A new device to measure the structural properties of the femur-anterior cruciate ligament-tibia complex

Previous studies of biomechanical properties of femur-anterior cruciate ligament-tibia complex (FATC) utilized a wide variety of testing methodologies, particularly with respect to ligament orientation relative to loading direction. A new device was designed and built to test the anterior-posterior displacement of the intact porcine knee at 30 and 90 deg of flexion, as well as the tensile properties of the FATC at any loading direction and flexion angle. Tensile tests were performed with the knees at 30 and 90 deg of flexion with the loading direction along either the axis of the tibia (tibial axis) or the axis of the anterior cruciate ligament (ligament axis). The results showed that the stiffness, ultimate load and energy absorbed were all significantly increased when the FATC was tested along the ligament axis. This study demonstrates the importance of alignment in the evaluation of the biomechanical characteristics of the femur-ACL-tibia complex.     

The codon 408 mutation associated with haplotype 2 is predominant in Polish families with phenylketonuria

Summary The incidence of phenylketonuria (PKU) in the western part of Poland is 1 in 5000 live births. Restriction fragment length polymorphism (RFLP) haplotypes at the phenylalanine hydroxylase locus have been analysed in 46 Polish families with PKU. Among 43 fully-informative families 16 RFLP haplotypes were identified. Haplotype 2 is the most frequently (62%) associated with Polish PKU alleles, and the codon 408 mutation is in complete linkage disequilibrium with this haplotype in Poland. This finding is in agreement with observations in other eastern European countries (German Democratic Republic, Czechoslovakia, and Hungary) and in contrast to the genotype distribution observed in western European countries. The present observation suggests the spread of classical PKU, due to the codon 408 mutation associated with haplotype 2, from east to west in European populations. Perhaps more important for genetic counselling, 62% of all PKU chromosomes in the Polish population can now be detected using only one mutantspecific oligonucleotide probe.     

Partial Purification and Characterization of Indol-3-Ylacetylglucosemyo-Inositol Indol-3-Ylacetyltransferase (Indoleacetic Acid-Inositol Synthase)

A procedure is described for the purification of the enzyme indol-3-ylacetylglucose:myo-inositol indol-3-ylacetyltransferase (IAA-myo-inositol synthase). This enzyme catalyzes the transfer of indol-3-ylacetate from 1-0-indol-3-ylacetyl-β-d-glucose to myo-inositol to form indol-3-ylacetyl-myo-inositol and glucose. A hexokinase or glucose oxidase based assay system is described. The enzyme has been purified approximately 16,000-fold, has an isoelectric point of pH 6.1 and yields three catalytically inactive bands upon acrylamide gel electrophoresis of the native protein. The enzyme shows maximum transferase activity with myo-inositol but shows some transferase activity with scyllo-inositol and myo-inosose-2. No transfer of IAA occurs with myo-inositol-d-galactopyranose, cyclohexanol, mannitol, or glycerol as acyl acceptor. The affinity of the enzyme for 1-0-indol-3-ylacetyl-β-d-glucose is, K_m = 30 micromolar, and for myo-inositol is, K_m = 4 millimolar. The enzyme does not catalyze the exchange incorporation of glucose into IAA-glucose indicating the reaction mechanism involves binding of IAA glucose to the enzyme with subsequent hydrolytic cleavage of the acyl moiety by the hydroxyl of myo-inositol to form IAA myo-inositol ester.     

Electron Paramagnetic Resonance and Spin Trapping Study of Radicals Formed During Reaction of Aromatic Amines with isoAmyl Nitrite Under Aprotic Conditions

Diazotization of primary aromatic amines with isoamyl nitrite in benzene at room temperature was studied employing EPR and spin trapping techniques. Nitrosodurene (ND). 2-methyl-2-nitrosopropane (MNP). and 5,5-dimethyl-pyrroline N-oxide (DMPO) were used as spin trapping agents. Aryl radicals were detected employing ND and MNP. Using DMPO as a spin trap most of the amines produced EPR spectra ascribed to adducts with aniline-type radicals (N-centred radicals). The assignments were verified using ¹⁵JN-labeled anilines. Similar spectra of DMPO adducts were recorded from amines treated with benzoyl peroxide or benzophenone plus UV. Possible mechanisms of formation of these adducts (radical trapping versus nucleophilic addition to DMPO followed by oxidation) during treatment of the amines with isoamyl nitrite are discussed.     

Species boundaries,phylogenetic relationships,and ecological differentiation inAnthriscus (Apiaceae)

Species boundaries and phylogenetic relationships of 17 taxa ofAnthriscus (Apiaceae), with special emphasis on the critical sect.Cacosciadium, were explored using morphological data with principal component analysis, phenetics, and phylogenetics. The analyses did not provide satisfactory resolution of taxa from sect.Cacosciadium and only four species were retained. The total number of species was reduced to nine. Sect.Cacosciadium is distinguished by only two synapomorphies while sects.Anthriscus andCaroides are better supported. Present geographic and ecological variation suggests that the radiation ofAnthriscus occurred through divergence of peripheral isolated populations adapting to different habitats: high montane meadows and screes, shady climax forests, and seasonally dry habitats at lower altitudes. The adaptive significance of particular morphological traits is discussed.     

Fluorescence study ofEscherichia coli cyclic AMP receptor protein

Time-resolved, steady-state fluorescence and fluorescence-detected circular dichroism (FDCD) have been used to resolve the fluorescence contributions of the two tryptophan residues, Trp-13 and Trp-85, in the cyclic AMP receptor protein (CRP). The iodide and acrylamide quenching data show that in CRP one tryptophan residue, Trp-85, is buried within the protein matrix and the other, Trp-13, is moderately exposed on the surface of the protein. Fluorescence-quenching-resolved spectra show that Trp-13 has emission at about 350 nm and contributes 76–83% to the total fluorescence emission. The Trp-85, unquenchable by iodide and acrylamide, has the fluorescence emission at about 337 nm. The time-resolved fluorescence measurements show that Trp-13 has a longer fluorescence decay time. The Trp-85 exhibits a shorter fluorescence decay time. In the CRP-cAMP complex the Trp-85, previously buried in the apoprotein becomes totally exposed to the iodide and acrylamide quenchers. The FDCD spectra indicate that in the CRP-cAMP complex Trp-85 remains in the same environment as in the protein alone. It has been proposed that the binding of cAMP to CRP is accompanied by a hinge reorientation of two protein domains. This allows for penetration of the quencher molecules into the Trp-85 residue previously buried in the protein matrix.     

Phytate dephosphorylation by free and immobilized cells ofSaccharomyces cerevisiae

Summary Saccharomyces cerevisiae in the form of baker's yeast, cells cultivated on a yeast extract-peptone-glucose medium, as well as cells immobilized in 18% (w/v) polyacrylamide gel showed the ability to hydrolyze 1.727 mM sodium phytate solution at 45°C, pH 4.6, in a stirred tank reactor. Seventy percent yield of dephosphorylation was observed after 2 h using a baker's yeast concentration of 5.8 g dry matter per 100 ml. Hydrolytic activity at 1.8–2.0 M Pi min^–1 was observed between 1st and 3rd h of the reaction in cells cultured 24 or 48 h. No inhibition by the substrate was found at sodium phytate concentrations of 0.587–1.727 mM. After 1.5 h of hydrolysis a single, well distinguished peak ofmyo-inositol-triphosphate was the main product found. By means of immobilization the stability of the biocatalyst was enhanced 3.3-fold and reached its half-life at 64 ninety-minute runs.     

Carbon uptake in Eurasian boreal forests dominates the high-latitude net ecosystem carbon budget

Arctic-boreal landscapes are experiencing profound warming, along with changes in ecosystem moisture status and disturbance from fire. This region is of global importance in terms of carbon feedbacks to climate, yet the sign (sink or source) and magnitude of the Arctic-boreal carbon budget within recent years remains highly uncertain. Here, we provide new estimates of recent (2003–2015) vegetation gross primary productivity (GPP), ecosystem respiration (R_eco), net ecosystem CO₂ exchange (NEE; R_eco − GPP), and terrestrial methane (CH₄) emissions for the Arctic-boreal zone using a satellite data-driven process-model for northern ecosystems (TCFM-Arctic), calibrated and evaluated using measurements from >60 tower eddy covariance (EC) sites. We used TCFM-Arctic to obtain daily 1-km² flux estimates and annual carbon budgets for the pan-Arctic-boreal region. Across the domain, the model indicated an overall average NEE sink of −850 Tg CO₂-C year⁻¹. Eurasian boreal zones, especially those in Siberia, contributed to a majority of the net sink. In contrast, the tundra biome was relatively carbon neutral (ranging from small sink to source). Regional CH₄ emissions from tundra and boreal wetlands (not accounting for aquatic CH₄) were estimated at 35 Tg CH₄-C year⁻¹. Accounting for additional emissions from open water aquatic bodies and from fire, using available estimates from the literature, reduced the total regional NEE sink by 21% and shifted many far northern tundra landscapes, and some boreal forests, to a net carbon source. This assessment, based on in situ observations and models, improves our understanding of the high-latitude carbon status and also indicates a continued need for integrated site-to-regional assessments to monitor the vulnerability of these ecosystems to climate change.     

Empirical testing of cryoconite granulation: Role of cyanobacteria in the formation of key biogenic structure darkening glaciers in polar regions

Cryoconite, the dark sediment on the surface of glaciers, often aggregates into oval or irregular granules serving as biogeochemical factories. They reduce a glacier's albedo, act as biodiversity hotspots by supporting aerobic and anaerobic microbial communities, constitute one of the organic matter (OM) sources on glaciers, and are a feeder for micrometazoans. Although cryoconite granules have multiple roles on glaciers, their formation is poorly understood. Cyanobacteria are ubiquitous and abundant engineers of cryoconite hole ecosystems. This study tested whether cyanobacteria may be responsible for cryoconite granulation as a sole biotic element. Incubation of Greenlandic, Svalbard, and Scandinavian cyanobacteria in different nutrient availabilities and substrata for growth (distilled water alone and water with quartz powder, furnaced cryoconite without OM, or powdered rocks from glacial catchment) revealed that cyanobacteria bind mineral particles into granules. The structures formed in the experiment resembled those commonly observed in natural cryoconite holes: they contained numerous cyanobacterial filaments protruding from aggregated mineral particles. Moreover, all examined strains were confirmed to produce extracellular polymeric substances (EPS), which suggests that cryoconite granulation is most likely due to EPS secretion by gliding cyanobacteria. In the presence of water as the only substrate for growth, cyanobacteria formed mostly carpet-like mats. Our data empirically prove that EPS-producing oscillatorialean cyanobacteria isolated from the diverse community of cryoconite microorganisms can form granules from mineral substrate and that the presence of the mineral substrate increases the probability of the formation of these important and complex biogeochemical microstructures on glaciers.