Developmental and cell biological functions of the Drosophila DEAD-box protein abstrakt.

BACKGROUND: DEAD-box proteins are a large family of proteins found in bacteria, plants and animals, but only few have been analysed functionally. They are involved in the regulation of various aspects of RNA processing and metabolism, including splicing, transport and translation. The study of their function in multicellular organisms has been restricted to a few special cases, such as the Vasa protein in the fruit fly Drosophila. RESULTS: We show that abstrakt, a gene originally identified genetically by its effect on axon outgrowth and fasciculation of the Bolwig nerve, encodes a new Drosophila DEAD-box protein of which the closest homologue is a human gene of unknown function. Using temperature-sensitive alleles to assay its function, we found that abstrakt is essential for survival at all stages throughout the life cycle of the fly. Mutants show specific defects in many developmental processes, including cell-shape changes, localisation of RNA and apoptosis. CONCLUSIONS: Abstrakt is not globally required for RNA splicing, transport, subcellular localisation or translation. Nevertheless, there is a widespread requirement for Abstrakt during post-transcriptional gene expression. Abstrakt must affect processing of specific subsets of RNAs, suggesting that differential post-translational control during development is more common than previously suspected.

Control of cell fates and segmentation in the Drosophila mesoderm.

The primordia for heart, fat body, and visceral and somatic muscles arise in specific areas of each segment in the Drosophila mesoderm. We show that the primordium of the somatic muscles, which expresses high levels of twist, a crucial factor of somatic muscle determination, is lost in sloppy-paired mutants. Simultaneously, the primordium of the visceral muscles is expanded. The visceral muscle and fat body primordia require even-skipped for their development and the mesoderm is thought to be unsegmented in even-skipped mutants. However, we find that even-skipped mutants retain the segmental modulation of the expression of twist. Both the domain of even-skipped function and the level of twist expression are regulated by sloppy-paired. sloppy-paired thus controls segmental allocation of mesodermal cells to different fates.

Technical considerations using a pulsed neodym-YAG laser for endoscopic shock wave lithotripsy.

First clinical experience with the use of a Q-switched pulsed Neodym-YAG Laser showed promising results. This paper focuses on two problems with respect to the optimal use of this laser: (1) is there any need for a special iron (Fe3+)-enriched irrigant, and (2) what is the best frequency for laser lithotripsy? To answer these questions, we used an in vitro model, measuring the laser-induced breakdown (LIB) photographically utilizing sodium chloride as an irrigant enriched with different amounts of Fe3+ ions. The disintegrative efficacy of the laser was tested utilizing a standard stone model (plaster cube) and working at different frequencies (1, 10, 40 Hz). The addition of Fe3+ ions resulted in significant improvement of LIB. However, in the presence of a test stone no difference between sodium chloride and Fe3+-enriched irrigants was noted. The use of lower frequencies (1, 10 Hz) lead to a remarkable improvement in the disintegrative efficacy of the laser compared to the standard frequencies (40, 50 Hz). For clinical use, addition of Fe3+ ions seems only necessary if optical breakdown (LIB) is insufficient despite the increase in generator voltage. In such a situation, we recommend the addition of an 1-ml Fe3+ solution to 10 liters of sodium chloride irrigant (= 0.5 mg Fe3+/dl). Moreover, the standard frequency for laser-induced intracorporeal lithotripsy should be 1-10 Hz.