[Show abstract][Hide abstract] ABSTRACT: Copepod oil (CO) from the marine zooplankton, Calanus finmarchicus, is a potential alternative to fish oils (FOs) for inclusion in aquafeeds. The oil is composed mainly of wax esters (WE) containing high levels of saturated fatty acids (SFAs) and monounsaturated fatty alcohols that are poorly digested by fish at low temperatures. Consequently, tissue lipid compositions may be adversely affected in salmon-fed CO at low temperatures. This study examined the lipid and FA compositions of muscle and liver of Atlantic salmon reared at two temperatures (3 and 12 °C) and fed diets containing either FO or CO, supplying 50% of dietary lipid as WE, at two fat levels (∼330 g kg−1, high; ∼180 g kg−1, low). Fish were acclimatized to rearing temperature for 1 month and then fed one of four diets: high-fat fish oil (HFFO), high-fat Calanus oil (HFCO), low-fat fish oil (LFFO) and low-fat Calanus oil (LFCO). The fish were grown to produce an approximate doubling of initial weight at harvest (220 days at 3 °C and 67 days at 12 °C), and lipid content, lipid class composition and FA composition of liver and muscle were determined. The differences in tissue lipid composition between dietary groups were relatively small. The majority of FA in triacylglycerols (TAG) in both tissues were monounsaturated, and their levels were generally higher at 3 °C than 12 °C. Polyunsaturated fatty acids (PUFA), particularly (n-3) PUFA, predominated in the polar lipids, and their level was not significantly affected by temperature. The PUFA content of TAG was highest (∼26%) in the muscle of fish fed the HFCO diet at both temperatures. Tissue levels of SFAs were lower in fish-fed diets containing HFCO than those fed HFFO, LFFO or LFCO, particularly at 3 °C. The results are consistent with Atlantic salmon being able to incorporate both the FA and fatty alcohol components of WE into tissue lipids but, overall, the effects of environmental temperature on tissue lipids were more pronounced in fish fed the CO diets than FO diets.
[Show abstract][Hide abstract] ABSTRACT: Oils extracted from the marine zooplankton, Calanus finmarchicus, have high levels of n-3 highly unsaturated fatty acids (HUFA) and are therefore of interest as an alternative lipid source in aquafeeds. Copepod lipid is composed mainly of wax esters (WE) with high levels of saturated fatty acids and monounsaturated fatty alcohols which are considered hard to digest, especially at low temperatures. This assumption has however not been verified and for this reason the present study examined the digestibility of diets containing high levels of WE and two fat levels in Atlantic salmon reared at 3 and 12 °C. The fish were acclimated for one month to 3 °C (485 g) and 12 °C (599 g) and then fed with one of four diets, high fat fish oil (33% lipid, HFFO), high fat Calanus oil (32% lipid, HFCO), low fat fish oil (17% lipid, LFFO) and low fat Calanus oil (19% lipid, LFCO). The fish meal lipid content was lowered by the use of lipid-extracted fish meal (2.3% lipid). This enabled a level of 50% WE in the LFCO and HFCO diets, compared to 0% in the LFFO and HFFO diets. The fish were then allowed to grow to around 100% of initial weight (220 days at 3 °C and 67 days at 12 °C) and then analysed for faecal lipid digestibility, bile volume, bile composition and intestinal lipolytic activity. Differences were observed in all of these parameters in relation to temperature, type of dietary oil and the lipid level in the diet. Faecal lipid content and lipid class composition were dependent on rearing temperature and the type of dietary lipid. Highest levels of undigested lipids were observed in the faeces of fish fed with CO. Wax ester-derived fatty alcohols, particularly 20:1n-9 and 22:1n-11, were less extensively digested than corresponding fatty acids from FO at both fat levels and temperatures. Fish kept at 12 °C had a significantly higher bile volume than fish at 3 °C and higher volumes were found in fish fed with CO diets compared to FO. Increased faecal holding time at lower temperature was not sufficient to ensure high digestibility since the lower bile volume and enzyme activities at 3 °C in the present trial exerted a greater effect. Although the compensatory mechanisms of increased bile volume and lipolytic activity are initiated upon feeding WE at a level of 50% of dietary lipid, these are not sufficient to compensate lipid digestibility and growth as in FO diets. Low inclusion of CO in diets during winter has to be considered as saturated fatty acids and monounsaturated fatty alcohols were poorly digested at 3 °C in fish fed with CO diets.
