SLO angiography: arterio-venous filling times in monkey and minipig

Confocal scanning laser ophthalmosocope (cSLO) is a new technique which enables ocular fundus image recording and dynamic retinal angiography to be performed. The ocular fundus image is acquired sequentially, point by point, and is reconstructed on a video monitor at the rate of 25 images per second. The aim of this paper is to evaluate the feasibility of measuring retinal arterio‐venous filling times (AVFT) with a I + Tech cSLO. Three young adult cynomolgus monkeys and three young adult Göttingen minipigs were used as experimental models. All animals were anesthetized using a zolazepam + tiletamine mixture injected intramuscularly; heart rate and rectal temperature were monitored and corneal irrigation was regularly performed. For all subjects, prior to examination, hematocrit and globe axial length were measured. The images were recorded, stabilized and analyzed. The retinal examination consisted of retinal images with 40° field cSLO, retinal fluorescein angiography and arterio‐venous 50% filling time measurements. For each subject all images were easily recorded while keeping the animals in a normally lighted room without having to use any additional optical device. AVFT using an I + Tech cSLO is easily performed in monkeys and minipigs. AVFT measurements in minipigs and monkeys are similar. These results suggest that minipigs can replace monkeys as an experimental species for AVFT investigations.     

The effect of the mode of application on the toxicity of Androctonus australis hector insect toxin

The toxicity of the insect toxin from the venom of the scorpion Androctonus australis Hector (AaH IT) was assayed using several ethods of application on various insect species. Activity was only demonstrated by opical application on Musca domestica. Three different solvents were assayed: ethanol + water (50 + 50 by volume), acetone + water (80 + 20 by volume) and acetone + dimethyl sulphoxide (50 + 50 by volume). When using the last two mixtures, LD₅₀ was found to be 1 μg 100 mg^?1 fly. When this activity is compared to that of five synthetic insecticides tested in the same conditions, AaH IT is about 1-5 times more active than propoxur and DDT, 10 times more active than malathion but 200 times less active than deltamethrin. No activity was observed against Aphis craccivora at 15 mg m^?2 in surface-contact tests on glass, or against Culex pipiens pipiens larvae at 2 × 10⁵ ng litre^?1 in water.     

Soil Covers for Controlling Acid Generation in Mine Tailings: a Laboratory Evaluation of the Physics and Geochemistry

To evaluate the effectiveness of soil covers, column experiments were conducted on tailings protected by a three-layer soil cover and tailings directly exposed in the open laboratory for a period of 760 days. Periodic rain application was performed to simulate field conditions, and at four times during the experiments the pore water was completely flushed out of each column for analysis. Profiles of oxygen, temperature, and volumetric water content were measured throughout the experiment, and the post-testing pore water quality was also characterized. A one-dimensional semi-analytic diffusion model was used to simulate oxygen profiles in the uncovered tailings. Modelling performed using the geochemical code MINTEQ showed that in the laboratory, aluminium concentrations in the tailings pore water were controlled by Al(OH)SO₄, sulphate by gypsum and Al(OH)SO₄and iron by lepidocrocite in the upper half and by ferrihydrite in the lower half. In the field, however, the iron oxyhydroxide minerals formed in the oxidized zone appear to be dissolving. It was found that the cover was effective in preventing significant desaturation of the clay, even over a 150-day drying period. The covered tailings did not oxidize much during the experiments. In the uncovered tailings, oxygen modelling and examination of the geochemistry show that the rate of gross oxidation and the advancement of the oxidation front decreases with time. However, pore water quality is controlled by geochemical processes other than oxidation, as reported in the field.     

Myeloperoxidase concentration in bronchoalveolar lavage fluid from healthy horses and those with recurrent airway obstruction

The aim of this work was to measure the myeloperoxidase (MPO) concentration in bronchoalveolar lavage (BAL) fluid collected from horses with recurrent airway obstruction (RAO), both in crisis and in remission, as well as from healthy horses. Seven horses with RAO were exposed to moldy hay until the maximum change in pleural pressure was greater than 1.5 kPa. At that point, BAL was performed, and the total cell counts and percentages in the fluid were immediately determined. To measure the MPO concentration in BAL-fluid supernatant, we used a specific enzyme-linked immunosorbent assay with polyclonal antibodies against equine MPO. The tests were repeated on the horses with RAO after they had spent 2 mo on pasture. Six healthy horses serving as controls underwent the same tests. The absolute and relative neutrophil counts and the MPO concentration in the BAL fluid were significantly greater in the horses with an RAO crisis than in the control horses. After 2 mo on pasture, the horses that had been in RAO crisis were clinically normal, and their neutrophil counts and MPO levels in BAL fluid had significantly decreased; during remission their neutrophil counts were not significantly different from those in the healthy horses, but their MPO concentration remained significantly higher. This study showed that determining the MPO concentration in a horse's BAL fluid is technically possible and that during remission from RAO the concentration remains higher than normal. Thus, MPO may be a marker of neutrophil presence and activation in the lower airways.     

Epidemiological Characteristics of Angular Leaf Spot of Bean: A Systems Analysis

In this review, available knowledge on angular leaf spot (ALS) of bean, caused by Phaeoisariopsis griseola, is analysed and synthesised. This is done through a systems-analytical approach, and successive flowcharts of the system, in order to identify knowledge gaps and guide further research. Six connected sub-models of the ALS monocycle are used as a framework: lesion establishment, lesion extension, defoliation, sporulation, spore liberation, and spore deposition. Each of the sub-models enables the linking of processes to various effects of environmental (physical and host) factors. Disease-induced defoliation is one feature of the pathosystem, leading to a depletion of infectious tissues from the canopy, which are transferred to the ground. Consequences of defoliation may include: strong reductions of the amount of inoculum and of vacant sites in the canopy, limited maximum disease severity, and progressive accumulation of inoculum below the canopy, which may become important a later stage of disease epidemics. These elements are hypothesised to explain the typical behaviour of ALS epidemics in the field, especially late onset, high apparent rate of disease increase, and low level of terminal disease severity in the standing canopy. Epidemiological consequences of lesion expansion, sporulation, and survival of spores deposited onto the canopy are other knowledge gaps in this pathosystem.     

Quantifying and Modelling the Mobilisation of Inoculum from Diseased Leaves and Infected Defoliated Tissues in Epidemics of Angular Leaf Spot of Bean

Daily multiplication factor (number of daughter lesions per mother lesion per day) values were experimentally measured in four replications of a monocyclic experiment on angular leaf spot (ALS) of bean, where sources of inoculum were artificially established within a bean canopy, on the ground (defoliated infected leaves), or both. Daily multiplication factor of lesions in the canopy (DMFRc) was higher than that of infectious, defoliated tissues (DMFRd) in all replications. Both DMFRc and DMFRd were strongly reduced under dry compared to rainy conditions. Under rainy conditions for spore dispersal DMFRd was about two to three times smaller than DMFRc. Defoliated leaves may nevertheless represent a significant source of infection, depending on the amount of infectious tissues. Mother lesions within the canopy generated more daughter lesions in the medium (or lower) layers of the canopy than at its upper level (DMFRc higher at the medium and lower layers of a canopy), whereas DMFRd values seemed to decrease with height in the canopy. A mechanistic simulation model that combines host growth and disease-induced defoliation was designed to simulate the respective contributions of the two components of the dual inoculum source of a diseased canopy (infected foliage and defoliated infectious tissues), and varying infectious periods in both sources. Simulations suggest that higher DMFRc values have a large polycyclic effect on epidemics whereas that of DMFRd is small, and that large effects of the infectious period of lesions in the canopy are found when DMFRc is high. Simulations using experimentally measured DMFRc and DMFRd values indicated much stronger epidemics in rainy compared to dry conditions for spore dispersal, but disease persistence in the latter. The implications of considering a dual source of inoculum in the course of a polycyclic process are discussed with respect to epidemic thresholds.     

