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[Quantitative determination of trace metals in frozen fish, fish oil and fish meal (author's transl)].

As a contribution to the discussion on the "Verordnung uber Umweltkontaminanten" (draft) we examined 73 double samples of the frequent types of edible fish and 2 samples each of fish oil and fish meal for their content of arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg). Arsenic was determined photometrically, cadmium and lead by anodic stripping voltammetry and mercury by flameless atomic absorption spectrometry. We found the following average contents (ppm): 0.84 As, 0.003 Cd, 0.08 Pb, 0.06 Hg. The limits (ppm) set up in the draft for a German "Höchstmengenverordnung" (regulation specifying the maximum concentrations allowed) were by far not reached in the case of Cd, Pb, and Hg with all samples while they were fulfilled in the case of As by only 18% of the samples. It seems that the limit for As of 0.5 ppm has been set up too low. In the average, the following proportion applies for the trace contents found: Cd:Hg:Pb:As = 1:20:27:280. Correlations between the contents of trace metals on the one hand and fishing grounds or trawler or sample piece on the other could not be found.

Arsenic

Polyunsaturated fatty acid metabolism in fish cells: differential metabolism of (n-3) and (n-6) series acids by cultured cells originating from a freshwater teleost fish and from a marine teleost fish.

1. The incorporation and metabolism of (n-3) and (n-6) polyunsaturated fatty acids (PUFA) supplemented to growing cultures were studied in rainbow trout (RTG-2) and turbot (TF) cell lines. 2. A fatty acid concentration of 20 microM considerably altered the fatty acid composition of the cells without affecting lipid class composition or the appearance of cytoplasmic lipid droplets. 3. Both cell lines exhibited considerable delta 6 desaturase activities. 4. Whereas delta 5 desaturase activity was expressed in RTG-2 cells, delta 4 desaturase activity was absent and, conversely, delta 4 desaturase activity was expressed in TF cells, but there was an apparent deficiency in the C18 to C20 elongase multi-enzyme complex. 5. The delta 6 desaturase activity in both cell lines showed little preference between 18:2(n-6) and 18:3(n-3) but the delta 5 desaturase activity of RTG-2 cells and the delta 4 desaturase activity of TF cells showed a preference for (n-3)PUFA. 6. Two fish oil concentrates were assessed for their ability to generate fatty acid compositions in the cell lines more closely resembling those of intact fish tissues.

Animals

Fish hypersensitivity. I. In vitro and oral challenge results in fish-allergic patients.

The purpose of this study was to determine whether patients allergic to one fish species can safely eat other fish species. Eleven atopic, food-allergic children and young adults with histories consistent with IgE-mediated fish hypersensitivity were skin prick tested to 10 fish species. Skin prick tests (SPTs) were positive to all 10 fish in eight of the 11 patients, and the remaining three patients had at least two positive fish SPTs. Positive oral challenges occurred to only one fish in seven of the patients, to two fish species in one patient, and to three fish species in two patients. One patient did not react to any of the fish tested. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analyses were performed on raw and cooked protein extracts from nine of the 10 fish species used in SPTs. Several protein bands in the raw-fish extracts appeared to denature with cooking and form high molecular weight conglomerates. Immunoblot analyses with sera from documented fish-allergic patients demonstrated specific IgE binding to protein bands from fish to which patients were not clinically allergic, as determined by oral challenge. In ELISA-inhibition assays, the concentration of fish antigen required to achieve 50% inhibition was similar for fish to which the patients were clinically allergic as compared to fish to which they were clinically tolerant. SPT and in vitro evidence of IgE-specific cross-reactivity does not necessarily correlate with symptomatic fish allergy. In addition, these fish-hypersensitive patients were able to consume one or more other fish species without adverse allergic reactions.

Adolescent

Fish and fish oil intake: effect on haematological variables related to cardiovascular disease.

To investigate the effects of practical amounts of n-3 highly-unsaturated fatty acids (HUFA) on a number of parameters involved in haemostasis, 12 healthy men were fed three diets in a 3 x 3 cross-over design. The diets, fed as the evening meal for 6-week periods, were: Control diet (essentially fish-free), Fish diet (200 g/d of lean Australian fish flesh) and the same fish-based diet but supplemented with 5 g/d fish oil (Fish + Oil). The diets supplied about 0, 0.6, and 2.0 g n-3 HUFA/d, respectively. Relative to the Control diet, the number of circulating leukocytes was significantly reduced after both the Fish and Fish + Oil diets (by 13% and 15%, respectively). This reduction occurred in the number of neutrophils, although this did not reach significance on the Fish diet alone. Platelet count fell on the Fish + Oil diet (by 6%) but not on the Fish diet alone. There was an apparent enhancement of fibrinolytic potential after both fish-containing diets, which tended to be accentuated with the fish oil supplementation. The mechanisms underlying some if not all of these observations may be eicosanoid-mediated as indicated by a diminution in the platelet arachidonic acid (20:4n-6) to eicosapentaenoic acid (20:5n-3) ratios after the Fish + Oil (13.7 +/- 1.8) and Fish (34.4 +/- 8.9) diets relative to the Control diet (66.1 +/- 15.6). These data suggest that a practical amount of lean fish can improve certain haematological parameters implicated in the etiology of cardiovascular disease.

Animals

Erythrocyte eicosapentaenoic acid versus docosahexaenoic acid as a marker for fish and fish oil consumption.

The fatty acid composition of erythrocyte membranes was investigated in 21 healthy men after 6 wk of varying intakes of eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). In one experiment, 12 subjects were fed three diets in a 3 x 3 crossover design: an essentially fish-free control diet, a fish diet (0.15 g EPA/d, 0.41 g DHA/d) and the same fish-based diet supplemented with 5 g/d fish oil (Fish + Oil: 0.99 g EPA/d, 0.99 g DHA/d). A 6 wk wash-out period was allowed between each diet. In another experiment, 11 subjects were supplemented with 5 g/d fish oil alone for 6 wk (0.84 g EPA/d, 0.48 g DHA/d). After fish or fish oil feeding, the percent proportion of EPA and DHA in the erythrocyte membranes rose at the expense of linoleic and arachidonic acids. After 6 wk on the fish-based diets, EPA incorporation approached saturation, with the incremental increases being proportional to the amounts supplied by the diets. In contrast, parallel increases were observed for erythrocyte DHA even though the Fish + Oil diet was supplying twice as much DHA as the fish alone diet. These observations imply different metabolic rates for EPA and DHA and their importance is discussed in terms of the value of erythrocyte EPA versus DHA as markers for fish and fish oil consumption.

Adolescent

Lipid, lipoprotein, and hemostatic effects of fish vs fish-oil n-3 fatty acids in mildly hyperlipidemic males.

The effects of fish and fish oil on lipids, hemostasis, and blood pressure were compared in 25 mildly hyperlipidemic men who received 4.5 g eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) daily for 5 wk. Six additional subjects served as controls. Fish and fish oil lowered plasma triglycerides 20% and 28% and very-low-density-lipoprotein (VLDL) triglycerides 42% and 52%, respectively (all P less than 0.05 compared with control). High-density-lipoprotein (HDL) cholesterol increased by 10% and 9%, with 34% and 32% increases in the proportion of HDL2 particles for fish and fish oil, respectively. Changes in total cholesterol, LDL cholesterol, apolipoprotein B, and blood pressure with fish and fish oil were not significantly different from changes for the control diet. The fish lowered fibrinogen (15.7%) and thromboxane (10.5%) and increased bleeding time (10.8%) (P less than 0.05 compared with control). Eating fatty fish and fish oil produced comparable lipid and lipoprotein changes, but only the fish improved hemostatic factors.

Adult

A mixed Australian fish diet and fish-oil supplementation: impact on the plasma lipid profile of healthy men.

Twelve healthy men were fed in turn three diets for 6 wk each in a 3 x 3 randomized block design: a control diet (essentially fish free), a fish diet (200 g lean Australian fish flesh/d), and the same fish-based meal but supplemented with 5 g fish oil/d. Dietary eicosapentaenoic acid [EPA, 20: 5n-3 (omega-3)] was strongly associated with erythrocyte membrane EPA (r = 0.908 at 6 wk), strengthening its value as a measure of compliance in fish and fish-oil feeding trials. On the fish diet, subjects had increased incorporation of n-3 polyunsaturated fatty acids (PUFAs) at the expense of n-6 PUFAs in their erythrocyte membranes. When the fish-based diet was supplemented with fish oil (5 g/d), there was a significant lowering of plasma triacylglycerol (-0.16 +/- 0.24 mmol/L; mean +/- SD). No change in plasma total cholesterol was detected although the fish + oil diet produced a reduction in very-low-density-lipoprotein cholesterol (-0.24 +/- 0.26 mmol/L).

Adult

Diet and fatty acids: can fish substitute for fish oil?

As fish oil has been shown to be beneficial in rheumatoid arthritis and in psoriasis, we examined whether a diet rich in fish has a similar effect on membrane and plasma lipids as a dietary fish oil supplement. Volunteers recruited by 2 rheumatology units in Switzerland formed three parallel groups eating respective diets during 2 months: a normal diet without fish; a normal diet including 700 g fish per week; a normal diet without fish but with additional fish oil (7.5 g daily). As outcome measures we determined the lipid composition of platelet-rich plasma, the serum cholesterol and triglycerides before the study and after 1 and 2 months of the designated diet. The relative amounts of both eicosapentaenoic acid and docosahexaenoic acid increased significantly in the fish oil group and in the group with the fish diet; no change was seen in the control group. The effect on triglycerides, which were low at the beginning of the study, was minor and no change in cholesterol was seen. In conclusion, 4 to 6 meals with fish per week without any other dietary changes can induce similar changes in lipids as a supplement of fish oil.

Adolescent

[Arsenic contamination in imported sea fish and fish products made from them].

The rate of arsenic contamination in sea-fish is, in comparison with freshwater fish, relatively high. An investigation of five kinds of sea-fishes--of mackerel, herring, cod, tunny, and plaice--that are most frequently put on the market showed that a permitted value up to 1 mg As per 1 kg of fish meat was found only in 24.0% of mackerel, 9.5% of herring, 33.4% of cod, 57.0% of plaice and 0.0% of tunny. Further investigation of dressed fish--of fillets--revealed that 15.8% of herring fillets and 0.0% of cod fillets met the permitted value. The values of a majority of studied sea-fish samples ranged from 1 to 2 mg As per 1 kg: 52% of mackerel, 63.5% of herring, 66.6% of cod, 43% of tunny, 28% of plaice. It is necessary to revalue the permitted values of arsenic content in sea-fish and in products made from their meat and to defend the upper limits of the permitted arsenic value, which will require the purposeful organization of effective laboratory tests the results of which will directly influence an estimation of fish raw material and will provide the corresponding hygienic quality of fish and fish products.

Animals

Fish hypersensitivity. II: Clinical relevance of altered fish allergenicity caused by various preparation methods.

In double-blind, placebo-controlled, oral food challenges with fish, a 12-fold higher false-negative rate was found compared with other food antigens. In an effort to elucidate this discrepancy, cooked lyophilized fish extracts (used in double-blind, placebo-controlled, oral food challenges) were compared with cooked, nonlyophilized fish extracts (used in open challenges) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblot, and ELISA-inhibition assays. Altered fish allergenicity as a result of food processing was examined with canned tuna and salmon. Forty-five children and young adults with food allergies, including 18 patients with IgE-mediated hypersensitivity to fish, were challenged with canned tuna. All 45 challenges with canned tuna were negative. Two of these patients are allergic to salmon and also have negative reactions to challenges with canned salmon. In vitro investigation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of tuna and salmon extracts revealed a striking loss of definable protein fractions in the canned fish extract when compared with raw and cooked fish extracts, and immunoblot analyses demonstrated minimal IgE-specific binding to the canned fish extracts. In addition, decreased allergenicity of the canned tuna and salmon was demonstrated by ELISA-inhibition assay and by negative oral challenges with canned salmon in two patients allergic to salmon. Collectively, these findings suggest that some of the major allergens responsible for IgE-mediated food allergy to fish are more labile than previously recognized.

Allergens

Fish mongers and public awareness on fish-food hygiene in Nigeria.

Sale of fish is a thriving business in Nigeria because of the high demand for fish. However, there is lack of public awareness on the need for fish hygiene by fish mongers and consumers. This paper discusses the issue of hygiene as it affects a fish shop environment, insects and pests of fish, preservation, handling, transportation, packaging, fish marketing and distribution. Suggestions on improving fish food hygiene and strategies for establishing fish guidelines and inspections are highlighted.

Animals

[Isolation of halphilic vibrios in marine fishes and fish products].

Examinations of 882 samples of newly caught, frozen, salted, sun-dried and smoked marine fish and of 50 samples of canned fish and preserves were conducted to study the contamination with halophil vibrios of the marine fish and fish products. The newly caught fish was found to be contaminated with Vibrio parahaemolyticus on the average in 28.6 per cent of the cases and with Vibrio alginolyitcus, on the average in 52.2 per cent of the instances. The Vibrio parahaemolyticus contamination of the marine fish during its processing and storage varied from 3.3 up to 21.7 per cent. The contamination of the fish was noted to be greatest in summer months. These microorganisms were not isolated in canned fish and preserves. In the course of research a total of 845 strains of halophil microorganisms were isolated, 240 of which were found to be similar to Vibrio parahaemolyticus. The properties of the cultures isolated were studied.

Animals

[Should I also eat fish oils? A critical assessment of the use of fish oils in the prevention of ischemic heart disease].

The effect of a daily dietary supplement of 6 g fish oil (3.4 g eicosapentaenoic and docosahexaenoic acid) on body weight, blood pressure, bleeding time and blood lipids was assessed in an open trial. The fish oil was taken for four weeks by nine 30-55 year-old individuals. An age- and sex-matched control group took equivalent amounts of safflower oil, which has an overall fatty acid composition similar to the tested fish oil. The fish oil supplement caused significant changes in body weight (median: +0.9 kg), systolic blood pressure (-10 mmHg), diastolic blood pressure (-5 mmHg), and high density lipoprotein (HDL) cholesterol concentration (+0.21 mmol/l), whereas serum triglycerides decreased insignificantly (-0.25 mmol/l). Low density lipoprotein (LDL) concentration were not affected. We observed no changes in the control group. In the discussion, it is underlined that fish oil supplementation may affect some risk markers of ischemic heart disease favourably. However, other important risk markers, including LDL cholesterol, are unaffected or unfavourably affected by fish oils. A more uni-directional reduction in risk can be attained by a change in dietary habits, which should be preferable to a fish oil supplement in the general population. Individuals who show critically low HDL/total cholesterol ratios, who are hypertriglyceridemic, or are mildly hypertensive may, however, benefit from a fish oil supplement of the amount tested here.

Adult

Treatment of fish parasites. 9. Effects of a medicated food containing malachite green on Ichthyophthirius multifiliis Fouquet, 1876 (Hymenostomatida, Ciliophora) in ornamental fish.

