Monocytoid differentiation of freshly isolated human myeloid leukemia cells and HL-60 cells induced by the glutamine antagonist acivicin

Previously we showed that starvation of HL-60 promyelocytic leukemia cells for a single essential amino acid induced irreversible differentiation into more mature monocyte-like cells. Although not an essential amino acid, glutamine is important in the growth of normal and neoplastic cells. The glutamine analogue, alpha S,5S-alpha-amino-3- chloro-4,5-dihydro-5-isoxazoleacetic acid (acivicin) inhibits several glutamine-utilizing enzymes and therefore depletes cells of certain metabolic end products. The current study was designed to examine in vitro the effects of acivicin on growth and differentiation of several established human myeloid leukemia cell lines, including the HL-60 cell line, and of freshly isolated cells from patients with acute nonlymphocytic leukemia (ANLL). Four-day culture of HL-60 cells with acivicin at concentrations of 0.1 to 10.0 micrograms/mL (0.56 to 56 nmol/L) decreased cell growth by 33% to 88% as compared with untreated control cells. Viability of cells was greater than 92% for untreated cells and 93% to 41% for acivicin-treated cells. Cells treated with acivicin differentiated along a monocytic pathway as shown by increased H2O2 production and alpha-naphthyl butyrate esterase (NSE) content. Differentiation was time and dose dependent, and was irreversible. Changes in H2O2 production and NSE content were partially abrogated by co-culture with 10 mmol/L exogenous cytidine and guanosine but not by co-culture with other nucleosides or glutamine. At these concentrations of acivicin, differentiation was associated with expression of the N- formyl-methyl-leucyl-phenylalanine-receptor (FMLP-R) on 8% to 29% of cells as compared with 8% for control cells. Acivicin potentiated the differentiating effects of interferon-gamma, tumor necrosis factor, dihydroxyvitamin D3, dimethylsulfoxide, and retinoic acid. Culture of cells from the U937 (monoblastic), K562 (erythroleukemia), and KG-1 (myeloblastic) cell lines resulted in decreased growth and viability, but not consistently in differentiation. Acivicin decreased survival of freshly isolated ANLL cells and increased their H2O2 production and NSE content. These results suggest that the glutamine analogue acivicin may be useful as a differentiating agent with antileukemia activity in patients with ANLL.     

Circle of Willis artery diameters on MR angiography: An Australian reference database

The aim was to establish a reference range of measurements for all major Circle of Willis (COW) arteries for an Australian population of patients presenting for brain magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) that is typical of a tertiary referral hospital; and to report the prevalence and disease associations of COW variants in our patient population. All technically diagnostic MRI and MRA studies performed at our magnetic resonance (MR) centre in the calendar year 2006 were re‐read by one reader who classified the COW anatomical layout and measured diameters of all the major vessels at defined locations. A subset of 30 was independently re‐read by another reader and the interobserver measurement variability analyzed. Graphical analysis, with 95% confidence intervals (95CI), summary statistics reporting, t‐testing for unpaired and for paired means, Hauck‐Anderson (H‐A) clinical equivalence testing and logistic regression analysis for categorical variables was performed as relevant. One hundred and seventy‐one studies (of 187 eligible) formed the analysis population. All of our patients had vessels of comparable calibre regardless of MRI disease status, gender or COW variant (P > 0.05). Basilar artery (BA) diameter showed significant association with age, but other vessel diameters did not. The reference range is widely applicable, methodology straightforward and appears tolerant of interobserver variability. A number of discontinuous COW variants become more prevalent with age, perhaps from atherosclerotic occlusive disease. There was no association between COW variants, gender, aneurysm location or MRI disease status.     

RP-HPLC法测定钩吻生物碱

用RP-HPLC法分离和测定了钩吻碱甲(G),钩吻碱戊(F),胡蔓藤碱丙(D)、胡蔓藤碱乙(B)及胡蔓藤碱甲(A)。用常山碱为内标。分析柱C₁₈,甲醇—水—正丁胺(78:22:0.1 V/V)为流动相,流速1.0 ml/min,检测波长256 nm。线性范围0.02～0.12μg,相关系数r=0.9835～0.9977,回收率95.01～99.70%。本方法简便、灵敏、重现性好,为生产及临床用药提供质量控制依据。     

Homocysteine inhibits von Willebrand factor processing and secretion by preventing transport from the endoplasmic reticulum

Intracellular protein transport in endothelial cells is selectively inhibited by homocysteine, a thiol amino acid associated with both thrombosis and atherosclerosis. In a previous study, homocysteine decreased cell surface expression of the surface transmembrane glycoprotein thrombomodulin without decreasing secretion of another endothelial cell protein, plasminogen activator inhibitor-1. To define further the effects of homocysteine on protein transport, we examined the processing and secretion of the multimeric glycoprotein von Willebrand factor (vWF) in human umbilical vein endothelial cells. Incubation with 2 mmol/L homocysteine resulted in complete loss of vWF multimers and prevented asparagine-linked oligosaccharide maturation, propeptide cleavage, and secretion; these effects are consistent with impaired exit from the endoplasmic reticulum (ER). Dimerization was only partially inhibited, suggesting that homocysteine causes retention of provWF in the ER without preventing dimer formation. In pulse-chase incubations, intracellular provWF was degraded before exiting the ER in homocysteine-treated cells. Homocysteine also inhibited the processing and secretion of a carboxyl-terminal truncation mutant of human provWF expressed in rat insulinoma cells, indicating that retention in the endoplasmic reticulum can be mediated by regions of provWF apart from the carboxyl-terminal 20-Kd segment. These results suggest that retention of secretory proteins in the ER is regulated by redox mechanisms and imply that the intracellular transport of multiple endothelial cell proteins may be altered in patients with homocystinuria.