L-Arginine-derived nitric oxide (NO) acts as an inter- and intra-cellular signal molecule in many mammalian tissues including brain, where it is formed by a flavin-containing Ca2+/calmodulin-requiring NO synthase with NADPH, tetrahydrobiopterin (H4biopterin) and molecular oxygen as cofactors. We found that purified brain NO synthase acted as a Ca2+/calmodulin-dependent NADPH:oxygen oxidoreductase, catalysing the formation of hydrogen peroxide at suboptimal concentrations of L-arginine or H4biopterin, which inhibited the hydrogen peroxide formation with half-maximal effects at 11 microM and 0.3 microM respectively. Half-maximal rates of L-citrulline formation were observed at closely similar concentrations of these compounds, indicating that the NO synthase-catalysed oxygen activation was coupled to the synthesis of L-citrulline and NO in the presence of L-arginine and H4biopterin. N omega-Nitro-L-arginine, its methyl ester and N omega-monomethyl-L-arginine inhibited the synthesis of L-citrulline from L-arginine (100 microM) with half-maximal effects at 0.74 microM, 2.8 microM and 15 microM respectively. The N omega-nitro compounds also blocked the substrate-independent generation of hydrogen peroxide, whereas N omega-monomethyl-L-arginine did not affect this reaction. According to these results, activation of brain NO synthase by Ca2+ at subphysiological levels of intracellular L-arginine or H4biopterin may result in the formation of reactive oxygen species instead of NO, and N omega-nitro-substituted L-arginine analogues represent useful tools to effectively block NO synthase-catalysed oxygen activation.

Brain nitric oxide synthase is a Ca2~/ca1modulin-re~lat~ enzyme which converts L-arginine into NO. Enzymatic activity of this enzyme essentially depends on NADPH and is stimulated by tetrahydrobiopterin (H,biopterin). We found that purified NO synthasc contains enzyme-bound H.,biopterin, explaining the enzymatic activity observed in the absence of added cofactor. Together with the finding that H.,biopterin was effective at substoichiomctrical concentrations, these results indicate that NO synthase essentially depends on H_,biopterin as a cofactor which is recycled during enzymatic NO formation. We found that the purified enzyme also contains FAD, FMN and non-hcme iron in equimolar amounts and exhibits striking activities. including a Ca2"/calmodulin-depcndent NADPH oxidase activity, leading to the formation of hydrogen peroxide at suboptimal concentrations of L-arginine or H_,biopterin.

L-Arginine-derived nitric oxide acts as an inter-and intracellular signal molecule with cytosohc guanylyl cyclase as the effector system. Two NO synthase isoenzymes are postulated: a cytokine-inducible enzyme in macrophages and a constitutive, Ca*+ -regulated enzyme in various other cells. An NO synthase was isolated from porcine cerebellum by ammonium sulfate precipitation and affinity chromatography on 2',5'-ADP-Sepharose. The enzyme was identified as an NO synthase with a specific NO-chemiluminescence method and with purified cytosohc guanylyl cyclase as an NO-sensitive detection system. The purified NO synthase was, besides Ca*'/calmodulin and NADPH, largely dependent on tetrahydrobiopterin as a cofactor.

BackgroundTelerehabilitation can contribute to the maintenance of successful rehabilitation regardless of location and time. The aim of this study was to investigate a specific three-month interactive telerehabilitation routine regarding its effectiveness in assisting patients with physical functionality and with returning to work compared to typical aftercare.ObjectiveThe aim of the study was to investigate a specific three-month interactive telerehabilitation with regard to effectiveness in functioning and return to work compared to usual aftercare.MethodsFrom August 2016 to December 2017, 111 patients (mean 54.9 years old; SD 6.8; 54.3% female) with hip or knee replacement were enrolled in the randomized controlled trial. At discharge from inpatient rehabilitation and after three months, their distance in the 6-minute walk test was assessed as the primary endpoint. Other functional parameters, including health related quality of life, pain, and time to return to work, were secondary endpoints.ResultsPatients in the intervention group performed telerehabilitation for an average of 55.0 minutes (SD 9.2) per week. Adherence was high, at over 75%, until the 7th week of the three-month intervention phase. Almost all the patients and therapists used the communication options. Both the intervention group (average difference 88.3 m; SD 57.7; P=.95) and the control group (average difference 79.6 m; SD 48.7; P=.95) increased their distance in the 6-minute-walk-test. Improvements in other functional parameters, as well as in quality of life and pain, were achieved in both groups. The higher proportion of working patients in the intervention group (64.6%; P=.01) versus the control group (46.2%) is of note.ConclusionsThe effect of the investigated telerehabilitation therapy in patients following knee or hip replacement was equivalent to the usual aftercare in terms of functional testing, quality of life, and pain. Since a significantly higher return-to-work rate could be achieved, this therapy might be a promising supplement to established aftercare.Trial RegistrationGerman Clinical Trials Register DRKS00010009; https://www.drks.de/drks_web/navigate.do? navigationId=trial.HTML&TRIAL_ID=DRKS00010009

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