Physiological responses underlying the timing of vernal activities in insects

Temperate zone insect species have evolved three general strategies for synchronizing the end of hibernation with the return of favorable conditions. Recent eco-physiological studies of insect dormancy and development indicate that the prevailing concepts of the adaptations regulating hibernation and the resumption of spring activity, need revision. In particular, experimental evidence shows that despite implications in the term, dormancy is a dynamic state; the organism, by constantly monitoring the constantly-changing environmental parameters, is kept in phase with the seasons at its particular locality. Furthermore, the insect's ability to respond to environmental factors generally changes as the season progresses. Therefore, the construction of realistic predictive models of insect seasonality should be based on investigations of natural populations undergoing hibernation in the field, combined with ecologically and physiologically meaningful laboratory studies.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, USA.     

Developmental shifts in computations used to detect environmental controllability

Accurate assessment of environmental controllability enables individuals to adaptively adjust their behavior—exploiting rewards when desirable outcomes are contingent upon their actions and minimizing costly deliberation when their actions are inconsequential. However, it remains unclear how estimation of environmental controllability changes from childhood to adulthood. Ninety participants (ages 8–25) completed a task that covertly alternated between controllable and uncontrollable conditions, requiring them to explore different actions to discover the current degree of environmental controllability. We found that while children were able to distinguish controllable and uncontrollable conditions, accuracy of controllability assessments improved with age. Computational modeling revealed that whereas younger participants’ controllability assessments relied on evidence gleaned through random exploration, older participants more effectively recruited their task structure knowledge to make highly informative interventions. Age-related improvements in working memory mediated this qualitative shift toward increased use of an inferential strategy. Collectively, these findings reveal an age-related shift in the cognitive processes engaged to assess environmental controllability. Improved detection of environmental controllability may foster increasingly adaptive behavior over development by revealing when actions can be leveraged for one’s benefit.     

Engineering mouse apolipoprotein A-I into a monomeric, active protein useful for structural determination

Apolipoprotein AI (apoAI), the major protein component of HDL, is one of the best predictors of coronary artery disease (CAD), with high apoAI and HDL levels being correlated with low occurrences of CAD. The primary function of apoAI is to recruit phospholipid and cholesterol for assembly of HDL particles. Like other exchangeable apolipoproteins, lipid-free apoAI forms a mixture of different oligomers even at 1.0 mg/mL. This self-association property of the exchangeable apolipoproteins is closely associated with the lipoprotein-binding activity of this protein family. It is unclear if the self-association property of apolipoprotein is required for its lipoprotein-binding activity. We developed a novel method for engineering an oligomeric protein to a monomeric, biologically active protein. Using this method, we generated a monomeric mouse apoAI mutant that is active. This mutant contains the first 216 residues of mouse apoAI and replaces six hydrophobic residues with either polar or smaller hydrophobic residues at the defined positions (V118A/A119S/L121Q/T191S/T195S/T199S). Cross-linking results show that this mutant is greater than 90% monomeric at 8 mg/mL. CD, DSC, and NMR results indicate that the mutant maintains an identical secondary, tertiary structure and stability as those of the wild-type mouse apoAI. Lipid-binding assays suggest that the mutant shares an equal lipoprotein-binding activity as that of the wild-type apoAI. In addition, both the monomeric mutant and the wild-type protein make nearly identical rHDL particles. With this monomeric mouse apoAI, high-quality NMR data has been collected, allowing for the NMR structural determination of lipid-free apoAI. On the basis of these results, we conclude that this apoAI mutant is a monomeric, active apoAI useful for structural determination.     

Method for the isolation of high-quality RNA from grape berry tissues without contaminating tannins or carbohydrates

Grape berries contain compounds that aggregate with and precipitate RNA in the presence of chaotropic agents or phenol. The procedure described here extracts RNA from finely ground tissues using mild denaturants, and selectively precipitates the aggregate-forming material with 30% ethanol. The resulting RNA is suitable for northern blot analysis and translationin vitro.     

High-level expression of murine terminal deoxynucleotidyl transferase inEscherichia coli grown at low temperature and overexpressingargU tRNA

Terminal deoxynucleotidyl transferase (TdT) is a highly conserved vertebrate enzyme that possesses the unique ability to catalyze the random addition of deoxynucleoside 5′-triphosphates onto the 3′-hydroxyl group of a single-stranded DNA. It plays an important role in the generation of immunoglobin and T-cell receptor diversity. TdT is usually obtained from animal thymus gland or produced in a baculovirus system, but both procedures are rather tedious, and proteolysis occurs during purification. Attempts to overexpress TdT in bacteria have been unsuccessful or have yielded an enzyme with a lower specific activity. A dearth of TdT has thus hampered detailed structural and functional studies. In the present study, we report that by lowering growth temperature and overexpressing a rare arginyl tRNA, it is possible to boost the production inEscherichia coli of murine TdT with minimal proteolysis and high specific activity.     

