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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↗
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↗
PubMed1987

Effects of plasticizers and plastic bags on granulocyte function during storage.

The influence of the plasticizers, di-(2-ethylhexyl)phthalate (DEHP) and tri-(2-ethylhexyl)trimellitate (TOTM), on granulocyte function was examined. Polyvinyl chloride (PVC) bags with DEHP (DEHP-PVC) leaked DEHP into plasma, but TOTM did not dissolve in plasma under the same conditions. Glow discharge treatment inhibited the leakage of DEHP from DEHP-PVC bags. Depending on the amount of DEHP added into granulocyte suspension, chemotaxis and bactericidal activity decreased, but cell counts and phagocytosis were not affected. During storage for 24 h at 22 degrees C, granulocyte function decreased greatly in DEHP-PVC, but was well maintained in the bags which did not leak plasticizers, TOTM-PVC and glow-discharged DEHP-PVC.

Benzoates↗
PubMedDate not supplied

Characteristics of A-150 plastic-equivalent gas in A-150 plastic ionization chambers for p(66)Be(49) neutrons.

The evaluation of a gas mixture having an atomic composition similar to that of A-150 tissue-equivalent (TE) plastic has been extended to a high-energy neutron therapy beam. "A-150" gas, air, and methane-based TE gas were each flowed through A-150 plastic-walled ion chambers of different sizes and irradiated with p(66)Be(49) neutrons. A tentative value for W(A-150) of 27.3 +/- 0.5 JC-1 was derived for this beam. The W value of the A-150 gas mixture is compared to those of methane-based TE gas and of air for the p(66)Be(49) neutron beam as well as to corresponding values found in similar experiments using 14.8-MeV monoenergetic neutrons.

Beryllium↗
PubMed1982

New plastic joints for plastic orthoses.

Plastic joints for orthoses have more advantages than metal joints. They are lightweight, noiseless comfortable to use, rust proof, corrosion free, and radiolucent. Two types of plastic joints were developed by the authors, one for the ankle joint and the other for the knee joint, elbow joint or hip joint. Polypropylene was chosen as the joint material because of its appropriate flexibility and toughness.

Ankle Joint↗
PubMed2000

Enhancing effect of a plastic plasticizer, di-2-ethylhexyl phthalate on umu C gene expression in Salmonella typhimurium (TA 1535/pSK 1002).

Di-2-ethylhexyl phthalate (DEHP) is the most extensively used phthalate ester as a plasticizer for plastic products made of polyvinyl chloride (PVC), and previous mutagenic and genotoxic studies have shown positive and negative results of DEHP-induced genotoxicity. To elucidate this discrepancy, we reestimated the genotoxicity of DEHP in more detail using the umu C gene expression system in Salmonella typhimurium (TA 1535/pSK 1002) which reflects SOS response against genotoxin-induced DNA damage. Although DEHP itself did not have a significant effect on umu C gene expression in tester bacteria at 0.5 to 4 mM, higher concentrations of DEHP (2 and 4 mM) caused a weak induction of umu C gene expression in the presence of commercially available S-9 mixture. Rat liver S-9 fraction alone also showed a similar weak inducing activity in the absence of substrates for drug-metabolizing enzymes. When DEHP was preincubated with S-9 fraction of various rat organs and applied to the umu C gene expression assay, S-9 fraction of rat pancreas had the strongest inducing activity, and S-9 fractions of liver and intestine homogenates showed weak but significant activities. However, S-9 fractions of lung and kidney homogenates did not exhibit any significant activities. These S-9 fractions have proportional lipase activities comparable with umu C gene expression activities. Furthermore, when DEHP was treated with highly purified lipase from porcine pancreas, a significant umu C gene expression was observed and this expression was enhanced in the presence of 1 or 5 mM bile acids such as choric acid and deoxychoric acid. These results suggest that DEHP itself has no or very low genotoxicity, but enzymatic and non-enzymatic factors in specific tissues induce DEHP-dependent genotoxic activity.

Animals↗
PubMed1982

[Detection of pores in plastic membranes. 74: Contributions to problems concerning the use of plastic receptacles for liquid pharmaceuticals].

The presence of pores in plastic membranes is detected by the permeability of the latter to electrolytes in the electric field. The plastics are not damaged by the electric field intensities applied. Lithium chloride and crystal violet are employed as electrolytes. In this way, pore-size differentiation becomes faesible. A dialyzing membrane is used for the purpose of comparison. The electrical resistance of the membrane permits conclusions to the amount of its porosity. On using crystal violet, the migration through the pores can be followed visually or colorimetrically.

