Faculty Bibliography

PURPOSE: The workup for oral malignancy involving the mandible typically involves a head and neck exam, laboratory studies, a panoramic radiograph, and computed tomography (CT) or magnetic resonance imaging of the head and neck to evaluate the primary lesion and cervical lymph nodes. Panoramic plain film radiography of the mandible is often unreliable for detecting bony invasion; therefore, other imaging studies are necessary before staging is complete. Bony invasion is typically imaged with the use of conventional CT scanners. In this article we relate the use of cone beam computed tomography (CBCT) to image the mandible with less cost and morbidity to the patient and its use in the evaluation and treatment planning of mandibular cancer. MATERIALS AND METHODS: A retrospective review of 3 patients with mandibular malignancies was performed. All patients had a panoramic radiograph, magnetic resonance imaging, and chest radiograph, in addition to laboratory studies. CBCT scans were ordered, after bony involvement was suspected, and compared with the other imaging studies. RESULTS: Two patients with squamous cell carcinoma of anterior mandible and 1 patient with osteogenic sarcoma were reviewed. In all cases CBCT aided the evaluation of the mandible. The cone beam panoramic view, as part of the CBCT, was used to determine extent of resection. CONCLUSION: CBCT can accurately aid in evaluating and treatment planning for malignant tumors of the mandible with less cost and decreased radiation to the patient relative to conventional CT

Reports an error in 'Channel, neuronal and clinical function in sodium channelopathies: From genotype to phenotype' by Stephen G. Waxman (Nature Neuroscience, 2007[Apr], Vol 10[4], 405-409). In the version of this article initially published, the online publication date was incorrectly given as 25 February 2007. The correct date is 27 March 2007. This error has been corrected in the PDF version of the article. (The following abstract of the original article appeared in record 2008-04974-022). In neural integrators, transient inputs are accumulated into persistent firing rates that are a neural correlate of short-term memory. Integrators often contain two opposing cell populations that increase and decrease sustained firing as a stored parameter value rises. A leading hypothesis for the mechanism of persistence is positive feedback through mutual inhibition between these opposing populations. We tested predictions of this hypothesis in the goldfish oculomotor velocity-to-position integrator by measuring the eye position and firing rates of one population, while pharmacologically silencing the opposing one. In complementary experiments, we measured responses in a partially silenced single population. Contrary to predictions, induced drifts in neural firing were limited to half of the oculomotor range. We built network models with synaptic-input thresholds to demonstrate a new hypothesis suggested by these data: mutual inhibition between the populations does not provide positive feedback in support of integration, but rather coordinates persistent activity intrinsic to each population. (PsycINFO Database Record (c) 2008 APA, all rights reserved)

The present experiments were undertaken to clarify the role of central alpha(1)-adrenoceptors in reward processes. Rats, trained to self-stimulate via electrodes in the medial forebrain bundle of the lateral hypothalamus, were administered alpha(1)-selective drugs near the locus coeruleus (LC), a site of a dense concentration of alpha(1)-receptors. Effects on reward potency were assessed from shifts in rate-frequency curves while effects on motor response capacity were judged from changes in the maximal rates of responding. It was found that local blockade of LC alpha(1)-receptors with terazosin produced a significant dose-dependent and site-dependent rightward shift of 0.08 log units and a significant decrease of 16.3% in the maximum response rate. Both effects were completely reversed by coadministration of the alpha(1)-agonist, phenylephrine and were not attributable to terazosin's weak action at alpha(2)-adrenoceptors. It is concluded that LC alpha(1)-adrenoceptors are involved both in reward/motivational processes and operant response elaboration which are postulated to work together to facilitate goal attainment.Neuropsychopharmacology advance online publication, 5 July 2006; doi:10.1038/sj.npp.1301145

Acetazolamide, a potent carbonic anhydrase (CA) inhibitor, is the most commonly used and best studied agent for the amelioration of acute mountain sickness (AMS). The actual mechanisms by which acetazolamide reduces symptoms of AMS, however, remain unclear. Traditionally, acetazolamide's efficacy has been attributed to inhibition of CA in the kidneys, resulting in bicarbonaturia and metabolic acidosis. The result is offsetting hyperventilation-induced respiratory alkalosis and allowance of chemoreceptors to respond more fully to hypoxic stimuli at altitude. Studies performed on both animals and humans, however, have shown that this explanation is unsatisfactory and that the efficacy of acetazolamide in the context of AMS is likely due to a multitude of effects. This review summarizes the known systemic effects of acetazolamide, and incorporates them into a model encompassing several factors that are likely to play a key role in the drug's efficacy. Such factors include not only metabolic acidosis resulting from renal CA inhibition, but also improvements in ventilation from tissue respiratory acidosis, improvements in sleep quality from carotid body CA inhibition, and effects of diuresis. Key words: carbonic anhydrase, periodic breathing, hypercapnic ventilatory response, metabolic acidosis, altitude sickness

