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Water vole (Arvicola amphibius) populations have\ud undergone a serious decline throughout the UK, and\ud yet a stronghold of these small mammals is found in\ud the greater Easterhouse area of Glasgow. The water\ud voles in this location are mostly fossorial, living a\ud largely subterranean existence in grasslands, rather\ud than the more typical semi-aquatic lifestyle in\ud riparian habitats. In this study, we carried out\ud capture-mark-recapture surveys on water voles at\ud two sites: Cranhill Park and Tillycairn Drive. We\ud made a total of 62 captures including retraps, and the\ud resulting population estimates were 78 individuals\ud (95% confidence interval 41-197) for Cranhill Park\ud and 42 individuals (20-141) for Tillycairn Drive.\ud From these figures we estimated a population\ud density of water voles, which appeared to be higher\ud than other reports from the UK. Despite the\ud difficulties of sampling in urban environments that\ud resulted in relatively low capture rates, our data\ud suggest that the greater Easterhouse area of Glasgow\ud holds water voles at relatively high population\ud densities. These results will inform future\ud conservation in the City of Glasgow and surrounding\ud areas, as well as raise awareness of important water\ud vole populations in urban environments.

The misfolded isoform of the prion protein (PrP(Sc)) possesses many unusual physiochemical properties. Previously, we and others reported on the differential partitioning of PrP(Sc) from plasma derived therapeutic proteins during their purification processes. To understand the driving force behind these partitioning differences, we investigated the effects of various solvent conditions on the precipitation of PrP(Sc). In a physiological buffer, PrP(Sc) remained in the supernatant after low speed centrifugation. At pH 5, PrP(Sc) precipitation was nearly complete regardless of the salt content. PrP(Sc) could also be precipitated at pH 8 by adding ethanol, but this precipitation was salt dependent. Based on these observations, an empirical mathematical model was constructed in which the PrP(Sc) precipitation trends were fully described as a function of solvent pH, salt, and ethanol concentration. This model consistently predicted PrP(Sc) partitioning during cold ethanol precipitation steps used in plasma protein purification processes, as shown by experimentally determined distributions of PrP(Sc) and transmissible spongiform encephalopathy (TSE) infectivity. These results indicate that pH, salt, and ethanol content are the major solvent factors determining the precipitation of the infectious PrP(Sc) in these processes and may provide a useful tool for assessing the differential partitioning of PrP(Sc) in a given solvent environment.

BACKGROUND: Experimental evidence from rodent models indicates that blood can contain transmissible spongiform encephalopathy (TSE) infectivity, which suggests a potential risk for TSE transmission via proteins isolated from human plasma. Because methods that can reduce TSE infectivity typically are detrimental to protein function, infectivity must be removed to ensure the safety of these therapeutic proteins. Animal bioassays are conventionally used to detect infectivity, but the pathogenic form of the prion protein (PrP Sc ) can serve as a marker for TSE infectivity. STUDY DESIGN AND METHODS: Seven plasma protein-purification steps were performed after the plasma intermediates were spiked with TSE-infected material. Resulting fractions were analyzed for PrP Sc by using a Western blot assay and for TSE infectivity by using an animal bioassay. Western blots were quantitated by an endpoint dilution analysis, and infectivity titers were calculated by the Spearman-Karber method. RESULTS: PrP Sc partitioning paralleled TSE infectivity partitioning, regardless of the nature of the protein-purification step. The detection ranges for PrP Sc and infectivity were 0 to 5.3 log and 1.1 to 8.9 log median infectious dose per unit, respectively. Clearance of PrP Sc and infectivity ranged from 1.0 to 6.0 log. CONCLUSION: Purification steps for isolating therapeutic proteins from human plasma showed the removal of both PrP Sc and TSE infectivity. PrP Sc partitioning coincided with infectivity partitioning, which showed a close relationship between PrP Sc and TSE infectivity. By exploiting this association, the in vitro Western blot assay for PrP Sc was valuable for estimating the partitioning of TSE infectivity during plasma protein purification.