Interconnection of state space structures and wave digital filters

State space structures (SSSs) and wave digital filters (WDFs) are two major paradigms for the realization of digital filters. Both approaches are well established, but there are no proven methods for a mixed design of digital filters consisting of parts which are realized as SSSs and parts realized as WDFs. This contribution shows how to add a wave port to the conventional SS representation. This wave port allows to interconnect SSSs and WDFs without creating delay-free loops. Such interconnections allow to build discrete-time structures by reusing existing designs from both classes of digital filters.     

Blocked-based physical modeling for digital sound synthesis

Block-based physical modeling is a methodology for modeling physical systems with different subsystems. It is an important concept for the physical modeling of real or virtual musical instruments where different components may be modeled according to different paradigms. Connecting systems of diverse nature in the discrete-time domain requires a common interconnection strategy. This contribution presents suitable interconnection strategies that incorporate a wide range of modeling blocks and considers the automatic implementation of block-based structures. Software environments are presented, which allow to build complex sound synthesis systems without burdening the user with problems of block compatibility     

A33scFv-green fluorescent protein, a recombinant single-chain fusion protein for tumor targeting

Chemical conjugates of monoclonal antibodies with fluorophores or enzymes have long been used for diagnostic purposes and experimental therapeutic approaches. Recombinant technology allows for the design and expression of tailored genuine fusion proteins, providing defined molecules as to size, molar ratios of the functional components and stability. The production of functional protein, however, is often limited or impossible due to refolding and solubility problems. Here, we report on the production of a soluble recombinant fusion construct, A33scFv-green fluorescent protein (A33scFv::GFP) in Pichia pastoris. A33scFv is a single-chain antibody recognizing the A33 antigen, which is expressed by approximately 95% of colorectal carcinomas and has become a focus of pre-clinical and clinical investigation. The fusion partner GFP was selected both as an experimental tool for functional studies of the A33 antigen and as a potential diagnostic for colon cancer detection and therapy planning. Pichia pastoris yeast strains were transformed with A33scFv::GFP cDNA under the methanol-inducible AOX1 promotor. The construct was properly expressed and secreted into culture supernatants as a soluble protein, which was bifunctional without additional renaturation or solubilization steps. The crude protein solution was purified by affinity chromatography. Surface plasmon resonance, flow cytometry and fluorescence microscopy on sections of normal and cancerous colon tissue revealed specific binding and the applicability of this fusion protein for diagnostic purposes. In addition, the biodistribution of A33scFv::GFP was analyzed in mice bearing A33-positive tumor xenografts, confirming specific tumor targeting.     

Axon outgrowth is regulated by an intracellular purine-sensitive mechanism in retinal ganglion cells

Although purinergic compounds are widely involved in the intra- and intercellular communication of the nervous system, little is known of their involvement in the growth and regeneration of neuronal connections. In dissociated cultures, the addition of adenosine or guanosine in the low micromolar range induced goldfish retinal ganglion cells to extend lengthy neurites and express the growth-associated protein GAP-43. These effects were highly specific and did not reflect conversion of the nucleosides to their nucleotide derivatives; pyrimidines, purine nucleotides, and membrane-permeable, nonhydrolyzable cyclic nucleotide analogs were all inactive. The activity of adenosine required its conversion to inosine, because inhibitors of adenosine deaminase rendered adenosine inactive. Exogenously applied inosine and guanosine act directly upon an intracellular target, which may coincide with a kinase described in PC12 cells. In support of this, the effects of the purine nucleosides were blocked with purine transport inhibitors and were inhibited competitively with the purine analog 6-thioguanine (6-TG). In PC12 cells, others have shown that 6-TG blocks nerve growth factor-induced neurite outgrowth and selectively inhibits the activity of protein kinase N, a partially characterized, nerve growth factor-inducible serine-threonine kinase. In both goldfish and rat retinal ganglion cells, 6-TG completely blocked outgrowth induced by other growth factors, and this inhibition was reversed with inosine. These results suggest that axon outgrowth in central nervous system neurons critically involves an intracellular purine-sensitive mechanism.