摘要:

AbstractThe lower extrinsic protractor muscle in the buccal mass ofAplysiaconsists of bundles of muscle fibers 4–12 m̈ in diameter, containing thick and thin filaments that are not arranged in a transversely striated pattern. Individual fibers come close to one another and form specialized junctional regions. Electrophysiological evidence indicates that the muscle fibers form an electrical syncytium. Muscle bundles are innervated by more than one excitatory axon at a number of points along their length. The presynaptic terminals contain spherical electron‐lucent vesicles and a few larger electron‐dense vesicles. There are no obvious structural postsynaptic specializations. Graded contraction can result from summation of excitatory junctional potentials in separate axons or from summation and facilitation of junctional potentials from a single axon. The buildup of facilitation during a train of stimuli results from the linear summation of facilitation remaining from preceding im

ISSN:0022-3034    

DOI:10.1002/neu.480060602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe distribution of radioactive RNA and RNA precursors in the goldfish optic tecta following intraocular injection of3H‐uridine has been studied during various stages of optic nerve regeneration.3H‐uridine was injected into the posterior chamber of the right eye 17, 30, or 60 days after both optic nerves were crushed. Fish were sacrificed at time intervals ranging from 0.5 to 21 days after injection. One day prior to sacrificing,14C‐proline was also injected into the right eye as a marker of fast axonal protein transport. Seventeen to 23 days after crushing, the approximate time of nerve reconnection, the amount of radioactive RNA appearing in the left optic tectum was increased by more than ten times control values. Approximately 30 days after crushing the nerve, when the reconnected nerve is maturing, RNA values were still elevated, but significantly decreased from the earlier stage. By 60 days after crushing the optic nerve, the amounts of RNA in the left tectum was close to normal. Evidence suggesting that, at least, some of the radioactive RNA in the tectum originated from RNA transported along optic axons rather than from RNA synthesized locally in the tectum was provided by autoradiographic experiments. Autoradiograms of paraffin sections taken from the goldfish optic tecta after the intraocular injection of3H‐uridine showed a distribution of grains in a linear pattern, suggesting a distribution over the incoming fibers during the reconnection stage of regeneration. Electron microscopic autoradiography of glutaraldehyde fixed epoxy sections confirmed that a significant number of grains (shown to be3H‐RNA) were, in fact, over regenerating optic axons. Intracranial injection of3H‐uridine, during the same stage of regeneration, on the other hand, resulted in a distribution of grains, specifically over cell perikarya. These experiments suggest that during the reconnection phase of nerve regeneration, large amounts of RNA may be carried within regenerating optic axons as they enter the o

ISSN:0022-3034    

DOI:10.1002/neu.480060603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe intraocular transplantation technique was used to study the ingrowth of peripheral sympathetic adrenergic nerves from the iris into transplants of fetal rat cerebellum, and the possible function of these nerves. The transplants, grownin oculofor one‐half to eight months, were analyzed by fluorescence histochemistry and electrophysiological techniques. Peripheral sympathetic adrenergic fibers from the iris were able to grow into the cerebellar transplants and arborize in a pattern similar to thatin situ, appearing in all three cortical layers and the noncortical areas of the transplants. The density of visible nerves without pretreatment and after preincubation in 10−6or 10−5Mα‐methylnorepinephrine was comparable to mature rat cerebellum.The spontaneous discharge of the Purkinje cellsin oculowas inhibited by microiontophoresis of norepinephrine (NE) and amphetamine in sympathetically innervated, as well as sympathectomized transplants denervated by ganglionectomy. The NE response was blocked by the adrenergic β‐receptor blocker MJ‐1999. GABA also inhibited the Purkinje cell activity while glutamate accelerated the discharge. Parenteral amphetamine inhibited Purkinje cell activity in sympathetically innervated transplants, but was ineffective in denervated transplants.The Purkinje cell spontaneous activity was inhibited by electrical stimulation of the NE fiber input through the cervical sympathetic trunk. This inhibition could be antagonized by parenteral reserpine or the β‐adrenergic antagonist propranolol.The responses of the Purkinje cells within the transplants to drugs and transmitters mimic those of the adult ratin situ.In view of the fluorescence histochemical evidence for an ingrowth of peripheral sympathetic adrenergic fibers into the cerebellar transplants, and the results of stimulating the sympathetic trunk, it is suggested that peripheral adrenergic fibers may be able to establish functional connections with the Purkinje cells similar to the cerebellar adrenergic synapses normally formedin situby fibers from the

ISSN:0022-3034    

DOI:10.1002/neu.480060604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe activities of catechol‐O‐methyl transferase (COMT), monoamine oxidase (MAO), and a methanol forming enzyme were studied in whole brain homogenates and in livers obtained from DBA/2J, C57B1/6J, and F1hybrid mice. DBA/2J mice are extremely susceptible to audiogenic seizures, where as C57B1/6J mice are resistant to sound‐induced convulsions. C57B1/6J mice were found to have significantly higher brain levels of COMT, while MAO activities were not different in animals of these genotypes. No methanol forming activity was detected in animals of either strain. No differences were found in hepatic activities of either COMT or MAO. Pyrogallol was shown to protect DBA/2J animals against audiogenic sei

ISSN:0022-3034    

DOI:10.1002/neu.480060605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractA study was made of the time course and kinetics of [3H]GABA uptake by dispersed cell cultures of postnatal rat cerebellum with and without neuronal cells. The properties of GABA neurons were calculated from the biochemical difference between the two types of cultures. It was found that for any given concentration of [3H]GABA, or any time up to 20 min, GABA neurons in cultures 21 daysin vitrohad an average velocity of uptake several orders of magnitude greater than that of nonneuronal cells. In addition, the apparentKmvalues for GABA neurons for high and low affinity uptake were 0.33 × 10−6Mand 41.8 × 10−4M, respectively. For nonneuronal cells, the apparentKmfor high affinity uptake was 0.29 × 10−6M.The apparentVmaxvalues for GABA neurons for high and low affinity uptake were 28.7 × 10−6mol/g DNA/min and 151.5 mmol/g DNA/min, respectively. For nonneuronal cells, the apparentVmaxfor high affinity uptake was 0.06 × 10−6mol/g DNA/min. No low affinity uptake system for nonneuronal cells could be detected after correcting the data for binding and diffusion. By substituting the apparent kinetic constants in the Michaelis‐Menten equation, it was determined that for GABA concentrations of 5 × 10−9Mto 1 mMor higher over 99% of the GABA should be accumulated by GABA neurons, given equal access of all cells to the label. In addition, high affinity uptake of [3H]GABA by GABA neurons was completely blocked by treatment with 0.2 mMouabain, whereas that by nonneuronal cells was only slightly decreased. Most (75–85%) of the [3H]GABA (4.4 × 10−6M) uptake by both GABA neurons and nonneuronal cells was sodium a

ISSN:0022-3034    

DOI:10.1002/neu.480060606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480060607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480060608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480060601

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY