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Georg-August-Universität Göttingen

1. Prahlad, Achintya. Mechanical Properties of the lch5 Organ in the Drosophila Larva.

Degree: PhD, Göttinger Graduiertenschule für Neurowissenschaften, Biophysik und molekulare Biowissenschaften, 2017, Georg-August-Universität Göttingen

I begin with a brief account of the topic of mechanosensation, followed by an outline of how the project evolved. The experimental techniques used and their rationale are described. The section ends with a short description of the thesis structure. Out of all sensory modalities, mechanosensation is of special interest to biophysicists, since its transduction mechanism in most cases involves a direct mechanical gating of ion channels, as opposed to gating by a chemical messenger. One important class of mechanosensory organs are the chordotonal organs. These perform proprioceptive and other mechanosensory functions in insects and crustaceans. There is a wide diversity of chordotonal organs across species and also within a single species, but there is a great deal of structural overlap. This makes them rather interesting to study, because results obtained by studying the mechanics of one type of chordotonal organ can in principle be applied to others. The mechanical properties of these organs are thought to be correlated to the sensory functions. Mutant studies, laser Doppler vibrometry and other techniques have given us some information on the functioning of these organs, but direct mechanical probing of their components had hitherto not been carried out. This was the motivation for my project, in which I measured mechanical properties of a particular chordotonal organ – the lateral pentascolopidial (lch5) organ – that plays a key role in proprioceptive locomotion control in Drosophila larvae. In the early stages of the project, the mechanical properties of Johnston’s organ – the antennal hearing organ in the adult fruit fly Drosophila melanogaster – appeared attractive, because it functions using an active process very similar to that operating in the vertebrate ear. The idea was to measure active fluctuations from the sensory cilia of the organs, which are believed to be the main transducing element. This would involve initially measuring forces at the arista, which is the external sound receiver of the antenna, and then moving inwards. Attempts to measure forces at the arista using optical tweezers were unsuccessful owing to thermal damage. There were also other difficulties, mainly that optical trapping requires a water sample and the fly does not survive under water. We also understood that probing the internal structures of Johnston’s organ would not yield conclusive results, since this would require perforating the cuticle and would impact the mechanics. We then shifted our attention to the lch5 organ since it is also a chordotonal organ, albeit simpler in structure than Johnston’s organ. We first decided to repeat the bead-trapping experiment on the lch5 organ. For these experiments I used a dissected fillet preparation of the larva. Here the muscles presented an obstacle to bringing the bead in contact with the organ. This was overcome by digesting the muscles with collagenase. However, once the bead was stuck to the organ it could not be trapped, and no fluctuations could be measured. Since the… Advisors/Committee Members: Schmidt, Christoph F. (advisor), Göpfert, Martin (referee), Heussinger, Claus (referee).

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APA (6th Edition):

Prahlad, A. (2017). Mechanical Properties of the lch5 Organ in the Drosophila Larva. (Doctoral Dissertation). Georg-August-Universität Göttingen. Retrieved from http://hdl.handle.net/11858/00-1735-0000-0023-3EF9-0

Chicago Manual of Style (16th Edition):

Prahlad, Achintya. “Mechanical Properties of the lch5 Organ in the Drosophila Larva.” 2017. Doctoral Dissertation, Georg-August-Universität Göttingen. Accessed November 19, 2017. http://hdl.handle.net/11858/00-1735-0000-0023-3EF9-0.

MLA Handbook (7th Edition):

Prahlad, Achintya. “Mechanical Properties of the lch5 Organ in the Drosophila Larva.” 2017. Web. 19 Nov 2017.

Vancouver:

Prahlad A. Mechanical Properties of the lch5 Organ in the Drosophila Larva. [Internet] [Doctoral dissertation]. Georg-August-Universität Göttingen; 2017. [cited 2017 Nov 19]. Available from: http://hdl.handle.net/11858/00-1735-0000-0023-3EF9-0.

Council of Science Editors:

Prahlad A. Mechanical Properties of the lch5 Organ in the Drosophila Larva. [Doctoral Dissertation]. Georg-August-Universität Göttingen; 2017. Available from: http://hdl.handle.net/11858/00-1735-0000-0023-3EF9-0

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