Oscillations in glycolysis: multifactorial quantitative analysis in muscle extract

A multifactorial quantitative analysis of oscillations in glycolysis was conducted in the postmicrosomal supernatant of rat muscle homogenates incubated in the presence of yeast hexokinase. Oscillations in adenine nucleotides, D-fructose 1,6-bisphosphate, triose phosphates, L-glycerol 3-phosphate, ³HOH generation from D-[5-³H]glucose, NADH and L-lactate production were documented. The occurrence of such oscillations were found to depend mainly on the balance between the consumption of ATP associated with the phosphorylation of D-glucose, as catalyzed by both yeast and muscle hexokinase, and the net production of ATP resulting from the further catabolism of D-fructose 6-phosphate, as initiated by activation of phosphofructokinase. The oscillatory pattern was suppressed in the presence of D-fructose 2,6-bisphosphate. It is proposed that the quantitative information gathered in this study may set the scene for further studies in extracts of cells other than myocytes, e. g. hepatocytes and pancreatic islet cells, in which no oscillation of glycolysis was so far observed.     

Gulf Stream warm core rings: phytoplankton in two fall rings of different ages

Warm core ring (WCR) 82-H was sampled in September–October(1982) as a Gulf Stream meander pinched off and became a ring.It is compared with the 3-month-old WCR 81-D, visited September–October(1981). Although the rings have different histories, their phytoplanktonassemblages share some characteristics. Using cluster analysesbased on quantitative group counts, a station from one ringoccasionally clusters most closely with a station from the otherring, showing a similar balance of organisms. The younger ringat the time of sampling, WCR 82-H, had lower diversity, fewershelf species, and greater consistency between stations, exceptfor a high level of Oscillatoria in the meander before the ringpinched off. Interaction with slope water was seen principallyat the ring margin. WCR 81-D, on the other hand, showed a greatdeal of structure, and immediate dilutions with slope waterand the Gulf Stream were apparent, with higher diversity beforeand a week after such interactions. The upper water column ofwarm core rings, although showing evidence of physical mixing,can exhibit stratification of species, even after a storm.     

Summer drought exposure,stand structure,and soil properties jointly control the growth of European beech along a steep precipitation gradient in northern Germany

Increasing exposure to climate warming-related drought and heat threatens forest vitality in many regions on earth, with the trees' vulnerability likely depending on local climatic aridity, recent climate trends, edaphic conditions, and the drought acclimatization and adaptation of populations. Studies exploring tree species' vulnerability to climate change often have a local focus or model the species' entire distribution range, which hampers the separation of climatic and edaphic drivers of drought and heat vulnerability. We compared recent radial growth trends and the sensitivity of growth to drought and heat in central populations of a widespread and naturally dominant tree species in Europe, European beech (Fagus sylvatica), at 30 forest sites across a steep precipitation gradient (500–850 mm year⁻¹) of short length to assess the species' adaptive potential. Size-standardized basal area increment remained more constant during the period of accelerated warming since the early 1980s in populations with >360 mm growing season precipitation (April–September), while growth trends were negative at sites with <360 mm. Climatic drought in June appeared as the most influential climatic factor affecting radial growth, with a stronger effect at drier sites. A decadal decrease in the climatic water balance of the summer was identified as the most important factor leading to growth decline, which is amplified by higher stem densities. Inter-annual growth variability has increased since the early 1980s, and variability is generally higher at drier and sandier sites. Similarly, within-population growth synchrony is higher at sandier sites and has increased with a decrease in the June climatic water balance. Our results caution against predicting the drought vulnerability of trees solely from climate projections, as soil properties emerged as an important modulating factor. We conclude that beech is facing recent growth decline at drier sites in the centre of its distribution range, driven by climate change-related climate aridification.     

PSEUDO-NITZSCHIA PUNGENS AND P. MULTISENES (BACILLARIOPHYCEAE): NUCLEAR RIBOSOMAL DNAS AND SPECIES DIFFERENCES1

The region of the nuclear ribosomal DNA (rDNA) operon containing the small subunit (SSU), internal transcribed spacer 1 (ITS1), and a portion of the 5.8s rDNA gene was sequenced in one isolate each of Pseudo-nitzschia multiseries (Hasle) Hasle and Pseudo-nitzschia pungens (Grunow in Cleve & Möller) Hasle. The SSUs of these two species were highly similar, differing only in 14 point mutations and one insertion/deletion in 1774 bp. The ITS1 sequences were more variable, with 57 point mutations and three insertion/deletions in 257 bp. There were no differences in 44 bp of the 5.8S sequences. Restriction fragment patterns (RFPs) for the restriction endonucleases HaeIII, Hha1, and Rsa1 for 13 isolates of P. multiseries from the Atlantic, Pacific, and Gulf coasts of the United States and 16 isolates of P. pungens from the three coasts of the United States, in addition to Japan and China, were compared. There were differences between the RFPs of P. multiseries and P. pungens that corresponded to sites mapped by the DNA sequences, but no infraspecific variation in RFPs was observed for either species. The differences in RFPs correlate with morphological, immunological, and other rDNA differences and support the recognition of these taxa as separate species.     