For systemic therapy against trophozoites of the skin-inhabiting stage of Ichthyophthirius multifiliis in ornamental fish, the latter were fed medicated food flakes containing malachite green once daily for 1-11 days ad libitum. Naturally or artificially infected cardinal tetras (Paracheirodon axelrodi), blue gouramis (Trichogaster trichopterus), or clown loach (Botia macracantha) were used in the trials. The fish were maintained in aerated 12.5- or 60-1 aquaria at 23 degrees C. Ultrastructural investigations (scanning and transmission electron microscopy) revealed clear deleterious effects of malachite green on the parasitic stages. Following the initial application, the inner membrane of the mitochondria was destroyed. In fish fed for 2 days, aggregation of the mucocysts and polymerization the microtubules within the macronucleus occurred. Finally, the trophozoite's membrane was completely destroyed. In fish fed for 4 days, the medicated food killed all trophozoites of I. multifiliis. Sensitive ornamental fish (e.g., P. axelrodi) showed no adverse effects after they had been fed with only the medicated food flakes for 2 months. Therefore, the oral administration of malachite green using this newly developed medicated food considerably reduces the risk of toxic effects on the fish hosts, which are sometimes caused by malachite green following its application by immersion therapy. The feeding of flakes medicated with malachite green provides and easy-to-handle and highly effective treatment of I. multifiliis in ornamental fish.

Animal Feed

Fish food, fish oil and cardiovascular disease.

During recent years there has been growing interest in the possibility that dietary fish confers some protection against ischaemic heart disease. In four prospective studies, people who ate moderate amounts of fish tend to have a lower mortality from heart disease than persons who ate little or no fish. A randomized controlled trial showed that mortality after myocardial infarction was less among men who were advised to increase their intake of fatty fish than in a control group. Studies of fish oil administered to volunteers suggest that it is the omega-3 fatty acids which are responsible. The effects of fish oil include a reduction in serum triglyceride concentration, a reduction in platelet activity, a reduction in blood pressure, and (in animals) prevention of arrhythmias. Some of these effects require doses much larger than those that would normally be supplied by dietary fish.

Animals

[Fish diseases in Switzerland. A statistical evaluation of the diagnostic materials of the fish research laboratory from 1979-1988. I. General aspects].

The entire diagnostic material of the Fish Disease Laboratory at the University of Berne from 1979 to 1988, a total of more than 3800 cases, is presented. Not included is material of import controls and material from experimental work. The following criteria were evaluated: fish species, origin and length of fish, season, infectious and noninfectious diseases. Furthermore, the results were investigated for changes of the composition of fish species and number of diseases within the ten-year period and for a seasonal influence on the outbreak of diseases. More than 40% of all fish investigated were rainbow trout, followed by brown trout, omamental fish and cyprinids. Over 40% of fish originated from private fishfarms whereas 20% were of governmental origin (governmental fishfarms, rivers, lakes) and 20% from aquaria. Parasites were present in more than 40% of all cases. Bacterial infections were diagnosed in nearly 30%, viral infections in 6% and fungal diseases in 5% of all cases. 20% of all cases concerning noninfectious diseases were caused by unfavourable environmental conditions whereas the incidence of diseases related to nutrition was less than 10%. The occurrence of the different diseases was waxing and waning over the period of ten years but no definite tendencies could be emphasized. However, most of the diseases investigated demonstrated a significant seasonal influence.

Animals

[Preparation and analysis of dehydrated mixtures of vegetables and underutilized fish species flours: I. Dehydrated mixtures of cereal-fish].

For the purpose of providing possible solutions to the malnutrition problems affecting those populations where cereals and tubers form an important portion of their daily intake, products were prepared from dehydrated mixtures of cereals and under-utilized fish, but which contain high-quality protein. Two cereals were selected for our experiments: rice and corn, and a marine under-utilized fish species (Macrodon ancyclodon). The minced fish muscle recovered by mechanical deboning was mixed with the cereal, obtaining mixtures with 5%, 10% and 15% fish on a dry basis. Feeding experiments using Wistar weaning rats were then carried out to evaluate the most important characteristics. An amino acid profile which reflected high-quality protein was obtained, as evidenced by the excellent PER, NPU, NPR and digestibility values determined. The dehydrated mixtures of fish/cereal flour prepared with 5% and up to 10% fish (dry basis), did not present any odour, but as of the 15% level, fish odour was perceived. Therefore, the use of dehydrated mixtures of fish/cereal flours with up to 10% fish in preparing food products, is recommended, since these would be of great help in solving the scarcity of good-quality protein, particularly in the developing countries.

Amino Acids, Essential