Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Target plasticity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed1998

Molecular and pharmacological analysis of cyclic nucleotide-gated channel function in the central nervous system.

Most functional studies of cyclic nucleotide-gated (CNG) channels have been confined to photoreceptors and olfactory epithelium, in which CNG channels are abundant and easy to study. The widespread distribution of CNG channels in tissues throughout the body has only recently been recognized and the functions of this channel family in many of these tissues remain largely unknown. The molecular biological and pharmacological properties of the CNG channel family are summarized in order to put in context studies aimed at probing CNG channel functions in these tissues using pharmacological and genetic methods. Compounds have now been identified that are useful in distinguishing CNG channel activated pathways from cAMP/cGMP dependent-protein kinases or other pathways. The ways in which these interact with CNG channels are understood and this knowledge is leading to the identification of more potent and more specific CNG channel subtype-specific agonists or antagonists. Recent molecular and genetic analyses have identified novel roles of CNG channels in neuronal development and plasticity in both invertebrates and vertebrates. Targeting CNG channels via specific drugs and genetic manipulation (such as knockout mice) will permit better understanding of the role of CNG channels in both basic and higher orders of brain function.

Animals↗
PubMed2005

Expression of Ndrg2 in the rat frontal cortex after antidepressant and electroconvulsive treatment.

Although the therapeutic action of antidepressants most likely involves the regulation of serotonergic and noradrenergic signal transduction, no consensus has been reached concerning their precise molecular or cellular mechanisms of action. In the present study, we demonstrated that chronic treatment with a tricyclic antidepressant (imipramine) and a selective serotonin reuptake inhibitor (sertraline) reduced the expression of Ndrg2 mRNA and protein in the rat frontal cortex. Ndrg2 is a member of the N-Myc downstream-regulated genes. Interestingly, repeated ECT also significantly decreased Ndrg2 expression in this region of the brain. These data suggest that Ndrg2 may be a common functional molecule that is decreased after antidepressant treatment and ECT. Although, the functional role of Ndrg2 in the central nervous system remains unclear, our findings suggest that Ndrg2 may be associated with treatment-induced adaptive neural plasticity in the brain, a chronic target of antidepressant action. In conclusion, we have identified Ndrg2 as a candidate target molecule of antidepressants and ECT.

Analysis of Variance↗
PubMedDate not supplied

Multiple oscillators, dynamic synchronization and sympathetic control.

1. Intermittent bursts of activity are a robust feature of the discharges of sympathetic nerves. There are at least two major mechanisms producing such discharges: (i) phasic inputs influencing sympathetic circuits; and (ii) oscillators embedded within sympathetic networks. The functional significance of patterned and synchronized activity underlying bursts of population activity may reside in their influence on information transfer between excitable cells. At the level of the single neuron, firing pattern appears to be an important determinant of synaptic/neuroeffector function (e.g. the probability of transmitter release, the types of transmitter released, the types of receptor activated and plasticity). Synchronization of inputs at a target favours summation and, therefore, may influence response (short term and long term). 2. In the present paper, I review the work from my laboratory that has focused on furthering understanding of the potential functional importance of pattern and synchrony coding in sympathetic nervous control of cardiovascular function. Because the rat tail artery has been used extensively as a model for studying neuroeffector transmission, in our investigations we have recorded from its sympathetic innervation. 3. In the anaesthetized preparation, under steady state conditions, we have established that the discharges of these sympathetic neurons have a distinct rhythm (frequency approximately 0.8 Hz). This can be detected both at single neuron and population levels. 4. A family of oscillators appears to control their discharge such that under some conditions all neurons do not have the same frequency of rhythmical activity. However, these weakly coupled or uncoupled oscillators can be synchronized dynamically by various inputs, such as central respiratory drive, lung inflation cycle-related inputs and inputs arising from visceral and somatic afferents. 5. The potential functional significance of dynamic synchronization of sympathetic oscillators in relation to sympathetic pattern generation and neuroeffector transmission is discussed.

Animals↗
PubMed2005

Glutamatergic reinnervation through peripheral nerve graft dictates assembly of glutamatergic synapses at rat skeletal muscle.

Acetylcholine is the main neurotransmitter at the mammalian neuromuscular junction (NMJ) where nicotinic acetylcholine receptors mediate the signaling between nerve terminals and muscle fibers. We show that under glutamatergic transmission, rat NMJ switches from cholinergic type synapse to glutamatergic synapse. Connecting skeletal muscle to the lateral white matter of the spinal cord by grafting the distal stump of the transected motor nerve produced functional muscle reinnervation. The restored neuromuscular activity became resistant to common curare blockers but sensitive to the glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist. Analysis of the regenerated nerve disclosed new glutamatergic axons and the disappearance of cholinergic fibers. Many axons belonged to the supraspinal neurons located in the red nucleus and the brainstem nuclei. Finally, the innervated muscle displayed high expression and clustering of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunits glutamate receptors 1 and 2. Our data suggest that supraspinal neurons can target skeletal muscle, which retains the plasticity to generate functional glutamatergic NMJ.

Action Potentials↗
PubMed1991

Age-dependent decrease in the affinity of muscarinic M1 receptors in neocortex of rhesus monkeys.

In vitro autoradiography on tissue sections and receptor assay in cortical membrane homogenates revealed that pirenzepine high-affinity muscarinic sites (M1) decrease in affinity in the prefrontal cortex and in other cortical areas of aged rhesus monkey (Macaca mulatta). Carbachol competition experiments detected only a single, low-affinity class of sites in old monkeys, while two classes of sites (low and high affinity) were observed in young adults. The change in affinity in the aged monkeys is not accompanied by a decrease in the density of these sites and, further, the age-related decline in the affinity of the M1 site is reversible. In the presence of Mg2+, the M1 muscarinic receptors in the aged monkeys were capable of forming carbachol high-affinity sites. These results provide evidence for age-dependent functional changes in receptor activity in cerebral cortex and indicate that these receptors maintain a degree of plasticity that could be a strategic target for research aimed at treatment of memory disorders in aged humans.

Aging↗
PubMed1993

Peripherin expression in hippocampal neurons induced by muscle soluble factor(s).

Previous studies have shown that neuronal cells in culture can switch neurotransmitters when grown in the presence of different target cells. To examine whether this plasticity extends to structural proteins, we cocultured hippocampal neurons and pituitary-derived neuroendocrine (AtT20) cells with astrocytes, kidney epithelial cells, or skeletal muscle cells. As a marker of phenotypic change we used the cytoskeletal protein peripherin, a type III intermediate filament (IF) subunit which is not expressed in hippocampal neurons and AtT20 cells. We show here that soluble factor(s) secreted specifically from skeletal muscle cells can induce the expression and de novo assembly of peripherin in a subset of post-mitotic neurons. We further demonstrate that one of these factors is the Leukemia Inhibitory Factor/Cholinergic Neuronal Differentiation Factor. The environmentally regulated expression of peripherin implies a remarkable degree of plasticity in the cytoskeletal organization of postmitotic CNS cells and provides a noninvasive model system to examine the de novo assembly of IF proteins under in vivo conditions.

Animals↗
PubMed2002

Complete genomic sequence of nitrogen-fixing symbiotic bacterium Bradyrhizobium japonicum USDA110.

