Eicosapentaenoic and docosahexaenoic acids production by and okara-utilizing potential of thraustochytrids

Nine thraustochytrid strains isolated from subtropical mangroves were screened for their eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) production potential in a glucose yeast extract medium. Their ability to utilize okara (soymilk residue) for growth and EPA and DHA production was also evaluated. EPA yield was low in most strains, while DHA level was high on glucose yeast extract medium, producing 28.1–41.1% of total fatty acids, for all strains, with the exception of Ulkenia sp. KF13. The DHA yield of Schizochytrium mangrovei strains ranged from 747.7 to 2778.9 mg/l after 52 h of fermentation at 25°C. All strains utilized okara as a substrate for growth, but DHA yield was lower when compared with fermentation in a glucose yeast extract medium. Journal of Industrial Microbiology & Biotechnology (2001) 27, 199–202. Received 11 December 2000/ Accepted in revised form 29 June 2001     

Social influences on foraging in vertebrates: causal mechanisms and adaptive functions

We summarize 20 years of empirical and theoretical research on causes and functions of social influences on foraging by animals. We consider separately studies of social influence on when, where, what and how to eat. Implicit in discussion of the majority of studies is our assumption that social influences on foraging reflect a biasing of individual learning processes by social stimuli rather than action of independent social-learning mechanisms. Our review of theoretical approaches suggests that the majority of formally derived hypotheses concerning functions of social influence on foraging have not yet been tested adequately and many models are in need of further refinement. We also consider the importance to the future of the field of integrating 'top-down' and 'bottom-up' approaches to the study of social learning. Copyright 2001 The Association for the Study of Animal Behaviour.     

Ultrasonic vocalizations and social learning of food preferences by female Norway rats

We examined whether ultrasonic vocalizations facilitate social learning of food preferences in female Norway rats, Rattus norvegicus. Females produced ultrasonic vocalizations at higher rates when they were reunited with a familiar conspecific if one member of the reunited pair had eaten an unfamiliar food while the pair members were separated. However, the influence of demonstrator rats on food choices of their observers was as great in pairs of rats that had been devocalized surgically as it was in sham-operated controls. The latter result is not consistent with the hypothesis that ultrasonic vocalizations facilitate social learning of food preferences in Norway rats.     

A phylogenetic survey of myotubularin genes of eukaryotes: distribution,protein structure,evolution, and gene expression

Background  

Phosphorylated phosphatidylinositol (PtdIns) lipids, produced and modified by PtdIns kinases and phosphatases, are critical to the regulation of diverse cellular functions. The myotubularin PtdIns-phosphate phosphatases have been well characterized in yeast and especially animals, where multiple isoforms, both catalytically active and inactive, occur. Myotubularin mutations bring about disruption of cellular membrane trafficking, and in humans, disease. Previous studies have suggested that myotubularins are widely distributed amongst eukaryotes, but key evolutionary questions concerning the origin of different myotubularin isoforms remain unanswered, and little is known about the function of these proteins in most organisms.     

Environmental enrichment for laboratory rodents: animal welfare and the methods of science

Because of the difficulty of' establishing objective measures of laboratory rodents' psychological well-being, developing environmental enrichment programs that are actually beneficial to rodents destined to participate in laboratory research is particularly challenging. Many studies of effects of environmental complexity, social housing, and increases in cage size suggest that professional judgments as to the impact of diverse types of environmental enrichment on rodent welfare are not a reliable basis for evaluating the outcomes of enrichment programs for laboratory rodents. Successful enrichment programs will vary from one rodent species to another, between sexes, as well as between age classes. There is a need for objective, measurable goals for proposed environmental enrichment programs for rodents, as well a s for empirical investigations of the beneficial and detrimental consequences of proposed environmental manipulations.     

Determining the evolutionary potential of a gene

In addition to information for current functions, the sequence of a gene includes potential information for the evolution of new functions. The wild-type ebgA (evolved beta-galactosidase) gene of Escherichia coli encodes a virtually inactive beta-galactosidase, but that gene has the potential to evolve sufficient activity to replace the lacZ gene for growth on the beta-galactoside sugars lactose and lactulose. Experimental evidence, which has suggested that the evolutionary potential of Ebg enzyme is limited o two specific amino acid replacements, is limited to examining the consequences of single base- substitutions. Thirteen beta-galactosidases homologous with the Ebg beta-galactosidase are widely dispersed, being found in gram-negative and gram-positive eubacteria and in a eukaryote. A comparison of Ebg beta-galactosidase with those 13 beta-galactosidases shows that Ebg is part of an ancient clade that diverged from the paralogous lacZ beta- galactosidase over 2 billion years ago. Ebg differs from other members of its clade at only 2 of the 15 active-site residues, and the two mutations required for full Ebg beta-galactosidase activity bring Ebg into conformity with the other members of its clade. We conclude that either these are the only acceptable amino acids at those positions, or all of the single-base-substitution replacements that must arise as intermediates on the way to other acceptable amino acids are so deleterious that they constitute a deep selective valley that has not been traversed in over 2 billion years. The evolutionary potential of Ebg is thus limited to those two replacements.