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PubMed1997

Reactions of epoxide monomers in food simulants used to test plastics for migration.

The reactions of four epoxides used as monomers for food contact plastics were studied in the food simulants distilled water, 15% aqueous ethanol, 3% aqueous acetic acid and olive oil. Loss of the parent substance and formation of products was monitored to establish the transformation products to be expected in each simulant following migration testing of plastics. Each epoxide was stable in olive oil but suffered extensive loss in the three aqueous simulants. Reaction half-lives were from < 1 to 10 h in aqueous acetic acid, 25-63 h in distilled water, and 33-87 h in aqueous ethanol simulant. Hydrolysis to the diol was the main reaction pathway. Epoxide ring opening in aqueous ethanol simulant gave the diol and also the diol monoethyl ether. It is concluded that, for aqueous simulants and by implication for most foods, testing plastics against specific migration limits for epoxides is not likely to give reliable results due to their reactivity. The present EC mode of control for these reactive monomers, via compositional limits in food contact plastics, is more practical since the hydrolysis products are less toxic than the parent epoxide.

Benzhydryl Compounds↗
PubMed2001

Effects of oil plastic extract on mice.

In the plastics industry, various chemical additives are used to improve certain properties of plastics. Some of these chemicals, that might be toxic, have been proved to leach from the plastic containers and mix with their contents such as food oils, beverages, drugs, etc. Locally manufactured polyvinyl chloride (PVC) jerrycans were bought from the market and cut into small chips of 0.5 cm in the larger dimension. Four grams of chips were extracted with 20 ml cottonseed oil in the autoclave for 1 h at 121 degrees C. The extract was prepared daily and given orally to adult MFI mice in a dose of 10 ml kg(-1) body weight. Pure cottonseed oil was prepared under the same conditions and given in a dose of 10 ml kg(-1) body weight to the control group. Treatment of both groups continued for 1 month. Each group comprised 60 animals, regardless of sex. Effects of the oil plastic extract were observed on blood elements, serum transaminases (aspartate aminotransferase, AST, and alanine aminotransferase, ALT), organ-to-body weight of the liver, kidneys and brain, and the nervous system (effects on the neuromuscular junction and analgesia, using the Rota-Rod(R) treadmill 'RRT', and the hot plate, respectively). All the results were subjected to Student's t-test. The results showed that the extract induced significant effects: an increase in the activities of AST (p< 0.001) and ALT (p< 0.02), an increase in the mean corpuscular haemoglobin concentration (MCHC) (p< 0.01), and the monocyte count (p< 0.01). It decreased the white blood cell count (WBC) (p< 0.01), the mean corpuscular volume (MCV) (p< 0.05), and the lymphocyte count (p< 0.05). It also reduced the weight of the liver (P< 0.01), kidneys (P< 0.05), and the endurance time on the RRT (p< 0.001).

Animals↗
PubMed2000

Phenotypic Integration and the Plasticity of Integration in an Amphicarpic Annual.

In annual plants, including amphicarpic annuals, variation in light availability can evoke phenotypic plasticity in multiple traits. We examined plasticity to light availability of vegetative and reproductive performance traits in Amphicarpaea bracteata (Fabaceae) by developing and evaluating three path-analysis models using data from a greenhouse study. To assess whether light availability altered the phenotypic integration of these performance traits, we examined the models' fit to data collected within a high- or a low-light treatment. We also examined whether a single model or alternate models were required to fit data from the two contrasting light treatments. Using our path-analysis approach, we also made comparisons among three population types: shade- and sun-native populations of the widespread variety A. bracteata var. bracteata and sun-native populations of the variety A. bracteata var. comosa. Although each type of population was somewhat distinctive in patterns of integration and in the plasticity of integration, patterns did not correspond to contrasting ecological affinity, i.e., shade- and sun-native population types or to genetic relatedness of the two varieties. Counter to the prediction that selection regimes involving variation in one or more environmental factor favor intermediate levels of integration, phenotypic integration in A. bracteata was very flexible, with plasticity occurring in a trait-by-trait manner. In particular, there was an inverse relationship between aerial and subterranean reproductive modes in low but not high light. Previous studies of amphicarpic annuals have not observed this type of environment-specific life history trade-off.

