Elektronenmikroskopische Untersuchungen am Pinealorgan von Pterophyllum scalare Cuv. et Val. (Cichlidae,Teleostei)

Zusammenfassung Das Pinealorgan (Epiphysis cerebri) des Knochenfisches Pterophyllum scalare besteht aus nervösen und gliösen Zellelementen. Sehr stark ausgebildet sind die ependymalen Stützzellen. Sie umhüllen mit ihren Ausläufern, die sich überlappen können, andere Zellelemente, z.B. Rezeptorzellen und marklose Nervenfasern. Neben dieser Neuroglia-Art finden sich auch noch oligodendrocytenähnliche Gliazellen. In ihrer Grundstruktur entsprechen die Rezeptoren den Epiphysensinneszellen anderer Knochenfische. Vom cilientragenden Teil des Außenglieds geht ein schürzenartiger Lamellenstapel aus. Dieser besteht aus 50–70 Lamellenplatten von etwa 6 m Länge. Im basalen Teil der Rezeptorzelle sind neben schlanken Mitochondrien mit unregelmäßigen Cristae und Tubuli auch noch große, runde Mitochondrien mit einer regelmäßigen Cristastruktur zu beobachten. Der basale Fortsatz der Rezeptorzelle ist auf die axial verlaufenden Axonbündel ausgerichtet. Synapsenartige Kontakte sind selten. Die Zahl der marklosen Axone nimmt hirnwärts zu; dieser Befund wurde in partiellen Rekonstruktionen gesichert. Am Übergang in den Epiphysenstiel treten einige markhaltige Axone auf. Zur Verteilung der Zelltypen und zum Verlauf der Axonbündel im Epiphysenstiel des Skalars liegen detailliertere Angaben vor als bei anderen bisher untersuchten Knochenfischepiphysen. In der Diskussion werden nach Vergleich der pinealen Rezeptoren verschiedener Fische drei Außengliedformen unterschieden: Bürsten-, Schürzen- und Kappentyp. Diese Varianten werden in Verbindung mit den bekannten physiologischen Reaktionsformen der Pinealorgane diskutiert. Die elektrophysio logischen Unterschiede lassen sich nicht mit verschiedenen Strukturtypen des Außenglieds erklären.

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Electron microscopic studies of the pineal organ in Pterophyllum scalare cuv. et val. (Cichlidae, Teleostei)

Summary The pineal organ (epiphysis cerebri) of Pterophyllum scalare is formed by neuronal and glial elements. Ependymal supportive cells are very abundant, and their cytoplasmic processes envelop adjacent receptor cells and unmyelinated nerve fibers by an intertwining network. In addition to this type of neuroglia, oligodendrocytic cells have also been identified. The receptor cells show the general structural pattern (outer segment, inner segment, basal process) of teleostean pineal receptors. The ciliary part of the outer segment bears a dome-like stack of 50–70 curved saccules each of average length of 6 m. In the basal part of the receptor cell, slender mitochondria containing irregular cristae and tubules, and also some more spherical mitochondria with a highly regular arrangement of cristae, can be observed. The basal cytoplasmic process radiates into neuropile-like areas that contain axial bundles of axons. Synaptoid contacts rarely occur. The number of unmyelinated axons of the pineal stalk, increases in a proximad direction (towards the brain). This finding has been verified in partial reconstructions. In the transitional zone leading from the pineal body into the pineal stalk, a few myelinated fibers become visible. With respect to cell types and the axonic bundles of the pineal stalk in Pterophyllum scalare, more detailed data are presented than for most other teleostean pineal organs examined thus far. The comparison of pineal sensory cells in several fishes allows a distinction among three different types of outer segments, i.e., a slender type, a dome-like type, and a cap-like type. These structural types are discussed with respect to the relevant physiological results. The existence of particular structural types of the outer segment does not explain the different electrophysiological reactions observed in different pineal organs.

Ein Druckkostenzuschuß wurde von beiden Instituten zur Verfügung gestellt.     

The morphology of the cement gland apparatus of Larval Pterophyllum scalare Cuv. & Val. (Cichlidae,Teleostei)

Summary The cement gland apparatus of newly hatched Pterophyllum scalare Cuv. & Val. was examined by histology, scanning and transmission electron microscopy. The whole organ is composed of three pairs of endoepithelial, ductless glands, which cause prominent elevations on the larval head and are found in a specific arrangement. Each single gland is represented by an aggregation of elongated, tubular secretory cells surrounding a pyriform acinus. It overlies a basal lamina and is covered by the outer layer of the bilaminar embryonic epidermis.Two different types of secretory cells can be distinguished. One type is restricted to the bottom of the cavity. It is characterized by multiform cytoplasmic protrusions, which project into the gland's cavity. The secretory granules contain a network of light filamentous material. The second type constitutes the side wall of the acinus. It does not develop any protrusions. The contents of the secretory granules is of very high and homogeneous electron density. The mechanism of extrusion is discussed for both cell types. All secretory cells show a strong PAS-reaction. In SEM a circular microridge pattern with attached mucus globules can be recognized on the larval epithelial surface.Dedicated to Prof. Dr. H. Leonhardt on the occasion of his 60th birthday     

Weitere Untersuchungen zur Feinstruktur und Innervation des Pinealorgans von Passer domesticus L.

Zusammenfassung Im Parenchym der Epiphysis cerebri von Passer domesticus kommen Nervenzellen vor. Ihre Neuriten ziehen im langgestreckten Epiphysenstiel zur Commissura habenularum. Im proximalen Endabschnitt des Epiphysenstiels wird ein Teil dieser Fasern myelinisiert. Zwischen die Nervenfasern schieben sich zahlreiche Pinealocytenausläufer; synaptische Bänder helfen die letzteren eindeutig zu identifizieren. Im Bereich der synaptischen Bänder liegen: 1. 300 Å Vesikel, 2. 300 Å Vesikel und 800–1200 Å Granula, 3. nur 800–1200 Å große granulierte Vesikel. Die Tatsache, daß in Pinealocytenausläufern nebeneinander synaptische Bänder und Granula vorkommen, und daß apikal in zilientragenden Zellen ebenfalls Granula nachweisbar sind, spricht dafür, daß bei Passer domesticus ein Pinealzelltyp sensorische und sekretorische Strukturmerkmale besitzen kann. Außerdem werden Kontaktsynapsen beobachtet; ihre praesynaptischen Fasern enthalten die gleichen Strukturelemente wie die Fasern mit synaptischen Bändern. Die Zahl der Mikrofibrillen und Mikrotubuli variiert in den Pinealocytenausläufern, in den postsynaptischen Dendriten und in den Neuriten so stark, daß es mitunter schwierig ist, diese Fortsatztypen einwandfrei zu unterscheiden und die Zahl der zum Gehirn ziehenden Neuriten exakt zu ermitteln.Efferente sympathische Nervenfasern dringen in die Bindegewebssepten der Epiphyse ein. Sie enthalten Granula mit einem Durchmesser von 300–500 Å und 800–1200 Å. Nach Injektion von Nialamid zeigen beide Granulatypen einen elektronendichten Kern. Mikrospektrographisch ist Serotonin und Noradrenalin in diesen Nervenfasern nachweisbar. Das Material dieser Studie enthält keinen fluoreszenzmikroskopischen oder elektronenmikroskopischen Hinweis darauf, daß die sympathischen Nervenfasern durch die Basalmembran in den Zellverband des Epiphysenparenchyms eintreten. Im elektronenmikroskopischen Bild haben manche Pinealocytenausläufer eine Ähnlichkeit mit autonomen Nervenfasern.Die funktionelle Bedeutung der Vogelepiphyse als photo-neuro-endokrines Organ wird diskutiert.

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Further investigations on the structure and innervation of the pineal organ of Passer domesticus L.

Summary The pineal organ of Passer domesticus contains nerve cells within its parenchyma. Axons of the nerve cells run within the elongated stalk of the pineal organ to the habenular commissure. At the proximal end of the stalk, some axons become myelinated. In the stalk, the axons intermingle with pinealocyte processes containing synaptic ribbons. The synaptic ribbons are in contact with (1) vesicles with a diameter of 300 Å; (2) 300 Å diameter vesicles and 800–1,200 Å diameter dense-core granules; or (3) the dense-core granules only. Dense-core granules are also present in pinealocytes with 9+0 type cilia. These results suggest that sensory and secretory structures are present in the same pineal cell type. Furthermore, conventional synapses are present between receptor and nerve cells: The presynaptic fibers have the same structure as the fibers containing synaptic ribbons. The numbers of microfibrils and microtubules vary among postsynaptic fibers (dendrites), the pinealocyte processes, and the neurites. Thus it is difficult to obtain an exact count of the number of axons running to the brain.Efferent sympathetic nerve fibers enter the pineal organ associated with the connective tissue surrounding blood vessels. The fibers show granules of 300–500 Å diameter or 800–1,200 Å diameter. After nialamide injection, both types of granules contain a dense core. Microspectrographically serotonin and noradrenaline are demonstrated in the sympathetic nerve fibers. There is no evidence found in the material of this study to suggest that sympathetic nerve fibers perforate the basement membrane and enter the parenchymal cell complexes of the pineal organ. Pinealocyte processes and sympathetic nerve fibers often show a very similar ultrastructural pattern.The role of the avian pineal organ in photo-neuro-endocrine regulation is discussed.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Weitere elektronenmikroskopische Untersuchungen am Pinealorgan vonPhoxinus laevis (Teleostei,Cyprinidae)

