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PubMed1996

Molecular recognition of phenobarbital in plasticizers equilibrium investigations on the solubility of the barbiturate artificial receptor and its binding to phenobarbital in plasticizers.

Environmental concern is renewing interest in selective, waste-free extractions. A recent report demonstrated an improved extraction of phenobarbital by means of a specifically designed molecular receptor. In that work, the solvent was CHCl3. The current work is the first step in extending extractions based on molecular recognition to reusable solvents, namely plasticizers. Phenobarbital aqueous/organic partition coefficients, receptor solubility, and phenobarbital-receptor-formation constants in several plasticizers and in their CHCl3 solutions are reported. In addition, by a thermodynamic cycle, the free energy for transfer of the barbiturate-receptor complex from CHCl3 to plasticizers has been calculated. Finally, the data have been displayed in coordinate systems representing extraction efficiency and selectivity. The most selective extraction medium yielding useful extraction efficiency is dioctyl phthalate.

Chemical Phenomena↗

PubMed1991

New plastic plates which enhance neurite extension in culture: roles of bisphenol-A and tricyclodecanyl units for growth and orientation of neurites on plastic plates with microstructures.

In order to study molecular mechanisms of contact guidance of neurites, dissociated culture of adult mouse dorsal root ganglion (DRG) cells was performed for 6 species of plastic plates different in monomer compositions. Microstructures (grooves of 5-10 microns wide and 1 micron deep) were grafted on the plates so as to guide neurite growth in their axial direction. Neurites were longer and more oriented on plates with larger water contact angle. The distribution of neurites was uneven between grooves and steps of the microstructures, exhibiting a bell-shaped curve in relation to the water contact angle of the plastic. These indicate that hydrophilic properties of the plastic plate surface, due to the presence of bisphenol-A and tricyclodecanyl units, are crucially involved in the elongation and orientation of neurites.

Animals↗

PubMed2006

Plastic reference electrodes and plastic potentiometric cells with dispersion cast poly(3,4-ethylenedioxythiophene) and poly(vinyl chloride) based membranes.

A simple procedure of preparing low cost, planar and disposable reference electrodes for potentiometric applications is presented. This method is essentially the same as used for obtaining all-plastic ion-selective electrodes and thus promising for simple fabrication of complete cells. Commercially available aqueous dispersion of poly(3,4-ethylenedioxythiophene) doped by poly(4-styrenesulfonate) ions (PEDOT-PSS, Baytron P) is simply cast on a non-conducting plastic support (transparent foil for laser printers). This layer is covered by a non-selective poly(vinyl chloride) based membrane containing solid AgCl and KCl, added to obtain a stable potential. The conducting polymer layer plays a double role, of electrical contact and ion-to-electron transducer, enhancing the potential stability. The reference electrodes obtained exhibit independence of the kind and concentration of electrolyte applied as well as very low sensitivity to interferences: redox reactants and H+ ions; they are also characterized by both potential stability and low polarisability, sufficient for potentiometric applications. Cells of plastic electrodes (indicator and reference ones) are tested using an arrangement with Pb2+ or Ca2+ selective sensors. Potentiometric characteristic of such cells is satisfactory, well comparable with that using a classical electrode arrangement.

Biosensing Techniques↗

PubMed1990

Hippocampal plasticity in normal aging and decreased plasticity in Alzheimer's disease.

Different patterns of age-related dendritic change have been reported in different zones of the human hippocampal region in the normal and Alzheimer's disease (AD) brain. In normal aging there is an increase in average (net) dendritic extent (which we interpret as plasticity) in the parahippocampal gyrus and dentate gyrus. There is net stability of dendritic extent in CA2-3, CA1, and subiculum. In regions that show plasticity in normal aging, dendrites in AD show reduced or aberrant plasticity. In regions that show stability in normal aging, dendrites either are stable or regress in AD, depending upon how severely involved the region is with the pathology of AD.

Aged↗

PubMed1996

Genetic dissection of structural and functional components of synaptic plasticity. III. CREB is necessary for presynaptic functional plasticity.

Increased cAMP (in dunce mutants) leads to an increase in the structure and function of the Drosophila neuromuscular junction. Synaptic Fasciclin II (Fas II) controls this structural plasticity, but does not alter synaptic function. Here, we show that CREB, the cAMP response element-binding protein, acts in parallel with Fas II to cause an increase in synaptic strength. Expression of the CREB repressor (dCREB2-b) in the dunce mutant blocks functional but not structural plasticity. Expression of the CREB activator (dCREB2-a) increases synaptic strength only in FasII mutants that increase bouton number. This CREB-mediated increase in synaptic strength is due to increased presynaptic transmitter release. Expression of dCREB2-a in a FasII mutant background genetically reconstitutes this cAMP-dependent plasticity. Thus, cAMP initiates parallel changes in CREB and Fas II to achieve long-term synaptic enhancement.

