Diurnal changes in the photochemical efficiency of the symbiotic dinoflagellates (Dinophyceae) of corals: photoprotection, photoinactivation and the relationship to coral bleaching

The photochemical efficiency of symbiotic dinoflagellates within the tissues of two reef-building corals in response to normal and excess irradiance at wafer temperatures < 30 C were investigated using pulse amplitude modulated (PAM) chlorophyll fluorescence techniques, Dark-adapted F-v/F-m showed clear diurnal changes, decreasing to a low at solar noon and increasing in the afternoon. However, F-v/F-m also drifted downwards at night or in prolonged darkness, and increased rapidly during the early morning twilight. This parameter also increased when the oxygen concentration of the wafer holding the corals was increased. Such changes have not been described previously, and most probably reflect state transition's associated with PQ pool reduction via chlororespiration. These unusual characteristics may be a feature of an endosymbiotic environment, reflective of the well-documented night-time tissue hypoxia that occurs in corals. F-v/F-m decreased to 0.25 in response to full sunlight in shade-acclimated (shade) colonies of Stylophora pistillata, which is considerably lower than in light-acclimated (sun) colonies. In sun colonies, the reversible decrease in F-v/F-m was caused by a lowering of F-m and F-o suggesting photoprotection and no lasting damage. The decrease in F-v/F-m, however, was caused by a decrease in F-m and an increase in F-o in shade colonies suggesting photoinactivation and long-term cumulative photoinhibition. Shade colonies rapidly lost their symbiotic algae (bleached) during exposure to full sunlight. This study is consistent with the hypothesis that excess light leads to chronic damage of symbiotic dinoflagellates and their eventual removal from reef-building corals. It is significant that this can occur with high light conditions alone.

Brain activity during the encoding, retention, and retrieval of stimulus representations

Studies of delayed nonmatching-to-sample (DNMS) performance following lesions of the monkey cortex have revealed a critical circuit of brain regions involved in forming memories and retaining and retrieving stimulus representations. Using event-related functional magnetic resonance imaging (fMRI), we measured brain activity in 10 healthy human participants during performance of a trial-unique visual DNMS task using novel barcode stimuli. The event-related design enabled the identification of activity during the different phases of the task (encoding, retention, and retrieval). Several brain regions identified by monkey studies as being important for successful DNMS performance showed selective activity during the different phases, including the mediodorsal thalamic nucleus (encoding), ventrolateral prefrontal cortex (retention), and perirhinal cortex (retrieval). Regions showing sustained activity within trials included the ventromedial and dorsal prefrontal cortices and occipital cortex. The present study shows the utility of investigating performance on tasks derived from animal models to assist in the identification of brain regions involved in human recognition memory.

Integrating technology to improve the efficiency of qualitative data analysis - A note on methods

Qualitative data analysis (QDA) is often a time-consuming and laborious process usually involving the management of large quantities of textual data. Recently developed computer programs offer great advances in the efficiency of the processes of QDA. In this paper we report on an innovative use of a combination of extant computer software technologies to further enhance and simplify QDA. Used in appropriate circumstances, we believe that this innovation greatly enhances the speed with which theoretical and descriptive ideas can be abstracted from rich, complex, and chaotic qualitative data. © 2001 Human Sciences Press, Inc.

Stay-green: A consequence of the balance between supply and demand for nitrogen during grain filling?

Retention of green leaf area in grain sorghum under post-anthesis drought, known as stay-green, is associated with greater biomass production, lodging resistance and yield. The stay-green phenomenon can be examined at a cell, leaf, or whole plant level. At a cell level, the retention of chloroplast proteins such as LHCP2, OEC33 and Rubisco until late in senescence has been reported in sorghum containing the KS19 source of stay-green, indicating that photosynthesis may be maintained for longer during senescence in these genotypes. At a leaf level, longevity of photosynthetic apparatus is intimately related to nitrogen (N) status. At a whole plant level, stay-green can be viewed as a consequence of the balance between N demand by the grain and N supply during grain filling. To examine some of these concepts, nine hybrids varying in the B35 and KS19 sources of stay-green were grown under a postanthesis water deficit. Genotypic variation in delayed onset and reduced rate of leaf senescence were explained by differences in specific leaf nitrogen (SLN) and N uptake during grain filling. Matching N supply from age-related senescence and N uptake during grain tilling with grain N demand found that the shortfall in N supply for grain filling was greater in the senescent than stay-green hybrids, resulting in more accelerated leaf senescence in the former. We hypothesise that increased N uptake by stay-green hybrids is a result of greater biomass accumulation during grain filling in response to increased sink demand (higher grain numbers) which, in turn, is the result of increased radiation use efficiency and transpiration efficiency due to higher SLN. Delayed leaf senescence resulting from higher SLN should, in turn, allow snore carbon and nitrogen to be allocated to the roots of stay-green hybrids during grain filling, thereby maintaining a greater capacity to extract N from the soil compared with senescent hybrids.

