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Evidence of adaptive divergence in plasticity: density- and site-dependent selection on shade-avoidance responses in Impatiens capensis.

We investigated the conditions under which plastic responses to density are adaptive in natural populations of Impatiens capensis and determined whether plasticity has evolved differently in different selective environments. Previous studies showed that a population that evolved in a sunny site exhibited greater plasticity in response to density than did a population that evolved in a woodland site. Using replicate inbred lines in a reciprocal transplant that included a density manipulation, we asked whether such population differentiation was consistent with the hypothesis of adaptive divergence. We hypothesized that plasticity would be more strongly favored in the sunny site than in the woodland site; consequently, we predicted that selection would be more strongly density dependent in the sunny site, favoring the phenotype that was expressed at each density. Selection on internode length and flowering date was consistent with the hypothesis of adaptive divergence in plasticity. Few costs or benefits of plasticity were detected independently from the expressed phenotype, so plasticity was selected primarily through selection on the phenotype. Correlations between phenotypes and their plasticity varied with the environment and would cause indirect selection on plasticity to be environment dependent. We showed that an appropriate plastic response even to a rare environment can greatly increase genotypic fitness when that environment is favorable. Selection on the measured characters contributed to local adaptation and fully accounted for fitness differences between populations in all treatments except the woodland site at natural density.

Adaptation, Physiological↗

Adaptive phenotypic plasticity and genetics of larval life histories in two Rana temporaria populations.

Phenotypic plasticity provides means for adapting to environmental unpredictability. In terms of accelerated development in the face of pond-drying risk, phenotypic plasticity has been demonstrated in many amphibian species, but two issues of evolutionary interest remain unexplored. First, the heritable basis of plastic responses is poorly established. Second, it is not known whether interpopulational differences in capacity to respond to pond-drying risk exist, although such differences, when matched with differences in desiccation risk would provide strong evidence for local adaptation. We investigated sources of within- and among-population variation in plastic responses to simulated pond-drying risk (three desiccation treatments) in two Rana temporaria populations originating from contrasting environments: (1) high desiccation risk with weak seasonal time constraint (southern population); and (2) low desiccation risk with severe seasonal time constraint (northern population). The larvae originating from the environment with high desiccation risk responded adaptively to the fast decreasing water treatment by accelerating their development and metamorphosing earlier, but this was not the case in the larvae originating from the environment with low desiccation risk. In both populations, metamorphic size was smaller in the high-desiccation-risk treatment, but the effect was larger in the southern population. Significant additive genetic variation in development rate was found in the northern and was nearly significant in the southern population, but there was no evidence for genetic variation in plasticity for development rates in either of the populations. No genetic variation for plasticity was found either in size at metamorphosis or growth rate. All metamorphic traits were heritable, and additive genetic variances were generally somewhat higher in the southern population, although significantly so in only one trait. Dominance variances were also significant in three of four traits, but the populations did not differ. Maternal effects in metamorphic traits were generally weak in both populations. Within-environment phenotypic correlations between larval period and metamorphic size were positive and genetic correlations negative in both populations. These results suggest that adaptive phenotypic plasticity is not a species-specific fixed trait, but evolution of interpopulational differences in plastic responses are possible, although heritability of plasticity appears to be low. The lack of adaptive response to desiccation risk in northern larvae is consistent with the interpretation that selection imposed by shorter growing season has favored rapid development in north (approximately 8% faster development in north as compared to south) or a minimum metamorphic size at the expense of phenotypic plasticity.

Adaptation, Physiological↗

Biodegradability of degradable plastic waste.

Plastic waste constitutes the third largest waste volume in Malaysian municipal solid waste (MSW), next to putrescible waste and paper. The plastic component in MSW from Kuala Lumpur averages 24% (by weight), whereas the national mean is about 15%. The 144 waste dumps in the country receive about 95% of the MSW, including plastic waste. The useful life of the landfills is fast diminishing as the plastic waste stays un-degraded for more than 50 years. In this study the compostability of polyethylene and pro-oxidant additive-based environmentally degradable plastics (EDP) was investigated. Linear low-density polyethylene (LLDPE) samples exposed hydrolytically or oxidatively at 60 degrees C showed that the abiotic degradation path was oxidative rather than hydrolytic. There was a weight loss of 8% and the plastic has been oxidized as shown by the additional carbonyl group exhibited in the Fourier transform infra red (FTIR) Spectrum. Oxidation rate seemed to be influenced by the amount of pro-oxidant additive, the chemical structure and morphology of the plastic samples, and the surface area. Composting studies during a 45-day experiment showed that the percentage elongation (reduction) was 20% for McD samples [high-density polyethylene, (HDPE) with 3% additive] and LL samples (LLDPE with 7% additive) and 18% reduction for totally degradable plastic (TDP) samples (HDPE with 3% additive). Lastly, microbial experiments using Pseudomonas aeroginosa on carbon-free media with degradable plastic samples as the sole carbon source, showed confirmatory results. A positive bacterial growth and a weight loss of 2.2% for degraded polyethylene samples were evident to show that the degradable plastic is biodegradable.

Air↗

Phenotypic plasticity opposes species invasions by altering fitness surface.

Understanding species invasion is a central problem in ecology because invasions of exotic species severely impact ecosystems, and because invasions underlie fundamental ecological processes. However, the influence on invasions of phenotypic plasticity, a key component of many species interactions, is unknown. We present a model in which phenotypic plasticity of a resident species increases its ability to oppose invaders, and plasticity of an invader increases its ability to displace residents. Whereas these effects are expected due to increased fitness associated with phenotypic plasticity, the model additionally reveals a new and unforeseen mechanism by which plasticity affects invasions: phenotypic plasticity increases the steepness of the fitness surface, thereby making invasion more difficult, even by phenotypically plastic invaders. Our results should apply to phenotypically plastic responses to any fluctuating environmental factors including predation risk, and to other factors that affect the fitness surface such as the generalism of predators. We extend the results to competition, and argue that phenotypic plasticity's effect on the fitness surface will destabilize coexistence at local scales, but stabilize coexistence at regional scales. Our study emphasizes the need to incorporate variable interaction strengths due to phenotypic plasticity into invasion biology and ecological theory on competition and coexistence in fragmented landscapes.

Adaptation, Physiological↗

Costs of plasticity in foraging characteristics of the clonal plant Ranunculus reptans.

In clonal plants, evolution of plastic foraging by increased lengths of leaves and internodes under unfavourable conditions may be constrained by costs and limits of plasticity. We studied costs and limits of plasticity in foraging characteristics in 102 genotypes of the stoloniferous herb Ranunculus reptans. We grew three replicates of each genotype with and three without competition by the naturally co-occuring grass Agrostis stolonifera. We used regression and correlation analyses to investigate potential costs of plasticity in lengths of leaves and stolon internodes, developmental instability costs of these traits, and a developmental range limit of these traits. We used randomization procedures to control for spurious correlations between parameters calculated from the same data. Under competition the number of rosettes, rooted rosettes, and flowers was 58%, 40%, and 61% lower, respectively, than in the absence of competition. Under competition lengths of leaves and stolon internodes were 14% and 6% smaller, respectively, than in the absence of competition. We detected significant costs of plasticity in stolon internode length in the presence of competition when fitness was measured in terms of the number of rosettes and the number of flowers (selection gradients against plasticity were 0.250 and 0.214, respectively). Within-environment variation (SD) in both foraging traits was not positively correlated with the corresponding plasticity, which indicates that there were no developmental instability costs. More plastic genotypes did not have less extreme trait values than less plastic genotypes for both foraging traits, which indicates that there was no developmental range limit. We conclude that in R. reptans costs of plasticity more strongly constrain evolution of foraging in the horizontal plane (i.e., stolon internode length) than in the vertical plane (i.e., leaf length).

Adaptation, Physiological↗

Combustion products of plastics as indicators for refuse burning in the atmosphere.

Despite all of the economic problems and environmental discussions on the dangers and hazards of plastic materials, plastic production worldwide is growing at a rate of about 5% per year. Increasing techniques for recycling polymeric materials have been developed during the last few years; however, a large fraction of plastics are still being discarded in landfills or subjected to intentional or incidental open-fire burning. To identify specific tracer compounds generated during such open-fire combustion, both smoke particles from burning and plastic materials from shopping bags, roadside trash, and landfill garbage were extracted for gas chromatography-mass spectrometry analyses. Samples were collected in Concón, Chile, an area frequently affected by wildfire incidents and garbage burning, and the United States for comparison. Atmospheric samples from various aerosol sampling programs are also presented as supportive data. The major components of plastic extracts were even-carbon-chain n-alkanes (C16-C40), the plasticizer di-2-ethylhexyl phthalate, and the antioxidants and lubricants/antiadhesives Irganox 1076, Irgafos 168, and its oxidation product tris(2,4-di-tertbutylphenyl) phosphate. Major compounds in smoke from burning plastics include the non-source-specific n-alkanes (mainly even predominance), terephthalic acid, phthalates, and 4-hydroxybenzoic acid, with minor amounts of polycyclic aromatic hydrocarbons (including triphenylbenzenes) and tris(2,4-di-tert-butylphenyl)phosphate. 1,3,5-Triphenylbenzene and tris(2,4-di-tert-butylphenyl)- phosphate were found in detectable amounts in atmospheric samples where plastics and refuse were burned in open fires, and thus we propose these two compounds as specific tracers for the open-burning of plastics.

Aerosols↗

The effect of increased plastic surgeon supply on fees for aesthetic surgery: an economic analysis.

The size of the plastic surgery workforce has important effects on the financial environment of the specialty. Economic theory predicts that increasing the area supply of surgeons performing aesthetic surgery will result in lower fees for their services. This study tested that theory in the actual aesthetic surgery marketplace. The study examined the ratio of plastic surgeons to the general population of several states. It then traced the aesthetic surgery fees resulting from different densities of area plastic surgeons. This information was economically analyzed to project the fee effects of possible future changes in the number of practicing plastic surgeons. For the states of New York, California, and Texas, there is a proportional decrease in fees as the density of plastic surgeons increases. For example, New York has 34 percent more plastic surgeons proportionally than Texas, and its fees are 30 percent lower in real dollars. Economic analysis can project the fee effects of changing the supply of surgeons performing aesthetic surgery. The analysis reveals that a 30 percent national increase in the supply of plastic surgeons would lower fees by approximately 32 percent. Similarly, if the number of plastic surgeons increases by 50 percent, fees will decrease by approximately 53 percent. However, these fee effects can be mitigated by expanding the demand for aesthetic surgery. In conclusion, the size of the plastic surgery workforce has profound effects on the fees paid for aesthetic surgery, and the magnitude of these effects can be understood, predicted, and optimized using the tools of economics.

Fees, Medical↗

Glucocorticoid stimulation of dopamine production in PC12 cells on extracellular matrix and plastic.

PC12 cells are spherical when cultured on plastic, but flatten and spread extensively when cultured on extracellular matrix (ECM) produced by bovine corneal endothelial cells. We previously demonstrated that cells which have spread on ECM release more dopamine and contain less intracellular dopamine than cells which are rounded on plastic cultureware. Glucocorticoids increase dopamine production in PC12 cells presumably via an increase in tyrosine hydroxylase gene transcription. We questioned whether cell shape as determined by ECM would change the response of PC12 cells to glucocorticoids. Dopamine release and cell content were measured by a radioenzymatic assay in serum-free cultures of PC12 cells on ECM and plastic treated with various glucocorticoids in a dose-response fashion for 24 or 48 h. In addition, the response of cells on both substrata to one dose of dexamethasone was examined from 3-48 h. PC12 cells on ECM and plastic exhibited a dose-related increase in dopamine release and content when treated for 24 h with corticosterone or for 48 h with dexamethasone, corticosterone or cortisol. The ED50s for dexamethasone- and corticosterone-stimulated release and content were similar for cells on ECM and plastic as were the doses at which the first significant increases were detected. The average times at which the first significant increase in release and content occurred were also similar for cells on ECM and plastic. PC12 cells on ECM continue to release more dopamine and store less dopamine than cells on plastic with glucocorticoid treatment. However, glucocorticoid-treated cells on ECM showed a greater percent increase over ECM controls in the cell content of dopamine, whereas glucocorticoid-treated cells on plastic showed a greater percent increase over controls in the release of dopamine. It is hypothesized that glucocorticoids increase dopamine production to a similar extent in cells on ECM and plastic, but that storage is facilitated in cells on ECM.

Animals↗

Alginate-magnesium aluminum silicate films: effect of plasticizers on film properties, drug permeation and drug release from coated tablets.

