William E. Cameron

Dendritic morphology and its effects on the amplitude and rise-time of synaptic signals in hippocampal CA3 pyramidal cells.

Detailed anatomical analysis and compartmental modeling techniques were used to study the impact of CA3b pyramidal cell dendritic morphology and hippocampal anatomy on the amplitude and time course of dendritic synaptic signals. We have used computer‐aided tracing methods to obtain accurate three‐dimensional representations of 8 CA3b pyramidal cells. The average total dendritic length was 6,332 ± 1,029 μm and 5,062 ± 1,397 μm for the apical and basilar arbors, respectively. These cells also exhibited a rough symmetry in their maximal transverse and septotemporal extents (311 ± 84 μm and 269 ± 106 μm). From the calculated volume of influence (the volume of the neuropil from which the dendritic structures can receive input), it was found that these cells show a limited symmetry between their proximal apical and basilar dendrites (2.1 ± 1.2 × 106 μm3 and 3.5 ± 1.1 × 106 μm3, respectively). Based upon these data, we propose that the geometry of these cells can be approximated by a combination of two cones for the apical arbor and a single cone for the basilar arbor.

Physiological changes accompanying anatomical remodeling of mammalian motoneurons during postnatal development.

The development of respiratory motoneurons provides unique data that may be generalized to other mammalian motoneuron populations. Like other motoneurons, respiratory motoneurons undergo developmental changes in the shape of the action potential and their repetitive firing. The unique observations concern the postnatal change in the recruitment pattern of cat phrenic motoneurons that is correlated with a halving of mean input resistance, a stasis of growth in the cell membrane and a reduction in the complexity of the dendritic tree. A similar pattern of change was observed for hypoglossal motoneurons studied in rat brainstem slices. Without an increase in total membrane surface area, the decreased resistance must result from a reduced specific membrane resistance. Two mechanisms are proposed to explain this decrease in resistance: proliferation and redistribution of either synaptic inputs and/or potassium channels. Although there was a significant contribution of synaptic input in determining input resistance throughout postnatal development, it was the density of cesium- or barium-sensitive potassium conductances that differentiated low resistance from high resistance motoneurons. Low resistance motoneurons had more cesium- and barium-sensitive channels than their high resistance counterparts. Based on the variations in the relative changes observed in input resistance versus membrane time constant with these two potassium channel blockers (cesium and barium), it is proposed that the distribution of these potassium channels change with age. Initially, their distribution is skewed toward the dendrites but as development progresses, the distribution becomes more uniform across the motoneuron membrane. During postnatal development, the rapid decrease in input resistance results from a proliferation of potassium channels in the membrane and of synaptic inputs converging onto developing respiratory motoneurons while the membrane is being spatially redistributed but not expanded.

A role for neuroscientists in engaging young minds.

Neuroscience receives little attention in elementary school education, although students at this age are active explorers of their environment and can relate easily to exercises that involve the science of their senses. The neuroscientist has an important role in supporting elementary educators who might be uncomfortable with teaching science. To encourage such scientist–teacher interactions, changes must be made in the culture of the scientific community to promote these partnerships, with the ultimate goal of improving neuroscience literacy.

Postnatal development of phrenic motoneurons in the cat

The postnatal growth of phrenic motoneurons in the cat was studied using retrograde transport of horseradish peroxidase (HRP). The mean somal surface area of these developing motoneurons increased 2.5 times from day 3 to adult while the mean somal volume increased four-fold. This change in mean somal surface area during postnatal development was found to be correlated with the change in mean axonal conduction velocity measured from phrenic motoneurons.

Morphology of developing motoneurons innervating the medial gastrocnemius of the cat

The morphology of medial gastrocnemius (MG) motoneurons labeled by retrograde transport of horseradish peroxidase was quantified in 5 postnatal ages (3 to 79-86 days) and in adults. A bimodal distribution of somal volumes was evident at birth which permitted separating the motoneurons into alpha and gamma subpopulations for analysis. There was a significant increase in the axial dimensions, surface area and volume calculated for both alpha and gamma cell bodies between each of the age-groups studied. A greater relative growth of the major over minor axis for the gammas produced a significant decrease in the form factor (i.e. greater eccentricity) between the youngest and oldest age-groups. The number of primary dendrites observed remained constant throughout postnatal development. The surface area of alpha somata more than tripled while that of the gammas doubled from 3 days to the adult. The mean somal volume of an alpha motoneuron at birth was only 17% of its adult value while the gamma cell bodies were 33% of their adult volume. A positive correlation was found for both alpha and gamma motoneurons when their somal surface area was plotted against postnatal age and weight. The rate of growth of the MG somal surface area is compared to the changes found in axonal conduction velocity and axonal diameter for MG in the literature.

