Brain Structure in Calamoichthys calabaricus Smith 1865 (Polypteridae,Brachiopterygii)

The brain of Calamoichthys calabaricus is reconstructed including the arrangement of the parts of the brain and the cranial nerves and their nuclei. Histologically, the analysis includes structure of the rhombencephalon with its cranial and tegmental nuclei, and the cerebellum.     

Feinstruktur des Riechepithels von Calamoichthys calabaricus J. A. Smith (Pisces,Brachiopterygii)

Zusammenfassung Die vorliegende Untersuchung befaßt sich mit der Feinstruktur der Riechfalten von Calamoichthys calabaricus unter besonderer Berücksichtigung des Riech- und Flimmerepithels. — Das Flimmerepithel ist aus 3 Zelltypen aufgebaut: Flimmerzellen, wenigen Stützzellen und Basalzellen. Die Flimmerzellen sind mitochondrienreich und tragen bis zu 160 Flimmerhärchen pro Zelle. Diese Kinocilien besitzen an ihren Basalkörpern Zilienwurzeln, von denen ein Teil ins Zellinnere bis in Kernnähe zieht, während der andere Teil parallel zur Oberfläche verläuft und benachbarte Basalapparate verbindet. — Auch das Riechepithel, das gegen das Flimmerepithel scharf abgesetzt ist, besteht aus 3 Zelltypen: Rezeptoren, Stützzellen und Basalzellen. Die Rezeptoren haben eine einheitliche Gestalt und Struktur. Sie sind schlank keulenförmig und überragen mit einer kleinen Vesicula olfactoria die Epitheloberfläche. Seitlich sitzen an der Vesicula — unter konstant 25–27° Ablenkung von der Senkrechten — in der Regel 12 sensorische Cilien, die alle auf gleicher Höhe entspringen. Basal setzt sich das Rezeptorperikaryon in ein Axon fort. Die Axone mehrerer Rezeptoren vereinigen sich noch innerhalb des Epithels zu Bündeln, die durch die Basalmembran ins Bindegewebe ziehen. Die stark osmiophilen Stützzellen des Riechepithels durchziehen das Riechepithel von der Basalmembran bis zur Epitheloberfläche und tragen einzelne Cilien. Der verbreiterte Apikalteil der Stützzellen enthält zahlreiche Schleimvesikel, die auf eine sezernierende Funktion dieser Zellen hinweisen. Die präparative Behandlung von Riechepithelien wird kritisch diskutiert.

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Ultrastructure of the olfactory epithelium of Calamoichthys calabaricus J. A. Smith (Pisces, Brachiopterygii)

Summary The ciliary epithelium of the olfactory folds in Calamoichthys calabaricus is composed of ciliary cells, supporting cells, and basal cells. All ciliary cells contain numerous mitochondria and bear up to 160 kinocilia. Some rootlets of the basal bodies of the kinocilia, project towards the nucleus, while others run parallel to the epithelial surface and connect with neighbouring basal bodies. Ciliary and olfactory epithelia are separated from each other. — The olfactory epithelium contains olfactory receptor cells, supporting cells, and basal cells. The club shaped olfactory receptor cells have a uniform ultrastructure. The terminal portions of the olfactory dendrites form small olfactory vesicles which are seen above the olfactory surface. 12 sensory cilia project constantly to the more basal portion of the olfactory vesicles, each cilium forming a 25–27° angle with the vertical cell axis. Basally, an axon originates from each olfactory receptor cell. Axons from a number of olfactory receptor cells may combine to form bundles within the epithelium. The supporting cells of the olfactory epithelia are strongly osmiophilic. Supporting cells occur in all parts of the olfactory epithelium and bear few cilia. Numerous mucous vesicles, located within the apical region of the supporting cells, probably have a secretory function.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Distribution and Structure of the Adrenocortical Homolog in the Reed-Fish (Calamoichthys calabaricus Smith)

The adrenocortical homolog (AH) was identified in the reed-fish ( Calamoichthys calabaricus Smith) using histochemistry for the enzyme δ⁵-3β-hydroxysteroid dehydrogenase (3β-HSD) and its distribution and structure were examined with both light and electron microscopy. AH appears as yellow corpuscles which extend as isolated bodies throughout the length of both kidneys in close apposition to the posterior cardinal veins. The yellow corpuscles are composed of convoluted cords of epithelial cells and tortuous sinusoids which empty directly into the cardinal veins. Wide lateral intercellular spaces and accompanying microvilli give the impression of pseudotubules or pseudofollicles to the cords of epithelial cells. The extensive network of tubules of smooth endoplasmic reticulum, the many mitchondria with tubulo-vesicular cristae, the conspicuous Golgi apparatus, lipid droplets, many pleomorphic granules and the presence of 3β-HSD are indicative of the steroidogenic nature of the cells. Large, pleomorphic mitochondria and gap junctions are also typical of most cells. The fine structure of the cells in the AH of the reed-fish most closely resembles that of other Polypteriformes, but the tissue is more widely distributed in the kidneys than in any osteichthylian so far reported.     

