Free amino acids in brain, liver, and skeletal muscle tissue of voles infected with Trypanosoma brucei gambiense.

The concentrations of several acidic and neutral amino acids of brain, liver, and skeletal muscle were determined in field voles, Microtus montanus, and compared to values obtained from voles harboring a chronic infection of Trypanosoma brucei gambiense. All of the amino acids examined were found at comparable levels in brain tissue from both groups of animals with the exception of tyrosine, which was reduced by approximately 45% in the infected voles. Similarly, the only difference noted in liver tissue was 32% decrease of free tyrosine in the infected animals. With respect to muscle tissue, in addition to a 45% reduction of free tyrosine in the infected voles, decreases of a smaller magnitude were also noted for threonine, glutamate, and valine. The relatively specific alteration of free tyrosine concentrations in the investigated tissues of trypanosome-infected animals suggests an alteration in host metabolism of this amino acid and/or parasite utilization.

Diurnal periodicity of uridine uptake by Hymenolepis diminuta.

A diurnal pattern in the uptake of uridine was displayed by the rat cestode Hymenolepis diminuta. No periodicity in the uptake of uracil was observed over a 48-hr period. A high level of uridine uptake occurred at 6 PM. when 10-day-old worms were in a posterior location in the intestine of rats maintained on a 6 PM.-6 AM. dark cycle-feeding regime, while low levels of uptake were correlated with an anteriad location at 6 AM. The lowest levels of uridine uptake were recorded at noon. Coincubation with thymine caused a stimulation of uridine uptake at midnight, 6 AM., and noon when uridine's transport rate in the absence of thymine was low. Stimulation was not demonstrable when uridine's transport rate was at its highest at 6 PM. Preincubation with uridine did not alter the diurnal uridine uptake pattern. This diurnal phenomenon is an important consideration essential to future studies on transport in parasitic and other organisms.

Alteration of free serum amino acids in voles infected with Trypanosoma brucei gambiense.

Free serum amino acid pools of field voles, Microtus montanus, were determined over a 24 hr period, and compared to values obtained from voles infected with Trypanosoma brucei gambiense. The majority of amino acids in the control animals demonstrated a diurnal variation, peaking predominantly during the dark portion of the photoperiod. This trend was not evident in the infected animals. In addition, infected voles possessed an apparent state of hypoaminoacidemia, with levels of threonine, serine, valine, isoleucine, leucine, tryosine, and tryptophan typically below uninfected values. Alanine and proline, in contrast, were markedly increased at certain time points. Tyrosine (reduced by approximately 50%) and tryptophan (reduced to levels below detection) underwent the most pronounced drop in trypanosome-infected animals, indicating the possibility of a related alteration in pools of derivative biogenic amines in other tissues. This suggests a role for the latter 2 amino acids in the neuropsychiatric syndromes of African trypanosomiasis.

Characterization of nucleoside transport in hymenolepidid cestodes.

Three species of cestodes, Hymenolepis diminuta, H. citelli, and H. microstoma, were shown to transport nucleosides by a mediated process. In H. diminuta the Ki values of various competitive inhibitors led to the conclusion that at least 2 different loci are involved in the transport of nucleosides. One of these loci has greater specificity for the purine nucleosides, the other for pyrimidine nucleosides. No significant difference was observed in their affinity for ribo- or deoxyribonucleosides, although thymidine was slightly less effective as an inhibitor of ribonucleosides than was uridine. Transport by the pyrimidine nucleoside locus was stimulated by thymine, but not by hypoxanthine, whereas transport by the purine nucleoside locus was stimulated by hypoxanthine but not by thymine. Preloading the worms with thymine gave less stimulation of transport than did the presence of eoxgenous modulator. Efflux of previously accumulated nucleoside was not blocked by the presence of exogenous modulator. The presence of exgenous thymine enhanced the incorporation of uridine into the nonextractable pool. Thymine also stimulated uracil transport in H. citelli, but not in H. microstoma, and had no effect on uridine transport in either of these species. The results of transport and modulator studies on H. diminuta grown in hamsters were not different from the results with worms grown in rats indicating that the regulatory effects observed were an inherent function of the parasite and not the host.