Phylogenetic scale in ecology and evolution

Aim

Many important patterns and processes vary across the phylogeny and depend on phylogenetic scale. Nonetheless, phylogenetic scale has never been formally conceptualized, and its potential remains largely unexplored. Here, we formalize the concept of phylogenetic scale, review how phylogenetic scale has been considered across multiple fields and provide practical guidelines for the use of phylogenetic scale to address a range of biological questions.

Innovation

We summarize how phylogenetic scale has been treated in macroevolution, community ecology, biogeography and macroecology, illustrating how it can inform, and possibly resolve, some of the longstanding controversies in these fields. To promote the concept empirically, we define phylogenetic grain and extent, scale dependence, scaling and the domains of phylogenetic scale. We illustrate how existing phylogenetic data and statistical tools can be used to investigate the effects of scale on a variety of well‐known patterns and processes, including diversification rates, community structure, niche conservatism or species‐abundance distributions.

Main conclusions

Explicit consideration of phylogenetic scale can provide new and more complete insight into many longstanding questions across multiple fields (macroevolution, community ecology, biogeography and macroecology). Building on the existing resources and isolated efforts across fields, future research centred on phylogenetic scale might enrich our understanding of the processes that together, but over different scales, shape the diversity of life.     

Groundwater promotes emergence of asporogenic mutants of emetic Bacillus cereus

Bacillus cereus is a ubiquitous endospore-forming bacterium, which mainly affects humans as a food-borne pathogen. Bacillus cereus can contaminate groundwater used to irrigate food crops. Here, we examined the ability of the emetic strain B. cereus F4810/72 to survive abiotic conditions encountered in groundwater. Our results showed that vegetative B. cereus cells rapidly evolved in a mixed population composed of endospores and asporogenic variants bearing spo0A mutations. One asporogenic variant, VAR-F48, was isolated and characterized. VAR-F48 can survive in sterilized groundwater over a long period in a vegetative form and has a competitive advantage compared to its parental strain. Proteomics analysis allowed us to quantify changes to cellular and exoproteins after 24 and 72 h incubation in groundwater, for VAR-F48 compared to its parental strain. The results revealed a significant re-routing of the metabolism in the absence of Spo0A. We concluded that VAR-F48 maximizes its energy use to deal with oligotrophy, and the emergence of spo0A-mutated variants may contribute to the persistence of emetic B. cereus in natural oligotrophic environments.     

Chemiluminescence of enterococci isolates from freshwater

All Enterococcus spp., isolated from environmental water samples (n=81), emitted a high chemiluminescence signal in the presence of luminol (10(-2) M). Kinetic studies of chemiluminescence show a close correlation between chemiluminescence and growth curves during the exponential phase, with a maximum chemiluminescence reached just before bacterial growth entered in the stationary phase. On the other hand, genera closely related to Enterococcus such as Streptococcus or Lactococcus produced a very weak chemiluminescent signal. Chemiluminescence of enterococci could therefore offer a rapid test, in aiding the identification of the genus Enterococcus and in the survey of the microbiological quality of water supplies.     

Brain Cytochrome Oxidase in Alzheimer''s Disease

A recent demonstration of markedly reduced (-50%) activity of cytochrome oxidase (CO; complex 4), the terminal enzyme of the mitochondrial enzyme transport chain, in platelets of patients with Alzheimer's disease (AD) suggested the possibility of a systemic and etiologically fundamental CO defect in AD. To determine whether a CO deficiency occurs in AD brain, we measured the activity of CO in homogenates of autopsied brain regions of 19 patients with AD and 30 controls matched with respect to age, postmortem time, sex, and, as indices of agonal status, brain pH and lactic acid concentration. Mean CO activity in AD brain was reduced in frontal (-26%: p less than 0.01), temporal (-17%; p less than 0.05), and parietal (-16%; not significant, p = 0.055) cortices. In occipital cortex and putamen, mean CO levels were normal, whereas in hippocampus, CO activity, on average, was nonsignificantly elevated (20%). The reduction of CO activity, which is tightly coupled to neuronal metabolic activity, could be explained by hypofunction of neurons, neuronal or mitochondrial loss, or possibly by a more primary, but region-specific, defect in the enzyme itself. The absence of a CO activity reduction in all of the examined brain areas does not support the notion of a generalized brain CO abnormality. Although the functional significance of a 16-26% cerebral cortical CO deficit in human brain is not known, a deficiency of this key energy-metabolizing enzyme could reduce energy stores and thereby contribute to the brain dysfunction and neurodegenerative processes in AD.