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At least 1,531 records · Page 85Linked to original sources
PubMed2004

Elasto-plastic contact analysis of an ultra-high molecular weight polyethylene tibial component based on geometrical measurement from a retrieved knee prosthesis.

The wear phenomenon of ultra-high molecular weight polyethylene (UHMWPE) in knee and hip prostheses is one of the major restriction factors on the longevity of these implants. Especially in retrieved knee prostheses with anatomical design, the predominant types of wear on UHMWPE tibial components are delamination and pitting. These fatigue wear patterns of UHMWPE are believed to result from repeated plastic deformation owing to high contact stresses. In this study, the elasto-plastic contact analysis of the UHWMPE tibial insert, based on geometrical measurement for retrieved knee prosthesis, was performed using the finite element method (FEM) to investigate the plastic deformation behaviour in the UHMWPE tibial component. The results suggest that the maximum plastic strain below the surface is closely related to subsurface crack initiation and delamination of the retrieved UHMWPE tibial component. The worn surface whose macroscopic geometrical congruity had been improved due to wear after joint replacement showed lower contact stress at macroscopic level.

Aged↗
PubMed2006

Mapping determinants of gene expression plasticity by genetical genomics in C. elegans.

Recent genetical genomics studies have provided intimate views on gene regulatory networks. Gene expression variations between genetically different individuals have been mapped to the causal regulatory regions, termed expression quantitative trait loci. Whether the environment-induced plastic response of gene expression also shows heritable difference has not yet been studied. Here we show that differential expression induced by temperatures of 16 degrees C and 24 degrees C has a strong genetic component in Caenorhabditis elegans recombinant inbred strains derived from a cross between strains CB4856 (Hawaii) and N2 (Bristol). No less than 59% of 308 trans-acting genes showed a significant eQTL-by-environment interaction, here termed plasticity quantitative trait loci. In contrast, only 8% of an estimated 188 cis-acting genes showed such interaction. This indicates that heritable differences in plastic responses of gene expression are largely regulated in trans. This regulation is spread over many different regulators. However, for one group of trans-genes we found prominent evidence for a common master regulator: a transband of 66 coregulated genes appeared at 24 degrees C. Our results suggest widespread genetic variation of differential expression responses to environmental impacts and demonstrate the potential of genetical genomics for mapping the molecular determinants of phenotypic plasticity.

Animals↗
PubMed2001

Plastic bronchitis and the role of bronchoscopy in the acute chest syndrome of sickle cell disease.

STUDY OBJECTIVES: To review the prevalence, clinical features, and role of bronchoscopy in patients with plastic bronchitis during the acute chest syndrome (ACS) of sickle cell disease (SCD). DESIGN: Eight-year review of clinical experience. SETTING: Tertiary referral children's hospital. PATIENTS: Twenty-six pediatric inpatients with 29 ACS episodes requiring diagnostic bronchoscopy. RESULTS: Of the pediatric inpatients with ACS who underwent bronchoscopy, plastic bronchitis was diagnosed in 21 of 29 episodes (72%). There was no difference in clinical features between the patients with and without plastic bronchitis. Bronchoscopy was an essential diagnostic tool, but its therapeutic benefits were doubtful. CONCLUSIONS: This is the first report of the prevalence of plastic bronchitis in patients with ACS of SCD. In our patient population, this condition was found to be common. The role of diagnostic bronchoscopy is essential. A large series, multicenter study is required to determine whether bronchoscopy and BAL are therapeutically beneficial when added to currently practiced supportive care.

Acute Disease↗
PubMed1975

[Solid phase radioimmunoassay for plasma testosterone using plastic microtiter tray (author's transl)].

