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S M Crain

Publications and source records attributed to S M Crain.

At least 109 records · Page 6Linked to original sources
PubMed1976

Electrophysiological studies of fetal mouse olifactory bulb explants during development of synaptic functions in culture.

Explants of 18- or 19-day fetal mouse olfactory bulb have been maintained in culture for periods up to 5 weeks. Compound action potentials can be evoked in the bulb explants by 1 day in vitro, and by 3-4 days, synaptically mediated slow wave discharges can be domonstrated in bicuculline (10(-5) m). The capability of the bulb explants to generate these slow-wave discharges has also been revealed by the introduction of picrotoxin (10(-5)m, d-tubocurarine (10(-4)m) and chloride-free medium, but not of strychnine (up to 3 X 10(-5)M. The data indicate early functional development of inhibitory, as well as excitatory, synaptic systems. In addition, the selective and reversible depression of these slow wave potentials by GABA (1-5 X 10(-4)M), but not by glycine (up to 3 X 10(-3)M), indicates a GABA-ergic component in the inhibitory network. Single unit extracellular recordings have been obtained from the presumptive mitral cells which, in culture, are spontaneously active even as early as 1-2 days after explantation. Correlative Bodian silver-impregnations demonstrate the presence of neurons in these explants which resemble typical mitral cells. Studies of mitral cells using paired stimuli suggest the development in vitro of an inhibitory system analogous to that known to suppress the excitability of their in situ counterparts following orthodromic or antidromic activation. These data, as well as the pharmacological sensitivities of the mitral cells in culture to GABA (5 X 10(-4)M) and bicuculline (10(-5)M), indicate that granule-to-mitral synapses may develop characteristic functions in olfactory bulb explants.

Action Potentials↗
PubMed1975

Development of specific sensory-evoked synaptic networks in fetal mouse cord-brainstem cultures.

Neurites of nerve growth factor-enhanced fetal mouse dorsal root ganglion cells can not only establish characteristic sensory synaptic network functions in dorsal regions of attached spinal cord explants, but some of the neurites may grow through the cord tissue in these cultures and make similar functional synaptic connections with specific types of "target" neurons in localized zones within nearby medulla explants.

Animals↗
PubMed1975

Circulation and turnover of synaptic vesicle membrane in cultured fetal mammalian spinal cord neurons.

Intact neurons in cultures of fetal rodent spinal cord explants show stimulation-dependent uptake of horseradish peroxidase (HRP) into many small vesicles and occasional tubules and multivesicular bodies (MVB) at presynaptic terminals. Presynaptic terminals were allowed to take up HRP during 1 h of strychnine-enhanced stimulation of synaptic transmitter release and then "chased" in tracer-free medium either with strychnine or with 10 mM Mg++ which depresses transmitter release. Tracer-containing vesicles are lost from terminals under both chase conditions; the loss is more rapid (4-8 h) with strychnine than with 10 mM Mg++ (8-16 h). There is a parallel decrease in the numbers of labeled MVB's at terminals. Loss of tracer with 10 mM Mg++ does not appear to be due to the membrane rearrangements (exocytosis coupled to endocytosis) that presumably lead to initial tracer uptake; terminals exposed to HRP and Mg++ for up to 16 h show little tracer uptake into vesicles. Nor is the decrease likely to the due to loss of HRP enzyme activity; HRP is very stable in solution. During the chases there is a striking accumulation of HRP in perikarya that is far more extensive in cultures initially exposed to tracer with strychnine than 10 mM Mg++ regardless of chase conditions. Much of the tracer ends up in large dense bodies. These findings suggest that synaptic vesicle membrane turnover involves retrograde axonal transport of membrane to neuronal perikarya for further processing, including lysosomal degradation. The more rapid (4-8 h) loss of tracer-containing vesicles with strychnine may reflect vesicle membrane reutilization for exocytosis.

Axons↗
PubMed1972

Organotypic bioelectric activity in cultured reaggregates of dissociated rodent brain cells.

Complex repetitive-spike or slow-wave discharges can be evoked, and can also occur spontaneously, in small clusters of neurons which reaggregate in vitro after dissociation of cerebral cortex, brainstem, or spinal cord from the fetal mouse. Even after random dispersion in culture, these cells still form functional synaptic networks with bioelectric discharge patterns and pharmacologic sensitivities characteristic of the organ (that is, organotypic).

Animals↗