Biomedical subjects

L Y Chen

Publications and source records attributed to L Y Chen.

At least 91 records · Page 5Linked to original sources

PubMed1996

Production of hematopoietic regulatory cytokines by peripheral blood mononuclear cells in patients with aplastic anemia.

The aim of this study was to measure the level of cytokines produced by peripheral blood mononuclear cells (PBMNC) in patients with aplastic anemia (AA) and determine their effect on normal bone marrow (BM) colony growth. Thirty-five patients with AA and 21 normal controls were enrolled in the study. Medium conditioned by PBMNC of AA patients in the presence of phytohemagglutinin (PHA) was found to be suppressive to the clonal growth of normal BM cells. Thus, we further determined the presence in the PBMNC conditioned medium (CM) of inhibitory cytokines (macrophage inflammatory protein-1 alpha [MIP-1 alpha], transforming growth factor-beta 2 [TGF-beta 2], interferon-gamma [IFN-gamma], and tumor necrosis factor-alpha [TNF-alpha]) and stimulatory cytokines (granulocyte-macrophage colony-stimulatory factor [GM-CSF], interleukin-3 [IL-3], and stem cell factor [SCF]). The results show no significant difference between AA patients and normal controls in the spontaneous production of all cytokines by PBMNC. After PHA stimulation, the production of MIP-1 alpha, IFN-gamma, TNF-alpha, and GM-CSF significantly increased in the cultures of AA patients (p = 0.0009, 0.0002, 0.0022, and 0.0156, respectively). However, both TGF-beta 2 and SCF were undetectable in most of the tested samples. IL-3 was measured in the conditioned medium only after PHA stimulation, but without significant difference between the two groups (p = 0.67). Furthermore, the myelopoietic suppressing effect of AA-PBMNC CM could be significantly blocked by pretreatment with specific antibodies to the corresponding inhibitory cytokines (MIP-1 alpha, IFN-gamma, and TNF-alpha). After antibody neutralization, an apparent change occurred in the clonal growth of normal BM cells incubated with AA-PBMNC CM, resulting in colony enhancement of 205, 131, and 237% by anti-MIP-1 alpha, anti-IFN-gamma, and anti-TNF-alpha, respectively. These results suggest that overproduction of inhibitory cytokines, rather than underproduction of stimulating cytokines, may play a role in the progression of at least some patients with AA.

Anemia, Aplastic↗

PubMed1996

Variable effects of L-arginine analogs on L-arginine-nitric oxide pathway in human neutrophils and platelets may relate to different nitric oxide synthase isoforms.

L-Arginine analogs are generally used as inhibitors of nitric oxide (NO) synthesis in a variety of tissues. We studied the effects of two analogs of L-arginine on L-arginine transport and NO synthase activity in human polymorphonuclear leukocytes (PMN) and platelets. Both NG-nitro-L-arginine methylester and N omega-nitro-L-arginine reduced the uptake of 3H-L-arginine in human PMN and platelets in a concentration-dependent fashion. The inhibitory effect of these analogs on the uptake of 3H-L-arginine was greater in PMN than in platelets (P < .05). Both agents also modestly inhibited NO synthase activity in platelet cytosol, whereas neither had significant and specific effect on NO synthase activity in the PMN cytosol. NO synthase activity in intact PMN, but not in platelets, was insensitive to exogenous Ca++. Reverse transcription-polymerase chain reaction products showed the presence of endothelial constitutive (756 bp) and the neuronal constitutive (629 bp) NO synthase isoforms in human platelets and PMN, respectively. This was further confirmed by Southern analysis. Thus the classic inhibitors of NO synthesis primarily decrease L-arginine uptake in PMN and platelets, and significantly affect NO synthase activity only in platelets. These differences may, at least in part, be due to the presence of different NO synthase isoform in platelets and PMN.

Arginine↗

PubMed1996

Constitutive production of colony-stimulating factors by human hepatoma cell lines: possible correlation with cell differentiation.

A panel of two poorly differentiated (HA22T/VGH and SK-Hep-1) and six well-differentiated (HuH-6-cl 5, HuH-7, PLC/PRF/5, Hep G2, Hep 3B, and Tong) human hepatocellular carcinoma (HCC) cell lines were studied for the production of colony-stimulating factors (CSFs) using the granulocyte and macrophage colony formation (CFU-GM) assay, immunocytochemical staining, and Northern blotting. Medium conditioned by untreated HA22T/VGH cells contained a high level of CSFs that could stimulate the in vitro colony formation of human myeloid progenitor cells. The HA22T/VGH cell-derived CSF had an apparent molecular weight of 23 kD. Its activity could be effectively neutralized by antiserum against granulocyte-macrophage CSF (GM-CSF) but not by antibodies to other hematopoietic growth factors, including G-CSF, M-CSF, interleukin-3 (IL-3), and IL-6. Correspondingly, immunocytochemical studies using monoclonal anti-GM-CSF showed a strong positive reaction in the cytoplasm of the HA22T/VGH cells. Northern blot analysis revealed that untreated HA22T/VGH cells expressed a considerable amount of GM-CSF mRNA, confirming that GM-CSF production was constitutive. At optimal concentrations, lipopolysaccharide (LPS), IL-1beta, interferon-gamma (IFN-gamma), and tumor-promoting phorbol diester (TPA) could all stimulate HA22T/VGH cells to secrete GM-CSF. In addition to HA22T/VGH, SK-Hep-1 cells could also produce GM-CSF, although less effectively, whereas all the well-differentiated HCC cell lines tested were negative for CSF production. Morphologic, cytochemical, and immunocytochemical examinations demonstrated that both poorly differentiated CSF-producing HCC cell lines (HA22T/VGH and SK-Hep-1) were macrophage-like in morphology, possessed nonspecific esterase (NSE) activity, and expressed CD14, CD68, and HLA-DR on their surface, while all the well-differentiated HCC cell lines were epithelioid and lacked myeloid differentiation antigens. These results suggest that monocytoid features and CSF production may be differentiation markers of hepatocytes at the immature stages, amd that the HA22T/VGH and SK-Hep-1 cell lines may be valuable tools for the study of hepatic function and differentiation.

Blotting, Northern↗

PubMed1996

Platelet inhibitory effect of nitroglycerin in platelet-rich plasma: relevance of glutathione-s-transferases in plasma.

BACKGROUND: Nitroglycerin (NTG) is believed to exert its platelet inhibitory effect via its biotransformation to nitric oxide (NO). We examined the relevance of glutathione-s-transferases (GST) in plasma in the conversion of NTG to NO and the platelet inhibitory effect of NTG. METHODS AND RESULTS: Nitroglycerin (1-100 micrograms/mL) was incubated with human platelet-rich plasma (PRP) for 10-60 minutes. Nitroglycerin caused a concentration-dependent inhibition of platelet aggregation in PRP with IC50 approximately 50 micrograms/mL. NTG also enhanced nitrite levels in PRP and stimulated cyclic GMP accumulation in platelets. In contrast, when NTG was incubated with washed platelets (WP) in concentrations as high as 100 micrograms/mL, there was no inhibition of platelet aggregation, formation of nitrite, or accumulation of cGMP. However, treatment of WP suspension with authentic NO exhibited diminished platelet aggregation, suggesting that NTG delivers NO in plasma that subsequently inhibits platelet aggregation. In keeping with this concept, the aggregation inhibitory effect of NTG in PRP was blocked by oxyhemoglobin. The platelet aggregation inhibition by NTG was potentiated by propylthiouracil (600 micrograms/mL), a GST inducer, and antagonized by ketoprofen (100 micrograms/mL), a GST inhibitor. Direct measurement indeed showed significant GST activity in plasma (24 +/- 3 mU/mL). CONCLUSIONS: We suggest that NTG inhibits platelet aggregation in PRP by its biotransformation to NO in plasma. The presence of GST, and perhaps other cofactors, in plasma is relevant in the platelet inhibitory effects of NTG in PRP.

Adult↗

PubMed1996

[Progress in the study of chymase].

Chymase is a kind of serine proteinase, mainly exists in secretory granules of mast cell and extracellular interstitium. The mature enzyme is a glycoprotein comprising 226 amino acid residues, with molecular weight of 30 kD. It can be inhibited by serine proteinase inhibitors but not by angiotensin I converting enzyme inhibitors. The cDNA and genomic DNA of human chymase were cloned and sequenced. Chymase has close relations with neurogenic inflammation, extracellular matrix catabolism, control of vasoactive peptide metabolism, and so on. It plays an important role in angiotensin II formation in human heart.

