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PubMed1984

A neural plasticity hypothesis of schizophrenia.

An extensive research effort has failed, thus far, to conclusively identify a specific disease process (or processes) underlying the behavioral symptoms of schizophrenia. The present paper will entertain the hypothesis that the structural and functional plasticity of the brain can constitute a "nonspecific" biological etiology of schizophrenia. This plasticity need not be accompanied by infectious processes or gross alterations in neurotransmitter levels, enzyme activities, etc. that are specific to schizophrenia. The monkey isolation syndrome provides a precedent for a causal relationship between brain plasticity and pathological behavior. In a speculative manner, it will be demonstrated that neural plasticity concepts can be invoked to potentially explain several aspects of schizophrenia: the various types of behavioral symptoms exhibited by schizophrenics, the regional alterations in brain structure and function seen in chronic schizophrenics, the involvement of genetic and environmental etiological factors, the pharmacological support for the dopamine hypothesis, and the delayed onset of neuroleptic antipsychotic action. Considering the explanatory potential of neural plasticity concepts, a research program which focuses on these concepts seems warranted.

Animals↗
PubMed1993

The development of myelin in the spinal cord of the North American opossum and its possible role in loss of rubrospinal plasticity. A study using myelin basic protein and galactocerebroside immuno-histochemistry.

The aims of this study were to observe the timing and sequence of myelin formation in the opossum's spinal cord by using myelin basic protein (MBP) immuno-histochemistry and to determine whether the onset of myelination, as demonstrated by the presence of MBP or galactocerebroside (GalC)-like immuno-reactivity (LI), correlates temporally with the end of the critical period for rubrospinal plasticity. Rubral axons grow around a lesion of their pathway during early development but they do not do so at later stages of development or in the adult animal. MBP-LI was first observed in the opossum's spinal cord at postnatal day 15 and its development in most tracts followed rostral to caudal gradients. MBP-LI occurred in some tracts before others, however, regardless of level. MBP- and GalC-LI first appeared in the lateral funiculus, the location of rubrospinal axons, around the end of the critical period for rubrospinal plasticity and it was found in the dorsal horn, an area traversed by rerouted axons in the plasticity experiments, shortly thereafter. Since there is a rough temporal correlation between the development of myelin, as demonstrated by the presence of MBP and GalC immuno-reactivity, and the end of the critical period for rubrospinal plasticity, it is possible that myelin proteins which inhibit axonal elongation contribute to loss of that plasticity.

Aging↗
PubMed1995

Developmental plasticity and memory.

The cerebral cortex of young kittens is known to be highly malleable during early postnatal development. However, most studies of developmental plasticity have been conducted in primary visual cortex. It has long been unclear to what extent similar plasticity exists in higher cortical areas. We have now studied developmental plasticity in the anterior ectosylvian (AE) region of the cat's parietal association cortex, which receives input from different sensory modalities. One area in this cortical region, which is predominantly visual in normal cats, area AEV, is taken over almost completely by auditory and somatosensory inputs, when cats are binocularly deprived of vision from birth. Furthermore, when single auditory neurons are tested with sound sources in free-field at different locations, they show sharper spatial tuning in visually deprived cats. This compensatory, crossmodal plasticity was explored at the behavioral level by testing visually deprived cats in an auditory localization task, and these cats could indeed localize sound sources more precisely than normal cats. These findings are interpreted as a form of adaptation of the young brain to an altered environment. Similar adaptation is still possible in adult brains by virtue of associative learning and long-term memory. It is argued that the synaptic mechanisms by which associative memories are stored in the cerebral cortex are similar to those in developmental plasticity, only the increment of learning is smaller in adult animals.

Aging↗
PubMed1982

Toxicity of 29 plasticizers to HeLa cells in the MIT-24 system.