Das geruchsorgan der Polypteridae (Pisces,Brachiopterygii)

The olfactory organ of the Polypteridae (Brachiopterygii) was studied histologically. It differs fundamentally from the olfactory organ of the Teleostei (Actinopterygii) and resembles that of Latimeria (Crossopterygii). The size of the olfactory organ indicates that the Polypteridae are macrosmatic.

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Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

On the origin of ganoine: histological and ultrastructural data on the experimental regeneration of the scales of Calamoichthys calabaricus (Osteichthyes, Brachyopterygii, Polypteridae)

In order to understand the process of ganoine formation on the ganoid scales, scale regeneration has been studied to overcome the lack of a growth series of scale ontogeny. Seven stages of ganoid scale regeneration have been defined over a period of five months in the polypterid fish Calamoichthys calabaricus. The study has been carried out using transmission electron microscopic techniques. After wound healing and differentiation of the osseous basal plate, a layer of vascular dentin is deposited at the upper surface of the basal plate owing to the presence there of odontoblasts closely applied to the dentin. When these cells move away, a close contact is then established between the stratified epidermis and the regenerating scale. Numerous alterations of the epidermal-dermal boundary occur until its disappearance and a thick layer of pre-ganoine is formed. This layer is progressively mineralized; and finally an organic intermediate layer differentiates between the ganoine, which is a hyper-mineralized tissue, and the overlying epidermis. This ultrastructural study demonstrates rather unequivocally the involvement of the inner epidermal layer (IEL) in the appearance and growth of the ganoine. It is suggested that these epidermal cells can be compared functionally to the inner dental epithelium (IDE) described during mammal tooth morphogenesis. Consequently, our results allow us to propose that ganoine can be identified as true enamel, although additional data are necessary to analyze the proteinaceous component or its organic matrix.     

Immunocytochemical demonstration of somatotropin-like and prolactin-like activity in the brain of Calamoichthys calabaricus (Actinopterygii)

Summary Cellular binding of anti-bSTH and anti-oPRL IgG is demonstrated in the brain and the pituitary gland of the African freshwater fish Calamoichthys calabaricus by means of the unlabeled antibody enzyme method at the light microscopic level. In the brain, somatotropin and prolactin are demonstrated in separate neurons in the preoptic area. The somatotropinergic and prolactinergic perikarya are distinct from those of the hypothalamic-hypophysial neurosecretory neurons, i.e., those stainable with aldehyde fuchsin presumed to be vasotocinergic and isotocinergic. The somatotropinergic and prolactinergic neuronal perikarya give rise to separate beaded axons which pass either ventroposteriorly into the infundibulum, terminating in the neurohypophysis, or ventro-laterally through the wall of the preoptic recess, terminating near the superficial capillary bed covering this part of the brain surface. Moreover, coarse dendrite-like processes of both kinds of immuno-reactive neurons extend towards, and end in, the third ventricle. Binding sites in the brain to antisera against hLH, hFSH, hTSH and anti-(1–24) ACTH IgG, all reactive in the pituitary, are not observed in the neurons confined to the preoptic area.Supported by the Danish Natural Sciences Research CouncilThe authors wish to thank Professor Dr K.G. Wingstrand, University of Copenhagen, Denmark, for placing two series of C. calabaricus at their disposal. They would also like to thank the National Institute of Arthritis, Metabolism and Digestive Diseases, Bethesda, USA, for the generous gift of antisera against the subunits of human LH, TSH and FSH, and likewise Dr L. Hummer, Glostrup Hospital, Copenhagen, Denmark, for the gift of the anti-(1-24)ACTH IgG     

Prolactin-producing Cells in Clupea harengus membras,Polypterus palmas and Calamoichthys calabaricus Studied by Immuno-histochemical Methods

The prolactin-producing cells in Clupea harengus membras, Polypterus palmas and Calamoichthys calabaricus have been localized by fluores-ceinlabelled antibodies to ovine prolactin. Pituitary sections were cut in a cryostat and both direct and indirect protein tracing methods have been used. As an additional method the paraffin embedding technique was carried out with Polypterus palmas. The prolactin-producing cells in Clupea harengus membras were localized to the follicle epithelium in the rostral pars distalis. In Polypterus palmas and Calamoichthys calabaricus the prolactin producing cells were scattered all over the pars distalis. A possible relationship between the erythrosinophilic prolactin cells and the epithelium cells in the buccohypophyseal canal is discussed.     

Scanning Electron Microscopy and X-ray Diffraction Studies of the Macular Crystals in the Chondrostean Fish Erpetoichthys calabaricus (Smith)

Morphologic and crystallographic studies of the otoliths of the reed-fish Erpetoichthys calabaricus showed (1) aragonite statoliths with a serrated surface, and (2) two populations of statoconia: one of numerous discoid biconvex crystals of vaterite, the other of pseudohexagonal crystals of aragonite. We suggest that the presence of two calcium carbonate polymorphs in the statoacoustic organs of this archaic fish may have an evolutionary, as well as a systematic and functional significance.     

Differential Effect of NMDA on Extracellular Serotonin in Rat Midbrain Raphe and Forebrain Sites

Abstract: The contribution of NMDA receptors to regulation of serotonin (5-HT) release was assessed by in vivo microdialysis in freely behaving rats. During infusion of NMDA (30, 100, and 300 µ M ) into the dorsal raphe nucleus (DRN), 5-HT was increased by ∼25, 100, and 280%, respectively. Competitive and noncompetitive NMDA-receptor antagonists blocked this effect on DRN 5-HT. Infusion of NMDA (300 µ M ) into the DRN also produced an 80% increase in extracellular 5-HT in the nucleus accumbens. During infusion of NMDA (100 and 300 µ M ) into the median raphe nucleus (MRN), 5-HT was increased by ∼15 and 80%, respectively. NMDA-receptor antagonists blocked this effect on MRN 5-HT. Infusion of NMDA into the MRN also produced a significant increase in hippocampal 5-HT. In contrast, infusion of NMDA into the nucleus accumbens, frontal cortex, or hippocampus produced small decreases in 5-HT in these forebrain sites. Taken together, these results suggest that NMDA receptors in the midbrain raphe, but not the forebrain, can have an excitatory influence on 5-HT neurons and, thus, produce increased 5-HT release in the forebrain. Furthermore, in comparison with the MRN, DRN 5-HT neurons were more sensitive to the excitatory effect of NMDA.     

Polypteridae (Actinopterygii: Cladistia) and DANA-SINEs insertions

SINE sequences are interspersed throughout virtually all eukaryotic genomes and greatly outnumber the other repetitive elements. These sequences are of increasing interest for phylogenetic studies because of their diagnostic power for establishing common ancestry among taxa, once properly characterized. We identified and characterized a peculiar family of composite tRNA-derived short interspersed SINEs, DANA-SINEs, associated with mutational activities in Danio rerio, in a group of species belonging to one of the most basal bony fish families, the Polypteridae, in order to investigate their own inner specific phylogenetic relationships. DANA sequences were identified, sequenced and then localized, by means of fluorescent in situ hybridization (FISH), in six Polypteridae species (Polypterus delhezi, P. ornatipinnis, P. palmas, P. buettikoferi P. senegalus and Erpetoichthys calabaricus) After cloning, the sequences obtained were aligned for phylogenetic analysis, comparing them with three Dipnoan lungfish species (Protopterus annectens, P. aethiopicus, Lepidosiren paradoxa), and Lethenteron reissneri (Petromyzontidae)was used as outgroup. The obtained overlapping MP, ML and NJ tree clustered together the species belonging to the two taxonomically different Osteichthyans groups: the Polypteridae, by one side, and the Protopteridae by the other, with the monotypic genus Erpetoichthys more distantly related to the Polypterus genus comprising three distinct groups: P. palmas and P. buettikoferi, P. delhezi and P. ornatipinnis and P. senegalus. In situ hybridization with DANA probes marked along the whole chromosome arms in the metaphases of all the Polypteridae species examined.     

Characteristics of the reparative regeneration of fins in the polypterid fish (Polypteridae,Actinopterygii)

Epimorphic regeneration of fins was studied in different ray-finned fishes (Actinopterygii), but species representing the phylogenetically basal lineages of the taxon have remained outside the attention of researchers. Information on the regenerative abilities of these groups is important both for understanding the evolutionary origins of the epimorphic regeneration phenomenon and for assessing the universality of regenerative potencies in Actinopterygii. Addressing this problem, we studied for the first time fin regeneration in two members of the archaic family Polypteridae: the ropefish (Erpetoichthys calabaricus) and the Senegal bichir (Polypterus senegalus). Along with the ability to regenerate the bony rays of fins, widespread among Actinopterygii, polypterids show the ability to effectively regenerate the endoskeleton and musculature of their fins. This unusual feature allows us to suggest polypterids as new model organisms for the study of the mechanisms of vertebrate limb regeneration.     

