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At least 1,351 records · Page 75Linked to original sources
PubMed1994

Incidence of lymphohematopoietic malignancies among styrene-exposed workers of the reinforced plastics industry.

OBJECTIVES: The goal of this study was to determine the risk of lymphohematopoietic malignancies for workers exposed to styrene. METHODS: This was a historical cohort study. The observed numbers of newly diagnosed cases of lymphohematopoietic malignancies in the study population were compared with expected numbers based on the national rates. The study took place in the Danish reinforced plastic industry, in which high exposure levels of styrene occur frequently in an environment free of most other suspected carcinogens. Altogether 36,525 male employees of 386 companies producing reinforced plastics and 14,254 nonstyrene exposed employees of similar industries were studied. RESULTS: An insignificantly increased standardized incidence ratio (SIR) of 1.22 [95% confidence interval (95% CI) 0.88-1.65] was found for leukemia among all employees of the reinforced plastics industry. Workers employed in the 1960s (the period with the highest recorded styrene levels) or in companies with the highest exposure probability showed increased SIR values of 1.54 (95% CI 1.04-2.19) and 1.38 (95% CI 0.75-2.32), respectively. Both estimates increased when a 10-year latency period was considered. CONCLUSIONS: An increased risk of leukemia was shown for workers in the early phase of the reinforced plastics industry in Denmark. If this association is not due to chance or confounding, the most likely cause is styrene exposure.

Cohort Studies↗
PubMed2006

A comparison of glass and plastic blood collection tubes for routine and specialized coagulation assays: a comprehensive study.

CONTEXT: Blood collection tubes made from plastic are beginning to replace glass tubes. Coagulation test results can be influenced easily by preanalytic factors, including exposure to surfaces that activate the clotting cascade. OBJECTIVE: To compare the effects of the blood collection tube material on 22 coagulation assays performed in clinical laboratories. DESIGN: Paired blood samples from 28 healthy volunteers were drawn into BD Vacutainer Glass Citrate Tubes and BD Vacutainer Plus Plastic Citrate Tubes, and the results of coagulation assays were determined in parallel. RESULTS: No statistically significant differences were observed between glass and plastic for 14 assays: prothrombin time (and international normalized ratio); activated partial thromboplastin time; activated protein C resistance; antithrombin activity; factors II, V, VIII, and IX; alpha2-antiplasmin; plasminogen activity; von Willebrand factor antigen; ristocetin cofactor; thrombin time; and reptilase time. Statistically significant differences were found for fibrinogen; chromogenic protein C activity; protein S activity; PTT-LA lupus anticoagulant-sensitive activated partial thromboplastin time; and factors VII, X, XI, and XII. Mean differences ranged from 0.4% to 5.5% and were unlikely to be of clinical significance. CONCLUSIONS: The results of this study suggest that plastic tubes can be used in place of glass tubes for a wide variety of coagulation assays.

Blood Coagulation Tests↗
PubMed2002

Stimulation-induced within-representation and across-representation plasticity in human motor cortex.

The human motor cortex contains a dynamic and distributed network of motor representations. Formation, maintenance, and modification of these representations is an activity-driven process. Repeated stimulation of one representation results in increased motor output from this representation, a process referred to as "within-representation plasticity." We showed previously that within-representation plasticity of the upper arm representation occurs when repetitive transcranial magnetic stimulation (rTMS) is delivered to that representation during transient ischemic nerve block (INB) of the contralateral hand. INB reduces inhibition in the motor cortex and thus lowers the threshold for stimulation-induced plasticity. Here we studied the effects of rTMS delivered to nearby body part representations on the motor output from the upper arm representation. Six healthy subjects underwent INB-alone (control), or INB plus 30 min of focal 0.1 Hz rTMS of either the face, hand, arm, leg, or overlap arm/hand representations in motor cortex. INB-alone and rTMS of the leg representation resulted in only a short-lasting (< 20 min) increase in motor output from the arm representation, as measured by motor evoked potentials in the biceps. rTMS of arm and arm/hand representations induced a prolonged (> 60 min) within-representation increase. In contrast, rTMS of face or hand representations canceled the short-lasting increase and even led to a long-lasting decrease of motor output from the arm representation. Therefore, rTMS of the experimentally disinhibited motor cortex induces within-representation increase, and across-representation decrease of motor cortical output. This bidirectional plasticity might be used for purposeful modulation of human cortical function.

Adult↗
PubMed1993

Plastics processing: statistics, current practices, and evaluation.

The health care industry uses a huge quantity of plastic materials each year. Much of the machinery currently used, or supplied, for plastics processing is unsuitable for use in a clean environment. In this article, the author outlines the reasons for the current situation and urges companies to re-examine their plastic-processing methods, whether performed in-house or subcontracted out. Some of the factors that should be considered when evaluating plastics-processing equipment are outlined to assist companies in remaining competitive and complying with impending EC regulations on clean room standards for manufacturing areas.

