Enhanced oxygen unloading in two marine percomorph teleosts.

Teleost fishes are diverse and successful, comprising almost half of all extant vertebrate species. It has been suggested that their success as a group is related, in part, to their unique O2 transport system, which includes pH-sensitive hemoglobin, a red blood cell ß-adrenergic Na+/H+ exchanger (RBC ß-NHE) that protects red blood cell pH, and plasma accessible carbonic anhydrase which is absent at the gills but present in some tissues, that short-circuits the ß-NHE to enhance O2 unloading during periods of stress. However, direct support for this has only been examined in a few species of salmonids. Here, we expand the knowledge of this system to two warm-water, highly active marine percomorph fish, cobia (Rachycentron canadum) and mahi-mahi (Coryphaena hippurus). We show evidence for RBC ß-NHE activity in both species, and characterize the Hb-O2 transport system in one of those species, cobia. We found significant RBC swelling following ß-adrenergic stimulation in both species, providing evidence for the presence of a rapid, active RBC ß-NHE in both cobia and mahi-mahi, with a time-course similar to that of salmonids. We generated oxygen equilibrium curves (OECs) for cobia blood and determined the P50, Hill, and Bohr coefficients, and used these data to model the potential for enhanced O2 unloading. We determined that there was potential for up to a 61% increase in O2 unloading associated with RBC ß-NHE short-circuiting, assuming a - 0.2 ∆pHa-v in the blood. Thus, despite phylogenetic and life history differences between cobia and the salmonids, we found few differences between their Hb-O2 transport systems, suggesting conservation of this physiological trait across diverse teleost taxa.

Differences in immune components of blood, spleen and head kidney between diploid and auto- and allotriploid Salmonidae.

Immune components were investigated in peripheral blood and in spleen and head kidney of autotriploid Salmo trutta f. lacustris, Salvelinus fontinalis, and Salvelinus umbla, and of allotriploid hybrids of S. trutta f. lacustris x Onchorynchus mykiss and S. fontinalis x O. mykiss in comparison to their diploid parents. In peripheral blood the number of lymphocytes was reduced in all investigated autotriploids and in the allotriploid S. trutta f. lacustris x O.mykiss, and the numbers of thrombocytes in autotriploid S. trutta f. lacustris and in both allotriploids. Alternative pathway of complement activity and immunoglobulin concentration were significantly decreased in all investigated auto- and allotriploids, lysozyme activity in autotriploid S. fontinalis and in both allotriploids. In the spleen of the 3 autotriploids the number of erythrocytes was increased, while the number of lymphoid precursor cells was decreased. In their head kidney the erythrocytes numbers were decreased and the numbers of erythropoietic precursor cells and the melanomacrophage centers were increased. Contrary, cytology of spleen and head kidney of the two allotriploid hybrids was similar to diploid controls. Caspase 1, caspase 6, lysozyme, and acid phosphatase activity and immunoglobulin concentration of spleen and head kidney showed specific changes which were related to cytological results. These data indicate alterations in immune system and in lymphoid organs of auto- and allotriploid Salmonidae.

Synergism between elevated temperature and nitrate: Impact on aerobic capacity of European grayling, Thymallus thymallus in warm, eutrophic waters.

Climate warming and nitrate pollution are pervasive aquatic stressors that endanger the persistence of fishes prevailing in anthropogenically disturbed habitats. Individually, elevated nitrate and temperature can influence fish energy homeostasis by increasing maintenance costs and impairing oxygen transport capacity. However, it remains unknown how fish respond to simultaneous exposure to elevated temperature and nitrate pollution. Hence, we examined the combined effects of nitrate and elevated temperatures on aerobic scope (AS, maximum-standard metabolic rates) and cardiorespiratory attributes (haemoglobin HB, haematocrit HCT, relative ventricle mass RVM, and somatic spleen index SSI) in a freshwater salmonid, Thymallus thymallus. A 3 × 2 factorial design was used, where fish were exposed to one of three ecologically relevant levels of nitrate (0, 50, or 200 mg NO3- l-1) and one of two temperatures (18 °C or 22 °C) for 6 weeks. Elevated temperature increased AS by 36 % and the improvement was stronger when coupled with nitrate exposure, indicating a positive synergistic interaction. HB was reduced by nitrate exposure, while HCT was independent of nitrate pollution and temperature. Stressor exposure induced remodeling of key elements of the cardiorespiratory system. RVM was 39 % higher in fish exposed to 22 °C compared to 18 °C but was independent of nitrate exposure. SSI was independent of temperature but was 85 % and 57 % higher in fish exposed to 50 and 200 mg NO3- l-1, respectively. Taken together, these results highlight that simultaneous exposure to elevated temperatures and nitrate pollution offers cross-tolerance benefits, which may be underscored by cardiorespiratory remodeling.

Influence of Thermal Pollution on the Physiological Conditions and Bioaccumulation of Metals, Metalloids, and Trace Metals in Whitefish (Coregonus lavaretus L.).

The Kola nuclear power plant, which discharges warm water into one of the bays of subarctic Lake Imandra, significantly changes fish habitats. The temperature gradient of the lake is between 2 and 8 °C, which makes it significantly different from the natural temperature of the lake water. The stenothermal cold-water native species (lake whitefish (Coregonus lavaretus L.)), living for more than 40 years under conditions of thermal pollution, has adapted to this stressor. Moreover, this population differs favorably from the population in the natural-temperature environment in terms of its physiological state. Firstly, the hemoglobin concentrations in the fish blood are in the range of the ecological optimum, and secondly, it has a higher somatic growth, as estimated by Fulton's condition factor. One of its main adaptive mechanisms of ion regulation is an intense metabolism of Na due to the high respiratory activity of the whitefish in warmer water. An increased accumulation of Rb and excretion of Se, Mo, and Si are associated more or less with that feature. Under conditions of an increased water temperature, the main metabolic need is due to a deficiency of Se in fish. The intensive metabolism of selenoproteins may involve risks of toxic effects and the bioaccumulation of Hg, As, and Cu in cases of increased existing stressors or the appearance of new ones.

Effects of dietary administration of Rose hip and Safflower on growth performance, haematological, biochemical parameters and innate immune response of Beluga, Huso huso (Linnaeus, 1758).

The aim of this study was to investigate effects of two dietary medicinal herbs, Rose hip (Rosa canina) and Safflower (Carthamus tinctorius) supplementation on growth performance, haematological, biochemical parameters and innate immune response of in juvenile beluga, Huso huso. Fish (26.3 ± 0.4 g) were allocated into 15 tanks (20 fish per tank) and triplicate groups were fed a control diet or diets containing 1% and 2% of medicinal herbs, respectively. Feed conversion ratio (FCR), specific growth rate (SGR) and condition factor (CF) did not show significant differences (P > 0.05) in fish given herbal diets. Significant differences were observed in number of white blood cells (WBC) and haemoglobin (Hb) values among the dietary treatments. The serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were significantly lower in supplemented diet groups compared with the control. Innate immune responses (lysozyme activity and ACH50) were significantly higher in 2% Safflower-fed fish compared with other groups (P < 0.05). These results indicate that medicinal herbs in diets can be considered as a beneficial dietary supplement for improving the physiological parameters and enhance the immune response of Persian sturgeon.

miR-122-5p as a plasma biomarker of liver injury in fish exposed to microcystin-LR.

Recent studies have shown the presence of large amounts of microRNAs (miRNAs; miRs) from damaged cells in the peripheral blood. In this study, we investigated the levels of miRNAs circulating in the blood plasma of whitefish (Coregonus lavaretus) after exposure to microcystin-LR. We used real-time PCR to examine the relative expression of plasma levels of 4 miRNAs (miR-122-5p and let-7c-5p, the liver-enriched microRNAs, miR-148a-3p which promotes the hapatospecific phenotype in mammals, and miR-92a-3p, a cell proliferation and angiogenesis promoter, potentially hepatocarcinogenic) during the first 48 h after exposure to MC-LR. We observed a rapid increase of miR-122-5p levels 8 h after exposure (P < 0.05), which continued to the end of the experiment. Our results demonstrated that the plasma miR-122-5p was indicative of MC-LR-induced liver injury, exhibiting areas under the curve close to 1 in ROC analysis (AUC = 0.976, P < 0.001). Although plasma levels of miR-148a-3p and miR-92a-3p were significantly elevated by the end of the experiment, their discriminative power was lower than reported for the miR-122-5p. Based on these results and reports on miRNA-based diagnosis of liver injuries in mammals, plasma miR-122-5p could be considered as a robust, new generation diagnostic biomarker in fish, helpful for the non-invasive diagnosis of liver damage.