Characteristics of the reparative regeneration of fins in the polypterid fish (Polypteridae, Actinopterygii)

Epimorphic regeneration of fins was studied in different ray-finned fishes (Actinopterygii), but species representing the phylogenetically basal lineages of the taxon have remained outside the attention of researchers. Information on the regenerative abilities of these groups is important both for understanding the evolutionary origins of the epimorphic regeneration phenomenon and for assessing the universality of regenerative potencies in Actinopterygii. Addressing this problem, we studied for the first time fin regeneration in two members of the archaic family Polypteridae: the ropefish (Erpetoichthys calabaricus) and the Senegal bichir (Polypterus senegalus). Along with the ability to regenerate the bony rays of fins, widespread among Actinopterygii, polypterids show the ability to effectively regenerate the endoskeleton and musculature of their fins. This unusual feature allows us to suggest polypterids as new model organisms for the study of the mechanisms of vertebrate limb regeneration.     

Cytogenetic analysis in Polypterus ornatipinnis (Actinopterygii, Cladistia, Polypteridae) and 5S rDNA

Polypteridae is a family of archaic freshwater African fish that constitute an interesting subject for the study of the karyological evolution in vertebrates, on account of their primitive morphological characters and peculiar relationships with lower Osteichthyans. In this paper, a cytogenetic analysis on twenty specimens of both sexes of Polypterus ornatipinnis the ornate "bichir", coming from the Congo River basin, was performed by using both classical and molecular techniques. The karyotypic formula (2n=36; FN=72) was composed of 26 M+10 SM. The Alu I banding, performed to characterize heterochromatin in this species, was mainly centromeric. Both the chromosome location of the ribosomal 5S and 18S rRNA genes were examined by using Ag-NOR, classical C-banding, CMA(3) staining and FISH. CMA(3) marked all centromerical regions and showed the presence of two GC rich regions on the p arm of the chromosome pair n°1 and on the q arm of the pair n°14. Staining with Ag-NOR marked the only telomeric region of the chromosome n°1 p arm. After PCR, the 5S rDNA in this species was cloned, sequenced and analyzed. In the 665bp 5S rDNA sequence of P.ornatipinnis, a conserved 120bp gene region for the 5S rDNA was identified, followed by a non-transcribed variable spacer (NTS) which included simple repeats, microsatellites and a fragment of a non-LTR retrotransposon R-TEX. FISH with 5S rDNA marked the subtelomeric region of the q arm of the chromosome pair n°14, previously marked by CMA(3). FISH with 18S rDNA marked the telomeric region of the p arm of the pair n°1, previously marked both by Ag-NOR and CMA(3). The (GATA)(7) repeats marked the telomeric regions of all chromosome pairs, with the exclusion of the n°1, n°3 and n°14; hybridization with telomeric probes (TTAGGG)(n) showed signals at the end of all chromosomes. Karyotype evolution in Polypterus genus was finally discussed, including the new data obtained.     

The haemoglobins of Labeo umbratus (Smith) and Labeo capensis (Smith)

The haemoglobins of both L. umbratus and L. capensis separated into four components on polyacrylamide electrophoresis. The isoelectric points of these fractions were found to be 9.35, 6.89, 6.63 and 6.40. Organic nucleotide triphosphate concentration in the blood of L. capensis was found to be 56.72 ± 18.01 mg% and 58.72 ± 17.9 mg% in the case of L. umbratus . It is not possible to distinguish between L. umbratus and L. capensis purely on the basis of the haemoglobin electropherogram.     

The epithelium of the gastro-intestinal tract of Polypterus senegalus (Pisces:Brachiopterygii)

Light and electron microscopic studies revealed ciliation of the epithelium of the entire gastro-intestinal tract of Polypterus. Acidophil cells were found in the different regions of the alimentary canal, including its derivatives (the lungs and hepato-pancreatic ducts). Compared to other primitive forms and modern teleosts, the extreme fusion of the intestinal caeca in Polypterus, the ciliation and the overall dispersion of acidophil cells may represent a special organization inherited from a palaeoniscoid ancestor. Attention is also drawn to a possible channel of early evolution and function of the stomach diverticulum.