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PubMed1996

Clear plastic cups: a childhood choking hazard.

The disposable plastic beverage cup is not usually regarded as hazardous to young children. Certain varieties of these products however, are manufactured from a brittle, clear plastic that easily cracks and fragments. While most conscientious parents keep their children safe from peanuts, balloons, and other known choking hazards, a child can surreptitiously bite a cup edge and aspirate the fragment. We report two cases of foreign body aspiration involving clear plastic cups that went undetected one of which remained 21 months following a negative rigid bronchoscopy. Diagnostic difficulties are related to the transparency and radiolucency of these objects. When suspicious of foreign body aspiration in children, otolaryngologists should inquire about the availability of clear plastic cups in the household and be mindful of the diagnostic pitfalls. Further investigations including CT scanning and repeat bronchoscopy may be helpful in cases of suspected missed foreign bodies. An educational campaign aimed at prevention and placement of product package warning labels should be established.

Airway Obstruction↗

PubMed1993

Do NMDA receptors have a critical function in visual cortical plasticity?

The theoretical framework, by which we understand the function of NMDA receptors, is derived, in large part, from work conducted on the hippocampal slice preparation, where NMDA receptors are crucial for a form of synaptic plasticity known as long-term potentiation (LTP). Establishing their role in plasticity mechanisms in the neocortex is proving to be far more difficult than originally envisaged, in part due to the fact that the operation of NMDA receptors is different in the intact animal than in vitro. For example, NMDA receptors are activated at low levels of sensory input in intact animals but only by high levels of input in slice preparations. Recent results suggest that a re-evaluation of the role of NMDA receptors in neocortical plasticity is required. Here we discuss some of the issues and introduce four criteria by which any factor supposedly involved in plasticity can be judged. NMDA receptors fulfill more of these criteria than any of the other factors so far investigated in the visual cortex, but maybe this is because they have been studied more intensively.

Animals↗

PubMed1989

Interaction of noradrenergic and cholinergic systems in regulation of ocular dominance plasticity.

We studied interactions among the noradrenergic (NA) and the muscarinic cholinergic (ACh) systems in the regulation of ocular dominance plasticity in kitten visual cortex. The cortex was bilaterally infused with 6-hydroxydopamine (6-OHDA) for a week. Upon termination of the 6-OHDA infusion, one hemisphere was infused with a muscarinic ACh agonist, bethanechol, through the same, chronically implanted cannula for the second week together with monocular lid suture. The other hemisphere received an infusion of the vehicle solution alone. (1) Only in the hemisphere infused with bethanechol at relatively high concentrations did we obtain a clear shift in ocular dominance. We also found that the effect of bethanechol was concentration-dependent. (2) By comparing necessary concentrations of bethanechol and NA for the respective maximal effects, we noted that the former was at least 100-fold less effective than the latter in restoring the plasticity. (3) The cortical infusion of bethanechol did not restore the plasticity to the propranolol-pretreated cortex; the ocular dominance distribution remained virtually unchanged. This result was interpreted as suggesting that functioning beta-adrenoreceptors are needed for the cortical effect of activating the muscarinic ACh receptors to become detectable. (4) The expected shift in ocular dominance following monocular deprivation was partially suppressed, when highly concentrated scopolamine, a muscarinic ACh antagonist, was used, indicating that the involvement of the ACh system in this matter was indirect. The concentration of scopolamine needed for the half-maximum effect was 172-fold higher than that of propranolol. We thus conclude that the involvement of the muscarinic ACh system in ocular dominance plasticity is secondary to that of the NA-beta-adrenoreceptor system.

Aging↗

PubMed1996

Survival of Vibrio cholerae O1 on plastic materials.

Survival of environmental and clinical strains of Vibrio cholerae O1 was studied on glass and on two varieties of plastic materials. V. cholerae survived at least 2 days on glass, but was not recovered from polystyrene spoons after 15-20 min. Escherichia coli survived for at least 2 days on both glass slides and plastic spoons. Extracts, 10 and 50% (w/v) of ground plastic spoons in isotonic saline water, inactivated 10(4) vibrios in less than 2 h. Isotonic saline water rinses from polyethylene bags inactivated (0% survival) 15 out of 23 strains of V. cholerae in 1 h. A strain of V. cholerae (100-200 CFU/ml) directly suspended in 25 ml of isotonic saline per bag and maintained at 20 degrees C was progressively inactivated. The number of viable cells diminished 95% in 4 h in bags taken from non-sterile rolls. In sterile bags the decrease was 44% and 93% after 4 and 24 h, respectively. A variability up to 50% was observed in the antibacterial effect among the different bags, either sterile or taken from non-sterile rolls. These decreases in V. cholerae viability may result in false negative reports if water samples are collected and carried out in plastic bags.

