PMC:6194691 / 77897-79255 JSONTXT

{"project":"MyTest","denotations":[{"id":"30340614-6406409-30706216","span":{"begin":532,"end":535},"obj":"6406409"},{"id":"30340614-27799072-30706217","span":{"begin":560,"end":561},"obj":"27799072"},{"id":"30340614-1337612-30706218","span":{"begin":753,"end":756},"obj":"1337612"},{"id":"30340614-4550111-30706219","span":{"begin":982,"end":985},"obj":"4550111"},{"id":"30340614-14257556-30706220","span":{"begin":1057,"end":1060},"obj":"14257556"}],"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":"Carbon dioxide\nIt has long been known that CO2 crosses the blood–brain barrier sufficiently rapidly that its removal from the parenchyma is largely blood-flow limited (see Sect. 6.1), i.e. pCO2 in the venous effluent is closer to that within the parenchyma than to that in arterial blood. Rapid transfer between blood and brain has been confirmed directly by the observation that when CO2 labelled with the short-lived isotope 11C is added to arterial blood more than 70% is extracted from the cerebral blood flow in a single pass [294] (see Section 6.4.2 in [4] for further discussion).\nA crude underestimate of the clearance for CO2 in humans can be calculated from the rate of CO2 production (in turn calculated from glucose and oxygen consumption) [295, 296], ~ 3.3 mol day−1, and the average difference in pCO2 between ISF and plasma along the length of the microvessels which must be less than the difference between the values in the parenchyma and arterial blood, ~ 8 mmHg [297]. 8 mmHg corresponds to a difference in free concentration of 0.24 mM [298] and thus the underestimate of the clearance for a 1400 g brain becomes9 CL\u003e2200μmolmin-1/1400g/0.24μmolmL-1=6.5mLg-1min-1.\nThis is more than 5000 times larger than would be possible by perivascular clearance, which simply restates that the clearance of CO2 must be across the blood–brain barrier."}

{"project":"2_test","denotations":[{"id":"30340614-6406409-30706216","span":{"begin":532,"end":535},"obj":"6406409"},{"id":"30340614-27799072-30706217","span":{"begin":560,"end":561},"obj":"27799072"},{"id":"30340614-1337612-30706218","span":{"begin":753,"end":756},"obj":"1337612"},{"id":"30340614-4550111-30706219","span":{"begin":982,"end":985},"obj":"4550111"},{"id":"30340614-14257556-30706220","span":{"begin":1057,"end":1060},"obj":"14257556"}],"text":"Carbon dioxide\nIt has long been known that CO2 crosses the blood–brain barrier sufficiently rapidly that its removal from the parenchyma is largely blood-flow limited (see Sect. 6.1), i.e. pCO2 in the venous effluent is closer to that within the parenchyma than to that in arterial blood. Rapid transfer between blood and brain has been confirmed directly by the observation that when CO2 labelled with the short-lived isotope 11C is added to arterial blood more than 70% is extracted from the cerebral blood flow in a single pass [294] (see Section 6.4.2 in [4] for further discussion).\nA crude underestimate of the clearance for CO2 in humans can be calculated from the rate of CO2 production (in turn calculated from glucose and oxygen consumption) [295, 296], ~ 3.3 mol day−1, and the average difference in pCO2 between ISF and plasma along the length of the microvessels which must be less than the difference between the values in the parenchyma and arterial blood, ~ 8 mmHg [297]. 8 mmHg corresponds to a difference in free concentration of 0.24 mM [298] and thus the underestimate of the clearance for a 1400 g brain becomes9 CL\u003e2200μmolmin-1/1400g/0.24μmolmL-1=6.5mLg-1min-1.\nThis is more than 5000 times larger than would be possible by perivascular clearance, which simply restates that the clearance of CO2 must be across the blood–brain barrier."}