Evolutionary Correlation Between Linker Histones and Microtubular Structures

Histones of the H1 group (linker histones) are abundant components of chromatin in eukaryotes, occurring on average at one molecule per nucleosome. The recent reports on the lack of a clear phenotypic effect of knock-out mutations as well as overexpression of histone H1 genes in different organisms have seriously undermined the long-held view that linker histones are essential for the basic functions of eukaryotic cells. In an attempt to resolve the paradox of an abundant conserved protein without a clear function, we re-examined the molecular and phylogenetic data on linker histones to see if they could reveal any correlation between the features of H1 and the functional or morphological characteristics of cells or organisms. Because of an earlier demonstration that in sea urchin the chromatin-type histone H1 is also found in the flagellar microtubules (Multigner et al. 1992), we focused on the correlation between the features of H1 and those of microtubular structures. A phylogenetic tree based on multiple alignment of over 100 available H1 sequences suggests that the first divergence of the globular domain of H1 (GH1) resulted in branching into separate types characteristic for plants/Dictyostelium and for animals/ascomycetes, respectively. The GH1s of these two types differ by a short region (usually 5 amino acids) placed at a specific location within the C-terminal wing subdomain of GH1. Evolutionary analysis of the diversification of H1 mRNA into cell-cycle-dependent (polyA⁻) and independent (polyA⁺) forms showed a mosaic occurrence of these two forms in plants and animals, despite the fact that the H1 proteins of plants and animals belong to two well-distinguished groups. However, among organisms from both animal and plant kingdom, only those with H1 mRNA of a polyA⁻ type have flagellated gametes. This correlation as well as the demonstration that in Volvox carteri the accumulation of polyA⁻ mRNA of H1 occurs concurrently with the production of new flagella (Lindauer et al. 1993), suggests a direct link between polyA⁻ phenotype of histone H1 mRNA and flagellogenesis. Received: 25 May 2000 / Accepted: 5 February 2001     

Beiträge zur Kenntnis der Regenerationsvorgänge nach künstlichen Verletzungen bei älteren Bachforellenembryonen (Salmo fario L.)

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Contrasting patterns in the occurrence and biomass centers of gravity among fish and macroinvertebrates in a continental shelf ecosystem

The distribution of a group of fish and macroinvertebrates (n = 52) resident in the US Northeast Shelf large marine ecosystem were characterized with species distribution models (SDM), which in turn were used to estimate occurrence and biomass center of gravity (COG). The SDMs were fit using random forest machine learning and were informed with a range of physical and biological variables. The estimated probability of occurrence and biomass from the models provided the weightings to determine depth, distance to the coast, and along‐shelf distance COG. The COGs of occupancy and biomass habitat tended to be separated by distances averaging 50 km, which approximates half of the minor axis of the subject ecosystem. During the study period (1978–2018), the biomass COG has tended to shift to further offshore positions whereas occupancy habitat has stayed at a regular spacing from the coastline. Both habitat types have shifted their along‐shelf distances, indicating a general movement to higher latitude or to the Northeast for this ecosystem. However, biomass tended to occur at lower latitudes in the spring and higher latitude in the fall in a response to seasonal conditions. Distribution of habitat in relation to depth reveals a divergence in response with occupancy habitat shallowing over time and biomass habitat distributing in progressively deeper water. These results suggest that climate forced change in distribution will differentially affect occurrence and biomass of marine taxa, which will likely affect the organization of ecosystems and the manner in which human populations utilize marine resources.     

Cranberry flavonoids prevent toxic rat liver mitochondrial damage in vivo and scavenge free radicals in vitro

The present study was undertaken for further elucidation of the mechanisms of flavonoid biological activity, focusing on the antioxidative and protective effects of cranberry flavonoids in free radical‐generating systems and those on mitochondrial ultrastructure during carbon tetrachloride‐induced rat intoxication. Treatment of rats with cranberry flavonoids (7 mg/kg) during chronic carbon tetrachloride‐induced intoxication led to prevention of mitochondrial damage, including fragmentation, rupture and local loss of the outer mitochondrial membrane. In radical‐generating systems, cranberry flavonoids effectively scavenged nitric oxide (IC₅₀ = 4.4 ± 0.4 µg/ml), superoxide anion radicals (IC₅₀ = 2.8 ± 0.3 µg/ml) and hydroxyl radicals (IC₅₀ = 53 ± 4 µg/ml). The IC₅₀ for reduction of 1,1‐diphenyl‐2‐picrylhydrazyl radicals (DPPH) was 2.2 ± 0.3 µg/ml. Flavonoids prevented to some extent lipid peroxidation in liposomal membranes and glutathione oxidation in erythrocytes treated with UV irradiation or organic hydroperoxides as well as decreased the rigidity of the outer leaflet of the liposomal membranes. The hepatoprotective potential of cranberry flavonoids could be due to specific prevention of rat liver mitochondrial damage. The mitochondria‐addressed effects of flavonoids might be related both to radical‐scavenging properties and modulation of various mitochondrial events. Copyright © 2015 John Wiley & Sons, Ltd.