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Biomedical subjects

Y C Liu

Publications and source records attributed to Y C Liu.

At least 145 records · Page 8Linked to original sources
PubMed1998

The effect of coagulation protection with combination of epsilon aminocaproic acid and plasma saver in open-heart surgery.

BACKGROUND: Bleeding remains a major complication and a major determinant in the prognosis of open-heart surgery. Coagulopathy related to cardiopulmonary bypass (CPB) seems to be the culprit. Since homologous blood transfusion in many occasions is not only responsible for mobidity and mortality but also increases medical costs. Therefore, the application of autologous blood transfusion including components such as PRBC, FFP and platelets concentrate is inevitable and comes in its stead. To reduce the use of homologous plasma and platelets transfusion in open-heart surgery, we designed a study to utilize the combination of autologous platelet rich plasma (PRP) and epsilon aminocaproic acid (EACA) to evaluate its effects on blood loss and blood component transfusion in open-heart patients. METHODS: Sixty patients who received elective cardiac surgery were randomly divided into 3 groups: 1. Control group; 2. EACA group (150 mg/kg, i.v. before CPB); 3. PRP-EACA group (PRP 10 ml/kg harvested with a plasma saver followed by i.v. EACA 150 mg/kg). Anesthesia was uniform in all patients. Coagulation profile was evaluated by thromboelastography (TEG) during the operation. Blood loss during operation and the amount of drainage from the chest tubes in the postoperative period were recorded and compared between groups. RESULTS: Patients who were given EACA injection before CPB saw less blood loss perioperatively and received less transfusion of blood components. TEG analysis showed that patients who received EACA injection had a better coagulation profile and the platelet function was also better after CPB. However, no additive effect can be attained from combination of autologous PRP transfusion and EACA injection. CONCLUSIONS: With Pre-CPB EACA as protection, reduction of both blood loss and blood transfusion could be realized in open-heart surgery.

Adult↗
PubMed1997

Glutathione peroxidase and catalase modulate the genotoxicity of arsenite.

The X-ray hypersensitive Chinese hamster ovary (CHO) cells, xrs-5, are also more sensitive to sodium arsenite in terms of cell growth and micronucleus induction than CHO-K1 cells. Since reactive oxygen species are suggested to be involved in arsenic toxicity, we have measured antioxidant mechanisms in xrs-5 as well as CHO-K1 cells. There were no apparent differences in the activities of superoxide dismutase, glutathione S-transferase, glutathione reductase, and the levels of glutathione between xrs-5 and CHO-K1 cells. However, the activities of glutathione peroxidase and catalase were 5.4- and 5.8-fold lower, respectively, in xrs-5 cells. The addition of catalase or glutathione peroxidase to cultures reduced the arsenite-induced micronuclei in xrs-5 cells. Whereas, simultaneous treatment with mercaptosuccinate, an inhibitor of glutathione peroxidase, and 3-aminotriazole, an inhibitor of catalase, synergistically increased the arsenite-induced micronuclei. These results suggest that both catalase and glutathione peroxidase are involved in defense against arsenite genotoxicity. The xrs-6 cells, another line of x-ray hypersensitive CHO cells, which had 1.6-fold higher catalase activity and 2.5-fold higher glutathione peroxidase activity than xrs-5 cells, were also more sensitive than CHO-K1 cells but were less sensitive than xrs-5 cells to cell growth inhibition of arsenite. Moreover, a 1.6-fold increase of glutathione peroxidase activity by selenite adaptation effectively removed the arsenite-induced micronuclei in CHO-K1 cells. These results suggest that glutathione peroxidase is more important than catalase in defending against arsenite toxicity. Our results also suggest that increasing the intracellular antioxidant level may have preventive or therapeutic effects in arsenic poisoning.

Amitrole↗
PubMed1997

Lesions in medial preoptic area and bed nucleus of stria terminalis: differential effects on copulatory behavior and noncontact erection in male rats.

The goal of these studies was to assess the regulatory roles of the medial preoptic area (MPOA) and the bed nucleus of the stria terminalis (BST) in sexual arousal, inferred from noncontact erection (NCE) evoked in male rats by remote cues from estrous females. NCE and copulatory behavior were recorded before and after quinolinic acid or radiofrequency (RF) lesions were made in the MPOA (Experiments 1-3) or RF lesions were made in the BST (Experiment 4). All males with MPOA lesions, particularly in the rostral region, displayed severe deficits in copulation but little or no decrement in NCE. In contrast, BST lesions caused relatively moderate deficits in copulation, but they severely impaired NCE. Animals with larger BST lesions, including rostral and caudal medial regions, had more deficits in both copulatory behavior and NCE than did males with smaller lesions confined to the rostral medial BST. These results suggest that (1) the MPOA is critical for copulatory behavior but not for NCE, (2) males that stop copulating after MPOA lesions are still sexually aroused by estrous females, and (3) the BST plays an important role in mediating NCE.

