DOCSLIB.ORG

Chapter 1. Epithelium (Epithelia)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chapter 1. Epithelium (Epithelia) Chapter 1. Epithelium (Epithelia) ▶ Epithelia separate the internal environment from the external environment by forming tightly cohesive sheets of polarized cells held together by specialized junctional complexes and cell adhesion molecules ▶ Epithelial cells participate in embryo morphogenesis and organ development This chapter address the structural characteristics of epithelial cells General Characteristics of epithelia 1) tightly cohesive sheet of cells that covers or lines body surface (skin, intestine, secretory ducts) and forms functional units of secretory gland (salivary gland, liver) 2) basic function; protection (skin) ; absorption (small and large intestine) ; transport of material at the surface (mediated by cilia) ; secretion (gland) ; excretion (tubules of kidney) ; gas exchange (lung alveolus) ; gliding between surface (mesothelium, 중피세포) 3) Most epithelial cells renew continuously by mitosis (regeneration) 4) Epithelia lack direct blood and lymphatic supply (avascular; no blood supply). Nutrients are delivered by diffusion 5) Epithelial cells have no free intercellular substance (in contrast to connective tissues) (Control of permeability) 6) The cohesive nature of an epithelium is maintained by cell adhesion molecules and junctional complexes (attachment). 7) Epithelia are anchored to a basal lamina (바닥판). The basal lamina and connective tissues components cooperate to form basement membrane (기저막) 8) Epithelia have structural and functional polarity Epithelial Tissue - Characteristics & Functions https://www.youtube.com/watch?v=xI2hsH-ZHR4 ( 6 min) ■ Classification based on two parameters 1. shape of individual cells 1) squamous cells (편평상피세포): flattened (width > height) 2) cuboidal cells (입방상피세포): equal dimension (width = height) 3) columnar cells (원주상피세포) : taller than wider (height > width) 2. arrangement of the cells (the number of cell layers) 1) Simple epithelia (단층상피세포): one layer 1st name last name : subdivided into simple squamous epithelium (단층편평상피세포), simple cuboidal epithelium (단층입방상피세포), simple columnar epithelium (단층원주상피세포), ▶ The specific name endothelium (내피세포) is used for simple squamous epithelium lining blood and lymphatic vessel. ▶ Mesothelium (중피세포) is simple squamous epithelium lining all body cavities (peritoneum (복막), pericardium (심장막), and pleura (흉막) Figure 1-2. Simple epithelium Hematoxylin (purple) and Eosin (rose pink) (H & E ) staining 2) Stratified epithelia (중층상피세포): more than one cell layer - subclassified into stratified squamous epithelium, stratified cuboidal epithelium, stratified columnar epithelium - Stratified squamous is the epithelium most frequently found and can be subdivided into moderately keratinized (known as nonkeratinizing) and highly keratinized types consist of basal cell (undifferentiated , specialized for mitotic division, replace differentiating cell of upper layers) and outer layer cells (highly differentiated cells, contain keratin) ▶ Stratified squamous epithelium with moderately keratin: esophagus, vagina ; The cells of outlayer have nuclei ▶ Stratified squamous epithelium with abundant keratin: epidermis of skin The cells of outlayer lack nuclei. 성숙과정동안 각질화 (keratinization) 일어남 (keratin으로 구성된 거칠고 죽어있는 표면층을 형성) ; basal cell (바닥쪽의 세포)은 계속적을 분열하고 딸세포들은 지속적으로 표층으로 밀려올라가 그곳 에서 긍극적으로 떨어져 나감 Although rare, there are also stratified cuboidal epithelia (ovarian follicle) and stratified columnar epithelia (lining the intralobular ducts of salivary gland). 3. Special categories 1) Pseudostratified epithelium (거짓증층상피): - consist of columnar cell and basal cell i) Pseudostratified columnar ciliated epithelium (trachea, 기관) - consist of columnar cell, basal cell, and Goblet cell(mucus-secreting cell) ii) Pseudostratified columnar epithelium with stereocilia (부동섬모)(epididymis, 부고환) 2) Urothelium (transitional epithelium, urinary bladder): can stretch without breaking - Consist of basal cells, intermediated cells and columnar dome-shaped cells - An important feature is transitional height that varies with distention and contraction of the organ Empty bladder: Stratified cuboidal Full bladder: Stratified squamous Plaques of aggregated proteins are found on the apical plasma membrane of columnar cells Classification of Epithelia https://www.youtube.com/watch?v=mpH0DHHQ2cs (see after 50 sec) Essential concept ▶ Four basic tissues ▶ Classification into three major group 1. Epithelial tissues 1. The number of cell layer (simple, stratified) 2. Connective tissues 2. Shape of cells (squamous, cuboidal, columnar) 3. Muscle tissues 3. Shape of cells at the outmost layer (stratified columnar, stratified squamous, stratified cuboidal for 4. Nervous tisues pseudostratified epithelium) ▶ Property and function of Epithelium ▶subdivision of stratified squamous epithelium - moderately keratinized (nonkeratinized), highly keratinized types (Keratin: a kind of cytoskeletal protein) ▶ apical differentiation such as cilia, microvilli, stereocilia (respiratory tract, oviduct, nephron, small intestine, epididymis (부고환) and hair cells of inner ear) Epithelia cells polarity - An important aspect of epithelium is polarity which is essential to carry out specific function of various organ system - Three geometrical domains represent polarity of epithelium. 1. Apical (uppermost) domain: exposed to lumen or external environment 2. Lateral domain: faces neighboring epithelial cell linked to each other by cell adhesion molecules and junctional complex :facilitates directional or vectorial transport function 3. Basal domain: associated with basal lamina (바닥판) that separate epithelium from underlying connective tissues. - basement membrane (기저막): basal lamina-connective tissue complex ▶Apical domain: protection of epithelial surface (cilia in respiratory tract) : absorption of substance (microvilli in intestinal epithelium) Apical differentiation ▶ Apical domain of some epithelial cells display three types of differentiation. 1. Cilia (섬모) 2. Microvilli (미세융모, 미세돌기) 3. Stereocilia (부동섬모) 1. Cilia ▶ Two types of cilia: multiple motile cilia and single or primary non-motile cilium ▶ Ciliogenesis, the assembly process of both types of cilia, is initiated by the basal body, a structure originated from a basal body precursor located in centrosome (중심체). ▶Failing to dock to apical plasma membrane of basal body disrupts ciliogenesis and give rise to human respiratory disease and primary ciliary dyskinesia (운동장애) ▶Under nomal condition, basal body migrate to apical membrane and extend into axoneme (축사), a basic structure of cilium. (축사: 섬모 또는 편모의 가운데존재하는 축의 탄성섬유) Multiple motile cilia ▶ function to coordinate fluid or cargo flow on the surface of epithelium ▶ cell projections originating from basal body anchored by rootlets ▶ Basal body contains nine triplet microtubules (93 [triplets] + 0 ) in a helicoid array without a central microtubular component ▶ Cilium consists of axoneme formed by a central pair of microtubules (92 [doublets] + 2) surrounded by nine concentrically arranged microtubular pairs. This assembly is known as 9 + 2 microtubular doublet arrangement. ; Axoneme is also a component of sperm tail, or flagella. ▶ Trachea (기관) and oviduct (난관) are lined by ciliated epithelial cells, In these epithelial cells, cilial activity is required for 1) the local defense of respiratory system, for 2) the transport of fertilized egg to uterine cavity Single or primary non-motile cilia ▶ The importance of single cilium emerge from rare recessive human disorders known as ciliopathies caused by functional abnormality of cilia ▶ Significant aspects of primary cilium 1) function as a sensor that provides the cells with information about the surrounding external environment 2) Participate in the early stage of embryonic patterning leading to organogenesis 3) The position of single cilium, called kinocilium, of the hair cells of the organ of Corti in the inner ear, determine the correct polarity of adjacent stereocilia, essential for maintaining body balance and for hearing. Cilia and flagella What is cilia? https://www.youtube.com/watch?v=ZRKUAG4IC2s ( 1 min) Primary Cilia - the cells' ultimate antennae: https://www.youtube.com/watch?v=NFAO65d7M3A (11 min) 2. Microvilli (미세돌기, singular , microvillus) ▶ finger-like cell projection of apical epithelial surface containing microfilament (polymer of G actin monomers) ▶ The intestinal epithelium and portion of the nephron in kidney are lined by epithelial cells with microvili forming a brush border (absorptive function) # brush border (솔가장자리) ; 세포표면이 분화된것으로 표면적증가시키는 둥근모양의 미세돌기로 구성 Structure of villi : https://www.youtube.com/watch?v=Onoq1Ok7_KM (1 .5 min) 3. Stereocilia (부동섬모, stereovilli) ▶ long and branching finger-like projection of apical epithelial cell surface ▶ contains actin microfilaments, similar to microvilli ▶ do not have axoneme ▶ typical of epithelial lining of epididymis and contributes to the process of sperm maturation in this organ Epithelial polarity ; https://www.youtube.com/watch?v=toTTLCpFXOY (7.5 min) Essential concepts ▶ Apical domain of some epithelial cells display differentiation projecting into lumen. Apical differentiation can be motile (multiple cilia) and non-motile (primary cilium, microvilli and stereocilia/stereovilli) ▶ Cilia contain an axoneme, formed by a concentric array of nine microtubule doublets ( 9 + 2) surrounding a central pair. ▶ Basal body and centriole are formed by nine microtubule triplet in a helicoid arrangement. ( no central microtubule in basal body) ▶ Nonmotile microvilli and stereocilia contain actin microfilament core..
Load more

Recommended publications
  • Stereocilia Rootlets: Actin-Based Structures That Are Essential for Structural Stability of the Hair Bundle
    International Journal of Molecular Sciences Review Stereocilia Rootlets: Actin-Based Structures That Are Essential for Structural Stability of the Hair Bundle Itallia Pacentine, Paroma Chatterjee and Peter G. Barr-Gillespie * Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; [email protected] (I.P.); [email protected] (P.C.) * Correspondence: [email protected]; Tel.: +1-503-494-2936 Received: 12 December 2019; Accepted: 1 January 2020; Published: 3 January 2020 Abstract: Sensory hair cells of the inner ear rely on the hair bundle, a cluster of actin-filled stereocilia, to transduce auditory and vestibular stimuli into electrical impulses. Because they are long and thin projections, stereocilia are most prone to damage at the point where they insert into the hair cell’s soma. Moreover, this is the site of stereocilia pivoting, the mechanical movement that induces transduction, which additionally weakens this area mechanically. To bolster this fragile area, hair cells construct a dense core called the rootlet at the base of each stereocilium, which extends down into the actin meshwork of the cuticular plate and firmly anchors the stereocilium. Rootlets are constructed with tightly packed actin filaments that extend from stereocilia actin filaments which are wrapped with TRIOBP; in addition, many other proteins contribute to the rootlet and its associated structures. Rootlets allow stereocilia to sustain innumerable deflections over their lifetimes and exemplify the unique manner in which sensory hair cells exploit actin and its associated proteins to carry out the function of mechanotransduction. Keywords: rootlet; actin; stereocilia; hair cell 1. Introduction Eukaryotic cells use actin as a basic building block of the cytoskeleton.
    [Show full text]
  • Purification and Initial Protein Characterization of Hair Cell Stereocilia
    Proc. Nail. Acad. Sci. USA Vol. 86, pp. 4973-4977, July 1989 Cell Biology "Bundle blot" purification and initial protein characterization of hair cell stereocilia (mechanotransduction/auditory system/vestibular system/cytoskeleton/ummunocytochemistry) GORDON M. G. SHEPHERD, BARBARA A. BARRES, AND DAVID P. COREY Neuroscience Group, Howard Hughes Medical Institute, and Department of Neurology, Wellman 414, Massachusetts General Hospital, Fruit Street, Boston, MA 02114; and Program in Neuroscience, Harvard Medical School, Boston, MA 02115 Communicated by Thomas S. Reese, April 4, 1989 ABSTRACT Stereocilia were isolated from bullfrog (Rana To study the biochemistry of stereocilia we developed a catesbeiana) saccular hair cells by nitrocellulose adhesion. The purification technique that exploits the adhesion of the apical high purity and high yield of the preparation were demon- ends of stereocilia to nitrocellulose paper and the mechanical strated by microscopy. SDS/PAGE of stereociliary proteins fiagility of the narrow basal ends. A related strategy has been resolved 12-15 major bands. Actin, previously identified as a used to adsorb small numbers of piscine stereocilia onto cov- component of the stereociliary core, was identified in purified erslips for ultrastructural studies (13). The nitrocellulose adhe- stereocilia as a band comi rating with authentic actin and by sion method, which we term "bundle blot" purification, gave a phalloidin labeling of intact isolated stereocilia. Fimbrin was sufficiently high yield of pure stereocilia for biochemical anal- identified in immunoblots of purified stereocilia. The most ysis. Some results have appeared in preliminary form (14). abundant other proteins migrated at 11, 14, 16-19, 27, and 36 kDa. Demembranated stereociliary cores consisted primarily METHODS of protein bands corresponding to actin and fimbrin and several proteins ranging from 43 to 63 kDa.
    [Show full text]
  • Nomina Histologica Veterinaria, First Edition
    NOMINA HISTOLOGICA VETERINARIA Submitted by the International Committee on Veterinary Histological Nomenclature (ICVHN) to the World Association of Veterinary Anatomists Published on the website of the World Association of Veterinary Anatomists www.wava-amav.org 2017 CONTENTS Introduction i Principles of term construction in N.H.V. iii Cytologia – Cytology 1 Textus epithelialis – Epithelial tissue 10 Textus connectivus – Connective tissue 13 Sanguis et Lympha – Blood and Lymph 17 Textus muscularis – Muscle tissue 19 Textus nervosus – Nerve tissue 20 Splanchnologia – Viscera 23 Systema digestorium – Digestive system 24 Systema respiratorium – Respiratory system 32 Systema urinarium – Urinary system 35 Organa genitalia masculina – Male genital system 38 Organa genitalia feminina – Female genital system 42 Systema endocrinum – Endocrine system 45 Systema cardiovasculare et lymphaticum [Angiologia] – Cardiovascular and lymphatic system 47 Systema nervosum – Nervous system 52 Receptores sensorii et Organa sensuum – Sensory receptors and Sense organs 58 Integumentum – Integument 64 INTRODUCTION The preparations leading to the publication of the present first edition of the Nomina Histologica Veterinaria has a long history spanning more than 50 years. Under the auspices of the World Association of Veterinary Anatomists (W.A.V.A.), the International Committee on Veterinary Anatomical Nomenclature (I.C.V.A.N.) appointed in Giessen, 1965, a Subcommittee on Histology and Embryology which started a working relation with the Subcommittee on Histology of the former International Anatomical Nomenclature Committee. In Mexico City, 1971, this Subcommittee presented a document entitled Nomina Histologica Veterinaria: A Working Draft as a basis for the continued work of the newly-appointed Subcommittee on Histological Nomenclature. This resulted in the editing of the Nomina Histologica Veterinaria: A Working Draft II (Toulouse, 1974), followed by preparations for publication of a Nomina Histologica Veterinaria.
