Giardia Flagellar Motility Is Not Directly Required to Maintain Attachment to Surfaces

Giardia trophozoites attach to the intestinal microvilli (or inert surfaces) using an undefined “suction-based” mechanism, and remain attached during cell division to avoid peristalsis. Flagellar motility is a key factor in Giardia's pathogenesis and colonization of the host small intestine. Specifically, the beating of the ventral flagella, one of four pairs of motile flagella, has been proposed to generate a hydrodynamic force that results in suction-based attachment via the adjacent ventral disc. We aimed to test this prevailing “hydrodynamic model” of attachment mediated by flagellar motility. We defined four distinct stages of attachment by assessing surface contacts of the trophozoite with the substrate during attachment using TIRF microscopy (TIRFM). The lateral crest of the ventral disc forms a continuous perimeter seal with the substrate, a cytological indication that trophozoites are fully attached. Using trophozoites with two types of molecularly engineered defects in flagellar beating, we determined that neither ventral flagellar beating, nor any flagellar beating, is necessary for the maintenance of attachment. Following a morpholino-based knockdown of PF16, a central pair protein, both the beating and morphology of flagella were defective, but trophozoites could still initiate proper surface contacts as seen using TIRFM and could maintain attachment in several biophysical assays. Trophozoites with impaired motility were able to attach as well as motile cells. We also generated a strain with defects in the ventral flagellar waveform by overexpressing a dominant negative form of alpha2-annexin::GFP (D122A, D275A). This dominant negative alpha2-annexin strain could initiate attachment and had only a slight decrease in the ability to withstand normal and shear forces. The time needed for attachment did increase in trophozoites with overall defective flagellar beating, however. Thus while not directly required for attachment, flagellar motility is important for positioning and orienting trophozoites prior to attachment. Drugs affecting flagellar motility may result in lower levels of attachment by indirectly limiting the number of parasites that can position the ventral disc properly against a surface and against peristaltic flow

Analog module generators for effective design assistance.

A set of analog device and macro module generators has been implemented in the GDT environment. The generators are technology and design rules independent and can assist effectively design of analog circuits in BiCMOS and I²L technologies. The design flow starts with a hierarchical schematic, generates automatically all components needed, and performs analog routing followed by a postprocessing. Design of a VCO circuit will be demonstrated as an example

Analog Expert Design System (AEDS) Abschlussbericht

Design automation has reached a considerable level in the digital field at the beginning of the project, whereas for analog and mixed analog/digital design it lags far behind. Therefore it has been the main objective of the project 'Analog Expert Design System' to support an environment for the analog and mixed analog/digital IC- and system design, which assures optimized performance combined with short time to market. Tools for analysis of analog and mixed analog/digital circuits were improved by new methods. In the field of analog circuit synthesis tools were evaluated and improved on the basis of knowledge and experience of analog experts. For the layout synthesis of analog circuits a new tool has been developed. For the verification of these tools an example library was designed including functional macro-models, layout module generators as well as acquired, documented and coded knowledge for analog circuit design. Furthermore new tools were implemented into frameworks or design environments. The work performed improved analog and mixed analog/digital design considerably. On this basis further development work will be done to make analog design even more effective and to close the gap between the design of digital and analog or mixed analog/digital circuits. (orig.)SIGLEAvailable from TIB Hannover: F95B1200+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Analog expert design system Final report (1995-1996)

The main objective of this JESSI project was the development of methods and tools for the analog and mixed analog/digital circuit design. During phase II of the project ('92-'94) major progress was achieved in the area of tools supporting and improving the different steps of the design flow. Based on these results the goals for phase III ('95-'96) were defined, aiming at even more optimized tools to be used in the design flow. TEMIC put the main emphasis on the following topics: In the area of Analog Simulation a design centring tool was evaluated in practical use and substantially enhanced. A prototype tool performing thermal-electrical simulation was developed together with ANACAD. For the development of macro models VHDL-A was tested and the visual programming environment ViCE was created. For the verification of the electrical behaviour of circuits the tool NWB was developed, which is based on netlists. As a requirement for Circuit Synthesis TEMIC performed a systematic analysis and documentation of selected circuit classes. Symbolic analysis techniques were evaluated for the investigation of circuits. For the implementation of knowledge as well as execution of circuit synthesis the tool ACSYN was further enhanced. It is also well suited to explore the property-space of a circuit. The developed Layout Synthesis tool ALSYN was used in production and further enhanced concerning interactivity. Concurrently placement and routing algorithms were improved. A major step in increasing efficiency for analog layout design was done by using these tools. The developed compaction tool CAMBIO-XT was especially applied to layouts being transferred to a new process, showing also big reduction in design time. For the extraction of substrate parasitics improvements were achieved concerning handling of higher frequencies. (orig.)Available from TIB Hannover: F97B906 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman