Pharmacokinetics and toxicity of 120-hour continuous-infusion hydroxyurea in patients with advanced solid tumors

This study investigated the thickness of a swollen layer between heat-activated and autopolymerized denture base polymer based on poly(methyl methacrylate) and autopolymerized repair acrylic resin. The repair surfaces of polymerized poly(methyl methacrylate) resin specimens (n = 5) were wet with methyl methacrylate liquid for 0, 0.5, 3, 30, or 60 minutes before the mixed repair resin was applied and polymerized to the surface of the specimen. The specimens were wet ground to a thickness of 0.15 mm, and the repair joint was examined using a light microscope. The thickness of the layer of swollen poly(methyl methacrylate) at the repair joint was measured from the micrographs. Both the type of polymer, ie, heat-activated or autopolymerized, and the wetting time of the repair surface with methyl methacrylate had a significant effect on the thickness of the swollen layer (P < .001). Prolonged wetting time of the repair surface of the autopolymerized poly(methyl methacrylate) increased the thickness of the swollen layer (r = .944, P = .000), but had less effect on the thickness of the swollen layer of heat-activated poly(methyl methacrylate) (r = .391, P = .005). This study suggests that methyl methacrylate diffuses more easily into an autopolymerized poly(methyl methacrylate) than into heat-activated poly(methyl methacrylate) during the repair of denture base polymer.     

Review of the biological response to a novel bone cement containing poly(ethyl methacrylate) and n-butyl methacrylate

This review describes work published independently elsewhere in which the biological reactions to poly(ethyl methacrylate) n-butyl methacrylate (PEMBMA) have been studied. This material has been compared throughout with conventional poly(methyl methacrylate) (PMMA). Butyl methacrylate monomer used in PEMBMA was slightly less toxic than methyl methacrylate monomer used in PMMA when injected intraperitoneally in mice. No differences in cardiorespiratory effects were found between n-butyl and methyl monomer infused intravenously into anaesthetized rabbits. The tissue reaction to the beaded polymers of poly(methyl methacrylate) and poly(ethyl methacrylate) implanted subcutaneously was identical. The surface appearance of the two materials differed significantly when viewed by scanning electron microscopy, showing a series of elevations resembling tightly packed spheres in the case of PMMA, but a smooth surface with only occasional smooth elevations in the case of PEMBMA. Intramuscular implantation showed more fibrous tissue and tissue damage in relation to PMMA cured in situ compared with PEMBMA and there was more bone necrosis and a thicker fibrous tissue layer adjacent to PMMA than PEMBMA when cured intraosseously.     

In vitro studies of poly(methyl methacrylate) adjuvants

Poly(methyl methacrylate) adjuvants, prepared by polymerizing monomeric methyl methacrylate in the presence of influenza virions or by addition of the virions to previously polymerized poly(methyl methacrylate) particles, were studied by means of the hemagglutination test, antibody binding, and electron microscopy. The results indicated that the virions were coated partly when the polymerization was carried out in the presence of the virus, whereas the virions were probably adsorbed when added to polymerized particles.     

Bond strength of six soft denture liners processed against polymerized and unpolymerized poly(methyl methacrylate)

The bond strength of six commercial soft denture liners was evaluated by a two-phase tensile test. The soft denture liners investigated were VinaSoft, Prolastic, Flexor, Molloplast-B, Novus, and SuperSoft. The samples were fabricated by processing them (1) against polymerized poly(methyl methacrylate), and (2) against unpolymerized poly(methyl methacrylate). The soft denture liners were processed according to the manufacturers recommendations. The samples were tested using an Instron Universal Testing Machine. The mode of failure, adhesive or cohesive, was also recorded. The bond strength when processed against unpolymerized poly(methyl methacrylate) ranged from 0.48 to 2.60 MPa, and when processed against polymerized poly(methyl methacrylate) the bond strength ranged from 0.94 to 2.56 MPa. A two-way analysis of variance (P = .05) revealed a significant increase in bond strength when the liners were processed against polymerized poly(methyl methacrylate), except for Novus, which had no change, and VinaSoft, which decreased. The Tukey interval between materials was .22 and between methods of polymerization was .08. Four of the six liners investigated demonstrated increased bond strength when processed against polymerized poly(methyl methacrylate). It was concluded that bonding can be influenced by the processing method.     

The modulation of cellular responses to poly(2-hydroxyethyl methacrylate) hydrogel surfaces: phosphorylation decreases macrophage collagenase production in vitro

We examined the regulation of collagenase production by the monocyte/macrophage THP-1 cell line when these cells were exposed to poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel surfaces with different chemistries and morphologies. Tissue culture modified polystyrene (TCP), used as a control surface, induced the maximum collagenase response. Copolymer hydrogels containing 2-ethoxyethyl methacrylate (EMA) or methyl methacrylate (MMA) also induced a high response, while PHEMA hydrogels induced a low level response and the phosphorylated hydrogel induced no response. This pattern was altered when the morphology of the hydrogels was changed to that of a sponge. The overall enzyme response to the sponge hydrogels was lower than that to the homogeneous hydrogels. Sponges containing EMA and MMA produced low level response relative to the TCP control. PHEMA and phosphorylated sponges produced little and no response respectively. The dramatically reduced enzyme response to phosphorylated surfaces was not a consequence of cell death, and may be a phenomenon related to changes in cell surface charge.     

Hyaline cartilage: in vivo and in vitro assessment with magnetization transfer imaging

PURPOSE: To determine whether the percentage of vertebral lesion filling and the leakage of methyl methacrylate have any clinical significance at follow-up. MATERIALS AND METHODS: Forty percutaneous vertebroplasties were performed for metastases (30 cases) and myeloma (10 cases) in 37 patients. A computed tomographic scan was obtained 1-8 hours after methyl methacrylate injection and was used to assess the percentage of lesion filling by methyl methacrylate and the leakage of methyl methacrylate into the epidural tissues, neural foramina, intervertebral disks, venous plexus, and paravertebral tissue. The results were correlated with those obtained at clinical follow-up. RESULTS: Partial or complete pain relief was sustained in 36 of 37 patients. Pain relief was not proportional to the percentage of lesion filling. Clinical improvement was maintained in most patients. The 15 epidural leaks, eight intradiskal leaks, and two venous leaks of methyl methacrylate had no clinical importance. Two of eight foraminal leaks produced nerve root compression that required decompressive surgery. One of 21 paravertebral leaks produced transitory femoral neuropathy. CONCLUSION: Pain relief can occur despite insufficient lesion filling. In most patients, intradiskal and paravertebral leaks of cement had no clinical importance.     

Cerebrospinal fluid fistula from fractured acrylic cranioplasty plate. Case report

The authors report a patient who developed a cerebrospinal fluid fistula secondary to a fractured methyl methacrylate cranioplasty plate. There was no external evidence of trauma. X-ray films showed no evidence of the fracture. It is suggested that the impregnation of methyl methacrylate with a radiopaque material would result in visualization of such fractures.     

Iodinated methacrylate copolymers as X-ray opaque denture base acrylics

OBJECTIVES: The purpose of this study was to evaluate novel iodinated methacrylate copolymers as X-ray opaque denture base resins. METHODS: The synthesis of specific monomers and suspension copolymerization with methyl methacrylate to produce copolymer beads. The resulting beads were processed in an identical manner to standard PMMA to produce test-pieces for mechanical testing. RESULTS: Samples prepared from beads containing 25 wt% of the iodinated copolymer exhibited an X-ray opacity equivalent to that exhibited by a similar thickness of aluminium. Furthermore, the appearance and mechanical properties were comparable to standard PMMA, while thermal stability proved superior. CONCLUSION: These novel iodinated methacrylate monomers show promise not only as polymerizable additives to methyl methacrylate to produce an X-ray opaque denture base but also as thermally stable copolymerizable additives to other applications where X-ray opacity would be advantageous.     

