WWW.ABSTRACT.XLIBX.INFO
FREE ELECTRONIC LIBRARY - Abstract, dissertation, book
 
<< HOME
CONTACTS



Pages:   || 2 |

«The organization of the sensory system of Oligochaeta worms PhD Thesis Gábor Kiszler Supervisor: László Molnár PhD Associate professor PÉCS, ...»

-- [ Page 1 ] --

UNIVERSITY OF PÉCS

Biological Doctoral School

Comparative Neurobiology PhD Program

The organization of the sensory system

of Oligochaeta worms

PhD Thesis

Gábor Kiszler

Supervisor:

László Molnár PhD

Associate professor

PÉCS, 2012

INTRODUCTION

In multicellular animals special cells were differentiated to detect various stimuli and

to convert these into electrical signals. The oldest form of these cells is the so-called primary sensory cell with central process, which occurs mainly in invertebrates. The secondary sensory cells have no process they connect to the peripheral processes of neurons with synapses and the electric signal is transported to the central nervous system by neurons. The third type is the so-called sensory neuron, its peripheral process can form free nerve endings or sensory corpuscle in the epithelium, connective and muscle tissues.

In the nervous system the interneurons decode the electrical signals (action potentials) induced by the stimuli from sensory cells or sensory neurons; they also evaluate and form a suitable response, which comes to the effector cells and tissues mediated by the so-called motoneurons. This process is an adequate stimulus-induced response, i.e. the reflex. The investigations of the reflex arc and the examinations of anatomical and mechanical features of each component promote a better understanding of the integrative neurological processes.

In Oligochaetes the epithelium of the body wall consists of column-shaped supporting cells, mucinous and serous gland cells, moreover primary sensory cells are represented in a large number. They were classified based on their localization and the morphology of the soma. Their types, numbers and distribution pattern were described on various body segments based on the investigation of the imprint pattern of sensory cells on cuticle further serial sections of the body wall. The histological investigation revealed that the majority of the primary sensory cells were grouped into sensory organs (sensillae), solitary cells were seldom found. Large sensillae are located at the chaetae row encircling the segments. This arrangement is typical most of the body segments excepting the prostomium and the last segments.

Based on histological and ultrastructural descriptions of the sensory cells, five distinct groups have been identified in earthworms: phaosomal photoreceptors, penetrative uni- and multiciliate sensory cells, nonpenetrative multiciliate sensory cells and basal ciliate sensory cells. The sensory cells are heterogeneous in neurochemical characteristics. Transmitterspecific cells have been identified in several species, thus peptidergic, aminergic, GABAergic and putative nitric oxide producing sensory cells. However, the possible functions of various transmitter-specific cells remained unknown.

The primary sensory cells have one central process, from which more peripheral processes are branching. The central processes without any ramification enter the central nervous system (CNS) via three pairs of segmental nerves. Their T- or Y-shape rami form five pairs of longitudinal sensory axon bundles, namely the intermediolateral, intermediomedial, ventrolateral, ventromedial and the dorsolateral ones. The peripheral processes of sensory cells ramifying at the border of epithelium and muscle layer produce the subepidermal plexus. This plexus contains sensory and motor fibres as well.

The physiological experiments suggested that the sensory fibres of the segmental nerves could come from not only one, but three neighbouring segments. However, the earlier morphological studies have not discussed the size of the peripheral area, whence the sensory fibres running to each ganglion could be collected, and neither the pattern of the transmitter specific sensory cells nor their central representation have been revealed.

AIMS

According to the previous experimental results it might be concluded, that a detailed anatomical and immuncitochemical description of the connections of the CNS and the peripheral nervous system (PNS) could contribute to understand thoroughly the neuronal mechanisms of the earthworms.

According to the literature data we considered it necessary to carry out the following tasks:

1. to determine the distribution patterns of sense organs and sensory cells at different body regions with examinations of whole-mount samples;

2. to characterize the morphology of the sensory cells and to describe exactly their process system;

3. to reveal the representation of the sensory cells in the CNS;

4. to identify the GABA-immunoreactive (GABA-IR) elements of the sensory system and to determine their distribution pattern as well;

5. to describe the representation of the central processes of the labelled cells at the central region.

These investigations could help to understand thoroughly the organization and the function of the sensory system of the Oligochaetes.

MATERIALS AND METHODS

Experiments were carried out on adult specimens of Eisenia fetida, Lumbricus terrestris and Limnodrilus hoffmeisteri (Annelida, Oligochaeta), which were collected from their natural habitat, or were bred at standard laboratory conditions. The model animals were selected according to the current investigation. Thus for the electronmicroscopical and immunocytochemical researches E. fetida and L. hoffmeisteri were used because of their small size; otherwise the neuronal tracing were carried out on L. terrestris because their axon could be easily isolated and manipulated.





Neural tracing We used carbocyanine dye (DiI, 1,1'-Dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine iodide) as a red colour, lipophilic, fluorescent tracer and Lucifer yellow (LY, 6-amino-2-(hydrazinecarbonyl)-1,3-dioxobenzo[de]isoquinoline-5,8-disulfonate de dilithium) as a water-soluble stain with relative low molecular weight.

DiI was applied to trace both peripheral and central neuronal pathways in postmortem fixed tissue. At peripheral labelling after removing the cuticle, DiI crystal was placed directly to the epithel surface. Thus we could investigate the central representation labelling the afferent branches. Central labelling was carried out by notching the ganglion sheath and after putting DiI microcrystal to the lateral part of the ganglion. Applying this technique we could record the sensory structure at the periphery.

LY stain was used in surviving samples. The dye was injected into the intact nerves using iontophoresis technique for minimum 3 hours.

Imaging was carried out with an Olympus FV1000 confocal microscope equipped with mixed krypton argon laser, or with a Nikon Eclipse 80i epifluorescence microscope.

Light-microscopic immunocytochemistry The samples were fixed during 3 hours in freshly prepared Boer-fixatives (3 ml saturated picric acid, 1 ml 25% glutaraldehyde and 40 µl concentrated acetic acid) at room temperature and in dark.

The specificity of the applied primary antibody was controlled by GABA preabsorption test. Samples were labelled with avidin-biotin-horseradish complex (ExtrAvidin kit, Sigma Co., Budapest) and visualised by 3,3’-diaminobenzidine (DAB). Most of the samples were used like whole-mount, others were embedded into epoxy resin and were sectioned in serial sections. Using DePeX conversation the samples were investigated with Nikon Eclipse 80i microscope system. Multispectral images were recorded using a Zeiss Axio Imager Z1 with a CRi NuanceTM Multispectral Imaging System.

Electron microscopic immunocytochemistry For electronmicroscopical investigation the samples were fixed during 3 hours into a mixture of 4% paraformaldehyd and 2,5% glutaraldehyd at room temperature and in dark.

After washing sacharose contained buffer solution the samples were embedded into Durcupan ACM resin. The ultrathin serial sections were cut and placed on nickel grids. The samples were placed to drops of goat anti-rabbit IgG secondary antibody conjugated with 10 nm colloidal gold particles and incubated for 2 hours in room temperature. The reaction was visualized using DAB or immunogold (18 nm), contrasted and observed by JEOL 1200 EX electron microscope system.

Quantification Whole-mount and serial sections were also used for quantitative microscopic investigation. The typical GABA-IR cell number of one segment was calculated based on the set which contained 4-12 specimens. Analysis of variance (ANOVA) was used for data analysis using SPSS 17.0 statistic software.

RESULTS AND DISCUSSION

The distribution pattern of the primary sensory cells and running of their processes By means of scanning electron microscopical investigation of E. fetida and L.

hoffmeisteri we recognized that the distribution pattern of sensory cells in the prostomium and the first 3-5 segments, furthermore in the last 3-5 segments and the pygidium was identical in these species. Our calculation showed that the number of the sensory organs -which localize randomly in appearance- was the highest in the prostomium and in the pygidium. Thus it can be presumed that these body regions have an important role in sensory function, as in the initiation of the withdrawal and the escaping reflexes.

The sensory organs of the investigated postclitellar segments were different from the anterior and the posterior segments in size and also in distribution pattern. The large sized sensillae were concentrated into the chaetae row, occurred rare in the anterior and posterior third part of the segments in scattered distribution pattern. This distribution pattern suggests that the sensory organs of the chaetae row have an important role in the sensory mechanism.

We compared the numbers of the sensory organs in anterior, midbody and posterior segments of the two investigated species. We found that the numbers of the sensillae per unit area were much higher in L. hoffmeisteri. Presumably these anatomical differences can be the consequence the way of life: from the water L. hoffmeisteri receives the chemical stimuli in dissolved form and in low concentration and this requires more sensitive detection.

In the second part of our investigations we combined a fluorescent tracing method with confocal laser scanning microscopy to reveal the organization of the sensory system of the earthworm L. terrestris. In this study we firstly revealed the three-dimensional structures of the primary sensory cells and their processes. We also determined the receptive field of the prostomial nerves, which was concentrated -according to the typical bilateral symmetry relation- in the ipsilateral side of the prostomium and the first two anterior segments, where the traced nerve was located.

After tracing an isolated postclitellar ventral nerve cord (VNC) ganglion, two types of peripheral sensory structures were identified in the body wall epithelium. Among the primary sensory cells free nerve endings were also found, which were identified as the peripheral processes of the central sensory neurons.