Capacity utilisation and profitability: A decomposition of short-run profit efficiency

The principal aim of this paper is to measure the amount by which the profit of a multi-input, multi-output firm deviates from maximum short-run profit, and then to decompose this profit gap into components that are of practical use to managers. In particular, our interest is in the measurement of the contribution of unused capacity, along with measures of technical inefficiency, and allocative inefficiency, in this profit gap. We survey existing definitions of capacity and, after discussing their shortcomings, we propose a new ray economic capacity measure that involves short-run profit maximisation, with the output mix held constant. We go on to describe how the gap between observed profit and maximum profit can be calculated and decomposed using linear programming methods. The paper concludes with an empirical illustration, involving data on 28 international airline companies. The empirical results indicate that these airline companies achieve profit levels which are on average US$815m below potential levels, and that 70% of the gap may be attributed to unused capacity. (C) 2002 Elsevier Science B.V. All rights reserved.

The efficiency and condition of oysters and macroalgae used as biological filters of shrimp pond effluent

Current shrimp pond management practices generally result in elevated concentrations of nutrients, suspended solids, bacteria and phytoplankton compared with the influent water. Concerns about adverse environmental impacts caused by discharging pond effluent directly into adjacent waterways have prompted the search for cost-effective methods of effluent treatment. One potential method of effluent treatment is the use of ponds or raceways stocked with plants or animals that act as natural biofilters by removing waste nutrients. In addition to improving effluent water quality prior to discharge, the use of natural biofilters provides a method for capturing otherwise wasted nutrients. This study examined the potential of the native oyster, Saccostrea commercialis (Iredale and Roughley) and macroalgae, Gracilaria edulis (Gmelin) Silva to improve effluent water quality from a commercial Penaeus japonicus (Bate) shrimp farm, A system of raceways was constructed to permit recirculation of the effluent through the oysters to maximize the filtration of bacteria, phytoplankton and total suspended solids. A series of experiments was conducted to test the ability of oysters and macroalgae to improve effluent water quality in a flow-through system compared with a recirculating system. In the flow-through system, oysters reduced the concentration of bacteria to 35% of the initial concentration, chlorophyll a to 39%, total particulates (2.28-35.2 mum) to 29%, total nitrogen to 66% and total phosphorus to 56%. Under the recirculating flow regime, the ability of the oysters to improve water quality was significantly enhanced. After four circuits, total bacterial numbers were reduced to 12%, chlorophyll a to 4%, and total suspended solids to 16%. Efforts to increase biofiltration by adding additional layers of oyster trays and macroalgae-filled mesh bags resulted in fouling of the lower layers causing the death of oysters and senescence of macroalgae. Supplementary laboratory experiments were designed to examine the effects of high effluent concentrations of suspended particulates on the growth and condition of oysters and macroalgae. The results demonstrated that high concentrations of particulates inhibited growth and reduced the condition of oysters and macroalgae. Allowing the effluent to settle before biofiltration improved growth and reduced signs of stress in the oysters and macroalgae. A settling time of 6 h reduced particulates to a level that prevented fouling of the oysters and macroalgae.

