ISSN:
1432-0878
Keywords:
Aesthetasc
;
Adenosine monophosphate
;
Cerium phosphate
;
Cytochemistry
;
Ectonucleotidase
;
Olfactory system
;
Phosphatase
;
Panulirus argus (Crustacea)
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Previous electrophysiological studies have shown that the olfactory organ (antennule) of the spiny lobster, Panulirus argus, has external chemoreceptors, which are selectively stimulated by adenosine 5′-monophosphate (AMP) when present in seawater. Subsequent biochemical investigations revealed that AMP can be rapidly dephosphorylated by 5′-ectonucleotidase/phosphatase activity associated with the olfactory sensilla (aesthetascs). In this study the deposition of cerium phosphate was used to examine the ultrastructural distribution of 5′-ectonucleotidase/phosphatase activity in aesthetascs. Utilizing AMP as substrate, we found dephosphorylating activity to be associated with the outer membranes of both dendrites and auxiliary cells. Moreover, this activity was specifically localized to a narrow band that approximately corresponds to the transitional zone where dendrites develop cilia and branch extensively to form the outer dendritic segments. A similar distribution of the cerium phosphate reaction product was found when β-glycerol phosphate was substituted for AMP. The alkaline-phosphatase inhibitor, levamisole, had no apparent effect on the deposition of reaction product when either AMP or β-glycerol phosphate was used as substrate. The ectoenzymatic activity in the transitional zone may be of importance in clearing exogenous chemoexcitatory nucleotides from this region.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00398087
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