The effect of activity state upon the production of lethalities due to the inhalation of the toxic pyrolysis products of polyacrylonitrile

Hydrogen cyanide is known to be produced upon the pyrolysis of the synthetic material polyacrylonitrile. Cyanide inhibits phosphorylation reactions, therefore, decreasing the amount of high energy bonds available for metabolic use. Since the energy requirements, as well as the respiratory minute volume, for an individual decrease with decreasing activity, it was of interest to investigate whether diminished physical activity would decrease the lethal potential of the pyrolysis products of polyacrylonitrile. In order to produce wide variations in physical activity, male ICR mice were pretreated with either 8.6 mg/kg dextroamphetamine sulfate ip 30 min prior to challenge, 75 mg/kg sodium pentobarbital ip 15 min prior to challenge, or 10 ml/kg of 70 proof ethyl alcohol ip 15 min prior to challenge. Control animals received injections of 10 ml/kg normal saline ip 15 min prior to challenge. Animals were subsequently challenged with the cooled/filtered smoke from the pyrolysis of polyacrylonitrile fibers at 660 C. Increased physical activity decreased the exposure time necessary to produce death. Animals pretreated with amphetamine appear to die more rapidly than control animals due to an increase in respiratory minute volume. Animals pretreated with sodium pentobarbital or ethanol appear to survive through long periods of exposure to the toxic gases due to both a decrease in minute volume and a decrease in energy utilization.

Composites for use in posterior teeth: composition and conversion

The purpose of this investigation was to determine the composition, as well as the conversion after polymerization, of some dental composite materials. Eight posterior composites and two anterior composites were investigated. The weight and volume fractions of inorganic fillers were determined by combustion and pycnometric analyses. The monomers were analyzed qualitatively and quantitatively by high performance liquid chromatography, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Infrared multiple internal reflection spectroscopy was applied for determination of conversion of the methacrylate groups. The conversion in light activated materials was examined at shallow depths, that is, the level of optimal conversion. This investigation demonstrated that the conversion can be correlated with the composition of monomers and oligomers used in the materials.

Polyacrylic acid-metal adhesive bond joint characterization by x-ray photoelectron spectroscopy

The adhesive force to human tooth and metallic restoration of dental cements which contain polyacrylic acid (PAA) is found to be stronger than that of previous cements. Chemical interaction at the interface between metals and carboxylate groups of PAA were studied by x-ray photoelectron spectroscopic method combined with Ar+-ion beam etching technique to examine the mechanism of adhesion. A 2.5 wt% aqueous solution of PAA was painted on the surface of metal plates which are usual elements of dental alloy. Ar+-ion etching was used to scrape off in situ the PAA film coated on the metal plate gradually in the sample chamber of the ESCA equipment. After a few minutes of etching, ESCA spectra were observed. The profile of the spectra and binding energy of 4f5/2 and 4f7/2 levels of Au coated with PAA show little change by the Ar+-ion etching, and remain in the same state as those of uncoated Au. Similar behaviors were obtained in case of Pt. There are three chemical states on Sn plate coated with PAA. The lowest binding energy peak is assigned to pure Sn. The middle one is assigned to SnO2. The highest one corresponds to Sn combined with carboxylate groups of PAA. The chemical reaction corresponding to the highest binding energy peak seems to contribute to the strong adhesive force of these cements to Sn. These aspects of spectra corresponded to McLean's results which showed that these cements had weak adhesion to Au and Pt, but strong adhesive force to tinned Au and Pt.

The effect of resin formulation on the degree of conversion and mechanical properties of dental restorative resins

The goal of this study was to determine the effects of resin formulation variables, such as diluent concentration, catalyst type and concentration and cure mode, on the degree of conversion of carbon double bonds and mechanical properties of dental restorative resins. Diametral tensile strength, compressive strength, hardness, flexural modulus and strength, and dynamic mechanical properties were tested, and the results were correlated to the degree of conversion results obtained by infrared analysis. The results showed a significant correlation between increased mechanical properties and higher degrees of conversion. Enhanced conversions were achieved by incorporating higher diluent and lower inhibitor concentrations into the resins. Ambient temperature properties were similarly enhanced by lower inhibitor concentrations, but were not enhanced by higher diluent concentration. Dynamic mechanical properties testing at oral and elevated temperatures elucidated possible differences in resin microstructure and network quality. The storage moduli decreased over the dental temperature range and was lower at all temperatures for resins with lower conversions. The glass transition temperature was also lower in resins with poorer conversions, suggesting that these resins may be more unstable at oral temperatures than more highly converted resins. Dynamic mechanical properties were most closely correlated to degree of conversion in these polymeric systems.