The toxicity to HeLa cells of 29 plasticizers was determined in the MIT-24 test system. The 7-day IC50 for HeLa cells varied from 260 to 1.5 g/l. Phthalates, adipates, sebacates, azelates and phosphates with long carbon chain alcohols were very non-toxic to the cells, probably due to insolubility in water of the compounds, while the citrates, some phosphates and the 2 polymer plasticizers had a higher toxicity to the cells. A comparison of the HeLa cytotoxicity with the toxicity in vitro to other cells for 7 plasticizers showed a similarity of the cytotoxicity to all cell types. A comparison of the HeLa cytotoxicity for 20 plasticizers with i.p. lethal dosage in rodents demonstrated a rough similarity of values, suggesting a toxicity in rodents of the compounds by toxic interference of the agents with basal functions and structures of tissues (basal cytotoxicity). Tissue culture studies of the cytotoxic mechanisms of the plasticizers therefore could reveal modes of toxic action in vivo.

Animals↗
PubMed1996

Polysialylated neural cell adhesion molecule and plasticity of ipsilateral connections in Xenopus tectum.

The optic tectum of Xenopus offers a readily manipulated system for testing the hypothesis that polysialylation of the neural cell adhesion molecule is associated with axonal plasticity. Axons relaying input to the tectum from the ipsilateral eye employ visual input to establish a topographic map in register with the contralateral map, despite naturally-occurring or surgically-induced repositioning of the eyes. This capacity for activity-dependent refinement or re-organization of the ipsilateral map is normally confined to a period between about one and four months postmetamorphosis but can be restored in adults by local application of N-methyl-D aspartate to the tectum. In addition, dark-rearing prolongs plasticity indefinitely. We have used immunohistochemical staining with antibodies to polysialic acid to determine whether conditions of high plasticity are correlated with high levels of polysialylated neural cell adhesion molecule in the tectum. We find that the staining level is high in tecta from one to three month postmetamorphic frogs but is low both before and after this period. Thus, in normal Xenopus frogs, anti-polysialic acid staining is heavier in the period of high plasticity than in the preceding or following postmetamorphic periods. As a further test of this relationship, we examined brains of adults with experimentally-induced plasticity. Tecta of N-methyl-D-aspartate-treated adults and of dark-reared adults showed higher levels of staining than did the tecta of normally-reared adults. These results also support the hypothesis that the presence of high levels of polysialic acid on neural cell adhesion molecules is causally related to activity-related changes in axonal growth patterns.

Animals↗
PubMed1991

Design of a plastic minicolpostat applicator with shields.

A plastic intracavitary applicator system for the treatment of cancer of the uterine cervix is described. This applicator has a minicolpostat and a mechanism for affixing the tandem to the colpostats. Traditional afterloading refers only to the radioactive source. Both the source and the ovoid shield are afterloaded together in this applicator in contrast to traditional afterloading systems which afterload the source alone. A potential advantage of our applicator system is that it allows high quality CT localization because the sources and shields can be removed and the applicator is made of plastic. The advantages and disadvantages of this variation to the Fletcher system as well as other aspects of applicator design are discussed. An experimentally verified dose calculation method for shielded sources is applied to the design problems associated with this applicator. The dose distribution calculated for a source-shield configuration of the plastic applicator is compared to that obtained with a commercial Fletcher-Suit-Delclos (FSD) applicator. Significant shielding improvements can be achieved for the smallest diameter ovoid, that is, in the minicolpostat. The plastic minicolpostat dose distributions are similar to those produced by the conventional larger diameter colpostats. In particular, the colpostat shielding for rectum and bladder, which is reduced in the metal applicator's minicolpostat configuration, is maintained for the plastic minicolpostat. Further, it is shown that, if desired, relative to the FSD minicolpostat, the mucosa dose can be reduced by a suitable change of the minicolpostat source position.

Brachytherapy↗
PubMedDate not supplied

Objectives to direct the training of emergency medicine residents in off-service rotations: plastic surgery.

This is the fourth article in a continuing series on objectives for emergency medicine training; plastic surgery objectives will be presented. Plastic surgery topics overlap many in emergency medicine. Specific behaviorally based objectives for mastery of skills in plastic surgery are outlined. Specific references are provided for additional information and reinforcement in skill mastery. The basic concepts of plastic surgery are probably best learned by observation and supervised performance. Specific objectives provide guidance and direction for the didactic as well as the supervised experiences in skill mastery. These objectives provide a structure for systematically learning and mastering the content presented on a plastic surgical rotation or experience in emergency medicine training.