Growth of Flavobacterium psychrophilum in fish serum correlates with pathogenicity.

Flavobacterium psychrophilum isolates, obtained from ayu, Plecoglossus altivelis, three species of salmonids and two species of cyprinids in Japan, were used in this study. Bacteria were inoculated to serum prepared from ayu or red spotted masu trout (RSMT), Oncorhynchus masou ishikawae, and incubated at 18 °C for 24 h. All isolates (n = 19) from ayu grew well with a 9- to 116-fold increase of CFU in ayu serum, while CFU decreased markedly in RSMT serum. In contrast, isolates (n = 17) from fish species other than ayu exhibited no growth in ayu serum, but some isolates from salmonids survived or grew (1.2-23.5 fold increase of CFU) in RSMT serum. The isolates that could not survive or grow in ayu and RSMT sera grew well in both heat-inactivated sera of ayu and RSMT. Experimental infection by intraperitoneal injection showed that ayu isolates examined were all pathogenic to ayu but not to RSMT, while none of the isolates from salmonids and cyprinids were pathogenic to ayu but some showed pathogenicity to RSMT. These results indicate that the in vitro growth ability of F. psychrophilum isolates in fish serum correlates well with their pathogenicity to fish, particularly in ayu.

[Specific features of blood cell composition and structure in fishes from the pelagial and coastal zones of Lake Baikal].

Differences in the proportions and ultrastructure of peripheral blood cells between the Baikal cisco and roach have been revealed. Both species contain all main cell types involved in the immune response in higher vertebrates. However, cells mediating the innate immune response are represented in the Baikal cisco only by monocytes and pseudogranulocytes, whereas the blood of roach additionally contains true granulocytes. Significantly greater numbers of leukocytes and thrombocytes per unit volume in the roach are evidence for mobilization of the immune system in this species. The peripheral blood of both species contains lymphocytes, which are responsible for adaptive immunity. The content of hemoglobin in erythrocytes is lower in the roach than in the Baikal cisco. The state of blood in the two species may be considered adapted to typical conditions in their habitats.

Effects of tebufenozide on some aspects of lake trout (Salvelinus namaycush) immune response.

Tebufenozide is a nonsteroid ecdysone agonist that causes premature and incomplete molting in Lepidoptera and is used on crops and in forest spray programs. Lake trout (Salvelinus namaycush) were exposed to one pulse of 0.25 ppm tebufenozide every 3 days (12 pulses in total). Cell ratios and respiratory burst responses of circulating white blood cells (WBCs) as well as head-kidney (HK) WBCs were investigated by using cell observation, Nitro-Blue Tetrazolium tests, and flow cytometry. Endpoints studied suggest a difference in sensitivity between HK and circulating blood cells to tebufenozide and show a stimulation of fish cell function and changes in percentages of cell types. Responses are not associated with a strong stress response as highlighted by the absence of effect on cortisol and blood protein levels. These results and tebufenozide persistence in water warrant further studies on pesticide impact on fish immunity when used on crops or in forest spray programs near lakes and streams.

Gonad histology and vitellogenin concentrations in brown trout (Salmo trutta) from Danish streams impacted by sewage effluent.

Brown trout (Salmo trutta) collected from a number of Danish streams impacted by sewage effluent were examined for alterations to gonadal development and induction of vitellogenin synthesis. Among fish collected in June/July 2000/2001 and November 2002 higher levels of plasma vitellogenin were found in males from six streams impacted by sewage effluent compared to males from their respective reference sites. A direct non-competitive ELISA was developed for brown trout vitellogenin in order to perform the vitellogenin measurements. Intersex in females with no apparent relation to sewage effluent exposure was observed at all sites. In one stream, male brown trout with a very high level of vitellogenin were concomitantly found to have a high degree of vacuolation of the testes and a presence of only the early spermatogenic stage, spermatogonia. The cause of these alterations to the testis structure is unclear. However, as a high level of plasma vitellogenin in these males indicated estrogenic exposure, the vacuolation might also be a result of endocrine disruption causing delayed or disrupted spermatogenesis.

Rapid adjustments of sperm characteristics in relation to social status.

