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Effect of dietary fish oil on renal function and rejection in cyclosporine-treated recipients of renal transplants.

BACKGROUND: Dietary fish oil exerts effects on renal hemodynamics and the immune response that may benefit renal-transplant recipients treated with cyclosporine. To evaluate this possibility, we studied the effect of fish oil on renal function, blood pressure, and the incidence of acute rejection episodes in cyclosporine-treated recipients of renal transplants. METHODS: In a randomized, double-blind trial, 33 recipients of first cadaveric kidney transplants who were treated with cyclosporine and prednisolone ingested 6 g of fish oil daily during the first postoperative year (the fish-oil group), whereas another 33 renal-graft recipients treated with cyclosporine and prednisolone ingested 6 g of coconut oil daily for three months after which time it was stopped (the control group). RESULTS: One year after transplantation, the fish-oil group had higher median values than the controls for glomerular filtration rate (53 vs. 40 ml per minute per 1.73 m2, P = 0.038) and effective renal plasma flow (214 vs. 178 ml per minute per 1.73 m2, P = 0.023) and lower mean arterial pressure (103 vs. 118 mm Hg, P = 0.0011). The cyclosporine doses in the two groups were similar. The cumulative number of rejection episodes was 20 in the controls, as compared with 8 in the fish-oil group (P = 0.029). One-year graft survival also tended to be better in the fish-oil group, (97 vs. 84 percent, P = 0.097). CONCLUSIONS: The daily administration of 6 g of fish oil during the first postoperative year has a beneficial effect on renal hemodynamics and blood pressure in renal-transplant recipients treated with cyclosporine. Although the fish-oil group had significantly fewer rejection episodes than the control group, graft survival at one year was not significantly better in the fish-oil group.

Adjuvants, Immunologic↗

Hyperlipidaemic effect of fish oil in Bio F1B hamsters.

We investigated the dietary influence of low and high levels of fish oil, supplemented with or without dietary cholesterol, on the plasma lipoprotein profile in Bio F1B hamsters, a model susceptible to diet-induced hyperlipidaemia. The MIX diet, a diet supplemented with a mixture of lard and safflower-seed oil, was used as the control diet to maintain the saturated MUFA and PUFA levels similar to the fish-oil diet. The animals were fed the specific diets for 2 weeks and fasted for 14 h before killing. The plasma from the animals fed high levels of fish oil was milky and rich in chylomicron-like particles. The plasma total cholesterol, VLDL- and LDL-cholesterol and -triacylglycerol concentrations were significantly higher, whereas HDL-cholesterol was lower in hamsters fed fish oil compared with the MIX-diet-fed hamsters. Increasing the amount of fat in the diet increased plasma lipids in both the fish-oil- and the MIX-diet-fed hamsters; however, this hyperlipidaemic effect of dietary fat level was greater in the hamsters fed the fish-oil diet. The hepatic lipid concentrations were not dramatically different between the fish-oil-fed and the MIX-diet-fed hamsters. However, the hepatic LDL-receptor mRNA levels were significantly low in the fish-oil-fed hamsters compared with the MIX-diet-fed hamsters. Increasing the amount of fish oil in the diet further decreased the hepatic LDL-receptor mRNA expression. It is concluded that F1B hamsters are susceptible to fish-oil-induced hyperlipidaemia, especially at high fat levels, and this increase is partially explained by the inhibition of hepatic LDL-receptor mRNA expression.

Animals↗

Fish-oil supplementation reduces stimulation of plasma glucose fluxes during exercise in untrained males.

The present study examined the effects of a 3-week fish-oil supplementation (6 g/d) on the rate of plasma glucose disappearance (Rd glucose), hepatic glucose production (HGP), carbohydrate oxidation and lipid oxidation during exercise. Six untrained males (23+/-1 years; 67.6+/-2.7 kg) performed two 90 min cycling exercise sessions at 60 % of maximal O2 output separated by 20 d. During the 20 d before the first test, they ingested 6 g olive oil/d, then 6 g fish oil/d during the 20 d before the second test. Plasma glucose fluxes and lipolysis were traced using 6,6-[(2)H2]glucose and 1,1,2,3,3-[(2)H5]glycerol respectively. Substrates oxidation was obtained from indirect calorimetry. At rest HGP and the Rd glucose were similar after olive oil and fish oil (1.83 (SE 0.05) v. 1.67 (SE 0.11) mg/kg per min). During exercise, fish oil reduced the stimulation of both the Rd glucose (5.06 (SE 0.23) v. 6.37 (SE 0.12) mg/kg per min; P<0.05) and HGP (4.88 (SE 0.24) v. 5.91 (SE 0.21) mg/kg per min; P<0.05). Fish oil also reduced glucose metabolic clearance rate (6.93 (SE 0.29) v. 8.30 (SE 0.57) ml/min). Carbohydrate oxidation tended to be less stimulated by exercise after fish oil than after olive oil (12.09 (SE 0.60) v. 13.86 (se 1.11) mg/kg per min; NS). Lipid oxidation tended to be more stimulated by exercise after fish oil (7.34 (SE 0.45) v. 6.85 (SE 0.17) mg/kg per min; NS). Glycaemia, lactataemia, insulinaemia and glucagonaemia were similarly affected by exercise after fish oil and olive oil. Lipolysis at rest was similar after fish oil and olive oil (2.92 (SE 0.42) v. 2.94 (SE 0.28) micromol/kg per min) and similarly stimulated by exercise (6.42 (SE 0.75) v. 6.77 (SE 0.72) micromol/kg per min). It is concluded that fish oil reduced the Rd glucose by 26 % by reducing glucose metabolic clearance rate, possibly by facilitating fat oxidation, and reduced HGP by 21%, possibly by a feedback mechanism.

Adult↗

Issues related to the use of fish models in toxicologic pathology: session introduction.

Ready or not, fish models are "here to stay." No longer are fish confined to a few specialized laboratories, nor are they exclusively the purview of zoologists or environmental toxicologists. In fact, the institution that does not house at least 1 fish facility is probably not at the forefront of cutting edge research. In toxicologic pathology, fish models are increasingly being used to provide high animal numbers at relatively low cost in carcinogenicity testing and developmental research, and to provide mechanistic information on fundamental cellular processes. In this session, we attempt to provide some perspective for the pathologist that is faced with planning or performing experiments or testing protocols using fish models, or with reading or interpreting fish studies. First, we cover how to approach fish studies from the contract laboratory standpoint, including sectioning, quality control, and GLP considerations. Then, we discuss specifics on the use of the rainbow trout, zebrafish, and Japanese medaka models. The rainbow trout has a rich history in carcinogenicity and mechanistic cancer research. Similarly, the 2 workhorses in the small fish category, zebrafish and medaka, have found their way into many laboratories doing developmental biology and genomics research as well as carcinogenicity testing. Some fascinating genetically altered fish models have been developed with both of these species. This manuscript provides a session overview of the use of small fish models in toxicologic pathology, along with some historical perspective on how these models have played a role in the current state of the science.

Animals↗

Fish flavor.

This article reviews features of flavor in three groups of fishes and summarizes them as follows: (1) fresh saltwater fish are nearly odorless because they contain a small quantity of volatiles; (2 freshwater fish give off pyrrolidine and earthy-odor compounds, which are responsible for their maturity and surrounding water pollution, and (3) euryhaline fish exhibit a variety of unsaturated carbonyls and alcohols derived from enzymatic and nonenzymatic oxidation of polyunsaturated fatty acids (PAs). These features are discussed, as are the effects of different enzymatic activities on PA oxidation and the effects of pH on mechanisms of formation of the volatiles. The monotonous volatile constitution of saltwater fish is likely caused by an unknown antioxidation system restraining the fish from oxidizing. The variety of constitution of euryhaline fish, especially that of anadromous fish under spawning conditions, could result from the loss of that system. The thermal environments of heated foods are also reviewed. The basic environment of fish, which allows the formation of flavor compounds, is discussed to confirm the volatiles found in unheated fish.

Animals↗

Randomized study of the safety and efficacy of fish oil (omega-3 fatty acid) supplementation with dietary and exercise counseling for the treatment of antiretroviral therapy-associated hypertriglyceridemia.

BACKGROUND: Omega-3 fatty acids (fish oils) reduce fasting serum triglyceride levels and cardiovascular disease risk in individuals without HIV infection. Whether omega-3 fatty acid supplementation can reduce hypertriglyceridemia associated with antiretroviral therapy is not known. METHODS: We conducted an open-label, randomized trial that enrolled 52 patients receiving > or =3 active antiretrovirals who had fasting triglyceride levels of >200 mg/dL and were randomized to receive nutritionist-administered dietary and exercise counseling with or without fish oil supplementation for 16 weeks. RESULTS: Patients assigned to receive fish oil experienced a 25% mean decline in fasting triglyceride levels at week 4 (95% CI, -34.6% to -15.7% change), compared with a 2.8% mean increase among patients assigned to receive counseling alone (95% CI, -17.5% to +23.1% change) (P=.007). By week 16, the mean reduction in triglyceride levels in the fish oil arm remained significant, at 19.5% (95% CI, -34.9% to -4.0% change), whereas the mean decrease in the diet and exercise only arm was 5.7% (95% CI, -24.6% to +13.2% change); however, the difference between study arms was no longer statistically significant (P=.12). Low-density lipoprotein cholesterol levels had increased by 15.6% (95% CI, +4.8% to +26.4% change) at week 4 and by 22.4% (95% CI, +7.91% to +36.8% change) at week 16 in the fish oil arm but did not change in the diet and exercise only group. Fish oil was well tolerated; only 1 patient experienced treatment-limiting toxicity. Patients assigned to receive fish oil experienced a 25% mean decline in fasting triglyceride levels at week 4 (95% CI, -34.6% to -15.7% change), compared with a 2.8% mean increase in patients assigned to receive counseling alone (95% CI, -17.5% to 23.1% change) (P=.007). By week 16, the mean reduction in triglyceride levels in the fish oil arm remained significant, at 19.5% (95% CI, -34.9% to -4.0% change), whereas the mean decrease in the diet and exercise only arm was 5.7% (95% CI, -24.6% to 13.2% change); however, the difference between study arms was no longer statistically significant (P=.12). Low-density lipoprotein cholesterol levels had increased by 15.6% (95% CI, 4.8%-26.4% change) at week 4 and by 22.4% (95% CI, 7.91%-36.8% change) at week 16 in the fish oil arm but did not change in the diet and exercise only group. Fish oil was well tolerated; only 1 patient experienced treatment-limiting toxicity. CONCLUSIONS: Supplementation with omega-3 fatty acids in combination with dietary and exercise counseling was well tolerated and reduced fasting triglyceride levels in patients receiving antiretrovirals. To what extent the increase in low-density lipoprotein cholesterol levels observed in patients assigned this intervention is attributable to omega-3 fatty acid supplementation and whether this increase attenuates any benefit in lowering triglyceride levels is unclear. Given these results, further investigation of omega-3 fatty acid supplementation for the treatment of hypertriglyceridemia in HIV-infected patients is warranted.

Adult↗

Iron absorption from fish sauce and soy sauce fortified with sodium iron EDTA.

