Abstract

Since 1974, sea-run Baltic salmon populations have been afflicted by an early life-stage mortality known as the M74 syndrome. The syndrome has been shown to be associated with a thiamine (vitamin B(1)) deficiency that causes neurological disturbances associated with necrotic brain cells. Treatment with thiamine may counteract development of M74. In this study, eyed eggs of sea-run Baltic salmon were given the thiamine antagonist oxythiamine and the commercial PCB-blend Clophen A50 by means of microinjection into the yolk sac. The aim was to study the effects of an experimentally induced thiamine deficiency and how it affected the biotransformation system CYP1A using the 7-ethoxyresorufin-O-deethylase (EROD) assay. After hatching, we attempted to reverse the deficiency in half of each exposure group by immersion in a thiamine solution and investigated its effect on survival and EROD-activity. Yolk-sac fry from groups of eggs that were injected with oxythiamine, either with or without Clophen A50, demonstrated a loss of coordination, lethargy, exophthalmia, and whitened liver followed by complete mortality (100%). Based on this and the time to death, between 124-193 posthatch degree-days (d degrees C), the effects of oxythiamine were comparable to those of M74-development, however, dissimilarities were also noted. Thiamine treatment of oxythiamine injected groups delayed mortalities that were reduced to between 64.8 and 91.8%. A dose and time-dependent induction of EROD-activity recorded for Clophen A50 groups was strongly suppressed in oxythiamine groups. Histopathological examination of oxythiamine groups at 103 and 182 d degrees C revealed reduced levels of hepatic glycogen, degenerating hepatocytes and a higher prevalence of necrotic brain cells, all of which are pathological features found in salmon yolk-sac fry affected by M74. Groups injected with Clophen A50 demonstrated no histopathological changes.

Published in

AMBIO: A Journal of the Human Environment
1999, Volume: 28, number: 1, pages: 55-66
Publisher: SPRINGER

SLU Authors

• Amcoff, Patric

  • Department of Pathology, Swedish University of Agricultural Sciences
    

• Lundström, Jenny

  • Department of Pathology, Swedish University of Agricultural Sciences
    

• Norrgren, Leif

  • Department of Pathology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Environmental Sciences


Permanent link to this page (URI)

https://res.slu.se/id/publ/43517