The distribution of mycotoxins in a heterogeneous wheat field in relation to microclimate, fungal and bacterial abundance.

AIM: To observe the variation in accumulation of Fusarium and Alternaria mycotoxins across a topographically heterogeneous field and tested biotic (fungal and bacterial abundance) and abiotic (microclimate) parameters as explanatory variables. METHODS AND RESULTS: We selected a wheat field characterized by a diversified topography, to be responsible for variations in productivity and in canopy-driven microclimate. Fusarium and Alternaria mycotoxins where quantified in wheat ears at three sampling dates between flowering and harvest at 40 points. Tenuazonic acid (TeA), alternariol (AOH), alternariol monomethyl ether (AME), tentoxin (TEN), deoxynivalenol (DON), zearalenone (ZEN) and deoxynivalenol-3-Glucoside (DON.3G) were quantified. In canopy temperature, air and soil humidity were recorded for each point with data-loggers. Fusarium spp. as trichothecene producers, Alternaria spp. and fungal abundances were assessed using qPCR. Pseudomonas fluorescens bacteria were quantified with a culture based method. We only found DON, DON.3G, TeA and TEN to be ubiquitous across the whole field, while AME, AOH and ZEN were only occasionally detected. Fusarium was more abundant in spots with high soil humidity, while Alternaria in warmer and drier spots. Mycotoxins correlated differently to the observed explanatory variables: positive correlations between DON accumulation, tri 5 gene and Fusarium abundance were clearly detected. The correlations among the others observed variables, such as microclimatic conditions, varied among the sampling dates. The results of statistical model identification do not exclude that species coexistence could influence mycotoxin production. CONCLUSIONS: Fusarium and Alternaria mycotoxins accumulation varies heavily across the field and the sampling dates, providing the realism of landscape-scale studies. Mycotoxin concentrations appear to be partially explained by biotic and abiotic variables. SIGNIFICANCE AND IMPACT OF THE STUDY: We provide a useful experimental design and useful data for understanding the dynamics of mycotoxin biosynthesis in wheat.

BEESCOUT: A model of bee scouting behaviour and a software tool for characterizing nectar/pollen landscapes for BEEHAVE.

Social bees are central place foragers collecting floral resources from the surrounding landscape, but little is known about the probability of a scouting bee finding a particular flower patch. We therefore developed a software tool, BEESCOUT, to theoretically examine how bees might explore a landscape and distribute their scouting activities over time and space. An image file can be imported, which is interpreted by the model as a "forage map" with certain colours representing certain crops or habitat types as specified by the user. BEESCOUT calculates the size and location of these potential food sources in that landscape relative to a bee colony. An individual-based model then determines the detection probabilities of the food patches by bees, based on parameter values gathered from the flight patterns of radar-tracked honeybees and bumblebees. Various "search modes" describe hypothetical search strategies for the long-range exploration of scouting bees. The resulting detection probabilities of forage patches can be used as input for the recently developed honeybee model BEEHAVE, to explore realistic scenarios of colony growth and death in response to different stressors. In example simulations, we find that detection probabilities for food sources close to the colony fit empirical data reasonably well. However, for food sources further away no empirical data are available to validate model output. The simulated detection probabilities depend largely on the bees' search mode, and whether they exchange information about food source locations. Nevertheless, we show that landscape structure and connectivity of food sources can have a strong impact on the results. We believe that BEESCOUT is a valuable tool to better understand how landscape configurations and searching behaviour of bees affect detection probabilities of food sources. It can also guide the collection of relevant data and the design of experiments to close knowledge gaps, and provides a useful extension to the BEEHAVE honeybee model, enabling future users to explore how landscape structure and food availability affect the foraging decisions and patch visitation rates of the bees and, in consequence, to predict colony development and survival.

The effect of exposure to diazepam through the placenta or through the mother's milk. Histological findings in slices of rat brain.

