Likelihood-based experimental design for estimation of ED50

In selecting the best dosage choice for the estimation of ED50, it is natural to try to minimize the length of the confidence intervals. In this presentation, the dose allocation that minimizes the length of the likelihood-based confidence intervals is presented and compared with alternative allocations that have been proposed based on the length of different types of confidence intervals, such as those based on the asymptotic variance or on Fieller's Theorem. Effective strategies to deal with the parameter dependence of these allocations are explored. A series of experiments to evaluate the effect of small doses per fraction on the radiation tolerance of the rat cervical spinal cord provide the motivation and an illustration for the proposed procedures.     

Buffering capacity of whole corn mash alters concentrations of organic acids required to inhibit growth of Saccharomyces cerevisiae and ethanol production

Growth of Saccharomyces cerevisiae and fermentative ethanol production in the presence of acetic and lactic acids was measured in whole corn mash. In this industrial medium, as compared to glucose minimal medium, the yeast had increased tolerance to organic acid stress. It was concluded that the increased buffering capacity of whole corn mash, resulting in decreased concentration of undissociated acid, was responsible for this phenomenon.     

Concentrations and flux of rare earth elements in a semifield plot as influenced by their agricultural application

The concentrations of rare earth elements (REs) in atmospheric particles, soil, soil water, surface runoff, and different parts of corn in an experimental plot in the suburb of Beijing, China were measured and the flux of REs was estimated. The concentration of REs in air particles with diameter less than 10 μm is 36 ng/m³ and, by ratio analysis, the origin of REs in the atmosphere was likely local soil. The concentration of soluble REs is 0.69 μg/L in rainwater, 5–7 μg/L in surface runoff, as well as 1–4 μg/L in soil water and the application of RE mixture has no observed influences on their concentrations. The concentration of soluble REs in surface runoff and soil water was dominated by aqueous-solid-phase partitioning. By estimation of the flux, most of the REs applied will remain in the soil phase and continued application of REs will cause an accumulation of REs in agricultural soil.     

In vitro activity of allicin against Staphylococcus epidermidis and influence of subinhibitory concentrations on biofilm formation

AIMS: The aim of this study is to determine the in vitro activity of allicin against Staphylococcus epidermidis and to evaluate the influence of allicin on biofilm formation. METHODS AND RESULTS: In vitro activity of allicin (diallyl thiosulphinate) against 38 strains of S. epidermidis was investigated. The activity of allicin was similar against S. epidermidis methicillin susceptible and methicillin resistant strains [minimum inhibitory concentration (MIC)90=8 mg l(-1)]. In general, subinhibitory concentrations (sub-MIC) of allicin diminished biofilm formation in the five strains analysed. CONCLUSION: The results confirm the antibacterial effect of allicin. Sub-MICs of allicin also diminished the biofilm formations by S. epidermidis. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study shows that allicin is active in vitro against S. epidermidis and that sub-MICs of allicin may play a role in the prevention of adherence of this bacteria to medical devices.     

Combined effects of air and soil pollution by fluoride emissions on Tibouchina pulchra Cogn., at Cubatão,SE Brazil,and their relations with aluminium

High deposition of gaseous/particulate fluorides and other air pollutants has resulted in an acidification and probable formation of soluble AlF_x complexes in the soil in the vicinity of the industrial complex of Cubatão, SE Brazil. With the present field study we aimed at determining the contribution of F and Al uptake from fluoride-contaminated soil, supposedly as AlF_x complexes, to the increase of foliar F and Al contents in saplings of an Al-accumulator tree species (Tibouchina pulchra) which were concomitantly exposed to fluoride-contaminated air and also the proportional contribution of both air and soil contamination to the mentioned foliar accumulation of these elements. The seasonal variations in F and Al accumulation and possible metabolic changes in the plants due to F and Al accumulation were also investigated. The saplings were exposed during three consecutive periods of 16 weeks to: (a) air and soil from a reference site (PV_noF); (b) air or soil from two polluted sites (CM-high air pollution, low F and MV-high air pollution, high F); and (c) both air and soil from these polluted sites. After exposure, the changes in the foliar concentrations of F and Al, the relations between both element contents and their relationships with oxidative stress indicators were determined. The data were grouped in three matrices: PV_noF–CM_lwF and PV_noF–MV_hgF, taking in account the possible air/soil exposure combinations in each, and soil/air from all sites. The slight F accumulation in plants of PV_noF–CM_lwF matrix was a result of higher uptake from soil than from air (54 and 46%, respectively). At PV_noF–MV_hgF matrix, the extremely high F accumulation in leaves of T. pulchra could be attributed to the combination of both air and soil contamination (83 and 17%, respectively). T. pulchra always showed higher foliar Al concentrations than 1000 g g^–1 dry mass, mainly after exposure to air and soil of both polluted sites (CM_lwF and MV_hgF). A highly significant linear regression was estimated between molar Al and F contents, taking in account the data obtained for saplings of T. pulchra cultivated in the different soils and exposed to ambient air of PV_noF, suggesting that both elements were taken as Al–F complexes from soil. The uptake of fluorides from air and/or soil of MV_hgF caused significant metabolic changes in T. pulchra, but visible injury supposedly induced by fluorides were observed only when the foliar F contents surpassed 700 g g^–1 dry mass. On the contrary, Al did not cause any metabolic stress to the plants.     

Dietary alterations in protein,carbohydrates and fat increase liver protein-turnover rate and decrease overall growth rate in the rainbow trout (Oncorhynchus mykiss

We have determined the protein-turnover rates and nucleic-acid concentrations in the liver of trout (Oncorhynchus mykiss) fed on two different isocaloric diets: low-protein/high-fat and non-carbohydrate/high-fat. Compared to controls, the partial replacement of protein with fat significantly decreased the protein accumulation rate and protein-retention efficiency in the liver whilst increasing the fractional protein-synthesis and protein-degradation rates as well as protein-synthesis efficiency. The complete replacement of carbohydrates with fat significantly lowered the protein-accumulation rate and protein-retention efficiency, but enhanced both the protein-synthesis and protein-degradation rates as well as protein-synthesis capacity. The protein:DNA and RNA:DNA ratios decreased considerably on both diets. Total DNA decreased in fish on a low-protein/high-fat diet but did not change in those on a non-carbohydrate/high-fat diet. The absolute protein-synthesis rate registered no significant change under any of the nutritional conditions. Both the experimental diets did however raise the fractional protein-synthesis rate significantly, due to enhanced protein-synthesis efficiency when protein was partially replaced with fat and to enhanced protein-synthesis capacity when carbohydrates were completely replaced with fat. Our results show the capacity of the liver to adapt its turnover rates and conform to different nutritional conditions. They also point to the possibility of controlling fish growth by dietary means.