B. Vigh

The infundibular cerebrospinal-fluid contacting neurons.

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ACTUAL PROBLEMS OF THE CEREBROSPINAL FLUID-CONTACTING NEURONS

Cerebrospinal fluid (CSF)‐contacting neurons form a part of the circumventricular organs of the central nervous system. Represented by different cytologic types and located in different regions, they constitute a CSF‐contacting neuronal system, the most central periventricular ring of neurons in the brain organized concentrically according to our concept. Because the central nervous system of deuterostomian echinoderm starfishes and the prochordate lancelet is composed mainly of CSF‐contacting‐like neurons, we hypothesize that this cell type represents ancient cells, or protoneurons, in the vertebrate brain.

Light- and electron-microscopic demonstration of immunoreactive opsin in the pinealocytes of various vertebrates

SummaryAn antibody to opsin isolated from rod outer segments of the frog retina was applied in light- and electron-microscopic immunocytochemical studies to the pineal organ of various vertebrates (Cyprinus carpio, Carassius auratus, Rana esculenta, Emys orbicularis, Pseudemys scripta elegans, Lacerta agilis and viridis, Gallus domesticus, Columba livia, Melopsittacus undulatus, Serinus canaria, Taeniopyga punctata, Didelphis virginiana, Erinaceus roumanicus, Myotis myotis, rabbit, rat, cat).A strong immunoreaction was visible in the outer segments of the pinealocytes of one anuran and several teleost species. The outer segments of pinealocytes in the chelonian reptiles and birds also contained immunoreactive opsin. Ultrastructurally, PAP complexes were localized to the photoreceptor membranes of the outer segments. Immunoreactivity for opsin could not be demonstrated in the lacertilian parietal eye and pineal organ.In the opossum (Marsupialia), pinealocytes remain in contact with the intrapineal invaginations of the pineal recess. In insectivores, the cilia of the pinealocytes exhibit a relation to glial cells similar to that between the outer segments of retinal photoreceptors and the pigment cells. The cilia of mammalian pinealocytes did not show a clear-cut immunoreactivity to opsin with the electron-microscopic technique employed.

Special dendritic and axonal endings formed by the cerebrospinal fluid contacting neurons of the spinal cord.

SummaryThe cerebrospinal fluid (CSF) contacting neurons have a dendritic process which protrudes into the central canal, and is provided with one long kinocilium and many shorter stereocilia (about 80 in the turtle) as revealed by scanning electron microscopy. The shape, number and arrangement of the cilia are similar to those of known receptor endings.The silver impregnated axons of these cells converge to a paired centrosuperficial tract forming terminal enlargements at the ventrolateral surface of the spinal cord. Lying among glial endfeet these terminals are ultrastructurally similar to those present in known neurosecretory areas. The nerve endings are attached to the basal lamina, and they comprise many synaptic vesicles (200 to 400 Å in diameter), as well as granular vesicles of different sizes (diameter 600 to 1800 Å). The axons may lie within finger-like protrusions on the surface of the spinal cord, or they may terminate around vessels.Morphological evidence suggests that these nerve terminals and the corresponding CSF contacting perikarya represent a spinal neurosecretory system possibly influenced by information taken up by its special dendrites protruding into the inner CSF space.

Cerebrospinal fluid-contacting neurons, ciliated perikarya and “peptidergic” synapses in the magnocellular preoptic Nucleus of teleostean fishes

SummaryThe magnocellular preoptic nucleus of fishes (Anguilla anguilla, Amiurus nebulosus, Cyprinus carpio, Carassius auratus, Ctenopharyngodon idella, Cichlasoma nigrofasciatum) has been studied by light and electron microscopy.Two kinds of neurons were found: a) large, electron-dense, Gomori-positive cells with moderate acetylcholinesterase (AChE) positivity which contain granulated vesicles of 1400 to 2200 Å (in average 1600 to 1800 Å), and b) small, strongly AChE-positive, electron-lucent neurons containing granulated vesicles of 900 to 1200 Å. The nerve cells are supplied with axo-somatic and axo-dendritic synapses. These are formed by axon terminals containing either 1. synaptic vesicles of 500 Å, or 2. synaptic vesicles of 500 Å and dense-core vesicles of 600 to 800 Å, or 3. synaptic vesicles of 600 Å and granulated vesicles of up to 1100 Å, or 4. synaptic vesicles of about 400 Å and granulated vesicles of up to 1800 Å. The presence of “peptidergic” and numerous other synapses shows the complexity of the organization and afferentation of the magnocellular preoptic nucleus.In the eel, both types of nerve cells form dendritic terminals within the cerebrospinal fluid (CSF). These CSF contacting dendrites are supplied with 9×2+0 cilia. In the other species investigated, only some large neurons build up intraventricular endings. The ependymofugal process of the CSF contacting neurons enters the preoptic-neurohypophysial tract.Perikarya of both the large and the small cells may give rise to single, paired or multiple 9×2+0 cilia extending into the intercellular space. The number of CSF contacting neurons is reciprocal to the number of perikarya with intercellular cilium. These latter cells may represent modified, more differentiated forms of the CSF contacting neurons. We think that atypical cilia protruding into the intercellular space may have the same significance for the intercellular fluid as the cilia of the intraventricular dendrites of the CSF contacting neurons for the CSF.

