Focus on polar research

A few of the scientific challenges of polar research are reviewed, with stress on the work being done by U.S. investigators. The accomplishments that have been made are impressive, but much remains to be done. An evaluation of future research goals and priorities in science per se and in the national interest is not attempted, but a research strategy for the future, presently planned by the National Research Council's Polar Research Board, should contribute to this end.     

Intussusception following renal transplantation in dogs (author's transl)]

In a consecutive and non-selected study of 54 kidney transplanted dogs, 12 cases of intussusception of the small intestine developed in 8 dogs. The patogenesis is still unknown. It has been postulated that the time of the operation (4--7 hours) and the segmental termination of the post-operative atony in the intestine are essential factors in this fatal complication. The last 16 dogs in this material were peroperatively treated with antikolinergics (Mestinon NFN), which was continued until normal function of the intestine. In these dogs there were no evidence of intussusception. The value of this profylaxis is open to discussion and it is essential to solve the problem of intussusception through a "blind" and controlled trial.     

Alternative complement pathway in bovine serum: lysis of human erythrocytes.

The hemolysis of unsensitized human erythrocytes by fresh bovine serums was investigated. Lysis occurred in ethylene glycol bis-amino tetraacetate buffers and with serums depleted of Clq. Serums extensively absorbed with packed human erythrocytes at 0 C effectively lysed human erythrocytes, but optimal lytic capacity required target cells "sensitized" with a heat-stable serum factor. Lysis did not occur with serums absorbed with zymosan at 17 C or heat inactivated at 50 C. These results indicate that human erythrocytes can activate the alternative pathway of complement in bovine serums. Lysis can proceed in the apparent absence of antibodies, although their presence may enhance the reaction.     

Host parasite relationships in Trypanosoma (duttonella) vivax with special reference to the influence of antigenic variation

A mouse model system was used to study various aspects of host and parasite relationships in Trypanosoma vivax infections. These included the phenomenon of antigenic variation, the variable parasite antigens responsible for this phenomenon, parasite-host adaption, host immune responses and the role of genes in the major histocompatibility complex in the control of infection. While the mouse model system has allowed investigation of these aspects of host parasite relationships, it is clear that the system is much more limited than those generally used in T. brucei spp and T. congolense infections. This is indicated by the discovery that not all VATs of T. vivax were equally infective for mice, though in some cases infectivity could be improved by bovine serum supplementation and/or immunosuppression of the mouse host. In the case of rats, infection was even restricted to a smaller number of the VATs studied. It was, however, possible to biochemically characterize the variable surface antigen carried by T. vivax and show its similarity to those carried by T. brucei and T. congolense. The H-2 complex was found not to influence acquired resistance of inbred strains. Cyclic transmissions of T. vivax infections to goats combined with chemotherapy were carried out in an attempt to induce protection to subsequent infection as has been shown in T. brucei and T. congolense infections. Such protection could, however, not be obtained, The failure of the metacyclic VATs to induce immunity, was perhaps due to rapid decrease in antibody titres to bloodstream VATs found after treatment and prior to rechallenge. The usefulness of the mouse model system in elucidating the mechanisms responsible for the non-H-2 linked differences in susceptibility to T. vivax infections should be further explored and its relevance to mechanisms of trypanotolerance in domestic ruminants defined.     

Effect of Tomanol on the pharmacokinetics and tissue distribution of penicillin G in dairy cows

Following concomitant intravenous administration of Tomanol and sodium penicillin G to six Dutch Friesian dairy cows a significant decrease in total body clearance of penicillin (34.7%) and a prolongation of the elimination half-life of penicillin (17.2%) was observed. Tomanol did not affect other pharmacokinetic parameters such as rate constants of drug transfer (k12/k21, alpha en beta), distribution volume of the central compartment (V1), and extrapolated serum drug levels. Intravenous or intramuscular administration of Tomanol had no effect on the tissue distribution of penicillin G, because neither a change in the ratios of muscle to serum and of kidney cortex to serum nor a change in an induced steady state level of low penicilline G serum concentrations was observed. From the data obtained it is concluded that concomitant Tomanol administration with penicillin induces an elevation of the serum penicillin concentration and prolongs the persistence of penicillin residues in carcass meat and organs.     

Aspects épizootiologiques des affections respiratoires porcines qui sévirent au Québec, de septembre 1980 à février 1981

Epizootiological aspects of porcine respiratory diseases which were encountered in Quebec from September 1980 until February 1981     

The shape of the response curve relating protein intake to egg output for flocks of laying hens

1. Two experiments were conducted to test the hypothesis that, as dietary protein concentration is increased, increments of response gradually diminish as egg output approaches an asymptotic value; and that the resulting response curve is consistent with a model (the “Reading model”) which assumes that the shape of the curve is a function of individual variation in body weight and potential egg output.

2. Each experiment involved a total of 3 888 laying pullets. Nine diets, with crude protein contents ranging from 87 to 212 g/kg, were used in the first experiment and ten diets, with protein contents ranging from 81 to 215 g/kg, in the second experiment. Diets were denned in terms of their calculated contents of essential amino acids and the same, well‐balanced amino acid profile was used at all protein contents within one experiment. Supplementary experiments were conducted to identify the limiting amino acid (s) in the experimental diets.

3. Treatments were applied for ten weeks, starting at 30 or 32 weeks of age. Average egg output on the highest protein diets was 57.0 g/bird d in the first experiment, which used White Leghorn pullets, and 53.7 g/bird d in the second experiment, which used a crossbred brown‐egg stock.

4. The response curves obtained showed diminishing returns and, in the second experiment, a clear plateau was reached. The Reading model was fitted and compared with a two‐straight‐line model and with curves derived from quadratic and inverse polynomial equations. Only the Reading model proved satisfactory for the interpretation of the data, as judged by goodness of fit and estimation of the optimum amino acid input. Although alternative models may provide a good fit when dealing with a single set of data, none of the alternatives is consistently satisfactory when considering the results of more than one experiment.