Effects of aminoguanidine and antioxidant erdosteine on bleomycin-induced lung fibrosis in rats.

Reactive oxygen and nitrogen species have been implicated in the pathogenesis of bleomycin-induced lung fibrosis. The effects of aminoguanidine and erdosteine on the bleomycin-induced lung fibrosis were evaluated in rats. The animals were placed into five groups: Vehicle + vehicle, vehicle + bleomycin (2.5 U/kg), bleomycin + aminoguanidine (200 mg/kg), bleomycin + erdosteine (10 mg/kg), and bleomycin + erdosteine + aminoguanidine. Bleomycin administration resulted in prominent lung fibrosis as measured by lung hydroxyproline content and lung histology, which is completely prevented by erdosteine and aminoguanidine. A strong staining for nitro tyrosine antibody in lung tissue and increased levels of lung NO were found in bleomycin group, that were significantly reduced by aminoguanidine and erdosteine. Aminoguanidine and erdosteine significantly prevented depletion of superoxide dismutase and glutathione peroxidase and elevated myeloperoxidase activities, malondialdehyde level in lung tissue produced by bleomycin. Data presented here indicate that aminoguanidine and erdosteine prevented bleomycin-induced lung fibrosis and that nitric oxide mediated tyrosine nitration of proteins plays a significant role in the pathogenesis of bleomycin-induced lung fibrosis. Also our data suggest that antifibrotic affect of antioxidants may be due to their inhibitory effect on nitric oxide generation in this model.     

在中国应用垂直波束雷达监测褐飞虱和其他水稻害虫迁飞的可行性

近年来,可用于昆虫迁飞研究且可自动运行的垂直波束雷达(vertical-looking radar,VLR)的发展使得对迁飞性害虫的周年长期自动监测成为可能。本文提供了我们对能否将这种雷达应用于中国的褐飞虱和其他水稻害虫的监测与预测体系以改善其综合治理的可行性研究结果。以往的研究已经表明,这些害虫一般在300—2000m高度迁飞;而我们根据褐飞虱的雷达和射有效截面的计算结果表明,目前使用的3．2cm波长的VLR对褐飞虱个体目标的最大可检测高度仅约240m;虽然建造一部8．8mm波长的VLR即可覆盖褐飞虱迁飞高度的绝大部分,但其造价和维护费用均过于昂贵。为此,一个更可行的解决方案是,以3．2cm波长的VLR作为包括大多数水稻害虫在内的个体较大的迁飞性害虫的监测工具。     

Mutation of active site residues Asn67 to Ile, Gln92 to Val and Leu204 to Ser in human carbonic anhydrase II: influences on the catalytic activity and affinity for inhibitors

Site-directed mutagenesis has been used to change three amino acid residues involved in the binding of inhibitors (Asn67Ile; Gln92Val and Leu204Ser) within the active site of human carbonic anhydrase (CA, EC 4.2.1.1) II (hCA II). Residues 67, 92 and 204 were changed from hydrophobic to hydrophilic ones, and vice versa. The Asn67Ile and Leu204Ser mutants showed similar k(cat)/K(M) values compared to the wild type (wt) enzyme, whereas the Gln92Val mutant was around 30% less active as a catalyst for CO(2) hydration to bicarbonate compared to the wt protein. Affinity for sulfonamides/sulfamates was decreased in all three mutants compared to wt hCA II. The effect was stronger for the Asn67Ile mutant (the closest residue to the zinc ion), followed by the Gln92Val mutant (residue situated in the middle of the active site) and weakest for the Leu204Ser mutant, an amino acid situated far away from the catalytic metal ion, at the entrance of the cavity. This study shows that small perturbations within the active site architecture have influences on the catalytic efficiency but dramatically change affinity for inhibitors among the CA enzymes, especially when the mutated amino acid residues are nearby the catalytic metal ion.     

