Characterisation of Leucaena condensed tannins by size and protein precipitation capacity

The ability of differently sized condensed tannins from the genus Leucaena, a fodder tree-legume, to bind protein at different pH values was evaluated to characterise their potential biological effects. Two factors affecting the ability of condensed tannin to bind protein, its major biological activity, have been purported to be the condensed tannin size and the pH of the reaction environment. To test these hypotheses, the protein-precipitating capacities of condensed tannin extracted from four Leucaena genotypes, L leucocephala (UHK636), L pallida (CQ3439), L trichandra (CP146568) and L collinsii (OFI52/88), were assessed. Condensed tannin from L leucocephala had approximately 50% of the ability to precipitate protein on a gg(-1) basis than L pallida or L trichandra, while L collinsii gave no measurable ability to precipitate protein (reaction environment pH 5.0). Increasing or decreasing the pH of the reaction solution away from pH 5.0 (approximately the isoelectric point of the protein) reduced the ability of condensed tannin from all the species to precipitate protein, the decrease being higher at pH 2.5 than at pH 7.5. Condensed tannins from each Leucaena species were also separated by size exclusion chromatography, and the fractions examined for protein-precipitating capacity. In general, it was found that the larger-sized condensed tannin of the accessions L pallida and L trichandra could precipitate more protein than the smaller-sized condensed tannin. This pattern was not found for L leucocephala. (C) 2001 Society of Chemical Industry.

Human cortical processing of colour and pattern

The present study investigates human visual processing of simple two-colour patterns using a delayed match to sample paradigm with positron emission tomography (PET). This study is unique in that we specifically designed the visual stimuli to be the same for both pattern and colour recognition with all patterns being abstract shapes not easily verbally coded composed of two-colour combinations. We did this to explore those brain regions required for both colour and pattern processing and to separate those areas of activation required for one or the other. We found that both tasks activated similar occipital regions, the major difference being more extensive activation in pattern recognition. A right-sided network that involved the inferior parietal lobule, the head of the caudate nucleus, and the pulvinar nucleus of the thalamus was common to both paradigms. Pattern recognition also activated the left temporal pole and right lateral orbital gyrus, whereas colour recognition activated the left fusiform gyrus and several right frontal regions. (C) 2001 Wiley-Liss, Inc.

Sox18 is transiently expressed during angiogenesis in granulation tissue of skin wounds with an identical expression pattern to Flk-1 mRNA

Sox18 encodes a member of the Sry-related high mobility group box (SOX) family of developmental transcription factors. Examination of Sox18 expression during embryogenesis has shown that Sox18 is expressed transiently in endothelial cells of developing blood vessels, and mutations in Sox18 have been found to underlie the mouse vascular and hair follicle mutant ragged. In this study we have examined the expression of Sox18 in angiogenesis during wound healing. Full-thickness skin wounds were created in mice, and subsequent expression of vascular endothelial growth factor (VEGF), the VEGF receptor Flk-1, alpha1 (iv) collagen (Col4a1), and Sox18 were studied using in situ hybridization. As has been previously reported, VEGF was expressed predominantly in the keratinocytes at the wound margins. Sox18 expression was found Rye days after wounding during capillary sprouting in granulation tissue and persisted through the proliferative phase of healing, but was not detected in fully epithelialized wounds 21 days after wounding. Sox18 mRNA expression was detected in capillaries within the granulation tissue and showed an identical pattern of distribution to Flk-1 and Col4a1 mRNA expression in endothelial cells. Immunostaining with a polyclonal anti-Sox18 antibody showed SOX18 protein localized in capillary endothelial cells within the granulation tissue. capillaries in the subcutaneous tissue of unwounded skin showed no Sox18 expression. Sox18 may therefore represent a transcription factor involved in the induction of angiogenesis during wound healing and tissue repair, but not in the maintenance of endothelial cells in undamaged tissue.

The role of homeotic genes in determining the segmental pattern of chordotonal organs in Drosophila

The homeotic genes are instrumental in establishing segment-specific characteristics. In Drosophila embryos there is ample evidence that the homeotic genes are involved in establishing the differences in the pattern of sense organs between segments. The chordotonal organs are compound sense organs made up of several stretch receptive sensilla. A set of serially homologous chordotonal organs, Ich3 in the 1(st) thoracic segment, dch3 in the 2(nd) and 3(rd) thoracic segments and Ich5 in abdominal segments 1 to 7, is composed of different numbers of sensilla with different positions and orientations. Here we examine this set of sense organs and a companion set, vchA/B and vch 1, in the wild type and mutants for Sex combs reduced, Antennapedia, Ultrabithorax, and abdominal-A, using immunostaining. Mutant phenotypes indicate that Ultrabithorax and abdominal-A in particular influence the formation of these sense organs. Differential expression of abdominal-A and Ultrabithorax within compartments of individual parasegments can precisely modulate the types of sense organs that will arise from a segment.

