bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biological monitoring of arsenic in semiconductor workers
Authors: Aizawa Yoshiharu , Takata Tsutomu , Kurihara Minoru , Tominaga Mamoru , Inoue Yoko 
Published: January 2005

AbstractIn the manufacture of integrated circuits involving semiconductors, various hazardous materials including arsenic compounds are used. This paper present an evaluation of the biological monitoring of arsenic in the urine, blood and hair of semiconductor workers. Eighty‐two blood samples were obtained from research and development workers in a semiconductor factory. Thirty‐one samples of urine were obtained from the same group of worker before and after a work period (one shift). Seventy‐three hair samples were similarly obtained from the workers. The concentration of arsenic in each sample was determined by arsine (AsH3) generation flame atomic absorption spectrometry after wet ashing of the sample. The mean concentration of arsenic in hair in these semiconductor workers was significantly higher than that of controls. The mean concentration of arsenic in hair from workers with a longer employment duration was higher than from those with a shorter employment duration. The mean concentration of arsenic in hair from workers engaged in epitaxial growth processes was higher than from workers engaged in other processes. The concentrations of arsenic in hair from semiconductor workers correlated with the duration of their employment. The mean concentration of arsenic in urine before a work a period (shift) was not significantly different from that of controls. The mean concentration of arsenic in urine after a work period was in fact lower than that of controls. The mean concentration of arsenic in blood was not significantly different from that of controls. The determination of arsenic in hair is therefore considered useful for the evaluation of relatively long‐term exposure to arsenic in semiconductor workers.
The mechanism of cytotoxicity of methylmercury: Inhibition of progression through the S phase of the cell cycle
Authors: Massaro Edward J 
Published: January 2005

AbstractThe effect of methylmercury (MeHg) on progression of the murine erythroleukemic cell (MELC) through the cell cycle was analyzed by flow cytometry (FCM). Exposure in vitro to 5.0‐10.0 μmol dm−3 MeHg for 6h resulted in a dose‐dependent decrease in the rate of cell replication, apparently as a result of inhibition of DNA synthesis (rate of passage through the S phase of the cell cycle). Thus, only a modest accumulation of cells with a G2/M (4n) DNA content was observed. At or above 10 μmol dm−3 MeHg, progression through all phases of the cell cycle was blocked. FCM revealed a dose‐dependent increase in cellular refractive index (90° light scatter), decrease in apparent cell volume (axial light loss), and increase in resistance to non‐ionic detergent (NP‐40)‐mediated cytolysis indicative of fixation (protein denaturation, cross‐linking, etc.) of the plasma membrane/cytoplasm complex. The data indicate DNA synthesis as the primary target of MeHg cytotoxicity.
Exceptionally high in vitro antitumor activity of substituted triphenyltin benzoates including salicylates against a human mammary tumor, MCF‐7, and a colon carcinoma, WiDr
Authors: Gielen M , Willem R , Biesemans M , Bouǎlam M , Khloufi A El , de Vos D 
Published: January 2005

AbstractNine new substituted triphenyltin benzoates of the type Ar3SnOOCC6H2XYZ [X = Y = H, Z = 2‐OCH3 and 4‐F; X = H, Y = 3‐F, Z = 5‐F; X = H, Y = 2‐OH, Z = 5‐Cl, 5‐NH2, 5‐OCH3 and 5‐SO3H; X = 2‐OH, Y = 3‐CH(CH3)2 and Z = 5‐CH(CH3)2] were prepared and possess considerable in vitro antitumor activity against two human tumor cell lines (MCF‐7, a mammary tumor, and WiDr, a colon carcinoma) comparable with that of mitomycin C.
Ethylalumoxanes and ethylchloroalumoxanes as components of catalyst for propylene polymerization
Authors: Pasynkiewicz S , Mańk B 
Published: January 2005

AbstractEthylalumoxanes and ethylchloroalumoxanes as components of Ziegler‐Natta catalysts for polymerization of propylene have been studied. The influence of the degree of hydrolysis of triethyl aluminium [(Et3Al) and diethylaluminium chlorilp (Et2AlCl)2] in the range 0.5–1.5:1 on the activity and the stereospecificity of the catalytic systems was determined (the degree of hydrolysis is defined as the molar ratio H2O/organoaluminium compound). It was found that the activity of the catalytic system ethylalumoxane‐ TiCl4 is a little higher than the activity of the Et2AlCl‐TiCl4 system. The ethylchloroalumoxane‐TiCl4 system is about six times more active than the classical Ziegler‐Natta system. Our studies showed that alumoxanes react with TiCl4 as follows: (a) to form compounds of the AlOTiCl3 type; (b) to exchange alkyl groups for chlorine; (c) to form donor‐acceptor complexes. Reactions of types (b) and (c) occur mainly in the cases of alumoxanes of low degree of hydrolysis (0.5–0.7). In cases of alumoxanes of a degree of hydrolysis equal to 0.7–1.0, reactions of all three types occur, and for alumoxanes of degree of hydrolysis >1.0 reactions of types (a) and (c) are preferred.
Determination of arsenic species by inductively coupled plasma mass spectrometry with ion chromatography
Authors: Kawabata Katsuhiko , Inoue Yoshinori , Takahashi Hiromitsu , Endo Ginji 
Published: January 2005

AbstractFive arsenic species, trimethylarsine oxide, dimethylarsenic acid, monomethylarsonic acid, arsenobetaine and sodium arsenite, in urine were analysed by inductively coupled plasma mass spectrometry with ion chromatography (IC ICP MS).Since the toxicities of different arsenic compounds are different, speciation of arsenic compounds is very important in the investigation of metabolisms. In this paper, we applied ion chromatography (IC) as a separation device and inductively coupled plasma mass spectrometry (ICP MS) as a detection device. For separation of the five arsenic compounds, an anion‐exchange column and, as mobile phase, tartaric acid were used. The eluent from the IC column was introduced directly into the nebulizer of the ICP MS and analysed at 75 amu. Detection limits were from 4 to 9 pg as arsenic.
Butyltin compounds in severn sound, lake huron, canada
Authors: Wong P. T. S. , Whittle D. M. , Chau Y. K. , Brown M. 
Published: January 2005

AbstractSevern Sound is a heavily used recreational and beating area in the southeast corner of Georgian Bay, Lake Huron, Canada. Because of the concern over the possible release of tributyltin species (TBT) from antifouling paints on boat hulls and marinas, surveys were carried out in 1989 and 1992 to determine the presence of this species and its degradation products dibutyltin (DBT) and monobutyltin (MBT) in this area. Many fish (pike and young–of–the–year spottail shiners) and sediment samples collected in 1989 contained detectable levels of TBT. A maximum concentration of TBT was recorded in northern pike in the spring to be 240 ng Sn g−1. Maximum levels occurred in marinas during the beginning of the boating season and significantly reduced during the summer and early autumn, although the maximum value of TBT in sediment (392 ng Sn g−1) was observed in the summer of 1989. The seasonal variation of TBT levels was further substantiated in the subsequent 1992 study, in which sediments from three areas in a marina were sampled at monthly intervals from May to October. TBT levels were much higher in May and then generally decreased with time. Mussels (Elliptio complanta) caged in the marina for three months also contained TBT. DBT was frequently detected in the sediments but less frequently in fish and mussels. MBT was generally below detection limits. Plants (macrophytes and cladophora) contained very small amounts of butyltin compounds.
Ion—Molecule reactions of environmentally significant organotin compounds in a triple quadrupole mass spectrometer system
Authors: Lawson Graham , Ostah Naaman 
Published: January 2005

AbstractTandem MS techniques have been used to examine the formation of cluster ions derived from organotin compounds of environmental significance. The cluster formation was based on the addition of either water or methanol molecules (common HPLC solvents) to a cationic species derived from the organotin compound. For the compounds and conditions studied, cluster adducts were only observed from trisubstituted tin cations. The results show that, in high‐pressure ionization methods used in the interface between HPLC and MS, the tin atom may be associated with a range of ions depending on the system parameters, and that care should be taken if selection ion monitoring (SIM) is to be used.
Stability of alkyl‐lead compounds in blood
Authors: Nygren Olle 
Published: January 2005

AbstractIn order to investigate occupational exposure to various chemicals, blood samples from exposed subjects may be used. Such samples are usually collected locally for transport to an analytical laboratory. It is therefore essential that the necessary transport is performed under such conditions that an adequate stability of the analytes in the samples is maintained. The stability of trimethyl‐ and dimethyl‐lead species in blood at various storage temperatures, as well as the insulation capacity of different transport packages for blood samples, were determined. The results showed that alkyl‐lead compounds in spiked blood stored at room temperature were stable for 6 h and in a refrigerator for up to one week. Only in spiked blood stored at −20°C were the alkyl‐lead compounds found to be stable for more than one month. Blood samples from exposed subjects stored at −20°C were found to be stable for at least two months. One transport package used, found to maintain this temperature of prefrozen samples for up to two days, was a polystyrene transport box filled with crushed dry ice. This packing procedure is therefore recommended for transport of blood samples collected for evaluation of occupational exposure to alkyl‐lead compounds.
Experiences with the analytical procedures for the determination of methylmercury in environmental samples
Authors: Lee Ying‐Hua , Munthe John , Iverfeldt ÅKe 
Published: January 2005

AbstractThe analytical method using ethylation, gas chromatography–cold vapor atomic fluorescence spectroscopy (GC–CV AFS), combined with different pretreatment procedures, has been used for the determination of methylmercury (MeHg) in various aqueous and solid environmental samples. Different types of samples with varying matrices and MeHg concentration levels require different pretreatment procedures in order to isolate/separate MeHg from the sample matrix, and to overcome interferences in the ethylation reaction process. Limitations of different pretreatment procedures (solvent extraction into methylene chloride, distillation under nitrogen flow and alkaline digestion) are discussed and recommendations are given. The influence of the quality of the ethylating reagent on the analytical results is also examined.
Interlaboratory study for the quality control of trimethyl‐lead determination in simulated rainwater and urban dust
Authors: Quevauviller Ph. , Wang Y. , Harrison R. M. 
Published: January 2005

AbstractAn interlaboratory programme has been started within the Measurements and Testing Programme (formerly BCR) of the European Commission to evaluate the performance of analytical techniques used for the determination of trimethyl‐lead in simulated rainwater and urban dust. A first interlaboratory study on solutions was successfully concluded in 1993 and a second exercise was organized, focusing on simulated rainwater and urban dust analysis. This paper reports the results of this second interlaboratory study, which is a preparatory step for a certification campaign of simulated rainwater (with representative contamination levels) and urban dust.
Anti‐Osteoporotic activity of metal complexes of amine carboxyboranes
Authors: Rajendran K. G. , Sood A. , Spielvogel B. F. , Hall I. H. , Norwood V. M. , Morse K. W. 
Published: January 2005

AbstractMetal complexes of trimethylamine carboxyborane successfully suppressed calcium flux from both paired pup calvaria bones and rat UMR‐106 osteosarcoma cultured cells over a 48 h period. These agents increased uptake of calcium into the cell cultures and accelerated [3H]proline incorporation into collagen. Copper and iron complexes of the trimethylamine carboxyborane were more potent compared with the cobalt and chromium complexes. The agents effectively reduced Iysosomal enzyme activity and also proteolytic enzyme activities of macrophages. Since macrophages invade the bone surface and assist in the demineralization and digestion of collagen, those agents may be potentially useful to retard diseases involving bone reconstruction. Influx of white blood cells and macrophages to sites of degradation most probably would be inhibited by the agents, based on sponge test observations in mice. Osteoporosis induced by ovariectomy was minimized by injections of tetrakis[u‐(trimethylamine‐boranecarboxylato)‐bis(trimethylamine‐carboxyborane)dicopper(II)] into rats at 3.5 mg kg−1 day−1 for 14 days. Bone volume, density, weight and calcium content returned to normal baseline control values. In addition, the copper complex returned serum calcium, serum parathyroid hormone (PTH) and vitamin D3 values to normal levels. One possible mode of action of these derivatives is the regulation of the production and release of chemical mediators initiating bone loss, e.g. tumor necrosis factor, TNF α and interleukins 11 or 11‐2.
Negative ion mass spectrometry of organotin compounds—an aid to environmental monitoring?
Authors: Dahm Ralf H. , Lawson Graham , Ostah Naaman 
Published: January 2005

AbstractPositive‐ion mass spectra of organotin compounds include a large number of different ions and therefore the absolute detection level is reduced. Negative‐ion mass spectra are usually less complex and detection levels may therefore be improved. The negative‐ion mass spectra of selected organotin compounds of the type R4Sn, R3SnCI, R2SnCI2 and RSnCl3 were investigated using conventional electron impact ionization conditions. Simplified mass spectra, suitable for compound speciation, were obtained for R3SnCI2 and R2SnCI2 materials but the same fragmentation product SnCI was obtained from all the RSnCI3 samples. R4Sn compounds produced no negative‐ion data in these studies. No significant gains in detection levels were noted but some interesting re‐arrangement reactions leading to the formation of compounds consisting of substituents from the original tin atom were identified. These reactions may be of synthetic importance.
Specific cation effects on the conformation of α‐poly‐L‐glutamic acid
Authors: Jacobson A. L. 
Published: December 2004

AbstractThe effect of the binding of the alkaline earth cations and of cupric and lanthanum ions on the dissociation of the sidechain carboxyl groups in α‐poly‐L‐glutamic acid has been measured by a modified titration technique. The α‐poly‐L‐glutamic acid was pretitrated with the strong base of a weakly bound counterion followed by addition of aliquots of the neutral salt, solution of the more strongly bound counterions. The changes in the ionization of the sidechain carboxyl groups were measured as a function of degree of poly acid pretitrated and the concentration of added salt. These changes were related to the helix‐coil transition in α‐poly‐L‐glutamic acid as a function of degree of ionization. pH titration data were used to delineate the helix, helix‐coil, and pure coil regions in α‐poly‐L‐glutamic acid.For the alkaline earth cations, the binding strength in the helical region is calcium > strontium > magnesium > barium. The more strongly bound cations produced much larger poly acid dissociation with the binding strength alkaline earths ≪ cupric < lanthanum at equivalent ionic strength. All results indicated that the helix conformation promoted ion binding. The binding of the alkaline earth cations in the random coil form was similar to that reported with other coiled polyelectrolytes. The cupric and lanthanum ions appeared to stabilize the helical structure against changes due to increased poly‐acid ionization.
Light‐scattering molecular weight of rabbit myosin A
Authors: Tomimatsu Yoshio 
Published: December 2004

AbstractProper correction of angular light‐scattering data for reflection effects results in agreement between determinations by light scattering and by sedimentation equilibrium of the molecular weight of rabbit myosin A prepared in the same manner. This leaves the question of molecular weight dependence on the method of sample preparation unsettled. Reflection corrections for angular light‐scattering measurements by the more exact Tomimatsu–Palmer (T–P) method are compared to those by the less adequate Sheffer–Hyde (S–H) method.
Reconstruction of protein and nucleic acid sequences. I. Systematics and computer program
Authors: Bradley Dan F. , Merril Carl R. , Shapiro Marvin B. 
Published: December 2004

AbstractThe protein sequences now known have been reconstructed as a kind of intriguing logical‐mathematical puzzle using information about fragments of the molecules. We wish to show that the reconstruction can be done systematically by repeating a series of elementary operations on these same data governed by a set of well‐defined rules. The completely automatic reconstruction of polymer sequences by a high speed digital computer using these operations and rules is demonstrated.
Statistical mechanics of noncovalent bonds in polyamino acids. VIII. Covalent loops in proteins
Authors: Poland Douglas C. , Scheraga Harold A. 
Published: December 2004

AbstractThe effect of covalently crosslinked loops on the entropy of polypeptide chains is discussed. Since the available theory applies to single, independent loops, this theory has been extended to cases where the chains are multiply crosslinked and, therefore, dependent. Multiply crosslinked loops are present in many proteins, e.g., ribonuclease. It is shown that, whereas in general there is a significant difference between the entropy computed with the present treatment of dependent chains and that incorrectly computed by applying the theory of independent chains to multiply crosslinked loops, the difference in the two procedures is not very great for ribonuclease (and well within the uncertainty of our knowledge of the residue conformational entropy) because the chains of ribonuclease are only slightly dependent even though they are multiply crosslinked. Specifically, estimates of the entropy losses per residue are: −0.45 e.u. for chains in a single, independent loop, −0.58 to −0.66 e.u. for dependent chains in multiply crosslinked loops, and −0.51 e.u. for a simplified model of ribonuclease. With this information, a treatment is given of a helix–coil transition in two chains, assumed to be polyglycine, connected at each end by disulfide bonds. The results of a previous theory for short chains are combined here with the results for the entropy loss on loop formation. It is seen that the presence of the loop stabilizes the helical forms (because of the lowering of the entropy of the random state) and broadens the transition (because of the increased importance of intermediate states).
Complexes of silver ion with natural and synthetic polynucleotides
Authors: Daune M. , Dekker C. A. , Schachman H. K. 
Published: December 2004

AbstractA study of silver‐ion binding by nucleic acids and synthetic ribo and deoxyribopolynucleotides, has been carried out by means of potentiometric titration, thermal transition, and difference spectra. It is clearly demonstrated that a strong complex between Ag+ and nitrogen atoms of bases is made reversibly. Binding constants and site numbers are determined for each type of polynucleotide. Base reactivity varies strongly with chain length, and a cooperative phenomenon is found in each case. Two successive complexes with DNA are seen in all the three techniques, and they have the same characteristics as complexes with respectively poly‐dGC and poly dAT. In the first complex, Ag+ is linked to four bases, provided two of them are a G‐C pair. Calculated and experimental values of site numbers agree very well for DNA of different G‐C content. Thermal stabilization occurs simultaneously, and the increase of melting temperature corresponds to calculated changes of stacking energy between base pairs. In the second complex a new ordered structure insensitive to temperature is formed, with simultaneous release of protons. The stoichiometry can be related to base sequence. Complexing with silver increases the resistance of TMV RNA to both temperature and ribonuclease; a tentative explanation is given in the latter case.
Polynucleotide synthesis at oligomeric templates
Authors: Volkenstein M. V. , Fishman S. N. 
Published: December 2004

AbstractThe theory of kinetics of polynucleotide synthesis at oligomeric templates is developed. It is shown that the dependence of oligomer efficacy on its size cannot be explained without taking into account the probability of separation of the oligomer from the growing chain. If such a possibility exists, the maximal size which can be achieved by the growing chain is determined by the ratio of the probability of proposed propagation and of the probability of separation. Without any models of the separation mechanism, the study of experimental kinetic data shows that two such mechanisms exist. Very short oligomers can be easily separated from the growing chain, but there is a critical size of oligomer after which the probability of separation is much smaller. The oligomers whose size is equal to or greater than the critical one form helices with growing chains.
Electronic spectrum, optical activity, and structure of the acridine orange complex with poly‐α,L‐glutamic acid
Authors: Ballard R. E. , McCaffery A. J. , Mason S. F. 
Published: December 2004

AbstractThe electronic absorption and circular dichroism spectra of the complex formed by acridine orange with poly‐α,L‐glutamic acid in the α‐helix conformation have been measured in aqueous solution over a range of glutamate residue‐to‐dye ratios. Three Cotton effects (circular dichroism bands) associated with the long wavelength absorption band of acridine orange at 4950 A. are induced by complex formation between the dye and the polypeptide, and further circular dichroism bands are observed in the ultraviolet region associated with the 2700 A., but not with the 2950 A. absorption band of the dye. The induced optical activity is found to be relatively insensitive to the glutamate residue‐to‐dye ratio and to be more dependent upon the ionic strength of the solution. By Measuring the circular dichroism spectrum of the complex in aqueous solution under streaming conditions with the light propagated along the direction of flow the observed circular dichroism bands are assigned to electronic transitions polarized parallel or perpendicular to the axis of the polypeptide α‐helix. From the spectroscopic data it is inferred that the dye aggregate in the L‐PGA–AO complex has the form of a left‐handed superhelix bound to the core of the right‐handed α‐helix of poly‐α,L‐glutamic acid. It is shown that the longer and the shorter of the in‐plane axes of the dye molecule are probably orientated respectively at a small angle, and radially, with respect to the axis of the α‐helix in the complex.
Protonation of cytosine in DNA
Authors: Zimmer Ch. , Venner H. 
Published: December 2004

AbstractSpectrophotometric acid titrations of DNA samples of different GC content were performed at different wavelengths. From the acid titration profile and absorbance changes of deoxycytidine‐5′‐monophosphate and DNA the extent of protonated cytosine within the DNA double‐stranded molecule was estimated (pK 3.65 at 25°C. in 0.02M KCl). At constant counterion concentration and temperature the maximum of protonated cytosine in DNA before denaturation occurs depends on the base composition and can exceed 50%. The thermal stability of the DNA secondary structure is strongly reduced with increasing amount of ionized cytosine residues. The degree of protonation of cytosine in DNA is decreased with increasing counterion concentration.