共查询到20条相似文献，搜索用时 46 毫秒
1.
Molecular cloning of a gene sequence regulated by nerve growth factor 总被引：22，自引：0，他引：22
Nerve growth factor (NGF) is essential for the development and differentiation of sympathetic or sensory neurons. A complementary DNA was cloned that corresponds to a gene sequence induced more than 50-fold in a cultured target cell line of pheochromocytoma cells (PC12 cells) 5 hours after the addition of NGF. The induced messenger RNA encodes a 90,000-dalton polypeptide that may represent one of the primary events in NGF-induced differentiation of neurons. 相似文献
2.
Localization of amyloid beta protein messenger RNA in brains from patients with Alzheimer's disease 总被引：43，自引：0，他引：43
S Bahmanyar G A Higgins D Goldgaber D A Lewis J H Morrison M C Wilson S K Shankar D C Gajdusek 《Science (New York, N.Y.)》1987,237(4810):77-80
The distribution of cells containing messenger RNA that encodes amyloid beta protein was determined in hippocampi and in various cortical regions from cynomolgus monkeys, normal humans, and patients with Alzheimer's disease by in situ hybridization. Both 35S-labeled RNA antisense and sense probes to amyloid beta protein messenger RNA were used to ensure specific hybridization. Messenger RNA for amyloid beta protein was expressed in a subset of neurons in the prefrontal cortex from monkeys, normal humans, and patients with Alzheimer's disease. This messenger RNA was also present in the neurons of all the hippocampal fields from monkeys, normal humans and, although to a lesser extent in cornu ammonis 1, patients with Alzheimer's disease. The distribution of amyloid beta protein messenger RNA was similar to that of the neurofibrillary tangles of Alzheimer's disease in some regions, but the messenger RNA was also expressed in other neurons that are not usually involved in the pathology of Alzheimer's disease. 相似文献
3.
Tail shock produces transient presynaptic inhibition and longer lasting presynaptic facilitation of the siphon sensory neurons in Aplysia. The facilitation undergoes activity-dependent enhancement that is thought to contribute to classical conditioning of the gill- and siphon-withdrawal reflex. Inhibition of the sensory neurons has now also been shown to undergo activity-dependent enhancement when action potential activity in the sensory neurons is paired with inhibitory transmitter. This effect appears to involve an amplification of the same cellular mechanisms that are involved in normal presynaptic inhibition. These results suggest that activity-dependent enhancement may be a general type of associative cellular mechanism. 相似文献
4.
Intracellular injection of cAMP induces a long-term reduction of neuronal K+ currents 总被引：5，自引：0，他引：5
Intracellular signals that trigger long-term (24-hour) changes in membrane currents in identified neurons of Aplysia have been examined in order to understand the cellular mechanisms underlying long-term sensitization. Adenosine 3',5'-monophosphate (cAMP) was directly injected into individual sensory neurons to mimic the effects of sensitization training at the single cell level. Potassium currents of these cells were reduced 24 hours after injection of cAMP; these currents were similar to those reduced 24 hours after behavioral sensitization. These results suggest that cAMP is part of the intracellular signal that induces long-term sensitization in Aplysia. 相似文献
5.
RNA complementary to a herpesvirus alpha gene mRNA is prominent in latently infected neurons 总被引：107，自引：0，他引：107
J G Stevens E K Wagner G B Devi-Rao M L Cook L T Feldman 《Science (New York, N.Y.)》1987,235(4792):1056-1059
6.
Neuronal correlates of habituation and dishabituation of the gill-withdrawal reflex in Aplysia 总被引：4，自引：0，他引：4
We have examinived the nieural correlates of habittuatiotn atid dishabitiuation of tlhe gill-withdrwal reflex in Aplysia. We obtained intracelllular recordings from identified gill motor neurons in the abdominal ganglionz of a semi-intact preparation of Aplysia wlhile we simultaneously recorded behavior responises of the gill. Habituation and dishabituation were not due to peripheral changes in either the sensory receptors or the gill musculature butt were caused by changes in the amplitlude of the excitatory synaptic potentials produced at the gill motor neurons. 相似文献
7.
Target-dependent structural changes accompanying long-term synaptic facilitation in Aplysia neurons 总被引：7，自引：0，他引：7
The mechanisms underlying structural changes that accompany learning and memory have been difficult to investigate in the intact nervous system. In order to make these changes more accessible for experimental analysis, dissociated cell culture and low-light-level video microscopy were used to examine Aplysia sensory neurons in the presence or absence of their target cells. Repeated applications of serotonin, a facilitating transmitter important in behavioral dishabituation and sensitization, produced growth of the sensory neurons that paralleled the long-term enhancement of synaptic strength. This growth required the presence of the postsynaptic motor neuron. Thus, both the structural changes and the synaptic facilitation of Aplysia sensorimotor synapses accompanying long-term behavioral sensitization can be produced in vitro by applying a single facilitating transmitter repeatedly. These structural changes depend on an interaction of the presynaptic neuron with an appropriate postsynaptic target. 相似文献
8.
