Plant Biology and Biogeochemistry Department annual report 1998

The annual report from the Plant Biology and Biogeochemistry Department aims to provide a summary of our research and achievements and to give an idea of the research directions in the Department. The Department is engaged in research to establish the scientific basis for new methods in industrial and agricultural production. Through basic and applied experimental research, the Department aspires to develop methods and technology for industrial and agricultural production, exerting less stress and strain on the environment. The research approach in the Department is mainly experimental. In the autumn of 1997 it was decided to reorganize and expand the Department and in 1998 the Department includes six research programmes and special facilities. Selected departmental research activities during 1998 are introduced and reviewed in seven chapters: 1. Introduction, 2. Plant-Microbe Symbioses, 3. Plant Products and Recycling of Biomass, 4. DLF-Risø Biotechnology, 5. Plant Genetics and Epidemiology, 6. Biogeochemistry, 7. Plant Ecosystems and Nutrient Cycling. The Department’s contribution to education and training are presented. Lists of publications, papers accepted for publications, guest lectures, exchange of scientists, lectures and poster presentations at international meetings are included in the report. Names of the scientific and technical staff members, visiting scientists, Postdoctoral fellows, Ph.D. students, M.Sc. students and apprentices are also listed

Calanus finmarchicus basin scale life history traits and role in community carbon turnover during spring

The copepod Calanus finmarchicus was investigated in four Subpolar Basins, Labrador, Irminger, Iceland, and Norwegian Seas, during spring, covering the time of ascent, grazing, and initiation of reproduction in the area. Lipid content, spawning activity, and stage composition and vital rates, such as egg and faecal pellet production were measured and linked to environmental parameters. Specific egg- and faecal pellet production rates varied with diatom biomass and were negatively correlated with temperature. Comparison of the various biological indicators revealed different life history traits C. finmarchicus has adopted in the different basins. In Labrador Sea, the females have invested in large eggs compared to the remaining basins. Labrador and Irminger Sea C. finmarchicus invest in size that we propose to be adaptation to cope with warmer overwintering habitats resulting in larger potential lipid storage capacity, while the Iceland and Norwegian Sea females can invest their remaining lipid storage in spring to fuel lipid-driven egg production. Grazing pressure on the phytoplankton community was estimated and compared between copepod and two dominating groups of protozooplankton; ciliates and heterotrophic dinoflagellates. Despite approximately the same biomass in the upper 100 m, the grazing impact of the protozoan grazers was an order of magnitude higher than the C. finmarchicus dominated mesozooplankton. This illustrates the importance to also include the smallest grazers when studying the spring bloom in high latitude marine ecosystems if the fate of the primary production should be fully understood.publishedVersio

Calcium Homeostasis in Myogenic Differentiation Factor 1 (MyoD)-Transformed, Virally-Transduced, Skin-Derived Equine Myotubes

Dysfunctional skeletal muscle calcium homeostasis plays a central role in the pathophysiology of several human and animal skeletal muscle disorders, in particular, genetic disorders associated with ryanodine receptor 1 (RYR1) mutations, such as malignant hyperthermia, central core disease, multiminicore disease and certain centronuclear myopathies. In addition, aberrant skeletal muscle calcium handling is believed to play a pivotal role in the highly prevalent disorder of Thoroughbred racehorses, known as Recurrent Exertional Rhabdomyolysis. Traditionally, such defects were studied in human and equine subjects by examining the contractile responses of biopsied muscle strips exposed to caffeine, a potent RYR1 agonist. However, this test is not widely available and, due to its invasive nature, is potentially less suitable for valuable animals in training or in the human paediatric setting. Furthermore, increasingly, RYR1 gene polymorphisms (of unknown pathogenicity and significance) are being identified through next generation sequencing projects. Consequently, we have investigated a less invasive test that can be used to study calcium homeostasis in cultured, skin-derived fibroblasts that are converted to the muscle lineage by viral transduction with a MyoD (myogenic differentiation 1) transgene. Similar models have been utilised to examine calcium homeostasis in human patient cells, however, to date, there has been no detailed assessment of the cells’ calcium homeostasis, and in particular, the responses to agonists and antagonists of RYR1. Here we describe experiments conducted to assess calcium handling of the cells and examine responses to treatment with dantrolene, a drug commonly used for prophylaxis of recurrent exertional rhabdomyolysis in horses and malignant hyperthermia in humans

