Carbon monoxide measurements in the troposphere

During the second flight of the space shuttle, the measurement of air pollution from satellites (MAPS) experiment in the OSTA-1 payload acquired approximately 35 hours of radiometric measurements of the carbon monoxide mixing ratio in the middle troposphere, upper troposphere, and lower stratosphere. A gas filter radiometer operating in the 4.67-micrometer band was used to acquire the data over the region from 38 degrees N to 38 degrees S during both daytime and nighttime. The performance of the measurement system was excellent. The data reduced to date indicate the presence of significant gradients in the middle tropospheric carbon monoxide mixing ratio with both latitude and longitude over the North Atlantic, the Mediterranean Sea, and the Middle East. On the basis of comparisons with directly measured values, the accuracy of the measurements is approximately 15 percent. Comparisons of data taken on successive orbits over the same geographic region indicate that the repeatability of the measurements is approximately 5 percent.     

Effects of delay in reapplication of nitrogen fertilizer following cutting silage from a ryegrass sward

Plots of a 2-year-old sward of Merlinda perennial ryegrass received a routine dressing of 100 kg N ha⁻¹ as compound fertilizer in March 1991, followed by further dressings of 100 kg N ha⁻¹ after cuts 1, 2 and 3 in a simulated four-cut silage system, either the same day as cutting or with a delay of 3, 7, 10 or 14 d. Partial irrigation ensured that fertilizer could be taken up immediately. Annual total dry matter yield, the dry matter yield for the experimental cuts 2–4 and their apparent response to N showed no effect of delays of 0–10 d in reapplication of fertilizer, but a significant ( P < 0·01) reduction for 14 d delay. Significantly ( P = 0·001) higher apparent recovery of N in the cut herbage was recorded where reapplication of fertilizer had been delayed by 7 or 10 d (93% and 91% respectively) in comparison with either smaller (0 delay, 78%; 3 d delay, 87%) or greater delay (14 d, 86%). It is suggested that lower recoveries at 0 and 3 d result from the sward's reduced NO₃ uptake following defoliation and that, while in practical situations the conditions may not be as rigorous as those imposed in this experiment, further experiments to determine the fate of N not recovered in the herbage are warranted, so defining management circumstances in which immediate reapplication of N might not be advisable.     

Refinement of an orthotopic lung cancer model in the nude rat

Over 85% of people with lung cancer eventually succumb to this disease, largely because current chemotherapies are ineffective. The testing and validation of promising new approaches generally rely on achieving responses with cell lines in vitro or in tumor xenografts in nude mice. However, quite often the results seen with these models are not recapitulated in the clinic, thus necessitating the need for better animal models of lung cancer for preclinical testing of new therapies. One promising model is that of orthotopic lung cancer, where xenografts of human lung cancer are established in lungs of immunodeficient rodents. The problems associated with this model include poor rates of engraftment, limited tumor multiplicity, and a heightened risk for surgical trauma. The purpose of our study was to develop an efficient approach to engraftment of orthotopic tumors throughout the lungs of the Rowett nude rat. Initially, we augmented immunosuppression in the rats with whole-body X-irradiation and then used orotracheal cannulas to intratracheally instill human cancer cells from the Calu-6 cell line. This protocol produced a low rate of engraftment and low tumor multiplicity. The hypothesis that slight disruption of the pulmonary epithelium or the surfactant layer would allow better tumor engraftment was tested by coadministration of either pancreatic elastase or ethylenediaminetetraacetic acid (EDTA) along with the cell instillations. Lung tumor engraftment was evaluated 8 weeks after instillation. The inclusion of elastase or EDTA with the Calu-6 cells resulted in an 80-100% engraftment rate, respectively. Coadministration of EDTA resulted in significantly larger and greater numbers of tumors/lung than those in elastase-treated animals. Temporal studies demonstrated that small nodules were scattered throughout the lung parenchyma 5 weeks after instilling Calu-6 cells and EDTA. These nodules grew to coalesce and form large masses that effaced >75% of the parenchyma at 9 weeks postinstillation. The refinements made through our studies have led to the development of an orthotopic lung cancer model that should facilitate the evaluation of novel therapies designed to treat or impede lung cancer development.     

Changes in volatile terpene and diterpene resin acid composition of resistant and susceptible white spruce leaders exposed to simulated white pine weevil damage

Induced (traumatic) resin in white spruce (Picea glauca (Moench) Voss) leaders resistant or susceptible to the white pine weevil (Pissodes strobi Peck) was analyzed for volatile terpenes and diterpene resin acids after simulated white pine weevil damage. Leaders from 331 trees were wounded just below the apical bud with a 1-mm diameter drill, coinciding with the natural time of weevil oviposition in the spring. Leaders were removed in the fall, and the bark and xylem from the upper and lower regions of the leader extracted and analyzed by gas chromatography. Unwounded trees had low amounts of resin in xylem compared with bark. In response to wounding, volatile terpenes and diterpene resin acids increased in the upper xylem (area of wounding), with resistant trees showing a greater increase than susceptible trees. Wounding caused monoterpenes in particular to decrease in the lower region of the leader (away from the drilled area) in greater amounts in susceptible trees than in resistant trees. In response to wounding, the proportion of monoterpene to resin acid increased in the upper and lower xylem of resistant trees, and slightly increased in the upper xylem of susceptible trees. Monoterpene-enriched resin is more fluid than constitutive resin, and probably flows more readily into oviposition cavities and larval mines, where it may kill immature weevils. Loss of resin components in the lower xylem suggested catabolism and transport of these materials to the site of wounding; however, energetic and regulatory data are necessary to confirm this hypothesis. This study provides a basis for measuring the ability of a tree to undergo traumatic resinosis that could be used to screen for resistance to white pine weevil.