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PubMedDate not supplied

Toxicological quandary of the use of bis (2-diethylhexyl) phthalate (DEHP) as a plasticizer for blood bags.

Plastic bags are very useful containers for the storage of blood and blood products since they are relatively transparent, hard to break, can be sealed aseptically with a radio-frequency current, and can be centrifuged for the isolation of blood components. In order to make the plastic more flexible, various agents are added, of which the most common is di- (2-ethylhexyl) phthalate (DEHP). This plasticizer has been found to leach from the plastic into the blood components during the storage period. Some animal studies have shown that this chemical can produce cancers and various tissue abnormalities. The human data from multi-transfused patients do not clearly indicate any specific damage: however, because of the animal studies, work has been carried out to find a non-leachable plasticizer. Several have been found: unfortunately, when survival studies are done, the red cell life span of the stored blood is decreased. Current work seems to indicate that DEHP has a membrane stabilizing function that prolongs the storage time of the red cell. Therefore, there currently is a trade off between plasticizer presence and red cell life span that must be considered when designing new blood storage bags.

Animals↗
PubMed1995

[Plastic surgery in stenoses and intraoperative injuries of the urinary tract].

The author showed the practical significance and expediency of performing reconstructive-plastic operations (57 patients) in surgical correction of severe pathology of the urinary tract. The indications for plastic operations were stenoses of various etiology, intraoperative traumas of the urinary tract, contracted bladder and the consequent ureterohydronephrosis, renal insufficiency. The choice of the tactics and method of surgical treatment should be strictly substantiated and based on the individual features of the urinary system pathology, the character of the intraoperative trauma of the ureter and bladder and its possible after-effect on the kidney. Taking into account the variability of the pathology and the length of the cicatricial narrowing of the pelvic-ureteral segment and ureter, and the degree of kidney constriction, variations of plastic operations differing in the complexity of the techniques were applied. These were small in volume flap plastics of the pelvic-ureteral segment and ureter (Calp-de-Virda, Baori, Demela) and intestinal plastics of the bladder in one of the modifications. The possibility of plastic operations in restoration of physiological urination and social rehabilitation of patients with urinary fistulas was determined. According to early and late-term postoperative follow-up, the results of the operation were favorable in 91.3% of cases. Postoperative mortality in different periods (7 days to 3 years) was 8.7%.

Adolescent↗
PubMed1994

NHS plastic surgery--is it what you think it is?

Many people who do not come into contact with plastic surgery in their hospitals may be under the popular misconception that plastic surgeons spend their time fixing noses and altering the size of breasts. Well, yes they do, but only occasionally in the NHS: they are more likely to do this type of surgery in their private practice. I would like to try to alter perceptions of plastic surgery, partly because I am Sister in Charge of a busy Regional Plastic, Burns and Reconstructive Theatre Unit and, partly, because I firmly believe that the psychology of the small number of patients who do have rhinoplasties and breast or cosmetic surgery in the NHS needs to be accepted and understood by busy health care workers. I hope to show that cosmetic or aesthetic surgery is a very small part of what happens in plastic surgery today. To do this I have used Plastic Surgery in the British Isles, a plan for the rest of the 1990s and my own hospital consultant episodes for the year 1992/93 as my background information.

Humans↗
PubMed1996

[Role of plastic surgery in the treatment of breast cancer].

The surgical treatment of breast cancer has changed dramatically since the last twenty years. Radical and super-radical mastectomy are almost no longer indicated except in certain cases of local recurrences. Breast saving procedures are the best indication for small tumors. And the psychological impact of the different treatments including radiotherapy and chemotherapy is considered as an important issue. Therefore, plastic surgeons are more and more frequently called upon to restore the breast appearance using some technique of breast reconstruction or to improve the bad results of a conservative treatment. Moreover, a good knowledge of the plastic surgery techniques allows a better exploration of the breast and large resections in case of fibrocystic diseases with extensive foci of microcalcifications. Such extensive explorations of the breast are more frequently indicated with the development of screening campaigns. When the mastectomy remains the best indication, it is mandatory to propose an immediate breast reconstruction. Insertion of a silicone implant is discussed in several countries, especially in France, although more and more studies are showing the inocuity of such material. A long experience at the Gustave-Roussy Institute of such material used for breast reconstruction showed us the inocuity of long term silicone exposure in patients treated for breast cancer. The conservative surgery should remove the tumor with a free margin of 1 to 2 or even 3 cm and the defect left is sometimes large enough to justify some local glandular mammoplasty in order to prevent from final mammary distorsion or local visible defect. Partial reconstructions could sometimes require more sophisticated techniques including musculo-cutaneous flaps or prosthesis implantation. Finally the integration of the plastic surgery in the surgical protocols of breast cancer treatment, requires a close collaboration between the plastic and the cancer teams. In certain cases, a special surgical training provides the surgeon with a double competence in oncology and in plastic surgery. With such breast surgeon competent both in oncology and plastic surgery, a patient can ask for an aesthetic operation without missing a complete cancer screening as well as she can be treated for a cancer with the best chance to obtain the best cosmetic result.

Breast Neoplasms↗
PubMed1997

Short-term functional plasticity of cortical and thalamic sensory representations and its implication for information processing.

We studied phenomena, constraints, rules, and implications of cortical plastic reorganization produced by input coactivation patterns in primary somatosensory cortex of adult rats. Intracortical microstimulation (ICMS) and an associative pairing of tactile stimulation (PPTS) induced plastic changes within minutes to hours that were fully reversible. Reorganization of receptive fields and topographic maps was studied with electrophysiologic recordings, mapping techniques, and optical imaging of intrinsic signals. Utilizing the specific advantages of local application of ICMS, we investigated lamina-specific properties of cortical representational plasticity, revealing a prominent role of the input layer IV during plastic reorganization. To study subcortical plasticity, we compared ICMS and intrathalamic microstimulation (ITMS), revealing robust thalamic reorganizations that were, however, much smaller than cortical changes. Using PPTS, we found significant reorganizational processes at the cortical level, including receptive fields, overlap, and cortical representational maps. The protocol was similarly effective at the perceptual level by enhancing the spatial discrimination performance in humans, suggesting that these particular fast plastic processes have perceptual consequences. The implications were discussed with respect to parallel changes of information processing strategies. We addressed the question of the possible role of RF size and size of cortical area, inhibitory mechanisms, and Hebbian and non-Hebbian learning rules. The short time scale of the effects and the aspect of reversibility support the hypothesis of fast modulations of synaptic efficiency without necessarily involving anatomic changes. Such systems of predominantly dynamically maintained cortical and adaptive processing networks may represent the neural basis for life-long adaptational sensory and perceptual capacities and for compensational reorganizations following injuries.

Animals↗
PubMed1997

[Neuronal growth-associated proteins in neural plasticity and brain aging].

This review summarizes current issues on neuronal structural plasticity and its molecular marker genes in the aged brain. Neuronal growth-associated proteins (nGAPs) are introduced as potential markers of neuronal structural plasticity in the brain. The expression of genes encoding nGAPs such as GAP-43, SCG10 and stathmin is increased following striatal and hippocampal neuronal deafferentation lesions in the adult rat brain. In aged brains, the magnitude of neuronal plasticity is reduced and nGAP gene induction is limited at least in part, while the kinetics of the response remains unchanged in comparison to young brains. These results suggest that nGAPs serve as molecular markers of neuronal structural plasticity in the aging brain and that neuronal plasticity decreases, at least in certain neuronal circuits, during aging. The expression of genes encoding SCG10, stathmin and GAP-43 is also altered in age-related neurodegenerative conditions such as Alzheimer's disease in humans. Thus, studies of nGAPs are important for the elucidation of the mechanisms of the reduction of neuronal structural plasticity in aged brains.

