David F. Russell

The stomatogastric nervous system: structure and function of a small neural network.

Introduction 1. Gross anatomy of the stomatogastric system and experimental procedure 1.1. Anatomy 1.2. Experimental procedure 2. Behavior 2.1. Gastric mill 2.2. Pyloric cycle 2.3. Higher order control over stomach behavior 3. Pyloric system 4. Gastric system 5. Pyloric-gastric interactions 6. Modulation of stomatogastric activity 6.1. Sources of inputs 6.1.1. The commissural ganglia 6.1.2. The esophageal ganglion 6.2. Central connections of pyloric neurons 6.2.1. Pathways 6.2.2. Synaptic events 6.2.3. Esophagus rhythm inputs to pyloric neurons 6.2.4. Through fiber bursts 6.2.5. Distribution of the pyloric system 6.2.6. Summary 6.3. Inputs to the gastric system 6.3.1. Continuous gastric cycling in vitro 6.3.2. Input pathways 6.3.3. Rhythmic inputs 6.3.4. E neurons 6.3.5. LI neurons 6.3.6. P neurons 6.3.7. Esophagus rhythm modulation 6.3.8. IVN through fibers 6.3.9. Effects of sensory nerve stimulation 6.3.10. Summary and general conclusions 7. EX cells and their inputs 8. Cellular properties of stomatogastric neurons 8.1. Soma potentials 8.2. Bursting and non-bursting cells 8.3. Postinhibitory rebound 8.4. Reversal potentials 8.5. Gating of cell output 9. Mechanisms of rhythm generation 9.1. Types of mechanisms 9.2. Pyloric system 9.3. Gastric mill system 10. Computer network modeling and neuron reconstruction studies 10.

Detection of arterial emboli using Doppler ultrasound in rabbits.

The purpose of this study was to develop an animal model that could be used to test the ability of Doppler ultrasound to detect arterial emboli composed of materials that are often involved in cerebral emboli. Emboli introduced into the rabbit aorta via the left renal artery consisted of clotted whole blood, platelets, atheromatous material, fat, or air. The ultrasound examination was carried out continuously during the studies using a multifrequency transcranial Doppler apparatus with a 2-MHz probe, a sample volume of 15 mm, at a depth of 15 mm. The intensity of the Doppler spectrum was measured and displayed as a 15-shade color scale, each shade representing a 3-dB difference. The diameter of the aorta at the site of the ultrasound examination was similar to the diameter of the middle cerebral artery in humans. All 125 emboli introduced were clearly detected because they caused a Doppler signal at least 15 dB greater than that of the surrounding blood. These results show that the potential for emboli detection using Doppler ultrasound in the clinical situation is now considerable.

Embedding of Neural Tissue in Agarose or Glyoxyl Agarose for Vibratome Sectioning

Agarose was used to embed the brain or spinal cord of lampreys or rats before cutting vibratome sections. Agarose embedding was compatible with immunocytochemistry or the use of horseradish peroxidase as a neuroanatomical tracer. Concentrated agarose with high intrinsic gel strength was optimal for embedding glutaraldehyde fixed neural tissue. A quick procedure was to blot tissue and embed in 5% (w/v) Sigma type I-A or Litex type LSL agarose at 45-55 C dissolved in 50 mM neutral-pH TRIS buffer before cutting 50-100 microns vibratome sections. An alternative procedure that improved retention of tissue sections in the agarose was to rinse the tissue in H2O, blot and embed in 5% (w/v) Sigma type I-A or Litex type LSL agarose at 45-55 C dissolved in H2O, then equilibrate the block overnight in buffer. Phosphate buffer prevented complete dissolving of agarose. Tissue could be covalently linked to the embedding matrix using a novel aldehyde-derived agarose (NuFix, FMC BioProducts). Slices of spinal cord from neonatal rats could be cut after embedding in 5% FMC SeaPrep agarose in rat Ringers at 23-26 C.

Cellular and Synaptic Properties

Little had been published about the cellular properties of STG neurons at the time of a previous review (Selverston et al. 1976). Since then we have learned much about rhythm activation, plateau potentials, synaptic modulation, nonspiking transmission, and the geometrical properties of the neurons, which are reviewed in this chapter and the appendix. New data on voltage clamp and photometric analyses are also summarized.