Solitary chemoreceptor cells of Ciliata mustela (Gadidae, Teleostei) are tuned to mucoid stimuli

Summed potentials were recorded from the dorsal recurrent facialnerve innervating the solitary chemoreceptor cells on the anteriordorsal fin (ADF), from the ventral recurrent facial nerve innervatingboth taste buds and solitary chemoreceptor cells on the pectoral(PEC) and pelvic (PEL) fins, and from the anterior dorsal finmuscles in the rockling, Ciliata mustela. There is little overlapbetween the sumulus spectra of solitary chemoreceptor cellsand taste buds. The ADF solitary cells are particularly sensitiveto body mucus (skin water) of non-congeners like Gadus, Solea,Cottus, Mugil, Zoarces, Gaidropsarus, and Encheliopus, but insensitiveto amino acids and a variety of body fluids of fish, invertebrates,and extracts of potential stimuli like algae and sand. Pectoraland pelvic fins are particularly sensitive to amino acids, bodyfluids of fish and invertebrates, but less sensitive to skinmucus of fish, probably due to the abundance of taste buds.Active sampling by undulation of the anterior dorsal fin isessential for proper functioning; it induces disadaptation ofthe receptor elements. Solitary chemoreceptor cells provide,apparently, cues to discriminate between conspecifics and non-conspecifics.It is unlikely that they are involved in pheromone detection.     

Central connections of the pineal organ in the three-spined stickleback,Gasterosteus aculeatus L. (Teleostei)

Cell and Tissue Research - Central connections of the pineal organ of the three-spined stickleback, Gasterosteus aculeatus L., were studied by the use of horseradish peroxidase (HRP) for...     

Ontogenetic development of the pineal organ,parapineal organ,and retina of the three-spined stickleback,Gasterosteus aculeatus L. (Teleostei)

The ontogenetic developments of the pineal organ, parapineal organ, and retina were studied by the use of light and electron microscopy in embryos and fry of the teleost, Gasterosteus aculeatus, from 60 to 168 h after fertilization. Sixty to 66 h after fertilization, the primordium of the pineal complex is discernible in the diencephalic roofplate; the parapineal anlage is located rostral to the pineal anlage. Photoreceptor cells endowed with outer segments are present in the embryonic pineal organ already after 72 h, whereas outer segments of retinal photoreceptors could not be demonstrated before 144 h (hatching occurs between 120-144 h). Furthermore, neuropil formations with synaptic specializations are present in the rostral part of the pineal organ 108 h after fertilization. At 72 h, the embryonic parapineal parenchyma is already differentiated into parapinealocytes, which give rise to the parapineal tract, and glia-resembling elements. Although parapinealocytes carry cilia (9 X 2 + 0), only a single outer segment of the photoreceptor type could be demonstrated in the parapineal organ of one adult stickleback. Photoreceptors present in the pineal organ of unhatched embryos are hardly involved in visual functions, but may already at this early developmental stage serve as photoneuroendocrine transducers.     

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     

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)     

Structure of the pineal organs of Anguilla anguilla L. and Lebistes reticulatus Peters (Teleostei)

Résumé Des fibres myocardiques ventriculaires de Rat et des fibres squelettiques rapides des orteils de Grenouille ont été examinées en microscopic électronique après imprégnation par le nitrate de Lanthane ou après traitement par l'acide phosphotungstique.Le nitrate de Lanthane a été utilisé comme marqueur d'espace extracellulaire. Dans le tissu myocardique, it est possible de l'observer dans toutes les ramifications du système T, alors que dans les fibres squelettiques, le glutaraldehyde du mélange fixateur provoque l'obturation de la plupart des tubules et empêche sa pénétration dans leur lumière. Dans tous les cas, cependant, la diffusion du Lanthane s'arrête à 50 Å environ du feuillet externe des membranes plasmatiques ou tubulaires.Le matériel mis en évidence par l'acide phosphotungstique, comportant vraisemblablement des polysaccharides et des glyco-protéines, est localisé à la périphérie de toutes les cellules examinées, y compris dans l'espace de 50 À où ne pénètre pas le Lanthane. Dans les fibres myocardiques, ce matériel est présent de plus dans l'ensemble du système T, mais dans les fibres squelettiques, par contre, il est présent dans les parties intermédiaires et terminales du système L.Il semble que la diversité de localisation et de nature des polyanions présents dans ces deux types de fibres musculaires striées puisse suffire à rendre compte d'un certain nombre de propriétés spécifiques de chacun d'eux.

