Correction to: Developmental delay and late onset HBSL pathology in hypomorphic Dars1M256L mice

Neurochemical Research -     

Models of deletion for visualizing bacterial variation: an application to tuberculosis spoligotypes

Background  

Molecular typing methods are commonly used to study genetic relationships among bacterial isolates. Many of these methods have become standardized and produce portable data. A popular approach for analyzing such data is to construct graphs, including phylogenies. Inferences from graph representations of data assist in understanding the patterns of transmission of bacterial pathogens, and basing these graph constructs on biological models of evolution of the molecular marker helps make these inferences. Spoligotyping is a widely used method for genotyping isolates of Mycobacterium tuberculosis that exploits polymorphism in the direct repeat region. Our goal was to examine a range of models describing the evolution of spoligotypes in order to develop a visualization method to represent likely relationships among M. tuberculosis isolates.     

Ageing in a variable habitat: environmental stress affects senescence in parasite resistance in St Kilda Soay sheep

Despite widespread empirical evidence for a general deterioration in the majority of traits with advancing age, it is unclear whether the progress of senescence is chronologically determined, or whether factors such as environmental conditions experienced over the lifespan are more important. We explored the relative importance of ‘chronological’ and ‘environmental’ measures of age to changes in parasite resistance across the lifespan of free-living Soay sheep. Our results show that individuals experience an increase in parasite burden, as indicated by gastrointestinal helminth faecal egg count (FEC) with chronological age. However, chronological age fails to fully explain changes in FEC because a measure of environmental age, cumulative environmental stress, predicts an additional increase in FEC once chronological age has been accounted for. Additionally, we show that in females age-specific changes are dependent upon the environmental conditions experienced across individuals'' life histories: increases in FEC with age were greatest among individuals that had experienced the highest degree of stress. Our results illustrate that chronological age alone may not always correspond to biological age, particularly in variable environments. In these circumstances, measures of age that capture the cumulative stresses experienced by an individual may be useful for understanding the process of senescence.     

The exchangeability of human erythrocyte membrane cholesterol

A new method has been used to determine what fraction of human erythrocyte cholesterol is available for exchange with plasma unesterified cholesterol. Erythrocytes labeled with ³H-cholesterol by this exchange process were incubated with sonicated phosphatidylcholine vesicles, giving rise to a net movement of cholesterol out of the cells. The specific activity of cholesterol taken up by the vesicles depended on the length of time of incubation. Initially the specific activity in the vesicles was greater than that in the cells, but after approximately 10% of cell cholesterol had been removed, the specific activity of subsequently removed cholesterol was equal to that of the remaining erythrocyte cholesterol. We conclude from these data that (a) all of the cholesterol in the erythrocyte is exchangeable with plasma, and (b) approximately 10% of erythrocyte cholesterol is in a more rapidly exchangeable pool than the remainder.