Arabidopsis H+-PPase AVP1 regulates auxin-mediated organ development

The transport of auxin controls developmental events in plants. Here, we report that in addition to maintaining vacuolar pH, the H+-pyrophosphatase, AVP1, controls auxin transport and consequently auxin-dependent development. AVP1 overexpression results in increased cell division at the onset of organ formation, hyperplasia, and increased auxin transport. In contrast, avp1-1 null mutants have severely disrupted root and shoot development and reduced auxin transport. Changes in the expression of AVP1 affect the distribution and abundance of the P-adenosine triphosphatase and Pinformed 1 auxin efflux facilitator, two proteins implicated in auxin distribution. Thus, AVP1 facilitates the auxin fluxes that regulate organogenesis.     

Neutron-mapping polymer flow: scattering, flow visualization, and molecular theory

Flows of complex fluids need to be understood at both macroscopic and molecular scales, because it is the macroscopic response that controls the fluid behavior, but the molecular scale that ultimately gives rise to rheological and solid-state properties. Here the flow field of an entangled polymer melt through an extended contraction, typical of many polymer processes, is imaged optically and by small-angle neutron scattering. The dual-probe technique samples both the macroscopic stress field in the flow and the microscopic configuration of the polymer molecules at selected points. The results are compared with a recent "tube model" molecular theory of entangled melt flow that is able to calculate both the stress and the single-chain structure factor from first principles. The combined action of the three fundamental entangled processes of reptation, contour length fluctuation, and convective constraint release is essential to account quantitatively for the rich rheological behavior. The multiscale approach unearths a new feature: Orientation at the length scale of the entire chain decays considerably more slowly than at the smaller entanglement length.     

Determination of deforestation rates of the world's humid tropical forests

A recently completed research program (TREES) employing the global imaging capabilities of Earth-observing satellites provides updated information on the status of the world's humid tropical forest cover. Between 1990 and 1997, 5.8 +/- 1.4 million hectares of humid tropical forest were lost each year, with a further 2.3 +/- 0.7 million hectares of forest visibly degraded. These figures indicate that the global net rate of change in forest cover for the humid tropics is 23% lower than the generally accepted rate. This result affects the calculation of carbon fluxes in the global budget and means that the terrestrial sink is smaller than previously inferred.     

Tuber growth and biomass partitioning of two potato cultivars grown under different n fertilization rates with and without irrigation

Nitrogen and water deficiencies are known to affect potato yield, but much less is known of their effect on tuber growth and biomass partitioning. The objective of this on-farm study conducted at two sites in each of three years, 1995 to 1997, was to determine the effects of supplemental irrigation and N fertilization rates on tuber growth and biomass partitioning of the cultivars Shepody and Russet Burbank. The N fertilization rates were 0,100, and 250 kg N ha^-1in 1995, and 0, 50,100, and 250 kg N ha_?1 in 1996 and 1997. The highest bulking rate observed in our study (7.3 g fresh tubers m^-2 °C^-1) can be considered near the potential bulking rate in New Brunswick. The water deficit in the absence of supplemental irrigation reduced this potential bulking rate by as much as 40%, but this reduction was much less at five of six sites and negligible at two of six sites. Nitrogen deficiency reduced the bulking rate at two of six sites. This negative effect of N deficiency on bulking rate was greater with irrigation than without irrigation at two of six sites; the tuber bulking rate with irrigation was reduced by as much as 50% with no N applied at one site. Shepody had a greater bulking rate than Russet Burbank. The tuber bulking of Russet Burbank, however, started earlier and lasted longer than that of Shepody. Water and N deficiencies increased biomass partitioning to tubers and large roots. Shepody partitioned a greater proportion of its biomass to large roots and had a greater root biomass than Russet Burbank. Our results demonstrate the ability of potatoes to modify biomass partitioning when grown under water and/or N stresses. As a result of this compensation, the reduction in tuber yield due to limited N and water stresses is minimized.     

Evaluation of platelet function screening tests to detect platelet procoagulant deficiency in dogs with Scott syndrome

Background: Clinical diagnosis of platelet dysfunction is complex and technically challenging. The wide repertoire of platelet responses requires a test panel to assess different parameters of platelet reactivity. While “global” hemostasis analyzers and whole blood assays have potential for testing platelet function, their ability to evaluate platelet procoagulant activity is ill‐defined. Objectives: The aim of this study was to determine whether platelet procoagulant deficiency, the pathophysiologic defect of Scott syndrome, could be detected in point‐of‐care and whole blood assays. Methods: Study subjects were 4 Scott syndrome‐affected German Shepherds and 8 control dogs. We evaluated 2 point‐of‐care instruments: the platelet function analyzer (PFA‐100) and thromboelastograph (TEG). TEG analysis was performed on recalcified citrated whole blood with and without tissue‐factor activation. A whole blood flow cytometric assay was configured to detect thrombin‐induced platelet P‐selectin expression and platelet‐derived microparticle release. Cytometric samples were analyzed after 1 hour and 1 day of storage. Results: We found no significant differences between Scott and control dogs in PFA‐100 COL/ADP closure times or in any TEG parameter in tissue‐factor–activated samples. In nonactivated samples, mean clotting time (K) and time to maximal rate of thrombus generation were significantly prolonged in Scott dogs; however, values overlapped with those of control dogs. Cytometric analysis of samples from Scott dogs showed significantly diminished platelet‐derived microparticle release. Samples from all dogs reanalyzed after 1 day of storage had nonspecific increases in basal P‐selectin expression and vesiculation. Conclusion: A whole blood cytometric assay to detect stimulated platelet microparticle release can be used to screen for Scott syndrome. However, platelet activation artifacts preclude overnight storage for next‐day analysis.     