Anti-Bacterial Agents↗

PubMed1984

Behavioural plasticity and the cholinergic system.

Evidence for the involvement of the cholinergic system in behavioural plasticity is reviewed by considering three forms of behavioural plasticity: habituation, learning and memory, and tolerance development. Although the cholinergic system may modulate the response tendencies of an animal, it does not appear to be involved in the process of habituation. A number of studies have indicated that the cholinergic system may be involved in learning and memory processes in infrahuman animals. In general, cholinergic antagonists tend to disrupt memory while agonists may, under the appropriate conditions, facilitate memory. Recent studies have pointed to a relation between dysfunctions of the cholinergic system and dysfunctions of memory in aged animals. Studies of tolerance development suggest that the cholinergic system may undergo plastic changes which may underlie the development of tolerance to some drugs, with receptor alterations being the most reproducible finding. However, more work is necessary to establish the degree of plasticity. The cholinergic system also appears to be involved in learning and memory processes in humans. However, attempts to correct the memory deficits in aged humans by manipulating the cholinergic system have met with limited success. The reasons for this lack of success are briefly considered.

Acetylcholine↗

PubMedDate not supplied

Mutation frequencies of Drosophila melanogaster reared in glass and plastic vials.

The mutation frequency of the sex-linked recessive lethal assay resulting from the examination of 9032 tests of Drosophila melanogaster reared in plastic vials (0.198%) was approximately twice that of Drosophila melanogaster reared in glass vials (0.085%) after examination of 9365 tests. This difference was found to be significant (P less than 0.05). This significant increase in the mutation frequency may be due to styrene which is one of the components of the plastic vials. Also, the frequency of failure was greater when using plastic vials (1.19%) compared to glass vials (0.71%). In the following study we examined D. melanogaster SLRL mutation frequencies and failure rates when using glass and plastic vials. Our results showed a doubling in the SLRL mutation rate.

Animals↗

PubMed1992

Age-dependent alterations of synaptic performance and plasticity in crustacean motor systems.

Age-related changes in synaptic performance and plasticity are surveyed in crustacean neuromuscular systems. These systems are functionally differentiated into phasic and tonic types, with different attributes of synaptic function and plasticity. Conversion of phasic neuromuscular junctions to a more phasic phenotype can be brought about by altering the activity of selected neurons. This type of plasticity disappears in older animals in some motor neurons, but is retained in others. Developmental programs set constraints on the age-dependent modifications of plasticity. Crustacean motor neurons are often characterized by great longevity, with progressive addition of new branches and synapses to keep up with growth of innervated muscle cells. Certain age-related compensatory mechanisms found in neuromuscular junctions of other species may not be required in crustaceans.

Aging↗

PubMed1990

Effects of NMDA antagonists on developmental plasticity in kitten visual cortex.

The existence of Hebb synapses in the visual cortex of young kittens has long been postulated. A mechanism for the correlation of activity in simultaneously active pre- and postsynaptic neurons could be provided by the properties of the N-methyl-D-aspartate (NMDA) receptor and its associated Ca2+ channel, which opens in a transmitter- and voltage-dependent manner. We have studied the effects on cortical plasticity of blocking NMDA receptors in different ways with competitive and non-competitive NMDA antagonists. In our first approach, the non-competitive NMDA antagonist ketamine, a short-acting dissociative anaesthetic, was injected systemically after each of a series of brief monocular exposures. This procedure prevented the development of an ocular dominance shift towards the experienced eye in the visual cortex. Other short-acting anaesthetics, such as xylazine or methohexital, while providing the same depth of anaesthesia, did not have the same effect on ocular dominance plasticity. We conclude, therefore, that ketamine quite specifically interferes with synaptic consolidation in the visual cortex. In order to establish a role of NMDA receptors for cortical plasticity directly in the visual cortex, we performed another series of experiments: 2-amino-5-phosphono-valerate (APV), a competitive NMDA antagonist, was infused intracortically by means of implanted osmotic minipumps in kittens, which were monocularly deprived for 1-2 weeks. Within a radius of 4-5 mm, the expected ocular dominance shift was prevented or reduced. In addition, however, physiologically determined cell density and responsiveness to visual stimuli were grossly abnormal around the infusion site, and histological cell density was also reduced. Similar effects were found when MK801 (a non-competitive NMDA antagonist) was used in the same type of experiment. The outcome of both experimental approaches makes it very likely that NMDA antagonists somehow interfere with cortical plasticity. Their mode of action, however, remains ambiguous. Although it is quite possible that blocking of the NMDA channel prevents the Hebbian correlative process necessary for synaptic consolidation, more complex effects, such as an interference with a neurotrophic action normally exerted via the NMDA receptor, may have to be taken into account as well.

2-Amino-5-phosphonovalerate↗

PubMed1988

Semen quality in workers producing reinforced plastic.

A comparison of semen parameters from 25 workers at a reinforced plastic production plant and from 46 age-matched male fertility patients was carried out. For a period of more than three months before the semen analyses, the 25 workers had been exposed to styrene and acetone in concentrations exceeding the Danish threshold limit values. Serum concentrations of follicle stimulating and luteinizing hormones, semen sample volume, and concentration of sperm showed no differences between the two groups. Significant differences between the two groups were found in the percentage of live sperm, immotile sperm, and normal sperm. The reinforced plastic plant workers showed, in terms of semen quality, better values in the percentages of live sperm and immotile sperm, whereas they had a reduced percentage of normally shaped sperm. It was found that the reinforced-plastic workers had increased percentages of the amorphous and the pyriform sperm head shapes as compared to the fertility clientele. In sperm midpiece and sperm tail defects, the two groups showed similar values. From the data it could be concluded that work with production of reinforced plastic might result in an increase in the number of abnormal sperm heads.

Acetone↗

PubMed2006

Atomoxetine enhances a short-term model of plasticity in humans.

OBJECTIVE: To evaluate the role of 2 noradrenergic drugs in modulating use-dependent plasticity in humans. DESIGN: Double-blind, randomized, and placebo-controlled crossover design. SETTING: A laboratory in a hospital. PARTICIPANTS: A convenience sample of 10 healthy subjects. INTERVENTION: An established paradigm that measures motor memory as a short-term model of use-dependent plasticity. Subjects attended 3 sessions, separated by at least 1 week to allow drug washout. Subjects received atomoxetine (Strattera), venlafaxine (Effexor), or placebo. MAIN OUTCOME MEASURE: Increase in the proportion of movements into the training target zone (TTZ), an indicator of enhanced plasticity. RESULTS: Atomoxetine, but not venlafaxine, significantly increased movements into the TTZ. CONCLUSIONS: These results support a role for norepinephrine in enhancing cortical plasticity and suggest potential benefits in using these drugs for improving motor recovery after stroke.

Adrenergic Uptake Inhibitors↗

PubMed2005

Repeated stress and structural plasticity in the brain.

Although adrenal steroid receptors are distributed widely throughout the central nervous system, specific limbic and cortical regions targeted by stress hormones play a key role in integrating behavioral and physiological responses during stress and adaptation to subsequent stressors. When the stressor is of a sufficient magnitude or prolonged, it may result in abnormal changes in brain plasticity that, paradoxically, may impair the ability of the brain to appropriately regulate and respond to subsequent stressors. Here we review how repeated stress produces alterations in brain plasticity in animal models, and discuss its relevance to behavioral changes associated with these regions. Interestingly, prolonged stress produces opposing effects on structural plasticity, notably dendritic atrophy and excitatory synapse loss in the hippocampus and prefrontal cortex, and growth of dendrites and spines in the amygdala. The granule cells of the dentate gyrus are also significantly affected through a decrease in the rate neurogenesis following prolonged stress. How functional impairments in these brain regions play a role in stress-related mental illnesses is discussed in this context. Finally, we discuss the cumulative impact of stress-induced structural plasticity in aging.

Aging↗

PubMed2005

Strain-dependent regulation of plasticity-related proteins in the mouse hippocampus.