The complete nucleotide sequence of the genome of a symbiotic bacterium Bradyrhizobium japonicum USDA110 was determined. The genome of B. japonicum was a single circular chromosome 9,105,828 bp in length with an average GC content of 64.1%. No plasmid was detected. The chromosome comprises 8317 potential protein-coding genes, one set of rRNA genes and 50 tRNA genes. Fifty-two percent of the potential protein genes showed sequence similarity to genes of known function and 30% to hypothetical genes. The remaining 18% had no apparent similarity to reported genes. Thirty-four percent of the B. japonicum genes showed significant sequence similarity to those of both Mesorhizobium loti and Sinorhizobium meliloti, while 23% were unique to this species. A presumptive symbiosis island 681 kb in length, which includes a 410-kb symbiotic region previously reported by Göttfert et al., was identified. Six hundred fifty-five putative protein-coding genes were assigned in this region, and the functions of 301 genes, including those related to symbiotic nitrogen fixation and DNA transmission, were deduced. A total of 167 genes for transposases/104 copies of insertion sequences were identified in the genome. It was remarkable that 100 out of 167 transposase genes are located in the presumptive symbiotic island. DNA segments of 4 to 97 kb inserted into tRNA genes were found at 14 locations in the genome, which generates partial duplication of the target tRNA genes. These observations suggest plasticity of the B. japonicum genome, which is probably due to complex genome rearrangements such as horizontal transfer and insertion of various DNA elements, and to homologous recombination.

Bradyrhizobium↗
PubMed2005

Differential role of inhibition in habituation of two independent afferent pathways to a common motor output.

Many studies of the neural mechanisms of learning have focused on habituation, a simple form of learning in which a response decrements with repeated stimulation. In the siphon-elicited siphon withdrawal reflex (S-SWR) of the marine mollusk Aplysia, the prevailing view is that homosynaptic depression of primary sensory afferents underlies short-term habituation. Here we examined whether this mechanism is also utilized in habituation of the tail-elicited siphon withdrawal reflex (T-SWR), which is triggered by an independent, polysynaptic afferent pathway that converges onto the same siphon motor neurons (MNs). By using semi-intact preparations in which tail and/or siphon input to siphon MNs could be measured, we found that repeated tail stimuli administered in the presence of a reversible conduction block of the nerves downstream of the tail sensory neurons (SNs) completely abolished the induction of habituation. Subsequent retraining revealed no evidence of savings, indicating that the tail SNs and their immediate interneuronal targets are not the locus of plasticity underlying T-SWR habituation. The networks closely associated with the siphon MNs are modulated by cholinergic inhibition. We next examined the effects of network disinhibition on S-SWR and T-SWR habituation using an Ach receptor antagonist d-tubocurarine. We found that the resulting network disinhibition disrupted T-SWR, but not S-SWR, habituation. Indeed, repeated tail stimulation in the presence of d-tubocurarine resulted in an initial enhancement in responding. Lastly, we tested whether habituation of T-SWR generalized to S-SWR and found that it did not. Collectively, these data indicate that (1) unlike S-SWR, habituation of T-SWR does not involve homosynaptic depression of SNs; and (2) the sensitivity of T-SWR habituation to network disinhibition is consistent with an interneuronal plasticity mechanism that is unique to the T-SWR circuit, since it does not alter S-SWR.

Afferent Pathways↗
PubMed2006

Gliding motility of Mycoplasma mobile can occur by repeated binding to N-acetylneuraminyllactose (sialyllactose) fixed on solid surfaces.

Mycoplasma mobile relies on an unknown mechanism to glide across solid surfaces including glass, animal cells, and plastics. To identify the direct binding target, we examined the factors that affect the binding of Mycoplasma pneumoniae to solid surfaces and concluded that N-acetylneuraminyllactose (sialyllactose) attached to a protein can mediate glass binding on the basis of the following four lines of evidence: (i) glass binding was inhibited by N-acetylneuraminidase, (ii) glass binding was inhibited by N-acetylneuraminyllactose in a structure-dependent manner, (iii) binding occurred on glass pretreated with bovine serum albumin attached to N-acetylneuraminyllactose, and (iv) gliding speed depended on the density of N-acetylneuraminyllactose on glass.

Bacterial Adhesion↗
PubMed1999

From visual experience to visual function: roles of neurotrophins.