---

Comparative study on physico-chemical properties of the t-system and sarcoplasmic reticulum in two types of striated muscle fibers: the fast muscle fiber of the frog and the myocardial fiber of the rat ventricle

Summary Rat ventricular myocardial fibers and frog toe fast skeletal fibers were examined electron microscopically after Lanthanum nitrate impregnation or after phosphotungstic acid staining.The Lanthanum nitrate was used as an extracellular tracer. In the myocardial tissue, it is possible to observe it in all the T system ramifications, while in the skeletal fibers, the glutaraldehyde fixative elicits the sealing of most tubules and prevents Lanthanum from penetrating into their lumen. In both cases, however, the Lanthanum diffusion stops at about 50 Å from the external plasma membrane layer.The material stained with phosphotungstic acid, probably including polysaccharides and glycoproteins, is localized at the surface of both cell types examined here, even in the 50 Å space where Lanthanum does not penetrate. In the myocardial fibers, this material is also present in the whole T system, but in the skeletal fibers, on the contrary, it is present in the intermediate and terminal parts of the L system.The diversity in localization and nature of the polyanions present in these both types of striated muscular tissue seems to be sufficient to explain some functional properties specific of each of them.

Travail réalisé dans le cadre du programme de recherches de l'équipe associée au C.N.R.S. n 111.     

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)     

The morphology and histology of the pineal organ in roach, Rutilus rutilus (L.)

The pineal organ in the roach, Rutilus rutilus (L.), is covered by a semi-transparent area, the pineal window. Beneath this the pineal is attached to a long robust stalk, lying just under the parietal bone. The pineal is attached to the brain through the dorsal sac. Three cell types have been identified histologically. These are the sensory cells, supporting cells and the ganglia cells. The inner segment of the sensory cells respond to PAS and AF staining, while the remaining cells respond to Orange G, LG, or Acid Fuchsin. The evidence suggests that the roach pineal may have a dual photosensory and glandular function.     

Indications for the presence of two populations of serotonin-containing pinealocytes in the pineal complex of the golden hamster (Mesocricetus auratus)

Summary Serotonin-like immunoreactivity was investigated in the pineal complex of the golden hamster by use of the indirect immunohistochemical technique. The superficial and deep portions of the pineal gland, and also the pineal stalk exhibited an intense cellular immunoreaction for serotonin. In addition, perivascular serotonin-immunoreactive nerve fibers were observed. Some serotonin-immunoreactive processes of the pinealocytes terminated on the surface of the ventricular lumen in the pineal and suprapineal recesses, indicating a receptive or secretory function of these cells. Several serotonin-immunoreactive processes connected the deep pineal with the habenular area. One week after bilateral removal of both superior cervical ganglia the serotonin immunoreaction of the entire pineal complex was greatly decreased. However, some cells in the pineal complex, of which several exhibited a neuron-like morphology, remained intensively stained after ganglionectomy. This indicates that the indoleamine content of some cells in the pineal complex of the golden hamster is independent of the sympathetic innervation.Supported by a Grant from the Italian Society for Veterinary Sciences     

The fourbeard rockling, Enchelyopus cimbrius (L.), in eastern Newfoundland

A population of fourbeard rocklings, Enchelyopus cimbrius, was studied in shallow water (<10 m) in eastern Newfoundland. They are nocturnal, occupying burrows in muddy substrate during the day. and often retreating into these burrows at night when disturbed. The population consisted mostly of 80–150 mm individuals, aged 2-3 years. Feeding was observed only at night, and food consisted mostly of polychaete worms, especially the scale worm Harmorhoe imbricara . The contribution of polychaetes increased with increasing size of fish.     

GABA-immunoreactive neurons in the photosensory pineal organ of the rainbow trout: two distinct neuronal populations

Summary The distribution of putative GABA-ergic neurons in the photosensory pineal organ of the rainbow trout was investigated by use of a specific antiserum against -aminobutyric acid (GABA). GABA-immunoreactive (GABA-IR) neurons were located in the rostral portion of the pineal end-vesicle, presumably constituting a population of interneurons. GABA-IR neurons were also found in the pineal stalk. The axons of these neurons were traced along the pineal stalk toward the brain. The terminal areas of these axons could not be established. GABA-IR glial cells were observed in the pineal end-vesicle, but not in the pineal stalk.     

Ultrastructure of serotonin-containing cells in the pineal organ of Lampetra planeri (Petromyzontidae)

Summary The ultrastructure of the cells containing residual bodies (Collin, 1969) was investigated in the pineal organ of Lampetra planeri. These cells are characterized by their indoleamine metabolism (Meiniel, 1978; Meiniel and Hartwig, 1980). Morphologically, they belong mainly to two types: (1) a photoreceptor cell type, and (2) a pinealocyte cell type. The first type is present in the pineal sensory epithelium and in the atrium, while the second is observed in the deep part of the atrium. Intermediate cell types are rare. All these cells are characterized by the presence of voluminous dense bodies, the 5-HT-storing structures, in their cytoplasm.The elongated cone-type photoreceptor cells show a segmental organization and well-developed outer segments consisting of short disks (2–3 m), while their basal pedicles form synapses with the dendritic processes of neurons. The pinealocytes are spherical or oval in shape, their receptor poles being regressed to cilia of the 9+0 type. In these cells, no synaptic ribbons have to date been observed. In both cell types a Golgi apparatus is present producing dense granules 130 nm in diameter and a polymorphous dense material.The photoreceptor cells most probably respond to light and transmit a sensory (i.e., nervous) message. In addition, they produce and metabolize indoleamines, probably including, melatonin (Meiniel, 1978; Meiniel and Hartwig, 1980). The pinealocytes, in spite of their loss of direct photosensitivity, retain their capacity to metabolize indoleamines (Meiniel, 1978; Meiniel and Hartwig, 1980).The presence, in the same pineal organ, of another photoreceptor cell type (cf. Collin, 1969–1971) differing morphologically as well as biochemically (no detectable indoleamine metabolism) from the photoreceptor cell type described in the present investigation, points to the existence of two different sensory cell lines: (1) a pure photoreceptor line, and (2) a photoneuroendocrine line. The phylogenetic evolution of these two cell lines is discussed in terms of functional analogy.     

