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Biomedical subjects

Y C Liu

Publications and source records attributed to Y C Liu.

At least 163 records · Page 9Linked to original sources
PubMed1996

Platelet-derived growth factor is an autocrine stimulator for the growth and survival of human esophageal carcinoma cell lines.

Platelet-derived growth factors (PDGF) are important mitogens for mesenchyme-derived cells. Neither PDGF nor PDGF receptors (PDGFR) are expressed in epithelial cells under normal physiological conditions. However, we have found that PDGF-BB induces c-jun expression and promotes the growth of the human esophageal carcinoma cell line CE48T/VGH. Scatchard analysis revealed the presence of 6 x 10(5) binding sites for PDGF-BB per cell, with a Kd of 9.7 nM. Furthermore, our data indicate that CE48T/VGH expresses beta type PDGFR (PDGFRbeta) with in vitro auto-kinase activity. We have also found that CE48T/VGH expresses the mRNA of the PDGF-A and PDGF-B chains and secretes PDGF molecules. Addition of anti-PDGF neutralizing antibody significantly decreased cell numbers of CE48T/VGH under serum-free conditions. The detached cells underwent apoptosis characterized by micronucleation. These results suggest that expression of the PDGF autocrine system may not only provide the growth advantage but also prevent the apoptosis for CE48T/VGH.

Apoptosis↗
PubMed1996

Remarkable enhancement of antioxidant activity of vitamin C in an artificial bilayer by making it lipo-soluble.

The reaction kinetics between 4-palmitoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO-16) and vitamin C (VC) and its lipophilic derivative ascorbyl-6-palmitate (VC-16) was studied by stopped-flow ESR spectroscopy in a synthetic surfactant vesicle sodium 1-pentadecyl hexadecyl sulfate (SPHS). TEMPO-16 reacted with VC very slowly and showed a biphasic first-order kinetics with rate constants of 9.6 x 10(-4) and 2.5 x 10(-4) s-1, corresponding to diffusion of TEMPO-16 from the external monolayer of SPHS to the bulk water and flip-flop of TEMPO-16 from the internal to external monolayer of the vesicle, respectively. On the other hand, the reaction of TEMPO-16 with VC-16 was second-order and over three orders of magnitude faster than that with VC, presumably due to VC-16 induced fusion of the vesicle.

Antioxidants↗
PubMed1996

Activation-modulated association of 14-3-3 proteins with Cbl in T cells.

14-3-3 proteins have recently been implicated in the regulation of intracellular signaling pathways via their interaction with several oncogene and protooncogene products. We found recently that 14-3-3 associates with several tyrosine-phosphorylated proteins and phosphatidylinositol 3-kinase (PI3-K) in T cells. We report here the identification of the 120-kDa 14-3-3tau-binding phosphoprotein present in activated T cell lysates as Cbl, a protooncogene product of unknown function which was found recently to be a major protein-tyrosine kinase (PTK) substrate, and to interact with several signaling molecules including PI3-K, in T lymphocytes. The association between 14-3-3tau and Cbl was detected both in vitro and in intact T cells and, in contrast to Raf-1, was markedly increased following T cell activation. The use of truncated 14-3-3tau fusion proteins demonstrated that the 15 C-terminal residues are required for the association between 14-3-3 and three of its target proteins, namely, Cbl, Raf-1, and PI3-K. The findings that 14-3-3tau binds both PI3-K and Cbl, together with recent reports of an association between Cbl and PI3-K, suggest that 14-3-3 dimers play a critical role in signal transduction processes by promoting and coordinating protein-protein interactions of signaling proteins.

14-3-3 Proteins↗
PubMed1996

CD4 Expression by erythroid precursor cells in human bone marrow.

Flow cytometry was used to assess CD4 expression in 62 consecutive bone marrow specimens from patients with a variety of clinical conditions. Using a lysed-whole-blood technique for labeling with monoclonal antibodies, two populations of CD4+ cells were identified within the lymphocyte/blast-cell fraction in 58 (94%) of these specimens. These consisted of (1) a population of T helper cells with high density expression of CD4 and (2) a second population of cells with low-density expression of CD4, which ranged from 1% to 36% of the gated cells. This latter population was present regardless of age, sex, or clinical condition including 21 of 21 specimens (100%) categorized as unremarkable bone marrows both morphologically and by flow cytometry and in four of four patients (100%) with human immunodeficiency virus-type 1 (HIV-1) infection. Coexpression of the erythroid lineage marker, glycophorin A, with the majority of cells in this second population was demonstrated in all 11 randomly selected samples using two-color flow cytometric analysis. These cells also expressed low levels of the myeloid markers, CD13 and CD33, but CD34 expression could not be demonstrated. These results provide evidence for expression of CD4 on cells of erythroid lineage in human marrow, and offer a potential mechanism for direct infection of erythroid precursor cells and deranged erythropoiesis in patients with HIV-1 infection.

