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Biomedical subjects

H Song

Publications and source records attributed to H Song.

At least 109 records · Page 6Linked to original sources
PubMed1999

A recombinant prodrug type approach for triggered delivery of streptokinase.

A novel prodrug type approach for triggered delivery of thrombolytic drugs without their associated hemorrhagic effects has been proposed. Presented herein is a rapid communication of preliminary observations that suggest the feasibility of the approach. A hirulog-streptokinase fusion protein (termed "HSK") possessing active thrombolytic functions has been successfully produced using recombinant DNA technology. The prodrug and triggered release features of this approach have been demonstrated by the inhibition of the plasminogen-activating activity of HSK via binding with thrombin and reversal of this inhibition by hirudin.

Amino Acid Sequence↗
PubMed1999

Direct gap junction communication between malignant glioma cells and astrocytes.

Gap junctions are intercellular channels that connect the interiors of coupled cells. We sought to determine the extent to which malignant glioma cells form gap junction channels with astrocytes from either adult human brain or rat forebrain. The astrocytic gap junction protein, connexin 43 (Cx43), was identified in immunoreactive plaques at areas of cell-to-cell contact between cocultured glioma cells and astrocytes. These gap junction plaques were composed of functional channels, because extensive dye coupling was evident between the glioma cells and astrocytes from both human and rat brain. Calcium signaling was also readily transmitted from glioma cells to astrocytes and vice versa. In live rat brain, injection of glioma cells prelabeled with the gap junction tracer, dicarboxy-dichlorofluorescein, revealed extensive dye transfer to host cells, demonstrating that malignant glioma cells directly couple with normal brain cells. These observations suggest that intercellular communication via gap junctions may play a role in regulating cellular interactions during tumor invasion. In fact, the presence of gap junctions between astrocytes and glioma cells was sufficient to induce a transformation of astrocytic phenotype. Astrocytes cocultured with C6 glioma cells overexpressing Cx43 were significantly smaller and expressed a lower level of glial fibrillary acidic protein than astrocytes cocultured with otherwise identical mock-transfected, gap junction-deficient C6 cells. Thus, direct cellular coupling with glioma cells result in a phenotypic transformation of astrocytes that may contribute to the susceptibility of surrounding tissue to glioma invasion.

Adult↗
PubMed1999

Crystal structure of intact elongation factor EF-Tu from Escherichia coli in GDP conformation at 2.05 A resolution.

The crystal structure of intact elongation factor Tu (EF-Tu) from Escherichia coli in GDP-bound conformation has been determined using a combination of multiple isomorphous replacement (MIR) and multiwavelength anomalous diffraction (MAD) methods. The current atomic model has been refined to a crystallographic R factor of 20.3 % and free R-factor of 26.8 % in the resolution range of 10-2.05 A. The protein consists of three domains: domain 1 has an alpha/beta structure; while domain 2 and domain 3 are beta-barrel structures. Although the global fold of the current model is similar to those of published structures, the secondary structural assignment has been improved due to the high quality of the current model. The switch I region (residues 40-62) is well ordered in this structure. Comparison with the structure of EF-Tu in GDP-bound form from Thermus aquaticus shows that although the individual domain structures are similar in these two structures, the orientation of domains changes significantly. Interactions between domains 1 and 3 in our E. coli EF-Tu-GDP complex are quite different from those of EF-Tu with bound GTP from T. aquaticus, due to the domain rearrangement upon GTP binding. The binding sites of the Mg2+ and guanine nucleotide are revealed in detail. Two water molecules that co-ordinate the Mg2+ have been identified to be well conserved in the GDP and GTP-bound forms of EF-Tu structures, as well as in the structure of Ras p21 with bound GDP. Comparisons of the Mg2+ binding site with other guanine nucleotide binding proteins in GDP-bound forms show that the Mg2+ co-ordination patterns are well preserved among these structures.

Bacterial Proteins↗
PubMed1999

Glucocorticoids-potent modulators of astrocytic calcium signaling.

