Purification and Properties of an S-Adenosylmethionine: 2,4-Disubstituted Phenol O-Methyltransferase from Phanerochaete chrysosporium

An enzyme catalyzing the O-methylation of acetovanillone (3-methoxy-4-hydroxyacetophenone) by S-adeno-sylmethionine was isolated from Phanerochaete chrysosporium and purified 270-fold by ultrafiltration, anion-exchange chromatography, and gel filtration. The enzyme exhibited a pH optimum between 7 and 9 and was rapidly denatured at temperatures above 55°C. The K_m values for acetovanillone and S-adenosylmethionine were 34 and 99 μM, respectively. S-Adenosylhomocysteine acted as a powerful competitive inhibitor of S-adenosylmethionine, with a K_i of 41 μM. The enzyme was also susceptible to inhibition by thiol reagents and low concentrations of heavy metal ions. Gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the enzyme was monomeric and had a molecular weight of approximately 53,000. Substrate specificity studies showed that 3-methoxy- and 3,5-dimethoxy-substituted 4-hydroxy-benzaldehydes, -benzoic acids, and -acetophenones were the preferred substrates for the enzyme. The corresponding 3,4-dihydroxy compounds were methylated relatively slowly, while the 3-hydroxy-4-methoxy compounds were almost inactive as substrates. Substituents in both the 2 and 4 positions relative to the hydroxyl group appeared to be essential for significant enzyme attack of a substrate. Provided that certain steric criteria were satisfied, the nature of the substituent was not critical. Hence, xenobiotic compounds such as 2,4-dichlorophenol and 2,4-dibromophenol were methylated almost as readily as acetovanillone. However, an extended side chain in the 4 position was not compatible with activity as a substrate, and neither homovanillic, caffeic, nor ferulic acid was methylated. The substrate range of the O-methyltransferase tends to imply a role in the catabolism or detoxification of lignin degradation products such as vanillic and syringic acids.     

Comparison of the murine humoral immune response to recombinant simian virus 40 large tumor antigen: Epitope specificity and idiotype expression

Baculovirus-derived recombinant simian virus 40 (SV40) large tumor antigen (SV40 T-Ag) was used to immunize inbred strains of mice to compare the humoral immune responses. Specifically we examined the epitope specificities and idiotype (Id) expression on anti-(SV40 T-Ag) responses induced in BALB/c and C57BL/6 inbred strains of mice. The predominant SV40 T-Ag epitopes recognized by the anti-(SV40 T-Ag) responses appeared to differ between these two inbred strains, this being based on the ability of sera to inhibit the binding of several murine monoclonal antibodies specific for SV40 T-Ag. In addition, anti-(SV40 T-Ag) responses produced in C57BL/6 mice failed to express a previously described cross-reactive Id expressed in the anti-(SV40 T-Ag) response in BALB/c mice. This cross-reactive Id is detected by a mouse monoclonal anti-Id, designated 58D, which has been shown to represent a potential focal point for manipulating the humoral immune response to SV40-induced tumors in BALB/c mice. Together, these data indicate that the functional duality of the humoral immune response, as assessed by epitope recognition and Id expression, differs between these two inbred strains of mice when immunized with a recombinant SV40 T-Ag.     

Landscape-scale patterns of biological invasions in shoreline plant communities

Little is known about the patterns and dynamics of exotic species invasions at landscape to regional spatial scales. We quantified the presence (identity, abundance, and richness) and characteristics of native and exotic species in estuarine strandline plant communities at 24 sites in Narragansett Bay, Rhode Island, USA. Our results do not support several fundamental predictions of invasion biology. Established exotics (79 of 147 recorded plant species) were nearly indistinguishable from the native plant species (i.e. in terms of growth form, taxonomic grouping, and patterns of spatial distribution and abundance) and essentially represent a random sub-set of the current regional species pool. The cover and richness of exotic species varied substantially among quadrats and sites but were not strongly related to any site-level physical characteristics thought to affect invasibility (i.e. the physical disturbance regime, legal status, neighboring habitat type, and substrate characteristics). Native and exotic cover or richness were not negatively related within most sites. Across sites, native and exotic richness were positively correlated and exotic cover was unrelated to native richness. The colonization and spread of exotics does not appear to have been substantially reduced at sites with high native diversity. Furthermore, despite the fact that the Rhode Island strandline system is one of the most highly-invaded natural plant communities described to date, exotic species, both individually and as a group, currently appear to pose little threat to native plant diversity. Our findings are concordant with most recent, large-scale investigations that do not support the theoretical foundation of invasion biology and generally contradict small-scale experimental work.     

