The effects of arachidonic acid on the endocrine and osmoregulatory response of tilapia (Oreochromis mossambicus) acclimated to seawater and subjected to confinement stress.

In previous studies in freshwater tilapia (Oreochromis mossambicus), dietary supplementation with arachidonic acid (ArA; 20:4n - 6) had considerable, opposing effects on the main ion-transporting enzyme Na(+)/K(+)-ATPase in gills and kidneys and changed the release of osmoregulatory hormones, such as cortisol. The present study was performed to assess the influence of dietary ArA on (1) the osmoregulatory capacity of tilapia acclimated to seawater (SW) (34‰) and (2) the osmoregulatory imbalance associated with acute stress. The increased ambient salinity was associated with significant alterations in the tissue fatty acid composition, particularly the n - 6 polyunsaturated fatty acids (PUFAs). Tissue levels of ArA were further increased as a result of dietary supplementation, whereas docosahexaenoic acid (DHA, 22:6n - 3) and eicosapentaenoic acid (EPA, 20:5n - 3) decreased in gills and kidneys. Basal plasma cortisol as well as lactate levels were elevated in the ArA-supplemented SW-acclimated tilapia compared with the control group. The 5 min of confinement (transient stress) increased plasma cortisol, glucose, and lactate levels with significantly higher levels in ArA-supplemented tilapia. Confinement was also associated with significantly elevated plasma osmolality, sodium, chloride, and potassium levels. ArA-supplemented tilapia showed markedly lower ionic disturbances after confinement, suggesting that dietary ArA can attenuate the hydromineral imbalance associated with acute stress. These results emphasize the involvement of ArA and/or its metabolites in the endocrine and osmoregulatory processes and the response to confinement stress.

Specific nutritional support accelerates pressure ulcer healing and reduces wound care intensity in non-malnourished patients.

OBJECTIVE: We investigated the potential of a high-protein, arginine- and micronutrient-enriched oral nutritional supplement (ONS) to improve healing of pressure ulcers in non-malnourished patients who would usually not be considered for extra nutritional support. METHODS: Forty-three non-malnourished subjects with stage III or IV pressure ulcers were included in a multicountry, randomized, controlled, double-blind, parallel group trial. They were offered 200 mL of the specific ONS or a non-caloric control product three times per day, in addition to their regular diet and standard wound care, for a maximum of 8 wk. Results were compared with repeated-measures mixed models (RMMM), analysis of variance, or Fisher's exact tests for categorical parameters. RESULTS: Supplementation with the specific ONS accelerated pressure ulcer healing, indicated by a significantly different decrease in ulcer size compared with the control, over the period of 8 wk (P

Dietary supplementation with arachidonic acid in tilapia (Oreochromis mossambicus) reveals physiological effects not mediated by prostaglandins.

This study aims to clarify the role of the polyunsaturated fatty acid arachidonic acid (ArA, 20:4n-6) in the stress response of Mozambique tilapia (Oreochromis mossambicus). ArA is converted into eicosanoids, including prostaglandins, which can influence the response to stressors. Tilapia, a species able to form ArA from its precursor, was supplemented with ArA for 18 days, after which they were confined for 5 min. Acetylsalicylic acid (ASA, COX-inhibitor) was subsequently administered to distinguish ArA-mediated effects from enhanced prostaglandin E(2) (PGE(2)) synthesis. ArA supplemented fish had higher ArA levels in gills and kidneys, and these levels were further enhanced after ASA treatment. Levels of total monounsaturated and polyunsaturated fatty acids as well as docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and ArA, were altered 24h after confinement, particularly in the kidneys. ArA supplementation had no effect on basal cortisol levels, while ArA + ASA reduced basal cortisol levels. ArA + ASA augmented the cortisol response to confinement. The combination of ArA + ASA also elevated plasma basal prolactin (tPRL)(177) and 3,5,3'-triiodothyronine (T(3)) levels. Neither ArA nor ASA affected the stress-associated increases in plasma glucose and lactate. Na(+), K(+)-ATPase activity in the gills was reduced after ArA supplementation and was even further suppressed by subsequent ASA treatment. In an additional feeding trial, ArA supplementation enhanced the renal Na(+), K(+)-ATPase activity. In vitro, ArA was a potent inhibitor of the Na(+), K(+)-ATPase activity of gill and kidney homogenates. In contrast, PGE(2) had no effect on branchial ATPase, whereas the effect on renal ATPase activity was concentration dependent. Modifying the dietary intake of ArA alters the response of tilapia to an acute stressor and influences osmoregulatory processes and it is unlikely that these effects are due to an enhanced production of prostaglandins.

Arachidonic acid reduces the stress response of gilthead seabream Sparus aurata L.

In this study the influence of the dietary level of the fatty acid arachidonic acid (ArA, 20:4n-6) was determined on the acute stress response and osmoregulation of adult gilthead seabream Sparus aurata L. Seabream were fed a diet containing either 0.9% or 2.4% of total fatty acids as ArA for 18 days before being subjected to a 5 min period of net confinement. Prior to this stressor, a subgroup of fish from both dietary treatment groups was treated with acetylsalicylic acid (ASA), an irreversible blocker of cyclooxygenase (COX). This would indicate whether any effects were caused by an enhanced synthesis of prostaglandins derived from ArA. The highest ArA levels were found in the kidneys, and these were further enhanced by dietary ArA-supplementation. In gill tissues, there were significant changes in all selected fatty acid classes 24 h after confinement, except for the docosahexaenoic acid (DHA, 22:6n-3): eicosapentaenoic acid (EPA, 20:5n-3) ratio. ArA feeding strongly reduced the cortisol response to confinement, which was partially counteracted by ASA treatment. ArA also attenuated the stress-associated increase in plasma osmolality and, in combination with ASA, enhanced the osmolality and plasma chloride levels, but reduced plasma sodium levels after confinement. Furthermore, ArA enhanced the branchial Na(+), K(+)-ATPase activity both before and after confinement, whereas feeding ASA diminished this effect. It appeared that the effects of ArA-supplementation could not always be ascribed to an increase in prostaglandin synthesis. It is advisable to determine the long-term effects of replacing fish oils in commercial diets with vegetable oils that contain no long-chain fatty acids, particularly in carnivorous/marine species with low fatty acid elongation and desaturation activities. The effects of a low dietary intake of ArA (and other polyunsaturated fatty acids) should be studied over a longer term, taking into account any consequences for the health of the fish.

Effects of iron sulfate dosage on the water flea (Daphnia magna Straus) and early development of carp (Cyprinus carpio L.).

Adult water fleas, Daphnia magna Straus, and the early life stages of carp, Cyprinus carpio L., were exposed to river water near an iron sulfate dosage installation to determine the effects of phosphate precipitation with iron(II)sulfate. Tests were conducted during two consecutive dosage periods of 3,000 and 5,000 kg/day iron sulfate (520 and 620 microg/L total Fe respectively) at the dosage site and at a reference site (60 microg/L total Fe) further downstream. Though survival remained unaffected, the filter-feeding D. magna accumulated iron and other metals at the dosage site. Viability of offspring was strongly reduced at the highest dose of iron sulfate compared to the lower dose and the reference site. Specific staining of microscopic sections revealed a strong accumulation of iron(III) in the digestive tract. The egg membranes of the carp embryos accumulated not only substantial amounts of iron but also other metals, including cadmium and aluminium. Hardly any of the metals passed the egg membranes and reached the embryos. After hatching the accumulation of cadmium by the larvae increased rapidly and iron levels were elevated at the highest dose of iron sulfate, parallel with the onset of exogenous feeding. Iron(III) particles were observed in the intestines at histological examination. In addition, at 620 microg/L total Fe a strong increase in whole-body levels of the stress hormone cortisol was observed in the carp larvae, indicating a physiological response to adverse conditions. The results indicate that the rapid oxidation of free Fe2+ into iron(III) forms and the precipitation of iron(III) into larger particles resulted in a low acute toxicity of the river water directly at the iron sulfate dosage site. The observed chronic and sublethal effects at the dosage site probably resulted from the intestinal uptake of iron(III) and other toxic metals associated with the food particles. However, these effects could no longer be observed at the reference site, 9 km downstream from the dosage site.