Fat Metabolism in Higher Plants XXXVI: Long Chain Fatty Acid Synthesis in Germinating Peas

A low lipid, high starch containing tissue, namely cotyledons of germinating pea seedlings was examined for its capacity to synthesize fatty acid. Intact tissue slices readily incorporate acetate-¹⁴C into fatty acids from C₁₆ to C₂₄. Although crude homogenates synthesize primarily 16:0 and 18:0 from malonyl CoA, subsequent fractionation into a 10,000g pellet, a 10⁵g pellet and supernatant (soluble synthetase) revealed that the 10⁵g pellet readily synthesizes C₁₆ to C₂₈ fatty acids whereas the 10,000g and the supernatant synthesize primarily C₁₆ and C₁₈. All systems require acyl carrier protein (ACP), TPNH, DPNH if malonyl CoA is the substrate and ACP, Mg²⁺, CO₂, ATP, TPNH, and DPNH if acetyl CoA is the substrate. The cotyledons of germinating pea seedlings appear to have a soluble synthetase and 10,000g particles for the synthesis of C₁₆ and C₁₈ fatty acid, and 10⁵g particles which specifically synthesize the very long chain fatty acid from malonyl CoA, presumably via malonyl ACP.     

Interannual variability of cyanobacterial blooms in lake erie

After a 20-year absence, severe cyanobacterial blooms have returned to Lake Erie in the last decade, in spite of negligible change in the annual load of total phosphorus (TP). Medium-spectral Resolution Imaging Spectrometer (MERIS) imagery was used to quantify intensity of the cyanobacterial bloom for each year from 2002 to 2011. The blooms peaked in August or later, yet correlate to discharge (Q) and TP loads only for March through June. The influence of the spring TP load appears to have started in the late 1990 s, after Dreissenid mussels colonized the lake, as hindcasts prior to 1998 are inconsistent with the observed blooms. The total spring Q or TP load appears sufficient to predict bloom magnitude, permitting a seasonal forecast prior to the start of the bloom.     

Desaturation of Oleic and Linoleic Acids by Leaves of Dark- and Light-grown Maize Seedlings

Oleate and linoleate desaturation in leaves of maize seedlings was largely independent of previous light treatment of the seedlings; there was no evidence of light-induced desaturase activities. These results are in sharp contrast to those observed with developing cucumber cotyledons in which pronounced increase in desaturation occurs after exposure of tissue to light. The rates of desaturation of oleate were about four times those of linoleate in both etiolated and 16-hour greened maize leaves. In both etiolated and greened tissues, about two-thirds of the label from oleate was esterified after 4 hours, half of which was in phosphatidylcholine. Phosphatidylcholine and diglyceride contained large proportions of [¹⁴C]linoleate formed from [¹⁴C]oleate but not [¹⁴C]linolenate. In monogalactolipid, about two-thirds of the labeled fatty acids were linolenate. In vivo desaturase activity was present in tissue of widely different levels of differentiation and chlorophyll content obtained from light-grown maize seedlings.     

Evolving proteins at Darwin's bicentenary

A report of the Biochemical Society/Wellcome Trust meeting 'Protein Evolution - Sequences, Structures and Systems', Hinxton, UK, 26-27 January 2009.     

Acute exercise boosts cell proliferation and the heat shock response in lymphocytes: correlation with cytokine production and extracellular-to-intracellular HSP70 ratio

Exercise stimulates immune responses, but the appropriate “doses” for such achievements are unsettled. Conversely, in metabolic tissues, exercise improves the heat shock (HS) response, a universal cytoprotective response to proteostasis challenges that are centred on the expression of the 70-kDa family of intracellular heat shock proteins (iHSP70), which are anti-inflammatory. Concurrently, exercise triggers the export of HSP70 towards the extracellular milieu (eHSP70), where they work as pro-inflammatory cytokines. As the HS response is severely compromised in chronic degenerative diseases of inflammatory nature, we wondered whether acute exercise bouts of different intensities could alter the HS response of lymphocytes from secondary lymphoid organs and whether this would be related to immunoinflammatory responses. Adult male Wistar rats swam for 20 min at low, moderate, high or strenuous intensities as per an overload in tail base. Controls remained at rest under the same conditions. Afterwards, mesenteric lymph node lymphocytes were assessed for the potency of the HS response (42 °C for 2 h), NF-κB binding activity, mitogen-stimulated proliferation and cytokine production. Exercise stimulated cell proliferation in an “inverted-U” fashion peaking at moderate load, which was paralleled by suppression of NF-κB activation and nuclear location, and followed by enhanced HS response in relation to non-exercised animals. Comparative levels of eHSP70 to iHSP70 (H-index) matched IL-2/IL-10 ratios. We conclude that exercise, in a workload-dependent way, stimulates immunoinflammatory performance of lymphocytes of tissues far from the circulation and this is associated with H-index of stress response, which is useful to assess training status and immunosurveillance balance.     

