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PubMed1986

Teratogenicity studies of alkylaryl phosphate ester plasticizers in rats.

Santicizer 141 plasticizer (2-ethylhexyldiphenyl phosphate) and Santicizer 148 plasticizer (isodecyldiphenyl phosphate) were tested for teratogenic activity in Charles River COBS CD rats. Groups of 25 mated females were given 0, 300, 1000, or 3000 mg/kg/day by gavage on Days 6 through 15 (Santicizer 141) or 6 through 19 (Santicizer 148) of gestation. Mean maternal body weight gains were slightly and severely reduced at the mid- and high-dose levels of Santicizer 141, respectively. Body weights were not affected by treatment with Santicizer 148. Most malformations found in groups treated with either plasticizer occurred as single incidences and have been observed in historical controls. Thus, no teratogenic response was observed in rats after treatment with either of these two alkylaryl phosphates during the period of organogenesis.

Animals↗

PubMed1988

Aspartame exposure and in vitro hippocampal slice excitability and plasticity.

Aspartame (APM) is a low-calorie sweetener recently approved and released for widespread use in the United States. However, concerns still exist that APM consumption may be responsible for adverse neurological and psychological effects in some people. In addition, recent reports indicate that APM exposure may alter regional brain neurotransmitter levels. The present study assessed the effects of APM and its amino acid moieties on rat hippocampal slice excitability and plasticity. Specifically, tests of excitatory systems, inhibitory systems, and synaptic plasticity (induction of long-term potentiation--LTP) were administered postexposure. Exposures of 0.01, 0.1, 1, and 10 mM APM potentiated the response of hippocampal CA1 pyramidal cells, but had no apparent effect on local inhibitory systems. APM exposure did not block the establishment of LTP at any dose despite the potentiation of pyramidal cell response observed postexposure. In addition, 0.1 mM phenylalanine (PHE) produced a greater increase in excitability than that produced by an equivalent dose of APM, 0.1 mM aspartic acid (ASP) and 0.1 mM phenylalanine methyl ester (PM) produced effects comparable to those produced a smaller, but reliable, change in hippocampal CA1 excitability relative to baseline. Like APM, none of the amino acids produced detectable changes in inhibitory systems or neuronal plasticity.

Animals↗

PubMed1983

Selection and application of a new volatile solvent as a fatty food simulant for determining the global migration of constituents of plastics materials.

A study was carried out to establish whether the draft EEC method for determining overall (global) migration of the constituents of plastics-packaging materials into a fatty-food simulant could be applied to samples of commercially available homogeneous plastics materials and whether it would be possible to use extraction with a volatile solvent under appropriate conditions of time and temperature in cases where, for some reason, the fat test cannot be used. The results obtained show that the draft EEC method can be applied without insuperable problems to most commercially available homogeneous plastics-packaging materials. Moreover, taking into account the poor reproducibility and accuracy associated in some cases with global-migration tests in olive oil, the determination of global migration into isooctane (contact time 2 hr at 40 degrees C) seems to be a suitable substitute for determinations using exposure to olive oil for 10 days at 40 degrees C.

Dietary Fats↗

PubMed1986

Global migration from plastic materials into olive oil and isooctane: an experimental comparison.

Global migration from several plastics (phthalate-plasticized PVC, polyurethane, polyether-polyamide copolymer and silicone rubber) into olive oil, used as a liquid simulant for fatty foods, was compared with global migration into isooctane, which has been proposed as a new fatty-food simulant. The results showed that the isooctane test (involving contact for 2 hr at 40 degrees C) is not suitable as a substitute for the olive oil test (contact for 10 days at 40 degrees C) for some types of commercial plastic materials.

Alkanes↗

PubMed1991

The calibration of 35S or 32P with 14C-labeled brain paste or 14C-plastic standards for quantitative autoradiography using LKB Ultrofilm or Amersham Hyperfilm.

