Trace amines and Tourette's syndrome

There has been considerable interest in recent years in possible neurochemical abnormalities in Tourette's Syndrome (TS). In studies combining neuropsychological and neurochemical measurements, we have investigated the possible roles of trace amines in this disorder. Urinary levels of free -phenylethylamine (PEA) and plasma levels of its precursor amino acid phenylalanine were decreased in TS patients when compared to values in normal children. These urinary PEA levels in TS patients were inversely related to several scores from the Tourette's Syndrome Global Scale (TSGS). Further investigation of the group of subjects with low urinary PEA indicated that they also had low levels of MHPG, normetanephrine, 5-HT andm- andp-tyramine. Patients with low PEA were also compared on an extensive battery of neuropsychological measures and observed to perform significantly worse than TS patients with normal urinary PEA levels. Biochemical measurements also suggest a possible abnormality in tryptamine turnover in TS since urinary levels of indole-3-acetic acid (IAA; the acid metabolite of tryptamine) are significantly lower in TS patients than in normal controls.     

Oxidative phosphorylation by membrane vesicles from Bacillus alcalophilus

ADP and Pi-loaded membrane vesicles from t-malate-grown Bacillus alcalophilus synthesized ATP upon energization with ascorbate/N,N,N',N'-tetra-methyl-P-phenylenediamine. ATP synthesis occurred over a range of external pH from 6.0 to 11.0, under conditions in which the total protonmotive force delta-mu-H+ was as low as -30 mV. The phosphate potentials (delta Gp) were calculated to be 11 and 12 kcal/mol at pH 10.5 and 9.0, respectively, whereas the delta-mu-H+ values in vesicles at these two pH values were quite different (-40 +/- 20 mV at pH 10.5 and -125 +/- 20 mV at pH 9.0). ATP synthesis was inhibited by KCN, gramicidin, and by N,N1-dicyclohexylcarbodiimide. Inward translocation of protons, concomitant with ATP synthesis, was demonstrated using direct pH monitoring and fluorescence methods. No dependence upon the presence of Na+ or K+ was found. Thus, ATP synthesis in B. alcalophilus appears to involve a proton-translocating ATPase which functions at low delta-mu-H+.     

Evidence contrary to the protein error hypothesis for in vitro senescence.

A strain of diploid fibroblasts, obtained from the skin of a male infant, was cultured in vitro and cells were tested throughout their lifespan for the appearance of altered glucose-6-phosphate dehydrogenase (G-6-PD) detected either by thermostability studies or by immunotitration. No significant difference was found in the proportion of thermolabile enzyme in 31 young cultures (4.8 +/- 1%, S.E.), in comparison with that in 19 old cultures (4.9 +/- 1%, S.E.). Old cultures had ceased active cell division (49-60 doublings); DNA replication, measured by [3H]thymidine uptake over a period of 24 hours, was limited to less than 5% of these cells. Young cells (5-22 doublings) had a [3H]thymidine labeling index of 75-85%. Titration of G-6-PD activity in extracts of young and old cells with neutralizing antibody directes specifically against G-6-PD failed to detect an increment of enzymatically defective G-6-PD in old cells. The thermostability studies were capable of detecting altered G-6-PD in skin fibroblasts from a female heterozygous for a thermolabile mutant of G-6-PD, and in fibroblasts treated with a proline analogue, azetidine carboxylic acid. The immunotitration technique was also capable of detecting catalytically altered G-6-PD from the thermolabile mutant and G-6-PD inactivated with N-ethylameimide. These findings argue against a protein error catastrophe as the cause of in vitro clonal senescence.     

The IAP-antagonist ARTS initiates caspase activation upstream of cytochrome C and SMAC/Diablo

ARTS (Sept4_i2) is a pro-apoptotic tumor suppressor protein that functions as an antagonist of X-linked IAP (XIAP) to promote apoptosis. It is generally thought that mitochondrial outer membrane permeabilization (MOMP) occurs before activation of caspases and is required for it. Here, we show that ARTS initiates caspase activation upstream of MOMP. In living cells, ARTS is localized to the mitochondrial outer membrane. In response to apoptotic signals, ARTS translocates rapidly to the cytosol in a caspase-independent manner, where it binds XIAP and promotes caspase activation. This translocation precedes the release of cytochrome C and SMAC/Diablo, and ARTS function is required for the normal timing of MOMP. We also show that ARTS-induced caspase activation leads to cleavage of the pro-apoptotic Bcl-2 family protein Bid, known to promote MOMP. We propose that translocation of ARTS initiates a first wave of caspase activation that can promote MOMP. This leads to the subsequent release of additional mitochondrial factors, including cytochrome C and SMAC/Diablo, which then amplifies the caspase cascade and causes apoptosis.