[Show abstract][Hide abstract] ABSTRACT: Calanoid copepods are a rich source of marine lipid for potential use in aquafeeds. Copepod oil is primarily composed of wax esters (WE) and there are concerns over the efficiency of wax ester, versus triacylglycerol (TAG), digestion and utilization in fish. As smoltification represents a period of major physiological adaptation, the present study examined the digestibility of a high WE diet (Calanus oil; 48% WE, 26% TAG), compared with a TAG diet (fish oil; 58% TAG), in Atlantic salmon freshwater presmolts and seawater postsmolts, of similar age (9 months) and weight (112 g and 141 g initial, respectively), over a 98-day period at constant temperature. Fish grew significantly better, and possessed lower feed conversion ratios (FCR), in seawater than freshwater. However, total lipid apparent digestibility coefficient (ADC) values were significantly lower in seawater fish, as were total fasted bile volumes. Dietary Calanus oil also had a significant effect, reducing growth and lipid ADC values in both freshwater and seawater groups. Postsmolts fed dietary Calanus oil had the poorest lipid ADC values and analysis of faecal lipid class composition revealed that 33% of the remaining lipid was WE and 32% fatty alcohols. Dietary prevalent 22:1n-11 and 20:1n-9 fatty alcohols were particularly poorly utilized. A decrease in primary bile acid, taurocholate, concentration was observed in the bile of dietary Calanus oil groups which could be related to the lower cholesterol content of the diet. The dietary WE : TAG ratio is discussed in relation to life stage and biliary intestinal adaptation to the seawater environment postsmoltification.
[Show abstract][Hide abstract] ABSTRACT: Total lipid content, fatty acid (FA) composition and lipid class composition of common dentex eggs spawned at different times and larvae reared under different culture conditions until 40 days posthatch (dph) were analysed to get a general pattern of lipid composition during larval development. Two groups of larvae were kept under starvation to compare their FA composition with that obtained from normally fed larvae. To compare FA use or accumulation during larval development, results were grouped according to the developmental stage of the larvae instead of age in days posthatch. Saturated and monounsaturated FAs decreased along larval development, while polyunsaturated fatty acid (PUFA) content increased. The ratio of docosahexaenoic acid (DHA)/eicosapentaenoic acid shifted from 4 to 5 in early developmental stages to lower than 1 after metamorphosis. Arachidonic acid levels remained constant along larval development. Larvae kept 6 days under starvation consumed most of their n-3 PUFA while conserving the DHA to values at day 0. The results presented here are useful for the design of nutritional experiments, because there were differences detected in terms of lipid and FA composition between developmental stages with higher differences mainly found in first-feeding larvae and early developmental stages.
[Show abstract][Hide abstract] ABSTRACT: The preparation of fish oil concentrates containing only (n-3) polyunsaturated fatty acids (PUFA) with different ratios of 20:5 (n-3)/22:6 (n-3) is described. Three groups of turbot were maintained on different diets containing: 1, 10% of the dry weight of the diet as natural fish oil, equivalent to 2.5% (n-3) PUFA and 0–23% (n-6) PUFA; 2, 10% of the dry weight of the diet as palmitic acid, i.e. no PUFA; 3, 8–7% palmitic acid and 1–3% of the dry weight as (n-3 PUFA and negligible (n-6) PUFA. Only the fish on the diet containing natural fish oil showed significant growth over a 15-week period. In addition there were high mortalities on the two experimental diets (2 and 3). Changing the ratio of 20:5 (n-3)/22:6 (n-3) from 13–8 to 2–2 in the diet containing 1 3% (n-3) PUFA and negligible (n-6) PUFA markedly decreased the mortalities. Fish fed the two experimental diets (2 and 3) developed gross changes in gill structure involving the disappearance of chloride cells, a ‘sloughing off’ of the epithelium along the primary and secondary filaments and an accumulation of cellular material in the inter-lamellar spaces. The tissue ultimately disintegrated to leave a skeleton of connective tissue and a mass of cellular material in the inter-lamellar spaces. It is concluded that 22:6 (n-3) is an essential fatty acid for turbot and that the gill epithelium is a sensitive indicator of this deficiency in this species.
Journal of Fish Biology 01/2006; 26(2):181 - 191. · 1.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The spawning quality, in terms of hatching rate, larval mortality at 3 and 5 days post-hatching (dph) and day of total mortality of two
broodstock groups of common dentex was evaluated for 1 month in 2005. Several biochemical parameters including total lipid content,
lipid class and fatty acid composition, carbohydrate content and metabolic enzyme activities were analysed in all the egg batches
collected. Comparison was carried out between low- (mortality at 3 dph higher than 35%) and high-quality (mortality at 3 dph lower than
10%) batches. No differences were observed in lipid content and/or lipid class and fatty acid composition although a slightly higher
content of neutral lipids was detected in high-quality batches. However, significant differences were obtained regarding carbohydrate
composition and the activity of enzymes such as alkaline phosphatase and pyruvate kinase being higher in low-quality egg batches.
[Show abstract][Hide abstract] ABSTRACT: Primary hepatocytes from wild northern pike Esox lucius were incubated with radiolabelled linolenic acid ([l-14C]-18:3(n-3)) to assess their ability to synthesize docosahexaenoic acid [22:6(n-3)]. The distribution of radioactivity in lipid classes and hepatocyte polyunsaturated fatty acids (PUFA) was measured over the time-course of 24h. The majority of radioactivity from [l-14C]-18:3(n-3) was recovered in hepatocyte triacylglycerols (TAG) and phosphatidylcholine (PC). The levels of radioactivity in TAG and in most of phospholipids, including PC, increased significantly over the incubation period. Radioactivity from [1-14C]-18:3(n-3) was recovered in several hepatocyte PUFA, including 22:6(n-3), and the Δ6 and Δ5-desaturation products 18:4(n-3) and 20:5(n-3). The presence of radioactivity in C24 (n-3) PUFA may be evidence that the biosynthesis of 22:6(n-3) in pike proceeds via a pathway independent of Δ4-desaturation. Analysis by radio gas chromatography revealed that radiolabelled 24:6(n-3) was present among the desaturation and elongation products of [l-14C]-18:3(n-3). The results establish that, under the in vitro conditions employed, pike hepatocytes are able to convert linolenic acid to 20:5(n-3) and 22:6(n-3).
Journal of Fish Biology 03/2005; 51(6):1197 - 1208. · 1.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The lipid composition of two species of Serrasalmid fish with different natural feeding habits were compared in relation to the polyunsaturated fatty acids (PUFA) supplied in their diets. Mylossoma aureum, a herbivorous piranha, was maintained on oatmeal flakes in which : 2(n-6) and : 3(n-3) were the only PUFA and accounted for 40–8 and 1.2%, respectively of dietary fatty acids. Serrasalmus nattereri, the carnivorous red piranha, was fed mosquito larvae containing .0-33.4% of their total fatty acids as : 2(n-6)+18 : 3(n-3) and 4.9-8.5% as 20 : 4(n-6)+20 : 5(n-3). The two species had similar lipid class compositions in liver, brain, viscera and carcass, except that lipids from M. aureum were generally richer in triacylglycerols. In both species, visceral and carcass lipid contained high levels of triacylglycerols whose principal PUFA was : 2(n-6). In M. aureum the major PUFA in liver total lipid and triacylglycerols was : 2(n-6) whilst the major PUFA in liver phospholipids were : 4(n-6) and : 5(n-6), with : 6(n-3) being a minor component. The level of : 6(n-3) in ethanolamine glycerophospholipids was significantly greater in brain than liver of M. aureum. Although absent from dietary lipid, : 6(n-3) was the major PUFA in phosphatidylcholine and ethanolamine glycerophospholipids from both the liver and brain of S, nattereri. In both species, the ratio of (n-6)/(n-3)PUFA was consistently lower in tissue lipids than in dietary lipids. The results are consistent with (i) the herbivorous M. aureum converting dietary C18 PUFA to their C20 and C22 homologues, (ii) the carnivorous S, nattereri forming : 6(n-3) from either 18:3(n-3) or 20: 5(n-3) and (iii) both species selectively desaturating and elongating (n-3) rather than (n-6) PUFA.
Journal of Fish Biology 03/2005; 48(3):522 - 538. · 1.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Against a background of decreasing availability of fish oils for use in aquaculture, the present study was undertaken to examine whether a wax ester-rich oil derived from the calanoid copepod Calanus finmarchicus, could be used effectively by Atlantic salmon when supplied in their diet. Individually tagged Atlantic salmon of initial weight around 500 g were divided into replicate tanks of two dietary groups and fed either a fish oil supplemented diet, or an experimental diet coated with Calanus oil. Wax esters accounted for 37.5% of the lipids in the Calanus oil diet but were absent from the fish oil diet in which triacylglycerols (TAG) were the major lipid class. Over the feeding period (140 days) the salmon fed fish oil displayed a greater increase in length, but there was no significant difference between the two groups in weight gained. The specific growth rates (0.75) and the feed conversion ratio of fish fed the two diets were similar throughout the study. No differences were observed in the apparent digestibility coefficients (ADC) of fish fed Calanus oil or fish oil. The ADC of fatty acids decreased with chain length and increased with unsaturation. Long-chain alcohol utilization showed a similar tendency although there was a notable difference in that saturated long-chain alcohols were utilized better than the comparable fatty acid homologue. In fecal lipid of fish fed Calanus oil, the content of 16:0 alcohol decreased in both the free long-chain alcohol and wax ester fractions, while the corresponding fatty acid increased in the feces of both dietary groups of fish. In contrast, the proportion of the 22:1n−11 alcohol increased in both fecal wax esters and free long-chain alcohol fractions whereas 22:1n−11 fatty acid displayed no accumulation. The observed patterns of fatty acid and long-chain alcohol compositions in fecal lipid compared to those of the initial dietary lipid are consistent with the digestive lipases of salmon preferentially hydrolyzing esters containing polyunsaturated fatty acid (PUFA) moieties. The wax esters of Calanus oil contained substantial amounts of the n−3 PUFA, 20:5n−3 and 22:6n−3, that were effectively deposited in muscle and liver tissues. No major differences were seen in either lipid content/lipid classes or in gross fatty acid composition of these tissues between the two dietary groups. It is concluded that that Atlantic salmon in seawater can effectively utilize diets in which a major lipid component is derived from zooplankton rich in wax ester without any detrimental change in growth or body lipid composition. This finding gives support to the use of lipid from zooplankton from high latitudes as an alternative or as a supplement to fish oil and a provider of long-chain n−3 PUFA in diets for use in salmon aquaculture.
