Successional dynamics in Neotropical forests are as uncertain as they are predictable.

Although forest succession has traditionally been approached as a deterministic process, successional trajectories of vegetation change vary widely, even among nearby stands with similar environmental conditions and disturbance histories. Here, we provide the first attempt, to our knowledge, to quantify predictability and uncertainty during succession based on the most extensive long-term datasets ever assembled for Neotropical forests. We develop a novel approach that integrates deterministic and stochastic components into different candidate models describing the dynamical interactions among three widely used and interrelated forest attributes--stem density, basal area, and species density. Within each of the seven study sites, successional trajectories were highly idiosyncratic, even when controlling for prior land use, environment, and initial conditions in these attributes. Plot factors were far more important than stand age in explaining successional trajectories. For each site, the best-fit model was able to capture the complete set of time series in certain attributes only when both the deterministic and stochastic components were set to similar magnitudes. Surprisingly, predictability of stem density, basal area, and species density did not show consistent trends across attributes, study sites, or land use history, and was independent of plot size and time series length. The model developed here represents the best approach, to date, for characterizing autogenic successional dynamics and demonstrates the low predictability of successional trajectories. These high levels of uncertainty suggest that the impacts of allogenic factors on rates of change during tropical forest succession are far more pervasive than previously thought, challenging the way ecologists view and investigate forest regeneration.

Polyphenol- and fibre-rich dried fruits with green tea attenuate starch-derived postprandial blood glucose and insulin: a randomised, controlled, single-blind, cross-over intervention.

Polyphenol- and fibre-rich foods (PFRF) have the potential to affect postprandial glycaemic responses by reducing glucose absorption, and thus decreasing the glycaemic response of foods when consumed together. A randomised, single-blind, cross-over study was conducted on sixteen healthy volunteers to test whether PFRF could attenuate postprandial blood glucose in healthy volunteers when added to a source of carbohydrate (starch in bread). This is the first study to examine the effects of a meal comprised of components to inhibit each stage of the biochemical pathway, leading up to the appearance of glucose in the blood. The volunteers were fasted and attended four visits: two control visits (bread, water, balancing sugars) and two test visits (single and double dose of PFRF) where they consumed bread, water and PFRF. Blood samples were collected at 0 (fasted), 15, 30, 45, 60, 90, 120, 150 and 180 min after consumption. The PFRF components were tested for α-amylase and α-glucosidase inhibitory potential in vitro. Plasma glucose was lower after consumption of both doses compared with controls: lower dose, change in mean incremental areas under the glucose curves (IAUC)=-27·4 (sd 7·5) %, P<0·001; higher dose, IAUC=-49·0 (sd 15·3) %, P<0·001; insulin IAUC was also attenuated by-46·9 (sd 13·4) %, P<0·01. Consistent with this, the polyphenol components of the PFRF inhibited α-amylase (green tea, strawberry, blackberry and blackcurrant) and α-glucosidase (green tea) activities in vitro. The PFRF have a pronounced and significant lowering effect on postprandial blood glucose and insulin response in humans, due in part to inhibition of α-amylase and α-glucosidase, as well as glucose transport.

Considerations Before Establishing an Environmental Health Registry.

Public health registries can provide valuable information when health consequences of environmental exposures are uncertain or will likely take long to develop. They can also aid research on diseases that may have environmental causes that are not completely well defined. We discuss factors to consider when deciding whether to create an environmental health registry. Those factors include public health significance, purpose and outcomes, duration and scope of data collection and availability of alternative data sources, timeliness, availability of funding and administrative capabilities, and whether the establishment of a registry can adequately address specific health concerns. We also discuss difficulties, limitations, and benefits of exposure and disease registries, based on the experience of the Agency for Toxic Substances and Disease Registry.

Absorption and isomerization of caffeoylquinic acids from different foods using ileostomist volunteers.

