Human immunodeficiency virus isolates from asymptomatic homosexual men and from AIDS patients have distinct biologic and genetic properties.

Human immunodeficiency virus type 1 (HIV-1) isolates from asymptomatic homosexual men and AIDS patients were compared for their in vitro biologic and genetic properties. Most of the HIV-1 isolates from asymptomatic men, but not from AIDS patients, failed to infect CD4+ H9 cells and phytohemagglutinin-stimulated peripheral blood lymphocytes. In a longitudinal study, serial HIV-1 isolates obtained from men who seroconverted to HIV-1 and later developed AIDS were able to infect H9 cells. In contrast, longitudinal isolates from men who remained asymptomatic did not infect H9 cells. HIV-1 isolates from AIDS patients in general exhibited increased production of intracellular viral DNA, RNA, and protein as compared to isolates from asymptomatic men. Cells infected with HIV-1 isolates from asymptomatic men produced very little gp120, p24, and p55 proteins as compared to those from AIDS patients. The overall restriction patterns of HindIII, Sac-1, Pst-1, EcoR1, and BamH1 were very similar between HIV-1 isolates from asymptomatic men and those from AIDS patients. However, the restriction endonuclease pattern of BglII was quite distinct for isolates from asymptomatic men as compared to AIDS patients. Preliminary studies mapped a unique BglII site in the gag region of most of the isolates from asymptomatic men, approximately 2.0 kb from the 5' end. Thus, HIV-1 isolates from asymptomatic subjects and from AIDS patients have distinct biologic and genetic properties which may be related to the various clinical outcomes of HIV-1 infection.     

成纤维细胞的力学生物学(下)

一、肌腱内成纤维细胞的力学生物学反应 肌腱内的成纤维细胞可以合成胶原蛋白及其他一些大分子。成纤维细胞可以将这些分子排列成组织性较高的单元，并使纤维的方向与张力方向平行。无论是培养的肌腱还是独立的成纤维细胞都可以对力做出相应的反应。     

Mechanism-based chemopreventive strategies against etoposide-induced acute myeloid leukemia: free radical/antioxidant approach.

Etoposide (VP-16) is extensively used to treat cancer, yet its efficacy is calamitously associated with an increased risk of secondary acute myelogenous leukemia. The mechanisms for the extremely high susceptibility of myeloid stem cells to the leukemogenic effects of etoposide have not been elucidated. We propose a mechanism to account for the etoposide-induced secondary acute myelogenous leukemia and nutritional strategies to prevent this complication of etoposide therapy. We hypothesize that etoposide phenoxyl radicals (etoposide-O(.)) formed from etoposide by myeloperoxidase are responsible for its genotoxic effects in bone marrow progenitor cells, which contain constitutively high myeloperoxidase activity. Here, we used purified human myeloperoxidase, as well as human leukemia HL60 cells with high myeloperoxidase activity and provide evidence of the following. 1) Etoposide undergoes one-electron oxidation to etoposide-O(.) catalyzed by both purified myeloperoxidase and myeloperoxidase activity in HL60 cells; formation of etoposide-O(.)radicals is completely blocked by myeloperoxidase inhibitors, cyanide and azide. 2) Intracellular reductants, GSH and protein sulfhydryls (but not phospholipids), are involved in myeloperoxidase-catalyzed etoposide redox-cycling that oxidizes endogenous thiols; pretreatment of HL60 cells with a maleimide thiol reagent, ThioGlo1, prevents redox-cycling of etoposide-O(.) radicals and permits their direct electron paramagnetic resonance detection in cell homogenates. VP-16 redox-cycling by purified myeloperoxidase (in the presence of GSH) or by myeloperoxidase activity in HL60 cells is accompanied by generation of thiyl radicals, GS(.), determined by HPLC assay of 5, 5-dimethyl-1-pyrroline glytathionyl N-oxide glytathionyl nitrone adducts. 3) Ascorbate directly reduces etoposide-O(.), thus competitively inhibiting etoposide-O(.)-induced thiol oxidation. Ascorbate also diminishes etoposide-induced topo II-DNA complex formation in myeloperoxidase-rich HL60 cells (but not in HL60 cells with myeloperoxidase activity depleted by pretreatment with succinyl acetone). 4) A vitamin E homolog, 2,2,5,7, 8-pentamethyl-6-hydroxychromane, a hindered phenolic compound whose phenoxyl radicals do not oxidize endogenous thiols, effectively competes with etoposide as a substrate for myeloperoxidase, thus preventing etoposide-O(.)-induced redox-cycling. We conclude that nutritional antioxidant strategies can be targeted at minimizing etoposide conversion to etoposide-O(.), thus minimizing the genotoxic effects of the radicals in bone marrow myelogenous progenitor cells, i.e., chemoprevention of etoposide-induced acute myelogenous leukemia.     

成纤维细胞的力学生物学(上)

由于重力、血液的流动及运动的原因，人体会不断受到力的作用。众所周知，结缔组织是承受与传导力的器官，其内的细胞可以通过多种机制将力转化为生物化学信号，但是有些机制尚未完全了解。结缔组织的成纤维细胞就是对力产生反应的细胞，在力的作用下，会通过改变自身细胞外基质（extracellular matrix，ECM）的基因及蛋白质表达的方法维持组织的结构和功能（如创伤修复）。当结缔组织承受到较大的压力时，可以使结缔组织保持正常的功能和组织的动态平衡。结缔组织的修复及维持主要由间充质细胞或成纤维细胞来完成。力可以调节细胞的多种功能，如细胞增殖、基因表达及蛋白质分泌。     

The cardioprotective and DNA topoisomerase II inhibitory agent dexrazoxane (ICRF-187) antagonizes camptothecin-mediated growth inhibition of Chinese hamster ovary cells by inhibition of DNA synthesis

Dexrazoxane (ICRF-187), which is clinically used to reduce doxorubicin-induced cardiotoxicity, has cell growth inhibitory properties through its ability to inhibit the catalytic activity of DNA topoisomerase II. A study was undertaken to investigate whether preincubating Chinese hamster ovary cells (CHO) with dexrazoxane prior to camptothecin treatment resulted in potentiation. Camptothecin is a DNA topoisomerase I poison. It was found that pretreating CHO cells with concentrations of dexrazoxane sufficient to strongly inhibit topoisomerase II for periods from 18 to 96 h resulted in significant antagonism of camptothecin-mediated growth inhibition. Lower concentrations that were sufficient to cause partial inhibition of topoisomerase II and partial dexrazoxane-mediated cell growth inhibition had little effect on camptothecin-mediated growth inhibition. Neither topoisomerase I protein levels nor camptothecin-induced topoisomerase I-DNA covalent complexes were affected by dexrazoxane concentrations that were sufficient to cause antagonism of camptothecin-induced growth inhibition. However, under these experimental conditions, dexrazoxane caused a decrease in DNA synthesis. Therefore, results presented here confirm the importance of the DNA synthesis-dependent replication fork interaction with topoisomerase I-DNA covalent complexes for the expression of camptothecin activity. It is concluded that dexrazoxane and camptothecin analogs should be used with caution in combination chemotherapy.     

Role of Endothelin-1 in Human Aneurysmal Subarachnoid Hemorrhage: Associations with Vasospasm and Delayed Cerebral Ischemia

Background

Endothelin-1 (ET-1) is a potent vasoconstrictor implicated in the pathogenesis of vasospasm and delayed cerebral ischemia (DCI) in aneurysmal subarachnoid hemorrhage (aSAH) patients. The aim of this study was to investigate the relationship between cerebrospinal fluid (CSF) ET-1 levels and angiographic vasospasm and DCI.

Methods

Patients with aSAH were consented (n?=?106). Cerebral vasospasm was determined by angiography. DCI was determined by transcranial Doppler (TCD) results and/or angiogram results with corresponding clinical deterioration. CSF ET-1 levels over 14?days after the initial insult was quantified by ELISA. ET-1 analysis included a group-based trajectory analysis and ET-1 exposure rate during 24, 48, and 72?h prior to, as well as 72?h post angiography, or clinical deterioration.

Results

Trajectory analysis revealed two distinct groups of subjects with 56% of patients in the low ET-1 trajectory group (mean at day 1?=?0.31?pg/ml; SE?=?0.04; mean at day 14?=?0.41?pg/ml; SE?=?0.15) and 44% of patients in the high ET-1 trajectory group (mean at day 1?=?0.65?pg/ml; SE?=?0.08; mean at day 14?=?0.61?pg/ml; SE?=?0.06). Furthermore, we observed that ET-1 exposure rate 72?h before angiography and clinical spasm was a significant predictor of both angiographic vasospasm and DCI, whereas, ET-1 exposure after angiography and clinical spasm was not associated with either angiographic vasospasm or DCI.

Conclusion

Based on these results we conclude that ET-1 concentrations are elevated in a sub-group of patients and that the acute (72?h prior to angiography and clinical neurological deterioration), but not chronic, elevations in CSF ET-1 concentrations are indicative of the pathogenic alterations of vasospasm and DCI in aSAH patients.     

Use of cryopreserved normal peripheral blood lymphocytes for isolation of human immunodeficiency virus from seropositive men.

The possibility was investigated of using frozen stocks of phytohemagglutinin (PHA)-stimulated normal human peripheral blood lymphocytes (PBL) in cocultivation with human immunodeficiency virus (HIV)-infected lymphocytes for the isolation of HIV. Fresh and cryopreserved PBL from eight healthy volunteers were compared for their susceptibility to HIV infection in vitro. Fresh lymphocytes, as well as lymphocytes that were stimulated with PHA before or after cryopreservation, displayed comparable susceptibilities to HIV infection in vitro. In addition, HIV was recovered in all cases when lymphocytes stimulated with PHA before or after cryopreservation were cocultured in parallel with PBL from 15 patients with acquired immune deficiency syndrome. However, the cryopreserved PBL were less efficient in isolating HIV from asymptomatic men.