Growth hormone and seawater adaptation in coho salmon, Oncorhynchus kisutch

1. Effects of growth hormone (GH) were examined on short-term aspects of seawater adaptation in coho salmon smolts. 2. Injection of somatostatin (SRIF) immediately prior to seawater entry suppressed plasma GH levels, but did not have any significant effects at 6 or 12 hr on hematocrits, plasma glucose or plasma Na+ levels. 3. Plasma GH levels increased 250% within 36 hr after seawater exposure. 4. Plasma glucose levels, in contrast, were significantly lower in the seawater fish after 36 hr post-exposure. 5. Plasma Na+ levels increased to 190 mEq/1 by 24 hr but subsequently returned to freshwater levels while hematocrits showed no significant changes over the 72 hr of exposure. 6. The significance of these results is discussed in terms of successful seawater adaptation in coho salmon.     

The effects of low pH on egg and alevin survival of kokanee and sockeye salmon, Oncorhynchus nerka

1. The effects of low pH water on embryogenesis and vitellogenesis in kokanee and sockeye salmon (Oncorhynchus nerka) were investigated. Eggs were exposed to low pH from fertilization to 45 days post-median hatch or to an episodic exposure at pH 4.0. Adult kokanee were also exposed to low pH just prior to ovulation and spawning. 2. The most sensitive stages of development during chronic or episodic exposure to low pH were early embryonic development and newly-hatched alevins. 3. Incubation of eggs at low pH caused a lower median survival, delayed hatching, higher alevin mortality and reduced the efficiency of yolk conversion to tissue of yolk-sac alevins. Those effects were more pronounced when the eggs were fertilized at low pH. 4. Exposure of sexually mature kokanee salmon to acidified water reduced egg and alevin survival, delayed embryo hatching and decreased the percent hatch. Those effects were more pronounced when their eggs were incubated at low pH.     

Efficient oligonucleotide-directed construction of mutations in expression vectors by the gapped duplex DNA method using alternating selectable markers.

An efficient method for the construction of multiple mutations in a sequential manner is described. It is based on the gapped duplex DNA approach to oligonucleotide-directed mutagenesis (Kramer et al. 1984, Nucl. Acids Res. 12, 9441-9456) and a set of newly constructed phasmid vectors. These are characterized by the following features. Presence of the phage fl replication origin permits ready conversion to the single stranded DNA form. An amber mutation within, alternatively, the bla or cat gene provides a means for ready selection of the strand into which the mutagenic oligonucleotide has been incorporated. By means of the alternating antibiotic resistance markers any number of mutations can be constructed in consecutive rounds of mutagenesis. The optional presence of gene expression signals allows the direct overproduction of structurally altered proteins without re-cloning. Both the mutagenesis and expression aspects were tested using the lacZ gene as a model.     

The effect of vasotocin on plasma glucose, free fatty acids and growth hormone in the frog, Rana catesbeiana

Injections of arginine vasotocin into bullfrogs had no effect on plasma glucose after 30 min. but caused hyperplycemia after 120 min. Plasma levels of growth hormone were elevated earlier (30 min.) and returned to control levels after 120 min. Plasma free fatty acids were unaltered following vasotocin administration. It is suggested that the hyperglycemic effect of vasotocin may be mediated via growth hormone.     

Evidence for sub-families of actin genes in Dictyostelium as determined by comparisons of 3' end sequences

We have sequenced the 3′ end of five actin genomic clones and three actin complementary DNA clones from Dictyostelium. Comparison of the sequences shows that the protein coding regions are highly conserved, while the region corresponding to the 3′ untranslated regions are divergent. Additional analysis indicates regions of homology in the 3′ untranslated region between sets of actin genes. Southern DNA blot hybridization studies using labeled 3′ ends suggest that there are sub-families of actin genes that are related within the 3′ untranslated regions. No homology is found in the sequences outside the messenger RNA encoding regions. Analysis of the sequence data has shown that the difference in length between the ~1.25 × 10³ and ~1.35 × 10³ base actin messenger RNAs is in the lengths of the 3′ untranslated region.