BACKGROUND: Polyphenols are thought to play important roles in human nutrition and health but these health effects are dependent on their bioavailability. This study is one of a series with the aim of determining possible effects of food matrices on caffeoylquinic acid (CQA) bioavailability using ileostomy volunteers. METHODS: After a CQA-free diet, ileostomists consumed coffee (746 µmol total CQA), and CQAs in excreted ileal fluid were subsequently identified and quantified with HPLC-diode array detection and HPLC-ESI-MS/MS. In our previous studies, other food sources such as cloudy apple juice (CAJ) (358 µmol CQA) and apple smoothie (AS) (335 µmol CQA) were investigated with the same model. RESULTS: Interesterification of CQA from both apple matrices was observed during gastrointestinal passage, whereas CQA consumed in coffee was not influenced by interesterification reactions. In total, 74.3, 22.4, and 23.8 % of the CQA from CAJ, AS, and coffee, respectively, were absorbed or degraded. CONCLUSION: Our results show that variations in food matrices and variations in phenolic composition have a major influence on intestinal bioavailability and interesterification of the investigated subclass of polyphenols, the CQAs.

Giant eucalypts - globally unique fire-adapted rain-forest trees?

Tree species exceeding 70 m in height are rare globally. Giant gymnosperms are concentrated near the Pacific coast of the USA, while the tallest angiosperms are eucalypts (Eucalyptus spp.) in southern and eastern Australia. Giant eucalypts co-occur with rain-forest trees in eastern Australia, creating unique vegetation communities comprising fire-dependent trees above fire-intolerant rain-forest. However, giant eucalypts can also tower over shrubby understoreys (e.g. in Western Australia). The local abundance of giant eucalypts is controlled by interactions between fire activity and landscape setting. Giant eucalypts have features that increase flammability (e.g. oil-rich foliage and open crowns) relative to other rain-forest trees but it is debatable if these features are adaptations. Probable drivers of eucalypt gigantism are intense intra-specific competition following severe fires, and inter-specific competition among adult trees. However, we suggest that this was made possible by a general capacity of eucalypts for 'hyper-emergence'. We argue that, because giant eucalypts occur in rain-forest climates and share traits with rain-forest pioneers, they should be regarded as long-lived rain-forest pioneers, albeit with a particular dependence on fire for regeneration. These unique ecosystems are of high conservation value, following substantial clearing and logging over 150 yr. Contents Summary 1001 I. Introduction 1001 II. Giant eucalypts in a global context 1002 III. Giant eucalypts - taxonomy and distribution 1004 IV. Growth of giant eucalypts 1006 V. Fire and regeneration of giant eucalypts 1008 VI. Are giant eucalypts different from other rain-forest trees? 1009 VII. Conclusions 1010 Acknowledgements 1011 References 1011.

Radial wood allocation in Schizolobium parahyba.

PREMISE OF THE STUDY: Pioneer species of tropical trees allocate wood specific gravity (SG) differently across the radius. Some species exhibit relatively uniform, low SG wood, whereas many others exhibit linear increases in SG across the radius. Here, we measured changes in SG across the radius of Schizolobium parahyba (Fabaceae-Caesalpinioideae), a wide-ranging, neotropical pioneer, used extensively in land reclamation and forest restoration in Brazil. METHODS: Pith-to-bark radial wood cores were extracted with increment borers from 42 trees at five sites, in Central and South America. Cores were cut into 1-cm segments whose specific gravities were determined and analyzed via linear and nonlinear regression. Wood specific gravity, very low initially at 0.15-0.20, doubled or tripled across the tree radius to 0.45-0.65 for large adults. KEY RESULTS: Unlike linear increases in other tropical pioneers, the increases in Schizolobium were nonlinear (convex up). At one site with even-aged trees, the magnitude of the radial increase was similar in all trees, despite a 4-fold difference in diameter among trees, implying that the radial increases in Schizolobium were regulated by tree age, not by tree size. CONCLUSIONS: This unique pattern of development should provide an extended period of growth when SG is low, facilitating hyper-extension of the bole, at some risk of structural failure. Later in growth, the SG rate of increase accelerates, reinforcing what was a precarious bole. Overall, these results suggest a third model for xylem allocation in tropical trees, a model that may be associated with monopodial stem development and limited life span.

Strong floristic distinctiveness across Neotropical successional forests.

