A computer simulation of the effects of specific environmental factors on the development of the sheep tick Ixodes ricinus L

A previously developed technique for predicting field development rates of the tick, Ixodes ricinus, has been modified and used in an attempt to test interpretations of field data and to gain further insight into the population dynamics of I. ricinus. The results of this study have provided encouraging evidence of the validity of the predictive technique, identified certain areas in the biology of I. ricinus which require further investigation and, in general, supported the suggestion that in Ireland a continuous interchange of ticks between spring and autumn populations occurs. This technique requires further refinement but it appears to have considerable potential for predicting the behaviour of tick populations in different localities and under the influence of different weather conditions.     

Cloning and expression of the cDNA for bovine granulocyte-macrophage colony-stimulating factor

A sequence encoding bovine granulocyte-macrophage colony-stimulating factor (GM-CSF) has been identified from a concanavalin A-stimulated bovine lymphocyte cDNA library. This sequence was isolated by hybridization with synthetic oligonucleotide probes based upon the human GM-CSF sequence. This bovine cDNA was engineered for expression and secretion of activity into the periplasmic space of E. coli. Periplasmic extracts contain a 14,500-dalton protein and stimulate colony formation of bovine bone marrow progenitor cells. The predicted protein is 70% homologous with human GM-CSF and 55% homologous with murine GM-CSF. Numerous structural features are conserved among these three proteins, such as location of cysteine residues, glycosylation sites, and overall change. The biological activity of bovine GM-CSF is species specific, since recombinant preparations do not cause proliferation of human or murine bone marrow cells. Similarly, murine GM-CSF does not exhibit activity on cells of bovine or human origin. However, human GM-CSF does stimulate colony formation of bovine bone marrow cells, although the specific activity appears reduced when compared to assays on human cells.     

Barriers as boundaries for metapopulations and demes of Peromyscus leucopus in farm landscapes

Effects of potential barriers (roads and cultivated fields) on both demographic and genetic features of subpopulations of white-footed mice were studied near Ottawa, Canada. Live trapping, colored bait and track registry were used to study animal movements across roads on four 1.44 ha areas each within a small forest bisected by a narrow gravel road. The genetic study was done in 11 other forest fragments separated from each other by cultivated fields. Frequencies of three electrophoretic variants of salivary amylases were established for mice caught in each patch of wood and genetic similarity of subpopulations was calculated. Movements of mice across the roads were very infrequent (quantitative barrier), although movements adjacent to roads were frequent and long enough to cross the roads. Salivary amylase data showed that studied subpopulations were genetically very similar although the sample was intentionally biased toward demographic isolation. Results are discussed in terms of possible hierarchical relationships of metapopulations and genetic demes in the context of landscape ecology, management and conservation practice.