Animals↗
PubMed1997

Serine phosphorylation of Cbl induced by phorbol ester enhances its association with 14-3-3 proteins in T cells via a novel serine-rich 14-3-3-binding motif.

Stimulation of the T cell antigen receptor (TCR).CD3 complex induces rapid tyrosine phosphorylation of Cbl, a protooncogene product which has been implicated in intracellular signaling pathways via its interaction with several signaling molecules. We found recently that Cbl associates directly with a member of the 14-3-3 protein family (14-3-3tau) in T cells and that the association is increased as a consequence of anti-CD3-mediated T cell activation. We report here that phorbol 12-myristate 13-acetate stimulation of T cells also enhanced the interaction between Cbl and two 14-3-3 isoforms (tau and zeta). Tyrosine phosphorylation of Cbl was not sufficient or required for this increased interaction. Thus, cotransfection of COS cells with Cbl plus Lck and/or Syk family protein-tyrosine kinases caused a marked increase in the phosphotyrosine content of Cbl without a concomitant enhancement of its association with 14-3-3. Phorbol 12-myristate 13-acetate stimulation induced serine phosphorylation of Cbl, and dephosphorylation of immunoprecipitated Cbl by a Ser/Thr phosphatase disrupted its interaction with 14-3-3. By using successive carboxyl-terminal deletion mutants of Cbl, the 14-3-3-binding domain was mapped to a serine-rich 30-amino acid region (residues 615-644) of Cbl. Mutation of serine residues in this region further defined a binding motif distinct from the consensus sequence RSXSXP, which was recently identified as a 14-3-3-binding motif. These results suggest that TCR stimulation induces both tyrosine and serine phosphorylation of Cbl. These phosphorylation events allow Cbl to recruit distinct signaling elements that participate in TCR-mediated signal transduction pathways.

14-3-3 Proteins↗
PubMed1997

Involvement of calcium-dependent protein kinase C in arsenite-induced genotoxicity in Chinese hamster ovary cells.

Arsenic is the first metal to be identified as a human carcinogen. Arsenite, one inorganic form of arsenic, has been found to induce sister chromatid exchange, chromosome aberrations, and gene amplification in a variety of in vitro systems. In this study of arsenite-induced genotoxicity represented a micronuclei production in Chinese hamster ovary cells (CHO-K1), we found that the calcium channel blocker, verapamil, can potentiate arsenite-induced micronuclei. And after arsenite treatment, the elevation of intracellular calcium was observed. When extracellular calcium was depleted during arsenite treatment, the arsenite-induced micronuclei formation was significantly suppressed. These data indicated that a calcium ion plays an essential role in arsenite-induced genotoxicity. Further, it was found that the cotreatment of arsenite and a calcium ionophore, A23187, can increase the micronuclei induction. In contrast, pretreatment of the intracellular calcium chelator, quin 2, significantly inhibited micronuclei production of arsenite administration. In addition, we measured the activity of calcium- and phospholipid-dependent protein kinase C (PKC) and found that arsenite can activate PKC activity in a dose-dependent manner. Subsequently, some PKC activators and inhibitors were applied to investigate the involvement of PKC on arsenite-induced micronuclei formation. It was found that H7, a PKC inhibitor, can depress but TPA, a PKC activator, can enhance arsenite-induced micronuclei significantly. These data indicated that arsenite exposure perturbs intracellular calcium homeostasis and activates PKC activity. As a result, the activation of PKC activity may play an important role in arsenite-induced genotoxicity.

Adenosine Triphosphate↗
PubMed1997

Conversion of inactive glycosylation inhibiting factor to bioactive derivatives by modification of a SH group.

Escherichia coli-derived recombinant human glycosylation inhibiting factor (rhGIF) contains three cysteine residues (Cys-57, -60, and -81). All SH groups in the cysteine residues are free, and the GIF molecule had no biologic activity. Carboxymethylation of the SH group of Cys-60 in the molecule resulted in the generation of bioactivity, although the activity of the carboxymethylated GIF was 10- to 20-fold less than that of suppressor T cell (Ts)-derived GIF. However, treatment of the inactive rhGIF with ethylmercurithiosalicylate or 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) resulted in the generation of derivatives whose bioactivity was comparable to that of the Ts-derived bioactive GIF. The activity of these derivatives was lost by treatment with DTT. Isolation and chemical analysis of the DTNB-treated GIF derivative revealed that binding the 5-thio-2-nitrobenzoic acid group with Cys-60 was responsible for the generation of the highly bioactive derivative. Inactive cytosolic GIF from mammalian cells could also be converted to bioactive derivative by treatment with the SH reagent, while Ts-derived bioactive GIF was inactivated by DTT. These results, together with an x-ray crystal structure of GIF molecules, strongly suggest that the generation of bioactivity of GIF in Ts cells is due to posttranslational modifications that result in conformational changes in the molecule.

Amino Acid Sequence↗
PubMed1997

Ras-dependent, Ca2+-stimulated activation of nuclear factor of activated T cells by a constitutively active Cbl mutant in T cells.

T cell receptor (TCR) stimulation induces rapid tyrosine phosphorylation of cellular proteins, including Cbl, a protooncogene product whose function remains unclear. As a first step toward elucidating the function of Cbl in TCR-initiated signaling, we evaluated the ability of wild-type Cbl or a transforming Cbl mutant (70Z/3) to induce transcriptional activation of a nuclear factor of activated T cells (NFAT) element derived from the interleukin 2 (IL2) promoter in transiently cotransfected Jurkat-TAg T cells. 70Z/3, but not Cbl, caused NFAT activation which was significantly enhanced by stimulation with calcium ionophore, and was drastically reduced by cyclosporin A pretreatment. A point mutation of a potential phosphatidylinositol 3-kinase (PI3-K) binding site (Y731EAM to Y731EAC) in 70Z/3 disrupted the association of PI3-K with 70Z/3, but did not reduce the induction of NFAT activity, suggesting that the interaction between Cbl and PI3-K is not required in the 70Z/3-mediated induction of NFAT. Additional mapping studies indicated that defined deletions of C-terminal 70Z/3 sequences affected to a variable degree its ability to stimulate NFAT activity. Strikingly, deletion of 346 C-terminal residues augmented this activity, whereas removal of 20 additional residues abolished it. Coexpression of dominant negative Ras abrogated the basal or ionomycin-stimulated, 70Z/3-mediated NFAT activation, suggesting a functional Ras is required for this activation. These results implicate Cbl in Ras-dependent signaling pathways which lead to NFAT activation.

Animals↗
PubMed1997

A hemophilia model in zebrafish: analysis of hemostasis.

We have developed artificial hemophilia in zebrafish by treating them with copper and measured their clotting function by a newly developed sensitive clotting time assay. The clotting function can be detected rapidly and reliably in 30 hr larvae and in adult fish by measuring the blood clotting time. We have used this assay to screen wild type zebrafish and identified fish with prolonged clotting time. This verifies the usefulness of this assay in future screening for recessive hemostasis defects generated by chemical and radiation mutagenesis methods.

Animals↗
PubMed1997

Developmental expression of thrombin in zebrafish embryos: a novel model to study hemostasis.

A partial cDNA encoding zebrafish prothrombin has been cloned and used as a probe to study the temporal expression of prothrombin mRNA during early embryonic development. The results revealed accumulation of prothrombin mRNA in diverse tissues such as the eyes and myotomes in early embryogenesis. We have also examined the enzymatic activity of thrombin in converting fibrinogen to fibrin in individual embryos at different stages of development. We found that the fibrin-forming activity does not temporally correlate with the first presence of thrombin mRNA in the early stages of embryogenesis, but does correlate with the initiation of blood formation. Our ability to observe the fibrin-forming activity in single individual embryo will facilitate studies on identifying recessive mutations affecting blood coagulation, such as the regulatory gene mutations controlling the clotting factor genes. Furthermore, the observation of thrombin activity will also facilitate studies on the blood coagulation pathways in the early embryogenesis in this zebrafish model.

Animals↗
PubMed1997

Effects of hirudin (thrombin specific inhibitor) in zebrafish embryos: a developmental role for thrombin.

To address the role of thrombin in early embryogenesis, hirudin, a thrombin specific inhibitor was microinjected into developing zebrafish embryos to inhibit the temporal activity of thrombin during early embryonic development. We found that the fibrin forming activity is inhibited by the presence of hirudin. We also found that hirudin affects development in zebrafish embryos suggesting thrombin's role in early embryogenesis. This ability to inhibit thrombin activity in developing embryos should facilitate studies on identifying signal transduction pathways affected by thrombin during embryogenesis.

Animals↗
PubMed1997

Role of nitric oxide in lipopolysaccharide-induced mortality from spontaneously hypertensive rats.

