摘要:

AbstractHeart ratios (heart weight/body weight. ×100) have been obtained for freshly killed and preserved (10% formalin) specimens of the lampreysPetromyzon marinus, Lampetra fluviatilisandL. planeri.Values for comparable stages were significantly higher in the preserved material, probably as a result of retention and fixation of blood in the heart chambers. The regression slope for the logarithmic relationship between heart and body weights was close to one in all stages of the three species investigated. A marked increase was observed in the heart ratio during metamorphosis, apparently attributable to an increase in the number and density of myocardial fibres. Heart ratios in the lamprey were generally higher than for most other fishes, with values of 0.1 and 0.3 being obtained for example in the case of freshly killed ammocoete and sexually mature adult stages ofL. fluviatilis

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1974.tb00180.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe caudal end of the neural tube of the tunicateOikopleura, the cephalochordateBranchiostomaand newly hatched fry of the clupeiform teleostsClupea, EngraulisandSardinopswas studied by means of the electron microscope. InOikopleuraand the teleost larvae either Reissner's fiber or an amorphous mass of fiber substance leaks out of the neural tube into the surrounding tissue spaces. InBranchiostomathe disintegrated fiber material is apparently engulfed by the caudal ependymal cells. A relationship seems to exist between the degree of fiber disintegration within the neural tube and the degree of specialization of the caudal neural tube ependymal cells, the two extremes being represented byBranchiostomawith a “closed” Reissner's fiber system with highly specialized caudal ependymal cells and a teleost fry with the intact fiber leaving the neural tube between almost undifferentiated ependymal cells. These observations on lower chordates are in accordance with the hypothesis that Reissner's fiber acts as a detoxicator for the neural tube fl

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1974.tb00181.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe Diastoporidan colony consists of three zones: The marginal common bud, a narrow middle zone with erect peristomes and active polypides nourishing the whole colony, and a large central zone where the erect peristomes are detached, the secondary orifices thus formed are closed by terminal diaphragms, and the feeding polypides have degenerated. In many Diastoporidae the terminal closure is complete, but in several species the diaphragm is raised into a narrow, open tubule. In the latter type a dwarfed polypide with one tentacle only is regenerated: The autozooid is transformed into a heterozooid (“secondary nanozooid”), a unique phenomenon. Its function is unknown. The single tentacle of the “true nanozooids” ofDiplosolenperforms sweeping movements indicating a cleaning function. In twoPlagioeciaspecies “occasional nanozooids” were found, induced by disturbances of the colony growth. The function, if any,

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1974.tb00182.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractRadioiodine, given as the iodide, localized in protein‐bound form in the ectoderm ofHydra fuscaandH. littoralis.The radioiodine was shown by autoradiography to be: (1) diffusely distributed in the ectoderm over the gonads and (2) precisely localized in the apical cytoplasm of cnidoblasts that carry stenotele nematocysts. The meaning of such precise cellular localization of iodoprotein inHydraremains to be determine

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1974.tb00183.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractHypophysial tissue of mink (Mustela vison) embryos, newborn young and kits aged 1 day to 27 weeks was examined by light and electron microscopy. Among the embryos five different ontogenetic stages were distinguished. It appears that the primordium of the pituitary gland differentiates in early embryonic life. Several types of glandular cells containing variable amounts of granular material were recognizable by the time of birth. The role of the granular cells and the origin of the lumina in the pars distalis are speculated upon (in the Discussion).

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1974.tb00184.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractPituitary glands of intact and experimental adult females of mink, Mustela vison, were examined by electron microscopy. Conventional methods involving removal of endocrine glands (ovaries and adrenals), administration of radioactive isotope,131I, blocking agents (thiouracil and metopirone) and hormones (thyroxine, hydrocortisone, thyrotropin and luteinizing hormone releasing hormones) were employed. Five categories of granular cells were distinguished both by their ultrastructural characteristics and qualitative changes throughout the year and following different treatments. The cell types are described and their functions discussed. From conventional electron microscopical studies it proved difficult to draw any satisfactory conclusions about the gonadotropic cells. Further investigation by means of immunocytochemistry and radioimmunoassay techniques is required to determine, whether the presumptive gonadotropic cell type produces both FSH and ICSH or only one of these hormones.Morphologically two types of agranular cells were identified. Their morphological inter‐relationship and function are discussed briefl

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1974.tb00185.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe development and differentiation of the ventro‐caudal part of the diencephalon, the saccus infundibuli, has been examined in salmon,Salmo salarL., and in pike,Esox luciusL. In salmon, the saccus infundibuli becomes the saccus vasculosus; but in pike, this does not occur. The question of saccus vasculosus and part of the neural lobe of the tetrapod pituitary being homologous is dealt wit

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1974.tb00186.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe investigation is a light microscopical study of the structural development of the lamprey labyrinth, especially inLampetra fluviatilis.Some comparisons have been made withLampetra planeriandPetromyzon marinus.The following parts of the ear have been investigated; macula communis, its subdivision and innervation; the semicircular ducts and their ampullae; the two endolymphatic ducts and the ciliated chambers. Particular attention has been paid to the origin of these parts, the function of the ciliated chambers and the ampullae. On the basis of the present knowledge of the labyrinth an attempt has been made to see how the structural changes in it during the life cycle of the river lamprey harmonize with its way of living. Also comparative and phylogenetic aspects of the lamprey labyrinth have been made.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1974.tb00188.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY