Effect of acclimation temperature on routine metabolic rate in triploid salmonids.

The objective of this research was to determine whether triploid fish differ from diploids in their routine metabolic rates across a range of acclimation temperatures. Sibling diploids and triploids were acclimated to 12, 15 and 18 degrees C (Atlantic salmon; Salmo salar) and to 9, 12 and 15 degrees C (brook charr; Salvelinus fontinalis) prior to experimentation. Routine metabolic rates were then determined three times over a two-month period. Triploids of both species had higher metabolic rates than diploids at lower temperatures, and lower metabolic rates than diploids at higher temperatures, demonstrating that triploids have different (i.e., lower) thermal optima than diploids. This likely explains prior observations of high mortality of triploids at chronically elevated, but sub-lethal, rearing temperatures for sibling diploids.     

X-ray fibre diffraction of cartilage proteoglycan aggregates containing hyaluronic acid (Short Communication)

Ordered conformations of proteoglycan-hyaluronic acid aggregates in the intercellular matrix in cartilage were observed by X-ray diffraction. The sodium salt form of three samples, (a) aggregated proteoglycan, (b) disaggregated proteoglycan and (c) reconstituted disaggregated proteoglycan, give essentially similar X-ray fibre-type diffraction photographs. The patterns correlate with the chondroitin 4-sulphate component and can be interpreted as twofold helical conformations, similar to that observed previously for the free acid form of chondroitin 4-sulphate (Isaac & Atkins, 1973). The information takes us one step nearer the situation found in cartilage in vivo.     

Fate of a bacteriophage in Aedes aegypti, Anopheles quadrimaculatus (Diptera: Culicidae), and Periplaneta americana (Orthoptera: Blattidae)

The viability of a bacteriophage of Escherichia coli was unaffected by injection into the hemocoel of the mosquitoes, Aedes aegypti and Anopheles quadrimaculatus, but was reduced by injection into the cockroach, Periplaneta americana. Treatment of the cockroach with India ink, known to be phagocytized in the cockroach hemocoel, did not block the reduction of phage viability. Phage viability was unaffected by incubation with gut homogenates of A. aegypti but was possibly affected by homogenates of P. americana.     

Speaker verification

The most significant developments impacting on the speaker verification sector appear to be the surge in support for speech recognition technology and the convergence of the telecom and datacom markets. In this survey, Btt looks at how the technology and markets are changing and examines the issues the sector is facing.     

Measurement error in the Hawksley random zero sphygmomanometer: what damage has been done and what can we learn?

The Hawksley random zero sphygmomanometer is used in all aspects of blood pressure research, from clinical trials to evaluation of new blood pressure recorders. It is designed to reduce observer bias in blood pressure measurement. The problem is that it also underestimates blood pressure. Furthermore, this was first reported more than two decades ago. In this paper Rónán Conroy and colleagues explore the consequences of using an inaccurate instrument for important research and why prestigious organisations like the World Health Organisation continue to use it.     

Genetic instability associated with the aroC321 allele in Salmonella typhimurium involves genetic duplication

Strains of Salmonella typhimurium that contain the aroC321 allele require phenylalanine, tyrosine, and tryptophan for growth but revert to tryptophan-prototrophy at high frequencies (about 10(-4) per cell plated). The Trp+ derivatives remain auxotrophic for phenylalanine and tyrosine and are genetically unstable, in that they readily give rise to cells that require all three aromatic amino acids. On the basis of growth characteristics and genetic instability, it has been proposed that reversion to tryptophan-prototrophy in aroC321 strains occurs by genetic duplication. This paper provides genetic evidence in support of that hypothesis. The data indicate, moreover, that the tryptophan prototrophs contain a duplication that extends at least from glpT to xyl, a region of greater than 30% of the Salmonella chromosome. The aroC locus is found within the duplicated region, and aroC321/aroC321 merodiploids apparently grow as tryptophan prototrophs because of a gene-dosage effect.