Postharvest organic matter removal effects on FH layer and mineral soil characteristics in four New Zealand Pinus radiata plantations

The effects of three postharvest organic matter removal treatments on fermentation-humus (FH) layer and soil characteristics were compared in replicated trials in four second rotation New Zealand Pinus radiata plantation forests, planted 8–16 years prior to sampling. All sites were sampled in early 2002 and 2003. Increasing organic matter removal significantly decreased the mass of the FH layer in the treatment plots, the moisture content in the FH layer and mineral soil, the concentration of carbon in the FH layer and mineral soil, the pool of carbon stored in the FH layer, the concentration of nitrogen in the mineral soil and the pool of nitrogen stored in the FH layer. Mineral soil pH was significantly increased with increasing organic matter removal. The persistence of the significant differences in the FH layer and mineral soil characteristics strongly suggested that variations in organic matter removal have long-term effects on forest floor properties, and significantly influences carbon storage over the life of the rotation.     

Antigenic stability of fimbriae of Bacteroides nodosus

Successful vaccination of sheep against footrot and attempts to eradicate the disease depend on there being a limit to the antigenic diversity of the causative bacterium, Bacteroides nodosus. Fimbrial antigenic variation was therefore investigated in vivo, both under conditions of chronic infection and under the pressure of a vaccine-induced immune response, to ascertain whether this represented an obstacle to such goals. Material was available from 5 experiments and although B. nodosus appeared to have undergone changes in its fimbrial antigens in one of these, the possibility that superinfection was responsible for the variation detected could not be ruled out because all sheep in this case were maintained at pasture. Overall, the results provided no evidence of fimbrial antigenic shift in B. nodosus in vivo and in conclusion, the survival of the organism in the sheep's foot, both in long-term natural infection and following vaccination, must therefore be related to factors other than the ability to undergo antigenic variation in order to evade the host's immune response.     

Bilateral recurrent laryngeal neurectomy as a model for the study of idiopathic canine laryngeal paralysis.

The purposes of this study were to develop an experimental model of canine laryngeal paralysis that mimicked the naturally occurring disease and to document the upper airway changes produced, both clinically and with pulmonary function testing. Ten dogs had bilateral recurrent laryngeal neurectomy performed and were recovered from anesthesia. Tidal breathing flow-volume loop analysis and upper airway resistance measurements were taken before and after the development of clinical laryngeal paralysis while dogs breathed room air and after the individual administration of 2 respiratory stimulants. Clinical signs of laryngeal paralysis developed 38 days (median) following denervation. Although some variations were present, tidal breathing flow-volume loop analyses on room air, following denervation, were similar to those reported in naturally occurring cases. Upper airway resistance increased following denervation and was significantly increased with both respiratory stimulants. We concluded that bilateral recurrent laryngeal neurectomy resulted in clinical signs and respiratory changes similar to those of idiopathic canine laryngeal paralysis.     

Bacteremia and bacterial translocation in the naturally occurring canine gastric dilatation-volvulus patient

This prospective study was performed to determine the prevalence of bacteremia in the naturally occurring gastric dilatation-volvulus (GDV) patient, the possible relationship between bacteremia and survival, and whether bacteremia was a result of translocation from the stomach. Blood cultures were collected from each patient. Bacterial cultures were collected from the liver, mesenteric lymph node, and stomach. Forty-three percent of the GDV cases and 40% of the controls developed positive blood cultures. Gram-negative rods were the most frequently isolated organisms. Evidence of bacterial translocation from the stomach could not be demonstrated in GDV patients, and survival was not affected by the presence of bacteremia.     

Distribution and dynamics of soil organic matter in an Antarctic dry valley

Terrestrial ecosystems in the Antarctic dry valleys function under extremely cold and dry climatic conditions that severely constrain C and N cycling and, like other polar regions, are likely to be sensitive to environmental change. To characterize the distribution and dynamics of soil organic C (SOC) and N in the various landscape elements of an Antarctic dry valley, we measured soil profile organic C and organic N stocks, inorganic N (NH₄-N and NO₃-N), soil CO₂ effluxes, water contents and soil temperatures in the Garwood Valley, a relatively small valley in southern Victoria Land. We also conducted laboratory measurements of basal respiration on soils collected from the Valley. SOC and respiration rates were low and SOC was highly stratified in the soil profile, with the largest values observed near the surface. Significant variations of SOC stocks and soil CO₂ effluxes were observed between landscape elements and spatial variability was closely related to the distance from the lake, the major site of primary production. The fastest rate of SOC turnover (residence time c. 30 years) was found in the soils at the lake edge, slower rates were found in landscape elements close to the lake (c. 52-67 years), and the slowest rates in other landscape elements (c. 84-123 years) further away. A mass balance of organic C indicates that the quantity of C fixed in the lake, accumulated on the lake edge, exposed and subsequently displaced on a 14-year basis can explain the near-surface SOC turnover within the entire valley. We conclude that the displacement of organic matter derived from the lake is an important external source for the microbial processes in these soils at a landscape scale. However, further investigations are needed in order to evaluate the importance of displaced C compared to other nutrients (e.g. N) on the spatial control of observed soil respiration rates.     

Host immune system gene targeting by a viral miRNA

Virally encoded microRNAs (miRNAs) have recently been discovered in herpesviruses. However, their biological roles are mostly unknown. We developed an algorithm for the prediction of miRNA targets and applied it to human cytomegalovirus miRNAs, resulting in the identification of the major histocompatibility complex class I-related chain B (MICB) gene as a top candidate target of hcmv-miR-UL112. MICB is a stress-induced ligand of the natural killer (NK) cell activating receptor NKG2D and is critical for the NK cell killing of virus-infected cells and tumor cells. We show that hcmv-miR-UL112 specifically down-regulates MICB expression during viral infection, leading to decreased binding of NKG2D and reduced killing by NK cells. Our results reveal a miRNA-based immunoevasion mechanism that appears to be exploited by human cytomegalovirus.