Relationship between grass species richness and ecosystem stability in Kruger National Park, South Africa

The relationship between grass species richness and ecosystem stability was investigated in the Kruger National Park. A total of 135 489 individual grasses were identified from 189 sites spread across 19 485 km² of savanna biome, making this one of the largest studies of its kind. At each site, grass percentage abundance and standing crop were measured at one year intervals to provide an index of ecosystem function. A severe drought that affected the region between 1991 and 1993 provided a convenient perturbation. At the height of the drought, mean species richness declined by 12.7% while standing crop declined by 38.1%, from 3199 to 1979 kg ha^?1. Percentage grass abundance declined to 87.5% of its pre‐drought value. After the drought had passed species richness, standing crop and percentage abundance recovered to 92.1%, 113.8% and 92.8% of their pre‐perturbation values, respectively. Statistical analysis of these responses revealed that grass assemblages of low species richness were more resistant to drought than assemblages of high species richness. Species‐poor sites also showed better recovery from perturbation after the drought had passed. These findings suggest that ecosystem stability may be negatively related to grass species richness in South African savanna grasslands.     

The relationship between a summer fry (0+) abundance index, derived from semi-quantitative electrofishing, and egg deposition of Atlantic salmon, in the River Bush, Northern Ireland

Atlantic salmon survival in the R. Bush (N. Ireland) from egg to summer 0+ was inversely density-dependent on egg deposition ( P <0.05). A stock-recruitment relationship derived from egg deposition and summer 0+ abundance index data was compared to that derived from adult and smolt counts based on total trapping. Fitted Ricker curves indicated maximum recruitment at around 2.35 million eggs and 2.46 million eggs for 0+ index and smolt count methods, respectively. Salmon 0+ abundance index data from semi-quantitative electrofishing could be obtained with relatively little effort, and used to derive whole-river stock-recruitment relationships on rivers where only adult count or some other estimator of parental stock is available. The derivation and expression of spawning targets from stock/recruitment relationships is discussed with reference to the R. Bush data.     

Application of a fry (0+;) abundance index, based on semi-quantitative electrofishing, to predict Atlantic salmon smolt runs in the River Bush, Northern Ireland

An abundance index for 0+ Atlantic salmon was based on semi-quantitative electrofishing estimates at 137 sites in typical juvenile habitat throughout the River Bush (N. Ireland). 0 + abundance was linearly related to total smolt numbers migrating through a downstream trap in subsequent years ( r ²= 0.716, P <0.001), suggesting a high degree of predictive ability. This predictive ability decreased as smolt age increased, suggesting influence of density-independent mortality. Potential application of the technique to estimate smolt production from rivers having no trapping facilities is discussed, together with sources of variability potentially affecting estimates.     

Calathea maasiorum (Marantaceae), a new species from French Guiana and Surinam

Calathea maasiorum from French Guiana and Surinam is described as new. It belongs toCalathea sectionBreviscapus Bentham. The foliage is patterned with a light green band along the midrib above. This new species has previously been confused withC. cyclophora Baker from Amazonian Colombia, Brazil, Venezuela, and Guyana but it is distinguished fromC. cyclophora by the absence of bracteoles, the elliptic to obovate leaf blade, and shorter (1–2 cm long) bracts.     

Data Quality

A methodology is presented to develop and analyze vectors of data quality attribute scores. Each data quality vector component represents the quality of the data element for a specific attribute (e.g., age of data). Several methods for aggregating the components of data quality vectors to derive one data quality indicator (DQI) that represents the total quality associated with the input data element are presented with illustrative examples. The methods are compared and it is proven that the measure of central tendency, or arithmetic average, of the data quality vector components as a percentage of the total quality range attainable is an equivalent measure for the aggregate DQI. In addition, the methodology is applied and compared to realworld LCA data pedigree matrices. Finally, a method for aggregating weighted data quality vector attributes is developed and an illustrative example is presented. This methodology provides LCA practitioners with an approach to increase the precision of input data uncertainty assessments by selecting any number of data quality attributes with which to score the LCA inventory model input data. The resultant vector of data quality attributes can then be analyzed to develop one aggregate DQI for each input data element for use in stochastic LCA modeling.