Characterization, size estimation and solubilization of α-macroglobulin complex receptors in liver membranes

Receptors for α₂-macroglobulin-proteinase complexes have been characterized in rat and human liver membranes. The affinity for binding of ¹²⁵I-labelled α₂-macroglobulin · trypsin to rat liver membranes was markedly pH-dependent in the physiological range with maximum binding at pH 7.8–9.0. The half-time for association was about 5 min at 37°C in contrast to about 5 h at 4°C. The half-saturation constant was about 100 pM at 4°C and 1 nM at 37°C (pH 7.8). The binding capacity was approx. 300 pmol per g protein for rat liver membranes and about 100 pmol per g for human membranes. Radiation inactivation studies showed a target size of 466 ± 71 kDa (S.D., n = 7) for α₂-macroglobulin · trypsin binding activity. Affinity cross-linking to rat and human membranes of ¹²⁵I-labelled rat α₁-inhibitor-3 · chymotrypsin, a 210 kDa analogue which binds to the α₂-macroglobulin receptors in hepatocytes (Gliemann, J. and Sottrup-Jensen, L. (1987) FEBS Lett. 221, 55–60), followed by SDS-polyacrylamide gel electrophoresis, revealed radioactivity in a band not distinguishable from that of cross-linked α₂-macroglobulin (720 kDa). This radioactivity was absent when membranes with bound ¹²⁵I-α₁-inhibitor-3 complex were treated with EDTA before cross-linking and when incubation and cross-linking were carried out in the presence of a saturating concentration of unlabelled complex. The saturable binding activity was maintained when membranes were solubilized in the detergent 3-[(3-cholamidopropyl)dimethylammonio]profane sulfonate (CHAPS) and the size of the receptor as estimated by cross-linking experiments was shown to be similar to that determined in the membranes. It is concluded that liver membranes contain high concentrations of an approx. 400–500 kDa α₂-macroglobulin receptor soluble in CHAPS. The soluble preparation should provide a suitable material for purification and further characterization of the receptor.     

The biology and feeding ecology of Arctic charr in the Kerguelen Islands

Subsequent to their introduction in the 1950s, Arctic charr Salvelinus alpinus have been able to establish a self-sustaining population that has adapted to the unique conditions of the sub-Antarctic Kerguelen Islands. Here, 48 individuals (198–415 mm) were caught with gillnets and their basic biology and feeding ecology were examined using stable isotope analysis. The Lac des Fougères population split use of littoral and pelagic resources evenly, although larger fish relied more heavily on littoral production and appear to follow the size-dependent life history habitat template seen in many Scandinavian lakes where smaller sized individuals occupy the pelagic zone and larger individuals dominate the littoral habitat. In Kerguelen, Arctic charr mature at the same ages (5.6 years) as Arctic charr in both sub-Arctic and Arctic lakes. Although mortality was average in comparison to comparator sub-Arctic lakes, it was high in comparison to Arctic lakes. Maximal age (>7+) was at the lower end of the range typically seen in sub-Arctic lakes. Although they inhabit a resource-poor environment, Kerguelen Arctic charr showed no evidence of cannibalism. Thus, while Arctic charr can survive and reproduce in the relatively unproductive Kerguelen lake environments, survival and growth nevertheless appear to be traded off against survival and longevity. The uniqueness of the population location and the recency of its introduction suggest that further monitoring of the population has the potential to yield valuable insights into both the adaptability of the species and its likely responses to ongoing large-scale environmental change as represented by climate change.     

Movement patterns of temperate wrasses (Labridae) within a small marine protected area

The movement patterns of three commercially important wrasse (Labridae) species inside a small marine protected area (~ 0.15 km²) on the west coast of Norway were analysed over a period of 21 months. The mean distance between capture and recapture locations varied between 10 and 187 m, and was species and season specific. The extent of movement was not related to body size or sex. These results imply that a network of small strategically located marine protected areas can be used as management tools to protect wrasses from size- and sex-selective fishing mortality.     

