Parasitoid behaviour: predicting field from laboratory

Abstract.  1. Most of what is known about parasitoid behaviour comes from laboratory observations: field quantitative observations on searching parasitoids are extremely difficult to do and are rare. The basic components of Aphytis melinus 's response to California red scale ( Aonidiella aurantii ) were studied in the laboratory: encounter, rejection, drumming, probing, oviposition, and host-feeding. It was then asked whether these observations provided a reliable guide to behaviour in the field in a situation that was very different from the laboratory.
2. Field observations were carried out on bark on the trunk and interior branches of trees where live scale density is extremely high in patches, dead scale make up 90% of all scale, and could be expected to interfere with Aphytis search.
3. The laboratory observations predicted well the time taken in the field for each basic event (drumming or probing) and average times spent on a scale. Also well predicted were the distributions of times spent on drumming, probing, and total time on a scale. Rejection rates were much higher in the field. Thus, the laboratory studies predicted foraging behaviour in the field with variable success; potential explanations for observed mismatch between laboratory and field and its possible larger implications are discussed.     

Effects of the sporulation conditions on the lovastatin production by Aspergillus terreus

The production of biomass and lovastatin by spore-initiated submerged fermentations of Aspergillus terreus ATCC 20542 was shown to depend on the age of the spores used for inoculation. Cultures started from older spores produced significantly higher titers of lovastatin. For example, the lovastatin titer increased by 52% when the spore age at inoculation rose from 9 to 16 days. The lovastatin titer for a spore age of 16 days was 186.5±20.1 mg L⁻¹. The time to sporulation on surface cultures was sensitive to the light exposure history of the fungus and the spore inoculation concentration levels. A light exposure level of 140 μE m⁻² s⁻¹ and a spore concentration of 1,320 spore cm⁻² produced the greatest extent of sporulation within about 50 h of inoculation. Sporulation was slowed in the dark and with diluted inoculants. A rigorous analysis of the data of statistically designed experiments showed the above observations to be highly reproducible.     

Self-excision of the antibiotic resistance gene nptII using a heat inducible Cre-loxP system from transgenic potato

Resistance to antibiotics mediated by selectable marker genes remains a powerful selection tool for transgenic event production. However, regulatory agencies and consumer concerns favor these to be eliminated from food crops. Several excision systems exist but none have been optimized or shown to be functional for clonally propagated crops. The excision of the nptII gene conferring resistance to kanamycin has been achieved here using a gene construct based on a heat-inducible cre gene producing a recombinase that eliminates cre and nptII genes flanked by two loxP sites. First-generation regenerants with the Cre-loxP system were obtained by selection on kanamycin media. Following a heat treatment, second generation regenerants were screened for excision by PCR using nptII, cre, and T-DNA borders primers. Excision efficiency appeared to be at 4.7% depending on the heat treatment. The footprint of the excision was shown by sequencing between T-DNA borders to correspond to a perfect recombination event. Selectable marker-free sprouts were also obtained from tubers of transgenic events when submitted to similar heat treatment at 4% frequency. Spontaneous excision was not observed out of 196 regenerants from untreated transgenic explants. Biosafety concerns are minimized because the expression of cre gene driven by the hsp70 promoter of Drosophila melanogaster was remarkably low even under heat activation and no functional loxP site were found in published Solanum sequence database. A new plant transformation vector pCIP54/55 was developed including a multiple cloning site and the self-excision system which should be a useful tool not only for marker genes in potato but for any gene or sequence removal in any plant.     

Improving wheat flour hydrolysis by an enzyme mixture from solid state fungal fermentation

In traditional cereal-based industrial processes, component separation is often incomplete resulting in a residue of mixed macromolecules including largely starch, protein, phytic acid and many others. The development of a viable cereal-based biorefinery would involve effective bioconversion of cereal components for the production of a nutrient-complete fermentation feedstock. Simultaneous starch and protein hydrolysis represents an effective approach to the production of platform chemicals from wheat. Solid state fermentations of wheat pieces and waste bread by Aspergillus oryzae and Aspergillus awamori have been combined in this study to enhance starch and protein hydrolysis. Kinetic studies confirmed that the proteolytic enzymes from A. oryzae introduced no negative effect on the stability of the amylolytic enzymes from A. awamori under the optimal conditions for starch hydrolysis. When applied to hydrolyse wheat flour, the enzyme solution from A. awamori converted nearly all of the starch into glucose and 23% of the total nitrogen (TN) into free amino nitrogen (FAN). Under the same reaction conditions the enzyme solution from A. oryzae hydrolysed 38% of the protein but only 18.5% of the starch. A mixture of the two enzyme solutions hydrolysed 34.1% of the protein, a 1.5-fold increase from that achieved by the enzyme solution from A. awamori, while maintaining a near completion of starch hydrolysis.     

