Life history traits as predictors of plant rarity, with particular reference to hemiparasiticOrobanchaceae

We made a comparison between life history and reproductive characteristics of a group of Dutch rare (30) and common (105) plant species, all dicotyledonous and insect-visited forbs. The traits life span, clonality, breeding system, seed production, seed dispersal, and soil seed bank longevity are considered. All trait values have been ranked according to their possible effect on the vulnerability of a species for extinction, where low values indicate a low risk and high values a high risk for a species. Rare and common plants differed significantly in four traits: seed production, breeding system, seed bank longevity and clonality. The discriminant analysis showed that 79% of the 135 species was correctly classified in the group they presently belong to. Especially species that are rare now but were much more common 50–100 years ago were classified as being common species, pointing at the detrimental effect of habitat loss these species encountered at which they have not yet been able to adapted to. The data set include eight hemiparasitic plant species (familyOrobanchaceae), of which six are endangered in The Netherlands and two more common. Both rare and common hemiparasites scored high traits values, indicating that they are vulnerable for extinction. The hemiparasites had several characteristics in common: they are all annuals or biennials that have no means of clonal reproduction. They all have non-clustered, zygomorphic flowers that produce nectar and have a precise pollen presentation and are mainly visited by (bumble) bees. Mean life span was significantly shorter in the eight hemiparasiticOrobanchaceae than in the non-hemiparasiticScrophulariaceae used for comparison (4 species). Overall, we concluded that hemiparasitic plants have a special combination of life history traits which makes them vulnerable for local and regional extinction.     

Metabolic stability of the nucleoside transport system of novikoff rat hepatoma cells

Rates of transport of uridine and thymidine, estimated with a rapid sampling technique, did not change with culture age. Inhibition of cellular RNA and protein synthesis for periods up to 6 h, did not lead to a loss of nucleoside transport activity. Mild treatment of cell suspensions with trypsin or neuraminidase had no effect on the kinetics of thymidine transport. Thus we conclude, contrary to previous reports, that nucleoside transporters are metabolically stable and that the decreases in nucleoside uptake rates observed with decreased protein synthesis reflect loss of nucleoside kinase activities. These kinases (which have narrow substrate specificity) rather than the membrane-associated, transport apparatus (which has broad substrate specificity) are the most likely sites for regulation of nucleoside uptake.     

Growth rate of cultured Novikoff rat hepatoma cells as a function of the rate of thymidine and hypoxanthine transport.

Novikoff rat hepatoma cells were propagated in suspension culture in the presence of 1 micron methotrexate and various concentrations of hypoxanthine (or adenosine plus guanosine) and thymidine and with or without the inhibitor of nucleoside and purine transport, Persantin (dipyridamole). Methotrexate-treated cells failed to replicate and died even if the medium was supplemented with either thymidine or a purine source, but normal replication occurred when both were present. The additional presence of Persantin reduced the rate of transport of thymidine or hypoxanthine and thus their incorporation into the nucleotide pool and decreased the rate of cell replication. The growth rate of the cells was directly proportional to the rate of incorporation of thymidine (in the presence of excess hypoxanthine) or of hypoxanthine (in the presence of excess thymidine) until the normal maximum growth rate was obtained. Normal cell replication in the presence of methotrexate and Persantin occurred only when the medium was supplemented with 500 micron hypoxanthine and 30 micron thymidine. The results illustrate a dependence of the growth rate of mammalian cells on the rate of transport of essential nutrients into the cell.     

Epicocconone staining: A powerful loading control for Western blots

Western blot analysis is routinely employed for quantifying differences in protein levels between samples. To control equal loading and to arithmetically compensate loading differences, immunodetection of housekeeping proteins is commonly used. Due to potential biases, this approach has been criticized. Here, we evaluate epicocconone‐based total protein staining (E‐ToPS) as an alternative. We compared it with two other total protein stainings (Coomassie and Sypro Ruby) and with immunodetection of housekeeping proteins (β‐tubulin and glyceraldehyde 3‐phosphate dehydrogenase). Evaluation comprised both the natural and the synthetic epicocconone compound. Both compounds produced highly congruent results and showed more sensitive (≤ 1 μg) and less variable staining properties than the other variants. The high sensitivity of E‐ToPS, covering minute protein amounts, makes it a powerful loading control, especially for precious samples. Regarding biological and technical variances, E‐ToPS outperformed immunostaining against β‐tubulin and glyceraldehyde 3‐phosphate dehydrogenase. Furthermore, E‐ToPS had no impact on subsequent immunodetection, allowing for an early control of proper loading prior to immunodetection. In contrast to earlier studies, we found logarithmic staining properties for E‐ToPS, which should be considered when using it for arithmetic normalization. In conclusion, we demonstrate the superior power of E‐ToPS as a loading control for Western blots.     

