The sesquiterpene lactone helenalin, which can be isolated from several plant species of the Asteraceae family, is a potent anti-inflammatory and antineoplastic agent. In agreement, alcohol extracts of these plants are used for local external treatment of inflammatory conditions. Since leukotrienes are important mediators in inflammatory processes, the inhibitory effects of helenalin and some derivatives on leukotriene (LT) biosynthesis were studied. Treatment of human platelets with helenalin provoked irreversible inhibition of LTC4 synthase in a concentration- and time-dependent manner with an ic50 of 12 μM after a 60 min preincubation. 11α,13-Dihydrohelenalin acetate was less potent. Interestingly, individual donors could be divided into two distinct groups with respect to the efficacy of helenalin to suppress platelet LTC4 synthase. In human granulocytes, helenalin inhibited both the 5-lipoxygenase (ic50 9 μM after 60 min preincubation) and LTC4 synthase in a concentration- and time-dependent fashion. In contrast, the drug was without effect on LTA4 hydrolase. The GSH-containing adducts (2β-(S-glutathionyl)-2,3-dihydrohelenalin and 2β-(S-glutathionyl)-2,3,11α,13-tetra hydrohelenalin acetate) did not significantly inhibit LTC4 synthase. The present results indicate a mechanism for the anti-inflammatory effect of helenalin and related compounds.

Microbial plaque accumulation on titanium dental implant surfaces can result in an inflammatory condition of the surrounding tissues. Cleaning of such a contaminated surface, in vivo, by means of a solution of amino-alcohol, following surgical exposure, has been proposed. However, the tissue healing following treatment resulted in formation of a fibrous capsule at the tissue-implant interface, i.e. improper implant re-integration. The present experiment was designed to investigate the possible influence of an amino-alcohol solution on machined titanium surface properties. Titanium samples with topography and chemical composition similar to the clinically used Brånemark implant surfaces were used in this experimental in-vitro study to investigate the adsorption of amino-alcohol to such surfaces, and the possibilities to chemically remove the adsorbed alcohols in order to recover a pristine titanium surface. The amino-alcohol solution was supplied to the sample surfaces and four different methods were subsequently used in order to remove the adsorbed alcohol molecules. It was shown that rinsing in water, saline solution, and 5% H2O2 did not remove the amino-alcohol from the surface. However, exposure to ozone produced by using a commercial mercury lamp in ambient air resulted in complete removal of the adsorbed amino-alcohol. The results show that the amino-alcohol used forms a stable and dense film at the implant surface in vitro. Presence of such a film most likely prevents re-integration to occur at the implant-tissue interface in vivo.

Human platelets have been demonstrated to possess leukotriene (LT)-C4 synthase activity and may thus be involved in transcellular 5(S)-hydroxy-6(R)-S-glutathionyl-7,9-trans-11,14-cis-eicosatetraenoic acid (LTC4) synthesis. In this study, platelets from seven different species were screened for LTC4 synthase activity. Very high enzyme activity was observed in suspensions of bovine platelets, with approximately 70% conversion of 5(S)-trans-5,6-oxido-7,9-trans-11,14-cis-eicosatetraenoic acid (LTA4) to LTC4. The capacity of equine platelets to produce LTC4 was similar to that of human platelets. In addition, ovine, rabbit, and rat platelets also produced LTC4 after incubation with LTA4. The results demonstrate that LTC4 synthase activity is a common feature among platelets from various species. In contrast, porcine platelets failed to transform LTA4 to LTC4. Instead, these cells produced 5(S),12(R)-dihydroxy-6,14-cis-8,10-trans-eicosatetraenoic acid (LTB4), indicating the presence of LTA4 hydrolase in porcine platelets. A protein with a molecular mass of approximately 18 kDa and LTC4 synthase activity was solubilised from lyophilised bovine platelet concentrates and purified to near homogeneity by affinity chromatography and gel filtration. The N-terminal amino acid sequence of this protein was analysed and found to be almost identical to the corresponding sequence of human LTC4 synthase (17 of 18 amino acid residues identical). Kinetic analysis of partially purified bovine platelet LTC4 synthase revealed Km (for LTA4) and Vmax values of 3.3 microM and 521 nmol x mg protein(-1) x min(-1), respectively. In addition, the presence of a mRNA transcript encoding LTC4 synthase was demonstrated in equine platelets by reverse transcription (RT) PCR using primers derived from the human LTC4 synthase cDNA sequence. Cloning and sequencing of the PCR fragment corresponding to a region near the N-terminus demonstrated very high identity between equine and human leukotriene-C4 synthase in this region. In summary, the present study establishes that platelets contain LTC4 synthase and indicates that this enzyme is widely distributed among platelets from various species.

