Gastrin and cholecystokinin in the Eastern Grey kangaroo, Macropus giganteus giganteus

Gastrin and CCK are believed to have a common ancestor. The gastrin structure has probably evolved from CCK-like peptides at a stage later than the amphibians. To trace the evolution of gastrin and CCK we have determined their structures in an Australian marsupial, the Eastern Grey kangaroo. The brain CCK was identical to CCK-8 of most mammals. The larger form of kangaroo gastrin was a 33mer with the sequence pELHPQDLPHLMTDLSKKKGPWQEEDAAY(SO₃)GWMDF-NH₂. The 11 italic residues indicate differences from human gastrin. Gastrin-15 and gastrin-16 comprised about 70% of the total immunoreactivity and resulted from cleavage after the second and third residue, respectively, of the unusual tribasic cleavage site. The smaller forms of kangaroo gastrin differ from most other mammalian gastrins in that the N-termini are not blocked with a pyroGlu moiety. Unlike other gastrins, kangaroo gastrin is more than 95% sulfated. The present study indicates that the gastrin structure, as defined by having a Tyr at position 6 from the C-terminus, evolved before the marsupials diverged from the other mammals 130 million years ago.     

Indigenous Bacteria in Hemolymph and Tissues of Marine Bivalves at Low Temperatures

Hemolymph and soft tissues of Pacific oysters (Crassostrea gigas) kept in sand-filtered seawater at temperatures between 1 and 8°C were normally found to contain bacteria, with viable counts (CFU) in hemolymph in the range 1.4 × 10² to 5.6 × 10² bacteria per ml. Pseudomonas, Alteromonas, Vibrio, and Aeromonas organisms dominated, with a smaller variety of morphologically different unidentified strains. Hemolymph and soft tissues of horse mussels (Modiolus modiolus), locally collected from a 6- to 10-m depth in the sea at temperatures between 4 and 6°C, also contained bacteria. The CFU in horse mussel hemolymph was of the same magnitude as that in oysters (mean, 2.6 × 10⁴), and the bacterial flora was dominated by Pseudomonas (61.3%), Vibrio (27.0%), and Aeromonas (11.7%) organisms. In soft tissues of horse mussels, a mean CFU of 2.9 × 10⁴ bacteria per g was found, with Vibrio (38.5%), Pseudomonas (33.0%), and Aeromonas (28.5%) constituting the major genera. After the challenge of oysters in seawater at 4°C to the psychrotrophic fish pathogen Vibrio salmonicida (strains NCIMB 2245 from Scotland and TEO 84001 from Norway) and a commensal Aeromonas sp. isolated from oysters, the viable count in hemolymph increased 1,000-fold to about 10⁵ bacteria per ml. In soft tissues, about a 1,000-fold increase in CFU to 6 × 10⁷ was observed. V. salmonicida NCIMB 2245 invaded hemolymph and soft tissues after 14 days and dominated these compartments after 41 days, whereas strain TEO 84001 did not invade soft tissues to the same extent. Challenge with V. salmonicida NCIMB 2245 resulted in 100% mortality, whereas about 50% of the oysters survived challenge with the Norwegian strain, TEO 84001. The commensal Aeromonas sp. invaded hemolymph and soft tissues and caused 100% mortality. Oyster hemolymph contained agglutinins for Vibrio anguillarum but not for V. salmonicida, whereas we did not find agglutinins for either of these bacteria in horse mussels. Agglutinins for horse and human erythrocytes were found in hemolymph from both animals. We found no differences in agglutinin titers in oysters from different Norwegian locations, and long-term challenge with bacteria in seawater did not result in changes of agglutinin activity. These studies demonstrate that bacteria exist in hemolymph and soft tissues of marine bivalves at temperatures below 8°C. Increased bacterial numbers in seawater at 4°C result in augmented invasion of bacteria in hemolymph and soft tissues. V. salmonicida, a bacterium pathogenic for fish at low temperatures, invades bivalve hemolymph and soft tissues, and thus bivalves may serve as a reservoir for pathogens of fish at low seawater temperatures.     

The Influence of Alarm Substance on Feeding in Zebra Danio Fish (Brachydanio rerio)

The effects of alarm substance on feeding behaviour of zebra danio fish (Brachydanio rerio) were tested by offering them high and low densities of enclosed waterfleas (Daphnia magna). Normally the fish attacked high densities of prey, but when exposed to alarm substance they preferred lower and presumably less confusing prey densities — also lowering their feeding rate.     