Zusammenfassung Auch im Pinealorgan adulter Elritzen (Phoxinus laevis) sind die Außenglieder der Sinneszellen nicht degeneriert. Der Vergleich wurde zwischen adulten Exemplaren (8,6 cm) und 19,5 Monate jüngeren Tieren (3 cm) durchgeführt. Im Verhältnis zu den Jungtieren sind die Neuropilformationen und die synaptischen Strukturen adulter Elritzen stärker ausgeprägt. Bei den letzteren enthalten die Endfüße der pinealen Rezeptoren zahlreiche synaptische Bänder und 300–400 Å große Bläschen. Die Neuropilzonen sind außerdem reich an verdichteten Membranstellen (tight junctions). Im Pinealorgan des adulten Phoxinus finden sich eigenartige Einschlußkörper, die aus konzentrischen Lamellen bestehen; ähnliche Membran wirbel hat Takahashi (1969) bei zweijährigen Goldfischen beschrieben. Häufig lassen sich in den Epiphysen adulter Elritzen Axone beobachten, die mit 500–1000 Å großen granulierten Vesikeln gefüllt sind und im Verband bahnartig zusammengefaßter markloser Nervenfasern verlaufen. Die Herkunft und Bedeutung dieser granulierten Fasern werden diskutiert, ebenso wie die funktionelle Rolle des pinealen Sinnesorgans.

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Further electron microscopic studies of the pineal organ inPhoxinus laevis (Teleostei, Cyprinidae)

Summary The outer segments of pineal receptor cells of adult (8.6 cm) European minnows (Phoxinus laevis), like the lamellated outer segments of 19.5 months younger (3 cm) specimens, did not show signs of degeneration (see also Oksche and Kirschstein, 1967). Neuropile formations and synaptic structures were more prominent in adult than in youngPhoxinus. In the adult group, the end-feet of pineal receptors contained numerous synaptic ribbons and vesicles (300–400 Å in diameter). The neuropile zones were rich in tight junctions. A peculiar structure of the pineal organ of agingPhoxinus was the inclusion body formed by concentric arrangement of lamellae. Membrane whorls similar to these inclusion bodies were described in the pineal organ of two years old goldfish (Takahashi, 1969). In the pineal organ of adultPhoxinus considerable numbers of axons containing dense-core vesicles (500–1,000 Å in diameter) were observed within tract-like bundles of unmyelinated nerve fibers. The origin and significance of these granulated fibers and the functional role of the pineal sense organ have been discussed.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Rasterelektronenmikroskopische Beobachtungen an pinealen Sinneszellen der Forelle,Salmo gairdneri (Teleostei)

Zusammenfassung Im rasterelektronenmikroskopischen Bild des Pinealorgans vonSalmo gairdneri kann man drei verschiedene Außengliedtypen der Photorezeptoren unterscheiden. Diese Ergebnisse werden im Hinblick auf die Ultrastrukturkonzepte von Rüdeberg (1969) und Bergmann (1971) diskutiert. Rasterelektronenmikroskopische Studien erleichtern die anatomische Klassifizierung von pinealen Sinneszellen aufgrund ihrer Außengliedform.

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Scanning electron microscopic observations of pineal photoreceptor cells in the trout,Salmo gairdneri (teleostei)

Summary The outer segments of pineal photoreceptor cells ofSalmo gairdneri were investigated with the scanning electron microscope. The scanning electron micrographs showed three different types of outer segments. These results are discussed with respect to the ultrastructural concepts of Rüdeberg (1969) and Bergmann (1971). Scanning electron microscopy permits better anatomical classification of pineal photoreceptor cells according to the form of their outer segments.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft (Arbeitsgruppe Prof. Dr. A. Oksche). Herrn Prof. Dr. G. Pfefferkorn, Direktor des Instituts für Medizinische Physik an der Westfälischen Wilhelms-Universität Münster, danke ich für einen Arbeitsplatz am Rasterelektronenmikroskop, Herrn Prof. Dr. H. G. Fromme, Münster, für die Unterstützung bei der präparativen Aufbereitung des Materials.     

