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Anders Kiessling - One of the best experts on this subject based on the ideXlab platform.

  • Postprandial changes in plasma free amino acid levels obtained simultaneously from the hepatic portal vein and the Dorsal Aorta in rainbow trout (Oncorhynchus mykiss).
    The Journal of experimental biology, 2020
    Co-Authors: Anders Karlsson, Erika J. Eliason, Liv Torunn Mydland, Anthony P. Farrell, Anders Kiessling
    Abstract:

    For the first time, changes in plasma concentrations of free amino acid (AA) and their metabolites were followed simultaneously in pre- and post-hepatic blood following a single meal in non-anaesthetized and free-swimming fish. Rainbow trout (Oncorhynchus mykiss), kept in 10 degrees C water and fitted with cannulae in the hepatic portal vein (HPV) and the Dorsal Aorta (DA), were force-fed 1% of their body mass and blood samples were taken from both cannulae at 0, 3, 6, 12, 24 and 48 h postprandially to follow the free AA profile. Almost all free AAs increased rapidly within the first 3 h and only a few free AAs did not change significantly over time. By 6 h, the total free AA concentration had peaked in blood taken from both the DA (7107+/-369 nmol ml(-1)) and HPV (9999+/-572 nmol ml(-1)). However, individual free AAs showed three main profiles beyond this time: for type I, a peak concentration occurred only at 6 h; for type II, there was a more gradual rise in concentration to a peak at 24 h; and for type III there were two peaks, at 6 h and 24 h. All free AAs returned to or were lower than baseline levels within 48 h, with the exception of threonine and proline. The total free AA concentrations were consistently higher (P

  • effect of nutritional status and sampling intensity on recovery after Dorsal Aorta cannulation in free swimming atlantic salmon salmo salar l
    Fish Physiology and Biochemistry, 2012
    Co-Authors: B Djordjevic, Anders Kiessling, T Kristensen, Oyvind Overli, Bjorn Olav Rosseland
    Abstract:

    Recovery from implantation of a cannula in the Dorsal Aorta (DA) of Atlantic salmon (Salmo salar) was studied in relation to nutritional status and sampling intensity. The incentive for the study was the inconsistency between published reports and our own experience of recovery and longevity of fish exposed to this protocol. In two studies using starved fish, blood (0.3 ml) was sampled 0, 1 and 24 h after DA-cannulation, and thereafter at 48 and 72 h and thereafter once weekly for four weeks. In a third study using fed fish, four consecutive samples (0, 3, 6 and 12 h after a meal) were obtained twice a week over a four-week period. All fish displayed a sharp increase in pCO2 and haematocrit (Hct) during surgery, followed by a marked raise in cortisol, glucose, sodium and potassium (1 h). pCO2, pH and Hct approached baseline levels as early as the 1 h post-surgery sample, while this was not the case for cortisol and electrolytes before the 24 h post-surgery sample. Glucose did not display any significant changes post surgery. From then on, all variables displayed minor but non-significant (P > 0.05) changes indicating a steady state close to baseline values for unstressed fish. This pattern was independent of sampling procedure, i.e. repeated single or multiple samples and thus volume of blood removed. Nutritional status (fed vs. starved) did not affect post-surgical recovery pattern. Only K+ and Hct displayed consistent and significant post-prandial patterns. We found marked differences between baseline level of cannulated fish and uncannulated control fish, in pH, K+ and Hct indicating that cannulation may be the preferred method to obtain representative resting values in fish.

  • pharmacokinetics plasma cortisol and effectiveness of benzocaine ms 222 and isoeugenol measured in individual Dorsal Aorta cannulated atlantic salmon salmo salar following bath administration
    Aquaculture, 2009
    Co-Authors: Anders Kiessling, David Johansson, Inger Hilde Zahl, Ole Bent Samuelsen
    Abstract:

    Abstract This study reports data on plasma clearance kinetics of anaesthetics concomitant with physiological stress responses in Dorsal Aorta (DA) cannulated Atlantic salmon ( Salmo salar ) both with and without influence of artificial gill ventilation during recovery from anaesthesia. For MS-222 the plasma data were best described by a one-compartment open model and first-order elimination, whereas a two-compartment open model and first-order elimination best described the plasma data for benzocaine and isoeugenol. The compartment analysis was not affected by ventilation. Distribution volumes from 1.99 l kg − 1 (isoeugenol) to 3.98 (MS-222) and 5.12 l kg − 1 (benzocaine) showed a moderate to large distribution of the drugs from plasma to tissues. MS-222 was eliminated most rapidly, with an elimination half-life of 1.7 min, while elimination half-lives of 18.7 and 25 min were calculated for benzocaine and isoeugenol, respectively. Ventilation following exposure increased the elimination rate. Anaesthetics were administered in two steps with an initial 10 min of sedation by a low dosage (1 × 10 − 1 of full dosage) before moving the fish to a full strength anaesthesia bath. All anaesthetics used caused a marked increase in plasma cortisol, apparent already at the end of the exposure. Marked differences were noted between anaesthetics, with time to regain consciousness and responsiveness to external stimuli paralleling the plasma clearance of the anaesthetic. Recovery from anaesthesia was accompanied by higher respiration frequency. Recovery was always faster when the fish was given artificial gill ventilation.

  • Postprandial changes in plasma free amino acid levels obtained simultaneously from the hepatic portal vein and the Dorsal Aorta in rainbow trout (Oncorhynchus mykiss).
    The Journal of Experimental Biology, 2006
    Co-Authors: Anders Karlsson, Erika J. Eliason, Liv Torunn Mydland, Anthony P. Farrell, Anders Kiessling
    Abstract:

    SUMMARY For the first time, changes in plasma concentrations of free amino acid (AA) and their metabolites were followed simultaneously in pre- and post-hepatic blood following a single meal in non-anaesthetized and free-swimming fish. Rainbow trout ( Oncorhynchus mykiss ), kept in 10°C water and fitted with cannulae in the hepatic portal vein (HPV) and the Dorsal Aorta (DA), were force-fed 1% of their body mass and blood samples were taken from both cannulae at 0, 3, 6, 12, 24 and 48 h postprandially to follow the free AA profile. Almost all free AAs increased rapidly within the first 3 h and only a few free AAs did not change significantly over time. By 6 h, the total free AA concentration had peaked in blood taken from both the DA (7107±369 nmol ml -1 ) and HPV (9999±572 nmol ml -1 ). However, individual free AAs showed three main profiles beyond this time: for type I, a peak concentration occurred only at 6 h; for type II, there was a more gradual rise in concentration to a peak at 24 h; and for type III there were two peaks, at 6 h and 24 h. All free AAs returned to or were lower than baseline levels within 48 h, with the exception of threonine and proline. The total free AA concentrations were consistently higher ( P

  • postprandial changes in plasma free amino acid levels obtained simultaneously from the hepatic portal vein and the Dorsal Aorta in rainbow trout oncorhynchus mykiss
    The Journal of Experimental Biology, 2006
    Co-Authors: Anders Karlsson, Erika J. Eliason, Liv Torunn Mydland, Anthony P. Farrell, Anders Kiessling
    Abstract:

    SUMMARY For the first time, changes in plasma concentrations of free amino acid (AA) and their metabolites were followed simultaneously in pre- and post-hepatic blood following a single meal in non-anaesthetized and free-swimming fish. Rainbow trout ( Oncorhynchus mykiss ), kept in 10°C water and fitted with cannulae in the hepatic portal vein (HPV) and the Dorsal Aorta (DA), were force-fed 1% of their body mass and blood samples were taken from both cannulae at 0, 3, 6, 12, 24 and 48 h postprandially to follow the free AA profile. Almost all free AAs increased rapidly within the first 3 h and only a few free AAs did not change significantly over time. By 6 h, the total free AA concentration had peaked in blood taken from both the DA (7107±369 nmol ml -1 ) and HPV (9999±572 nmol ml -1 ). However, individual free AAs showed three main profiles beyond this time: for type I, a peak concentration occurred only at 6 h; for type II, there was a more gradual rise in concentration to a peak at 24 h; and for type III there were two peaks, at 6 h and 24 h. All free AAs returned to or were lower than baseline levels within 48 h, with the exception of threonine and proline. The total free AA concentrations were consistently higher ( P <0.05) in the HPV than in the DA at 3 h, 6 h, 12 h and 24 h. Our data provide clear evidence that, during the first pass through the liver, hepatic modification altered individual free AA concentrations as indicated by variable ratios among the simultaneous blood samples. Furthermore, the elevation of ammonium and urea in the HPV indicates intestinal catabolism of ingested free AA before release into the HPV. In conclusion, the dual HPV and DA cannulation shows promise as a useful technique for qualitative and quantitative investigations of absorption and turnover of nutrients, especially if the measurements can be combined with reliable estimates of blood flow and labelled substances.

