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Reports on a study in which gonadotropin (GTH) was purified from the pituitaries of the Pacific chinook salmon using a combination of stepwise ethanol precipitation and concanavalin-A affinity chromatography. Reverse-phase high-performance liquid chromatography; Screening of an enriched cDNA library for the β-GTH genes using two synthetic oligonucleotides; Effect of testosterone implantation on pituitary PTH and β-GTH mRNA; Corresponding increase in both the pituitary GTH and mRNA levels.

The reproductive effects of induced triploidy were assessed in 3-year-old yellowtail flounder. Diploids of this small flatfish show a propensity for early sexual maturation in culture. Triploidy was effective in reducing gonadal development in yellowtail flounder, but permitted physiological maturation in both sexes. Triploid males sampled during the regular spawning period in captivity had small testes and variable plasma androgen levels (n=7; age, 34 months). A limited production of spermatozoa and evidence of spermatogenetic dysfunction were noted histologically. Spermatozoa from triploids exhibited poor or no motility and further demonstrated reduced fertility in fertilization trials with eggs from diploid females. Most larvae resulting from fertilization trials were abnormal and nonviable; however, some triploid males produced a few larvae of normal appearance which may indicate long-term viability. Females sampled at 37 and 40 months of age had small ovaries with varying numbers of oocytes, previtellogenic to vitellogenic, that were developing amid oogonial tissue (oog). Evidence of prior summer ovulatory activity was found in 2 of the 17 females. A high proportion of the remaining 3-year-old females had vitellogenic oocytes and was likely to become fully mature by 4 years of age. Plasma estradiol-17β (E2) levels were low in triploid females despite the fact that ovarian tissue from pubertal triploids can demonstrate a strong steroidogenic response to gonadotropic stimulation in vitro. The production of triploids will help to reduce the energetic costs of reproduction in the yellowtail flounder. [Copyright &y& Elsevier]

To better understand the evolution of pituitary adenylate cyclase-activating polypeptide (PACAP) and growth hormone-releasing hormone (GHRH), we isolated the cDNAs encoding these peptides from the brains of five species of fish: sturgeon, whitefish, grayling, flounder and halibut. Both hormones are encoded in tandem in full-length cDNAs. We compared the phylogenetic relationship among these and other known sequences encoding PACAP. In closely related species, transcripts encoding PACAP and GHRH are strongly conserved in the hormone coding regions, moderately conserved in the signal peptide, cryptic peptide and 3′-untranslated regions, but are most varied in the 5′-untranslated regions.Next, we compared the deduced amino acid sequences for the peptides to known sequences. Sturgeon and whitefish have a PACAP38 peptide sequence that is 92% conserved compared to human PACAP38, the highest for a fish reported to date. GHRH is the lesser conserved of the two peptides with only 39% to 45% conservation between fish and human.Each of the five fish species had a second cDNA encoding a short precursor lacking GHRH1–32, the bioactive portion of GHRH. This suggests that exon skipping in GHRH–PACAP transcripts may be an important mechanism for regulating the ratio of PACAP to GHRH peptides. [Copyright &y& Elsevier]