Showing papers by "James Cook University published in 2000"

Classification and regression trees: a powerful yet simple technique for ecological data analysis

Abstract: Classification and regression trees are ideally suited for the analysis of com- plex ecological data. For such data, we require flexible and robust analytical methods, which can deal with nonlinear relationships, high-order interactions, and missing values. Despite such difficulties, the methods should be simple to understand and give easily interpretable results. Trees explain variation of a single response variable by repeatedly splitting the data into more homogeneous groups, using combinations of explanatory var- iables that may be categorical and/or numeric. Each group is characterized by a typical value of the response variable, the number of observations in the group, and the values of the explanatory variables that define it. The tree is represented graphically, and this aids exploration and understanding. Trees can be used for interactive exploration and for description and prediction of patterns and processes. Advantages of trees include: (1) the flexibility to handle a broad range of response types, including numeric, categorical, ratings, and survival data; (2) invariance to monotonic transformations of the explanatory variables; (3) ease and ro- bustness of construction; (4) ease of interpretation; and (5) the ability to handle missing values in both response and explanatory variables. Thus, trees complement or represent an alternative to many traditional statistical techniques, including multiple regression, analysis of variance, logistic regression, log-linear models, linear discriminant analysis, and survival models. We use classification and regression trees to analyze survey data from the Australian central Great Barrier Reef, comprising abundances of soft coral taxa (Cnidaria: Octocorallia) and physical and spatial environmental information. Regression tree analyses showed that dense aggregations, typically formed by three taxa, were restricted to distinct habitat types, each of which was defined by combinations of 3-4 environmental variables. The habitat definitions were consistent with known experimental findings on the nutrition of these taxa. When used separately, physical and spatial variables were similarly strong predictors of abundances and lost little in comparison with their joint use. The spatial variables are thus effective surrogates for the physical variables in this extensive reef complex, where infor- mation on the physical environment is often not available. Finally, we compare the use of regression trees and linear models for the analysis of these data and show how linear models fail to find patterns uncovered by the trees.

The prevalence of low back pain: A systematic review of the literature from 1966 to 1998

Abstract: A systematic literature review of population prevalence studies of low back pain between 1966 and 1998 was conducted to investigate data homogeneity and appropriateness for pooling. Fifty-six studies were analyzed using methodologic criteria that examined sample representativeness, data quality, and pain definition. Acceptable studies were assessed for homogeneity and appropriateness for pooling. Thirty were methodologically acceptable. Of these there were significant differences in study design, patient age, mode of data collection, potential temporal effects, and prevalence results. Point prevalence ranged from 12% to 33%, 1-year prevalence ranged from 22% to 65%, and lifetime prevalence ranged from 11% to 84%. A limited number of studies were left for analysis, making the pooling of data difficult. A model using uniform best-practice methods is proposed.

Bleaching of corals on the Great Barrier Reef: differential susceptibilities among taxa

Abstract: Large-scale coral bleaching episodes are potentially major disturbances to coral reef systems, yet a definitive picture of variation in assemblage response and species susceptibilities is still being compiled. Here, we provide a detailed analysis of the bleaching response of 4160 coral colonies, representing 45 genera and 15 families, from two depths at four sites on reefs fringing inshore islands on the Great Barrier Reef. Six weeks after the onset of large-scale bleaching in 1998, between 11 and 83% of colonies along replicate transects were affected by bleaching, and mortality was 1 to 16%. There were significant differences in bleaching response between sites, depths and taxa. Cyphastrea, Turbinaria and Galaxea were relatively unaffected by bleaching, while most acroporids and pocilloporids were highly susceptible. The hydrocorals (Millepora spp.) were the most susceptible taxa, with 85% mortality. Spatial variation in assemblage response was linked to the taxonomic composition of reef sites and their bleaching history. We suggest, therefore, that much of the spatial variation in bleaching response was due to assemblage composition and thermal acclimation.

Recruitment failure, life histories, and long‐term decline of caribbean corals

Abstract: Population decline, local extinction, and recovery are profoundly influenced by variation in demography and life-history traits. In open populations, changes in patterns of recruitment may also have a major influence on the size of local populations, particularly for short-lived organisms. We examine here the demographic processes underlying a slow decline of corals on Jamaican reefs, where coral cover has decreased by fourfold over a 16-yr period. We divided the study into three approximately equal intervals (1977–1982, 1982–1987, and 1987–1993) and constructed size-based transition matrices for each of three abundant species of corals (Montastrea annularis, Agaricia agaricites, and Leptoseris cucullata) that differ substantially in life history: Montastrea is slower-growing, longer-lived, and has lower rates of recruitment than the other two species. Rates of survival, population growth (λ), and recruitment declined substantially over time for all species and the stable size structures became increasingly dominated by small colonies. Elasticity and life table response analysis showed that changes in the persistence of large colonies had the biggest impact on population growth in all species. Simulations indicated that the levels of larval recruitment required to maintain populations at 1977 levels increased sharply over time, even as the actual recruitment rate declined. Recruitment failure was much more important to A. agaricites and L. cucullata than to M. annularis, which could survive long periods with minimal larval input. Recovery of these populations will require an increase in both survival and recruitment. The likelihood of the latter will depend on the scale of larval dispersal, and on the impact of large-scale mortality of adults on stock-recruitment relationships. Differences in connectivity and life histories of corals will determine future patterns of recovery or further decline.

Genotypic diversity and gene flow in brooding and spawning corals along the Great Barrier Reef, Australia.

Abstract: Marine organisms exhibit great variation in reproductive modes, larval types, and other life-history traits that may have major evolutionary consequences. We measured local and regional patterns of genetic variation in corals along Australia's Great Barrier Reef to determine the relative contributions of sexual and asexual reproduction to recruitment and to infer levels of gene flow both locally (among adjacent sites, < 5 km apart) and regionally (among reefs separated by 500-1,200 km). We selected five common brooding species (Acropora cuneata, A. palifera, Pocillopora damicornis, Seriatopora hystrix, and Stylophora pistillata) and four broadcast spawners (Acropora hyacinthus, A. cytherea, A. millepora, and A. valida), which encompassed a wide range of larval types and potential dispersal capabilities. We found substantial genotypic diversity at local scales in six of the nine species (four brooders, two spawners). For these six, each local population displayed approximately the levels of multilocus genotypic diversity (Go) expected for outcrossed sexual reproduction (mean values of Go:Ge ranged from 0.85 to 1.02), although consistent single-locus heterozygous deficits indicate that inbreeding occurs at the scale of whole reefs. The remaining three species, the brooder S. hystrix and the spawners A. valida and A. millepora displayed significantly less multilocus genotypic diversity (Go) than was expected for outcrossed sexual reproduction (Ge) within each of several sites. Acropora valida and A. millepora showed evidence of extensive localized asexual replication: (1) a small number of multilocus (clonal) genotypes were numerically dominant within some sites (Go:Ge values were as low as 0.17 and 0.20): (2) single-locus genotype frequencies were characterized by both excesses and deficits of heterozygotes (cf. Hardy-Weinberg expectations), and (3) significant linkage disequilibria occurred. For the brooding S. hystrix Go:Ge values were also low within each of four sites (x = 0.48). However, this result most likely reflects the highly restricted dispersal of gametes or larvae, because levels of genetic variation among sites within reefs were extremely high (FSR = 0.28). For all species, we detected considerable genetic subdivision among sites within each reef (high FSR-values), and we infer that larval dispersal is surprisingly limited (i.e., Nem among sites ranging from 0.6 to 3.3 migrants per generation), even in species that have relatively long planktonic durations. Nevertheless, our estimates of allelic variation among reefs (FRT) also imply that for all four broadcast spawning species and three of the brooders, larval dispersal is sufficient to maintain moderate to high levels of gene flow along the entire Great Barrier Reef (i.e., Nem among reefs ranged from 5 to 31). In contrast, widespread populations of S. hystrix and S. pistilata (the two remaining brooders) are relatively weakly connected (Nem among reefs was 1.4 and 2.5, respectively). We conclude that most recruitment by corals is very local, particularly in brooders, but that enough propagules are widely dispersed to ensure that both broadcast spawning and brooding species form vast effectively panmictic populations on the Great Barrier Reef.

