Virulence of Aspergillus fumigatus double mutants lacking restriction and an alkaline protease in a low-dose model of invasive pulmonary aspergillosis

To investigate the pathogenicity of Aspergillus fumigatus mutants lacking putative virulence factors, we have developed a new murine model of invasive pulmonary aspergillosis based on neutropenia, the major factor predisposing patients to this infection. Mice were treated with cyclophosphamide and inoculated by the intranasal route with 5 x 10(3) conidia, a significant reduction from inoculum levels used in previous models. Evidence for the production of the extracellular alkaline protease (Alp) in lung tissue was obtained by using a fungal transformant harboring an alp::lacZ reporter gene fusion. The pathogenicities of single mutant strains lacking either Alp or the ribotoxin restrictocin and of a double mutant strain lacking both proteins were assessed in this infection model. There were no significant differences between the mutant and the wild-type strains in terms of mortality or histological-features. Inoculations with mixtures of conidia showed that the double mutant strain is slightly less virulent than the wild-type strain. We conclude that Alp and restrictocin are not important virulence determinants in pulmonary infection.     

Purification and crystallization of complexes modeling the active state of the fragile histidine triad protein

Fragile histidine triad protein (Fhit) is a diadenosine triphosphate (ApppA) hydrolase encoded at the human chromosome 3 fragile site which is frequently disrupted in tumors. Reintroduction of FHIT coding sequences to cancer cell lines with FHIT deletions suppressed the ability of these cell lines to form tumors in nude mice even when the reintroduced FHIT gene had been mutated to allow ApppA binding but not hydrolysis. Because this suggested that the tumor suppressor activity of Fhit protein depends on substrate-dependent signaling rather than ApppA catabolism, we prepared two crystalline forms of Fhit protein that are expected to model its biologically active, substrate-bound state. Wild-type and the His96Asn forms of Fhit were overexpressed in Escherichia coli, purified to homogeneity and crystallized in the presence and absence of ApppA and an ApppA analog. Single crystals obtained by vapor diffusion against ammonium sulfate diffracted X-rays to beyond 2.75 A resolution. High quality native synchrotron X-ray data were collected for an orthorhombic and a hexagonal crystal form.      

有限精度时间自动机的可达性检测

为了缓解状态空间爆炸问题,减小模型检测过程中生成的状态空间,加快模型检测速度,引入有限精度时间自动机(finite precision timed automata,简称FPTA)作为实时系统的形式模型,并提出了一种数据结构SDS(series of delay sequence)符号化表示状态空间中的状态集.FPTA只记录时钟变量的整数值及时钟变化的先后次序,从而减小生成的状态空间.在一定的时间约束下,Alur与Dill提出的时间自动机的可达性检测可简化为FPTA的可达性检测.举例描述了状态空间的生成过程和表示方法.最后,列出部分初步的实验结果,分析了SDS的特点及不足.     

Ada图形用户界面的实现策略

在UNIX环境下实现Ada的图形用户界面一直是一个比较困难的问题。X/Motif Ada Bindings是一个Ada与Motif工具箱的低级接口工具集,它可用于实现Ada的图形用户界面,本文从它的解决方案、体系结构及接口机制等几个方面对此软件包的实现进行了比较深入的研究分析,并基于此软件包和现有操作平台提供了一种高效的Ada GUI实现策略。     

Factors affecting outcome in hypoxic-ischemic encephalopathy in term infants

Forty-nine term infants were prospectively shown to have hypoxic-ischemic encephalopathy (HIE). All infants survived the neonatal period, and all but two infants (seen at 12 months) were followed up to at least 27 months of age. Factors that significantly correlated with outcome included the Sarnat encephalopathy stage and the occurrence of intractable seizures not controlled by phenobarbital sodium alone. There was no association between the one- or five-minute Apgar score, the need for early ventilation, the EEG, the occurrence of seizures, and the subsequent outcome. There was no significant difference in outcome for those infants who received dexamethasone sodium phosphate (n = 29) v those who did not receive the drug (n = 20). A review of 97 term infants with HIE from a regional perinatal program during a one-year period (1979), including 35 of the 49 infants in the present study, did show a significant increase in morbidity and mortality for transported infants.     

A new reference ionization gauge for vacuum pressure measurement in the range 10−5 to 1 Pa

A new type of reference ionization gauge is described. This gauge is similar to the triode type ionization gauge but has a smaller residual current and better high pressure performance. One version of the new gauge has a nitrogen sensitivity of 0.073 Pa^?1, which is constant to within 1% at pressures up to 0.3 Pa, and a nitrogen pressure equivalent to its residual current of 10^?6 Pa. The long term behaviour of its sensitivity was compared with Bayard-Alpert and triode type ionization gauges over several hundred operating hours. The sensitivity of the new type of gauge changed by less than 0.1% per 100 h while under similar conditions the triodes drifted at rates of up to 0.45% per 100 h and the Bayard-Alpert gauge sensitivities drifted unpredictably, sometimes changing sharply by several percent. A second version of the new gauge showed similar long term behaviour to the triode with a residual current equivalent to a pressure of potentially less than 10^?7 Pa.     

Redox control of exofacial protein thiols/disulfides by protein disulfide isomerase

Protein disulfide isomerase (PDI) facilitates proper folding and disulfide bonding of nascent proteins in the endoplasmic reticulum and is secreted by cells and associates with the cell surface. We examined the consequence of over- or underexpression of PDI in HT1080 fibrosarcoma cells for the redox state of cell-surface protein thiols/disulfides. Overexpression of PDI resulted in 3.6-4. 2-fold enhanced secretion of PDI and 1.5-1.7-fold increase in surface-bound PDI. Antisense-mediated underexpression of PDI caused 38-53% decreased secretion and 10-33% decrease in surface-bound PDI. Using 5,5'-dithio-bis(2-nitrobenzoic acid) to measure surface protein thiols, a 41-50% increase in surface thiols was observed in PDI-overexpressing cells, whereas a 29-33% decrease was observed in underexpressing cells. Surface thiol content was strongly correlated with cellular (r = 0.998) and secreted (r = 0.969) PDI levels. The pattern of exofacial protein thiols was examined by labeling with the membrane-impermeable thiol reactive compound, 3-(N-maleimidylpropionyl)biocytin. Fourteen identifiable proteins on HT1080 cells were labeled with 3-(N-maleimidylpropionyl)biocytin. The intensity of labeling of 11 proteins was increased with overexpression of PDI, whereas the intensity of labeling of 3 of the 11 proteins was clearly decreased with underexpression of PDI. These findings indicated that secreted PDI was controlling the redox state of existing exofacial protein thiols or reactive disulfide bonds.