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PubMed1975

[Use of the plastic "Terphane" for the maintenance and the study of cell cultures].

Terphane plastic used as substrate for tissue culture, facilitates both cytochemcial, biochemical and ulstratructural studies of cells in situ. Particularly pliable, thin and resistant, the sheet of Terphane plastic is held tense by a system of two plaques of Petri dish type. This apparatus is perfectly waterproof, sterilisable and may be used indefinitely. Growth, morphology, ultrastructure and enzyme activities of primary or subcultures of rat and human liver maintained on terphane plastic are comparable with those of cells cultivated on Falcon polystyrene. Furthermore, terphane offers several advantages over the Melinex plastic: its thinness, resistance and plasticity render easy all manipulations.

Animals↗

PubMed2000

Plastic wrapping of cot mattresses: results from a pilot study.

AIM: To assess the prevalence of plastic wrapping of cot mattresses and their thickness. METHODS: Mothers of infants less than six months attending Plunket clinics in Central Auckland were interviewed. The thickness of the plastic was measured. RESULTS: 99 of 110 (90%) mothers invited to participate were visited at home. The sample was socioeconomically advantaged. Most infants were breastfed and few slept prone. The prevalence of plastic wrapped cot mattresses was 23.2%, of which sixteen (out of 23) used BabeSafe and seven used other types. The mean thickness of the BabeSafe was 0.15 mm (range 0.12-0.19 mm) and the other types were 0.10 mm (range 0.04-0.13 mm). One sample of plastic was 0.04 mm. CONCLUSION: Thin plastic wrapping is being used and is potentially dangerous.

Adult↗

PubMed2000

Stable Hebbian learning from spike timing-dependent plasticity.

We explore a synaptic plasticity model that incorporates recent findings that potentiation and depression can be induced by precisely timed pairs of synaptic events and postsynaptic spikes. In addition we include the observation that strong synapses undergo relatively less potentiation than weak synapses, whereas depression is independent of synaptic strength. After random stimulation, the synaptic weights reach an equilibrium distribution which is stable, unimodal, and has positive skew. This weight distribution compares favorably to the distributions of quantal amplitudes and of receptor number observed experimentally in central neurons and contrasts to the distribution found in plasticity models without size-dependent potentiation. Also in contrast to those models, which show strong competition between the synapses, stable plasticity is achieved with little competition. Instead, competition can be introduced by including a separate mechanism that scales synaptic strengths multiplicatively as a function of postsynaptic activity. In this model, synaptic weights change in proportion to how correlated they are with other inputs onto the same postsynaptic neuron. These results indicate that stable correlation-based plasticity can be achieved without introducing competition, suggesting that plasticity and competition need not coexist in all circuits or at all developmental stages.

Action Potentials↗

PubMed2000

[Chemical substances used in plastics intended for manufacture of food packaging in light of European Union legislation].

In the EU countries the use of the chemical substances for plastics intended to come into contact with foodstuffs is regulated by Directive 89/109/EEC and the several specific Directives. Positive lists of the chemical substances for plastics intended to manufacturing of food packaging are placed in Directive 90/128/EEC on plastics materials. This 90/128/EEC Directive so-called "Monomer Directive" has been amended five times by Directives 92/39/EEC, 93/9/EEC, 95/3/EC, 96/11/EC and 99/91/EC. Directive 90/128/EEC so-called "Monomer Directive" provides: list of monomers and other starting substances that can be used in the manufacture of plastics materials and articles, placed in two Sections (A and B), and list of additives initiated from Directive 95/3/EC. Other additives will be added to this list on the basis of their positive national regulatory status in the EU countries and limits of migration (global, specific). According to the EU legislation all the substances before placing on the positive lists are the evaluated and authorized by the scientific bodies (SCF and/or JECFA). The EU legislation on the plastics materials and articles intended to come into contact with foodstuffs will be implemented into Polish law. However all the regulations relating to the chemical substances and limits of migration (global and specific) are already accepted by the National Institute of Hygiene.

European Union↗

PubMed1997

[Preliminary evaluation of plastic crown restoration supported by osseointegrated implants].

This study was to evaluate the feasibility of plastic crown restoration supported by osseointegrated implants. The following conclusions were drawn from this study: plastic crown gave better biomechanical consideration than porcelain fused to metal (PFM) crown in osseointegrated prostheses, but plastic crown gave worse wearability, tensile strength, compression strength and flexuaral strength than PFM crown. After restoration the disadvantages of the plastic crown were beyond the clinical acceptable range. It showed plastic crown designed dental prothetic implantation was unfeasible.

Crowns↗

PubMed2001

[Calcium ions and the nervous system plasticity].

The nervous system is different from all other systems of the organism by extreme flexibility of the structural and functional properties of its elements. This unique feature of the nervous system can be best described as plasticity in a broad sense of the word. All forms of plastic changes in the nervous system functioning have common basic mechanisms, the changes at the free Ca2+ cytosol ions being the most important one. These "calcium signals" trigger an extremely complicated intracellular machinery capable of controlling the structural and functional properties of the nervous system during the whole life span. This review summarises data on the intracellular Ca2+ ions mechanisms controlling the developmental plasticity of neuronal elements, synaptic plasticity of the mature nervous system, and the decline of plastic capabilities with ageing.

Aging↗

PubMed2001

Elevated postsynaptic [Ca2+]i and L-type calcium channel activity in aged hippocampal neurons: relationship to impaired synaptic plasticity.

Considerable evidence supports a Ca(2+) dysregulation hypothesis of brain aging and Alzheimer's disease. However, it is still not known whether (1) intracellular [Ca(2+)](i) is altered in aged brain neurons during synaptically activated neuronal activity; (2) altered [Ca(2+)](i) is directly correlated with impaired neuronal plasticity; or (3) the previously observed age-related increase in L-type voltage-sensitive Ca(2+) channel (L-VSCC) density in hippocampal neurons is sufficient to impair synaptic plasticity. Here, we used confocal microscopy to image [Ca(2+)](i) in single CA1 neurons in hippocampal slices of young-adult and aged rats during repetitive synaptic activation. Simultaneously, we recorded intracellular EPSP frequency facilitation (FF), a form of short-term synaptic plasticity that is impaired with aging and inversely correlated with cognitive function. Resting [Ca(2+)](i) did not differ clearly with age. Greater elevation of somatic [Ca(2+)](i) and greater depression of FF developed in aged neurons during 20 sec trains of 7 Hz synaptic activation, but only if the activation triggered repetitive action potentials for several seconds. Elevated [Ca(2+)](i) and FF also were negatively correlated in individual aged neurons. In addition, the selective L-VSCC agonist Bay K8644 increased the afterhyperpolarization and mimicked the depressive effects of aging on FF in young-adult neurons. Thus, during physiologically relevant firing patterns in aging neurons, postsynaptic Ca(2+) elevation is closely associated with altered neuronal plasticity. Moreover, selectively increasing postsynaptic L-VSCC activity, as occurs in aging, negatively regulated a form of short-term plasticity that enhances synaptic throughput. Together, the results elucidate novel processes that may contribute to impaired cognitive function in aging.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed2002

Assessing the role of calcium-induced calcium release in short-term presynaptic plasticity at excitatory central synapses.

Recent evidence suggests that internal calcium stores and calcium-induced calcium release (CICR) provide an important source of calcium that drives short-term presynaptic plasticity at central synapses. Here we tested for the involvement of CICR in short-term presynaptic plasticity at six excitatory synapses in acute rat hippocampal and cerebellar brain slices. Depletion of internal calcium stores with thapsigargin and prevention of CICR with ryanodine have no effect on paired-pulse facilitation, delayed release of neurotransmitter, or calcium-dependent recovery from depression. Fluorometric calcium measurements also show that these drugs have no effect on the residual calcium signal that underlies these forms of short-term presynaptic plasticity. Finally, although caffeine causes CICR in Purkinje cell bodies and dendrites, it does not elicit CICR in parallel fiber inputs to these cells. Taken together, these results indicate that for the excitatory synapses studied here, internal calcium stores and CICR do not contribute to short-term presynaptic plasticity on the milliseconds-to-seconds time scale. Instead, this plasticity is driven by the residual calcium signal arising from calcium entry through voltage-gated calcium channels.

Animals↗

PubMed2003

Neocortical long-term potentiation and experience-dependent synaptic plasticity require alpha-calcium/calmodulin-dependent protein kinase II autophosphorylation.

Experience-dependent plasticity can be induced in the barrel cortex by removing all but one whisker, leading to potentiation of the neuronal response to the spared whisker. To determine whether this form of potentiation depends on synaptic plasticity, we studied long-term potentiation (LTP) and sensory-evoked potentials in the barrel cortex of alpha-calcium/calmodulin-dependent protein kinase II (alphaCaMKII)T286A mutant mice. We studied three different forms of LTP induction: theta-burst stimulation, spike pairing, and postsynaptic depolarization paired with low-frequency presynaptic stimulation. None of these protocols produced LTP in alphaCaMKIIT286A mutant mice, although all three were successful in wild-type mice. To study synaptic plasticity in vivo, we measured sensory-evoked potentials in the barrel cortex and found that single-whisker experience selectively potentiated synaptic responses evoked by sensory stimulation of the spared whisker in wild types but not in alphaCaMKIIT286A mice. These results demonstrate that alphaCaMKII autophosphorylation is required for synaptic plasticity in the neocortex, whether induced by a variety of LTP induction paradigms or by manipulation of sensory experience, thereby strengthening the case that the two forms of plasticity are related.

Animals↗

PubMed2003

Activation of erbB-1 signaling in tanycytes of the median eminence stimulates transforming growth factor beta1 release via prostaglandin E2 production and induces cell plasticity.

The activation of transforming growth factor alpha (TGFalpha)-erbB-1 and neuregulin-erbB-4 signaling pathways in hypothalamic astrocytes has been shown to play a key role in the process by which the neuroendocrine brain controls luteinizing hormone-releasing hormone (LHRH) secretion. Earlier studies suggested that tanycytes, an ependymoglial cell type of the median eminence, regulate LHRH release during the estrous cycle by undergoing plastic changes that alternatively allow or prevent direct access of the LHRH nerve terminals to the portal vasculature. Neither the molecules responsible for these plastic changes nor the underlying controlling mechanisms have been identified. Here we show that cultured tanycytes express erbB-1 and erbB-2, two of the four members of the erbB receptor family, and respond to TGFalpha with receptor phosphorylation, release of prostaglandin E2 (PGE2), and a PGE2-dependent increase in the release of TGFbeta1, a growth factor previously implicated in the glial control of LHRH secretion. Blockade of either erbB-1 receptor signal transduction or prostaglandin synthesis prevented the stimulatory effect of TGFalpha on both PGE2 and TGFbeta1 release. Time-lapse studies revealed that TGFalpha and TGFbeta1 have dramatically opposite effects on tanycyte plasticity. Whereas TGFalpha promotes tanycytic outgrowth, TGFbeta1 elicits retraction of tanycytic processes. Blockade of metalloproteinase activity abolished the effect of TGFbeta1, suggesting that TGFbeta1 induces tanycytic retraction by facilitating dissolution of the extracellular matrix. Prolonged (>12 hr) exposure of tanycytes to TGFalpha resulted in focal tanycytic retraction, an effect that was abolished by immunoneutralization of TGFbeta1 action, indicating that the retraction was attributable to TGFalpha-induced TGFbeta1 formation. These in vitro results identify tanycytes as targets of TGFalpha action and demonstrate that activation of erbB-1-mediated signaling in these cells results in plastic changes that, involving PGE2 and TGFbeta1 as downstream effectors, mimic the morphological plasticity displayed by tanycytes during the hours encompassing the preovulatory surge of LHRH.

Animals↗

PubMedDate not supplied

Influence of storage conditions and type of plasticizers on ethylcellulose and acrylate films formed from aqueous dispersions.

PURPOSE: To investigate the influence of storage conditions and types of plasticizers on the properties and stability of ethylcellulose and polymethacrylate films and to elucidate the mechanism for the changes observed. METHODS: Films were prepared from Surelease, Aquacoat and Eudragit L 30D dispersions by the casting method. The effects of different plasticizers on the morphology, transparency, mechanical property and water vapour permeability of the prepared films were studied. The film samples were exposed to storage conditions of 30 degrees C and 50 or 75 %RH. Samples were removed at pre-determined time intervals for mechanical testing and analysis of plasticizer content in the films. RESULTS: It was found that films prepared from aqueous ethylcellulose dispersions were relatively weaker and more brittle than acrylate films. Acrylate films did not show any significant change in mechanical property when stored at high humidity. However, the properties of ethylcellulose films stored at high humidity varied depending on the type of plasticizers present. CONCLUSIONS: The changes in mechanical property of ethylcellulose films on storage were mainly attributed to the loss of plasticizers during storage, causing further coalescence of ethylcellulose films and to a smaller extent, reduction in moisture content of the film.

Acrylates↗

PubMed2004

Changes in some hormones by low doses of di (2-ethyl hexyl) phthalate (DEHP), a commonly used plasticizer in PVC blood storage bags & medical tubing.

BACKGROUND & OBJECTIVES: Di (2-ethyl hexyl) phthalate (DEHP), a plasticizer commonly used in PVC blood storage bags leaches out in significant amounts into blood during storage. In view of many reports on the toxicity of this compound, it was considered necessary to investigate the effect of DEHP at the low level solubilized in blood on some important hormones in rats and in human blood stored in DEHP plasticized blood bags. METHODS: Rats were administered DEHP at a low level of 750 microg/100 g body weight on alternate days for 14 days. Changes in the serum insulin, blood glucose, liver glycogen level and T3, T4 and thyroid stimulating hormone (TSH) as well as cortisol in the serum were studied. Changes in the hormones were also studied in blood stored in DEHP plasticized PVC bags. RESULTS: The results indicated decrease in serum insulin, cortisol and liver glycogen, and increase in blood glucose, serum T3 and T4 in rats receiving DEHP. These changes were reversed when administration of DEHP was stopped. Similar changes in hormones were also observed in the blood stored in DEHP plasticized blood bags. INTERPRETATION & CONCLUSION: The results indicated that administration of DEHP at low levels to rats caused symptoms of diabetes, thyroid and adrenocortical dysfunction. Though the results obtained in rats cannnot be extrapolated to human, the fact that similar hormonal changes seen in human blood stored in DEHP plasticized blood bags may suggest possibility of DEHP causing similar changes in human. The fact that these changes were reversed in rats when DEHP administration was stopped, indicates that transfusion of a few units of blood to a recipient may not be harmful, but it may pose a problem during repeated transfusions such as in thalassaemia patients.

Animals↗

PubMed1991

Calcium, network activity, and the role of NMDA channels in synaptic plasticity in vitro.

Functionally effective neuronal circuits are constructed through a competitive process that requires patterned neuronal activity elicited by structured input from the environment. To explore the mechanisms of this activity-dependent synaptic restructuring, we have developed an in vitro preparation of mouse spinal cord neurons maintained in a 3-chambered cell-culture system. Sensory afferents that received chronic electrical stimulation for 3-5 d developed stronger synaptic connections than unstimulated afferents converging onto the same postsynaptic spinal cord neuron. Exposure to 100 microM DL-2-amino-5-phosphonovaleric acid (APV), an antagonist of the NMDA channel, during the stimulation period prevented the competitive advantage associated with electric stimulation. However, when APV was applied with a higher concentration of calcium (3 mM), activity-dependent synaptic plasticity was no longer inhibited by the NMDA receptor antagonist. This reversal of APV block of the plasticity was not impaired by reducing transmitter release with 3 mM magnesium (in addition to 3 mM calcium and APV). A suppressant effect of APV on spontaneous activity was observed, which was attributed to loss of the NMDA component of the EPSP. Activity-dependent plasticity was also blocked if spontaneous activity was suppressed with dilute tetrodotoxin (TTX; 5-10 nM), a dosage that reduces excitability of neurons but is insufficient to block sodium-dependent action potentials. These experiments bring into question how NMDA channel activation is involved in the processes of synaptic remodeling during development. The data suggest that postsynaptic activity is required for synaptic remodeling, but this activity need not involve NMDA receptor activation specifically for activity-evoked synaptic plasticity. Instead, the mechanism for plasticity appears to operate through calcium-dependent processes in general.

2-Amino-5-phosphonovalerate↗

PubMed2006

[Progress and investigation of neuronal plasticity interfered by Borna disease virus infection].

Borna disease virus (BDV) is highly neuronotropic. Recently, more and more investigations indicated that BDV infection was close related to human neuropsychic disorders. However, the mechanism underlying the disorders was unclear to date. Some investigators thought neuronal plasticity changes by BDV infection in the central nervous system may be it's cardinal basis. Many researchers have studied the molecular mechanisms, which might lead to disturbances in neuronal plasticity by BDV infection, through infection-based animal modes such as gerbils modes, rats modes, mice modes and transgenic mice modes. The results showed that neuronal plasticity was interfered by BDV infection through interference with trophic support from astrocytes to neurons, interference with amphoterin signaling and interference with neurotrophin signaling. The disturbances in neuronal plasticity would result in cerebral disorders and cause behavior alterations and psychic alterations of host. In the following years, the ability to manipulate the BDV genome may help uncover unrecognized aspects of the basic mechanisms operating in the regulation of neuronal plasticity of interference with neuronal physiology caused by BDV, give academic foundation for clinical prevention and therapy of BD.

Animals↗

PubMed2005

Study on long-term potentiation in developing rat visual cortex during the critical period of plasticity.

PURPOSE: To study the property of LTP in layers II -IV of the rats visual cortex at different postnatal days induced by pairing low-frequency stimulation at layer IV with post synaptic depolarization in order to explore the synaptic and cellular mechanism of experience-dependent plasticity in the visual cortex. METHODS: Postsynaptic currents (PSCs) of layers II -IV in visual cortex slices of Wistar rats aged P0-29 d were recorded by patch-clamp whole cell recording method. Long-term potentiation (LTP) was induced by low-frequency stimulation (LFS) at 1Hz for 60-90 s. Each pulse of the LFS paired with depolarization of post-synaptic neurons to -20 mV.100 microM APV, a kind of competitive N-methyl-d-aspartate (NMDA) receptor antagonist, was both applied to some slices to test the property of LTP. RESULTS: 1. The LTP incidence was very low before PlOd (5/34), and increased rapidly to the top at P15-24 d (17/28), then decreased sharply to 1/5 at P25-29 d, coinciding well with the critical period of plasticity of rat visual cortex. The LTP incidence of P15-29 d (after eye opening, 18/33) was significantly higher than that of P0-14 d (before eye opening, 12/43, P < 0.05). 2. Compared with non-APV applied group (30/76), LTP incidence of APV applied group (4/33) was significantly decreased (P < 0.01). There were 4 LV-IV horizontal synapses. APV application could not block the LTP induction. CONCLUSIONS: 1. LTP was a reflection of naturally occurring, experience-dependent plasticity in rat visual cortex. The patterned visual stimuli received after eye opening might be an activation factor of the synaptic plasticity. 2. LTP of visual cortex induced by LFS in layer IV paired with postsynaptic depolarization was NMDA receptor dependent during the critical period of visual plasticity. However, there were LTP existed in IV-IV horizontal synapses which could not be blocked by 100microM APV.

Animals↗

PubMed1991

Changes in oxygen measurements when whole blood is stored in iced plastic or glass syringes.