Environment, Controlled↗
PubMed1999

[Plastic surgery training missions in developing countries. A 10-year experience at missions in Mali].

Humanitarian plastic surgery missions are often a substitute, as plastic surgery training missions are essential for the development of plastic surgery in developing countries. This training must be progressive and adapted to the country's needs. Several simple plastic surgery techniques are sufficient to treat a large number of patients: split-skin grafts, full-thickness skin grafts, Z-plasties, latissimus dorsi myocutaneous pedicle flap.

Adult↗
PubMed1999

[Effect of the cytoskeleton dynamic condition on the neuronal plasticity].

Infringement of the Lymnaea stagnalis cytoskeleton condition affected preservation and repeated development of plastic responses. Stabilising of the microtubules led to a dependence of the development and preservation dynamics of the plastic responses. Stabilising of the microfilaments transformed short-term plastic responses into long-term ones. The findings suggest a key role of reorganisation of the cytoskeleton in neuronal plasticity.

Action Potentials↗
PubMed1999

Simulations of cerebellar motor learning: computational analysis of plasticity at the mossy fiber to deep nucleus synapse.

We question the widely accepted assumption that a molecular mechanism for long-term expression of synaptic plasticity is sufficient to explain the persistence of memories. Instead, we show that learning and memory require that these cellular mechanisms be correctly integrated within the architecture of the neural circuit. To illustrate this general conclusion, our studies are based on the well characterized synaptic organization of the cerebellum and its relationship to a simple form of motor learning. Using computer simulations of cerebellar-mediated eyelid conditioning, we examine the ability of three forms of plasticity at mossy fiber synapses in the cerebellar nucleus to contribute to learning and memory storage. Results suggest that when the simulation is exposed to reasonable patterns of "background" cerebellar activity, only one of these three rules allows for the retention of memories. When plasticity at the mossy fiber synapse is controlled by nucleus or climbing fiber activity, the circuit is unable to retain memories because of interactions within the network that produce spontaneous drift of synaptic strength. In contrast, a plasticity rule controlled by the activity of the Purkinje cell allows for a memory trace that is resistant to ongoing activity in the circuit. These results suggest specific constraints for theories of cerebellar motor learning and have general implications regarding the mechanisms that may contribute to the persistence of memories.

Cerebellar Cortex↗
PubMed1975

[Material-testing studies for the rationalization of the technology of stomatological cold curing-plastics].

Materials scientific studies on the rationalization of the processing of stomatological cold-curing plastics. Hydropneumatic overpressure polymerization leads to a considerable rationalization of the processing of stomatological cold-curing plastics, but its effects on the course of polymerization and the properties of the polymerizate are yet not sufficiently elucidated. For this reason, the author studied in several test series the effects of various processing parameters (flask and overpressure vessel; varying mixing ratios, pressures and temperatures) on the polymerization of Kallocryl-AS, a cold-curing plastic. The results obtained indicate that, under certain processing conditions, overpressure polymerization of cold-curing plastics may be recommended from the viewpoint of materials science.

Cold Temperature↗
PubMed2000

Integrin-mediated regulation of synaptic morphology, transmission, and plasticity.

Volado, the gene encoding the Drosophila alphaPS3-integrin, is required for normal short-term memory formation (Grotewiel et al., 1998), supporting a role for integrins in synaptic modulation mechanisms. We show that the Volado protein (VOL) is localized to central and peripheral larval Drosophila synapses. VOL is strongly concentrated in a subpopulation of synaptic boutons in the CNS neuropil and to a variable subset of synaptic boutons at neuromuscular junctions (NMJs). Mutant morphological and functional synaptic phenotypes were analyzed at the NMJ. Volado mutant synaptic arbors are structurally enlarged, suggesting VOL negatively regulates developmental synaptic sprouting and growth. Mutant NMJs exhibit abnormally large evoked synaptic currents and reduced Ca(2+) dependence of transmission. Strikingly, multiple forms of Ca(2+)- and activity-dependent synaptic plasticity are reduced or absent. Conditional Volado expression in mutant larvae largely rescues normal transmission and plasticity. Pharmacologicially disrupting integrin function at normal NMJs phenocopies features of mutant transmission and plasticity within 30-60 min, demonstrating that integrins acutely regulate functional transmission. Our results provide direct evidence that Volado regulates functional synaptic plasticity processes and support recent findings implicating integrins in rapid changes in synaptic efficacy and in memory formation.

Animals↗
PubMed2000

Radial head dislocation with plastic deformation of the ulna in children. A rare and frequently missed condition.

