Solubilization and Mineralization of Lignin by White Rot Fungi

The white rot fungi Lentinula edodes, Phanerochaete chrysosporium, Pleurotus sajor-caju, Flammulina velutipes, and Schizophyllum commune were grown in liquid media containing ¹⁴C-lignin-labelled wood, and the formation of water-soluble ¹⁴C-labelled products and ¹⁴CO₂, the growth of the fungi, and the activities of extracellular lignin peroxidase, manganese peroxidase, and laccase were measured. Conditions that affect the rate of lignin degradation were imposed, and both long-term (0- to 16-day) and short-term (0- to 72-h) effects on the production of the two types of product and on the activities of the enzymes were monitored. The production of ¹⁴CO₂-labelled products from the aqueous ones was also investigated. The short-term studies showed that the different conditions had different effects on the production of the two products and on the activities of the enzymes. Nitrogen sources inhibited the production of both products by all species when differences in growth could be discounted. Medium pH and manganese affected lignin degradation by the different species differently. With P. chrysosporium, the results were consistent, with lignin peroxidase playing a role in lignin solubilization and manganese peroxidase being important in subsequent CO₂ production.     

Population structure and mycelial phenotypic variability of the ectomycorrhizal basidiomycete Laccaria bicolor (Maire) Orton

Mating type allele distribution and phenotypic variability were investigated in field populations of Laccaria bicolor. Sporophores associated with Norway spruce (Picea abies), colonized by natural sources of inoculum and growing in a seed orchard, were sampled to obtain dikaryotic strains and assay their phenotypic variability for traits important to the symbiosis. Basid-iospores were also collected for mating type analysis of different mycelia. Four sporophore mating types were identified containing seven A and five B factors. Out-breeding efficiency was estimated at 73.8% and the population was slightly inbred. Crosses with previously characterized L. bicolor strains from two nearby populations identified in total six sporophore mating types and ten A and nine B factors, for an estimated outbreeding efficiency (85.7%) similar to previous studies of more spatially disparate Laccaria spp. populations. Dikaryotic strains were tested for mycelial growth rate, as a measure of their competitive ability, on agar media containing a soluble (NaH₂PO₄), or an insoluble (CaHPO₄) phosphate source. Their ability to solubilize the latter was also tested to assess their relative capacity to access insoluble, inorganic phosphate. In most cases, significant variation was detected among strains from the same site for all variables. On three sites (VC4, VC5 and VC7), each determined previously to possess a uniform mycelial genotype, phenotypic variability was likely due to epigenetic variation among different strains of the same genotype. Possible evidence for dikaryon-monokaryon crosses was observed in vivo on one sample site (VC2) where adjacent mycelia shared two mating factors. The phenotypic variability of different mycelial genotypes reflected their genetic variability observed as mating type allele diversity and underlined the importance of basidiospore dispersal in introducing new genotypes into the population. The reproductive strategies of L. bicolor are discussed and compared to those of other basidiomycete species.     

Variation in Fine Root Characteristics and Nutrient Dynamics Across Alaskan Ecosystems

Ecosystems - Carbon cycle perturbations in high-latitude ecosystems associated with rapid warming can have implications for the global climate. Belowground biomass is an important component of the...     

The design and synthesis of purine inhibitors of CDK2. III

Cyclin-dependent kinases (CDKs) belong to a class of enzymes that control the ability of a cell to enter into and proceed through the cell division cycle. Using purine as a scaffold, we have synthesized a number of nanomolar inhibitors of CDK-2/cyclin E. In this report, the synthesis of a series of piperidine-substituted purine analogs will be presented, as well as some of their in vitro and in vivo biological effects.     

Stable isotopic studies of n-alkane metabolism by a sulfate-reducing bacterial enrichment culture

Gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy were used to study the metabolism of deuterated n-alkanes (C6 to C12) and 1-13C-labeled n-hexane by a highly enriched sulfate-reducing bacterial culture. All substrates were activated via fumarate addition to form the corresponding alkylsuccinic acid derivatives as transient metabolites. Formation of d14-hexylsuccinic acid in cell extracts from exogenously added, fully deuterated n-hexane confirmed that this reaction was the initial step in anaerobic alkane metabolism. Analysis of resting cell suspensions amended with 1-13C-labeled n-hexane confirmed that addition of the fumarate occurred at the C-2 carbon of the parent substrate. Subsequent metabolism of hexylsuccinic acid resulted in the formation of 4-methyloctanoic acid, and 3-hydroxy-4-methyloctanoic acid was tentatively identified. We also found that 13C nuclei from 1-13C-labeled n-hexane became incorporated into the succinyl portion of the initial metabolite in a manner that indicated that 13C-labeled fumarate was formed and recycled during alkane metabolism. Collectively, the findings obtained with a sulfate-reducing culture using isotopically labeled alkanes augment and support the previously proposed pathway (H. Wilkes, R. Rabus, T. Fischer, A. Armstroff, A. Behrends, and F. Widdel, Arch. Microbiol. 177:235-243, 2002) for metabolism of deuterated n-hexane by a denitrifying bacterium.     

