PubMed · 7024344
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J B Russell, R B Hespell. 1981. Microbial rumen fermentation.. https://doi.org/10.3168/jds.s0022-0302(81)82694-x
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The snowshoe hare and the Canadian lynx in the boreal forests of North America show 9- to 11-year density cycles. These are generally assumed to be linked to each other because lynx are specialist predators on hares. Based on time series data for hare and lynx, we show that the dominant dimensional structure of the hare series appears to be three whereas that of the lynx is two. The three-dimensional structure of the hare time series is hypothesized to be due to a three-trophic level model in which the hare may be seen as simultaneously regulated from below and above. The plant species in the hare diet appear compensatory to one another, and the predator species may, likewise, be seen as an internally compensatory guild. The lynx time series are, in contrast, consistent with a model of donor control in which their populations are regulated from below by prey availability. Thus our analysis suggests that the classic view of a symmetric hare-lynx interaction is too simplistic. Specifically, we argue that the classic food chain structure is inappropriate: the hare is influenced by many predators other than the lynx, and the lynx is primarily influenced by the snowshoe hare.
Mouse apolipoprotein (apo) A-II has three variants (type A, B, and C) among inbred strains. To clarify the role of ApoA-II in the metabolism of high density lipoproteins (HDL), we constructed a new congenic mouse strain (P1.R1-Apoa2b) with type B ApoA-II of the SAMR1 strain on the genetic background of the SAMP1 strain, and examined it together with another ApoA-II congenic strain (R1.P1-Apoa2c) containing type C ApoA-II of the SAMPI strain on the SAMR1 strain and the parental SAMP1 and SAMR1 strains. Genetic characterization of the congenic strains indicated that only small regions surrounding the ApoA-II gene of the parental strains had been transferred. The strains with Apoa2c had lower plasma concentrations of HDL and ApoA-II, and a smaller HDL particle size than strains with Apoa2b. We detected no significant differences in the mRNA levels of ApoA-II or in the in vitro translational efficiency of the ApoA-II mRNA among the four strains. These findings suggested that the differences in the post-translational modification or efficiency of secretion between the Apoa2b and Apoa2c protein regulates the ApoA-II concentration which in turn determines the concentration and size of HDL in mice.