Delay discounting refers to the degree to which immediate outcomes exhibit more influence over behavior than outcomes which are delayed. Impulsive choice, in the context of delay discounting, is generally considered as an increased preference for immediate over delayed outcomes, even where the delayed outcomes are more advantageous. In the past decade, there has been increasing use of delay-discounting paradigms to elucidate the physiological, pharmacological, and behavioral aspects of the putative neural circuitry underlying impulsive choice. This unit describes the assessment of impulsive choice in the rat using a delay-discounting procedure involving an operant response choice between a small reinforcer delivered immediately and a larger reinforcer delivered after a delay, which is progressively increased within a session. Variations of some of the main task parameters are also discussed, as well as their significance and interpretation.

CONCLUSION: Neither speech understanding nor frequency discrimination ability was better in Nucleus Contour users than in Nucleus 24 straight electrode users. Furthermore, perimodiolar electrode placement does not result in better frequency discrimination. OBJECTIVES: We addressed three questions related to perimodiolar electrode placement. First, do patients implanted with the Contour electrode understand speech better than with an otherwise identical device that has a straight electrode? Second, do these groups have different frequency discrimination abilities? Third, is the distance of the electrode from the modiolus related to frequency discrimination ability? SUBJECTS AND METHODS: Contour and straight electrode users were matched on four important variables. We then tested these listeners on CNC word and HINT sentence identification tasks, and on a formant frequency discrimination task. We also examined X-rays and measured the distance of the electrodes from the modiolus to determine whether there is a relationship between this factor and frequency discrimination ability. RESULTS: Both speech understanding and frequency discrimination abilities were similar for listeners implanted with the Contour vs a straight electrode. Furthermore, there was no linear relationship between electrode-modiolus distance and frequency discrimination ability. However, we did note a second-order relationship between these variables, suggesting that frequency discrimination is worse when the electrodes are either too close or too far away from the modiolus

Delayed contrast-enhanced MRI (ce-MRI) pulse sequence is a promising modality for the assessment of myocardial viability. However, conventional ce-MRI using a non-selective inversion recovery (IR) pulse can often yield poor edge definition or contrast-to-noise ratio (CNR) between the non-transmural scar and blood (i.e. the blood and scar appear isointense). Subtraction and multicontrast ce-MRI methods can be used to improve the CNR between the non-transmural scar and blood, but they require two image acquisitions. The authors have developed a single-acquisition ce-MRI pulse sequence that utilizes a slice-selective IR pulse to generate bright-blood contrast using inflow effects for an improved edge definition between the non-transmural scar and blood. Six patients with myocardial infarction were imaged at 1.5 T using both non-selective and slice-selective IR ce-MRI acquisitions with identical imaging parameters. The CNR between the non-transmural scar and normal myocardium was not different between the two acquisitions. The CNR between the blood and non-transmural scar (16.9 +/- 12.3 versus 3.2 +/- 7.9; p < 0.001) was significantly higher for the slice-selective IR acquisition than for the non-selective IR acquisition. This study demonstrates the feasibility of using a slice-selective IR pulse to improve the visualization of a non-transmural scar in ce-MRI, without increasing the acquisition time.

We have shown that neuropeptide Y (NPY) regulates neurogenesis in the normal dentate gyrus (DG) via Y(1) receptors (Howell, O.W., Scharfman, H.E., Herzog, H., Sundstrom, L.E., Beck-Sickinger, A. and Gray, W.P. (2003) Neuropeptide Y is neuroproliferative for post-natal hippocampal precursor cells. J Neurochem, 86, 646-659; Howell, O.W., Doyle, K., Goodman, J.H., Scharfman, H.E., Herzog, H., Pringle, A., Beck-Sickinger, A.G. and Gray, W.P. (2005) Neuropeptide Y stimulates neuronal precursor proliferation in the post-natal and adult dentate gyrus. J Neurochem, 93, 560-570). This regulation may be relevant to epilepsy, because seizures increase both NPY expression and precursor cell proliferation in the DG. Therefore, the effects of NPY on DG precursors were evaluated in normal conditions and after status epilepticus. In addition, potentially distinct NPY-responsive precursors were identified, and an analysis performed not only of the DG, but also the caudal subventricular zone (cSVZ) and subcallosal zone (SCZ) where seizures modulate glial precursors. We show a proliferative effect of NPY on multipotent nestin cells expressing the stem cell marker Lewis-X from both the DG and the cSVZ/SCZ in vitro. We confirm an effect on proliferation in the cSVZ/SCZ of Y(1) receptor(-/-) mice and demonstrate a significant reduction in basal and seizure-induced proliferation in the DG of NPY(-/-) mice