Biomedical subjects
A Selverston
Publications and source records attributed to A Selverston.
Lobster stomatogastric neurons in primary culture. I. Basic characteristics.
1. A method for the isolation of stomatogastric neurons with neuropilar processes and an axon < or = 2 mm long is described. Isolated neurons adhered to an uncoated plastic surface and demonstrated neurite outgrowth for > or = 7-10 days in a simple medium (salt-adjusted Leibovitz-15). Neurite outgrowth started immediately after plating and was maximal during the first 2-3 days. The electrical activity of neurons and their responses to bath application of pilocarpine were studied between 2 and 10 days after plating. 2. Identified neurons [pyloric dilator (PD), pyloric (PY), and lateral pyloric (LP) neurons from the pyloric pattern generator as well as gastric mill (GM) and lateral posterior gastric (LPG) neurons from the gastric mill pattern generator], isolated with neuropilar processes and axons, behaved in general like corresponding neurons in the isolated stomatogastric ganglion (STG). PD neurons were tonically active or silent in culture; pilocarpine caused them to begin rhythmic activity, which at particular levels of imposed polarization was similar to the pyloric rhythm in vitro. PY and LP neurons were silent. Pilocarpine produced some rhythmicity in the PY neuron, whereas in LP neurons it decreased the firing threshold to depolarizing current and accentuated postinhibitory rebound. LPG neurons were tonically active. Pilocarpine depolarized the LPG neurons and accelerated their tonic activity; neuron hyperpolarization by current injection led to bursting pacemaker activity that was similar to the gastric rhythm in vitro. GM neurons were silent; pilocarpine did not cause them to generate rhythmic activity but did lower their thresholds to depolarizing current. Simultaneous recordings from the soma and axon under direct visual control demonstrated that the intrasomatic spikes (15-20 mV in amplitude) were attenuated action potentials generated in the axon. 3. Neurons isolated with short primary neurites, including those without any noticeable primary neurite (in contrast to neurons isolated with longer neuropilar processes and axons), never generated any kind of electrical activity immediately after extraction from the STG. After 2 days in culture, these "short-neurite" neurons became capable of generating different types of electrical activity (e.g., fast spikes with amplitudes of < or = 40-45 mV, plateau potentials, bursting potentials, etc.). The capability of isolated somata to generate electrical activity did not depend on whether or not the cell had adhered to the substrate and demonstrated neurite outgrowth.(ABSTRACT TRUNCATED AT 400 WORDS)
Neurophysiology. Twitching and switching.
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Rapid killing of single neurons by irradiation of intracellularly injected dye.
A simple technique for rapidly killing all or part of single neurons consists of filling the cell with Lucifer Yellow CH and irradiating all or part of it with intense blue light. Such treatment kills the irradiated part of the cell within a few minutes. Adjacent cells are not affected.
Antidromic action potentials fail to demonstrate known interactions between neurons.
An identified motor neuron in the stomatogastric ganglion of Panulirus interruptus inhibits four other motor neurons when it fires spontaneously or in response to depolarization of its soma. It does not inhibit these neurons when it is fired antidromically, although the attenuated antidromic spike is visible at its soma. These findings point out the difficulty of interpreting negative results from antidromic stimulation experiments and the importance of neuronal structure to the integrative activities of nervous systems.
Lateral giant fibers of cray fish: location of somata by dye injection.
Using a new technique for injecting fluorescent dye, we have analyzed the intraganglionic architectutre of the lateral giant interneuron in crayfish. Each lateral giant interneuron comprises a giant axon, an ipsilateral dendritic arborization of fairly constant form, and a contralateral soma. Antidromic axon spikes produce only, small, electronic potentials in the soma; direct depolarization there fails to produce electrically excitable membrane responses and cannot discharge the main axon.
Mechanism of supercontraction in a striated muscle.
The phenomenon of contraction of a striated muscle down to below 50 per cent rest length has been examined for the scutal depressor of the barnacle Balanus nubilus by a combination of phase contrast and electron microscopy. It was found that neurally evoked contraction down to 60 per cent rest length results from the shortening of the I band. At the same time the Z disc changes in structure by an active process which results in spaces opening up within it. Thick filaments can now pass through these spaces from adjacent sarcomeres, interdigitating across the discs. Interdigitation permits repetitive contraction in the living muscle to below 30 per cent rest length. In non-neurally evoked contractions most thick filaments do not find spaces in the Z disc and bend back, giving rise to contraction band artifacts. Expansion of the Z disc can be produced in glycerinated material by the addition of solutions containing a high concentration of ATP.