Functional changes in human leukemic cell line HL-60. A model for myeloid differentiation

Polar solvents induce terminal differentiation in the human promyelocytic leukemia cell line HL-60. The present studies describe the functional changes that accompany the morphologic progression from promyelocytes to bands and poly-morphonuclear leukocytes (PMN) over 9 d of culture in 1.3 percent dimethylsulfoxide (DMSO). As the HL-60 cells mature, the rate of O(2-) production increase 18-fold, with a progressive shortening of the lag time required for activation. Hexosemonophosphate shunt activity rises concomitantly. Ingestin of paraffin oil droplets opsonized with complement or Ig increases 10-fold over 9 d in DMSO. Latex ingestion per cell by each morphologic type does not change significantly, but total latex ingestion by groups of cells increases with the rise in the proportion of mature cells with greater ingestion capacities. Degranulation, as measured by release of β-glucuronidase, lysozyme, and peroxidase, reaches maximum after 3-6 d in DMSO, then declines. HL-60 cells contain no detectable lactoferrin, suggesting that their secondary granules are absent or defective. However, they kill staphylococci by day 6 in DMSO. Morphologically immature cells (days 1-3 in DMSO) are capable of O(2-) generation, hexosemonophosphate shunt activity, ingestion, degranulation, and bacterial killing. Maximal performance of each function by cells incubated in DMSO for longer periods of time is 50-100 percent that of normal PMN. DMSO- induced differentiation of HL-60 cells is a promising model for myeloid development.     

Carbonic anhydrase inhibitors. Inhibition of red blood cell ostrich (Struthio camelus) carbonic anhydrase with a series of aromatic and heterocyclic sulfonamides

The purification of red blood cell carbonic anhydrase (CA, EC 4.2.1.1) from ostrich (scCA) blood is reported, as well as an inhibition study of this enzyme with a series of aromatic and heterocylic sulfonamides. The ostrich enzyme showed a high activity, comparable to that of the human isozyme II, with kcat, of 1.2 x 10(6) s(-1) and kcat/KM of 1.8 x 10(7) M(-1)s(-1), and an inhibition profile quite different from that of the human red blood cell cytosolic isozymes hCA I and II. scCA has generally a lower affinity for sulfonamide inhibitors as compared to hCA I and II. The only sulfonamide which behaved as a very potent inhibitor of this enzyme was ethoxzolamide (KI = 3.9 nM) whereas acetazolamide and sulfanilamide behaved as weaker inhibitors (inhibition constants in the range 303-570 nM). Several other aromatic and heterocyclic sulfonamides, mostly derivatives of sulfanilamide, homosulfanilamide, 4-aminoethylbenzenesulfonamide or 5-amino-1,3,4-thiadiazole-2-sulfonamide, showed good affinities for the ostrich enzyme, with KI values in the range 25-72 nM.     

Thermodynamics of aminoglycoside binding to aminoglycoside-3'-phosphotransferase IIIa studied by isothermal titration calorimetry

The aminoglycoside-3'-phosphotransferase IIIa [APH(3')-IIIa] phosphorylates aminoglycoside antibiotics and renders them ineffective against bacteria. APH(3')-IIIa is the most promiscuous aminoglycoside phosphotransferase enzyme, and it modifies more than 10 different aminoglycoside antibiotics. A wealth of information exists about the enzyme; however, thermodynamic properties of enzyme-aminoglycoside complexes are still not known. This study describes the determination of the thermodynamic parameters of the binary enzyme-aminoglycoside and the ternary enzyme-metal-ATP-aminoglycoside complexes of structurally related aminoglycosides using isothermal titration calorimetry. Formation of the binary enzyme-aminoglycoside complexes is enthalpically driven and exhibits a strongly disfavored entropic contribution. Formation of the ternary enzyme-metal-ATP-aminoglycoside complexes yields much smaller negative DeltaH values and more favorable entropic contributions. The presence of metal-ATP generally increases the affinity of aminoglycosides to the enzyme. This is consistent with the kinetic mechanism of the enzyme in which ordered binding of substrates occurs. However, the observed DeltaH values neither correlate with kinetic parameters k(cat), K(m), and k(cat)/K(m) nor correlate with the molecular size of the substrates. Comparison of the thermodynamic properties of the complexes formed by structurally similar aminoglycosides indicated that the 2'- and the 6'-amino groups of the substrates are involved in binding to the enzyme. Thermodynamic properties of the complexes formed by aminoglycosides differing only at the 3'-hydroxyl group suggested that the absence of this group does not alter the thermodynamic parameters of the ternary APH(3')-IIIa-metal-ATP-aminoglycoside complex. Our results also indicate that protonation of ligand and protein ionizable groups is coupled to the complex formation between aminoglycosides and APH(3')-IIIa. Comparison of DeltaH values for different aminoglycoside-enzyme complexes indicates that enzyme and substrates undergo significant conformational changes in complex formation.     

