Effect of thermal shock treatments on symptom expression in test plants inoculated with potato aucuba mosaic virus

Potato aucuba mosaic virus (PAMV) has few reliable local lesion assay hosts. However, lesions formed when PAMV-inoculated leaves were exposed to thermal shock (dipping for 40 s in water at 50 or 2 °C). Leaves of Nicotiana tabacum (cv. Xanthi-nc, Samsun or Samsun NN), Hyoscyamus niger and Datura metel consistently developed necrotic lesions, leaves of Chenopodium amaranticolor developed whitish rings, and leaves of N. glutinosa developed diffuse cream-coloured rings and spots. In PAMV-inoculated leaves of Xanthi-nc tobacco, C. amaranticolor and D. metel, lesions formed only in areas exposed to light. Thermal shocks applied to systemically infected leaves of Xanthi-nc tobacco induced necrotic vein banding patterns. In inoculated Xanthi-nc tobacco leaves, PAMV seemed confined to local lesions. The rate of lesion enlargement was therefore a measure of rate of virus spread. Lesion size increased as the interval between inoculation and shock treatment increased. The mean rates of increase in lesion radius were 17 and 27 Cμm/h at 15 and 25°C respectively. ‘Target’ lesions, composed of concentric necrotic rings, formed when inoculated Xanthi-nc tobacco leaves were given two or more 50°C shocks. The first of two 50°C treatments decreased subsequent rates of lesion enlargement.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Spatial and temporal distribution patterns of drifting pupal exuviae of Chironomidae (Diptera) in streams of tropical northern Australia

1. Periodic collecting of floating cast pupal cuticles of chironomids (exuviae) in two tropical northern Australian streams demonstrates (i) spatial heterogeneity in species composition across a wide stream, (ii) temporal heterogeneity in the maximum abundance of each species, and that (iii) species accumulate as a function of sample size and duration of sampling, 2. Spatial heterogeneity is ascribed to variation in larval microhabitat across the wide stream, combined with short exuvial drift duration and restricted upstream mixing. 3. Temporal heterogeneity is ascribed to diel periodicity in adult emergence and, as with spatial heterogeneity, to the short floating life. 4. The consequences of spatial and temporal variation for the sampling of exuvial drift are discussed in relation to the objectives of particular programmes. Thus, if the objective is assessment of chironomid species composition for inventory purposes such as faunistics or conservation, the large sample sizes attained by 24-h sampling are necessary and appropriate. However, for rapid assessment that requires comparable samples at different sites, species numbers may be optimized by temporally and spatially restricted sampling of the maximal emergence period, which in this study is at dusk, or by subsampling from a 24-h sample.     

Delimitation of the maritime boundary in the gulf of Maine area

The compulsory dispute settlement regime included in the 1982 Law of the Sea Convention is recognized as one of the most comprehensive in a modern international convention. Yet, in the recent application of this regime, the question has arisen as to whether the procedural prerequisites associated with the LOS Convention's compulsory dispute settlement mechanism are so arduous as to avoid binding and compulsory jurisdiction in most instances. This article addresses that question by examining, in particular, the reasoning of the Southern Bluefin Tuna arbitration tribunal, which found Article 281 of Section 1 of the LOS Convention to bar jurisdiction to the compulsory dispute settlement mechanism prescribed by the Convention, and offers suggestions as to how states might distinguish or overcome the barriers imposed by the Southern Bluefin Tuna tribunal in future cases.     

Inter‐regional comparison of land‐use effects on stream metabolism

1. Rates of whole‐system metabolism (production and respiration) are fundamental indicators of ecosystem structure and function. Although first‐order, proximal controls are well understood, assessments of the interactions between proximal controls and distal controls, such as land use and geographic region, are lacking. Thus, the influence of land use on stream metabolism across geographic regions is unknown. Further, there is limited understanding of how land use may alter variability in ecosystem metabolism across regions. 2. Stream metabolism was measured in nine streams in each of eight regions (n = 72) across the United States and Puerto Rico. In each region, three streams were selected from a range of three land uses: agriculturally influenced, urban‐influenced, and reference streams. Stream metabolism was estimated from diel changes in dissolved oxygen concentrations in each stream reach with correction for reaeration and groundwater input. 3. Gross primary production (GPP) was highest in regions with little riparian vegetation (sagebrush steppe in Wyoming, desert shrub in Arizona/New Mexico) and lowest in forested regions (North Carolina, Oregon). In contrast, ecosystem respiration (ER) varied both within and among regions. Reference streams had significantly lower rates of GPP than urban or agriculturally influenced streams. 4. GPP was positively correlated with photosynthetically active radiation and autotrophic biomass. Multiple regression models compared using Akaike’s information criterion (AIC) indicated GPP increased with water column ammonium and the fraction of the catchment in urban and reference land‐use categories. Multiple regression models also identified velocity, temperature, nitrate, ammonium, dissolved organic carbon, GPP, coarse benthic organic matter, fine benthic organic matter and the fraction of all land‐use categories in the catchment as regulators of ER. 5. Structural equation modelling indicated significant distal as well as proximal control pathways including a direct effect of land‐use on GPP as well as SRP, DIN, and PAR effects on GPP; GPP effects on autotrophic biomass, organic matter, and ER; and organic matter effects on ER. 6. Overall, consideration of the data separated by land‐use categories showed reduced inter‐regional variability in rates of metabolism, indicating that the influence of agricultural and urban land use can obscure regional differences in stream metabolism.