Leaching and cytotoxicity of formaldehyde and methyl methacrylate from acrylic resin denture base materials

Acrylic resin dentures have the potential to elicit irritation, inflammation, and an allergic response of the oral mucosa. Studies of substances leachable from acrylic resins, their cytotoxicity to cultured cells, and means of reducing their leaching were systematically conducted. Under in vivo and in vitro conditions, formaldehyde and methyl methacrylate were significantly leached into human saliva and saliva-substitute buffer, especially from autopolymerized resins. Both leachable substances showed cytotoxic potentials in the range of their leaching concentrations. Formaldehyde was cytotoxic at lower concentrations than methyl methacrylate. Preleaching in water reduced subsequent leaching of both formaldehyde and methyl methacrylate, and the amount of reduction depended on an increase in the preleaching temperatures. Immersion of acrylic resin dentures in hot water (50 degrees C) before insertion is recommended, especially for autopolymerized resins used either for rebasing or as denture base materials, to minimize the risk of adverse reactions in patients who wear acrylic resin dentures.     

Alterations in nasal sensibility following open rhinoplasty

Scanning electron microscopy (SEM) of methyl methacrylate casts and light microscopy (LM) of tissue are well-established methods for studying the microcirculation. The two are complimentary, but methacrylate is transparent and thus its presence is often not appreciated by LM. Applying histologic stains to sections of tissue embedded in methyl methacrylate would allow the relationships of light microscopic and scanning electron microscopic views of cast vasculature to be better appreciated. We sought to test different stains on cast tissue to find one that would accent the cast. Surgically removed and autopsied human lungs were cast with methacrylate and processed by routine light microscopic methods. They were stained with the hematoxylin and eosin, Masson trichome, elastic--van Gieson, Grocott methenamine silver, Brown-Brennan, and Ziehl-Neelsen methods. The Ziehl-Neelsen procedure stained the methacrylate best, giving it a red color. This procedure also worked well without heating. We conclude that (1) cast methacrylate lung can be processed for routine LM with excellent results; (2) methacrylate stains well with the Ziehl-Neelsen technique; (3) the acid--fast stained cast lung shows capillaries and cells in both normal and diseased lung better than the routine hematoxylin and eosin stain; (4) this technique can be used to assess filling and correlate findings on the same tissue with the two different microscopic methods.     

铕铽混合掺杂聚合物的发光性能与微观形貌

将具有荧光性质的铕、铽以三异丙氧基稀土单一或混合的形式掺入甲基丙烯酸甲酯(MM A)或甲基丙烯酸甲酯与苯乙烯(S t)的混合单体中,形成凝胶,经原位聚合制备铕、铽单一或混合掺杂的PMM A或P(MM A-co-S t)聚合物,研究铕铽混合掺杂对材料发光性能的影响,并观察聚合物的微观形貌。结果表明:铕、铽混合掺杂PMM A或P(MM A-co-S t)中,主要呈现Eu3+的特征荧光,并使Eu3+发射强度显著提高;T b3+544nm处最强的发射峰消失了,而较弱的621nm处的发射峰却显著增强。ESEM显示了掺杂聚合物呈交联网络状的微观形貌。     

Use of 2-isocyanatoethyl methacrylate and iron (II) perchlorate for bonding tri-n-butylborane-initiated luting agents to dentin