Glucocorticoids are the first line of choice in the treatment of cerebral edema associated with brain tumors. High-dose glucocorticoids reduce the extent of edema within hours, often relieving critical increases in intracranial pressure, but the mechanisms by which glucocorticoids modulate brain water content are not well-understood. A possible target of action may be glucocorticoid receptor-expressing astrocytes, which are the primary regulators of interstitial ion homeostasis in brain. In this study, we demonstrate that two glucocorticoids, methylprednisolone and dexamethasone, potentiate astrocytic signaling, via long-range calcium waves. Glucocorticoid treatment increased both resting cytosolic calcium (Ca2+i) level and the extent and amplitude of Ca2+ wave propagation two-fold, compared to matched controls. RU-486, a potent steroid receptor antagonist, inhibited the effects of methylprednisolone. The glucocorticoid-associated potentiation of Ca2+ signaling may result from upregulation of the cellular ability to mobilize Ca2+ and release ATP, because both agonist-induced Ca2+i increments (via ATP and bradykinin) and ATP release were proportionally enhanced by glucocorticoids. In contrast, neither gap junction expression (as manifested connexin 43 immunoreactivity) nor functional coupling was significantly affected by methylprednisolone. Confocal microscopy revealed both the expression of glucocorticoid receptors and nuclear translocation of these receptors when exposed to methylprednisolone. We postulate that the edemolytic effects of glucocorticoids may result from enhanced astrocytic calcium signaling.

Adenosine Triphosphate↗
PubMed1999

Phospholipase C-gamma and phosphoinositide 3-kinase mediate cytoplasmic signaling in nerve growth cone guidance.

Expression of rat TrkA in Xenopus spinal neurons confers responsiveness of these neurons to nerve growth factor (NGF) in assays of neuronal survival and growth cone chemotropism. Mutational analysis indicates that coactivation of phospholipase C-gamma (PLC-gamma) and phosphoinositide 3-kinase (PI3-kinase) by specific cytoplasmic domains of TrkA is essential for triggering chemoattraction of the growth cone in an NGF gradient. Uniform exposure of TrkA-expressing neurons to NGF resulted in a cross-desensitization of turning responses induced by a gradient of netrin-1, brain-derived neurotrophic factor (BDNF), or myelin-associated glycoprotein (MAG) but not by a gradient of collapsin-1/semaphorin III/D or neurotrophin-3 (NT-3). These results, together with the effects of pharmacological inhibitors, support the notion that there are common cytosolic signaling pathways for two separate groups of guidance cues, one of which requires coactivation of PLC-gamma and PI3-kinase pathways.

Animals↗
PubMed1999

Increased p53 protein expression in human failing myocardium.

BACKGROUND: The p53 gene is a tumor-suppressor gene which involves apoptosis and cell-cycle arrest under certain stress stimulate. However, the status of the p53 gene expression in human myocardium in congestive heart failure (CHF) remains unclear. Therefore, the current study was designed to investigate the expression of the p53 protein in human myocardium in normal subjects and in patients with severe CHF. METHODS: Human ventricular cardiac tissue was obtained from 7 normal subjects and 7 end-stage CHF patients during cardiac transplantation. The expression of p53 protein was determined by immunohistochemical staining. The cardiac apoptosis was determined by TUNEL staining. RESULTS: The p53 protein was minimally stained in normal human ventricular cardiomyocytes. In contrast, the staining density and positive stained nuclear (%) of p53 was significantly increased in ventricular cardiomyocytes of patients with severe CHF. Apoptosis in CHF human myocardium also markedly increased. CONCLUSIONS: The significantly increased expression of p53 in CHF human cardiomyocytes suggests that p53 may play an important pathophysiological role in the process of CHF through mechanisms involving myocardial apoptosis.

Adult↗
PubMed1999

Regulation of VH gene repertoire and somatic mutation in germinal centre B cells by passively administered antibody.

