13C nuclear magnetic resonance spectra of diastereomeric C-24 alkyl sterols have been assigned. Differences in the chemical shifts of side-chain carbons permitted the determination of the absolute configuration at C-24 in several sterols since these chemical shifts are insensitive to structural changes remote from the asymmetric centre. An unknown sterol from Tetraselmissuecica has been identified as (24R)-24-methylcholest-5-en-3β-ol and the configuration assigned from 1H nmr data to the sterol from Phaeodoctylumtricornutum has been confirmed. The utility and potential of this method in characterising new sterols and their biological precursors is discussed.

We have developed an "all fish" growth hormone (GH) chimeric gene construct by using an antifreeze protein gene (AFP) promoter from ocean pout linked to a chinook salmon GH cDNA clone. After microinjection into fertilized, nonactivated Atlantic salmon eggs via the micropyle, transgenic Atlantic salmon were generated. The presence of the transgene was detected by polymerase chain reaction (PCR) using specific oligonucleotide primers. A number of these transgenic fish showed dramatic increases in their growth rate. At one year old, the average increase of the transgenic fish was 2 to 6 fold and the largest transgenic fish was 13 times that of the average non-transgenic control.

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The reproductive status of winter flounder was analyzed in individuals collected at regular intervals throughout the year. Although spawning occurred in May–June, sperm could be activated in January, and male gonadosomatic indices in November were approximately twice those recorded immediately before spawning. Oocyte recruitment occurs close to spawning, and oocyte changes are compatible with a 3-year cycle. Vitellogenesis of the oldest year class of oocytes is initiated during the summer feeding season and maintained over the nonfeeding winter season. Some females after spawning do not enter the vitellogenic stage but overwinter with two year classes of immature oocytes. This nonreproductive phase in females in related to condition rather than age. Nonreproductive males also occur in the population sampled and in the fall there was a trend towards an increased number with advancing age. The protracted gametogenesis in winter flounder demonstrates the need for caution when assessing spawning condition and reproductive capacity of some fish stocks.

No abstract