Biomedical subjects
Publications and source records attributed to T Baltz.
The cure of Trypanosoma equiperdum infected Mice obtained after treatment with an association of electromagnetic waves and a magnetic field is probably linked with the immune state of the host. A severe depression of the immune system suppresses the ability of the animals to eliminate the parasites after physical stimulation.
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Trypanosoma equiperdum is an African trypanosome that causes dourine in horses. Like the other African trypanosomes, T. equiperdum escapes elimination by the immune system of its host by using an elaborate system of antigenic variant. The trypanosomes are covered by a coat consisting of a single protein called the variable surface glycoprotein (VSG) that acts as the major trypanosome immunogen. As the host responds to one VSG, trypanosomes covered with another VSG become dominant. There is a loose order of appearance of these VSG during the infection. The factors that affect the timing of VSG expression and the effective size of the VSG repertoire in T. equiperdum are reviewed. The VSG genes are generally activated by a process of duplicative transposition involving the duplication of a silent VSG gene and inserting a copy of the gene into an expression site. The order of VSG expression is related to the amount of homology between the silent gene and the expression site. The genes expressed late in infection lack extensive homology with the expression site and depend on homology with the gene in the expression site. The genes coding for VSG expressed late in infection are hybrid genes because of this mode of transfer. This transfer mechanism allows the trypanosome to create complex VSG genes from parts of several different silent genes that are each pseudogenes. Additionally, data are presented showing that only a limited portion of the VSG is actually seen by the host immune system. These factors indicate that the effective VSG repertoire is greater than the number of VSG genes in the trypanosome genome.
A series of (3-(2-methoxy)ethoxypropyl)tin derivatives were synthesized as potential trypanocidal drugs. The series included an alkyltin trichloride, a dialkyltin dichloride and the corresponding dialkyltin oxide, and six dialkyltin dithio derivatives. Compounds were evaluated for trypanocidal activity using in vitro cultures of Trypanosoma equiperdum and mice infected with the same strain of parasite for in vivo tests. Two of the title derivatives, the bis (3-(2-methoxy)ethoxypropyl)tin dichloride 2 and the corresponding bis (3-(2-methoxy)ethoxypropyl)tin oxide 3, appeared to be water soluble reagents. Furthermore, they are the first examples of organotin compounds presenting interesting in vivo trypanocidal activity.
African trypanosomes evade clearance in immune-competent hosts by periodically replacing their major surface glycoprotein with an antigenically different glycoprotein. Expression of many of these variant surface glycoproteins (VSGs) is associated with the duplication and transposition of silent basic copy genes (BCs) into unlinked genomic expression sites. The new expression-linked VSG gene copies (ELCs) are oriented with their 3' ends proximal to chromosome telomeres. Other VSG genes are activated without the production of an ELC. The 3' ends of these VSG genes are near chromosome telomeres both when they are active and when they are inactive. Recently, we have shown that activation of the VSG-1 gene in the BoTaR (Bordeaux trypanozoon antigen repertoire) serodeme of Trypanosoma equiperdum involves the duplication and transposition of a telomeric BC gene into one of at least three unlinked telomeric sites. Here we show that the VSG-1 ELC is inactivated but not eliminated in some antigenic variants derived from a VSG-1 expressor. In addition, a subsequent variant that again expresses VSG-1 has not reactivated the residual VSG-1 ELC (R-ELC), but instead contains a new, active VSG-1 ELC in an unlinked telomeric site. These results show that the simple presence of an ELC in a potential expression site is not sufficient for its expression.
African trypanosomes are thought to evade the host immune system by periodically changing their variable surface glycoprotein (VSG). VSG genes are activated by a complex process involving the duplicative transposition of silent basic copy genes to one of several expression sites. These expression-linked copies (ELCs) of the VSG genes are also subject to regulation within expression sites by as yet unknown mechanisms. It is generally assumed that trypanosomes can express only one VSG gene at a time. Nevertheless, the finding that they contain multiple VSG gene expression sites suggests that multiple expression is possible. We show here that Trypanosoma equiperdum can stably express two VSG genes in a simple axenic culture system and that both antigens are present on the cell surface. The two antigens do not co-cap or form heterodimers. Their corresponding genes show no cross-hybridization and are situated in different telomere-linked expression sites. Northern blot analysis reveals that both genes are active in the double expressors.
With a biological assay and atomic absorption spectrometry we determined the level of melarsoprol in the serum and cerebrospinal fluid of 19 patients treated with melarsoprol in Daloa, Ivory Coast. Most serum levels were between 2 and 4 micrograms/ml 24 h after administration, and were still > or = 0.1 microgram/ml after 120 h. Levels in the cerebrospinal fluid were between 0 and 0.1 microgram/ml. Elimination was biphasic, with a pronounced beta 1 phase. Mean terminal elimination half-life of melarsoprol was about 35 h, volume of distribution was about 100 l and total clearance was about 50 ml/min. The results of these first pharmacokinetic studies on melarsoprol were used to simulate possible alternative therapy schemes which might avoid some of the problems that arise with melarsoprol use.
Binding of concanavalin A by different clones of Trypanosoma equiperdum was checked by its ability to agglutinate living trypanosomes. The clones differ by their agglutinability, showing differences in the distribution of the binding sites. However, the property of concanavalin A to form precipitates with the crude antigen preparations of all the clones studied, allowed to isolate by affinity chromatography the glycoprotein fraction responsible for the antigenic variation and to enter upon its physicochemical study.