A Zooarchaeological Test for Dietary Resource Depression at the End of the Classic Period in the Petexbatun,Guatemala

Zooarchaeological analyses of animal remains from the Petexbatun sites in the Guatemalan lowlands provide proxy evidence to test a hypothesis of dietary insufficiency during the Maya “collapse.” Ecological foraging theory and resource depression models are used to interpret animal use patterns before and after the disintegration of the Petexbatun polity at the end of the Late Classic period (around a.d. 800). Environmental failure models of the Maya “collapse” at the end of the Late Classic imply that a dietary insufficiency, and particularly a lack of animal resources, was associated with the political and social transitions of this period. However, the results of this zooarchaeological study do not support this hypothesis and point instead to very limited early reductions of only highest-ranked dietary species. The lack of evidence for specific resource depression associated directly with the period of political collapse does not support a model of environmental failure during political disintegration in the Petexbatun. Correlations are found between animal use patterns and the specifics of site size and periods of peak political activity, suggesting that small-scale resource depressions might have resulted at some sites during early periods of human population growth, site expansion, and increasing political activity.     

Spatial variation of species diversity across scales in an old-growth temperate forest of China

Species richness and abundance are the two most important diversity variables. Species abundance is additive when aggregated across spatial scale, whereas species richness is non-additive. This study analyzes the effect of spatial scale and site on species abundance and richness in a 25-ha temperate forest plot in the Changbai Mountains, northeastern China. The result shows that species abundance and richness are not only dependent on spatial scales, but also dependent on site. Species abundance responds linearly to changes of spatial scale with no intersection in different sites of the study area. However, although species richness also increases with the increase of spatial scale, there are some intersections for the different sites, suggesting that a species-rich site does not always have a high value if the spatial scale is changed. In all, with respect to additive variables, it is relatively easy to extrapolate them from one spatial scale to another spatial scale, as they and the spatial scale usually form a linear relationship. In contrast, non-additive variables are difficult to extrapolate across spatial scales, because they often respond nonlinearly to spatial scale changes. In order to extrapolate these non-additive variables across spatial scales, it is necessary to estimate the relationships between them and spatial scales. As a result, extrapolation of information among spatial scales may be possible, but very difficult, especially for non-additive variables. Because the 25-ha Changbai plot is very small compared to the extent of the world temperate forests, and the vegetation is a relatively uniform type, more such studies in other ecosystems are needed before theories and generalization about scaling effects can be formulated.     

Managing private,commercial rangelands for agricultural production and wildlife diversity in Namibia and Zambia

The private game industry has grown across Africa since the mid-20th century. While considerable research has documented wildlife production on commercial land in many eastern and southern African countries, few studies have focused specifically on the integration of livestock and game production in Namibia and Zambia. This paper reports a survey of 43 commercial conservancy members in Namibia and 23 game farmers in Zambia conducted between September 2004 and June 2005. The survey was based on inductive sampling theory and queried farmers on how they have integrated wildlife production into their management practices. Farmers in each country reported considerable integration of wildlife conservation and agricultural production. Namibian farmers reported substantial problems with bush encroachment, whereas none of their Zambian counterparts raised similar complaints. This paper describes the state of rangeland management on commercial farms in Namibia and Zambia and identifies important areas where further research can contribute to the enhancement of this conservation-production system.     

Preparation of validoxylamine A by biotransformation of validamycin A using resting cells of a recombinant <Emphasis Type="Italic">Escherichia coli</Emphasis>

A gene encoding β-glucosidase was cloned and over-expressed in Escherichia coli. Validamycin A was then biotransformed into validoxylamine A by using the resting recombinant cells. The biotransformation yield reached 92% when the reaction was performed at 37°C for 1 h in the presence of 100 ml sodium phosphate buffer (0.1 M, pH 7.0), 32 mM validamycin A and 0.71 mg dry cell w/ml.     

Effect of <Emphasis Type="Italic">poxB</Emphasis> gene knockout on metabolism in <Emphasis Type="Italic">Escherichia coli</Emphasis> based on growth characteristics and enzyme activities

The effect of poxB gene knockout on metabolism in Escherichia coli was investigated in the present paper based on the growth characteristics and the activities of the enzymes involved in the central metabolic pathways. The absence of pyruvate oxidase reduced the glucose uptake rate and cell growth rate, and increased O₂ consumption and CO₂ evolution. The enzyme assay results showed that although glucokinase activity increased, the flux through glycolysis was reduced due to the down-regulation of the other glycolytic enzymes such as 6-phosphofructosekinase and fructose bisphosphate aldolase in the poxB mutant. TCA cycle enzymes such as citrate synthase and malate dehydrogenase were repressed in the poxB mutant when the cells were cultivated in LB medium. The pyruvate oxidase mutation also resulted in the activation of glucose-6-phosphate dehydrogenase and acetyl-CoA synthetase. All these results suggest that pyruvate oxidase is not only a stationary-phase enzyme as previously known, and that the removal of the poxB gene affects the central metabolism at the enzyme level in E. coli.     

