BRAIN 4-AMINOBUTYRATE

A systematic study was made of aminobutyrate transaminase (4-aminobutyrate: 2-oxoglutarate aminotransferase, I.U.B.2.6.1.19) in the developing rat brain. Assays of enzymic activity were made in whole brain of seven to twenty-one animals at each day of age from birth to day 30. The numerous analyses allowed statistical treatment and recognition of an abrupt change in the rate of synthesis of aminobutyrate transaminase, as judged by activity/g wet wt., beginning at day 12. From birth through day 11 there was a linear increase of low slope in enzymic activity, from day 12 through day 26 there was a linear increase of markedly increased slope. During the first period γ-aminobutyrate increased from 14 to 25 m-moles/kg fresh wt./hr; during the second the increase was from 25 to 113. The change of slope of linear increase in rat brain aminobutyrate transaminase began abruptly midway in the ‘critical period’ of rat brain development which extends roughly from day 10 to day 14. The onset of peak increase of rat brain succinate semialdehyde dehydrogenase (I.U.B.1.2.1.16) by contrast, occurred at day 6, heralded the ‘critical period’, and preceded by 6 days the onset of peak increase of the transaminase. These time-locked changes in rate of increase of two enzymes of a biochemical pathway uniquely functional in neural tissue may be of significance in determining the development of the nervous system in the young animal.     

EFFECT OF BRAIN CORTEX PHOSPHOLIPIDS ON ADENYLATE-CYCLASE ACTIVITY OF MOUSE BRAIN

Intravenous injection of a sonicated dispersion of bovine brain phospholipids results in a significant change in both NaF-dependent and dopamine dependent adenylate cyclase activity. High dosage of phospholipids inhibits the dopamine dependent, but not the NaF dependent, adenylate cyclase activity. The stimulation of cyclase activity is accompanied by an increased level of cAMP in mice brains. Treatment with haloperidol abolishes the increase in cAMP. Among individual phospholipids, phosphatidylserine is the most active component for inducing the activation of DA-dependent adenylate cyclase activity.     

ANOXEMIA AND BRAIN DISEASE

The author advances the concept that anoxemia, either in its general or restricted form, or both, is probably responsible for a considerable portion of “degenerative diseases,” whose etiologic delineation has not yet been traced. It is necessary, he believes, to enlarge greatly the comprehension of the disordered circulatory states to include oxygen want and thereby account for a number of conditions hitherto considered to be of unknown cause. More than this, he finds in oxygen want an explanation of the mechanism of a number of individual lesions or details of lesions otherwise not well understood. The author believes it is very likely that an understanding of cerebral anoxia in its ultimate ramifications will open still wider doors to the understanding of certain clinical syndromes the cause of which remains obscure.     

THE HYALURONIDASE OF BRAIN

Abstract— Hyaluronidase (hyaluronate glycanohydrolase, EC 3.2.1.35), with a pH optimum of 3.7, was detected in rat and bovine brain. It degraded hyaluronic acid and, at a slower rate, chondroitin sulphate to a mixture of higher oligosaccharides with N-acetylhexosamine at the reducing end. The enzyme was enriched 5- and 6-fold in a crude lysosomal fraction of rat brain or bovine cerebral cortex, and was further purified to a total enrichment of 9-fold by ammonium sulphate fractionation. The enzyme activity in grey matter was more than twice that found in white matter, and there was no significant change in enzyme activity as a function of increasing age from the neonatal to the adult rat brain. The level of hyaluronidase activity in rat brain is considerably greaterthan that required to account for the rate of catabolism of hyaluronic acid and chondroitin sulphate measured in vivo.