Supply-side ecology works both ways: The link between benthic adults, fecundity, and larval recruits

Abstract: "Supply-side" ecology recognizes the potential role that recruitment plays in the local population dynamics of open systems. Apart from the applied fisheries literature, the converse link between adults and the production of cohorts of recruits has received much less attention. We used a hierarchical sampling design to investigate the relationships between adult abundance, fecundity, and rates of larval recruitment by acroporid corals on 33 reefs in five sectors (250-400 km apart) stretching from north to south along the length of the Great Barrier Reef, Australia. Our goal was to quantify patterns of recruitment at multiple scales, and to explore the underlying mechanisms. Specifically, we predicted that large-scale patterns of recruitment could be driven by changes in the abundance of adults and/or their fecundity, i.e., that corals exhibit a stock-recruitment relationship. The amount of recruitment by acroporids in each of two breeding seasons varied by more than 35-fold among the five sectors. Adult density varied only twofold among sectors and was not correlated with recruitment at the sector or reef scale. In contrast, fecundity levels (the proportion of colonies on each reef that contained ripe eggs) varied from 15% to 100%, depending on sector, year, and species. Spatial and temporal variation in the fecundity of each of three common Acropora species explained most of the variation (72%) in recruitment by acroporids, indicating that the production of larvae is a major determinant of levels of recruitment at large scales. Once fecundity was accounted for, none of the other variables we examined (sector, reef area, abundance of adults, or year) contributed significantly to variation in recruitment. The relationship between fecundity and recruitment was nonlinear, i.e., rates of recruitment increased disproportionately when and where the proportion of gravid colonies approached 100%. This pattern is consistent with the hypothesis that enhanced fertilization success and/or predator satiation occurs during mass-spawning events. Furthermore, it implies that small, sublethal changes in fecundity of corals could result in major reductions in recruitment.

Disturbance, habitat structure, and the dynamics of a coral-reef fish community

Abstract: Coral reef fishes occupy habitats that are patchy and subject to frequent natural disturbances. Although different types of disturbance are likely to generate different community responses, the relationship between different disturbance agents and their effects on reef fish communities has not been examined experimentally. We studied a set of natural patch reefs, dominated by a diverse array of soft and hard coral cover, at Lizard Island on the Great Barrier Reef (northeastern Australia). The fish assemblages on the reefs were sampled over 4 mo to establish baseline values and then experimentally disturbed. Two types of disturbance were carried out in a factorial combination: pulsed mortality by removing all fish from reefs and pulsed habitat disturbance. Habitat disturbance was applied at two levels: Level 1 consisted only of damaging all live hard corals with a hammer; Level 2 consisted of damaging all live hard corals, and in addition, using a hammer to reduce the height and complexity of the reef matrix. We then monitored the experiment for a further 19 mo, including two recruitment seasons. Unmanipulated control assemblages persisted through time, and despite large changes in total abundance, species composition remained consistent relative to disturbed treatments. Assemblages disturbed by fish removal were resilient, with recolonization from both immigration and larval settlement effectively removing differences between removal treatments and controls 3 mo after manipulation. Habitat disturbance alone generated differences between experimental and control assemblages, which persisted for the duration of the experiment. The more extreme level of habitat disturbance generated more extreme changes in fish assemblages when no pulsed mortality occurred. Habitat disturbance in combination with pulsed mortality generated similar community responses as the habitat disturbance treatment alone. However, fish removal had the effect of eliminating the difference between fish assemblages on reefs subjected to different levels of habitat disturbance. Community response to habitat disturbance was driven by species-specific patterns of reduced abundance of species associated with live coral in combination with increased numbers of those associated with rubble. Declines in the abundance of coral associates on damaged reefs were abrupt, with no recovery observed for the duration of the experiment. In contrast, increases in the abundance of rubble associates were more ephemeral, in that initial high levels of recruitment and immigration were followed by a high rate of loss. Habitat disturbance also generated reefs that typically supported lower fish abundance, fewer species, and increased evenness relative to controls. Our results support a model of patch-reef fish assemblages organized by a combination of deterministic factors (such as habitat structure) and stochastic processes (such as recruitment). These disparate mechanisms operate in concert to generate reasonably consistent patterns of community structure. Habitat structure appears to mediate much of the apparent determinism and is likely to operate both as a reflection of species-specific habitat preferences and by modifying interactions among fish species. Consequently, disturbance plays a substantial role in structuring communities of coral-reef fishes by modifying both spatial and temporal heterogeneity.

