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PubMedDate not supplied

Enriched environment, nitric oxide production and synaptic plasticity prevent the aging-dependent impairment of spatial cognition.

In rodents, neuronal plasticity decreases and spatial learning and working memory deficits increase upon aging. Several authors have shown that rats reared in enriched environments have better cognitive performance in association with increased neuronal plasticity than animals reared in standard environments. We hypothesized that enriched environment could preserve animals from the age-associated neurological impairments, mainly through NO-dependent mechanisms of induction of neuronal plasticity. We present evidence that 27 months old rats from an enriched environment show a better performance in spatial working memory than standard reared rats of the same age. Both mtNOS and cytosolic nNOS activities were found significantly increased (73% and 155%, respectively) in female rats from enriched environment as compared with control animals kept in a standard environment. The enzymatic activity of complex I was 80% increased in rats from enriched environment as compared with control rats. We conclude that an extensively enriched environment prevents old rats from the aging-associated impairment of spatial cognition, synaptic plasticity and nitric oxide production.

Aging↗
PubMed2006

Layers of exercise hyperpnea: modulation and plasticity.

Despite the fundamental biological significance of the ventilatory response to mild or moderate physical activity (the exercise hyperpnea), we still know remarkably little concerning its underlying mechanisms. Part of the difficulty in revealing those mechanisms may arise due to confusion between multiple mechanistic layers, each contributing to the impressive degree of regulation achieved. The primary, feedforward exercise stimulus or stimuli increase ventilation in approximate proportion to changes in metabolic rate. Chemoreceptor feedback then minimizes deviations from optimal blood gas regulation, most often preventing excessive hypocapnia in non-human mammals. Recent evidence has accumulated, suggesting that adaptive control strategies including modulation and plasticity may adjust the feedforward and/or feedback contributions when blood gas homeostasis proves inadequate. In this review, we present evidence from a goat model of exercise hyperpnea concerning the existence of modulation and plasticity, and specifically mechanisms known as short-term and long-term modulation of the exercise ventilatory response. Throughout the review, we consider available evidence concerning the relevance of these mechanisms to humans. Plasticity is a property only recently recognized in the neural system subserving respiratory control, and the application of these concepts to the exercise ventilatory response in humans is in its infancy. Modulation and plasticity may confer an ability of individuals to adapt their exercise ventilatory response so that it remains appropriate in the face of life-long changes in endogenous (e.g. development, aging, onset of disease) or exogenous (e.g. altitude, wearing a breathing apparatus during physical exertion) physiological conditions.

Adaptation, Physiological↗
PubMed2006

The evolutionary consequences of plasticity in host-pathogen interactions.

Interactions between individuals such as hosts and pathogens are often characterized by substantial phenotypic plasticity. Pathogens sometimes alter their exploitation strategies in response to defensive strategies adopted by their host and vice versa. Nevertheless, most game-theoretic models developed to explain the evolution of pathogen and host characteristics assume that no such plasticity occurs. Allowing for phenotypic plasticity in these models is difficult because one must focus on the evolution of pathogen and host reaction norms, and then allow for the potentially indefinite reciprocal changes in pathogen and host behaviour that occur during an infection as a result of their interacting reaction norms. Here, we begin to address these issues for a simple host-pathogen system in which the pathogen exhibits a level of virulence and the host exhibits a level of immune clearance. We find, quite generally, that plasticity promotes the evolution of higher levels of cooperation, in this case leading to reduced levels of both virulence and clearance.

Biological Evolution↗
PubMed2003

Adhesion in elastic-plastic spherical microcontact.

An elastic-plastic adhesion model for a metallic deformable sphere pressed by a rigid flat is presented. Analytical dimensionless expressions for the local separation outside the contact area and for the adhesion force are provided covering a large range of interference values from a point contact to a fully plastic contact. Two main dimensionless parameters of the problem are identified and their effect on the adhesion is investigated. The significance of the adhesion in the elastic-plastic contact force balance is discussed and the regimes where adhesion is important or negligible are pointed out. A comparison of the present results with a previously published approximate elastic-plastic model shows substantial differences in the local separation and in the adhesion force.

