Submicroscopic structure of the membranous labyrinth

Summary Investigations were performed by light and electron microscope on the submicroscopic structure of the epithelium of Corti's organ in the white rat.Morphological and structural differences between the inner hair cells and the outer hair cells are revealed.The inner hair cells are closely inter-related with the inner supporting cells and have a polyhedral shape, whereas the outer hair cells look like cylinders and are surrounded by an intraepithelial fluid.The structural peculiarities consist of differences in the dimensions of the hairs, in the arrangement of cytoplasmic organoids and in the aspect of the receptoneural junction. In both sensory hair cells 4 zones of different structure can be distinguished from the surface inwards: apical zone, intermediate zone, perinuclear zone and receptoneuronal junction. The functional value of these different zones is discussed and compared with what has been demonstrated in other receptors.The pillar cells and the Deiters' cells are supporting cells which have a filamentous skeleton, composed of submicroscopic individual filaments. These filaments have a diameter of about 215 Å and present some analogies with the tonofilaments of the stratified squamous epithelium. The filaments are arranged differently in the pillar cells and in the Deiters' cells. Possible functional differences between these patterns are discussed.The reticular membrane is not an extracellular cuticle. It consists of intracellular cementitious material (like the terminal bars of the epithelial cells).The Hensen's and Claudius cells, the Böttcher's cells, the inner supporting cells, the inner and outer spiral sulcus cells are regular prismatic cells with few endoplasmic organoids and without filaments.This work is dedicated to the memory of the late Prof. L. Pietrantoni.     

Submicroscopic structure of the membranous labyrinth

Zusammenfassung Der Verfasser hat eine Methode entwickelt, die es gestattet, die einzelnen Teile der Schnecke (Membrana tectoria, Basilarmembran, Ligamentum spirale, Limbus spiralis, Reissnersche Membran, Cortisches Organ) in ausreichendem Reinheitsgrad und in solchen Mengen zu isolieren, daß mikroskopische Untersuchungen mit polarisiertem Licht sowie mit dem Elektronenmikroskop, diffraktographische sowie chemische Analysen durchgeführt werden können.Chemische und diffraktographische Untersuchungen haben ergeben, daß die Membrana tectoria hauptsächlich aus Proteinen bestellt. Das Vorhandensein von Kollagenprotein ist auszuschließen. Das Protein dürfte zur Gruppe der weichen Kératine mit geringem Cystingehalt gehören. Auf Grund der ausgezeichneten Übereinstimmung der Befunde am Phasenkontrastmikroskop, mit polarisiertem Licht (bei Vorhandensein Eigen- und Form-Doppelbrechung) und am Elektronenmikroskop ergibt sich, daß das in Frage stehende Protein aus Protofäden von etwa 90 Å Durchmesser besteht. Die Protofäden verlaufen leicht wellenförmig radiär, doch wurden (entlang dem exzentrischen Membranrande) auch Bereiche mit longitudinalem Faserverlauf beobachtet. Im ganzen sind sie mit einer gewissen Gleichartigkeit angeordnet, obwohl Bereiche mit dichterer — Longitudinalfasern — oder lockerer Anordnung — dem Limbus spiralis eingefügter Teil — vorhanden sind. Die Membrana tectoria ist somit epithelialer Herkunft mit augenscheinlich fadenförmig ausgerichteter Struktur.Der Verfasser nimmt an, daß die Ausrichtung der Fasern mit dem Spannungszustand der Membran in Zusammenhang steht, die sich zwischen Limbus spiralis und Hensenschen Zellen bildet. Diese entfernen sich ihrerseits während der Bildung des Cortischen Organs voneinander.

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Research financed by C.N.R. grant.

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Acknowledgements. The author expresses his thanks to Dr. S. De Petris of the INAIL Laboratory of Electron Microscopy of the Clinic for Occupational Diseases of the University of Milan for the help and technical assistance given in obtaining X-ray diagrams and electron photograms with the Siemens Elmiskop I. Grateful acknowledgements are also made to Dr. L. Amante for the —SH and —S—S— groups determinations.     

Behavior of fibrinogen in diabetic patients in comparison with objective vascular measurements in the ocular fundus

Objective measurements of vessels were performed in vivo in 10 patients affected with diabetes mellitus, the fibrinogen concentrations in the venous blood being determined simultaneously. Whereas the ensured correlations with fibrinogen concentration could be recognized from the diameter of arteries and veins and from the flow velocity, a linear correlation could be found to exist between the fibrinogen level and the volume flowing through a retinal artery. These findings prove that the very existence of a hyperfibrinogen anemia does not justify the assumption of the blood volume flow being decreased. In patients with diabetes mellitus the enhanced volume flowing through retinal arteries is rather connected with an increased fibrinogen level.     

Submicroscopic structure of the membranous labyrinth

Summary Investigations were performed by light and electron microscope on the basilar membrane, limbus spiralis and spiral ligament.These different parts continue one into the other and make up a single morphological and functional structure which may be called the supporting structure of Corti's organ (s.s.C.o.).It is formed by a tissue the components of which are the cells and an intercellular substance in which are arranged the capillary vessels.The cells can be classed in two groups, the first consisting of the cells proper (basilar membrane, limbus spiralis and spiral ligament cells) which present structural changes parallel with the growth mechanism of the intercellular substance; the second of the cochlear duct covering cells (Corti's organ cells, inner and outer spiral sulcus cells, interdental cells, stria vascularis cells).The intercellular substance is organised in laminae, fibrolaminae, bundles and microscopic fibers composed of filaments with an intervening ground substance.The filaments have a diameter ranging from 85 to 105 Å. Topochemical tests with polarised light microscope, enzymatic tests, diffractographic and chemical analyses suggest that these filaments unquestionably consist of protein material which have nothing to do with collagen or elastic fibers. Perhaps it may be classed in the K.E.M.F. group.The ground substance generally appear anhistous and transparent but in some parts of the basilar membrane it presents a cottony appearance.The possible different hypotheses about the classification of the s.s.C.o. tissue are discussed.The quantity and architecture of the cells and the intercellular substance vary appreciably in the basilar membrane, limbus spiralis and spiral ligament, which are examined in detail one by one.The demonstration that the s.s.C.o. is formed of a tissue possessing an intercellular substance containing filamentous scleroproteins clearly corroborates the theory that is performs supporting activity in respect of Corti's organ. The term supporting structure of Corti's organ is based on this interpretation.Research financed by C.N.R. grant.