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Physiology of amoebic gill disease and its treatment with freshwater bathing in atlantic salmon salmo salar.
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Abstracts / Comparative Biochemistry and Physiology, Part B 126 (2000) $1-S108
A COMPARISON OF THE MOLECULAR SPECIES COMPOSITIONS OF MAMMALIAN LUNG SURFACTANT PHOSPHOLIPIDS
Tony Postle, Child Health, Allergy & Inflammation Sciences, University o f Southampton, U K An essential role in surfactant function for a precise molecular species composition of phosphatidyicholine (PC) has long been recognised. The requirement to maintain equivalent control over molecular compositions of the other major surfactant phosphofipids, phosphatidyiglycerol (PG) and phmphatidylinositol (PI), has not been evaluated. Consequently, we have used eleetrmpray ionisation mass speetrometry to quantify molecular species compositions of surfaetont PC, PG and PI purified from human, rat, rabbit and guinea pig lungs. As expected, PC compositions displayed minimal variation across the animal speeies studied, consistent with the eritieal role of PC16:0/16:0 in surfaetaat function. In contrast there were wide variations of PG and PI, in terms both of concentration and composition. For instance, human surfactant contains a high PG concentration, composed of three monounsaturated species (PC16:0/18:1, PG18:1/18:1 and PG18:0/18:1) with minimal amounts of PC16:0/16:0 or polyunsaturated species. Rat surfaetant is similarly enriehed in PG, but this is composed of elevated PC16:0/16:0 and PC16:W18:2. The combined physical properties of these two species wffi again be effeetively monounsaturated. Rat surfaetant PI is enriched in P118:0/20:4 (29%), but as PI is present at low concentration (<3%), this polyunsaturated species does not make a signifleant contribution to overall surfaetant phospholipid composition. In contrast for the guinea pig and rabbit, where PI contributes respectively 5 and 6% to total phesholipid, PG and PI composition are both monounsaturated with esseniiaBy no polyunsaturated species (<8%~ As these four animal species have equivalent surfaetant function, all these varied compositions of acidic phosphoHpid must be equally effective at promoting adsorption of PC16:0/16:0 to the air:liquid interface within the lungs. An effective monounsaturated composition of anionic phospholipid molecular species is apparently essential for this function; too high a content of disaturated species would maintain surfaetant phespholipid in a rigid gel phase, while increased concentrations of polyunsaturated species would promote formation of fluid bilayer structures with poor surface tension lowering copaeity.
PHYSIOLOGY O F A M O E B I C G I L L D I S E A S E AND I T S T R E A T M E N T WITH F R E S H W A T E R B A T H I N G IN A T L A N T I C S A L M O N S A L M O SALAR. M.D. Powell, and B.F. N o w a k School o f Aquaculture, Tasmanian Institute o f Aquaculture and Fisheries, University o f Tasmania, Launceston, Tasmania 7250 Australia. Amoebic gill disease is caused by the protozoan parasite Paramoeba pemaquidensis and is responsible for substantial mortalities and financial losses of cultured Atlantic salmon in Tasmania. AGD is characterised grossly by raised white patches on the gills, and histologically by multi-focal lesions consisting of localised inter-lamellar hyperplasia and fusion of adjacent lamellae most typically in the proximal regions of the gill filaments. Often associated with the lesions are accumulations of cell debris, mucus and Paramoeba. We have examined the effects of AGD infection in fish challenged with a graded hypoxia, exposed to a hyperoxic and normoxic ~eshwater pulse (the standard treatment for the disease commercially is to balhe the fish in hyperoxic freshwater) and recovery from net confinement. Ahttough differences in arterial/'02, PCO2 and pH under normoxic conditions indicating a respiratory acidosis, when challenged with a graded hypoxia, these differences were ameliorated under hypoxiamost probably due to increased gill perfusion. When exposed to a 2-3 hour freshwater pulse there were no significant changes in blood gases or pH under either normoxic or hyperoxic conditions and no effects on plasma ion levels or gill Na+/K+ ATPase activity, although gill SDH levels were significantly reduced. Following 5 minutes of net confinement (in water), blood pH and oxygen content levels dropped significantly and progressively recovered by 9 hours post-confinement. However, some fish died during the recovery phase even though blood pH and respiratory variable s were recovering to pre-confinement levels or the levels seen in non-confined (control) fish. These results indicate that AGD results in mortality most probably as a consequence of the acute drop in ex~acellular pH and that mortality appears to be independent of respiratory or ionic status of the fish.