Impact of point source pollution on nitrogen isotope signatures (delta N-15) of vegetation in SE Brazil

This study presents novel evidence that N-15 natural abundance can be used as a robust indicator to detect pollutant nitrogen in natural plant communities. Vegetation from the heavily polluted industrial area of Cubatao in Sao Paulo State, SE Brazil, was strongly N-15 depleted compared to plants at remote sites. Historic herbarium samples from Cubatao were significantly less N-15 depleted than extant plants, indicating that N-15 depletion of vegetation is associated with present-day nitrogen pollution in Cubatao. The heavy load of nitrogenous atmospheric pollutants in Cubatao provides a nitrogen source for plants, and strongly N-15 depleted air NH3 is likely to contribute to plant and soil N-15 depletion. Epiphytic plants from Cubatao were extremely N-15 depleted (average -10.9parts per thousand) contrasting with epiphytes at remote sites (averages -1.0parts per thousand and -3.0parts per thousand). Nitrogen isotope composition of vegetation provides a tool to determine input of pollutant nitrogen into plant communities. The strong isotopic change of epiphytes suggests that epiphytes are particularly sensitive biomonitors for atmospheric pollutant nitrogen.

A hedging point strategy - balancing effluent quality, economy and robustness in the control of wastewater treatment plants

An operational space map is an efficient tool to compare a large number of operational strategies to find an optimal choice of setpoints based on a multicriterion. Typically, such a multicriterion includes a weighted sum of cost of operation and effluent quality. Due to the relative high cost of aeration such a definition of optimality result in a relatively high fraction of the effluent total nitrogen in the form of ammonium. Such a strategy may however introduce a risk into operation because a low degree of ammonium removal leads to a low amount of nitrifiers. This in turn leads to a reduced ability to reject event disturbances, such as large variations in the ammonium load, drop in temperature, the presence of toxic/inhibitory compounds in the influent etc. Hedging is a risk minimisation tool, with the aim to "reduce one's risk of loss on a bet or speculation by compensating transactions on the other side" (The Concise Oxford Dictionary (1995)). In wastewater treatment plant operation hedging can be applied by choosing a higher level of ammonium removal to increase the amount of nitrifiers. This is a sensible way to introduce disturbance rejection ability into the multi criterion. In practice, this is done by deciding upon an internal effluent ammonium criterion. In some countries such as Germany, a separate criterion already applies to the level of ammonium in the effluent. However, in most countries the effluent criterion applies to total nitrogen only. In these cases, an internal effluent ammonium criterion should be selected in order to secure proper disturbance rejection ability.

Sediment yield and impacts from river catchments to the Great Barrier Reef lagoon

Land use intensification is estimated to result in an overall increase in sediment delivery to the Great Barrier Reef lagoon by a factor of approximately four. Modelling suggests that, following land use intensification, croplands cause the greatest increase of sediment yield and sediment concentration, whereas erosion of grazing land is the main contemporary source of sediments, primarily owing to the large spatial extent of this land use. The spatial pattern of sediment yield to the coast after land use intensification is strongly correlated with the pattern under natural conditions, although the greatest increase is estimated to have occurred in the wet-dry catchments. Sediment transport and resuspension processes have led to the development of a strongly sediment-partitioned shelf, with modern mud-rich sediments almost exclusively restricted to the inner and inner-middle shelf, northward-facing embayments and in the lee of headlands. Elevated sediment concentrations increase the potential transport rates of nutrients and other pollutants. Whether increased sediment supply to the coastal zone has impacted on reefs remains a point of contention. More sediment load data need to be collected and analysed in order to make detailed estimates of catchment yields and establish the possible sediment impact on the Great Barrier Reef.

Fixed point theorems of upper semicontinuous multivalued mappings with applications in hyperconvex metric spaces

In the present paper, we establish two fixed point theorems for upper semicontinuous multivalued mappings in hyperconvex metric spaces and apply these to study coincidence point problems and minimax problems. (C) 2002 Elsevier Science (USA). All rights reserved.

