Dynamic transcriptomic response to acute hypertension in the nucleus tractus solitarius.

Baroreceptor afferents project to the cardiovascular region of the nucleus tractus solitarius (cvNTS), and their cvNTS target neurons may play a role in governing the sensitivity and operating range of the arterial baroreceptor reflex (baroreflexes). Recent studies have shown differential gene and protein expression in the cvNTS in response to changed arterial pressure. However, the extent of these responses is unknown. Therefore, we collected differential global gene expression data in a time series following acute hypertension in awake, freely moving rats. To acquire statistically significant results and place them in functional context, we overcame several quality control requirements and developed novel analytical approaches. The physiologically new findings from the study are that acute hypertension causes very extensive, time-varying gene regulatory changes, many involving neuronal function-specific genes and systems of genes. We use standard genomic analysis methods to manage the large data sets and to develop results such as heat maps to examine patterns and clusters in the gene regulation. We used the Gene Ontology categories to provide functional context. To place our findings in the context of the relevant literature, we developed two graphical representations of the networks implicated, linking receptors and channels to signaling pathways. The results point to the multivariate complexity of the response and implicate a group of receptors as candidates for mediating nucleus tractus solitarius baroreflex function in hypertension by identifying concurrent upregulation of receptor genes. We were able to make transcription factor binding predictions and record dysregulation of heart rate correlated with the transcriptional response.

Comparing McRoberts' and Rubin's maneuvers for initial management of shoulder dystocia: an objective evaluation.

OBJECTIVE: This study was undertaken to objectively compare delivery traction force, fetal neck rotation, and brachial plexus elongation after 3 different initial shoulder dystocia maneuvers: McRoberts', anterior Rubin's, and posterior Rubin's. STUDY DESIGN: We developed a laboratory birthing simulator comprised of a maternal model with a 3-dimensional bony pelvis, an instrumented fetal model, a force-sensing glove, and a computer-based data acquisition system. A single operator performed 30 simulated shoulder dystocia deliveries using standard downward traction after 1 maneuver was performed. Ten deliveries simulated McRoberts' maneuver with fetal shoulders in the anteroposterior diameter. Ten deliveries involved approximately 30-degree oblique rotation of the anterior shoulder with the spine oriented anteriorly (anterior Rubin's maneuver). Ten deliveries involved approximately 30-degree rotation of the posterior shoulder to the opposite oblique pelvic diameter, with the spine oriented posteriorly (posterior Rubin's maneuver). Peak traction force, brachial plexus elongation, and neck rotation were compared between groups using analysis of variance, with P < .05 considered significant. RESULTS: Rubin's maneuvers were found to require less traction force than McRoberts': 16.2 +/- 2.1 lbs for McRoberts' compared with 8.8 +/- 2.2 lbs and 6.5 +/- 1.8 lbs for posterior and anterior Rubin's respectively (P < .0001). Brachial plexus extension was significantly lower after anterior Rubin's maneuver compared with McRoberts' or posterior Rubin's maneuvers. CONCLUSION In a laboratory model of initial maneuvers for shoulder dystocia, anterior Rubin's maneuver requires the least traction for delivery and produces the least amount of brachial plexus tension. Further study is needed to validate these results clinically.

Simulating complicated human birth for research and training.

We report on the design, testing and implementation of a novel birthing simulator developed specifically to research the delivery process and improve clinical training in uncommon but inevitable complicated human births. The simulator consists of a maternal model and an instrumented fetal model, used in conjunction with an existing force-sensing system and a data-acquisition system. The maternal model includes a bony, rotatable pelvis, flexible legs, and a uterine expulsive system. The fetal model, which can be delivered repeatedly through the maternal model, is instrumented with potentiometers to measure neck extension, rotation and flexion during delivery. Simulation of the brachial plexus within the model fetal neck allows measurement of stretch in those nerves at risk for injury during difficult deliveries. Wooden elements mimic the properties of neonatal bone and can break either spontaneously or purposely. Two methods for measuring clinician-applied force during simulated deliveries provide trainees with real-time assessment of their own traction force and allow researchers to correlate fetal neck motion and nerve stretch parameters with clinician-applied traction. Preliminary testing indicates the system is biofidelic for the final stages of the birthing process, and can be used for training and research in obstetrics.