Journal Article↗
PubMed2005

Differences in plastic responses to defoliation due to variation in the timing of treatments for two species of Sesbania (Fabaceae).

BACKGROUND AND AIMS: Plastic responses to stress in components of reproduction can have important effects on plant fitness and can vary both within and between species. Responses may also depend on when in the life cycle stress occurs. Here, it is predicted that the timing of initiation of a stress, defoliation, would affect the pattern of plastic responses. These differences should occur because some components of reproduction, such as flower number, are determined earlier in a plant's life than others, such as individual seed mass. METHODS: To test this prediction, 50 % artificial defoliation treatments were initiated at four different times for Sesbania macrocarpa and S. vesicaria. Responses were measured in plant size, number of flowers, number of flowers/plant size, fruit set, number of seeds per fruit, individual seed mass and total seed mass per plant. KEY RESULTS: For S. vesicaria, changes in the timing of stress changed the severity, but not the pattern of response. For S. macrocarpa, plastic responses to defoliation varied strikingly between early and late treatments. Late treatments resulted in over-compensation in this species. Sesbania macrocarpa was generally more plastic than S. vesicaria and the species showed opposite responses for most components of reproduction. CONCLUSIONS: While there were effects of timing of defoliation and differences between species, the nature of these effects did not precisely fit our predictions. Our results suggest that differences in the length and flexibility of the life cycles of the two species allowed for unexpected variation in responses. For example, because flower production continued after the last treatment in S. vesicaria, responses were not constrained to reductions in individual seed mass.

Conservation of Natural Resources↗
PubMed2004

Physiological, morphological and allocational plasticity in understory deciduous trees: importance of plant size and light availability.

In a 4-year study, we investigated changes in leaf physiology, crown morphology and whole-tree biomass allocation in seedlings and saplings of shade-tolerant sugar maple (Acer saccharum Marsh.) and intermediate shade-tolerant yellow birch (Betula alleghaniensis Britt.) growing in natural understory light (0.5 to 35% of full sunlight) or in understory light reduced by 50% with shade nets to simulate the effect of gap closure. Leaf physiological parameters were mainly influenced by the light gradient, whereas crown morphological and whole-tree allocational parameters were mainly influenced by tree size. No single physiological, morphological or allocational trait was identified that could explain the difference in shade tolerance between the species. Yellow birch had higher growth rates, biomass allocation to branches and leaf physiological plasticity and lower crown morphological plasticity in unmodified understory light than sugar maple. Sugar maple did not display significant physiological plasticity, but showed variation with tree size in both crown morphology and whole-tree biomass allocation. When sugar maple was small, a greater proportion of whole-tree biomass was allocated to roots. However, physiological differences between the species decreased with decreasing light and most morphological and allocational differences tended to disappear with increasing tree size, suggesting that many species differences in shade-tolerance are expressed mainly during the seedling stage. Understory trees of both species survived for 4 years under shade nets, possibly because of higher plasticity when small and the use of stored reserves when taller.

Acer↗
PubMed1990

Quantitative and qualitative characteristics of the stages and transitions in the cycle of the rat seminiferous epithelium: light microscopic observations of perfusion-fixed and plastic-embedded testes.

The stages of the cycle in the rat seminiferous epithelium are illustrated for testes fixed by vascular perfusion and embedded in plastic resins. Improved cellular resolution in plastic sections permitted a clearer demarcation of the stages than in paraffin. Quantitative data are presented to support the recognition of stages, particularly those in transition. Stages IV, V, VII, XI, and XII had the highest frequencies of transitional characteristics. Stage IV was redefined to be more consistent with the occurrence of a high percentage of mitotic figures and to clarify transitions in this stage. Although the resolution of cellular detail was greatly improved with the use of plastics, the thinner sections contained fewer identifying features together within a single tubule cross section and sometimes major characteristics were absent. Therefore, additional characteristics were used for stage classification, such as nuclear diameter and the presence or absence of mitotic figures. A binary decision key is provided to improve consistency among laboratories in the identification of the stages in plastic-embedded testes.