Vergleichende histophysiologische Tracer-Untersuchungen an verschiedenen Organsystemen von Branchiostoma lanceolatum (Cephalochordata) und Brachydanio rerio (Teleostei)

Zusammenfassung In vergleichend autoradiographischen Untersuchungen wurde der Einbau von percutan applizierten 3H-Uridin, 3H-Histidin und 3H-Glucose in die wichtigsten Organsysteme (Epidermis, ZNS, Muskeln, Chorda, Leber, Kiemendarm, Darm) von Branchiostoma lanceolatum (Acranier) und Brachydanio rerio (Teleosteer) nach Inkorporationszeiten von 11 min bis zu 7 Tagen verfolgt. Der Stoffwechsel der markierten Substanzen in den einzelnen morphologisch miteinander zu homologisierenden Organen war bei den beiden Spezies sehr ähnlich, bei Branchiostoma allerdings (mit Ausnahme des ZNS) 4–5mal stärker als bei Brachydanio. Bei dem letzteren wurde außerdem eine zeitliche Verzögerung in der Tracer-Aufnahme (lag-Phase) beobachtet. Insbesondere der ZNS-Stoffwechsel von Acraniern zeigte ähnliche Charakteristika wie der von Vertebraten: Verbleib des Hauptanteils der neusynthetisierten RNS im Perikaryon, axonalen Protein-Transport, Vorwiegen der Glykogensynthese in den Nervenfaserendformationen. Allerdings fanden sich im ZNS von Branchiostoma niedrigere Stoffwechselraten als im ZNS von Brachydanio.

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Comparative histophysiological investigations of different organs in Branchiostoma lanceolatum (Cephalochordata) and Brachydanio rerio (Teleostei)

Summary Incorporation of 3H-uridine, 3H-histidine and 3H-glucose into some organs (epidermis, CNS, muscles, spinal cord, notochord, liver, gills, intestine) of Branchiostoma lanceolatum (Acrania) and Brachydanio rerio (Teleostei) was investigated by means of comparative autoradiograms following incorporation periods of 11 min to 7 days. The metabolism of the labeled substances in the various homologous organs examined was quite similar, although it was 4 to 5 times higher in Branchiostoma than in Brachydanio; in the latter there was also a delay of tracer incorporation of about 3 hrs, a so-called lag-phase. In particular the metabolism of the CNS of Branchiostoma showed the same characteristics as the CNS of vertebrates, e. g. storage of neuronally synthesized RNA in the neuronal perikarya, axonal flow of proteins, glycogen synthesis in nerve endings. However, metabolic activity of the CNS was lower in Branchiostoma.

Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Substance P-like-immunoreactive neurons in the photosensory pineal organ of the rainbow trout,Salmo gairdneri Richardson (Teleostei)

Summary Restricted numbers of substance P-like-immuno-reactive (SPL-IR) neurons were demonstrated in the photosensory pineal organ of the rainbow trout. The small parapineal organ of this teleost species receives a distinct SPL-IR innervation via the habenular nuclei, but displays no intrinsic SPL-IR neurons. Intrapineal SPL-IR neurons were located in the rostral portion of the pineal end-vesicle. Neuronal somata were found in a lateral position with smooth axonal processes extending mediad. Immunoreactive somata and axonal processes were observed intraparenchymally as well as in the pineal lumen. The pattern of immunoreactivity was not changed in excised pineal organs that had been incubated in tissue culture medium in the dark for 18 h. The possibility that the intrapineal SPL-IR neurons are not part of the neural circuitry involved in the transduction of photic information, but may have other functions, is discussed.Fellow of the Alexander von Humboldt-Stiftung, Bonn, Federal Republic of GermanySupported by research funds from the Deutsche Forschungsge-meinschaft (Ko 758/2-4)     

Photoreceptor development in the pineal organ and the eye of Plecoglossus altivelis and Paralichthys olivaceus (Teleostei)

