Contrasting patterns of density‐dependent selection at different life stages can create more than one fast–slow axis of life‐history variation

There has been much recent research interest in the existence of a major axis of life‐history variation along a fast–slow continuum within almost all major taxonomic groups. Eco‐evolutionary models of density‐dependent selection provide a general explanation for such observations of interspecific variation in the "pace of life." One issue, however, is that some large‐bodied long‐lived “slow” species (e.g., trees and large fish) often show an explosive “fast” type of reproduction with many small offspring, and species with “fast” adult life stages can have comparatively “slow” offspring life stages (e.g., mayflies). We attempt to explain such life‐history evolution using the same eco‐evolutionary modeling approach but with two life stages, separating adult reproductive strategies from offspring survival strategies. When the population dynamics in the two life stages are closely linked and affect each other, density‐dependent selection occurs in parallel on both reproduction and survival, producing the usual one‐dimensional fast–slow continuum (e.g., houseflies to blue whales). However, strong density dependence at either the adult reproduction or offspring survival life stage creates quasi‐independent population dynamics, allowing fast‐type reproduction alongside slow‐type survival (e.g., trees and large fish), or the perhaps rarer slow‐type reproduction alongside fast‐type survival (e.g., mayflies—short‐lived adults producing few long‐lived offspring). Therefore, most types of species life histories in nature can potentially be explained via the eco‐evolutionary consequences of density‐dependent selection given the possible separation of demographic effects at different life stages.     

Hepatic DNAJB9 Drives Anabolic Biasing to Reduce Steatosis and Obesity

1. Download : Download high-res image (127KB)
2. Download : Download full-size image

     

A Dynamic Folded Hairpin Conformation Is Associated with α-Globin Activation in Erythroid Cells

1. Download : Download high-res image (171KB)
2. Download : Download full-size image

     

Vesicle Shrinking and Enlargement Play Opposing Roles in the Release of Exocytotic Contents

1. Download : Download high-res image (176KB)
2. Download : Download full-size image

     

Effects of the Addition of Humic Substances on Soil Protease Activities in Andosols in the Presence of Cadmium

Cadmium extraction, sorption, and immobilization seem to be the effective mechanisms in detoxification of Cd-contaminated soil. Humic substances present in soils may play an important role both in controlling the negative effects of pollution with Cd and in stabilizing soil enzymes. In this context, we have compared the effects of humic substances on soil protease activities in the presence and absence of Cd in forest and cultivated field soil samples. The samples were taken from surface soils of Andosols in a single upland area of the Kanto district in Japan. Humic substances extracted from the two soils showed differences in elemental composition, the degree of condensation of aromatic groups, and the proportions of major functional groups. Compared with the control soil samples, those with added humic substances showed a significant increase in protease activities, even in the presence of Cd (10 and 50 mg Cd kg^?1 soil). However, the addition of Cd decreased the protease activities, protein contents, and soil pH in both soil samples at each of the two levels of humic substance fortification (+5% and +10%). Moreover, protease activities showed significant negative correlation with exchangeable Cd, but adding humic substances did not lead to a reduction in either sample. Thus, although the addition of humic substances increased and stabilized protease activities, it did not lead to a clear reversal of enzyme inhibition by Cd. The obtained results indicate that in both soil samples the humic substances used in this study did not have sufficient affinity to adsorb Cd, and the impact on enzyme activities depends on the difference in chemical characteristics of the added organic matter, as suggested by the difference in enhancement of protease activities between forest and cultivated field soil samples.     

Stepwise sRNA targeting of structured bacterial mRNAs leads to abortive annealing

1. Download : Download high-res image (137KB)
2. Download : Download full-size image

     

Protection of CDC25 phosphatases against oxidative stress in breast cancer cells: Evaluation of the implication of the thioredoxin system

Abstract

Reactive oxygen species regulate protein functionality. Cell cycle CDC25 phosphatases are targets of such oxidative regulation in vitro. We sought to evaluate if a thioredoxin (trx)-dependent redox regulation of CDC25 exists in cancer cells. For that purpose, we used MCF7 and MDA-MB 231 breast cancer cells, which express trx1 differentially, together with two trx/thioredoxin reductase (trxR) inhibitors, Auranofin and Acrolein. Auranofin could induce a full trxR inhibition associated with ROS production in both cell lines. Acrolein could provoke similar effects only in MDA-MB 231 cells with a low trx1 expression. Simultaneous trx1 oxidation and trxR inactivation occurred only in the presence of Acrolein and resulted in a G2-M cell cycle arrest, without full CDC25 inhibition in MDA-MB 231 cells. Our data suggest that the maintenance of CDC25 activity does not fully rely on the trx system in breast cancer cells, even in the presence of a major oxidative stress.