Cobalt accumulation in horses following repeated administration of cobalt chloride.

OBJECTIVE: To monitor cobalt concentrations in urine, red blood cells and plasma after chronic parenteral administration of cobalt chloride evaluate these results against the current International Federation of Horseracing Authorities thresholds for detecting cobalt misuse. DESIGN: Eight mares were randomly assigned to four treatment groups, with two mares in each group: Group 1 - control group, Group 2 - 25 milligrams cobalt intravenously as CoCl2 weekly, Group 3 - 50 milligrams cobalt intravenously as CoCl2 weekly, and Group 4 - 25 milligrams cobalt intravenously mid-week and at the end of the week. Urine and blood samples were collected before each weekly administration so that trough levels were assessed. In the group receiving two doses per week, urine and blood were collected prior to the dose given at the end of each week. Samples were initially collected at time zero then weekly for 10 weeks. Three further collections of urine and blood were made at days 81, 106 and 127. METHODS: Urine creatinine measurements to assess horse hydration status were performed by the Jaffe reaction method. Cobalt determinations in plasma, blood and urine were by inductively coupled plasma-mass spectrometry. Haematocrit concentrations, used to calculate red cell cobalt levels, were performed using a microhematocrit centrifuge. Statistical analyses were conducted in Genstat (v17, VSNi). RESULTS: Marked cobalt accumulation was evident with increasing cobalt concentrations for all sample matrices in specimens collected immediately prior to cobalt administration. Correlation between the sample matrices improved when urine cobalt concentration was adjusted for creatinine level. Red cell cobalt levels remained elevated for at least 12 weeks after cessation of administration, consistent with the lifespan of the red cell. There was no significant change in haematocrit concentrations for the duration of the study. CONCLUSION: The current urine cobalt threshold was only effective at detecting acute cobalt exposure while the plasma cobalt threshold was able to consistently identify chronic high-level cobalt exposure and potential cobalt misuse. The threshold values legislated for urine cobalt do not correlate with those set for plasma. The acute nature of urinary cobalt excretion provides a relatively small window through which cobalt administration is detected. Plasma and red cell cobalt concentrations can provide a clearer picture of potential cobalt misuse.

Efficient stimulated Raman scattering due to absence of second Stokes growth.

Stimulated Raman scattering of a XeCl laser at 308 nm in a high-pressure H(2) cell shows high conversion into first Stokes (S1) because of an unexpected holdoff of the second Stokes (S2) component. Specifically, a photon efficiency of 88% is obtained into S1. Comparison with a plane-wave model indicates that a theory including a spatially nonuniform gain and higher-order mode generation may be necessary to understand the holdoff of the S2 growth.

Parametric oscillator: HF oscillator-amplifier pumped CdSe parametric oscillator tunable from 14.1 microm to 16.4 microm.

A singly resonant CdSe parametric oscillator with tunable output from 14.1 microm to 16.4 microm is described. The oscillator, pumped by the 2.87-microm line from an HF oscillator-amplifier, is resonant on the signal near 3.5 microm and has produced idler outputs of 100 microJ at 16 microm. Bandwidths varied over the tuning range from 9 cm(-1) to 1.8 cm(-1). Techniques for obtaining a highly coherent HF laser pump beam are presented. The uniform beam from the gain-saturated amplifier allows the use of Fresnel diffraction theory to produce a nearly uniform pump beam at the oscillator cavity.