NEUROSPORA MUTANT LACKING AN ARGININE-SPECIFIC CARBAMYL PHOSPHOKINASE

An arginine-requiring mutant of Neurospora lacks the carbamyl phosphokinase activity present in other strains. Although carbamyl phosphate, the product of this enzyme, is required in both arginine and pyrimidine synthesis, the enzymne appears to serve only the arginine pathway. A pyrimidine specific mode of carbamyl phosphate synthesis is inferred, although it has not yet been demonstrated.     

Behavioural determinants of distribution and survival in early stages of walleye pollock, Theragra chalcogrammai a synthesis of experimental studies

This review summarizes results of an extensive series of laboratory studies on the behavioural responses of early life stages of walleye pollock, Theragra chakogramma to key environmental factors including light, temperature, gravity, turbulence, food availability and predator presence. Experiments focused on vertical distribution of egg through 0-age stages, and social interactions of age-0 juveniles. Key factors were modified either singly or in concert to determine their direct and indirect influence on fish behaviour. The observed results suggest that the behaviour of individual fish depends on the integration of a continually changing hierarchy of both intrinsic and extrinsic factors, with the relative importance of a specific factor varying with ontogeny and over time and space. The broad range of responses displayed by early life stages suggests that behaviour plays an important role in determining the consequences of environmental variability on walleye pollock populations. In general, results from our laboratory experiments are consistent with patterns observed in field studies, supporting the efficacy of using experimental behavioural research to define some of the underlying mechanisms controlling distribution and survival in the field, and eventual recruitment to adult populations.     

The enhancement of resistance of the American eel, Anguilla rostrata Le Sueur, to a pathogenic bacterium, Aeromonas hydrophila, by an extract of the tunicate, Ecteinascidia turbinata

Abstract. Extracts of the tunicate Ecteinascidia turbinate were used in preventing Aeromono hydrophila infection in the American eel, Anguilla rostrata. Intraperitoneal injection of the extract 2 days after bacterial challenge was shown to increase dramatically eel phagocytic activity and resistance to disease. Intravenous injection of the extract 2 days post-bacterial injection was shown to increase antibody titres. This study helps to substantiate the possible use of E. turbinata extract in treating eel diseases. The exact nature of its protective effect will be dependent on the time and route of its delivery.     

Pharmacokinetics and elimination of salicylic acid in rabbits

Sodium salicylate was administered to rabbits in order to compare its disposition with that in other major and minor agricultural species. A dose of 44 mg/kg was given orally (p.o.) or intravenously (i.v.), and plasma and urine samples were collected for 36 h and 96 h, respectively. The majority of the drug was excreted as salicylic acid (SA) within 12 h. The major metabolites following an oral dose were salicyluric acid (SUA) and the glucuronide conjugates of SA and SUA. Following i.v. dosing, sulfate conjugates of both SA and SUA were also evident. Both SA and SUA were detected in plasma. Following i.v. administration, SA was distributed with a Vss of 0.249 +/- 0.082 l/kg and cleared at a rate of 0.0432 +/- 0.006 l/h/kg. The biological half-life, calculated from the terminal disposition-rate constant, was 4.3 h (i.v.) or 9.7 h (p.o.). The urinary elimination pattern of SA and metabolites in the rabbit was similar to that previously reported by our laboratories for cattle and goats, although total recovery of the administered dose was not as high as for the latter two species. However, the volume of distribution was larger than for cattle and goats, and rabbits cleared the drug more slowly than those species. As a consequence, the biological half-life was eight to ten times longer than in the ruminants studied previously.