Journal Article↗
PubMed1998

Feeding is not necessary for triggering plasticization of the abdominal cuticle in haematophagous bugs.

A simple device was used to quantify changes in the mechanical properties of the cuticle of Rhodnius prolixus and Triatoma infestans that take place when these insects feed, i.e., plasticization. Different stimuli were presented for 1min to test for their ability to trigger plasticization. These were: a blood meal, a Ringer solution meal, contact with a warm surface and thermal stimulation without such contact. Our results supplant any previous hypotheses that have supposed that the presence of food in the alimentary tract is necessary to evoke plasticization. We find that mere contact of the proboscis with a warm surface (without any food intake) is sufficient to trigger plasticization indistinguishable from that produced by a blood meal. Thermal stimulation alone, i.e., without physical contact, was not effective.

Journal Article↗
PubMed2000

Endoscopic plastic surgery.

This article discusses three of the most popular endoscopic procedures in plastic surgery. Brow lift, transaxillary breast augmentation, and abdominoplasty are all cosmetic procedures with a high demand on inconspicuous scars; however, many investigators are working on reconstructive endoscopically assisted procedures. The treatment of many facial fractures involving the upper third of the facial skeleton usually requires long bicoronal incisions similar to the incisions used in the traditional brow lift. Attempts are under way to use endoscopically assisted minimal-access techniques to reduce and fixate these fractures. Many flaps used in plastic surgery require long scars for harvest, as in the case of the latissimus dorsi muscle flap. A relatively long incision on the back is needed to gain access to the muscle so that it can be elevated from structures superficial and deep to it. Although it is unpopular, investigators have reported harvesting latissimus dorsi muscle flaps through fairly small incisions with the assistance of balloon dissectors and endoscopes. In the field of hand surgery, carpal tunnel release surgery has had more than one method proposed to transect the carpal ligament using endoscopes and special instrumentation. Although some reported series claim excellent results, many hand surgeons are reluctant to use endoscopes because of associated complications and a high recurrence rate of carpal tunnel syndrome. Plastic surgery has special demands that emphasize aesthetics in cosmetic and reconstructive procedures. Although the lack of natural optical cavities has slowed the incorporation of endoscopic surgery in the specialty, surgically created cavities are used to allow for minimal access incisions. The future of plastic surgery will include an ever-increasing number of endoscopically assisted procedures. Cosmetic and reconstructive procedures will benefit from this new technology.

Abdomen↗
PubMed1988

Antigen localization in immunoperoxidase-stained plastic-embedded soft tissues.

Immunoperoxidase stains were performed on normal and neoplastic tissue from prostate, colon, thyroid, lung, nerve, uterus, and placenta embedded in both plastic (glycolmethacrylate [GMA]) and paraffin. Positive results in plastic section were obtained for carcinoembryonic antigen (CEA), keratin, epithelial membrane antigen (EMA), thyroglobulins, S-100, prostate-specific antigen, human chorionic gonadotrophin (HCG), and beta-HCG. More delicate staining with more precise localization of antigens is noted. Superior (paraformaldehyde) fixation and cold processing followed by GMA polymerization (4 degrees C) allow for optimum antigen survival. After fixation, tissue processing involves a series of 0.1 mol/L phosphate buffer rinses with sucrose and ammonium chloride in a conventional dip-and-dunk processor placed in a 4 degrees C cold room. Acetone dehydrations are used before GMA infiltration, cold polymerization, and sectioning. Before immunoperoxidase staining, the plastic section is digested in .25% bovine trypsin for ten minutes. The immunoperoxidase methods described can be useful when small biopsies are routinely embedded in plastic to obtain improved histologic (hematoxylin-eosin) sections. There may also be research applications in quantifying antigen expression in benign, dysplastic, and neoplastic tissues by examining the stains under high power.

Adenocarcinoma↗
PubMed2001

Maternity leads to morphological synaptic plasticity in the oxytocin system.