Population genomics: ageing by association

Mutations in the gene Klotho lead to premature ageing in mice. Recent work on human genetic variation has identified an association between a particular allele of Klotho and human lifespan. A harbinger of things to come, this work illustrates the power and growth potential for association studies of human ageing.     

Model Selection in Systems Biology Depends on Experimental Design

Experimental design attempts to maximise the information available for modelling tasks. An optimal experiment allows the inferred models or parameters to be chosen with the highest expected degree of confidence. If the true system is faithfully reproduced by one of the models, the merit of this approach is clear - we simply wish to identify it and the true parameters with the most certainty. However, in the more realistic situation where all models are incorrect or incomplete, the interpretation of model selection outcomes and the role of experimental design needs to be examined more carefully. Using a novel experimental design and model selection framework for stochastic state-space models, we perform high-throughput in-silico analyses on families of gene regulatory cascade models, to show that the selected model can depend on the experiment performed. We observe that experimental design thus makes confidence a criterion for model choice, but that this does not necessarily correlate with a model''s predictive power or correctness. Finally, in the special case of linear ordinary differential equation (ODE) models, we explore how wrong a model has to be before it influences the conclusions of a model selection analysis.     

Über den Verlauf eines schuppenorientierenden Gefälles beiGalleria mellonella

Summary Evidence for the existence of a concentration gradient in the segments ofGalleria mellonella and ofRhodnius prolixus has been reported elsewhere. InGalleria it is possible to determine the functional form of the gradient by measuring the deviation of the scales from their normal direction after the transplantation of a piece of the intersegmental integument from the anterior or the posterior margin into the segment. The calculated values indicate the force with which the scales are oriented in an axial direction. This force corresponds to the slope of the concentration gradient.Different curves are found for the forces depending on the origin of the graft (anterior or posterior margin). This seems to be the result of unequal shrinking of the grafts. The geometrical mean of the average of the forces for anterior grafts and that for posterior grafts is nearly constant all over the segment (only the parts near the segment margins could not be included in the measurement). Thus the concentration gradient declines almost linearly. Linearly declining concentrations are expected between two different but constant concentrations which may be assumed to be located in the anterior and the posterior margin of the segment.

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Ich danke Herrn Dr.Marcus für die großzügige Überlassung seiner Präparate und Herrn Dr.Schmidt-König für die hilfreiche Diskussion der statistischen Möglichkeiten dieses Falles. Die Arbeit wurde mit Unterstützung der Deutschen Forschungsgemeinschaft ausgeführt.     

Oligomerization,F-actin interaction,and membrane association of the ubiquitous mammalian coronin 3 are mediated by its carboxyl terminus

Coronin 3 is a ubiquitously expressed member of the coronin protein family in mammals. In fibroblasts and HEK 293 cells, it is localized both in the cytosol and in the submembranous cytoskeleton, especially at lamellipodia and membrane ruffles. The carboxyl terminus of all coronins contains a coiled coil suggested to mediate dimerization. We show here that in contrast to other coronin homologues, the recombinant human coronin 3 carboxyl terminus forms oligomers rather than dimers, and that this part is sufficient to bind to and cross-link F-actin in vitro. The carboxyl terminus alone also conferred membrane association in vivo, and removal of the coiled coil abolished membrane localization but not in vitro F-actin binding. Coronin 3 is exclusively extracted as an oligomer from both the cytosol and the membrane fraction. Because oligomerization was not reported for other coronins, it might be a key feature governing coronin 3-specific functions. Cytosolic coronin 3 showed a high degree of phosphorylation, which is likely to regulate the subcellular localization of the protein.     

Fat metabolism in higher plants. Further characterization of wheat germ acetyl coenzyme A carboxylase.

Wheat germ acetyl CoA carboxylase was purified 600-fold over the crude homogenate. The purified enzyme gave rise to complex electrophoretic patterns in dissociating gels. As isolated, the activity of wheat germ acetyl CoA carboxylase exhibited profound dependence on the composition of the reaction mixture. In addition to the substrates MgATP, HCO₃, and acetyl CoA, the enzyme required both free Mg²⁺ and K⁺ for optimal activity. The effects of the two ions were additive. At pH 8.5, Mg²⁺ activated the carboxylase by adding to the enzyme prior to the other reactants in an equilibrium ordered reaction mechanism.