Animals↗

PubMedDate not supplied

Migration from plasticized films into foods. 6. Hydrolysis of polymeric plasticizers under simulated gastric and intestinal conditions.

The polymeric plasticizers poly(butylene adipate) and poly(propylene adipate), and a low molecular weight oligomer fraction from each, were exposed in vitro to simulated gastric and intestinal hydrolysis in order to study their likely fate after ingestion of foods contaminated by migration from plastics packaging. Analysis for loss of the parent compounds indicated that partial hydrolysis occurred under simulated gastric conditions, with the low molecular weight oligomers being the most susceptible. Analysis for one of the starting materials, adipic acid, revealed however that the hydrolysis did not result in a significant conversion to free monomer under either simulated gastric or intestinal conditions. This is explained on the basis of partial hydrolysis of the plasticizers to smaller oligomer units but with the more resistant ester linkages resisting complete breakdown to monomer.

Adipates↗

PubMed2006

Is being plastic fantastic? Mechanisms of altered plasticity after developmental traumatic brain injury.

Traumatic brain injury (TBI) is predominantly a clinical problem of young persons, resulting in chronic cognitive and behavioral deficits. Specifically, the physiological response to a diffuse biomechanical injury in a maturing brain can clearly alter normal neuroplasticity. To properly evaluate and investigate developmental TBI requires an understanding of normal principles of cerebral maturation, as well as a consideration of experience-dependent changes. Changes in neuroplasticity may occur through many age-specific processes, and our understanding of these responses at a basic neuroscience level is only beginning. In this article, we will particularly discuss mechanisms of TBI-induced altered developmental plasticity such as altered neurotransmission, distinct molecular responses, cell death, perturbations in neuronal connectivity, experience-dependent 'good plasticity' enhancements and chronic 'bad plasticity' sequelae. From this summary, we can conclude that 'young is not always better' and that the developing brain manifests several crucial vulnerabilities to TBI.

Aging↗

PubMed1981

[Retention of organic solvent vapors in plastic bags. Part 5. A basic study about correction methods of concentration of organic solvent vapors in plastic bags (author's transl)].

The concentration of organic solvents in plastic bags is decreased with time elapsed. It was supposed to permeate in plastic films. Therefore, we assumed that this phenomenon will be approximately regulated by the first order order reaction (C = C0e-kt). We got the permeation coefficient (k) by experiments and used it to correct organic solvent concentrations in the plastic bags. In the present experiment, we used Tedlar bags, toluene and ethyl methyl ketone (MEK) as organic solvents and determined the values by gas chromatography. Initial organic solvents concentration and that after t hr standing being taken as C0 and C. k Values are obtained by the formula C = C0e-kt. Mean values of k about toluene and MEK were found: k = 6.00 X 10(-3) and k = 4.86 X 10(-3). The results by this correction were as follows: Retention of toluene concentration in 24 hr standing bags showed to increase from 81% to 93%, or, in the case of 96 hr standing bags, it was shown to increase from 56% to 100%. Retention of MEK concentration in 24 hr standing bags showed to increase from 86% to 97%, or, in the case of 96 hr standing bags, it was shown to increase from 68% to 109%.

Butanones↗

PubMedDate not supplied

[Synaptic plasticity in the hippocampus during afferent activation reproducing a theta-rhythm pattern (theta plasticity)].

The data are reviewed concerning synaptic plasticity of the hippocampal monosynaptic pathways evoked by afferent activation which simulates activity of neurons in theta-rhythm. Activation with short high-frequency bursts applied with 5 Hz frequency effectively induces long-term potentiation. In contrast, activation with single pulses at 5 Hz causes the depotentiation or even long-term depression of the activated synapses. "In-phase" activation of two afferent pathways in the theta-rhythm induces long-term potentiation, while the "out-of-phase" activation induces long-term depression of a "weak"" pathway. A train of 30-50 pulses at 5 Hz evokes heterosynaptic short-term depression, i.e., a suppression of all synaptic inputs for 1 min. So-called "hidden" plasticity (the enhancement of the effect of delayed activation in producing long-term depression) is also effectively evoked by the theta-like activatory patterns. Therefore, practically all known types of synaptic plasticity can be effectively evoked by the afferent activation which reproduce the pattern of the hippocampal theta-rhythm. These phenomena can underlie the theta-rhythm participation in learning and memory.

Afferent Pathways↗

PubMed1991

Radiation grafting of hydrophilic monomers on to plasticized poly(vinyl chloride) sheets. II. Migration behaviour of the plasticizer from N-vinyl pyrrolidone grafted sheets.

The grafting of N-vinyl pyrrolidone, a hydrophilic monomer, on to flexible poly(vinyl chloride) sheets used in medical applications using ionizing radiation from a 60Co source was studied. The graft yield was found to increase linearly with monomer concentration and also with increasing radiation doses. The migration of the plasticizer di-(2-ethylhexyl)phthalate into a strong organic extractant such as n-hexane was studied at different time intervals for different grafted systems of poly(vinyl chloride) at 30 degrees C. The results indicated a drastic reduction in the leaching of the plasticizer from grafted systems versus ungrafted controls. Incorporation of ethylene dimethacrylate cross-linker during grafting did not seem to affect the graft yield considerably but appeared to further reduce the plasticizer migration. Surface energy calculations of the grafted samples indicate that the surfaces are highly hydrophilic compared to ungrafted poly(vinyl chloride) and the polar and dispersion components tend to vary with increasing cross-linker concentration.

Biocompatible Materials↗

PubMed1979

Attempts to control clothes-borne infection in a burn unit, 3. An open-roofed plastic isolator or plastic aprons to prevent contact transfer of bacteria.

An open-roofed plastic isolator was built in a single patient isolation room in a burn unit. It was designed to prevent contact contamination only, as this had been shown to be the important route of cross-colonization in the unit. To exclude any possible effect on airborne transfer of bacteria, the isolator was first examined by means of an airborne particle tracer of the same size as bacteria-carrying particles. Such experiments indicated that the isolator might prevent some transfer out of but not into the isolator. This was not confirmed in simulated nursing experiments nor in a patient study, where the air counts of bacteria were practically the same inside and outside the isolator wall. Two patients only were nursed in the isolator. Both patients acquired exogenous colonizations from other patients, one with Ps. aeruginosa and the other with S. aureus. Nursing in the isolator was difficult and staff-demanding. In simulated nursing experiments, plastic aprons and gauntlets as the only protective measures against contact contamination gave as much protection to a mock patient as did the isolator. S. aureus were released from nurses' clothes more easily during work with the isolator than in open nursing with aprons and gauntlets. In conclusion, the isolator did not seem to be a realistic alternative to impermeable clothes such as plastic aprons as a means of preventing clothes-borne cross-contamination between burn patients.

Adult↗

PubMed1999

Blood interactions with plasticized poly(vinyl chloride): relevance of plasticizer selection.

An investigation has been made of blood interactions with plasticized poly(vinyl chloride) (PVC) biomaterials in tubular form, taking into account the influence on the blood response of the polymer, antithrombotic agent, blood condition and test procedure. In vitro and ex vivo procedures were used to achieve a comparison between PVC plasticized with di- (2-ethylhexyl)phthalate (DEHP) and with tri-(2-ethylhexyl)trimellitate (TEHTM). The blood response was monitored in terms of the measurement of fibrinogen adsorption capacity, thrombin-antithrombin III complex (TAT) and the complement component C3a. Surface characterization of the polymers was performed by X-ray photoelectron spectroscopy (XPS). The data obtained indicate that in comparison with DEHP-PVC, there is a higher reactivity for TEHTM-PVC, which correlates with the plasticizer distribution at the polymer surface.

Journal Article↗

PubMed2004

The evolution of phenotypic plasticity in spatially structured environments: implications of intraspecific competition, plasticity costs and environmental characteristics.

We model the evolution of reaction norms focusing on three aspects: frequency-dependent selection arising from resource competition, maintenance and production costs of phenotypic plasticity, and three characteristics of environmental heterogeneity (frequency of environments, their intrinsic carrying capacity and the sensitivity to phenotypic maladaptation in these environments). We show that (i) reaction norms evolve so as to trade adaptation for acquiring resources against cost avoidance; (ii) maintenance costs cause reaction norms to better adapt to frequent rather than to infrequent environments, whereas production costs do not; and (iii) evolved reaction norms confer better adaptation to environments with low rather than with high intrinsic carrying capacity. The two previous findings contradict earlier theoretical results and originate from two previously unexplored features that are included in our model. First, production costs of phenotypic plasticity are only incurred when a given phenotype is actually produced. Therefore, they are proportional to the frequency of environments, and these frequencies thus affect the selection pressure to avoid costs just as much as the selection pressure to improve adaptation. This prevents the frequency of environments from affecting the evolving reaction norm. Secondly, our model describes the evolution of plasticity for a phenotype determining an individual's capability to acquire resources, and thus its realized carrying capacity. When individuals are distributed randomly across environments, they cannot avoid experiencing environments with intrinsically low carrying capacity. As selection pressures arising from the need to improve adaptation are stronger under such extreme conditions than under mild ones, better adaptation to environments with low rather than with high intrinsic carrying capacity results.

Adaptation, Physiological↗

PubMed1982

Draft EEC method for the determination of the global migration of plastics constituents into fatty-food simulants: applicability to lacquers, plastics and laminates.