The present study investigated the effect of 2-isocyanatoethyl methacrylate (IEM) and iron (II) perchlorate on dentin adhesion. Four primers were evaluated, consisting of aqueous 2-hydroxyethyl methacrylate (HEMA) solutions containing 5, 10, 20 or 50 micromol/g iron (II) perchlorate. Five luting agents were prepared with methyl methacrylate (MMA), poly(methyl methacrylate) (PMMA), tri-n-butylborane (TBB) initiator and IEM. The concentrations of IEM in the luting agents were 0.2, 0.4, 0.8, 2.0 and 4.0 wt%. Extracted bovine teeth were ground to expose the dentin, etched with an aqueous solution of 10 wt% phosphoric acid, primed, and then bonded with stainless-steel rods; tensile bond strengths were determined after 1 d immersion in water. The highest bond strength (20.7 MPa) was recorded for the group using 10 micromol/g iron (II) perchlorate and 2.0 wt% IEM. The use of IEM was effective in decreasing the optimal concentration of iron (II) perchlorate, and this may contribute to the color stability of iron-containing pretreatment agents.     

A new method of acrylic cranioplasty

BACKGROUND: Previous acrylic cranioplasty techniques have relied on wire or suture fixation of the acrylic to the skull. A new methyl methacrylate cranioplasty technique, using acrylic with titanium plating, is described. METHODS: Titanium plates were bent into a "Z" shape and attached to the skull at the perimeter of the skull defect, extending into the defect. The acrylic was then poured into the defect and held in place during setting with a sheet of plastic. The plates are thereby embedded in the acrylic. RESULTS: Standard methyl methacrylate and titanium plates and screws were used to perform a new method of cranioplasty. CONCLUSIONS: A rigid, form-fitting, aesthetic construct can be easily and quickly created. This technique also offers the benefit of allowing secondary craniotomy, if necessary.     

Reinforcement of acrylic resins for provisional fixed restorations. Part I: Mechanical properties

Acrylic resins are commonly used in many dental applications; especially in the fabrication of provisional fixed partial dentures. Among noticed technical drawbacks associated with this material are unsatisfactory mechanical properties. Moreover, if acrylic resins are exposed to moist environment, water sorption results in further mechanical deterioration. In order to improve the mechanical properties, aluminum, magnesium, and zirconium oxide powders and pulverized E-glass particles were separately admixed with pre-polymerized acrylic resin beads prior to mixing with monomer liquid. Particle loading ratios were 1, 2 and 3 vol.% with respect to pre-polymerized beads. Poly(methyl methacrylate), poly(ethyl methacrylate) and poly(isobutyl methacrylate) were used as resin matrices. Furthermore, a metal primer agent was employed in order to form a strong interphase between admixed particles and polymer matrix phase. Samples were subjected to three-point transverse bending tests at a crosshead speed of 10 mm/min. It was concluded that (1) addition of particles generally increases the water sorbed by the composite resins systems, (2) however, two vol.% admixtures in a PMMA resin matrix showed significant improvements in the mechanical properties (p < 0.05), (3) among the oxide particles, zirconia exhibited the greatest improvements in modulus of elasticity, transverse strength, toughness and hardness, and (4) mechanical properties (transverse strength, 0.2% offset yield strength and modulus of elasticity) were linearly correlated to hardness numbers.     

Cauda equina syndrome after spinal anaesthesia in a patient with severe vascular disease

The effect of pendent side-chain length and crosslinking agent concentration in methyl methacrylate/dimethylaminoethyl methacrylate as a polybasic/hydrophobic pH-sensitive hydrogel was studied. Increasing both side-chain length and crosslinking agent concentration decreased the sharpness of response to pH and water-uptake capacity of the polymer. A case-II water transport mechanism and a nonlinear swelling kinetic was observed for the homologues of this hydrogel.     

