No abstract

Conspicuous cyclic changes in population density characterize many populations of small northern rodents. The extreme crashes in individual number are expected to reduce the amount of genetic variation within a population during the crash phases of the population cycle. By long-term monitoring of a bank vole (Myodes glareolus) population, we show that despite the substantial and repetitive crashes in the population size, high heterozygosity is maintained throughout the population cycle. The striking population density fluctuation in fact only slightly reduced the allelic richness of the population during the crash phases. Effective population sizes of vole populations remained also relatively high even during the crash phases. We further evaluated potential mechanisms contributing to the genetic diversity of the population and found that the peak phases are characterized by both a change in spatial pattern of individuals and a rapid accession of new alleles probably due to migration. We propose that these events act together in maintaining the high genetic diversity within cyclical populations.

T he aim of this study was to examine whether maximal walking speed, maximal isometric muscle strength, leg extensor power and lower leg muscle cross-sectional area (CSA) shared a genetic effect in common. In addition, we wanted to identify the chromosomal areas linked to maximal walking speed and these muscle characteristics and also investigate whether maximal walking speed and these three skeletal muscle characteristics are regulated by the same chromosomal areas. We studied 217 monozygotic (MZ) and dizygotic (DZ) female twin pairs aged 66 to 75 years in the Finnish Twin Study on Aging study. The DZ pairs (94) were genotyped for 397 microsatellite markers in 22 autosomes and Xchromosome. Genetic modeling showed that, muscle CSA, strength, power and walking speed shared a genetic effect in common which accounted for 7% of the variation in CSA, 51% in strength, 37% in power and 35% in walking speed. The results of an explorative multipoint linkage analysis suggested that the highest LOD score found for each phenotype was 2.41 for walking speed on chromosome 13q22.1, 2.14 for strength on chromosome 15q14, 2.84 for power on chromosome 8q24.23, and 2.93 for muscle CSA on chromosome 20q13.31. Also a suggestive LOD score, 2.68, for muscle CSA was found on chromosome 9q34.3. The chromosomal areas of a suggestive linkage for strength and power partly overlapped LOD scores higher than 1.0 being seen for these phenotypes on chromosome 15. The present study was the first genome-wide linkage analysis to be conducted for these multifactorial and clinically important phenotypes underlying functional independence in older women.

We describe a set of 66 highly polymorphic microsatellite loci isolated from the bank vole, Myodes (Clethrionomys) glareolus. These microsatellites were characterized for a long-term study on periodically fluctuating density of the bank vole population in Central Finland. We detected six to 38 alleles per locus in the population sampled at two different density phases, and the levels of observed and expected heterozygosities varied between 0.17 and 1.00, and between 0.72 and 0.95, respectively. This microsatellite panel serves as an informative tool for population and molecular genetic studies.

The effects of long-term, low-dose ultraviolet B (UVB) radiation on immune functions of two fish species representing different taxonomic groups, carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss), were assessed in this study. The fish were exposed to 7, 20 or 60 mJ cm )2 UVB three times per week, for 6 weeks. In carp, UVB exposure affected the respiratory burst activity of blood and head kidney phagocytes, differential blood leukocyte counts and blood chemistry. Phytohemagglutinin (PHA)-stimulated in vitro proliferation responses of blood and head kidney lymphocytes, however, remained unchanged. Rainbow trout tolerated the irradiations with fewer alterations, but significant changes were detected in blood chemistry and hematocrits of the irradiated fish. These results indicate that long-term exposure to low doses of UVB induces immunomodulation in fish, and that there are species-specific differences in sensitivity to irradiation.