Animals↗

PubMed1995

Effect of lymphocytes on the production of granulomonopoietic enhancing factor by fully mature macrophages.

The granulomonopoietic enhancing factor (GM-EF) is a novel myelopoietic regulator produced by human monocyte-derived lipid-containing macrophages (MDLMs). In the present study, we examined the effect of lymphocytes on GM-EF production by preincubation of MDLMs with various preparations of lymphocyte subpopulations in cell-mixed and in double agar layer cultures. Our results showed that a cell concentration-dependent suppression of GM-EF production was noted in cultures with mitogen-activated T cells, and mitogen-activated/resting B cells, while those containing resting T cells had no such effect. Thus, GM-EF production in the presence of 1 x 10(5)/ml activated T cells or activated/resting B cells was greatly reduced to 5% or 20%, respectively. The lymphocyte-induced suppression was evident in both cell-mixed and double layer cultures, implying that the effector cells might exert their influences via mediators. Assay for cytokine activity revealed that a high level (648.2-685.2 pg/ml) of tumor necrosis factor-alpha (TNF-alpha) was found in MDLM cultures with resting/activated B cells, and in those with activated T cells high levels of both TNF-alpha (510.5 pg/ml) and interferon-gamma (IFN-gamma) (321.3 pg/ml) could be detected, whereas in cultures with MDLMs and/or resting T cells, these cytokines were not measurable. Treatment of MDLMs with either recombinant (r) TNF-alpha or rIFN-gamma invariably resulted in a dose-dependent decrease in GM-EF production with intense suppression at doses between 400-800 U/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

B-Lymphocytes↗

PubMed1995

Overproduction of inhibitory hematopoietic cytokines by lipopolysaccharide-activated peripheral blood mononuclear cells in patients with aplastic anemia.

The aim of this study was to measure the level of cytokines produced by peripheral blood mononuclear cells (PBMNC) in patients with aplastic anemia (AA) and to determine their effect on the clonal growth of normal bone marrow (BM) cells. Twenty-one patients with AA and 11 normal controls were enrolled in this study. Medium conditioned by PBMNC of AA patients in the presence of lipopolysaccharide (LPS) was found to be suppressive to the colony growth of normal BM cells. Thus, we further determined the presence in the PBMNC-conditioned medium (CM) of both inhibitory cytokines: macrophage inflammatory protein-1 alpha (MIP-1 alpha), tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta 2 (TGF-beta 2), and interferon-gamma (IFN-gamma), and stimulatory cytokines: interleukin-3 (IL-3) and stem cell factor (SCF). Spontaneous production of MIP-1 alpha was higher in the AA patients than the normal controls (1887 +/- 174 pg/ml vs 1643 +/- 93 pg/ml), but the difference was not significant. After LPS stimulation, the production of MIP-1 alpha was markedly increased in the AA patients, and its level was significantly higher than that of the normal controls (2360 +/- 149 pg/ml vs 1517 +/- 92 pg/ml, p = 0.0022). The level of TNF alpha was also higher in the AA patients. However, IFN-gamma, TGF-beta 2, SCF, and IL-3 were not detectable in the PBMNC-CM of either AA patients or normals. The myelopoietic suppressing effect of AA-PBMNC-CM from each AA patient was significantly blocked by pretreatment with anti-TNF-alpha, resulting in a colony-forming enhancement of 174% +/- 12%. A similar effect was noted in six of 11 AA patients by pretreatment with anti-MIP-1 alpha. We conclude that TNF alpha and MIP-1 alpha can be overproduced by the PBMNC of some AA patients, which may play a role in the progression of AA.

Anemia, Aplastic↗

PubMed1995

Myocardial neutrophil infiltration, lipid peroxidation, and antioxidant activity after coronary artery thrombosis and thrombolysis.