Exposure to diazepam during the prenatal or early postnatal developmental period has been reported to result in later behavioural deficits. In the present study morphological changes in the brains of rats that were exposed to diazepam (DZP) prenatally or through the mother's milk postnatally were investigated. The results showed that prolonged prenatal exposure (16 days) to diazepam (10 mg/kg) resulted in characteristic and extensive pathological changes, i.e. gliosis and perivascular cuffing in the brains of the rats. These changes could be observed under the light microscope a long time after exposure to the drug had been terminated. Limiting the prenatal exposure to a single trimester of 7 days reduced somewhat the number of lesions but did not prevent their occurrence. Rats exposed to diazepam postnatally through the mothers' milk showed very few lesions.

Pattern formation triggered by rare events: lessons from the spread of rabies.

Understanding of large-scale spatial pattern formation is a key to successful management in ecology and epidemiology. Neighbourhood interactions between local units are known to contribute to large-scale patterns, but how much do they contribute and what is the role of regional interactions caused by long-distance processes? How much long-distance dispersal do we need to explain the patterns that we observe in nature? There seems to be no way to answer these questions empirically. Therefore, we present a modelling approach that is a combination of a grid-based model describing local interactions and an individual-based model describing dispersal. Applying our approach to the spread of rabies, we show that in addition to local rabies dynamics, one long-distance infection per 14000 km2 per year is sufficient to reproduce the wave-like spread of this disease. We conclude that even rare ecological events that couple local dynamics on a regional scale may have profound impacts on large-scale patterns and, in turn, dynamics. Furthermore, the following results emerge: (i) Both neighbourhood infection and long-distance infection are needed to generate the wave-like dispersal pattern of rabies; (ii) randomly walking rabid foxes are not sufficient to generate the wave pattern; and (iii) on a scale of less than 100 km x 100 km, temporal oscillations emerge that are independent from long-distance dispersal.

The effect of chronic diazepam treatment on discrimination performance and 3H-flunitrazepam binding in the brains of shocked and nonshocked rats.

The purpose of the present study was: (1) to investigate the effects of unavoidable shock on an appetitively motivated discrimination task; (2) to evaluate the effect of chronic diazepam treatment on the performance of a previously learned discrimination task in shocked and nonshocked animals; (3) to measure the binding of 3H-flunitrazepam (an analogue of diazepam) to selected brain regions of chronically diazepam-treated shocked and nonshocked rats, in comparison to saline-treated controls. Results indicated that unavoidable shock significantly interfered with the learning of a new, nonshock-related discrimination task. The effect of chronic diazepam treatment on the performance depended on the previous experience of the animal; chronic diazepam treatment significantly improved the maze performance of shocked animals. On the other hand, chronic diazepam treatment in the nonshocked animals tended to interfere with the performance of the discrimination task. Neurochemical data showed significant reduction in 3H-flunitrazepam binding to diazepam receptors in membranes from the brains of a nonshocked diazepam-treated (CD) group in comparison to a nonshocked saline-treated (CS) group. In contrast, the unavoidable shock-treated diazepam group (SD) showed opposite effects, the binding of 3H-flunitrazepam increasing significantly. A significant increase in the maximal binding sites in the frontal cortex from shocked rats treated with diazepam, compared to the nonshocked diazepam-treated rats, was detected by Scatchard analysis.

The effect of prenatal exposure to diazepam on aspects of postnatal development and behavior in rats.

In the present study the effects of chronic treatment of pregnant rats with diazepam on the physical and behavioral development of their offspring were investigated. Rats that were diazepam-exposed prenatally were compared to age-matched controls in terms of the following: number of littermates; birth weight and weight gain until weaning: motor development and coordination; simple motor learning; open field activity; performance on learning tasks of varying complexity; retention of these tasks. Nulliparous Wistar rats were injected s.c. for 16 days of their pregnancy was either 2.5, 5, of 10 mg/kg diazepam or an equal volume of vehicle. Prenatal diazepam treatment did not alter litter size, birth weight, or the righting reflex, but seemed to retard early motor development transiently. Diazepam pups showed longer latencies and less rearing in the open field. There were no differences between animals exposed to drug and vehicle in simple motor learning or in acquiring a simple successive discrimination task. However, there were significant dose-dependent differences on a complex six-choice simultaneous discrimination learning task, the diazepam-exposed rats making more errors and taking more time to reach the goal. A significant difference was seen again between diazepam- and vehicle-exposed rats on the retention test 10 days later. The results indicate that diazepam administered to pregnant rats has long-range effects on the behavior of the offspring, some becoming manifest even in maturity.

The effects of exposure to diazepam during various stages of gestation or during lactation on the development and behavior of rat pups.

In the present study we have investigated the effects of diazepam (DZP) (10 mg/kg) treatment of rat dams during different periods of gestation or during lactation on the development and behavior of their offspring. The results show that DZP exposure during different phases of early development has differing effects on later behavior. Exposure during mid-gestation resulted in early and transient hyperactivity, but no learning or memory deficits at 2 months of age were observed. However, both late prenatal and early postnatal exposure to DZP resulted in significant behavioral changes. Late prenatal treatment caused no hyperactivity but resulted in poor performance on the learning and retention of a choice discrimination task, while early postnatal exposure resulted in consistent and lasting hyperactivity and in substantial discrimination learning and retention deficits at 2 months of age.

Reduction of MOPEG levels in cerebrospinal fluid of psychotic women after electroconvulsive treatment.

The effect of ECT on concentrations of monoamine metabolites in lumbar CSF of psychotic women with a schizophrenic symptomatology was examined. After a series of ECT there was a significant reduction of the concentration of the major noradrenaline metabolite, MOPEG. Levels of HVA, 5-HIAA, prolactin, or total protein in CSF were not significantly influenced by treatment. The results indicate a specific alteration of central noradrenaline metabolism in relation to ECT.

Behavioural examinations of the anti-aggressive drug fluprazine.

The behavioural influence of the anti-aggressive drug Fluprazine (DU 27716) was examined using an ethological technique. The drug inhibited aggressive behaviour but not in an entirely specific way. Fluprazine also stimulated non-social and defensive/flight behaviours; there was a greater tendency for drug-treated animals to avoid their opponents. Using an automatic recording technique the drug's anti-aggressive action was monitored for 23 h. There was a potent anti-aggressive influence that lasted for up to 4 h. However, when the drug-effect wore off there were bouts of fighting. Over 23 h Fluprazine did not significantly decrease the total aggression recorded.

The effects of postnatal anoxia on behaviour and on the muscarinic and beta-adrenergic receptors in the hippocampus of the developing rat.

Exposure of rats to 25 min anoxia within 24 h following birth caused behavioural as well as biochemical changes during their development and maturity. Following postnatal anoxia, a significant increase in the concentration of the cholinergic muscarinic receptors in the hippocampus was noted at the early stages of development, between 6 and 20 days of age, but reached normal values at 40 days of age. However, at this age, significant increase in the concentration of beta-adrenergic receptors in the hippocampus was found, which remained significantly high during maturity and adulthood, as compared to controls. Rats submitted postnatally to anoxia exhibited hyperactivity in the open field which was maximal at 20-25 days of age and declined towards normal values at 40 days of age. At maturity, between 60 and 80 days of age, these rats showed poor performance in a complex 6-choice discrimination learning but not in simple differential conditioning. Possible correlations between the behavioural and biochemical findings are discussed.

New approaches to the isolation of DNA by ion-exchange chromatography.

The performance of different anion-exchange media have been compared for the isolation of plasmid DNA and genomic DNA from bacterial cells and human whole blood. Whatman DEAE-Magarose, based on an agarose bead containing a paramagnetic component, has been compared with prepacked gravity-flow columns containing a derivatised silica matrix. In each case the DNA isolation at various scales of operation was similar both in terms of yield and quality. The magnetic susceptibility of DEAE-Magarose is very high, facilitating the use of this separation technique for rapid flexible batch chromatographic processes, a limitation of the prepacked column techniques.

The gonadotropic-axis involvement in the course of the filial following response in the domestic fowl chick.

The detachment process of the domestic chick from its mother, or any other imprinting object occurs between the sixth and tenth week after hatching. The present study (Experiment I), examines whether the detachment process parallels endocrine events that precede prepuberty. Immediately upon hatching, groups of heavy strain chicks were imprinted to a colored foam rubber ball for 72 hours. The bond between these chicks and the imprinting object was then tested, and plasma LH and testosterone were assayed once a week until the chicks were 10 weeks of age; the sexual development of chicks of the same strain was studied at the same time. At the outset of the detachment period (5-7 weeks) an increase in plasma testosterone and a decrease in plasma LH was found. In addition, the comb and testes showed a definite weight increase while the bursa of Fabricius showed a significant decline in weight. In Experiment II, the beginning of the detachment process was induced by injecting 3 to 4 week old chicks with testosterone-propionate, estradiol-benzoate and 5 alpha-dihydrotestosterone. Our evidence therefore appears to demonstrate that testosterone and its metabolites induce the detachment process by the same mechanism used to stimulate sexual behavior in juvenile chicks.