Recently, a role for neurotrophins in regulating cortical developmental plasticity has clearly emerged. We present in this review a summary of the early data on the action of nerve growth factor (NGF) in visual cortical development and plasticity in the rat and of other neurotrophins in the visual cortex of other mammals. In addition, to clarify the differences in the results obtained with the various neurotrophins in different animal preparations, we also report new data on the action of NGF, brain-derived neurotrophic factor (BDNF), neurotrophin (NT)3, and NT4 in the same preparation-namely, the visual cortex of the rat. We discuss old and new results in a physiological model in which different neurotrophins play different roles in regulating visual cortical development and plasticity by acting on different neural targets, such as lateral geniculate nucleus (LGN) afferents, intracortical circuitry, and subcortical afferents, and propose a tentative scheme summarizing these actions.

Animals↗
PubMed2000

Effects of unilateral labyrinthectomy on the norepinephrine content in forebrain and cerebellar structures of albino rats.

Albino (Wistar) rats were used to investigate whether unilateral labyrinthectomy (UL) modified the concentration of norepinephrine (NE) as well as of dopamine (DA) and the corresponding metabolite 3, 4-dihydroxyphenylacetic acid (DOPAC) in different areas of the cerebral and the cerebellar cortex and the striatum. The results obtained in 38 rats submitted to UL were compared to those of 18 rats submitted to sham-operation. The animals were operated under sodium pentobarbital anesthesia and sacrificed 1.5, 3 and 6 h after surgery. All rats submitted to UL showed phenomena of deficit (1.5-3 h after the lesion) followed by partial vestibular compensation (3-6 h after the lesion). Significant changes in the content of NE were neither found in different areas of the cerebral and the cerebellar cortex, nor in the striatum of rats sacrificed 1.5 h after UL. Three h after the lesion a bilateral increase in the NE content occurred in all the explored areas of the cerebral cortex (i.e., frontal, parieto-temporal and occipital) and the cerebellar cortex (i.e., the vermis and flocculus), as well as in the striatum. This increase, however, was more prominent in the parieto-temporal areas of the neocortex of the intact side, in all the explored areas of the cerebellar cortex of that side, as well as in the striatum of the lesioned side. This asymmetric increase in NE content could not be attributed, at least exclusively, to a generalized activation of the noradrenergic LC nuclei of both sides, due to waking and/or stress which may occur after UL, but did rather depend on asymmetric changes in unit discharge of the vestibular nuclei projecting to the LC of both sides, following UL. In particular, the increased discharge of the vestibular nuclei of the intact side would lead to activation of noradrenergic neurons projecting particularly to the parieto-temporal cortex and the cerebellar cortex of the intact side, as well as to the striatum of the lesioned side. A bilateral increase in NE content was still observed in different areas of the cerebral and cerebellar cortex of rats sacrificed 6 h after UL. This increase, however, was of smaller entity than that observed in the same areas 3 h after UL and quite symmetric. The content of DA and its metabolite DOPAC decreased bilaterally in the striatum of rats sacrificed 1.5 h after UL. This effect was attributed to a reduced synthesis and release of DA, which probably resulted from a reduced facilitatory influence that the deafferented vestibular nuclei exert on the dopaminergic, nigrostriatal system of both sides, although mainly on the intact side. The corresponding values, however, bilaterally recovered to slightly increase with respect to the control values in rats sacrificed 3 and 6 h after UL. In these experiments the content of both DA and DOPAC remained symmetric on both sides after UL, in contrast with the bilateral but asymmetric increase in NE concentration observed in the same structure 3 h the lesion. The present results integrate and extend those of previous experiments showing that: 1) albino rats sacrificed 6 h after UL displayed an increased synthesis of NE, which affected particularly the LC of the intact side as well as the medial vestibular nuclei of both sides (21); and 2) the structures which showed an increased content of NE at given time intervals after UL also displayed an increase in the expression of the immediate early gene c-fos (cf. 16 for ref.). These findings suggest that bilateral but asymmetric activation of the noradrenergic LC neurons following UL may lead to an asymmetric increase in c-fos expression in several target structures, thus contributing to the plastic changes responsible for vestibular compensation. In conclusion, it appears that UL induces in several brain structures of albino rats a short-term increase in synthesis and release of NE. (ABSTRACT TRUNCATED)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1999

Role of neurotrophins in neural plasticity: what we learn from the visual cortex.

