[Light and electron microscopic studies on the development of the spiral prominence of the cochlear duct of the fetal guinea pig]. / 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 prominence more distinctly protrudes by augmentation of the vascularized connective tissue. In the epithelial cells pinocytotic vesicles near the plasmalemma are seen earliest lateral and basal on the 37th day, apical on the 39th day. The epithelial cells send basal cytoplasmic extensions towards the connective tissue. Starting on the 44th day, small invaginations of connective tissue extend into the epithelium, remaining separated from the epithelial cells by the basal lamina. Until the 48th day, the monostratified epithelium remains columnar, thereafter it changes to cuboidal or flat. Towards the end of the development, the invaginations of the connective tissue nearly reach the surface of the epithelium, being separated from the endolymph by a small epithelial area.

[Light and electron microscopy studies of the development of Reissner's membrane in the cochlear duct of guinea pig fetuses]. / Licht- und elektronenmikroskopische Untersuchungen zur Entwicklung der Reissnerschen Membran im Ductus cochlearis von Meerschweinchenfeten.

Differentiation of the Reissner's membrane (membrana vestibularis) is described in precisely dated guinea pig fetuses. In newborn and adult animals, the Reissner's 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 Reissner's 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.

Immunohistochemistry of vasopressin, oxytocin and neurophysin in the hypothalamus and extrahypothalamic regions of the human and primate brain.

Vasopressin, oxytocin and neurophysin were localized in the brains and spinal cords of four primates (tree shrew, squirrel monkey, rhesus monkey and human) using antisera to these peptides and the unlabelled antibody-enzyme peroxidase antiperoxidase method. Magnocellular neurons in the hypothalamus stained positively for vasopressin, oxytocin or neurophysin. Parvocellular neurons of the suprachiasmatic nucleus (SCN) stained positively for vasopressin and neurophysin but not for oxytocin, in all four species. Magnocellular oxytocin, vasopressin and neurophysin neurons project to permeable capillaries in the neurohypophysis, as well as to various extrahypothalamic neural target areas including the central amygdala, nucleus of the solitary tract, dorsal motor nucleus of the vagus, lateral reticular nucleus, dorsal horn, central grey and intermediolateral nucleus of the spinal cord. In target areas, terminals contact somata and dendrites. Parvocellular vasopressin and neurophysin neurons of the SCN do not project to the neurohypophysis, and project only to neural target areas, including the lateral septum, mediodorsal thalamus, lateral habenula, mesencephalic central grey, medial amygdala and ventral hippocampus. (Due to the relatively poor tissue preservation in human autopsy specimens not all projections found in the other primates could be confirmed in humans.) These findings confirm and correlate well with previous descriptions made in rodents, and indicate that vasopressin, oxytocin and neurophysin projections to neural targets are present in primates. Peptides released from these projections probably do not enter the bloodstream, but are rather involved in neural mechanisms.

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

The 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.

The distribution of vasopressin-, oxytocin-, and neurophysin-producing neurons in the guinea pig brain. I. The classical hypothalamo-neurophypophyseal system.

The location, cytology and projections of vasopressin-, oxytocin-, and neurophysin-producing neurons in the guinea pig were investigated using specific antisera against vasopressin, oxytocin or neurophysin in the unlabeled antibody enzyme immunoperoxidase method. Light microscopic examination of the neurons of the supraoptic and paraventricular nuclei shows that hormone is transported not only in axons, but also in processes having the characteristics of dendrites. Neurons were found to contain only vasopressin or oxytocin; all neurons containing neurophysin appear to contain either vasopressin or oxytocin. In the neural lobe, vasopressin and oxytocin terminals are intermingled. In the median eminence, vasopressin and oxytocin fibers are intermingled in the internal zone. In a caudal portion of the median eminence, a number of vasopressin and neurophysin (but few oxytocin) axons enter the external zone from the internal zone, and surround portal capillaries. In the supraotic nucleus, vasopressin neurons outnumber oxytocin neurons with a ratio of at least 5:1. The paraventricular nucleus is separated into two distinct groups of neurons, a lateral group consisting of only vasopressin neurons, and a medial group consisting of only oxytocin neurons. In addition to axons passing to the neurohypophysis, a number of axons appear to interconnect the supraoptic and paraventricular nuclei.

[Light and electron microscopic studies of the greater epithelial ridge and its relationship to the developing tectorial membrane in the cochlear duct of the guinea pig (author's transl)]. / Licht- und elektronenmikroskopische Untersuchungen des grossen Epithelwulstes und seiner Beziehungen zu der sich entwickelnden Membrana tectoria im Ductus cochlearis von Meerschweinchenfeten.

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.

Lyophilized veins studied by scanning electron microscopy.

Human saphenous veins were studied by scanning electron microscopy. The intention was to analyze the suitability of lyophilized homologous veins for homografting when no autologous venous material is available for replacement of obstructed arterial segments. Cross-sectioned specimens revealed the intimal layer of the venous wall to be compactly structured, while the median and external parts were found to be loosely organized and contained numerous cavities. The luminal surface coat displayed the typical aspects of an intact endothelium with occasional fine deposits of fibrin. Defects of the inner layer were only rarely observed, and are caused when the endothelium was stuck to the PVC catheter prior to lyophilization. From a morphological point of view, lyophilized veins seem to be sutiable for replacement of arterial segments. Based on our findings suggestions are made for optimal preparation of the venous material.