Immunoreactive somatolactin cells in the pituitary of young,migrating, spawning and spent chinook salmon,Oncorhynchus tshawytscha |
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Authors: | Madeleine Olivereau Mariann Rand-Weaver |
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Institution: | (1) Laboratoire de Physiologie, Institut Océanographique, 195, rue Saint-Jacques, 75005 Paris, France;(2) Department of Biology and Biochemistry, Brunel University, Uxbridge, Middlesex, UB8 3PH, England |
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Abstract: | Immunocytochemical techniques using an antiserum to cod somatolactin (SL) demonstrated the presence of SL cells in the intermediate
lobe of the pituitary in Oncorhynchus tshawytscha. The cells were small in yearling fish. Two groups of maturing fish were studied. In the spring run salmon collected in April
and May during the upstream migration, the SL cells appeared stimulated. In September, during spawning, SL cell stimulation
was maximal with indices of hypertrophy and degranulation often more marked in females than in males. In the other group,
salmon of the fall run collected in the Pacific Ocean in August had well developed gonads, large gonadotropes and abundant
SL cells. In spawning salmon (September) the SL cells were stimulated, mainly in females. However, the final stimulation was
less intense than in spring run spawning fish. The SL cells were smaller, without evident granule release, but still abundant
in spent salmon of the fall run caught at the end of November. Various factors (time spent in rivers before spawning, starvation,
decalcification, stress, hypothalamic influences) were considered which might explain differences between spring and fall
run salmon. These observations suggest that SL may play a role in the control of gonadal maturation in chinook salmon as it
may also do in sockeye and chum salmon previously studied, and that SL cells may be sensitive to the ambient salinity. |
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Keywords: | somatolactin pituitary intermediate lobe pacific salmon Oncorhynchus tshawytscha migration reproductive cycle immunocytochemistry |
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