Regression and development of epidermal papillomas affecting white suckers, Catostomus commersoni (Lacépède), from Lake Ontario, Canada

Abstract. Epidermal papillomas affect white suckers, Catostomus commersoni (Lacepede), from various areas of the Great Lakes of North America, particularly regions receiving industrial pollution. Three morphologically distinct but histologically similar papillomas were found on a group of fish from a polluted site. The diameter of focal soft-skin plaques, focal hard-skin papillomas and focal lip tumours was monitored on individual fish before and after a 12–week observation period in our laboratory. Many papillomas disappeared completely, while others persisted. Individually lip tumours had a lesser frequency of regression (22%), compared to skin plaques (79%) or papillomas (64%). Papillomas which persisted had only slightly smaller diameters after 12 weeks. New tumours developed on 23 and 60% of the survivors in two separate groups. The development of tumours in the laboratory suggests a cause unrelated to the environmental pollution which is correlated with papilloma incidences in wild white suckers. The behaviour of white sucker papillomas under laboratory conditions contrasts with the persistence and often enlargement of similar papillomas reported for other poikilothermic species.     

The effect of dietary n-3 and n-6 fatty acid balance on the growth of the prawn Penaeus monodon

A post-hoc study of the influence of dietary fatty acids of the n-3 and n-6 series on the growth of the prawn, Penaeus monodon showed a clear example of interaction by these nutrients to influence growth. Data from three independent growth studies examining the dietary requirements for linoleic (LOA, 18:2n-6), linolenic (LNA, 18:3n-3), arachidonic (ARA, 20:4n-6), eicosapentaenoic (EPA, 20:5n-2) and docosahexaenoic (DHA, 22:6n-3) acids were standardized through a common reference to allow comparison. Analysis of the variation within the experiments was able to define effects attributable to the individual experiments or the overall dietary n-3 and n-6 levels. A generalized additive model (GAM) indicated that both parameters (experiment, and n-3 and n-6 levels) had significant ( P  < 0.05) effects on growth. Loess nonparametric modelling of the data clearly demonstrates `the effect of relationship' on prawn growth to the levels of dietary n-3 and n-6 fatty acids. The response surface model shows clear effects of both n-3 and n-6, and that the effect of n-3 changes with the level of n-6 (and vice versa). Parametric examination of the relationship ( y =–37.149 x ³ + 160.84 x ² – 118.64 x  + 290.6, r ²=0.492, P  < 0.05) between growth and the ratio between the two fatty acid classes suggested that the optimal ratio of n-3 and n-6 fatty acid is about 2.5 to 1. The results of this study demonstrated that the interaction of the dietary n-3 and n-6 fatty acid classes is an important factor of prawn fatty acid nutrition.     

Nitrous oxide emission from a grassland soil fertilized with slurry and calcium nitrate

Concentrations of nitrous oxide (N₂O) and oxygen were monitored over a 2-yr period in an imperfectly drained grassland soil receiving applications of N as cattle slurry or Ca(NO₃)₂. In both years N₂O concentrations in the different treatments were in the order nitrate > slurry > control. Gaseous diffusion coefficients were determined in soil cores by a krypton-85 tracer method and used to calculate approximate N₂O fluxes from the soil. Only 1–5 kg N ha^?1 was lost as N₂O after a single application of > 1200 kg N ha ^?1 as slurry compared with 3–11 kg N ha ^?1 lost after 100 kg was added as NO₃^?. Total gaseous losses (N₂O+N₂) could be expected to be higher in both cases.     

Water and oxygen regimes of four soil types at Newcastleton Forest, south Scotland

The water and oxygen status of four upland soils under Sitka spruce plantations was studied for 2 years. In a brown earth, waterlogging only occurred ephemerally in the subsoil and oxgen concentrations were generally high. In contrast, waterlogged and near-anaerobic conditions persisted for much of the year in stagnogley and stagnohumic gley soils. In a peaty stagnopodzol moist conditions occurred above and below the thin ironpan, but while high oxygen concentrations generally persisted in the subsoil, low concentrations were common in the soil above. In the brown earth, healthy roots of Sitka spruce were present at a depth of 85 cm, but in the gley soils rooting was mainly limited to 25 cm and many roots were dead. In the peaty stagnopodzol, roots penetrated the ironpan and grew in the subsoil to 75 cm depth.     

EFFECT OF pH ON THE REACTION OF SODIUM FLUORIDE WITH HYDROUS OXIDES OF SILICON, ALUMINIUM, AND IRON, AND WITH POORLY ORDERED ALUMINOSILICATES

The release of hydroxyl ions from silica and ferric oxide gels on treatment with sodium fluoride solution is very small above pH values of 7.6 and 9 respectively. Hydroxyl release from alumina gel and poorly ordered aluminosilicates is appreciable at pH 9 and varies little with pH, but that from crystalline forms of alumina decreases with decrease of pH. For poorly ordered aluminosilicates, the ratio (OH′ released at pH 8.0): (OH′ released at pH 6.8) is directly proportional to the mole fraction Al/(Al+Si). The measurement of hydroxyl release at differing pH values may enable determination of hydrous alumina separately from the total poorly ordered inorganic gel material; moreover, the amount of hydroxyl released at high pH values is related to phosphate sorption capacity.     

Studies on 4-keto-L-proline

The administration of ketoproline to chick embryos resulted in an increase in the free hydroxyproline. This phenomenon is explained by the inhibitory action of ketoproline on the catabolism of hydroxyproline as well as by the conversion of the former to the latter. Ketoproline was found to be reduced to hydroxyproline by the supernatant fraction of rat-kidney homogenate in the presence of a reduced pyridine nucleotide.     

A function for tissue mast cells

Experimental elimination of mast cells from the peritoneal tissues of the rat by distilled water treatment inhibited the increase of vascular permeability which normally follows a passively induced antigen-antibody reaction in peritoneal tissue. Thus mast cells may contribute to the initiation of inflammation which follows antigen-antibody reactions.