A role for neurotrophins in regulating cortical developmental plasticity has clearly emerged in these last years. In this review we first present a summary of the early data on the action of NGF in visual cortical development and plasticity in the rat and of the actions of the other neurotrophins in the visual cortex of other mammals. In addition, in order to clarify the differences in the results obtained with the various neurotrophins in different animal preparations we also report new data on the action of NGF, BDNF, NT3 and NT4 in the same preparation, namely the visual cortex of the rat. We discuss old and new results in a physiological model where different neurotrophins play different roles in regulating visual cortical development and plasticity by acting on different neural targets, such as LGN afferents, intracortical circuitry and subcortical afferents and propose a tentative scheme summarizing these actions.

Journal Article↗
PubMedDate not supplied

Comparative study of colorimetric DNA hybridization method and conventional culture procedure for detection of Salmonella in foods.

A second generation nucleic acid hybridization assay has been developed and evaluated against the conventional culture method for detection of salmonellae in foods. The assay involves a liquid hybridization with Salmonella-specific oligonucleotide probes, capture of probe:target hybrids onto a solid support (plastic dipstick), and a colorimetric end point detection. The assay can be completed in 2.5 h, following approximately 44 h of culture enrichment. One thousand samples representing 20 food types were analyzed in parallel by both methods. Samples included uninoculated test product, and product inoculated with Salmonella at 2 levels. Eighteen Salmonella serotypes were used as inocula. The data demonstrate that the colorimetric hybridization method and the conventional culture method are equivalent in their ability to detect Salmonella contamination of foods.

Animals↗
PubMed1988

A novel glycoprotein expressed on sheep T and B lymphocytes is involved in a T cell activation pathway.

We have produced a new mouse mAb that identifies a sheep T cell activation Ag. The mAb B5-5 is specific for low m.w. components on nearly all sheep thymocytes and peripheral T and B lymphocytes but does not label immature B cells in Peyer's patches or germinal centers. After cross-linking of target structures either directly by plastic-bound mAb or indirectly using anti-Ig reagents, peripheral T cells, but not thymocytes or peripheral B cells, were activated. IL-2 was secreted by T cells after cross-linking and activation was strongly augmented in the presence of PMA. The addition of soluble B5-5 mAb to mitogen-stimulated cultures of sheep lymphocytes resulted in a suppression of PHA responses and augmentation of PWM responses and had a variable effect on Con A responses but had no effect on LPS- or protein A-induced proliferation. When added to alloantigen-stimulated cultures, B5-5 augmented the proliferative response. The B5-5 membrane component consists of 14- to 19-kDa glycoproteins but the banding patterns obtained during SDS-PAGE analysis of 125I-labeled Ag differed between thymocytes, peripheral T cells, and peripheral B cells. On the basis of its range of expression on lymphoid cells and known biochemical and functional properties, we conclude that the B5-5 component on sheep lymphocytes is different from T cell activation Ag in other species.

Animals↗
PubMed1999

Visual representation of space in congenital and acquired strabismus.

The aim of the present work was to readdress the problem of altered spatial localization in strabismic subjects and to assess whether and how spatial representation is affected by the degree of plasticity of the brain. We therefore compared targeting performance in adult subjects affected by acquired strabismus versus children affected by congenital strabismus. Our data confirm the correlation between deviation of the eye and targeting errors, but they also show that this correlation is not present when strabismus occurs early in life. We suggest that the neuronal machinery involved in the building of an internal representation of space reaches its full maturity several years after birth and that this might explain the limited differences observed in targeting errors between normal and strabismic children.

