Urinary excretion of lignans after administration of isolated plant lignans to rats: the effect of single dose and ten-day exposures

The difference in urinary excretion of mammalian and plant lignans in rats was determined after oral administration of equivalent doses (25 mg/kg of body weight) of 7-hydroxymatairesinol (HMR), lariciresinol (LAR), matairesinol (MR), and secoisolariciresinol (SECO). Twenty-four hours-urine samples were collected after a single dose and after administration of one dose/day for 10 days. Eight lignans were analysed in urine extracts using a high-performance liquid chromatography-tandem mass spectrometry method showing good sensitivity and repeatability. After a single dose of HMR, LAR, MR, and SECO, the main metabolites were 7-hydroxyenterolactone (HENL), cyclolariciresinol (CLAR), enterolactone (ENL), and enterodiol (END), respectively, but after 10-day exposure ENL was the main metabolite of all the tested lignans, showing a considerably higher excretion than after a single dose. Metabolic transformations of plant lignans into each other could also be observed.     

Lipid metabolism in the adipose tissues of a carnivore, the raccoon dog, during prolonged fasting

Previous studies on laboratory rodents, rabbits, and humans have demonstrated that adipose tissue fatty acid (FA) mobilization is selective, and its efficiency is related to the molecular structure of FAs. This study was undertaken to find out whether such preferences of FA mobilization are a general feature of mammalian white adipose tissue (WAT) and are also manifested in carnivores. Fractional mobilization of a wide spectrum of FAs was studied by gas-liquid chromatography from six subcutaneous (scapular, rump, ventral) and intra-abdominal (omental, mesenteric, retroperitoneal) WAT depots of raccoon dogs (Nyctereutes procyonoides) fed or fasted for 2 months. Fasting stimulated the mobilization of shorter-chain saturated, mono-unsaturated (MUFAs), and polyunsaturated FAs (PUFAs). The effects of unsaturation and the position of the first double bond from the methyl end were more inconsistent. The effect of double-bond position may be due to chain shortening of longer-chain MUFAs and preferential utilization of n-3 PUFAs over n-6 PUFAs. Moreover, there were site-specific differences in fractional mobilization, the omental adipose tissue being the most divergent. The in vivo FA mobilization from the regional WAT depots of a carnivore was selective, and the molecular structure of the FA affected its efficiency.     

Long-term forest composition and its drivers in taiga forest in NW Russia

Understanding the processes behind long-term boreal forest dynamics can provide information that assists in predicting future boreal vegetation under changing environmental conditions. Here, we examine Holocene stand-scale vegetation dynamics and its drivers at the western boundary of the Russian taiga forest in NW Russia. Fossil pollen and conifer stomata records from four small hollow sites and two lake sites are used to reconstruct local vegetation dynamics during the Holocene. Variation partitioning is used to assess the relative importance of the potential drivers (temperature, forest fires and growing site wetness) to the long-term stand-scale dynamics in taiga forest. All the main tree taxa, including the boreal keystone species Picea abies (Norway spruce) and Larix sibirica (Siberian larch), have been locally present since 10,000 cal yr bp. The constant Holocene presence of L. sibirica at three small hollow sites suggests a fast postglacial immigration of the species in northern Europe. Picea was present but not dominant at all study sites until its expansion between 8,000 and 7,000 cal yr bp markedly changed the forest structure through the suppression of Betula (birch), Pinus (pine) and Larix. Our results demonstrate that in general, the Holocene forest dynamics in our study region have been driven by temperature, but during short intervals the role of local factors, especially forest fires, has been prominent. The comparison between sites reveals the importance of local factors in stand-scale dynamics in taiga forests. Therefore, the future responses of taiga forest to climate change will be predominantly modulated by the local characteristics at the site.     

Clinical and genetic heterogeneity in Meckel syndrome

Meckel syndrome (MKS) is a lethal malformation syndrome characterised by posterior meningoencephalocele, polycystic kidneys, fibrotic changes of the liver, and polydactyly. We have previously shown a linkage to chromosome 17q in 17 Finnish Meckel families. In this study we have analysed one Italian, one Austrian (of Turkish origin) and three British MKS families (Caucasian, Pakistani, and Bangladeshi families) for linkage to the MKS locus on chromosome 17q22–q24. We did not observe co-segregation of the disease and marker haplotypes in the Austrian family or in the three British families, of which two represented classical MKS and one a slightly atypical MKS phenotype with longer survival of the patient. In the Italian family the affected and non-affected children did not share the same maternal chromosome and thus this family could represent the same allelic disease as the Finnish MKS families. These results suggest locus heterogeneity in Meckel syndrome – a feature previously suspected based on the highly variable clinical phenotype. Received: 2 June 1997 / Accepted: 12 June 1997     

Internal and external loading as regulators of nutrient concentrations in the agriculturally loaded Lake Pyhäjärvi (southwest Finland)

This study assesses the effects of external and internalloading on the nutrient concentrations in an agriculturallyloaded shallow lake. Using 13 years of observations of thelake's input and outflow, we calculated the long-term balancesof Tot-P and Tot-N. A more detailed balance, which includeddissolved nutrients and suspended solids, was estimated for anice-free period of one year. The contribution of the externalload was assessed using a mass-balance model. The internalload was estimated from the nutrient balances and on the basisof sedimentation measurements and bioassays. The drainagebasin of the lake provided most of the external nutrientinput; the remaining load was derived from atmosphericdeposition to the lake. The proportions of river-transported Pand N in dissolved form were 25% and 77%, respectively. Thelake retained >80% of the external load. Particulatenutrients settled to the bottom and were probably resuspendedseveral times before permanent sedimentation. Dissolvednutrients were bound by primary producers and a highproportion of dissolved P was removed with the fish catch.Dissolved N was also lost via denitrification. Themass-balance model showed that external loading only partlyregulated the mean annual nutrient concentrations in the lake.The regulation was probably due to internal loading, which washigh despite the efficient net retention of nutrients. Duringthe ice-free period, the temporal variations in nutrientconcentrations were controlled almost solely by internalprocesses, such as resuspension of inorganic and organicbottom matter. Although the internal load of bioavailable Pmay, under favourable conditions, exceed the external load,the mechanism by which bioavailable P is translocated from thebottom sediments to the water could not be fully identified.Abbreviations used in this paper follow the editor'srules.     

EcM fungal community structure, but not diversity, altered in a Pb-contaminated shooting range in a boreal coniferous forest site in Southern Finland

Boreal forests contain diverse fungal communities that form essential ectomycorrhizal symbioses with trees. To determine the effects of lead (Pb) contamination on ectomycorrhizal fungal communities associated with the dominant pine (Pinus sylvestris L.), we surveyed sporocarps for 3 years, analyzed morphotyped ectomycorrhizal root tips by direct sequencing, and 454-sequenced fungal communities that grew into in-growth bags during a 2-year incubation at a shooting range where sectors vary in the Pb load. We recorded a total of 32 ectomycorrhizal fungi that formed conspicuous sporocarps, 27 ectomycorrhizal fungal phylotypes from 294 root tips, and 116 ectomycorrhizal fungal operation taxonomic unit (OTUs) from a total of 8194 internal transcribed spacer-2 454 sequences. Our ordination analyses by nonparametric multidimensional scaling (NMS) indicated that the Pb enrichment induced a shift in the ectomycorrhizal community composition. This was visible as indicative trends in the sporocarp and root tip data sets, but was explicitly clear in the communities observed in the in-growth bags. The compositional shift in the ectomycorrhizal community was mainly attributable to an increase in the frequencies of OTUs assigned to genus Thelephora and to a decrease in the OTUs assigned to Pseudotomentella, Suillus, and Tylospora in Pb-contaminated areas when compared with the control. While the compositional shifts are clear, their functional consequences for the dominant trees or soil ecosystem function remain undetermined.     

Habitat heterogeneity drives the geographical distribution of beta diversity: the case of New Zealand stream invertebrates

To define whether the beta diversity of stream invertebrate communities in New Zealand exhibits geographical variation unexplained by variation in gamma diversity and, if so, what mechanisms (productivity, habitat heterogeneity, dispersal limitation, disturbance) best explain the observed broad‐scale beta diversity patterns. We sampled 120 streams across eight regions (stream catchments), spanning a north–south gradient of 12° of latitude, and calculated beta diversity (with both species richness and abundance data) for each region. We explored through a null model if beta diversity deviates from the expectation of stochastic assembly processes and whether the magnitude of the deviation varies geographically. We then performed multimodel inference analysis on the key environmental drivers of beta diversity, using Akaike's information criterion and model and predictor weights to select the best model(s) explaining beta diversity. Beta diversity was, unexpectedly, highest in the South Island. The null model analysis revealed that beta diversity was greater than expected by chance in all eight regions, but the magnitude of beta deviation was higher in the South Island, suggesting differences in environmental filtering and/or dispersal limitation between North and South Island. Habitat heterogeneity was the predominant driver of beta diversity of stream macroinvertebrates, with productivity having a secondary, and negative, contribution. This is one of the first studies accounting for stochastic effects while examining the ecological drivers of beta diversity. Our results suggest that local environmental heterogeneity may be the strongest determinant of beta diversity of stream invertebrates, more so than regional‐ or landscape‐scale variables.     

The N terminus of the adhesion G protein-coupled receptor GPR56 controls receptor signaling activity

GPR56 is an adhesion G protein-coupled receptor that plays a key role in cortical development. Mutations to GPR56 in humans cause malformations of the cerebral cortex, but little is known about the normal function of the receptor. We found that the large N terminus (NT) of GPR56 is cleaved from the rest of the receptor during processing but remains non-covalently associated with the seven-transmembrane region of the receptor, as indicated by coimmunoprecipitation of the two GPR56 fragments from both transfected cells and native tissue. We also found that truncation of the GPR56 NT results in constitutive activation of receptor signaling, as revealed by increased GPR56-stimulated signaling upon transfection of HEK-293 cells with truncated GPR56, greatly enhanced binding of β-arrestins by truncated GPR56 relative to the full-length receptor, extensive ubiquitination of truncated GPR56, and cytotoxicity induced by truncated GPR56 that could be rescued by cotransfection of cells with β-arrestin 2. Furthermore, we found that the GPR56 NT is capable of homophilic trans-trans interactions that enhance receptor signaling activity. On the basis of these findings, we suggest a model of receptor activation in which the large N terminus of GPR56 constrains receptor activity but N-terminal interactions (GPR56 NT with an extracellular ligand and/or GPR56 NT homophilic trans-trans associations) can remove this inhibitory influence of the N terminus to activate receptor signaling.