Rubber production of salt-stressed guayule at various plant populations

Summary The hypothesis that increasing the plant population of guayule (Parthenium argentatum) to compensate for the reduced plant canopy size caused by soil salinity coupled with an anticipated enchancement of rubber production under the moderate environmental stress imposed by salinity was tested in a field plot experiment in the Imperial Valley of California. Irrigation waters having electrical conductivities (EG _i ) of 1.2, 3.2, 6.5, and 9.4 dS/m were applied for 4 years to plots having plant populations of 28,000, 56,000, and 84,000 plants per hectare. The influence of salinity on rubber and resin production was independent of plant population. The salt tolerance threshold, maximum average salinity level of the root zone measured as the electrical conductivity of saturated soil extracts ( ) without yield reduction, was 7.5 dS/m; beyond this threshold, rubber production was reduced 6.1% per unit increase of soil salinity. The salinity values were averaged through the root zone from planting to harvest. The average rubber content — 7.9% — was altered little by treatment or harvest age for 2- to 4-year-old plants. Resin content averaged 8.4% but increased salinity and increased plant population increased the resin content slightly in some cases. Dry matter production of shoots for the nonsaline treatment was 259 kg/ha/month for pollarded (clipped) shoots after 31 months, 203 kg/ha/month for shoots harvested after 43 months, and 401 kg/ha/month for the 24-month period after pollarding. Combining the shoot mass after 31 and 55 months gave an average growth rate of 321 kg/ha, supporting the recommendation for pollarding. Monthly growth rates for the lowest salt treatment (3.2 dS/m) were about 10% less than for the nonsaline treatment (1.2 dS/m). The hypothesis tested was proven to be false because neither increased salinity nor increased plant population increased rubber production.     

Comparison of opioid and alpha-2 adrenergic receptor location and density in the horse and dog using radioligand binding

Ketamine, a noncompetitive NMDA receptor antagonist, has been shown to provide analgesia in some species. To target the NMDA receptor specifically and to potentially minimize some untoward side-effects, ketamine had been used epidurally. The objective of this study was to determine the analgesic effect of epidurally administered ketamine in dogs with chemically induced synovitis.
Sixteen healthy dogs were used. Dogs were anesthetized with propofol (4 mg kg⁻¹ IV). Synovitis was induced by injecting 1 mL of sodium urate crystal solution (10 mg mL⁻¹) into the right stifle. Dogs were allowed to recover and the synovitis was allowed to develop for 12 hours. The dogs were then anesthetized again using propofol (4 mg kg⁻¹ IV). Lumbosacral epidural injections were performed with each dog receiving either 2 mg kg⁻¹ of ketamine (20 mg mL⁻¹) or an equal volume of placebo (sterile water containing not more than 0.1 mg mL⁻¹ benzethonium chloride). Analgesia was assessed at baseline and then at 12, 14, 16, 18, 20, and 24 hours after induction of synovitis. Ground reaction forces (peak vertical force and impulse area) and overall pain were measured using a force platform and a pain scoring system (numerical rating scale).
Analysis of the data by Repeated Measures anova showed that the dogs developed a significant lameness between the baseline and 12 hours. However, no significant difference in ground reaction forces or total pain score was demonstrated between the treatment and control groups at any other time.
In conclusion, ketamine administered epidurally at a dose of 2 mg kg⁻¹ did not provide significant analgesia in dogs with chemically induced synovitis.     

The control of lymphoid leukosis in a flock White Plymouth Rock chickens

Summary

Lymphoid leukosis (LL) was successfully controlled in a commercial basic breeding line of White Plymouth Rock chickens. The control method has been developed for breeder flocks and consists of three elements: - In the flock under study, homogenates of embryos from all eggs collected during a number of I4‐day periods are tested for the presence of LL viruses.

- Only eggs from hens that have been shown not to shed virus in their eggs are used for the production of progeny. The offspring are reared in isolation during the first two months of life, at which time the age‐related resistance against tumour formation by LL viruses appears to be sufficiently developed.

- The chickens are subsequently inoculated intramuscularly with LL viruses of subgroups A and B transferred to a conventional chicken house.

The vaccination raises a solid immunity to horizontal LL virus exposure and, due to the age‐related resistance, tumour formation does not follow.

No excretion of LL viruses could be detected in three generations of White Plymouth Rock chickens to which the three elements of the control procedure were applied. Clinical disease was not observed in any of the chickens under notice.