    [Show full text]
  • Quadriceps Myopathy Caused by Skeletal Muscle- Specific Ablation of Cyto-Actin
    Research Article 951 Quadriceps myopathy caused by skeletal muscle- specific ablation of cyto-actin Kurt W. Prins1, Jarrod A. Call2, Dawn A. Lowe2 and James M. Ervasti1,* 1Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA 2Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis, MN 55455, USA *Author for correspondence ([email protected]) Accepted 8 November 2010 Journal of Cell Science 124, 951-957 © 2011. Published by The Company of Biologists Ltd doi:10.1242/jcs.079848 Summary Quadriceps myopathy (QM) is a rare form of muscle disease characterized by pathological changes predominately localized to the quadriceps. Although numerous inheritance patterns have been implicated in QM, several QM patients harbor deletions in dystrophin. Two defined deletions predicted loss of functional spectrin-like repeats 17 and 18. Spectrin-like repeat 17 participates in actin-filament binding, and thus we hypothesized that disruption of a dystrophin–cytoplasmic actin interaction might be one of the mechanisms underlying QM. To test this hypothesis, we generated mice deficient for cyto-actin in skeletal muscles (Actb-msKO). Actb-msKO mice presented with a progressive increase in the proportion of centrally nucleated fibers in the quadriceps, an approximately 50% decrease in dystrophin protein expression without alteration in transcript levels, deficits in repeated maximal treadmill tests, and heightened sensitivity to eccentric contractions. Collectively,
    [Show full text]
  • LMO7 Deficiency Reveals the Significance of the Cuticular Plate For
    ARTICLE https://doi.org/10.1038/s41467-019-09074-4 OPEN LMO7 deficiency reveals the significance of the cuticular plate for hearing function Ting-Ting Du1, James B. Dewey2, Elizabeth L. Wagner1, Runjia Cui3, Jinho Heo4, Jeong-Jin Park5, Shimon P. Francis1, Edward Perez-Reyes6, Stacey J. Guillot7, Nicholas E. Sherman5, Wenhao Xu8, John S Oghalai2, Bechara Kachar3 & Jung-Bum Shin1 Sensory hair cells, the mechanoreceptors of the auditory and vestibular systems, harbor 1234567890():,; two specialized elaborations of the apical surface, the hair bundle and the cuticular plate. In contrast to the extensively studied mechanosensory hair bundle, the cuticular plate is not as well understood. It is believed to provide a rigid foundation for stereocilia motion, but specifics about its function, especially the significance of its integrity for long-term maintenance of hair cell mechanotransduction, are not known. We discovered that a hair cell protein called LIM only protein 7 (LMO7) is specifically localized in the cuticular plate and the cell junction. Lmo7 KO mice suffer multiple cuticular plate deficiencies, including reduced filamentous actin density and abnormal stereociliar rootlets. In addition to the cuticular plate defects, older Lmo7 KO mice develop abnormalities in inner hair cell stereocilia. Together, these defects affect cochlear tuning and sensitivity and give rise to late-onset progressive hearing loss. 1 Department of Neuroscience, University of Virginia, Charlottesville, VA 22908, USA. 2 Caruso Department of Otolaryngology-Head and Neck Surgery, University of Southern California, Los Angeles, CA 90033, USA. 3 National Institute for Deafness and Communications Disorders, National Institute of Health, Bethesda, MD 20892, USA. 4 Center for Cell Signaling and Department of Microbiology, Immunology and Cancer Biology, University of Virginia, Charlottesville, VA 22908, USA.
