Contrasting ability of deep and shallow rooting rice genotypes to grow through plough pans containing simulated biopores and cracks

Plant and Soil - Cracks and biopores in compacted soil such as plough pans could aid deep rooting, mitigating constraints to seasonal upland use of paddy fields for rice production. This research...     

Quantal secretion and response lag demonstrated in single rat neutrophils

The release of 9-aminoacridine loaded into neutrophil granules has been monitored using quantitative fluorescence microscopy of individual rat neutrophils. Within the granule, the fluorescence of the dye was substantially quenched, but release into the surrounding medium restored fluorescence. From kinetic analysis of the increase in fluorescence it was shown that secretion from a single neutrophil in response to a low concentration of chemotactic peptide occurred in 'bursts'. Each 'burst' of secretion was of equal size and kinetics, which were equal to the size and kinetics of the smallest evoked response possible. A significant time-lag of 5-10 s between the arrival of the stimulus at the cell and the onset of secretion was recorded. It was therefore concluded that secretion from neutrophils was the result of release of quantal amounts of dye following a delay period.     

Pulling or drilling, does size or species matter? An experimental study of prey handling in Octopus dierythraeus ()

The influence of both predator and prey size on the shift from a pulling to a drilling predatory response was examined in the intertidal octopus Octopus dierythraeus, using an experimental program. Additionally, selective drilling, where particular regions of the prey are targeted, was examined for a variety of bivalve and gastropod prey. O. dierythraeus always initially attempted to pull bivalves apart. Shells that were eventually drilled were always subjected to significantly more pulling attempts than those that could be pulled apart, indicating that octopus are willing to expend more energy to access the flesh quickly. There was no defined threshold where bivalve size caused an octopus to switch from a pulling to a drilling response. Instead, there was a broad size range where the octopus could adopt either handling method and it varied for each individual. Octopus may only able to pull open bivalves before the molecular ratchet or ‘catch’ mechanism that many bivalves possess is engaged. This might explain the lack of a relationship between either octopus or bivalve size and the success of pulling, as it is likely that when the bivalves were presented to individual octopus they were either setting the ‘catch’ mechanism, or had already engaged it. O. dierythraeus demonstrated selective drilling on a variety of molluscan prey, with penetration sites differing between prey species. O. dierythraeus targeted the valve periphery, which was the thinnest part of the shell, therefore minimizing handling time. O. dierythraeus always drilled gastropods, but did not target the thinnest regions of the shells, with drill site varying according to the morphology of the prey. Elongate species with pronounced aperture lips were drilled in the apical region, close to the columella on the side of the opercula whereas nonelongate species were drilled immediately above the aperture. The location of drilling sites may represent a trade-off between targeting the most effective places to inject paralyzing secretions and the mechanically simplest places to drill.     

Extracellular production of a heat-stable somatic antigen by Bacillus thuringiensis

Extracellular production of a heat-stable somatic antigen (HSSA) by Bacillus thuringiensis subsp. dendrolimus strain T84A1-A [flagellar (H) serotype 4a: 4b] was serologically detected. In Ouchterlony tests, the HSSA antiserum gave single precipitin lines against both untreated and heat-treated culture supernatants. These two precipitin lines fused completely. When colonies of strain T84A1-A were grown on nutrient agar plates containing the homologous HSSA antiserum, precipitin halos were formed around the colonies. Of 27 type strains of B. thuringiensis subspecies tested, only the type strains of B. thuringiensis subsp. sotto (H serotype 4a: 4b) and B. thuringiensis subsp. israelensis (H serotype 14) formed [precipitin halos on nutrient agar plates containing antiserum against the HSSA of strain T84A1-A.     

Reversible cell damage by T-cell perforins. Calcium influx and propidium iodide uptake into K562 cells in the absence of lysis.

The non-lethal effects of the lymphocyte-derived pore-forming toxin perforin on the human erythroleukaemia cell line K562 were investigated. By using the fluorescent Ca2+ indicator fura-2, perforin was shown to cause intracellular Ca2+ concentration to rise transiently into the micromolar range in the absence of cell death. By fluorescence-activated cell sorting it was demonstrated that K562 cells took up the membrane-impermeant nuclear stain propidium iodide (PI) when exposed to non-lethal doses of perforin. The permeability to PI was short-lived, confirming the transience of the perforin pore. Analogies with non-lethal effects and recovery processes occurring in nucleated cells exposed to the membrane-attack complex of complement are drawn.