The permeability of SPION over an artificial three-layer membrane is enhanced by external magnetic field

Background  

Sensorineural hearing loss, a subset of all clinical hearing loss, may be correctable through the use of gene therapy. We are testing a delivery system of therapeutics through a 3 cell-layer round window membrane model (RWM model) that may provide an entry of drugs or genes to the inner ear. We designed an in vitro RWM model similar to the RWM (will be referred to throughout the paper as RWM model) to determine the feasibility of using superparamagnetic iron oxide (Fe₃O₄) nanoparticles (SPION) for targeted delivery of therapeutics to the inner ear.     

Cryptolepiota, a new sequestrate genus in the Agaricaceae with evidence for adaptive radiation in western North America

Phylogenetic analyses based on nLSU and ITS sequence data indicate that the sequestrate genus Gigasperma is polyphyletic. Gigasperma cryptica, which is known only from New Zealand, has affinities with the Cortinariaceae whereas G. americanum and two additional undescribed taxa from western North America are derived from Lepiota within the Agaricaceae. The three North American taxa appear to be recently evolved and are closely related. They occur in similar environments and form a well supported clade indicating that adaptive radiation has occurred within this group of fungi. An independent genus with sequestrate fructifications, Cryptolepiota is proposed to accommodate the three species in this clade. Cryptolepiota microspora and C. mengei are described as new, and G. americanum is transferred to Cryptolepiota. Gigasperma cryptica is illustrated and compared with the species of Cryptolepiota.     

Impact of Dental Atmosphere and Behaviour of the Dentist on Children’s Cooperation

During dental treatment children are usually under psychological pressure. With the Sarnat Behaviour Score five different types of patients can be distinguished. There is no method that measures the impact of dental atmosphere and dentist's behaviour on the young patients' readiness to cooperate. The objective of the present study was the implementation and evaluation of a questionnaire on this subject. Eighty-eight patients participated in this study. In the first part of the new questionnaire personal information was collected. The second part consists of 43 items and investigates the relationship between dentist and patient and reflects the atmosphere of the environment. Statistical analysis was performed using the Chi-square test. There were statistically significant differences between the cooperative and non-cooperative group, as regards the perceived honesty of the dentist, the ability to explain and wish to help. Uncooperative children are significantly more often afraid of the dental environment. Sympathy alone has only a minor effect on children's cooperation. Children should be treated with empathy. Especially younger patients appreciate detailed explanations by the dentist. Children's non-cooperative behaviour results often from their aroused interest in the unknown environment, which causes an unpleasant perception of the whole setting.     

Modified "4 + 1" mixed ligand technetium-labeled fatty acids for myocardial imaging: evaluation of myocardial uptake and biodistribution

Our group previously synthesized 99m Tc-labeled fatty acids suitable for myocardial metabolism and flow imaging. In this set of experiments, 29 new analogues were synthesized according to the "4 + 1" mixed ligand approach with some specific differences. Conventional "4 + 1" 99m Tc-fatty acids are built in the sequence: Tc-chelate, alkyl chain, and carboxylic group. We developed compounds following a new design with the sequence: carboxylic group, alkyl chain, Tc-chelate, and lipophilic tail. Therefore, the 99m Tc-chelate was transferred to a more central position of the compound, aiming toward an improved myocardial profile and an accelerated liver clearance. In this context, several functional groups incorporated in the lipophilic tail section were tested to evaluate their influence on the compound's character. In addition to biodistribution studies in vivo, the myocardial first-pass extraction of the compounds was tested in an isolated Langendorff rat heart model. A satisfactory myocardial uptake of up to 20% of the injected dose (% ID) in the perfused heart and a fast liver clearance in vivo with only 0.29% ID/g at 60 min postinjection demonstrate that the induced molecular modifications affect the kinetics of 99m Tc-radiolabeled fatty acid compounds favorably. From the data set, rules for estimating the biodistribution of fatty acids tracers are deduced.