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At least 883 records · Page 49Linked to original sources
PubMed1988

Malignant hyperthermia in plastic surgery.

Malignant hyperthermia is a seemingly rare genetic myopathy. Hypermetabolic crisis accompanied by a rise in body temperature to as high as 44 degrees C is its hallmark. Malignant hyperthermia is usually triggered by potent inhalated anesthetics and/or depolarizing muscle relaxants. Because of the extraordinary risk of death in patients who are at risk, plastic surgeons may be reluctant to operate on these patients. Five such patients were referred to the Plastic Surgery Service and the UCLA Malignant Hyperthermia Center for anesthetic and surgical management following plastic surgical procedures aborted for first episodes of malignant hyperthermia. They were anesthetized with nitrous oxide, barbiturates, opiates, tranquilizers, and nondepolarizing muscle relaxants. The patients were not treated prophylactically with dantrolene. Cardiac monitoring, end-tidal pCO2, and rectal temperatures were followed. After completion of their plastic surgical procedures, all five patients had a vastus lateralis muscle biopsy performed and subsequent caffeine/halothane contracture studies completed. The contracture study was positive in all patients studied. No anesthetic or surgical complications were encountered. This study demonstrates that patients at risk of developing malignant hyperthermia crisis can have plastic surgical procedures performed safely while undergoing appropriately selected general anesthesia.

Adult↗
PubMed1986

Stability and availability of cyclosporine stored in plastic syringes.

The stability and availability of cyclosporine from the oral dosage form when stored in plastic syringes were examined. Solutions of cyclosporine were stored in plastic syringes for 28 days at 25 degrees C. Half of the solutions remained in room light, and samples were obtained at 3, 6, and 12 hours and 1, 2, 3, 4, 5, 6, 7, 14, 21, and 28 days. The remaining samples were protected from light, and samples were obtained at 1, 3, 5, 7, 14, 21, and 28 days. Samples stored in plastic were compared with control solutions stored in the original amber bottle. All samples were analyzed for unchanged cyclosporine by high-pressure liquid chromatography. Cyclosporine was stable and completely available from the oral dosage form when stored in plastic syringes for up to 28 days. There was no difference in the stability of cyclosporine between the solutions exposed to room light and those protected from light. Solutions of the oral dosage form of cyclosporine may be stored in plastic syringes without protection from light for up to 28 days.

Chromatography, High Pressure Liquid↗
PubMed1985

Rapid changes in surface antigen expression by blood monocytes cultured in suspension or adherent to plastic.

Cell surface antigens used as markers of in vivo differentiation may not be stable on monocytes maintained under different conditions of in vitro culture. Monocytes were isolated from blood by centrifugation over Percoll or by adherence to plastic dishes, and the cells cultured in suspension or as adherent monolayers. Initially, monocytes obtained by both methods were similar in size, morphology, and surface antigen expression detected with the antimonocyte monoclonal antibodies OKM1, FMC17, PHM2, and PHM3. After culture, cells maintained in suspension were predominantly small, whereas those adherent to plastic rapidly increased in size; however, cytochemical staining for nonspecific esterase and acid phosphatase showed increased enzymic activity by monocytes in both systems, possibly reflecting increased cell maturation. The most striking difference was a substantial loss of FMC17 antigen by most monocytes within four hours in suspension culture, as compared with a qualitative and quantitative increase in expression by plastic adherent cells within two hours. These changes occurred even if the cells were first reacted with lipopolysaccharide. Monocytes taken from suspension culture and allowed to adhere to plastic rapidly synthesized the antigen, a process inhibited by cycloheximide, and conversely, cells removed from plastic progressively displayed decreased FMC17 antigen expression when transferred to suspension culture. No functional role in adherence or phagocytosis has been found for the FMC17 antigen. The results suggest that antigen expression may depend as much on the physical state of the cells as on apparent activation or maturation events.

Acid Phosphatase↗
PubMed1981

Plastic-embedded human marrow biopsy specimens: improved histochemical methods.

Improved methods for processing, sectioning, and staining plastic (glycol methacrylate)-embedded human marrow biopsy specimens were studied. Special stains, including naphthol AS-D-chloro-acetate esterase, PAS, reticulin, and iron, have been modified so that they are suitable for undecalcified, 2-microns-thick, plastic-embedded human marrow biopsy specimens. These adaptations permit plastic-embedded marrow specimens to be used for clinical diagnosis. Marrow biopsy specimens embedded in plastic were compared with biopsy specimens preserved by the conventional paraffin method. The plastic-embedded marrows provide better results from morphologic examination (enhancing diagnostic accuracy), permit assessment of bone as well as of marrow, and allow histochemical analysis to be performed.

Anemia, Aplastic↗
PubMed1983

John Staige Davis: pioneer American plastic surgeon.

John Staige Davis was the first surgeon to devote his entire practice to plastic surgery and worked exclusively for its recognition as a specialty. He wrote the first American text on plastic surgery, published 78 papers on a wide range of subjects in plastic surgery, was the first to establish a formal training program in plastic surgery in 1924, and was the first Chairman of the American Board of Plastic Surgery.

History, 20th Century↗
PubMed1984

Compatibility of paraldehyde with plastic syringes and needle hubs.

The compatibility of paraldehyde with plastic syringes and needle hubs was evaluated. Paraldehyde, USP, was stored in three types of 5-ml syringes: Plastipak, Glaspak, and all glass; the latter type served as the control. At specified times up to 24 hours, the contents of the syringes was evaporated to constant weight, and the residue was weighed. To evaluate the effect of paraldehyde on plastic needle hubs, needles with plastic and metal hubs were immersed in paraldehyde for 24 hours, and the paraldehyde was evaporated. No measurable change in residue weight was noted in any syringes for up to three hours. Compared with the control, there was a significant increase in the average weight of residue in the Glaspak and in the Plastipak syringes at 6, 12, and 24 hours. There was no significant difference in the weight of residue between the Glaspak and Plastipak syringes at those times, however. The amount of residue for the plastic and metal needle hubs was not significantly different. The source of the extractive residue appeared to be the rubber plunger tip. Since the nature of the extractive material in the residue is not known, paraldehyde should be administered in all-glass syringes if possible; other syringe types can be used only if the drug is administered immediately. The use of needles with plastic hubs is acceptable.

Acetaldehyde↗
PubMed1984

Physiological plasticity of single neurons in auditory cortex of the cat during acquisition of the pupillary conditioned response: II. Secondary field (AII).

The discharges of 22 single neurons were recorded in the secondary auditory cortical field (AII) during acquisition of the pupillary dilation conditioned defensive response in chronically prepared cats. All 22 neurons developed discharge plasticity in background activity, and 21/22 cells developed plasticity in their responses to the acoustic conditioned stimulus (CS). Nonassociative factors were ruled out by the use of a sensitization phase (CS and US [unconditioned stimulus] unpaired) preceding the conditioning phase and by ensuring stimulus constancy at the periphery by neuromuscular paralysis. Changes in background neuronal activity were related to measures of behavioral learning or to changes in the level of arousal. Specifically, decreases in background activity (17/22 cells) developed at the time that subjects began to display conditioned responses. Increases in background activity (5/22) developed in animals that became more tonically aroused during conditioning. However, both increases (11/22) and decreases (10/22) in evoked activity developed independently of the rate of pupillary learning, tonic arousal level, or changes in background activity. These findings indicate that changes in background activity are closely related to behavioral processes of learning and arousal whereas stimulus-evoked discharge plasticity develops solely as a consequence of stimulus pairing. A comparative analysis of the effects of conditioning on secondary and primary (AI) auditory cortex indicates that both regions develop neuronal discharge plasticity early in the conditioning phase and that increases in background activity in primary auditory cortex are also associated with elevated levels of tonic arousal. In addition, the overall incidence of single neurons developing learning-related discharge plasticity is significantly greater in AII than in AI. The relevance of these findings is discussed in terms of parallel processing in sensory systems and multiple sensory cortical fields.

Animals↗
PubMed1978

[Use of biological methods in the testing of extracts of plastics (preliminary report)].

In the first part of the paper the problem of toxicological testing of medical plastics is discussed. Particularly attention was given to the biological testing of extracts of plastics. The results of own investigations on the toxicological testing of extracts in water for injection of three types of polyester vascular prostheses, two types of technical rubber and one type of silicon caouthouc are presented. The author presents a proposal of a new testing method for the toxicological evaluation of extracts in water of medical grade plastics utilizing diluted fresh bull's sperm. The results of the preliminary investigations on different materials proved the bull's spermatozoons to be sensitive to even small qualities of toxic substances composed in various medical grade plastic fabrics. In the author's estimation, there is a good reason to ascertain, that the presented method will be a new biololgical test destined to the preliminary evaluation and the current check-up of plastic medical materials.

Animals↗
PubMed1981

[Hygienical assessment of swimming pool water covers made of plastic (author's transl)].

Swimming pool water covers made of different plastics were investigated in laboratory experiments. The possible influence on the chemical and the bacteriological water quality (test bacterium Ps. (fluorescens) was observed. Strong-PVC-plastics proved to have no respectively hardly any chemical or bacteriological influence on the water quality. PE-soft-plastics showed clearly higher chlorine consumption and TOC counts. The influence on bacterial growth was here either inhibition or of nutrient character. A direct colonisation of the plastic was not to be seen--neither in vivo nor in vitro. There are no principal objections against the use of plastics swimming pool covers from hygienical point of view. Some limitating aspects are discussed.

Chlorine↗
PubMed1995

A comparison between the effects of paraffin and plastic embedding of the normal and obstructed minipig detrusor muscle using the optical dissector.

PURPOSE: The purpose of this study was to estimate the relative shrinkage of the normal, obstructed and recovery minipig urinary bladder by comparing tissues from the same bladders embedded in paraffin or plastic. MATERIALS AND METHODS: Optical dissectors were used to make nucleus numerical density estimates in thick paraffin and plastic sections from the same bladder. The ratio of the 2 numerical densities depends only on differences in tissue shrinkage. In 9 minipigs a partial bladder outlet obstruction was created by implanting a 6 to 7 mm. Teflon ring around the proximal urethra. After an obstruction period (median 63 days) the ring was removed and after a recovery period (median 60 days) the animals were sacrificed. Biopsies were taken prior to obstruction, at removal of obstruction, and after recovery and were processed for paraffin and plastic sections to evaluate relative shrinkage. Two control pigs were sham-operated and biopsies taken at the same 3 time points. RESULTS: The optical dissector method was found to be an easy way to estimate the relative shrinkage of paraffin-embedded bladder tissue in proportion to plastic-embedded tissue. Both in human and minipig bladders, paraffin embedding caused a relative shrinkage of about 30% in proportion to plastic embedding. Both the obstructed and recovery detrusor muscles responded to embedding by either method in a manner indistinguishable from the normal bladder. CONCLUSION: When dealing with stereological evaluation of the detrusor muscle, the relative shrinkage of the embedded normal, obstructed and recovery bladder tissue can be ignored.

Animals↗
PubMed1994

Atropine and ephedrine adsorption to syringe plastic.

The purpose of this study was to compare daily changes in the concentration of atropine or ephedrine sulfate solutions that had been stored up to 4 days in plastic or glass syringes. Sets of three plastic and one glass syringe were used for each drug; the glass syringes acted as controls. Each set of syringes was labeled as day 0, 1, 2, 3, or 4. Syringes with medication were laid horizontally, had needles attached, and were stored in the dark at an ambient temperature. Each day, the assigned set of syringes was analyzed by high-performance liquid chromatography. Results showed that the change in the ephedrine sulfate concentration in the plastic syringes from day 0 to day 4 was less than 1.4%. Atropine sulfate decreased 52% over 4 days, with the largest single drop occurring during the first 24 hours. It can be concluded that the two brands of ephedrine sulfate stored up to 4 days at ambient temperature in the brand of syringe used do not significantly decrease in concentration. However, this was not the case with the brand of atropine sulfate studied. The practice of storing atropine sulfate in plastic syringes should be discouraged, because of the possibility of loss of potency due to medication adsorption to syringe plastic.

Adsorption↗
PubMed1994

A spaceflight study of synaptic plasticity in adult rat vestibular maculas.

Behavioral signs of vestibular perturbation in altered gravity have not been well correlated with structural modifications in neurovestibular centers. This ultrastructural research investigated synaptic plasticity in hair cells of adult rat utricular maculas exposed to microgravity for nine days on a space shuttle. The hypothesis was that synaptic plasticity would be more evident in type II hair cells because they are part of a distributed modifying macular circuitry. All rats were shared with other investigators and were subjected to treatments unrelated to this experiment. Maculas were obtained from flight and control rats after shuttle return (R + 0) and nine days post-flight (R + 9). R + 9 rats had chromodacryorrhea, a sign of acute stress. Tissues were prepared for ultrastructural study by conventional methods. Ribbon synapses were counted in fifty serial sections from medial utricular macular regions of three rats of each flight and control group. Counts in fifty additional consecutive sections from one sample in each group established method reliability. All synapses were photographed and located to specific cells on mosaics of entire sections. Pooled data were analyzed statistically. Flown rats showed abnormal posture and movement at R + 0. They had statistically significant increases in total ribbon synapses and in sphere-like ribbons in both kinds of hair cells; in type II cells, pairs of synapses nearly doubled and clusters of 3 to 6 synapses increased twelve-fold. At R + 9, behavioral signs were normal. However, synapse counts remained high in both kinds of hair cells of flight maculas and were elevated in control type II cells. Only counts in type I cells showed statistically significant differences at R + 9. High synaptic counts at R + 9 may have resulted from stress due to experimental treatments. The results nevertheless demonstrate that adult maculas retain the potential for synaptic plasticity. Type II cells exhibited more synaptic plasticity, but space flight induced synaptic plasticity in type I cells.

Acoustic Maculae↗
PubMed1993

Functional plasticity and neurotransmitter receptor binding in the vibrissal barrel cortex.

A form of activity dependent, functional plasticity can be induced in the barrel cortex by sensory deprivation without damage to the sensory receptors. Changes of cortical representation of a spared C3 vibrissa, when all other whiskers were plucked out, were mapped with 2-deoxyglucose autoradiography in mice and rats after a short-lasting deprivation. An increase in the volume of cortical column activated by the spared vibrissa was found already after one week of deprivation. We have found previously that if deprivation is commenced immediately after birth, the changes in cortical representation of the spared whisker appeared in the third week of life. In search of a possible reason for the delayed expression of functional plasticity in neonatal animals we examined the developmental curves of neurotransmitter receptor binding for several transmitters though to be involved in plastic processes of the cerebral cortex. We found that the beta noradrenergic and muscarinic cholinergic receptor binding increased rapidly at the end of the second postnatal week and subsequently remained high. By contrast, the metabotropic glutamate receptor binding decreased during the first month of postnatal development. The AMPA receptors binding values rose during the first two weeks of life, and then decreased. Together with our previous data on the development of NMDA and GABAa receptor and voltage dependent calcium channel binding, the results suggest that slow development of functional plasticity in neonatal animals may be due to low levels of receptors of several neurotransmitters implicated in brain plasticity.

Animals↗
PubMed1996

Experience-dependent plasticity of binocular responses in the primary visual cortex of the mouse.

An activity-dependent form of synaptic plasticity underlies the fine tuning of connections in the developing primary visual cortex of mammals such as the cat and monkey. Studies of the effects of manipulations of visual experience during a critical period have demonstrated that a correlation-based competitive process governs this plasticity. The cellular mechanisms underlying this competition, however, are poorly understood. Transgenic and gene-targeting technologies have led to the development of a new category of reagents that have the potential to help answer questions of cellular mechanism, provided that the questions can be studied in a mouse model. The current study attempts to characterize a developmental plasticity in the mouse primary visual cortex and to demonstrate its relevance to that found in higher mammals. We found that 4 d of monocular lid suture at postnatal day 28 (P28) induced a maximal loss of responsiveness of cortical neurons to the deprived eye. These ocular dominance shifts occurred during a well-defined critical period, between P19 and P32. Furthermore, binocular deprivation during this critical period did not decrease visual cortical responses, and alternating monocular deprivation resulted in a decrease in the number of binocularly responsive neurons. Finally, a laminar analysis demonstrated plasticity of both geniculocortical and intracortical connections. These results demonstrate that an activity-dependent, competitive form of synaptic plasticity that obeys correlation-based rules operates in the developing primary visual cortex of the mouse.

Animals↗
PubMed1995

Instrumentation and setup for endoscopic plastic surgery.

The use of endoscopic techniques mandates the need for basic understanding of endoscopic instrumentation and operating room setup in order to avoid procedural delays and surgeon frustration. The electronic systems for endoscopic surgery-cameras, light sources, monitors, and so on-have been well developed for other specialties and are fully adaptable to endoscopic plastic surgical procedures. Hand instruments, however, are in the early phases of refinement for subcutaneous plastic surgical procedures and will undoubtedly improve over the next several years. Adaptation of existing instrumentation and development of new operating tools continue and promise to make endoscopic plastic surgical procedures of the future more ergonomic and efficient. Similarly, while operating room setup for endoscopic plastic surgical procedures varies depending on individual circumstances, application of a few basic principles will help in making this step quick and simple. The knowledge and experience of scrub technicians and nurses experienced in endoscopic techniques can be invaluable to the surgeon just beginning to use endoscopic techniques in plastic and reconstructive surgery.

Endoscopy↗
PubMed1997

Amygdalar lesions block discriminative avoidance learning and cingulothalamic training-induced neuronal plasticity in rabbits.

Learning to fear dangerous situations requires the participation of neurons of the amygdala. Here it is shown that amygdalar neurons are also involved in learning to avoid dangerous situations. Amygdalar lesions severely impaired the acquisition of acoustically cued, discriminative instrumental avoidance behavior of rabbits. In addition, the development of anterior cingulate cortical and medial dorsal thalamic training-induced neuronal plasticity in the early stages of behavioral acquisition was blocked in rabbits with lesions. The development of training-induced neuronal plasticity in the medial dorsal and anterior thalamic nuclei in late stages of behavioral acquisition was also blocked in rabbits with lesions. These results indicate that the integrity of the amygdala is essential for the establishment of both early and late training-induced cingulothalamic neuronal plasticity. It is hypothesized that amygdalar training-induced neuronal plasticity in the initial trials of conditioning represents a substrate of learned fear, essential for the early and late cingulothalamic plasticity that is involved in mediation of acquisition of the instrumental avoidance response.

Amygdala↗
PubMed1998

Effects of the metabotropic glutamate receptor antagonist MCPG on phosphoinositide turnover and synaptic plasticity in visual cortex.

The neurotransmitter glutamate, in addition to activating ligand-gated ion channels, also stimulates phosphoinositide (PI) hydrolysis in neurons by activating a group of G-protein-coupled metabotropic glutamate receptors (mGluRs). A role for mGluRs in synaptic plasticity originally was hypothesized based on the observation that the developmental decline in glutamate-stimulated PI turnover is well correlated with the decline in experience-dependent synaptic plasticity in visual cortex. Over the past few years, the compound alpha-methyl-4-carboxyphenylglycine (MCPG) has been widely used to test the role of PI-coupled mGluRs in a number of types of synaptic plasticity, including long-term potentiation (LTP), long-term depression (LTD), ocular dominance plasticity in visual cortex, and the neural plasticity underlying learning and memory. The conclusions of most of these studies were based on the assumption that MCPG blocks the actions of glutamate at PI-coupled mGluRs in the cerebral cortex. Here we show that this assumption is not valid in visual cortex. Although MCPG does antagonize the actions of the synthetic mGluR agonist 1S, 3R-aminocyclopentane-1,3-dicarboxylic acid, it fails to block PI turnover and changes in spike adaptation stimulated by glutamate, the endogenous mGluR ligand. In addition, we find that MCPG fails to block the NMDA receptor-dependent forms of LTP, LTD, and depotentiation in visual cortex.

Action Potentials↗
PubMed1998

Modulation of plasticity in human motor cortex after forearm ischemic nerve block.

Deafferentation leads to cortical reorganization that may be functionally beneficial or maladaptive. Therefore, we were interested in learning whether it is possible to purposely modulate deafferentation-induced reorganization. Transient forearm deafferentation was induced by ischemic nerve block (INB) in healthy volunteers. The following five interventions were tested: INB alone; INB plus low-frequency (0.1 Hz) repetitive transcranial magnetic stimulation of the motor cortex ipsilateral to INB (INB+rTMSi); rTMSi alone; INB plus rTMS of the motor cortex contralateral to INB (INB+rTMSc); and rTMSc alone. Plastic changes in the motor cortex contralateral to deafferentation were probed with TMS, measuring motor threshold (MT), motor evoked-potential (MEP) size, and intracortical inhibition (ICI) and facilitation (ICF) to the biceps brachii muscle proximal to the level of deafferentation. INB alone induced a moderate increase in MEP size, which was significantly enhanced by INB+rTMSc but blocked by INB+rTMSi. INB alone had no effect on ICI or ICF, whereas INB+rTMSc reduced ICI and increased ICF, and conversely, INB+rTMSi deepened ICI and suppressed ICF. rTMSi and rTMSc alone were ineffective in changing any of these parameters. These findings indicate that the deafferented motor cortex becomes modifiable by inputs that are normally subthreshold for inducing changes in excitability. The deafferentation-induced plastic changes can be up-regulated by direct stimulation of the "plastic" cortex and likely via inhibitory projections down-regulated by stimulation of the opposite cortex. This modulation of cortical plasticity by noninvasive means might be used to facilitate plasticity when it is primarily beneficial or to suppress it when it is predominately maladaptive.

Adult↗