The relationship between 14C-labeled brain paste or plastic standards and 35S- or 32P-labeled brain paste was characterized with quantitative autoradiography. Film was exposed to both sets of 14C-labeled standards and 35S- and 32P-labeled standards for 15-148 h and the film was analyzed with computer densitometry. Subsequently, the tissue pastes were scraped from the slides, dissolved in tissue solubilizer and radioactivity determined by scintillation spectroscopy. A linear relationship was observed between the plastic and brain paste 14C standards as well as between both sets of 14C-labeled standards and 35S-labeled brain paste standards. The 32P-labeled standards demonstrated a poor linear relationship with the 14C-labeled standards and greater variability in the autoradiographic estimates than was seen with 35S or 14C. Results were similar for both Ultrofilm and Hyperfilm with all the radioisotopes. These findings demonstrate a simple linear relationship between plastic and brain paste 14C-labeled standards and between either 14C-labeled standards and 35S-labeled brain paste for use in quantitative autoradiography.

Animals↗

PubMed1992

Cytochalasin inhibits light-dependent synaptic plasticity of horizontal cells in teleost retina.

Previous studies have shown that the horizontal cell-->cone photoreceptor negative feedback synapse in teleost fish retinae is 'plastic', being suppressed in the dark and potentiated by light adaptation. The possible involvement of filamentous actin in ultrastructural and electrophysiological aspects of this plasticity has been investigated using cytochalasins, which inhibit actin turnover, in the cyprinid fish (roach) retinae. Cytochalasin B or D (40 microM) inhibited both the light-dependent formation and maintenance of spinules, and enhancement of the feedback interaction involved in generation of biphasic spectral responses in horizontal cells. The results suggest that actin turnover is essential for both ultrastructural and electrophysiological plasticity of horizontal cell feedback and that spinules could mediate this dynamic interaction.

Animals↗

PubMed1994

Central plasticity in rat trigeminal primary sensory neurons innervating vibrissae after neonatal peripheral nerve injury.

This study was undertaken to investigate whether a neonatal vibrissa lesion in the rat may lead to a central plasticity in undamaged vibrissae innervating primary sensory neurons. One vibrissa follicle was removed on the day of birth. After 3-4 months, choleragenoid-horseradish-peroxidase was injected in an adjacent vibrissa follicle either within the row of the missing follicle or across the rows and in the corresponding contralateral follicle. The trigeminal ganglion and nucleus caudalis was studied following retrograde and transganglionic transport of the tracer. The number of labeled cells was not significantly different on the two sides, whereas the central terminal field of labeling was considerably increased on the side of the lesion, but only when the injected follicle was located in the same row as the missing one. Cortical plasticity after neonatal vibrissae follicle lesions may thus be associated with a corresponding plasticity in primary sensory neurons innervating the vibrissae.

Animals↗

PubMed1990

Tonic 5-HT modulation of spinal dorsal horn neuron activity evoked by both noxious and non-noxious stimuli: a source of neuronal plasticity.

The influence of tonic serotonergic modulation on the responses of spinal dorsal horn neurons to natural peripheral stimulation was examined in physiologically intact, awake, drug-free cats. Systemically administered methysergide (maximum cumulative dose 2 mg/kg) caused significant changes in responses of some dorsal horn neurons to both mildly noxious and non-noxious stimulation. Individual changes provide evidence, in this model, for tonic 5-HT modulation of many aspects of sensory transmission at the level of the spinal cord. Taken together, the changes demonstrate the significant degree of plasticity that exists for some spinal dorsal horn neurons. It is clear that the plasticity of some spinal dorsal horn neurons allows for a much broader response profile than would be apparent under the restricted circumstances of a normal neurophysiologic study. Removal of tonic inhibition on responses to noxious stimuli may be an aspect of neuronal plasticity that functions to provide an immediate change in the way that the nervous system responds to a noxious stimulus.

Action Potentials↗

PubMed1986

Development of plastic mechanisms related to learning at identified chemical synaptic connections in Aplysia.

