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91.
Proliferative kidney disease (PKD) is caused by the infection of susceptible salmonid fish with spores of the myxozoan Tetracapsula bryosalmonae , a parasite harboured and released by several species of bryozoans. Under natural conditions, PKD is a water-borne infection of fish, whose outcome and spatio-temporal dissemination depend on the viability of spores present in the water. In order to evaluate the duration of parasite infectivity, juvenile rainbow trout, Oncorhynchus mykiss , were exposed for 20 h to T. bryosalmonae -infected water at various times post-water collection or after different filtration procedures. When infected water was held in a temperature range of 14.5–17 °C for up to 14 days, PKD was transmitted to the fish only between 0 and 12 h post-water collection and its infectivity vanished between 12 and 24 h. Similarly, the infectivity of water passed through 25 μm but not through 1 μm mesh filters, and was lost in the material eluted from the 1 μm filtration membrane although the parasite's DNA was amplified from this material. The parasitic infectivity in water appears to be fragile and this may offer opportunities to decrease the impact of PKD in trout farms by the implementation of management procedures aimed at reducing the number of the bryozoan-holding surfaces located in the river, immediately upstream from these farms. 相似文献
92.
Dr. Jeffrey R. Hazel 《Fish physiology and biochemistry》1996,15(3):195-204
Most previous studies of the temperature-induced restructuring of phospholipid molecular species composition have examined steps in the biosynthesis of phospholipids to explain the accumulation of unsaturated fatty acids in membranes of cold-acclimated poikilotherms. In contrast, the present study explores the role of phospholipases in this restructuring process by determining the rates of degradation of specific molecular species of phosphatidylcholine, using enzymes (microsomes) freshly isolated from the liver of rainbow trout. (Oncorhynchus mykiss) acclimated to either 5° or 20°C. The substrate preparation employed to assay phospholipase activity possessed a range of molecular species, all radiolabeled with 1-14C-palmitic acid at thesn-1 position, similar to that present in native trout liver microsomes. After defined periods of incubation (120 and 240 min at 5°C; 60 and 120 min at 20°C), phospholipids were extracted from the reaction mixture and the distribution of radioactivity among the molecular species of phosphatidylcholine was determined by HPLC/liquid scintillation counting. In general, molecular species catabolism was not significantly influenced by either assay or acclimation temperature. Only in 20°C-acclimated fish did a reduction in assay temperature (from to 20 to 5°C) result in significantly increased proportions of radioactivity being recovered in one polyunsaturated fatty acid-containing species (16:0/22:6-PC). It is concluded: 1) that phospholipase specificity, assayed under conditions approximating thosein situ, is not significantly influenced by temperature; and 2), that the increased proportions of unsaturated fatty acid-containing molecular species of phosphatidylcholine observed at low temperatures must reflect the specificity of biosynthetic rather than degradative processes. 相似文献
93.
94.
Plasma amino acid profiles in the systemic circulation of rainbow trout acclimated to diets containing different protein sources, with and without supplementation with free amino acids, were monitored for up to 120 hours after consumption of the diets. Plasma concentrations of lysine, methionine, and isoleucine increased more rapidly after feeding a diet supplemented with these amino acids in free form and, depending upon the increase in plasma concentration, remained at concentrations above those in fish fed the basal diet for at least 24h after feeding. Dietary supplementation with isoleucine increased plasma concentrations of leucine and valine as well as of isoleucine. Maximum plasma concentrations for most amino acids were attained between 12 and 24h postprandial. Dietary inclusion of gelatin caused more rapid elevations in plasma glycine and serine than did free glycine. Feeding at three hour intervals resulted in stable plasma concentrations of individual amino acids in contrast to the fluctuations occurring when fish were fed once daily. Frequent feeding favoured a higher proportion of protein to lipid in body composition. 相似文献
95.
Goldfish,Carassius auratus, were acclimated for 2 to 3.5 weeks to three temperature regimes: [1] temporally-constant (10, 20 and 30°C), [2] diurnally-cycling
(20 ± 10°C) and [3] randomly-fluctuating (± 2°C at approximately 2h intervals between extremes of 10 and 30°C). No significant
differences in hematocrit were evident. Hemoglobin levels in fish at constant 30°C and under randomly fluctuating temperature
were significantly elevated. Of the three hemoglobin isomorphs observed, the two minor components (G1, G3) tended to decrease in relative abundance with increase in constant temperature, but increased under varying temperature
regimes. The converse was true of the principal hemoglobin, G2. Extent of isomorph variation was correlated with extent of temperature variability. These observations confirm that temperature
variability significantly effects thermoacclimatory response. The functional significance of changes in isomorph abundances
during the acclimatory process is considered. 相似文献
96.
The presumptive Na+/H+ exchange sites of trout and eel erythrocytes were quantified using amiloride-displaceable 5-(N-methyl-N-[3H]isobutyl)-amiloride (3H-MIA) equilibrium binding to further evaluate the mechanisms of i) hypoxia-mediated modifications in the trout erythrocyte -adrenergic signal transduction system and ii) the marked differences in the catecholamine responsiveness of this system between the trout and eel. MIA was a more potent inhibitor of both trout apparent erythrocyte proton extrusion (IC50 = 20.1 ± 1.1 mol l–1, N = 6) activity (as evaluated by measuring plasma pH changes after addition of catecholamine in vitro) and specific 3H-MIA binding (IC50 = 257 ± 8.2 nmol l–1, N = 3) than amiloride, which possessed a proton extrusion IC50 of 26.1 ± 1.6 mol l–1 (N = 6) and a binding IC50 of 891 ± 113 nmol l–1 (N = 3). The specific Na+ channel blocker phenamil was without effect on adrenergic proton extrusion activity or specific 3H-MIA binding. Trout erythrocytes suspended in Na+-free saline and maintained under normoxic conditions possessed 37,675 ± 6,678 (N = 6) amiloride-displaceable 3H-MIA binding sites per cell (Bmax, presumptive Na+/H+ antiporters) with an apparent dissociation constant (KD) of 244 ± 29 nmol l–1 (N = 6). Acute hypoxia (PO2 = 1.2 kPa; 30 min) did not affect the KD, yet resulted in a 65% increase in the number of presumptive Na+/H+ antiporters. Normoxic eel erythrocytes, similarly suspended in Na+-free saline, possessed only 17,133 ± 3,716 presumptive Na+/H+ antiporters (N = 6), 45% of that of trout erythrocytes, with a similar KD (246 ± 41 nmol l–1, N = 6). These findings suggest that inter- and intra-specific differences in the responsiveness of the teleost erythrocyte -adrenergic signal transduction system can be explained, in part, by differences in the numbers of Na+/H+ exchange sites. 相似文献
97.
98.
Use of a probiotic to control lactococcosis and streptococcosis in rainbow trout, Oncorhynchus mykiss (Walbaum) 总被引:2,自引:0,他引:2
From a comparison of 125 bacterial isolates recovered from the digestive tract of rainbow trout, Oncorhynchus mykiss, and carp, Cyprinus sp., a culture was obtained which was effective at preventing clinical disease caused by Lactococcus garvieae and Streptococcus iniae when used as a feed additive. The culture, Aeromonas sobria GC2, was incorporated into the feed and fed to rainbow trout (average weight = 20 g) for 14 days at a dose equivalent to 5 x 10(7) cells g(-1) of feed. Whereas the untreated controls experienced losses of 75-100% when challenged intraperitoneally with L. garvieae and S. iniae, the probiotic-treated groups remained healthy with total mortalities of only 0-6%. Formalized and sonicated preparations of GC2 and cell-free supernatant fared less well. The mode of action reflected stimulation of innate immunity, namely an increased number of leucocytes and enhanced phagocytic and respiratory burst activity. 相似文献
99.
100.