Relationship between membrane properties and cell size of developing rat genioglossal motoneurons studied in vitro

Electrical properties and morphology of 21 genioglossal motoneurons were measured in a slice preparation of the rat brainstem at four different postnatal ages. The motoneurons labeled with neurobiotin were reconstructed and quantified in three-dimensional space. There was no strong correlation found between the input resistance or membrane time constant and the total membrane surface area. We conclude that there is no electrical property of these developing motoneurons that can accurately predict their anatomical size.

Let's Get Healthy! Health awareness through public participation in an education and research exhibit.

Background: Health information technology (HIT) offers a resource for public empowerment through tailored information.Objective: Use interactive community health events to improve awareness of chronic disease risk factors while collecting data to improve health.Methods:Lets Get Healthy! is an education and research program in which participants visit interactive research stations to learn about their own health (diet, body composition, blood chemistry). HIT enables computerized data collection that presents participants with immediate results and tailored educational feedback. An anonymous wristband number links collected data in a population database.Results and Lessons Learned: Communities tailor events to meet community health needs with volunteers trained to conduct research. Participants experience being a research participant and contribute to an anonymous population database for both traditional research purposes and open-source community use.Conclusions: By integrating HIT with community involvement, health fairs become an interactive method for engaging communities in research and raising health awareness.

Endoscopic Endonasal Transclival Approach versus Dual Transorbital Port Technique for Clip Application to the Posterior Circulation: A Cadaveric Anatomical and Cerebral Circulation Simulation Study

Purpose Simulation training offers a useful opportunity to appreciate vascular anatomy and develop the technical expertise required to clip intracranial aneurysms of the posterior circulation. Materials and Methods In cadavers, a comparison was made between the endoscopic transclival approach (ETA) alone and a combined multiportal approach using the ETA and a transorbital precaruncular approach (TOPA) to evaluate degrees of freedom, angles of visualization, and ergonomics of aneurysm clip application to the posterior circulation depending on basilar apex position relative to the posterior clinoids. Results ETA alone provided improved access to the posterior circulation when the basilar apex was high riding compared with the posterior clinoids. ETA + TOPA provided a significantly improved functional working area for instruments and visualization of the posterior circulation for a midlevel basilar apex. A single‐shaft clip applier provided improved visualization and space for instruments. Proximal and distal vascular control and feasibility of aneurysmal clipping were demonstrated. Conclusions TOPA is a medial orbital approach to the central skull base; a transorbital neuroendoscopic surgery approach. This anatomical simulation provides surgical teams an alternative to the ETA approach alone to address posterior circulation aneurysms, and a means to preoperatively prepare for intraoperative anatomical and surgical instrumentation challenges.

Experiential Learning Through Participatory Action Research in Public Health Supports Community-Based Training of Future Health Professionals.

Engaging community members in research can help cultivate effective partnerships while providing experiential training and continuing education opportunities. Several studies have involved communities in this way, though many have been small in the scale of community involvement or have included little detail of the institutional review board process by which community members became approved researchers in the study. This article presents findings on an evaluation of the training procedures and experiences of 703 first-time community-based volunteer researchers who were recruited in their communities and trained on-site to enroll research participants, collect data, and provide individualized consultation of results at travelling health education and research fairs. Open-ended registration prompts and postfair surveys assessed volunteers’ reasons for participating, comfort with their volunteer experiences, and attitudes toward the biomedical research process. An open-ended survey assessed two key community partners’ perspectives about their organizations’ involvement with supporting the research throughout the process. Volunteers reported their experience to be a unique training opportunity, citing its ability to help them engage with their community, advance research, and obtain additional experience in their health field of interest, particularly nursing, allied health, and medicine-related careers. Community partners cited that their community’s participation as volunteer researchers served as a tool to educate the larger community about research, which enabled other research projects to gain acceptance. Together, these results demonstrate that using volunteer researchers can strengthen community research partnerships while providing valuable training experience in public health research for current and aspiring health personnel.