Topographical relationships between catecholamine-and neuropeptide-containing fibers in the median eminence of the newt,Triturus alpestris

Summary Dopaminergic and peptidergic nerve fibers were simultaneously demonstrated with a double-labeling technique at the ultrastructural level. The first antibody, raised against tyrosine hydroxylase, was applied during the preembedding phase and visualized with the peroxidase method. The second antibody, raised against one of the peptides met-enkephalin, somatostatin or gonadotropin-releasing hormone (GnRH), was applied to the ultrathin sections and visualized with gold-labeled goat anti-rabbit IgG. The fibers of both categories were present in the zona externa of the median eminence, frequently contacting the basal lamina of the portal vessels. In addition, topographical relationships between different types of nerve fibers were observed in the perivascular areas, although there were no morphological signs of synaptic specializations. Using serial sections, it could be established that one GnRH-fiber contacted both a dopaminergic fiber and a fiber immunoreactive for met-enkephalin. The observations support earlier physiological data concerning the regulation of the hypothalamo-hypophyseal axis, with special emphasis on the release of neurohormones in the median eminence of the newt.     

中国小鲵科属、种分类变更的回顾

小鲵科为亚洲特有的有尾两栖动物,是现生有尾目10科中第三大科.中国是小鲵科动物属、种分布的主要区域,且研究其分类历史较久,学者较多,故导致学术观点差异较大.本文对中国小鲵科分类地位发生变更的部分属(巴鲵属Liua、拟小鲵属Pseudohynobius、肥鲵属Pachyhynobius)、种(秦巴巴鲵L. tsinpaensis、满洲小鲵Hynobius mantchuricus、豫南小鲵H. yunanicus、弱唇褶山溪鲵Batrachuperus cochranae和太白山溪鲵B. taibaiensis)的变更历史进行回顾,旨在为小鲵科动物的分类提供一个清晰的背景知识.     

Distribution of NCAM-180 and polysialic acid in the developing tectum mesencephali of the frog Discoglossus pictus and the salamander Pleurodeles waltl

The 180 kDa component of the neural cell adhesion molecule (NCAM-180), total NCAM (NCAM-total) and the polysialic acid modification of NCAM (PSA) show similar temporal and spatial regulation in the developing tecta of Pleurodeles waltl (salamander) and Discoglossus pictus (frog). Whereas NCAM-total is found throughout the tectal tissue on neurons and glia, NCAM-180 is only found on nonproliferating neurons and in fiber layers. PSA is expressed by a subset of NCAM-180-positive cells. Western blots show that there is little polysialylated NCAM-140 in the developing amphibian tectum. Regions unstained for PSA and NCAM-180 correspond precisely to the growth zones of the tectum. NCAM-180 and PSA are not present in tecta of early larvae. Staining intensity is strongest at midlarval stages for both antigens. At metamorphosis, PSA is strongly downregulated, whereas NCAM-180 is downregulated in juvenile animals. Both antigens are still present in fiber layers of adult animals. In dissociated tissue culture of the frog tectum, NCAM-180 is not present on astrocytes, but on neuronal cells. Expression is enhanced at cell contact sites, suggesting that NCAM-180 is involved in cell contact stabilization. This study shows that general features of temporal and spatial regulation of NCAM isoforms and PSA are highly conserved in frog and salamander tecta, despite large differences in the rate of cell migration and the degree of lamination in these homologous brain regions.     

Morphological,histochemical, and ultrastructural characterization of the accessory cells of neuromasts in the salamander Pleurodeles waltlii

Summary The ultrastructural and histochemical features of the accessory cells of the neuromast of the salamander P. waltlii have been examined. Three types of accessory cells, supporting, mantle, and basal, were found, but only the first 2 are considered in this article. Supporting cells characterized by a highly dilated endoplasmic reticulum occur among and surrounding sensory cells. Mantle cells, morphologically different from the supporting cells, surround the remainder of the neuromast. Both types of accessory cells exhibit histochemically different secretory materials. Our morphological results suggest that both accessory cells contribute to the formation of cupular material.     

