Functional impairment of rat Kupffer cells induced by aflatoxin B1 and its metabolites

Abstract Contamination of food with mycotoxins is a major health problem. Impairment of several immune functions has been repeatedly reported in animals fed with contaminated fodder. Since the liver is a major target of toxicity by aflatoxins, the effects of aflatoxins B1, and its hepatic metabolites Q₁ and M₁ on Kupffer cell function was investigated in vitro. Aflatoxin B₁ induced significant ( P < 0.05) inhibition of phagocytosis, intracellular killing of Candida albicans , and intrinsic anti-Herpes virus activity at concentrations as low as 0.01 pg ml⁻¹. Aflatoxin Q₁ and M₁ had similar effects on phagocytosis and microbicidal activity, but were two- to ten-fold less potent than aflatoxin B₁.     

The Arabidopsis REF8 gene encodes the 3-hydroxylase of phenylpropanoid metabolism

The activity of p-coumarate 3-hydroxylase (C3H) is thought to be essential for the biosynthesis of lignin and many other phenylpropanoid pathway products in plants; however, no conditions suitable for the unambiguous assay of the enzyme are known. As a result, all attempts to purify the protein and clone its corresponding gene have failed. By screening for plants that accumulate reduced levels of soluble fluorescent phenylpropanoid secondary metabolites, we have identified a number of Arabidopsis mutants that display a reduced epidermal fluorescence (ref) phenotype. Using radiotracer-feeding experiments, we have determined that the ref8 mutant is unable to synthesize caffeic acid, suggesting that the mutant is defective in a gene required for the activity or expression of C3H. We have isolated the REF8 gene using positional cloning methods, and have verified that it encodes C3H by expression of the wild-type gene in yeast. Although many previous reports in the literature have suggested that C3H is a phenolase, the isolation of the REF8 gene demonstrates that the enzyme is actually a cytochrome P450-dependent monooxygenase. Although the enzyme accepts p-coumarate as a substrate, it also exhibits significant activity towards other p-hydroxylated substrates. These data may explain the previous difficulties in identifying C3H activity in plant extracts and they indicate that the currently accepted version of the lignin biosynthetic pathway is likely to be incorrect.     

Do Humans Optimally Exploit Redundancy to Control Step Variability in Walking?

It is widely accepted that humans and animals minimize energetic cost while walking. While such principles predict average behavior, they do not explain the variability observed in walking. For robust performance, walking movements must adapt at each step, not just on average. Here, we propose an analytical framework that reconciles issues of optimality, redundancy, and stochasticity. For human treadmill walking, we defined a goal function to formulate a precise mathematical definition of one possible control strategy: maintain constant speed at each stride. We recorded stride times and stride lengths from healthy subjects walking at five speeds. The specified goal function yielded a decomposition of stride-to-stride variations into new gait variables explicitly related to achieving the hypothesized strategy. Subjects exhibited greatly decreased variability for goal-relevant gait fluctuations directly related to achieving this strategy, but far greater variability for goal-irrelevant fluctuations. More importantly, humans immediately corrected goal-relevant deviations at each successive stride, while allowing goal-irrelevant deviations to persist across multiple strides. To demonstrate that this was not the only strategy people could have used to successfully accomplish the task, we created three surrogate data sets. Each tested a specific alternative hypothesis that subjects used a different strategy that made no reference to the hypothesized goal function. Humans did not adopt any of these viable alternative strategies. Finally, we developed a sequence of stochastic control models of stride-to-stride variability for walking, based on the Minimum Intervention Principle. We demonstrate that healthy humans are not precisely “optimal,” but instead consistently slightly over-correct small deviations in walking speed at each stride. Our results reveal a new governing principle for regulating stride-to-stride fluctuations in human walking that acts independently of, but in parallel with, minimizing energetic cost. Thus, humans exploit task redundancies to achieve robust control while minimizing effort and allowing potentially beneficial motor variability.     

Stability of spatial pattern of fish species diversity in the Strait of Sicily (central Mediterranean)

In this paper, species diversity of demersal fish communities was analysed over an area covering about 45,000 km² of the Italian side of the Strait of Sicily (central Mediterranean). Fish abundance data come from a 10-year series (1994–2003) of experimental bottom trawl surveys carried out within the framework of the international program MEDITS. A simple GIS-based method was proposed to identify areas supporting high or low values of diversity and evaluate their temporal stability. A well-defined spatio-temporal pattern in diversity emerged from the analysis, with some areas of great ecological relevance being identified. Importantly, the greatest diversity within the fish communities was consistently seen at the offshore bank on the western part of the south Sicilian shelf (Adventure Bank). The site also supports high total biomass of demersal resources and shows the presence of species of great concern to fisheries. Results suggest that Adventure Bank represents a priority site for investigating the possibility of innovative management of marine ecosystems and demersal fisheries in offshore zones.     