Abstracts / Comparative Biochemistry and Physiology, Part B 126 (2000) $1-S108
A COMPARISON OF THE MOLECULAR SPECIES COMPOSITIONS OF MAMMALIAN LUNG SURFACTANT PHOSPHOLIPIDS
Tony Postle, Child Health, Allergy & Inflammation Sciences, University o f Southampton, U K An essential role in surfactant function for a precise molecular species composition of phosphatidyicholine (PC) has long been recognised. The requirement to maintain equivalent control over molecular compositions of the other major surfactant phosphofipids, phosphatidyiglycerol (PG) and phmphatidylinositol (PI), has not been evaluated. Consequently, we have used eleetrmpray ionisation mass speetrometry to quantify molecular species compositions of surfaetont PC, PG and PI purified from human, rat, rabbit and guinea pig lungs. As expected, PC compositions displayed minimal variation across the animal speeies studied, consistent with the eritieal role of PC16:0/16:0 in surfaetaat function. In contrast there were wide variations of PG and PI, in terms both of concentration and composition. For instance, human surfactant contains a high PG concentration, composed of three monounsaturated species (PC16:0/18:1, PG18:1/18:1 and PG18:0/18:1) with minimal amounts of PC16:0/16:0 or polyunsaturated species. Rat surfaetant is similarly enriehed in PG, but this is composed of elevated PC16:0/16:0 and PC16:W18:2. The combined physical properties of these two species wffi again be effeetively monounsaturated. Rat surfaetant PI is enriched in P118:0/20:4 (29%), but as PI is present at low concentration (<3%), this polyunsaturated species does not make a signifleant contribution to overall surfaetant phospholipid composition. In contrast for the guinea pig and rabbit, where PI contributes respectively 5 and 6% to total phesholipid, PG and PI composition are both monounsaturated with esseniiaBy no polyunsaturated species (<8%~ As these four animal species have equivalent surfaetant function, all these varied compositions of acidic phosphoHpid must be equally effective at promoting adsorption of PC16:0/16:0 to the air:liquid interface within the lungs. An effective monounsaturated composition of anionic phospholipid molecular species is apparently essential for this function; too high a content of disaturated species would maintain surfaetant phespholipid in a rigid gel phase, while increased concentrations of polyunsaturated species would promote formation of fluid bilayer structures with poor surface tension lowering copaeity.
PHYSIOLOGY O F A M O E B I C G I L L D I S E A S E AND I T S T R E A T M E N T WITH F R E S H W A T E R B A T H I N G IN A T L A N T I C S A L M O N S A L M O SALAR. M.D. Powell, and B.F. N o w a k School o f Aquaculture, Tasmanian Institute o f Aquaculture and Fisheries, University o f Tasmania, Launceston, Tasmania 7250 Australia. Amoebic gill disease is caused by the protozoan parasite Paramoeba pemaquidensis and is responsible for substantial mortalities and financial losses of cultured Atlantic salmon in Tasmania. AGD is characterised grossly by raised white patches on the gills, and histologically by multi-focal lesions consisting of localised inter-lamellar hyperplasia and fusion of adjacent lamellae most typically in the proximal regions of the gill filaments. Often associated with the lesions are accumulations of cell debris, mucus and Paramoeba. We have examined the effects of AGD infection in fish challenged with a graded hypoxia, exposed to a hyperoxic and normoxic ~eshwater pulse (the standard treatment for the disease commercially is to balhe the fish in hyperoxic freshwater) and recovery from net confinement. Ahttough differences in arterial/'02, PCO2 and pH under normoxic conditions indicating a respiratory acidosis, when challenged with a graded hypoxia, these differences were ameliorated under hypoxiamost probably due to increased gill perfusion. When exposed to a 2-3 hour freshwater pulse there were no significant changes in blood gases or pH under either normoxic or hyperoxic conditions and no effects on plasma ion levels or gill Na+/K+ ATPase activity, although gill SDH levels were significantly reduced. Following 5 minutes of net confinement (in water), blood pH and oxygen content levels dropped significantly and progressively recovered by 9 hours post-confinement. However, some fish died during the recovery phase even though blood pH and respiratory variable s were recovering to pre-confinement levels or the levels seen in non-confined (control) fish. These results indicate that AGD results in mortality most probably as a consequence of the acute drop in ex~acellular pH and that mortality appears to be independent of respiratory or ionic status of the fish.