Functional Characterization of Key Enzymes involved in l-Glutamate Synthesis and Degradation in the Thermotolerant and Methylotrophic Bacterium Bacillus methanolicus

Bacillus methanolicus wild-type strain MGA3 secretes 59 g/liter⁻¹ of l-glutamate in fed-batch methanol cultivations at 50°C. We recently sequenced the MGA3 genome, and we here characterize key enzymes involved in l-glutamate synthesis and degradation. One glutamate dehydrogenase (GDH) that is encoded by yweB and two glutamate synthases (GOGATs) that are encoded by the gltAB operon and by gltA2 were found, in contrast to Bacillus subtilis, which has two different GDHs and only one GOGAT. B. methanolicus has a glutamine synthetase (GS) that is encoded by glnA and a 2-oxoglutarate dehydrogenase (OGDH) that is encoded by the odhAB operon. The yweB, gltA, gltB, and gltA2 gene products were purified and characterized biochemically in vitro. YweB has a low K_m value for ammonium (10 mM) and a high K_m value for l-glutamate (250 mM), and the V_max value is 7-fold higher for l-glutamate synthesis than for the degradation reaction. GltA and GltA2 displayed similar K_m values (1 to 1.4 mM) and V_max values (4 U/mg) for both l-glutamate and 2-oxoglutarate as the substrates, and GltB had no effect on the catalytic activities of these enzymes in vitro. Complementation assays indicated that GltA and not GltA2 is dependent on GltB for GOGAT activity in vivo. To our knowledge, this is the first report describing the presence of two active GOGATs in a bacterium. In vivo experiments indicated that OGDH activity and, to some degree, GOGAT activity play important roles in regulating l-glutamate production in this organism.     

Initiating Change: Negotiations of Subjectivity in a Danish Activation Programme for Young Adults with Psychosocial Problems and Common Mental Disorders

Culture, Medicine, and Psychiatry - An increasing number of young adults in Denmark experience difficulties in completing their education and holding down a job. Many of these young adults have...     

A nationwide school fruit and vegetable policy and childhood and adolescent overweight: A quasi-natural experimental study

BackgroundSchool free fruit and vegetable (FFV) policies are used to promote healthy dietary habits and tackle obesity; however, our understanding of their effects on weight outcomes is limited. We assess the effect of a nationwide FFV policy on childhood and adolescent weight status and explore heterogeneity by sex and socioeconomic position.Methods and findingsThis study used a quasi-natural experimental design. Between 2007 and 2014, Norwegian combined schools (grades 1–10, age 6 to 16 years) were obligated to provide FFVs while elementary schools (grades 1–7) were not. We used 4 nationwide studies (n = 11,215 children) from the Norwegian Growth Cohort with longitudinal or cross-sectional anthropometric data up to age 8.5 and 13 years to capture variation in FFV exposure. Outcomes were body mass index standard deviation score (BMI_SDS), overweight and obesity (OW/OB), waist circumference (WC), and weight to height ratio (WtHR) at age 8.5 years, and BMI_SDS and OW/OB at age 13 years. Analyses included longitudinal models of the pre- and post-exposure trajectories to estimate the policy effect. The participation rate in each cohort was >80%, and in most analyses <4% were excluded due to missing data. Estimates were adjusted for region, population density, and parental education. In pooled models additionally adjusted for pre-exposure BMI_SDS, there was little evidence of any benefit or unintended consequence from 1–2.5 years of exposure to the FFV policy on BMI_SDS, OW/OB, WC, or WtHR in either sex. For example, boys exposed to the FFV policy had a 0.05 higher BMI_SDS (95% CI: −0.04, 0.14), a 1.20-fold higher odds of OW/OB (95% CI: 0.86, 1.66) and a 0.3 cm bigger WC (95% CI: −0.3, 0.8); while exposed girls had a 0.04 higher BMI_SDS (95% CI: −0.04, 0.13), a 1.03 fold higher odds of OW/OB (95% CI: 0.75, 1.39), and a 0-cm difference in WC (95% CI: −0.6, 0.6). There was evidence of heterogeneity in the policy effect estimates at 8.5 years across cohorts and socioeconomic position; however, these results were inconsistent with other comparisons. Analysis at age 13 years, after 4 years of policy exposure, also showed little evidence of an effect on BMI_SDS or OW/OB. The main limitations of this study are the potential for residual confounding and exposure misclassification, despite efforts to minimize their impact on conclusions.ConclusionsIn this study we observed little evidence that the Norwegian nationwide FFV policy had any notable beneficial effect or unintended consequence on weight status among Norwegian children and adolescents.

Bente Øvrebø and colleagues assess whether a nationwide free school fruit and vegetable policy was associated with weight outcomes in children and early adolescents in Norway.