Although often reported in the literature, 'isolated' traumatic radial head dislocation in children is a rare condition which has not been studied extensively. There is very often a delay in diagnosis and treatment. Lincoln and Mubarak described the 'ulnar bow sign' in 1994. They accurately described the plastic deformity of the ulna and explained how to make a correct diagnosis from the radiographs. Probably most 'isolated' radial head dislocations in children are associated with plastic deformation of the ulna as stated in 1984 by Dubuc et al. (2). The recognition of these "plastic" Monteggia fractures is mandatory, as action on the ulna plays a central role in the treatment. On the other hand, the 'ulnar bow sign' may be used to detect subtle changes in the position of the radial head. We present 4 cases of chronic radial head dislocation associated with plastic deformation of the ulna. Open reduction of the radial head and reconstruction of the annular ligament was performed. An osteotomy of the ulna was deemed necessary in 3 cases.

Bone Nails↗
PubMedDate not supplied

Cost outcomes of facial plastic surgery: regional and temporal trends.

OBJECTIVE: To describe the geographic and temporal trends in cosmetic facial plastic surgery procedure costs and frequency during the last decade and to evaluate factors that may influence changes in the demand for cosmetic procedures. METHODS: A survey sent to every (N = 1727) active fellow, member, or associate of the American Academy of Facial Plastic and Reconstructive Surgery assessing the costs and frequency of 4 common cosmetic facial plastic surgery procedures (ie, face-lift, brow lift, blepharoplasty, and rhinoplasty) for 1999 and 1989. RESULTS: The annual frequency of the aging-face procedures (ie, face-lift, brow lift, and blepharoplasty) have increased 41% over the last decade while rhinoplasties have declined slightly (18%). Each of the procedures studied have increased in cost since 1989; however, only face-lifts have increased at a rate greater than inflation during this period (average surgeon's fees, $3154-$4582). Although the average cost of each of these procedures is stable across US geographic areas, there seem to be fewer aging-face procedures being performed in the East (represented largely by New England and the northeastern states) compared with the Midwest, South, and West (P< or = .03), while rhinoplasty frequency across these regions is essentially unchanged. In addition to variables such as age, years in practice, and degree of marketing, the strongest correlates with increased cosmetic procedure frequency were the costs of these procedures (P< or = .008). CONCLUSIONS: Although the cost and frequency of cosmetic facial plastic surgery procedures continues to rise across the United States, there are interesting differences in these trends between different regions and procedure type during the last decade. There also seems to be an association between increased cost and increased frequency of these cosmetic procedures.

Aged↗
PubMedDate not supplied

[Brain plasticity].

The ability to undergo lasting changes of neuronal response properties i.e. plasticity, is one of the most important aspects of functioning of the nervous system. The paper reviews the plastic changes of adult mammalian cerebral cortex. It describes compensatory plasticity induced by peripheral denervation and compensatory plasticity following central trauma. Neuronal mechanisms of cortical neuroplastic changes are presented and the common rules of all forms of cortical modifications are discussed. The paper stresses the therapeutic value of training in various sensory modalities for corrections of functional maladaptation of cortical maps and compensation of function after stroke.

Adaptation, Physiological↗
PubMedDate not supplied

[The problem of adequacy of the methods applying for testing of synaptic plasticity during processes of learning].

Analysis of only the postsynaptic responses seems to be insufficient for studying the synaptic plasticity in learning, because they reflect not only synaptic modifications. The adequacy of brain slices application for investigation of the synaptic plasticity in learning per se has not been strictly specified. Learning processed can be adequately studied only in awake animals. However, traditional methods of field potential recording in response to stimulation of certain inputs that are well interpretable in vitro studies seem to be inadequate for in vivo testing synaptic plasticity. Single unit activity recording in pre- and postsynaptic fields during learning and direct threshold stimulation of monosynaptic inputs to a postsynaptic cell are suggested as a promising strategy for investigation of synaptic plasticity. Since the recording area is not deafferrented in a freely moving animal (as distinct from brain slices), the spontaneous activity in the neural network can interfere with responses to a testing stimulus. Computer simulation demonstrates that the interaction between spontaneous afferentation and testing stimulation can produce an illusion of synaptic modifications. Computer simulation of a neurophysiological experiment is proposed as a preliminary method for the reduction of the effect of spontaneous afferentation on the probability of the postsynaptic response.

Animals↗
PubMed2000

[Probing the origin of plastic surgery and its early development in China].

The modern plastic surgery, accompanied with western medical science, was transmitted to our country by missionary since the opium war (1840). By looking into the medical journal, literature materials published before 1949, it may be confirmed that the department of plastic surgery first appeared in 1934 and was established by Dr. Ni Bao - Chun. At the same time, this author found 27 papers totally belong to plastic surgery in that historical stage and the contents of these papers would basically reflected the scientific level during that period. It might be considered that by then the plastic surgery in our country is in a primative period.

China↗
PubMed2001

New directions in plastic surgery research.

