Thiodiglycollic acid in neonatal urine: an indication of novel metabolism, not toxic exposure to vinyl chloride.
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Environmental Exposure↗
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Results for “Vinyl Compounds”
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Biomimetic apatite formation on polyethylene photografted with vinyltrimethoxysilane and hydrolyzed.
A photografting technique to produce functional groups of silanol able to induce apatite nucleation was attempted on polyethylene substrate for biomimetic formation of bone-mineral-like apatite layer on its surface. The polyethylene surface was subjected to vapor-phase photografting of vinyltrimethoxysilane and subsequently to hydrolysis. The photografting formed methoxysilyl groups on the polyethylene substrate, which was changed into silanol groups successively by the hydrolysis in a hydrochloric solution. The polyethylene modified in this way formed a dense and homogeneous bone-mineral-like apatite layer in a solution with ion concentrations 1.5 times that of human blood plasma. This result indicates that the biomimetic process in combination with a polymeric grafting technique might provide a homogeneous bone-mineral-like apatite coating even on polymer fibers to be woven into an apatite-polymer composite with three-dimensional structure analogous to that of natural bone.
Apatites↗
Volumetric contraction and methacrylate conversion in photo-polymerized amorphous calcium phosphate/methacrylate composites.
Because of its relatively high solubility in aqueous media and its rapid transformation to hydroxyapatite, amorphous calcium phosphate (ACP) has been utilized as the filler phase of resin-based bioactive composites that have remineralization potential. The objectives of this study were to determine how various methacrylate resins and various types of ACP fillers affect acrylic vinyl conversion and polymerization shrinkage (PS). Several types of photo-crosslinkable resin systems were prepared and admixed with a mass fraction of 40% of either unhybridized, silica- or zirconia-hybridized ACP. After visible light-activated photo-polymerization ACP composites were assessed by near infrared spectroscopy for degree of vinyl conversion and by mercury dilatometry for PS. It was found for these composites that vinyl conversion was independent of filler type but strongly dependent on the type and composition of the resin phase. PS, on the other hand, showed more complex dependence both on the resin type and composition and, in some cases, on the type of ACP. In order to obtain ACP/methacrylate-based composites with maximal vinyl conversion, resin type and composition are of primary importance. However, in order to minimize volume contraction on polymerization it appears necessary to consider both the resin and filler type of these bioactive composites.
Biocompatible Materials↗
Human osteoblast response in vitro to platelet-derived growth factor and transforming growth factor-beta delivered from controlled-release polymer rods.
The purpose of this work was (1) to develop extrudable ethylene-vinyl acetate (EVA) copolymer delivery systems capable of sustained release of bioactive proteins and (2) to determine the effect of platelet-derived growth factor (PDGF-BB) and/or transforming growth factor-beta2 (TGF-beta2) on human osteoblast proliferation and differentiation. Human osteoblasts were plated in vitro and proliferation and protein synthesis assayed at 48 and 96 h. EVA-PDGF rods releasing about 34 ng per ml PDGF per day produced a dramatic early increase in osteoblast proliferation and no effect on protein synthesis. EVA-TGF-beta2 rods releasing about 23 ng per ml per day increased protein synthesis but had no effect on proliferation. PDGF and TGF-beta2 together resulted in moderate increases in proliferation and a marked increase in protein synthesis. Morphologically, PDGF-treated cells became confluent as early as 48 h, while TGF-beta2-treated cells formed into nodules. This work shows that (1) it is possible to deliver physiological levels of bioactive proteins from an extrudable EVA delivery system, and (2) bone cell response is dependent on the sequence and timing of delivery. Controlled-release delivery systems which mimic injury-induced healing cascades may be useful in evaluating the role of various molecules in osseous repair.
Biocompatible Materials↗
Enzymatic synthesis of trehalose esters having lipophilicity.
To improve trehalose lipophilicity, trehalose was regioselectively esterified with vinyl fatty acid esters in dimethyl formamide by protease from Bacillus subtilis to give 6-O-lauroyltrehalose, 6-O-myristoyltrehalose, 6-O-palmitoyltrehalose, 6-O-stearoyltrehalose, 6-O-oleoyltrehalose and 6-O-linoleoyltrehalose. The influence of structural variation by changing fatty acid substitute was examined by measurement of the surface tension and biodegradability.
