Seasonal changes in thyroidal status in the plaice, <i>Pleuronectes platessa</i> L.

Osborn, Robert H.; Simpson, T. H.

doi:10.1111/j.1095-8649.1978.tb04197.x

Cited by 37 publications

(7 citation statements)

References 15 publications

(16 reference statements)

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“…Whatever the mode of action, it has been shown that thyroid integrity is necessary and essential for normal growth. In plaice Pleuronectes platessa L., seasonal bimodality in the concentrations of both T 3 and T 4 has been observed, with maxima occuring in winter and summer (Osborn & Simpson, 1978). Turbot juveniles, previously held in constant environmental conditions for several months, showed little change in TH levels after exposure to very different situations (temperature 8-20 C; salinity 8-35 psu; photoperiod 6-24 h daylight; hypoxia 3·5-7·5 mg l 1 ; and ammonia exposure 0-20 mg l 1 ).…”

Section: Thyrotropic Axismentioning

confidence: 99%

Control of the somatic growth in turbot

Bœuf

Boujard

Ruyet

1999

Journal of Fish Biology

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The development of a recombinant turbot somatotropin (rtuGH) in Escherichia coli and an homologous antibody in rabbit has produced a sensitive and specific RIA allowing the measurement of blood levels and pituitary contents of tuGH and their responses to environmental change. Turbot IGF-1 (insulin growth factors) and IGF type 1 receptor (R) cDNA have also been cloned and sequenced. The deduced IGF-1 R primary sequence contains all the topological features characteristics of mammalian IGF-1 R and the turbot R appears highly conserved, compared to its mammalian counterpart, particularly within the catalytic domain. IGF-1 R mRNA polyadenylation status varies during development with polyadenylation occuring in oocytes and early stage larvae. It disappears in later stages and in adult somatic tissues, indicating that IGF-1 R mRNA undergoes complex post-transcriptional regulation. Thyroid hormones (TH, both T 3 and T 4 ), are also involved in growth control, but are less affected by environmental changes than GH, except in very extreme conditions. The thyroid stimulating hormone (TSH) -subunit cDNA fragment has also been cloned and sequenced. mRNA expression levels have been quantified under conditions where blood circulating TH were modified by dietary treatments or hormone supplementation. Specific growth rate in turbot is related to food intake and is doubled with a temperature increase from 8 to 20 C. Lipid storage by contrast was higher at low temperatures. Over a long time course, growth rate in turbot can be improved in brackish water (8-20 psu) but it cannot adapt to very low salinities. Photoperiod appears to have little influence on growth when feeding is unrestricted. Under intensive farming conditions, ammonia, the major nitrogen waste product in teleosts, may increase to levels that can reduce growth. Safe ambient levels for growth are <2-3 mg l 1 TAN above which a 10-20% decrease in growth was recorded within 3 months. Over 20 mg l 1 , feeding stops and no growth occurs. Turbot juveniles can cope efficiently with relatively large fluctuations in ambient oxygen, but major disruptions to physiological functions occur below 20% of air saturation. Under moderate hypoxia growth is reduced by 20% within 1·5 months. The primary response to hypoxia or ammonia accumulation is always a decrease of food intake. 1999 The Fisheries Society of the British Isles

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Section: Thyrotropic Axismentioning

confidence: 99%

Control of the somatic growth in turbot

Bœuf

Boujard

Ruyet

1999

Journal of Fish Biology

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“…The criteria in earlier use for assessment of thyroidal status and criticised by Osborn & Simpson (1978) are being replaced by assessments based on analytical determinations of the concentrations of thyroid hormones in the blood fluids bathing target tissues. Gas-liquid chromatography (Osborn & Simpson, unpublished) provides a chemically specific analytical procedure for all the iodoamino acids of blood plasma.…”

Section: Introductionmentioning

confidence: 99%

Seasonal and diurnal rhythms of thyroidal status in the rainbow trout, Salmo gairdneri Richardson

Osborn

Simpson

Youngson

1978

Journal of Fish Biology

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The concentrations of thyroxine (T4) and triiodothyronine (T3) in the blood plasma of rainbow trout (Sulmo gairdneri Richardson) at intervals throughout the year have been measured by a chemically specific gas-liquid chromatographic (GLC) method. Mean hormone levels showed a seasonal variation, maximal levels of both hormones occurring in winter and minimal concentrations in mid summer. An apparent secondary maximum in mean T4 and T, concentrations was observed in spring. (T4)/(T8) ratios have been found to be highest in winter and lowest in summer. A radioimmunoassay procedure, validated by GLC analyses, revealed the presence of a diurnal rhythm in serum T4 levels of trout sampled in September and in April.

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“…Being the pro-hormone for T,, it is perhaps not surprising that T, levels varied greatly, while levels of the active hormone remained within narrower and more strictly-regulated levels (Eales and Brown 1993). While it is difficult to establish a direct action of a hormone from correlation studies like this one, it is clear that male striped bass are in an euthyroid state during the spermiation pe-nod, with plasma T4 and T, reaching levels that are three-to 10-fold higher than reported in other fishes (Osborn and Simpson 1978;MacKenzie et al 1989;Soyano et al 1993). Wild striped bass during the spermiation period had somewhat higher levels of T, compared to captive males, ranging between 23 and 33 n g / d (Mylonas et al 1997c), pointing to the possibility that culture conditions may influence thyroid status, as well as pituitary GtH I1 release.…”

Section: Discussionmentioning

confidence: 69%

Hormone Profiles of Captive Striped Bass Morone saxatilis During Spermiation, and Long‐Term Enhancement of Milt Production

Mylonas

Zohar

Woods

et al. 1998

J World Aquaculture Soc

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Abstract— Plasma profiles of reproductive and thyroid hormones were studied in captive striped bass Morone saxatilis during an 11‐wk period encompassing the spawning season, and the effect of a sustained‐release gonadotropin‐releasing hormone agonist (GnRHa)‐delivery system (GnRHa‐implant) on milt production was evaluated. The highest percentage of spermiating fish was observed between mid‐April and mid‐May, and mean total expressible milt ranged from 3.5 to 6.0 mL/kg. Plasma gonadotropin II (GtH II) increased significantly, though inconsistently, during the spermiation period, whereas testosterone and 11‐ketotestosterone levels declined continually. Plasma 17,20β‐dihydroxy‐4‐pregnen‐3‐one and 17,20β,21‐dihydroxy‐4‐pregnen‐3‐one remained low and unchanged during the peak of the spermiation period, while thyroid hormones were high and fluctuated without exhibiting a trend consistent with spermiation. The observed endocrine profiles suggest that captivity can diminish plasma GtH II and triiodothyronine levels in striped bass. Transfer of spermiating males from large holding tanks to small spawning tanks reduced total expressible milt after 14 d, but treatment with a GnRHa‐implant restored milt volume, presumably due to the prolonged elevation of plasma GnRHa and GtH II induced by the GnRHa‐implant. Also, treatment with the GnRHa‐implant induced a two‐ to four‐fold elevation of expressible milt for at least 20 d compared to control fish, while resulting in only a 5 to 15% decrease in sperm density. It appears that captivity and hatchery operations can diminish milt production in striped bass, and that GnRHa‐delivery systems, via sustained elevation of plasma GtH II, can induce long‐term enhancement in milt volume without affecting sperm density greatly.

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Seasonal changes in thyroidal status in the plaice, Pleuronectes platessa L.

Cited by 37 publications

References 15 publications

Control of the somatic growth in turbot

Control of the somatic growth in turbot

Seasonal and diurnal rhythms of thyroidal status in the rainbow trout, Salmo gairdneri Richardson

Hormone Profiles of Captive Striped Bass Morone saxatilis During Spermiation, and Long‐Term Enhancement of Milt Production

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