Long-circulating nanoparticles bearing heparin or dextran covalently bound to poly(methyl methacrylate)

PURPOSE: In a biomimetic approach to the development of drug carriers escaping early capture by phagocytes, nanoparticles made of amphiphilic copolymers of either heparin or dextran and methyl methacrylate were evaluated relative to their in vivo blood circulation time. They were compared to bare PMMA nanoparticles. METHODS: Owing to the fluorescent properties of the covalently attached N-vinyl carbazole, the particles could be detected directly in mouse plasma. Samples were drawn at different time intervals and fluorescence was recorded. RESULTS: After an initial phase of elimination from the blood with a half-life of 5 h, the remaining heparin nanoparticles circulated for more than 48 h and were still detectable in the plasma at 72 h. Dextran nanoparticles were also eliminated very slowly over 48 h. Bare poly (methyl methacrylate) nanoparticles were found to have a half-life of only 3 min. CONCLUSIONS: Both types of nanoparticles proved to be long-circulating. The potent capacity for opsonisation of the poly(methyl methacrylate) core were hidden by the protective effect of either polysaccharide, probably due to a dense brush-like structure. In the case of heparin nanoparticles, the "stealth" effect was probably increased by its inhibiting properties against complement activation.     

Inhibition of parathyroid hormone-stimulated resorption in cultured fetal rat long bones by the main metabolites of ipriflavone

Among 1619 patients suspected of occupational contact dermatitis examined during the years 1990-1994, sensitivity to acrylates was diagnosed in 9 persons (4 dental technicians, 4 dentists, 1 textile printer). Ethyleneglycol dimethacrylate (5 positive patch tests), methyl methacrylate (4), 2-hydroxyethyl methacrylate (4) and triethyleneglycol dimethacrylate (4) were the most common sensitizers. Comparison of patch test results in dental technicians and dentists indicated that dentists were sensitive to a greater number of (meth)acrylate (acrylate and methacrylate) allergens and also to certain other allergens (metals and rubber additives). Dental technicians were sensitive almost exclusively to methacrylates, while the textile printer only to acrylates.     

Studies on blood compatibility of terpolymers composed of methyl methacrylate, methoxypolyethyleneglycol methacrylate, and dimethylsiloxane methacrylate

Terpolymers composed of methyl methacrylate (MMA), polydimethylsiloxane methacrylate (PDMSMA), and methoxypolyethyleneglycol methacrylate (MPEGMA), having different compositions were synthesized. Platelets were not adsorbed onto terpolymer surfaces composed of 50 wt% MMA, 25 wt% PDMSMA and 25 wt% MPEGMA, while on terpolymers with the other compositions, platelet adsorption and fibrin clot were observed. It was shown that PDMS segment was predominant on these terpolymer surfaces via XPS. Receding contact angles of terpolymers, on which no platelet was observed, showed intermediate values between PDMS- and MPEG-rich surfaces. It was suggested that these terpolymers had blood compatibility.     

阴离子交换纤维的制备及应用研究

文中主要研究了以聚丙烯无纺布为基材,丙烯酸为单体,采用预辐照固相接枝聚合的方法制备接枝共聚物,再采用功能化处理的方法制成阴离子交换纤维,并对它在含氰废水中的应用做了初步的研究.     

Effect of cement modulus on the shear properties of the bone-cement interface

Shear tests of the bone-cement interface were performed in vitro using two types of bone cement, standard poly(methyl methacrylate) (PMMA) and a reduced-modulus formulation with poly(butyl methacrylate) beads in a methyl methacrylate matrix (PBMMA). Tests of shear properties were also calculated on cancellous bone and on each cement alone. The tests were done using the Iosipescu shear test method which generates a pure shear force in a zero-moment section of the specimen. With this method, shear properties can be determined at specified locations throughout the specimen. Tests were performed across the entire interface region, specifically in the middle of the region of cement bone interdigitation and at both the bone and cement ends of that region. Ultimate shear strengths and shear moduli were calculated. The shear modulus of the PBMMA is less than 3% that of PMMA. The strength and modulus of cancellous bone had a direct relation to the apparent density of the bone, as did the strength and modulus of the bone-composite interface and the composite region. Strength and modulus were dictated by the bone at the bone-composite interface, and by the cement at the cement composite interface. Through the composite region, the stiffer of the two materials in the composite determined the shear properties. Reduced-modulus bone cement substantially decreases the interfacial shear stresses at the bone-cement interface which should decrease the rate of resorptive bone remodelling at this interface.