Occurrence of gamma-aminobutyric acid-transaminase activity in nerve fibers of human thymus

The specific localization of gamma-aminobutyric acid-transaminase (GABA-iot a) in the thymus of young and elderly men was studied. Our results show a s pecific vascular localization of GABA-iota in the human thymus, and deal wi th the amount and distribution of GABA-iota and its changes with age. Sampl es of human thymus were harvested throughout of 12 autopsies in infants (n = 3), as well as young (n = 3), adult (n = 3) and elderly (n = 3) men. Hist ologic staining of the human thymus was performed with eosin-orange, while histologic staining of nerve fibers was performed with the Bodian method. H istochemical and biochemical demonstration of GABA-iota, including protein dosage, was performed by the methods of Van Gelder and Jung, respectively. Finally, quantitative analysis of images was performed. Staining with eosin -orange reveals the micro-anatomical details of the rhymic micro-environmen t. The Bodian method shows the nerve fibers and neurofibrils. Histochemical staining for GABA-iota shows an increase of this enzyme with age and a mar ked localization in the nerve fibers of the thymus in infant, young, adult, and elderly men, as well as specific vascular localization of this enzyme. These biochemical data are in accordance with the histoenzymatic results a nd confirm all of our previous observations. Finally, quantitative analysis of images performed on slices let us confirm all the mort changes induced induced by age. We can conclude that GABA is an inhibitory neurotransmitter of the human thymus, while GABA-t plays an important role in GABA (C) Amer ican Society for Histocompatibility and Immunogenetics, 1999. Published by Elsevier Science Inc.