Aging↗
PubMed1998

Comparison of plasticity in vivo and in vitro in the developing visual cortex of normal and protein kinase A RIbeta-deficient mice.

Developing sensory systems are sculpted by an activity-dependent strengthening and weakening of connections. Long-term potentiation (LTP) and depression (LTD) in vitro have been proposed to model this experience-dependent circuit refinement. We directly compared LTP and LTD induction in vitro with plasticity in vivo in the developing visual cortex of a mouse mutant of protein kinase A (PKA), a key enzyme implicated in the plasticity of a diverse array of systems. In mice lacking the RIbeta regulatory subunit of PKA, we observed three abnormalities of synaptic plasticity in layer II/III of visual cortex in vitro. These included an absence of (1) extracellularly recorded LTP, (2) depotentiation or LTD, and (3) paired-pulse facilitation. Potentiation was induced, however, by pairing low-frequency stimulation with direct depolarization of individual mutant pyramidal cells. Together these findings suggest that the LTP defect in slices lacking PKA RIbeta lies in the transmission of sufficient net excitation through the cortical circuit. Nonetheless, functional development and plasticity of visual cortical responses in vivo after monocular deprivation did not differ from normal. Moreover, the loss of all responsiveness to stimulation of the originally deprived eye in most cortical cells could be restored by reverse suture of eyelids during the critical period in both wild-type and mutant mice. Such an activity-dependent increase in response would seem to require a mechanism like potentiation in vivo. Thus, the RIbeta isoform of PKA is not essential for ocular dominance plasticity, which can proceed despite defects in several common in vitro models of neural plasticity.

Action Potentials↗
PubMedDate not supplied

Palliative treatment of malignant esophageal stenosis: experience with plastic versus metal stents.

BACKGROUND/AIMS: We report on the palliative treatment of 44 patients with malignant dysphagia by placement of plastic (Celestin tubes, n = 24) vs metal stents (Wall stents, Nitinol stents, Gianturco stents, n = 20). METHODOLOGY: Prior to stent insertion, esophageal stenosis was dilated stepwise to 16 mm (plastic tube) and to 10 mm (metal stent). RESULTS: Stent insertion was technically successful in all cases and led to a reduction of dysphagia. Risk of perforation was comparable in both groups (n = 1 in each group). Most of the plastic stents were placed when the tumor was localized in the proximal part of the esophagus close to the upper esophageal sphincter, when esophageal-bronchial fistula was present and in the risk of fistula development after radiation. During follow-up, tumor ingrowth (TI) and stent migration (SM) were the major complications. Whereas tumor ingrowth predominantly occurred in metal stents (TI after 6 weeks, 45% vs. SM, 10%) that required repeated argon beamer therapy, tube migration and bolus impaction (BI) often occurred in patients with plastic stents (TI, 0% vs. SM, 16%; BI, 4%). CONCLUSIONS: The findings of the study suggest that the decision whether plastic tubes or metal stents used should be taken individually considering tumor localization, axis deviation and the presence of esophago-respiratory fistulas. When stepwise dilation of malignant stenoses is performed carefully, perforation risk appears not to be different between placement of plastic prostheses and metal stents.

Aged↗
PubMed1991

Prediction of solute sorption by polyvinyl chloride plastic infusion bags.

The time course of the sorption of drugs by polyvinylchloride infusion bags has been approximated using a diffusion model in which the plastic is assumed to act as an infinite sink. This model appears to be suitable for estimation of storage times relevant to clinical usage and enables the magnitude of the uptake in a specific time to be described by a single parameter, referred to as the sorption number. This parameter is defined by the plastic-infusion solution partition coefficient, the diffusion coefficient in the plastic, the fraction un-ionized in solution, the volume of the infusion solution, and the surface area of the plastic. An approximation of the model allows a ready estimation of the sorption number from the fraction remaining in solution at a given time. The sorption number can be extrapolated to allow prediction of the effects of time, plastic surface area, solution volume, and solution pH on fractional solute loss. A reasonable correlation was established between the logarithm of this parameter and the logarithm of the octanol-water partition coefficients of various solutes. The model allows the fraction of a solute remaining in a plastic infusion bag at a given storage time to be estimated from the octanol-water partition coefficient of the solute and other readily available data.

Adsorption↗
PubMed1993

Evaluation of various solvent systems for modeling solute sorption with plasticized polyvinyl chloride materials.

The partitioning behavior of 16 chemically diverse model solutes was determined for four model solvents (octanol, hexane, heptane, and chloroform) and two components of plasticized polyvinyl chloride [PVC; PVC resin and dioctyl phthalate (DOP) plasticizer]. Interactions between these model solutes and four plasticized PVC polymers, differing in their PVC-to-DOP weight ratio, were studied. The data were used to evaluate the utility of the solvents and components to act as PVC interaction models (correlating the interaction constant of the plastic with the solvent-water partition coefficients of the solute). The ability of any single solvent to model the material-solute interaction was limited because of the multiple mechanisms by which the PVC and the solute can interact. Several bimodal solvent systems, including octanol and hexane, DOP and PVC resin, and octanol and heptane, mimic the behavior of polymers studied with a higher degree of accuracy. The success of these pairings is directly related to their ability to target different potential material-solute interaction mechanisms. The interaction properties of the test plastics are strongly impacted by the amount of plasticizer in the material. The interaction properties of the materials studied could be effectively represented as a mass-related average of the interaction properties of the major components of the material.

Absorption↗
PubMed2004

Stem cell plasticity, beyond alchemy.

Cell plasticity is a central issue in stem cell biology. Differentiated somatic nuclei have the flexibility to dedifferentiate when transferred into oocytes or when fused to pluripotent embryonic stem cells. Recent publications also claim that somatic stem cells can convert into developmentally unrelated cell types both in vivo and ex vivo without such drastic cell manipulations. Some of these claims are still controversial, making it difficult for us to determine the reality of somatic stem cell plasticity. Indeed, we have heard enough about the "potentials" of cell plasticity; how much do we know about mechanisms? A fundamental issue in current stem cell biology is to understand the mechanisms underlying cell plasticity. In this short review, we overview three research fields related to cell plasticity: nuclear transfer, transdifferentiation, and cell fusion, with an emphasis on studies of molecular mechanisms underlying cell plasticity.

Adult↗
PubMed2005

Plasticity of grasshopper vitellogenin production in response to diet is primarily a result of changes in fat body mass.

Life history plasticity is the developmental production of different phenotypes by similar genotypes in response to different environments. Plasticity is common in early post-embryonic or adult development. Later in the developmental stage, the transition from developmentally plastic to canalized (i.e., inflexible) phases is often associated with the attainment of a threshold level of storage. Thresholds are often described simply as total body mass or cumulative consumption of food. The physiological characteristics of thresholds, such as the contributions of the growth of particular organs or the production rate of proteins, are largely unstudied. To address the physiology underlying a threshold-induced developmental transition, total vitellogenin production in response to diet quality in the lubber grasshopper was studied. For individuals that differed in age or dietary protein, somatic mass, ovarian mass, fat body mass, mass-specific vitellogenin production, vitellogenin titer, and storage protein titer were measured. Age and diet strongly affected these parameters, with ovarian mass and fat body mass contributing most to the differences. During mid vitellogenesis, females were highly plastic in response to changing food quality. Only during late vitellogenesis were females unresponsive to changes in food quality. Fat body mass was a more important component of plasticity than was mass-specific vitellogenin production. Because these two variables together make up total vitellogenin production, the greater contribution of fat body mass than mass-specific vitellogenin production suggests that growth factors may be more important than tissue stimulators in producing developmental changes in total vitellogenin production. To our knowledge, this is the first study to demonstrate that mass gain of an organ is more important to developmental plasticity than is the output of that same organ.

Age Factors↗
PubMed2006

Population differences in host use by a seed-beetle: local adaptation, phenotypic plasticity and maternal effects.

For insects that develop inside discrete hosts, both host size and host quality constrain offspring growth, influencing the evolution of body size and life history traits. Using a two-generation common garden experiment, we quantified the contribution of maternal and rearing hosts to differences in growth and life history traits between populations of the seed-feeding beetle Stator limbatus that use a large-seeded host, Acacia greggii, and a small-seeded host, Pseudosamanea guachapele. Populations differed genetically for all traits when beetles were raised in a common garden. Contrary to expectations from the local adaptation hypothesis, beetles from all populations were larger, developed faster and had higher survivorship when reared on seeds of A. greggii (the larger host), irrespective of their native host. We observed two host plant-mediated maternal effects: offspring matured sooner, regardless of their rearing host, when their mothers were reared on P. guachapele (this was not caused by an effect of rearing host on egg size), and females laid larger eggs on P. guachapele. This is the first study to document plasticity by S. limbatus in response to P. guachapele, suggesting that plasticity is an ancestral trait in S. limbatus that likely plays an important role in diet expansion. Although differences between populations in growth and life history traits are likely adaptations to their host plants, host-associated maternal effects, partly mediated by maternal egg size plasticity, influence growth and life history traits and likely play an important role in the evolution of the breadth of S. limbatus' diet. More generally, phenotypic plasticity mediates the fitness consequences of using novel hosts, likely facilitating colonization of new hosts, but also buffering herbivores from selection post-colonization. Plasticity in response to novel versus normal hosts varied among our study populations such that disentangling the historical role of plasticity in mediating diet evolution requires the consideration of evolutionary history.

Acacia↗
PubMed1989

Water sorption of plasticized denture acrylic lining materials.

The objective was to characterize water sorption of plasticized denture acrylic lining materials, with determination both of uptake and diffusion coefficient (D). Feasibility was investigated first for simple binary mixtures of poly(methyl methacrylate), PMMA, and various phthalate plasticizers prepared by radiation polymerization of methyl methacrylate/plasticizer solutions. These were shown to be tractable when samples were saturated with water and then characterized in desorption measurements. Plasticizers were found to decrease the uptake of water. This decrease was attributed to the hydrophobic nature of the plasticizers and also to their ability to fill microvoids in PMMA which, in their absence, would be available to water. Values of D increased monotonically with increasing volume fractions of plasticizer. It appeared that values of D increased more rapidly in cases where large proportions of plasticizer resulted in samples which were above their glass transition temperature, Tg, at the temperature of testing water sorption. Desorption measurements were extended satisfactorily to a model system made from poly(ethyl methacrylate) powder, methyl methacrylate, and dibutyl phthalate, which was polymerized with a conventional redox initiator. Water desorption results were compared with various proprietary materials which were also characterized with respect to Tg and, cursorily, to composition.

Acrylic Resins↗
PubMed1991

Plastic pellets, tar, and megalitter on Beirut beaches, 1977-1988.

In the spring of 1988, five beaches along the coast of Beirut were surveyed for the presence of plastic pellets, tar, and megalitter--a follow-up to the studies conducted on the coast of Lebanon in 1977 for plastic pellet and tar occurrence, and in 1978 for containers and other megalitter on Beirut beaches. Plastic pellets were more abundant than they were in 1977 on three beaches and less so on two. Tar, however, seemed to occur much more abundantly on all five beaches. Megalitter, chiefly plastic but also paper, metal, and glass, had increased greatly compared with that seen 10 years ago. As in 1977, the unrestricted waste disposal practices of the plastic manufacturers, plus the possible loss of cargo from ships loading and unloading raw materials, are the most likely sources of plastic pellets. The abundance of tar is not surprising, considering that the Mediterranean Sea is tar-polluted and that two oil terminals occur on Lebanon's coast. Further, local gas stations frequently dump oil and grease onto the beaches, and numerous fires have occurred at coastal refineries over the past 10-15 years. All of these factors are likely to contribute to the presence of tar on the beaches. The main source of the vast quantities of megalitter on the beaches is undoubtedly the Lebanese people themselves, due to numerous population shifts and the lack of order and regulatory enforcement as a result of the civil chaos in the country. In addition, the ships docking or waiting for days, and sometimes weeks, to get into the Lebanese ports probably affect the abundance of megalitter (and tar) on the beaches.

