摘要:

AbstractBy means of histochemical and pharmacological analysis it is shown that acetylcholine has an inhibitive effect on regeneration in the planariaDugesia tigrina.It seems that serotonin and adrenaline on the one hand, and acetylcholine on the other hand, play a role in a mechanism of regulation in which the latter plays a role in a negative feed‐back proces

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1976.tb00206.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractA light microscopic study of the endocrine pancreas in some myxinoids has revealed a striking difference in the occurrence of follicles. Islet tissue follicles are regularly occurring and also abundant inMyxine glutinosa, but are sparse or absent inEptatretus burgeriandEptatretus stouti.Whether this is caused by a decreased need for insulin inMyxine glutinosais discussed but remains an open question.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1976.tb00207.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractRegional variations of cone density, cone types and cone mosaic were investigated by light microscopy in yolk sac fry, parr and adults of salmon (Salmo salar) and trout (Salmo trutta trutta) and related to the feeding habits of different stages. The retinal organization of the two species is similar, as are their feeding habits. In parr and adults of both species a region with high cone density was found in the ventro‐temporal part of the retina. The lowest values of cone density were found centrally in the dorsal half of the retina. An increase in cone density towards theora serratawas noted in all retinae investigated. There is a good agreement between the density distribution of the cones in parr of salmon and trout and their feeding habits. The parr feed to a great extent on the invertebrate drift. Facing the current, the parr search the water region in front and above themselves for food organisms, thereby probably making use of the ventro‐temporal area of high cone density. The connection between the cone density distribution and the feeding habits is less clear in adult salmon and trout, but the high cone density region is probably used when they feed on surface organisms and schooling prey. The ecological significance of cone types and cone mosaics is discussed.During growth there was a change of the cone mosaic from a regular square pattern in the fry towards a less regular square or row pattern in the adults. The position of regions with high and low cone density did not change during development in each species and had a similar distribution in the two species. On the other hand, the range of cone density values becomes relatively greater as the animal grows older. The cone density distribution seems to be more homogeneous in parr than in adults. Differences in the relative density distribution of the cones are influenced by recruitment at the retinal periphery and by spreading out of existing cells. In addition to theora serrata, mitoses were also observed in more central parts of the retina having well‐differentiated receptors and a cone mosaic. Mitoses were noted in all three nuclear layers but were most frequent in the outer nuclear layer, in which the resulting cells probably differentiate into rods. Undifferentiated zones similar to the peripheral growth zone of the retina were found on both sides of the falciform process in fry. In parr and adults an undifferentiated zone persisted only on the temporal side. It probably contributes to the high cone density in the ventro‐temporal part of the retina by a delivery of ne

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1976.tb00208.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe hair cell polarization of the various sensory epithelia in the inner ear was examined in two species of flatfish, the Plaice (Pleuronectes platessa) and the Dab (Limanda limanda). The hair cells in themacula utriculiare polarized in the pattern usually seen for this macula in vertebrates. In themacula sacculiandmacula lagenaethe hair cell polarization is different from that hitherto described from bony fishes and other vertebrates. The polarization seen in these maculae in the flatfish explains their ability to sense movements in all directions, which is necessary if these sensory areas are the most important inner ear organs in the regulation of postural orientation.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1976.tb00209.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractEndocrine cells of so‐called basal‐granulated‐open type in the intestinal epithelium of a cyclostome, the Atlantic hagfish (Myxine glutinosa), are characterized ultrastructurally and fluorescence microscopically. These cells regularly extend from the basal lamina to the gut lumen, ending in an apical process with microvilli and a filamentous surface coat. Fasting results in an accumulation of secretion granules in all cytoplasmic portions, except for the terminal web area. A similarity is recorded between the distribution of secretion granules and the finely granular fluorescamine‐induced fluorescence, suggesting that the fluorescence is associated to some component(s) of the secretory granules. Granule release may take place at the base after an adequate stimulus (presence of food?) at the luminal portion of the cells.The formaldehyde condensation technique shows that insulin‐containing hagfish islet parenchymal cells, but not intestinal endocrine cells, store dopamine after intestinal supply of the amine precursor. Acidification of formaldehyde vapour‐fixed intestinal epithelium induces fluorescence in the granules of zymogen cells but not of endocrine cells, indicating a low concentration of tryptophyl‐peptide(s) in the secretory granules of hagfish intestinal en

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1976.tb00210.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe fine structure of the cuticle in the archiannelidsPolygordius, Protodrilus, Trilobodrilus, andDiurodrilusis described.PolygordiusandProtodrilusare unique with respect to the filiform microvilli penetrating through the cuticle. Basically all forms conform to the most common type of cuticular structure in the Annelida: a fibrous matrix of varying complexity penetrated by micro‐villar‐like cell processes. Following the ideas expressed by Lyons (1970), a hypothesis on the evolution of the cuticle within the vermiform Spiralia (e.g. Turbellaria, Nemertea, Annelida) is proposed. New data on interstitial Turbellaria and other new forms of interstitial worms suggest a morphological and functional sequence from the multiciliated epidermis of Turbellaria to the cuticularized hypodermis of Annel

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1976.tb00211.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY