Simultaneous Expression of Two Different Types of Intermediate Sized Filaments in Mouse Keratinocytes Proliferating in vitro

The intermediate-sized filaments present in epidermal keratinocytes derived from mouse skin and in an established cell line (HEL) derived from spontaneous transformation of murine keratinocytes grown in vitro, have been examined by immunofluorescence microscopy, using antibodies directed against subunit proteins of different classes of intermediate-sized filaments, as well as by electron microscopy and gel electrophoresis of cytoskeletal preparations highly enriched in intermediate-sized filaments. The keratinocytes derived from neonatal skin, which are capable of only limited replication in vitro, show only a single type of intermediate-sized filaments, i.e., the tonofibril-like arrays of filaments containing prekeratin. HEL cells, which proliferate indefinitely in vitro, retain the tonofilament-like structures typical of differentiated epidermal cells but in addition display intermediate-sized filaments of the vimentin type, i.e., the filament system typically found in mesenchymal and mesenchyme-derived cells. We discuss the possibility that (i) the advent of vimentin-type filaments in epidermal cells in culture is related either to the transformed state or the in vitro growth conditions as such and (ii) other differentiated epithelial cells proliferating in vitro may have more than one system of intermediate-sized filaments.     

Site‐to‐site variability and temporal trends of DOC concentrations and fluxes in temperate forest soils

Here, we report site‐to‐site variability and 12–14 year trends of dissolved organic carbon (DOC) from organic layers and mineral soils of 22 forests in Bavaria, Germany. DOC concentrations in the organic layer were negatively correlated with mean annual precipitation and elevation whereas air temperature had a positive effect on DOC concentrations. DOC fluxes in subsoils increased by 3 kg ha^?1 yr^?1 per 100 mm precipitation or per 100 m elevation. The highest DOC concentrations were found under pine stands with mor humus. Average DOC concentrations in organic layer leachates followed the order: pine>oak>spruce>beech. However, the order was different for mean DOC fluxes (spruce>pine>oak>beech) because of varying precipitation regimes among the forest types. In 12 of 22 sites, DOC concentrations of organic layer leachates significantly increased by 0.5 to 3.1 mg C L^?1 yr^?1 during the sampling period. The increase in DOC concentration coincided with decreasing sulfate concentration, indicating that sulfate concentration is an important driver of DOC solubility in the organic layer of these forest sites. In contrast to the organic layer, DOC concentrations below 60 cm mineral soil depth decreased by <0.1–0.4 mg C L^?1 yr^?1 at eight sites. The negative DOC trends were attributed to (i) increasing adsorption of DOC by mineral surfaces resulting from desorption of sulfate and (ii) increasing decay of DOC resulting from decreasing stabilization of DOC by organo‐Al complexes. Trends of DOC fluxes from organic layers were consistent with those of DOC concentrations although trends were only significant at seven sites. DOC fluxes in the subsoil were with few exceptions small and trends were generally not significant. Our results suggest that enhanced mobilization of DOC in forest floors contributed to the increase of DOC in surface waters while mineral horizons did not contribute to increasing DOC export of forest soils.     

Spatial distributions of European Tenebrionidae point to multiple postglacial colonization trajectories

Many studies have found that species richness in the Western Palaearctic follows a latitudinal trend, yet the importance of geographical and ecological factors in shaping species ranges remains obscure. In this article, we present geographical patterns of darkling beetles (Tenebrionidae), a species‐rich group of arthropods. We relate the spatial distributions of species, instead of simply species richness, to spatial and climatic gradients, and test the effects of area (by species–area relationships), latitude (by various climatic gradients) and environmental diversity (by elevation) using simultaneous autoregressive models to identify major correlates of species richness. We then use nestedness and co‐occurrence analyses to identify glacial refugial centres and postglacial dispersal trajectories responsible for current species ranges. Our results indicate the presence of two refugial centres (in the Iberian and Balkan peninsulas) that appear to have been particularly important in shaping extant tenebrionid ranges. Northern countries were selectively colonized by more tolerant and, possibly, more mobile species, which survived in southern refugia during the Pleistocene glacial maxima, whereas the low dispersal capabilities of many species that evolved in these southern isolated areas prevented their spread northwards. High levels of endemism recorded in Spain and Sardinia suggest that the faunas of these regions originated during the Tertiary period and have remained substantially isolated. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 318–329.     

Swimming out of Africa: mitochondrial DNA evidence for late Pliocene dispersal of a cichlid from Central Africa to the Levant

The rich Levantine fauna and flora were shaped by millions of years of migration across the region, from Africa to Eurasia and vice versa. Most large-scale processes that led to this diversity have been relatively well studied. However, small-scale processes, and details such as the area of origin of particular groups, and the route and time of dispersal are often not as clear. This is the case with the endemic Levantine representatives of the fish family Cichlidae. In this work we combine genetic, palaeontological and geological data in an attempt to understand the dispersal of the cichlid fish Astatotilapia flaviijosephi (Lortet, 1883) from sub-Saharan Africa to the Levant. A. flaviijosephi is unique among the Levantine cichlids in being the only non-tilapiine. It is also the only haplochromine cichlid to be found out of Africa. A partial sequence of the control region of the mitochondrial DNA was used to determine A. flaviijosephi 's phylogenetic relationships with other African haplochromines, and to estimate its time of divergence from this group. Combining our findings with palaeontological and geological data, we suggest that A. flaviijosephi separated from the other haplochromines during the middle to late Pliocene (2.5–3.3 Mya) and probably dispersed from Africa to the Levant via the Nile.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 103–109.     

