Evidence for kinetoplast and nuclear DNA homogeneity in Trypanosoma evansi isolates.

The kinetoplast DNA minicircles from 13 stocks of trypanosomes designated as Trypanosoma evansi were digested with various restriction enzymes. We also examined the distribution of restriction site polymorphisms in the nuclear DNA of 9 of these stocks, using 7 different variable surface glycoprotein (VSG) and non-VSG probes. Restricted kinetoplast DNA (kDNA) fragments of some of these strains were cloned into M13 or PUC 18 vectors and sequenced. The restriction and sequence mapping showed that most of T. evansi isolates belonged to the A1 and A2 types of Borst and to two new closely related types A3 and A4. A notable exception was RoTat 4/1 derived from a Sudanese stock which was found to display a characteristic brucei-like minicircle heterogeneity. The T. evansi minicircles analysed are not only homogeneous in sequence but also the region similar to the conserved region in Trypanosoma brucei and Trypanosoma equiperdum is flanked on its 5' end by a palindromic repeat of part of the conserved region. The highly conserved sequence GGGCGGT which appears to correspond to the initiation of synthesis of one of the Okazaki fragments contains an additional G and is located as in T. brucei and T. equiperdum about 73 bp 5' from the ORI. The nuclear DNA analysis confirms the kDNA study in that all the T. evansi stocks are members of a very homogeneous group in terms of sequence divergence. Moreover, our analysis also confirms that T. evansi is more closely related to the West African T. b. brucei and T. b. gambiense than to other African trypanosomes.

Wet combing for head lice: feasibility in mass screening, treatment preference and outcome.

There is no scientific consensus on the best way to control head louse infestation in schoolchildren. A study was conducted to test the feasibility and acceptability of a screening campaign by wet combing and a community approach to head-louse control with home visits, and to explore parents' treatment preferences and treatment outcomes. A non-controlled intervention (advice on treatment options offered to all positive children) was nested within an epidemiological prevalence study. All children in three primary schools in Ghent, Belgium, were invited to take part in screening by wet combing (n=677, 3-11 years). Positive children were offered structural treatment advice, a home visit on day 7, and a check by wet combing on day 14. 83% of the children were screened. The prevalence of active infestation (living moving lice) was 13.0% in school 1 and 19.5% in school 3. In school 2, prevalence of signs of active and past infestation was 40.7%. A home visit was made to 58% of the positive children. 85% of the positive children were screened again on day 14. Wet combing was the most widely used treatment, followed by chemical treatment and a combination of the two. In school 1 and 3 51% were cured, and in school 2 24% became nit-free. A wet combing screening campaign and a community-oriented approach to head-louse control is feasible though resource-intensive. The prevalence of head lice was high and the cure rate was low, with either topical treatments or wet combing.

Phylogeny of the rabbit gamma-chain determinants: a d12-like antigenic determinant in Pronolagus rupestris.

A survey for constant region gamma-chain allotypes (de locus) was undertaken in different lagomorph genera. As yet only Pronolagus rupestris, a paleolaginae, showed the presence of a determinant similar to rabbit d12 although it lacked the widespread e15 determinant. All seven individuals possessed the d12 like determinant which was studied by immunodiffusion, haemagglutination inhibition, radiobinding and binding inhibition assays. In addition, a new enzymic method for typing for d12, based on the presence of the asymmetric rabbit hinge carbohydrate linked to the d12 characteristic threonine, is presented. This method suggests, however, that, unlike the d12 rabbit, Pronolagus does not seem to have a majority of IgG molecules with a glycosylated hinge.

Detection and differentiation of microbial siderophores by isoelectric focusing and chrome azurol S overlay.

Siderophores are microbial, low molecular weight iron-chelating compounds. Fluorescent Pseudomonads produce different, strain-specific fluorescent siderophores (pyoverdines) as well as non-fluorescent siderophores in response to low iron conditions. We present an isoelectric focusing method applicable to unpurified as well as to purified pyoverdine samples where the fluorescent siderophores are visualized under UV illumination. Siderophores from different Pseudomonas sp., amongst which are P. aeruginosa, P. fluorescens and P. putida, including egg yolk, rhizospheric and clinical isolates as well as some derived Tn5 mutants were separated by this technique. Different patterns could be observed for strains known to produce different siderophores. The application of the chrome azurol S assay as a gel overlay further allows immediate detection of non-fluorescent siderophores or possibly degradation products with residual siderophore activity. The method was also applied to other microbial siderophores such as deferrioxamine B.

Double line phenotypes in rabbit IgG allotypes and their relation to the cis/trans configuration of the IgG markers.

Rabbit antiallotype sera raised against heavy chain markers sometimes show double precipitin lines with all or some of the corresponding antigens (double and single line phenotypes). In a number of cases the double line phenotypes behave as alleles of the single line phenotypes and this feature allows a genetic and immunochemical analysis of these systems. In three cases that have been analysed, the double line phenotype arise when a precipitating a locus allotype and a non-precipitating d or e locus allotype are present on the same molecule (a1 and d14), (a1 and d11), (a3 and d11). This only happens when the corresponding genes are present on the same chromosome (cis configuration) of the diploid pair. These sera are therefore useful for determining directly the genotype of the animals.