In the marine snail Aplysia californica learned changes in behavior have been traced to alterations in synaptic efficacy. With the ability to raise the animals in the laboratory, we have explored the development of four types of plastic mechanisms at identified synapses: post-tetanic potentiation and pre-synaptic inhibition, which do not as yet have known behavioral functions, and homosynaptic depression, the cellular mechanism of short-term habituation, and heterosynaptic facilitation, the basis of short-term sensitization. Homosynaptic depression and pre-synaptic inhibition are present early in juvenile life. In contrast, post-tetanic potentiation and heterosynaptic facilitation appear only later, after a discrete interval. The step-wise ontogeny of synaptic plastic mechanisms in Aplysia parallels the gradual emergence of behavior in successive developmental stages. Interestingly, senescence reverses the developmental sequence for habituation and sensitization mechanisms. To pursue further an understanding of the relationship between synapse formation and plasticity underlying learning it will be necessary to extend these studies to dissociated cell culture where mechanisms can be explored on the molecular level. Cell culture may also permit examination of the development of cellular mechanisms underlying classical and operant conditioning which may clarify differences between associative and non-associative mechanisms.

Animals↗

PubMed1995

Maintenance of ultrastructural plasticity of the hypothalamic supraoptic nucleus in the ovariectomized rat.

In the present experiments, we examined the effect of ovariectomy on the increases in litter weight and structural plasticity of MNCs in the supraoptic nucleus (SON) during lactation. Female rats were ovariectomized 2 days after parturition, and the increases in litter weight were measured as the index of milk let-down from dams during lactation. The lactation period was elongated up to 6 weeks by providing new litter to obtain more apparent effects of the ovariectomy. There was no significant difference in the increases in litter weight between non-operated and ovariectomized females. After lactation for 6 weeks, the ultrastructures such as juxtaposition (surface membrane apposition) and multiple synapses (terminals contacting with two or more postsynaptic elements) of MNCs in the SON in nonoperated and ovariectomized females were examined to compare with those of virgins. The percentage of juxtaposition and the number of multiple synapses significantly increased in nonoperated lactating females as compared with those of virgins. Ovariectomized rats showed similar structural changes to those of nonoperated females during lactation. Therefore, we conclude that ultrastructural plasticity of MNCs in the SON is maintained even in the absence of an ovary, and direct or indirect actions of suckling stimulation may be important in maintaining the plasticity during lactation.

Animals↗

PubMed2006

Patterns of normal human brain plasticity after practice and their implications for neurorehabilitation.

OBJECTIVES: To illustrate how our knowledge about normal patterns of experience-induced plasticity can provide insights into the mechanisms of neurorehabilitation; to provide an overview of the practice-effects literature in order to simplify and amalgamate a large number of heterogeneous findings and identify typical patterns of practice effects and their determining factors; and to concentrate on the impact of practice on higher cognitive functions, such as working memory, and present some preliminary but promising behavioral data that show how practice on a complex cognitive task can benefit cognitive functioning more generally. DATA SOURCES: We performed a systematic search for peer-reviewed journal articles using computerized databases (PubMed, ISI Web of Science, PsycINFO). DATA SELECTION: Neuroimaging studies using functional magnetic resonance imaging (fMRI) or positron-emission tomography (PET) to examine functional activation changes as a result of practice on sensory, motor, or cognitive tasks in normal (healthy) populations were included in the review. Further studies were identified that examined the effects of rehabilitative training on functional activations in clinical populations using fMRI or PET. DATA EXTRACTION: Important characteristics of the selected studies were summarized in a systematic manner so to enable the extraction of specific factors impacting on the pattern of practice effects observed. DATA SYNTHESIS: We identified a number of factors that impact on the patterns of practice effects observed and discuss how the insights gained from the study of healthy populations can by applied to rehabilitation of cognitive deficits in clinical populations. CONCLUSIONS: Progress in our understanding of neurorehabilitative plasticity will be enabled by neuroimaging examinations of cognitive rehabilitation training grounded in a knowledge of normal (healthy) patterns of brain activation and practice-induced plasticity.

