Differential perturbation of erythrocyte membrane-associated transport and enzyme activities by structurally related lipophilic compounds

The alteration of two erythrocyte plasma membrane functions, acetylcholine hydrolysis and glucose exchange, by a series of structurally related small lipophilic compounds which exhibit similar antihemolytic behavior was studied. 2-Methyldimethylaminoazobenzene is a more potent inhibitor of acetylcholinesterase than the 3′-methyl analogue, while the unsubstituted compound fails to inhibit. Esterase inhibition by the 2-methyl compound is noncompetitive and dependent on the anion composition of the assay buffer. The temperature dependence of acetylcholinesterase activity in the presence of the 2-methyl compound suggests that interaction with inhibitor is influenced by the state of lipids tightly bound to the enzyme. Glucose exchange is inhibited to the same extent by both methyl derivatives but not by the unsubstituted dye, and the temperature dependence in the presence of inhibitor is not grossly altered. The lack of correlation between inhibition of membrane function and stabilization of erythrocytes against osmotic hemolysis is discussed.     

Perspectives of reducing the deleterious effect of de-icing salt upon vegetation

Summary The protective effect of a nutrient solution upon young forest plants, seriously stressed by de-icing salt (NaCl) were investigated. The results show, that the adsorbed salt ions in the soil are already exchanged at low concentrations (2 bars), whilst plant survival and growth showed only at higher concentrations (10 bars) a significant optimum.     

Understanding seagrass resilience in temperate systems: the importance of timing of the disturbance

Temperate seagrass meadows form valuable ecosystems in coastal environments and present a distinct seasonal growth. They are threatened by an increasing amount of stressors, potentially affecting their capacity to recover from disturbances. We hypothesized that their resilience to disturbances is affected by seasonal dynamics. Hence, we investigated the effect of the timing of the disturbance on seagrass Leaf Area Index (as a proxy for presence, or ‘visible’ status), recovery from disturbance (as a proxy for meadow resilience), and rhizome carbohydrates (as a proxy for longer term resilience) by a series of four disturbance-recovery field experiments spread over the growing season at two sites in Shandong Province, China. During the course of the growing season, we found the highest recovery at the start of the growing season, lowest recovery when Leaf Area Index peaked around mid-growing season, and intermediate recovery when Leaf Area Index decreased at the end of the growing season. Rhizome carbohydrates were not affected by disturbances during any of the four experimental periods and could not explain the low recovery during mid-growing season. The two sites differed in exposure and in the occurrence of incidents like a green tide and storms, which affected recovery. However, general patterns were similar; timing strongly influenced the indicator of meadow resilience and its correlation with presence during the two main seagrass growth phases. Our results emphasize the importance of carefully considering timing in the evaluation of seagrass resilience in temperate systems. Furthermore, our study implies that, to effectively protect seagrass beds, conservation management should aim at avoiding disturbances particularly during the peak of the growing season, when resilience is lowest.     

Niche construction and the behavioral context of plant and animal domestication

Many animal species attempt to enhance their environments through niche construction or environmental engineering. Such efforts at environmental modification are proposed to play an important and underappreciated role in shaping biotic communities and evolutionary processes. 1 , 2 Homo sapiens is acknowledged as the ultimate niche constructing species in terms of our rich repertoire of ecosystem engineering skills and the magnitude of their impact. We have been trying to make the world a better place—for ourselves—for tens of thousands of years. I argue here that it is within this general context of niche‐construction behavior that our distant ancestors initially domesticated plants and animals and, in the process, first gained the ability to significantly alter the world's environments. The general concept of niche construction also provides the logical link between current efforts to understand domestication being conducted at two disconnected scales of analysis. At the level of individual plant and animal species, on one hand, there recently have been significant advances in our knowledge of the what, when, and where of domestication of an ever‐increasing number of species worldwide. 3 At the same time, large‐scale regional or universal developmental models of the transition to food production continue to be formulated. These incorporate a variety of “macro‐evolutionary” causal variables that may account for why human societies first domesticated plants and animals. 4 , 5 This essay employs the general concept of niche construction to address the intervening question of how, and to connect these two scales of analysis by identifying the general behavioral context within which human societies responded to “macroevolutionary” causal variables and forged new human plant or animal relationships of domestication.     

Ca2+-induced isotropic motion and phosphatidylcholine flip-flop in phosphatidylcholine-cardiolipin bilayers

Ca²⁺ induces a structural change in phosphatidylcholine-cardiolipin bilayers, which is visualised by freeze-fracturing as lipidic particles associated with the bilayer and is detected by ³¹P-NMR as isotropic motion of the phospholipids. In this structure a rapid transbilayer movement of phosphatidylcholine and a highly increased permeability towards Mn²⁺ are observed.     

Prize Crossword

This article describes four rapid tests for the viability of stored seeds. Since each test is easily applied, and does not require any apparatus other than a conductance bridge and a conductivity cell, it is suggested that the tests could be employed as a basis for class experiments, individual projects at sixth-form level, or for more advanced research work. Typical results are given and some possible applications of the tests are discussed.     

Modelling the effects of climate change on the distribution and production of marine fishes: accounting for trophic interactions in a dynamic bioclimate envelope model

Climate change has already altered the distribution of marine fishes. Future predictions of fish distributions and catches based on bioclimate envelope models are available, but to date they have not considered interspecific interactions. We address this by combining the species‐based Dynamic Bioclimate Envelope Model (DBEM) with a size‐based trophic model. The new approach provides spatially and temporally resolved predictions of changes in species' size, abundance and catch potential that account for the effects of ecological interactions. Predicted latitudinal shifts are, on average, reduced by 20% when species interactions are incorporated, compared to DBEM predictions, with pelagic species showing the greatest reductions. Goodness‐of‐fit of biomass data from fish stock assessments in the North Atlantic between 1991 and 2003 is improved slightly by including species interactions. The differences between predictions from the two models may be relatively modest because, at the North Atlantic basin scale, (i) predators and competitors may respond to climate change together; (ii) existing parameterization of the DBEM might implicitly incorporate trophic interactions; and/or (iii) trophic interactions might not be the main driver of responses to climate. Future analyses using ecologically explicit models and data will improve understanding of the effects of inter‐specific interactions on responses to climate change, and better inform managers about plausible ecological and fishery consequences of a changing environment.