[Show abstract][Hide abstract] ABSTRACT: The influence of feeding high levels of polyunsaturated fatty acids (PUFA) on muscle fatty acid composition and indices of oxidative damage was examined in Arctic charr, Salvelinus alpinus (L.). All diets contained 100 g kg−1 lipid of dry weight. Two diets contained marine fish oils giving a PUFA level of 250 g kg−1 and 500 g kg−1 of lipid. The remaining two diets contained vegetable oils high in either 18:2n-6 or 18:3n-3, giving a PUFA level of more than 500 g kg−1 of dietary lipid. The charr were maintained at 8°C until their weight doubled, and were then transferred to 0.8°C for 30 days. Growth was similar in all groups. The fatty acid compositions of muscle were influenced by dietary PUFA but were less diverse than those of the diets. The overall pattern of fatty acid compositions indicated preferential desaturation and elongation of n-3 PUFA coupled with selective oxidation of 18:2n-6. Total n-3 PUFA content in TAG was always lowered compared with the diet, suggesting a specific mechanism for the removal of these fatty acids. Subjecting the fish to low temperature increased PUFA content in muscle of charr fed the 250 g kg−1 marine n-3 PUFA diet, but had no effect on the other treatments. For fish at 8°C, no significant differences were found between groups in terms of haematocrit, plasma alanine aminotransferase (ALAT), and plasma and muscle thiobarbituric acid reactive substances (TBARS), although there was a tendency towards increased levels of TBARS in the group receiving 500 g kg−1 marine n-3 PUFA of lipid. Subjecting the muscle to forced oxidative conditions resulted in increases in TBARS in all groups, particularly those fed 500 g kg−1 marine n-3 PUFA. Lowering the environmental temperature corresponded with a further increase in the plasma ALAT and muscle TBARS in this group. It is concluded that feeding diets containing high levels of long-chain n-3 PUFA may be detrimental to the fish's health and flesh quality, particularly at low environmental temperatures.
[Show abstract][Hide abstract] ABSTRACT: The in vitro incorporation of 3H-radio-labeled arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acids by the photosensitive trout pineal gland was visualized using photon and electron microscopy. After 6 hr of incubation, 3H-20:4n-6 appeared distributed in photoreceptors, as well as in glial cells, whereas 3H-22:6n-3 was preferentially taken up by photoreceptors, mainly in the apical part (including the photoreceptive outer segment). Radioactivity was mainly seen over membranes of glia when the incorporation of 3H-20:4n-6 was followed by 12-18 hr of chase. We also report differences in the incorporation of 14C-radio-labeled linoleic (18:2n-6), linolenic (18:3n-3), eicosapentenoic (20:5n-3), 20:4n-6, and 22:6n-3 acids into the lipids in glands cultured under different lighting regimes. Phosphatidylcholine and triacylglycerols contained most of the radio-labeled polyunsaturated fatty acids (PUFA) incorporated. The proportion of incorporated 20:4n-6 recovered in phosphatidylinositol was always significantly higher than that found with the other PUFA. At least 10% of radioactivity from each incorporated substrate, except 22:6n-3, was recovered in elongation products. It is concluded that the pineal gland of the trout can assimilate exogenous PUFA into cellular lipids in vitro, in a manner consistent with our previous in vivo findings. In terms of lipid composition, the trout pineal gland resembles more the vertebrate retina than the rat pineal gland. This might be related to the loss of direct photosensitivity of the mammalian pineal. Together, the differences reported herein between 22:6n-3 and 20:4n-6 suggest the former plays an important role in the phototransduction process, whereas the latter might be more specifically involved in the production of phosphoinositide-derived second messengers.