Termites and Soil Properties

Abstract: This chapter reviews the advances made in our knowledge of the effects of termites on the physical, chemical and biological properties of soils. Emphasis has been placed on more recent contributions, particularly those that explore new concepts in the ecology of termites and soils. There are sections dealing with the effects of termite activity on soil profile development, soil physical properties, soil chemical properties, soil microbiology and plant growth. The physical effects of termites on soils range from micromorphological to soil profile evolution and structure. Recent evidence points to the substantial positive influence of termites on soil hydraulic conductivity and infiltration rates. Their influence on organic matter decomposition and nutrient recycling rates are well recognized and in some landscapes termite mounds act as foci for nutrient redistribution. New information on the microbiology of termite mounds suggests that most are sites of diverse bacterial and fungal activity. Furthermore, the association between mound-building termites and the microbial population present in the structures has a synergistic effect on organic matter decomposition and hence nutrient cycling and availability. Examination of the effects of termite activity on plant production generally indicates a positive influence.

Negative genetic correlation between male sexual attractiveness and survival.

Abstract: [Extract] Indirect selection of female mating preferences may result from a genetic association between male attractiveness and offspring fitness1, 2 The offspring of attractive males may have enhanced growth3, 4, 5, fecundity3, 4, viability5, 6, 7, 8 or attractiveness4, 9, 10, 11 However, the extent to which attractive males bear genes that reduce other fitness components has remained unexplored Here I show that sexual attractiveness in male guppies (Poecilia reticulata) is heritable and genetically correlated with ornamentation Like ornamentation12, 13, 14, attractiveness may be substantially Y-linked The benefit of mating with attractive males, and thus having attractive sons, is opposed by strong negative genetic correlation between attractiveness and both offspring survival and the number of sons maturing Such correlations suggest either antagonistic pleiotropy between attractiveness and survival or linkage disequilibrium between attractive and deleterious alleles The presence of many colour pattern genes on or near the non-recombining section of the Y chromosome may facilitate the accumulation of deleterious mutations by genetic hitch-hiking15, 16 These findings show that genes enhancing sexual attractiveness may be associated with pleiotropic costs or heavy mutational loads

Reef fish assemblages: a re-evaluation using enclosed rotenone stations

Abstract: The reef fish assemblage at Orpheus Island, Great Barrier Reef, was examined using visual censuses and the ichthyocide rotenone. Small 3.5 m 2 quantitative rotenone samples, using a fine-mesh net to enclose the site, were compared with visual-point censuses (prior to the placement of the net), random-point censuses and strip censuses. Furthermore, the fishes collected inside and outside the net were examined to determine the relative efficiency of enclosed versus open rotenone samples. Rotenone samples comprised 128 species in 28 families. Of these, only 49% of the species overlapped between the enclosed (inside net) and open (outside net) samples. Only 17.7% of the species in the enclosed rotenone sample were seen prior to collection. Rotenone samples reveal that visual censuses underestimated the abundance of small taxa. Overall, rotenone samples increased the estimated number of species by 40.4% and the total fish abundance by 50.1% (75.3% for fishes <50 mm). Biomass increased by less than 1.0%. However, through relatively high energetic de- mands, high turnover rates and their role as potential prey, small fish taxa may play a greater role in reef processes than previously assumed. The limits of visual censusing techniques are highlighted, emphasising the value of small, enclosed, intensive rotenone samples for providing reliable quanti- tative samples of small taxa.

Development of swimming abilities in reef fish larvae

Abstract: Recent studies have revealed that reef fish larvae have excellent sustained swimming capabilities and considerable potential for modifying their dispersal patterns by active swimming. However, these studies concentrate solely on the late pelagic phase. We examined the development of swimming abilities from hatching through to settlement in 3 reef fish species (Pomacentrus amboinensis, Sphaeramia nematoptera, Amphiprion melanopus). Larval rearing provided larvae at all stages of development. Experiments were conducted in flow chambers designed for measuring the critical and sustained swimming capability of young larvae. In all 3 species, critical swimming ability increased steadily with age, size, relative propulsive area and developmental stage of the larvae. In contrast, sustained swimming ability showed a marked inflection during development. Differences among species throughout development appear to reflect variations in the developmental patterns of the 3 species. Propulsive area was highly correlated with swimming ability and may prove useful for estimating swimming capabilities among species. The results suggest that some species have the potential to actively modify their dispersal patterns from an early age.