9.
Expression of a calcium-mobilizing parathyroid hormone-like peptide in lactating mammary tissue 总被引：23，自引：0，他引：23
A survey of rat tissues by RNA analysis, aimed at uncovering the physiological function of the parathyroid hormone-like peptide (PTH-LP) associated with hypercalcemia of malignancy, revealed the presence of a 1.5-kilobase messenger RNA encoding this peptide in lactating mammary glands. PTH-LP messenger RNA is expressed in mammary tissue only during lactation; it appears and disappears rapidly (2 to 4 hours) as a function of the sucking stimulus. The identity of this messenger RNA was confirmed by cloning the rat PTH-LP complementary DNA, which predicts a peptide with strong similarity to the human homolog. Moreover, extracts from lactating mammary tissue stimulated parathyroid hormone-dependent adenylate cyclase. These findings suggest that PTH-LP plays a physiological role in lactation, possibly as a hormone for the mobilization or transfer (or both) of calcium to the milk. 相似文献
10.
11.
A critical period for macromolecular synthesis in long-term heterosynaptic facilitation in Aplysia 总被引：24，自引：0，他引：24
P G Montarolo P Goelet V F Castellucci J Morgan E R Kandel S Schacher 《Science (New York, N.Y.)》1986,234(4781):1249-1254
Both long-term and short-term sensitization of the gill and siphon withdrawal reflex in Aplysia involve facilitation of the monosynaptic connections between the sensory and motor neurons. To analyze the relationship between these two forms of synaptic facilitation at the cellular and molecular level, this monosynaptic sensorimotor component of the gill-withdrawal reflex of Aplysia can be reconstituted in dissociated cell culture. Whereas one brief application of 1 microM serotonin produced short-term facilitation in the sensorimotor connection that lasted minutes, five applications over 1.5 hours resulted in long-term facilitation that lasted more than 24 hours. Inhibitors of protein synthesis or RNA synthesis selectively blocked long-term facilitation, but not short-term facilitation, indicating that long-term facilitation requires the expression of gene products not essential for short-term facilitation. Moreover, the inhibitors only blocked long-term facilitation when given during the serotonin applications; the inhibitors did not block the facilitation when given either before or after serotonin application. These results parallel those for behavioral performance in vertebrates and indicate that the critical time window characteristic of the requirement for macromolecular synthesis in long-term heterosynaptic facilitation is not a property of complex circuitry, but an intrinsic characteristic of specific nerve cells and synaptic connections involved in the long-term storage of information. 相似文献
12.
Endothelin: a novel peptide in the posterior pituitary system 总被引：21，自引：0，他引：21
T Yoshizawa O Shinmi A Giaid M Yanagisawa S J Gibson S Kimura Y Uchiyama J M Polak T Masaki I Kanazawa 《Science (New York, N.Y.)》1990,247(4941):462-464
Endothelin (ET), originally characterized as a 21-residue vasoconstrictor peptide from endothelial cells, is present in the porcine spinal cord and may act as a neuropeptide. Endothelin-like immunoreactivity has now been demonstrated by immunohistochemistry in the paraventricular and supraoptic nuclear neurons and their terminals in the posterior pituitary of the pig and the rat. The presence of ET in the porcine hypothalamus was confirmed by reversed-phase high-pressure liquid chromatography and radioimmunoassay. Moreover, in situ hybridization demonstrated ET messenger RNA in porcine paraventricular nuclear neurons. Endothelin-like immunoreactive products in the posterior pituitary of the rat were depleted by water deprivation, suggesting a release of ET under physiological conditions. These findings indicate that ET is synthesized in the posterior pituitary system and may be involved in neurosecretory functions. 相似文献
13.
Long-term synaptic changes produced by a cellular analog of classical conditioning in Aplysia 总被引：1，自引：0，他引：1
A change in synaptic strength arising from the activation of two neuronal pathways at approximately the same time is a form of associative plasticity and may underlie classical or Pavlovian conditioning. A cellular analog of a classical conditioning protocol produces short-term associative plasticity at the connections between sensory and motor neurons in Aplysia. A similar training protocol produced long-term (24-hour) enhancement of excitatory postsynaptic potentials (EPSPs). EPSPs produced by sensory neurons in which activity was paired with a reinforcing stimulus were significantly larger than unpaired controls 24 hours after training. Thus, associative plasticity at the sensory to motor neuron connection can occur in a long-term form in addition to the short-term form. In this system, it should be possible to analyze the molecular mechanisms underlying long-term associative plasticity and classical conditioning. 相似文献
14.
Neuronal mechanisms of habituation and dishabituation of the gill-withdrawal reflex in Aplysia 总被引：14，自引：0，他引：14
The cellular mechanisms of habituation and dishabituation of the gill-withdrawal reflex in Aplysia were studied with an isolated abdominal ganglion connected to a piece of skin from the tactile receptive field of the reflex. By obtaining simultaneous intracellular recordings from both the sensory neurons and one of the main identified motor neurons, we have been able to reduce the reflex to its monosynaptic components. The monosynaptic excitatory postsynaptic potentials showed a profound low-frequency depression when repeatedly elicited and showed heterosynaptic facilitation after application of a strong stimulus to another pathway. Thus, both habituation and dishabituation can be explained in part and perhaps entirely by changes in the efficacy of specific excitatory synapses. 相似文献
15.
Vasopressin mRNA in the suprachiasmatic nuclei: daily regulation of polyadenylate tail length 总被引：13，自引：0，他引：13
Daily variation has been found in the length of the polyadenylate tail attached to vasopressin messenger RNA in the suprachiasmatic nuclei, which is the location of an endogenous circadian pacemaker in mammals. No such variation was found in the supraoptic or paraventricular nuclei. This variation in the length of the polyadenylate tail may underlie the circadian rhythm of vasopressin peptide levels in cerebrospinal fluid and is a unique example of a daily rhythm in messenger RNA structure. 相似文献
16.
Contributions of two types of calcium channels to synaptic transmission and plasticity 总被引：7，自引：0，他引：7
In Aplysia sensory and motor neurons in culture, the contributions of the major classes of calcium current can be selectively examined while transmitter release and its modulation are examined. A slowly inactivating, dihydropyridine-sensitive calcium current does not contribute either to normal synaptic transmission or to any of three different forms of plasticity: presynaptic inhibition, homosynaptic depression, and presynaptic facilitation. This current does contribute, however, to a fourth form of plasticity--modulation of transmitter release by tonic depolarization of the sensory neuron. By contrast, a second calcium current, which is rapidly inactivating and dihydropyridine-insensitive, contributes to release elicited by the transient depolarization of an action potential and to the other three forms of plasticity. 相似文献
17.
An endogenous polysomal cyclic AMP-dependent protein kinase specifically phosphorylates a 150,000-dalton peptide bound to an adrenocortical polyadenylated messenger ribonucleoprotein complex. There is a possibility that this protein is a physiological substrate of cyclic AMP-dependent protein kinase and that the phosphorylation and dephosphorylation of this substrate may be important in the translation control of adrenal polyadenylated messenger RNA. 相似文献
18.
Aurintricarboxylic acid and initiation factors of wheat embryo 总被引：11，自引：0，他引：11
In extracts of wheat embryo, aurintricarboxylic acid inhibits attachment of ribosomes to messenger RNA and has little effect on aminoacyl transfer to peptide. This specificity of inhibition allows (i) the demonstration that the initial phase of amino acid incorporation dependent on RNA of tobacco mosaic virus involves an "initiation" reaction between ribosome and messenger RNA which requires two soluble factors, (ii) an assay facilitating purification of the initiation factors, and (iii) the demonstration that these factors are distinct from aminoacyl transfer enzymes. 相似文献
19.
Associative conditioning of single sensory neurons suggests a cellular mechanism for learning 总被引：10，自引：0，他引：10
A cellular analog of associative learning has been demonstrated in individual sensory neurons of the tail withdrawal reflex of Aplysia. Sensory cells activated by intracellular current injection shortly before a sensitizing shock to the animal's tail display significantly more facilitation of their monosynaptic connections to a tail motor neuron than cells trained either with intracellular stimulation unpaired to tail shock or with tail shock alone. This associative effect is acquired rapidly and is expressed as a temporally specific amplification of heterosynaptic facilitation. The results suggest that activity-dependent neuromodulation may be a mechanism underlying associative information storage and point to aspects of subcellular processes that might be involved in the formation of neural associations. 相似文献
20.
A fundamental problem in the cellular analysis of learning and memory is the identification of the neuronal substrates of long-term information storage and their relation to short-term cellular alterations. In this report, biophysical correlates of long-term sensitization of a simple withdrawal reflex in the mollusc Aplysia were examined. A voltage-clamp analysis of the sensory neurons that control the reflex, 24 hours after sensitization training, revealed a significant reduction in net outward current. The results indicate that one mechanism for the storage of long-term sensitization is the regulation of membrane currents that influence the characteristics of the action potential and the excitability of individual neurons. The results also provide insights into the relation between short- and long-term sensitization in that the biophysical loci involved in the storage of long-term sensitization appear similar to those involved in short-term sensitization. 相似文献