Adult↗
PubMed2003

Disturbed function and plasticity in multiple sclerosis as gleaned from functional magnetic resonance imaging.

PURPOSE OF REVIEW: This review is intended to provide an up-to-date summary of the main functional magnetic resonance imaging studies conducted in patients with multiple sclerosis, and to show how such studies are changing our views on the ability of the multiple sclerosis brain to limit the clinical consequences of irreversible structural tissue damage. RECENT FINDINGS: Brain cortical reorganization is a common phenomenon occurring in patients with multiple sclerosis, independent of disease duration and clinical phenotype, which can be elicited by macroscopic lesions, as well as by the presence of 'occult' multiple sclerosis-related damage of the brain and cervical cord. An increased recruitment of the cerebral networks involved in the performance of given tasks might represent a first step in cortical reorganization with the potential to maintain a normal level of function in the course of multiple sclerosis. The progressive failure of these mechanisms, because of accumulating tissue damage, might, on the one hand, result in the activation of previously silent 'second-order' compensatory areas, and, on the other, contribute to the accumulation of irreversible disability. SUMMARY: Functional magnetic resonance imaging has the potential to provide important information about cortical reorganization following multiple sclerosis-related tissue damage, which should improve our understanding of the factors associated with the accumulation of irreversible disability in this disease. The enhancement of any beneficial effects of this cortical adaptive plasticity should be considered as a potential target of therapy for multiple sclerosis.

Cerebral Cortex↗
PubMed2003

Post-lesion transcommissural growth of olivary climbing fibres creates functional synaptic microzones.

In the adult mammalian central nervous system, reinnervation and recovery from trauma is limited. During development, however, postlesion plasticity may generate alternate paths, providing models to investigate reinnervating axon-target interactions. After unilateral transection of the neonatal rat olivocerebellar path, axons from the ipsilateral inferior olive grow into the denervated hemicerebellum and develop climbing fibre (CF)-like arbors on Purkinje cells (PCs). However, the synaptic function and extent of PC reinnervation remain unknown. In adult rats pedunculotomized on postnatal day 3 the morphological and electrophysiological properties of reinnervating olivocerebellar axons were studied, using axonal reconstruction and patch-clamp PC recording of CF-induced synaptic currents. Reinnervated PCs displayed normal CF currents, and the frequency of PC reinnervation decreased with increasing laterality. Reinnervating CF arbors were predominantly normal but 6% branched within the molecular layer forming smaller secondary arbors. CFs arose from transcommissural olivary axons, which branched extensively near their target PCs to produce on average 36 CFs, which is six times more than normal. Axons terminating in the hemisphere developed more CFs than those terminating in the vermis. However, the precise parasagittal microzone organization was preserved. Transcommissural axons also branched, although to a lesser extent, to the deep cerebellar nuclei and terminated in a distribution indicative of the olivo-cortico-nuclear circuit. These results show that reinnervating olivocerebellar axons are highly plastic in the cerebellum, compensating anatomically and functionally for early postnatal denervation, and that this reparation obeys precise topographic constraints although axonal plasticity is modified by target (PC or deep nuclear neurons) interactions.

Animals↗
PubMed1976

Striate cortex ablation and spatial vision.

Normal and visually decorticate rats were trained to orient to a luminous target. All subjects reached the same criterion of orientation accuracy, but operated subjects required more training and exhibited greater response latency throughout testing. To determine if visually decorticate subjects located the target according to the retinal position of its image, or only by sampling luminous flux density at different points in space, field-displacing wedge prisms were placed before the subjects' eyes to laterally displace the retinal locus of the target image without affecting luminous flux information. Prism imposition shifted orientation toward the virtual target position for all subjects. In a second study, translucent plastic was place over the subjects' eyes to disrupt the retinal topography and location of the target image while again leaving luminoux flux unaffected as a potential cue. All animals showed a dramatic and complete disruption of target localization once the diffusing material was applied. The data were considered as support for the hypothesis that 'spatial' vision survives visual decortication.

Animals↗