Sperm competition models predict that males typically mating in disfavoured roles should be selected to compensate for their disadvantage by investing more into sperm. We studied the effect of rapid changes in social status on ejaculate investments during experimental trials with an externally fertilizing teleost--the Arctic charr (Salvelinus alpinus). We document that males becoming dominant produce less sperm with lower velocity, but have higher sex steroid concentrations than subordinate males. These differences in sperm characteristics seem mainly to result from a decreased investment in sperm among fish that become dominant compared to pre-trial levels. Moreover, these adjustments of sperm production and sperm velocity seem not to be traded against sperm longevity. Our results support theoretical models of sperm competition, as males forced to mate in disfavoured roles seem to invest more into ejaculate quality than males in favoured roles. Additionally, we are the first to report that males, in a species with status-dependent shifts in reproductive tactics, have evolved rapid tactic specific adjustments of sperm production and sperm velocity corresponding to what could be predicted from their reproductive roles.

Evidence of complement-mediated killing of Discocotyle sagittata (Platyhelminthes, Monogenea) oncomiracidia.

Discocotyle sagittata oncomiracidia were rapidly killed when incubated in naïve plasma and immune sera from both rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta), the killing proceeding at a faster rate with blood material from the latter fish species. The lethal activity of naïve plasma and immune sera was comparable. This was abolished after incubation at 45 degrees C for 30 min and by the addition of EDTA but not EGTA supplemented with Mg(2+), indicating that complement acting via the alternative pathway is responsible for the parasiticidal effect observed. Scanning electron micrographs showed varying degrees of surface disruption in larvae exposed to fish plasma, suggesting that complement acts by breaching the oncomiracidial tegument. Control (untreated) oncomiracidia showed no damage. Ultrastructural damage was more extensive in oncomiracidia exposed to brown trout plasma than to rainbow trout plasma for equal periods, suggesting that the complement cascade may be involved in mediating host susceptibility.

Sex steroids in plasma of lake whitefish Coregonus clupeaformis during spawning in Lake Erie.

Lake whitefish, Coregonus clupeaformis, were collected from the Western basin of Lake Erie during spawning. Free and conjugated (sulfated and glucuronidated) steroids including testosterone (T), 11-ketotestosterone (11-kT), estradiol-17beta (E2) and 17,20beta-dihydroxy-4-pregnen-3-one (17,20betaP) were measured in the plasma by radioimmunoassay. In males, the progression of spermiation was characterized by a significant decrease in plasma free steroids, whereas the levels of conjugated steroids remained similar and low, except for sulfated and glucuronidated testosterone. Plasma sex steroids did not correlate with the density or the motility of the spermatozoa. In females, the concentration of plasma T was significantly higher in preovulating than in ovulating females. The levels of E2 and 17,20betaP in ovulating lake whitefish exhibited large variations ranging from below detection limit to 0.9 ng ml(-1) and from 0.2 to 13 ng ml(-1), respectively. Analysis of conjugated steroids revealed high levels of glucuronidated and sulfated 17,20betaP and glucuronidated T in females ovulating in December. However, no significant differences in the proportion of the conjugated steroids were observed.

Altered challenge response in whitefish subchronically exposed in areas polluted by bleached kraft mill effluents.

Exposure to impaired water quality, as in bleached kraft mill effluents (BKMEs), has recently been demonstrated to impair the ability of fish to elicit an acute stress response. Acute stress caused by catching is, in most field studies, an unavoidable incident that may markedly affect physiological functions. Consistently, dissimilar stress responses to catching procedures in exposed and reference animals may lead to altered results. In this study, juvenile whitefish (Coregonus levaretus) were caged for 30 days in two reference areas and three areas affected by different BKMEs, and the immediate effects of low-level handling on physiological functions in four periods within an hour of the start of the disturbance were clarified. Both primary and secondary stress responses were evident and consistent in fish caged in the two reference areas. Instead, despite the strong cortisol response in fish caged in polluted areas, the secondary stress response was weak or altered with respect to all other measured parameters excluding blood glucose in two of the three polluted areas. Thus, exposed fish may, when compared with reference fish, give different results depending on the exact period from the onset of the catching disturbance to sampling, and therefore, the results may be masked or totally inverted. Because the impacts of acute stress on physiological parameters are immediate and, in exposed areas after low-level handling, dissimilar in nature, this study points to the necessity for time-dependent standardization in field studies whenever sampling is delayed.

Purification of the precursors to vitelline envelope proteins from serum of Sakhalin taimen, Hucho perryi.

