Evaluation of Pseudomonas aeruginosa exotoxin A and elastase as virulence factors in acute lung infection.

Acute Pseudomonas aeruginosa pneumonia was established in guinea pigs by intratracheal instillation of bacteria. Challenge strains included PAO-1, a strain known to produce exotoxin A, alkaline protease, and elastase, and several PAO-1 mutants deficient in either biologically active exotoxin A or elastase production. Survival, intrapulmonary killing of bacteria, and blood cultures were compared among the groups. Strains of P. aeruginosa deficient in active elastase production appeared to be less virulent than the parent strain and were more easily cleared from the lung. Opposite results were obtained for the exotoxin A-deficient mutants. These data suggest that elastase, but not exotoxin A, was an important virulence factor during acute pneumonia due to P. aeruginosa.     

Isolation and characterization of a Pseudomonas aeruginosa mutant producing a nontoxic, immunologically crossreactive toxin A protein.

Nitrosoguanidine mutagenesis of Pseudomonas aeruginosa strain PAO-1 yielded a mutant strain, PAO-PR1, which produced a protein that was immunologically indistinguishable from native toxin A and was nontoxic for cultured Chinese hamster ovary cells. In contrast to native toxin, the cell-associated and extracellular crossreactive material (CRM), designated "CRM protein," possessed no adenosine diphosphate-ribosylating activity. This CRM protein comigrated with native toxin A on sodium dodecyl sulfate/polyacrylamide gels, could be immunoprecipitated with antitoxin from culture supernatants of strain PAO-PR1, and gave a reaction of identity in immunological assays. Equivalent amounts of toxin A antigen and CRM protein antigen were produced in liquid culture by their respective strains as quantitated in a radioimmunoassay for toxin A. These data suggest that mutant strain PAO-PR1 possesses one or more missense mutations within the structural gene for toxin A that adversely affect enzymatic activity, thereby rendering the molecule nontoxic.     

Effects of pseudomonas toxin A, diphtheria toxin, and cholera toxin on electrical characteristics of turtle bladder.

Rapidly developing changes in the short-circuiting current (Isc), conductance (G), and potential (PD) of turtle bladders in Na-rich or Na-free media are seen after the mucosal addition, at 10 nM, of each of three toxins that contain ADP-ribosylation activity: Pseudomonas aeruginosa toxin A, diphtheria toxin, and cholera toxin. Toxin A irreversibility decreased the Isc, PD, and G of bladders in Na-rich media and the Isc and PD of bladders in Na-free media. Diphtheria or cholera toxin reversibly increased Isc and PD (not G), but only in Na-free media. The effects of toxin A in the turtle bladder, like those in other host cell systems, were eliminated by preexposure of this toxin to heat, specific antitoxin, or dithiothreitol and urea. Because exposure to this last condition increases the ADP-ribosylation activity of toxin A, it is suggested that the proenzyme is the required transport-inhibiting form of toxin A. The effects of all three toxins occurred rapidly, possibly before any of the possible intracellular ADP-ribosylation reactions are initiated. Whereas a recognition binding of toxin of toxin to receptors on the apical membrane completely accounts for the reversible effects of diphtheria or cholera toxin, this and additional toxin-membrane interactions (e.g., translocation) are needed to account for the irreversible effects of toxin A.     

Analysis of mononuclear cell infiltrate and cytokine production in murine autoimmune gastritis

BACKGROUND & AIMS: Murine autoimmune gastritis, induced by day-3 thymectomy, is characterized by cellular infiltrates and circulating autoantibodies to gastric hydrogen/potassium adenosine triphosphatase. The aim of this study was to analyze the cellular infiltrates and cytokines in autoimmune gastritis. METHODS: Stomachs and blood samples from day-3 thymectomized BALB/c mice were obtained from 2 to 12 weeks after thymectomy for analysis. RESULTS: At 4 weeks, the gastritic infiltrates were composed of macrophages and CD4+ T cells, accompanied by major histocompatibility complex class II expression on gastric epithelial cells. Mucosal B cells, scant at 4 weeks, were abundant at 8 weeks, coincident with the peaking of autoantibodies to gastric hydrogen/potassium adenosine triphosphatase. CD8+ T cells increased marginally during the 12 weeks. Mononuclear cells from diseased stomachs transferred gastritis to nu/nu recipients. At 4 weeks, interleukins 2, 3, 5, 6, and 10; interferon gamma; tumor necrosis factor alpha; and granulocyte-macrophage colony-stimulating factor were detected in gastritic mucosa, but interleukin 4 was not. CONCLUSIONS: The early lesion of autoimmune gastritis is composed of macrophages and CD4+ T cells with major histocompatibility complex class II expression in gastric epithelial cells. Autoantibody production is a late event. Our results are consistent with a lesion mediated by CD4+ T cells producing a mix of Th1- and Th2-type cytokines. (Gastroenterology 1996 Jun;110(6):1791-802)     