Colorimetry↗
PubMed1993

[Blood products stored in plastic bags: release of plasticizers from the bag material].

The plasticizer di-(2-ethyl-hexyl)phthalate (DEHP) is slowly leached from the wall of the PVC blood bags into the blood products. It will be partly incorporated into the membranes of the blood cells, and finally will be transfused together with the blood products into the recipient, where DEHP might exert toxic effects. DEHP content was determined by HPLC in different blood products stored in plastic bags manufactured by different firms (Medicor--Hungary, MacoPharma--France, Terumo--Japan, Baxter--USA). In whole blood DEHP is present mainly in the plasma and blood bags of different firms show similar results. 1 unit of whole blood contains 20-50 mg DEHP on day 14 of storage, and 30-55 mg on day 28, while red blood cells resuspended in plasma contained only 2-15 mg on day 14. 15-20 mg DEHP was found in 1 unit of plasma stored for 4 days at +4 degrees C. Only 1-4 mg DEHP was detected in 1 unit of erythrocytes (cca. 200 ml) even on day 14 of storage. The supernatant of platelet concentrates contained the relatively highest amount of DEHP (even 50-65 mg was found in 1 unit of platelet concentrates on day 5 of storage). When platelet concentrates were studied, essential differences were recorded between the bags manufactured by different firms. Platelet reactivity is better maintained in storage bags manufactured without DEHP.

Blood↗
PubMed1995

In vitro and in vivo studies of the effect of the concentration of plasticizer di(2-ethylhexyl) phthalate on the blood compatibility of plasticized poly(vinyl chloride) drain tubes.

Evaluation of the effect of the plasticizer di(2-ethylhexyl) phthalate (DEHP) has been carried out on the properties of blood compatibility of plasticized poly(vinyl chloride) (PVC) through an in vitro registering of the amount of total protein in relation to the amount of DEHP. The influence of DEHP on the properties of blood compatibility has also been evaluated in vivo by tracing through a modified method of Gott (LV Gott and A Feruse, Bull NY Acad Med 1972; 48(2): 482-491) the presence of a thrombus and the patency of tubes made from the material tested, as well as the patency of tubes made from the same material having surfaces coated with paraffin and complexone. For all implanted samples the changes in coagulation time and the amount of haemoglobin after their stay inside a blood vessel in the abdominal cavity of a dog have been registered.

Animals↗
PubMed1993

Interactions between six psychotherapeutic drugs and plastic containers. Influence of plastic material and infusion solutions.

The interactions of chlorpromazine, clomipramine, maprotiline and viloxazine hydrochlorides, and of clorazepate dipotassium salt and diazepam with polyvinyl chloride (PVC) and Stedim 6 infusion bags were studied. Stedim 6, is anew multilayer film whose inner layer is made of polyethylene. The drugs were in 5% dextrose and 0.9% sodium chloride isotonic solutions and the influence of these was also considered. The remaining concentrations of each drug were determined at regular time intervals in a 24-h period, by a spectrofluorometric method for chlorpromazine hydrochloride and by ultraviolet spectrophotometric methods for the other drugs. No binding was observed for viloxazine and maprotiline hydrochlorides whatever the infusion solution and the plastic container. A slight retention in PVC bags, but not in Stedim 6 ones, was noted for clomipramine hydrochloride and clorazepate dipotassium salt. This was more marked in the sodium chloride solution than in the dextrose one. Diazepam and chlorpromazine hydrochloride were bound both in PVC and Stedim 6 bags, but more in the former and more again in the sodium chloride solution than in the dextrose one. The results were explained in terms of the degree of crystallinity of the plastic material and the degree of lipophilicity of the drugs. Practical consequences are discussed.

Chlorpromazine↗
PubMed1994

Cellular plasticity at the climbing fibre-Purkinje cell synapse as a model of plasticity in adulthood and ageing.

In the adult brain there is a high degree of plasticity which is documented here for climbing fibre terminal arborization impinging upon the proximal Purkinje cell dendrites. Such an arborization presents a more distal compartment, including 90% of branches and varicosities, whose integrity depends on the target and a more proximal compartment which survives to target degeneration. The same terminal arborization enlarges its territory of innervation through collateral sprouting when nearby Purkinje cells are deprived of their climbing fibres or when embryonic Purkinje cells are placed on the surface of an intact cerebellum. In the latter case axonal elongation occurs in the absence of degeneration products and of macrophage/microglia or astrocyte activation. In addition, the embryonic Purkinje cells are able to invade the intact host molecular layer where they develop dendritic arbours which become also innervated by climbing fibre collaterals.

Aging↗