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The method can therefore be extended to the characterization of outdoor wideband radio channels. This characterization was previously an expensive task, since it required the use of specific and highly sophisticated instruments.Taking into account that the error committed for margins between 90 and 95% of the locations is between 15 and 20%, the method has a high value in the planning of existing wireless systems or the development of new systems. Furthermore, the data presented in the Letter provide useful information on bands of 1.8 and 2.45 GHz.

Administration of epidermal growth factor (EGF) to neonatal mice resulted in rapid tyrosine phosphorylation of a number of specific substrates in liver, kidney, lung, bladder, skin, and brain as detected by Western blot analysis of tissue homogenates with anti-phosphotyrosine antibodies. In the liver, three prominent EGF-dependent substrates of Mr 170,000, 120,000, and 55,000 were detected. A number of less prominent EGF-dependent substrates also were noted. Maximal tyrosine phosphorylation of ppl7O, pp120, and pp55 occurred within 5 min of subcutaneous injection and the levels of these phosphoproteins remained elevated for at least 45 min.Direct hepatic injection of EGF resulted in the tyrosine phosphorylation of these substrates within 60 sec of treatment. Tyrosine-phosphorylated ppl70 was identified as the EGF receptor (EGFR). The tyrosine-phosphorylated pp55 substrate appeared to be associated with EGFR; both ppS5 and EGFR were adsorbed to EGF-Affi-Gel, wheat germ lectin-Sepharose, and anti-EGFR antibodies bound to protein A-Sepharose. ppS5 was not immunoreactive with anti-EGFR antiserum by Western blot analysis, indicating that it was not a fragment of the receptor. These results were confirmed by repeating the liver experiments using 32P-labeled neonatal mice. Increased amounts of 32P-labeled ppl70 and pp55 were detected in anti-EGFR immunoprecipitates from liver extracts of EGFtreated animals as compared with controls. Phospho amino acid analysis of the 32P-labeled phosphoproteins revealed that EGF stimulated both serine and tyrosine phosphorylation in pp55 as well as in EGFR. The neonatal mouse may be a useful model for the study ofsignal transduction mediated by a variety of growth factors.The administration of epidermal growth factor (EGF) to newborn or adult animals evokes a wide variety of morphological and physiological responses. These include such diverse effects as increased cell proliferation in skin and other organs as well as inhibition ofgastric acid secretion (reviewed in refs. 1-3).At the cellular level, the receptor for EGF (EGFR) is a 170-kDa transmembrane glycoprotein with intrinsic proteintyrosine kinase activity. The binding of EGF to its receptor results in the activation of its tyrosine kinase activity and the phosphorylation of a number of intracellular substrates as well as the receptor itself (reviewed in refs. 4-6).Many studies have addressed the question of the nature and function of protein substrates that are phosphorylated on tyrosine in the presence of an activating ligand. Among the substrates that have been implicated are phospholipase Ca1, GTPase-activating protein (GAP), protein-serine kinases, phosphatidylinositol 3-kinase, structural proteins such as vinculin and talin, and proteins of unknown physiological function such as lipocortin (reviewed in refs. 7-9). Almost all of these studies have employed a variety of cell culture systems to detect these putative signal-transducing molecules.We have begun studies to examine both the normal physiological role of EGF ...