Avoiding injury and surviving injury: two coexisting evolutionary strategies in lizards

Congenital morphological differences between injured and intact individuals in a population may reflect adaptations to avoid injury, to survive injury, or both. We explore the possible occurrence of such adaptations, analysing the relationship between tail state (original, O; regenerated, R) and morphology (20 scale characters) in 23 taxa of Lacertidae. In some taxa, such as Acanthodactylus opheodurus , morphologies of O and R lizards differed significantly. In these, usually O individuals were morphologically typical (modal), while R individuals were extreme; in others, the contrary occurred. Indices of pattern similarity detected fewer differences between O and R lizards than those based on absolute values. We developed unbiased estimates of classification rates of discriminant analysis. The order of inclusion of characters in the discriminant functions of males and females of the same species differed more than the order for the same sex in other species. Some morphological differences between O and R lizards seem adaptive or linked by pleiotropy to adaptive traits. Congenital morphological differences between O and R lizards are probably more frequent than detected because we show that age and geographical heterogeneity of our samples are confounding factors to O–R differences. R-morphologies might reflect microevolution in favour of paedotypic forms, possibly possessing greater regenerating capacities than relatively more peratypic forms.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78 , 307–324.     

Reproductive ecology of female caecilian amphibians (genus Ichthyophis): a baseline study

The remarkable diversity of reproductive modes, including levels of parental care that are extensive relative to those of the other major amphibian groups, makes the limbless tropical caecilians ideally suited for evolutionary reproductive studies. Here we present key life history data for the oviparous caecilian Ichthyophis cf. kohtaoensis. We used non-invasive methods to analyse reproductive traits, seasonality of breeding and characteristics of oviposition sites in the field (Mekong valley, north-eastern Thailand). A correlation was established between reproductive activity and season, indicated by the age of egg clutches found in the field. Eggs at early developmental stages were found at the beginning of the rainy season, those with well-developed embryos at the peak of the monsoon. The body condition of females guarding younger clutches was superior to that of females with older clutches, indicative of a loss of energy reserves during the period of parental care. Maternal total length correlated positively with the number of eggs as well as with the total length of newly hatched larvae. The terrestrial oviposition sites of females were located close to temporary and permanent ponds, small brooks and rivers. It is hoped that the study will, in addition to contributing to our understanding of the evolution of caecilian reproduction, provide a basis for further comparisons of reproductive strategies among amphibians and other terrestrial tetrapods.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 207–217.     

Muscle Fiber Types in Crabs: Studies on Single Identified Muscle Fibers

SYNOPSIS. Based on electrophysiological and histochemical data,four types of muscle fibers (types I, II, III and IV) can beidentified in the closer of the crab Eriphia. Although characteristicsused for typing vary among the fibers of a particular type,the combination of several parameters permits an assignment.Of particular significance for typing is the myosin ATPase activityand its stability after preincubation at different pH levels.The fiber types defined for the closer muscle can also be foundin the other leg muscles of riphia. Single, electrophysiologically identified fibers of each typewere quantitatively analyzed for several key enzymes of oxidativeand glycolytic energy metabolism (GAPDH, LDH, CS, IDH, HAD).Despite the variations found, different metabolic types canbe defined. The typing derived from biochemical studies correlateswell with that obtained electrophysiologically and histochemically.The variability of the biochemical properties, however, seemsto be considerably larger. The type I fibers can be regarded as slow oxidative, the typeII and III fibers as fast oxidative glycolytic, and the typeIV fibers as fast glycolytic.     

Nature of DNA Precursors

No topic in molecular biology has been more controversial than DNA replication. So far, no postulated mechanisms or replicating enzymes have adequately withstood close scrutiny and now, Werner questions the basic assumption that 5′ nucleoside triphosphates are the precursors for in vivo DNA replication.     

Antiviral Activity of L-Asparaginase

L-ASPARAGINASE has anti-leukaemic and immunosuppressive activities¹ and following the observation that L-asparaginase inhibits plaque formation in L mouse fibroblast cultures by herpes simplex virus², we report studies of the activity of the enzyme on the multiplication of several human and animal viruses in cell cultures. A preparation of L-asparagine-amidohydrolase (Farbenfabriken Bayer AG, Wuppertal), extracted from Escherichia coli and containing 240 IU/mg, was used. The cell culture synthetic media used (Eagle basal or minimum essential and 199) contain no asparagine, but small amounts of this amino-acid may be supplied by the calf serum added (10%) to the medium.