Summary The ontogenetic apperance of pineal photo-receptors was compared with that of retinal photoreceptors in the ayu Plecoglossus altivelis and the lefteye flounder Paralichthys olivaceus, which hatched 10 days and 3 days after fertilization, respectively. Despite the disparity in incubation time, the outer segments (containing membranous lamellae) of the pineal photoreceptors first appeared from 3 to 4 days after fertilization in both species. In contrast, the outer segments of the retinal photoreceptors first became visible 5 to 6 days after fertilization, although a characteristic retinal stratification and the optic tract leaving the ganglion cell layer were already found 4 days after fertilization in both species. The functional significance of these temporal disparities and/or similarities in photoreceptor development are discussed with special reference to the timing of daily rhythmic activities during the early developmental period of the teleosts.The results were presented at the Annual Meeting of the Japanese Society of Scientific Fisheries on April 2, 1990 (Tokyo)     

Untersuchungen zur Dotterbildung in den Oocyten von Xiphophorus helleri (Heckel, 1848) (Teleostei,Poeciliidae)

Zusammenfassung Die Verteilung von Nucleinsäuren, Polysacchariden, Proteinen und Fetten in den verschiedenen Entwicklungsstadien der Oocyten von Xiphophorus helleri wurde histochemisch untersucht. Junge Oocyten enthalten viel RNS und Proteine, aber wenig Fett. Während der Vitellogenese steigt der Gehalt an Fetten, Glycoproteide werden eingebaut. Die dazu nötigen Stoffe werden aus dem mütterlichen Körper in niedermolekularer, löslicher Form über das Follikelepithel zur Oocyte transportiert. Diese histochemischen Befunde werden durch Ergebnisse der Elektrophorese gestützt. In elektronenmikroskopischen Untersuchungen wurden den histochemischen Fakten weitere morphologische Grundlagen zugeordnet. Während der Prävitellogenese tritt ein Dotterkern auf, der sich vor Beginn der Dotterbildung auflöst. Coated vesicles nehmen Material aus dem perioocytären Interzellularraum auf. Zellstrukturen der Oocyte beteiligen sich am Dotteraufbau. Besonders auffallend sind die Veränderungen an den Mitochondrien. In der Zusammensetzung des Dotters und in der Beteiligung der Organellen gibt es Unterschiede zu Lebistes. Injektionen von Myofer runden die Ergebnisse ab. Vom maternalen zum embryonalen Gewebe erfolgt ein Transport von Nährstoffen, nicht nur Gasaustausch. Die Definition der Ovoviviparie muß daher erweitert werden.

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Studies on yolk formation in oocytes of Xiphophorus helleri

Summary The distribution of nucleic acids, polysaccharides, proteins, and fats in different developmental stages of oocytes of Xiphophorus helleri was studied using histochemical methods. Young oocytes had high RNA and protein contents. During vitellogenesis, the fat content increased and glycoproteins were deposited. These substances were transported from the maternal body into the oocyte in a soluble, small molecular form. The histochemical results were supported by our studies using electrophoretic and electron microscopic methods. During previtellogenesis, a yolk nucleus appeared. Coated vesicles took up material from the intercellular space around the oocyte. Differences between Xiphophorus and Lebistes were observed in the composition of yolk and in the prevalent types of ultrastructural organelles present. In Xiphophorus, labelling by Myofer (intraperitoneal or intramuscular injections) verified the transport of nutritive material from the maternal body into oocytes (Stage III and IV) and embryonic tissues. This suggests that in Xiphophorus the definition of ovoviviparity has to be modified.

     

Synapse-like contacts between axons of the pineal tract and the subcommissural organ in Rana perezi (Anra) and their absence in Carassius auratus (Teleostei): ultrastructural tracer studies

The present study was designed to investigate the controversial subject of the existence of a neural input from the pineal organ via the pineal tract to the subcommissural organ (SCO) in teleosts and anurans. Horseradish peroxidase was injected into the pineal organ and pineal tract of Carassius auratus and Rana perezi. Within the pinealofugal fibers the tracer was visualized at the light-and electron-microscopic levels either by immunocytochemistry using an anti-peroxidase serum, or by revealing the enzymatic activity of peroxidase. In both species, labeled myelinated and unmyelinated fibers of the pineal tract were readily traced by means of electron microscopy. In R. perezi, numerous terminals contacting the SCO cells in a synapse-like (synaptoid, hemisynaptic) manner bore the label, whereas a different population of endings was devoid of the tracer, indicating that in this species the SCO receives a dual neural input, one of pineal origin, the other of unknown source and nature. In the SCO of C. auratus, neither labeled nor unlabeled synapse-like contacts were found. Thus, in this latter species, a direct neural input to the SCO is missing. It is concluded that the secretory activity of the SCO can be controlled by different mechanisms in different species, and that more than one neural input mechanism may operate in the same species.     

