Dietary impacts on the resistance of Merino lambs to Trichostrongylus colubriformis

AIM: To evaluate and compare the effects of a variety of diets on the resistance of young, lightweight Merino lambs to repeated low-dose infections of Trichostrongylus colubriformis.

METHODS: Ninety-six 12-week-old lambs were fed balanced or unbalanced diets, and given primary (at 19 weeks of age) or both primary (at 12 weeks) and secondary (at 19 weeks) infections of T. colubriformis. Suboptimal diets were low in total intake, rumen undegradable protein, total protein, readily available carbohydrate or minerals, or supplemented with cod liver oil. Liveweight was monitored fortnightly, protection was assessed from worm counts at the end of the study (25 weeks) and faecal nematode egg counts (FEC) conducted weekly, and mast-cell response assessed at the conclusion of the study from concentration of mast-cell protease in the jejunum. Concentrations of glucose in plasma were measured at 21 weeks.

RESULTS: Diets unbalanced for total protein, readily available carbohydrate, Mo or cod liver oil each increased the worm counts after 6 weeks of secondary infection (at 25 weeks of age) and FEC during secondary infection. Low intake of a highnutrient diet restricted liveweight gain but did not affect the development of resistance, as indicated by worm counts and FEC. Defi ciency of available carbohydrate resulted in reduced liveweight gain and reduced concentration of glucose in plasma. There was a reduction in jejunal mast-cell protease concentration in sheep fed unbalanced rations.

CONCLUSIONS: The parasitology results and reduction in the concentration of jejunal mast-cell protease observed in sheep fed unbalanced rations suggest that the nutrient defi ciencies and the fi sh-oil supplement may have acted via inhibition or retardation of the host's acquired immune response. Diets unbalanced for a range of components adversely affected the acquired protective response to T. colubriformis to a similar extent and appeared to involve a similar mechanism as each other. The quality of the diet was more important than quantity for the development of resistance, and soluble carbohydrate was an essential component.     

Challenges obtaining a biowaiver for topical veterinary dosage forms

Obtaining a biowaiver for topical drugs used in veterinary species faces many of the same challenges associated with human topicals. However, the skin of domestic animals varies anatomically and biochemically and experimental approaches to assess bioequivalence (BE) in veterinary species have challenges that are not often encountered with human skin. This is especially the situation with locally acting drugs. The focus of this paper is to address several of the challenges associated with (i) determining the BE of these locally acting drugs and (ii) critically examine the current technological advances that can act as a surrogate for clinical trials.     

High-Tc superconductors in the two-dimensional limit:

The free modulation of interlayer distance in a layered high-transition temperature (high-Tc) superconductor is of crucial importance not only for the study of the superconducting mechanism but also for the practical application of high-Tc superconducting materials. Two-dimensional (2D) superconductors were achieved by intercalating a long-chain organic compound into bismuth-based high-Tc cuprates. Although the intercalation of the organic chain increased the interlayer distance remarkably, to tens of angstroms, the superconducting transition temperature of the intercalate was nearly the same as that of the pristine material, suggesting the 2D nature of the high-Tc superconductivity.     

Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission

The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of approximately 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (<2 x 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported.     

Microscale patchiness of nutrients in plankton communities

Autoradiography was used to identify the presence of nutrient patches produced by zooplankton. Algal cells which encounter patches of phosphorus-33 released by swimming animals accumulate more label than cells that do not enter the patches. Differential labeling of algae does not occur when turbulence in the fluid is increased by stirring. Nutrient patchiness at the scale of millimeters or less in nature probably influences the course of competition and coexistence among the phytoplankton.