Inbred mouse strains have different genetic backgrounds that can result in impairment of synaptic plasticity and memory. Strain-dependent performance in behavioral and cognitive tasks is well-documented. Hippocampal long-term potentiation (LTP), an activity-dependent enhancement of synaptic transmission that may underlie some forms of learning and memory has been shown to differ significantly between inbred mouse strains. However, an effect of strain on the expression of proteins, critically involved in synaptic plasticity, learning and memory has not been described yet. We have been addressing this question by determining expressional levels of a panel of proteins involved in neuronal information processing in hippocampus of five mouse strains by immunoblotting. Four inbred strains (FVB/N, C57Bl/6J, 129S2/Sv and Balb/c), commonly used for generating genetically modified mice and for conventional experiments in pharmacology and toxicology and one outbred strain (OF1) have been selected. A significant effect of strain was detected for total and phosphorylated calcium-calmodulin dependent kinase IIalpha (CaMKII, pCaMKII), phosphorylated mitogen-activated protein kinase (pMAPK), total and phosphorylated calcium-responsive element binding 1 (creb, pcreb), early-growth response protein 1 (egr 1), brain derived neurotrophic factor (BDNF), drebrin and postsynaptic density-95 (PSD-95). These results may indicate genetic determination of synaptic plasticity-related mechanisms relevant for the molecular events mediating hippocampal information processing and storage. Data presented herein highlight the importance of careful selection of the mouse strain for studies of synaptic plasticity.

Animals↗

PubMed2006

Extensive enriched environments protect old rats from the aging dependent impairment of spatial cognition, synaptic plasticity and nitric oxide production.

In aged rodents, neuronal plasticity decreases while spatial learning and working memory (WM) deficits increase. As it is well known, rats reared in enriched environments (EE) show better cognitive performances and an increased neuronal plasticity than rats reared in standard environments (SE). We hypothesized that EE could preserve the aged animals from cognitive impairment through NO dependent mechanisms of neuronal plasticity. WM performance and plasticity were measured in 27-month-old rats from EE and SE. EE animals showed a better spatial WM performance (66% increase) than SE ones. Cytosolic NOS activity was 128 and 155% higher in EE male and female rats, respectively. Mitochondrial NOS activity and expression were also significantly higher in EE male and female rats. Mitochondrial NOS protein expression was higher in brain submitochondrial membranes from EE reared rats. Complex I activity was 70-80% increased in EE as compared to SE rats. A significant increase in the area of NADPH-d reactive neurons was observed in the parietotemporal cortex and CA1 hippocampal region of EE animals.

Aging↗

PubMed2006

Group I mGluR regulates the polarity of spike-timing dependent plasticity in substantia gelatinosa neurons.

The spinal synaptic plasticity is associated with a central sensitization of nociceptive input, which accounts for the generation of hyperalgesia in chronic pain. However, how group I metabotropic glutamate receptors (mGluRs) may operate spinal plasticity remains essentially unexplored. Here, we have identified spike-timing dependent synaptic plasticity in substantia gelatinosa (SG) neurons, using perforated patch-clamp recordings of SG neuron in a spinal cord slice preparation. In the presence of bicuculline and strychnine, long-term potentiation (LTP) was blocked by AP-5 and Ca2+ chelator BAPTA-AM. The group I mGluR antagonist AIDA, PLC inhibitor U-73122, and IP3 receptor blocker 2-APB shifted LTP to long-term depression (LTD) without affecting acute synaptic transmission. These findings provide a link between postsynaptic group I mGluR/PLC/IP3-gated Ca2+ store regulating the polarity of synaptic plasticity and spinal central sensitization.

2-Amino-5-phosphonovalerate↗

PubMed2026

Discovering hidden candidate plastic-degrading enzymes: Combined multi-omics and machine learning strategy.

Plastic pollution poses a major threat to the stability of natural ecosystems as well as human health. Microbial enzymes have long been considered a potential resource for targeted biodegradation but, except for a few successful cases, the discovery of efficient enzymes has proved challenging. Aiming to accelerate the process, we propose an approach combining metagenomics, metatranscriptomics and semi-supervised learning that selects promising plastic-degrading candidate enzymes from the proteome of relevant microorganisms. Tested on a dataset of over 10,000 microbial proteins, ranking models consistently prioritize known plastic-degrading enzymes, achieving an area under the cumulative distribution function curve above 0.96, with leave-one-family-out cross-validation indicating that performance is largely retained across protein families. As a case study, this work focuses on mixed microbial cultures exposed for extended periods to polyethylene, polyethylene terephthalate, and polyurethane substrates. The prevalent species after selective enrichment were functionally characterized, finding Rhodococcus aetherivorans as the most relevant species in two of the five cultures under investigation. Among the top-ranked proteins, several have high structural similarity with known enzymes despite not being identified by sequence similarity search. Moreover, according to metatranscriptomics results, several of these enzymes were found to be expressed at the same level or above that of annotated enzymes, suggesting that they may have functional relevance. Overall, this work highlights the potential of integrating multi-omics with data-driven methods for enzyme discovery and for accelerating the development of biotechnological solutions to plastic pollution.