Immunization with T-dependent antigens induces a rapid differentiation of B cells to plasmacytes that produce the primary immunoglobulin M (IgM) and IgG antibodies with low affinities for the immunogen. It is proposed that the IgG antibody forms immune complexes with the residual antigen which provide an important stimulus for the formation of germinal centres (GC) and the activation of somatic mutation. This hypothesis was tested by passive administration of hapten-specific antibody into mice shortly after the immunization with nitrophenyl (NP) coupled to chicken gamma globulin (NP-CGG) in an environment of limited T-cell help. Athymic mice that received normal T helper cells at 72 hr after the administration of antigen produced low levels of anti-NP antibody and the splenic GC formation was delayed until day 12 after the antigen administration. The analysis of VDJ segments from NP-reactive GC B cells showed very few mutations in the VH genes. Passive injection of anti-NP IgG1 monoclonal antibody - but, not IgM - stimulated the GC formation up to normal levels and the somatic mutation activity in the GC B cells was fully restored. In addition, GC B cells in the recipients of IgG1 antibody demonstrated a change in the usage of germline-encoded VH genes which was not apparent among the primary antibody-forming cells. These results suggest the existence of a specific feedback mechanism whereby the IgG antibody regulates the GC formation, clonotypic repertoire and somatic mutation in GC B cells.

Animals↗
PubMed1999

Panax ginseng protects the testis against 2,3,7, 8-tetrachlorodibenzo-p-dioxin induced testicular damage in guinea pigs.

OBJECTIVES: To investigate histopathologically the beneficial effects of Panax ginseng extract on guinea pig testes damaged by 2,3, 7,8-tetrachlorodibenzo-p-dioxin (TCDD). MATERIALS AND METHODS: Ninety guinea pigs were divided into six equal groups. The normal controls (group 1) received vehicle and saline; group 2 received TCDD (1 microgram/kg) intraperitoneally; group 3 and 4 received 100 or 200 mg/kg per day of Panax ginseng water extract (PG-WE) intraperitoneally for 28 days from 1 week before TCDD injection; groups 5 and 6 received PG-WE for 14 days from 1 week after TCDD treatment. RESULTS: The gain in body weight was less in groups treated with TCDD than in controls. Moreover, the body weight of group 2 decreased from 14 days after TCDD exposure, while that of groups 3 and 4 increased; there was no decrease in body weight in groups 3-6. The decrease in testicular weight caused by TCDD was prevented by PG-WE. Light microscopy showed smaller tubules and late maturation arrest in group 2; electron microscopy showed a dissolution of the germinal epithelium, disrupted tight junctions between adjacent Sertoli cells, and altered germ cells at all developmental stages. The maturation arrest in germ cells caused by TCDD was ameliorated in groups 3-6. The testes almost completely recovered in groups 3 and 4 and there was some therapeutic effect of PG-WE in groups 5 and 6. CONCLUSIONS: These results confirm the protective and therapeutic effects of Panax ginseng on atrophy and testicular damage induced by TCDD, providing evidence that ginseng might be a useful agent in preventing and treating testicular damage induced by environmental pollutants.

Animals↗
PubMed1999

In vitro transcription assay with the purified 40kDa NF1-like protein binding to the rat p53 promoter.

The rat p53 promoter has several potential transcription factor-recognition motifs. They include NF1-like, bHLH family, and AP1-like proteins binding sites. The binding protein to NF1-like motif was previously identified. The protein has about 40kDa of molecular mass, which is smaller than that of NF1. Anti-NF1 polyclonal antibody does not recognize the protein. In this study, we isolated the 40kDa protein by sequence-specific DNA affinity chromatography. The isolated protein was assayed by DNase I footprinting analysis. To determine the transactivation effect of the protein, in vitro transcription with the purified 40kDa protein was carried out. After the addition of the purified 40kDa protein into the transcription reaction mixture, the transcription level of the p53 promoter was increased. This suggests that the 40 kDa NF1-like protein is a transcription activator for the rat p53 gene.

Animals↗
PubMed1999

Amino acids within the extracellular matrix (ECM) binding region (201-218) of rat insulin-like growth factor binding protein (IGFBP)-5 are important determinants in binding IGF-I.

The highly conserved N-and C-terminal domains of IGFBPs are believed to participate in IGF binding, but only recently have some of the critical residues in the IGFBP sequence involved in ligand binding been identified. Here we describe two highly conserved amino acids in the C-terminal domain of rat IGFBP-5 that are involved in binding IGF-I. Site-directed mutagenesis was used to produce two mutants, G203K and Q209A, of rIGFBP-5. Relative to wild-type rIGFBP-5, an 8-fold reduction in affinity for human IGF-I was found for recombinant G203K protein in both IGF-I ligand blots and solution phase ligand binding assays, and a 7-and 6-fold reduction for Q209A respectively. This shows that Gly203 and Gln209 in IGFBP-5 are important determinants in binding IGF-I, and due to their complete conservation in all IGFBP sequences, we suggest that they are likely to be involved in binding IGF-I in all six binding proteins. In addition, these two non-basic residues lie within the ECM binding region (201-218) of IGFBP-5, demonstrating that the C-terminus contains partially overlapping IGF-I and ECM binding sites. We therefore propose that heparin binding to basic amino acids in IGFBP-5 between 201-218 may physically occlude subsequent interaction between IGF-I and Gly203/Gln209, and that this may explain previous work of others showing reduced affinity of ECM bound IGFBP-5 for IGF-I.