Work in progress: hybrid temporal-energy subtraction in digital fluoroscopy

Initial clinical results using a digital fluoroscopic implementation of the combined time-energy ("hybrid") subtraction technique are described, with emphasis on carotid and renal imaging. Where patient motion artifacts are due to soft-tissue motion alone, hybrid subtraction can remove them. Due to the need for a finite separation time between high- and low-energy pairs, however, the present implementation of the hybrid technique is not completely immune to soft-tissue motion. The intrinsic signal-to-noise ratio of hybrid imaging is less than that of conventional temporal subtraction. However, since the low-energy temporal subtraction images are included in the hybrid data set, the diagnostic quality of the examination is not compromised.     

Identification of Pseudomonas aeruginosa genes involved in virulence and anaerobic growth

Pseudomonas aeruginosa is a gram-negative, opportunistic pathogen and a significant cause of acute and chronic infections in patients with compromised host defenses. Evidence suggests that within infections P. aeruginosa encounters oxygen limitation and exists in microbial aggregates known as biofilms. However, there is little information that describes genes involved in anaerobic growth of P. aeruginosa and their association with virulence of this pathogen. To identify genes required for anaerobic growth, random transposon (Tn) mutagenesis was used to screen for mutants that demonstrated the inability to grow anaerobically using nitrate as a terminal electron acceptor. Of approximately 35,000 mutants screened, 57 mutants were found to exhibit no growth anaerobically using nitrate. Identification of the genes disrupted by the Tn revealed 24 distinct loci required for anaerobic growth on nitrate, including several genes not previously associated with anaerobic growth of P. aeruginosa. Several of these mutants were capable of growing anaerobically using nitrite and/or arginine, while five mutants were unable to grow anaerobically under any of the conditions tested. Three mutants were markedly attenuated in virulence in the lettuce model of P. aeruginosa infection. These studies have identified novel genes important for anaerobic growth and demonstrate that anaerobic metabolism influences virulence of P. aeruginosa.     

樟叶胡椒中新木脂素成分的研究

自胡椒科胡椒属植物樟叶胡椒(Piper polysyphorum C. DC)中分离到六个新木脂素(neolignans)类化合物,经光谱(UV,IR,MS,¹H-NMR,¹³C-NMR,2D-NMR,CD)分析及衍生物制备,确定Ⅱ为新化合物,即threo-△⁷-7-羟基-3,4,5,3′,5′-五甲氧基-8-O-4′-新木脂素,为一对对映体,命名为樟叶素(polysyphorin),Ⅰ,Ⅲ,Ⅳ为新的对映体,分別为(+)-virolongin,(+)-grandisin及(+)-lancifolin D.化合物Ⅴ为南藤素(wallichinine),Ⅵ为山蒟素D(hancinone D)。血小板活化因子(PAF)受体结合实验及PAF引起的血小板聚集实验证明化合物Ⅰ～Ⅴ具有明显的抑制活性。     

2-甲基-5-取代苯氧基伯氨喹的合成及其抗疟活性

为寻找高效低毒的间日疟根治药,合成了7个2-甲基-5-取代苯氧基伯氨喹Ⅱ_1～7,以与强效的4-甲基取代类似物比较,探索构效关系。初步生物评价结果表明,化合物Ⅱ_1～7对鼠疟Plasmodium berghei的抑制性治疗作用及对鼠疟P.yoelii的病因性预防作用均明显弱于其4-甲基对应物,略低于伯氨喹。     

雷酚内酯的结构修正

雷公藤别名黄藤,系卫矛科植物雷公藤(Tripterygium wilfordii Hook.f.)。其根有舒筋活血,祛风湿,消肿止痛的功效,多用于类风湿关节炎的治疗。根皮中含有生物碱、甙、萜以及其它成分,其中多种二萜内酯成分有抗肿瘤活性和免疫