Pattern of synaptic connections in the pineal organ of the ayu,Plecoglossus altivelis (Teleostei)

Summary Synaptic connections were studied by means of electron microscopy in the sensory pineal organ of the ayu, Plecoglossus altivelis, a highly photosensitive teleost species. Three types of specific contacts were observed in the pineal end-vesicle: 1) symmetrically organized gap junctions between the basal processes of adjacent photoreceptor cells; 2) sensory synapses endowed with synaptic ribbons, formed by basal processes of photoreceptor cells and dendrites of pineal neurons; 3) conventional synapses between pineal neurons, containing both clear and dense-core vesicles at the presynaptic site. Based on these findings, the following interpretations are given: (i) The gap junctions may be involved in an enhancement of electric communication and signal encoding between pineal photoreceptor cells. (ii) The sensory synapses transmit photic signals from the photoreceptor cells to pineal nerve cells. (iii) The conventional synapses are assumed to be involved in a lateral interaction and/or summation of information in the sensory pineal organ. A concept of synaptic relationships among the sensory and neuronal elements in the pineal organ of the ayu is presented.Fellow of the Alexander von Humboldt Foundation, Federal Republic of Germany     

Putative cholinergic elements in the photosensory pineal organ and retina of a teleost,Phoxinus phoxinus L. (Cyprinidae)

Summary Putative cholinergic neurons in the photosensory pineal organ of a cyprinid teleost, the European minnow, were studied by use of choline acetyltransferase (ChAT) immunocytochemistry and acetylcholinesterase (AChE) histochemistry. Pinealofugally projecting neurons were visualized using retrograde HRP-filling through their cut axons. For comparison, the distribution of choline acetyltransferase immunoreactivity (ChAT-IR) and AChE-positive elements in the retina was investigated.While the distributional patterns of ChAT-IR and strongly AChE-positive perikarya in the retina are similar and may represent the same neuronal population, ChAT-IR and AChE-positive elements in the pineal organ appear to belong to separate populations. In the retina, small- to medium-sized perikarya in the inner nuclear layer, and small perikarya in the ganglion cell layer are ChAT-IR and AChE positive. The entire inner plexiform layer is AChE positive, while only sublaminae 1, 2 and 4 are ChAT-IR. No indication of cholinergic activity was observed in the optic axon layer.In the pineal organ, ChAT-IR is restricted to small perikarya situated rostrally and dorsally in the pineal end-vesicle. AChE-positive neurons are present throughout the pineal end-vesicle and the pineal stalk. The pineal tract (the pinealofugally projecting axons of intrapineal neurons) is strongly AChE positive, but displays no ChAT-IR. The distribution of pinealofugally projecting neurons, labeled with retrogradely transported HRP, is markedly dissimilar to that of the ChAT-IR elements. It is proposed that the photosensory pineal organ transmits photic information to the brain via a non-cholinergic pathway. The possibility that the ChAT-IR neurons represent small local interneurons is discussed in the light of comparative physiological and anatomical findings.     

Zur Entstehung des Golgi-Apparates. Elektronenmikroskopische Untersuchungen an Spermatiden von Eisenia foetida (Annelidae)

Zusammenfassung An Spermatiden von Eisenia foetida wurde die Zelldifferenzierung zu Beginn der Spermiohistogenese untersucht. Die mit der zentralen, kernlosen Nährmasse, dem Cytophor, ein Syncytium bildenden Spermatiden besitzen zu Anfang der Zelldifferenzierung Vesikel, die im peripheren Kernbereich und im Lumen der perinucleären Zisterne liegen. Die Zellmembran am Verbindungsstück zum Cytophor trägt einen fuzzy coat, die Spermatidenmembran weist deutliche coated vesicles auf. Der Golgi-Apparat entsteht am prospektiven Schwanzende durch Auswachsen der ersten vesikelbildenden Lamelle aus der Kernmembran, die zuvor typische morphologische Veränderungen durchmacht. Die weiteren Lamellen eines Dictyosoms bilden sich durch Umfaltung der zuvor entstandenen. Anschließend werden an der Kernmembran die Mitochondrien differenziert. Die Genese der Cristae und der äußeren Mitochondrienmembran bleibt problematisch. Im Cytophor findet man annulierte Lamellen, degenerierte Golgi-Apparate und vesikelhaltige, abgeschnürte Zisternen des ER. Diese Formationen werden im Zusammenhang mit einer Reduktion des Cytoplasmas von den Spermatiden an das Cytophor abgegeben.

