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Mouse olfactory receptor proteins have relatively broad odorant tuning profiles, so single odorants typically activate a substantial subset of glomeruli in the main olfactory bulb, resulting in stereotyped odorant- and concentration-dependent glomerular input maps. One of the functions of the olfactory bulb may be to reduce the extent of this rather widespread activation before transmitting the information to higher olfactory centers. Two circuits have been studied in vitro that could perform center-surround inhibition in the olfactory bulb, one circuit acting between glomeruli, the other through the classical reciprocal synapses between the lateral dendrites of mitral cells and the dendrites of granule cells. One unanswered question from these in vitro measurements was how these circuits would affect the response to odorants in vivo. We made measurements of the odorant-evoked increase in calcium concentration in the olfactory receptor neuron terminals in the anesthetized mouse to evaluate the role of presynaptic inhibition in reshaping the input to the olfactory bulb. We compared the glomerular responses in 2- to 4-wk-old mice before and after suppressing presynaptic inhibition onto the receptor neuron terminals with the GABAB antagonist, CGP46381. We find that the input maps are modified by an apparent center-surround inhibition: strongly activated glomeruli appear to suppress the release from receptor neurons terminating in surrounding glomeruli. This form of lateral inhibition has the effect of increasing the contrast of the sensory input map.

This paper presents three examples of imaging brain activity with voltage- or calcium-sensitive dyes and then discusses the methodological aspects of the measurements that are needed to achieve an optimal signal-to-noise ratio. Internally injected voltage-sensitive dye can be used to monitor membrane potential in the dendrites of invertebrate and vertebrate neurons in in vitro preparations. Both invertebrate and vertebrate ganglia can be bathed in voltage-sensitive dyes to stain all of the cell bodies in the preparation. These dyes can then be used to follow the spike activity of many neurons simultaneously while the preparations are generating behaviors. Calcium-sensitive dyes that are internalized into olfactory receptor neurons in the nose will, after several days, be transported to the nerve terminals of these cells in the olfactory bulb. There they can be used to measure the input from the nose to the bulb. Three kinds of noise are discussed. a. Shot noise from the random emission of photons from the preparation. b. Vibrational noise from external sources. c. Noise that occurs in the absence of light, the dark noise. Three different parts of the light measuring apparatus are discussed: the light sources, the optics, and the cameras. The major effort presently underway to improve the usefulness of optical recordings of brain activity are to find methods for staining individual cell types in the brain. Most of these efforts center around fluorescent protein sensors of activity.

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Purpose We sought to evaluate correlation between tissue biomarker expression (using standardized, quantitative immunofluorescence) and clinical outcome in E2303 trial. Experimental Design Sixty-three eligible patients with operable stage III/IV HNSCC participated in ECOG 2303, phase II trial of induction chemotherapy with weekly cetuximab, paclitaxel and carboplatin followed by chemoradiation with same regimen. A tissue microarray (TMA) was constructed and epidermal growth factor receptor (EGFR), ERK1/2, Met, Akt, STAT3, β-catenin, E-cadherin, EGFR Variant III, insulin-like growth factor-1 receptor, NF-kappa b, p53, PI3Kp85, PI3Kp110a, PTEN, NRAS, and pRb protein expression levels were assessed using automated quantitative protein analysis (AQUA). For each dichotomized biomarker, overall survival (OS), progression-free survival (PFS) and event-free survival (EFS) were estimated by Kaplan-Meier method and compared using log-rank tests. Multivariable Cox proportional hazards models were used to estimate hazard ratios (HR) and test for significance. Results Forty-two of 63 patients with TMA data on at least one biomarker were included in the biomarker analysis. Tumor ERK1/2 levels were significantly associated with PFS (HR (low/high)=3.29, p=0.026) and OS (HR (low/high)=4.34, p=0.008). On multivariable Cox regression analysis, ERK1/2 remained significantly associated with OS (p=0.024) and PFS (p=0.022) after controlling for primary site (oropharynx vs. non-oropharynx) and disease stage (III vs. IV), respectively. Clustering analysis revealed that clusters indicative of activated RAS/MAPK/ERK and/or PI3K/Akt pathways were associated with inferior OS and/or PFS and maintained significance in multivariable analysis. Conclusions These results implicate PI3K/Akt and RAS/MAPK/ERK pathways in resistance to cetuximab-containing chemoradiation in HNSCC. Large prospective studies are required to validate these results.