UNLABELLED: In order to simply radioimmunoassay for plasma testosterone and to measure many samples at the same time, a method of solid phase radioimmunoassay utilizing a plastic disposable microtiter tray (DMT) by which chromatography can be omitted was investigated. METHOD: The antiserum was obtained by immunizing rabbits with testosterone-3 BSA which had been synthesized according to the Erlarnger's method. Plasma samples (male: 0.05ml, female: 0.2 ml) were extracted with 1.0 ml of ether. After freezing the plasma layer in an acetone-dryice bath, the ether phase was transfered to a glass tube and evaporated to dryness. These samples and the dried standard testosterone were dissolved with borate buffer containing 3H-testosterone and transfered to plastic DMT which had been precoated with the diluted antiserum, and incubated for 24 hrs. After removal of the incubated solution, the cups of DMT were cut off and were dissolved with toluene scintillator in counting vials. The radioactivity was counted with a liquid scintillation counter. RESULT: Other steroids except for 5alpha-dihydrotestosterone (5alpha-DHT) had a low degree of cross reactivity with the antiserum. Five alpha-DHT which could be measured together with testosterone in this assay was not a problem clinically because of its strong androgenic activity. The best standard curve was obtained when the antiserum was diluted to 1:1000. The sensitivity of this assay was 10 pg/tube. The maximal adsorption of antibody to plastic DMT was observed when the pH of antiserum was within the range of 6.5-9.5 and the precoating time was 24 hr at room termperature. The best pH of incubation buffer was 8.0, and the antigen-antibody reaction became a plateau when the incubation exceeded 6 hrs. Water blank in this assay was 4.6 +/- 2.1 pg/tube. The recovery of testosterone (50, 100, 200 pg) added to 0.1 ml female plasma was 99 +/- 6.8%. Coefficients of variation within assay and between assay were below 11.2% and 20.0%, respectively. Correlation between this method and the dextran-coated charcoal method was fairly good (r=0.938). Plasma testosterone levels in 10 normal males and 12 normal females were 616 +/- 202 (mean +/- SD) ng/dl and 66 +/- 29 (mean +/- SD) ng/dl, respectively. The levels were low in patients with hypopituitarism, hypogonadism and acromegaly. They were normal in patients with Cushing's syndrome due to adrenal hyperplasia and adenoma, but they were high in a patient with adrenal carcinoma. In a patient with testicular feminization, the level was 632 ng/dl. This increased after the administration of HCG, and decreased to 127.5 ng/dl after castration. This solid phase radioimmunoassay (using plastic DMT) is economically feasible as well as simple because it is possible to separate the bound hormone from the free hormone of all samples at the same time and there is little restriction in time and temperature. According to the above results, this method is suitable for routine clinical use.

Acromegaly↗
PubMed2006

Reciprocal phenotypic plasticity in a predator-prey interaction between larval amphibians.

In biological interactions, phenotypic change in interacting organisms induced by their interaction partners causes a substantial shift in some environmental factor of the partners, which may subsequently change their phenotype in response to that modified environmental factor. Few examples of such arms-race-like plastic responses, known as reciprocal phenotypic plasticity, have been identified in predator-prey interactions. We experimentally identified a reciprocal defensive plastic response of a prey species against a predator with a predaceous phenotype using a model system of close predator-prey interaction. Rana pirica tadpoles (the prey species) were reared with larvae of the salamander Hynobius retardatus (the predator species) having either a predaceous or a typical, nonpredaceous phenotype. The H. retardatus larvae with the predaceous phenotype, which is known to be induced by the presence of R. pirica tadpoles, induced a more defensive phenotype in the tadpoles than did larvae with the typical phenotype. The result suggests that the reciprocal phenotypic plasticity of R. pirica tadpoles is in response to a phenotype-specific signal under a close-signal recognition process.

Adaptation, Physiological↗
PubMed2006

Ecological opportunity and phenotypic plasticity interact to promote character displacement and species coexistence.