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On the origin of the golgi-apparatus. electron microscopical observations on spermatids of Eisenia foetida (Annelidae)

Summary The early cytodifferentiation is studied in developing spermatids of Eisenia foetida. The spermatids are attached to a central, anucleate mass of cytoplasm, the cytophore. They contain vesicles in the periphery of their nuclei and the perinuclear space. The cell membrane of the connecting bridge to the cytophore is covered with a fuzzy coat. The spermatid membrane is provided with coated vesicles. The Golgi apparatus develops at the prospective tailside by outgrowth of a vesicle producing lamella from the nuclear membrane, which before has undergone typical structural changes. Further dyctiosomal lamellae are formed by folding of already existing lamellae. Finally the mitochondria adhering to the nuclear membrane differentiate. The genesis of the cristae and the outer mitochondrial membrane remains problematical. In the cytophore there are annulate lamellae, degenerated dictyosomes and vesicle-containing cisternae of the endoplasmic reticulum. These formations are transferred from the spermatids to the cytophore, thus reducing the volume of their cytoplasm.

Herrn Prof. Dr. med. J. Staubesand danke ich für wertvolle Hinweise und Kritik.     

Fine structure of the developing frontal bones and scales of the cranial vault in the cichlid fish Hemichromis bimaculatus (Teleostei,Perciformes)

The development of the frontal bone and the formation of the first head scales are described during post-embryonic ontogeny of Hemichromis bimaculatus, using light and transmission electron microscopy. The frontal bone originates close to the cartilaginous taenia marginalis in a loose mesenchymal cell condensation (=primordium) lying 1 m from the epidermis with which it establishes no cell contacts. The anlage appears at 4.2 mm standard length (SL) in the form of the membranodermal component of the bone, and extends first over the brain and then over the eye; the neurodermal component forms later to surround the supraorbital canal. The first head scales appear at 10.0 mm SL in a dense cell condensation (papilla) adjoining the epidermal-dermal junction and, once formed, remain in this position. In both organs, the initial matrix is similarly composed of woven-fibred bone that soon mineralizes in a similar manner to other dermal elements. In some areas of the frontal bone, parallel-fibred bone is deposited unequally on both surfaces, whereas isopedine is deposited in scales on the deep surface only. Osteoblastic features confirm this eccentric growth. Differences in the shape, organization and localization of the mesenchymal condensations giving rise to the frontal bone and to the scale reflect the existence of two types of dermal cell condensations. Our data are compared with those available for the post-cranial dermal skeleton of fishes both from a developmental and structural viewpoint. Structural differences in the matrices of the frontal bone and scales are discussed in a phylogenetic perspective.     

Opsin-immunoreactive outer segments and acetylcholinesterase-positive neurons in the pineal complex of Phoxinus phoxinus (Teleostei,Cyprinidae)

Summary The pineal complex of the teleost, Phoxinus phoxinus L., was studied light-microscopically by the use of the indirect immunocytochemical antiopsin reaction and the histochemical acetylcholinersterase (AChE) method.Opsin-immunoreactive outer segments of photoreceptor cells were demonstrated in large numbers in all divisions of the pineal end-vesicle and in the pineal stalk. Moreover, they were found in the roof of the third ventricle, adjacent to the orifice of the pineal recess as well as scattered in the parapineal organ. These immunocytochemical observations provide direct evidence of the presence of an opsin associated with a photopigment in the photosensory cells of the pineal and parapineal organs of Phoxinus. By means of the AChE reaction (Karnovsky and Roots 1964) inner segments of pineal photoreceptors, intrinsic nerve cells, several intrapineal bundles of nerve fibers, and a prominent pineal tract were specifically marked. The pineal neurons can be divided into two types: one is located near the pineal lumen, the other near the basal lamina. The latter perikarya bear stained processes directed toward the photoreceptor layer. A rostral aggregation of two types of AChE-positive nerve cells occurs in the ventral wall of the pineal end-vesicle. The main portion of the AChE-positive pineal tract, which lies within the dorsal wall of the pineal stalk, can be followed to the posterior commissure where some of the nerve fibers course laterally. A few AChE-positive pineal nerve fibers run toward the lateral habenular nucleus via the habenular commissure. In the region of the subcommissural organ single AChE-positive neurons accompany the pineal tract. The nerve cells of the parapineal organ exhibit a moderate AChE activity.These findings extend the structural basis for the remarkable light-dependent activity of the pineal organ of Phoxinus phoxinus. To the memory of Professor Karl von Frisch, pioneer and master in the field of photoneuroendocrine systemsThis investigation was supported by grants from the Deutsche Forschungsgemeinschaft to A.O. (Ok 1/24; 1/25: Mechanismen biologischer Uhren) and to H.-W. K. (Ko 758/1; 758–2)On leave from the 2nd Department of Anatomy, SOTE, Budapest, Hungary     