    [Show full text]
  • Male Ducts.Pdf (419.1Kb)
    Male Ducts The male ducts consist of a complex system of tubules that link each testis to the urethra, through which the exocrine secretion, semen, is conducted to the exterior during ejaculation. The duct system consists of the tubuli recti (straight tubules), rete testis, ductus efferentes, ductus epididymis, ductus deferens, ejaculatory ducts, and prostatic, membranous, and penile urethra. Tubuli Recti Near the apex of each testicular lobule, the seminiferous tubules join to form short, straight tubules called the tubuli recti. The lining epithelium has no germ cells and consists only of Sertoli cells. This simple columnar epithelium lies on a thin basal lamina and is surrounded by loose connective tissue. The lumina of the tubuli recti are continuous with a network of anastomosing channels in the mediastinum, the rete testis. Rete Testis The rete testis is lined by simple cuboidal epithelium in which each of the component cells bears short microvilli and a single cilium on the apical surface. The epithelium lies on a delicate basal lamina. A dense bed of vascular connective tissue surrounds the channels of the rete testis. Ductuli Efferentes In men, 10 to 15 ductuli efferentes emerge from the mediastinum on the posterosuperior surface of the testis and unite the channels of the rete testis with the ductus epididymis. The efferent ductules follow a convoluted course and, with their supporting tissue, make up the initial segment of the head of the epididymis. The luminal border of the efferent ductules shows a characteristic irregular contour due to the presence of alternating groups of tall and short columnar cells.
    [Show full text]
  • Stereocilia Mediate Transduction in Vertebrate Hair Cells (Auditory System/Cilium/Vestibular System) A
    Proc. Nati. Acad. Sci. USA Vol. 76, No. 3, pp. 1506-1509, March 1979 Neurobiology Stereocilia mediate transduction in vertebrate hair cells (auditory system/cilium/vestibular system) A. J. HUDSPETH AND R. JACOBS Beckman Laboratories of Behavioral Biology, Division of Biology 216-76, California Institute of Technology, Pasadena, California 91125 Communicated by Susumu Hagiwara, December 26, 1978 ABSTRACT The vertebrate hair cell is a sensory receptor distal tip of the hair bundle. In some experiments, the stimulus that responds to mechanical stimulation of its hair bundle, probe terminated as a hollow tube that engulfed the end of the which usually consists of numerous large microvilli (stereocilia) and a singe true cilium (the kinocilium). We have examined the hair bundle (6). In other cases a blunt stimulus probe, rendered roles of these two components of the hair bundle by recording "sticky" by either of two procedures, adhered to the hair bun- intracellularly from bullfrog saccular hair cells. Detachment dle. In one procedure, probes were covalently derivatized with of the kinocilium from the hair bundle and deflection of this charged amino groups by refluxing for 8 hr at 1110C in 10% cilium produces no receptor potentials. Mechanical stimulation -y-aminopropyltriethoxysilane (Pierce) in toluene. Such probes of stereocilia, however, elicits responses of normal amplitude presumably bond to negative surface charges on the hair cell and sensitivity. Scanning electron microscopy confirms the as- sessments of ciliary position made during physiological re- membrane. Alternatively, stimulus probes were made adherent cording. Stereocilia mediate the transduction process of the by treatment with 1 mg/ml solutions of lectins (concanavalin vertebrate hair cell, while the kinocilium may serve-primarily A, grade IV, or castor bean lectin, type II; Sigma), which evi- as a linkage conveying mechanical displacements to the dently bind to sugars on the cell surface: Probes of either type stereocilia.
    [Show full text]
  • Cell Adhesion: Ushering in a New Understanding of Myosin VII Markus Maniak
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Dispatch R315 Cell adhesion: Ushering in a new understanding of myosin VII Markus Maniak The myosin VII motor protein has recently been found namely along the length of stereocilia beside the lateral to have a role in cell adhesion. This new function is linkers that tie stereocilia together, and in the pericuticu- conserved from amoebae to man and provides an lar necklace — a band of apical cytoplasm surrounding the explanation for deafness in Usher syndrome patients. cuticular plate that is densely populated with vesicles. Address: Abteilung Zellbiologie, Universität GhK, Heinrich-Plett-Str. 40, D-34109 Kassel, Germany. Myosin VIIa must be specifically important for hair cell E-mail: [email protected] function, because patients carrying mutations in the corre- sponding gene suffer from deafness [4]. This disease is Current Biology 2001, 11:R315–R317 called Usher syndrome type 1B and also affects retinal 0960-9822/01/$ – see front matter integrity [5]. Mutant model systems that replicate the © 2001 Elsevier Science Ltd. All rights reserved. auditory symptoms and balancing defects of Usher disease are the shaker-1 mouse [6] and the mariner zebrafish [7]: Myosins are largely seen as molecular motors that trans- hair cells are used in the zebrafish for detection of water port cargo along cables of actin filaments. These motor movements in the lateral line organ. Cells and tissue proteins consist of a head domain bearing the motor activ- obtained from these model organisms allow us to study ity and a variable tail region.