Forests that regrow naturally on abandoned fields are important for restoring biodiversity and ecosystem services, but can they also preserve the distinct regional tree floras? Using the floristic composition of 1215 early successional forests (≤20 years) in 75 human-modified landscapes across the Neotropic realm, we identified 14 distinct floristic groups, with a between-group dissimilarity of 0.97. Floristic groups were associated with location, bioregions, soil pH, temperature seasonality, and water availability. Hence, there is large continental-scale variation in the species composition of early successional forests, which is mainly associated with biogeographic and environmental factors but not with human disturbance indicators. This floristic distinctiveness is partially driven by regionally restricted species belonging to widespread genera. Early secondary forests contribute therefore to restoring and conserving the distinctiveness of bioregions across the Neotropical realm, and forest restoration initiatives should use local species to assure that these distinct floras are maintained.

Effect of carcase decomposition on the inactivation of foot-and-mouth disease virus under northern Australian conditions.

OBJECTIVE: The control of foot-and-mouth disease virus (FMDV) across northern Australia would likely result in animal carcases that will often be inaccessible for disposal. The aim of this preliminary study was to determine whether the natural pH and/or temperature changes that occur within the skeletal muscle and/or body cavities of a decomposing carcase shot and left in situ in this environment would be sufficient to inactivate FMDV. METHODS: Study pigs (n = 30), cattle (6), sheep (6) and goats (8) were shot in one of four locations in Queensland. Carcase temperature and pH and ambient temperature were measured every 15-60 min for up to 46 h in two sites per animal: central (thoracic/abdominal cavity) and peripheral (skeletal muscle) or brain. A target pH ≤ 6.0 at any time and/or a target temperature ≥ 43°C for ≥ 7 h or ≥ 49°C for ≥ 1 h were used as proxies for achievement of FMDV inactivation. RESULTS: The target temperature was achieved in only one goat carcase. However, within 16 h of death, the target central and/or peripheral pH was attained in 88-100% of pig, cattle and sheep carcases. Increasing hours since death and death in the late morning/afternoon, relative to the early morning, were positively associated with attaining the target central carcase pH. CONCLUSION: This preliminary study provided evidence that FMDV inactivation may be achieved in the skeletal muscle and/or body cavities of carcases left under northern Australian conditions, though further work on pH changes in bone marrow are required.

An Amazonian rainforest and its fragments as a laboratory of global change.

We synthesize findings from one of the world's largest and longest-running experimental investigations, the Biological Dynamics of Forest Fragments Project (BDFFP). Spanning an area of ∼1000 km2 in central Amazonia, the BDFFP was initially designed to evaluate the effects of fragment area on rainforest biodiversity and ecological processes. However, over its 38-year history to date the project has far transcended its original mission, and now focuses more broadly on landscape dynamics, forest regeneration, regional- and global-change phenomena, and their potential interactions and implications for Amazonian forest conservation. The project has yielded a wealth of insights into the ecological and environmental changes in fragmented forests. For instance, many rainforest species are naturally rare and hence are either missing entirely from many fragments or so sparsely represented as to have little chance of long-term survival. Additionally, edge effects are a prominent driver of fragment dynamics, strongly affecting forest microclimate, tree mortality, carbon storage and a diversity of fauna. Even within our controlled study area, the landscape has been highly dynamic: for example, the matrix of vegetation surrounding fragments has changed markedly over time, succeeding from large cattle pastures or forest clearcuts to secondary regrowth forest. This, in turn, has influenced the dynamics of plant and animal communities and their trajectories of change over time. In general, fauna and flora have responded differently to fragmentation: the most locally extinction-prone animal species are those that have both large area requirements and low tolerance of the modified habitats surrounding fragments, whereas the most vulnerable plants are those that respond poorly to edge effects or chronic forest disturbances, and that rely on vulnerable animals for seed dispersal or pollination. Relative to intact forests, most fragments are hyperdynamic, with unstable or fluctuating populations of species in response to a variety of external vicissitudes. Rare weather events such as droughts, windstorms and floods have had strong impacts on fragments and left lasting legacies of change. Both forest fragments and the intact forests in our study area appear to be influenced by larger-scale environmental drivers operating at regional or global scales. These drivers are apparently increasing forest productivity and have led to concerted, widespread increases in forest dynamics and plant growth, shifts in tree-community composition, and increases in liana (woody vine) abundance. Such large-scale drivers are likely to interact synergistically with habitat fragmentation, exacerbating its effects for some species and ecological phenomena. Hence, the impacts of fragmentation on Amazonian biodiversity and ecosystem processes appear to be a consequence not only of local site features but also of broader changes occurring at landscape, regional and even global scales.