Unusual cell organelles during spermiogenesis in two species of gobies (Gobiidae,Teleostei)

Summary Testes of Lesuerigobius friesii and Gobius bucchichi were studied in adult reproductive fish. During the onset of spermatid development, a peculiar system of alternating rough (RER) and smooth (SER) endoplasmic reticular tubules form rings distally to the cell nucleus. The RER tubules are seen to possess up to 12 ribosomes in cross-section, whereas the SER are strongly electron-dense. Nanotubules connect these stacks of tubules to the developing head and tail of the sperm. With ripening of the sperm these tubules disintegrate within the excessive cytoplasm. It seems likely that these are special forms of Macro-Golgi System that possibly provide protamines for the developing sperm.     

Immunocytochemical identification of prolactin cells in the pituitary gland of tilapia larvae (Oreochromis mossambicus: Teleostei)

Summary Using an antiserum to highly purified chum salmon prolactin, prolactin cells were identified in the putative rostral pars distalis of newly hatched tilapia larvae (Oreochromis mossambicus) by the immunogold method for the electron microscope. In the putative rostral pars distalis, some cells had another kind of secretory granule which was much less numerous, much smaller in size, and without immunoreactivity to salmon prolactin antiserum. Controls incubated with salmon prolactin-preabsorbed antiserum or normal serum showed no immunoreactive cells, confirming the specificity of the antiserum. The possible role of prolactin in the osmoregulation of tilapia larvae is discussed.     

Ultrastruktur des Pseudoculus vonEosentomon (Protura,Insecta)

Zusammenfassung In der Feinstruktur unterscheidet sich der Pseudoculus vonEosentomon nicht wesentlich von dem der Acerentomiden. Durch einen Endokutikulaporus treten die dendritischen Fortsätze zweier Sinneszellen, jeweils umgeben von einer Hüllzelle, in den Außenraum des Pseudoculus ein. Der Außenraum wird nach distal von einer äußeren Kutikulaschicht — vermutlich Epikutikula — abgeschlossen. Sie vermittelt durch regelmäßig angeordnete lange Spalten die Verbindung zur Außenwelt. Am Grunde der Spalten finden sich Porentubuli, die mit den Hüllzellen oder den distalen Fortsätzen der Dendriten Kontakt haben können. Aus der Feinstruktur kann geschlossen werden, daß der Pseudoculus als Chemo-, Hygro- und/oder Thermorezeptor fungiert.

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Ultrastructure of the pseudoculus ofEosentomon (Protura, Insecta)

Summary Concerning its fine structure the pseudoculus of Eosentomon is quite similar to that of Acerentomide Protura. There are two sensory cells innervating the organ. From each of them one dendritic process derives, surrounded by one enveloping cell. The processes of these four cells enter the distal cavity of the pseudoculus through a pore in the endocuticular layer. The cuticular layer of the cap seems to consist of epicuticle only. It is furrowed by long clefts connecting the distal cavity of the organ with the outside. Poretubules insert at the base of the clefts and may have contact with the cell membranes of both enveloping cells and dendritic processes. According to its structure the pseudoculus may function as chemo-, hygro- and/or thermoreceptor.

Für technische Mitarbeit danke ich Frau G. Raabe, für die Anfertigung der Zeichnung Frau C. St. Friedemann.     

Peroxisomes in intestinal and gallbladder epithelial cells of the stickleback,Gasterosteus aculeatus L. (Teleostei)

Summary The occurrence of microbodies in the epithelial cells of the intestine and gallbladder of the stickleback, Gasterosteus aculeatus L., is described. In the intestine the organelles are predominantly located in the apical and perinuclear zone of the cells and may contain small crystalline cores. In gallbladder epithelial cells the microbodies are distributed randomly. The latter organelles are characterized by the presence of large crystalloids. Cytochemical and biochemical experiments show that catalase and D-amino acid oxidase are main matrix components of the microbodies in both the intestinal and gallbladder epithelia. These organelles therefore are considered peroxisomes. In addition, in intestinal mucosa but not in gallbladder epithelium a low activity of palmitoyl CoA oxidase was detected biochemically. Urate oxidase and L- hydroxy acid oxidase activities could not be demonstrated.