BACKGROUND: Fish sauce and soy sauce have been suggested as food vehicles for iron fortification in Asia. NaFeEDTA is a potentially useful fortificant because it can be added to these condiments without causing precipitation during storage. OBJECTIVES: The objectives were to evaluate iron absorption from NaFeEDTA-fortified fish sauce and soy sauce against a reference fortificant (FeSO(4)), to compare iron absorption from NaFeEDTA-fortified fish sauce and soy sauce, and to evaluate the influence of fish sauce and soy sauce per se on iron absorption. DESIGN: Five separate iron-absorption studies were made in adult women (10 women per study). Iron absorption was measured on the basis of erythrocyte incorporation of (57)Fe or (58)Fe 14 d after the intake of labeled meals of rice or rice and vegetables. Fish sauce or soy sauce (10 g) fortified with 5 mg Fe as NaFeEDTA or FeSO(4) was fed with selected meals. The results are presented as geometric means. RESULTS: Iron absorption from NaFeEDTA- and FeSO(4)-fortified fish sauce (3.3% and 3.1%, respectively) and soy sauce (6.1% and 5.6%, respectively) was not significantly different. No significant difference was observed when NaFeEDTA-fortified fish sauce and soy sauce were compared directly (6.7% and 7.9%, respectively). Soy sauce inhibited iron absorption from rice-based meals (8.5% without and 6.0% with soy sauce; P < 0.02), whereas fish sauce did not affect iron absorption significantly. CONCLUSION: The relatively high iron absorption from NaFeEDTA-fortified fish sauce and soy sauce and the acceptable organoleptic properties of NaFeEDTA indicate the potential usefulness of this iron fortificant in fish sauce and soy sauce fortification programs.

Adult↗

Dietary fish oil alters specific and inflammatory immune responses in chicks.

Two experiments were designed to determine the effects of dietary (n-3) fatty acids and grain source on the growth-suppressive effects of the inflammatory response and indices of specific immunity. In Experiment 1, chicks were fed diets containing 0.5, 1, or 2 g/100 g of either corn oil or fish oil. In Experiment 2, chicks were fed diets containing up to 2 g/100 g of either fish oil, linseed oil or corn oil as the source of dietary fat, in either cereal grain- or corn-based diets. In each experiment, subsets of chicks within each dietary treatment were either vaccinated with infectious bronchitis virus (IBV) vaccine, injected with Salmonella typhimurium lipopolysaccharide (LPS), heat-killed Staphylococcus aureus, or remained noninjected. Increasing dietary fish oil, but not corn oil increased body weight and lessened the growth-suppressing effect of heat-killed S. aureus or S. typhimurium LPS. Increasing the concentration of dietary fish oil decreased febrile response, circulating hemopexin and metallothionein concentrations. Dietary fish oil resulted in decreased release relative to dietary corn oil of interleukin-1 by peritoneal macrophages. Although IBV titers were not significantly affected by dietary oil treatment, phytohemagglutination-induced wattle swelling was greater among chicks fed fish oil. In Experiment 2, the modulating effects of fish oil on the immune system were dependent on the type of grain used in the diet, with fish oil/cereal diets resulting in greater cell-mediated immunity and lower indices of inflammation than fish oil/corn diets. Inclusion of increasing amounts of fish oil in the diet improved performance, decreased indices of the inflammatory response and either improved or did not change indices of the specific immune response of growing chicks.

Animals↗

Fish oil affects blood pressure and the plasma lipid profile in healthy Danish infants.

Animal and epidemiologic studies indicate that early nutrition has lasting effects on metabolism and cardiovascular disease risk. In adults, (n-3) long-chain PUFA (LCPUFA) from fish oils improve blood pressure, the lipid profile, and possibly cardiovascular disease mortality. This randomized trial is the first to investigate the effects of fish oil on blood pressure and the lipid profile in infancy. Healthy term 9-mo old infants (n = 83) were randomly assigned to 5 mL fish oil daily or no fish oil for 3 mo and to 2 different milk types. Before and after the intervention, blood pressure was measured with an oscillometric device, and blood was sampled for analysis of erythrocyte fatty acid composition and the plasma lipid profile. This paper examines the effects of the fish oil supplement, with adjustment for the effects of the milk intervention when relevant. The fish oil intervention increased erythrocyte (n-3) LCPUFA content (P < 0.001). At 12 mo, infants administered fish oil had a lower systolic blood pressure [adjusted mean difference (95% CI)] 6.3 mm Hg (0.9, 11.7) (P = 0.02), a 0.51 mmol/L (0.07, 0.95) higher plasma total cholesterol (P = 0.02), and a 0.52 mmol/L (0.02,1.01) higher LDL cholesterol (P = 0.04) than infants not administered fish oil. Plasma triacylglycerol was inversely associated with the erythrocyte content of eicosapentaenoic acid (r = 0.34, P < 0.01), a biomarker of fish oil dose. The observed effects of fish oil are in accordance with findings in adults. The long-term health implications warrant further investigation.

Blood Pressure↗

Effect of fish diets and weight loss on serum leptin concentration in overweight, treated-hypertensive subjects.

BACKGROUND: Leptin, a circulating hormone secreted from adipocytes, is an index of adiposity and is reduced by caloric restriction and weight loss. A recent population study suggested that dietary-derived omega3 fatty acids lower leptin levels independent of body fat. OBJECTIVE: To examine whether dietary fish enhanced the effects of weight loss on serum leptin levels, in 69 overweight, treated hypertensive men and women. METHODS: Participants were randomized to a daily fish meal, a weight-reduction regimen, the two regimens combined or a control group for 16 weeks. RESULTS: A total of 63 individuals completed the study. Weight fell 5.6 +/- 0.8 kg with energy-restriction. Blood pressure (BP) reductions in the combined fish-weight loss group were twice that seen with either intervention alone. At baseline, in all groups combined, serum leptin levels correlated with serum insulin (r = 0.307, P = 0.014), but not with body weight. The greatest change in serum leptin occurred in the fish-weight loss group (control, 0.60 +/- 0.76 ng/ml; fish, 1.20 +/- 0.79 ng/ml; weight loss, -1.40 +/- 1.05 ng/ml; fish-weight loss, -5.08 +/- 1.64 ng/ml). In the fish-weight loss group, the change in serum leptin was predicted by changes in serum insulin (r = 0.488, P = 0.038), 24-h BP (systolic BP (SBP): r = 0.435, P = 0.060; diastolic BP (DBP): r = 0.563, P = 0.018) and 24-h heart rate (0.584, P = 0.028). Using general linear models, there was a significant fish x weight-loss interaction (P = 0.008) on post-intervention serum leptin after adjustment for baseline levels, independent of post-intervention insulin. CONCLUSION: A daily fish meal as part of a weight-reducing regimen was more effective than either measure alone at reducing leptin levels. Reductions in leptin may be related to the substantial fall in BP seen with the fish-weight loss program.

Animals↗

Fish oil decreases serum homocysteine in hyperlipemic men.

BACKGROUND: Because of the inverse relation between dietary fish consumption and coronary heart disease and because of the importance of serum homocysteine as an independent risk factor for atherosclerosis, the effect of fish oil on serum homocysteine was studied in hyperlipemic men. METHODS: Fifteen men with either type IIa or IIb lipoproteinemia or hypertriglyceridemia were maintained on a controlled, balanced diet and given either fish oil or olive oil supplements, 12 g/d for 3 weeks, followed by a cross-over period of 3 weeks during which the olive oil or fish oil supplements were given in reverse order. Serum homocysteine was determined by liquid chromatography of acid hydrolyzates of whole serum. RESULTS: Fish oil was found to diminish serum homocysteine levels in 14 of 17 subjects (P < 0.01). Serum homocysteine was 48% +/- 33% less than control values in seven of nine patients and 36% +/- 22% less than values in seven of eight subjects who had first received olive oil. There was no effect of olive oil supplements on serum homocysteine, compared with control values, but olive oil produced an increase in serum homocysteine in those who had first received fish oil. Serum triglycerides and very low-density lipoprotein were decreased by fish oil in patients who were first given olive oil, in agreement with previous studies. There was no effect of either fish oil or olive oil on total cholesterol, apolipoprotein B, low-density lipoprotein, or high-density lipoprotein. CONCLUSIONS: The protection against coronary heart disease afforded by a diet rich in fish may be attributed to the lowering of serum homocysteine levels by the n-3 polyunsaturated fatty acids of fish oils.

Adult↗

Betanodavirus infection in the freshwater model fish medaka (Oryzias latipes).

Betanodaviruses, the causal agents of viral nervous necrosis in marine fish, have bipartite, positive-sense RNA genomes. As their genomes are the smallest and simplest among viruses, betanodaviruses have been studied in detail as model viruses by using a genetic-engineering system, as has occurred with the insect alphanodaviruses, the other members of the family Nodaviridae. However, studies of virus-host interactions have been limited, as betanodaviruses basically infect marine fish at early developmental stages (larval and juvenile). These fish are only available for a few months of the year and are not suitable for the construction of a reverse-genetics system. To overcome these problems, several freshwater fish species were tested for their susceptibility to betanodaviruses. It was found that adult medaka (Oryzias latipes), a well-known model fish, was susceptible to both Striped jack nervous necrosis virus (the type species of the genus Betanodavirus) and Redspotted grouper nervous necrosis virus (RGNNV), which have different host specificities in marine fish species. Infected medaka exhibited erratic swimming and the viruses were localized specifically in the brain, spinal cord and retina of the infected fish, similar to the pattern of infection in naturally infected marine fish. Moreover, medaka were susceptible to RGNNV at the larval stage. This is the first report of a model virus-model host infection system in fish. This system should facilitate elucidation of the mechanisms underlying RNA virus infections in fish.

Animals↗

Modeling possible cooling-water intake system impacts on Ohio River fish populations.

To assess the possible impacts caused by cooling-water intake system entrainment and impingement losses, populations of six target fish species near power plants on the Ohio River were modeled. A Leslie matrix model was constructed to allow an evaluation of bluegill, freshwater drum, emerald shiner, gizzard shad, sauger, and white bass populations within five river pools. Site-specific information on fish abundance and length-frequency distribution was obtained from long-term Ohio River Ecological Research Program and Ohio River Sanitation Commission (ORSANCO) electrofishing monitoring programs. Entrainment and impingement data were obtained from 316(b) demonstrations previously completed at eight Ohio River power plants. The model was first run under a scenario representative of current conditions, which included fish losses due to entrainment and impingement. The model was then rerun with these losses added back into the populations, representative of what would happen if all entrainment and impingement losses were eliminated. The model was run to represent a 50-year time period, which is a typical life span for an Ohio River coal-fired power plant. Percent changes between populations modeled with and without entrainment and impingement losses in each pool were compared to the mean interannual coefficient of variation (CV), a measure of normal fish population variability. In 6 of the 22 scenarios of fish species and river pools that were evaluated (6 species x 5 river pools, minus 8 species/river pool combinations that could not be evaluated due to insufficient fish data), the projected fish population change was greater than the expected variability of the existing fish population, indicating a possible adverse environmental impact. Given the number of other variables affecting fish populations and the conservative modeling approach, which assumed 100% mortality for all entrained fish and eggs, it was concluded that the likelihood of impact was by no means assured, even in these six cases. It was concluded that in most cases, current entrainment and impingement losses at six Ohio River power plants have little or no effect at the population level.

Animals↗

Renal carcinogenicity of concurrently administered fish meal and sodium nitrite in F344 rats.