Neutrophil accumulation and free radical release are implicated in the genesis of reperfusion injury. However, little is known about the changes in myocardial lipid peroxidation and antioxidant activity in relation to coronary artery thrombosis and thrombolysis. To investigate this issue, 18 dogs with electrically induced occlusive thrombus in the left anterior descending (LAD) coronary artery were given tissue-type plasminogen activator (TPA). Sustained reflow (lasting > 120 min) occurred in 4 dogs, reocclusion after initial thrombolysis (transient reflow, duration of reflow 5 to 25 min) occurred in 7 dogs, and no reperfusion was evident in 7 dogs. Myocardial neutrophil infiltration was determined by measuring myeloperoxidase (MPO) activity, lipid peroxidation by malondialdehyde (MDA) levels and antioxidant activity by superoxide dismutase (SOD) activity in the myocardial regions supplied by the nonischemic left circumflex (Cx) and the ischemic LAD coronary arteries. In dogs with ischemia alone (no reperfusion), MPO activity and MDA levels in the LAD-supplied myocardium were modestly higher and SOD activity modestly lower than in the corresponding Cx-supplied myocardium. In dogs with sustained reperfusion there was a marked increase in MPO and MDA and a marked reduction in SOD activity in the reperfused myocardium. The MPO and MDA values in the myocardium of dogs with transient reperfusion, although much higher than the corresponding normal myocardial values, were less marked than in the myocardium of dogs with sustained reperfusion, and the SOD activity was preserved in the transiently reperfused regions. Myocardial shortening fraction in the LAD region was worse in dogs with sustained reperfusion than in those with sustained ischemia or transient reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

A quantitative analysis of the structure of right ventricle-pulmonary artery junction for balloon pulmonary valvuloplasty in children.

Percutaneous balloon valvuloplasty (PBVP) was performed in 55 children, aged from four days to twelve years and nine months, with different severity of congenital pulmonary stenosis (PS). To evaluate its efficacy, a quantitative analysis of the structure of right ventricle-pulmonary artery junction was conducted. Significant reductions of peak systolic right ventricular pressure, ratio of peak right-to-left ventricular pressure, and pressure gradients between the right ventricle and pulmonary artery were obtained in 48 children who scored 3 or less (Group I) and 7 children who scored over 3 (Group II) (P < 0.05). After two to forty-six months (M +/- SD = 17.1 +/- 15.5 months) of follow-up study, the residual gradients between right ventricle and pulmonary artery over 36 mmHg were higher in children who scored over 3 than in those who scored 3 or less (71.4% vs 20.8%) (P < 0.01). Repeated percutaneous balloon valvuloplasty was successfully performed in 4 children, 2 each in Group I and Group II. Surgical open pulmonary valvotomy was needed in 1 in Group II because of the dysplastic pulmonary valve and the need for repair of atrial septal defect and in 2 in Group I because of the failure to complete repeated PBVP in the catheterization laboratory or the need for repair of associated atrial septal defect.

Blood Pressure↗

PubMed1995

Identification of constitutive and inducible forms of nitric oxide synthase in human platelets.

A number of cell types possess an L-arginine-nitric oxide (NO) pathway. We studied the presence of constitutive and inducible forms of NO synthase in human platelets. N omega-nitro-L-arginine, an inhibitor of NO synthase, potentiated thrombin-induced aggregation of washed human platelets, whereas L-arginine inhibited it. The direct evidence for the presence of constitutive form of NO synthase came from the observation of conversion of tritium-labeled L-arginine to tritium-labeled L-citrulline by washed platelets suspended in Ca(++)-rich but not in Ca(++)-free buffer. Incubation of washed platelets in Ca(++)-free buffer with cytokines (tumor necrosis factor-alpha and interferon-gamma) or cytokines plus lipopolysaccharide caused a marked increase in the conversion of [3H]L-arginine to [3H]L-citrulline, suggesting the presence of inducible form of NO synthase. Gel electrophoresis identified an approximately 130 kd protein band with NO synthase in the platelet cytosol, which on isolation converted [3H]L-arginine to [3H]L-citrulline. This 130 kd protein required the presence of Ca++, reduced nicotinamide adenine dinucleotide phosphate tetrahydro-L-biopterin, and flavin adenine dinucleotide for expression of NO synthase activity. Platelet sonicates demonstrated presence of nitrite, and its concentrations were lowered by preincubation of platelets with NG-nitro-L-arginine methyl ester and enhanced in cytokine-treated platelets. Reverse-transcription polymerase chain reaction demonstrated messenger RNA expression of the constitutive endothelial (but not brain) and inducible isoforms of NO synthase in platelets. These observations indicate that human platelet cytosol possesses both constitutive and inducible forms of NO synthase.

Amino Acid Oxidoreductases↗

PubMed1995

Prevalence of permanent primary congenital hypothyroidism in Taiwan.

The purpose of this study was to find the prevalence of permanent primary congenital hypothyroidism in Taiwan. From January 1988 to December 1990, there were 991,132 live births in Taiwan. Of these, 329,891 neonates were screened for primary congenital hypothyroidism. Fifty-seven cases of permanent primary congenital hypothyroidism were confirmed. Hence, the prevalence of permanent primary congenital hypothyroidism in that period in Taiwan was 1 in every 5,788 live births. There was a female preponderance with a female to male ratio of 1.7. Of 54 infants who had a thyroid scan, 36 were found to have an ectopic thyroid gland, while 11 were found to have dyshormonogenesis. Among the 57 infants, one case with a delayed rise in the serum thyrotropin level was missed on initial screening. When compared with other studies, these data suggest that the prevalence of permanent primary congenital hypothyroidism varies in different ethnic groups throughout the world.

Congenital Hypothyroidism↗

PubMed1995

Aspirin does not potentiate effect of suboptimal dose of the thrombin inhibitor inogatran during coronary thrombolysis.

OBJECTIVES: Coronary artery often reoccludes after thrombolytic therapy with recombinant tissue-plasminogen activator (rt-PA). This reocclusion is thought to be due to in situ platelet activation mediated by thromboxane (Tx) A2 and thrombin; hence, aspirin and thrombin inhibitors are often used in patients with acute myocardial infarction. This study was designed to examine the modulation of coronary artery reocclusion by a novel low molecular weight direct thrombin inhibitor inogatran with or without aspirin. METHODS: 22 dogs with electrically-induced occlusive intracoronary thrombus were treated with saline (n = 7, group A), or high dose inogatran (0.25 mg/kg bolus followed by 0.6 mg/kg per h for 2 h, n = 5, group B), or low dose inogatran (0.125 mg/kg bolus followed by 0.3 mg/kg per h for 2 h, n = 5, group C), or aspirin+low dose inogatran (n = 5, Group D). Recombinant tissue-plasminogen activator (rt-PA) was infused for 20 min starting 2 min after the bolus in all dogs. Coronary artery blood flow was monitored for 120 min after rt-PA administration. RESULTS: Reperfusion rates were similar in all groups, but the time to reperfusion was shortest in group B dogs (18 +/- 2 min vs. 32 +/- 7 min in group A dogs, P < 0.05). Reocclusion rates were 80%, 0%, 50%, and 60% in groups A, B, C, and D dogs, respectively. The restored blood flow persisted for 19 +/- 10, > 120 min, 71 +/- 30 and 54 +/- 26 min in groups A, B, C, and D dogs, respectively. At the end of rt-PA infusion, prothrombin time (PT) and activated partial thromboplastin time (APTT) were increased 1.3-2 times the control value, and the changes in PT and APTT were similar in all groups. Thrombin generation and activity, assessed by rise in thrombin-antithrombin complex and fibrinopeptide A levels, and decrease in fibrinogen levels were most marked in group A dogs, and less so in group B, C and D dogs. CONCLUSIONS: These data show that high dose of direct thrombin inhibitor inogatran shortens time to reflow and abolishes coronary artery reocclusion. However, aspirin does not potentiate the effect of suboptimal doses of inogatran.

Animals↗

PubMed1994

Reduction in human neutrophil superoxide anion generation by n-3 polyunsaturated fatty acids: role of cyclooxygenase products and endothelium-derived relaxing factor.

Dietary supplementation with n-3 polyunsaturated acids (PUFAs) results in augumented vasorelaxation and reduction in superoxide anion generation. Augmented vasorelaxation may be mediated by enhanced generation of vasodilator prostaglandins and/or endothelium-derived relaxing factor (EDRF), now thought to be nitric oxide (NO). To determine the importance of enhanced vasodilator prostaglandins or EDRF-NO in reduction in superoxide anion generation during n-3 PUFAs intake, human polymorphonuclear leukocytes (PMNs) were incubated with n-6 PUFA arachidonic acid (AA), or n-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (each 10(-7) M) for 1 hr at 37 degrees C. Parallel sets of PMNs were treated with the cyclooxygenase inhibitors indomethacin (10(-5) M), or aspirin (10(-5) M), or the EDRF-NO synthase inhibitor L-NMMA (10(-3) M) prior to incubation with PUFAs. Superoxide anion generation by PMNs was determined by measuring the superoxide dismutase (SOD) inhibitable reduction of ferricytochrome C. PMNs incubated with EPA or DHA, but not AA, demonstrated marked reduction in superoxide anion generation. This reduction in superoxide anion generation by n-3 PUFAs was abolished by treatment of PMNs with indomethacin or aspirin, but not by L-NMMA. These observations suggest that n-3 PUFAs decrease superoxide anion generation primarily by a prostaglandin-dependent pathway.

