Mapping quantitative trait loci for infectious salmon anaemia resistance in a North American strain of Atlantic salmon

Infectious salmon anaemia (ISA) is a highly virulent viral disease of Atlantic salmon that causes massive economic losses to infected aquaculture operations. Our goal was to detect and map quantitative trait loci (QTL) that confer resistance to ISA in an admixed commercial strain of Atlantic salmon that was largely founded from the Saint John River (SJR) in North America. Full‐sibling families were challenged with a virulent strain of ISA virus. Mortality was tracked during two annual trials with individual fish that survived to the end of the trial being classified as ‘resistant’, and those that died were classified as ‘susceptible’. Ten families with intermediate levels of mortality and an average size of 54.2 individuals were chosen for genotyping with a 50K SNP array designed for the SJR strain. Single nucleotide polymorphisms that were segregating within families were first used to make a composite 11K female linkage map that was then used to find the positions of QTL for ISA resistance using a half‐sib model. The dam‐based HS model detected a total of three QTL for ISA resistance including an experiment‐wide significant QTL on Ssa25 that accounted for 8.3% of the phenotypic variance and chromosome‐wide significant QTL on Ssa03 and on Ssa04 that accounted for 6.0% and 6.6% respectively. We conclude that classic linkage mapping within families continues to be an important method of detecting QTL for oligogenic traits in strains founded from multiple populations. Single nucleotide polymorphisms with moderate trait effects are being used to select within families for more ISA‐resistant strains of Atlantic salmon.     

A binding protein for fatty acids in cytosol of intestinal mucosa, liver, myocardium, and other tissues

A protein of molecular weight approximately 12,000 which binds long-chain fatty acids and certain other lipids has been identified in cytosol of intestinal mucosa, liver, myocardium, adipose tissue, and kidney. Binding is noncovalent and is greater for unsaturated than for saturated and medium-chain fatty acids. This protein appears to be identical with the smaller of two previously described cytoplasmic anion-binding proteins. Binding of long-chain fatty acids by this protein is greater than that of other anions tested, including sulfobromophthalein, and does not depend on negative charge alone. The presence of this binding protein may explain previously observed differences in intestinal absorption among fatty acids, and the protein may participate in the utilization of long-chain fatty acids by many mammalian tissues.     

Early distribution of radioactive liposomes and scrapie infectivity in mouse tissues following administration by different routes

Mice were injected with ^99mtechnetium-labelled liposomes or with a standard homogenate of scrapie-affected brain. Four different routes of injection were used, intracerebral (i.c.), intravenous (i.v.), intraperitoneal (i.p.) and subcutaneous (s.c.). Blood and a range of other tissues were removed between 5 min and several hours after injection. The tissues included spleen and salivary gland in which appreciable agent replication (or at least accumulation) is known to occur and, liver where replication of scrapie agent does not occur.Within 30 min of injection by any of the four routes used, radioactivity, and infectivity were detected in tissues remote from the site of injection. The distribution of radioactivity in various tissues was similar to that of infectious scrapie agent, but in both cases it occurred much more rapidly after i.v. injection than after injection by the i.p. or s.c. route. It is suggested that the 1000-fold reduced efficiency of scrapie infection by the s.c. route, compared to the i.v. route, is related to the extensive localisation of inoculum at the site of injection. Despite the relatively high efficiency of infection of the i.v. route, much of the detectable agent is taken up by liver where the agent does not replicate. It is concluded that only a very small proportion of the agent injected i.v. (and presumably by other routes) is involved in establishing scrapie infection of mice.     

Thyroid gland and arterial lesions of Beagles with familial hypothyroidism and hyperlipoproteinemia.

Primary hypothyroidism with marked hyperlipoproteinemia and modest to severe atherosclerosis was described in a family of Beagles. The disease was familial and probably hereditary, but the mode of inheritance was unknown. Signs of the disease occurred as early as 1.5 years of age and as late as 5 years of age. The onset of the disease was heralded by reduced concentrations of serum thyroxine, increased binding capacity of thyroxine-binding globulin, and reduced response to injected thyroxine-stimulating hormone. Thereafter, serum lipids, particularly serum cholesterol, increased markedly even though the dogs consumed a diet low in fats and cholesterol. Thyroxine administration resulted in a precipitous decline in serum cholesterol concentrations. Microscopic changes in the thyroid glands included neoplastic transformation, adenomatous hyperplasia, lymphocytic thyroiditis, and atrophy. Moderate to severe atherosclerosis occurred mainly in the coronary and renal arteries. Atherosclerotic arteries were stenotic but patent, and there was no evidence of prior occlusion or thrombosis.     

Observations of the immunopathology and therapy of canine pemphigus and pemphigoid

Immunopathologic evaluation of 27 dogs with pemphigus and pemphigoid demonstrated that direct immunofluorescence testing was vastly superior to indirect immunofluorescence testing for diagnosis. Therapeutic studies in 31 dogs with pemphigus and pemphigoid demonstrated that glucocorticoids given for systemic effect were unsatisfactory as the sole form of treatment because of lack of efficacy of unacceptable side effects, or both, in over 50% of the cases.     

Responses of the immature fowl to a single injection of adrenocorticotrophic hormone.

Chicks, aged 1 or 21 d, were injected with long-acting ACTH (6, 12, 30 or 60 IU/kg) and changes in plasma glucose and cholesterol and in adrenal weight and cholesterol measured. 2. No consistent response was observed in the 1-d-old chicks. 3. Hyperglycaemia and adrenal cholesterol depletion could be demonstrated in the 3-week-old bird at all doses. 4. The duration of the hyperglycaemic response was dose-dependent but there was only limited evidence that adrenal cholesterol depletion was similarly dependent. 5. Starving the 3-week-old bird overnight led to a significant hypercholesteraemia which was reduced after ACTH. In contrast no change in plasma cholesterol concentration was noted in fully fed birds.     

Some responses of the immature fowl to the withdrawal of a stressor

1. Light Sussex chicks were treated with corticotrophin (30 IU/kg) five times a week from hatching to 3 weeks of age. Their responses to the cessation of treatment were determined over the subsequent 2 weeks. 2. Growth rate was impaired by the treatment but had returned to normal after 7 d. 3. Adrenal mass was not affected by treatment but hypertrophy was evident after 14 d of recovery. Relative adrenal weight was greater in the treated group throughout the recovery period. 4. Adrenal cholesterol stores were depleted at the end of treatment, were repleted after 7 d but significantly depleted again at 14 d. 5. Plasma glucose concentration was not affected by treatment but birds were hyperglycaemic 7 and 14 d after treatment had ceased. 6. Plasma free fatty acid (FFA) concentrations were not affected at any time. 7. Plasma corticosterone concentration was not affected by the treatment but 7 d later it was greater in the treated birds. 8. Significant correlations between plasma glucose, FFA and corticosterone were found.     

The response of the immature fowl to multiple injections of adrenaline.

Chicks were injected, from one to 21 days of age, with either L-adrenaline (500 mug/kg) or the solvent three times a week. Birds treated with adrenaline showed an imparied growth rate. Relative (mg/kg0.75), but not absolute (mg) adrenal weight was significantly increased. No changes in adrenal cholesterol content or concentration were noted.