Amino Acid Sequence↗
PubMed1999

The role of glutathione in p-aminophenol-induced nephrotoxicity in the mouse.

p-Aminophenol (PAP) produces nephrotoxicity in rats through a mechanism presumably involving oxidation and conjugation with glutathione (GSH). Recently it was found that PAP also causes nephrotoxicity in mice as evidenced by elevated blood urea nitrogen (BUN) and serum creatinine levels. The objective of this study was to further investigate the mechanism and elucidate the role of GSH in PAP-induced nephrotoxicity in the mouse. Male C57BL/6 mice injected i.p. with various doses of PAP were sacrificed at 12 hr for measurement of BUN and serum creatinine levels and determination of the extent of renal cortical nonprotein sulfhydryl (NPSH) and GSH depletion. PAP depleted renal cortical NPSH content in a dose- and time-dependent manner. Depletion of NPSH in mouse kidney did not occur at PAP doses below 600 mg/kg. Buthionine sulfoximine, an inhibitor of GSH synthesis, decreased nephrotoxicity. Ascorbate, a reducing agent, prevented PAP-induced nephrotoxicity and attenuated renal cortical NPSH depletion. However, acivicin and aminooxyacetic acid, inhibitors of gamma-glutamyltranspeptidase and beta-lyase, respectively, did not prevent toxicity in the mouse. Piperonyl butoxide, an inhibitor of cytochrome P-450 enzymes, enhanced nephrotoxicity and renal cysteine depletion but not GSH depletion. The results suggest that PAP-induced nephrotoxicity in the mouse may involve oxidation and formation of a GSH conjugate.

Aminophenols↗
PubMed1999

[Improvement in affinity of phage antibodies against HBsAg by light chain shuffling].

OBJECTIVE: We had cloned an Fd gene of human antibody against HBsAg previously. The objective of this experiment is to improve the affinity phage antibody by chain-shuffling. METHODS: Human antibody light chain gene repertoire was generated by RT-PCR from human peripheral blood lymphocyte, and then phage antibody sublibrary was constructed by inserting the repertoire into the phagmid which contained the Fd gene. The matched gene of light chain was selected by biopaning. RESULTS: After three rounds of selection, eight clones with higher absorbance than that of original clone at 490 nm in ELISA were obtained. DNA sequencing showed three of the five VL genes were kappa type, and the other two were lambda type. CONCLUSION: The results indicated that the affinity of chain shuffled phage antibodies(phab) were improved. The specificity of the selected phab was also confirmed.

Antibody Affinity↗
PubMed1999

A 40-kDa NF1-like protein, not YY1, binds to the rat p53 promoter for transactivation in various rat organs.

Two recognition motifs of a 40-kDa NF1-like protein were previously identified in the rat p53 promoter. One is located between -296 and -312 (NF1-like element 1) and the other between -195 and -219 (NF1-like element 2). The latter one was also identified as a NF1/YY1 recognition motif in the human p53 promoter. NF1 or YY1 binds to the motif and regulates the expression of the human p53 gene in a tissue-specific manner. In this study, we investigated the binding protein for NF1-like element 2 in various rat tissues. Unlike the human p53 transcription, an NF1-like protein, not YY1, bound to the motif in every tested tissue: thymus, kidney, and spleen. In vitro transcription assay also confirmed that the NF1-like protein regulated the p53 transcription in rat spleen, although the human p53 transcription was regulated by YY1 in that organ. The molecular mass of the binding protein was determined to be 40 kDa, which was the same as that of the NF1-like protein identified in liver. Therefore, the 40-kDa NF1-like protein may be a universal transcription regulator for the rat p53 gene.