Immunohistochemical localization of substance P and ACTH-like activity in the central nervous system of the earthworm Lumbricus terrestris L.

The peroxidase-antiperoxidase (PAP) method was used for the immunohistological demonstration of substances P and ACTH in the cerebral and subesophageal ganglia of the earthworm, Lumbricus terrestris L. With rabbit antibody to substance P a positive immunoreaction was found in nerve cells smaller than the type A neurons of the cerebral ganglion. Their perikarya and nerve processes as well as their terminal enlargements in the synaptic zone were immunoreactive. ACTH-like activity was visible in a larger perikaryon type of the A neurons. Their nerve processes did not show any reaction. However, a part of the nerve terminals of the synaptic zone and a few neurons of type B of the cerebral ganglion, further some cells of the subesophageal ganglion reacted positively.

Licht- und elektronenmikroskopische Untersuchungen am Recessus praeopticus-Organ von Amphibien

SummaryThe preoptic recess organ (PRO) of the 3rd brain ventricle of urodela and anura has been studied by light and electron microscopy. — The PRO consists of a special ependyma and a parvocellular group of neurons. The latter is built up of intraependymal, hypendymal and distal nerve cells. The neurons send processes into the preoptic recess where they form free, club-like nerve terminals. In the perikarya, their ventricular dendrites and liquor endings as well as in their peripheral axons a primary catecholamine, probably noradrenaline, can be demonstrated by fluorescence histochemistry.As demonstrated electron microscopically, the ventricular nerve endings contain mitochondria, a few ergastoplasmic cisternae, microtubuli and dense-core vesicles of various amounts and size (500–850 Å). It characterizes the neurons that they mostly possess a cilium; its basal body and accessory centriol give rise to long rootlet fibers. Cross sections of atypical cilia (type 8+1, 9+0, 10+1, 20+0) are described. The ventricular nerve processes are connected with the surrounding ependymal cells by zonulae adhaerentes. The perikarya of the intraependymal and hypendymal neurons contain various amounts of dense-core vesicles. The distal nerve cells and their processes contain relatively few catecholamine granules. In the neuropil, different types of synapses are to be observed probably acting in different manner. — On the basis of the morphological data, the question of a receptor function of the PRO is discussed.ZusammenfassungDas Recessus praeopticus-Organ (RPO) des 3. Ventrikels von Urodelen und Anuren wurde licht- und elektronenmikroskopisch untersucht. Es besteht aus einem speziellen Ependym und einer kleinzelligen Neuronengruppe, in der sich intraependymale, hypendymale und distale Nervenzellen unterscheiden lassen. Die Neurone senden Fortsätze in den Recessus praeopticus, wo sie freie, knöpfchenförmige Endigungen bilden. In den Nervenzellen, ventrikulären Dendriten und Liquorendigungen sowie in den peripheren Axonen ist fluoreszenzhistochemisch ein primäres Katecholamin, wahrscheinlich Noradrenalin, nachweisbar.Mit dem Elektronenmikroskop sind in den ventrikulären Nervenendigungen Mitochondrien, wenige Ergastoplasmacisternen, Mikrotubuli und „dense-core vesicles“ in wechselnder Menge und Größe (Durchmesser 500–850 Å) nachweisbar. Es ist charakteristisch für die Nervenendigung, daß sie meist über ein Zilium verfügt, von dessen Basalkörper und akzessorischem Zentrosom lange, quergestreifte Basalwurzeln ausgehen. Querschnitte atypischer Zilien (Typ 8+1, 9+0, 10+1, 20+0) werden beschrieben. Die ventrikulären Nervenfortsätze sind durch Zonulae adhaerentes mit den benachbarten Ependymzellen verbunden. Die Perikaryen der intraependymalen und hypendymalen Neurone enthalten „dense-core vesicles“ in wechselnder Menge. Die distalen Nervenzellen und ihre Fortsätze weisen relativ wenige Katecholamingranula auf. Im Neuropil wurden verschiedene Synapsen beobachtet, die wahrscheinlich unterschiedliche Funktionen ausüben. — An Hand der morphologischen Daten wird die Frage einer etwaigen Rezeptorfunktion des RPO diskutiert.

Elektronenmikroskopische Untersuchung der Neurosekretion im Cerebralganglion des Regenwurmes (Lumbricus terrestris)

ZusammenfassungDie Feinstruktur der neurosekretorischen Nervenzellen und der Gliazellen im Cerebralganglion des Regenwurmes (Lumbricus terrstris) wurde untersucht.Die Nervenzellen zeigen verschiedenartige Erscheinungsformen. Einzelne sind mit reifen Neurosekretgranula (Durchmesser von rund 280 mμ) gefüllt („Speicherzellen“). In anderen dominieren leere Vesikel, oder das Ergastoplasma nimmt die ganze Zelle ein. In einzelnen Fällen erweitern sich die Ergastoplasmacysternen sackartig, so daß die Zelle ein vakuolisiertes Aussehen gewinnt. Der für ein Sekret charakteristische Stoff wird zuerst in den flachen Cysternen des Golgi-Apparates und in den Golgi-Vesikeln der entleerten Zellen gefunden. Daraus kann geschlossen werden, daß der Golgi-Apparat in enger Beziehung zur Sekretbildung steht. In einigen Zellen werden reife Sekretgranula im Interzellularraum zwischen den Fortsätzen der Glia- und Nervenzellen beobachtet.Charakteristisch für die Gliazellen sind ein gut entwickelter Golgi-Apparat, Stützfilamente und einzelne Vesikelreihen. Letztere stehen vermutlich mit der Pinocytose und Phagocytose in Zusammenhang. Oft kommen in den Gliazellen — aber in geringer Menge auch in den Nervenzellen — große, dunkle Körper (Durchmesser 0,5–2,5 μ) mit feinkörnigem, homogenem oder lamellärem Inhalt vor. Anscheinend bestehen zwischen diesen Körpern und den Gliamitochondrien Übergangsformen.Erweiterungen des Interzellularraumes an isolierten Abschnitten stehen aller Wahrscheinlichkeit nach mit der Entleerung des Sekretes in Verbindung. In ihnen ist ein blasser, fein präzipitierter Stoff zu finden. Die Wand der Kapillaren wkd von einer feinen Basalmembran und einer Myoendothelzellschicht gebildet. Oft sind zwischen benachbarten Endothelzellen und zwischen ihnen und der Basalmembran kleine homogene, dunkle Gebilde mit verwaschenem Umriß zu beobachten, die vielleicht mit der Entleerung der Sekretgranula in die Kapillaren in Zusammenhang stehen.

Cerebrospinal fluid-contacting neurons, sensory pinealocytes and Landolt's clubs of the retina as revealed by means of an electron-microscopic immunoreaction against opsin

SummaryOpsin-immunoreactive sites of hypothalamic cerebrospinal fluid (CSF)-contacting neurons, pinealocytes and retinal cells were studied in various vertebrates (Carassius auratus, Phoxinus phoxinus, Triturus cristatus, Bombina bombina, Rana esculenta) by means of postembedding immuno-electron microscopy with the use of the protein A-gold labeling method. The retina of the rat served as a general reference tissue for the quality of the immunocytochemical reaction.A strong opsin immunoreaction (rat-antibovine opsin serum) was obtained in the rod-type outer segments of photoreceptors in the retina of all species studied. Cone-type outer segments exhibited only very few antigenic binding sites. In the pineal organ of the goldfish and the frog, outer segments of the photoreceptor cells displayed strong immuno reactivity.No immunoreaction was found in hypothalamic CSF-contacting neurons and Landolts clubs of nerve cells of the bipolar layer of the retina. The morphological similarity between the ciliated dendritic terminal of the Landolts club and the intraventricular dendritic ending of the CSF contacting neurons is emphasized.

Serotonin and opsin immunoreactivities in the developing pineal organ of the three-spined stickleback, Gasterosteus aculeatus L.

Summary5-hydroxytryptamine (5-HT, serotonin)- and opsin-immunoreactive sites were studied in the developing pineal complex of the stickleback, Gasterosteus aculeatus L., by use of light-microscopic indirect immunoperoxidase techniques.5-HT immunoreactivity first occurs in the pineal organ at the age of 80 h after fertilization and appears to be localized in cells of the photoreceptor type. The outer segments of a few pineal photosensory cells exhibit opsin immunoreactivity at the age of 84 h after fertilization. The number of cells seems to increase until the pineal organ is completely developed. The increase in the number of 5-HT immunoreactive perikarya runs parallel in time to that of the opsinimmunoreactive outer segments. The cells of the parapineal organ show neither opsin nor 5-HT immunoreactivity. The retina of the embryonic stickleback does not display opsin immunoreactivity until after hatching, which takes place about 144 h after fertilization.These results suggest, in the three-spined stickleback, an earlier light-perception capacity for the developing pineal organ than for the retina.