Anterograde TNFα Transport From Rat Dorsal Root Ganglion To Spinal Cord And Injured Sciatic Nerve

Spontaneous activity originating in the injured nerve or the dorsal root ganglion (DRG) has been implicated in the development and maintenance of neuropathic pain. The inherent characteristics of spontaneous activity and the causal factors that modulate its firing pattern and frequency are not fully understood. We attempted to assess the thermosensitivity of spontaneous activity in dorsal root ganglion (DRG) neurons in normal rats and in rat, with cl-ironic compression of the DRG (CCD) in an in vitro nerve-DRG preparation. Extracellular, dorsal root recording from 66 spontaneously active CCD Abeta fibers indicate that: (1) decreasing bath temperature from 37 to 36-26 °C significantly decreased the firing rate (FR) in 85% (56/66) of fibers tested, of which 19 fibers (34%) responded to temperature change at physiological range (36-37 °C), whereas the remaining fibers responded at lower temperature levels (26-36 °C); (2) cooling of the DRG increased the FR in 12% (8/66) of fibers tested; (3) similarly, the firing rate of 21/26 spontaneously active Abeta fibers from normal rats was decreased following temperature decrease; (4) intracellular recordings from 38 normal neurons revealed that cooling the DRG significantly increased the action potential (AP) threshold, A-P duration, AP amplitude and afterhyperpolarization (AHP) duration, but decreased AHP amplitude, maximal depolarizing and repolarizing rates. There was no significant change in the rheobase currents or the resting membrane potential. The present study indicates that large sensory neurons with myelinated axons are temperature dependent. It also suggests that maintenance of a stable temperature is critical for reliable characterization of spontaneous activity of sensory neurons.     

Nanotoxicity of iron oxide nanoparticle internalization in growing neurons

Magnetic nanoparticles (MNPs) have shown great promise for use as tools in a wide variety of biomedical applications, some of which require the delivery of large numbers of MNPs onto or into the cells of interest. Here we develop a quantifiable model cell system and show that intracellular delivery of even moderate levels of iron oxide (Fe(2)O(3)) nanoparticles may adversely affect cell function. More specifically, we show that exposure to increasing concentrations of anionic MNPs, from 0.15 to 15 mm of iron, results in a dose-dependent diminishing viability and capacity of PC12 cells to extend neurites in response to their putative biological cue, i.e. nerve growth factor. The cytotoxicity results of biomaterials in our model system imply that more study into the acute and long-term effects of cellular Fe(2)O(3) internalization is both warranted and necessary.     

Implementing and Evaluating a Four-Year Integrated End-of-Life Care Curriculum for Medical Students

Problem: Meeting the needs of patients with life-limiting and terminal illness requires effectively trained physicians in all specialties to provide skillful and compassionate care. Despite mandates for end-of-life (EoL) care education, graduating medical students do not consistently feel prepared to provide this care. Intervention: We have developed a longitudinal, integrated, and developmental 4-year curriculum in EoL care. The curriculum's purpose is to teach basic competencies in EoL care. A variety of teaching strategies emphasize experiential, skill-building activities with special attention to student self-reflection. In addition, we have incorporated interprofessional learning and education on the spiritual and cultural aspects of care. We created blended learning strategies combining interactive online modules with live workshops that promote flexibility, adaptability, and interprofessional learning opportunities. Context: The curriculum was implemented and evaluated in the 4-year program of studies at Yale School of Medicine. Outcome: A mixed-method evaluation of the curriculum included reviews of student written reflections and questionnaires, graduating student surveys, and demonstration of 4th-year students’ competency in palliative care with an observed structured clinical examination (OSCE). These evaluations demonstrate significant improvements in students’ self-reported preparedness in EoL care and perceptions of the adequacy in their instruction in EoL and palliative care, as well as competency in primary palliative care in a newly developed OSCE. Lessons Learned: A 4-year longitudinal integrated curriculum enhances students’ skills and preparedness in important aspects of EoL care. As faculty resources, clinical sites, and curricular structure vary by institution, proven and adaptable educational strategies as described in this article may be useful to address the mandate to improve EoL care education. Teaching strategies and curricular components and design as just described can be adapted to other programs.     

Differential distribution of PI3K isoforms in spinal cord and dorsal root ganglia: Potential roles in acute inflammatory pain

PI3-kinases (PI3Ks) participate in nociception within spinal cord, dorsal root ganglion (DRG), and peripheral nerves. To extend our knowledge, we immunohistochemically stained for each of the 4 class I PI3K isoforms along with several cell-specific markers within the lumbar spinal cord, DRG, and sciatic nerve of naive rats. Intrathecal and intraplantar isoform specific antagonists were given as pretreatments before intraplantar carrageenan; pain behavior was then assessed over time. The α-isoform was localized to central terminals of primary afferent fibers in spinal cord laminae IIi to IV as well as to neurons in ventral horn and DRG. The PI3Kβ isoform was the only class I isoform seen in dorsal horn neurons; it was also observed in DRG, Schwann cells, and axonal paranodes. The δ-isoform was found in spinal cord white matter oligodendrocytes and radial astrocytes, and the γ-isoform was seen in a subpopulation of IB4-positive DRG neurons. No isoform co-localized with microglial markers or satellite cells in naive tissue. Only the PI3Kβ antagonist, but none of the other antagonists, had anti-allodynic effects when administered intrathecally; coincident with reduced pain behavior, this agent completely blocked paw carrageenan-induced dorsal horn 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl) propanoic acid (AMPA) receptor trafficking to plasma membranes. Intraplantar administration of the γ-antagonist prominently reduced pain behavior. These data suggest that each isoform displays specificity with regard to neuronal type as well as to specific tissues. Furthermore, each PI3K isoform has a unique role in development of nociception and tissue inflammation.     

Dynamic visual acuity during passive and self-generated transient head rotation in normal and unilaterally vestibulopathic humans

To determine whether dynamic visual acuity (DVA) during head rotations on the stationary body can lateralize unilateral vestibular deafferentation and detect non-labyrinthine compensation mechanisms, 15 normal and 11 subjects with unilateral vestibular deafferentation underwent manually imposed and self-generated transient yaw head rotations during measurement of binocular DVA. DVA was measured by a four-alternative, forced choice, staircase procedure with optotype presentation only when head velocity exceeded thresholds of 50 degree or 75 degree/s. Eye and head movements were recorded using search coils to characterize ocular motor strategies. During directionally unpredictable, manually imposed contralesional rotation, unilaterally deafferented subjects had decreases in DVA from the static condition of 0.36 +/- 0.22 and 0.47 +/- 0.53 log of the minimum angle resolvable (logMAR, mean +/- SD), respectively, for 50 degree and 75 degree/s thresholds, not significantly greater than those of normal subjects (0.26 +/- 0.13 and 0.36 +/- 0.14, P>0.05). However, during manually imposed ipsilesional rotation, vestibulopathic subjects had decreases in DVA of 0.66 +/- 0.36 and 1.08 +/- 0.47 logMAR, significantly greater than during contralesional rotation ( P<0.01). The DVA reduction difference for the ipsi- and contralesional directions was less during self-generated than during manually imposed head rotations. The directional difference for manually administered head rotations yielded a robust diagnostic measure with essentially no overlap in performance with normal subjects. Diagnostic performance for DVA during self-generated head rotation was poorer. Recordings of eye and head movements made using search coils during DVA testing confirmed a deficient vestibulo-ocular reflex (VOR) during ipsilesional rotation, with most unilaterally vestibulopathic subjects employing predictive smooth eye movements and vestibular catch-up saccades. Measurement of DVA during transient head rotation on the body thus reliably can detect and lateralize vestibular pathology and compensatory mechanisms. Extravestibular mechanisms for compensation appear more effective during self-generated than manually imposed head rotations.     

Impairments in the initial horizontal vestibulo-ocular reflex of older humans

To determine age-related changes, the initial horizontal vestibulo-ocular reflex (VOR) of 11 younger normal subjects (aged 20–32 years) was compared with that of 12 older subjects (aged 58–69 years) in response to random transients of whole-body acceleration of 1,000 and 2,800°/s² delivered around eccentric vertical axes ranging from 10 cm anterior to 20 cm posterior to the eyes. Eye and head positions were sampled at 1,200 Hz using magnetic search coils. Subjects fixed targets 500 cm or 15 cm distant immediately before the unpredictable onset of rotation in darkness. For all testing conditions, younger subjects exhibited compensatory VOR slow phases with early gain (eye velocity/head velocity, interval 35–45 ms from onset of rotation) of 0.90±0.02 (mean ± SEM) for the higher head acceleration, and 0.79±0.02 for the lower acceleration. Older subjects had significantly (P<0.0001) lower early gain of 0.77±0.04 for the higher head acceleration and 0.70±0.02 for the lower acceleration. Late gain (125–135 ms from onset of rotation) was similar for the higher and lower head accelerations in younger subjects. Older subjects had significantly lower late gain at the higher head acceleration, but gain similar to the younger subjects at the lower acceleration. All younger subjects maintained slow-phase VOR eye velocity to values ≥200°/s throughout the 250-ms rotation, but, after an average of 120 ms rotation (mean eccentricity 13°), 8 older subjects consistently had abrupt declines (ADs) in slow-phase VOR velocity to 0°/s or even the anticompensatory direction. These ADs were failures of the VOR slow phase rather than saccades and were more frequent with the near target at the higher acceleration. Slow-phase latencies were 14.4±0.4 ms and 16.8±0.4 ms for older subjects at the higher and lower accelerations, significantly longer than comparable latencies of 10.0±0.5 ms and 12.0±0.6 ms for younger subjects. Late VOR gain modulation with target distance was significantly attenuated in older subjects only for the higher head acceleration. Electronic Publication