Comparative ontogenesis of gamma-glutamyl transpeptidase in rat tissues

Summary In rats, placental gamma glutamyl transpeptidase (GGTP) specific activity declined linearly during the last third of gestation. In contrast, the kidney enzyme activity progressively increased 15-fold. In the gut, peak activity was reached at mid-lactation (age 12 days). Hepatic GGTP levels were maximal during the foetal stage. Brain GGTP was negligible at birth and attained its highest specific activity at weaning.This work was supported in part by USPHS NIH SO8 RR-09128-03.     

Kinesin-mediated axonal transport of a membrane compartment containing beta-secretase and presenilin-1 requires APP.

Proteolytic processing of amyloid precursor protein (APP) generates amyloid-beta peptide and has been implicated in the pathogenesis of Alzheimer's disease. However, the normal function of APP, whether this function is related to the proteolytic processing of APP, and where this processing takes place in neurons in vivo remain unknown. We have previously shown that the axonal transport of APP in neurons is mediated by the direct binding of APP to the kinesin light chain subunit of kinesin-I, a microtubule motor protein. Here we identify an axonal membrane compartment that contains APP, beta-secretase and presenilin-1. The fast anterograde axonal transport of this compartment is mediated by APP and kinesin-I. Proteolytic processing of APP can occur in the compartment in vitro and in vivo in axons. This proteolysis generates amyloid-beta and a carboxy-terminal fragment of APP, and liberates kinesin-I from the membrane. These results suggest that APP functions as a kinesin-I membrane receptor, mediating the axonal transport of beta-secretase and presenilin-1, and that processing of APP to amyloid-beta by secretases can occur in an axonal membrane compartment transported by kinesin-I.     

Studies on enzymicβ-hydroxylation of phenylethyl amines

Zusammenfassung Phenylethylamin, 3-Methoxy-dopamin undp-Hydroxyamphetamin werden durch Dopamin--oxidase in die entsprechende-Hydroxy-Verbindung umgewandelt.

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This work was supported by grants from the National Institutes of Health.     

The metabolism of 3-hydroxytyramine-1-C14 in brain tissue homogenates

Zusammenfassung Homogenate aus Gehirn wurden mit 3-Hydroxytyramine-1-C¹⁴ inkubiert. Als Stoffwechselprodukt wurde aus der sauren Fraktion radioaktive 3,4-Dioxyphenylessigsäure isoliert. Aus der basischen Fraktion wurden drei radioaktive Zonen papierchromatographisch isoliert. Die erste Zone konnte noch nicht identifiziert werden. Die zweite wurde als 3-Hydroxytyramin und die dritte als 3-Methoxytyramin erkannt. Die mögliche Rolle der Stoffwechselprodukte von 3-Hydroxytyramin beim Parkinson-Syndrom wird diskutiert.

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This study was supported in part by United States Public Health Service Grant M 2717.The authors are grateful toR. J. Floody, M. D. of Hoffmann-La Roche Inc., for providing us with iproniazid.     

The effect of pH on enzymatic formation and inhibition of norepinephrine synthesis

Zusammenfassung Die enzymatische Bildung des Norepinephrins und des Epinephrins wurde als Funktion des pH und der Zusammensetzung der Puffergemische untersucht. Eine maximale enzymatische Aktivität wurde bei einem pH von 5,5 beobachtet. Durch Zusatz von Phosphatpuffer wird die Aktivität gehemmt. Eine maximale Hemmung der enzymatischen Norepinephrinbildung durch DPA und Tryptamin wurde bei einem pH von 5,5 und durch Adrenalon bei einem pH von 6,5 festgestellt. Der Reaktionsmechanismus wurde auf Grund der Ergebnisse erläutert.     

An extreme distortion of the Van Allen belt arising from the 'Hallowe'en' solar storm in 2003

The Earth's radiation belts--also known as the Van Allen belts--contain high-energy electrons trapped on magnetic field lines. The centre of the outer belt is usually 20,000-25,000 km from Earth. The region between the belts is normally devoid of particles, and is accordingly favoured as a location for spacecraft operation because of the benign environment. Here we report that the outer Van Allen belt was compressed dramatically by a solar storm known as the 'Hallowe'en storm' of 2003. From 1 to 10 November, the outer belt had its centre only approximately 10,000 km from Earth's equatorial surface, and the plasmasphere was similarly displaced inwards. The region between the belts became the location of high particle radiation intensity. This remarkable deformation of the entire magnetosphere implies surprisingly powerful acceleration and loss processes deep within the magnetosphere.