ISSN:
1432-0878
Schlagwort(e):
Infracerebral complex
;
Polychaeta, Nereidae
;
Neurosecretion
;
Fine structure
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Medizin
Notizen:
Summary The infracerebral complex consists of: (a) two types of ependymoid infracerebral cells located on the ventral surface of the brain, adjacent to a coelomic sinus and blood vessels; (b) a noncellular stroma, the neural lamella, which separates the infracerebral cells from cerebral nervous tissue; (c) two types of cerebral neurosecretory endings (one with many mitochondria) which abut on the neural lamella opposite from the infracerebral cells. The infracerebral a cells become columnar and develop abundant apical caveolae and Golgi elements in older worms. The infracerebral b cells, filled with electron opaque granules, resemble neurosecretory cells; their axon-like processes contain microtubules and make synaptoid contacts with the neural lamella. Both cell types are present in young worms of about 10 segments but the b cells, relatively abundant in younger worms, are outnumbered by a cells in mature individuals. However, during reproductive development neither a nor b cells display any structural changes which would indicate that they represent glandular tissue. Basal processes originating both from a and b cells form entanglements which become progressively more intricate during maturation. Neurosecretory endings are present in 10-segment worms and become very numerous in mature worms but at no time do they penetrate the neural lamella and contact the infracerebral cells. It is unlikely that the infracerebral cells per se constitute a gland but they are strategically located to influence the release of hormones from neurosecretory endings.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00219671
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