Hemoglobin enhances the production of tissue factor by endothelial cells in response to bacterial endotoxin

Human endothelial cells respond to bacterial endotoxin (lipopolysaccharide [LPS]) with changes that transform the endothelium into a surface with prominent procoagulant properties. Production of tissue factor (TF) in response to LPS is a major alteration that favors coagulation. Biologic activities of LPS have previously been shown to be enhanced by the presence of hemoglobin. Therefore, the ability of human hemoglobin (Hb) to modulate TF production by cultured human umbilical vein endothelial cells (HUVEC) was investigated. Cell-free Hb (10 mg/mL), either purified native (HbAo) or chemically cross-linked (alpha alpha Hb), was incubated with LPS (0.1 microgram/mL), and the mixtures then were added to HUVEC in culture. TF activity was quantified with a clotting assay and TF protein was measured with an enzyme-linked immunosorbent assay. Hb preparations greatly enhanced the production of TF activity (11- to 25-fold greater than TF produced by HUVEC alone) compared with minimal TF activity generated by LPS alone (only twofold greater than HUVEC alone). The enhancement of LPS-induced TF activity was Hb concentration-dependent over a range of 1 to 100 mg/mL. Cross-linked alpha alpha Hb also greatly enhanced the production of TF protein compared with TF protein generated by LPS alone (12-fold greater v 3.5-fold greater than HUVEC alone, respectively). The enhancement of LPS-induced TF protein was Hb concentration-dependent over a range of 0.1 to 2 mg/mL. Enhancement of TF activity by Hb required new protein synthesis. These results show that human Hb can augment the ability of LPS to induce endothelial cell TF and suggest that hemolysis associated with disseminated intravascular coagulation during sepsis may further stimulate coagulation. In addition, these results suggest a potential mechanism for generalized thrombosis in animals that has been associated with the infusion of cell-free Hb for resuscitation.     

In vitro tumor cell cytolysis mediated by peptide defensins of human and rabbit granulocytes

We examined the activity of defensins, cysteine-rich cationic peptides that are abundant in the cytoplasmic granules of human and rabbit granulocytes, against various tumor targets. The three human defensins, HNP-1, HNP-2, and HNP-3, lysed human and murine targets in chromium release and dye exclusion assays. Defensin-mediated tumor cell lysis was concentration-dependent, inhibited by serum, and dependent on temperature-sensitive events. Lysis was first detected by three hours of incubation and it reached a plateau between eight and 14 hours. In vitro exposure of murine teratocarcinoma cells to HNP 1-3 abrogated their oncogenicity in vivo. Nonmalignant target cells were also susceptible to defensin-mediated lysis. Four rabbit granulocyte defensins exerted marked (NP-1, NP-2) or moderate (NP-3a, NP-3b) cytotoxic activity, whereas defensin NP-5 was not cytotoxic. When tumor cells were incubated with human defensins in combination with hydrogen peroxide, synergistic cytotoxicity was detected. As defensins are released from granulocytes by various stimuli, their release could contribute to extracellular cytotoxicity which is independent of reactive oxygen intermediates.     

An antifibrin monoclonal antibody useful in immunoscintigraphic detection of thrombi

Balb/c mice were immunized with human plasmin-generated fibrinogen degradation product Y. Spleen cells were fused with P3X63-Ag8.653 myeloma cells. A clone (Y22) was found that produces monoclonal antibodies (MoAbs) with a strong reactivity with human fibrin and only a weak reactivity with fibrinogen in an enzyme immunoassay (EIA). Y22 also reacts with fibrin of rabbits, rats, sheep, and dogs. The antibodies are of the IgG1 kappa-type and appear to be directed against a conformation-dependent epitope in the D-domain of fibrin. Experiments with 99mTc-labeled Y22 in vitro show that Y22 binds rapidly to forming clots. 99mTc-Y22 also binds to preformed plasma clots in a plasma milieu, even in the presence of high concentrations of heparin. Clot localization experiments in rabbits and rats confirm the high fibrin specificity and the potential of 99mTc-Y22 for thrombus imaging in vivo.     

Transforming growth factor beta inhibits endomitosis in the Dami human megakaryocytic cell line

Megakaryocyte development is a carefully controlled process that is at least partially regulated by cytokines. Previous investigations of megakaryocyte development have focused primarily on defining growth factors that induce or enhance differentiation. In this study we demonstrate that a specific cytokine, transforming growth factor beta 1 (TGF beta 1), inhibits the phorbol myristate acetate (PMA)-induced differentiation of the Dami human megakaryocytic cell line. The addition of purified platelet TGF beta 1 inhibits PMA-induced endomitosis in a dose-dependent manner. Inhibition of endomitosis occurs with as little as 0.4 pmol/L TGF beta 1, is half-maximal at 6.4 pmol/L, and is maximal between 40 and 200 pmol/L TGF beta 1. Inhibition does not require other growth factors or nonmegakaryocytic cells. Removal of TGF beta 1 from the cultures decreases inhibition, suggesting that the continuous presence of TGF beta 1 is required and that its effects are reversible. This effect occurs even though the Dami cells constitutively express TGF beta 1 messenger RNA (mRNA) and the TGF beta 1 mRNA levels are increased by PMA. TGF beta 1 also has been shown to inhibit endomitosis during short-term culture of primary human megakaryocytes. These results suggest a model in which negative as well as positive regulatory factors modulate a critical stage of megakaryocyte development.     

儿科医学论文英文摘要的撰写(八)

3．结果 在这一段介绍最主要的研究结果。时态用一般过去时。一般不主张用图表，可以介绍一些关键的数据。国内外不少杂志都主张结果中要包括一些统计学处理的结果（具有可信区间的有关数据或P值等）。     

The Mitochondrial Genome And Human Mitochondrial Diseases

To date, more than 100 point mutations and several hundreds of structural rearrangements of mitochondrial DNA (mtDNA) are known too be connected with characteristic neuromuscular and other mitochondrial syndromes varying from those causing death at the neonatal stage to diseases with late ages of onset. The immediate cause of mitochondrial disorders is a defective oxidative phosphorylation. Wide phenotypic variation and the heteroplasmy phenomenon, which some authors include in mutation load, are characteristic of human mitochondrial diseases. As the numbers of cases identified and pedigrees described increase, data on the genotype-phenotype interaction and the structure and frequency of pathogenic and conditionally pathogenic mtDNA mutations in human populations are rapidly accumulated. The data on the genetics and epidemiology of mitochondrial diseases are not only important for differential diagnosis and genetic counseling. Since both neutral and mildly pathogenic mutations of mtDNA are progressively accumulated in maternal phyletic lines, molecular analysis of these mutations permits not only reconstruction of the genealogical tree of modern humans, but also estimation of the role that these mutations play in natural selection.     

Alcohol and coronary heart disease: the roles of HDL-cholesterol and smoking

Objectives. To study the role of HDL-cholesterol (HDLc) in the causal pathway mediating the effect of alcohol on coronary heart disease (CHD).
Design. Cox proportional hazard models were used to compare the relative CHD risks in various HDLc–smoking categories.
Setting. A prospective, multicentre, placebo-controlled, double-blind CHD primary prevention trial with gemfibrozil in primary (occupational) health care units, the Helsinki Heart Study.
Subjects. Dyslipidaemic middle-aged men with available alcohol consumption data (1924 of 2035) in the placebo arm of the 5-year study.
Main outcome measures. Seventy-seven (of 84) cases of nonfatal myocardial infarction or cardiac death.
Results. A U-shaped association was detected between alcohol consumption and CHD. The protection was found both in subjects with low (mean 0.94 mmol L⁻¹) and normal (mean 1.25 mmol L⁻¹) HDLc with corresponding reductions of 23% and 36% in relative risks. In contrast to previous data, alcohol offered virtually no protection against CHD in non-smokers. In subjects consuming more than 800 g pure ethanol annually, the CHD incidence was 6/1000 in subjects with more than three weekly drinking occasions, compared to 11/1000 in 'weekend' drinkers.
Conclusions. Our results confirm the protective effect of alcohol against CHD. However, in contrast to previous data the effect in our population is restricted to smokers and the role of HDLc in mediating the effect is less central than suggested previously.