Inhibition of tissue plasminogen activator activity by aspirin in vivo and its relationship to levels of tissue plasminogen activator inhibitor antigen, plasminogen activator and their complexes

The observation that aspirin inhibits the increment in tissue plasminogen activator (t-PA) activity induced by venous occlusion of the forearm became controversial with the publication of several nonconfirmatory studies. The current study was performed to confirm the original observation and determine the mechanism by which aspirin suppresses the incremental t-PA activity induced by venous occlusion. Aspirin (650 mg/d X 2) caused no change in resting levels of t-PA antigen (t-PA:Ag) or activity, plasminogen activator inhibitor 1 antigen (PAI-1:Ag), or activity or t-PA-PAI-1 complexes. In contrast, aspirin reduced the increments induced by venous occlusion as follows: t-PA:Ag by 45% (P = .001); t-PA activity (euglobulin lysis time, ELT) by 43% (P = .006); and t-PA activity (alpha 2-plasmin inhibitor-plasmin complexes, PIPC) by 41% (P = .003). The inhibition of incremental t-PA activity measured as ELT or PIPC was linearly correlated with the inhibition of incremental t-PA:Ag (respectively, r = .75, P less than .02; r = .67, P less than .05). Aspirin had no effect on the increment in PAI-1:Ag induced by venous occlusion, but similar to the effect on t- PA:Ag, aspirin induced a 51% inhibition of the increment in t-PA-PAI-1 complex formation. Aspirin did not alter the ability of alpha 2-plasmin inhibitor to bind plasmin, nor the ability of plasma to support the fibrin-catalyzed generation of plasmin by t-PA, nor the subsequent formation of PIPC. Aspirin inhibits the t-PA activity induced by venous occlusion primarily by inhibiting the release of t-PA antigen.     

Upstream promoter mutation associated with a modest elevation of fetal hemoglobin expression in human adults

In hereditary persistence of fetal hemoglobin, Hb F (alpha 2 gamma 2) is elevated after birth. Screening of sickle cell patients has revealed a family with elevated Hb F and high A gamma values. The propositus was a sickle cell patient with approximately 25% Hb F and 68.4% A gamma. He was heterozygous for the Benin (#19) and Mor beta S haplotypes. Five AS relatives with the Mor haplotype had 2.5% +/- 0.9% fetal hemoglobin and 92.8% +/- 2.8% A gamma, whereas two with the Benin haplotype had normal fetal hemoglobin (0.5%). The Mor haplotype is thus associated with the elevated Hb F in this family. The 13-kilobase (kb) Bg/II fragment containing the G gamma and A gamma genes of the Mor haplotype was cloned, and the G gamma and A gamma promoters sequenced from -383 to beyond the Cap sites. The Mor G gamma gene was normal, but the A gamma gene had a unique C----T mutation at -202. A different mutation at -202 of G gamma (C----G) was previously detected by other researchers in association with considerably higher Hb F in AS cases (15% to 25%). These data suggest either that -202 mutations affect the G gamma and A gamma promoters differently or that different nucleotide substitutions at -202 have divergent effects. Alternatively, additional unknown mutations could cause the differences in gene expression.     

Cytosolic inactivation of translocated neutrophil plasma membrane protein tyrosine phosphatase

Phosphotyrosine phosphatases (PTPases) regulate cellular metabolic activation by reversing the effects of tyrosine kinases activated earlier in intracellular signaling pathways. We coupled fluorescence- activated cell sorter analysis using anti-CD45 monoclonal antibody with direct measurements of enzyme activity in resolved subcellular fractions to define mechanisms that potentially regulate the availability and activity of CD45-PTPase on neutrophil plasma membranes. Neutrophils in freshly obtained blood as well as neutrophils freshly isolated from blood were found to possess detectable levels of plasma membrane CD45 as assessed by immunofluorescence. However, plasma membranes from these cells were essentially devoid of PTPase catalytic activity, which was largely confined to the specific granules. Granulocyte-macrophage colony-stimulating factor (GM-CSF) upregulated both the catalytic and antigenic components of CD45-PTPase on the plasma membrane of these cells. Upregulation was associated with a shift in the particulate subcellular PTPase catalytic activity from the specific granule fraction to the plasma membrane fraction. The tyrosine kinase inhibitor genistein abrogated GM-CSF-promoted upregulation of plasma membrane CD45 PTPase but did not prevent the GM-CSF-dependent decrease in specific granule catalytic activity. Anti-CD45 antibody immunoprecipitated PTPase activity from both specific granules of resting cells and plasma membranes of GM-CSF-treated cells. However, antiphosphotyrosine immunoprecipitated only activity that had translocated to the plasma membrane, suggesting a role for CD45 phosphorylation in translocation. Western analysis confirmed the tyrosine phosphorylation of CD45 in plasma membranes of GM-CSF-treated neutrophils. Preincubation of plasma membranes of GM-CSF-stimulated neutrophils with cytosol from resting cells resulted in a time- and temperature-dependent loss in membrane PTPase as a consequence of the effects of a cytosolic inactivator. Cytosol obtained from stimulated neutrophils possessed substantially reduced levels of this PTPase inactivator. We conclude that activity of the catalytic component of membrane PTPase in circulating neutrophils is regulated by a cytosolic inactivator. Upon stimulation, intact CD45 PTPase is incorporated into the plasma membrane by a process that requires tyrosine phosphorylation. As a result of inhibition of the cytosolic inactivator, the translocated PTPase expresses full activity, thereby amplifying the potential regulatory influence of the enzyme on the cells' functional response.     

Enhanced metabolism of 1-beta-D-arabinofuranosylcytosine in Down syndrome cells: a contributing factor to the superior event free survival of Down syndrome children with acute myeloid leukemia

Down syndrome (DS) children with acute myeloid leukemia (AML) have significantly higher event-free survival (EFS) rates compared with non- DS children when treated with protocols containing 1-beta-D- arabinofuranosylcytosine (ara-C). Sensitivity and metabolism of ara-C was examined in myeloblasts from DS and non-DS patients with AML, DS infants with the transient myeloproliferative disorder, and Epstein- Barr Virus (EBV) transformed lymphoblastoid cell lines with and without trisomy 21. DS myeloblasts were approximately 10-fold more sensitive to ara-C (measured by the 3-[4,5-dimethyl-thiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) colorimetric sensitivity assay), compared with non-DS myeloblasts, following exposure to ara-C for 72 hours. Mean levels of l-beta-D-arabinofuranosylcytosine 5'-triphosphate (ara-CTP) were significantly higher in DS myeloblasts compared with non-DS myeloblasts after incubation with 5 micromol/L ara-C (621.4 v 228.4 pmol/mg protein). DS cell lines also generated higher levels of ara-CTP compared with cell lines with diploid chromosome numbers (66.5 v 13.6 pmol/mg protein and 137.6 v 41.7 pmol/mg protein at 1 and 5 micromol/L ara-C, respectively). Elevated ara-CTP levels in the DS cells were accompanied by slightly lower levels of endogenous deoxycytidine triphosphate (dCTP) pools, slightly greater extent of ara-C incorporation into DNA, and increased relative numbers of double strand DNA strand breaks. There were no significant differences in the cell cycle distributions of DS and non-DS cells. These in vitro studies support our hypothesis that enhanced metabolism of ara-C in DS cells may be a contributing factor to the superior survival rate of DS children with AML and is possibly based on a gene dosage effect of genes localized to chromosome 21 including cystathionine-beta-synthase. Further study of the mechanisms (ie, alterations in dCTP pools and DNA methylation) involved may lead to improvements in the treatment of all AML patients.     

Fluorescence in situ hybridization analysis of t(3; 12)(q26; p13): a recurring chromosomal abnormality involving the TEL gene (ETV6) in myelodysplastic syndromes

We have identified a new recurrent reciprocal translocation between chromosome 3 and 12 with breakpoints at bands 3q26 and 12p13, t(3;12)(q26;p13) in the malignant cells from five patients with acute transformation of myelodysplastic syndrome or blast crisis of chronic myelogenous leukemia. t(3;12)(q26;p13) appears as a rare but nonrandom event present in various myeloid leukemia subtypes, which is frequently associated with dysplasia of megakaryocytes, multilineage involvement, short duration of any blastic phase, and a very poor prognosis. Here, we report the molecular cytogenetic analysis of the t(3;12). Fluorescence in situ hybridization results indicate that the 3q26 breakpoints are quite heterogeneous and occur 5' of MDS1, 3' of EVI1, or between MDS1 and EVI1. Our results are very similar to those observed in other 3q26 rearrangements in which breakpoints were shown to occur over considerable distances 5' and 3' of EVI1. Fluorescence in situ hybridization investigations proved that, in three myelodysplastic syndrome cases with t(3;12)(q26;p13), the 12p 13 breakpoint occurred within the TEL gene.     

Sex differences in the antithrombotic effects of aspirin

Aspirin inhibits platelet function by acetylating platelet cyclooxygenase. Recent clinical trials indicate that aspirin is a promising antithrombotic agent against both venous and arterial thrombosis, but somewhat surprisingly this protective effect appears to be limited to males. To examine the potential sex-related differences in response to aspirin, we developed an animal model for quantitating fibrin accretion into an injury-induced thrombus and used it to study the effects of aspirin on thrombus size in male and female rabbits. Platelet prostaglandin synthesis was estimated by assay of platelet malondialdehyde and was significantly decreased in both male and female rabbits following treatment with 10 mg/kg aspirin (p less than 0.001). This inhibitory effect was not different for platelets from male and female rabbits. Thrombus size was significantly decreased in aspirin- treated male rabbits when compared to controls (p less than 0.05), but this aspirin effect was not apparent in female rabbits or rabbits of either sex treated with 10 mg/kg sodium salicylate. These findings support the results of clinical trials that were obtained by retrospective subgroup analysis. The reason for the sex difference is not known, but the findings raise an important issue in relationship to this mechanism of the antithrombotic effect of aspirin.     

生物陶瓷在骨科的应用

学术背景:生物陶瓷作为植入物能满足人工骨的一般要求,而且具有亲水性、能与细胞等生物组织表现出良好的亲和性,因此具有广阔的发展前景。生物陶瓷作为生物硬组织的代用材料,可用于骨科、整形外科、牙科、口腔外科、心血管外科、眼外科、耳鼻喉科及普通外科等方面。目的:介绍生物陶瓷的分类、结构、生物学特性及其在骨科的应用,并展望生物陶瓷的发展方向。检索策略:由作者应用计算机检索Pubmed数据库和"Orthopaedics"数据库1984-01/2007-08相关文献,检索词为"Bioceramic",限定语言种类为"English";同时检索维普中文期刊数据库,万方数据库1984-01/2007-08相关文献,检索词为"生物陶瓷",限定语言种类为中文。同时手工翻阅相关书籍。纳入标准:文章内容与生物陶瓷的结构、生物学特性、临床应用有关。排除标准:较陈旧的文献和重复研究。文献评价:共收集到52篇相关文献,26篇文献符合标准,其中5篇是综述和述评类文献,其余21篇为基础研究。26篇中5篇介绍生物陶瓷的结构和生物特性,21篇介绍生物陶瓷在骨科的应用。资料综合:根据生物组织的作用机制,被用于人工关节植入体内的生物陶瓷大致可分为生物活性陶瓷、生物惰性陶瓷、可控表面活性陶瓷。生物活性陶瓷主要介绍了磷酸钙陶瓷,包括羟基磷灰石和磷酸三钙,还简单说明了生物活性玻璃和生物活性骨水泥的特性和临床应用现状。生物惰性陶瓷主要介绍了临床广泛应用的氧化铝陶瓷和氧化锆陶瓷的生物学特性和优势,并展望生物陶瓷的发展方向。结论:生物陶瓷具有良好的生物相容性,在骨科中被广泛应用,通过控制其制备过程可改变生物陶瓷的理化性能以达到不同的应用目的。     

Prevalence and risk factors for hepatitis C antibodies in volunteer blood donors in Brazil

BACKGROUND: Little is known about the prevalence, risk factors, and transmission of hepatitis C virus (HCV) in a nontransfused population, particularly in developing countries. STUDY DESIGN AND METHODS: To investigate the association between HCV seropositivity and some demographic variables, a case-control study was conducted on 138 seropositive donors among 4762 consecutive volunteer blood donors and 1101 seronegative controls in Rio de Janeiro, Brazil. Donors were initially screened by interview for male homosexuality, use of illicit drugs, tattoos, previous transfusions, venereal diseases, and jaundice. Eligible donors were then tested for HCV antibodies by enzyme-linked immunosorbent assay. A multivariate analysis was performed on age, ethnic group, gender, and prior donation. RESULTS: The overall prevalence of HCV seropositivity was 2.89 percent. An increased risk of seropositivity was demonstrated for nonwhite donors at an odds ratio of 2.11 (95% CI, 1.43-3.13), for males at 2.39 (95% CI, 1.01-5.7), and for prior donors at 1.66 (95% CI, 1.09-2.52). The risk of anti-HCV positivity increased markedly with age. Those at highest risk were the group 40 to 49 years old, with an odds ratio of 4.37 (95% CI, 2.39- 7.99) versus the group 20 to 29 years old. The group under 20 years old showed an odds ratio of 0.50 (95% CI, 0.06-3.87) compared to the group 20 to 29 years old. These findings were equally significant in a univariate analysis. CONCLUSION: Our results suggest that HCV seropositivity is strongly associated with male sex, nonwhite ethnicity, and greater age. A significant number of seropositive donors were not detected by screening interview.