Brain↗

PubMedDate not supplied

Reusability of plastic scintillators used in beta emitter activity determination.

The use of plastic scintillation in the measurement of beta emitter activity is a suitable alternative to classical detection techniques in spite of the high cost and potential memory effects. Reuse of the plastic scintillator beads after a cleanup procedure would overcome both drawbacks. In the present paper, we tested several cleaning solutions (water, HCl 0.1M, commercial soap, EDTA 0.01 M pH=3, citric acid 0.1 M pH=3). The recommended procedure consists of the immersion of the beads in three consecutive citric acid baths for 24 h. If this protocol is followed, plastic beads contaminated with 90Sr/90Y, 14C, and 3H recover their initial condition, and can be used in successive determinations.

Beta Particles↗

PubMed2006

Synaptic plasticity in early aging.

Studies of how aging affects brain plasticity have largely focused on old animals. However, deterioration of memory begins well in advance of old age in animals, including humans; the present review is concerned with the possibility that changes in synaptic plasticity, as found in the long-term potentiation (LTP) effect, are responsible for this. Recent results indicate that impairments to LTP are in fact present by early middle age in rats but only in certain dendritic domains. The search for the origins of these early aging effects necessarily involves ongoing analyses of how LTP is induced, expressed, and stabilized. Such work points to the conclusion that cellular mechanisms responsible for LTP are redundant and modulated both positively and negatively by factors released during induction of potentiation. Tests for causes of the localized failure of LTP during early aging suggest that the problem lies in excessive activity of a negative modulator. The view of LTP as having redundant and modulated substrates also suggests a number of approaches for reversing age-related losses. Particular attention will be given to the idea that induction of brain-derived neurotrophic factor, an extremely potent positive modulator, can be used to provide long periods of normal plasticity with very brief pharmacological interventions. The review concludes with a consideration of how the selective, regional deficits in LTP found in early middle age might be related to the global phenomenon of brain aging.

Aging↗

PubMed2005

Short-term synaptic plasticity in rabbit pancreatic ganglia.

The extrinsic innervation of the pancreas converges on a plexus of intrinsic pancreatic ganglia whose cholinergic neurons innervate acini, ducts, islets and blood vessels. Therefore, understanding ganglionic transmission is essential for understanding neural control of pancreatic secretion. Intracellular recordings of nicotinic fast excitatory postsynaptic potentials (fEPSPs) and action potentials (APs) were used to characterize and compare transmission in ganglia from the head/neck and body regions of the rabbit pancreas. Paired-pulse facilitation (PPF) or depression (PPD) of fEPSPs was observed in ganglia from both regions with PPF peaking and disappearing at shorter inter-stimulus intervals than PPD. PPF was most frequent in the head/neck (60%) and PPD (50%) in the body. Repetitive stimulation (10 Hz/5 s) evoked multiple forms of mid- and post-train plasticity. Facilitation during the first 1-2 s of train stimulation was reduced or reversed with continued stimulation due to development of synaptic depression and mid-train depression was of greater magnitude in the head/neck region. A brief (approximately 10 s) post-train augmentation was followed by a 1-2 min post-train depression that appeared to result from inhibition of ACh release. Regional differences in the frequency, magnitude, or duration of all forms of synaptic plasticity suggested regional differences in the extrinsic innervation patterns and possibly the function of pancreatic ganglia. In conclusion, rabbit pancreatic ganglia exhibit multiple forms of short-term synaptic plasticity that markedly alter the probability of postsynaptic firing, consistent with these ganglia being critical sites of synaptic integration and autonomic regulation of pancreatic secretion.

Animals↗

PubMed2003

Calcineurin in memory and bidirectional plasticity.