We investigated the roles of resource availability and phenotypic plasticity in promoting ecological character displacement (i.e., trait evolution stemming from resource competition between species). Because ecological character displacement generates new populations that differ in resource use, this process should only occur when exploitable resources are available. We tested this hypothesis in two species of spadefoot toads (Spea bombifrons and S. multiplicata) whose tadpoles use phenotypic plasticity to develop into either an omnivore morph, which specializes on detritus, or a physically distinctive carnivore morph, which specializes on shrimp. Both species grow best on shrimp, but when reared together, S. bombifrons outcompetes S. multiplicata for shrimp and S. multiplicata outcompetes S. bombifrons for detritus. We found that when each species occurred alone in the field, they produced similar proportions of omnivores and carnivores. When the two species occurred together, however, they underwent ecological character displacement in larval development, with S. multiplicata producing mostly omnivores, and S. bombifrons producing mostly carnivores. We combined observations of natural populations with experiments to evaluate whether such character displacement was only possible when both shrimp and detritus were relatively abundant. Mixed-species ponds contained abundant detritus and shrimp, in contrast with nearby pure-species ponds, which were deficient in one resource. Experiments revealed that S. multiplicata competed poorly when detritus was rare and that S. bombifrons competed poorly when shrimp was rare. In nature, when one of these two resources was scarce, one species was missing, perhaps through competitive exclusion by the species that was the superior competitor for the remaining resource. Thus, ecological character displacement and, therefore, coexistence of close competitors, was only possible when diverse resources were available. Finally, even if exploitable resources are available, character displacement is not guaranteed to transpire if species cannot utilize such resources expeditiously. Phenotypic plasticity provides a general and important mechanism for facilitating resource partitioning. Thus, by facilitating shifts in resource use, phenotypic plasticity and ecological opportunity may often interact to promote divergence and coexistence of competitors.

Adaptation, Physiological↗
PubMed1975

Roentgen recognition of acute plastic bowing of the forearm in children.

Traumatic bowing of one or both forearm bones in children represents an acute plastic deformation of bone. Plastic curvatures have been produced in the dog ulna, but have been recognized only recently in man. The biomechanics and histologic changes of the experimental model explain the roentgenological features found in children with traumatically bowed bones: (1) broad fixed curvatures which hold fractures in angulation and resist orthopedic reduction; (2) absence of periosteal new bone formation following the injury; and (3) partial correction of the plastic corvature by cortical remodeling in young children. In a series of 17 patients, eight children had bowing of the ulna with an angulated fracture of the radius, five had bowing of the radius with an angulated ulna fracture, and four children had both the radius and ulna bowed without fracture. Manipulative reduction in the majority of children with fractures failed to reduce the plastic curvature, causing partial loss of pronation and supination.

Adolescent↗
PubMed1984

Spontaneous autoradiographic grain activation associated with mast cells in methacrylate plastic embedded tissue sections.

Autoradiographic tracing using tritium labeled compounds or cells is a common laboratory technique for light and electron microscopy. This report describes a chemographic effect associated with certain cells in sections from tissues embedded in the new methacrylate plastic embedding compounds. When tissue sections from rats and rhesus monkeys that received no radioisotope were coated with nuclear track emulsion and subsequently developed, cells with morphologic characteristics of mast cells showed significant grain formation over the entire cell. Three different types of methacrylate plastics were tested using rat and monkey tissues and all three were found to promote grain formation over mast cells; however, this phenomenon was not seen in similar tissue sections from paraffin or epoxy embedded material. The properties of methacrylate plastics which promote positive chemography by mast cells may reflect the greater permeability of this class of plastics. Due to their wide tissue distribution, the presence of such chemographically active cells could cause false estimates of the distribution of either exogenous radiolabeled cells or radioisotopes within many tissues.

Animals↗
PubMed1999

Plastic adherent stromal cells from the bone marrow of commonly used strains of inbred mice: variations in yield, growth, and differentiation.

Bone marrow stroma contains a unique cell population, referred to as marrow stromal cells (MSCs), capable of differentiating along multiple mesenchymal cell lineages. A standard liquid culture system has been developed to isolate MSCs from whole marrow by their adherence to plastic wherein the cells grow as clonal populations derived from a single precursor termed the colony-forming-unit fibroblast (CFU-F). Using this liquid culture system, we demonstrate that the relative abundance of MSCs in the bone marrow of five commonly used inbred strains of mice varies as much as 10-fold, and that the cells also exhibit markedly disparate levels of alkaline phosphatase expression, an early marker of osteoblast differentiation. For each strain examined, the method of isolating MSCs by plastic adherence yields a heterogeneous cell population. These plastic adherent cells also exhibit widely varying growth kinetics between the different strains. Importantly, of three inbred strains commonly used to prepare transgenic mice that we examined, only cells derived from FVB/N marrow readily expand in culture. Further analysis of cultures derived from FVB/N marrow showed that most plastic adherent cells express CD11b and CD45, epitopes of lymphohematopoietic cells. The later consists of both pre-B-cell progenitors, granulocytic and monocytic precursors, and macrophages. However, a subpopulation of the MSCs appear to represent bona fide mesenchymal progenitors, as cells can be induced to differentiate into osteoblasts and adipocytes after exposure to dexamethasone and into myoblasts after exposure to amphotericin B. Our results point to significant strain differences in the properties of MSCs and indicate that standard methods cannot be applied to murine bone marrow to isolate relatively pure populations of MSCs.