The effect of hydrophilic plasticizers, namely glycerin and polyethylene glycol 400 (PEG400), on physicochemical properties of sodium alginate-magnesium aluminum silicate (SA-MAS) microcomposite films was characterized and application of the films for controlling drug release from tablets was evaluated as well. The plasticizers could possibly interact with SA or MAS by formation of hydrogen bonding, as revealed using FTIR spectroscopy. PXRD studies presented that glycerin or PEG400 could intercalate into the silicate layers of MAS and higher crystallinity of the films with PEG400 was obtained. This led to a different thermal behavior of the films. Glycerin gave more flexibility of the films than PEG400. Incorporation of plasticizers into the films did not affect water uptake in acid medium, but increasing an erosion of the films because of the leaching of the plasticizers. Water vapor permeability of the films decreased with increasing amount of plasticizers in the range of 10-30% (w/w). Diffusion coefficient (D) of acetaminophen (ACT) across the films in acid medium increased with addition of the plasticizers because the leaching of plasticizers could reduce tortuosity of aqueous pore channels of the films. The tablets coated with plasticized films had a quite smooth surface without defect as shown by SEM. The ACT release profiles from the coated tablets showed a zero-order release kinetic with drug diffusion mechanism across in situ insoluble composite films in acid medium, and coating film swelling and erosion mechanism in pH 6.8 phosphate buffer. Moreover, neither the release rate nor the release pattern of the ACT coated tablets was obviously changed. The findings show that glycerin or PEG400 could improve physicochemical properties of the SA-MAS films and the plasticized films could control the drug release from tablets in gastro-intestinal condition.

Acetaminophen↗

Distortion of disposable plastic stock trays when used with putty vinyl polysiloxane impression materials.

STATEMENT OF PROBLEM: Impressions are made using high-viscosity putty vinyl polysiloxane impression materials in conjunction with disposable plastic stock trays. The impression materials have been shown to be dimensionally stable. However, it remains unclear if the disposable plastic stock trays are rigid enough to resist deformation thus yielding potentially unreliable results. PURPOSE: This study evaluated the rigidity and ability to resist deformation of 6 commercially available disposable plastic stock trays and 1 metal stock tray when used in conjunction with a high-viscosity vinyl polysiloxane impression material. MATERIAL AND METHODS: Ten impressions were made with 1 putty vinyl polysiloxane material (Reprosil Putty) using each of the 6 tested disposable plastic stock trays, Sani-Trays (perforated), Sani-Trays (nonperforated), COE Disposable Spacer Tray (perforated), COE Disposable Spacer Tray (nonperforated), Bosworth Tray-Aways (perforated), Track-it Trays (perforated), and 1 metal stock tray (nonperforated), Cadco Dental Products, as a control on a mandibular plastic model. The dimensions of the tray in cross section at the mandibular right first molar area were measured before, during, and after the impression procedures with an electronic digital caliper. The cross-arch dimensions of the tray were measured at similar intervals. One examiner made all measurements and each measurement was repeatable within +/-0.01 mm. A split plot repeated measures analysis of variance (ANOVA) was performed and 2-sided P -values were calculated (alpha=.05). RESULTS: The results indicated that the disposable plastic trays tested were not sufficiently rigid to resist deformation when used with very high-viscosity putty material. Metal stock trays showed significantly less change in cross-arch dimension than plastic trays (F(1.68)=11.25, P =.001). Metal stock trays also showed significantly less change in cross-sectional arch dimension than plastic trays (F(1.68)=15.15, P<.001). CONCLUSION: When disposable plastic stock trays were tested in conjunction with very high-viscosity impression materials there was distortion of the tray both across the arch and in cross section.

Dental Impression Materials↗

Self-expanding plastic stents for benign esophageal lesions.

BACKGROUND: A benign condition is a relative contraindication to the use of self-expanding metallic stents, because these devices usually are not retrievable. The self-expanding plastic stent is removable and induces less tissue hyperplasia. This study prospectively evaluated the use of a self-expanding plastic stent to treat benign esophageal conditions. METHODS: Over 4 years, 21 patients underwent self-expanding plastic stent placement for various benign esophageal disorders, including refractory peptic (n = 2), caustic (n = 3), post-radiotherapy (n = 3), and anastomotic (n = 4) stenoses; hyperplastic (n = 5) stenosis within a previously implanted metallic stent; and anastomotic leak (n = 4) after esophagectomy. The self-expanding plastic stent was removed from all patients. Patients were followed for at least 8 months after stent removal. RESULTS: Implantation was successful in all cases. Temporary self-expanding plastic stent placement was curative in 17/21 patients, especially those with caustic and hyperplastic strictures and anastomotic fistula, all of which were treated successfully without re-intervention. Median follow-up was 21 months (range 8-39 months) after stent removal. Moreover, by inducing tissue ischemia, self-expanding plastic stent allowed delayed removal of metallic stents. Only one severe complication (tracheal compression) was encountered, and this resolved after stent removal. CONCLUSIONS: A range of benign stenosing disorders of the esophagus can be treated safely with a self-expanding plastic stent. Because the long-term results were highly favorable, self-expanding plastic stent placement could be used as the initial treatment for various conditions. Self-expanding plastic stent insertion within an esophageal self-expanding metallic stent allowed removal of the latter, theoretically unretrievable, stent.

Adult↗

Clinical disorders of brain plasticity.

Clinical disorders of brain plasticity are common in the practice of child neurology. Children have an enhanced capacity for brain plasticity compared to adults as demonstrated by their superior ability to learn a second language or their capacity to recover from brain injuries or radical surgery such as hemispherectomy for epilepsy. Basic mechanisms that support plasticity during development include persistence of neurogenesis in some parts of the brain, elimination of neurons through apoptosis or programmed cell death, postnatal proliferation and pruning of synapses, and activity-dependent refinement of neuronal connections. Brain plasticity in children can be divided into four types: adaptive plasticity that enhances skill development or recovery from brain injury; impaired plasticity associated with cognitive impairment; excessive plasticity leading to maladaptive brain circuits; and plasticity that becomes the brain's 'Achilles' Heel' because makes it vulnerable to injury. A broad group of pediatric neurologic disorders can be understood in terms of their impact on fundamental mechanisms for brain plasticity. These include neurofibromatosis, tuberous sclerosis, Fragile X syndrome, other inherited forms of mental retardation, cretinism, Coffin-Lowry syndrome, lead poisoning, Rett syndrome, epilepsy, hypoxic-ischemic encephalopathy and cerebral palsy.

Animals↗

Plasticization of poly(L-lactide) with poly(propylene glycol).

A new plasticizer for poly(L-lactide) (PLA)-poly(propylene glycol) (PPG) is proposed. The advantage of using PPG is that it does not crystallize, has low glass transition temperature, and is miscible with PLA. PLA was plasticized with PPGs with nominal Mw of 425 and 1000 g/mol. Poly(ethylene glycol) (PEG), long known as a plasticizer for PLA, with nominal Mw of 600 g/mol, was also used to plasticize PLA for comparison. The thermal and tensile properties of PLA and PLA with 5-12.5 wt % of the plasticizers were studied. In blends of PLA with PPGs the glass transition temperature was lower than that of neat PLA. Both PPGs enhanced the crystallizability of PLA albeit less than PEG. All of the plasticizers increased also the ability of PLA to plastic deformation which was reflected in a decrease of yield stress and in an increase of elongation at break. The effect was enhanced by the higher PPG content and also by lower molecular weight of PPG. A phase separation occurred only in the blend containing 12.5 wt % of PPG with higher molecular weight. The evidences of crazing were found in deformed samples of PLA with low plasticizer content, whereas the samples with higher content of plasticizers crystallized due to deformation.

Calorimetry, Differential Scanning↗

Stability of red cell antigens and plasma coagulation factors stored in a non-diethylhexyl phthalate-plasticized container.

Red cell antigen stability studies were performed to evaluate whether the storage of red cells in plastic segments made up of a new non-di-2(ethylhexyl)phthalate (DEHP)-plasticized material resulted in poststorage antigenic reactivity different from that seen in segments made from DEHP-containing plastic. Serial 1-in-2 dilutions of commercially available antisera were prepared and tested by using stored red cells obtained from segments on Days 0, 28, 42, and, in some instances, 49. Antigenic determinants tested included A, B, D, c, K, Le(a), Fya, Jka, M, and P1. To minimize variability, the same reagent lots were used throughout each study, and the same technologists performed the assays in each laboratory. No significant differences in titration scores were seen when cells stored in segments made of the test plastic were compared with cells obtained from the same donor and stored for the same length of time in segments made of control plastic. In addition, plasma coagulation factor stability was studied in fresh-frozen plasma and cryoprecipitate stored for up to 1 year in the non-DEHP-plasticized plastic containers. No significant differences were seen in prothrombin time, activated partial thromboplastin time, fibrinogen content, or factor V, VII, VIII, IX, or X activity as compared with plasma stored for equal periods of time in control plastic containers. It is concluded that the test plastic does not adversely affect red cell antigenic reactivity or plasma coagulation factor stability and that it is suitable for use in clinical transfusion practice.

Blood Coagulation Factors↗

Plastic endoprostheses versus metal stents in the palliative treatment of malignant hilar biliary obstruction. A prospective and randomized trial.

This prospective and randomized trial sought to compare large-bore plastic endoprostheses (14 French) and self-expanding metal stents (24 French) in the palliative treatment of obstructive jaundice due to biliary hilar malignancies. Twenty patients with Type II-IV (Bismuth classification) hilar obstruction were randomized to treatment with either plastic or metal stents. Both treatment groups were well matched with regard to all assessed clinical criteria before stenting. Stent placement was uniformly successful in the metal group and in 88.9% of the plastic group. Early stent failure (< 30 days) occurred in two patients of the plastic stent group. Longterm (> 30 days), stent failure was observed in 50% of the plastic group and 18.2% of the metal stent group. All differences were not statistically significant. The number of re-interventions required to manage stent-related problems proved to be significantly higher in the plastic group (2.4 +/- 2.6) compared to the metal group (0.4 +/- 0.5). Hospitalization for treatment of stent complications was also significantly higher in the plastic treatment group. The costs calculated for stents and hospital stay for required re-interventions were therefore higher in the plastic stent group. In conclusion, metal stent insertion for palliation of hilar malignancies does not only offer higher success rates and higher patency rates compared to plastic stent insertion, but is also cost-effective since patients require fewer re-interventions.

Aged↗

Influence of plasticization time, curing conditions, storage time, and core properties on the drug release from Aquacoat-coated pellets.

Theophylline or chlorpheniramine maleate pellets were coated with an aqueous ethylcellulose dispersion, Aquacoat. The influence of the plasticization time, curing conditions, storage time, and core properties on the drug release were investigated. The plasticization time (time between plasticizer addition to the polymer dispersion and the spraying process) did not affect the drug release, when the water-soluble plasticizer triethyl citrate, was used because of its rapid uptake by the colloidal polymer particles. In contrast, with the water-insoluble plasticizer acetyltributyl citrate (ATBC), plasticization time (1/2 h vs 24 h) influenced the drug release, the longer plasticization time resulted in a slower drug release because of a more complete plasticizer uptake prior to the coating step. However a thermal aftertreatment of the coated pellets at eleylated temperatures (curing step) reduced/eliminated the effect of the plasticization time with ATBC. In general, curing reduced the drug release and resulted in stable drug release profiles. The time period between the coating and the curing step was not critical when the pellets were cured for a longer time. The structure of the pellet core (high dose matrix vs low dose layered pellet) strongly affected the drug release. A slow, zero-order drug release was obtained with high dose theophylline pellets, while a more rapid, first-order release pattern was obtained with low dose theophylline-layered nonpareil pellets.

Cellulose↗

The effect of the Accreditation Council for Graduate Medical Education Duty Hours Policy on plastic surgery resident education and patient care: an outcomes study.

The Accreditation Council for Graduate Medical Education (ACGME) Work-Hours Duty Policy became effective on July 1, 2003, mandating the reduction of resident duty work hours. The Baylor College of Medicine Multi-Institutional Integrated Plastic Surgery Program instituted a resident duty work-hours policy on July 1, 2002 (1 year ahead of the national mandate). Outcomes data are needed to facilitate continuous improvements in plastic surgical residency training while maintaining high-quality patient care. To assess the effect of this policy intervention on plastic surgery resident education as measured through the six core competencies and patient/resident safety, the investigators surveyed all categorical plastic surgery residents 6 months after implementation of the policy. This work represents the first empiric study investigating the effect of duty hours reduction on plastic surgery training and education. The categorical plastic surgery residents at the Baylor College of Medicine Multi-Institutional Integrated Plastic Surgery Program completed a 68-item survey on a five-point Likert scale (1 = strongly disagree to 5 = strongly agree). Residents were asked to rate multiple parameters based on the ACGME six core competencies, including statements on patient care and clinical/operative duties, resident education, resident quality of life, and resident perceptions on this policy. All surveys were completed anonymously. The sample size was n = 12 (program year 3 through program year 6), with a 100 percent response rate. Univariate and bivariate statistical analysis was conducted with SPSS version 10.0 statistical software. Specifically, interquartile deviations were used to find consensus among resident responses to each statement. Descriptive statistics indicated higher percentages of agreement on a majority of statements in three categories, including patient care and clinical/operative duties, academic duties, and resident quality of life. Using interquartile deviation, the highest levels of consensus among the residents were found in positive statements addressing resident alertness (both in and out of the operative environment), time to read/prepare for cases/conferences, efficacy of the didactic curriculum, and overall satisfaction with this policy for surgery resident education. Residents also felt that their patients favored this work hours policy. In addition, there was high consensus that this policy improved overall patient care. The majority of residents identified a negative effect of this policy through an increase in cross-coverage responsibilities, however, and half of the residents perceived that faculty negatively viewed their unavailability postcall. In addition, no consensus among the residents was achieved regarding perceptions on overall weekly operative experience. Plastic surgery residents perceived that the reduction of resident work hours through adherence to the ACGME guidelines has beneficial effects on patient care and clinical/operative duties, academic duties, and resident quality of life. Residents felt, however, that these benefits may increase cross-coverage workloads. Furthermore, residents were concerned about faculty perception of their changes in postcall duties. In contrast to previously published findings in the general surgery literature, the current results indicate that residents do not believe that this policy negatively affects continuity of patient care. In fact, the current findings suggest that adherence to this policy improves patient care on multiple levels. The effect on the operative experience remains to be elucidated. Further large-scale and longitudinal research design and analysis is warranted to better assess the results of the ACGME resident duty work-hours policy in plastic surgery resident education.

Accreditation↗

Sensory input directs spatial and temporal plasticity in primary auditory cortex.

The cortical representation of the sensory environment is continuously modified by experience. Changes in spatial (receptive field) and temporal response properties of cortical neurons underlie many forms of natural learning. The scale and direction of these changes appear to be determined by specific features of the behavioral tasks that evoke cortical plasticity. The neural mechanisms responsible for this differential plasticity remain unclear partly because important sensory and cognitive parameters differ among these tasks. In this report, we demonstrate that differential sensory experience directs differential plasticity using a single paradigm that eliminates the task-specific variables that have confounded direct comparison of previous studies. Electrical activation of the basal forebrain (BF) was used to gate cortical plasticity mechanisms. The auditory stimulus paired with BF stimulation was systematically varied to determine how several basic features of the sensory input direct plasticity in primary auditory cortex (A1) of adult rats. The distributed cortical response was reconstructed from a dense sampling of A1 neurons after 4 wk of BF-sound pairing. We have previously used this method to show that when a tone is paired with BF activation, the region of the cortical map responding to that tone frequency is specifically expanded. In this report, we demonstrate that receptive-field size is determined by features of the stimulus paired with BF activation. Specifically, receptive fields were narrowed or broadened as a systematic function of both carrier-frequency variability and the temporal modulation rate of paired acoustic stimuli. For example, the mean bandwidth of A1 neurons was increased (+60%) after pairing BF stimulation with a rapid train of tones and decreased (-25%) after pairing unmodulated tones of different frequencies. These effects are consistent with previous reports of receptive-field plasticity evoked by natural learning. The maximum cortical following rate and minimum response latency were also modified as a function of stimulus modulation rate and carrier-frequency variability. The cortical response to a rapid train of tones was nearly doubled if BF stimulation was paired with rapid trains of random carrier frequency, while no following rate plasticity was observed if a single carrier frequency was used. Finally, we observed significant increases in response strength and total area of functionally defined A1 following BF activation paired with certain classes of stimuli and not others. These results indicate that the degree and direction of cortical plasticity of temporal and receptive-field selectivity are specified by the structure and schedule of inputs that co-occur with basal forebrain activation and suggest that the rules of cortical plasticity do not operate on each elemental stimulus feature independently of others.

Acoustic Stimulation↗