Acrosome↗
PubMed1998

Expandable stents compared to conventional plastic endoprostheses in malignant oesophageal obstruction, especially in cardiac cancer and fistulas: the experience of the Netherlands Cancer Institute.

BACKGROUND: Advanced oesophageal carcinoma usually causes debilitating dysphagia. An endoprosthesis can offer adequate palliation. The self-expandable metal stents provide several advantages over the plastic endoprostheses: less traumatic introduction and stronger attachment to the oesophageal wall. OBJECTIVE: To evaluate whether the self-expandable stents are more effective, especially in the technically challenging group of patients with a cardiac carcinoma or a fistula. SETTING: A single-institution study (cancer hospital). METHODS: A retrospective study of 132 consecutive patients (92 men and 40 women; median age 67 years) in whom a stent was inserted between 1991 and 1996. A plastic stent was applied in 72 patients, and from 1994 onwards an expandable stent in 60 subsequent patients. RESULTS: Overall technical success rate was high for both types of stents: 93 vs 88%. Clear improvement of dysphagia occurred more often with the expandable stents (80%) compared to the plastic stents (62%). Unfortunately, loss of appetite remained a problem in 30% of the patients. In the more troublesome subgroup of cardiac carcinoma (n = 55) and (imminent) fistula (n = 42) stenting was equally effective. Early complications were significantly less often encountered for the self-expandables: 3 vs 45%, the same was true for insertion related mortality: 0 vs 10%. Also the need for reintervention was less frequent: 12 vs 23%. This was especially on the account of the plastic stent in fistulas. CONCLUSIONS: Technical success rate was excellent for all types of stents, but in particular for the self-expandable stents which were also associated with fewer side effects. The subgroups of fistula and cardia carcinoma did equally well, probably related to adequate choice of stent.

Adult↗
PubMed1999

Results of percutaneous plastic stents for malignant distal biliary obstruction following failed endoscopic stent insertion and comparison with current literature on expandable metallic stents.

BACKGROUND: Endoscopic stenting is an effective method of relieving biliary obstruction in patients with unresectable malignancy. If this fails, optimal management is controversial. Percutaneous insertion of plastic or mesh metal stents has been advocated. AIM: To review the outcome of percutaneous plastic stents and compare this with contemporary data from the literature on mesh metal stenting. PATIENTS AND METHODS: Over a period of six years, 400 patients had attempted endoscopic stenting for distal malignant biliary obstruction which failed in 54 (13.5%). These 54 patients were treated with percutaneously placed plastic stents. RESULTS: Percutaneous stenting was technically successful in 48 patients (89%). Early complications occurred in 13 patients (24%), the commonest being acute cholangitis in seven (12%). There was no procedure-related mortality but a 30-day mortality of 11 % (n = 6). Ten patients (18%) required re-admission after 30 days for stent block (mean period 4 months). Forty-seven patients (87%) were followed up until death. The median survival for the patients undergoing palliative stenting was 3 months (5 days to 17 months). CONCLUSIONS: These results suggest that percutaneous plastic stents can be used safely and effectively in patients who have failed endoscopic stenting.

Adult↗
PubMed2005

Long-term treatment of plastic bronchitis with aerosolized tissue plasminogen activator in a Fontan patient.