Journal of Pineal Research 10/2001; 31(2):127-37. · 7.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Duplicate groups of Atlantic salmon parr were fed diets containing either fish oil (FO), rapeseed oil (RO), linseed oil (LO) or linseed oil supplemented with arachidonic acid (20:4n-6; AA) (LOA) from October (week 0) to seawater transfer in March (week 19). From March to July (weeks 20–34) all fish were fed a fish oil-containing diet. Fatty acyl desaturation and elongation activity in isolated hepatocytes incubated with [1-14C]18:3n-3 increased in all dietary groups, peaking in early March about one month prior to seawater transfer. Desaturation activities at their peak were significantly greater in fish fed the vegetable oils, particularly RO, compared to fish fed FO. Docosahexaenoic acid (22:6n-3:DHA) and AA in liver and gill polar lipids (PL) increased in all dietary groups during the freshwater phase whereas eicosapentaenoic acid (20:5n-3; EPA) increased greatly in all groups after seawater transfer. The AA/EPA ratio in tissue PL increased up to seawater transfer and then decreased after transfer. AA levels and the AA/EPA ratio in gill PL were generally higher in the LOA group. The levels of 18:3n-3 in muscle total lipid were increased significantly in the LO, LOA and, to a lesser extent, RO groups prior to transfer but were reduced to initial levels by the termination of the experiment (week 34). In contrast, 18:2n-6 in muscle total lipid was significantly increased after 18 weeks in fish fed the diets supplemented with RO and LO, and was significantly greater in the FO and RO groups at the termination of the experiment. Gill PGF production showed a large peak about two months after transfer to seawater. The production of total PGF post-transfer was significantly lower in fish previously fed the LOA diet. However, plasma chloride concentrations in fish subjected to a seawater challenge at 18 weeks were all lower in fish fed the diets with vegetable oils. This effect was significant in the case of fish receiving the diet with LOA, compared to those fed the diet containing FO. The present study showed that during parr-smolt transformation in Atlantic salmon there is a pre-adaptive increase in hepatocyte fatty acyl desaturation/elongation activities that is controlled primarily by environmental factors such as photoperiod and temperature but that can also be significantly modulated by diet. Feeding salmon parr diets supplemented with rapeseed or linseed oils prevented inhibition of the desaturase activities that is induced by feeding parr diets with fish oils and thus influenced the smoltification process by altering tissue PL fatty acid compositions and eicosanoid production. These effects, in turn, had a beneficial effect on the ability of the fish to osmoregulate and thus adapt to salinity changes.
Fish Physiology and Biochemistry 06/2000; 23(1):59-73. · 1.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The bed-forming brittlestars Ophiothrixfragilis, Ophiocominanigra and Amphiurachiajei from Oban Bay, Scotland were studied using methods previously employed to study chemoautotrophic symbioses. Ophiothrixfragilis and A.chiajei both contain symbiotic bacteria (SCB) while Ophiocominanigra is non-symbiotic. Samples were taken of Ophiothrixfragilis at approximately two-week intervals for one year. Symbiotic bacteria numbers were determined by direct counting of homogenates of the arms of 50 individual brittlestars. Water samples were analysed for chlorophyll content. Stable isotope ratios for carbon and nitrogen were determined for each homogenate sample. Regular SCB counts were made on the infaunal brittlestar A.chiajei. Homogenate samples of Ophiothrixfragilis, A.chiajei and the non-symbiotic Ophiocominanigra were analysed to produce fatty acid profiles for each species. Symbiotic bacteria count varied by up to one order of magnitude in both Ophiothrixfragilis and A.chiajei with no evidence of seasonality in this variation. Symbiotic bacteria number was inversely correlated with 13C. 16:17 fatty acids were used as putative bacterial markers. Both symbiotic species had higher percentages of 16:17 from its SCB. The SCB are heterotrophic and may contribute to the nitrogen budget of the host. The two symbiotic species studied here derive the bulk of their nutrition from conventional feeding but SCB make significant, additional contributions.
Journal of the Marine Biological Association of the UK 04/2000; 80(02). · 1.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To study the intestinal fatty acid absorption in fish in vitro, enterocytes were isolated from the intestine of rainbow trout and incubated with an equimolar mixture of seven fatty acids [16:0, 18:1n-9, 18:2n-6, 18:3n-3, 20:4n-6, 20:5n-3 and 22:6n-3] in which the component carrying a radioactive label was varied. The fatty acid mixture was presented in the form of micelles formed by sonication with sodium taurocholate. Control studies showed that the presence of sodium taurocholate in the incubation medium caused an immediate 23% increase in the mortality of the cells but the remaining cells were viable. The effect of the bile salt on cellular permeability was evident at longer exposure periods. The proportions of 14C-labelled 20:5n-3 and 22:6n-3 present as monomeric fatty acids in the micellar solutions were higher than those of 16:0, 18:1n-9, 18:2n-6, 18:3n-3 and 20:4n-6. The rates of uptake of 14C-labelled 20:4n-6, 20:5n-3 and 22:6n-3 by enterocytes were significantly lower than those of the other fatty acid substrates over the first minute of incubation but no significant differences in uptake rate between fatty acids were obvious over a 15 min incubation period. Notable differences were observed between substrates in their distribution pattern in enterocyte lipid classes. Although most of the radioactivity from all radiolabelled substrates was recovered in triacylglycerols, the amounts of 14C- labelled 16:0, 20:4n-6, 20:5n-3 and 22:6n-3 recovered in the polar lipid fraction were higher than those of 14C-labelled C18 substrates, particularly after 15 min. Conversely, the initial esterification rates of 18:1n-9, 18:2n-6 and 18:3n-3 into triacylglycerols were significantly higher than those of 20:4n-6, 20:5n-3 and 22:6n-3. It is concluded that isolated enterocytes can be used for the study of the mechanism of intestinal fatty acid absorption in fish.