The distributions of howling monkeys (Alouatta pigra and A. palliata) in southeastern Mexico and Central America.

We compared the distributions of Alouatta palliata and A. pigra in southeastern Mexico and Central America with geographic and ecological features to infer current barriers and ecological preferences. Distribution data were obtained from museum specimen localities, study sites, historic records and field surveys and integrated into digital elevation and ecosystem maps using GIS. A. pigra evidently occurs at a number of sites above 2,000 m, where temperatures can even drop below zero on some days of the year, thus indicating a broader ecological tolerance than previously reported. Both species occupy a number of vegetation types and can be found in seasonal and nonseasonal forests. We identified the highland massif of northern Central America and its associated coniferous and subalpine vegetation as a geographic barrier that separates the species. In the past, distribution maps for these species have indicated adjacent contiguous ranges, but we propose that they are largely separated by these mountains. There are two contact zones: a broad area of sympatry north of the highland massif in Mexico and a narrow zone in eastern Guatemala where parapatry is maintained by a river barrier and where only A. pigra occurs in the high elevations and cooler habitats inland. We explore an alternative biogeographic scenario for the split of the two species that accounts for the current distribution and differences in elevation and cold tolerances.

The role of polyphenols in modern nutrition.

Polyphenols are found in plant-based foods and beverages, notably apples, berries, citrus fruit, plums, broccoli, cocoa, tea and coffee and many others. There is substantial epidemiological evidence that a diet high in polyphenol-rich fruit, vegetables, cocoa and beverages protects against developing cardiovascular disease and type 2 diabetes. The absorption and metabolism of these compounds have been well described and, for many, the gut microbiota play a critical role in absorption; taking into consideration the parent compound and the metabolites from colon bacteria catabolism, more than 80% of a dose can be absorbed and ultimately excreted in the urine. Common polyphenols in the diet are flavanols (cocoa, tea, apples, broad beans), flavanones (hesperidin in citrus fruit), hydroxycinnamates (coffee, many fruits), flavonols (quercetin in onions, apples and tea) and anthocyanins (berries). Many intervention studies, mechanistic in vitro data and epidemiological studies support a role for polyphenols against the development of chronic diseases. For example, flavanols decrease endothelial dysfunction, lower blood pressure and cholesterol, and modulate energy metabolism. Coffee and tea both reduce the risk of developing type 2 diabetes, through action of their constituent polyphenols. Despite extensive research, the exact mechanisms of action of polyphenols in the human body have not been decisively proven, but there is strong evidence that some targets such as nitric oxide metabolism, carbohydrate digestion and oxidative enzymes are important for health benefits. Consumption of polyphenols as healthy dietary components is consistent with the advice to eat five or more portions of fruit and vegetables per day, but it is currently difficult to recommend what 'doses' of specific polyphenols should be consumed to derive maximum benefit.

Vasorelaxant activity of twenty-one physiologically relevant (poly)phenolic metabolites on isolated mouse arteries.

Polyphenols are beneficial for health, but are metabolised after consumption. We compared the vasorelaxant capacity of twenty-one physiologically relevant polyphenol metabolites in isolated mouse arteries. Hesperetin, urolithins and ferulic acid-4-O-sulfate - not their glucuronidated forms or ferulic acid - caused vasorelaxation. Therefore, we advise the use of relevant conjugates in future mechanistic research.

Solution structure of the granular starch binding domain of Aspergillus niger glucoamylase bound to beta-cyclodextrin.