High and low molecular weight vitelline envelope-related proteins (hVERP and lVERP) were purified from serum of vitellogenic female Sakhalin taimen (Hucho perryi) by a combination of ion-exchange, hydroxylapatite and gel filtration chromatography. The molecular weight of hVERP was estimated to be 83 kDa by gel filtration, and 48 kDa and 54 kDa in SDS-PAGE under non-reduced and reduced conditions, respectively. The molecular weight of lVERP was 56 kDa by gel filtration, and 42 kDa and 46 kDa on SDS-PAGE (non-reduced and reduced, respectively). Amino acid composition of hVERP was characterized by high content of proline (15.9%) and glutamic acid (13.8%). The lVERP had high contents of glutamic acid (10.8%) and aspartic acid (10.5%). Specific antibodies against hVERP and against lVERP were prepared by immunizing rabbits. The antiserum to hVERP stained bands corresponding to 98 kDa and 48 kDa of vitelline envelope (VE) in SDS-PAGE without reduction, whereas the antiserum to lVERP immunostained 98 kDa and 42 kDa bands. Both specific antibodies recognized the vitelline envelope of vitellogenic oocytes immunocytochemically. Thus, hVERP and lVERP are precursors to vitelline envelope proteins in this species.

Transition of serum vitellogenin cycle in Sakhalin taimen (Hucho perryi).

A specific and sensitive enzyme-linked immunosorbent assay (ELISA) and a single radial immunodiffusion (SRID) were developed for measurement of serum vitellogenin (Vg) levels in Sakhalin taimen (Hucho perryi). Regarding specificity for serum Vg, an antiserum raised against lipovitellin of taimen (a-Lv) was adequate for both assays. ELISA and SRID could detect Vg in serum at concentrations as low as 10 ng/ml and 25 micrograms/ml, respectively. In estrogen administration experiments, the level of serum Vg began clearly increasing within 12 to 24 hr after injection of immature females with estradiol-17 beta (E2). The appearance and levels of Vg in males treated with E2 were delayed and smaller, respectively, than for females. Vg levels varied throughout natural vitellogenesis from 0-4 micrograms/ml (3 years old) to approximately 30 mg/ml (5-6 years old). We observed an early transitory peak of serum Vg levels (primary reaction) at the time of early vitellogenesis and chronic high Vg levels (for 6-7 months) in winter period before ovulation. Changes of serum E2 levels were correlated with Vg levels. However, E2 levels decreased a month earlier than Vg levels near ovulation. It appears that the duration of vitellogenesis in taimen is considerably longer than that in other salmonids, lasting more than 2 years.

Physiological toxicity of low-chlorine bleached pulp and paper mill effluent on whitefish (Coregonus lavaretus L. s.l.): a laboratory exposure simulating lake pollution.

In order to validate previous field observations by the authors on whitefish, Coregonus lavaretus L. s.l., a 30-day laboratory experiment with concentrations (0, 1.3, 2.3, 3.5, and 7 vol%) of bleached kraft pulp and paper mill effluent (BKME) simulating those occurring in a polluted lake was conducted. Chlorine dioxide had almost entirely replaced chlorine gas in the bleaching of pulp. As a consequence, the concentrations of adsorbable organic halogens and chlorinated phenolics (CPs) in BKME were significantly lowered compared to earlier studies. This reduction was also seen in the concentrations of CPs in the bile and CPs and extractable organic halogens in the intestinal lipids: the concentrations were low and did not depend on the dilution of BKME. In contrast, the resin acid content of bile decreased with decreasing BKME concentration. The growth of fish was speeded up in all BKME concentrations. However, at the highest BKME concentration (7 vol%) the increase was lowest. The induction of hepatic ethoxyresorufin O-deethylase (EROD) activity revealed strong dose-response relationship with BKME. At 3.5 vol% BKME (corresponding to a distance of 3.3 km from the mill sewer in the field) the EROD activity increased 12-fold. There was a tendency for lower activity of uridinediphosphate glucuronosyltransferase in the liver, but the decrease (34%; P < 0.05) was statistically significant only at 7 vol% BKME. The activity of liver glutathione S-transferase remained unchanged. All dilutions of BKME significantly depressed the concentrations of plasma immunoglobulin M (IgM). Erythrocytic concentrations of nucleotide triphosphates decreased and of sodium increased as the BKME concentration increased. Also some other blood parameters (hematocrit, hemoglobin, plasma glucose, and aspartate aminotransferase) were changed in all BKME exposures, although without obvious dependence on effluent concentration. In conclusion, there was a good agreement between field studies and laboratory experiments using BKME concentrations occurring in the field, confirming close or similar causes for responsive toxicity endpoints.