Adult↗
PubMed1996

Plasmid insertional mutation may confer glucocorticoid responsiveness of cell growth.

Culture of CHO.K1, a Chinese hamster ovary cell line, requires no particular care about the glucocorticoid level in media. Cell growth of CHO.K1 is little affected by dexamethasone at concentrations up to 3 microM. A clone of CHO.K1 stably transfected with an expression vector displayed a favored growth in dexamethasone-containing media. Ironically, dexamethasone was used to trigger the expression of antisense PCNA from the expression vector to impede the cell growth. Proliferating cell nuclear antigen (PCNA), an auxiliary factor of DNA polymerase delta, is required for cell proliferation. The stable cell clone, designated as B11 had a retarded growth rate as compared to its parental cell. However, the B11 cell growth rate and the cell cycle progression were increased by dexamethasone. The glucocorticoid produced no similar effect on the parental cell or other stable transfectants of the same plasmid. Thus, the stimulatory effect of dexamethasone on B11 has little connection with the expression of antisense PCNA and possibly involves a relevant gene in the B11 genome that was mutated due to the random plasmid insertion. A preliminary effort in identifying the targeted gene was made by using plasmid rescue method, and two plasmids were obtained. The rescued DNA of both plasmids specifically hybridized genomic DNA of the parental cells, and one of these plasmids detected a cellular transcript that was absent in B11 cells, suggesting its potential for further investigation.

Animals↗
PubMed1996

Mycotic aneurysm due to non-typhi salmonella: report of 16 cases.

From 1990 through 1994, we collected information on all cases of mycotic aneurysms due to non-typhi Salmonella that occurred at the Veterans General Hospital in Kaohsiung, Taiwan. All cases of salmonella bacteremia were reviewed to find any additional cases. A total of 16 cases of salmonella mycotic aneurysms occurred. The mortality rate was 100% among the three patients treated with medical therapy alone. Nine (70%) of the 13 patients who received surgical and medical therapy survived. Ten of the 16 cases were due to Salmonella choleraesuis. Diagnosis was established by computed tomography or aortography. Gallium scans were of no diagnostic utility. A culture of blood from a patient with underlying atherosclerosis that is positive for invasive Salmonella should prompt a search for a mycotic aneurysm. Treatment with a third-generation cephalosporin and resection of the infected vessel is usually successful.

Aged↗
PubMed1996

Lowering extracellular calcium content protects cells from arsenite-induced killing and micronuclei formation.

The present study demonstrated that calcium ions were accumulated in nuclei of Chinese hamster ovary (CHO)-K1 cells after arsenite treatment. This process was enhanced by verapamil (a calcium channel blocker). Verapamil also significantly increased the cytotoxic effects of arsenite. In contrast, ethylene glycol-bis[beta-aminoethylether] N,N, N1,N1,-tetraacetic acid (EGTA, a calcium-specific chelator), or calcium-free conditions significantly reduced the cytotoxicity or arsenite. Similarly, the strategy of lowering extracellular calcium concentration by modifying the medium or lowering intracellular calcium concentration by administration of the intracellular calcium chelator quin 2, protected cells from arsenite-induced micronuclei formation. These data indicate that the disturbances in intracellular calcium homeostasis maybe involved in arsenite-induced cytotoxicity and micronuclei formation.

Animals↗
PubMed1996

Comparison of the Roche AMPLICOR MYCOBACTERIUM assay and Digene SHARP Signal System with in-house PCR and culture for detection of Mycobacterium tuberculosis in respiratory specimens.

Two commercial primer kits and detection systems, the Roche AMPLICOR MYCOBACTERIUM test and the Digene primer-probe kit with the SHARP Signal System, were compared to in-house PCR as well as standard culture techniques. For the 27 culture-positive specimens, the Roche AMPLICOR MYCOBACTERIUM test detected 20 specimens, the Digene system detected 19, and in-house PCR detected 21. Of the 86 culture-negative specimens, 13 were positive by the Roche AMPLICOR MYCOBACTERIUM test, 16 were positive by the Digene system, and 21 were positive by in-house PCR. When clinical situations were evaluated, 11 of 13 culture-negative Roche AMPLICOR MYCOBACTERIUM test-positive specimens, 10 of 16 culture-negative Digene system-positive specimens, and 13 of 21 culture-negative-in-house PCR-positive specimens were diagnosed as true-positive specimens. The sensitivities of Roche AMPLICOR MYCOBACTERIUM test, the Digene system, and in-house PCR were 73.81, 69.05, and 80.95%, and the specificities were 97.18, 91.55 and 88.73%, respectively. The positive predictive values were 93.94, 82.86, and 80.95%, and the negative predictive values were 86.25, 83.33, and 88.73%, respectively. For the commercial kits, the Roche AMPLICOR MYCOBACTERIUM test seems to be more sensitive and specific than the Digene system. However, the Roche AMPLICOR MYCOBACTERIUM test cannot be used on nonrespiratory specimens.

Bacteriological Techniques↗
PubMed1996

Direct interaction between protein kinase C theta (PKC theta) and 14-3-3 tau in T cells: 14-3-3 overexpression results in inhibition of PKC theta translocation and function.

Recent studies have documented direct interactions between 14-3-3 proteins and several oncogene and proto-oncogene products involved in signal transduction pathways. Studies on the effects of 14-3-3 proteins on protein kinase C (PKC) activity in vitro have reported conflicting results, and previous attempts to demonstrate a direct association between PKC and 14-3-3 were unsuccessful. Here, we examined potential physical and functional interactions between PKC theta, a Ca(2+)-independent PKC enzyme which is expressed selectively in T lymphocytes, and the 14-3-3 tau isoform in vitro and in intact T cells. PKC theta and 14-3-3 tau coimmunoprecipitated from Jurkat T cells, and recombinant 14-3-3 tau interacted directly with purified PKC theta in vitro. Transient overexpression of 14-3-3 tau suppressed stimulation of the interleukin 2 (IL-2) promoter mediated by cotransfected wild-type or constitutively active PKC theta, as well as by endogenous PKC in ionomycin- and/or phorbol ester-stimulated cells. This did not represent a general inhibition of activation events, since PKC-independent (but Ca(2+)-dependent) activation of an IL-4 promoter element was not inhibited by 14-3-3 tau under similar conditions. Overexpression of wild-type 14-3-3 tau also inhibited phorbol ester-induced PKC theta translocation from the cytosol to the membrane in Jurkat cells, while a membrane-targeted form of 14-3-3 tau caused increased localization of PKC theta in the particulate fraction in unstimulated cells. Membrane-targeted 14-3-3 tau was more effective than wild-type 14-3-3 tau in suppressing PKC theta-dependent IL-2 promoter activity, suggesting that 14-3-3 tau inhibits the function of PKC theta not only by preventing its translocation to the membrane but also by associating with it. The interaction between 14-3-3 and PKC theta may represent an important general mechanism for regulating PKC-dependent signals and, more specifically, PKC theta-mediated functions during T-cell activation.

14-3-3 Proteins↗
PubMed1996

Pulse therapy with cyclophosphamide and methylprednisolone in patients with moderate to severe paraquat poisoning: a preliminary report.

BACKGROUND: Severe paraquat poisoning causes considerable morbidity and mortality. High doses of cyclophosphamide and dexamethasone have been used to treat patients with paraquat poisoning, but with mixed results. The use of pulse methylprednisolone and cyclophosphamide was investigated in the treatment of moderately severe paraquat poisoning. METHODS: During a six-year period 87 patients with paraquat poisoning were admitted to hospital, of whom 33 had moderate to severe intoxication. Seventeen patients received conventional treatment and served as historical controls, and 16 received intravenous infusions of cyclophosphamide 1 g daily for two days and methylprednisolone 1 g daily for three days. RESULTS: There were no differences between the groups in age, sex, severity of paraquat poisoning (as assessed by urine dithionite tests), or in the time elapsed from ingestion to presentation at hospital or to the beginning of haemoperfusion. No differences were seen in biochemical measurements on the third day after paraquat poisoning. The mortality in the pulse therapy group was lower than that in the control group (4/16 (25%) versus 12/17 (70.6%), p = 0.01). All fatalities were from progressive respiratory failure. CONCLUSIONS: Pulse therapy with cyclophosphamide and methylprednisolone may be effective in preventing respiratory failure and reducing mortality in patients with moderate to severe paraquat poisoning. Further controlled studies are needed to confirm this and to establish the mechanisms.

Adult↗
PubMed1996

[Laboratory evaluation of automated enzyme linked fluorescent assay for detecting serum specific IgG antibodies against rubella virus].

The VIDAS rubella IgG(RBG) is a new, automated, enzyme-linkad fluorescent assay(ELFA) for detecting IgG antibodies to rubella virus in serum. The purpose of this study was to evaluate the usefulness of the qualitative and quantitative VIDAS RBG as laboratory tests in the rapid detecting anti-rubella IgG antibodies. Simultaneous parallel testing was performed by using the qualitative and quantitative RBG along with RUBAZYME(ABBOTT LABORATORIES) and the standard hemagglutination-inhibition(HI) test(R-HI kit, SEIKEN) on 200 blood samples submitted for anti-rubella IgG antibodies testing from patients at the VGH-Kaohsiung(Mar.-Sep., 1993). The qualitative and quantitative VIDAS RBG and RUBAZYME assay were compared to the standard R-HI test. Significant differences among the sensitivities of these three methods were found (100% sensitivity for the qualitative VIDAS RBG, 88.89% for the quantitative VIDAS RBG and 97.67% for the RUBAZYME). However, the specificities of these three methods were all the same, 100%. With these results we can conclude that the qualitative VIDAS RBG will provide a very good, precise and reliable method to determine serum specific IgG antibodies against rubella virus. Furthermore, the VIDAS RBG is fully automated and time-saving procedures (for every batch of test, it takes 25 minutes with VIDAS RBG, 2.5 hours with RUBAZYME and 4.5 hours with R-HI) in clinical laboratories.

Antibodies, Viral↗
PubMed1996

Human foamy virus genome in the thymus of myasthenia gravis patients.

The etiological relationship of human foamy virus (HFV), which is a spumaretrovirus, with human diseases is not clear. We analyzed thymus specimens from four patients with myasthenia gravis for the presence of HFV proviral genome by polymerase chain reaction (PCR). The results showed the presence of both 257 base pair (bp) and 299 bp DNA fragments representing a part of gag and bel-2 sequences, respectively, in all four thymuses. Their specificity was confirmed by Southern blot hybridization with the corresponding probes. This was also confirmed by sequence analysis, although there were some point mutations. We confirmed the presence of gag related sequence, a 1353 bp Xba I-cleaved DNA fragment in all four thymus samples, a 693 bp fragment in two (#3 and #4) and a 4300 bp Hind III-cleaved DNA fragment in another two (#1 and #4), indicating possible chromosomal integration of the HFV partial genome. To our knowledge, this is the first report on the presence of HFV genome in thymus tissues of myasthenia gravis patients. Our efforts to isolate the infectious HFV by cultivation of the tissues were not successful. Low titers of neutralizing antibody were detected in all four patients' serum samples. The possible role of the HFV in this autoimmune disease needs further investigation.

Adult↗
PubMed1996

Endogenous Escherichia coli endophthalmitis.

Metastatic bacterial endophthalmitis caused by Klebsiella pneumoniae is a unique but well-known phenomenon in Taiwan, where most cases occur in diabetic patients with pyogenic liver abscesses. However, endogenous Escherichia coli endophthalmitis is quite rare. The most common primary site of this infection is the urinary tract and the incidence of concurrent systemic infections, such as abscess formation and infective endocarditis, is high. This illness has a rapidly progressive clinical course associated with a poor prognosis for recovery of visual acuity. This is a report of a case of endogenous E. coli endophthalmitis originating from a renal abscess in a diabetic woman. Despite aggressive local and systemic treatment, evisceration was required to prevent the infection from spreading.

Abscess↗
PubMed1996

Alcaligenes xylosoxidans neonatal meningitis: a case report.

Neonatal meningitis caused by Alcaligenes xylosoxidans is associated with a high mortality rate. The causative microorganism is resistant to most antimicrobials. Generally, once the organism has been isolated from the cerebrospinal fluid of the infected neonate, initial therapy with a third-generation cephalosporin and trimethoprim-sulfamethoxazole is recommended before determining its susceptibility to antimicrobials. There present this is the first of neonatal meningitis with transient diabetes insipidus cause by A. xylosoxidans. The patient was treated with dDAVP for seven days and a combination of imipenem plus trimethoprim-sulfamethoxazole for 28 days. The patient was discharged in a stable condition and the end of that time, but with sequelae of hydrocephalus and hearing impairment.

Alcaligenes↗
PubMed1996

Evaluation of polymerase chain reaction-restriction enzyme analysis of mycobacteria cultured in BACTEC 12B bottles.

Polymerase chain reaction with restriction enzyme analysis (PRA) was first tested on 15 reference strains and 50 subcultured clinical isolates of mycobacteria according to the reference algorithm by Telenti et al [1]. Next, we evaluated the application of this method to 108 isolates from liquid media (BACTEC 12B). Of them, 15 M. tuberculosis complex and 81 mycobacteria other than tuberculosis (MOTT) had comparable results with both PRA and the BACTEC 460 TB systems. However, seven M. tuberculosis complex and three potentially pathogenic MOTT were identified by PRA rather than the BACTEC TB system. PRA seems to be an efficient method for the identification of mycobacteria to the species level and a good aid to detect potentially pathogenic mycobacteria, especially in mixed mycobacterial cultures.

Humans↗