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Techniques for production of triploids are well described for commercially reared salmonids (e.g., rainbow trout Oncorhynchus mykiss and Atlantic salmon Salmo salar). Among less commonly used species, including brook trout Salvelinus fontinalis, these protocols have not been optimized. As a prelude to investigating the regional potential for commercial culture of brook trout with all‐female and all‐female triploid stocks, we conducted experiments to test the effects of the primary variables of thermal shock used to induce retention of second polar bodies. The objective was to identify a protocol that maximizes yield of both triploid and gynogenetic diploid progeny. The first experiment measured survival of gynogenetic embryos produced by heat shocks involving combinations of different temperatures (26, 27, 28, or 29°C) and durations (7, 10, 13, 16, 19, or 22 min). In three subsequent experiments, production of triploids was assessed for thermal shocks involving variable times of initiation (7, 10, 13, 16, 19, or 22 min postactivation) in addition to the above temperatures and durations. Significant trends for decrease in survival and increase in percent triploidy were observed with increase in temperature and duration of thermal shock. Effects for time of initiation in two of three experiments were nonsignificant; in the third, survival tended to increase and percent triploidy to decrease with increase in time of initiation. With a preshock incubation temperature of 11–12°C, the most generally effective protocol involved a thermal shock of 28°C for 10 min duration initiated at 10–16 min postactivation, for which relative survival was 68–71%, percent triploidy was 79–99%, and triploid yield was 54–70%. In a fifth experiment, the fertilized eggs of 14 females were treated separately with a 28°C shock of 10 min applied at 10 min postactivation. Although relative survival to initiation of feeding ranged between 42% and 100%, percent triploidy was consistently 98–100%.

Ascorbic acid rapidly decays in plant tissue culture media. Within 50 min to 3 h after preparing 100 mM solutions, ascorbic acid was destroyed. Autoclaving, shaking flasks, high light intensity and increasing pH over a range from 4.5-7 accelerated decay. Ascorbic acid was oxidized to dehydroascorbic acid which also underwent decay. Within 11 h and 15 min after adding ascorbic acid both ascorbic acid and its oxidation product, dehydroascorbic acid, disappeared from medium. Since ascorbic acid is rapidly destroyed in plant tissue culture media it may not exert its effect as an intact molecule. Instead its antioxidant/antibrowning role in plant cell, tissue and organ cultures may be mediated by some product of further oxidation.

No abstract

In mammalian systems, platelet-activating factor, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, (PAF) is rapidly inactivated by a deacetylation/reacylation system that produces 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine which is highly enriched in arachidonic acid. There is some evidence that n-3 fatty acids may have an impact on this system in humans but the nature of this impact is unclear. In rainbow trout, n-3 fatty acids are known to be essential dietary components which are derived through the food chain. Substantial quantities of n-3 fatty acids are found in trout membrane phospholipids. We show here that in sharp contrast to mammalian cells, trout cells acylate lyso platelet-activating factor, alkyl-GPC, 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine, (lyso-PAF) with a high degree of specificity for n-3 fatty acids. When [3H]lysoPAF was incubated with these cells, only three molecular species of alkylacylglycerophosphocholine were produced, and 92% contained n-3 fatty acids. Since isolated membranes yielded similar results, it appears that the acylation proceeds via a coenzyme A-independent transacylase as found in mammalian systems.