Lessons,narratives, and research directions for a sustainable circular economy

The current enthusiasm for the circular economy (CE) offers a unique opportunity to advance the impact of research on sustainability transitions. Diverse interpretations of CE by scholars, however, produce partly opposing assessments of its potential benefits, which can hinder progress. Here, we synthesize policy-relevant lessons and research directions for a sustainable CE and identify three narratives—optimist, reformist, and skeptical—that underpin the ambiguity in CE assessments. Based on 54 key CE scholars’ insights, we identify three research needs: the articulation and discussion of ontologically distinct CE narratives; bridging of technical, managerial, socio-economic, environmental, and political CE perspectives; and critical assessment of opportunities and limits of CE science–policy interactions. Our findings offer practical guidance for scholars to engage reflexively with the rapid expansion of CE knowledge, identify and pursue high-impact research directions, and communicate more effectively with practitioners and policymakers.     

The application of rapid kinetic techniques to the transport of thymidine and 3-O-Methylglucose into Mammalian cells in suspension culture.

Techniques are described by which the transport of nutrients into mammalian cells in suspension can be measured at intervals of 1.5 seconds. By application of these techniques, the existence of a saturable (Km = 85 muM), non-concentrative, transport system for thymidine was demonstrated in Novikoff rat hepatoma cells depleted of ATP. At concentrations of thymidine less than the Km, this system operated at velocities sufficient to nearly completely equilibrate intra- and extra-cellular thymidine pools within 8 seconds. In phosphorylating cells, the transport system operated with similar rapidity, so that intracellular phosphorylation was rate-limiting for the incorporation of thymidine into nucleotides. Uptake of 3-O-methylglucose occurred at comparable velocities, attaining 90% of equilibrium between internal and external pools within 25 seconds. Uptake of cytosine by simple diffusion was 100 times slower.     

A new sea cow record from the lower Oligocene of western Germany: new indications on the skeletal morphology of Halitherium schinzii (Mammalia: Sirenia)

Since the discovery of the extinct species Halitherium schinzii in the Mainz Basin, sirenian remains from the German Oligocene are usually assigned to this taxon according to the assumption that this would be the only sea cow species there. The attempts of several authors to determine morphological distinctions on the species level remain unconsidered until today. The new find of a partial sea cow skeleton from the lower Oligocene of Bottrop-Kirchheller Heide (western Germany) stirs up the debate on splitting the species currently referred to as H. schinzii. The Bottrop specimen morphologically corresponds to skullcaps from the Mainz Basin and the Belgian Oligocene, which were the basis for the introduction of new species in the past, but are considered synonymous with H. schinzii today. Despite its fragmentary preservation, the new sirenian record reveals shared morphological features mainly referring to the supraoccipital, such as a distinctly rostrad indenting nuchal crest and a reduced external occipital protuberance. These features are in contrast to the prominent morphology of the specimens generally associated with H. schinzii and support the assumed presence of at least two morphotypes in the Oligocene of Central Europe. Additionally, the sea cow from Bottrop-Kirchheller Heide represents the first occurrence of skeletal elements, which are not preserved in the known specimens from this morphotype so far and may contribute to a better understanding of intra- and/or interspecific differences within Sirenia.     

Towards a comprehensive picture of alloacceptor tRNA remolding in metazoan mitochondrial genomes

Remolding of tRNAs is a well-documented process in mitochondrial genomes that changes the identity of a tRNA. It involves a duplication of a tRNA gene, a mutation that changes the anticodon and the loss of the ancestral tRNA gene. The net effect is a functional tRNA that is more closely related to tRNAs of a different alloacceptor family than to tRNAs with the same anticodon in related species. Beyond being of interest for understanding mitochondrial tRNA function and evolution, tRNA remolding events can lead to artifacts in the annotation of mitogenomes and thus in studies of mitogenomic evolution. Therefore, it is important to identify and catalog these events. Here we describe novel methods to detect tRNA remolding in large-scale data sets and apply them to survey tRNA remolding throughout animal evolution. We identify several novel remolding events in addition to the ones previously mentioned in the literature. A detailed analysis of these remoldings showed that many of them are derived from ancestral events.