Fish Physiology and Biochemistry 01/1999; 20(2):125-134. · 1.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cultures of a species of Vibrio isolated from fish intestines and known to synthesize the polyunsaturated fatty acid eicosapentaenoic acid (20:5n-3) were incubated with di-[1-14C]palmitoyl phosphatidylcholine to determine if lipolytic enzymes are produced by the bacteria. After two days of culture, most radioactivity was recovered in the phospholipids of the bacterial cells. When supernatants from cultures of the Vibrio were incubated with either di-[1-14C]palmitoyl phosphatidylcholine, 1-palmitoyl-2-[1-14C]linoleoyl phosphatidylcholine or 1-[1-14C]palmitoyl lysophosphatidylcholine almost all radioactivity was recovered in the free fatty acid fraction after 24 h. Only very small levels of radioactivity from di-[1-14C]palmitoyl phosphatidylcholine were recovered in diacylglycerols and phosphatidic acid. Over the same incubation period 61% and 5% of the radioactivity originally present in glycerol tri-[1-14C]oleate and cholesteroyl [1-14C]oleate, respectively, was released to free fatty acids. Soybean phosphatidylcholine and cod roe phosphatidylcholine, which differed in polyunsaturated fatty acid profile, were both hydrolyzed by culture supernatant. The results suggest that the Vibrio species examined produces a phospholipase B capable of hydrolyzing both intact phospholipids and lysophospholipids.
Journal of Marine Biotechnology 09/1998; 6(3):168-73. · 1.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effects of long chain n-3 polyunsaturated fatty acids (PUFA) on the desaturation and elongation systems involved in the conversion of 18:3n-3 to 24:6n-3 were investigated. Microsomes were prepared from the livers of rainbow trout and incubated with 14C-labelled 18:3n-3 and cofactors required for elongation and/or desaturation in the presence of 22:6n-3, 24:5n-3 or 24:6n-3. The formation of 24:6n-3 was significantly inhibited in the presence of 50 microM 22:6n-3, 24:5n-3 or 24:6n-3, whereas the amount of radiolabelled 20:5n-3 formed was inhibited by only 24:5n-3 or 24:6n-3 at the same concentration. When malonyl-CoA was omitted from the incubation system to allow the measurement of desaturation in the absence of elongation, the Delta6 desaturation of 14C-18:3n-3 to 14C-18:4n-3 was inhibited by approximately 25% in the presence of 24:5n-3 or 24:6n-3 but was not affected by 22:6n-3. The Delta5 desaturation of 14C-20:4n-3 was not affected by the presence of any of the long chain PUFA and no significant effect of 18:3n-3, 22:6n-3 or 24:6n-3 on the Delta6 desaturation of 24:5n-3 to 24:6n-3 was observed. To permit the measurement of individual elongation reactions, KCN was included in the incubation medium to inhibit desaturation and 14C-labelled 18:3n-3, 18:4n-3, 20:4n-3, 20:5n-3 and 22:5n-3 were examined as substrates. 18:4n-3 and 22:5n-3 were more extensively used for elongation than 18:3n-3, 20:4n-3 and 20:5n-3. The presence of 22:6n-3, 24:5n-3 or 24:6n-3 in the incubation system had no effect on any of the specific elongations of any of the substrates examined. It is concluded that, in the conversion of 18:3n-3 to 24:6n-3 by trout liver microsomes, the Delta6 desaturation of 18:3n-3 may be subjected to direct feedback inhibition and that 24:5n-3 may be preferred over 18:3n-3 as a substrate for Delta6 desaturation.