BACKGROUND: Carbohydrate-binding domains are usually small and physically separate from the catalytic domains of hydrolytic enzymes. Glucoamylase 1 (G1) from Aspergillus niger, an enzyme used widely in the food and brewing industries, contains a granular starch binding domain (SBD) which is separated from the catalytic domain by a semi-rigid linker. The aim of this study was to determine how the SBD binds to starch, and thereby more generally to throw light on the role of carbohydrate-binding domains in the hydrolysis of insoluble polysaccharides. RESULTS: The solution structure of the SBD of A. niger G1 bound to beta-cyclodextrin (betaCD), a cyclic starch analogue, shows that the well-defined beta-sheet structure seen in the free SBD is maintained in the SBD-betaCD complex. The main differences between the free and bound states of the SBD are observed in loop regions, in or near the two starch-binding sites. The two binding sites, each of which binds one molecule of betaCD, are structurally different. Binding site 1 is small and accessible, and its structure changes very little upon ligand binding. Site 2 is longer and undergoes a significant structural change on binding. Part of this site comprises a flexible loop, which appears to allow the SBD to bind to starch strands in a range of orientations. CONCLUSIONS: The two starch-binding sites of the SBD probably differ functionally as well as structurally; site 1 probably acts as the initial starch recognition site, whereas site 2 is involved in specific recognition of appropriate regions of starch. The two starch strands are bound at approximately 90 degrees to each other. This may be functionally important, as it may force starch strands apart thus increasing the hydrolyzable surface, or alternatively it may localize the enzyme to noncrystalline (more hydrolyzable) areas of starch. The region of the SBD where the linker to the catalytic domain is attached is flexible, allowing the catalytic site to access a large surface area of the starch granules.

Detection of a nuclear protein which binds specifically to the antioxidant responsive element (ARE) of the human NAD(P) H:quinone oxidoreductase gene.

We have detected a protein or complex of proteins with a native molecular mass of 160 kDa from the nuclear extract of HeLa cells, which binds specifically to the human antioxidant responsive element (ARE) in the 5'-flanking region of the NAD(P)H:quinone oxidoreductase gene. Binding of the 160 kDa protein to oligonucleotides containing the ARE in gel mobility shift assays is diminished or abolished by increasing concentrations of the reducing agent dithiothreitol, but not by anti-Jun or anti-Fos antibodies. The effect of dithiothreitol is opposite to that observed for the Ref-1-mediated binding of Fos/Jun to the ARE or to the related 12-O-tetradecanoyl phorbol-13-acetate responsive element (TRE). Competition assays indicated that the binding of the 160 kDa protein requires the ARE sequence, TGACNNNGCA, with T as the most important base, and that the TRE sequence (TGACTCA) is not sufficient. F9 cells, which contain no AP-1 protein, were able to form a complex with the same mobility as the 160 kDa protein in gel mobility shift assays. We conclude that a 160 kDa protein or complex of proteins binds specifically to the human ARE sequence but not to the TRE. The 160 kDa protein does not contain Fos or Jun proteins, and its binding is abolished by the reducing agent, dithiothreitol.

Transcriptional regulation of the human NAD(P)H:quinone oxidoreductase (NQO1) gene by monofunctional inducers.

The upstream region of the human NAD(P)H:quinone oxidoreductase (NQO1) gene contains a functional antioxidant responsive element (ARE) and an overlapping 12-O-tetradecanoyl-phorbol-13-acetate responsive element (TRE), with the sequence TGACTCAGCA. We show that the ARE (TGACNNNGCA) is required for induction by redox cycling phenolics (p-benzoquinone, catechol and hydroquinone), which are monofunctional inducers and induce NQO1 without the requirement for activation by cytochrome P-450. The TRE (TGACTCA) is involved only in basal expression. A plasmid containing overlapping ARE-TRE (TGACTCAGCA) sequences (-587 to -379) from the NAD(P)H:quinone oxidoreductase gene was transiently transfected into Hep G2 cells. In the absence of inducers, basal expression was 4-fold higher than in F9 cells (which lack AP-1 activity). Using subcloned oligonucleotides containing the ARE-TRE sequence (-473 to -440), the ARE sequence alone (TCA changed to GAC) and the TRE sequence alone (GC changed to TA), the basal level of expression was in the order: TRE > TRE-ARE > ARE in Hep G2 cells. Using F9 cells, basal expression was detected using the combination ARE-TRE sequence or the ARE, but not the TRE alone, p-Benzoquinone, catechol and hydroquinone, but not resorcinol, induced gene expression in both Hep G2 and F9 cells via the ARE-TRE and ARE sequences, but the TRE sequence did not contribute to this induction. We therefore conclude that induction of human NAD(P)H:quinone oxidoreductase by monofunctional inducers is via the ARE and not the TRE, and that the induction is mediated by proteins other than Fos and Jun.

Interaction of beta-cyclodextrin with the granular starch binding domain of glucoamylase.

The granular starch binding domain of glucoamylase 1 (EC 3.2.1.3 1,4-alpha-D-glucan glucohydrolase) binds two molecules of beta-cyclodextrin, with a dissociation constant (Kd) for the second ligand of 1.68 microM. The catalytic domain showed no interaction with beta-cyclodextrin. Beta-cyclodextrin competitively inhibited the adsorption of the binding domain onto granular starch with an inhibition constant (Ki) of 11.0 +/- 1.9 microM. The results show that beta-cyclodextrin binds to the binding domain of glucoamylase at the same site(s) as granular starch.

A convenient and rapid method for the complete removal of CoA from butyryl-CoA dehydrogenase.

The commercially available gel, 2-pyridyl disulphide hydroxypropyl ether-Sepharose (thiopropyl-Sepharose 6B), can be used to remove bound ligand completely from butyryl-CoA dehydrogenase (EC 1.399.2) in two simple operations. The resultant enzyme forms normal complexes with acetoacetyl-CoA and CoA persulphide, contains no bound CoA as determined by the enzymatic assay for CoA, and retains full catalytic activity.

Antigenic relatedness of small ribonucleoprotein particles.

We have examined the relationships among small ribonucleoprotein particles found in eucaryotic cells by an antigen depletion technique using autoimmune antibodies. We have confirmed that the (U1) ribonucleoprotein particle antigen is found on the same complex as the Sm antigen. We have also shown that the Ro antigen is found on the same complexes as the La antigen. However, both Sm and La antigens are also found on complexes that are never associated with (U1) ribonucleoprotein particle and Ro, respectively. Further, U1 containing complexes can exist that contain the Sm antigen but not the (U1) ribonucleoprotein particle antigen. In a similar manner, we find several La-Ro RNA containing complexes that carry the La antigen but do not always carry the Ro antigen. Sm and La antigen are quantitatively associated with their specific ribonucleoprotein complexes.

Oxidation-reduction potential studies on p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens.

The oxidation-reduction potential of p-hydroxybenzoate hydroxylase (4-hydroxybenzoate, NADPH: oxygen oxidoreductase (3-hydroxylating), EC 1.14.13.2) from Pseudomonas fluorescens has been measured in the presence and absence of p-hydroxybenzoate using spectrocoulometry. The native enzyme demonstrated a two-electron midpoint potential of -129 mV during the initial reductive titration. The midpoint potential observed during subsequent oxidative and reductive titrations was -152 mV. This marked hysteresis is proposed to arise from the oxidation and reduction of the known air-sensitive thiol group on the enzyme (Van Berkel, W.J.H. and Müller, F. (1987) Eur. J. Biochem. 167, 35-46). Redox titrations of the enzyme in the presence of substrate showed a two-electron midpoint potential of -177 mV. No spectral or electrochemical evidence for the thermodynamic stabilization of any flavin semiquinone was observed in the titrations performed. These data show that the affinity of the apoenzyme for the hydroquinone form of FAD is 150-fold greater than for the oxidized flavin and that the substrate is bound to the reduced enzyme with a 3-fold lower affinity than to the oxidized enzyme. These data are consistent with the view that the stimulatory effect of substrate binding on the rate of enzyme reduction by NADPH is due to the respective geometries of the bound FAD and NADPH rather than to a large perturbation of the oxidation-reduction potential of the bound flavin coenzyme.

Specificity of an esterase (XYLD) from Pseudomonas fluorescens subsp. cellulosa.

Activity of an esterase from Pseudomonas fluorescens subsp. cellulosa (XYLD) on an insoluble feruloylated hemicellulose substrate (de-starched wheat bran) was dependent on the source of added endo-xylanase. The esterase exhibited high selectivity for the nature, position of linkage and size of the feruloylated oligosaccharides generated by hydrolysis of the hemicellulose. Increased affinity of XYLD with increasing size of the oligosaccharide substrate suggests that optimal activity is observed on substrates with at least 4 sugars.