Behavioral response of the egg parasitoid <Emphasis Type="Italic">Ooencyrtus telenomicida</Emphasis> to host-related chemical cues in a tritrophic perspective

The response of the generalist egg parasitoid Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae) to host-related chemical cues from tomato plants, Solanum lycopersicum L., and adults of Nezara viridula (L.) (Heteroptera: Pentatomidae) was investigated in laboratory-based no-choice and paired-choice tests. In Y-tube olfactometer experiments, when female wasps were exposed to volatiles from plants in different conditions, they were attracted only to volatiles produced by N. viridula adult-infested tomato plants. When female wasps were exposed to adults of N. viridula, they were attracted to volatiles from virgin males, and, at a lower level, to volatiles from mated females in preoviposition state. Finally, studies in open arena showed that chemical footprints left by adults of N. viridula did not induce arrestment responses in wasp females. These results are discussed in terms of extrinsic competition with other beneficial egg parasitoids that in field can compete for the same egg mass, since intraguild interactions may affect the success of a biological control program.     

The intercalation to DNA of bipyridyl complexes of platinum(II) with thioureas

The non-covalent interaction of the complexes [Pt(bpy)(R,R'NCSNR',R')(2)]Cl(2) (bpy=2,2'-bipyridine; R=R'=R'=R'=H; R=Me, R'=R'=R'=H; R=n-Bu, R'=R'=R'=H; R=p-tolyl, R'=R'=R'=H; R=Et, R'=H, R'=Et, R'=H) with calf thymus DNA has been studied at pH 7 and 25 degrees C. The processes give rise to: (i) reversible bathochromic shifts and strong hypochromicity of the absorption bands of the complexes, (ii) induced circular dichroism and (iii) an increase both in the melting temperature and viscosity of the DNA comparable to that observed for other well known metallointercalators. The binding constants, K(B), have been determined spectrophotometrically using the McGhee von Hippel equation. Plot of logK(B) vs -log[Na(+)] for the complex with unsubstituted thiourea gives a straight line with a slope value close to that expected for a dicationic intercalator. The binding affinity of the various complexes for DNA is independent of the thiourea nature; this suggests that the intercalation occurs through stacking of the bpy moiety while the ancillary ligands lie outside the nucleobases far away from the sugar phosphate backbone. The data show also that the electronic effects of the ligand substituents are not transmitted to the intercalating unit.     

Body-goal Variability Mapping in an Aiming Task

Given the number of joints and muscles in the human body, there are typically an infinite number of ways to perform the same action, a feature of directed movements known as equifinality (Bernstein, The coordination and regulation of movements, Oxford, Pergamon, 1967). Here we present a new type of performance analysis based on the idea of a body-goal variability mapping. We show how this mapping arises naturally from the idea of a goal function that theoretically defines a task and, in the presence of equifinality, determines the set of all possible task solution strategies, the goal equivalent manifold (GEM). The approach also yields estimates of the sensitivity of goal-level errors to body-level perturbations, and we derive a general formula expressing the relationship between the two. We apply these ideas to the analysis of redundant kinematic data from subjects performing an aiming task carried out with and without a laser pointer. It is shown that in order to characterize performance one must consider two factors in addition to the body variability: first, the degree of alignment between body variability and the GEM; and second, the sensitivity parameters that control the degree to which goal-relevant body variability is amplified at the target. Both of these factors can be computed using the estimated body-goal mapping. We show that the performance for three conditions involving two different nominal postures and two different sensory conditions (laser/no laser) can be classified by examining the clustering of data in an orientation- sensitivity parameter plane associated with the map.     

First report of Melittobia australica Girault in Europe and new record of M. acasta (Walker) for Italy

Melittobia acasta and Melittobia australica are newly recorded from Sicily, Italy, and the second species is reported in Europe for the first time. A short historical background about Melittobia parasitoid wasps, their hosts, and distribution, with emphasis in those two species is presented together with illustrations to facilitate their identification. Brief discussion about the presence and possible distribution of the species in Sicily is also included.