Arachidonic Acid↗

PubMed1994

Lys- and glu-plasminogen potentiate the inhibitory effect of recombinant tissue plasminogen activator on human platelet aggregation.

To examine the basis of enhanced thrombolytic effect of tissue-type plasminogen activator (t-PA) in the presence of lys- or glu-plasminogen, studies were performed with human platelet-rich plasma (PRP) and washed platelets (WP). t-PA inhibited platelet aggregation in PRP and this effect was potentiated by lys-plasminogen as well as glu-plasminogen. t-PA inhibited WP aggregation only in the presence of lys- or glu-plasminogen. The potentiation of the effects of t-PA was greater (P < 0.05) with lys-plasminogen than with glu-plasminogen. t-PA alone also decreased 14C-serotonin release from WP, and lys- as well as glu-plasminogen reversed this effect of low concentrations of t-PA in WP. Aggregation of WP was also inhibited by plasmin, a proteolytic product of plasminogen. Low, but not high concentrations, of plasmin increased the release of 14C-serotonin. Anti-aggregatory effects of plasmin and lys-plasminogen plus t-PA on platelets were attenuated by preincubation of PRP or WP suspension with aprotinin. These observations suggest enhanced inhibitory effect of t-PA on platelet function in the presence of lys-plasminogen as potential basis of salutary interaction in models of arterial thrombosis.

Drug Synergism↗

PubMed1994

Homologous and heterologous neutralization antibody responses after immunization with Japanese encephalitis vaccine among Taiwan children.

Because 21 immunized children (13%) among the 162 confirmed Japanese encephalitis (JE) cases during 1986-1991 occurred in Taiwan, we collected 320 serum samples from Taiwan children aged 15-31 and 27-44 months immediately before the 1st dose (n = 41) and 1-3 months after the 2nd dose (n = 78, 27 pairs), and immediately before (n = 58) and 1-3 months after the 3rd dose (n = 143, 44 pairs) to determine neutralization antibody (Nt Ab) against the Nakayama (N) and Beijing-1 (B) strains and two Taiwan wild type JE viruses (JEV): CC-27 and CH-1392. Our Nt results showed that (1) B vaccine stimulated a better homologous Ab response than N vaccine for Nt Ab seropositivity rate (NASR), produced a higher level of Nt titer after the primary immunization [2 doses = 100% vs. 91%, geometric mean titer (GMT) = 115 vs. 22], had a greater booster effect (3 doses: 100% vs. 95%; GMT = 320 vs 33), and showed a better capability to neutralize two local Taiwan JEV strains, particularly only after 3 doses (ave. NASR for B vs. N = 90% vs. 10%; and GMT for B vs. N = 154 vs. 1); (2) the two wild type JEV strains had different plaque morphology and antigenic variation and the CC-27 strain was not neutralized as well as the CH-1392 strain after 3 doses of vaccine (BBB or NNN or NNB); and (3) 30% of the children had lost JEV Nt Ab one year after the 2nd dose of N vaccine and natural infection with JE virus did occur among those children after immunization. In conclusion, (1) three doses of mouse-brain vaccine are the minimum requirement to protect children against the local Taiwan JEV-, (2) the best strain for a JE vaccine depends on level of Nt Ab it induced, the molecular epidemiology and antigenic variation of the JEV in each local area; and (3) future vaccine must produce better B- and T-cell memory.

Antibodies, Viral↗

PubMed1994

Inhibitory effect of high-density lipoprotein on platelet function is mediated by increase in nitric oxide synthase activity in platelets.

