The incidence of Alzheimer’s disease (AD), which is characterized by progressive cognitive decline that correlates with the spread of tau protein aggregation in the cortical mantle, is strongly age-related. It could be that age predisposes the brain for tau misfolding and supports the propagation of tau pathology. We tested this hypothesis using an experimental setup that allowed for exploration of age-related factors of tau spread and regional vulnerability. We virally expressed human tau locally in entorhinal cortex (EC) neurons of young or old mice and monitored the cell-to-cell tau protein spread by immunolabeling. Old animals showed more tau spreading in the hippocampus and adjacent cortical areas and accumulated more misfolded tau in EC neurons. No misfolding, at any age, was observed in the striatum, a brain region mostly unaffected by tangles. Age and brain region dependent tau spreading and misfolding likely contribute to the profound age-related risk for sporadic AD.

Molluscs, ostracodes, diatoms, pollen, plant macrofossils, peat, and wood have been found in glacial Lake Algonquin sediments, and estuarine-alluvial sediments of the same age, in southern Ontario. Molluscs and ostracodes are particularly abundant and widespread. Pollen analysis of Lake Algonquin sediments, bogs on the Algonquin terrace, and upland bogs above the Algonquin terrace, indicate that Lake Algonquin was still in existence at the time of the spruce-pine pollen transition, previously dated at an average of 10,600 yr BP at a number of sites in Michigan, Ohio, and southern Ontario. Wood in estuarine-alluvial sediments graded to the Algonquin level is of similar radiocarbon age. Evidence from several sites in the eastern Great Lakes area suggests the presence of a preceding low-water stage (Kirkfield outlet stage); drowned and alluviated valleys and fining-upward sediment sequences have been identified in this study as further supporting evidence. Lake Algonquin drained from the southern sites by isostatic tilting and eventual opening of the “North Bay outlet” some time shortly after 10,400 yr BP.Our radiocarbon dates suggest the low-water stage has an age of about 11,000 yr BP, and that Lake Algonquin drained 10,000–15,000 y. a. Dates previously published for the Lake Michigan basin are generally too young in comparison with ours, and dates on the Champlain Sea are generally too old. More critical evaluation of all dating results is desirable.From fossil remains we suggest a rapidly expanding fauna in the waters of Lake Algonquin. The spruce pollen period was a time of rapid faunal and floral migration, when the ice front was retreating from Kirkfield to North Bay, Ontario. Diversity of some species and fossil numbers increased substantially at the transition from spruce to pine just before Lake Algonquin drained.

The family Candonidae is represented in Canada by 33 species belonging to three genera Candona, Paracandona, and Candocyprinotus. The genus Candona is represented by 31 species of which two, Candona facetus and Candona subacuminata, are new. A new genus, intermediate between Candona and Cyprinotus, has been found in Canada, namely Candocyprinotus ovatus.

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Quantitative and specific distribution of ostracodes are dependent on the physical and chemical limitations imposed by their environment, which in turn are controlled by geological, hydrological, botanical, and climatic factors. Once the nature of these controls has been defined for a region, the ecological limitation of specific ostracodes can be determined. Knowing the ostracode's tolerance limits then allows one to reconstruct the environments of the past, through paleoclimatic, paleoecologic, paleogeologic, and paleohydrologic interpretations.

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Members of the crustacean subclass Ostracoda show a high incidence of transitions from sexual to asexual reproduction.The cause of these shifts remains uncertain, perhaps because there have been few genetic studies on the group. The present study examined sex ratios and allozyme variation in 7 sexual species of ostracodes from ponds at a low Arctic site. Sex ratios in most species were strongly female-biased. Detailed study of Cyprinotus glaucus indicated that sex ratios were heterogeneous among populations, but stable during juvenile-adult development. Among 6 species, the proportion of polymorphic loci ranged from O-33 %, and individual heterozygosities 0-14 %. Genotypic frequencies at polymorphic loci conformed to Hardy-Weinberg expectations in all species, but gene frequency differences among local populations of C. glaucus suggest restricted gene Bow for this passively-dispersed species. Averaged over 5 species, approximately 27 % of the polymorphic loci were sex-linked. Linkage relationships were variable, with an individual locus being sex-linked in some species and autosomal in others.