    [Show full text]
  • The Organization of Actin Filaments in the Stereocilia of Cochlear Hair Cells
    The Organization of Actin Filaments in the Stereocilia of Cochlear Hair Cells LEWIS G . TILNEY, DAVID J. DEROSIER, and MICHAEL J . MULROY Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104; The Rosenstiel Center, Brandeis University, Waltham, Massachusetts 02154, Department of Anatomy, Medical Center, University of Massachusetts, Worcester, Massachusetts 01605 ABSTRACT Within each tapering stereocilium of the cochlea of the alligator lizard is a bundle of actin filaments with >3,000 filaments near the tip and only 18-29 filaments at the base where the bundle enters into the cuticular plate ; there the filaments splay out as if on the surface of a cone, forming the rootlet . Decoration of the hair cells with subfragment 1 of myosin reveals that all the filaments in the stereocilia, including those that extend into the cuticular plate forming the rootlet, have unidirectional polarity, with the arrowheads pointing towards the cell center . The rest of the cuticular plate is composed of actin filaments that show random polarity, and numerous fine, 30 A filaments that connect the rootlet filaments to each other, to the cuticular plate, and to the membrane . A careful examination of the packing of the actin filaments in the stereocilia by thin section and by optical diffraction reveals that the filaments are packed in a paracrystalline array with the crossover points of all the actin helices in near-perfect register . In transverse sections, the actin filaments are not hexagonally packed but, rather, are arranged in scalloped rows that present a festooned profile . We demonstrated that this profile is a product of the crossbridges by examining serial sections, sections of different thicknesses, and the same stereocilium at two different cutting angles .
    [Show full text]
  • A Hair Bundle Proteomics Approach to Discovering Actin Regulatory Proteins in Inner Ear Stereocilia
    -r- A Hair Bundle Proteomics Approach to Discovering Actin Regulatory Proteins in Inner Ear Stereocilia by Anthony Wei Peng SEP 17 2009 B.S. Electrical and Computer Engineering LIBRARIES Cornell University, 1999 SUBMITTED TO THE HARVARD-MIT DIVISION OF HEALTH SCIENCES AND TECHNOLOGY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN SPEECH AND HEARING BIOSCIENCES AND TECHNOLOGY AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY ARCHIVES JUNE 2009 02009 Anthony Wei Peng. All rights reserved. The author hereby grants to MIT permission to reproduce and to distribute publicly paper and electronic copies o this the is document in whole or in art in any medium nov know or ereafter created. Signature of Author: I Mr=--. r IT Division of Health Sciences and Technology May 1,2009 Certified by: I/ - I / o v Stefan Heller, PhD Associate Professor of Otolaryngology Head and Neck Surgery Stanford University ---- .. Thesis Supervisor Accepted by: -- Ram Sasisekharan, PhD Director, Harvard-MIT Division of Health Sciences and Technology Edward Hood Taplin Professor of Health Sciences & Technology and Biological Engineering. ---- q- ~ r This page is intentionally left blank. I~~riU~...I~ ~-- -pyyur~. _ A Hair Bundle Proteomics Approach to Discovering Actin Regulatory Proteins in Inner Ear Stereocilia by Anthony Wei Peng B.S. Electrical and Computer Engineering, Cornell University, 1999 Submitted to the Harvard-MIT Division of Health Science and Technology on May 7, 2009 in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Speech and Hearing Bioscience and Technology Abstract Because there is little knowledge in the areas of stereocilia development, maintenance, and function in the hearing system, I decided to pursue a proteomics-based approach to discover proteins that play a role in stereocilia function.