OBJECTIVE: To report the successful treatment of plastic bronchitis with aerosolized tissue plasminogen activator. DESIGN: Case report. PATIENTS: A 4-yr-old boy with congenital heart disease, who developed plastic bronchitis 33 months after a Fontan operation INTERVENTIONS: Long-term treatment with aerosolized tissue plasminogen activator. MEASUREMENTS AND MAIN RESULTS: We describe the case of a boy who developed recurrent episodes of life-threatening airway obstruction secondary to plastic bronchitis. Following the failure of multiple therapeutic interventions, his condition improved significantly with aerosolized tissue plasminogen activator. Several attempts to wean him off this treatment resulted in clinical deterioration. He has remained on long-term aerosolized tissue plasminogen activator. CONCLUSION: Treatment of plastic bronchitis with aerosolized tissue plasminogen activator may benefit patients in whom other therapies have failed.

Administration, Inhalation↗
PubMed2003

The Danish Registry for Plastic Surgery of the Breast: establishment of a nationwide registry for prospective follow-up, quality assessment, and investigation of breast surgery.

Although numerous epidemiologic studies have examined the long-term safety of silicone breast implants during the past decade, there is a relative lack of surveillance data on short-term health effects and complications following cosmetic surgery of the breast. The Danish Registry for Plastic Surgery of the Breast, established in May of 1999, provides plastic surgeons with a nationwide system for the collection of preoperative, perioperative, and postoperative data on women undergoing breast implantation, breast reduction, or mastopexy. The purpose of the Registry is to examine short-term and, eventually, long-term local complications and possible health effects, and to contribute to an ongoing evaluation of surgical results and surveillance of the products. Furthermore, the Registry will allow the identification of new areas for research into cosmetic and reconstructive breast surgery. Women accepting registration in the Danish Registry for Plastic Surgery of the Breast complete a self-administered questionnaire focusing on medical history and demographic and behavioral factors. Preoperative blood samples are drawn for storage. Surgical data, postoperative results, and complications are registered following surgery and at postoperative visits. Currently, registration has been initiated at 24 private and public clinics, representing more than 80 percent of the plastic surgery clinics in Denmark. As of November of 2001, a total of 1472 women with breast implants and 560 women with breast reduction were included in the Registry. These figures are expected to increase annually by 1000 women undergoing breast implantation and 500 women undergoing breast reduction or mastopexy. The authors present their experience of establishing the first nationwide comprehensive clinical-epidemiologic database and biological bank for cosmetic and reconstructive surgery procedures.

Breast Implants↗
PubMed2007

Completing the metamorphosis: building a center of excellence in postbariatric plastic surgery.

Postbariatric body contouring is an expanding and rapidly evolving specialty within plastic surgery. To best address the many clinical issues related to the safe and effective care of the postbariatric patient, the authors have established a dedicated multidisciplinary treatment center. Team building efforts have brought together attending plastic surgeons who specialize in body contouring, nurses focused on body contouring after weight loss, and an administrative staff well trained in the issues related to managing these specific types of cases. Through core partnerships, nutritionists, lifestyle counselors, and psychologic professionals are present in the clinic to evaluate patients alongside the plastic surgeon. A dedicated physician assistant and body-contouring fellow work in both the clinic and the operating room (OR). This team approach has allowed for the establishment of defined screening procedures and patient care algorithms. Outreach and patient education initiatives have allowed the center to forge strong alliances with the regional bariatric surgeons and make patients aware of the role of plastic surgery as they start the process of weight loss. A strong research mission is demonstrated by an IRB-approved clinical registry and database that facilitate outcomes studies.

Algorithms↗
PubMed2003

Cooler butterflies lay larger eggs: developmental plasticity versus acclimation.