Discovery of non-carbohydrate inhibitors of aminoglycoside-modifying enzymes

Chemical modification and inactivation of aminoglycosides by many different enzymes expressed in pathogenic bacteria are the main mechanisms of bacterial resistance to these antibiotics. In this work, we designed inhibitors that contain the 1,3-diamine pharmacophore shared by all aminoglycoside antibiotics that contain the 2-deoxystreptamine ring. A discovery library of molecules was prepared by attaching different side chains to both sides of the 1,3-diamine motif. Several of these diamines showed inhibitory activity toward two or three different representative aminoglycoside-modifying enzymes (AGMEs). These studies yielded the first non-carbohydrate inhibitor N-cyclohexyl-N'-(3-dimethylamino-propyl)-propane-1,3-diamine (Compound G,H) that is competitive with respect to the aminoglycoside binding to the enzyme aminoglycoside-2'-nucleotidyltransferase-Ia (ANT2'). Another diamine molecule N-[2-(3,4-dimethoxyphenyl)-ethyl]-N'-(3-dimethylamino-propyl)-propane-1,3-diamine (Compound H,I) was shown to be a competitive inhibitor of two separate enzymes (aminoglycoside-3'-phosphotransferase-IIIa (APH3') and ANT2') with respect to metal-ATP. Thermodynamic and structural-binding properties of the complexes of APH3' with substrates and inhibitor were shown to be similar to each other, as determined by isothermal titration calorimetry and NMR spectroscopy.     

Attention and the detectability of weak taste stimuli

Subjects detected weak solutions of sucrose or citric acid under conditions in which attention was directed toward one of the tastants or the other. Detection thresholds were measured using an adaptive, forced-choice procedure, with a three-down one-up rule, which computer simulations suggest should be more reliable than the popular two-down one-up rule. The thresholds were modestly but systematically lower for attended tastants than for unattended ones. Similar results have been reported in other sense modalities, including vision (greater sensitivity to stimuli presented to attended versus unattended spatial locations) and hearing (greater sensitivity to stimuli presented at attended versus unattended sound frequencies). Taken together, the findings are consistent with a general hypothesis regarding attention in sensory systems: gains or losses in detectability occur when a central attentional mechanism (or, conceivably, a preattentive mechanism) selectively and preferentially monitors signals arising from particular subsets of peripheral neural inputs.      

CONFIDENCE ELLIPSES APPLIED TO THE COMPARISON OF SENSORY PROFILES

Our experiment involved seven panels and six chocolates – five dark chocolates and one milk chocolate. The aim of the study was to compare the sensory profiles of the chocolates. A natural question to ask is “Did the panelists detect any differences among the five dark chocolates or did they systematically contrast them with the milk chocolate?” The scatter plot of the chocolates obtained by principal component analysis was useless to answer that question, because of the proximity of the points. To overcome that, we used confidence ellipses calculated using bootstrap. The originality of the study lies in the fact that we applied those ellipses to hierarchical multiple factor analysis (HMFA): among the seven panels, six were composed of trained professionals and the last one was composed of untrained students, and through that method, we managed to compare the two types of panels and balance the role of each trained panel. HMFA provides in a single scatter plot a representation of the six chocolates for each panel, the trained panels and all the panels. Confidence ellipses around each chocolate show that the combined panels – the six trained panels and also the untrained panel – differentiate the five dark chocolates. They also show how much larger the untrained panel's variability is than that of the trained panels, and how comparable are the trained panels' variability to each other.