L. Thorn

The limbus spiralis and its relationship to the developing tectorial membrane in the cochlear duct of the guinea pig fetus

SummaryThe development of the interdental cells of the limbus spiralis and of the inner spiral sulcus cells as well as the formation of the mesenchymal teeth of Huschke are described during fetal life up to the day of birth in the guinea pig. Additionally, the changes of the developing tectorial membrane are studied. The ultrastructural observations allow the conclusion that during fetal development at least a considerable part of the material of the tectorial membrane is secreted by the interdental cells of the limbus spiralis.

Licht- und elektronenmikroskopische Untersuchungen des großen Epithelwulstes und seiner Beziehungen zu der sich entwickelnden Membrana tectoria im Ductus cochlearis von Meerschweinchenfeten

SummaryIn early stages of fetal development (36th day, 3rd turn) the thickening of the epithelium at the basal side of the cochlear duct forms two ridges. Later in fetal development the laterally situated lesser epithelial ridge forms the major part of the organ of Corti, whereas the medially situated greater epithelial ridge contributes only a small part to this organ. The medial part of the greater ridge consists of the columnar inner supporting cells, which bear a border of closely packed microvilli at their upper surface. Up to the time of the opening of the internal spiral sulcus in the 48th day of fetal development, there is a close spacial relationship between microvilli and filaments of the tectorial membrane. We conclude that the inner supporting cells contribute to the formation of the tectorial membrane. However, thus far we cannot entirely exclude a different possibility, that the inner supporting cells absorb material of the tectorial membrane. During the opening of the sulcus spiralis internus the inner supporting cells become considerably smaller, some of them undergo complete destruction by cytolysis, with pyknosis and karyorrhexis.ZusammenfassungIn einem frühen Entwicklungsstadium (36. Entwicklungstag, 3. Windung) differenziert sich die Epithelverdickung am Boden des Ductus cochlearis in zwei Wülste. Aus dem lateral gelegenen kleinen Epithelwulst entsteht später der Großteil des Cortischen Organs, während der medial gelegene große Sonderdruckanfragen an: P.D. Dr. Lieselotte Thorn (Adresse s. oben) Epithelwulst zu diesem nur wenig beiträgt. Der mediale Teil des großen Wulstes besteht aus den hochprismatischen inneren Stützzellen, die an ihrer apikalen Oberfläche einen dichten Mikrovillibesatz tragen. Bis zur Einsenkung des Sulcus spiralis internus am 48. Entwicklungstag besteht eine enge räumliche Beziehung von Mikrovilli zu Filamenten der Membrana tectoria. Wir nehmen an, daß die inneren Stützzellen zum Aufbau der Membrana tectoria beitragen. Allerdings können wir bisher das Gegenteil nicht ganz ausschließen, daß Material der Membrana tectoria durch die inneren Stützzellen resorbiert wird. Bei der Einsenkung des Sulcus spiralis internus werden die inneren Stützzellen erheblich niedriger, einige gehen unter Erscheinungen der Cytolyse mit Kernpyknose und Karyorrhexis ganz zugrunde.In early stages of fetal development (36th day, 3rd turn) the thickening of the epithelium at the basal side of the cochlear duct forms two ridges. Later in fetal development the laterally situated lesser epithelial ridge forms the major part of the organ of Corti, whereas the medially situated greater epithelial ridge contributes only a small part to this organ. The medial part of the greater ridge consists of the columnar inner supporting cells, which bear a border of closely packed microvilli at their upper surface. Up to the time of the opening of the internal spiral sulcus in the 48th day of fetal development, there is a close spacial relationship between microvilli and filaments of the tectorial membrane. We conclude that the inner supporting cells contribute to the formation of the tectorial membrane. However, thus far we cannot entirely exclude a different possibility, that the inner supporting cells absorb material of the tectorial membrane. During the opening of the sulcus spiralis internus the inner supporting cells become considerably smaller, some of them undergo complete destruction by cytolysis, with pyknosis and karyorrhexis.

Epithelioid Cell Granulomata in the Mucosa of the Small Intestine in Whipple's Disease*

This report is the first description of sarcoid-like epithelioid cell granulomata in the mucosa of the small intestine in a case of Whipples disease. The epithelioid cells do not contain PAS-positive material or products of bacterial degradation. Their ultrastructural features characterize them as histiocytes which have become secretory rather than phagocytic. These sarcoid-like lesions are considered to be a morphological manifestation of an immunological process in Whipples disease and not to represent evidence of sarcoidosis as a concomitant or associated disorder.

Synaptic bar in the efferent part of a synapse in the organ of CORTI

Synapsenstäbchen (synaptic bars) wurden bisher im präsynaptischen Abschnitt afferenter Synapsen in Sinnesorganen beschrieben. Überrachenderweise fanden wir im Cortischen Organ eines Meerschweinchenfeten einen «synaptic bar» in einer efferenten Synapse, und zwar im basalen Cytoplasma einer äusseren Haarzellen senkrecht zur synaptischen Membran stehend und von Vesikeln (Durchmesser 33 nm) ungeben.

[Functional morphology of stria vascularis after treatment with ethacrynic acid or atoxyl (author's transl)].

