PMC:6194691 / 111019-112237 JSONTXT

{"project":"MyTest","denotations":[{"id":"30340614-4691272-30706334","span":{"begin":233,"end":236},"obj":"4691272"},{"id":"30340614-36379-30706334","span":{"begin":233,"end":236},"obj":"36379"},{"id":"30340614-27799072-30706335","span":{"begin":609,"end":610},"obj":"27799072"},{"id":"30340614-2882529-30706336","span":{"begin":612,"end":615},"obj":"2882529"},{"id":"30340614-16916905-30706337","span":{"begin":617,"end":620},"obj":"16916905"},{"id":"30340614-2882529-30706338","span":{"begin":750,"end":753},"obj":"2882529"},{"id":"30340614-2882529-30706339","span":{"begin":1003,"end":1006},"obj":"2882529"},{"id":"30340614-8094741-30706340","span":{"begin":1008,"end":1011},"obj":"8094741"},{"id":"30340614-2882529-30706341","span":{"begin":1119,"end":1122},"obj":"2882529"}],"namespaces":[{"prefix":"_base","uri":"https://www.uniprot.org/uniprot/testbase"},{"prefix":"UniProtKB","uri":"https://www.uniprot.org/uniprot/"},{"prefix":"uniprot","uri":"https://www.uniprot.org/uniprotkb/"}],"text":"Because the brain parenchyma must be in N balance and there must be net inputs of essential amino acids, there must also be a route or routes for N removal. As the brain normally doesn’t produce urea as a means of disposing of NH4+ [364–366], the two main routes for exit to be considered are efflux of NH4+ and efflux of glutamine. Fluxes of NH4+ are easily demonstrated to occur in both directions across the blood–brain barrier and are almost certainly by diffusion across the membranes of NH3 combined with transport either of H+ in the same direction or, more likely, of HCO3− in the opposite direction [4, 359, 367]. Because concentrations of NH4+ in brain, 150–300 µM, and CSF, 100–300 µM, normally exceed those in arterial plasma, 50–250 µM [359], it is likely that there is some net NH4+ efflux. However, an arterio-venous difference in NH4+ concentration and thus its net transport have only been demonstrated in the brain when plasma NH4+ concentration is raised as in hepatic insufficiency [359, 368]. There is then net NH4+ entry, rapid incorporation of the NH4+ into glutamine by reaction with glutamate [359], and efflux of the resultant glutamine. Glutamine efflux is considered further in Sect. 5.5.4."}

{"project":"2_test","denotations":[{"id":"30340614-4691272-30706334","span":{"begin":233,"end":236},"obj":"4691272"},{"id":"30340614-36379-30706334","span":{"begin":233,"end":236},"obj":"36379"},{"id":"30340614-27799072-30706335","span":{"begin":609,"end":610},"obj":"27799072"},{"id":"30340614-2882529-30706336","span":{"begin":612,"end":615},"obj":"2882529"},{"id":"30340614-16916905-30706337","span":{"begin":617,"end":620},"obj":"16916905"},{"id":"30340614-2882529-30706338","span":{"begin":750,"end":753},"obj":"2882529"},{"id":"30340614-2882529-30706339","span":{"begin":1003,"end":1006},"obj":"2882529"},{"id":"30340614-8094741-30706340","span":{"begin":1008,"end":1011},"obj":"8094741"},{"id":"30340614-2882529-30706341","span":{"begin":1119,"end":1122},"obj":"2882529"}],"text":"Because the brain parenchyma must be in N balance and there must be net inputs of essential amino acids, there must also be a route or routes for N removal. As the brain normally doesn’t produce urea as a means of disposing of NH4+ [364–366], the two main routes for exit to be considered are efflux of NH4+ and efflux of glutamine. Fluxes of NH4+ are easily demonstrated to occur in both directions across the blood–brain barrier and are almost certainly by diffusion across the membranes of NH3 combined with transport either of H+ in the same direction or, more likely, of HCO3− in the opposite direction [4, 359, 367]. Because concentrations of NH4+ in brain, 150–300 µM, and CSF, 100–300 µM, normally exceed those in arterial plasma, 50–250 µM [359], it is likely that there is some net NH4+ efflux. However, an arterio-venous difference in NH4+ concentration and thus its net transport have only been demonstrated in the brain when plasma NH4+ concentration is raised as in hepatic insufficiency [359, 368]. There is then net NH4+ entry, rapid incorporation of the NH4+ into glutamine by reaction with glutamate [359], and efflux of the resultant glutamine. Glutamine efflux is considered further in Sect. 5.5.4."}