Inhibitors of sphingolipid metabolism enzymes

Sphingolipids are a family of lipids that play essential roles both as structural cell membrane components and in cell signalling. The cellular contents of the various sphingolipid species are controlled by enzymes involved in their metabolic pathways. In this context, the discovery of small chemical entities able to modify these enzyme activities in a potent and selective way should offer new pharmacological tools and therapeutic agents.     

Predator-induced flow disturbances alert prey,from the onset of an attack

Many prey species, from soil arthropods to fish, perceive the approach of predators, allowing them to escape just in time. Thus, prey capture is as important to predators as prey finding. We extend an existing framework for understanding the conjoint trajectories of predator and prey after encounters, by estimating the ratio of predator attack and prey danger perception distances, and apply it to wolf spiders attacking wood crickets. Disturbances to air flow upstream from running spiders, which are sensed by crickets, were assessed by computational fluid dynamics with the finite-elements method for a much simplified spider model: body size, speed and ground effect were all required to obtain a faithful representation of the aerodynamic signature of the spider, with the legs making only a minor contribution. The relationship between attack speed and the maximal distance at which the cricket can perceive the danger is parabolic; it splits the space defined by these two variables into regions differing in their values for this ratio. For this biological interaction, the ratio is no greater than one, implying immediate perception of the danger, from the onset of attack. Particular attention should be paid to the ecomechanical aspects of interactions with such small ratio, because of the high degree of bidirectional coupling of the behaviour of the two protagonists. This conclusion applies to several other predator–prey systems with sensory ecologies based on flow sensing, in air and water.     

Fertility after post-cervical artificial insemination with cryopreserved sperm from boar ejaculates of good and poor freezability

This study compared the field fertility outcomes in frozen–thawed (FT) sperm from boar ejaculates with different freezability (good, GFE/poor, PFE) while testing the reliability of the post-cervical artificial insemination (post-CAI) in FT sperm. The assay was conducted over eight months with 86 weaned sows being inseminated by post-CAI. Every ejaculate in a total of 26 from 15 Piétrain boars was divided into a refrigerated semen portion (FS; control treatment) and a cryopreserved portion (FT sperm), and the ejaculates were in turn classified as GFE or PFE in function of the sperm progressive motility and viability at 240 min post-thaw. As result, one of four possible treatments was randomly given to each sow: FS-GFE, FS-PFE, FT-GFE and FT-PFE. The number of pregnant and farrowing sows in FT-GFE did not significantly differ from those of FS control treatments. Contrarily, the probabilities of pregnancy were two times lower after inseminations with FT-PFE (P < 0.05) compared to FT-GFE, which indicates that ejaculates with high post-thaw sperm progressive motility and viability are more likely to result in pregnancies than those with poor in vitro sperm function. There were no differences in litter size or the risk of backflow among treatments. Further trials are required to determine the optimal volume and concentration of FT sperm in post-CAI to obtain a more reliable method for farmers interested in cryopreserved sperm.     

Major Cardiovascular Risk Factors in Latin America: A Comparison with the United States. The Latin American Consortium of Studies in Obesity (LASO)

Background

Limited knowledge on the prevalence and distribution of risk factors impairs the planning and implementation of cardiovascular prevention programs in the Latin American and Caribbean (LAC) region.

Methods and Findings

Prevalence of hypertension, diabetes mellitus, abnormal lipoprotein levels, obesity, and smoking were estimated from individual-level patient data pooled from population-based surveys (1998–2007, n = 31,009) from eight LAC countries and from a national survey of the United States (US) population (1999–2004) Age and gender specific prevalence were estimated and age-gender adjusted comparisons between both populations were conducted. Prevalence of diabetes mellitus, hypertension, and low high-density lipoprotein (HDL)-cholesterol in LAC were 5% (95% confidence interval [95% CI]: 3.4, 7.9), 20.2% (95% CI: 12.5, 31), and 53.3% (95% CI: 47, 63.4), respectively. Compared to LAC region’s average, the prevalence of each risk factor tended to be lower in Peru and higher in Chile. LAC women had higher prevalence of obesity and low HDL-cholesterol than men. Obesity, hypercholesterolemia, and hypertriglyceridemia were more prevalent in the US population than in LAC population (31 vs. 16.1%, 16.8 vs. 8.9%, and 36.2 vs. 26.5%, respectively). However, the prevalence of low HDL-cholesterol was higher in LAC than in the US (53.3 vs. 33.7%).

Conclusions

Major cardiovascular risk factors are highly prevalent in LAC region, in particular low HDL-cholesterol. In addition, marked differences do exist in this prevalence profile between LAC and the US. The observed patterns of obesity-related risk factors and their current and future impact on the burden of cardiovascular diseases remain to be explained.