Status and trends of amphibian declines and extinctions worldwide

The first global assessment of amphibians provides new context for the well-publicized phenomenon of amphibian declines. Amphibians are more threatened and are declining more rapidly than either birds or mammals. Although many declines are due to habitat loss and overutilization, other, unidentified processes threaten 48% of rapidly declining species and are driving species most quickly to extinction. Declines are nonrandom in terms of species' ecological preferences, geographic ranges, and taxonomic associations and are most prevalent among Neotropical montane, stream-associated species. The lack of conservation remedies for these poorly understood declines means that hundreds of amphibian species now face extinction.     

Chromosomal locations of human tissue plasminogen activator and urokinase genes

A panel of human-mouse somatic cell hybrids and specific complementary DNA probes were used to map the human tissue plasminogen activator and urokinase genes to human chromosomes 8 and 10, respectively. This result is in contrast to a previous assignment of a plasminogen activator gene to chromosome 6. As neoplastic cells produce high levels of plasminogen activator, it is of interest that aberrations of chromosome 8 have been linked to various leukemias and lymphomas and that two human oncogenes, c-mos and c-myc, have also been mapped to chromosome 8.     

Root distribution and nitrate interception in eleven temperate forage grasses

Agrostis capillaris, Arrhenatherum elatius, Bromus willdenowii, Cynosurus cristatus, Dactylis glomerata, Elytrigia repens, Lolium multiflorum, L. perenne, Phalaris aquatica, Phleum pratense, Schedonorus phoenix, and a ryegrass selected for high surface root mass, were grown in 1 m deep × 90 mm diameter tubes of sand. Tubes were irrigated with a low ionic‐strength nutrient solution and ¹⁵N‐labelled nitrate was leached down the tubes prior to harvest. Shoot weights, root weights in 10‐cm depth increments, and shoot and root nitrogen concentrations were determined. Plants of L. multiflorum were the heaviest and plants of A. capillaris were the lightest. Root system shape was analysed by comparing the decay constant from an exponential model fitted to the proportion of root mass in 10‐cm depth increments, and, also, by analysis of the proportion of root mass in the top 10 cm. Cynosurus cristatus was strongly surface‐rooted and the perennial ryegrass, selected for high surface root mass, had more root mass between 0 and 10 cm than did the unselected perennial ryegrass cultivar. There were only small differences in root shape between the other grasses. There was a strong and positive correlation between plant dry weight and the proportion of the pulse of labelled nitrate that was intercepted. The variation in root system shape shown in this experiment had no effect on nitrate interception. Nitrate interception per unit root weight was significantly higher in A. capillaris than in the other grasses. Developing winter‐active grasses that have finely divided root systems should contribute to pastures with better nitrate retention characteristics.     

Anthelmintic resistance and the future for roundworm control

Anthelmintic resistance has emerged as the most important problem confronting the successful control of nematode parasites of grazing animals. Although the significance of the problem varies between, and within, countries and farming enterprises, there is little likelihood that it will disappear of its own accord. On the contrary, it is reasonable to assume that it will increase if there is no change in traditional methods of parasite control. Although progress is being made in non-chemotherapeutic methods of control, these are unlikely to provide any practical alternatives in the short-term future. Nor can the pharmaceutical industry be expected to solve the problem because of the long period and the exceedingly high costs involved in bringing a completely new class of drug on to the market. The answer must lie in carefully husbanding the currently available anthelmintics, by providing farmers with programs which give good levels of parasite control and maintain high productivity in animals with fewer anthelmintic treatments. To be enthusiastically adopted by farmers, the programs require a commitment by both research and advisory workers. Such success can be achieved, as exemplified by the "Drenchplan" and "Wormkill" programs in Australia. It behoves workers in all countries which have a significant grazing livestock industry, not only those with an existing resistance problem, to consider how such schemes could be implemented.