Embryonic sex steroids affect mating behavior and plasma LH in adult chickens.

Chicken embryos of both sexes were treated with either antiestrogen (tamoxifen = T), antiandrogen (flutamide = F), aromatization inhibitor (ATD = A), estradiol (E), or oil (control = C). Before puberty, some males of each group were castrated. At puberty, birds were tested under the following regimes: castrated males injected daily with testosterone propionate (CAS + TP) or estradiol benzoate (CAS + EB), intact males (M-INT), intact females (F-INT), and females injected daily with TP (F-TP). In the M-INT and CAS + TP males, E treatment suppressed masculine mating behavior. The embryonic treatments with T, F, and A demasculinized only the frequency of copulations. None of the antihormone treatments caused any masculinization of the sexual activity in the F-TP birds. Untreated males had higher plasma LH than females. The embryonic treatment with E reduced (feminized) the LH levels in CAS + EB birds. This effect was less pronounced in M-INT birds. The results suggest that in chickens, estradiol plays a role in the masculinization of copulatory behavior potential in the developing male embryo. High embryonic estradiol reduces the potential for displaying male sexual behavior at puberty. Feminization of LH secretion requires a high level of estradiol in both embryonic and adult life.

Babel, or the ecological stability discussions: an inventory and analysis of terminology and a guide for avoiding confusion.

We present an inventory and analysis of discussions of ecological stability, considering 163 definitions of 70 different stability concepts. Our aim is to derive a strategy that can help to dispel the existing "confusion of tongues" on the subject of "stability" and prevent its future recurrence. The strategy consists of three questions that should be kept in mind when communicating about stability properties. These three questions should overcome the three main sources of confusion in terminology. Firstly, which stability properties are being addressed in the stability statement? Our analysis shows that the general term "stability" is so ambiguous as to be useless.It can be replaced by the stability properties "staying essentially unchanged" (constancy), "returning to the reference state (or dynamic) after a temporary disturbance" (resilience), and "persistence through time of an ecological system" (persistence). Second, to what ecological situation does the statement refer? An ecological situation is defined by a set of features that, taken as a whole, determine the domain of validity of a stability statement. The six most important features form the "ecological checklist", which serves to classify ecological situations and thereby provides a system of coordinates for communication. The six points are: variable of interest, level of description, reference state, disturbance, spatial scale and temporal scale. Thirdly, is the statement anchored in the situation in question, or is there unacceptable generalisation by inferring "stability" of the whole system from a certain stability property in a certain ecological ecological situation? This question separates the scientifically valuable content of a statement from the desire for general statements which is often projected through stability statements.

The level of GABA in the brain and locomotor behavior.

GABA content was measured in the brains of animals injected with AOAA, DPA or Saline. Significant increases in GABA were found in the motor cortex and cerebellum after treatment with both drugs as compared to saline injected controls. Increased GABA levels were associated with interference with the smooth execution of locomotor acts, especially where balancing and coordination of the hind limbs were necessary.

Feeding and satiation observed in the runway: the effects of d-amphetamine and d-fenfluramine compared.

A paradigm involving feeding to satiety over the course of repeated trials in the runway was used to examine the effects of d-amphetamine (1.0, 1.5 mg/kg) and d-fenfluramine (2.0, 3.0 mg/kg). 1.0 mg/kg d-amphetamine was found to have no significant effect on running performance or feeding in the runway. 1.5 mg/kg d-amphetamine significantly reduced the total food intake during the test but had little impact during the first three trials. In contrast, d-fenfluramine, even at the lower dose and during the initial trials, significantly reduced running performance and feeding to levels normally associated with satiation in the non-drugged animals. The results are discussed in relation to the contrasting modes of action of amphetamine and fenfluramine on food intake.