Surface alterations of the stria vascularis and Reissners membrane were studied in guinea pigs following intravenous or intraperitoneal administration of ethacrynic acid or atoxyl. DC-potential was measured in the same animals during intoxication. In addition we studied changements in potassium concentration (perilymph, endolymph) of the atoxyl-treated animals.SummarySurface alterations of the stria vascularis and Reissners membrane were studied in guinea pigs following intravenous or intraperitoneal administration of ethacrynic acid or atoxyl. DC-potential was measured in the same animals during intoxication. In addition we studied changements in potassium concentration (perilymph, endolymph) of the atoxyl-treated animals.ZusammenfassungAn Meerschweinchen wurden die an der Stria vascularis und an der Reissnerschen Membran nach der Gabe von Ethacrynsäure bzw. von Atoxyl auftretenden Veränderungen mit dem Rasterelektronenmikroskop untersucht. Nach der gleichen Behandlung wurde das DC-Potential gemessen, bei den Versuchen mit Atoxyl auch die Kaliumionenkon/entration in Peri- und Endolymphe verfolgt.

Licht- und elektronenmikroskopische Untersuchungen zur Entwicklung der Stria vascularis im Ductus cochlearis von Meerschweinchenfeten

Our studies on exactly dated guinea pig fetuses show (1) Already in early stages of development (37th day), in the anlage of the vascular stria vesicular invaginations of the apical plasmalemma of epithelial cells are noted and regarded as a sign of an exchange of substances between epithelial cells and the endolymph. As to the direction of substance transport, the morphological finding allows no decision.(2) From the 42nd to the 44th day of development, the subepithelial basal lamina becomes progressively indistinct. From the 45th day onward, the basal lamina is not yet demonstrable.(3) The largest part of the chromophobe cells of the vascular stria derives from the mesenchyme. The question, whether some of the chromophobe cells are of epithelial origin, as some authors propose, will hopefully be clarified in further studies.

Observation of an endothelial mitosis in a mesenchymal capillary of the scala tympani during the development of the guinea-pig.

A mitosis in an endothelial cell during the development of the cochlea of the guinea-pig is described; the occurrence of endothelial mitoses is discussed.

Licht- und elektronenmikroskopische Untersuchungen zur Entwicklung der Reissnerschen Membran im Ductus cochlearis von Meerschweinchenfeten*

Differentiation of the Reissners membrane (membrana vestibularis) is described in precisely dated guinea pig fetuses. In newborn and adult animals, the Reissners membrane consists of two layers of flat cells, an epithelial one and a mesenchymal one, separated by a basement membrane. The epithelial part develops from the initially simple columnar epithelium of the upper wall of the cochlear duct. The mesenchymal part arises from the embryonic connective tissue, which in early developmental stages occupies the space of the later scala vestibuli. The studies show that during fetal life, a mixture of the endolymph of the cochlear duct with the perilymph of the scala vestibuli is prevented by zonulae occludentes between the epithelial cells of Reissners membrane. On the other hand, even at an early stage an exchange of material between the two fluids is to a small extent possible by means of cytopempsis through the cytoplasm of the epithelial cells.SummaryDifferentiation of the Reissners membrane (membrana vestibularis) is described in precisely dated guinea pig fetuses. In newborn and adult animals, the Reissners membrane consists of two layers of flat cells, an epithelial one and a mesenchymal one, separated by a basement membrane. The epithelial part develops from the initially simple columnar epithelium of the upper wall of the cochlear duct. The mesenchymal part arises from the embryonic connective tissue, which in early developmental stages occupies the space of the later scala vestibuli. The studies show that during fetal life, a mixture of the endolymph of the cochlear duct with the perilymph of the scala vestibuli is prevented by zonulae occludentes between the epithelial cells of Reissners membrane. On the other hand, even at an early stage an exchange of material between the two fluids is to a small extent possible by means of cytopempsis through the cytoplasm of the epithelial cells.ZusammenfassungDie Differenzierung der Reissnerschen Membran (Membrana vestibularis) wird an genau datierten Meerschweinchenfeten geschildert. Beim neugeborenen und beim adulten Tier besteht die Reissnersche Membran aus zwei Lagen platter Zellen, einer epithelialen und einer mesenchymalen, die durch eine Basalmembran getrennt sind. Der epitheliale Anteil entwickelt sich aus dem zunächst einschichtigen hochprismatischen Epithel der oberen Wand des Ductus cochlearis. Der mesenchymale Anteil entsteht aus dem embryonalen Bindegewebe, das bei frühen Entwicklungsstadien den Raum der späteren Scala vestibuli einnimmt. Die Untersuchungen zeigen, daß bereits während des Fetallebens eine Vermischung der Endolymphe des Ductus cochlearis mit der Perilymphe der Scala vestibuli durch Zonulae occludentes zwischen den Epithelzellen der Reissnerschen Membran verhindert wird, andererseits aber ein Stoffaustausch geringen Ausmaßes zwischen beiden Flüssigkeiten durch Cytopempsis durch das Cytoplasma der Epithelzellen hindurch möglich ist.

Licht- und elektronenmikroskopische Untersuchungen zur Entwicklung der Prominentia spiralis im Ductus cochlearis von Meerschweinchenfeten

The anlage of the spiral prominence can be seen on the 37th day of development as a small protrusion of the epithelium towards the lumen of the cochlear duct. During the further progress, the spiral p

Abkürzungen in Abbildungen

Zellen: HEZ Hensensche Zelle, HZ Haarzelle, PhZ Phalangenzelle, PZ Pfeilerzelle, StZ Stutzzelle, a ausere, i innere.