The sensory cells had 8-10 μm diameter and most of them grouped into sensory organs in the chaetae row, in the middle line of a segment. The central processes of sensory cells situated at the anterior part of a segment entered via the 1st segmental nerve to the VNC, otherwise the processes of sensory cells located the chaetae row entered via the 2nd one. The 3rd segmental nerve collected the processes of the sensory cells from the caudal part of a segment. This distribution pattern was typical of the most segments of the earthworm. Along the central axis of the animal the density of the stained cells increased in caudal direction and parallel of this the dominance of the chaetae row started to break up, and in the last 3-4 segments it was difficult to identify any characteristic pattern.

We determined the sensory and motor fields of a midbody segment after tracing one isolated ganglion. The stained cell bodies were concentrated in one segment, but we found stained cells and processes in the neighbouring segments as well. Therefore it seems that the reflex centre function of one ganglion is not restricted to one segment. Based on the results of the applied pathway tracing investigations we could assume that the sensory structures of the neighbouring segments modulate directly the interneuronal system of the VNC and might play a role in the formation of motor responses. However, we can not rule out that the sensory structures of the neighbouring segments connect with electrical synapses. Using DiI tracing method we showed five pairs of axon bundles in the VNC ganglion.

GABA immunoreactivity in the sensory system After immunostain clearly labelled structures were identified in different level of the sensory system of E. fetida and L. hoffmeisteri. The stained cells of the body wall were identified as primary sensory cells based on their morphological features. The photoreceptors were not labelled.

The distribution pattern of the GABA-IR primary sensory cells followed the previously described pattern using neuronal tracers. We revealed a typical pattern in the clitellum, where the stained cells concentrated into two parallel lines in the area of the adolescent bump. Presumably these GABA-IR cells, represented in high number with central processes which run directly to the VNC have a role in shaping of the mating behaviour to perceive the body surface of the partner. In the sensillae of the postclitellar segments the labelled cells were heterogeneous but we could define some characteristic cell types.

Solitary GABA-IR cell types were also detected. Their function could be relatively simply explained. According to the results of anatomical and physiological experiments they were supposed to be stretch receptors, because they prevented the strain of the epithelium of the body wall. Our results partly corroborate with this hypothesis, since the central processes of the majority of solitary sensory cells directly project to the ventral ganglia without making any synapses with the subepidermal plexus.



Pages:   || 2 |


Similar works:

«Volume 10 No. 1 January 2010 PHYSICO-CHEMICAL CHARACTERISTICS OF SHEA BUTTER (Vitellaria paradoxa C.F. Gaertn.) OIL FROM THE SHEA DISTRICTS OF UGANDA Okullo JBL*1, Omujal F2, Agea JG3, Vuzi PC4, Namutebi A5, Okello JBA6 and SA Nyanzi2 John Bosco Okullo *Corresponding author email: jblokullo@forest.mak.ac.ug / okullo66@yahoo.com Department of Forest Biology and Ecosystems Management, Makerere University, P.O. Box 7062 Kampala, Uganda. Department of Chemistry, Makerere University, P.O. Box 7062...»

«South Western Journal of Vol.3, No.1, 2012 Horticulture, Biology and Environment pp.73-83 P-Issn: 20679874, E-Issn: 2068-7958 EFFECTS OF ALCOHOL SUGARS ON IN VITRO POTATO MICROTUBERIZATION Alireza MOTALLEBI-AZAR* and Samaneh KAZEMIANI Department of Horticultural Sciences, Faculty of Agriculture, University of Tabriz, Tabriz 51666, Iran. *Corresponding Author: motallebiazar@gmail.com Abstract. This study was conducted to evaluate the effects of alcohol sugars induced via; mannitol, sorbitol on...»

«Plant-frugivore interactions in a heterogeneous forest landscape of South Africa Dissertation In partial fulfilment of the requirements for the award of a Doctorate Degree in Natural Sciences (Dr. rer. nat) The Faculty of Biology, Philipps-University of Marburg Lackson Chama, MSc Sinazongwe (Zambia) June 2012, Marburg From the Faculty of Biology, Philipps-University Marburg als Dissertation am angenommen. Dekan: Prof. Dr. Paul Galland Erstgutachterin: Prof. Dr. N. Farwig Zweitgutachter: Prof....»

«Mining an Ocean of Data: Application of modern statistical methods for addressing biological oceanography questions Joaquim Goes1 and Rahul Mazumder2 Lamont Doherty Earth Observatory, Palisades, New York, 10964 Department of Statistics, Columbia University, New York, 10027 Summary: The explosive growth of oceanographic databases in recent years resulting from the advent of satellites and autonomous floats capable of measuring ocean properties beyond those possible by traditional research ships,...»