Yoshiko Takahashi - One of the best experts on this subject based on the ideXlab platform.

  • sympatho adrenal morphogenesis regulated by the Dorsal Aorta
    Mechanisms of Development, 2015
    Co-Authors: Daisuke Saito, Yoshiko Takahashi
    Abstract:

    The autonomic nervous system, composed of sympathetic- and para-sympathetic neurons, plays essential roles in a variety of physiological functions including homeostasis and responses to external stimuli. We here present an overview of recent findings concerning how the sympathetic nervous system is formed during the early development, paying particular attention to the morphogenesis of those tissues derived from migrating neural crest cells. Neural crest cells, originally multipotent, are progressively specified to sympathetic ganglia neurons and adrenomedullary cells during their migration through the body. Importantly, the Dorsal Aorta, the first-forming blood vessel, acts as a signaling center for their migration and differentiation. BMP signals emanating from the Dorsal Aorta are essential for establishing environmental cues that directly act on the migrating cells. The mechanisms underlying these early neuro-vascular interactions provide insights into understanding diseases caused by malfunctions and malformations of the autonomic nervous system.

  • the Dorsal Aorta initiates a molecular cascade that instructs sympatho adrenal specification
    Science, 2012
    Co-Authors: Daisuke Saito, Yoshiko Takahashi, Yuta Takase, Hidetaka Murai
    Abstract:

    The autonomic nervous system, which includes the sympathetic neurons and adrenal medulla, originates from the neural crest. Combining avian blood vessel–specific gene manipulation and mouse genetics, we addressed a long-standing question of how neural crest cells (NCCs) generate sympathetic and medullary lineages during embryogenesis. We found that the Dorsal Aorta acts as a morphogenetic signaling center that coordinates NCC migration and cell lineage segregation. Bone morphogenetic proteins (BMPs) produced by the Dorsal Aorta are critical for the production of the chemokine stromal cell–derived factor–1 (SDF -1) and Neuregulin 1 in the para-aortic region, which act as chemoattractants for early migration. Later, BMP signaling is directly involved in the sympatho-medullary segregation. This study provides insights into the complex developmental signaling cascade that instructs one of the earliest events of neurovascular interactions guiding embryonic development.

  • p90 reciprocal interactions between neural crest cells and Dorsal Aorta in developing embryos
    Differentiation, 2010
    Co-Authors: Yuta Takase, Yosuke Mukoyama, Yoshiko Takahashi
    Abstract:

    When neural- and vascular networks are formed and patterned in the body, they appear to influence each other. However, cellular and molecular mechanisms underlying these interactions remain unknown. We have recently found that the developing Dorsal Aorta (DA), the first-forming-blood vessel in embryos, is accompanied with neural crest cells (NCCs), the progenitor of peripheral nervous system. A subpopulation of NCCs migrates toward the DA, and differentiates into sympathetic ganglia. After the migration, these NCCs accumulate near the DA at a specific site from which the thin blood vessel, called intersegmental vessel (ISV), sprouts. To understand whether the NCCs at the ISV-sprouting site instruct the formation of these vessels, we have surgically ablated NCCs using chicken embryos. Without NCCs, ISVs fail to form correctly, suggesting that NCCs are required for the ISV formation. The instruction by NCCs on the DA/ISV appears to act for a short period of time since in PhoxB2 knockout mice, where NCCs migrate correctly but fail to be maintained around DA, the ISVs formation is unaffected. Toward the understanding of the molecular nature of the interactions between NCCs and DA/ISV, we have developed novel methods with which early blood vessels are directly manipulated with exogenous genes, by modifying the techniques of DNA in ovo electroporation. We will discuss intimate relationships between NCCs and developing blood vessels, which appear to be important for the formation of neuro-vascular networks.

  • Notch signal is sufficient to direct an endothelial conversion from non-endothelial somitic cells conveyed to the aortic region by CXCR4
    Developmental Biology, 2009
    Co-Authors: Emi Ohata, Yuki Sato, Daisuke Saito, Ryosuke Tadokoro, Yoshiko Takahashi
    Abstract:

    Abstract During the early formation of the Dorsal Aorta, the first-forming embryonic vessel in amniotes, a subset of somitic cells selected as presumptive angioblasts, migrates toward the Dorsal Aorta, where they eventually differentiate into endothelial cells. We have recently shown that these processes are controlled by Notch signals (Sato, Y., Watanabe, T., Saito, D., Takahashi, T., Yoshida, S., Kohyama, J., Ohata, E., Okano, H., and Takahashi, Y., 2008. Notch mediates the segmental specification of angioblasts in somites and their directed migration toward the Dorsal Aorta in avian embryos. Dev. Cell 14, 890–901.). Here, we studied a possible link between Notch and chemokine signals, SDF1/CXCR4, the latter found to be dominantly expressed in developing Aorta/somites. Although CXCR4 overexpression caused a directed migration of somitic cells to the aortic region in a manner similar to Notch, no positive epistatic relationships between Notch and SDF1/CXCR4 were detected. After reaching the aortic region, the CXCR4- electroporated cells exhibited no endothelial character. Importantly, however, once provided with Notch activity, they could successfully be incorporated into developing vessels as endothelial cells. These findings were obtained combining the tetracycline-inducible gene expression method with the transposon-mediated stable gene transfer technique. We conclude that Notch activation is sufficient to direct naive mesenchymal cells to differentiate into endothelial cells once the cells are conveyed to the aortic region.

  • notch mediates the segmental specification of angioblasts in somites and their directed migration toward the Dorsal Aorta in avian embryos
    Developmental Cell, 2008
    Co-Authors: Yuki Sato, Daisuke Saito, Tadayoshi Watanabe, Teruaki Takahashi, Shosei Yoshida, Jun Kohyama, Emi Ohata, Hideyuki Okano, Yoshiko Takahashi
    Abstract:

    We studied, using avian embryos, mechanisms underlying the three-dimensional assembly of the Dorsal Aorta, the first-forming embryonic vessel in amniotes. This vessel originates from two distinct cell populations, the splanchnic and somitic mesoderms. We have unveiled a role for Notch signaling in the somitic contribution. Upon activation of Notch signaling, a subpopulation of cells in the posterior half of individual somites migrates ventrally toward the primary Dorsal Aorta of splanchnic origin. After reaching the primary Aorta, these somitic cells differentiate into the definitive aortic endothelial cells. This Notch-induced ventral migration is mediated by EphrinB2 and by an attractant action of the primary Aorta. Furthermore, long-term chasing of cells by transposon-mediated gene transfer reveals that the segmentally provided endothelial cells of somitic origin in the Dorsal Aorta ultimately populate the entire region of the vessel. We demonstrate the molecular and cellular mechanisms underlying the formation of embryonic blood vessels from mesenchymal cells.

Roger Patient - One of the best experts on this subject based on the ideXlab platform.

  • FGF signalling restricts haematopoietic stem cell specification via modulation of the BMP pathway
    Nature Communications, 2014
    Co-Authors: Claire Pouget, David Traver, Tessa Peterkin, Filipa Costa Simões, Roger Patient
    Abstract:

    BMP signalling is required for the emergence of haematopoietic stem cells (HSCs) from the zebrafish Dorsal Aorta. Here the authors show that FGF signalling negatively regulates HSC emergence by downregulating BMP activity in the zebrafish subaortic mesenchyme and upregulating the expression of BMP antagonists in the somite.

  • hedgehog and bmp polarize hematopoietic stem cell emergence in the zebrafish Dorsal Aorta
    Developmental Cell, 2009
    Co-Authors: Robert N Wilkinson, Claire Pouget, Martin Gering, Angela J Russell, Stephen G Davies, David Kimelman, Roger Patient
    Abstract:

    Hematopoietic stem cells (HSCs) are first detected in the floor of the embryonic Dorsal Aorta (DA), and we investigate the signals that induce the HSC program there. We show that while continued Hedgehog (Hh) signaling from the overlying midline structures maintains the arterial program characteristic of the DA roof, a ventral Bmp4 signal induces the blood stem cell program in the DA floor. This patterning of the DA by Hh and Bmp is the mirror image of that in the neural tube, with Hh favoring Dorsal rather than ventral cell types, and Bmp favoring ventral rather than Dorsal. With the majority of current data supporting a model whereby HSCs derive from arterial endothelium, our data identify the signal driving this conversion. These findings are important for the study of the production of HSCs from embryonic stem cells and establish a paradigm for the development of adult stem cells.

  • scl is required for Dorsal Aorta as well as blood formation in zebrafish embryos
    Blood, 2005
    Co-Authors: Lucy J Patterson, Martin Gering, Roger Patient
    Abstract:

    Blood and endothelial cells arise in close association in developing embryos, possibly from a shared precursor, the hemangioblast, or as hemogenic endothelium. The transcription factor, Scl/Tal1 (stem cell leukemia protein), is essential for hematopoiesis but thought to be required only for remodeling of endothelium in mouse embryos. By contrast, it has been implicated in hemangioblast formation in embryoid bodies. To resolve the role of scl in endothelial development, we knocked down its synthesis in zebrafish embryos where early precursors and later phenotypes can be more easily monitored. With respect to blood, the zebrafish morphants phenocopied the mouse knockout and positioned scl in the genetic hierarchy. Importantly, endothelial development was also clearly disrupted. Dorsal Aorta formation was substantially compromised and gene expression in the posterior cardinal vein was abnormal. We conclude that scl is especially critical for the development of arteries where adult hematopoietic stem cells emerge, implicating scl in the formation of hemogenic endothelium.

Giulio Cossu - One of the best experts on this subject based on the ideXlab platform.

  • noggin recruits mesoderm progenitors from the Dorsal Aorta to a skeletal myogenic fate
    Developmental Biology, 2012
    Co-Authors: Gonzalo Ugarte, Ornella Cappellari, Laura Perani, Anna Pistocchi, Giulio Cossu
    Abstract:

    Embryonic mesoangioblasts are the in vitro counterpart of vessel-associated progenitors, able to differentiate into different mesoderm cell types. To investigate signals recruiting these progenitors to a skeletal myogenic fate, we developed an in vitro assay, based upon co-culture of E11.5 Dorsal Aorta (from MLC3 F-nLacZ transgenic embryos, expressing nuclear beta galactosidase only in striated muscle) with differentiating C2C12 or primary myoblasts. Under these conditions muscle differentiation from cells originating from the vessel can be quantified by counting the number of beta gal + nuclei. Results indicated that Noggin (but not Follistatin, Chordin or Gremlin) stimulates while BMP2/4 inhibits myogenesis from Dorsal Aorta progenitors; neutralizing antibodies and shRNA greatly reduce these effects. In contrast, TGF-β1, VEGF, Wnt7A, Wnt3A, bFGF, PDGF-BB and IGF1 have no effect. Sorting experiments indicated that the majority of these myogenic progenitors express the pericyte marker NG2. Moreover they are abundant in the thoracic segment at E10.5 and in the iliac bifurcation at E11.5 suggesting the occurrence of a cranio-caudal wave of competent cells along the Aorta. BMP2 is expressed in the Dorsal Aorta and Noggin in newly formed muscle fibers suggesting that these two tissues compete to recruit mesoderm cells to a myogenic or to a perithelial fate in the developing fetal muscle.

  • smooth muscle of the Dorsal Aorta shares a common clonal origin with skeletal muscle of the myotome
    Development, 2006
    Co-Authors: Milan Esner, Giulio Cossu, Sigolene M Meilhac, Frederic Relaix, Jeanfrancois Nicolas, ME Buckingham
    Abstract:

    We show that cells of the Dorsal Aorta, an early blood vessel, and of the myotome, the first skeletal muscle to form within the somite, derive from a common progenitor in the mouse embryo. This conclusion is based on a retrospective clonal analysis, using a nlaacZ reporter targeted to the α-cardiac actin gene. A rare intragenic recombination event results in a functional nlacZ sequence, giving rise to clones ofβ -galactosidase-positive cells. Periendothelial and vascular smooth muscle cells of the Dorsal Aorta are the main cell types labelled, demonstrating that these are clonally related to the paraxial mesoderm-derived cells of skeletal muscle. Rare endothelial cells are also seen in some clones. In younger clones, arising from a recent recombination event, myotomal labelling is predominantly in the hypaxial somite, adjacent to labelled smooth muscle cells in the Aorta. Analysis of Pax3 GFP/+ embryos shows that these cells are Pax3 negative but GFP positive, with fluorescent cells in the intervening region between the Aorta and the somite. This is consistent with the direct migration of smooth muscle precursor cells that had expressed Pax3. These results are discussed in terms of the paraxial mesoderm contribution to the Aorta and of the mesoangioblast stem cells that derive from it.