Vertical root separation and light interception in a temperate tree-based intercropping system of Eastern Canada

We analysed the spatial distribution of fine roots and light availability in a tree-based intercrop system (TBI) composed of Quercus rubra L. (QUR), hybrid poplar (Populus deltoides × Populus nigra—HYP) and hay (CROP) in southern Québec (Canada) to evaluate interactions between trees and crop. Trees in the 8-year-old TBI system had superficial fine root profiles, which is common in tree species grown in conventional plantations and natural forests. More than 95 % of fine roots were found within the first 25 and 45 cm for QUR and HYP, respectively, and 35 cm for CROP. However, vertical separation between the fine root systems of QUR and CROP was evident, as QUR allocated less fine roots to the top 10 cm of soil, and more to depths between 10 and 30 cm, as opposed to CROP which had a greater proportion of fine roots in the top 10 cm. HYP fine roots showed no adaption when intercropped with hay. High tree fine root length density (FRLD) in the top soil layer was observed near the tree stems while hay FRLD was reduced by 45 %, suggesting strong competition for resources. Hay yield analysis revealed significant reduction near trees, particularly HYP. However, light did seem to be the main driver of intercrop yield, as it not only accounted for the effect of competition by roots (being correlated), but also had a singular effect.     

Retention of Staphylococci and Total Coliforms During Wastewater Percolation Through Equatorial Soil in Central Africa: The Role of the Soil Column Near Soil Surface and that Closely Above Groundwater Table

Groundwater protection from pollutants depends mostly on retention potentials of soil above groundwater table. Soil separating soil surface from groundwater table is made up of several layers and can be divided into different columns along its vertical transect. Wastewater percolation tests were carried out through one soil column CA, in contact with soil surface and through another CB, closely above groundwater table. The aim of the study was to assess the importance of soil columns CA and CB, in total coliforms and staphylococci retention during wastewater infiltration or groundwater recharge, in equatorial soils in Central African region. The results showed that, the fraction of total coliforms retained through soil column CA varied with respect to wastewater loads applied on top of soil column, from 69.22% to 99.95%, relative to the total coliforms concentration deposited on top. The fraction of total coliforms retained through CB varied with respect to wastewater loads applied, from 96.98 to 99.89% relative to the total coliforms deposited on top. Through both soil columns, fractions of staphylococci retained was in the order of 99.99% relative to the total staphylococci concentration deposited on top. For the whole bacteriological analysis, the fractions of total coliforms retained seems to be greater through deeper soil column than that of upper soil column. The bacterial contaminants retained relative to their concentrations in wastewater poured on soil column surfaces, varied from 6.17 log units to 9.73 log units. An applied load of 100 ml seemed to lead to the bacterial pollutants transported through both soil columns studied. NH₄ ⁺ was retained by fractions varying from 97.37 to 98.74%. Concentrations of various contaminants found in groundwater would be a tiny part, relative to quantities deposited on soil surface. Bacterial retention potentials of soil column separating soil surface from groundwater table during wastewater percolation, varies along its transect. It would be due to numerous and variable physical, chemical and structural properties of soil layers and bacteria on the one hand, and to results of various interactions between soil layer particles and cell bacteria, on the other hand.     

Transient gene expression in transformed banana (Musa cv. Bluggoe) protoplasts and embryogenic cell suspensions

Summary In order to introduce currently-available genes with agronomical value into banana, two genetic transformation protocols have been optimized.Firstly, regenerable protoplasts isolated from embryogenic cell suspensions of the cultivar Bluggoe have been used for the introduction of several chimaeric uidA gene constructs by electroporation. With the inclusion of polyethylene glycol and heat shock, the frequency of transiently expressing protoplasts reached 1.8% as shown by an in situ -glucuronidase assay. A duplicated 35S promoter with an alfalfa mosaic virus leader sequence (pBI-426) induced the highest expression rate among the constructs tested.Embryogenic cell suspensions of cv. Bluggoe have also been bombarded with accelerated particles coated with a high expression uidA gene construct (pEmuGN) using a biolistic gun. After a partial optimization of the procedure, transient GUS assays reproducibly demonstrated the presence of 400 blue foci in 30 l of settled cell volume (approximately 25 mg cells). Selection and characterization of antibiotic-resistant transformed cultures is in progress.Abbreviations AMV alfalfa mosaic virus - GUS -glucuronidase - TGE transient GUS expression - uidA gene for -glucuronidase