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P F Drake

Publications and source records attributed to P F Drake.

7 recordsLinked to original sources
PubMed1985

Synthesis and fast axonal transport of proteins in the isolated Aplysia nervous system.

Fast axonal transport and neuronal protein synthesis was studied in the isolated nervous system of Aplysia californica. The abdominal ganglion with attached pleural-abdominal connectives (PAC) was removed and the ganglion pulse-labelled with [35S]methionine for 30 min in vitro. The axon containing connectives were ligated 24-28 mm from the ganglia and the system was perfused with chase media for 6-72 h to allow labelled rapidly transported proteins to accumulate at the ligature. One-dimensional polyacrylamide gel electrophoresis (PAGE) and fluorography was used to analyze the distribution of rapidly transported proteins along the right PAC. By 12 h, a significant accumulation of labelled proteins at the ligature was present but the build up was not complete until 48 h when almost no trailing of rapidly transported proteins was observed. Quantitation of the transport profiles of several rapidly transported proteins suggested a discontinuous release of proteins from the cell body. Analysis using two-dimensional PAGE revealed 10 major groups of rapidly transported proteins. These proteins were all identified among the total complement of newly synthesized proteins in cell R2. Not all rapidly transported proteins are cleared from the cell body at the same rate. Several of the major groups were no longer present in the neuron cell body 24 h after labelling, indicating that these species are selectively exported; others were still present after 3 days, suggesting that these proteins with a longer residence time have functions in both somatic and axonal regions of the neuron.

Animals↗
PubMed1984

Regional differences in the neuronal cytoskeleton.

Regional differences in the neuronal cytoskeleton were investigated in the giant neurons of Aplysia. Using SDS-PAGE, we have compared the proteins which comprise the cytoskeletons of cell bodies and axons. Separate populations of cell bodies and axons were collected and the proteins stained by the Coomassie brilliant blue method. Individual identified cell bodies, with long segments of their axons attached, were isolated, and the proteins were labeled with the [125I]Bolton-Hunter reagent. The proteins which are stably associated with the cytoskeleton were obtained by extracting the neuronal material in a physiological buffer containing Triton X-100. As a correlative measure to the biochemical analyses, electron microscopy was performed on the cell body and axonal fractions. Our results demonstrate that the composition and biochemical properties of the cytoskeletal proteins in the neuron cell bodies differ from those associated with axons. Specifically, the amount of neurofilament proteins, designated NF60 and NF65 , is 5 times more abundant in the axon than in the cell body. The relative amounts of actin and tubulin are comparable in these two regions of the neuron. In addition, the ratio of NF60 and NF65 is different in the cell body and axon. The cell bodies contain proportionally more NF60 than the axons. However, the physical properties of the tubulin in the cell body, as measured by relative solubility, differ from that of the axon. The substantial differences between the composition of the cytoskeleton of the cell bodies and axons of Aplysia suggests that at least two distinct cytoskeletal networks exist in these neurons, one specific for the cell body and the other specific for the axon.

Animals↗
PubMed1981

Mechanisms of action of cyclic nucleotides on a bursting pacemaker and silent neuron in Aplysia.

Cyclic nucleotides are believed to mediate a long-lasting synaptic hyperpolarization in the bursting pacemaker neuron, R15, and are capable of inducing bursting pacemaker activity in the usually silent metacerebral giant cell. Steady state voltage clamp techniques were used to examine the alterations of membrane characteristics produced in these different cell types by cyclic nucleotides. In both cells, IBMX, a phosphodiesterase inhibitor, increased two components: (1) voltage-dependent sodium current and (2) slope conductance believed to reflect potassium flux. The effects of 8-benzylthio-cAMP were identical to those of IBMX in the metacerebral cell. In R15, 8-benzylthio-cAMP affected only the slope conductance. These results are discussed in terms of cyclic nucleotide of bursting pacemaker activity.

1-Methyl-3-isobutylxanthine↗
PubMed1980

Alteration of neuronal activity in response to cyclic nucleotide agents in Aplysia.

Responsiveness of Aplysia neurons to agents that affect cyclic nucleotide levels was not limited to neurons exhibiting a spontaneous bursting activity pattern. Analyses of the I-V relationship elicited by triangular current ramps within cells exposed to different agents presumably causing elevated cyclic nucleotide levels showed qualitatively similar alterations. These included an increased slope conductance at more negative potentials, possibly related to anomalous rectification, and the induction of a hysteresis in response to a triangular ramp. The paired metacerebral giant cells showed induction of synchronous bursting when exposed to phosphodiesterase inhibitors, and we examined this phenomenon more closely. Classical methods to inactivate a presynaptic source did not eliminate the induction of synchronous bursting. Intracellular injection of a phosphodiesterase inhibitor into a metacerebral giant cell caused changes in the current-voltage relationship similar to those described above for other cells. Subsequent perfusion with the inhibitor caused an enhancement of these effects and the induction of bursting. The alteration of the current-voltage plot in the metacerebral cells and abdominal ganglion cells is qualitatively similar to that induced in the similarly treated bursting neuron R15, suggesting a similar mechanism of action in both burster and nonburster neurons. The implications of these results for cyclic nucleotide mediation of neuronal events are discussed.

1-Methyl-3-isobutylxanthine↗