6 Transplantation of neuronal cells in animal models of neurological damage Rupam Choudhury We had generated a number of conditionally-immortalized neuronal cell lines from specific areas of the mouse brain. These cell lines have been grown for many years and continue to exhibit neuronal characteristics. Some of these have been generated from neonatal and adult hipoocampus. In collaboration with researchers fm NIMHANS, Bangalore, we have transplanted these cells into the brains of ventral subicular-lesioned rats, which have specific spatial memory deficits and examined functional recovery. Our results indicate that the rats recover from their deficit substantially and the transplanted cells also migrate into specific areas of the lesioned brain. Further studies are underway to determine the mechanisms of recovery and cell migration. Collaborators: Bindu Kutty and T.R. Raju, National Institute of Mental Health and Neurosciences, Bangalore 101 MITRADAS M PANICKER MITRADAS NCBS_AR_05_07.indd 101 7/10/08 5:35:15 PM SANJAY P. SANE Neural and physical basis of insect flight [email protected] The spectacular evolutionary success of insects owes much to the evolution of flight. Insect flight is characterized by speed, control and manoeuvrability. Their wings flap at very rapid rates Selected publications (typically on the order of 10-100 Hz) and hence their sensory system must acquire and process Sane, S. P. (2003). The aerodynamics of information at similar rates. How do the nervous systems of insects tackle the extraordinary insect flight.Journal of Experimental Biology 206, 4191-4208. challenges of acquiring, integrating and processing sensory information and generating rapid Sane, S. P. (2006). Induced airflow in flying behavioral responses to ensure stable flight? A rigorous study of this question requires multi- insects I. A theoretical model of the induced flow. Journal of Experimental Biology, 209, disciplinary research in the areas of physics, biomechanics, neurobiology and behavior. Our 34-42. work combines the input from these various sub-disciplines to address diverse flight-related Sane, S. P. and Jacobson, N. P. (2006). Induced airflow in flying insects II. Measurement phenomena. of induced flow. Journal of Experimental Biology, 209, 43-56. Sane, S. P., Dieudonne, A., Willis, M. A. and Daniel, T. L. (2007). Antennal mechanosensors mediate flight control in moths. Science, 315, 863-866. The hawk moth, Manduca sexta, feeding while hovering over an artificial flower. NCBS_AR_05_07.indd 102 7/10/08 5:35:16 PM 1 The physical basis of insect flight On the physical front, how do the flapping wings of insects generate sufficient aerodynamic forces to make flight possible and how do insects modulate these forces to determine their flight trajectories when chasing territorial interlopers, locating odor sources or finding mates? To address this question, 6ISUALSTIMULUS 6ERTICALFORCE we built a dynamically scaled robotic flapper (affectionately called Robofly) to study the basic fluid (ORIZONTALFORCE !XIAL)NFLOW 2ADIAL/UTFLOW dynamical principles that make flapping flight of insects fundamentally distinct from fixed-wing !NEMOMETER A B !NEMOMETER flight of airplanes. From these studies, we were able to show that the high lift generated by flapping U wings can be sustained over the entire duration of the wing stroke, unlike their fixed wing counterpart which tends to stall. This study resulted in a semi-empirical model that could predict the instantaneous U forces generated by a flapping wing performing any arbitrary kinematic pattern. Figure 1. Air flow measurements around a flying insect. Currently, we are extending these techniques to study the effect of wing flexibility on aerodynamic force generation. With increase in size of the insect, their wings tend to show greater flexibility with direct consequences to their ability to generate aerodynamic forces. This study will also extend into 103 the biomaterial aspects of wing flexibility to address how wing flexibility may influence longevity of the wing structure through the typical lifetime of an animal. In addition, we are also studying the gross flows around insect bodies during flight and trying to understand how these flows influence various aspects of insect physiology such as thermoregulation, odor detection etc. Apart from the obvious biological implications of these studies, these results will also help in development of SANE SANJAY optimally performing wings for micromechanical robotic insects. These aspects are being studied in close collaboration with roboticists and engineers, at the University of Delaware. Figure 2. Antennal Anatomy. !NTENNAL.ERVE &LAGELLUM !NTENNAL.ERVE *OHNSTON´S/RGAN 0EDICEL "OHM´S"RISTLES 3CAPE )NTRINSIC!NTENNAL-USCLES 2 The neural