Although high-density lipoprotein (HDL) has been found to decrease platelet function per se, little is known regarding the mechanism of its platelet inhibitory effect. In this study, we confirmed the inhibitory effect of HDL on platelet aggregation and 14C-serotonin release in thrombin-activated washed human platelets. The inhibition of platelet function was associated with an increase in nitric oxide synthase activity, measured as the conversion of 3H-L-arginine to 3H-L-citrulline as well as nitrite release in the platelet supernates. The inhibition of platelet function by HDL was reversed by preincubation of washed platelets with an inhibitor of nitric oxide synthase, NG-nitro-L-arginine methyl ester (L-NAME), and potentiated by co-incubation with the precursor of nitric oxide, L-arginine. These observations suggest that HDL decreases platelet function by increasing nitric oxide synthase activity in human platelets.

Amino Acid Oxidoreductases↗

PubMed1994

Mutation specificity of 8-methoxypsoralen plus two doses of UVA irradiation in the hprt gene in diploid human fibroblasts.

To investigate which specific kinds of base changes are induced by psoralen adducts in the genomic DNA of diploid human fibroblasts, cells were exposed to 8-methoxypsoralen (8-MOP) at 2-12 microM followed by one dose of UVA (365 nm) irradiation (PUVA-I treatment) or two doses of UVA (PUVA-II treatment). While PUVA-I treatment produced little effect on the induction of cytotoxicity, PUVA-II treatment significantly reduced the fibroblasts' colony-forming ability and resulted in about 10-fold increases in mutation frequency at the D0 dose. Mutations in the hypoxanthine (guanine) phosphoribosyltransferase (hprt) gene of 36 independent PUVA-II mutants were characterized by direct sequencing of cDNA amplified by the polymerase chain reaction (PCR). Seventeen mutants contained single base substitutions and the other 19 mutants either lacked one or more exons, or had deleted or gained nucleotides in the exon boundaries in their cDNA. The intron--exon boundaries of 10 of these 19 putative splicing mutants were further characterized by direct sequencing of the PCR-amplified hprt gene. The results showed that nine contained single base substitutions at the consensus splicing donor and acceptor sites. One splicing mutant possessed two base substitutions located at exon 8, whereas its splicing sites were intact. Most of the base substitutions occurred at T-A base pairs (24/29). The majority of T.A changes occurred at thymine of 5'TA and 5'ATA on the non-transcribed strand. Four of the five G.C base substitutions were located at guanines of 5'TG sites adjacent 3' to AT or TA sequences. In addition, the occurrence of a specific type of mutation was highly correlated to the 5' flanking bases of TA sites. The mutagenesis of 13 of the 16 mutational events at 5'TA sites on the non-transcribed strand can be explained by the preferential incisions of the photoadducts on the transcribed strand followed by misalignment--realignment during translesion repair synthesis of the bulky lesions on the non-transcribed strand.

Base Sequence↗

PubMed1994

Monoclonal antibody to P-selectin (PB1.3) protects against myocardial reperfusion injury in the dog.

OBJECTIVE: The aim was to determine whether a monoclonal antibody directed at P-selectin (PB1.3) would diminish neutrophil accumulation and protect against decrease in coronary flow reserve and myocardial function after coronary occlusion-reperfusion. METHODS: Sixteen open chest anaesthetised dogs were randomly given PB1.3 (2 mg.kg-1) or buffer intravenously after 50 min of total left anterior descending coronary artery occlusion. Ten minutes later, the artery was reperfused for 1 h. Coronary flow reserve was measured as peak reactive hyperaemic flow and as increase in coronary flow in response to acetylcholine and glyceryl trinitrate. Myocardial contractile fraction was measured by ultrasonic crystals. Neutrophil infiltration and oxidative burst in the reperfused area were also measured. RESULTS: Coronary flow reserve and myocardial contractile function were markedly impaired in the supply region following left anterior descending coronary artery occlusion-reperfusion in the buffer treated dogs. In contrast, both coronary flow reserve and contractile fraction were preserved in PB1.3 treated dogs despite coronary occlusion-reperfusion. Myeloperoxidase, an index of neutrophil infiltration, was increased in the reperfused region in buffer treated dogs, but not in the PB1.3 treated dogs. Myocardial histology confirmed the reduction in neutrophil accumulation in the reperfused regions in PB1.3 treated dogs. Flow cytometry of the regions supplied by the left anterior descending coronary artery showed a marked decrease in neutrophil oxidative burst in the reperfused region in these dogs. CONCLUSIONS: Antibody to P-selectin (PB1.3) protects against attenuation of coronary flow reserve and myocardial contractile function after coronary occlusion-reperfusion, and decreases neutrophil deposition and activation in the reperfused region.

Animals↗