SECTION V. HISTOCHIMIE DU SYSTEME NERVEUX 



SOME MECHANISMS CONTROLING 



THE CHEMICAL ACTIVITY 

 OF THE NEURON MITOCHONDRIA 



V. V. PORTUGALOV 



Laboratory of histochemistry of the Institute 

 of Brain Research Academy of Médical Sciences of the U.S.S.R., Moscow 



The increase of the function of the nervous cell is accompanied by visible 

 changes in the mitochondria. When the enzyme activity of dehydrogenases 

 and oxidases is histochemically revealed thèse changes are manifested 

 by an increase in size of intramitochondrial deposits of coloured reaction 

 products. Such observations hâve been obtained in experiments with the 

 irritation of the nervous structures by electric currents, with epileptiform 

 attacks, arising under strong sound irritation and so on. In experiments 

 with the excitation of the brain cortex by irritating the sciatic nerves by 

 electric current, thèse mitochondrial changes were most démonstrative. 

 Such changes are réversible and are not revealed after stopping the 

 irritation. Mitochondrial altération of the excited neurons show that 

 enzymatic activity is changed in such cells, however, thèse altérations 

 cannot be regarded as characteristic for increased enzymatic activity. 

 It was found with the aid spectrophotometric methods that the activity 

 of oxidative enzymes was, in fact, not increased but decreased in condi- 

 tions of our experiments. When chemically determining the SH-groups in 

 soluble proteins and nonprotein thiol compounds of the cortex tissue it 

 had been shown that the excitation is accompanied by a sharp rise of 

 the titrable SH-groups. The incubation of sections of normal and patholo- 

 gically changed nervous tissue (ischemia, toxemia etc.) in the média of 

 varions ion and amino acid composition invariably lead to the change of 

 physical and chemical properties of the protein-lipoid frame of mitochond- 

 rial and that of the activity of localized in them enzymes. It may be 

 suggested that thiol groups play significant rôle in the permeability of 

 the mitochondria frame and in controUing the activity of intramitochond- 

 rial enzyme Systems. 



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