The Atmospheric and Environmental Research, Inc., photochemical model has been used to simulate the concentrations and time development of key trace gases in the Antarctic stratosphere before, during, and after the Airborne Antarctic Ozone Experiment (AAOE). The model includes complete gas phase photochemistry and heterogeneous reactions of C1NO 3 (g) and N205 (g) with HC1 (s) and H20 (s). Observations of long-lived species by the AAOE instruments have been used to constrain the initial conditions in our calculations. We present results from four cases illustrating the evolution of the trace gases for a range of possible initial conditions and duration of heterogeneous activity. The amount of C10 produced by heterogeneous conversion of HC1 is determined not only by the initial concentrations of NOx (NO + NO2 + NO3), N205, and C1NO 3 during winter, but also by the rate at which NOx is resupplied by photolysis of N205 and HNO3, or by transport. Results from the four cases presented bracket column measurements of HC1, C1NO3, and HNO 3 by the Jet Propulsion Laboratory and National Center for Atmospheric Research infrared spectrometers onboard the NASA DC-8, and in situ measurements of C10 and NOy by instruments aboard the NASA ER-2. Comparison of results and measurements of HC1 and C10 suggests that heterogeneous chemistry was maintained throughout the month of September in 1987. We suggest field observations and kinetic data which would further constrain the photochemistry of the spring Antarctic stratosphere. The behavior of ozone is discussed in a companion paper (Ko et al., this issue). 1. 1986; Bojkov, 1986], of satellite data [Stolarski et al., 1986; Krueger et al., 1987] and of balloon measurements [Chubachi, 1984; Holmann et al., 1986, 1987] has established beyond doubt the existence and extent of the so-called "ozone hole" during Antarctic spring, and the decreasing trend of the October minimum values during the past 10 years. These observations have greatly intensified research activities in stratospheric ozone and led to a reevaluation of recent ozone trends at other latitudes [NASA, 1988]. The first National Ozone Expedition (NOZE I) conducted ground-based and balloon measurements from McMurdo station, Antarctica, during the austral spring.of 1986. Balloon measurements from this campaign confirmed the occurrence of large depletions of ozone between 12 and 20 km, often exhibiting a layered structure [Hofmann et al., 1987]. Measurements of the column abundances of C10, OC10, NO2, NO, HNO3, HC1, and C1NO3 indicated a highly perturbed chemical composition, unlike any other environment on Earth. In particular, concentrations of C10 and OC10 were about a factor of 100 higher than predicted by models [P. Solomon et al., 1987; de Zafra et al., 1987; S. Solomon et al., 1987], while column abundances of NO2, HC1, and HNO3 were considerably reduced [Mount et al., 1987; Farmer et al., 1987]. Column densities of C1NO3 as high as 4 x 1015 cm -2 were observed by the Jet Propulsion 16,683 16,684 RODRIGUEZ ET AL.: COMPARI...

We determined the differential response of a novel SERM, SP500263, on estrogen receptor (ER) ␣ and the more recently cloned ER-␤. Because of the high homology of amino acid residues in the ligand-binding domain of ER-␣ and ER-␤, we were not surprised to find that SP500263 binds to both ERs equally well. In contrast, SP500263 acts as a strong estrogen agonist in a strictly ER-␣-specific manner in U2OS osteosarcoma cell lines blocking the production of interleukin (IL) 6 and granulocyte macrophage colony-stimulating factor. SP500263 also blocked IL-6 production in primary bone cells. The mechanism of this inhibition is different from the classic estrogen stimulation involving an estrogen response element (ERE). SP500263 does not activate gene expression through an ERE.In contrast to the results observed in U2OS cells, SP500263 acts as a strong estrogen antagonist in an MCF-7 breast cancer proliferation assay. Therefore, SP500263 is a member of a series of next-generation SERMs with functional selectivity toward ER-␣ and a mixed agonist/antagonist profile in a bone cell assay versus a breast cancer assay. The panel of assays described herein allow for the development of receptor-specific ligands that may be further developed into novel pharmaceuticals with an improved profile for the treatments of osteoporosis and breast cancer.

No abstract