Isolation and characterization of ten polymorphic microsatellite loci in Ixodes arboricola, and cross-amplification in three other Ixodes species.

We characterized ten polymorphic microsatellite loci from the tree-hole tick, Ixodes arboricola. Loci were screened in 11-18 individuals from three Belgian populations and five to ten alleles were found at each locus. Seven loci did not show deviations from Hardy-Weinberg equilibrium conditions and there were no indications for null alleles at these loci. The three other loci showed significant heterozygote deficiencies in at least one population, and a high potential for the occurrence of null alleles. We observed no effect of potential host DNA on the scoring of the microsatellites. Cross-amplification of the microsatellites was tested in eight specimens of three congeneric species: I. ricinus, I. hexagonus and I. frontalis. Depending on the species, six or seven of the loci were amplified in ≥ 4 of the 8 specimens and were polymorphic in each of these species (except for Ixaf 11 in I. frontalis and I. ricinus). These loci thus provide a tool for population genetic analysis of I. arboricola. The suitability of these markers needs to be further investigated in its congeners.

Correlation of variations in intraluminal pressure and potential differences in the perfused colen.

To investigate the nature of variations in the large intestine potential differences, a continuous perfusion of isotonic saline was carried out in the colon of 14 rats. Intraluminal pressure and potential differences between the lumen and the peritoneal cavity were continuously and simultaneously recorded, while impedance of the system and respiration were also constantly monitored. To obtain a quantitative evaluation of the data, Fast Fouier Transform was performed on the signals and their derivatives which were auto- and cross-correlated. While there was no obvious relation between pressure and potential in the unperfused colon, there was clear visual qualirative evidence that, during steady state conditions of perfusion, an increase in intraluminal pressure was accompanied by a decrease in potential differences, while impedance of the recording system remained unchanged. Computer analysis disclosed four narrow ranges of stable frequencies for both pressure and potential. They were centred around 0-3, 1-75, 10-7, and 75 cycles per minute, the latter being synchronous with respiration. It is concluded that the variations of potential differences recorded during perfusion, a well-know phenomenon, are not electrical artefacts: the fast rhythm is probably induced by respiration, which increases intracolonic pressure and that, in turn, reduces the absolute value of potential differences, which remain negative mucosa versus serosa. The slower rhythms are synchronous for pressure and potential. Mechanisms responsible for the decrease in potential related to the increase in pressure remain unknown.