Chromosome aberrations in pressure-induced triploid Atlantic salmon.

BACKGROUND: Triploid organisms have three sets of chromosomes. In Atlantic salmon, hydrostatic pressure treatment of newly fertilized eggs has been extensively used to produce triploids which are functionally sterile due to their unpaired chromosomes. These fish often perform poorly on commercial farms, sometimes without explanation. Inheritance patterns in individuals subjected to pressure treatment have not been investigated in Atlantic salmon thus far. However, work on other species suggests that this treatment can result in aberrant inheritance. We therefore studied this in Atlantic salmon by genotyping 16 polymorphic microsatellites in eyed eggs and juveniles which had been subjected to pressure-induction of triploidy. Communally reared juveniles including fish subjected to pressure-induction of triploidy and their diploid siblings were included as a control. RESULTS: No diploid offspring were detected in any of the eggs or juveniles which were subjected to hydrostatic pressure; therefore, the induction of triploidy was highly successful. Aberrant inheritance was nevertheless observed in 0.9% of the eggs and 0.9% of the juveniles that had been subjected to pressure treatment. In the communally reared fish, 0.3% of the fish subjected to pressure treatment displayed aberrant inheritance, while their diploid controls displayed 0% aberrant inheritance. Inheritance errors included two eyed eggs lacking maternal DNA across all microsatellites, and, examples in both eggs and juveniles of either the maternal or paternal allele lacking in one of the microsatellites. All individuals displaying chromosome aberrations were otherwise triploid. CONCLUSIONS: This is the first study to document aberrant inheritance in Atlantic salmon that have been subjected to pressure-induction of triploidy. Our experiments unequivocally demonstrate that even when induction of triploidy is highly successful, this treatment can cause chromosome aberrations in this species. Based upon our novel data, and earlier studies in other organisms, we hypothesize that in batches of Atlantic salmon where low to modest triploid induction rates have been reported, aberrant inheritance is likely to be higher than the rates observed here. Therefore, we tentatively suggest that this could contribute to the unexplained poor performance of triploid salmon that is occasionally reported in commercial aquaculture. These hypotheses require further investigation.

Water temperature and dietary histidine affect cataract formation in Atlantic salmon (Salmo salar L.) diploid and triploid yearling smolt.

The aim of the present study was to investigate cataract development in diploid (2N) and triploid (3N) Atlantic salmon smolts and post-smolts at two water temperatures (10 and 16 °C) given diets with different histidine supplementation (LH, 10.4 and HH, 13.1 g kg-1 ) before and after seawater transfer. In freshwater, a severe cataract outbreak was recorded in both ploidies reared at 16 °C. The cataract score was significantly higher in triploids compared to diploids, and the severity was lower in both ploidies fed the HH diet. The cataract development at 10 °C was minor. Low gill Na+ , K+ -ATPase activity in fish reared at 16 °C before seawater transfer was followed by osmoregulatory stress with elevated plasma electrolyte concentrations and high mortality in sea water. Both diploids and triploids reared at 10 °C developed cataracts during the seawater period, with higher severities in triploids than diploids and a reduced severity in the fish fed the HH diet. The findings of this study demonstrate the importance of environmental conditions in the husbandry of Atlantic salmon, and particularly triploids, with regard to smoltification and adjusted diets to mitigate cataract development in fresh and sea water.

Effects of laboratory salmon louse infection on Arctic char osmoregulation, growth and survival.

High salmon lice (Lepeophtheirus salmonis) infestation levels resulting from intensive salmonid sea-cage aquaculture can threaten populations of wild salmonid hosts. This includes anadromous Arctic char (Salvelinus alpinus), which rely on short migrations into more productive seawater environments to build energy stores for maturation, spawning and over-wintering in freshwater. Elevated salmon lice burdens may limit the benefits of migration by constraining osmoregulation, growth, survival and reproduction. To test for these effects, we simulated anadromous migration in tanks by transferring individually tagged Arctic char smolts (n = 352, averaging 133 g) to seawater where they were infected with salmon lice or left as uninfected controls for 1 month, and then transferring them back to freshwater for 2 months. After the seawater phase, infected post-smolts had a mean of 0.33 (range of 0.09-0.91) mobile lice g-1 fish weight. At this point, specific growth rates (SGRs) dropped in infected compared to control fish (0.1% vs. 1.6% day-1). Higher plasma Na+ and osmolality in infected fish also indicate osmoregulatory impairment. Throughout the study, mortality was 18.2% and 1.7% in infected and control groups, but sexual maturation was low and comparable between groups. Infection intensity correlated positively with mortality rate and plasma Cl-, and correlated negatively with SGR and condition factor (CF). CF dropped (ΔCF < 0) at intensities of >0.09 lice g-1 fish weight, and intensities of >0.3 causing zero or negative SGRs and increased mortality were particularly concerning. If infection intensities reach these levels in the wild, char could be impacted by growth restrictions and increased mortality rates, which potentially cause shorter migration durations, lowered reproductive success and possibly also selection against anadromy. This study provides vital information for conservation practitioners wanting to understand the physiologically derived burden salmon lice can have on Arctic char populations, and can be used to define thresholds in the monitoring and conservation of Arctic char populations affected by aquaculture-driven salmon lice infestations.

Methotrexate-anticollagen conjugate inhibits in vitro lens cell outgrowth.

After-cataract, or posterior lens capsule opacification, is an undesirable but common sequela to extracapsular cataract surgery. We are investigating biochemical means to prevent after-cataract formation, which can be applied at the time of the original surgery. Based on similar research efforts in cancer chemotherapy, we have prepared a conjugate of the antimetabolic agent methotrexate with an antibody specific for basement membrane collagen, the major protein in the lens capsule. The conjugate was evaluated using biochemical measurements, and retained both antimetabolic and antibody activities. When the conjugate was applied to bovine posterior capsules in vitro, or in vivo in rabbits, it was an effective inhibitor of lens epithelial cell outgrowth in cell culture.

Ames mutagenicity tests on purified 3-nitropropionic acid.

3- Nitropropionic acid is a toxic compound produced by several moulds involved in food fermentation or spoilage. An impure commercial sample of this compound was previously reported as being mutagenic to Salmonella typhimurium strains TA1535 and TA100. In the present study, a sample from the same lot of 3- nitropropionic acid was mutagenic in strain TA100 without metabolic activation, but this activity was diminished after recrystallization. This sample was not mutagenic in strain TA98, before or after recrystallization. A new, purer commercial sample was non-mutagenic in strains TA98, TA100 and TA1538, with or without metabolic activation. Therefore the mutagenicity reported to be due to 3- nitropropionic acid was considered to be due to the impurity(ies).

Reducing nitrosamine contamination in cutting fluids.

In simulated metalworking coolants that contained both nitrite and di- or triethanolamine at pH 9, N-nitrosodiethanolamine formed at an initial rate of 11 or 6 ppm/wk, respectively. This rate was increased on heating the fluids, on acidification or by the addition of paraformaldehyde, 1,3,5-trimethylhexahydro-s-triazine, ferricyanide or ferric ethylenediaminetetraacetate. N-Nitrosodiethanolamine also formed when nitrite-free coolants containing either of the two amines above were exposed to nitric oxide in air. No nitrosamines were detected in fluids containing primary amines in place of the secondary and tertiary amines, except that N-nitrosooxazolidine was formed in the fluid containing monoethanolamine after addition of formaldehyde-releasing agents, and N-nitrosodiethanolamine and N-nitrosomorpholine were found in fluid containing diglycolamine (HOCH2CH2OCH2CH2NH2) after the fluid was heated at 100 degrees C for 48 hr. These data suggest several steps by which nitrosamine formation in commercial cutting fluids might be substantially reduced: avoiding acid-splitting as a disposal procedure; removing nitrite from the fluid and/or scavenging adventitious nitrosating agents; avoiding unnecessary heating; adding preservatives to the diluted fluid rather than to the commercial concentrate; replacing inherently nitrosatable amine additives by substitutes which are resistant to nitrosamine formation; minimizing concentrations of catalytically active metal complexes.

Carcinogenesis in rats by cyclic N-nitrosamines containing sulphur.

The effects of chronic exposure to three sulphur-containing heterocyclic N-nitrosamines were determined after repeated oral administration to female Fischer 344 rats. Nitrosothiazolidine did not significantly affect the survival of the rats or the incidence of tumours at a total dose of 3.5 mmol. Nitrosodithiazine, an analogue of nitrosothiazolidine which contains an extra sulphur atom inserted between the carbons of its CH2-CH2 moiety, produced only three tumours (two of the nasal mucosa) in a group of 20 rats at a total dose of 1.75 mmol/rat. Nitrosothialdine, the all-cis 2,4,6-trimethyl analogue of nitrosodithiazine, was a potent carcinogen that significantly shortened the lifespan and produced oesophageal tumours in 70% of treated rats as well as numerous tumours of the tongue and liver; this outcome was unexpected because alpha-methyl substitution in other heterocyclic nitrosamines usually reduces or eliminates tumorigenicity. The results extend the data base on the carcinogenic activity of molecules containing both divalent sulphur and the nitrosamino function. The lack of significant carcinogenicity of nitrosothiazolidine in this study suggests that its presence in the human food supply presents a relatively minor risk.

Compounds formed by treatment of corn (Zea mays) with nitrous acid.

Nitrohexane has been identified as a major product formed following treatment of corn (Zea mays) with nitrous acid. Preliminary evidence suggests that another compound isolated from the nitrosated corn is an unsaturated nitrolic acid. As an aid to the analysis of N-nitro compounds, we have characterized the response of a chemiluminescence detector (Thermal Energy Analyzer) as a function of pyrolysis chamber temperature for several nitrosamines and for an aliphatic C-nitroso compound, an aromatic C-nitro compound, a nitramine and an alkyl nitrite. The response-temperature profiles are valuable in distinguishing among the various compounds and in optimizing the sensitivity of the detector for use in chromatography. Other tests, including photolysis and stability toward nitrite-scavenging reagents, further aid in distinguishing among the various compounds.

N-nitrosation of secondary amines by nitric oxide via the 'Drago complex'.

Diethylamine (DEA) and nitric oxide (NO) form a stable 1:1 complex (DEA/NO) which can be oxidized to N-nitrosodiethylamine (NDEA). Spectroscopic data for the complex are consistent with the ionic structure originally proposed by Drago & Paulik (1960). Attempts to confirm this structure by X-ray crystallography are continuing. Oxidation of DEA/NO to NDEA appears to be effected by an acid-catalysed dissociation to DEA and NO, followed by autoxidation of NO to an N-nitrosating higher oxide of nitrogen.

Immunoaffinity column coupled with solution fluorometry or liquid chromatography postcolumn derivatization for determination of aflatoxins in corn, peanuts, and peanut butter: collaborative study.

An AOAC/IUPAC (International Union of Pure and Applied Chemistry) collaborative study was conducted to evaluate the effectiveness of an immunoaffinity column for the determination of aflatoxin. The test portion is extracted with methanol-water (7 + 3), filtered, diluted to less than 30% methanol with water, and applied to the affinity column. The column is washed with water and the concentrated aflatoxins are eluted with methanol. Total aflatoxins are determined by solution fluorometry with bromine (SFB), and individual toxins are determined by reverse-phase liquid chromatography with postcolumn derivatization with iodine (PCD). Corn naturally contaminated with aflatoxins, and peanuts, peanut butter, and corn containing added aflatoxins (B1:B2:G1:G2 = 7:1:3:1) were sent to 24 collaborators in the United States, France, Canada, and the Republic of South Africa. Twelve collaborators used the SFB method, 9 used the PCD method, and 3 used both SFB and PCD methods. Twenty collaborators completed the study (10 used the SFB method, 7 used the PCD method, and 3 used both SFB and PCD methods). Test portions were spiked at 10, 20, and 30 ng/g. For SFB analyses, recoveries of total aflatoxins were 123, 105, and 107%, respectively; the relative standard deviation for repeatability (RSDr) ranged from 11.75 to 16.57%, and the relative standard deviation for reproducibility (RSDR) ranged from 10.97 to 33.09%. For PCD analyses, recoveries were 81, 81, and 83%, respectively; the RSDr ranged from 5.20 to 17.22%, and the RSDR ranged from 4.68 to 50.77%. The RSDr for aflatoxins B1 and G1 for spiked test portions ranged from 5.45 to 23.55%, and the RSDR ranged from 4.21 to 57.28%.(ABSTRACT TRUNCATED AT 250 WORDS)