Reconciling behavioral, bioenergetic, and oceanographic views of bowhead whale predation on overwintering copepods at an Arctic hotspot (Disko Bay, Greenland)

Bowhead whales (Balaena mysticetus) visit Disko Bay, West Greenland in winter and early spring to feed on Calanus spp., at a time of year when the copepods are still mostly in diapause and concentrated in near-bottom patches. Combining past observations of copepod abundance and distribution with detailed observations of bowhead whale foraging behaviour from telemetry suggests that if the whales target the highest-density patches, they likely consume 26–75% of the Calanus standing stock annually. A parallel bioenergetic calculation further suggests that the whales’ patch selection must be close to optimally efficient at finding hotspots of high density copepods near the sea floor in order for foraging in Disko Bay to be a net energetic gain. Annual Calanus consumption by bowhead whales is similar to median estimates of consumption by each of three zooplankton taxa (jellies, chaetognaths, and predatory copepods), and much greater than the median estimate of consumption by fish larvae, as derived from seasonal abundance and specific ingestion rates from the literature. The copepods’ self-concentration during diapause, far from providing a refuge from predation, is the behaviour that makes this strong trophic link possible. Because the grazing impact of the whales comes 6–10 months later than the annual peak in primary production, and because Disko Bay sits at the end of rapid advective pathways (here delineated by a simple numerical particle-tracking experiment), it is likely that these Calanus populations act in part as a long-distance energetic bridge between the whales and primary production hundreds or thousands of km away

Human skeletal muscle plasmalemma alters its structure to change its Ca2+-handling following heavy-load resistance exercise

High-force eccentric exercise results in sustained increases in cytoplasmic Ca2+ levels ([Ca2+]cyto), which can cause damage to the muscle. Here we report that a heavy-load strength training bout greatly alters the structure of the membrane network inside the fibres, the tubular (t-) system, causing the loss of its predominantly transverse organization and an increase in vacuolation of its longitudinal tubules across adjacent sarcomeres. The transverse tubules and vacuoles displayed distinct Ca2+-handling properties. Both t-system components could take up Ca2+ from the cytoplasm but only transverse tubules supported store-operated Ca2+ entry. The retention of significant amounts of Ca2+ within vacuoles provides an effective mechanism to reduce the total content of Ca2+ within the fibre cytoplasm. We propose this ability can reduce or limit resistance exercise-induced, Ca2+-dependent damage to the fibre by the reduction of [Ca2+]cyto to help maintain fibre viability during the period associated with delayed onset muscle soreness

Factor Xa Generation by Computational Modeling: An Additional Discriminator to Thrombin Generation Evaluation

Factor (f)Xa is a critical enzyme in blood coagulation that is responsible for the initiation and propagation of thrombin generation. Previously we have shown that analysis of computationally generated thrombin profiles is a tool to investigate hemostasis in various populations. In this study, we evaluate the potential of computationally derived time courses of fXa generation as another approach for investigating thrombotic risk. Utilizing the case (n = 473) and control (n = 426) population from the Leiden Thrombophilia Study and each individual's plasma protein factor composition for fII, fV, fVII, fVIII, fIX, fX, antithrombin and tissue factor pathway inhibitor, tissue factor-initiated total active fXa generation was assessed using a mathematical model. FXa generation was evaluated by the area under the curve (AUC), the maximum rate (MaxR) and level (MaxL) and the time to reach these, TMaxR and TMaxL, respectively. FXa generation was analyzed in the entire populations and in defined subgroups (by sex, age, body mass index, oral contraceptive use). The maximum rates and levels of fXa generation occur over a 10- to 12- fold range in both cases and controls. This variation is larger than that observed with thrombin (3–6 fold) in the same population. The greatest risk association was obtained using either MaxR or MaxL of fXa generation; with an ∼2.2 fold increased risk for individuals exceeding the 90th percentile. This risk was similar to that of thrombin generation(MaxR OR 2.6). Grouping defined by oral contraceptive (OC) use in the control population showed the biggest differences in fXa generation; a >60% increase in the MaxR upon OC use. FXa generation can distinguish between a subset of individuals characterized by overlapping thrombin generation profiles. Analysis of fXa generation is a phenotypic characteristic which may prove to be a more sensitive discriminator than thrombin generation among all individuals