A new analytical method for the characterization of sulfur in wood and chemical pulps has been developed. The method involves fractionated pyrolysis using pyrolysis-gas chromatography (Py-GC). In fractionated pyrolysis, the sample is pyrolyzed at different temperatures in order to study particular fractions of the sample and to minimize secondary effects. In the new method, each sample is pyrolyzed at progressively increasing temperatures from 300 to 1350°C and afterwards combusted at 1350°C. The pyrolysis products are separated using a gas chromatograph equipped with a flame photometric detector (FPD) for selective detection of the sulfur-containing pyrolysis products. To develop the suggested new method, the influence of different pyrolysis parameters on the formation of sulfur-containing pyrolysis products from sulfur-treated softwoods was studied. Reference materials such as human protein and wood primary cell wall layer, rich in wood protein, were pyrolyzed in order to understand the formation of sulfur-containing products from different chemical functionalities in the biomolecules. The detection limit of the method is 1 ng.

The formation rates of sulfur dioxide were studied when iron and calcium sulfates were pyrolyzed sequentially at different temperatures in order to calculate the activation energies and frequency factors. These will be used to provide qualitative information concerning the formation of SO2 when different coals are pyrolyzed. It is possible to calculate the pyrolysis temperature needed to degrade the salts totally in a fixed time. In practice the temperature had to be higher to obtain close to 100% conversion, probably due to effects from the platinum filament. The activation energies and frequency factors were 220 ± 5 kJ mol−1 and 1012 s−1 for FeSO4 · 7H2O and 205 ± 5 kJ mol−1 and 107 s−1 for CaSO4 · 2H2O. The yield of sulfur dioxide at different temperatures and the influence of sample size were also studied. Fractionated pyrolyses were carried out in order to quantify the two sulfates in a blend.

The thermal degradation products of four polythiophenes were investigated by using pyrolysis-gas chromatography with a flame ionisation detector (FID) and a sulphur-selective flame photometric detector (FPD). The influence of pyrolysis temperature (550-1400 degrees C) and sample size (5-20 mu g) were studied, and the rates of formation and yields of sulphur and hydrocarbons were determined. At low temperatures most of the sulphur was found as H2S and the most abundant hydrocarbons were hexane and heptene. At high temperatures CS2 and C-1,C-2 hydrocarbons were formed secondarily. Only a very small amount of thiophenes was found. The ratio between the hydrocarbons changed somewhat with sample size, because of a change of the temperature gradient in the sample. Rates of formation for C-6 and C-7 hydrocarbons were the same for the different polythiophenes. The different chemical environment of the thiophenic ring influenced the rate of formation of H2S and the yield of sulphur. The yields of the aromatic and thiophenic hydrocarbons were much less than aliphatics, because of a higher degree of carbonisation for the aromatic and thiophenic hydrocarbons.

Fifteen standard coal samples from the European Centre for Coal Specimens (SBN) were analyzed by pyrolysis-gas chromatography equipped with a flame ionization detector and a name photometric detector (PST-GC(FID/FPD)). The yields of sulfur obtained when coal samples were pyrolyzed and combusted were between 56 and 80% of the total amount of sulfur present. The total amount of sulfur in the pyrolysis products was proportional to the sulfur content of the coals. The data obtained were evaluated with principal component analysis (PCA) and partial least-squares (PLS) regression. Predictive models for the content of total sulfur, organic sulfur, pyritic sulfur, and inorganic sulfur (the sum of pyritic and sulfate sulfur) were built. It was also possible to obtain a predictive model for the content of volatile matter.

The thermal degradation of poly(1,4-phenylene ether—sulfone) (PES), Mw 47000, and of a polysulfone resin (PSR) Mw 75000, was studied by flash-pyrolysis, with a temperature rise time (TRT) of 8 ms. Pyrolysis products were monitored by a pyrolysis-gas chromatography flame ionisation detector/flame photometric detector (Py-GC-FID/FPD) and pyrolysis-gas chromatography mass spectrometry (Py-GC/MS). Special attention was given to the formation of sulphur-containing pyrolysis products. The kinetics of SO2 formation were studied by sequential pyrolysis of PES and PSR. It was possible to differentiate between the rates of formation of SO2 from PES and PSR. The rate of formation of SO2 was somewhat higher for PES than for PSR. The activation energies were 270 and 280 kJ/mol, respectively, and the frequency factors were 1014 and 1015s−1.

A method for determination of a surfactant, sodium dodecyl sulfate (SDS), in the presence of a charged water soluble polymer is presented. SDS was determined by pyrolysis GC using a flame photometric detector. SDS was pyrolyzed at an optimized pyrolysis temperature of 700 degrees C. The SO2 peak was used for quantification of SDS, which was determined in the range between 10 ng and 20 mu g.

The present results demonstrate leukotriene and lipoxin synthesis in human bone marrow and link these findings to biological effects in the same tissue. However, the mechanisms behind the described effects on myeloid progenitor cell growth are presently unknown. It is conceivable that both leukotrienes and lipoxins may act through modulation of endogenous cytokine production. However, it should be noted, that these lipoxygenase products totally failed to induce colony growth in the absence of GM-CSF. Moreover, the role of lipoxins in the bone marrow needs to be further clarified, since LXA4 induced both synergistic (with GM-CSF) and antagonistic (with LTC4) effects on progenitor cell growth. A possible pathophysiological role for leukotrienes and lipoxins may be suggested in chronic myelogenous leukemia. Thus, the capacity of hematological cells from CML patients to synthesize LTC4 was significantly increased. In addition, we have recently reported that CML platelets possessed a markedly decreased ability to participate in transcellular synthesis of the potential inhibitors of myelopoiesis, LXA4 and 5(S),12(S)-diHETE (Stenke et al., 1991b). Moreover, the production of these compounds was totally abolished in platelets obtained from CML patients in blastic crisis. Further studies should aim at defining the mechanisms behind the regulatory actions of leukotrienes and lipoxins in normal and leukemic human myelopoiesis.

An SBN standard coal 136 (20-100 mug) was pyrolysed in order to characterise the sulphur in coal by Py-GC. The sulphur-containing pyrolysis products were separated and detected by a flame photometric detector. Simultaneously, a flame ionisation detector was used to measure the total amount of organic pyrolysis products.The influence of different conditions, sample handling, inertness of the system and pyrolysis temperature on the yield of sulphur was tested.The repeatability was good, even with sample sizes of less than 100 mug. The maximum yield of sulphur was about 40% at pyrolysis temperatures of between 1000 and 1400-degrees-C. When the coal samples were combusted after pyrolysis, an additional 30% was detected. The reason for the low yield is discussed.

Nachrichten aus Chemie, Technik und LaboratoriumVolume 39, Issue 11 p. 1280-1281 Korrespondenz Curie-Punkt versus Platinfilament-Pyrolysatoren Prof. Dr. Inger Ericsson, Prof. Dr. Inger Ericsson Analytical Department University of Lund und Geschäftsführerin von PYROLAB, LundSearch for more papers by this author Prof. Dr. Inger Ericsson, Prof. Dr. Inger Ericsson Analytical Department University of Lund und Geschäftsführerin von PYROLAB, LundSearch for more papers by this author First published: November 1991 https://doi.org/10.1002/nadc.19910391111AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume39, Issue11November 1991Pages 1280-1281 RelatedInformation

The possibilities of using pyrolysis-gas chromatography as a technique for selective determination of polyvinylpyrrolidone (PVP) in trace quantities and the use of an appropriate detector such as a thermionic specific detector (TSD) have been investigated. However, the determination down to 0.2 ppm in the presence of polyhydric alcohols and high hydrophilic polymers such as polyethylene oxide was obtained with a flame ionization detector.