  • skeletal myogenic progenitors originating from embryonic Dorsal Aorta coexpress endothelial and myogenic markers and contribute to postnatal muscle growth and regeneration
    Journal of Cell Biology, 1999
    Co-Authors: Luciana De Angelis, Libera Berghella, M Coletta, Laura Lattanzi, Malvina Zanchi, M Gabriella, Carola Ponzetto, Giulio Cossu
    Abstract:

    Skeletal muscle in vertebrates is derived from somites, epithelial structures of the paraxial mesoderm, yet many unrelated reports describe the occasional appearance of myogenic cells from tissues of nonsomite origin, suggesting either transdifferentiation or the persistence of a multipotent progenitor. Here, we show that clonable skeletal myogenic cells are present in the embryonic Dorsal Aorta of mouse embryos. This finding is based on a detailed clonal analysis of different tissue anlagen at various developmental stages. In vitro, these myogenic cells show the same morphology as satellite cells derived from adult skeletal muscle, and express a number of myogenic and endothelial markers. Surprisingly, the latter are also expressed by adult satellite cells. Furthermore, it is possible to clone myogenic cells from limbs of mutant c-Met-/- embryos, which lack appendicular muscles, but have a normal vascular system. Upon transplantation, Aorta-derived myogenic cells participate in postnatal muscle growth and regeneration, and fuse with resident satellite cells. The potential of the vascular system to generate skeletal muscle cells may explain observations of nonsomite skeletal myogenesis and raises the possibility that a subset of satellite cells may derive from the vascular system.

D A Higgs - One of the best experts on this subject based on the ideXlab platform.

  • relationship between blood and muscle levels of astaxanthin in Dorsal Aorta cannulated atlantic salmon
    Aquaculture, 2006
    Co-Authors: Anders Kiessling, Bakshish Dosanjh, Wolfgang Koppe, D A Higgs
    Abstract:

    Abstract Twelve previously unpigmented Atlantic salmon with a body weight of 545 ± 39 (SE) g were kept individually and fed a diet containing 69 mg·kg − 1 astaxanthin for 63 days. On day 35 each fish was fitted with a Dorsal Aorta cannula. During the last 28 days blood levels of astaxanthin were measured on three separate occasions. At 63 days the fish were slaughtered and muscle content of astaxanthin was analysed. The fish had grown by an average of 171 ± 29 g, with an SGR of 0.61 ± 0.08, with a feed conversion ratio of 0.84 ± 0.10 and astaxanthin retention of 7–10%, during the 63-day period. The average blood concentration of astaxanthin was 0.65 ± 0.09 μg·g − 1 and muscle content was 0.68 ± 0.12 mg·kg − 1 . Muscle content and retention of astaxanthin varied closely with that of blood concentration ( R 2  = 0.92, p R 2  = 0.88, p R 2 p  > 0.05) related to either astaxanthin blood or muscle level. On the basis of the data and provided that feed intake and fish is included in the analysis, we concluded that the level of astaxanthin in blood is indicative of long-term muscle deposition and can be used as a rapid scanning method to distinguish between the effects of different dietary treatments on long-term deposition of astaxanthin in muscle.

  • Dorsal Aorta cannulation a method to monitor changes in blood levels of astaxanthin in voluntarily feeding atlantic salmon salmo salar l
    Aquaculture Nutrition, 1995
    Co-Authors: Anders Kiessling, Bakshish Dosanjh, D A Higgs, G Deacon, N Rowshandeli
    Abstract:

    This study was undertaken to assess Dorsal Aorta cannulation as a method to evaluate alterations in diet composition and feeding protocol on pigment retention in salmonid fish. Temporal changes in blood astaxanthin concentrations of Dorsal Aortacannulated Atlantic salmon, Salmo salar L., were followed in relation to variations in dietary pigment concentration and fish-feeding husbandry protocol. The fish were held individually in 200-L fibreglass tanks supplied with running sea water. Each fish was forced to swim at 0.5 body lengths s−1 and was fed daily by hand to satiation. The fish had an average growth rate of 1% day−1. Blood astaxanthin concentrations were noted to be highly correlated (r= 0.995) with dietary levels of astaxanthin, but not as well correlated (r= 0.71) with total gut content of this pigment. Marked variations in blood astaxanthin concentration were noted between individual fish at each dietary pigment concentration, but the ranking of the fish was generally unaffected between each dietary pigment level. After cessation of feeding a diet supplemented with 75 mg of astaxanthin kg−1, salmon fed a diet with no pigment showed more-rapid blood pigment clearance than those that were starved. Likely, feed remaining in the alimentary tract of the starved fish functioned as a reservoir of pigment for the blood until the intestinal tract was empty. Blood pigment levels were not depressed in salmon fed a diet supplemented with 75 mg of astaxanthin kg−1 once daily instead of twice daily.