Supply chain management as beyond operational efficiency

The orthodoxy of supply chain management (SCM) emphasises competitive advantage through increased operational efficiency and market responsiveness from production and distribution processes into the hands of consumers. It anticipates that future competition will be between chains rather than between firms. While well established in other industry sectors, the SCM concept is newly developed in the Australian agri-food sector. Critical review of the concept has identified key issues of power among channel members, processes of chain initiation and innovation, and the inability of SCM to offer a viable business strategy for some firms. Building on those insights, this paper examines the supply chain concept for horticulture. Horticultural products are characterised by perishability, heterogeneity and lags in production response to market signals. Producers’ profits are vulnerable to quantity, timing of supply and product specification. Many supply chains in smaller industries are loose, fragmented, interwoven, unstable and unique! Firms operating within these environments need an astute understanding of the chains, the hierarchy of channel members and their relative position. Effective business strategies – for individual firms and supply chains - need to be developed and redeveloped to accommodate the dynamic nature of horticulture. Two case studies are discussed as contributions to this early stage of the theoretical development of supply chain management. The SCM concept also has implications for horticultural researchers, involving a wider range of industry stakeholders, technical problems and research skills. As for business management, the usefulness of the concept will depend on its capacity to increase responsiveness to customers’ preferences and customer value.

Identification of research to improve the efficiency of breeding strategies for white clover in Australia - a review

A major challenge faced by today's white clover breeder is how to manage resources within a breeding program. It is essential to utilise these resources with sufficient flexibility to build on past progress from conventional breeding strategies, but also take advantage of emerging opportunities from molecular breeding tools such as molecular markers and transformation. It is timely to review white clover breeding strategies. This background can then be used as a foundation for considering how to continue conventional plant improvement activities and complement them with molecular breeding opportunities. In this review, conventional white clover breeding strategies relevant to the Australian dryland target population environments are considered. Attention is given to: (i) availability of genetic variation, (ii) characterisation of germplasm collections, (iii) quantitative models for estimation of heritability, (iv) the role of multi-environment trials to accommodate genotype-by-environment interactions, (v) interdisciplinary research to understand adaptation to dryland environments, (vi) breeding and selection strategies, and (vii) cultivar structure. Current achievements in biotechnology with specific reference to white clover breeding in Australia are considered, and computer modelling of breeding programs is discussed as a useful integrative tool for the joint evaluation of conventional and molecular breeding strategies and optimisation of resource use in breeding programs. Four areas are identified as future research priorities: (i) capturing the potential genetic diversity among introduced accessions and ecotypes that are adapted to key constraints such as summer moisture stress and the use of molecular markers to assess the genetic diversity, (ii) understanding the underlying physiological/morphological root and shoot mechanisms involved in water use efficiency of white clover, with the objective of identifying appropriate selection criteria, (iii) estimation of quantitative genetic parameters of important morphological/physiological attributes to enable prediction of response to selection in target environments, and (iv) modelling white clover breeding strategies to evaluate the opportunities for integration of molecular breeding strategies with conventional breeding programs.

Prolonged retention after aggregation into secretory granules of human R183H-growth hormone (GH), a mutant that causes autosomal dominant GH deficiency type II

Human R183H-GH causes autosomal dominant GH deficiency type II. Because we show here that the mutant hormone is fully bioactive, we have sought to locate an impairment in its progress through the secretory pathway as assessed by pulse chase experiments. Newly synthesized wild-type and R183H-GH were stable when expressed transiently in AtT20 cells, and both formed equivalent amounts of Lubrol-insoluble aggregates within 40 min after synthesis. There was no evidence for intermolecular disulfide bond formation in aggregates of wild-type hormone or the R183H mutant. Both wildtype and R183H-GH were packaged into secretory granules, assessed by the ability of 1 mm BaCl2 to stimulate release and by immunocytochemistry. The mutant differed from wildtype hormone in its retention in the cells after packaging into secretory granules; 50% more R183H-GH than wild-type aggregates were retained in AtT20 cells 120 min after synthesis, and stimulated release of R183H-GH or a mixture of R183H-GH and wild-type that had been retained in the cell was reduced. The longer retention of R183H-GH aggregates indicates that a single point mutation in a protein contained in secretory granules affects the rate of secretory granule release.

Effect of vehicle pretreatment on the flux, retention, and diffusion of topically applied penetrants in vitro

Purpose. The flux of a topically applied drug depends on the activity in the skin and the interaction between the vehicle and skin. Permeation of vehicle into the skin can alter the activity of drug and the properties of the skin barrier. The aim of this in vitro study was to separate and quantify these effects. Methods. The flux of four radiolabeled permeants (water, phenol, diflunisal, and diazepam) with log K-oct/water values from 1.4 to 4.3 was measured over 4 h through heat-separated human epidermis pretreated for 30 min with vehicles having Hildebrand solubility parameters from 7.9 to 23.4 (cal/cm(3))(1/2). Results. Enhancement was greatest after pretreatment with the more lipophilic vehicles. A synergistic enhancement was observed using binary mixtures. The flux of diazepam was not enhanced to the same extent as the other permeants, possibly because its partitioning into the epidermis is close to optimal (log K-oct 2.96). Conclusion. An analysis of the permeant remaining in the epidermis revealed that the enhancement can be the result of either increased partitioning of permeant into the epidermis or an increasing diffusivity of permeants through the epidermis.

