81 research outputs found

    Taxonomy and biochronology of Early Triassic conodonts

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    Chronic Granulomatous Disease; fundamental stages in our understanding of CGD

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    It has been 50 years since chronic granulomatous disease was first reported as a disease which fatally affected the ability of children to survive infections. Various milestone discoveries from the insufficient ability of patients' leucocytes to destroy microbial particles to the underlying genetic predispositions through which the disease is inherited have had important consequences. Longterm antibiotic prophylaxis has helped to fight infections associated with chronic granulomatous disease while the steady progress in bone marrow transplantation and the prospect of gene therapy are hailed as long awaited permanent treatment options. This review unearths the important findings by scientists that have led to our current understanding of the disease

    Three-dimensional morphometric ontogeny of mollusc shells by micro-computed tomography and geometric analysis

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    As one of the essential components of the fossil record, shells of molluscs provide crucial data for taxonomic, phylogenetic or evolutionary studies. The mollusc shell has often very few discrete morphological characters, and its most important character is its three-dimensional (3-D) geometry, which is well diversified, continuous and highly integrated. However, standard morphometric methods remain mostly two-dimensional (2-D) and do not account for the ontogenetic changes of the shell, which are preserved thanks to its accretionary mode of growth. This study proposes a new non-destructive method enabling acquisition of three-dimensional quantitative morphometric parameters that thoroughly describe the geometry of coiled mollusc shells throughout their ontogeny. First, digital three-dimensional data of a shell is acquired by means of microcomputed tomography, which produces a series of grey-scaled, two-dimensional images. Second, all these stacked images are processed to obtain a three-dimensional reconstruction of the shell, from which a centreline is extracted. Finally, the geometry of shell aperture through ontogeny is extracted by successive cross-sectioning of the shell with a succession of planes, each of these being perpendicular to this centreline. The resulting outlines of the successive apertures can be quantified by elliptic Fourier analysis. These geometric parameters, coupled with the displacement vector of the successive cross-sectioning planes, constitute an n-dimensional morphometric space, in which ontogenetic trajectories of different individuals and species can be compared. The approach proposed in this study provides a basis for the quantitative analysis of growth patterns within and across species

    Smithian (Early Triassic) ammonoids from Tulong, South Tibet

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    Intensive sampling of the Tulong Formation in South Tibet has facilitated the construction of a highly-resolved middle and late Smithian ammonoid succession. The new biostratigraphical sequence comprises the middle Smithian Brayardites compressus beds, Nammalites pilatoides beds, and the Nyalamites angustecostatus beds followed by the late Smithian Wasatchites distractus beds and Glyptophiceras sinuatum beds. This faunal succession correlates very well with that of other Tethyan sequences such as the Salt Range (Pakistan), Spiti (India), Oman and South China. The Smithian faunal sequence from Tulong contains several taxa with broad geographic distribution (e.g., Owenites, Paranannites spathi, Shigetaceras, Wasatchites), thus enabling correlation with faunal successions from areas outside the Tethys (e.g., USA, British Columbia, Arctic Canada, South Primorye, Siberia). Early Smithian ammonoid faunas are almost absent in Tulong because of a preservation bias (absence of carbonate rocks). Five new ammonoid genera (Brayardites, Nammalites, Nyalamites, Shigetaceras, Tulongites) and six new species (Brayardites crassus, Brayardites compressus, Prionites involutus, ?Subflemingites compressus, Tulongites xiaoqiaoi, Urdyceras tulongensis) are described

    Dose-dependent stuttering and dystonia in a patient taking clozapine.

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    Smithian (Early Triassic) ammonoid faunas from exotic blocks from Oman: taxonomy and biochronology

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    Ammonoid-rich exotic bocks of Hallstatt facies in Jebel Safra, in Wadi Musjah and at Baid (Oman Mountains) have yielded several well preserved and highly diversified Smithian (Early Triassic) ammonoid faunas (Baidites hermanni fauna, Rohillites omanensis fauna, Flemingites rursiradiatus fauna, Nammalites pilatoides fauna, Owenites koeneni fauna and Anasibirites multiformis fauna). The comparison of these assemblages with data from other Tethyan basins such as the Salt Range, Spiti, Tibet and South China shows that nearly all known Smithian ammonoid faunal assemblages are present in the exotic blocks from Oman. The new Oman data strengthens the remarkably uniform biogeographic distribution of the Smithian ammonoid faunas within the Tethys. One new ammonoid family (Galfettitidae), five new genera (Baidites, Goudemandites, Lucasites, Omanites, Safraites), and twelve new species (Baidites hermanni, Galfettites kyrae, G. omani, Goudemandites sinensis, Kashmirites baidi, Lucasites involutus, L. evolutus, Omanites musjahensis, Paranannites baudi, Pseudaspidites planus, Rohillites omanensis, Safraites simplex) are described. Additionally, a new early Spathian (late Early Triassic) species (Procolumbites safraensis) is described

    Dose-dependent stuttering and dystonia in a patient taking clozapine.

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    International audienc

    Growth-dependent phenotypic variation of molluscan shells: implications for allometric data interpretation

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    In recent years, developmental plasticity has received increasing attention. Specifically, some studies highlighted a possible association between shell shape and growth rates in intertidal gastropods. We use a growth vector model to study how hypothetical growth processes could underlie developmental plasticity in molluscs. It illustrates that variation in instantaneous shell growth rate can induce variability in allometric curves. Consequently, morphological variation is time-dependent. Basing our model parameters on a study documenting the results of transplants experiments of three gastropods ecomorphs, we reproduce the main aspects of the variation in size, shape, and growth rates among populations when bred in their own habitat or transplanted to another ecotype habitat. In agreement with empirical results, our simulation shows that a flatter growth profile corresponds to conditions of rapid growth. The model also allows the comparison of allometric slopes using different subdata sets that correspond to static and ontogenetic allometry. Our model highlights that depending on subdata sets, the main effects could be attributed to source population or environment. In addition, convergence or divergence of allometric slopes is observed depending on the subdata sets. Although there is evidence that shell shape in gastropods is to some extent growth rate dependent, gaining a general overview of the issue is challenging, in particular because of the scarcity of studies referring to allometry. We argue that the dynamics of development at the phenotypic level constitute a non-reducible level of investigation if one seeks to relate the observed amount of phenotypic variation to variability in the underlying factors

    High-resolution biochronology and diversity dynamics of the Early Triassic ammonoid recovery: the Smithian faunas of the Northern Indian Margin

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    Based on new collections of abundant and well preserved material from the Salt Range (Pakistan), Spiti (Northern India) and Tulong (South Tibet), several recent studies focused on the taxonomic revision and detailed biostratigraphy of Smithian ammonoids. In this work, biochronological data for these three well-documented basins are analyzed by means of the Unitary Associations method, resulting in a biochronological scheme of unprecedented high-resolution for the Smithian of the Northern Indian Margin (NIM). Data for each basin are first processed separately, thus yielding three local biochronological zonations. Then, the three sequences are processed together as a regional three-section data set for the construction of an inter-basin sequence at the NIM level. The latter zonation comprises 16 Unitary Associations grouped into 13 zones for the entire Smithian. Analysis of ammonoid diversity dynamics based on this new highly resolved time frame highlights (i) a marked diversification during the early Smithian, (ii) a severe extinction during the late Smithian, and (iii) an overall very high turnover throughout the Smithian. At a global spatial scale and stage resolution, the diversity of Smithian ammonoid genera appears surprisingly high, as highlighted by a previous study. It is shown that at a smaller geographic scale and with the most highly resolved time frame, Smithian ammonoids of the NIM reached their explosive diversity peak essentially through extremely high turnover rates rather than through a classic diversification process of high origination rates coupled with low extinction rates. Based on recently published U/Pb ages, regional apparent total rates of origination and extinction of more than 100 species per My can be inferred for the Smithian ammonoids of the NIM
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