Tonometered whole-blood and plasma specimens were tested in plastic and glass syringes to determine whether clinically significant changes in gas tensions occur during sample storage. When whole blood was tonometered with 60 and 100 mL/L (6% and 10%) oxygen and then stored for 30 min in iced plastic syringes, the pO2 of the samples remained stable (mean change = +0.4 and +0.8 mmHg, respectively). However, for 140 mL/L (14%) oxygen tonometry, the pO2 increased significantly (mean change = +8.4 mmHg; P less than 0.0001). When tonometered plasma was stored in iced plastic syringes, the pO2 increased progressively at all three concentrations, with the smallest change occurring at 140 mL/L (mean change = +12.6 mmHg) and the greatest at 60 mL/L oxygen (mean change = +20.9 mmHg). In contrast, when iced glass syringes were used for storing plasma or whole blood, no clinically significant changes in pO2 were found at any of the tonometered oxygen values for 60 min. When whole blood was stored in plastic syringes at ambient temperature for 30 min, again no clinically significant changes in pO2 were found at these tonometry conditions. Apparently, some blood gas samples stored in iced plastic syringes may yield clinically significant errors in oxygen tension.

Blood Gas Analysis↗

PubMed1990

Biliary endoprostheses. Plastic versus metal stents.

Plastic biliary endoprostheses relieved malignant obstructive jaundice in 80% to 90% of the patients. The comfort of a completely indwelling endoprosthesis should be offered to all palliatively treated tumor patients, and external-internal catheters should be reserved for the minority of patients who return with reoccluded endoprostheses. These patients have bacterial flora that rapidly contaminates the endoprosthesis and causes encrustations and reocclusions. Thus, a second endoprosthesis also would reocclude quickly. The mechanism of reocclusion of plastic and metal endoprostheses is completely different. In plastic endoprostheses, bacterial contamination causes decomposition of the bile and subsequent encrustation. In metal endoprostheses tumor ingrowths between the struts of the stent cause reocclusion. Tumor ingrowths were observed in only 6.5% of metal prostheses with a narrow woven mesh (Wallstent), whereas prostheses with large distances between the struts (Gianturco stent) had ingrowth rates of 19% to 50%. This fact shows that tumor ingrowths can be reduced by narrowing the spaces between the metallic network, and, therefore, improvements in the design of the metal stents should reduce the occlusion rate to or below that of plastic endoprostheses, which currently have a lower encrustation rate. The major advantages of expandable metal prostheses are the relative ease and the minimal trauma of the implantation procedure. The Wallstent endoprosthesis, in particular, can be inserted through a 7-F introducer sheath and offers the chance of single-step placement. The 30-day mortality rate, therefore, was only 5%. This is significantly lower than the 30-day mortality rate after insertion of plastic prostheses (15% to 24%). Even simple external catheter drainage procedures have a higher reported 30-day mortality rate (27%). Expandable metal endoprostheses would be the most useful device if the occlusion rate could be kept under 10% in large series. Increasing the length of the endoprostheses to 10 cm in the expanded state could also improve the long-term patency rates.

Bile Ducts↗

PubMed1989

Monocyte long-term cultivation on microvascular endothelial cell monolayers: morphologic and phenotypic characterization and comparison with monocytes cultured on tissue culture plastic.

Human monocytes were cultured on monolayers of a newly established microvascular endothelial cell strain. As compared to monocytes cultured on plastic, these endothelium-"derived" monocytes (EDM) showed distinct morphology, higher motility, and different antigen-expression pattern for several surface markers, as detected by cytofluorimetry. The MO-1- and the Leu-M1-marker were maintained on EDMs while they were lost on plastic-cultured cells. The MAX 1-26-termed markers failed to increase on EDMs, in contrast to plastic-cultured monocytes. For seven additional markers, expression after two weeks in vitro was higher on EDMs than on plastic-cultured monocytes. Functionally EDMs showed typical monocyte/macrophage behavior and were easily removable from the culture system for further experimentation. Our data suggest that monocytes cultured on microvascular endothelial cells are maintained for several weeks in a more physiologic state than monocytes cultured on plastic.

Animals↗