Plastic surgery research affords tremendous opportunities in a variety of affluent mode systems. Only recently have researchers applied molecular biologic techniques to common plastic surgery problems. For example, investigating the fundamental biomolecular mechanisms of normal palate and cranial suture morphogenesis will improve the understanding of the etiopathogenesis of CLP and craniosynostosis and facilitate the development of biologically-based interventions. Furthermore, as interdisciplinary collaborations improve, surgeons can expect to see remarkable progress in de novo tissue synthesis, replacement, and repair. Ultimately, they may one day find that gene-modified endogenous tissue engineering will succeed today's biocompatible scaffolds and allogeneic or zenogeneic replacement strategies. In general, plastic surgeons can look forward to the development of highly effective biomolecular treatments for clinical problems such as complex wound repair, prolific scarring, bone deficits (or surpluses), and organ system replacement or repair. Researchers believe that biologically-based strategies like these will be combined with technical advances that harness minimally invasive approaches. Together, clinicians expect these new tactics will reduce morbidity and improve the results of clinical problems treated by plastic surgeons.

Animals↗
PubMed2001

Experience-dependent plasticity of mouse visual cortex in the absence of the neuronal activity-dependent marker egr1/zif268.

Neuronal activity elicits a rapid increase in the expression of several immediate early genes (IEGs). To clarify a role for IEG response in activity-dependent development, we examined the contribution of the egr1/zif268 gene during visual cortical processing and plasticity in mice. We first analyzed the expression of egr1 mRNA in wild-type (WT) mice using Northern blot hybridization. In the visual cortex, expression of egr1 mRNA increased dramatically after eye opening, systemic injection of kainate, or 30 min of photostimulation after a brief (5 d) period of dark adaptation. Thus, the expression of egr1 is regulated by synaptic activity in the mouse visual cortex, as it is in other species (e.g., monkeys, cats, and rats). To evaluate whether this transcription factor is directly involved in activity-dependent plasticity, mice lacking Egr1 were deprived of the use of one eye during the developmental critical period [postnatal day 24 (P24)-P34]. Extracellular in vivo single-unit recordings from the binocular zone of the visual cortex revealed that visual responses developed normally in egr1 knock-out (KO) mice. Moreover, a similarly significant shift of responsiveness in favor of the open eye was produced in both KO and WT mice by either brief (4 d) or long-term (>2 weeks) occlusion of one eye. There was no apparent compensation among egr2, egr3, or c-fos mRNA and protein expression in the visual cortex of egr1 KO mice. Taken together, these results indicate that egr1 is a useful marker of sensory input in mice but is not intrinsically necessary for the experience-dependent plasticity of the visual cortex. Our findings underscore a mechanistic distinction between sensory plasticity and long-lasting forms of synaptic potentiation in the hippocampus, for which egr1/zif268 was recently found to be essential.

Aging↗
PubMed2001

[Clinical application of narcotic analgesics in patients with burn and plastic surgery].

OBJECTIVE: To investigate the effects of narcotic analgesics (opioids) on the patients with burn and plastic surgery. METHODS: Retrospective statistical analysis was carried out in 452 patients with burn and plastic surgery in terms of the clinical signs of pain, the number of the patients who used the drug, the kinds of the drugs used, the doses and the number of use each day. RESULTS: Inappropriate and insufficient application of narcotic analgesics was common in the past due to our incomplete knowledge of the importance of postburn and post-operative pain in patients with burn and plastic surgery, and also confused concepts of the pain and misuse of opioids, often leading to insufficient analgesia. CONCLUSION: Much attention should be paid to navcotic analgesia in patients with burn plastic surgery. Some measures were suggested.

Adolescent↗
PubMed2002

Rearrangement of receptive field topography after intracortical and peripheral stimulation: the role of plasticity in inhibitory pathways.

Intracortical microstimulation (ICMS) of a single site in the somatosensory cortex of rats and monkeys for 2-6 h increases the number of neurons responsive to the skin region corresponding to the ICMS-site receptive field (RF), with very little effect on the position and size of the ICMS-site RF, and the response evoked at the ICMS site by tactile stimulation. Large changes in RF topography are also observed following several weeks of repetitive stimulation of a restricted skin region during tactile frequency discrimination training in monkeys. It has been suggested that these changes in RF topography are caused by competitive learning in excitatory pathways. This paper analyses the possible role of lateral inhibitory synaptic plasticity in producing cortical plasticity after ICMS and peripheral conditioning in adult animals. The 'EXIN' (afferent excitatory and lateral inhibitory) synaptic plasticity rules are used to model RF changes after ICMS and peripheral stimulation. The EXIN model produces RF topographical changes similar to those observed experimentally. It is shown that lateral inhibitory pathway plasticity is sufficient to model RF changes and increase in position discrimination after peripheral stimulation. Several novel and testable predictions are made based on the EXIN model.

Algorithms↗