Comparative transcriptomics enlarges the toolkit of known developmental genes in mollusks.

BACKGROUND: Mollusks display a striking morphological disparity, including, among others, worm-like animals (the aplacophorans), snails and slugs, bivalves, and cephalopods. This phenotypic diversity renders them ideal for studies into animal evolution. Despite being one of the most species-rich phyla, molecular and in silico studies concerning specific key developmental gene families are still scarce, thus hampering deeper insights into the molecular machinery that governs the development and evolution of the various molluscan class-level taxa. RESULTS: Next-generation sequencing was used to retrieve transcriptomes of representatives of seven out of the eight recent class-level taxa of mollusks. Similarity searches, phylogenetic inferences, and a detailed manual curation were used to identify and confirm the orthology of numerous molluscan Hox and ParaHox genes, which resulted in a comprehensive catalog that highlights the evolution of these genes in Mollusca and other metazoans. The identification of a specific molluscan motif in the Hox paralog group 5 and a lophotrochozoan ParaHox motif in the Gsx gene is described. Functional analyses using KEGG and GO tools enabled a detailed description of key developmental genes expressed in important pathways such as Hedgehog, Wnt, and Notch during development of the respective species. The KEGG analysis revealed Wnt8, Wnt11, and Wnt16 as Wnt genes hitherto not reported for mollusks, thereby enlarging the known Wnt complement of the phylum. In addition, novel Hedgehog (Hh)-related genes were identified in the gastropod Lottia cf. kogamogai, demonstrating a more complex gene content in this species than in other mollusks. CONCLUSIONS: The use of de novo transcriptome assembly and well-designed in silico protocols proved to be a robust approach for surveying and mining large sequence data in a wide range of non-model mollusks. The data presented herein constitute only a small fraction of the information retrieved from the analysed molluscan transcriptomes, which can be promptly employed in the identification of novel genes and gene families, phylogenetic inferences, and other studies using molecular tools. As such, our study provides an important framework for understanding some of the underlying molecular mechanisms involved in molluscan body plan diversification and hints towards functions of key developmental genes in molluscan morphogenesis.

[The value of magnetic resonance tomography using gadolinium-DTPA in the diagnosis of the post-lumbar disk surgery syndrome]. / Wert der Kernspintomographie mit Gadolinium-DTPA bei der Diagnostik des lumbalen Postdiscotomie-Syndroms.

Our results have shown that MR tomography - especially if gadolinium-DTPA is used as a contrast medium - is an excellent method to differentiate between the various possible causes of the post-discotomy syndrome. In particular, it is definitely possible to differentiate between a relapsed hernia of an intervertebral disc and a postoperative development of cicatricial tissue which is practically inevitable. This differentiation is of vital importance to the clinician, because a second operation should be performed only in case of a relapse, whereas cicatricial tissue is best left alone, because no matter how carefully the operation is performed with preparation of the neural structures, even more extensive cicatricial plates are bound to develop. Instability of the vertebral column in the operated disc segment, or other causes of complaints, can be identified via MR equally well if not better than by other means. Hence, the method should be the method of choice in postdiscotomy syndrome, since it facilitates the difficult choice between conservative therapy and reoperation.

[Computer tomography following splenectomy]. / Computertomographie nach Splenektomie.

After splenectomy a displacement of the left kidney, stomach, colon and pancreas can be observed. The scar tissue regularly contains fat. The differentiation between haematoma and empyema may be difficult in certain cases. Large holes and those containing liquid and air may be attributed wrongly to the stomach or colon. Additional investigations are often necessary. Differential diagnosis between a residual spleen and a tumour recurrency may be difficult, if there is no follow-up examination.