Biodegradation, Environmental↗

PubMed2004

Hirudo Medicinalis and the plastic surgeon.

Medicinal leech therapy is an ancient craft that dates back to ancient Egypt and the beginnings of civilisation. The popularity of Hirudo Medicinalis has varied throughout history, reaching such a peak in Europe in the early 19th century that supplies were exhausted. During the latter half of the 19th century, their use fell out of favour, as they did not fit in with the emerging concepts of modern medicine. Leeches have enjoyed a renaissance in the world of reconstructive microsurgery during recent years, and their first reported use in alleviating venous engorgement following flap surgery was reported in this journal [M Derganc, F Zdravic, Venous congestion of flaps treated by application of leeches, Br J Plast Surg 13 (1960) 187]. Contemporary plastic and reconstructive surgeons in units throughout the United Kingdom and Ireland continue to use leeches to aid salvage of failing flaps. We carried out a survey of all 62 plastic surgery units in the United Kingdom and the Republic of Ireland to assess the current extent of use, and to investigate current practice. We have shown that the majority of plastic surgery units in the UK and Ireland use leeches post-operatively and that the average number of patients requiring leech therapy was 10 cases per unit per year. Almost all units use antibiotic prophylaxis, but the type of antibiotic and combination used is variable. We outline current practice and suggest a protocol for the use of leeches. Whilst the use of leeches is widespread, the plastic surgery community has progressed little in defining indications for their use or in achieving an accepted protocol for their application in units throughout the UK and Ireland.

Health Care Surveys↗

PubMed2004

Plastic surgery in the undergraduate curriculum: the importance of considering students' perceptions.

As the undergraduate medical curriculum becomes increasingly crowded the competition for time inevitably increases and surgical specialties have decreasing representation. Plastic surgery is regarded with some confusion in terms of its relevance to the generic doctor. Plastic surgeons have no doubt about the relevance of the specialty to undergraduates. Others see this as a very technical specialty dealing with complex reconstructions and surgical interventions or, as a rather indulgent specialty focusing mainly on glamour and cosmesis. This study focuses on students' perceptions of an undergraduate teaching program in plastic surgery. The reality is that highly pressured undergraduates do not have the luxury of time to consider the finer details of the specialties to which they are exposed. Their priority is to pass their examinations and, having addressed that concern, further information becomes an acceptable bonus. The conclusion is that if plastic surgeons are going to gain greater involvement in the undergraduate curriculum they must start with involvement in examinations and assessments. The students will then ensure that adequate and appropriate teaching time is allocated.

Attitude of Health Personnel↗

PubMed2006

Psychiatric assessment of patients with self-inflicted lacerations to the wrist and forearm admitted to a nonpsychiatric ward: the experience of a regional plastic surgery unit.

In 1984, the Department of Health (DoH) recommended that all patients with deliberate self-harm (DSH) must have a mental assessment before discharge. DSH patients, especially those with lacerations to wrist and forearm, are a regular source of admission to plastic surgery units. In Northern Ireland, the regional plastic surgery service is provided at the Ulster Hospital, which does not have an on-site psychiatric department. Consequently, it was often difficult to arrange a psychiatrist assessment for these patients on the ward even when the assessment was required urgently. The objective of this study was to develop and validate a protocol that would ensure that these patients were assessed and followed up for their mental health as recommended by the DoH. In the absence of clear guidelines from the DoH and utilising the existing arrangement between Accident and Emergency (A&E) and the psychiatric services, all referring A&E departments were instructed at the time of referring patients with DSH to wrist and forearm to arrange a psychiatric examination before transferring the patient to the plastic surgery unit. Data were collected retrospectively (August 2002-October 2002) and prospectively (November 2002-October 2003) and comprised demographic features, previous history of self-harm, conduct of the patient in A&E and the ward, length of stay in the hospital and various aspects of psychiatric assessment and follow-up. In total, 42 referrals were made during the period studied. The average age was 28 years with a male to female ratio of 2:1. The average hospital stay was two days. Despite difficulties, our practice was found effective in ensuring psychiatry assessment and follow-up without risking the patient's physical health. The study also highlighted the need for collaboration between plastic surgeons and psychiatrists to improve services in regards to DSH patients.

Adolescent↗