    [Show full text]
  • Epithelial Tissue 1
    Epithelial Tissue-1 Hanan Jafar. BDS.MSc.PhD Introduction Epithelial tissues are composed of closely aggregated polyhedral cells adhering strongly to one another and to a thin layer of ECM, forming cellular sheets that line the cavities of organs and cover the body surface. Epithelium lines all external and internal surfaces of the body and all substances that enter or leave an organ must cross this type of tissue. Functions Covering, lining, and protecting surfaces (eg, epidermis) Absorption (eg, the intestinal lining) Secretion (eg, parenchymal cells of glands) Specific cells of certain epithelia may be contractile (myoepithelial cells) Some are specialized sensory cells, such as those of taste buds or the olfactory epithelium. General Characteristics Epithelium is an avascular tissue. It forms the secretory portion of glands and their ducts. Specialized epithelial cells function as receptors for the special senses. Epithelial cells show polarity and rest on basement membrane. Most epithelia are adjacent to connective tissue. The connective tissue that underlies the epithelia lining the organs of the digestive, respiratory, and urinary systems is called the lamina propria Epithelium creates a selective barrier between the external environment and the underlying connective tissue. Cell Polarity Polarity means that organelles and membrane proteins are distributed unevenly within the cell. The region of the cell contacting the ECM and connective tissue is called the basal pole. The opposite end, usually facing a space, is the apical pole. Regions of cells that adjoin neighboring cells comprise the cells’ lateral surfaces. Basement Membrane Apical Lateral Basal Lumen Apical Basal Apical Domain Modifications/Specializations In many epithelial cells, the apical domain shows special structural surface modifications to carry out specific functions.
    [Show full text]
  • Fate of Mammalian Cochlear Hair Cells and Stereocilia After Loss of the Stereocilia
    The Journal of Neuroscience, December 2, 2009 • 29(48):15277–15285 • 15277 Development/Plasticity/Repair Fate of Mammalian Cochlear Hair Cells and Stereocilia after Loss of the Stereocilia Shuping Jia,1 Shiming Yang (㧷Ⅴ㢝),2 Weiwei Guo (捼冃冃),2 and David Z. Z. He1 1Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178, and 2Department of Otolaryngology, Head and Neck Surgery, Institute of Otolaryngology, 301 Hospital, Beijing 100853, People’s Republic of China Cochlear hair cells transduce mechanical stimuli into electrical activity. The site of hair cell transduction is the hair bundle, an array of stereocilia with different height arranged in a staircase. Tip links connect the apex of each stereocilium to the side of its taller neighbor. The hair bundle and tip links of hair cells are susceptible to acoustic trauma and ototoxic drugs. It has been shown that hair cells in lower vertebrates and in the mammalian vestibular system may survive bundle loss and undergo self-repair of the stereocilia. Our goals were to determine whether cochlear hair cells could survive the trauma and whether the tip link and/or the hair bundle could be regenerated. We simulated the acoustic trauma-induced tip link damage or stereociliary loss by disrupting tip links or ablating the hair bundles in the culturedorganofCortifromneonatalgerbils.Hair-cellfateandstereociliarymorphologyandfunctionwereexaminedusingconfocaland scanning electron microscopies and electrophysiology. Most bundleless hair cells survived and developed for ϳ2 weeks. However, no spontaneous hair-bundle regeneration was observed. When tip links were ruptured, repair of tip links and restoration of mechanotrans- duction were observed in Ͻ24 h.
    [Show full text]