Inhibition of Luminescence and Virulence in the Black Tiger Prawn (Penaeus monodon) Pathogen Vibrio harveyi by Intercellular Signal Antagonists

Abstract: Expression of luminescence in the Penaeus monodon pathogen Vibrio harveyi is regulated by an intercellular quorum sensing mechanism involving the synthesis and detection of two signaling molecules, one of which is N-hydroxy butanoyl-L-homoserine lactone and the other of which is uncharacterized. Indirect evidence has suggested that virulence, associated with a toxic extracellular protein, and luminescence in V. harveyi are coregulated. In this study the effects of an acylated homoserine lactone antagonist produced by the marine alga Delisea pulchra on luminescence and toxin production in a virulent strain of V. harveyi were analyzed. Luminescence and toxin production were both inhibited by the signal antagonist at concentrations that had no impact on growth. Toxin production was found to be prematurely induced in V. harveyi cultures incubated in a 10% conditioned medium. Additionally, a significant reduction in the toxicity of concentrated supernatant extracts from V. harveyi cultures incubated in the presence of the signal antagonist, as measured by in vivo toxicity assays in mice and prawns, was observed. These results suggest that intercellular signaling antagonists have potential utility in the control of V. harveyi prawn infections.

Enhanced particle-feeding capacity of corals on turbid reefs (Great Barrier Reef, Australia)

Abstract: Reef corals occur across a wide range of habitats, from offshore clear waters to nearshore sediment-laden environments. This study tests the hypothesis that corals from turbid nearshore areas have greater capacity to utilise suspended sediment as a food source than conspecifics from less turbid and midshelf areas. The hypothesis was tested on two common and widespread coral species on the Great Barrier Reef (Pocillopora damicornis and Acropora millepora). The particle clearance rates of samples from more turbid reefs were two-fourfold those of conspecifics from less turbid and midshelf reefs. Rates of sediment ingestion were generally a linear function of sediment load indicating no significant saturation within the concentration range of 1–30 mg dry weight l−1. Estimated assimilation efficiency of particulate 14C varied between 50 and 80%, and was maximised for midshelf A. millepora at the lowest sediment concentration, suggesting that heterotrophy is more efficient in oligotrophic habitats. Based on feeding-response curves, assimilation efficiencies, and published records of ambient particle concentrations, representatives of these species on turbid inshore reefs are 10–20 times more heterotrophic on suspended sediment than their conspecifics on less turbid and midshelf reefs.

Examination of species boundaries in the Acropora cervicornis group (Scleractinia, cnidaria) using nuclear DNA sequence analyses.

Abstract: Although Acropora is the most species-rich genus of the scleractinian (stony) corals, only three species occur in the Caribbean: A cervicornis, A palmata and A prolifera Based on overall coral morphology, abundance and distribution patterns, it has been suggested that A prolifera may be a hybrid between A cervicornis and A palmata The species boundaries among these three morphospecies were examined using DNA sequence analyses of the nuclear Pax-C 46/47 intron and the ribosomal DNA Internal Transcribed Spacer (ITS1 and ITS2) and 58S regions Moderate levels of sequence variability were observed in the ITS and 58S sequences (up to 52% overall sequence difference), but variability within species was as large as between species and all three species carried similar sequences Since this is unlikely to represent a shared ancestral polymorphism, the data suggest that introgressive hybridization occurs among the three species For the Pax-C intron, A cervicornis and A palmata had very distinct allele frequencies and A cervicornis carried a unique allele at a frequency of 0769 (although sequence differences between alleles were small) All A prolifera colonies examined were heterozygous for the Pax-C intron, whereas heterozygosity was only 0286 and 0333 for A cervicornis and A palmata, respectively These data support the hypothesis that A prolifera is the product of hybridization between two species that have a different allelic composition for the Pax-C intron, ie A cervicornis and A palmata We therefore suggest that A prolifera is a hybrid between A cervicornis and A palmata, which backcrosses with the parental species at low frequency

Rapid Smothering of Coral Reef Organisms by Muddy Marine Snow

Abstract: Estuarine mud, when resuspended in nutrient-rich near-shore water, aggregates to marine snow, and within minutes to hours can exert detrimental or even lethal effects on small coral reef organisms. In a pilot study, estuarine mud was suspended in near-shore and off-shore waters of the Great Barrier Reef to a final concentration of 170 mg l−1. The short-term responses of a coral (Acropora sp.) and coral-inhabiting barnacles (subfamily Pyrgomatidae), exposed to either near-shore or off-shore water, were microscopically observed and video recorded. In the off-shore water treatment, flocculation was minor, and aggregate sizes were c. 50 μm. The organisms were able to clean themselves from these small settling aggregates at low siltation (

Transcription of the FMR1 gene in individuals with fragile X syndrome

Abstract: Fragile X syndrome generally arises as a consequence of a large expansion of a CGG trinucleotide repeat element that is located in the GC-rich promoter region of the fragile X mental retardation gene (FMR1). In the conventional model for fragile X, clinical involvement arises as a consequence of silencing of the FMR1 gene, with the attendant loss of FMR1 protein (FMRP). However, it has recently been demonstrated that most males with large premutation alleles (100-200 repeats), or with unmethylated full mutation alleles, have FMR1 mRNA levels that are higher than normal, despite reduced levels of FMRP. In the current work, we extend and confirm these observations using quantitative (fluorescent) reverse transcription polymerase chain reaction on larger sample populations, establishing that even for smaller premutation alleles (55-100 repeats) the mRNA levels are significantly elevated (mean 2.1-fold elevation; P = 3.9 x 10(-3)), relative to normal controls. Thus, an abnormal molecular phenotype is established close to the upper end of the normal range. We also demonstrate that the levels of FMR1 mRNA are elevated in females with premutation alleles; however, the mRNA levels are more varied than in the males, and are attenuated in a manner that is consistent with the fraction of normal alleles that are active in any given individual. Finally, we demonstrate that in lymphoblastoid cells derived from a patient with a severe form of fragile X caused by a point mutation in the second KH domain of the gene, but with a normal CGG element (25 repeats), the FMR1 mRNA level is normal. Thus, although models in which FMRP level (or level of function) modulates transcriptional activity remain viable, other explanations for the elevated message levels, including direct (cis) effects of the CGG element on transcription, must also be considered.

Developing a Typology for Understanding Visiting Friends and Relatives Markets

Abstract: This study seeks to classify visiting friends and relatives (VFR) travel and to explore the linkage between VFR travel types and commercial tourism in an empirical study. The VFR phenomenon is multifaceted, making it hard to integrate research findings. This article proposes an initial typology of VFR travel and positions the major existing studies within this typology. Using data from Queensland, Australia, an examination is made of the relationships between the proposed variables and VFR travel and behavior patterns. The data set gave the researchers the ability to identify VFR as either a prime trip motive or one of a set of activities or regional attractions. The study provides an activities-based segmentation of this type of VFR traveler and attempts to connect different segments to both travel patterns and the variables in the proposed typology.

Cytokine gene expression in innately susceptible BALB/c mice and relatively resistant C57BL/6 mice during infection with virulent Burkholderia pseudomallei.

Abstract: Production of cytokines including gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) is an important early-stage host response following infection with intracellular pathogens. Development of immunity to these pathogens is determined to a large extent by the timing and relative level of expression of the cytokines. Numerous studies have shown that early cytokine responses involving interleukin-12 (IL-12) and IFN-gamma are important for resistance to intracellular pathogens, whereas responses involving IL-4 and IL-10 increase host susceptibility. These often-indistinct early cytokine responses influence the differentiation of naive CD4(+) T helper cells, which later develop into what have commonly been termed Th1- and Th2-type cells. The characterization of CD4(+) T-helper-cell responses as Th1 or Th2 type is based largely on the cytokine profiles during the specific phase and has been used in recent years to account for the innate resistance and susceptibility of different inbred strains of mice to several intracellular pathogens. Studies investigating cytokine production in terms of CD4(+) T-helper-cell polarization in Burkholderia pseudomallei infection have not been undertaken. In this study, we used semiquantitative reverse transcription-PCR to assess induction of cytokine mRNA in liver and spleen of B. pseudomallei-susceptible BALB/c and relatively resistant C57BL/6 mice following infection with virulent B. pseudomallei. The levels of mRNA for IFN-gamma, TNF-alpha, IL-1beta, IL-6, IL-10, and IL-12 increased in both BALB/c and C57BL/6 mice 24 to 36 h after infection. A comparison of BALB/c and C57BL/6 responses revealed the relative levels of expression of mRNA for several of these cytokines, including IFN-gamma, were greater in BALB/c mice, suggesting a role for endotoxic shock and cytokine-mediated immunopathology in the development of acute melioidosis. Early induction of mRNA for the cytokines classically associated with development of Th1- and Th2-type responses was absent or minimal, and induction levels in both strains of mice were similar. During the specific phase, cytokine mRNA profiles occurred as a combination of Th1- and Th2-type patterns. Collectively, these results demonstrate that cytokine mRNA responses in BALB/c and C57BL/6 mice following infection with virulent B. pseudomallei do not develop as polarized Th1- or Th2-type profiles. Considering the role of TNF-alpha and IFN-gamma in the processes of endotoxic shock, these results also indicate that selected cytokines, while important for resistance to B. pseudomallei infection, are also potential contributors to immunopathology and the development of acute fulminating disease.

