Cycling of nutrients from dying roots to living plants,including the role of mycorrhizas

This paper presents information about the release of nitrogen and phosphorus from dying grass roots and the capture of phosphorus by other, living plants. We have paid particular attention to the part played by mycorrhizas in this phosphorus capture, and the possible importance of mycorrhizal links between dying and living roots.WhenLolium perenne plants were grown with ample nutrients and their roots then detached and buried in soil, about half the nitrogen and two-thirds of the phosphorus was lost in three weeks, but only one-fifth of the dry weight. The C:N and C:P ratios suggest that microbial growth in the roots would at first be C-limited but would become N- and P-limited within three weeks.Rapid transfer of³²P can occur from dying roots to those of a living plant if the two root systems are intermingled. The amount transferred was substantially increased in two species-combinations that are known to form mycorrhizal links between their root systems. In contrast, in a species-combination where only the living (receiver) plant could become mycorrhizal no significant increase of³²P transfer occurred. This evidence, although far from conclusive, suggests that mycorrhizal links between dying and living roots can contribute to nutrient cycling. This research indicates a major difference in nutrient cycling processes between perennial and annual crops.     

Sex allocation theory aids species conservation

Supplementary feeding is often a key tool in the intensive management of captive and threatened species. Although it can increase such parameters as breeding frequency and individual survival, supplementary feeding may produce undesirable side effects that increase overall extinction risk. Recent attempts to increase breeding frequency and success in the kakapo Strigops habroptilus using supplementary feeding inadvertently resulted in highly male-biased chick sex ratios. Here, we describe how the inclusion of sex allocation theory has remedied this conservation dilemma. Our study is the first to manipulate chick sex ratios in an endangered species by altering maternal condition and highlights the importance of incorporating evolutionary theory into modern conservation practice.     

Use of a disposable water filter for prevention of false-positive results due to nontuberculosis mycobacteria in a clinical laboratory performing routine acid-fast staining for tuberculosis

A point-of-use 0.2-microm filter was evaluated for elimination of nontuberculosis mycobacteria in laboratory water to reduce false-positive acid-fast bacillus staining results. Use of the point-of-use filter can significantly reduce the false-positive rate to 1.2% compared to samples treated with tap water (10.7%) and deionized water (8.7%).     

Tumour cell inhibition of macrophage cytokine activity

Abstract Macrophages elaborate both effector and regulatory immune functions. It was hypothesised that tumours can exert a local alteration of macrophage function. Murine peritoneal macrophage-derived cytokines were assayed in the presence and absence of cells, cytosol fractions or conditioned media (TCCM) from established murine tumour lines. Interleukin-1β, interleukin-6 and tumour necrosis factor-α activities were significantly inhibited by tumour cells or their products, as were the corresponding recombinant human cytokines. Intracellular protein kinase C activation was also measured and was significantly inhibited by murine TCCM, thus suggesting one possible site of inhibitor action. Data analyses indicate that the inhibitory factor(s) is probably not an already well-characterised macrophage inhibitor.     

The subunit structure of horse spleen apoferritin: the molecular weight of the oligomer and its stability to dissociation by dilution (Short Communication)

The oligomer molecular weight of horse spleen apoferritin was determined by sedimentation-equilibrium techniques and a value of 443000 found. It is concluded that the apoferritin molecule consists of 24 subunits. At concentrations as low as 0.01mum there is no evidence of subunit dissociation.