Neuroscience
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We have developed procedures for dissociating neurons from the myenteric plexus of the small intestine of newborn rats and for growing those neurons in cell cultures for up to 3 months. Neurons in these cultures retain many of the differentiated properties of myenteric neurons in vivo. This is the first of a series of 3 papers describing those properties. ⋯ An antiserum directed against choline acetyltransferase stained 40-50% of the neurons. We conclude that myenteric neurons continue to express much of their normal differentiated properties even when they are removed from the gut, dissociated into a suspension of single cells and grown in culture. Such cultures will be useful for correlating the morphological, biophysical, pharmacological and synaptic properties of individual myenteric neurons and for testing the ability of altered environmental conditions to change those properties.
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The projections from the medullary and spinal dorsal horns to the dorsolateral pons were investigated in the cat utilizing both the retrograde and anterograde transport of a wheat germ agglutinin-horseradish peroxidase complex and the retrograde transport of the fluorescent dyes Fast Blue and Nuclear Yellow. After injections of wheat germ agglutinin-horseradish peroxidase into the area surrounding the brachium conjunctivum, numerous neurons were labeled ipsilaterally near levels of the obex in the paratrigeminal nucleus. Such neurons were located in connected pockets of neuropil located within the spinal trigeminal tract and along its medial edge. ⋯ The anterograde transport of wheat germ agglutinin-horseradish peroxidase was used to determine the termination of the projections from neurons in the medulary dorsal horn and the cervical spinal cord to the peribrachial area. After injections into these areas a moderate to sparse labeling of the lateral parabrachial nucleus and the Kolliker-Fuse nucleus was seen. It was mostly ipsilateral in cases with injections of the medullary dorsal horn but was bilateral following injections into the cervical enlargement.(ABSTRACT TRUNCATED AT 400 WORDS)
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The spinal projections from the raphe-associated brainstem areas containing serotonergic neurons were studied with aldehyde-induced fluorescence in combination with the retrograde fluorescent tracer True Blue in the rat. This technique makes it possible to determine simultaneously the projections of individual neurons and to detect whether serotonin is present in the same neurons. After tracer injections into the spinal cord retrogradely labeled serotonergic and non-serotonergic neurons were found in the medullary raphe nuclei and adjacent regions and to a lesser extent in association with the dorsal and median raphe nuclei in the mesencephalon. ⋯ Summarizing the results obtained from small injections restricted to subregions of the cord we feel that it is possible to distinguish three fairly distinct pathways for spinal projections from the medullary raphe and adjacent regions: The dorsal pathway originates mainly from cells in the caudal pons and rostral medulla oblongata (rostral part of nucleus raphe magnus, nucleus raphe magnus proper, nucleus reticularis gigantocellularis pars alpha and nucleus paragigantocellularis). This pathway, which contains a large non-serotonergic component, descends through the dorsal part of the lateral funiculus and terminates mainly in the dorsal horn at all spinal cord levels. The intermediate pathway is largely serotonergic with its cell bodies located within the arcuate cell group (situated just ventral and lateral to the pyramids very close to the ventral surface of the brainstem) and in the nucleus raphe obscurus and pallidus and terminates in the intermediate grey at thoracolumbar and upper sacral levels.(ABSTRACT TRUNCATED AT 400 WORDS)
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The sequence of developmental events leading to the innervation of the cochlea and the differentiation of its receptor cells has been studied in chick embryos with Golgi methods. We describe the morphogenesis of cochlear ganglion cell peripheral processes from their appearance in early embryos to the formation of their mature endings on hair cells in the basilar papilla (organ of Corti) of prehatching chicks. In the stage of peripheral fiber outgrowth, embryonic days 3-5, the fibers emerge from the ganglion cell bodies and grow, in a uniform fashion, toward the undifferentiated receptor epithelium of the otocyst. ⋯ During mid-synaptogenesis, when the ganglion cells develop swellings in the periphery, their central axons ramify extensively. Late in synaptogenesis, while the peripheral swellings disappear, there is a corresponding condensation of the central terminals to form the end-bulbs of Held. Thus, specific connections of the cochlear ganglion cells and their target cells in the ear and brain may result from two sequential developmental phases: (1) loosely organized and overabundant initial growth of branches from the fibers entering their target tissue; (2) reorganization of these fibers with the disappearance or resorption of the surplus branches during the transformation of their endings into mature synaptic arrangements.(ABSTRACT TRUNCATED AT 400 WORDS)
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Comparative Study
Factors influencing the cholinesterases of cerebrospinal fluid in the anaesthetized cat.
Both acetylcholinesterase and non-specific cholinesterase are found in cerebrospinal fluid and blood plasma of the cat; the ratio of activities acetylcholinesterase/non-specific cholinesterase is about 1.5 in cerebrospinal fluid and 0.15 in plasma. A search was made for factors capable of influencing the concentration of the two cholinesterases in cerebrospinal fluid. Either the ventricular system was perfused with artificial cerebrospinal fluid from a lateral ventricle to the aqueduct, or the atlanto-occipital membrane was punctured and cerebrospinal fluid was collected continuously from the cisterna magna. ⋯ A rise in acetylcholinesterase concentration was obtained upon stimulation of the central ends of the sciatic nerves; this was inhibited by atropine but not by N-methylatropine, indicating that the rise was due to increased nervous activity and not to the circulatory effects of the stimulation, since the changes in blood pressure caused by the stimulation remained the same after atropine administration. Amphetamine or leptazol raised the levels of acetylcholinesterase but it was not possible to determine whether this was due only to increased central nervous activity, since there was invariably leakage through the blood-brain barrier which by itself would be sufficient to produce the effect. A rise in the level of acetylcholinesterase was seen after administration of pyrogen; this was apparently not a simple effect of warming the body, but due to the action of the pyrogen on centers concerned with temperature control, since warming the animal by external heat failed to produce a similar change.(ABSTRACT TRUNCATED AT 400 WORDS)