Methane oxidation during the late Palaeocene thermal maximum

Abstract: Carbon isotope records across the Latest Palaeocene Thermal Maximum (LPTM) display by a remarkable delta 13 C excursion of at least -2.5 per mil that occurred within 10X10 3 yrs. Thermal dissociation of marine gas hydrate and release of massive quantities of CH 4 to the exogenic carbon cycle appears to be the only plausible explanation for this geochemical perturbation. Three numerical simulations of the scenario are compared here. Each simulation involved release of 1.12X10 18 g of CH 4 over 10X10 3 yrs into the pre-industrial steady-state exogenic carbon cycle. The only difference between the simulations is whether CH 4 was oxidized in the atmosphere, deep Atlantic Ocean, or deep Pacific Ocean. Important conclusions from this work are that massive CH 4 release into any carbon reservoir will cause a negative delta 13 C excursion, increased atmosphere pCO 2 , elevated global surface temperature, and pelagic carbonate dissolution, but that the timing and magnitude of these responses depends on the location of CH 4 oxidation. Oxygen deficiency must also occur if significant quantities of CH 4 are oxidized in an ocean reservoir. Release and oxidation of massive quantities of CH 4 in the deep Atlantic Ocean is consistent with several observations from the geological record across the LPTM. However key data sets and additional modeling are needed before geochemical perturbations during this extraordinary time interval can be well understood.

Time trends of cutaneous melanoma in Queensland, Australia and Central Europe

Abstract: BACKGROUND The objective of this study was to describe recent developments in cutaneous melanoma from the German speaking countries in Europe (Germany, Austria, and Switzerland) and from Queensland, Australia. METHODS All incident invasive cutaneous melanoma cases recorded between 1986 and 1996 by the Queensland Melanoma Register and by the Central Malignant Melanoma Registry of the German Dermatological Society were included in the analysis. Weighted linear trend analyses were performed to assess significant changes over the years using yearly sample sizes as weights. RESULTS In Central Europe, the median tumor thickness decreased from 1.2 mm in 1986 to 0.8 mm in 1996 (P < 0.001), whereas it varied insignificantly between 0.5 mm and 0.6 mm in Queensland. The percentage of patients with Clark Level II invasion increased significantly in Queensland (P < 0.001; 1996, 61.1%) and in Central Europe (P = 0.041; 1996, 24.5%). The percentage of superficial spreading melanomas rose in Central Europe (P = 0.043; 1996, 64.4%), whereas it decreased slightly in Queensland (P = 0.032; 1996, 75%). In Queensland and in Central Europe, younger people and women presented more frequently with thinner melanomas (≤ 0.75 mm). CONCLUSIONS In both Central Europe and Queensland, trends toward thinner and less invasive melanomas were observed between 1986 and 1996, although the median tumor thickness decreased significantly only for Central European data. Men and elderly individuals should be the focus of health-promotion activities, because they tended to present on average with thicker and prognostically poorer melanomas. Cancer 2000;89:1269–78. © 2000 American Cancer Society.

A review of the evaluation of clinical teaching: new perspectives and challenges

Abstract: Purpose: This article discusses the importance of the process of evaluation of clinical teaching for the individual teacher and for the programme. Measurement principles, including validity, reliability, efficiency and feasibility, and methods to evaluate clinical teaching are reviewed. Context: Evaluation is usually carried out from the perspective of the learner. This article broadens the evaluation to include the perspectives of the teacher, the patient and the institutional administrators and payers in the health care system and recommends evaluation strategies. Results: Each perspective provides specific feedback on factors or attributes of the clinical teacher’s performance in the domains of medical expert, professional, scholar, communicator, collaborator, patient advocate and manager. Teachers should be evaluated in all domains relevant to their teaching objectives; these include knowledge, clinical competence, teaching effectiveness and professional attributes. Conclusions and implications: Using this model of evaluation, a connection can be made between teaching and learning about all the expected roles of a physician. This can form the basis for systematic investigation into the relationship between the quality of teaching and the desired outcomes, the improvement of student learning and the achievement of better health care practice. It is suggested that the extent of effort and resources devoted to evaluation should be commensurate with the value assigned to the evaluation process and its outcomes.