An experimental study was carried out to establish whether the draft EEC method for the determination of the global migration of constituents from plastics packaging materials into fatty food simulants could be applied to all plastics, including lacquers and laminates. Some difficulties were encountered in the use of the EEC method for melamine, for hotmelt-coated packaging materials and for laminates containing one or more layers of materials sensitive to moisture, such as paper, cardboard or regenerated cellulose film.

Dietary Fats↗

PubMed2003

Functional plasticity in the human primary somatosensory cortex following acute lesion of the anterior lateral spinal cord: neurophysiological evidence of short-term cross-modal plasticity.

The primary somatosensory cortex (S1) in adult animals and humans is capable of rapid modification after deafferentation. These plastic changes may account for a loss of tonic control by nociceptive inputs over inhibitory mechanisms within structures of the dorsal column-medial lemniscal system. Most studies, however, have been performed under conditions where deafferentation of C and A delta fibres coexists with large-diameter fibres deafferentation. In this study the effect of the acute lesion of one ascending anterior lateral column on neuronal activity within the dorsal column-medial lemniscal system was assessed by recording somatosensory evoked potentials (SEPs) in seven patients who underwent unilateral percutaneous cervical cordotomy (PCC) as treatment for drug-resistant malignant pain.Spinal, brainstem and cortical SEPs were recorded 2h before and 3h after PCC by stimulating the posterior tibial nerve at both ankles. Amplitudes of cortical potentials obtained by stimulation of the leg contralateral to PCC were significantly increased after PCC. No significant changes in spinal or brainstem potentials were observed. PCC did not affect SEP components obtained by stimulation of the leg ipsilateral to PCC. Our results suggest that nociceptive deafferentation may induce a rapid modulation of cortical neuronal activity along the lemniscal pathway, thus providing the first evidence in humans of short-term cortical plasticity across the spinothalamic and lemniscal systems.

Aged↗

PubMed2002

Complexities in ETS-domain transcription factor function and regulation: lessons from the TCF (ternary complex factor) subfamily. The Colworth Medal Lecture.

The ETS-domain transcription factor family can be divided into a series of subfamilies. Elk-1 represents the founding member of the ternary complex factor (TCF) subfamily. By focusing on the TCF subfamily, we can demonstrate the complexities that exist in the function and regulation of ETS-domain transcription factors. This article focuses on Elk-1 in detail and summarizes the functions of other TCFs. The key themes covered include the domain structure of the TCFs, the mechanisms of complex formation with serum response factor, regulation of TCFs by mitogen-activated protein kinase cascades, and transcriptional regulatory properties of the TCFs. Finally, the emerging role of the TCFs in vivo is discussed. A picture is developing indicating that, while these proteins exhibit significant sequence and functional conservation, key differences in their structure and regulation are being identified which may relate to unique functions of these proteins in vivo.

Amino Acid Sequence↗

PubMedDate not supplied

Fate in humans of the plasticizer, di-2-ethylhexyl phthalate, arising from transfusion of platelets stored in vinyl plastic bags.

Platelet concentrates were shown to contain 18 to 38 mg/dl of a phthalate plasticizer (DEHP) which arose by migration from the vinyl plastic packs in which the platelets were prepared and stored. Transfusion of these platelets into six adult patients with leukemia resulted in peak blood plasma levels of DEHP ranging from 0.34 to 0.83 mg/dl (approximately 0.02 mg/dl plasma per mg DEHP administered per square meter of surface area). The blood levels fell monoexponentially with a mean rate of 2.83 per cent per minute and a half-life of 28.0 minutes. Urine was assayed by a method that would measure unchanged DEHP as well as all phthalic acid-containing metabolites. In two patients, at most 60 and 90 per cent of the infused dose, respectively, was excreted in the urine collected for 24 hours posttransfusion. These estimates, however, could be high due to the simultaneous excretion of DEHP remaining from previous transfusions or arising from uncontrolled environmental exposures.

Blood Platelets↗

PubMed2000

[Aspects of quality assurance in plastic surgery. Subjective well-being and satisfaction of 420 plastic surgery patients with preoperative counseling, surgical intervention and after-care].

The aim of quality assurance should be the improvement of medical treatment. Beside quality assurance measures, which are mainly based on clinical parameters and medical ratings, subjective opinions of patients gain more and more in importance. In the present study results of an inquiry of 420 plastic-surgical patients with preoperative consultation, plastic surgery, and postoperative consultation are shown. The priority weakness on the wards was a high dissatisfaction of the patients with the lounges, the sanitary facilities, equipment and size of the rooms. Information about treatment after discharge was often not quickly and completely passed on, besides, there was in many cases a delay in the recommended physiotherapy after discharge. As a consequence of this study, improvements based on the results shown are required.

Adolescent↗