Bacillus subtilis↗
Enantioselectivity of a recombinant esterase from Pseudomonas fluorescens towards alcohols and carboxylic acids.
A recombinant esterase from Pseudomonas fluorescens (PFE) was produced from E. coli cultures and the enantioselectivity towards a series of racemic substrates was investigated. PFE exhibited high rate and enantioselectivity in the acylation of alpha-phenyl ethanol with vinyl acetate in toluene (E > 100) and the hydrolysis of the corresponding acetate in phosphate buffer (E = 58). In sharp contrast, extremely low enantioselectivity (E from 1.1 to 7) was found for the acylation of a series of 1,2-O-protected glycerol derivatives and the hydrolysis of 3-phenylbutyric acid methylester. Almost no reaction occurred with alpha-phenyl propanol and its acetate and 2-phenylbutyric acid ethylester.
1-Propanol↗
Effect of supersaturation and crystallization phenomena on the release properties of a controlled release device based on EVA copolymer.
This study describes the influence of steroid concentration, manufacturing and storage on the release properties of etonogestrel from polyethylene vinylacetate (EVA) based coaxial fibers. Coaxial fibers were manufactured by extrusion technology. As a consequence of the high extrusion temperatures large amounts of etonogestrel dissolve in the polymeric melt. Since the release from the coaxial fibers is directly proportional to the concentration gradient over the membrane, the amount of dissolved drug that recrystallizes upon cooling is of crucial importance. Therefore crystallization kinetics were studied using thermal analysis and hot stage microscopy. It was found that if the amount of etonogestrel is below a critical nucleation concentration at room temperature, the dissolved steroid remains in a supersaturated state. If on the other hand the amount of dissolved steroid is just above the critical nucleation concentration, the supersaturated steroid recrystallizes very slowly. It is concluded that the release of etonogestrel from an extruded coaxial fiber is a result of a complicated set of parameters, where, respectively process conditions, concentration of etonogestrel and both time and temperature of storage are of importance.
Calorimetry, Differential Scanning↗
Latex: a cause of allergic contact eczema in users of natural rubber gloves.
BACKGROUND: Latex is a common cause of contact urticaria in glove users. We recently found that 1.2% of patients attending a contact dermatitis investigation unit had delayed type hypersensitivity to latex as a cause of eczema. OBJECTIVE: We reassessed the relevant contact allergens in users of natural rubber gloves with hand dermatitis. Particular emphasis was placed on allergens not included in the standard patch test series. METHODS: Consecutive natural rubber glove users with hand dermatitis were investigated for the presence of contact dermatitis and urticaria. RESULTS: One hundred seventeen consecutive patients were tested. The American standard series missed 34% and the European 40% of patients with positive patch test reactions to rubber related chemicals. Six percent of patients (20% of those with a positive reaction) demonstrated delayed type hypersensitivity to latex, often in the absence of other relevant contact allergens and contact urticaria to latex. CONCLUSION: Latex is a relatively common cause of allergic contact eczema in the absence of contact urticaria. Latex should be included in a rubber series for screening patients with hand dermatitis who are glove users.
Adolescent↗
In vitro versus in-use considerations for testing the permeability of gloves.
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Gloves, Protective↗
In-use barrier integrity of gloves: latex and nitrile superior to vinyl.