We use a full factorial design to investigate the effects of maternal and paternal developmental temperature, as well as female oviposition temperature, on egg size in the butterfly Bicyclus anynana. Butterflies were raised at two different temperatures and mated in four possible sex-by-parental-temperature crosses. The mated females were randomly divided between high and low oviposition temperatures. On the first day after assigning the females to different temperatures, only female developmental temperature affected egg size. Females reared at the lower temperature laid larger eggs than those reared at a higher temperature. When eggs were measured again after an acclimation period of 10 days, egg size was principally determined by the prevailing temperature during oviposition, with females ovipositing at a lower temperature laying larger eggs. In contrast to widely used assumptions, the effects of developmental temperature were largely reversible. Male developmental temperature did not affect egg size in either of the measurements. Overall, developmental plasticity and acclimation in the adult stage resulted in very similar patterns of egg size plasticity. Consequently, we argue that the most important question when testing the significance of acclamatory changes is not at which stage a given plasticity is induced, but rather whether plastic responses to environmental change are adaptive or merely physiological constraints.

Acclimatization↗
PubMedDate not supplied

The role of dendritic filtering in associative long-term synaptic plasticity.

Several forms of synaptic plasticity in the neocortex and hippocampus depend on the temporal coincidence of presynaptic activity and postsynaptic trains of action potentials (APs). This requirement is consistent with the Hebbian, or correlational, type of cellular learning rule used in many studies of associative synaptic plasticity. Recent experimental evidence suggests that APs initiated in the axosomatic area are actively back-propagated to the dendritic arborization of neocortical and pyramidal cells. High-frequency trains of postsynaptic APs that are used as conditioning stimuli for the induction of Hebbian-like plasticity in both neocortical and hippocampal pyramidal cells display attenuation of the dendritic AP amplitude during the train. This attenuation has been shown to be modulated by neurotransmitters and by electrical activity. We suggest here that both spike train attenuation in the dendrite and its modulation by neurotransmitters and electrical activity may have important functional consequences on the magnitude and/or the sign of the synaptic plasticity induced by a Hebbian pairing procedure.

Animals↗
PubMed2000

Evolutionary implications of phenotypic plasticity in the hindlimb of the lizard Anolis sagrei.

Species of Anolis lizards that use broad substrates have long legs, which provide enhanced maximal sprint speed, whereas species that use narrow surfaces have short legs, which permit careful movements. We raised hatchling A. sagrei in terraria provided with only broad or only narrow surfaces. At the end of the experiment, lizards in the broad treatment had relatively longer hindlimbs than lizards in the narrow treatment. These results indicate that not only is hindlimb length a plastic trait in these lizards, but that this plasticity leads to the production of phenotypes appropriate to particular environments. Comparison to hindlimb lengths of other Anolis species indicates that the range of plasticity is limited compared to the diversity shown throughout the anole radiation. Nonetheless, this plasticity potentially could have played an important role in the early stages of the Caribbean anole radiation.

Adaptation, Physiological↗
PubMed2000

Different mechanisms underlie phenotypic plasticity and interspecific variation for a reproductive character in drosophilids (Insecta: Diptera).

The insect ovary is a modular structure, the functional unit of which is the ovariole. Ovariole number is positively correlated with potential reproductive output. Among drosophilids (Insecta: Diptera), ovariole number shows both phenotypic plasticity and substantial interspecific and interpopulational variation. Here we examine the mechanistic connection between phenotypic plasticity and genetically fixed variation in ovariole number within the melanogaster species group. When a laboratory population of Drosophila melanogaster was reared under reduced food conditions, differences in ovariole number were entirely due to alterations in cell differentiation during the wandering stage at the very end of larval development. Cell growth and cell death were not affected. When these same flies were reared under a variety of temperatures, ovariole number differences arose during the latter half of the third (final) larval instar. Cell differentiation was affected, although cell number was not, and ovariole number differences were established before metamorphosis. In contrast, genetically fixed, interspecific and interpopulational variability in ovariole number was caused by alterations in the dynamics of cell differentiation and by cell number differences. Furthermore, the stages affected were different in different species and populations in the melanogaster species group, ranging from the first (D. sechellia) through the middle of the third (D. simulans and D. mauritiana) larval stage. Therefore, the mechanistic bases for plasticity-based variability are largely distinct from the mechanistic bases for interspecific and interpopulational variability. Our results suggest that phenotypic plasticity indicates evolutionary flexibility in underlying ontogenetic processes.

Animals↗
PubMed2001

The contribution of phenotypic plasticity to adaptation in Lacerta vivipara.

Correlation between intraspecific phenotypic variability and variation of environmental conditions could reflect adaptation. Different phenotypes may result from differential expression of a genotype in different environments (phenotypic plasticity) or from expression of different genotypes (genetic diversity). Populations of Lacerta vivipara exhibit larger adult body length, lower age at maturity, higher fecundity, and smaller neonatal size in humid habitats compared to dry habitats. We conducted reciprocal transplants of juvenile L. vivipara to test for the genetic or plastic origin of this variation. We captured gravid females from four populations that differed in the relative humidity of their habitats, and during the last 2 to 4 weeks of gestation, we manipulated heat and water availability under laboratory conditions. Juveniles were released into the different populations and families were divided to compare growth rate and survival of half-sibs in two environments. Growth rate and survival were assessed using capture-recapture techniques. Growth rate was plastic in response to postnatal conditions and did not differ between populations of origin. Survival differed between populations of origin, partially because of differences in neonatal body length. The response of juvenile body length and body condition to selection in the different habitats was affected by the population of origin. This result cannot be simply interpreted in terms of adaptation; however, phenotypic plasticity of fecundity or juvenile size most probably resulted in adaptive reproductive strategies. Adaptation to the habitat by means of genetic specialization was not detected. Further investigation is needed to discriminate between genetic and long-term maternal effects.

Adaptation, Physiological↗
PubMed2004

Adaptive divergence vs. environmental plasticity: tracing local genetic adaptation of metamorphosis traits in salamanders.

In order to assess the significance of local adaptation relative to environmental plasticity on the evolution of life history traits, we analysed the possible genetic basis of differences between pond- and stream-breeding fire salamanders (Salamandra salamandra) in Germany. These salamanders typically deposit their larvae in small streams, where they grow until they are sufficiently large to metamorphose. However, some populations in Western Germany use ponds as larval habitat. Because habitat quality of streams differs from that of ponds one expects life history differences in the pond animals, which may result either from a plastic response or through genetic differentiation (i.e. local adaptation). Using a phylogeographical analysis of mitochondrial D-loop sequences, we show that both stream and pond populations in Western Germany are derived from a single lineage that recolonized following the last glaciation. This finding suggests that pond breeding originated very recently. Our studies of habitat quality and metamorphic behaviour of larvae in natural ponds and streams disclosed that pond larvae experience a significantly reduced food supply and greater risk of drying than do stream larvae. Pond larvae metamorphose earlier at the cost of reduced mass. Common-environment experiments with pond and stream larvae show that metamorphic behaviour of pond larvae under limited-food conditions is determined genetically and is not simply a plastic response to the differing habitat conditions. These results show that phenotypic plasticity is less important than local adaptation in explaining differences in ecological diversification within this species and suggests the possibility of rapid evolution of genetic adaptations when new habitats are exploited.

Adaptation, Physiological↗
PubMed2005

A comparative analysis of predator-induced plasticity in larval Triturus newts.

Species that occupy similar habitats are expected to show convergent phenotypes. If habitats are defined by the presence of predators, then traits that modify vulnerability to predation, including predator-induced phenotypic plasticity, should be similar within habitats. We tested this idea using larvae of six syntopic newt species belonging to the two Triturus clades. Behavioural plasticity induced by odonate predators was strongly dissimilar between the two main clades but similar within them. Morphological plasticity was variable among species, even between one pair of closely related species. A predation experiment tested whether differences between clades could be caused by differences in body size. Size-specific vulnerability differed between newts in the small-bodied and large-bodied clades, indicating that similar predators may affect the two clades differently. The results showed both similarity and dissimilarity in predator-induced phenotypic plasticity in syntopic larval newts although theory suggests that divergence is unlikely in such ecologically similar species.

Animals↗