Clinical teaching: maintaining an educational role for doctors in the new health care environment.

Abstract: Context and objectives: Good clinical teaching is central to medical education but there is concern about maintaining this in contemporary, pressured health care environments. This paper aims to demonstrate that good clinical practice is at the heart of good clinical teaching. Methods: Seven roles are used as a framework for analysing good clinical teaching. The roles are medical expert, communicator, collaborator, manager, advocate, scholar and professional. Results: The analysis of clinical teaching and clinical practice demonstrates that they are closely linked. As experts, clinical teachers are involved in research, information retrieval and sharing of knowledge or teaching. Good communication with trainees, patients and colleagues defines teaching excellence. Clinicians can 'teach' collaboration by acting as role models and by encouraging learners to understand the responsibilities of other health professionals. As managers, clinicians can apply their skills to the effective management of learning resources. Similarly skills as advocates at the individual, community and population level can be passed on in educational encounters. The clinicians' responsibilities as scholars are most readily applied to teaching activities. Clinicians have clear roles in taking scholarly approaches to their practice and demonstrating them to others. Conclusion: Good clinical teaching is concerned with providing role models for good practice, making good practice visible and explaining it to trainees. This is the very basis of clinicians as professionals, the seventh role, and should be the foundation for the further development of clinicians as excellent clinical teachers.

Patterns of fish calling in a nearshore environment in the Great Barrier Reef

Abstract: Long-term sea-noise statistics have been obtained from a region of the central section of the Great Barrier Reef. Fish calling was a major contributor to sea-noise levels. Calling was either in choruses, where groups of fishes called en masse, or as isolated calls repeated ad nauseam. Four calling types predominated, with each displaying unique call characteristics and calling patterns through time and space. Analysis of call types offered information on the fish's calling physiology, behaviour and, through the call's interaction with the local environment, on the location of the caller. Call types ranged from less than 10 ms to several seconds long, and were comprised from one to nearly 40 pulses. The structure of each pulse was related to swim-bladder mechanics; normally swim-bladders were lightly damped. Fish calling was most common during the Australian summer with one call type also displaying lunar trends. All calls had daily patterns of sound production with highest activity levels generally at night. There was some spatial separation of zones of highest call rates, but sources avoided competition for the 'sound space' primarily by offsetting the time of chorus or maximum call rate. On some occasions, a call type attributed to nocturnal planktivorous fishes may have ensonified much of the Great Barrier Reef.

Passive irrigation and functional morphology of crustacean burrows in a tropical mangrove swamp.

Abstract: Flushing measurements and a resin cast of a burrow inhabited by Sesarma messa and Alpheus cf macklay were taken from a Rhizophoraspp. forest. The burrow had 9 openings and occupied a swamp surface area of 0.64 m2. Passive irrigation of the burrow was investigated by recording change in conductivity of burrow water in a chamber 45 cm below the swamp surface during tidal inundation of the swamp. The chamber was completely flushed within approximately one hour, i.e. by a single tidal event. Burrow morphology was determined by means of resin casting. The investigated burrow was of discrete structure, with an overall depth of 1.2 m and a total volume of 68 l, i.e. ca. 9% of the volume of swamp soil. The below ground surface area of chambers and tunnels was 3.8 m2. The mean and maximum chamber/tunnel diameter was 7 cm and 11 cm respectively. The soil in the close vicinity of the burrow was extensively penetrated by roots, and any two parts of the burrow were located no further than 20 cm away from each other. By reducing diffusion distances within the soil and by being well flushed, the burrows provide an efficient mechanism for removal of excess salt accumulated in the soil around mangrove roots due to exclusion.

Calcification by crustose coralline algae on the northern Great Barrier Reef, Australia

Abstract: Calcification by four species of crustose coralline algae was estimated on the windward reef at Lizard Island, northern Great Barrier Reef, Australia, by combining measurements of O2, pH, and total alkalinity with equations describing the seawater carbonate equilibrium Calcification (C) was regressed against irradiance (I ) and modeled using a general exponential function C‐Imodels yielded estimates of gross calcification that ranged from 96 mmol CaCO3 m 22 h 21 at 0 m to 20 mmol CaCO3 m 22