Cloud-point extraction and preconcentration of cyanobacterial toxins (microcystins) from natural waters using a cationic surfactant

A new cloud-point extraction and preconcentration method, using a cationic, surfactant, Aliquat-336 (tricaprylyl-methy;ammonium chloride), his-been developed for the determination of cyanobacterial toxins, microcystins, in natural waters. Sodium sulfate was used to induce phase separation at 25 degreesC. The phase behavior of Aliquat-336 with respect to concentration of Na2SO4 was studied. The cloud-point system revealed a very high phase volume ratio compared to other established systems of nonionic, anionic, and cationic surfactants: At pH 6-7, it showed an outstanding selectivity in ahalyte extraction for anionic species. Only MC-LR and MC-YR, which are known to be predominantly anionic, were extracted (with averaged recoveries of 113.9 +/- 9% and 87.1 +/- 7%, respectively). MC-RR, which is likely to be amphoteric at the above pH range, was. not cle tectable in.the extract. Coupled to HPLC/UV separation and detection, the cloud-point extraction method (with 2.5 mM Aliquat-336 and 75 mM Na2SO4 at 25 degreesC) offered detection limits of 150 +/- 7 and 470 +/- 72 pg/mL for MC-LR and MC-YR, respectively, in 25 mL of deionized water. Repeatability of the method was 7.6% for MC-LR and 7.3% for MC-YR: The cloud-point extraction process can be. completed within 10-15 min with no cleanup steps required. Applicability of the new method to the determination of microcystins in real samples was demonstrated using natural surface waters, collected from a local river and a local duck pond spiked with realistic. concentrations of microcystins. Effects of salinity and organic matter (TOC) content in the water sample on the extraction efficiency were also studied.

A uniform white-noise model for fixed-point roundoff errors in digital systems

Fixed-point roundoff noise in digital implementation of linear systems arises due to overflow, quantization of coefficients and input signals, and arithmetical errors. In uniform white-noise models, the last two types of roundoff errors are regarded as uniformly distributed independent random vectors on cubes of suitable size. For input signal quantization errors, the heuristic model is justified by a quantization theorem, which cannot be directly applied to arithmetical errors due to the complicated input-dependence of errors. The complete uniform white-noise model is shown to be valid in the sense of weak convergence of probabilistic measures as the lattice step tends to zero if the matrices of realization of the system in the state space satisfy certain nonresonance conditions and the finite-dimensional distributions of the input signal are absolutely continuous.

Matching SOX: partner proteins and co-factors of the SOX family of transcriptional regulators

SOX transcription factors perform a remarkable variety of important roles in vertebrate development, either activating or repressing specific target genes through interaction with different partner proteins. Surprisingly, these interactions are often mediated by the conserved, DNA-binding HMG domain, raising questions as to how each factor's specificity is generated. We propose a model whereby non-HMG domains may influence partner protein selection and/or binding stability.

Point source inoculation of Mesocyclops (Copepoda : Cyclopidae) gives widespread control of Ochlerotatus and Aedes (Diptera : Culicidae) immatures in service manholes and pits in North Queensland, Australia

This study details the novel application of predacious copepods, genus Mesocyclops, for control of Ochlerotatus tremulus (Theobald) group and Aedes aegypti (L.) mosquito larvae in subterranean habitats in north Queensland, Australia. During June 1997, 50 Mesocyclops sp. I were inoculated into one service manhole in South Townsville. Wet season rainfall and flooding in both 1998 and 2000 was responsible for the dispersal of copepods via the underground pipe system to 29 of 35 manholes over an area of 1.33 km(2). Significant reductions in Aedes and Ochlerotatus larvae ensued. In these habitats, Mesocyclops and Metacyclops were able to survive dry periods, when substrate moisture content ranged from 13.8 to 79.9%. At the semiarid inland towns of Hughenden and Richmond, cracking clay soil prevents drainage of water from shallow service pits where Oc. tremulus immatures numbered from 292-18,460 per pit. Introduction of Mesocyclops copepods into these sites during May 1999 resulted in 100% control of Oc. tremulus for 18 mo. One uninoculated pit subsequently became positive for Mesocyclops with resultant control of mosquito larvae.

The nonexistence of spurious solutions to discrete, two-point boundary value problems

We investigate difference equations which arise as discrete approximations to two-point boundary value problems for systems of second-order, ordinary differential equations. We formulate conditions under which all solutions to the discrete problem satisfy certain a priori bounds which axe independent of the step-size. As a result, the nonexistence of spurious solutions are guaranteed. Some existence and convergence theorems for solutions to the discrete problem are also presented. (C) 2002 Elsevier Science Ltd. All rights reserved.