The interaction of arginine 106 of human prostaglandin G/H synthase-2 with inhibitors is not a universal component of inhibition mediated by nonsteroidal anti-inflammatory drugs

The three-dimensional cocrystal structures of ovine prostaglandin G/H synthase-1 (PGHS-1) with S-flurbiprofen and murine PGHS-2 with S-flurbiprofen and indomethacin reveal that the carboxylate acid groups of these nonsteroidal anti-inflammatory drugs (NSAIDs) form a salt bridge with the guanidinium group of Arg120 in PGHS-1 and Arg106 in PGHS-2. Mutagenesis studies confirmed that the Arg120 residue of PGHS-1 is critical for binding of substrate and inhibitors through ionic interactions of its guanidinium group with the carboxylate moieties of arachidonic acid and certain NSAIDs. We report here that the analogous R106E substitution in human PGHS-2 results in a catalytically active enzyme with a 30-fold higher Km value for arachidonic acid. Comparison of the inhibition of hPGHS-2(R106E) with wild-type hPGHS-2 by 11 structurally diverse selective and nonselective PGHS inhibitors revealed a 0-1000-fold decrease in inhibitory potency on the mutant enzyme. The loss of inhibitory potency of NSAIDs on hPGHS-2(R106E) could not be correlated with the presence or absence of a carboxylate functional group in the inhibitor, as was demonstrated previously for the PGHS-1(R120E) mutant, or with the selective or nonselective nature of the PGHS inhibitor. The decreases in the inhibitory potencies on hPGHS-2(R106E) by the carboxylate-containing NSAIDs flurbiprofen, indomethacin, meclofenamic acid, and diclofenac on hPGHS-2(R106E) were 965-, 48-, 5.5-, and 4.5-fold, respectively. The nonuniversal requirement for interaction of the carboxylate group of certain NSAIDs with the Arg106 residue in hPGHS-2 is supported by the observation that the methyl ester derivative of indomethacin was a more potent inhibitor than indomethacin on both hPGHS-2 and hPGHS-2(R106E). The greatest loss of potency for inhibition of hPGHS-2(R106E) was observed with the hPGHS-2-selective sulfonamide-containing inhibitors NS-398 and flosulide. The PGHS-2-selective inhibitor DuP697 and a desbromo-sulfonamide analogue of DuP697 displayed equivalent potency on hPGHS-2(R106E) and hPGHS-2. The change in inhibitory potency of NS-398 on hPGHS-2(R106E) was due to a difference in the kinetics of inhibition, with NS-398 displaying time-dependent inhibition of hPGHS-2 but time-independent inhibition of PGHS-2(R106E). The time-dependent inhibition of hPGHS-2 by DuP697 was not affected by the presence of the R106E mutation. We conclude that the Arg106 residue of hPGHS-2 is involved in binding arachidonic acid and certain NSAIDs, but interactions with Arg106 are not a universal requirement for inhibition by either carboxylate-containing NSAIDs or PGHS-2-selective inhibitors.     

Water mollusc communities and bioindication of lower salzach floodplain waters

The lower Salzach River lost its natural river dynamics as a result of channelization, which caused its bed to deepen, its groundwater table to be lowered, and its floodplains to gradually dry out. These changes of the floodplain have lead to a loss of natural biotopes with their biocoenoses. By using water mollusc communities as bioindicators these losses are detectable at a landscape level. A numerical analysis of a water mollusc survey in 1989 defined six water mollusc communities identifying six water-body types: three flowing (streams, ditches, and rivers) and three standing (young former meanders, large deep groundwater-influenced backwaters and small shallow groundwater-influenced backwaters) within the lower Salzach valley. These communities and water-body types are interpreted using results from water mollusc communities of other floodplain systems and by comparison with earlier water mollusc surveys in the lower Salzach valley. Then predictions are made on the future fate of the investigated floodplain water. Finally the investigated water bodies are evaluated for nature conservation in the face of plans to impound the lower Salzach River.     

SIMULTANEOUS WATER AND SOLUTE TRANSPORT IN SHRINKING MEDIA - PART 2

A simple compartmental model of simultaneous water and solute transport was developed on agar gel cubes, for particular situations in which high water loss is accompanied by shrinkage and flux interaction. The model provided a good fit for the different situations tested, and proved to behave adequately in a wider application field. Furthermore, it made it possible to obtain a simulation of the evolution of the solute contents in both compartments which was consistent with the previous studies.     

Extinguishing class B fires with dry chemicals: Scaling studies

In a continuing study of flame extinguishment,^1,2,3,4 we report on scaling studies for dry chemicals on larger heptane diffusion flames (0.29 m² and 2.32 m² pans). We demonstrate again that small particle sizes extinguish most effectively. Extinguishment is related to heat absorption by decomposing or vaporizing particles. We show that the limiting particle size for each dry chemical—that is, the maximum size which completely decomposes or vaporizes in the flame—is independent of flame size for the systems studied. We broaden and apply the concept of latent or maximum effectiveness^2,3 to pan fires of all sizes. Finally, we describe and characterize an aerodynamic effect in the transport of powders, where large particles with their higher momentum entrain and drag smaller, more effective particles into the flame.We also show that extinction curves, involving the ratio of real-to-latent extinction weight and the proportion of small to large particles, have predictable shapes and predictable quantitative levels for most dry chemicals. We have developed the real-to-latent concept along with scaling equations for agent mixtures and for a wide spectrum of agents and particle sizes.     