Development of a homologous radioimmunoassay for coho salmon insulin-like growth factor-I.

A specific homologous radioimmunoassay (RIA) for measurement of insulin-like growth factor-I (IGF-I) in plasma of salmonid and a few non-salmonid fish species was developed using recombinant coho salmon IGF-I (rsIGF-I) as tracer and standard, and antiserum against this peptide raised in rabbits. The minimum detection level of IGF-I was 1.5 ng/ml and linearity was obtained in a range from 1.5 to 23 ng/ml. No cross-reaction was detected in the salmon IGF-I RIA with mammalian growth factors, salmon pituitary hormones, salmon or mammalian insulin, or any peptide in rat plasma. Although salmon IGF-I has high sequence similarity to mammalian IGF-I, it did not cross-react with anti-human IGF-I serum in human RIA and serial dilutions of plasma from salmon were not parallel to the human IGF-I standards in this assay system. In contrast, dilution curves for plasma of salmonids, such as coho (Oncorhynchus kisutch), Atlantic (Salmo salar), and sockeye (O. nerka) salmon, rainbow trout (O. mykiss), some other teleost fish, such as tilapia (Oreochromis mossabmica), carp (Cyprus carpio), eel (Anguilla rostrata), Atlantic halibut (Hippoglossus hippoglossus), and agnathan, the sea lamprey (Petromyzon marinus), assessed in salmon IGF-I RIA were parallel to the rsIGF-I standards. Acid-ethanol extraction of plasma samples altered the molecular weight, but not the quantity, of immunoreactive IGF-I, implying that IGF-I binding proteins in salmon plasma do not affect the performance of the salmon IGF-I RIA. Gel filtration of nonacidified plasma on a Sephadex G-75 superfine column produced two immunoreactive IGF-I peaks of molecular weights of approximately > 70 k and 7 kDa, whereas acidification of plasma increased the relative amount of the 7-kDa peak (IGF-I) and the > 70-kDa peak disappeared. The recoveries of rsIGF-I added to extracted or nonextracted plasma were 97.4 and 94.9%, respectively. Inter- and intraassay coefficients of variation were 3.6 and 3.3%, respectively. Plasma IGF-I levels in coho salmon smolts were 117.4 +/- 19.1 ng/ml as compared to IGF-I levels in parr (45.3 +/- 2.5 ng/ml) or in adult fish (45.2 +/- 5.4 ng/ml) measured in the same assay. Injection of salmon growth hormone, but not prolactin or somatolactin, caused a significant and dose-dependent elevation of plasma IGF-I levels, while either fasting or injection of streptozotocin led to a significant decline in systemic IGF-I.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification of a haptoglobin-hemoglobin complex in the Alaskan Least Cisco (Coregonus sardinella).

The hemoglobin and a hemoglobin binding protein have been characterized in the Arctic fish (Coregonus sardinella). The evolutionary significance of the hemoglobin and plasma protein differences between fish and mammals is still unresolved. Blood samples from the Alaskan Least Cisco were separated into plasma and hemoglobin fractions and the proteins in these fractions were analyzed both by alkaline agarose gel electrophoresis, by isolelectric focusing, and by capillary electrophoresis. Staining the plasma proteins gels with o-dianisidine revealed hemoglobin containing protein complexes. A hemoglobin-containing band was observed in hemolyzed plasma which did not migrate with free hemoglobin, and is believed to be hemoglobin-haptoglobin complex. Size exclusion chromatography further characterized the hemoglobin as disassociating freely into dimers, and hemoglobin-haptoglobin complex having a molecular weight greater then 200,000 daltons.

The role of alpha 2-macroglobulin in furunculosis: a comparison of rainbow trout and brook trout.

1. The molecular basis for the high survival rate of rainbow trout, Oncorhynchus mykiss, infected with furunculosis was investigated. 2. Alpha 2-macroglobulin (alpha 2M), a major serum protease inhibitor, was partially purified from rainbow trout and brook trout, Salvelinus fontinalis, sera; the latter species shows marked disease susceptibility. 3. It is shown that a 10-fold species-based difference in alpha 2M inhibitory activity exists against a furunculosis associated bacterial protease. 4. A possible basis for the observed disparity is discussed. 5. Results suggest that the high mol. wt form of teleost (trout) albumin is a dimer composed of two 85,000 subunits.