The oxytocinergic system, which plays a major role in the control of different aspects of maternity, undergoes extensive synaptic and neuronal-glial remodelling during parturition and lactation and has thus become a remarkable example of activity-dependent morphological synaptic plasticity in the adult mammalian brain. The use of different comparative ultrastructural analyses on the rat supraoptic and paraventricular nuclei, together with identification of pre- and post-synaptic elements, has allowed us to show that there is a significant increase in the number of GABAergic, glutamatergic and noradrenergic synapses impinging on oxytocin neurons, concomitant with a reduction of glial coverage of the neurons. This synaptic plasticity involves axo-dendritic and axo-somatic contacts originating from terminals making one or several synaptic contacts in one plane of section. While noradrenergic afferents arise from medullary catecholaminergic neurons, our recent in vitro observations indicate that GABAergic and glutamatergic afferents derive, at least partly, from local intrahypothalamic neurons, in close proximity to oxytocin neurons. The cellular mechanisms underlying this morphological synaptic plasticity remain to be determined but it is highly likely that they depend on increased activity in both pre- and post-synaptic elements. Moreover, the oxytocin system continues to express 'embryonic' molecular features that may allow the morphological plasticity to occur. In particular, it expresses high levels of cell surface adhesion molecules currently thought to intervene in synaptic remodelling in the developing and lesioned central nervous system, including the weakly adhesive polysialylated isoform of the Neural Cell Adhesion Molecule, the axonal glycoprotein F3 and its ligand, the extracellular matrix glycoprotein, tenascin-C.

Afferent Pathways↗
PubMed2005

Structural plasticity in the developing visual system.

The visual system has been used extensively to study cortical plasticity during development. Seminal experiments by Hubel and Wiesel (Wiesel, T.N. and Hubel, D.H. (1963) Single cell responses in striate cortex of kittens deprived of vision in one eye. J. Neurophysiol., 26: 1003-1017.) identified the visual cortex as a very attractive model for studying structural and functional plasticity regulated by experience. It was discovered that the thalamic projections to the visual cortex, and neuronal connectivity in the visual cortex itself, were organized in alternating columns dominated by input from the left or the right eye. This organization was shown to be strongly influenced by manipulating binocular input during a specific time point of postnatal development known as the critical period. Two chapters in this volume review the molecular and functional aspects of this form of plasticity. This chapter reviews the structural changes that occur during ocular dominance (OD) plasticity and their possible functional relevance, and discusses developments in the methods that allow the analysis of the molecular and cellular mechanisms that regulate them.

Animals↗
PubMed2003

Phosphorylation of the AMPA receptor GluR1 subunit is required for synaptic plasticity and retention of spatial memory.

Plasticity of the nervous system is dependent on mechanisms that regulate the strength of synaptic transmission. Excitatory synapses in the brain undergo long-term potentiation (LTP) and long-term depression (LTD), cellular models of learning and memory. Protein phosphorylation is required for the induction of many forms of synaptic plasticity, including LTP and LTD. However, the critical kinase substrates that mediate plasticity have not been identified. We previously reported that phosphorylation of the GluR1 subunit of AMPA receptors, which mediate rapid excitatory transmission in the brain, is modulated during LTP and LTD. To test if GluR1 phosphorylation is necessary for plasticity and learning and memory, we generated mice with knockin mutations in the GluR1 phosphorylation sites. The phosphomutant mice show deficits in LTD and LTP and have memory defects in spatial learning tasks. These results demonstrate that phosphorylation of GluR1 is critical for LTD and LTP expression and the retention of memories.

Animals↗
PubMedDate not supplied

Synaptic plasticity is preserved in the temporal cortex of 20-month-old rats.

