The intrinsic microbial stability of water-in-oil emulsions II. Experimental

Summary The microbial stability of water-in-oil emulsions is calculated as a function of the initial contamination, the concentration of carbon and energy sources, the size-distribution of the water droplets and of the storage time. The calculated values appear to be in good agreement with the experimental data.     

Olfactory Coding in Antennal Neurons of the Malaria Mosquito, Anopheles gambiae

Olfactory receptor neurons (ORNs) in the antenna of insects serve to encode odors in action potential activity conducted to the olfactory lobe of the deuterocerebrum. We performed an analysis of the electrophysiological responses of olfactory neurons in the antennae of the female malaria mosquito Anopheles gambiae s.s. and investigated the effect of blood feeding on responsiveness. Forty-four chemicals that are known to be present in human volatile emanations were used as odor stimuli. We identified 6 functional types of trichoid sensilla and 5 functional types of grooved-peg sensilla (GP) based on a hierarchical cluster analysis. Generalist ORNs, tuned to a broad range of odors, moderate specialist ORNs and 2 ORNs tuned to only one odor were identified in different sensilla types. Neurons in GP were tuned to more polar compounds including the important behavioral attractant ammonia and its synergist L-lactic acid, responses to which were found only in GP. Combinatorial coding is the most plausible principle operating in the olfactory system of this mosquito species. We document for the first time both up- and downregulation of ORN responsiveness after blood feeding. Modulation of host-seeking and oviposition behavior is associated with both qualitative and quantitative changes in the peripheral sensory system.     

High-Level folate production in fermented foods by the B12 producer Lactobacillus reuteri JCM1112

We observed that Lactobacillus reuteri JCM1112 produces B(12) and folate. However, the folate/B(12) mass ratio found was far below that desired for human consumption ( approximately 170:1). We used metabolic engineering applying genetic and physiological approaches to improve this ratio and developed a generic and natural process that significantly increases folate production.     

Curcumin binds to the alpha-helical intermediate and to the amyloid form of prion protein - a new mechanism for the inhibition of PrP(Sc) accumulation

Conversion of the native, predominantly α-helical conformation of prion protein (PrP) into the β-stranded conformation is characteristic for the transmissible spongiform encephalopathies such as Creutzfeld–Jakob disease. Curcumin, an extended planar molecule and a dietary polyphenol, inhibits in vitro conversion of PrP and formation of protease resistant PrP in neuroblastoma cell lines. Curcumin recognizes the converted β-form of the PrP both as oligomers and fibrils but not the native form. Curcumin binds to the prion fibrils in the left-handed chiral arrangement as determined by circular dichroism. We show that curcumin labels the plaques of the brain sections of variant Creutzfeld–Jakob disease cases and stains the same structures as antibodies against the PrP. In contrast to thioflavin T, curcumin also binds to the α-helical intermediate of PrP present at acidic pH at stoichiometry of 1 : 1. Congo red competes with curcumin for binding to the α-intermediate as well as to the β-form of PrP but is toxic and binds also to the native form of PrP. We therefore show that the partially unfolded structural intermediate of the PrP can be targeted by non-toxic compound of natural origin.     

Consequences of constitutive and induced variation in the host's food plant quality for parasitoid larval development

Constitutive and induced changes in plant quality impact higher trophic levels, such as the development of parasitoids, in different ways. An efficient way to study how plant quality affects parasitoids is to examine how the parasitoid larva is integrated within the host during the growth process. In two experiments, we investigated the effects of varying nutritional quality of Brassica oleracea on parasitoid larval development inside the host, the diamondback moth (Plutella xylostella). First, we compared larval growth of the specialist Diadegma semiclausum and the generalist Diadegma fenestrale, when the host was feeding on Brussels sprout plants that were either undamaged or were previously induced by caterpillar damage. Larvae of the generalist D. fenestrale showed lower growth rates than larvae of the specialist D. semiclausum, and this difference was more pronounced on herbivore-induced plants, suggesting differences in host-use efficiency between parasitoid species. The growth of D. semiclausum larvae was also analyzed in relation to herbivore induction on Brussels sprouts and on a wild B. oleracea strain. Parasitoid growth was more depressed on induced than on undamaged control plants, and more on wild cabbage than on Brussels sprouts, which was largely explained by differences in host mass. The effects of induction of wild Brassica on parasitoid development were pronounced early on, but as P. xylostella feeding began inducing the previously undamaged control plants, the effect of induction disappeared, revealing a temporal component of plant-parasitoid interactions. This study demonstrates how insights into the physiological aspects of host-parasitoid interactions can improve our understanding of the effects of plant-related traits on parasitoid wasps.     

Allopurinol enhances the activity of hypoxanthine-guanine phosphoribosyltransferase in inflammatory bowel disease patients during low-dose thiopurine therapy: preliminary data of an ongoing series

Thiopurines are crucial in the treatment of inflammatory bowel disease. The phenotype of pivotal metabolic enzymes determines whether thioguanine nucleotides (6-TGN) are generated in clinically sufficiently high levels. The first step in activation of thiopurine prodrugs to 6-TGN is catalysis by hypoxanthine-guanine phosphoribosyltransferase (HGPRT). Often, patients exhibit a clinically unfavorable metabolism, leading to discontinuation of conventional thiopurine therapy. The combination of allopurinol and low-dose thiopurine therapy may optimize this variant metabolism, presumably by affecting enzyme activities. We performed a prospective pharmacodynamic study to determine the effect of combination therapy on the activity of HGPRT. The activity of HGPRT and 6-TGN concentrations was measured in red blood cells during thiopurine monotherapy and after 4 weeks of combination therapy. The activity of HGPRT was also measured after 12 weeks of combination therapy. From the results, we conclude that combination therapy increases the activity of HGPRT and subsequently 6-TGN concentrations.     

Comparative study on the action of S-(+)-carvone, in situ, on the potato storage fungi Fusarium solani var. coeruleum and F. sulphureum

Growth of Fusarium sulphureum was inhibited by S-(+)-carvone administered via the gas phase. Under the same conditions, the related fungus F. solani var. coeruleum was not inhibited. In liquid medium, both fungi were found to convert S-(+)-carvone with the same rate, mainly into isodihydrocarvone, isodihydrocarveol and neoisodihydrocarveol. Only a slight difference in the relative amounts of the bioconversion products was observed. Since the bioconversion products did not inhibit the growth of the fungi to the same extent as S-(+)-carvone, the process can be considered as a detoxification mechanism. The bioconversion as such cannot account for the observed difference in growth inhibition.