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Low-emission zones are currently one of several tools which are in use for the improvement of air quality thanks to the limited entry of vehicles to European city centres. This article describes basic characteristics and parameters of low-emission zones in comparison with other types of used restrictions and explains the evaluation system of particularly environmental benefits and impacts. These theoretic assumptions are confronted with established low-emission zones in selected European urban areas; measured benefits and impacts of individual measures are evaluated and compared.

Wings are probably the most advanced evolutionary novelty in insects. In the fruit fly Drosophila melanogaster, proper development of wings requires the activity of so-called wing hearts located in the scutellum of the thorax. Immediately after the imaginal ecdysis, these accessory circulatory organs remove hemolymph and apoptotic epidermal cells from the premature wings through their pumping action. This clearing process is essential for the formation of functional wing blades. Mutant flies that lack intact wing hearts are flightless and display malformed wings. The embryonic wing heart progenitors originate from two adjacent parasegments corresponding to the later second and third thoracic segments. However, adult dipterian flies harbor only one pair of wings and only one pair of associated wing hearts in the second thoracic segment. Here we show that the specification of WHPs depends on the regulatory activity of the Hox gene Ultrabithorax. Furthermore, we analyzed the development of wing hearts in the famous four-winged Ultrabithorax (Ubx) mutant, which was first discovered by Ed Lewis in the 1970s. In these flies, the third thoracic segment is homeotically transformed into a second thoracic segment resulting in a second pair of wings instead of the club-shaped halteres. We show that a second pair of functional wing hearts is formed in the transformed third thoracic segment and that all wing hearts originate from the wild-type population of wing heart progenitor cells., (© The Author(s) 2021. Published by Oxford University Press on behalf of Genetics Society of America. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Hand proteins belong to the highly conserved family of basic Helix-Loop-Helix transcription factors and are critical to distinct developmental processes, including cardiogenesis and neurogenesis in vertebrates. In Drosophila melanogaster a single orthologous hand gene is expressed with absence of the respective protein causing semilethality during early larval instars. Surviving adult animals suffer from shortened lifespan associated with a disorganized myofibrillar structure being apparent in the dorsal vessel, the wing hearts and in midgut tissue. Based on these data, the major biological significance of Hand seems to be related to muscle development, maintenance or function; however, up to now the physiological basis for Hand functionality remains elusive. Thus, the identification of genes whose expression is, directly or indirectly, regulated by Hand has considerable relevance with respect to understanding its biological functionality in flies and vertebrates. Beneficially, hand mutants are viable and exhibit affected tissues, which renders Drosophila an ideal model to investigate up- or downregulated target genes by a comparative microarray approach focusing on the respective tissues from mutant specimens. Our present work reveals for the first time that Drosophila Hand regulates the expression of numerous genes of diverse physiological relevancy, including distinct factors required for proper muscle development and function such as Zasp52 or Msp-300. These results relate Hand activity to muscle integrity and functionality and may thus be highly beneficial to the evaluation of corresponding hand phenotypes.

The Hand basic helix-loop-helix transcription factors play an important role in the specification and patterning of various tissues in vertebrates and invertebrates. Here, we have investigated the function of Hand in the development of the Drosophila wing hearts which consist of somatic muscle cells as well as a mesodermally derived epithelium. We found that Hand is essential in both tissues for proper organ formation. Loss of Hand leads to a reduced number of cells in the mature organ and loss of wing heart functionality. In wing heart muscles Hand is required for the correct positioning of attachment sites, the parallel alignment of muscle cells, and the proper orientation of myofibrils. At the protein level, α-Spectrin and Dystroglycan are misdistributed suggesting a defect in the costameric network. Hand is also required for proper differentiation of the wing heart epithelium. Additionally, the handC-GFP reporter line is not active in the mutant suggesting an autoregulatory role of Hand in wing hearts. Finally, in a candidate-based RNAi mediated knock-down approach we identified Daughterless and Nautilus as potential dimerization partners of Hand in wing hearts., (© 2013 Elsevier Inc. All rights reserved.)

Wing hearts are small pumping organs that maintain the flow of hemolymph through the wing veins of insects. In Drosophila, these organs consist of parallel oriented muscle cells and a simple epithelium of connective tissue. Both tissues originate from eight embryonic wing heart progenitors (WHPs), which remain dormant until late larval stages. Most of the differentiation and maturation takes place during the pupal stage following head eversion. In this study, we have used the tissue specific expression of Gal4 enhancer lines, in combination with the live cell markers GFP and DsRed to investigate pupal wing heart development in conjunction with the surrounding tissues. We found that WHPs interact with the tracheal system and specific expression domains of the adult epidermis. Additionally, wing heart development occurs simultaneously with the remodeling of the dorso-lateral epidermis into the scutellum and the scutellar arms. Myogenesis in wing hearts comprises known processes such as founder cell specification, but also new features like removal of growing myotubes, and nuclei movement. Wing heart epithelium development is accomplished by the mesenchymal-epithelial transition of WHPs and occurs slightly delayed to muscle development. The epithelium represents a novel mesodermally derived secondary epithelium. Moreover, we have identified a nerve that runs along the epithelium and innervates the wing heart muscle cells.

In Drosophila, hemolymph circulation in the wings is accomplished by a pair of wing hearts located in the thorax. The embryonic progenitors of these organs were only recently discovered and found to belong to the cardiac mesoderm. In this study, the functional morphology and the structure of mature organs were studied by light and electron microscopy to characterize the tissues arising from this new set of progenitors. Each wing heart consists of 7-8 muscle cells providing the pumping force, a thin layer of non-contractile mononucleated cells separating the muscle cells from the body cavity, and acellular suspending strands opposing the muscle contractions. The muscle cells are multinucleated syncytia attached to the cuticle via epidermal tendon cells. They have central nuclei and sarcomeres with discontinuous Z-discs, A-bands, and I-bands, whereas H-bands and M-bands are indiscernible. From 9 to 11 actin filaments surround each myosin filament. Mitochondria are abundantly interspersed between myofibrils and accumulated in characteristic outpockets of the plasma membrane. The analysis revealed that the wing heart muscles resemble in their ultrastructure and their mode of attachment adult somatic muscles. This suggests that, despite their origin in the cardiac mesoderm, wing heart progenitors are functionally related to somatic adult muscle precursors.

In addition to the heart proper, insects possess wing hearts in the thorax to ensure regular hemolymph flow through the narrow wings. In Drosophila, the wing hearts consist of two bilateral muscular pumps of unknown origin. Here, we present the first developmental study on these organs and report that the wing hearts originate from eight embryonic progenitor cells arising in two pairs in parasegments 4 and 5. These progenitors represent a so far undescribed subset of the Even-skipped positive pericardial cells (EPC) and are characterized by the early loss of tinman expression in contrast to the continuously Tinman positive classical EPCs. Ectopic expression of Tinman in the wing heart progenitors omits organ formation, indicating a crucial role for Tinman during progenitor specification. The subsequent postembryonic development is a highly dynamic process, which includes proliferation and two relocation events. Adults lacking wing hearts display a severe wing phenotype and are unable to fly. The phenotype is caused by omitted clearance of the epidermal cells from the wings during maturation, which inhibits the formation of a flexible wing blade. This indicates that wing hearts are required for proper wing morphogenesis and functionality.

The microtubule-associated proteins 1B and 1A are synthesized as polyprotein precursors which are rapidly cleaved to give rise to heavy and light chains constituting the respective microtubule-associated protein 1B or microtubule-associated protein 1A complex. To identify domains necessary for precursor processing, we expressed microtubule-associated protein 1B deletion mutants in fibroblasts and monitored proteolytic cleavage of the precursor proteins by immunoblot analysis. We found that a novel hydrophilic, proline-rich 45 amino acid domain containing the cleavage site is necessary and sufficient for processing. This domain is conserved in microtubule-associated protein 1A. Additional sequences in the N-terminal half of the heavy chain contribute to the efficiency of cleavage.

Previous studies on the role of microtubule-associated protein 1B (MAP1B) in adapting microtubules for nerve cell-specific functions have examined the activity of the entire MAP1B protein complex consisting of heavy and light chains and revealed moderate effects on microtubule stability. Here we have analyzed the effects of the MAP1B light chain in the absence or presence of the heavy chain by immunofluorescence microscopy of transiently transfected cells. Distinct from all other MAPs, the MAP1B light chain-induced formation of stable but apparently flexible microtubules resistant to the effects of nocodazole and taxol. Light chain activity was inhibited by the heavy chain. In addition, the light chain was found to harbor an actin filament binding domain in its COOH terminus. By coimmunoprecipitation experiments using epitope-tagged fragments of MAP1B we showed that light chains can dimerize or oligomerize. Furthermore, we localized the domains for heavy chain-light chain interaction to regions containing sequences homologous to MAP1A. Our findings assign several crucial activities to the MAP1B light chain and suggest a new model for the mechanism of action of MAP1B in which the heavy chain might act as the regulatory subunit of the MAP1B complex to control light chain activity.

Recently, the concept of microtubule-associated protein 1B as an intracellular 2460 amino acid protein was challenged by the suggestion that only the N-terminal 1022 codons are utilized and encode the core protein of the extracellular proteoglycan claustrin (Burg and Cole (1994) J. Neurobiol. 25, 1-22). We expressed this N-terminal MAP1B fragment in tissue culture cells and found that it bound to microtubules and was not localized in the extracellular matrix. In addition, epitope mapping demonstrated that MAP1B consisted of more than 1022 amino acids and that the reported cDNA of claustrin is incomplete.