Improved method for extraction of hydroperoxide lyase from Chorella

Summary Hydroperoxide lyase converts fatty acid hydroperoxides to oxo-fatty acids which, after further oxidation, are suitable for the synthesis of higher polyamides. An improved method utilizing an acetone powder step for isolation of this enzyme from the unicellular alga Chlorella was developed. Using this procedure a five fold increase in hydroperoxide lyase activity from Chlorella pyrenoidosa was obtained compared to previously used extraction methods. Other Chlorella species were assayed, and it was found that C. fusca also contained significant hydroperoxide lyase activity.     

Conformational change in yeast tRNAAsp

The structure of yeast tRNA^Asp in aqueous solutions has been analyzed in the light of results obtained from Raman spectra recorded at from 5 to 82°C and compared to those of tRNA^Phe. Firm evidence is given of a reversible conformation transition for tRNA^Asp at 20°C. This transition is observed for the first time in the tRNA series. The low-temperature conformation appears to have a more regular ribose–phosphate backbone and a more effective G base-stacking. This conformational change, which occurs essentially in the D loop, could be connected to the existence of two (A and B) crystal forms obtained depending on crystallization conditions. The melting temperatures, which are different for each base stacking in tRNA^Asp, lie in a range of about 70°C, much higher than for tRNA^Phe. This fact is interpreted by a higher ratio of G-C base pairs in tRNA^Asp.     

Purification of Hydrogenase from Chlamydomonas reinhardtii

A method is described which results in a 2750-fold purification of hydrogenase from Chlamydomonas reinhardtii, yielding a preparation which is approximately 40% pure. With a saturating amount of ferredoxin as the electron mediator, the specific activity of pure enzyme was calculated to be 1800 micromoles H₂ produced per milligram protein per minute. The molecular weight was determined to be 4.5 × 10⁴ by gel filtration and 4.75 × 10⁴ by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme has an abundance of acidic side groups, contains iron, and has an activation energy of 55.1 kilojoules per mole for H₂ production; these properties are similar to those of bacterial hydrogenases. The enzyme is less thermally stable than most bacterial hydrogenases, however, losing 50% of its activity in 1 hour at 55°C. The K_m of purified hydrogenase for ferredoxin is 10 micromolar, and the binding of these proteins to each other is enhanced under slightly acidic conditions. Purified hydrogenase also accepts electrons from a variety of artificial electron mediators, including sodium metatungstate, sodium silicotungstate, and several viologen dyes. A lag period is frequently observed before maximal activity is expressed with these artificial electron mediators, although the addition of sodium thiosulfate at least partially overcomes this lag.     

Biology of the minnow Phoxinus phoxinus and its interactions with brown trout Salmo trutta in Øvre Heimdalsvatn, Norway

Minnows have recently been introduced into the mountain lakes of southern Norway. In Øvre Heimdalsvatn, an intensively studied lake, the minnow population has increased rapidly during the last decade. Studies were performed on feeding habits, habitat preferences, age, growth, energy content, densities, parasites, predation and spawning activities. Several aspects were found to be different from other studies, e.g. higher age of sexual maturation, lower growth rate, no feeding on plants, and low infection of parasites. The interaction with the only other fish, the brown trout, is discussed in relation to the minnow population. In 1978 the minnows constituted little more than 10% of production and food consumption of the trout population, and only limited food competition and predation was documented. Increasing competition is likely with a greater minnow population.     

Detection and regulation of δ-aminolevulinic acid synthetase activity in rat skeletal muscle

The presence of δ-aminolevulinic acid synthetase (ALAS) in mitochondria obtained from rat skeletal muscles has been observed. Optimal conditions for the meausurement of this activity are described. The activity of skeletal muscle ALAS was investigated under conditions known to affect the activity of this enzyme in other tissues. ALAS activity in skeletal muscle mitochondria was decreased 55% by a 48-h fast. Treatment with dexamethasone did not reverse the effect of starvation on ALAS activity and did not change the activity in the fed controls. ALAS activity was decreased 56% in skeletal muscle mitochondria obtained from rats in which diabetes mellitus had been induced by streptozotocin. Administration of insulin to the diabetic animals partially reversed the effect of diabetes on skeletal muscle ALAS; however, administration of insulin to control animals caused a 21% decrease in skeletal muscle ALAS activity. By contrast, treatment with inducers of hepatic ALAS such as allylisopropylacetamide or 3,5-dicarbethoxy-1,4-dihydrocollidine had no effect on skeletal muscle ALAS. These results confirm our previous suggestion that ALAS activity is regulated in a tissue-specific manner.     

Studies on the Cambodian I strain of Plasmodium falciparum in Aotus monkeys

The Cambodian I strain of Plasmodium falciparum, originally from Kampuchea was adapted for development in three different types of Aotus monkeys. High-level parasitemias were readily produced in splenectomized Colombian A. trivirgatus griseimembra monkeys. Initially, only minimal parasitemias developed in A. t. trivirgatus monkeys from Colombia. However, in one animal, adaptation occurred and high-level parasitemias were obtained during the second recrudescence of the infection. Passage to other A. t. trivirgatus monkeys indicated that the parasite was well adapted for development in splenectomized animals; low to moderate parasitemias were still produced in intact animals. This line of the parasite produced high level parasitemias when inoculated into splenectomized Aotus monkeys from Peru. Infections in Anopheles freeborni mosquitoes were obtained as late as the 7th passage in A. t. griseimembra monkeys and as late as the 7th recrudescence of the infection in an individual monkey (348 days after inoculation). The sporogonic cycle was completed in An. freeborni mosquitoes, and one transmission to an A. t. griseimembra monkey via the bites of infected mosquitoes was obtained.     

Route of administration as a factor in the selectivity of hormone suppression of a somatostatin analog in rats

The method of administration of [D-Ala5,D-Trp8] somatostatin is of central importance in determining the degree and duration of suppression of insulin and glucagon release. The analog decreased insulin levels in rats when injected by s.c. or i.v. routes, with a nadir 15 minutes following injection. After i.v. injection, insulin levels rapidly returned to basal values while s.c. injection produced significant suppression for 60 minutes. Neither type of injection altered glucagon levels. Intravenous infusion resulted in inhibition of both insulin and glucagon release, with rebound hyperglucagonemia, but not hyperinsulinemia in the post-infusion period. Plasma glucose levels reflected these hormonal changes. Thus, dramatic alterations in the specificity of this somatostatin analog may be achieved by employing different methods of administration.     

Effects of inhibitors of protein and RNA synthesis on aldosterone-stimulated changes in phospholipid fatty acid metabolism in the toad urinary bladder.

The effects of an inhibitor of RNA synthesis, cordycepin, and an inhibitor of protein synthesis, cycloheximide, on aldosterone-induced changes in lipid metabolism and phospholipid fatty acid composition have been studied in the toad urinary bladder. At the concentrations employed, the inhibitors abolish the hormone-induced increases in total lipid synthesis, phospholipid fatty acid specific activities, and weight percentage of phospholipid long-chain polyunsaturated fatty acids as well as blocking the aldosterone-mediated increase in sodium transport.