Education↗
PubMedDate not supplied

Possible role of S-100 in glia-neuronal signalling involved in activity-dependent plasticity in the developing mammalian cortex.

Using Western blot analyses and a quantitative ELISA, we identified the presence and developmental accumulation of the astroglial S-100 protein(s) in rat and cat visual cortex. There is a steep rise in the S-100 content, comprising mainly S-100 beta, during the time period of highest cortical malleability in both species. A possible role of the astroglial S-100 protein(s) in experience-dependent plasticity of the visual cortex of kittens was tested by infusing antiserum against this protein during the critical period for cortical malleability. Following 1 week of monocular deprivation, the ocular dominance of single cells in the visual cortex was investigated. The vast majority of cells in the hemispheres infused with anti-S-100 serum maintained binocular responses. This finding suggests that extracellular S-100 protein is essential for ocular-dominance plasticity. Infusion of S-100 beta during the critical period of cortical malleability had no effect on deprivation-induced ocular-dominance plasticity, but interfered with the experience-dependent refinement of orientation selectivity of visual cortical neurons. It is suggested that S-100 beta may play an important role in the refinement of cortical circuitries by selectively affecting active or activated neuronal compartments. As S-100 beta is synthesized in astroglial cells, the effects on neuronal plasticity imply that glia-neuronal information transfer occurs during activity-dependent plasticity. Possible underlying mechanisms are discussed on the basis of current knowledge on the S-100 protein family, especially S-100 beta (Marshak, 1990).

Aging↗
PubMed2006

Synaptic plasticity and dysconnection in schizophrenia.

Current pathophysiological theories of schizophrenia highlight the role of altered brain connectivity. This dysconnectivity could manifest 1) anatomically, through structural changes of association fibers at the cellular level, and/or 2) functionally, through aberrant control of synaptic plasticity at the synaptic level. In this article, we review the evidence for these theories, focusing on the modulation of synaptic plasticity. In particular, we discuss how dysconnectivity, observed between brain regions in schizophrenic patients, could result from abnormal modulation of N-methyl-D-aspartate (NMDA)-dependent plasticity by other neurotransmitter systems. We focus on the implication of the dysconnection hypothesis for functional imaging at the systems level. In particular, we review recent advances in measuring plasticity in the human brain using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) that can be used to address dysconnectivity in schizophrenia. Promising experimental paradigms include perceptual and reinforcement learning. We describe how theoretical and causal models of brain responses might contribute to a mechanistic understanding of synaptic plasticity in schizophrenia.

Acetylcholine↗
PubMed2004

Patient-based measures of outcome in plastic surgery: current approaches and future directions.

OBJECTIVES: To evaluate current approaches to patient-based outcome measurement in plastic surgery and make recommendations for future research. METHODS: Comprehensive review of the plastic surgery literature relevant to patient-based outcomes. RESULTS: Two main types of patient-based outcome measure have been used in the plastic surgery literature: generic and disease-specific. The majority of studies using generic measures investigate aspects of psychological functioning with fewer studies focussing on wider aspects of health-related quality of life. Disease-specific measures are mainly used to assess symptoms. However, almost all of these are ad-hoc measures produced for a particular study, with no psychometric evaluation. CONCLUSIONS: There is a lack of psychometrically sound measures, and there is scope for improvement in methodology used in plastic surgery research. The development and psychometric testing of new plastic surgery specific measures is encouraged.

Adult↗
PubMed2004

Plastic surgery senior house officers in the UK and Ireland: academic background, publication rates and research plans.

Academic achievements by surgical trainees may vary according to the competitiveness of the subspecialty and desirability of the consultant post. Plastic and reconstructive surgery is a competitive specialty. In order to assess the level of achievement of current trainees, we investigated the academic qualifications, publication rates and future research plans of 100 senior house officers in plastic surgery working in units in the United Kingdom and Ireland. Selected results from our survey show that 30% had intercalated degrees, 6% had higher degrees, 58% of trainees had MRCS, 37% had previous plastic surgery experience and 57% had published (range 1-13). We believe this study provides interesting information concerning the current crop of plastic surgery trainees in the United Kingdom and Ireland. This survey may provide a benchmark for consultants to refer to when shortlisting for SHO posts. We also believe it will be of interest to those junior trainees hoping to pursue a career in plastic surgery.