The molecular mechanisms associated with age-related alterations in the plasticity of the cortical neurons in response to chemically-induced seizure are largely unknown. Administration of pentylenetetrazole (PTZ) (50 mg/kg body weight) to rats of various ages evoked tonic-clonic seizures. Using immunoblotting and in situ hybridization analysis we found that 72 h after the onset of seizure, the mRNA for microtubule-associated protein 1B (MAP1B), a marker of synaptic plasticity, was increased in the cortex of 3-month-old rats. The levels of MAP1B mRNA in the cortex of 3-month-old rats returned to control levels by 10 days after PTZ administration. The levels of MAP1B mRNA in the hippocampus and cortex of 20 months at later times (10 days) and returned nearly to basal levels by 20 days following PTZ treatment. Immunohistochemical analysis revealed that MAP1B-like immunoreactivity was confined to layer II and neuronal processes extending into layer I. In contrast, the staining of MAP1B in the temporal cortex of 20-month-old animals was restricted to neuronal cell bodies of layer II. Since synaptic plasticity is associated mainly with neuronal processes we conclude that synaptic plasticity is reduced in the temporal cortex of 20-month-old rats. Remarkably, the induction of MAP1B in neuronal extensions was not impaired in the temporal cortex of older animals following intense neuronal activity. However, the aged rat brain responded more slowly to chemically-induced seizure although the levels of MAP1B induction are not decreased as compared to the levels expressed by 3-month-old rats.

Journal Article↗
PubMed1995

Comparison of polydioxanone and silicone plastic in the prevention of adhesive otitis media in the Mongolian gerbil.

Adhesion of the tympanic membrane to the promontory may occur in chronic otitis media or in the postoperative ear. Silicone plastic sheets are commonly used to form a physical barrier to adhesion. These sheets are generally well tolerated, but they are subject to occasional extrusion, encapsulation, or foreign body reaction. The ideal barrier to adhesion formation would be a nonreactive, flexible, absorbable substance that would obviate long-term toxicity considerations. In this study polydioxanone sheets were compared with silicone plastic sheets in the middle ear of the Mongolian gerbil. The eustachian tube was cauterized to create severe tympanic membrane retraction. A fabricated sheet of polydioxanone was implanted in the middle ear of 30 Mongolian gerbils and compared with silicone plastic sheets implanted in another group of 30 animals. A sham operation was performed on the other ear to serve as a surgical control. Evaluation of the temporal bones at 5, 10, and 15 weeks showed no significant differences in the rate of adhesion formation, effusion formation, or polymorphonuclear infiltration by the Fisher exact test. There was histologic evidence that polydioxanone was still providing an effective barrier at 10 weeks. The results of this study demonstrate that polydioxanone sheets are as effective and as well tolerated as silicone plastic sheets in an animal model. Further study of polydioxanone in this role is warranted.

Animals↗
PubMed1998

Gravity and developmental plasticity.

Living organisms, especially plants, show some plasticity in their overall development, usually as a response to the external environment. Plasticity may apply not only to the external form of organisms but also to their physiology as well as to the detailed structure of their genome. A further example of plasticity may be developmental instability, where anomalous development seems to appear spontaneously, probably as a result of some transient environmental perturbation. Whether the absence of gravity would have sufficient impact on any living process to evoke a specific course of plastic development is unknown, though it is possible that in certain circumstances special forms, or 'agravimorphs', could be produced. Through such new forms, it should be possible to identify processes required for development in which 1 x g gravity is a necessary participant.

Adaptation, Physiological↗
PubMed2002

Plasticizer contamination from vacuum system O-rings in a quadrupole ion trap mass spectrometer.

The outgassing of plasticizers from Buna-N and Viton o-rings under vacuum lead to undesired ion-molecule chemistry in an Electrospray Quadrupole Ion Trap Mass Spectrometer. In experiments with the helium bath gas pressure >1.2 mTorr, or whenever analyte ions were stored for >100 ms, extensive loss of analyte ions by proton transfer or adduction with o-ring plasticizers bis(2-ethylhexyl) phthalate and bis(2-ethylhexyl) adipate occurred. A temporary solution to this contamination problem was found to be overnight refluxing in hexane of all the o-rings in the vacuum system. This procedure alleviated this plasticizer contamination for approximately 100 hours of operation. These results, and those that lead to identification of the contamination as plasticizers outgassing from o-rings are described.

Journal Article↗
PubMed2000

Use of a lacrimal stent retrieval hook in the removal of occluded plastic and expandable metallic lacrimal stents.