Journal Article↗
PubMed2005

Evolution of phenotypic plasticity: where are we going now?

The study of phenotypic plasticity has progressed significantly over the past few decades. We have moved from variation for plasticity being considered as a nuisance in evolutionary studies to it being the primary target of investigations that use an array of methods, including quantitative and molecular genetics, as well as of several approaches that model the evolution of plastic responses. Here, I consider some of the major aspects of research on phenotypic plasticity, assessing where progress has been made and where additional effort is required. I suggest that some areas of research, such the study of the quantitative genetic underpinning of plasticity, have been either settled in broad outline or superseded by new approaches and questions. Other issues, such as the costs of plasticity are currently at the forefront of research in this field, and are likely to be areas of major future development.

Journal Article↗
PubMed1999

Agonist-induced adherence of equine neutrophils to fibronectin- and serum-coated plastic is CD18 dependent.

Adherence to vascular endothelium and extracellular matrix proteins is a pre-requisite for neutrophil accumulation at sites of inflammation. In this study, equine neutrophil adherence to fibronectin and autologous serum-coated plastic in response to PAF, hrIL-8, hrC5a and PMA has been measured. In addition, the mechanisms involved have been investigated using monoclonal antibodies (MoAbs) against the beta2 integrin CD18. PAF and hrC5a caused similar, concentration dependent, increases in adherence to fibronectin- and serum-coated plastic (maximum responses 19 +/- 4% and 19 +/- 3% for PAF and 15 +/- 4% and 16 +/- 2% for hrC5a on fibronectin- and serum-coated plastic, respectively). Adherence in response to PMA, although not reaching a maximum over the time course studied, was of a similar magnitude on the two surfaces (41 +/- 1% and 38 +/- 2% with 10(-7) M PMA on fibronectin- and serum-coated plastic, respectively). In contrast, the maximum adherence caused by hrIL-8 was significantly lower on fibronectin- than on serum-coated plastic (9 +/- 3% vs. 17 +/- 2%; 10(8) x M hrIL-8). Pre-incubation with MoAbs against CD18 (H20A and 6.5E) caused concentration related inhibition of stimulus-induced adherence to both fibronectin- and serum-coated plastic. Equine neutrophil adherence in response to PAF, hrIL-8, hrC5a and PMA therefore appears to be mediated by a CD18 dependent mechanism.

Animals↗
PubMed2000

Plastic microfluidic devices modified with polyelectrolyte multilayers

Control of the polymer surface chemistry is a crucial aspect of development of plastic microfluidic devices. When commercially available plastic substrates are used to fabricate microchannels, differences in the EOF mobility from plastic to plastic can be very high. Therefore, we have used polyelectrolyte multilayers (PEMs) to alter the surface of microchannels fabricated in plastics. Optimal modification of the microchannel surfaces was obtained by coating the channels with alternating layers of poly(allylamine hydrochloride) and poly(styrene sulfonate). Polystyrene (PS) and poly(ethylene terephthalate) glycol (PETG) were chosen as substrate materials because of the significant differences in the polymer chemistries and in the EOF of channels fabricated in these two plastic materials. The efficacy of the surface modification has been evaluated using XPS and by measuring the EOF mobility. When microchannels prepared in both PS and PETG are modified with PEMs, they demonstrate very similar electroosmotic mobilities. The PEMs are easily fabricated and provide a means for controlling the flow direction and the electroosmotic mobility in the channels. The PEM-coated microchannels have excellent wettability, allowing facile filling of the channels. In addition, the PEMs produce reproducible results and are robust enough to withstand long-term storage.

Journal Article↗