Clinical Competence↗
PubMed2004

Psychiatric morbidity in a regional plastic surgery centre--one-year review with a proposed categorisation.

Few studies describe the incidence and nature of psychiatric morbidity in plastic surgery patients. We undertook a review of all referrals from the Plastic Surgery Service to the Psychological Medicine Service over a 1-year period (January-December 2001). Standardised socio-demographic information, nature and cause of injury/defect, surgical intervention, surgical outcome, psychiatric diagnosis and psychiatric follow-up were determined. The majority of patients referred had a significant existing psychiatric illness, had made a suicide/parasuicide attempt, or were burns patients. There was a high rate of referral of plastic surgery inpatients. Liaison with plastic surgery staff to allow rapid identification and early management of psychiatric morbidity is an important role for psychological medicine. We outline a defined categorisation of common contexts in which psychiatric morbidity may present to plastic surgery services.

Adolescent↗
PubMed2006

Randomised clinical trials in plastic surgery: survey of output and quality of reporting.

Randomised clinical trials (RCTs) are considered the best level of evidence when evaluating interventions. Report quality is often used as a surrogate measure of methodological quality, with poorly reported trials assumed to be poorly conducted. To address this problem the CONsolidated Standards of Reporting Trials (CONSORT) statement was published, encouraging authors to explicitly report certain items of information. The aim of this study was to survey RCTs published in the plastic surgery literature and determine quality of reporting. All RCTs published in Plastic & Reconstructive Surgery, British Journal of Plastic Surgery and Annals of Plastic Surgery from 1980 to 2004 were retrieved using a Medline search. Quality of reporting was assessed using a 17-item checklist derived from the CONSORT statement. One hundred and thirty three trials were eligible for assessment. 56 (42.1%) originated from European countries. Anaesthesia/analgesia was the most popular topic addressed and accounted for 23 (17.3%) of all studies. Quality of reporting analysis revealed wide variation between items. Sample size calculation was only reported in 17(12.8%) trials. Randomisation methodology, allocation concealment and blind investigator/assessment was reported in 39 (29.3%), 25 (18.8%) and 69 (51.9%) trials respectively. Study limitations were also infrequently reported and present in only 45 (33.8%) trials. This study indicates the annual output of plastic surgery RCTs is increasing and a variety of topics are covered. However, reporting of certain key items is inadequate. Awareness of the CONSORT statement and more attention to the quality of reporting may improve matters.

Anesthesia↗
PubMed2004

Nicotine-mediated plasticity in robust nucleus of the archistriatum of the adult zebra finch.

Activation of neuronal nicotinic acetylcholine receptors (nAChRs) modulates the induction of long-term potentiation (LTP), a possible cellular mechanism for learning. This study was undertaken to determine the effects of activation of nAChRs by nicotine on long-term plasticity in the songbird zebra finch, which is a valuable model to study synaptic plasticity and its implications to behavioral learning. Electrophysiological recordings in the robust nucleus of the archistriatum (RA) in adult zebra finch brain slices reveal that tetanic stimulation alone does not produce LTP. However, LTP is induced by such stimulation in the presence of nicotine. The nicotine-mediated LTP is blocked by dihydro-beta-erythroidine (DHbetaE, 1 microM), an antagonist having a greater effect against nAChRs containing the alpha 4 subunit. In the presence of methyllcaconitine (MLA, 10 nM), an antagonist of nAChRs containing the alpha 7 subunit, a long-term depression (LTD) is unmasked, implicating a bi-directional type of plasticity in the zebra finch RA, which is modulated by differential activation of nAChR subtypes. Intracellular recordings from single neurons show a depression of the afterhyperpolarization (AHP) and an increase in frequency of evoked and spontaneous action potentials in the presence of nicotine. These results suggest that nicotinic cholinergic mechanisms may play a critical role in synaptic plasticity in the zebra finch song system and thereby influence song learning and plasticity.