The term “gas chromatography” (GC) implies that the analytes exist in the vapor phase during analysis somewhere within the temperature range employed by the instrumentation. This would include compounds that are quite volatile even at low temperatures, such as small hydrocarbons, fragrances, solvents, and many liquids with low boiling points. It also includes many compounds that are solids or heavy liquids at room temperature but can vaporize at the temperatures used in the GC oven, such as oils, waxes, PAHs, plasticizers, and so on. It specifically does not include polymers, natural or synthetic, since the molecules are too large to volatilize, and GC was never intended for the analysis of such macromolecules.Analytical pyrolysis is one of a family of thermal techniques that permits the introduction of a sample using control of the sample temperature to generate volatiles, without solvents or syringes normally used for GC sample introduction. In the case of pyrolysis, the large molecule is intentionally fragmented to form smaller compounds that are volatile and amenable to GC analysis, creating a pyrogram. This is typically performed very quickly in the GC carrier stream, but can also be done off-line, slowly, in multiple steps, and in reactive atmospheres. This extends the range of sample materials suitable for GC and GC/MS analysis to include complex polymeric systems such as biomass, cross-linked polymers, adhesives, petrochemical fuel sources, sealants, rubbers, textile fibers, paint, ink, and essentially any organic macromolecule.

Different parameters were varied when pyrolysing a low-boiling polyol (b.p. 267°C, 39 mmHg), polybutadiene, polystyrene, poly(methyl methacrylate) and a copolymer of styrene and methyl methacrylate. The parameters varied were the temperature-time profile, the temperature rise time, the ambient temperature, the carrier gas flow-rate, the sample size and the material of the sample holder. The results show that it is not always necessary or even recommendable to pyrolyse under “ideal pyrolysis” conditions. In practice, the pyrolysis conditions should be chosen on the basis of the practical problem to be solved. Therefore, the more possibilities the operator has to change the parameters, the more problems one can solve by studying the qualitative, quantitative, kinetic and catalytic effects of pyrolysis.

AbstractNatural rubber vulcanizates of two formulations, with sulfur/N‐cyclohexyl‐2‐benzothiazolesulfenamide (CBS) and tetramethylthiuram disulfide (TMTD), respectively, were analyzed by pyrolysis gas chromatography. A sulfur‐selective flame‐photometric detector was utilized. The main pyrolysis products were identified as CS2 and some thiophenes. The yields of the pyrolysis products from the two types of rubber were very different. The yields also varied with the curing time of the rubbers.

Samples of polystyrene, cis-1,4-polybutadiene, poly(methyl methacrylate) and poly-acrylonitrile were pyrolysed on filaments made from iron, nickel and platinum. Iron generally gave the highest yields of pyrolysis products. Nickel gave high yields at low temperatures, but at higher temperatures the secondary degradation became important. Platinum generally gave the lowest yields.

The temperature—time profile (TTP) of a pyrolyzer can be checked or determined by pyrolyzing a standard substance, cis-1,4-polybutadiene. This was demonstrated with a home-built and with a commercially available filament pyrolyzer. At low temperatures the TTP of these pyrolyzers can be determined with sequential pulse pyrolyses where the time of the pulse is varied. At high temperatures, when the reaction rate is fast, the yield of pyrolysis products at different pyrolysis time will give information about the temperature rise time of the pyrolyzer.

Samples of polystryrene, polybutadiene and poly(methyl methacrylate) were pyrolysed in amounts from nanograms to miligrams. With a gas cromatograph equipped with a flame-ionization detector it was possible to detec: 1 ng of polystryrene, 10 ng of polybutadiene and 100 ng of poly(methyl methacrylate).

The mean temperature-time profile in a sample has been determined in order to establish whether it is possible to equate the temperature of the pyrolyzer with that of the sample being pyrolyzed. This was done by studying the degradation of cis-1,4-polybutadiene be sequential pyrolysis. The rate of degradation was determined for different amounts (0.5–20 μg) of sample. The temperature dependence of the degradation rate was determined from an Arrhenius plot. The experimental results were combined with theoretically derived expressions for the heating of samples subjected to pyrolysis. The temperature–time profiles of different amounts of sample could then be calculated.