BACKGROUND: Although gloves manufactured with different materials have comparable barrier properties when removed directly from the box and tested, their actual on-the-job barrier performance may be extremely different. Although effective in static, pre-use conditions, barrier properties may be compromised once challenged by the rigorous hand and finger movements associated with many health care procedures. Gloves are meant to act as barriers, protecting persons by reducing the risk of exposure to bloodborne pathogens. Ineffective barriers or barriers that are easily breached during risk-associated procedures have the potential to place health care professionals at risk. Multiple studies attesting to the barrier attributes of vinyl and latex gloves during varied controlled clinical situations are available. Studies are available that address the permeation characteristics of nitrile, but no studies document the effectiveness of nitrile as a barrier to bloodborne pathogens or compare the barrier effectiveness of nitrile to gloves made of other materials during simulated use or clinical situations. OBJECTIVE: This study was undertaken to compare the barrier integrity of latex, vinyl, and nitrile gloves during controlled, simulated clinical use conditions that were specifically designed to mimic patient care activities. This study compares the performance of gloves made of natural rubber latex, long considered the gold standard; polyvinyl chloride (vinyl), a synthetic copolymer; and nitrile (acrylonitrile butadiene), a recently available synthetic for use in the health care environment. METHODS: A total of 2000 gloves (800 latex gloves, 800 vinyl gloves, and 400 nitrile gloves) were evaluated for baseline determinations in unused gloves and for failure rates after specific simulated use conditions. Potential bias was avoided through strict control of all actions and manipulations. Gloves were graded on a pass or fail system for leaks as defined by American Society for Testing and Materials D5151, Standard Test Method for Detection of Holes in Medical Gloves. To more fully characterize the gloves evaluated, individual products were also tested for physical dimensions (finger and palm thickness), powder levels, total protein (Modified Lowry), and antigenic protein (Latex ELISA [enzyme-linked immunosorbent assay] for Antigenic Proteins). RESULTS: With the exception of one vinyl glove brand with a 12% failure rate, no significant differences in failure rates were detected among the 3 types of gloves when tested directly out of the box with no manipulation. However, after manipulation intended to simulate in-use conditions, vinyl gloves failed 12% to 61% of the time. Latex and nitrile performed significantly better, with failure rates of only 0% to 4% and 1% to 3%, respectively. All latex gloves, with one exception, tested at less than 50 microg/g of total water extractable protein. The antigenic protein levels, with one exception, tested from less than 0.2 microg/g to 5.5 microg/g. The one latex product that fell outside these values had 154 microg/g of total protein and 105.7 microg/g of antigenic protein. CONCLUSIONS: This study indicates that the latex and nitrile gloves evaluated were comparable in terms of barrier performance characteristics both unused and during manipulations mimicking patient care procedures. Whereas stretch vinyl exhibited lower failure rates than standard vinyl, the higher in-use leakage rates associated with all vinyl gloves tested indicate decreased durability and, potentially, compromised barrier protection when this synthetic is used. Careful consideration to the degree of barrier effectiveness should be given before glove selection when the potential exposure to bloodborne pathogens or biohazard risks is a concern.
Equipment Failure↗
Repeatability and reproducibility of determinations of vinyl chloride in foodstuffs.
In the spring of 1978 and the autumn of 1979, two collaborative investigations were carried out with the aim of determining the variability of measurements of the vinyl chloride (VC) content of foodstuffs. The first investigation was a preliminary test on VC standards in N,N-dimethylacetamide. The results of this test were considered to be satisfactory. In a second test, lemonade and oil samples spiked with VC were investigated. The methods used were based on the headspace gas-chromatographic technique. The amount of VC added was 3 micrograms/kg for the lemonade sample and 20 micrograms/kg for the oil sample. The external standard method yielded a reproducibility of 53 and 39% and a repeatability of 18 and 17% for the lemonade and oil, respectively. The corresponding findings with the addition method were a reproducibility of 119 and 40% and repeatability of 33 and 9%.
Chemistry Techniques, Analytical↗
Effects of vinyl chloride exposure alone and in combination with trypan blue--applied systematically during all thirds of pregnancy on the fetuses of CFY rats.
Vinyl chloride (VC) has been shown to be present in the fetal and maternal blood as well as in the amniotic fluid after the exposition of pregnant CFY rats to VC at an atmospheric concentration of 5500, 18 000 or 33 000 mg/m3 (approximately 2000, 7000 or 12 000 ppm) for 2.5 h on the 18th day of pregnancy, indicating the permeability of the placenta to the agent. Teratological investigation of the offspring of pregnant rats exposed continuously to VC at an atmospheric concentration of 4000 mg/m3 air (1500 ppm) during the first, second or last third of pregnancy has shown that VC has no teratological effect in the rat and has no embryotoxic effects either, when applied during the second or last third of pregnancy in the above concentration. Exposition to VC during the first third of pregnancy resulted in an increased fetal mortality and in the manifestation of embryotoxic effects. Fetal losses and induction of central nervous system malformation due to trypan blue administration were not potentiated by a combined exposure of pregnant rats to VC and the dye.
Amniotic Fluid↗
Cytochrome P-450 and the metabolism of vinyl chloride.
The oxidation of vinyl chloride to non-volatile products is dependent on NADPH and microsomal enzymes. The addition of vinyl chloride to microsomes causes a Type 1 spectra shift, similar to that seen for phenobarbital [11[ which indicates the direct involvement of a cytochrome P-450 species; this difference spectrum is characteristic of substrate binding to this type of enzyme. A glutathione conjugate is probably formed, perhaps via a reactive intermediate.
Animals↗
Induction of single-strand breaks in DNA of mice after inhalation of vinyl chloride.
Female mice were exposed to 500 ppm vinyl chloride (VC) for 6 h/day 5 days/week for 1-8 weeks. Groups of mice were killed at different times during this period. DNA damage, expressed as single-strand breaks (SSB), was studied in liver, kidneys, lungs, spleen and brain. The level of SSB increased in liver, kidneys, spleen and lungs with time of exposure and reached a plateau for kidneys and lungs after 80 and 120 h of exposure. In spleen there was only a slight increase in the SSB, and in brain no detectable increase was found.
Animals↗
Regional distribution and kinetics of vinyl acetate hydrolysis in the oral cavity of the rat and mouse.
Vinyl acetate is an ester that is used to make polyvinyl acetate based polymers that are used in the manufacture of latex paints and adhesives. Chronic oral exposure to high concentrations of vinyl acetate induces oral tumors in rodents. Since carboxylesterase-dependent hydrolysis of VA to acetic acid and acetaldehyde has been implicated in the nasal inhalation carcinogenesis of this ester, the potential for oral mucosa of the F344 rat and BDF mouse to hydrolyze VA was examined. Homogenates were prepared by scraping the mucosa from four regions of the oral cavity: dorsal interior (all tissues interior to the teeth), dorsal tongue surface, ventral interior (sublingual area and lower interior tissues) and exterior (all tissues exterior to the teeth). The oral cavity was rinsed once with saline prior to dissection to determine if oral secretions possessed metabolic capacity. Aliquots of the homogenates or rinse fluid were incubated for 30 min with varying concentrations of vinyl acetate (0.05-10 mM), and the production of acetaldehyde was quantitated by HPLC. All tissue regions possessed VA hydrolysis activity. In both species the hydrolysis activity was greatest in the dorsal interior region (Vmax of 90 and 6 nmol/min in the rat and mouse, respectively, Km values of 0.5 and 0.9 mM). Activity in the other oral regions was 2-15-fold lower. Activity was observed in the rinse fluid, but was 20-fold or more lower than the dorsal interior region. Finally, solutions of vinyl acetate were placed in the mouth of anesthetized rats for 10 min and then analyzed for acetaldehyde concentrations. Acetaldehyde was detected in these solutions providing evidence that metabolism of this ester occurs in vivo in oral tissues.
Acetaldehyde↗
Differentiating between local cytotoxicity, mitogenesis, and genotoxicity in carcinogen risk assessments: the case of vinyl acetate.