The molecular mechanisms of learning and memory, and the underlying bidirectional changes in synaptic plasticity that sustain them largely implicate protein kinases and phosphatases. Specifically, Ca(2+)-dependent kinases and phosphatases actively control neuronal processing by forming a tightly regulated balance in which they oppose each other. In this balance, calcineurin (PP2B) is a critical protein phosphatase whose main function is to negatively modulate learning, memory, and plasticity. It acts by dephosphorylating numerous substrates in different neuronal compartments. This review outlines some of CN neuronal targets and their implication in synaptic functions, and describes the role of CN in the acquisition, storage, retrieval, and extinction of memory, as well as in bidirectional plasticity.

Animals↗

PubMed2006

Cellular plasticity cascades: genes-to-behavior pathways in animal models of bipolar disorder.

BACKGROUND: Despite extensive research, the molecular/cellular underpinnings of bipolar disorder (BD) remain to be fully elucidated. Recent data has demonstrated that mood stabilizers exert major effects on signaling that regulate cellular plasticity; however, a direct extrapolation to mechanisms of disease demands proof that manipulation of candidate genes, proteins, or pathways result in relevant behavioral changes. METHODS: We critique and evaluate the behavioral changes induced by manipulation of cellular plasticity cascades implicated in BD. RESULTS: Not surprisingly, the behavioral data suggest that several important signaling molecules might play important roles in mediating facets of the complex symptomatology of BD. Notably, the protein kinase C and extracellular signal-regulated kinase cascades might play important roles in the antimanic effects of mood stabilizers, whereas glycogen synthase kinase (GSK)-3 might mediate facets of lithium's antimanic/antidepressant actions. Glucocorticoid receptor (GR) modulation also seems to be capable to inducing affective-like changes observed in mood disorders. And Bcl-2, amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors, and inositol homeostasis represent important pharmacological targets for mood stabilizers, but additional behavioral research is needed to more fully delineate their behavioral effects. CONCLUSIONS: Behavioral data support the notion that regulation of cellular plasticity is involved in affective-like behavioral changes observed in BD. These findings are leading to the development of novel therapeutics for this devastating illness.

Animals↗

PubMed2006

The polymerase chain reaction and its application to clinical plastic surgery.

Molecular biology has become an essential component in many fields of modern medical research, including plastic surgery. Research into the molecular mechanisms underlying many disease processes offer increased understanding of the pathogenesis of disease and provide exciting therapeutic possibilities. Yet for many clinicians, the presentation of much research into molecular biological processes is couched in confusing terminology and based on scientific techniques, the basis of which are frequently difficult for the clinician to understand. The purpose of this review is to present an introduction to some of the molecular biological techniques currently in use, namely the polymerase chain reaction (PCR) and explore its applications to different aspects of plastic surgery. This review explores the role PCR now plays in all aspects of modern plastic surgery practise, with particular emphasis on normal and abnormal wound healing, the diagnosis of craniofacial anomalies, the diagnosis and treatment of cancer including melanoma and squamous cell carcinoma of the head and neck, and burns.

Burns↗

PubMed2006

Duplicate publications: redundancy in plastic surgery literature.

The practice of duplicate publication has been condemned widely in the scientific community and several studies have been conducted to establish the level of the problem in various surgical fields. A retrospective review of original articles from the British Journal of Plastic Surgery and Plastic and Reconstructive Surgery during 2000 was conducted, using Medline (PubMed). A total of 431 abstracts were screened, from which 27 index articles related to 33 'suspected redundant' publications. Further evaluation was carried out by comparing the full text versions of these articles and assigning a grade of non-dual, dual, potentially dual and 'salami-slicing'. Only four suspect articles were confirmed as having some degree of redundancy, and these related to three index articles (3/431, <1%). The incidence of duplication in plastic surgery literature seems to be much lower compared to other surgical specialties, providing reassurance for reviewers, editors and readers of these journals.

Bibliometrics↗