basis of flight behavior On the neurobiological front, how do flying insects use various sensors distributed over their body to acquire information about their environment and how is this information used in stabilizing their flight? We have recently begun investigating this question with specific focus on the role of antennae in acquisition and processing of self-generated and externally-generated sensory cues that mediate flight control in hawk moths. Our behavioral studies revealed that antennae play a very crucial role in mediating flight control: insects lacking the distal segment of their antennae (i.e. flagella) are unable to fly in a coordinated manner. However, when the flagellar integrity is restored, their flight ability can be rescued. Our electrophysiological studies show that individual mechanosensory neurons at the base of the antennae are tuned to vibratory motion of the antennae and capable of transducing cues essential for flight control. Visualization of the underlying neural circuitry reveals that a bulk of the antennal mechanosensory information is relayed to an area of the brain called the AMMC (Antennal Motor and Mechanosensory Centre), before it is transmitted to the flight motor units. Thus, antennal mechanosensors are involved in mediating flight control in insects. Our studies will endeavour to throw light on the evolution of antennal diversity among insects in relation to their flight mechanics, as well as the specific roles of the antenna and the AMMC in flight control. Ongoing research from my laboratory also addresses flight under natural circumstances. We will study how the antennal mechanosensory modality combines with visual inputs to enable flight in moths and butterflies. We are keen to diversify this study into the area of flight energetics, thermoregulation and behavioral ecology of live, migrating insects. NCBS_AR_05_07.indd 103 7/11/08 2:59:13 PM OBAID SIDDIQI Genetic analysis of chemosensory perception [email protected] Olfactory behavior in Drosophila is partly inborn and partly acquired. Our group is studying ontogeny of olfactory behavior and odor learning ability in the fly. The report by Sarit Pati Goswami et al. shows that newly born larvae are attracted by low concentration of ethyl acetate within minutes of eclosion irrespective of the odor environment, but sensitivity to odorants increases with age. Aversion to high concentration takes several hours to develop. In the previous report, we had shown that the multiphasic learning retention curves, in the third instar larvae can be decomposed by a simple graphic procedure into three distinct phases; short term memory (STM), middle term memory (MTM) and long term memory (LTM). We now show that these phases Selected publications correspond to exactly STM, MTM and LTM as revealed by study of learning mutants and effect of Chakraborty, T.S., Prabhakar, S., Kumar, S. anesthetics and other memory ablating treatments. and Siddiqi, O. (2006). Neural correlates of imaginal conditioning in Drosophila melanogaster. 4th IBRO-FAONS Congress, Hong Kong. Tuhin Subhra Chakraborty et al. describe changes in the sensitivity of chemoreceptors that Chakraborty, T.S., Prabhakar, S., Mahapatra, accompany imaginal conditioning. They find that odor imprinting increases the affinity of the S., Goswami, S.P., Kumar, S. and Siddiqi, O. chemoreceptor to several different ligands, all acting on the same receptor but as Jawaid Ahsan (2007). Increased sensitivity of olfactory receptor neurons correlate to imaginal shows, there is no indication of transcriptional regulation. The first effect of odor imprinting is conditioning in Drosophila melanogaster. Society for Neuroscience, San Diego, USA. thus, an enhancement of peripheral sensitivity. Or22a Type III sensillae contain two receptors Or22a and Or85b. The A neuron projects to the glomerulus DM2. Recordings from the sensillum permit us to study the effect of conditioning on the olfactory pathway described in this report. DM2 Odor NCBS_AR_05_07.indd 104 7/10/08 5:35:17 PM 1 Early development of olfactory response in Drosophila larvae Sarit Pati Goswami, Sunil Prabhakar, Latha Murugesan and Agila Somasundaram The olfactory responses of Drosophila imago undergo distinctive changes after eclosion. When the flies are exposed to certain odorants, attraction towards these chemicals increase. This phenomenon called ‘Imaginal conditioning’ has been described in these reports. We are now studying the development of olfactory behavior in the larva. Larval response can be analyzed by tracking individual larvae in an odor gradient. Single larvae are placed at the centre of a petri dish and their movement towards an odor source is tracked videographically (Figure 1c). Analysis of these tracks provides information