To investigate whether nitric oxide (NO) contributed to a higher mortality induced by lipopolysaccharide (LPS) in spontaneously hypertensive rats (SHR), NO synthase inhibitors were used to examine the mortality from LPS in SHR and normotensive Wistar-Kyoto (WKY) rats. We evaluated the mortality from LPS in a series of doses (5, 10, or 20 mg/kg, i.v.) in the anesthetized rat. Plasma nitrite was measured before and at 1, 2, and 3 h after treated rats with LPS (5 mg/kg, i.v.). Pressure responses to N omega-nitro-L-arginine methyl ester (L-NAME) and aminoguanidine (AG) were performed in rats treated with or without LPS for 3 h. Thoracic aortic cyclic guanosine 3',5'-monophosphate (cGMP) levels were also assessed. Our results demonstrated that injection of LPS caused a dose-dependent mortality in both strains, having a more marked effect in SHR. The survival time of rats after injection of LPS (5 mg/kg, i.v.) was much shorter in SHR. A higher basal level of plasma nitrite was observed in SHR and this difference was further augmented by LPS. The administration of L-NAME (3 mg/kg, i.v.) and AG (15 mg/kg, i.v.) 3 h after LPS had no significant effects on the survival time of WKY rats, but significantly prolonged that of SHR to a similar time of WKY rats. The injecton of L-NAME prior to LPS increased blood pressure of WKY rats by 28+/-5 mmHg and increased that of SHR by 38+4 mmHg. At 3 h after LPS, L-NAME had a greater pressor effect in SHR than in WKY rats. By contrast, before rats injected with LPS, AG slightly increased blood pressure of SHR by 7+/-3 mmHg but not of WKY rats (3+/-2 mmHg), whereas it also had a greater pressor effect in SHR than in WKY rats after treated rats with LPS for 3 h. In addition, LPS induced a higher level of cGMP in SHR than in WKY rats, which was attenuated by in vitro treatment of aortic rings from LPS-rats with L-NAME or AG to a similar level in SHR and WKY rats. These results suggest that a higher level of NO evoked by LPS is associated with a higher mortality in SHR and we propose that the elevated NO synthesis in SHR may play an important role in the compensatory mechanisms activated to combat the hypertensive state.

Animals↗
PubMed1997

Production of bioactive salmon calcitonin from the nonendocrine cell lines COS-7 and CHO.

To produce bioactive salmon calcitonin from the conventional nonendocrine cell lines, COS-7 and CHO, we devised a salmon calcitonin expression vector by combining the amino-terminus of human calcitonin precursor with a salmon calcitonin sequence, inserting the efficient furin-cleavable processing sequence Arg-X-Arg-X-Lys-Arg before salmon calcitonin, and deleting the carboxyl-terminal extension peptide. This chimeric calcitonin precursor terminates at glycine to easily receive an amidation reaction. COS-7 and CHO produced a high level of bioactive calcitonin by the resorption pit formation assay. Although amidating activity is highly expressed in CHO, but only a little in COS-7 cells, both cells produced a similar level of bioactive calcitonin. Thus, the engineered salmon calcitonin expression vector enables nonendocrine cells even with low amidation activity to produce bioactive calcitonin.

Animals↗
PubMed1997

Impaired sexual response after lesions of the paraventricular nucleus of the hypothalamus in male rats.

N-methyl-D-aspartic acid (NMDA) or radiofrequency (RF) lesions were made in the paraventricular nucleus of the hypothalamus (PVH) of male rats. The rats were tested for copulation, noncontact erection (NCE) evoked by remote cues from estrous females, and (after RF lesions) reflexive erection. NMDA, which destroyed parvocellular but spared magnocellular neurons, caused no deficits in copulation but caused longer NCE latencies and fewer NCEs. Rats with RF lesions had parvo- and magnocellular neuron damage; these males copulated to ejaculation, but they had lower intromission ratios and longer ejaculatory latencies. RF-lesioned rats also had longer NCE latencies, and a smaller proportion of males displayed reflexive erection. Results indicate that the PVH participates in mediating erectile function in copula and ex copula, and that the parvo- and magnocellular PVH neurons may have different roles in mediating erection.

Animals↗
PubMed1997

Role of benzathine penicillin G in prophylaxis for recurrent streptococcal cellulitis of the lower legs.

Cellulitis of the lower leg is an infection caused by streptococci or, less commonly, Staphylococcus aureus and other gram-negative rods. Recurrence of cellulitis is a common problem. In the present study, we evaluated the use of monthly intramuscular injections of benzathine penicillin G to prevent recurrences of cellulitis. A total of 115 patients with definite or presumptive cases of streptococcal cellulitis were enrolled in this study. Eighty-four of these patients who declined follow-up or received incomplete prophylaxis were considered controls. Recurrence occurred in four (12.9%) of 31 cases who received prophylaxis and 16 (19%) of the 84 cases who did not receive prophylaxis. The difference was not statistically significant. Predisposing factors for cellulitis were found in 57 (49.6%) of the 115 enrolled cases and were mostly related to the impairment of local circulation. Administration of prophylaxis successfully reduced the recurrence rate to zero among patients without predisposing factors but failed to prevent recurrence in those with predisposing factors (20%). We conclude that monthly benzathine penicillin G prophylaxis benefits only patients without predisposing factors for cellulitis.

Cellulitis↗
PubMed1997

Skin and soft-tissue manifestations of Shewanella putrefaciens infection.

Shewanella putrefaciens, a saprophytic gram-negative rod, is infrequently recovered from clinical specimens. Although a number of clinical syndromes have been attributed to S. putrefaciens, the pathogenic role of this agent remains largely undefined. We report 16 cases of S. putrefaciens infection that occurred at the Veterans General Hospital-Kaohsiung in Taiwan between 1990 and 1995. S. putrefaciens infection was associated with a wide clinical spectrum including bacteremia/septicemia, skin and soft-tissue infection, biliary tract infection, peritonitis, and empyema. Five of our patients had skin and soft-tissue manifestations, including fulminant periorbitofacial cellulitis, dacryocystitis, perineal abscess, finger abscess, and postcholecystectomy wound infection. These clinical features deviated from the chronic ulcers or infected burns of the lower extremities that have been described in previous reports. Seven (44%) of our 16 patients had bacteremia/septicemia, and all seven had underlying hepatobiliary diseases. S. putrefaciens was isolated in mixed cultures of specimens from 14 patients; Escherichia coli was the most common coisolate. Hepatobiliary diseases and malignancy were the major predisposing factors for S. putrefaciens infection of the biliary tract and S. putrefaciens bacteremia/septicemia.

Aged↗
PubMed1997

Correlation of serum immunoglobulin G Helicobacter pylori antibody titers with histologic and endoscopic findings in patients with dyspepsia.

Serum immunoglobulin G (IgG) antibody tests are used extensively. We attempted to find out whether the titers of anti-Helicobacter pylori IgG antibody correlated with the degree of macroscopic gastrointestinal damage, the severity of antral gastritis, and the density of antral H. pylori colonization in symptomatic patients. Peripyloric antral biopsy specimens were obtained from 50 consecutive patients with dyspepsia undergoing upper gastrointestinal endoscopy. The macroscopic gastrointestinal damage and the histologic grades of antral gastritis were scored by a modified Lanza scale and Sydney system, respectively. In addition, the densities of antral H. pylori colonization were graded semiquantitatively. Serum IgG antibodies to H. pylori were measured by enzyme-linked immunosorbent assay. Thirty-six (M/F = 29/7) of the 50 patients had H. pylori infection documented by histologic examination or rapid urease test or both. Among the subjects, the IgG antibody titers to H. pylori correlated significantly with the grades of antral polymorphonuclear cell infiltration (p = 0.002) and antral bacterial density (p = 0.01) but not with endoscopic scores, the grades of mononuclear cell infiltration, mucosal atrophy, or intestinal metaplasia (p > 0.05). In addition, endoscopic scores also were found to be significantly correlated with antral bacterial density (p = 0.049) and the grade of polymorphonuclear cell infiltration (p = 0.012). We therefore conclude that high titers of IgG antibody to H. pylori in patients with dyspepsia indicate dense H. pylori colonization and severe antral polymorphonuclear cell infiltration. However, it cannot replace endoscopic examination to evaluate the degree of macroscopic gastrointestinal damage.

Aged↗
PubMed1997

Cryptococcal meningitis and primary CNS lymphoma in a patient with acquired immunodeficiency syndrome: a case report.

This report describes a case of cryptococcal meningitis as the initial manifestation of acquired immunodeficiency syndrome (AIDS). During the admission, computed tomography (CT) of brain revealed multiple lesions with ring-enhancement over the cerebellum, frontal and temporal lobes. Autopsy findings showed diffuse cryptococcal meningoencephalitis and central nervous system (CNS) lymphoma forming multiple round ring abscesses. The case demonstrated that opportunistic cryptococcal infection and primary CNS lymphoma may coexist in a patient with AIDS.

AIDS-Related Opportunistic Infections↗