Hyaline tissue of thermally unaltered conodont elements and the enamel of vertebrates

Comparison of the ultrastructure of the hyaline tissue of conodont elements and the enamel of vertebrates provides little support for a close phylogenetic relationship between conodonts and vertebrates. Transmission and scanning electron microscopy shows that the mineralised component of the hyaline tissue of Panderodus and of Cordylodus elements consists of large, flat, oblong crystals, arranged in layers that run parallel to the long axis of the conodont. Enamel in the dentition of a living vertebrate, the lungfish Neoceratodus forsteri, has crystals of calcium hydroxyapatite, arranged in layers, and extending in groups from the dentine-enamel junction; the crystals are slender, elongate spicules perpendicular to the surface of the tooth plate, Similar crystal arrangements to those of lungfish are found in other vertebrates, but none resembles the organisation of the hyaline tissue of conodont elements, The crystals of hydroxyapatite in conodont hyaline tissue are exceptionally large, perpendicular or parallel to the surface of the element, with no trace of prisms, unlike the protoprismatic radial crystallite enamel of fish teeth and scales, or the highly organised prismatic enamel of mammals.

A mixture model-based approach to the clustering of microarray expression data

Motivation: This paper introduces the software EMMIX-GENE that has been developed for the specific purpose of a model-based approach to the clustering of microarray expression data, in particular, of tissue samples on a very large number of genes. The latter is a nonstandard problem in parametric cluster analysis because the dimension of the feature space (the number of genes) is typically much greater than the number of tissues. A feasible approach is provided by first selecting a subset of the genes relevant for the clustering of the tissue samples by fitting mixtures of t distributions to rank the genes in order of increasing size of the likelihood ratio statistic for the test of one versus two components in the mixture model. The imposition of a threshold on the likelihood ratio statistic used in conjunction with a threshold on the size of a cluster allows the selection of a relevant set of genes. However, even this reduced set of genes will usually be too large for a normal mixture model to be fitted directly to the tissues, and so the use of mixtures of factor analyzers is exploited to reduce effectively the dimension of the feature space of genes. Results: The usefulness of the EMMIX-GENE approach for the clustering of tissue samples is demonstrated on two well-known data sets on colon and leukaemia tissues. For both data sets, relevant subsets of the genes are able to be selected that reveal interesting clusterings of the tissues that are either consistent with the external classification of the tissues or with background and biological knowledge of these sets.

The life-history basis of latitudinal diversity gradients: how do species traits vary from the poles to the equator.

1. Latitudinal variation among species in life-history traits is often suggested to contribute to high tropical species richness. However, traditional methods of analysing such variation rarely control for phylogeny and latitudinal range overlap between species, potentially giving misleading results. 2. Using a method of pairwise independent contrasts which overcomes these problems, I tested for latitudinal variation among bird species in a number of traits which have been linked, theoretically or empirically, with both latitude and species richness. 3. This method indicates strong support for Rapoport's Rule and decreasing clutch size towards the equator in both hemispheres, but only partial support for decreasing body size and ecological generalism towards the equator. 4. Indirect measures of sexual selection (sexual dichromatism and size dimorphism) show no variation with latitude; an apparent increase in dichromatism towards the equator is shown to be an artefact of phylogeny. 5. Many of the associations between life history and latitude were not detected by traditional cross-species analyses, highlighting the importance of incorporating phylogeny and overlap in studies of geographical life-history variation. Establishing associations between life-history traits and latitude does not prove, but is a necessary prerequisite for., a link between these traits and latitudinal diversity gradients.

Marx as a Critical Discourse Analyst: The genesis of a critical method and its relevance to the critique of global capital

In this paper we identify elements in Marx´s economic and political writings that are relevant to contemporary critical discourse analysis (CDA). We argue that Marx can be seen to be e n gaging in a form of discourse analysis. We identify the elements in Marx´s historical materialist method that support such a perspective, and exemplify these in a longitudinal comparison of Marx´s texts.

Reconciling paleodistribution models and comparative phylogeography in the Wet Tropics rainforest land snail Gnarosophia bellendenkerensis (Brazier 1875)

Comparative phylogeography has proved useful for investigating biological responses to past climate change and is strongest when combined with extrinsic hypotheses derived from the fossil record or geology. However, the rarity of species with sufficient, spatially explicit fossil evidence restricts the application of this method. Here, we develop an alternative approach in which spatial models of predicted species distributions under serial paleoclimates are compared with a molecular phylogeography, in this case for a snail endemic to the rainforests of North Queensland, Australia. We also compare the phylogeography of the snail to those from several endemic vertebrates and use consilience across all of these approaches to enhance biogeographical inference for this rainforest fauna. The snail mtDNA phylogeography is consistent with predictions from paleoclimate modeling in relation to the location and size of climatic refugia through the late Pleistocene-Holocene and broad patterns of extinction and recolonization. There is general agreement between quantitative estimates of population expansion from sequence data (using likelihood and coalescent methods) vs. distributional modeling. The snail phylogeography represents a composite of both common and idiosyncratic patterns seen among vertebrates, reflecting the geographically finer scale of persistence and subdivision in the snail. In general, this multifaceted approach, combining spatially explicit paleoclimatological models and comparative phylogeography, provides a powerful approach to locating historical refugia and understanding species' responses to them.

