Lewis B. James

Excitotoxin lesions suggest an aspartatergic projection from rat medial prefrontal cortex to ventral tegmental area

High affinity D-[3H]aspartate uptake and amino acid concentrations were examined in synaptosome-enriched preparations of microdissected rat ventral tegmental area 6-7 days following N-methyl-D-aspartate lesions confined to medial prefrontal cortex. Specific reductions were observed in the high affinity uptake of D-[3H]aspartate (59% of control, P less than 0.005) and concentrations of L-aspartate (79% of control, P less than 0.05) in the ventral tegmental area suggesting the presence of an aspartatergic projection from medial prefrontal cortex to this area.

An Excitant Amino Acid Projection from the Medial Prefrontal Cortex to the Anterior Part of Nucleus Accumbens in the Rat

Abstract: High‐affinity uptake of neurotransmitter substrates in synaptosome‐containing homogenates and tissue concentrations of amino acids were examined in subcortical areas 5–6 days after bilateral N‐methyl‐D‐aspartate lesions confined to rat medial prefrontal cortex. D‐[3H]Aspartate (32% of control) and [3H]γ‐aminobutyric acid ([3H]GABA) (60% of control) uptakes were significantly reduced in medial prefrontal cortex, whereas [3H]choline (110% of control) uptake was unchanged, suggesting the production of axon‐sparing lesions. The uptake of D‐[3H]aspartate (76% of control), but not of [3H]GABA or [3H]choline, was significantly reduced in nucleus accumbens, with no concomitant reduction in amino acid concentrations. When examined in serial coronal sections, reduced D‐[3H]aspartate uptake was confined to the most anterior 500 μm of nucleus accumbens (67% of contralateral sample). No significant reductions of uptake or amino acid concentrations were observed in caudate putamen or ventral tegmental area. These results suggest a role for glutamate or aspartate as neurotransmitters in projections from medial prefrontal cortex to anterior nucleus accumbens. Medial prefrontal cortex may represent the major excitatory cortical input to the nucleus accumbens.

An excitatory amino acid projection from rat prefrontal cortex to periaqueductal gray

High affinity D-[3H]aspartate and [3H]GABA uptake, and amino acid concentrations were examined in synaptosome-enriched preparations of rat periaqueductal gray matter 6-7 days following N-methyl-D-aspartate lesions confined to medial prefrontal cortex. Specific reductions were observed in the high affinity uptake of D-[3H]aspartate (78% of control, p less than 0.025), but not of [3H]GABA. Concentrations of glutamate, aspartate, GABA, glycine and alanine were not significantly reduced in lesioned animals. These results suggest the presence of glutamatergic and/or aspartatergic projections from medial prefrontal cortex to periaqueductal grey matter.

The F1F0-ATPase of Escherichia coli. The substitution of alanine by threonine at position 25 in the c-subunit affects function but not assembly

A mutant strain of Escherichia coli carrying a mutation in the uncE gene which codes for the c-subunit of the F1F0-ATPase has been isolated and examined. The mutant allele, designated uncE513, results in alanine at position 25 of the c-subunit being replaced by threonine. The mutant F1F0-ATPase appears to be fully assembled and is partially functional with respect to oxidative phosphorylation. The ATPase activity of membranes from the mutant strain is resistant to the inhibitor dicyclohexylcarbodiimide, but this is due to the F1-ATPase being lost from the membranes in the presence of the inhibitor. Mutant membranes from which the F1-ATPase has been removed have a greatly reduced proton permeability compared with similarly treated normal membranes. The results are discussed in relation to a previously proposed mechanism of oxidative phosphorylation.

Amico acids analysis: the humin problem

Abstract To minimize the development of coloured condensation products (humin) from proteins (expecially glycoproteins) undergoing acid hydrolysis, the inclusion of mercaptosuccinic acid or oxalic acid in the hydrolysate is proposed. The presence of either of these compounds was shown to retard the production of dark brown precipitates and the development of highly coloured hydrolysates due to tryptophan degradation. Amino acid analyses of lysozyme and fetuin were obtained after hydrolysis in the presence of mercaptosuccinic acid or oxalic acid (thioglycollic acid and mercaptopropionic acid were also tested). The clarification of coloured hydrolysates with a resin—norit mixture was also investigated.

Amino acid analysis. III: Reduction of ninhydrin with titanous chloride

Abstract In the reaction of ninhydrin with amino acids the presence of hydrindantin (reduced ninhydrin) is advantageous. This work compares the stability of a ninhydrin reagent which has been reduced with titanous chloride with that of a commercial preparation requiring addition of hydrindantin to the mixture. Aside from its greater stability, the advantages of the titanous chloride-containing preparation are: 1. no necessity to filter the reagent while being used in the analyzer; 2. the reagent is quicker and easier to prepare; 3. no waiting period for maturation of the reagent is required; and 4. the cost of the reagent is cheaper.