Elimination of Left-Right Reciprocal Coupling in the Adult Lamprey Spinal Cord Abolishes the Generation of Locomotor Activity.

The contribution of left-right reciprocal coupling between spinal locomotor networks to the generation of locomotor activity was tested in adult lampreys. Muscle recordings were made from normal animals as well as from experimental animals with rostral midline (ML) spinal lesions (~13%→35% body length, BL), before and after spinal transections (T) at 35% BL. Importantly, in the present study actual locomotor movements and muscle burst activity, as well as other motor activity, were initiated in whole animals by descending brain-spinal pathways in response to sensory stimulation of the anterior head. For experimental animals with ML spinal lesions, sensory stimulation could elicit well-coordinated locomotor muscle burst activity, but with some significant differences in the parameters of locomotor activity compared to those for normal animals. Computer models representing normal animals or experimental animals with ML spinal lesions could mimic many of the differences in locomotor activity. For experimental animals with ML and T spinal lesions, right and left rostral hemi-spinal cords, disconnected from intact caudal cord, usually produced tonic or unpatterned muscle activity. Hemi-spinal cords sometimes generated spontaneous or sensory-evoked relatively high frequency "burstlet" activity that probably is analogous to the previously described in vitro "fast rhythm", which is thought to represent lamprey locomotor activity. However, "burstlet" activity in the present study had parameters and features that were very different than those for lamprey locomotor activity: average frequencies were ~25 Hz, but individual frequencies could be >50 Hz; burst proportions (BPs) often varied with cycled time; "burstlet" activity usually was not accompanied by a rostrocaudal phase lag; and following ML spinal lesions alone, "burstlet" activity could occur in the presence or absence of swimming burst activity, suggesting the two were generated by different mechanisms. In summary, for adult lampreys, left and right hemi-spinal cords did not generate rhythmic locomotor activity in response to descending inputs from the brain, suggesting that left-right reciprocal coupling of spinal locomotor networks contributes to both phase control and rhythmogenesis. In addition, the present study indicates that extreme caution should be exercised when testing the operation of spinal locomotor networks using artificial activation of isolated or reduced nervous system preparations.

Provider Perceptions of Treatment Options for Immature Permanent Teeth.

INTRODUCTION: Current treatment options for immature permanent teeth with pulpal necrosis include both apexification and regenerative endodontics. The purpose of this study was to survey endodontists on the use of these 2 treatment options. METHODS: Surveys were created by using Qualtrics and Teleform software and distributed by using the Salant and Dillman method. Endodontists (n = 1615) in 4 geographically and demographically diverse states, North Carolina, New York, Texas, and California, were surveyed. Data were analyzed by using descriptive statistics and χ2 analysis. Level of significance was set at 0.05. RESULTS: A 32.9% response rate was obtained. The majority of responders reported that apexification was the treatment of choice when considering the evidence base supporting the treatment (60%) and the predictability of treatment outcome (77.8%). Apexification was also the preferred treatment by 57.3% of respondents when asked to consider patient compliance, by 51.2% when considering the number of required patient appointments, and by 53.3% when considering the likelihood of tooth discoloration. Regenerative endodontics was reported as the preferred treatment by 89% of respondents when considering continued root development and by 66.7% when considering apical closure. The respondents' age and continuing education courses taken were significantly associated with their preferred treatment option. CONCLUSIONS: The results of our study indicate that endodontists consider both clinical and patient factors when treating immature teeth with pulpal necrosis. Increase in continuing education options may increase adoption of regenerative endodontic therapy.