Evolution of precopulatory and post‐copulatory strategies of inbreeding avoidance and associated polyandry

Inbreeding depression is widely hypothesized to drive adaptive evolution of precopulatory and post‐copulatory mechanisms of inbreeding avoidance, which in turn are hypothesized to affect evolution of polyandry (i.e. female multiple mating). However, surprisingly little theory or modelling critically examines selection for precopulatory or post‐copulatory inbreeding avoidance, or both strategies, given evolutionary constraints and direct costs, or examines how evolution of inbreeding avoidance strategies might feed back to affect evolution of polyandry. Selection for post‐copulatory inbreeding avoidance, but not for precopulatory inbreeding avoidance, requires polyandry, whereas interactions between precopulatory and post‐copulatory inbreeding avoidance might cause functional redundancy (i.e. ‘degeneracy’) potentially generating complex evolutionary dynamics among inbreeding strategies and polyandry. We used individual‐based modelling to quantify evolution of interacting precopulatory and post‐copulatory inbreeding avoidance and associated polyandry given strong inbreeding depression and different evolutionary constraints and direct costs. We found that evolution of post‐copulatory inbreeding avoidance increased selection for initially rare polyandry and that evolution of a costly inbreeding avoidance strategy became negligible over time given a lower‐cost alternative strategy. Further, fixed precopulatory inbreeding avoidance often completely precluded evolution of polyandry and hence post‐copulatory inbreeding avoidance, but fixed post‐copulatory inbreeding avoidance did not preclude evolution of precopulatory inbreeding avoidance. Evolution of inbreeding avoidance phenotypes and associated polyandry is therefore affected by evolutionary feedbacks and degeneracy. All else being equal, evolution of precopulatory inbreeding avoidance and resulting low polyandry is more likely when post‐copulatory inbreeding avoidance is precluded or costly, and evolution of post‐copulatory inbreeding avoidance greatly facilitates evolution of costly polyandry.     

Enantioselective inclusion complexation of 2,3,4,6-tetra-O-acetyl-D-glycopyranose as a chiral host with (+)-(r)-phenylethylamine: x-ray characterization of the complex

X-ray analysis of the crystalline product obtained by reaction of 2,3,4,6-Tetra-O-acetyl-D-glycopyranose with phenylethylamine revealed the formation of a real one-to-one inclusion complex. This complexaion is highly stereoselective, because only the (+)-R-enantiomeric form of the amine is included. Analogies to the mode of complexation of cellulose triaceate with chiral molecules in ?inclusion chromatography”? are discussed.     

An Invasive Fish and the Time-Lagged Spread of Its Parasite across the Hawaiian Archipelago

Efforts to limit the impact of invasive species are frustrated by the cryptogenic status of a large proportion of those species. Half a century ago, the state of Hawai''i introduced the Bluestripe Snapper, Lutjanus kasmira, to O''ahu for fisheries enhancement. Today, this species shares an intestinal nematode parasite, Spirocamallanus istiblenni, with native Hawaiian fishes, raising the possibility that the introduced fish carried a parasite that has since spread to naïve local hosts. Here, we employ a multidisciplinary approach, combining molecular, historical, and ecological data to confirm the alien status of S. istiblenni in Hawai''i. Using molecular sequence data we show that S. istiblenni from Hawai''i are genetically affiliated with source populations in French Polynesia, and not parasites at a geographically intermediate location in the Line Islands. S. istiblenni from Hawai''i are a genetic subset of the more diverse source populations, indicating a bottleneck at introduction. Ecological surveys indicate that the parasite has found suitable intermediate hosts in Hawai''i, which are required for the completion of its life cycle, and that the parasite is twice as prevalent in Hawaiian Bluestripe Snappers as in source populations. While the introduced snapper has spread across the entire 2600 km archipelago to Kure Atoll, the introduced parasite has spread only half that distance. However, the parasite faces no apparent impediments to invading the entire archipelago, with unknown implications for naïve indigenous Hawaiian fishes and the protected Papahānaumokuākea Marine National Monument.     

Negative density-dependent dispersal emerges from the joint evolution of density- and body condition-dependent dispersal strategies

Empirical studies have documented both positive and negative density-dependent dispersal, yet most theoretical models predict positive density dependence as a mechanism to avoid competition. Several hypotheses have been proposed to explain the occurrence of negative density-dependent dispersal, but few of these have been formally modeled. Here, we developed an individual-based model of the evolution of density-dependent dispersal. This model is novel in that it considers the effects of density on dispersal directly, and indirectly through effects on individual condition. Body condition is determined mechanistically, by having juveniles compete for resources in their natal patch. We found that the evolved dispersal strategy was a steep, increasing function of both density and condition. Interestingly, although populations evolved a positive density-dependent dispersal strategy, the simulated metapopulations exhibited negative density-dependent dispersal. This occurred because of the negative relationship between density and body condition: high density sites produced low-condition individuals that lacked the resources required for dispersal. Our model, therefore, generates the novel hypothesis that observed negative density-dependent dispersal can occur when high density limits the ability of organisms to disperse. We suggest that future studies consider how phenotype is linked to the environment when investigating the evolution of dispersal.