An updated paleontological timetree of lissamphibians,with comments on the anatomy of Jurassic crown-group salamanders (Urodela)

We present an update of our time-calibrated supertree of extant and extinct lissamphibians (Marjanovi? D, Laurin M. 2007. Fossils, molecules, divergence times, and the origin of lissamphibians. Syst Biol 56(3):369–388) and of the divergence dates that can be inferred from it. The present version contains 319 extinct species or possible species of lissamphibians, compared to 223 previously. Discoveries of new fossiliferous sites, advances in phylogeny and recently obtained radiometric dates have offered opportunities to test our results, including the conclusion that the fossil record of Lissamphibia is dense enough to provide reliable calibration constraints for molecular divergence dating. By and large, the results are upheld. Some of the divergence dates we infer from the tree are up to 15 Ma younger than we previously published, some are up to 15 Ma older, some have had their range of uncertainty drastically reduced and the maximum age for the origin of Urodela (the salamander crown group) is no longer well constrained. The dermal bone plates in the gill region of the Jurassic urodeles Beiyanerpeton, Seminobatrachus and Chunerpeton and the grooves for the lateral line organ on the skull of the first require either unexpected reversals or several independent losses in other lissamphibians and indeed other urodeles.     

Cranial anatomy of the stem salamander Kokartus honorarius (Amphibia: Caudata) from the Middle Jurassic of Kyrgyzstan

The cranial anatomy of the stem salamander Kokartus honorarius, from the Middle Jurassic of Kyrgyzstan, is redescribed in detail on the basis of all available material using conventional methods and high‐resolution computed microtomography. In contrast to previous interpretations, the skull is characterized by posteriorly positioned external nostrils, the presence of an internarial fenestra between the premaxillae, the maxillae are not shortened, the overlapping of the frontal by the nasal and the parietal by the frontal, a dentate vomer, a dentate pterygoid with a long, strongly arcuate and anteromedially orientated anterior process, the absence of a fontanelle between frontals and pineal pit on the ventral surface of the frontals, and an inferred unique attachment of the adductor mandibulae internus to the lateral border and ventral ridge of the frontals and parietals. Kokartus is closely related to Karaurus and both these taxa constitute the monophyletic taxon Karauridae, which forms the sister group of crown‐group salamanders (Urodela). Karaurids were neotenic forms and neoteny was probably the ancestral life history strategy of salamanders. The morphological analysis of Kokartus supports the current phylogenetic hypothesis that Permian amphibamids (including branchiosaurids) are the closest relatives of salamanders amongst known non‐lissamphibian temnospondyls. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161 , 816–838.     

Immunocytochemical identification of growth hormote (GH) cells in the pituitary of three anuran species using an antiserum against purified bullforg GH

An antiserum was prepared against the recently purified bullfrog (bf) growth hormone (GH); it was applied to sections of brain and pituitary of three urodele (Ambystoma, Pleurodeles and Cynops) and three anuran (Xenopus, Bufo vulgaris and B. japonicus) species. No immunostaining was obtained in the urodele pituitary, being consistent with the results of immunoblot analysis of the pituitary homogenate. In the three anuran species, strong immunoreactivity was observed in GH cells that were concentrated in the posterodorsal region of the pars distalis. No GH-like immunoreactivity was detectable in the brain of any of the species. A comparison using adjacent sections stained with anti-bf prolactin (PRL) confirmed the anteroventral localization of PRL cells. Colocalization of GH and PRL was not apparent. These data suggest that the molecular structure of amphibian GHs is considerably different between anurans and urodeles. The antiserum used in the present work shows a high species specificity, recognizing only anuran GHs. In contrast anti-bfPRLlabeled PRL cells in all the amphibian species studied in the present work, suggesting that PRLs possess common amino acid sequences recognized by the anti-bfPRL.     

Evidence for a frontal-organ homologue in the pineal complex of the salamander,Hynobius dunni

The pineal complex of larval and adult salamanders, Hynobius dunni, was examined by light and scanning electron microscopy. This pineal complex displays an anterior and a posterior portion, both of which possess a lumen. The anterior lumen is small and closed, whereas the posterior lumen is in open communication with the third ventricle. Cell processes of the photoreceptor cells and microvilli of the supportive cells are visible in both lumina. The anterior part of the complex is formed by an independent, second evagination from the common pineal anlage; this process takes place immediately after hatching. The anterior body of the pineal complex of H. dunni appears to be homologous to the frontal organ of anurans.