Animals↗
PubMed1999

Genetic alterations in the transforming growth factor receptor complex in sporadic endometrial carcinoma.

Cellular responses to the transforming growth factor beta (TGFbeta) ligand, including inhibition of cell proliferation, are mediated by a heteromeric receptor complex composed of TGFbeta types I and II receptors (TbetaR-I and TbetaR-II). Loss of responsiveness to TGFbeta, attributed to inactivation of the TbetaR complex, has been implicated in the development of tumors in a number of human epithelial and lymphoid tissues. To gain a better understanding of TGFbeta signal transduction pathways in endometrial carcinogenesis, we have investigated the role of the TbetaR complex by evaluating the TbetaR-I and TbetaR-II genes for mutations throughout the entire coding region in human sporadic endometrial tumors. Using reverse transcription-PCR, "Cold" single-strand conformation polymorphism analysis, and direct DNA sequencing, it was found that 1 of 39 (2.6%) and 7 of 42 samples (17%) contained code-altering changes in the kinase domain of TbetaR-I and TbetaR-II, respectively. In 7betaR-I, a 3-bp deletion was found resulting in replacement of Arg and Glu at codon 237 and 238 by Lys. With TbetaR-II, mutations were found in the kinase, the extracellular, and the C-terminal domains. No frameshift mutations were detected; however, a silent population polymorphism (AAC-->AAT at codon 389) in TbetaR-II was found in 19 of 42 (44%) tumor samples. These results suggest that alteration in TbetaR-II, but not TbetaR-I, has an important role in the development of endometrial carcinoma.

Activin Receptors, Type I↗
PubMed1999

[Clinical significance of changes of interleukin 6 level in pregnancy induced hypertension].

OBJECTIVE: To assess the clinical significance of changes of interleukin-6 (IL-6) level in patients with pregnancy induced hypertension (PIH). METHODS: IL-6 level in urine and blood were measured by sandwich enzyme labeled immunosorbent assay (ELISA) in 82 patients with PIH and 30 normal pregnant women. RESULTS: Blood IL-6 level in severe PIH patients was significantly higher than that in mild PIH patients and normal pregnant women. IL-6 level of urine in PIH patients were significantly higher than that in normal pregnant women and was associated with the severity of disease. There was a positive correlation between urinary IL-6 level and severity of renal damage in PIH. CONCLUSION: Determination of IL-6 level is useful to understand the severity of PIH and its renal damage.

Adult↗
PubMed1999

[Pregnancy of patients conceived within one year after chemotherapy for gestational trophoblastic tumor].

OBJECTIVE: To explore the risk of pregnancy in patients conceived within one year after successful chemotherapy for gestational trophoblastic tumor. METHODS: 22 patients conceived within one year after chemotherapy were followed up and analysed about abnormal pregnant result, wastage rate and the time of interval between chemotherapy and pregnancy. RESULTS: Among 22 cases, 9 cases were full term birth, 6 cases were wastage. The wastage rate was 27.3%. The wastage rate of these patients conceived within half a year was higher than one year (P < 0.05). 1 repeated hydatidiform mole and one post term choriocarcinoma occurred in 22 patients. They both were conceived within 5 months after chemotherapy. CONCLUSIONS: Preservation of fertility is feasible in patients suffering from choriocarcimona and invasive mole. But these patients should practise contraception at least half a year after chemotherapy, and it's better to advise patients to take contraception for one year.

Adult↗
PubMed1999

[Radioimmunodetection in the diagnosis of trophoblastic disease].

OBJECTIVE: To study the efficiency of radioimmunodetection (RID) to locate the loci of trophoblastic disease. METHOD: 24 RIDs were performed with 131I labeled mouse anti-hCG monoclonal antibodies on 21 patients with trophoblastic disease. RESULTS: Of 24 RIDs performed, 13 were positive, including one false positive; 11 were negative, including two false negative. The sensitivity of RID was 85.7%, the specificity was 90.0%, the accuracy was 87.5%. In 8 patients who underwent operations after RID, the findings of RID were in accordance with the pathologic and immunohistologic findings. CONCLUSIONS: RID is an efficient imaging method for trophoblastic disease. In some cases, RID showed its value as a functional diagnostic method.

Adult↗