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.     

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.     

Chromosomal diversification in populations of Characidium cf. gomesi (Teleostei, Crenuchidae)

Comparative cytogenetic studies carried out in two populations of Characidium cf. gomesi from Botucatu region, SP, Brazil, showed a similar karyotypic structure in a diploid number of 50 chromosomes, 32 metacentric and 18 submetacentric chromosomes for males and 31 metacentric and 19 submetacentric chromosomes for females as well as a ZZ-ZW sex chromosome system. Differences between both populations, however, were found in relation to the occurrence of B chromosomes and the distribution of 18S and 5S ribosomal DNA (rDNA) sites. Characidium cf. gomesi from the Alambari Stream, a component of the Tietê River basin, revealed 18S rDNA on Z and W chromosomes, while this gene was located on autosomes in the sample from the Paranapanema River basin. The 5S rDNA sites were observed in a single chromosomal pair (number 25) in the populations from Paranapanema and in two pairs in the specimens from Tietê (numbers 20 and 25). Besides that, in the sample from Paranapanema, both inter and intra-individual variations were found due to the occurrence of up to four heterochromatic supernumerary chromosomes in the cells. The life mode of this fish, restricted to headwaters and subjected to frequent breakdown into sub-populations, may have contributed to the fixation of such chromosomal differences. The karyotypic similarities found in the analysed populations, however, suggest that all are descended from the same ancestor group whereas their differences indicate that they are already existing in reproductively isolated populations.     

The pineal organ is the first differentiated light receptor in the embryonic salmon,Salmo salar L.

Summary The initial appearance of S-antigen, -transducin, opsin and 5-HT during embryogenesis of the pineal organ and retina was studied by means of immunocytochemistry in the Atlantic salmon, Salmo salar L. The presence of these substances may be taken as a good indication of photoreceptor differentiation; -transducin and S-antigen are involved in the phototransduction process, opsin is the proteinaceous component of the photopigment rhodopsin, and 5-HT is a neurotransmitter or neurohormone produced by pineal photoreceptors. Two days after the retinal pigment layer became visible in the eggs, the outer segments of a few pineal photosensory cells showed immunoreactivity to opsin and -transducin. At the same time S-antigen and serotonin were present in pineal cells of the photoreceptor type. The number of immunoreactive cells in the pineal organ increased up to hatching. In the differentiating retina of the salmon, no immunoreactivity to antibodies raised against the mentioned substances was detectable until after hatching. These results indicate that in ontogeny the developing pineal organ of the salmon embryo has the ability to perceive light information much earlier than the retina.A preliminary account of this work was presented at the Tenth European Neuroscience Congress, Marseille, France, September 14–18, 1986     

Ultrastructure of the extracutaneous pigment cells in the plaice (Pleuronectes platessa,L., Teleostei)

Summary The extracutaneous pigment cell system of the plaice (Pleuronectes platessa L.) was examined by light and electron microscopy in selected regions, including two cutaneous regions for comparison. The extracutaneous pigmentation consists of guanocytes and melanocytes with differing distributions within the body. The eyeless side lacks melanocytes. The pigment cells are differentiated as very flat elements with long processes. They display an affinity for loose connective tissue at boundary layers such as the peritoneal epithelium, organ capsules or blood vessels, to which they are parallelly arranged at a very constant distance. In some locations guanocytes are intimately associated with melanocytes forming reduced chromatophore units. Extracutaneous pigment cells are poor in mitochondria, endoplasmic reticulum, microfilaments, caveolae intracellulares, ribosomes and glycogen granules, all of which are more abundant in cutaneous pigment cells and pigment cells of the eye. In extracutaneous guanocytes the crystals are loosely arranged parallel to the cell surface, in cutaneous guanocytes perpendicular. Cells with rod-like vesicular cisternae are described as guanoblasts. No single pigment cell was found exhibiting different types of pigment granules. The varying colors of extracutaneous pigmentation arise from varying combinations of guanocytes and melanocytes in addition to the color of the tissue itself.In partial fulfillment for the degree of Doctor of Medicine under the direction of Prof. Dr. Dr. H.-R. Duncker (Giessen)