Intoxication by cyanide in fires: a study in monkeys using polyacrylonitrile

It is suspected that hydrogen cyanide (HCN) may be an important factor in incapacitating fire victims, but the effects of sublethal exposures are not well characterized. Also, the incapacitating effects of fire atmospheres result from exposure to a mixture of toxic products so that the contribution from each component is difficult to determine. The mechanisms of incapacitation in monkeys exposed to the pyrolysis products of polyacrylonitrile (PAN) were compared to those resulting from low level HCN gas exposures. The physiological effects of the PAN atmospheres were almost identical to those of HCN gas alone. They consisted of hyperventilation, followed by loss of consciousness after 1-5 min, bradycardia with arrhythmias and T-wave abnormalities, and were followed by a rapid recovery after exposure. Hydrogen cyanide is considered to be the major toxic product formed by the pyrolysis of PAN. It is suggested that HCN may produce rapid incapacitation at low blood levels of cyanide in fires, while death may occur later due to carbon monoxide poisoning or other factors.

Improved photochemical bonding of composites to dentin using 4-methacryloxyethyl trimellitate anhydride

The main objective was to evaluate the use of 4-methacryloxyethyl trimellitate anhydride (4-META) to improve bonding of composite materials to dentin. Bowen's resin, containing camphoroquinone, was polymerized by exposure to visible light. In composites, made with a silanated silicate, inclusion of 4-META (3%) had little effect in increasing mechanical strength or adhesion to bovine teeth. However, direct application of 4-META via acetone solution was found to be an effective way of increasing tensile adhesive strength; by 240% to dentin (to 7.2 MPa) and by 160% to enamel (to 10.8 MPa). Applying the experience mentioned above, 4-META was used to bond a proprietary photocuring microfilled composite material to Class V cavities in freshly extracted human teeth. After thermal cycling between water baths held at 5 degrees C and 60 degrees C, all dentin restorations without 4-META failed, as judged by marginal leakage of a dyestuff. In contrast, using 4-META there was no leakage in 9 out of 10 cases. In restorations involving enamel, 4-META failed to prevent marginal leakage at the enamel margins but did prevent penetration along the dentin/composite interface. It is concluded that 4-META shows great promise for preventing marginal leakage at dentin/composite interfaces.

[Use of polyacrylate dispersions for nebulization of phenobarbital. 2. In vitro testing of tablets with phenobarbital polyacrylate microspheres]

Using factorial design the authors investigate the qualification of phenobarbital microcapsules with polyacrylate to produce retard tablets. The drug release of the tablets depended significantly on the pressure, the drug concentration and the form of the tablets (microcapsules or corresponding physical mixtures of the ingredients. The drug release from the tablets with microcapsules was more slowly than from tablets with physical mixtures, because there are additional barriers and the formation of a more fixed matrix. The increase of the polyacrylate (from 20 up to 40%) and of the pressure (from 50 up to 100 MPa) inhibits significantly the drug release from the matrices. REM-pictures explain the structure of the tablet surfaces before and after the liberation test.

Protein contaminants of sodium dodecyl sulfate-polyacrylamide gels

Many artifacts and confusing results have arisen following the use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis and highly sensitive detection methods such as silver staining, in vitro iodination, and immunological reactions ("Western blotting"). Investigations into many areas of biology, from proteins tightly bound to DNA to common antigenic determinants of intermediate filaments, may have been affected by this confusion. Some who have suspected contamination believed 2-mercaptoethanol to be the source, but data in this report show that the contaminating proteins are skin proteins, especially keratins ranging from 54 to 57 kDa and 65 to 68 kDa.

Detection of enzymatic activities in sodium dodecyl sulfate-polyacrylamide gels: DNA polymerases as model enzymes

Recent techniques for detecting the catalytic activity of enzymes in sodium dodecyl sulfate (SDS)-polyacrylamide gels have been hampered by lack of reproducibility associated with variability in commercial SDS preparations. Simple expedients which facilitate reproducible detection of DNA polymerase activity and which appear to be widely applicable to detection of other enzymes are reported here. It was observed that reproducibility of a reported procedure for DNA polymerase detection (Spanos, A., Sedgwick, S. G., Yarranton, G. T., Hübscher, U., and Banks, G. R. (1981) Nucl. Acids Res. 9, 1825-1839) depends on the SDS used for electrophoresis, and that sensitivity is markedly reduced if currently available SDS is substituted for the discontinued product specified by Spanos et al. A modified procedure yielding sensitivity with contemporary commercial SDS, which exceeds the sensitivity observed when using the protocol and the SDS originally specified, is described. The modifications employed, which presumably promote renaturation of enzymes, are (1) embedding fibrinogen in gels and (2) washing detergent from gels with aqueous isopropanol after electrophoresis. These expedients permit detection of picogram amounts of Escherichia coli DNA polymerase 1 and its Klenow fragment and nanogram amounts of calf thymus alpha and rat liver (Novikoff hepatoma) beta polymerases. Finally, it is shown that sensitivity of DNA polymerase detection is reduced by lipophilic contaminants in contemporary commercial SDS, and that the expedients employed here mitigate the deleterious effect of these impurities.