Chapter-1 / Physiological Foundations - WHNLive Public Library

,,,;tt cola;, ofH1e 88JIJitKIJIIl " toe.4J117, -~7 I\., ,5 1\4\3 I\.z "-,pH"6 " ""-, , 10........~7, ~ sItidJ/iI....~ to-- -r-pl/-5543zheart ktpenCJ:, r- 384 450 H 435 - I- 480 - llgemino/ rlrJH1m fl5mitr'- 051 I I , • I , -, I Io 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23".,t ..Fig. 119 pH registration in the cerebral cortex of a rat under ~vere hyperglycemia ending in irrewrsible hyper-.glycemic coma. At very high blood glucose concentrations, ether anesthesia contributes to labilization and brea ­through of the blood-brain barrierhave a considerable aerobic glycolysis, whichleads in vivo in the nerve fibres to a pH of approximately6.8-7 (unexcited state) [215).The known experiences with diabetics having a .temporarily severely increased blood glucoseconcentration suggest that, for the peripheralnerves too, the glucose concentration must leveloff to a constant value largely independent ofthe blood glucose concentration. The existenceof a blood-nerve barrier (BNB) [210] whichlimits the passage of glucose can be seen experimentallyin that no nerve pains are observed insuch cases. This observation means that, dueto the high sensitivity of the nerves to overacidification[32], no significant reduction ofthe neural pH occurs.ew results of electron microscopic tissueresearch show that the structure of the B B ismainly represented either by a multi-layeredcover of the nerve fibres (myelin sheath of elarger fibres) or by an oligo-layered coat onplasma membrane of the Schwann cells. Thstructures can be clearly seen on the elec romicrograph in Fig. 120 from (81).In connection with this we should refer tooutdated formulation [32 p. 5] on the ign. ­cance of the myelin sheaths or glia cells: I .unclear whether the glia cells play a role in hmetabolism of neurons. The knowledge of thexistence of the B B should lead to neaspects in the explanation and therap 0various complaints and disease of the peripheralnervous system (action of ertain netoxins, atrophy of the m elin heath dia e .neuropathie with welling of the basal membranes,partial pare e multiple lero .neuralgia etc.).