History of the events leading to the formulation of the apoptosis concept

Histological studies of ischaemic liver injury performed between 1962 and 1964 distinguished two types of cell death: classical necrosis, and a process involving conversion of scattered cells into small round masses of cytoplasm that often contained specks of condensed nuclear chromatin. Enzyme histochemistry demonstrated rupture of lysosomes in the former, but preservation of lysosomes in the latter. Similar small round masses were also observed sparsely in normal liver. Electron microscopy showed that the small round bodies resulted from cellular condensation and budding, that they were bounded by membranes and contained intact organelles, and that they were phagocytosed and digested by resident tissue cells, including epithelial cells. In work done in association with Jeffrey Searle, the process was found to occur spontaneously in a variety of malignant tumours and to be enhanced in squamous cell carcinomas of skin responding to radiotherapy. During 1971-1972, I collaborated with Andrew Wyllie and Alastair Currie while on sabbatical leave in Scotland. The newly defined type of cell death was shown to be regulated by hormones in the adrenal cortex and in breast carcinomas. Further, review of published electron micrographs of the cell death known to play an essential role in normal development revealed the same morphological pattern. We proposed that this distinctive phenomenon subserves a general homoeostatic function and suggested it be called apoptosis. © 2002 Elsevier Science Ireland Ltd. All rights reserved.

Genetic linkage analysis of the lesser grain borer Rhyzopertha dominica identifies two loci that confer high-level resistance to the fumigant phosphine

High levels of inheritable resistance to phosphine in Rhyzopertha dominica have recently, been detected in Australia and hi art effort to isolate the genes responsible For resistance we have used random amplified DNA fingerprinting (RAF) to produce a genetic linkage map of R. dominica. The map consists of 94 dominant DNA markers with art average distance between markers of 4.6 cM and defines nine linkage groups with a total recombination distance of 390.1 cM. We have identified two loci that are responsible for high-level resistance. One provides similar to50x resistance to phosphine while the other provides 12.5x resistance and in combination, the two genes act synergistically to provide a resistance level 250 x greater than that of fully susceptible beetles. The haploid genome size has been determined to be 4.76 x 10(8) bp, resulting in an average physical distance of 1.2 Mbp per map unit. No recombination has been observed between either of the two resistance loci and their adjacent DNA markers in a population of 44 fully resistant F-5 individuals, which indicates that the genes are likely to reside within 0.91 cM (1.1 Mbp) of the DNA markers.

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.

Development of a fully quantitative approach to the interpretation of stress echocardiography using radial and longitudinal myocardial velocities

Background: Tissue Doppler may be used to quantify regional left ventricular function but is limited by segmental variation of longitudinal velocity from base to apex and free to septal walls. We sought to overcome this by developing a composite of longitudinal and radial velocities. Methods and Results. We examined 82 unselected patients undergoing a standard dobutamine echocardiogram. Longitudinal velocity was obtained in the basal and mid segments of each wall using tissue Doppler in the apical views. Radial velocities were derived in the same segments using an automated border detection system and centerline method with regional chords grouped according to segment location and temporally averaged. In 25 patients at low probability of coronary disease, the pattern of regional variation in longitudinal velocity (higher in the septum) was the opposite of radial velocity (higher in the free wall) and the combination was homogenous. In 57 patients undergoing angiography, velocity in abnormal segments was less than normal segments using longitudinal (6.0 +/- 3.6 vs 9.0 +/- 2.2 cm/s, P = .01) and radial velocity (6.0 +/- 4.0 vs 8.0 +/- 3.9 cm/s, P = .02). However, the composite velocity permitted better separation of abnormal and normal segments (13.3 +/- 5.6 vs 17.5 +/- 4.2 cm/s, P = .001). There was no significant difference between the accuracy of this quantitative approach and expert visual wall motion analysis (81% vs 84%, P = .56). Conclusion: Regional variation of uni-dimensional myocardial velocities necessitates site-specific normal ranges, probably because of different fiber directions. Combined analysis of longitudinal and radial velocities allows the derivation of a composite velocity, which is homogenous in all segments and may allow better separation of normal and abnormal myocardium.