Environmental changes in Lake Taihu during the past century as recorded in sediment cores

The Lake Taihu drainage basin is an economically developed area with some of the highest population densities in China. The lake has deteriorated due to ecological destruction and eutrophication. Three short sediment cores from eastern, northeastern and southwestern Lake Taihu were collected. Total organic carbon (TOC), total nitrogen (TN), pigments, elements and particle size were analyzed for the purpose of understanding past trophic status and pollution levels. Sedimentation rates were based on ¹³⁷Cs or ²¹⁰Pb methods. Results indicated that sediment particle size became coarser since the 1920s, and the lake was contaminated by heavy metals, such as Cu and Zn, since the 1970s. A remarkable increase in eutrophication since the 1980s due to increased loading of untreated effluents from industry, agriculture and urbanization is reflected by total organic carbon, total nitrogen and pigments in the studied cores. However the onset times of eutrophication in different parts of Lake Taihu were not synchronous.     

A novel technique to study pore-forming peptides in a natural membrane

The biophysical characteristics and the pore formation dynamics of synthetic or naturally occurring peptides forming membrane-spanning channels were investigated by using isolated photoreceptor rod outer segments (OS) recorded in whole-cell configuration. Once blocking the two OS endogenous conductances (the cGMP channels by light and the Na⁺:Ca²⁺,K⁺ exchanger by removing one of the transported ion species from both sides of the membrane, i.e. K⁺, Na⁺ or Ca²⁺), the OS membrane resistance (R _m ) was typically larger than 1 GΩ in the presence of 1 mM external Ca²⁺. Therefore, any exogenous current could be studied down to the single channel level. The peptides were applied to (and removed from) the extracellular OS side in ∼50 ms with a computer-controlled microperfusion system, in which every perfusion parameter, as the rate of solution flow, the temporal sequence of solution changes or the number of automatic, self-washing cycles were controlled by a user-friendly interface. This technique was then used to determine the biophysical properties and the pore formation dynamics of antibiotic peptaibols, as the native alamethicin mixture, the synthesized major component of the neutral fraction (F50/5) of alamethicin, and the synthetic trichogin GA IV.     

Gene inactivation mediated by <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis> in the filamentous fungi <Emphasis Type="Italic">Metarhizium anisopliae</Emphasis>

The list of fungal species with known complete genome and/or expressed sequence tag collections is extending rapidly during the last couple of years. Postgenomic gene function assignment is an obvious follow-up and depends on methodologies to test gene function in vivo. One of such methods is the generation of null mutants via homologous recombination at the wild–type loci by using inactivation cassettes. In this paper, the ability of Agrobacterium tumefaciens to genetically transform filamentous fungi was exploited to drive homologous recombination at the trp1 locus of the enthomopathogenic fungus Metarhizium anisopliae. The trp1 disruptants exhibited a clearly distinguishable phenotype from wild-type cells and were recovered with high efficiency of homologous recombination (22%). The complementation of such mutants with the wild-type gene generates only transformants with homologous integration.     

Universal markers for comparative mapping and phylogenetic analysis in the Asteraceae (Compositae)

The development of universal markers that can be assayed across taxa, but which are polymorphic within taxa, can facilitate both comparative map-based studies and phylogenetic analyses. Here we describe the development of such markers for use in the Asteraceae, which includes the crops lettuce, sunflower, and safflower as well as dozens of locally important crop and weed species. Using alignments of a conserved orthologous set (COS) of ESTs from lettuce and sunflower and genomic sequences of Arabidopsis, we designed a suite of primer pairs that are conserved across species, but which are predicted to flank introns. We then tested 192 such primer pairs in 8 species from across the family. Of these, 163 produced an amplicon in at least 1 taxon, and 125 amplified in at least half of the taxa surveyed. Thirty-nine amplified in all 8 species. Comparisons amongst sequences within the lettuce and sunflower EST databases indicate that the vast majority of these loci will be polymorphic. As a direct test of the utility of these markers outside the lettuce and sunflower subfamilies, we sequenced a subset of ten loci from a panel of cultivated safflower individuals. All 10 loci proved to be single-locus, and nine of the 10 loci were polymorphic with an average of 12.8 SNPs per kb. Taken together, these loci will provide an initial backbone for comparative genetic analyses within the Asteraceae. Moreover, our results indicate that these loci are phylogenetically informative, and hence can be used to resolve evolutionary relationships between taxa within the family as well as within species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Mark A. Chapman and JianCheng Chang have contributed equally to this work.     

A trypsin inhibitor from <Emphasis Type="Italic">Cassia obtusifolia</Emphasis> seeds: isolation,characterization and activity against <Emphasis Type="Italic">Pieris rapae</Emphasis>

A trypsin inhibitor was isolated from Cassia obtusifolia by ammonium sulfate precipitation, Sepharose 4B-trypsin affinity and Sephadex G-75 chromatography. The inhibitor consisted of a single polypeptide chain with a molecular mass of 19, 812.55 Da. It was stable from pH 2 to 12 for 24 h, whereas it was unstable either above 70°C for 10 min or under reduced conditions. The inhibitor, which inhibited trypsin activity with an apparent Ki of 0.3 μM, had one reactive site involving a lysine residue. The native inhibitor was resistant to pepsin digestion, whereas the heated inhibitor produced 40% degree of susceptibility. The disulfide linkage and lysine residue were important in maintaining its conformation. Partial amino acid sequence of the purified protein showed a high degree of homology with various members of the Kunitz inhibitor family. Moreover, the inhibitor showed significant inhibitory activity against trypsin-like proteases present in the larval midgut on Pieris rapae and could suppress the growth of larvae.