Acetylcholine↗
PubMed2006

Alkaline hydrothermal treatment of brominated high impact polystyrene (HIPS-Br) for bromine and bromine-free plastic recovery.

A method to recover both Br and Br-free plastic from brominated flame retardant high impact polystyrene (HIPS-Br) was proposed. HIPS-Br containing 15% Br was treated in autoclave at 280 degrees C using water or KOH solution of various amounts and concentrations. Hydrothermal treatment (30 ml water) leads to 90% debromination of 1g HIPS-Br but plastic is strongly degraded and could not be recovered. Alkaline hydrothermal treatment (45 ml or 60 ml KOH 1M) showed similar debromination for up to 12 g HIPS-Br and plastic was recovered as pellets with molecular weight distribution close to that of the initial material. Debromination occurs at melt plastic/KOH solution interface when liquid/vapour equilibrium is attained inside autoclave (280 degrees C and 7 MPa in our experimental conditions) and depends on the plastic amount/KOH volume ratio. The antimony oxide synergist from HIPS-Br remains in recovered plastic during treatment. A pictorial imagination of the proposed debromination process is presented.

Alkalies↗
PubMed2005

Cortical plasticity following upper extremity injury and reconstruction.

Today's view of the adult central nervous system is that of an adaptive and responsive system. Plastic surgeons, because of the motor and sensory reconstructions they perform, need to have an understanding of brain plasticity following upper extremity injury, reconstruction, and rehabilitation. Functional MRI and transcranial magnetic stimulation can identify cortical plasticity in humans. For instance, these techniques have identified changes in excitability and body site representation in the motor cortex in patients following motor reconstruction and motor relearning. Therefore, cortical plasticity and its manipulation may be an important contributor to functional outcome following reconstruction. In the future, cortical plasticity may have implications for reconstruction and rehabilitation.

Amputation, Traumatic↗
PubMed2006

Role of delayed nonsynaptic neuronal plasticity in long-term associative memory.

BACKGROUND: It is now well established that persistent nonsynaptic neuronal plasticity occurs after learning and, like synaptic plasticity, it can be the substrate for long-term memory. What still remains unclear, though, is how nonsynaptic plasticity contributes to the altered neural network properties on which memory depends. Understanding how nonsynaptic plasticity is translated into modified network and behavioral output therefore represents an important objective of current learning and memory research. RESULTS: By using behavioral single-trial classical conditioning together with electrophysiological analysis and calcium imaging, we have explored the cellular mechanisms by which experience-induced nonsynaptic electrical changes in a neuronal soma remote from the synaptic region are translated into synaptic and circuit level effects. We show that after single-trial food-reward conditioning in the snail Lymnaea stagnalis, identified modulatory neurons that are extrinsic to the feeding network become persistently depolarized between 16 and 24 hr after training. This is delayed with respect to early memory formation but concomitant with the establishment and duration of long-term memory. The persistent nonsynaptic change is extrinsic to and maintained independently of synaptic effects occurring within the network directly responsible for the generation of feeding. Artificial membrane potential manipulation and calcium-imaging experiments suggest a novel mechanism whereby the somal depolarization of an extrinsic neuron recruits command-like intrinsic neurons of the circuit underlying the learned behavior. CONCLUSIONS: We show that nonsynaptic plasticity in an extrinsic modulatory neuron encodes information that enables the expression of long-term associative memory, and we describe how this information can be translated into modified network and behavioral output.

Animals↗
PubMed2005

Early alcohol exposure impairs ocular dominance plasticity throughout the critical period.

Animal models of fetal alcohol syndrome (FAS) have revealed an impairment of sensory neocortex plasticity. Here, we examine whether early alcohol exposure leads to a permanent impairment of ocular dominance plasticity (OD) or to an alteration in the timing of the critical period. Ferrets were exposed to alcohol during a brief period of development prior to eye opening and effects of monocular deprivation examined during early, mid and late critical period. Single-unit electrophysiology revealed markedly reduced OD plasticity at every age examined. This finding provides evidence that early alcohol exposure does not affect the timing or duration of the critical period of OD plasticity and suggests an enduring impairment of neural plasticity in FAS.

Action Potentials↗