1 / 41

Feeding physiology in nematode parasites: A Consumer’s Guide

Feeding physiology in nematode parasites: A Consumer’s Guide. Nick Sangster & Jeff Song Faculty of Veterinary Science University of Sydney. WORMS Haemonchus and Trichostrongylus. Life Cycle. Costs of internal parasites. Estimates for 1995: $ AUD 81M for control measures

warren
Download Presentation

Feeding physiology in nematode parasites: A Consumer’s Guide

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Feeding physiology in nematode parasites: A Consumer’s Guide Nick Sangster & Jeff Song Faculty of Veterinary Science University of Sydney

  2. WORMSHaemonchus and Trichostrongylus

  3. Life Cycle

  4. Costs of internal parasites • Estimates for 1995: • $AUD 81M for control measures • $AUD 141M production costs • Wool • Meat • Deaths • Animal suffering

  5. Why study feeding physiology? • Essential for worm survival • Critical in the host-parasite interface • Site of action of ivermectins • Could be important for delivery of RNAi • Excellent organ for studying functional genomics • C. elegans model • visible in live worms • self contained nervous system so functions when dissected • amenable to electrophysiology, manipulation of medium • IVM resistance as selectable phenotype • complex pharmacology, so many receptors • developmental changes • Functional in free living stages

  6. C. elegansTransgenesis Laser ablation of cell nuclei

  7. T. colubriformis fed rhodamine in vitro Control IVM

  8. Effects of mectins on inulin uptake x103

  9. Physiology - electrophysiology Electropharyngograms Trichostrongylus colubriformis Caenorhabditis elegans

  10. Effects of mectins on pharyngeal pumping frequency x103

  11. Aims • Describe the structure and physiology of larval and adult stages of parasitic nematodes • Describe the pharmacology of pumping • Describe the action of neuropeptides in somatic and pharyngeal muscle function

  12. L1 pharynx • Pharyngeal structure • Pumping events • Neurotransmitters • Anthelmintics

  13. Triradiate arrangement of pharyngeal muscle.Contraction opens the lumen

  14. The pharynges of free-living T. colubriformis

  15. Action of pharyngeal pumping

  16. Mechanism of pharyngeal pumping

  17. Pharyngeal pumping rate & duration Observation of microscopy Observation of video recording (L1)

  18. 5-HT & ACh initiate pharyngeal pumping

  19. Glutamate, ACh and IVM inhibit pharyngeal pumping

  20. GABA has a biphasic effect on pharyngeal pumping

  21. Conclusions • The structure of pharynxes in different stages of free-living T. colubriformis differ • L1/L2 has single stage pumping, L3 no pumping • 5-HT and ACh initiate pumping, but the actions are different • Glutamate and GABA do not initiate pumping, but decrease and increase pumping rate, respectively • IVM inhibits pumping, the inhibition is probably via GluCl receptor.

  22. Feeding in adults • Transition to a parasitic life style • Change from relatively short pharynx with terminal bulb and flaps to long thin pharynx • Anterior pharynx has typical pumping • Posterior pharynx pumps at a slower rate

  23. Pharyngeal pumping in adult T.c.

  24. Aims • To compare physiology (transmitters, anthelmintics) with L1 • To identify the FMRFamide-related peptides (FaRPs) in H. contortus • To describe the location of peptides and neurotransmitters in worms • To determine the actions of FaRPs native to H. contortus.

  25. The team travels to Belfast to perform 3D reconstruction of H.c. nervous system

  26. ICC (5-HT) of H. contortus pharynx

  27. Electropharyngogram

  28. 5-HT in adult Tc Effect of 5-HT on pumping frequency. Trace: 10-5 M 5-HT added at arrow

  29. Pharynx ACh GABA Glu IVM 10-9 M

  30. Gene Name Sequence species Method Ref. HF3 LQPNFLRFG H. c Characterization Collaborative project flp-6 PF3/AF8 KSAYMRFG H. c Characterization [Marks, 1999 #1061] flp-9 KPSFVRFG T. c Gene prediction Leech, pers. commu. flp-14 AF2 KHEYLRFG H. c & T. c Characterization Gene prediction [Keating, 1995 #1888] Leech, pers. commu. flp-16 AF15 AQTFVRFG H. c & T. c EST search Gene prediction This study Leech, pers. commu. flp-17 KSAFVRFG H. c EST search This study flp-17 KSQYIRFG H. c EST search This study flp-18 EMPGVLRFG H. c EST search This study flp-18 SVPGVLRFG H. c EST search This study flp-21 AF9 GLGPRPLRFG H. c EST search This study afp-1 AF14 SMPGVLRFG H. c EST search This study afp-1 AF20 GMPGVLRFG H. c EST search This study tcflp-2 AKWMRFG T. c Gene prediction Leech, pers. commu. FaRPs in H. contortus

  31. Anti AF9 staining

  32. Effects of FaRPs on T.c. adult pharynx AF15 AF1

  33. KSAFVRFamide in T.c.Cholinergic inhibition?

  34. Effects on drug susceptible and LEV-resistant (Lawes) L4 Haemonchus ACh KSAFVRFamide

  35. Method—body muscle contraction Sangster et al (1991), International Journal for Parasitology 21, 689-695

  36. ACh and LEV have excitatory effects, inhibited by nicotinic antagonists

  37. The effects of KSAFVRFamide & KSQYIRFamide on susceptible and LEV-resistant worms

  38. The effects are reduced in LEV-resistant worms

  39. Conclusions • Although the pumping mechanisms are different the pharmacology in pharynxes from L1 and adult is similar. • 8 EST sequences coding H. contortus FaRPs were identified. • 3 FaRPs were extracted from L3 and sequenced. • On pharynx, ACh and LEV plus the flp-coded FaRPs, KSAFVRFamide and KSQYIRFamide, were inhibitory. • On body muscle ACh and LEV plus the flp17-coded FaRPs were excitatory and blocked by nicotinic antagonists d-tubocurarine and macamylamine. • The dose response was shifted (both on pharynx and muscle) in Lawes worms (which have reduced nicotinic receptors) indicating that the flp-17 FaRPs are cholinomimetic or presynaptically release ACh.

  40. Acknowledgements • Jeff Song’s PhD work • Aaron Maule, QUB • Pharmacia & Upjohn company for funding • Special thank for Ms Sally Pope’s excellent drawing

More Related