CD3+4-8-TCR gamma/delta+ lymphocytes were efficiently induced by bimAb to lyse human hepatoma cells, whereas no induction of cytolysis could be observed when CD3 + 4 + 8-TCR alpha/beta+ cells were used as effectors. DQ-33 bimAb was also able to induce lymphokine secretion (IL-2, GM-CSF and TNF-alpha) by all the different subsets of lymphocytes analyzed in the presence of target cells expressing the relevant antigen, independent of the expression of cytolytic activity.

Antibodies, Monoclonal↗
PubMed1991

Trichosanthin-monoclonal antibody conjugate specifically cytotoxic to human hepatoma cells in vitro.

A plant single-chain ribosome-inactivating protein derived from the root tuber of Trichosanthes kirilowii, termed trichosanthin (TCS), was modified with 2-iminothiolane. It was not like trichokirin, a ribosome-inactivating protein derived from the seeds of the same plant, in that TCS retained full activity when 1.5 sulfhydryl groups were introduced into each TCS molecule by 2-iminothiolane modification. The 2-iminothiolane-TCS was conjugated to Hepama-1, a monoclonal antibody directed against human hepatoma with a cross-linking reagent, N-succinimidyl-3-(2-pyridyl)-dithiopropionate. The hepatoma cytotoxicity of the immunotoxin, TCS-Hepama-1, was 500-fold higher than that of free TCS and only 1 log lower than that of free ricin. However, the immunotoxin was approximately 600-fold less cytotoxic to HeLa cells. The results suggested that the immunotoxin was a potent and quite specific antihepatoma agent and might have considerable potential in hepatoma therapy.

Antibodies, Monoclonal↗
PubMed1991

Characterization of a membrane-associated glycoprotein (gp 43) on human hepatocellular carcinoma by a monoclonal antibody.

A monoclonal antibody, Hepama-1, produced by immunizing mice with cells of a human hepatocellular carcinoma cell line, has been used to identify and characterize a previously unreported antigen present on the surface of human hepatocellular carcinoma cells. The antigen occurred on the membranes of human hepatoma cell lines and tumor biopsies but was not detectable in tumors of other origin or normal tissues. Binding was determined by enzyme-linked immunoabsorbent assay and immunofluorescence on cell lines and by immunoperoxidase staining of tissue sections. In immunofluorescence studies, Hepama-1 antibodies stained five out of six human hepatoma cell lines, showed only slight binding to breast tumor cell lines, but failed to stain colon tumor or normal cell lines. The antihepatoma antibody exhibited positive immunoperoxidase staining of human liver tumor sections but did not stain tumors of other origin. Hepama-1 bound specifically to a membrane glycoprotein with an approximate molecular weight of 43,000. Western blot and solid phase enzyme-linked immunoabsorbent assay analysis showed that the 43-kD antigen occurred on five of six human hepatoma cell lines and was expressed by every human hepatocellular carcinoma biopsy tested. This cell surface molecule represents a potentially useful target for immunotherapy and localization of human hepatocellular carcinomas.

Antibodies, Monoclonal↗