Biochimica et Biophysica Acta 07/1998; 1392(2-3):309-19. · 4.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The fatty acid compositions of neutral lipid, glycolipid and phospholipid fractions from ice algae sampled from the Barents
Sea in spring and autumn were examined for seasonal differences. The ice-algal assemblages were dominated by diatoms. In spring,
Nitzschia frigida was the most common species whereas resting stages of Thalassiosira bioculata and Actinocyclus cf curvatulus predominated in autumn. With the exception of one spring sample, neutral lipids predominated over glycolipids and phospholipids
in all algal samples. The lipid fractions displayed characteristic fatty acid compositions. In the spring samples the major
fatty acids of the neutral lipid fraction were 16:0, 16:1(n-7) and 20:5(n-3) whilst the glycolipid fraction was characterised
by higher levels of 20:5(n-3) and C16 polyunsaturated fatty acids, particularly 16:4(n-1). Phospholipids contained higher
levels of 22:6(n-3) than the other two lipid fractions although 20:5(n-3) was still the major polyunsaturated fatty acid.
In the autumn samples, the neutral lipid fraction contained higher proportions of saturated fatty acids and 16:1(n-7) than
the two polar lipid fractions and 22:6(n-3) was most abundant in phospholipids. As with the spring samples, 20:5(n-3) was
the major polyunsaturated fatty acid in all lipid fractions of the autumn algae. Overall, the fatty acid compositions of the
lipid fractions from spring and autumn algal samples were similar and are consistent with diatoms being the predominant group
in the ice algae studied. The high level of neutral lipids observed in both spring and autumn samples suggests that the production
of neutral lipids is characteristic of ice algae regardless of season. Nevertheless, some species-specific differences in
lipid production may exist since the neutral lipid content of autumn samples containing mainly A. curvatulus was substantially higher than those in which T. bioculata predominated.
[Show abstract][Hide abstract] ABSTRACT: To study the potential of fluorescence based assays in the study of lipid digestion in fish, acyl esters of 4-methylumbelliferone and 1-acyl-2-[6 (7 nitro-1,3 benzoxadiazol-4-yl)amino]caproyl labeled phosphatidylcholine compounds (NBD-PC) were used as substrates for the assay of neutral lipase and phospholipase, respectively, in the gut contents of turbot. 4-Methylumbelliferyl hepatanoate (4-MUH) was hydrolysed at a higher rate than the butyrate or oleate esters whilst the hexanoic (C6) ester of NBD-PC was a more convenient substrate for the phospholipase assay than the dodecanoic (C12) ester. Neutral lipase activity was almost 10% higher when 50 mm potassium phosphate buffer pH 7.8 was used instead of 0.01 m citrate/sodium phosphate buffer pH 7.2. Both assays were very sensitive: neutral lipase and phospholipase activities were detectable at a minimum protein concentration in the digesta of 0.04 and 1.25 mg/ml, respectively. When the variations in lipolytic activities with gut segment and with size of fish were examined neutral lipase activity was always found to be higher in the hindgut and rectum segments than in the foregut. Although phospholipase activity was also found to be highest in the hindgut of the largest fish examined (av. wt. 182.3g), in fish of average weight 8g fish the activity was similar in all three segments. In the digesta from the whole gut of smaller fish (av. wt. 0.2, 0.6 and 1.43g) neutral lipase and phospholipase activities increased with increasing body mass when expressed as per ml of digesta. It is concluded that fluorescence-based assays are applicable to the study of lipid digestion in fish of different size.
Fish Physiology and Biochemistry 01/1998; 19(2):153-162. · 1.55 Impact Factor