Axonal dysfunction and disability in a relapse of multiple sclerosis: longitudinal study of a patient

In a 6-year longitudinal study of a patient with relapsing progressive multiple sclerosis (MS), we used proton magnetic resonance spectroscopy to assess N-acetylaspartate (NAA) from a large central brain volume to evaluate the relationship between this marker of neuronal integrity and clinical disability. During the follow-up period, there was one major relapse and its subsequent partial remission. Changes in the brain NAA to creatine ratio correlated strongly with clinical disability (Spearman rank coefficient = -0.73, p < 0.001). We interpret this as evidence that axonal dysfunction or loss contributes to functional impairment of patients with MS. Because the NAA signal in the large volume of interest originated predominantly from white matter that appeared normal on conventional MRI, these results also suggest that some degree of axonal dysfunction may be widespread in acute, severe relapses.     

Immunologic events during the incubation period of hepatitis C virus infection: the role of antibodies to E2 glycoprotein. Multicentre Hemodialysis Cohort Study on Viral Hepatitis

BACKGROUND: The study of the sensitivity of screening assays is greatly facilitated by testing the sequential changes in seroconverting individuals. The aim of this study was to investigate the early immunologic response after hepatitis C virus (HCV) infection and to evaluate whether HCV envelope (E2) recombinant antigen would provide a significant increase in sensitivity for detection of anti-HCV. STUDY DESIGN AND METHODS: Twenty hemodialysis patients who were seroconverting to anti-HCV were included in this study. They were followed up for a mean period (+/- SD) of 10.5 +/- 3.3 months, in which 13 to 46 serum samples per case were collected. Each sample was tested for anti-HCV by second- and third-generation enzyme immunoassay (EIA-2 and EIA-3) and recombinant immunoblot assay (RIBA-3). E2 antibodies were tested by a prototype EIA in which E2 was expressed as a recombinant antigen in Chinese hamster ovary cells. RESULTS: Alanine aminotransferase elevation was observed in 18 of 20 cases. Reactivity against c100, c33c, c22, NS5, and E2 was detected in 15 (75%), 19 (95%), 15 (75%), 2 (10%), and 17 (85%) patients, respectively; c33c was the most immunogenic antigen, followed in descending order by E2, c22, c100, and NS5. E2 antibody reactivity resolved the two RIBA-3-indeterminate cases. However, there was no case in which E2 reactivity preceded all other HCV antigens. Anti-E2 was found to react in all patients of genotypes 1a, 1b, and 3a but in only 2 of 4 patients of genotype 4a. CONCLUSION: In this group of seroconverting individuals, E2 antigen was shown to be highly immunoreactive and did resolve some RIBA-3-indeterminate samples as being positive, on the basis of reactivity to multiple antigens, but it did not improve early detection of seroconversion.     

Bradykinin antagonists in human systems: correlation between receptor binding, calcium signalling in isolated cells, and functional activity in isolated ileum

The determination of the relationship between ligand affinity and bioactivity is important for the understanding of receptor function in biological systems and for drug development. Several physiological and pathophysiological functions of bradykinin (BK) are mediated via the B2 receptor. In this study, we have examined the relationship between B2 receptor (soluble and membrane-bound) binding of BK peptidic antagonists, inhibition of calcium signalling at a cellular level, and in vitro inhibition of ileum contraction. Only human systems were employed in the experiments. Good correlations between the studied activities of BK antagonists were observed for a variety of different peptidic structures. The correlation coefficients (r) were in the range of 0.905 to 0.955. In addition, we analyzed the effect of the C-terminal Arg9 removal from BK and its analogs on B2 receptor binding. The ratios of binding constants (Ki(+Arg)/Ki(-Arg)) for the Arg9 containing compounds and the corresponding des-Arg9 analogs varied from about 10 to 250,000. These ratios strongly depend on the chemical structures of the compounds. The highest ratios were observed for two natural agonist pairs, BK/des-Arg9-BK and Lys0-BK/des-Arg9-Lys0-BK.     

Characteristics of glaucoma drainage implants during dynamic and steady-state flow conditions

OBJECTIVE: This study aimed to ascertain whether the Optimed, Krupin, and Ahmed drainage devices function as valves that vary resistance depending on flow conditions to maintain pressure within a desired range. STUDY DESIGN: Experimental study. INTERVENTION: The three devices and a control cannula were submerged in fluid and perfused with balanced salt solution using a computer-driven apparatus that continuously monitors flow (Q) and pressure (P). In one set of experiments, the flow rates were maintained at 2, 5, 10, 25, or 50 microliters/min until steady-state pressures were achieved. In another set of experiments, the flow rate was increased linearly from 0 to 100 microliters/min over 15 to 20 minutes. MAIN OUTCOME MEASURES: The resistance of each implant was calculated from the first set of experiments by dividing the change in pressure (P) by the change in flow (Q) between successive perfusion rates. Flow-pressure curves were plotted from the experiments in which perfusion rate was increased linearly. RESULTS: Resistance remained relatively constant for the cannula (0.18-0.24 mmHg/microliter/min), the Krupin (0.09-0.25 mmHg/microliter/min), and the Optimed implants (0.04-0.08) throughout the tested flow rates. For the Ahmed device, conversely, resistance decreased proportionally (2.86-0.05 mmHg/microliter/min) to the increase in flow. When flow rate was increased linearly from 0 to 100 microliters/min, the Optimed and Krupin devices as well as the cannula generated a linear pressure response with a constant slope. The pressure in the two devices increased at a rate of 0.11 mmHg/microliter compared to 0.23 mmHg/microliter/min for the cannula. The flow-pressure curve for the Ahmed implant was distinct with a steep initial pressure rise and an essentially constant pressure of 12 mmHg thereafter. CONCLUSION: The Optimed and Krupin devices displayed resistance and pressure responses to various flow conditions that were similar to those of a cannula or flow resistor. In these devices, resistance remained relatively stable and pressure increased linearly with flow. The Ahmed device, conversely, functioned as a valve that closely regulated pressure within a desired range by decreasing or increasing resistance as a function of flow.