Studies on the major histocompatibility complex of indigenous cattle in the Ivory Coast.

The MHC (BoLA) type has been determined for cattle from three breeds in West Africa. Seventy Baoule, 50 N'Dama and 30 Zebu cattle from the centre and north of the Ivory Coast were tested. Lymphocytes from these cattle were tested in a lymphocytotoxicity test with alloantisera detecting all of the internationally recognised BoLA sera. 78 sera prepared in Edinburgh and 57 in Jouy-en-Josas were used in the study. The results showed that sera prepared in Europe detect similar specificities in West Africa. Although with some specificities the frequencies differ from those seen in Europe. The frequency of null alleles is higher than in Europe in the Ndama and Zebu animals indicating the existence of additional specificities which will require the production of alloantisera in these breeds. However in the Baoule the null allele frequency is lower even then in some European breeds. The population data in which no animals have more than two workshop specificities is consistent with a single locus control in West Africa as in Europe.

In vitro evaluation of the DP-4M PennCentury insufflator.

Dry powder formulations for inhalation have to be screened in animal studies for therapeutic efficacy and safety aspects and both are significantly affected by the dose and the particle size distribution (PSD) of the aerosol that is given. One of the most frequently used apparatus for pulmonary delivery of dry powder formulations in mice studies is the PennCentury DP-4M Dry Powder Insufflator. To make researchers of future preclinical animal studies with the DP-4M insufflator aware of the pitfalls regarding the conclusions to be drawn from their data, we investigated the dispersion behaviour by the DP-4M insufflator using two to three different powder preparation techniques for four different compounds. The primary PSDs of the different formulations were determined in duplicate by laser diffraction analysis. To measure the PSDs of the aerosols obtained with the DP-4M insufflator, the same diffractometer was used in combination with an in-house constructed adapter for the insufflator. The dispersion efficiency and delivered dose were highly affected by the amount of air available for dispersion; the 200 µL of air recommended for the type of insufflator used was insufficient for adequate dispersion. In contrast, the weighed dose did not have a profound effect on the dispersion behaviour and the delivered dose of the DP-4M insufflator. Also the physico-chemical powder properties and the applied particle preparation technique influenced the amount and PSD of the delivered aerosol only to a limited extend, with a few exceptions. We advise researchers to investigate the dispersion efficiency and delivered dose from the DP-4M insufflator with the formulation under investigation prior to in vivo studies and it may be necessary to optimise the formulation for administration to mice.

Cell biology of H2O2 generation in the thyroid: investigation of the control of dual oxidases (DUOX) activity in intact ex vivo thyroid tissue and cell lines.

H2O2 generation by dual oxidase (DUOX) at the apex of thyroid cells is the limiting factor in the oxidation of iodide and the synthesis of thyroid hormones. Its characteristics have been investigated using different in vitro models, from the most physiological thyroid slices to the particulate fraction isolated from transfected DUOX expressing CHO cells. Comparison of the models shows that some positive controls are thyroid specific (TSH) or require the substructure of the in vivo cells (MßCD). Other controls apply to all intact cell models such as the stimulation of the PIP(2) phospholipase C pathway by ATP acting on purinergic receptors, the activation of the Gq protein downstream (NaF), or surrogates of the intracellular signals generated by this cascade (phorbol esters for protein kinase C, Ca(++) ionophore for Ca(++)). Still, other controls, exerted by intracellular Ca(++) or its substitute Mn(++), the intracellular pH, or arachidonate bear directly on the enzyme. Iodide acts at the apical membrane of the cell through an oxidized form, presumably iodohexadecanal. Cooling of the cells to 22°C blocks the activation of the PIP(2) phospholipase C cascade. All these effects are reversible. Their kinetics and concentration-effect characteristics have been defined in the four models. A general scheme of the thyroid signaling pathways regulating this metabolism is proposed. The probes characterized could be applied to other H2O2 producing cells and to pathological material.

Potential role of Noxes in the protection of mucosae: H(2)O(2) as a bacterial repellent.

Duox proteins are members of the NADPH oxidase (Nox) family and are responsible for hydrogen peroxide (H(2)O(2)) production by various tissue types including bronchial and intestinal mucosae. The antimicrobial killing role of H(2)O(2) in leukocytes and macrophages is generally considered as the paradigm of its function. We investigated here the positive role of H(2)O(2) in the prevention of cellular invasion by Salmonella. We show that H(2)O(2), under conditions that preserved bacterial growth, has a repellent effect on Salmonella motility on agar plates. In addition, H(2)O(2) produced by PCCl3, a rat thyroid cell line, reduces bacterial invasion of the cells by around 40%. To test whether the observed phenotype is attributable to H(2)O(2) production, we constructed a CHO stable cell line expressing Duox2 protein at the cell surface (CHO-D2). The transfected cells produce a high amount of H(2)O(2). Upon infection with Salmonella, the invasion of CHO-D2 cells was reduced by up to 60%. In both PCCl3 and CHO expressing Duox2 cells, normal invasion was restored upon incubation with catalase. Our data suggest that H(2)O(2) at reduced concentrations acts as a repellent for bacteria, keeping them away from cells, a situation that could naturally prevent mucosal cells infection in vivo.

Zebu-taurine variation in Y chromosomal DNA: a sensitive assay for genetic introgression in west African trypanotolerant cattle populations.

Owing to increasing scientific and agricultural interest in the disease-resistant (trypanotolerant), indigenous cattle breeds of West and Central Africa, there is a need for a rational genetically based description of populations in the region. The greatest threat to the invaluable genetic resource represented by these animals is that of extensive genetic introgression of distantly related zebu cattle from northern populations which do not share their inherited tolerances. Southern blotting with a chromosome Y-specific probe, btDYZ-1 (locus DYZ1) is shown to be a sensitive assay to detect such introgression. Evidence of historical crossbreeding is reported in two important N'Dama populations previously classed as purely taurine.