The effects of long-term concurrent administration of powdered fish meal and sodium nitrite were examined in F344 rats. A total of 600, 6-week-old rats were divided into 6 male and 6 female groups, each consisting of 50 animals. Rats in groups 1-3 and 7-9 were respectively fed diets supplemented with 64%, 32% and 8% (basal diet) fish meal, and simultaneously given 0.12% sodium nitrite in their drinking water. Groups 4-6 and 10-12 were respectively given 64%, 32% and 8% fish meal and tap water. At the 104th week, all surviving animals were killed and examined histopathologically. Treatment with fish meal dose-dependently increased the incidences and multiplicities of atypical tubules, adenomas and renal cell carcinomas in sodium nitrite-treated males. Females were less susceptible than males for renal tumor induction. In males given the 64% fish meal diet alone, the incidence and multiplicity of atypical tubules were also significantly increased as compared with the 8% fish meal alone case. Nephropathy was apparent in fish meal-treated groups in a clear dose-dependent manner, irrespective of the sodium nitrite treatment, and was more prominent in males than in females. Dimethylnitrosamine was found in the stomach contents after 4-week treatment with 64% fish meal plus 0.12% sodium nitrite, at a level twice that in the 8% fish meal plus 0.12% sodium nitrite group. The results clearly indicate that concurrent administration of fish meal and sodium nitrite induces renal epithelial tumors. Further studies are required to elucidate how nephropathy and nitrosamines produced in stomach contents may contribute to the observed renal tumor induction.

Animals↗

Bacterial pollution indicators in the intestinal tract of freshwater fish.

A study was made of the occurrence, distribution, and persistence of coliforms, fecal coliforms, and fecal streptococci in the intestinal tract of freshwater fish. A total of 132 fish representing 14 different species were used in various phases of these experiments. Examination of the intestinal contents of 78 fish from moderately polluted sections of the Little Miami River indicated that fecal coliform densities were lowest in bluegills (less than 20 per gram) and highest in catfish (1,090,000 per gram). Levels of fecal streptococci for these two species were 220 and 240,000 per gram, respectively. The occurrence of fecal coliforms in fish caught in this stream reflected the warm-blooded-animal-pollution level of the water. All fish used in this phase of the study were caught during July, August, and September when the water temperatures were between 13 and 18 C. The fate of fecal coliforms and Streptococcus faecalis in the fish intestine indicated that these organisms can probably survive and multiply when fish and water temperatures are 20 C or higher, but only when the organisms are retained in the gut for periods beyond 24 hr. Based on the biochemical reactions for 3,877 coliform strains isolated from 132 freshwater fish of 14 different species, 91.4% of all strains were composed of five IMViC types. In a similar study of the biochemical reactions of 850 streptococci isolated from the intestinal tract of 55 freshwater fish, the predominant strains included S. faecalis and various closely associated biotypes. No consistently recurring pattern for either coliforms or streptococci could be developed to identify species of fish investigated. The composition of the intestinal flora is, however, related in varying degree to the level of contamination of water and food in the environment.

Animals↗

Atrial natriuretic factor and salt adaptation in the teleost fish Gila atraria.

It is unknown whether atrial natriuretic factor (ANF) is a mediator of environmental salt tolerance in euryhaline teleost fish. This was investigated in anesthetized Gila atraria, a euryhaline teleost native to springs of pleistocene Lake Bonneville. Plasma levels of immunoreactive (ir) ANF [using anti-human ANF-(99-126) antibodies] in fish obtained from a "fresh water" spring were significantly lower (146 +/- 27) than those in fish obtained from a "1% NaCl" spring (347 +/- 21 pg/ml, P less than 0.01). Electron micrographs of fish atrial and ventricular cardiocytes demonstrated many perinuclear granules, which closely resembled ANF-containing secretory granules seen in mammalian atriocytes. Fish heart extract contained ANF-like material of 3 kDa, which caused a marked diuresis and natriuresis in rats. In a second study, fish from a 1% NaCl spring were kept in tanks. One-third of the fish were maintained in 1% NaCl and one-third each were either adapted to fresh- or high-salt water. After 12 days, plasma irANF levels in 1% NaCl fish were 343 +/- 55, in fresh water fish 213 +/- 20 and in high-NaCl fish 691 +/- 79 pg/ml. These values differed significantly from each other (P less than 0.01). There was a close correlation between plasma irANF levels and both environmental and internal salt concentration. These data suggest that piscine ANF is an as yet unrecognized mediator of salt tolerance in this teleost and that ANF in these animals closely resembles mammalian ANF.

Acclimatization↗

Lack of triglyceride-lowering properties of fish oil in apolipoprotein e-deficient mice.

Fish oil is a potent triglyceride (TG)-lowering agent in humans. The goal of the present study was to assess the contribution of decreased triglyceride synthesis and of apoE in mediation of the triglyceride-lowering effect of fish oil. To this end, apoE-deficient mice and wild-type control mice were supplemented with either coconut oil, sunflower oil, or fish oil (20% wt/wt) for 2 weeks. Compared with coconut oil and sunflower oil, fish oil reduced the concentrations of cholesterol and triglycerides in the wild-type mice, whereas it had no effect on cholesterol concentration and it had a triglyceride-raising effect in apoE-deficient mice. The latter was due to increased triglyceride concentrations in the d<1.019 g/mL plasma density fraction. In apoE-deficient mice, but not in wild-type mice, the postprandial triglyceride area under the curve was higher after an intragastric load of fish oil than after a sunflower oil load. These data indicate an impairment of triglyceride metabolism in the fish oil-fed apoE-deficient mice. Compared with coconut oil and sunflower oil, fish oil lowered triglyceride production rates measured with the Triton method in both wild-type (P<0.0001) and apoE-deficient mice (P<0.0001). Similarly, in vitro lipoprotein lipase-mediated lipolysis of VLDL was lowered in the fish oil-fed wild-type and apoE-deficient mice, suggesting an alteration in VLDL lipolysis independent of the mice genotype. In conclusion, fish oil does not decrease triglyceride concentrations in apoE-deficient mice despite reducing triglyceride production rates, suggesting that decreased triglyceride synthesis is not sufficient to lower triglyceride concentrations in mice. ApoE appears to be necessary for fish oil to lower plasma triglyceride concentrations, indicating a critical role of apoE in this process.

Analysis of Variance↗

Fish consumption and stroke in men. 30-year findings of the Chicago Western Electric Study.

BACKGROUND AND PURPOSE: Evidence of a relationship of fish intake to stroke incidence or mortality is weak. This report examines the association of fish consumption with stroke. METHODS: A cohort of 2107 men aged 40 to 55 years from the Chicago Western Electric Study who were free of coronary heart disease and stroke through their first annual reexamination was investigated in relation to baseline fish intake and 30-year risk of fatal and nonfatal stroke. Data on baseline fish intake, categorized into four levels (> or = 35 g/d, 18 to 34 g/d, 1 to 17 g/d, and 0 g/d), were available for 1847 men. Average values of macronutrients and micronutrients from the first two examinations and major coronary and stroke risk factors were assessed in relation to fish consumption. Stroke mortality was ascertained from death certificates and nonfatal stroke from records of the Health Care Financing Administration. RESULTS: During 46,426 person-years of follow-up, 76 stroke deaths occurred. Men consuming > or = 35 g/d of fish (highest level) had a higher age-adjusted death rate from stroke (23.5 per 10,000 person-years) than men in the three other categories of fish consumption. Based on a Cox proportional hazards regression model with adjustment for age, systolic blood pressure, cigarette smoking, serum cholesterol level, diabetes, electrocardiographic abnormalities, and table salt use, hazards ratios (and 95% confidence intervals) for fish consumers compared with nonconsumers were 1.34 (0.53 to 3.41) for > or = 35 g/d, 0.96 (0.41 to 2.21) for 18 to 34 g/d, and 1.00 (0.43 to 2.33) for 1 to 17 g/d. Age-adjusted and multivariate analyses for fatal and nonfatal strokes (n = 222) yielded similar results. CONCLUSIONS: With stroke rates highest in the subgroup reporting highest fish intake, these data do not support the hypothesis of an inverse association of fish consumption with strokes.

Adult↗