Crop uptake and leaching losses of15N labelled fertilizer nitrogen in relation to waterlogging of clay and sandy loam soils

Summary Ammonium nitrate fertilizer, labelled with¹⁵N, was applied in spring to winter wheat growing in undisturbed monoliths of clay and sandy loam soil in lysimeters; the rates of application were respectively 95 and 102 kg N ha⁻¹ in the spring of 1976 and 1975. Crops of winter wheat, oilseed rape, peas and barley grown in the following 5 or 6 years were treated with unlabelled nitrogen fertilizer at rates recommended for maximum yields. During each year of the experiments the lysimeters were divided into treatments which were either freelydrained or subjected to periods of waterlogging. Another labelled nitrogen application was made in 1980 to a separate group of lysimeters with a clay soil and a winter wheat crop to study further the uptake of nitrogen fertilizer in relation to waterlogging. In the first growing season, shoots of the winter wheat at harvest contained 46 and 58% of the fertilizer nitrogen applied to the clay and sandy loam soils respectively. In the following year the crops contained a further 1–2% of the labelled fertilizer, and after 5 and 6 years the total recoveries of labelled fertilizer in the crops were 49 and 62% on the clay and sandy loam soils respectively. In the first winter after the labelled fertilizer was applied, less than 1% of the fertilizer was lost in the drainage water, and only about 2% of the total nitrogen (mainly nitrate) in the drainage water from both soils was derived from the fertilizer. Maximum annual loss occurred the following year but the proportion of tracer nitrogen in drainage was nevertheless smaller. Leaching losses over the 5 and 6 years from the clay and sandy loam soil were respectively 1.3 and 3.9% of the original application. On both soils the percentage of labelled nitrogen to the total crop nitrogen content was greater after a period of winter waterlogging than for freely-drained treatments. This was most marked on the clay soil; evidence points to winter waterlogging promoting denitrification and the consequent loss of soil nitrogen making the crop more dependent on spring fertilizer applications.     

A modified method of UDS detection in vitro suitable for screening the DNA-damaging effects of chemicals

The UDS induced in cultured FL cells by exposure to chemicals was measured as hydroxyurea-resistant incorporation of 3H-TdR in the acid-insoluble fraction of the 14C-TdR-prelabelled cells synchronized by the combination of arginine starvation and pretreatment with hydroxyurea. The level of UDS is represented by the ratios of 3H/14C radioactivities which are measures of specific activities of 3H. Two direct-acting alkylating agents, MMS and MNNG, a cross-linking agent, mitomycin C, and 3 procarcinogens, B(a)P, AFB1 and cyclophosphamide elicited UDS in the absence or presence of the liver-metabolizing system. Three chemicals of unknown carcinogenicity were also able to induce UDS in this assay system, i.e., bis-(O,O-diethylphosphinothioyl)-disulphide, 4-chlorophenoxy acetic acid (sodium salt) and caramelized malt sugar. With the exception of 4-chlorophenoxy acetic acid, they were also active in the Ames test.     

Calcium reduces the sodium permeability of luminal membrane vesicles from toad bladder. Studies using a fast-reaction apparatus

Regulation of the sodium permeability of the luminal membrane is the major mechanism by which the net rate of sodium transport across tight epithelia is varied. Previous evidence has suggested that the permeability of the luminal membrane might be regulated by changes in intracellular sodium or calcium activities. To test this directly, we isolated a fraction of the plasma membrane from the toad urinary bladder, which contains a fast, amiloride-sensitive sodium flux with characteristics similar to those of the native luminal membrane. Using a flow-quench apparatus to measure the initial rate of sodium efflux from these vesicles in the millisecond time range, we have demonstrated that the isotope exchange permeability of these vesicles is very sensitive to calcium. Calcium reduces the sodium permeability, and the half-maximal inhibitory concentration is 0.5 microM, well within the range of calcium activity found in cells. Also, the permeability of the luminal membrane vesicles is little affected by the ambient sodium concentration. These results, when taken together with studies on whole tissue, suggest that cell calcium may be an important regulator of transepithelial sodium transport by its effect on luminal sodium permeability. The effect of cell sodium on permeability may be mediated by calcium rather than by sodium itself.     

SMAS-platysma face lift

Correction of laxity in the submental area and of hypertrophic neck cords has been enhanced with the SMAS-platysma face life over that which was achieved with a standard skin face lift. Evaluation of a 6-year experience with the SMAS-platysma face lift reveals that the operation can be safely performed with an acceptably low incidence of complications. The incidence of hematoma and associated complications is less than that which occurs when cervical and submental defatting is performed in conjunction with a skin face lift.     

Resistance to tedion in haploid and diploid offspring of Tetranychus urticae Koch

The susceptibility to Tedion of haploid and diploid-haploid mixtures of eggs of Tetranychus urticae Koch was examined. It was concluded for a normal susceptible strain that haploid eggs are more susceptible to Tedion than diploid eggs. This difference in tolerance between haploid and diploid eggs could not be established for a strain resistant to Tedion.Mass crosses between the susceptible and the resistant strain were made. Susceptible females, mated by resistant males, produce susceptible haploid and resistant diploid offspring. Resistant females, mated by susceptible males, gave a resistant offspring. Both sexes can also transmit resistance to Tedion. As there was a difference in tolerance between diploid offspring in the reciprocal crosses, it is assumed that either a maternal or a cytoplasmic component is also present in the genetical mechanism of Tedion-resistance.

---

Zusammenfassung Es wurde die Empfindlichkeit haploider und diploid-haploider Gemische von Eiern von Tetranychus urticae Koch gegenüber Tedion untersucht. Für einen normal empfindlichen Stamm wurde aus toxikologischen Daten und einer Verschiebung des Geschlechterverhältnisses erschlossen, daß haploide Eier gegenüber Tedion empfindlicher sind als diploide. Dieser Toleranzunterschied zwischen haploiden und diploiden Nachkommen konnte bei einem gegen Tedion resistenten Stamm nicht nachgewiesen werden.Es wurden Massenkreuzungen zwischen empfindlichen und resistenten Stämmen durch-geführt. Empfindliche Weibchen, mit resistenten Männchen gepaart, produzierten empfindliche haploide und resistente diploide Nachkommen. Resistente Weibchen, mit empfindlichen Männchen gepaart, ergaben eine resistente Nachkommenschaft. Beide Geschlechter können also die Resistenz gegen Tedion übertragen. Da bei den reziproken Kreuzungen ein Toleranzunterschied zwischen den diploiden Nachkommen auftritt, wird angenommen, daß in dem genetischen Mechanismus der Tedion-Resistenz auch eine mütterliche oder eine zytoplasmatische Komponente vorhanden ist.