摘要:

AbstractElimination of most granule, basket, and stellate interneurons in the rat cerebellum was achieved by repeated doses of low level x‐irradiation applied during the first two weeks of postnatal life. Purkinje neurons in these rats, studied when adults, exhibited sustained spiking activity in Halothane anesthetized preparations. Mean firing rates were 35‐‐40/sec, no different from normal. Spontaneous bursts presumed to be generated by climbing fiber synaptic activity differed from normal by often consisting of full sized spikes rather than characteristic inactivation responses. Intracellularly observed correlates of bursts consisted ofepsp'sof several discretely different amplitudes appearing independently in time. Stimulation of white matter revealed evidence for, (a) graded synaptic excitation of Purkinje cells indicating more than one converging excitatory synapse, and (b) inhibitory actions on Purkinje cells either through a few remaining inhibitory interneurons or through Purkinje cell recurrent collaterals. Iontophoretic drug application studies showed normal chemosensitivity of the Purkinje cell membrane, i.e., excitation by glutamate and inhibition by gamma‐amino butyric acid, serotonin, norepinephrine, and 3′5′ cyclic AMP.These studies indicate considerable autonomy of Purkinje cell ontogenesis in the absence of normal interneuronal input. A unique synaptic relation only rarely found in normal cerebellum is the innervation of single Purkinje cells by more than one cli

ISSN:0022-3034    

DOI:10.1002/neu.480050402

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

年代:1974

数据来源: WILEY

摘要:

AbstractCholine acetyltransferase (ChAc) and acetylcholinesterase (AChE) activities have been studied in organotypic cultures of early chick neural tube. During the first week in culture the ChAc activity remains extremely low at which time it can not be demonstrated histochemically in early neurons. It increases rapidly during the second and third weeks in culture, as demonstrated biochemically and histochemically. AChE activity rises rapidly during the first week, and then more gradually for the remainder of the culture period; it can be demonstrated histochemically in early neurons and well differentiated multipolar neurons throughout this period. In our culture system biochemical differentiation (ChAc and AChE activity) occurs concomitantly with morphological differentiation.

ISSN:0022-3034    

DOI:10.1002/neu.480050403

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe conditions for thein vitropolymerization of beef brain tubulin have been examined using turbidity and electron microscopic examination as methods of following the reaction. The optimal conditions are 37°, pH 6.0‐‐6.4, and an ionic strength of approximately 0.08 to 0.1 μ. The ionic strength is particularly critical, at 0.25 μ the polymerization does not occur and increasing the ionic strength of a solution contaning microtubules to this value causes the tubules to depolymerize. GTP and Mg2+are required. After an initial lag period the rate of polymerization appears to follow first‐order kinetics. Although colchicine inhibits the polymerization reaction it does not cause the tubules formedin vitroto depolymerize. Binding studies show that colchicine binds to free tubulin better than to tubules. Calcium also inhibits polymerization and causes the depolymerization of

ISSN:0022-3034    

DOI:10.1002/neu.480050404

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe characteristic features of individual neurons in leech ganglia are highly consistent from animal to animal. Hy chance a leech was dis‐ covered that had more cells to be seen than usual in many of its ganglia.In some segmental ganglia of the abnormal animal there were four or even five sensory cells responding independently to touch (T cells) instead of the usual complement of three on each side. Ganglia also contained three or four pressure sensitive cells (P cells) and three or four nociceptive cells (N cells) instead of two of each. The membrane properties, as well as the shapes, sizes, and positions, of all these cells were normal. Their axons reached the skin by the appropriate nerve bundles.Two sensory neurons of one modality, often independently innervated, overlay regions of skin that normally would be supplied by one cell. On the other hand, the areas innervated by some supernumerary cells were abnormal in their shape and position.In some ganglia instead of one motor neuron that raised the skin into bumps (the annulus erector, or AE cell) there were two, each of which could independently erect annuli. The regions innervated by the extra AE cells appeared normal and overlapped extensively.Normal synaptic interactions were found between supernumerary sensory cells and motor cells.The results with this animal indicate that two or more nerve cells can form effective connections with other neurons and with skin that normally would be innervated by a single cel

ISSN:0022-3034    

DOI:10.1002/neu.480050405

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

年代:1974

数据来源: WILEY

摘要:

AbstractPolyamine levels vary markedly throughout the brain of the rhesus monkey. In general, there is an inverse relationship between spermine and spermidine concentrations; i.e., areas with high spermine levels have low spermidine levels and vice versa. The ratio of spermidine to spermine is as high as 13 in the optic nerve, and as low as 1.2 in the vermis. The variability of this ratio suggests that the functions of the polyamines in the adult brain may be different from those in other tissues. For instance, the ratio of spermidine to spermine in adult rat liver and most other organs is approximately 1, and this ratio increases in growth‐stimulated systems. The precursor of spermidine, diaminobutane, is present in very low quantities in the brain. Electrical stimulation of the precentral gyrus was found to decrease the content of both spermidine and spermine, and these data provide further evidence for a separate brain function of the polyamines. Depletion of spermidine and spermine in the motor cortex by electrical stimulation suggests that these amines may be involved in transmission phenomen

ISSN:0022-3034    

DOI:10.1002/neu.480050406

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

年代:1974

数据来源: WILEY

摘要:

AbstractPurified neuronal fractions from dissociated mouse dorsal root ganglia were cultured in the presence of variable amounts of homologous ganglionic nonneuronal cells, and with or without addition of variable amounts of exogenous Nerve Growth Factor in the culture medium. The ability of the nonneurons to support long‐term neuronal survival in the absence of exogenous Nerve Growth Factor increased linearly with their numbers and maximal neuronal performance was achieved with a 4:1 ratio of non‐neurons to neurons; however, neuronal attachment was elicited maximally as soon as that ratio reached or slightly exceeded a value of one. Besides this Nerve Growth Factor‐like function, the nonneurons were also involved in determining whether and to what extent the factor was capable of supporting neuronal performance. In the absence of non‐neurons, even high concentrations of the factor failed to elicit neuronal attachment. As more nonneuronal cells were made available, Nerve Growth Factor progressively raised neuronal performance and did so at sharply declining requirement levels: with 12,000 nonneurons/dish maximal performance required only 10−2biological unit/ml of the factor. Further increases of the nonneurons reduced the scope of a neuronal response to Nerve Growth Factor between the maximal performance of the culture system and the increasing performance elicited without the factor. The results indicate that, given a minimal level of nonneurons, the performance in culture of these ganglionic neurons could be promoted in very similar patterns by either increasing the exogenous Nerve Growth Factor in the medium or increasing the ganglionic nonneurons on the culture floors, with an approximate and fixed ratio of 10−7biological unit per nonneuron. Possibilities are discussed of a common mechanism underlying the supportive properties of the

ISSN:0022-3034    

DOI:10.1002/neu.480050407

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

年代:1974

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480050408

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

年代:1974

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480050401

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

年代:1974

数据来源: WILEY