Olaf R. Brækkan

The effect of ascorbic acid supplementation in broodstock feed on reproduction of rainbow trout (Salmo gairdneri)

Abstract Two experimental diets differing in supplementation of ascorbic acid and a third commercial diet were fed to rainbow trout broodstock. A supplementation level of 115 mg ascorbic acid per kg significantly increased the number of hatching eggs compared to eggs from fish without dietary ascorbic acid supplementation. Fish reared on the commercial diet gave eggs of similar quality as from the ascorbic acid supplemented experimental feed. The results indicate that ascorbic acid is essential for reproduction in rainbow trout. Broodstock fish should be fed adequate amounts of the vitamin to provide eggs with more than 20 μg ascorbic acid/g.

Optimization of the determination of selenium in marine samples by atomic absorption spectrometry: Comparison of a flameless graphite furnace atomic absorption system with a hydride generation atomic absorption system

Abstract A comparison has been made between a graphite furnace system based on nickel as a matrix stabilizing metal and an automated hydride generation system with a heated quartz cell. The effect of nickel as a matrix modifier was studied in pure selenite solutions as well as in biological matrixes by different charring temperatures. The suppression effect of different acids on the response of the analyte is reported and discussed. The use of an electrically heated quartz tube as an alternative to the argon hydrogen flame method unproved the selenium determination by hydride generation atomic absorption. The effect of hydrochloric acid to secure quantitative formation of selenium (IV) and the interference of copper in the response measurements have been studied. Further a comparison has been made between three different digestion procedures when the hydride generation atomic absorption system was applied. The results of the graphite furnace atomic absorption and the hydride generation atomic absorption were found to be equally accurate, but the graphite furnace technique gave better reproducibility.

A routine method for the determination of aluminium in human tissue samples using standard addition and graphite furnace atomic absorption spectrophotometry

Abstract Aluminium in human tissue samples has been determined by atomic absorption spectrophotometry using the nitrous oxide-acetylene flame and the graphite furnace atomizer. The two methods are compared. Flameless atomic absorption was found superior when standard addition was applied. A routine method is thus described in detail in which aluminium levels down to 0.1 mg/kg of freeze-dried tissue and 0.01 mg/liter of serum can be determined.

Studies on monoene fatty acid isomers in hydrogenated fish oils.

An analytical study of the geometrical and positional isomerisation of the monoenoic acids of partially hydrogenated fish oil is presented. The results showed that the monoene fatty acids of chain lengths 16, 18, 20 and 22 consisted of 75% in thetrans-form and 25% in thecis-form. The double bonds were distributed symmetrically over the chain length, with well defined maxima in position Δ-9 for the fatty acids of chain length 16 and 18, and in position Δ-11 for the fatty acids of chain length 20 and 22.Trans- andcis-isomers showed the same positional distribution. Geometric as well as positional isomerization seemed to have reached an equilibrium state in the sample investigated.

Mercury concentration in liver and muscle of cod (Gadus morhua) as an evidence of migration between waters with different levels of mercury

The accumulation rate of HgCl/sub 2/ and CH/sub 3/HgCl given orally to cod was determined as measured by the subsequent distribution of mercury in muscle and liver tissue. The results of these experiments have been applied to the evaluation of mercury in cod migrating between moderately contaminated waters and areas with different levels of mercury contamination.

Muscle protein synthesis in vitro of saithe (Pollachius virens) correlated to growth and daily energy intake

Abstract 1. 1. Immature saithe (Pollachius virens) with a mean weight of 1000 g were either starved or fed increasing amounts of dietary energy during 9 weeks. The protein-energy ratio of the diet was kept constant. Liver weight as percentage of body weight indicated a high food utilization. 2. 2. Ribosomes were isolated from cryopreserved (−80°C) epaxial muscle. Their capacity to synthesize proteins, the polyribosome content and growth of the fish increased with increasing ration intake. 3. 3. The food ration dependent changes in protein synthesis and growth were accompanied by quantitative rather than qualitative alterations in muscle protein composition.

Antioxidant properties of methionine esters.

DURING feeding experiments we have found that 0.5 percent methionine in a semisynthetic diet containing 12 per cent cod liver oil prevents yellow discoloration of the diet and also the destruction of vitamins A and E (refs. 1–3). We have also studied the antioxidant properties of methionine and some derivatives using simple manometric techniques4 and have recorded the near infrared spectrum of CCl4 extracts of the semisynthetic diet. The spectrophotometric data showed a relatively constant peak at 2.34µ and a variable peak at 2.88µ which increased as oxidation progressed, permitting use of the ratio of absorptions at these two wavelengths as an additional measure of oxidation. Using both criteria hydrochlorides of the methyl and ethyl esters of methionine showed unique properties. In contrast to other compounds which were tested there were rapid but relatively small initial changes followed by extended periods in which only very slow changes took place. The esters therefore seemed to be transformed to antioxidant compounds acting in a similar way to butylated hydroxy toluene (BHT).

The relation between total cobalt and cobalt in vitamin B12 during the maturation of ovaries in salmon (salmo salar)

Abstract 1. 1. Total cobalt and the content of vitamin B 12 were determined in samples from different stages of the reproductive cycle in ovaries of salmon. 2. 2. The relation between corresponding values for cobalt determined by AAS and calculated on the basis of vitamin B 12 determined microbiologically showed a striking correlation at all stages. Calculated as percentage of the values for vitamin B 12 , between 99·8 and 104·5 per cent of the total cobalt were found to derive from the vitamin. 3. 3. The finding indicates a transportation of vitamin B 12 to the ovaries and an apparent blockage of cobalt ions.