«The Handy Biology Answer Book The Handy Answer Book His/her because rate than realtor fixed-line can achieve that situation though our SaaS type of the changes can then require much of you start applying a other download choosing their programs. Very, managers do a bank because owners and staid payment and home as reviewing the pdf is defined along convenient industry. You was do other people teaching related, genuinely interpersonal may all take project offers in the air of their agreement....»

«Version 4.0 Statistics Guide Statistical analyses for laboratory and clinical researchers Harvey Motulsky  1999-2005 GraphPad Software, Inc. All rights reserved. Third printing February 2005 GraphPad Prism is a registered trademark of GraphPad Software, Inc. GraphPad is a trademark of GraphPad Software, Inc. Citation: H.J. Motulsky, Prism 4 Statistics Guide −Statistical analyses for laboratory and clinical researchers. GraphPad Software Inc., San Diego CA, 2003, www.graphpad.com. This book...»

«Corals & Waves Calcification and bioerosion in Large Amplitude Internal Wave (LAIW) affected coral reefs Dissertation submitted by Gertraud Maria Schmidt In partial fulfilment of the requirements for the degree of doctor of natural sciences (Dr. rer. nat.) Faculty of Biology/Chemistry, University of Bremen February 2010 The present study has been realized from October 2006 to February 2010 at the Leibniz Center for Tropical Marine Ecology in Bremen and at the Alfred Wegener Institute for Polar...»

«Chemical Synthesis and Biological Evaluation of Cell Surface Carbohydrate Antigens for Rational Vaccine Design Inaugural-Dissertation to obtain the academic degree Doctor rerum naturalium (Dr. rer. nat.) Submitted to the Department of Biology, Chemistry and Pharmacy of Freie Universität Berlin by Christopher E. Martin from Sparta, Greece January 2014 The work on this dissertation was performed between January 2010 and December 2013 at the Department of Biomolecular Systems of the Max Planck...»

«Functional analysis of ATM and ATR in the moss Physcomitrella patens Inaugural-Dissertation Zur Erlangung des Doktorgrades Der Mathematisch-Naturwissenschaftlichen Fakultät vorgelegt von Martin Martens aus Bonn, Deutschland Diese Arbeit wurde am Max-Planck-Institut für Pflanzenzüchtungsforschung in Köln in der Arbeitsgruppe von Dr. Bernd Reiss durchgeführt. Berichterstatter (Gutachter): Prof. Dr. Maarten Koornneef Prof. Dr. Martin Hülskamp Prüfungsvorsitzende: Prof. Dr. Karin Schnetz Tag...»

«Curriculum Vitae Eric John Olson Heller School for Social Policy and Management Program in Sustainable International Development P.O. Box 549110 Waltham, MA 02454-9110 Phone: (781) 736-8363 Email: eolson@brandeis.edu Current Primary Teaching Position: Senior Lecturer in Ecology. I teach courses in in the following subject areas: Principles of Ecology; Environmental Impact Assessment; Sustainable Agriculture (co-taught); Ecology of Water and Sanitation (co-taught); Tourism and Development...»

«DIPLOMARBEIT Titel der Diplomarbeit Cell cycle and DNA damage dependent control of transcription of the DNA repair gene AtCOM1 Verfasser Stefan Bailey angestrebter akademischer Grad Magister der Naturwissenschaften (Mag. rer. nat.) Wien, 2012 Studienkennzahl lt. Studienblatt: A 490 Studienrichtung lt. Studienblatt: Diplomstudium Molekulare Biologie Betreuerin / Betreuer: Dr. Peter Schlögelhofer Table of contents 1 Abstract 6 2 Zusammenfassung 7 3 Introduction 9 3.1 The Cell Cycle 10 3.2...»

«Arch. Tierz., Dummerstorf 48 (2005) 2, 130-137 VPISU, Dairy Science Department, Blacksburg, USA Genetics and Genomics, Roslin Institute (Edinburgh), Roslin, UK Research Institute for the Biology of Farm Animals (FBN), Dummerstorf, Germany GERTRAUDE FREYER3, JULES HERNÁNDEZ-SÁNCHEZ2 and BENNET G. CASSELL1 A note on inbreeding in dairy cattle breeding Dedicated to Prof. Dr. sc. Lothar Panicke on the occasion of his 65th birthday Abstract Starting from the study at the beginning of the East...»





 
<<  HOME   |    CONTACTS
2016 www.abstract.xlibx.info - Free e-library - Abstract, dissertation, book

Materials of this site are available for review, all rights belong to their respective owners.
If you do not agree with the fact that your material is placed on this site, please, email us, we will within 1-2 business days delete him.