Transdermal penetration of vasoconstrictors - Present understanding and assessment of the human epidermal flux and retention of free bases and ion-pairs

Purpose. As reductions in dermal clearance increase the residence time of solutes in the skin and underlying tissues we compared the topical penetration of potentially useful vasoconstrictors (VCs) through human epidermis as both free bases and ion-pairs with salicylic acid (SA). Methods. We determined the in vitro epidermal flux of ephedrine, naphazoline, oxymetazoline, phenylephrine, and xylometazoline applied as saturated solutions in propylene glycol: water (1: 1) and of ephedrine, naphazoline and tetrahydrozoline as 10% solutions of 1: 1 molar ratio ion-pairs with SA in liquid paraffin. Results. As free bases, ephedrine had the highest maximal flux, Jmax = 77.4 +/- 11.7 mug/cm(2)/h, being 4-fold higher than tetrahydrozoline and xylometazoline, 6-fold higher than phenylephrine, 10-fold higher than naphazoline and 100-fold higher than oxymetazoline. Stepwise regression of solute physicochemical properties identified melting point as the most significant predictor of flux. As ion-pairs with SA, ephedrine and naphazoline had similar fluxes (11.5 +/- 2.3 and 12.0 +/- 1.6 mug/cm(2)/h respectively), whereas tetrahydrozoline was approximately 3-fold slower. Corresponding fluxes of SA from the ion-pairs were 18.6 +/- 0.6, 7.8 +/- 0.8 and 1.1 +/- 0.1 respectively. Transdermal transport of VC's is discussed. Conclusions. Epidermal retention of VCs and SA did not correspond to their molar ratio on application and confirmed that following partitioning into the stratum corneum, ion-pairs separate and further penetration is governed by individual solute characteristics.

Nitrate retention under sugarcane in wet tropical Queensland deep soil profiles

Nitrate leaching below the crop root-zone in variable charge soils may be adsorbed at anion exchange sites, thereby temporarily reducing the risk of contamination of water bodies. The objectives of this study were (i) to investigate whether nitrate adsorption, accumulation, and retention in the Johnstone River Catchment of Far North Queensland wet tropics is widespread; (ii) to assess the capacity of soil in the Johnstone River Catchment to retain nitrate; and (iii) to deduce the consequences of nitrate adsorption/desorption on contamination of water bodies. Soil cores ranging from 8 to 12.5 m depth were taken from 28 sites across the catchment, representing 9 Ferrosol soil types under sugarcane (Saccharum officinarum-S) cultivation for at least 50 years and from rainforest. The cores were segmented at 0.5-m depth increments and subsamples were analysed for nitrate-N, cation and anion exchange capacities, pH, exchangeable cations (Ca, Mg, K, Na), soil organic C, electrical conductivity, sulfate-S, and chloride. Nitrate-N concentration under sugarcane ranged from 0 to 72.5 mg/kg, compared with 0 to 0.31 mg/kg under rainforest, both Pin Gin soils. The average N load in 1-12 m depth across 19 highly oxidic profiles of the Pin Gin soil series was 1550 kg/ha, compared with 185 kg/ha under 8 non-Pin Gin soils and 11 kg/ha in rainforest on a Pin Gin soil. Most of the nitrate retention was observed at depth of 2-12 m, particularly at 4-10 m, indicating that the accumulation was well below the crop root-zone. The average maximum potential nitrate retention capacity was 10.8 t/ha for the Pin Gin and 4.7 t/ha for the non-Pin Gin soil. Compared with the current N load, the soils still possess a large capacity to adsorb and retain nitrate in profiles. Retention of large quantities of the leached nitrate deep in most of the profiles has reduced the risk of contamination of water bodies. However, computations show that substantial quantities of the nitrate leached below the root-zone were not adsorbed and remain unaccounted for. This unaccounted nitrate might have entered both on- and off-site water bodies and/or have been denitrified.