Repeatability of mate choice in female red jungle fowl

We staged female mate choice trials between pairs of males andrepeated the process for each female to determine the repeatabilityof female preference for males in red jungle fowl (Gallus gallus)in the first and second half of the breeding season. We measuredmale morphological traits (the size and color of the comb andthe brightness of the hackle feathers) that females are knownto use in choosing a mate. In the first half of the breedingseason, females showed repeatability in their choices of matewith respect to the male's comb characters. Females did notshow a repeatable preference with respect to male hackle feathers,and we found no repeatability of mate choice in the second halfof the season. Females seem to primarily look at the male'scomb when choosing a mate, and other ornaments seem only ofsecondary importance.[Behav Ecol 7: 243-246 (1996)]     

RNA secondary structure and translation inhibition: analysis of mutants in the rplJ leader

We have carried out measurements of the stable binding of the ribosomal protein (r-protein) complex L10-L7/L12 to mutant forms of the mRNA leader of the rplJ operon of Escherichia coli. One of the point mutations, base 1548, which lies within the L10-L7/L12-protected region, almost completely abolishes in vitro formation of a stable complex of L10-L7/L12 with rplJ mRNA leader, and a second point mutation, base 1634, strongly reduces it. These observations constitute strong support for the proposition that L10-L7/L12 binds to the rplJ leader in bringing about translational feedback. To account for the action of these and other mutations, and to explain the mechanism of translation feedback inhibition, we suggest a secondary structure model involving alternate forms of the rplJ mRNA leader.     

Effect of CO2, CO2 and Diamox on photosynthesis and photorespiration in Chlamydomonas reinhardtii (green alga) and Anacystis nidulans (Cyanobacterium, blue-green alga)

Photorespiration by Chlamydomonas reinhardtii and Anacystis nidulans was measured as the oxygen inhibition of CO₂ uptake and the CO₂ compensation points. Net photosynthesis was oxygen dependent in Chlamydomonas grown in 5% CO₂, but CO₂ insensitive in cultures bubbled with air. Anacystis, even when cultured in 5% CO₂, exhibited an CO₂ insensitive net photosynthesis. The CO₂ compensation point of Chlamydomonas grown in cultures bubbled with air and Anacystis grown in 5% CO₂ enriched air, were reached shortly after the measurement was begun and the values were very low, less than 10 μl CO₂ 1^?1; while Chlamydomonas grown in 5% CO₂ enriched air for 4 days showed a high, but temporary CO₂ compensation point (60 μl CO₂ 1^?1). After a two hour adaptation in low CO₂, a stable, low CO₂ compensation point was reached. It seems that photorespiration can only be detected by the methods used in this study when the algae are cultured in high CO₂, but a mechanism exists which blocks photorespiration when the green algae are adapted to low CO₂ concentrations. When Chlamydomonas was treated with Diamox, an inhibitor of carbonic anhydrase, after cultivation in low CO₂ (air), the cells behaved as if they had been grown in high CO₂. They showed an oxygen sensitive net photosynthesis and a high CO₂ compensation point. This indicates that carbonic anhydrase plays an important role in the regulation of a measurable photorespiration in Chlamydomonas. The results are discussed in relation to previous observations of photorespiration measured by enzyme assay, metabolic products and gas exchange properties.     

Two new C-methylated flavonoids from Myrica gale

From the leaves of Myrica gale 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone has been isolated. The fruits yielded 2′-hydroxy-4′,6′-dimethoxy-3′-methyldihydrochalcone. The constitutions were deduced from spectroscopic data and confirmed by synthesis.     

Infestations by Gyrodactylus sp. of Atlantic salmon, Salmo salar L., in Norwegian rivers

Young Atlantic salmon, Salmo salar , brown trout, Salmo trutta , and Arctic char, Salvelinus alpinus , from eight rivers in North and Mid Norway were examined for Gyrodactylus. The fish were collected from 1975 to 1980. A Gyrodactylus salaris type was observed infecting salmon from six of these rivers. No trout or char were infected. A high frequency and intensity of infection of salmon were observed in all but one of the rivers surveyed. In the Saltdalselva, only one specimen of Gyrodactylus infecting one fish was observed. No subsequent mortality of salmon was observed in this river while there were signs of a high mortality of salmon in the other rivers. The salmon parr were more frequently attacked than the fry, the mortality of salmon seemed to have happened in most of the rivers one year after the first observations of Gyrodactylus were made. The mortality of salmon and the high infection rate of Gyrodactylus in these rivers appears unique, and as far as known to the authors there are no other described cases of mortality due to Gyodactylus in Atlantic salmon in natural waters. The reasons for the outbreak of Gyrodactylus in these rivers are not known. Two theories are discussed: one that the fish were weakened by environmental factors and the other that Gyrodactylus was introduced from some of the infected salmon hatcheries in Scandinavia.