PURPOSE: To evaluate the clinical usefulness of a stent retrieval hook in the removal of occluded lacrimal stents. MATERIALS AND METHODS: The hook consisted of an inner hook part and an outer pusher part. Under administration of local anesthetic, the retrieval hook was introduced into the nasal cavity and aimed laterally toward the inferior meatus to grasp the distal end of the stent. After grasping the end of the stent, the sheath was pushed to fully grasp it. After that, the hook was pulled out of the external naris. The retrieval hook was used to remove 267 occluded lacrimal plastic or metallic stents. RESULTS: Technical success rate was 97% in the removal of plastic stents and 96% in the removal of metallic stents. The causes of technical failure were entrenchment of granulation tissue into the stent in six plastic stents and one metallic stent, and inaccessibility of the hook to the distal tip of the stent in one plastic stent. These eight stents were removed by an otorhinolaryngologist or an ophthalmologist. Epistaxis occurred in six patients, which was controlled by a nasal pack. CONCLUSIONS: The lacrimal stent retrieval hook seems useful for the removal of occluded stents.

Adolescent↗
PubMed1998

Developmental phenotypic plasticity: where internal programming meets the external environment.

Developmental plasticity has long been the focus of research in both evolutionary ecology and molecular genetics. Recently, the concept of ontogenetic contingency has been proposed to indicate the dependence of plastic responses on the timing and sequence of developmental events. Also, the idea of the developmental reaction norm has been put forward to indicate the complex interactions among development, phenotypic plasticity, and allometry of different structures. Finally, for the first time, studies ranging from the ecological to the molecular aspects of the same plastic response are available on insect and flowering plant model systems.

Biological Evolution↗
PubMed2002

Arousal deficiency theory in sudden infant death syndrome with reference to neuronal plasticity.

OBJECTIVE: Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age (including 26 infant victims of sudden infant death syndrome (SIDS), five with congenital cardiac abnormalities, two from infected pulmonary dysplasia, two from septic shock with multi-organ failure, one with a prolonged seizure, one from prolonged neonatal hypoxemia and one from meningitis and brain infarction). METHOD: The frequency and duration of sleep apnea events recorded some 3-12 weeks before the infants' deaths were analyzed. Brainstem material from these 38 infants was studied in an attempt to elucidate the relationship between sleep apnea and neuronal pathological changes in the arousal pathway. The histochemical analyses included Bielschowsky staining and the immunohistochemical analyses included the evaluation of growth-associated phosphoprotein 43 (GAP43) and of synaptophysin as markers for synaptic plasticity. Neurofibrae with positive pathological reactions were quantitatively analyzed. Pathological and physiological data were linked for each infant. RESULTS: The correlation between sleep apnea and neuronal plasticity in the arousal pathway of the SIDS victims was not seen in the control infants and the correlation between sleep apnea and neuronal plasticity in the arousal pathway found in the control infants was not seen in the SIDS victims. CONCLUSION: These findings suggest that neuronal plasticity in the brainstem arousal pathway is related with SIDS.

Journal Article↗
PubMed2005

Patterned solvent delivery and etching for the fabrication of plastic microfluidic devices.

A very simple method for micropatterning flat plastic substrates that can be used to build microfluidic devices is demonstrated. Patterned poly(dimethylsiloxane) elastomer is used as a template to control the flow path of an etching solvent through a channel design to be reproduced on the plastic substrate. The etching solvent was a acetone/ethanol mixture for poly(methyl methacrylate) substrates or a dimethylformamide/acetone mixture for polystyrene. The method is extremely fast in that duplicate plastic substrates can be patterned in just a few minutes each. We identified conditions that lead to smooth channel surfaces and characterized the rate of etching under these conditions. We determined that, for sufficiently short etching times (shallow channel depths), the etch rate is independent of the linear flow rate. This is very important since it means that the etch depth is approximately constant even in complex channel geometries where there will be a wide range of etchant flow rates at different positions in the pattern to be reproduced. We also demonstrate that the method can be used to produce channels with different depths on the same substrate as well as channels that intersect to form a continuous fluid junction. The method provides a nice alternative to existing methods to rapidly fabricate microfluidic devices in rigid plastics without the need for specialized equipment.

Journal Article↗