Understanding the mode of action of carcinogens is critical to scientifically assessing exposure-related risk. Regulatory hazard classification schemes and dose-response assessment paradigms generally require basic knowledge of genotoxic potential to guide decisions on which scheme or paradigm is most appropriate. Although convention suggests that classification and dose-response assessment of genotoxic chemicals should be assessed using conservative assumptions of no threshold, several examples, such as vinyl acetate, exist that challenge this assumption. Vinyl acetate is carcinogenic at portals of entry (nasal cavity and upper gastrointestinal tract). Local metabolism of vinyl acetate produces DNA-reactive acetaldehyde but also produces acetic acid and protons, which contribute to intracellular acidification, cytotoxicity and cell proliferation. This paper reviews their relative contributions to the overall mode of action. Elevated cellular proliferation, well understood to be a risk factor for carcinogenesis, is observed at concentrations associated with tumor formation. Cytotoxicity and compensatory tissue regeneration is one pathway for stimulating cellular proliferation while intracellular acidification is a mitogenic stimulus. Both of these pathways may be operative in nasal tissues while mitogenic proliferation alone appears to be induced in the upper gastrointestinal tract. Using a physiologically-based pharmacokinetic model, quantitative relationships between critical tissue dosimeters and tissue responses are developed to assess the relative importance of genotoxicity and cell proliferation in the overall mode of action of vinyl acetate. This approach supports the concept that intracellular acidification is the sentinel response that precedes cytotoxicity and cellular proliferation. Secondarily, the carcinogenic potential of vinyl acetate is expressed only when tissue exposure to acetaldehyde is high and when cellular proliferation is simultaneously elevated. This mode of action suggests that exposure levels that do not increase intracellular acidification beyond homeostatic bounds will be adequately protective of adverse downstream responses including cancer. These mechanistic insights provide the scientific basis for a cancer classification that incorporates thresholds for cytotoxic and/or mitogenic cell proliferation secondary to intracellular acidification.
Animals↗
In vitro release properties of etonogestrel and ethinyl estradiol from a contraceptive vaginal ring.
The release properties of steroids from a combined contraceptive vaginal ring have been investigated. The product design is based on a coaxial fiber consisting of two types of polyethylene vinylacetate copolymers. Inside the core of the fiber, two steroids are present in a molecularly dissolved state. In order to design a controlled release system with specified release characteristics, values of diffusion coefficient and solubility are required. These data can either be determined during pre-formulation studies on e.g. polymeric flat films or from in-vitro release measurements of the actual coaxial fibers. It can be concluded from this study that polyethylene vinylacetate copolymers exhibit suitable properties to develop a controlled release system with the two steroids etonogestrel and ethinyl estradiol. It has been found that the permeability data obtained in the pre-formulation studies are useful in semi-quantitative terms, but deviate from the permeability data found from the in-vitro release of coaxial fibers. This is most likely due to differences in the polymeric structure of films and coaxial fibers. As a consequence, further studies should be initiated to evaluate the relationship between the manufacturing process and the resulting polymeric structure. It has also been found that the solubility and release of etonogestrel are influenced by the concentration of ethinyl estradiol. By investigating this phenomenon by thermoanalysis, it was shown that the steroids form an eutectic. The lower melting point of the steroids results in an increase in solubility and hence in altered permeability properties.
Chemistry, Pharmaceutical↗
Evaluation of childhood exposure to di(2-ethylhexyl) phthalate from perfusion kits during long-term parenteral nutrition.
Leachability of the plasticizer di(2-ethylhexyl) phthalate (DEHP) from administration sets into intravenous parenteral emulsions containing fat was investigated. DEHP is added to polyvinyl chloride (PVC) to impart flexibility. However, DEHP is a lipid-soluble suspected carcinogen that is hepatotoxic and teratogenic in rodents, and has been shown to leach from PVC products containing lipophilic mixtures. Consequently, total parenteral nutrition (TPN) mixtures containing fat emulsions should be stored in ethylvinyl acetate (EVA) bags rather than PVC packs. However, while TPN bags are made of EVA, they contain PVC-DEHP residues and the lines used between TPN bags and venous catheters are made of PVC-DEHP. The present study quantified the amount of DEHP leached from bags and tubing that could potentially contaminate patients during home TPN. Four types of emulsions containing fat were studied. Levels of DEHP in the bag and at the outlet tubing were measured by high-performance liquid chromatography (HPLC). This was measured during simulated TPN at different times after starting perfusion, 1 day after reconstitution of solutions in the bags, and 1 week later after storage at 4 degrees C. Detectable and stable amounts of DEHP were found to leach from bags (0.2 +/- 0.008 mg to 0.7 +/- 0.02 mg) and DEHP content increased in the outlet tubing (0.8 +/- 0.09 mg to 2 +/- 0.07 mg) during simulated infusions. The same phenomenon was observed after 1 week of storage at 4 degrees C. DEHP extraction by TPN depends on the lipid content of each TPN preparation and the flow rate. These results suggest that children treated with prolonged TPN are regularly exposed to significant amounts of DEHP.
Child↗