A novel genome-wide screen that combines patient outcome analysis with array comparative genomic hybridization and mRNA expression profiling was developed to identify genes with copy number alterations, aberrant mRNA expression, and relevance to survival in glioblastoma. The method led to the discovery of physical gene clusters within the cancer genome with boundaries defined by physical proximity, correlated mRNA expression patterns, and survival relatedness. These boundaries delineate a novel genomic interval called the functional common region (FCR). Many FCRs contained genes of high biological relevance to cancer and were used to pinpoint functionally significant DNA alterations that were too small or infrequent to be reliably identified using standard algorithms. One such FCR contained the EphA2 receptor tyrosine kinase. Validation experiments showed that EphA2 mRNA overexpression correlated inversely with patient survival in a panel of 21 glioblastomas, and ligand-mediated EphA2 receptor activation increased glioblastoma proliferation and tumor growth via a mitogen-activated protein kinase-dependent pathway. This novel genome-wide approach greatly expanded the list of target genes in glioblastoma and represents a powerful new strategy to identify the upstream determinants of tumor phenotype in a range of human cancers. (Cancer Res 2006; 66(22): 10815-23)

We recorded the a‐wave of the human electroretinogram from subjects with normal vision, using a corneal electrode and ganzfeld (full‐field) light stimulation. From analysis of the rising phase of rod‐isolated flash responses we determined the maximum size (amax) of the a‐wave, a measure of the massed circulating current of the rods, and the amplification constant (A) of transduction within the rod photoreceptors. During light adaptation by steady backgrounds the maximal response was reduced, as reported previously. amax declined approximately as I0/(I0+IB), where IB is retinal illuminance and I0 is a constant. In different subjects I0 ranged from 40 to 100 trolands, with a mean of 70 trolands, corresponding to about 600 photoisomerizations s−1 per rod. (1 troland is the retinal illuminance that results when a surface luminance of 1 cd m−2 is viewed through a pupil area of 1 mm2.) The amplification constant A decreased only slightly in the presence of steady backgrounds. Following a full bleach amax recovered along an S‐shaped curve over a period of 30 min. There was no detectable response for the first 5 min, and half‐maximal recovery took 13‐17 min. The apparent amplification constant decreased at early times after large bleaches. However, upon correction for reduced light absorption due to loss of pigment, with regeneration of rhodopsin occurring with a time constant of 9‐15 min in different subjects, it appeared that the true value of A was probably unchanged by bleaching. The recovery of amax following a bleach could be converted into recovery of equivalent background intensity, using a ‘Crawford transformation’ derived from the light adaptation results. Following bleaches ranging from 10 to > 99 %, the equivalent background intensity decayed approximately exponentially, with a time constant of about 3 min. The time taken for amax to recover to a fixed proportion of its original level increased approximately linearly (rather than logarithmically) with fractional bleach, with a slope of about 12 min per 100 % bleach. Similar behaviour has previously been seen in psychophysical dark adaptation experiments, for the dependence of the ‘second component’ of recovery on the level of bleaching.

Double-flash techniques have been used for decades to monitor the recovery of the a-wave and b-wave of the electroretinogram (ERG) following a first flash (e.g. Dodt, 1952;Mahneke, 1957;Burian & Spivey, 1959;Elenius, 1967Elenius, , 1969Gjötterberg, 1974). In the 1960s, it became clear that the a-wave of the ERG reflected photoreceptor activity (Brown & Wiesel, 1961), though it was not until the 1990s that quantitative analysis of the a-wave provided a faithful measure of photoreceptor currents (see, for example, Hood & Birch, 1990. Even so, the a-wave itself only provides information about photoreceptor currents at the very earliest times after a flash, before the b-wave and other post-receptoral signals intrude.With the insight provided by recent knowledge, several groups have monitored photoreceptor responses at later times, by recording the a-wave elicited by what has become known as a 'paired-flash' stimulus, in which an arbitrary test flash is followed at a range of time intervals by an intense probe flash (in human: Birch et al. 1995;Pepperberg et al. 1996Pepperberg et al. , 1997Cideciyan et al. 1998; in mouse: Lyubarsky & Pugh, 1996;Goto et al. 1996;Hetling & Pepperberg, 1999; reviewed in Pepperberg et al. 2000). In this technique, the amplitude of the response to the intense probe flash (i.e. the maximal response that can be elicited) provides a measure of the remaining circulating current in the photoreceptors at a particular time after the test flash. Although the method is tedious, in requiring numerous repetitions with different intervals between test and probe flashes, it currently provides the only means for extracting the response from photoreceptors in the living eye, at more than about 10 ms after a flash. 1. The a-wave of the electroretinogram was recorded from human subjects with normal vision, using a corneal electrode and ganzfeld stimulation. We applied the paired-flash technique, in which an intense 'probe' flash was delivered at different times after a 'test' flash. The amplitude of the probe-flash response provided a measure of the circulating current remaining at the appropriate time after the test flash.2. We extended previous methods by measuring not at a fixed time, but at a range of times after the probe flash, and then calculating the ratio of the 'test-plus-probe' response to the 'probealone' response, as a function of time.3. Under dark-adapted conditions the rod response derived by the paired-flash technique (in response to a relatively dim test flash) peaked at ca 120 ms, with a fractional sensitivity at the peak of ca 0.1 Td _1 s _1 .4. As reported previously, background illumination reduced the maximal response, reflecting a reduction in rod circulating current. In addition, it shortened the time to peak (to ca 70 ms at an intensity of 170 Td), and reduced the flash sensitivity measured at the peak. The flash sensitivity declined approximately according to Weber's Law, with a 10-fold reduction occurring at an intensity of 100-200 Td. We could not reliably measure responses ...