Yield response of two potato culivars to supplemental irrigation and N fertilization in New Brunswick

Nitrogen and water are important factors influencing potato production, and crop response to these two factors may vary with cultivars. The yield response of two potato cultivars (Russet Burbank and Shepody) to six rates of N fertilization (0-250 kg N ha^-1) with and without supplemental irrigation was studied at four onfarm sites in each of three years, 1995 to 1997, in the upper St-John River Valley of New Brunswick, Canada. On average, irrigation increased total yield from 31.9t ha^-1 without irrigation to 38.41 ha^-1 with irrigation and marketable yield from 25.61 ha^-1 without irrigation to 30.71 ha^-1 with irrigation. Potato yields were increased by irrigation at nine out of the 12 sites, and the irrigation response was similar for both cultivars. Nitrogen fertilization significantly increased both total and marketable yields at all sites except one. The yield response to N fertilization was greater with irrigation. The N fertilization rate (Nmax) required to reach maximum total and marketable yield, however, was similar with and without irrigation. A large variation in Nmax was observed among sites. With irrigation Nmax varied between 158 and 233 kgN ha^-1 for total yield, and between 151 and 250 kg N ha^-1 for marketable yield. There was no interaction between N fertilization and potato cultivar for both total and marketable yields. The two cultivars had similar total yields (35 t ha^-1). Shepody, however, had a greater marketable yield (28.9 t ha^-1) than Russet Burbank (27.4 t ha^-1). Our results indicate that the response to two of the most significant factors of potato production, irrigation and N fertilization, varies greatly with sites and climatic conditions, and that field specific recommendations are required for the optimum management of N and irrigation.     

Immunohistochemical and PCR studies of wild fish for Tetracapsula bryosalmonae (PKX), the causative organism of proliferative kidney disease

Tetracapsula bryosalmonae, previously referred to as PKX, causes proliferative kidney disease (PKD) in salmonids and is an economically important myxozoan pathogen in salmonid culture. A variety of molecular and immunological tools have been developed to detect the parasite. To determine the specificity of four monoclonal antibodies (MAbs) raised against T. bryosalmonae, archive material of fish infected with various myxosporean species was obtained and immunostained. Wild fish were also collected from enzootic waters and examined for T. bryosalmonae infection using immunohistochemistry and the polymerase chain reaction (PCR). Three of the MAb probes appear to be specific for T. bryosalmonae while only two of the five sets of primers tested appeared to specifically amplify T. bryosalmonae DNA. The results of the immunostaining and the PCR demonstrate that T. bryosalmonae occurs in the tubules of grayling Thymallus thymallus L., brown trout, Salmo trutta L. and Atlantic salmon, Salmo salar L. outside of the PKD season (June‐September) in the UK. This confirms the results of previous studies that these species are the preferred fish hosts for the parasite in the UK.     

Primary hyperaldosteronism in two cats.

A condition of primary hyperaldosteronism resulting from an adrenal tumor in two cats is presented and was characterized by hypertension, hypokalemia, inappropriate kaliuresis, low normal plasma renin activity, and markedly increased serum aldosterone concentration. One of the two cats underwent a laparotomy, and in this case hypertension and hypokalemia resolved following the removal of an adrenal tumor.     

Atrazine intoxication in cattle,confirmed by gas chromatography–mass spectrometry

Ten of 40 cows died within 48 h of gaining access to a barn in which various chemicals were stored. Some of the surviving cows exhibited drooling, muscle tremors, and agitation. Postmortem examinations of 2 cows were performed in the field, and revealed nonspecific, moderate-to-severe pulmonary congestion. Liver and rumen contents, each from a different cow, were analyzed using a qualitative, multi-residue GC-MS method validated for the detection of pesticides and other chemical analytes. Using this method, extracts from the liver and rumen content samples were compared to atrazine (neat standard) and matrix-matched, control samples fortified with atrazine. GC-MS analysis detected atrazine at 215 m/z (NIST match >97%) with a retention time of ~13 min in liver and rumen content samples from our case. Detection of atrazine in the samples from the cows in this herd, combined with the clinical history, indicate that atrazine toxicity was the likely cause of clinical signs and death observed in this herd.