Alkaline Phosphatase↗
PubMed2000

[Plastic surgery in patients with obesity late after horizontal banded gastroplasty].

The results of 361 plastic operations in 296 patients with morbid obesity late after horizontal gastroplasty were analyzed. Plastic and corrective operations aimed at removal of redundant lipocutaneous "aprons" at the anterior abdominal wall, thighs, thoracic wall, gluteal region and the arms, represent a final stage of surgical treatment of patients with morbid obesity. The indications, technique and the results of plastic operations performed from 1985 to 1998, are thoroughly elucidated. The analysis of early postoperative complications has established, that it a reasonable to perform such operations 1-3 years after gastroplasty when body weight stabilizes and there are no vitamin deficiency, iron deficient anemia, hypoproteinemia, hydroionic disturbances or other complications of the later period. Complex prophylactic measures for prevention of pyoseptic and thromboembolic complications in patients with obesity late after gastroplasty permits to avoid severe complications and lethal outcomes in patients after plastic operations.

Adolescent↗
PubMed2000

Consequences of phenotypic plasticity vs. interspecific differences in leaf and root traits for acquisition of aboveground and belowground resources.

Trade-offs between acquisition capacities for aboveground and belowground resources were investigated by studying the phenotypic plasticity of leaf and root traits in response to different irradiance levels at low nutrient supply. Two congeneric grasses with contrasting light requirements, Dactylis glomerata and D. polygama, were used. The aim was to analyze phenotypic covariation in components of leaf area and root length in response to above- and belowground resource limitation and the consequences of this variation for resource acquisition and plant growth. At intermediate shading (30 and 20% of full sunlight) the plants were able to maintain their total root length, despite a strongly increased total leaf area and a reduced biomass allocation to roots. This was associated with an unaltered or slightly increased nutrient uptake and growth. At 5.5% relative irradiance, growth was severely reduced, especially in the shade-tolerant D. polygama. The results show that constraints on acquisition capacities for aboveground and belowground resources, caused by biomass allocation, may be alleviated by plasticity in other traits such as tissue-mass density and thickness of roots and leaves. The results also suggest different adaptive constraints for phenotypic plasticity and for genetically determined interspecific variation. Phenotypic plasticity tends to maximize resource acquisition and growth rate in the short term, whereas the higher tissue-mass density and the longer leaf life-span of shade-tolerant species indicate reduced loss rates as a more advantageous species-specific adaptation to shade in the long term.

Journal Article↗
PubMed2000

[Randomized prospective study to compare the efficiency between standard plastic and polyurethane stents in biliary tract malignant obstruction].

UNLABELLED: The aim of this paper is to compare the efficiency between standard plastic stents and polyurethane stents used in biliary tract malignant obstruction. The main problem of the plastic prosthesis is their early occlusion. On the other hand there is the hypothesis that due to the less porousness of the polyurethane surface, there might be lesser adherence and consequently a late occlusion. Thirty-eight patients in two groups of 19 were evaluated prospectively and at random in the Jerusalem Hadassah Hospital and the HIGA San Martín La Plata. They had biliary tract obstruction due to inoperable tumors. Biliary endoprosthesis (plastic standard or polyurethane 10 French diameter) were placed, according to the randomization, after a previous staging with clinical examination, laboratory analysis and images. The follow-up with the same parameters was monthly done. Twelve of the 38 patients were female and 26 male; age average 62.73 (range 81-49). The stents were placed in 17 patients with biliary cancer, 14 pancreatic cancer, 2 papila cancer, 2 gallbladder cancer with bile duct invasion and 3 liver metastasis with biliary tract compression. The clinical and laboratory parameters in 36 patients at 30 days improved. On the contrary, 2 (1 plastic standard and 1 polyurethane stent) did not improve. There were 29 deaths due to the basic illness and not related to the endoscopic method. The mean obstruction occurred at 12.76 weeks (range 32-4) in the standard stents and 12.05 (range 24-2) in the polyurethane ones. CONCLUSION: There were no significant differences in the two groups patients.

Aged↗
PubMed2001

[Plastic bronchitis and mucoid impaction--uncommon disease syndromes with expectoration mucus plugs].

Mucoid impaction and plastic bronchitis are relatively rare disorders caused by the formation of obstructive airway plugs. We observed from February 1999 to June 2000 seven patients with mucoid impaction and one with plastic bronchitis. In the group of mucoid impaction there were 4 patients with bronchial asthma and 3 without history of lung disease. At the admission to hospital all patients suffered from cough, chest pain and effort dyspnea. Two of them expectorated during cough "bronchial casts". The chest X-ray of 5 patients revealed atelectasis of one of the lung's lobes and diffuse opacities in 2 others. In 4 cases during bronchoscopy one bronchus and in another three--numerous bronchi were obstructed with mucoid casts. Removing of the casts caused both the improvement of the patients' condition and withdrawal of atelectasis in 4 cases. In 5 patients the final diagnosis was allergic bronchopulmonary aspergillosis and in two mucoid impaction in the course of asthma without aspergillosis. Plastic bronchitis was observed in 44 years old man, who expectorated white, branching, bronchial casts for three months. On admission he was in respiratory failure. The chest X-ray revealed diffuse alveolar infiltrates and HRCT glass-ground opacities in both lungs and bronchiectasis in the middle lobe. The bronchofiberoscopy disclosed diffuse tracheobronchitis with casts occluding the middle lobe bronchus. Microscopic examination of the removed casts showed aggregates of mucus, macrophages, neutrophils and cells of respiratory epithelium. Precipitins against Aspergillus fumigatus were not found. Staphyloccocus coagulase (-) was cultured from urine and sputum specimens. We administered Vancomycin with Netylmycin, acetylocysteine, oxygen therapy and humid inhalation and the patient recovered. HRCT made six months after admission revelated total withdrawal of glass-ground opacities. The pathogenesis of plastic bronchitis in this case was unclear.

Adult↗
PubMed2001

[Effect of plastic film mulching on crop yield and nitrogen efficiency in semiarid areas].

The effect of plastic film mulching, water storage in soil profile before sowing, and nitrogen fertilization on crop yield and nitrogen efficiency was examined in this paper. The study site was on the cultivated lossial soil in semiarid areas with 415 mm of annual rainfall and the test crop was spring wheat, Triticum aestivum. In order to study the effect of plastic film mulching, 4 levels of mulching were designed, including mulching of 0, 30 and 60 days after sowing and mulching over the whole growing period. The results showed that increase of soil water storage, plastic film mulching and nitrogen fertilization increased crop yield significantly(alpha < 0.01), and their effect followed in the order of nitrogen fertilization > increase of water storage > plastic film mulching. The effect of mulching on crop yield varied with water storage, nitrogen fertilization and mulching periods. When the water storage was low, there was no significant difference in crop yield between mulching and no mulching, although mulching increased crop yield slightly, and the nitrogen efficiency was higher for no mulching and mulching 30 days. When the water storage was high, the difference between the yield of mulching 60 days and no mulching was significant, but no difference in nitrogen efficiency was found for mulching 30 days, 60 days and over whole growing period. It was suggested that mulching over whole growing period was of less significance in practice.

Crops, Agricultural↗
PubMed1975

Contribution of collagen and mineral to the elastic-plastic properties of bone.

Tension testing of wet bovine haversian cortical bone demonstrated marked plastic behavior. Progressive surface decalcification of this bone with dilute hydrochloric acid resulted in progressive decreases in the tension yield point and the ultimate stress with no change in the yield strain or ultimate strain unless decalcification was complete. The slope of the plastic region remained identical throughout decalcification. These findings are consistent with an elastic-perfectly plastic model for the mineral phase of bone tissue in which the mineral contributes the major portion of the tension yield strength. The slope or stiffness of the plastic region of the stress-strain curve is a function only of the properties of collagen, which itself plays a minor role in the tension yield strength of bone.

Animals↗
PubMed2002

[Architectural plasticity of the stoloniferous herb, Duchesnea indica in response to different elevation].

Architectural plasticity of clonal plant may modify its ways of utilization of resources through clonal growth and be of ecologically importance. The plasticity of clonal architecture in response to ecological conditions at different altitudes in a stoloniferous herb, Duchesnea indica, was investigated in an experiment with different elevations of 400, 800, 1200, and 1600 m. The results showed that the change patterns of spacer length, ramet density, branching intensity, and branching angle of Duchesnea indica were in a quadratic curve when the elevation increased. The architectural plasticity of D. indica was simulated through dynamic Logistic model, and the imitative effect was statistically preferable. Combining with the resources utilization of Duchesnea indica under different environments, the architectural plasticity was also discussed in this paper.

Altitude↗
PubMed1995

Special report: the truth about condoms. Restrictive label could impede plastic condom sales.

You walk into a drugstore to buy a package of plastic condoms. You happen to notice the label says that no one's sure how well they protect you from pregnancy or sexually transmitted diseases (STDs) like AIDS. Then, the label indirectly points you in the direction of latex condoms. What would you do? Some observers familiar with the condom industry speculate that the restrictive labeling carried on each package of the new plastic condoms for men will not interfere with consumers' purchasing decisions. Other predict an instant replay of the situation faced by makers of the polyurethane Reality female condom: A lack of data on pregnancy rates and STD rates resulted in a label touting latex as a superior product, which in turn caused an onslaught of negative press about the first plastic condom. The US Food and Drug Administration, finding itself in a similar position with approving plastic condoms for men, recently released interim labeling to be followed by all manufacturers who want to sell the new male condoms. Essentially, the manufacturers must point out on the front of the condom box that the product is "for latex-sensitive condom users," and on the back of the box must tell a potential buyer that risks for pregnancy and STDs are not known for the product. Upon reading this disclaimer, the consumer then reads that "latex condoms for men, if used correctly with every act of vaginal intercourse, are highly effective at preventing pregnancy, as well as STDs, including AIDS (HIV infection)."

Condoms↗
PubMed2002

Experimental life-history evolution: selection on the allocation to sexual reproduction and its plasticity in a clonal plant.

Allocation to sexual reproduction is an important life-history trait in clonal plants. Different selection pressures between competitive and competition-free environments are likely to result in the evolution of specialized genotypes and to maintain genetic variation in reproductive allocation. Moreover, selection may also result in the evolution of plastic allocation strategies. The necessary prerequisite for evolution, heritable genetic variation, can best be studied with selection experiments. Starting from a base population of 102 replicated genotypes of the clonal herb Ranunculus reptans, we imposed selection on the proportion of flowering rosettes in the absence of competition (base population: mean = 0.391, broad-sense heritability = 0.307). We also selected on the plasticity in this trait in response to competition with a naturally coexisting grass in a parallel experiment (base population: 14% lower mean in the presence of competition, broad-sense heritability = 0.072). After two generations of bidirectional selection, the proportion of flowering rosettes was 26% higher in the high line than in the low line (realized heritability +/- SE = 0.205 +/- 0.017). Moreover, genotypes of the high line had 11% fewer carpels per flower, a 22% lower proportion of rooted rosettes, and a 39% smaller average distance between rosettes within a clone. In the second experiment, we found no significant responses to selection for high and low plasticity in the proportion of flowering rosettes (realized heritability +/- SE = -0.002 +/- 0.013). Our study indicates a high heritability and potential for further evolution of the proportion of flowering rosettes in R. reptans, but not for its plasticity, which may have been fixed by past evolution at its current level. Moreover, our results demonstrate strong genetic correlations between allocation to sexual reproduction and other clonal life-history characteristics.

Biological Evolution↗