Tetramethylthiuram Research Articles

Use of IL-18 production in a human keratinocyte cell line to discriminate contact sensitizers from irritants and low molecular weight respiratory allergens

Assessment of allergenic potential of chemicals is performed using animal models, such as the murine local lymph node assay, which does not distinguish between respiratory and contact allergens. Progress in understanding the mechanisms of skin sensitization, provides us with the opportunity to develop in vitro tests as an alternative to in vivo sensitization testing. The aim of the present study was to evaluate the possibility to use intracellular interleukin-18 (IL-18) production to assess in vitro the contact sensitization potential of low molecular weight chemicals. The human keratinocyte cell line NCTC2455 was used. Cells were exposed to contact allergens (cinnamaldehyde, dinitrochlorobenzene, glyoxal, isoeugenol, p-phenylediamine, resorcinol, tetramethylthiuram disulfide, 2-mercaptobenzothiazole, 4-nitrobenzylbromide), to proaptens (cinnamyl alcohol, eugenol), to respiratory allergens (diphenylmethane diisocyanate, trimellitic anhydride, ammonium hexachloroplatinate) and to irritants (sodium lauryl sulphate, salicylic acid, phenol). Cell associated IL-18 were evaluated 24 later. At not cytotoxic concentrations (cell viability higher of 75%, as assessed by MTT reduction assay), all contact sensitizers, including proaptens, induced a dose-related increase in IL-18, whereas both irritants and respiratory failed. Similar results were also obtained using primary human keratinocytes. Results were reproducible, and the method could be transferred to another laboratory, suggesting the potential use of the test in immunotoxicity testing strategies. Overall, results obtained indicated that cell-associated IL-18 may provide an in vitro tool for identification and discrimination of contact versus respiratory allergens and/or irritants.

Synthesis and reactivity of ruthenium complexes with 1,1′-dithiolate ligands

Reactions of [Ru(PPh 3) 3Cl 2] with ROCS 2K in THF at room temperature and at reflux gave the kinetic products trans-[Ru(PPh 3) 2(S 2COR) 2] (R = n Pr 1, i Pr 2) and the thermodynamic products cis-[Ru(PPh 3) 2(S 2COR) 2] (R = n Pr 3, i Pr 4), respectively. Treatment of [RuHCl(CO)(PPh 3) 3] with ROCS 2K in THF afforded [RuH(CO)-(S 2COR)(PPh 3) 2] (R = n Pr 5, i Pr 6) as the sole isolable products. Reaction of [RuCl 2(PPh 3) 3] with tetramethylthiuram disulfide [Me 2NCS 2] 2 gave a Ru(III) dithiocarbamate complex, [Ru(PPh 3) 2(S 2CNMe 2)Cl 2] ( 7). This reaction involved oxidation of ruthenium(II) to ruthenium(III) by the disulfide group in [Me 2NCS 2] 2. Treatment of 7 with 1 equiv. of [M(MeCN) 4][ClO 4] (M = Cu, Ag) gave the stable cationic ruthenium(III)–alkyl complexes [Ru{C(NMe 2)QC(NMe 2)S}(S 2CNMe 2)(PPh 3) 2][ClO 4] (Q = O 8, S 9) with ruthenium–carbon bonds. The crystal structures of complexes 1, 2, 4·CH 2Cl 2, 6, 7·2CH 2Cl 2, 8, and 9·2CH 2Cl 2 have been determined by single-crystal X-ray diffraction. The ruthenium atom in each of the above complexes adopts a pseudo-octahedral geometry in an electron-rich sulfur coordination environment. The 1,1′-dithiolate ligands bind to ruthenium with bite S–Ru–S angles in the range of 70.14(4)–71.62(4)°. In 4·CH 2Cl 2, the P–Ru–P angle for the mutually cis PPh 3 ligands is 103.13(3)°, the P–Ru–P angles for other complexes with mutually trans PPh 3 ligands are in the range of 169.41(4)–180.00(6)°. The alkylcarbamate [C(NMe 2)QC(NMe 2)S] − (Q = O, S) ligands in 8 and 9 are planar and bind to the ruthenium centers via the sulfur and carbon atoms from the C S and N C double bonds, respectively. The Ru–C bond lengths are 1.975(5) and 2.018(3) Å for 8 and 9·2CH 2Cl 2, respectively, which are typical for ruthenium(III)–alkyl complexes. Spectroscopic properties along with electrochemistry of all complexes are also reported in the paper.

Formulation and curing characteristics of EPDM/NR and EPDM/SBR polyblends used in metallic surfaces rubber lining

AbstractIn this work, a new elastomeric liner was introduced to protect the metal surfaces of storage tanks against corroding materials in petrochemical industries. This new liner was prepared on the basis of EPDM/NR and EPDM/SBR compounds. The elastomeric compounds were cured by using super‐heated water vapor at atmospheric pressure. To increase the rate of curing in these rubber samples, the optimum curing system contained 15 phr sulfur and 1.5 phr mercaptobenzothiazole, 1.5 phr zinc diethyl dithiocarbamate, and 1.8 phr tetramethylthiuram disulfide accelerators. Mechanical tests showed that ultimate tensile strength, elongation at break, and hardness of both polyblend samples were comparable to the SBR/NR blend, which is widely used in the rubber lining of metallic surfaces. In the next step, the chemical resistance of the samples was measured by placing them in a 30 wt % HCl solution. The tensile strength, elongation at break, and weight loss of the samples were measured before and after immersion in HCl. Also, the chemical resistances for EPDM/NR, EPDM/SBR, and SBR/NR samples were qualitatively measured in caustic solution. The cracking, blistering, permeability, and adhesion of the rubber samples to steel surface were observed. Finally, the results showed that EPDM/SBR (70/30) polyblend can be a suitable substitute for conventionally used SBR/NR (50/50) for a successful rubber used to line metallic surfaces. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

THP-1 monocytes but not macrophages as a potential alternative for CD34 + dendritic cells to identify chemical skin sensitizers

Early detection of the sensitizing potential of chemicals is an emerging issue for chemical, pharmaceutical and cosmetic industries. In our institute, an in vitro classification model for prediction of chemical-induced skin sensitization based on gene expression signatures in human CD34 + progenitor-derived dendritic cells (DC) has been developed. This primary cell model is able to closely mimic the induction phase of sensitization by Langerhans cells in the skin, but it has drawbacks, such as the availability of cord blood. The aim of this study was to investigate whether human in vitro cultured THP-1 monocytes or macrophages display a similar expression profile for 13 predictive gene markers previously identified in DC and whether they also possess a discriminating capacity towards skin sensitizers and non-sensitizers based on these marker genes. To this end, the cell models were exposed to 5 skin sensitizers (ammonium hexachloroplatinate IV, 1-chloro-2,4-dinitrobenzene, eugenol, para-phenylenediamine, and tetramethylthiuram disulfide) and 5 non-sensitizers ( l-glutamic acid, methyl salicylate, sodium dodecyl sulfate, tributyltin chloride, and zinc sulfate) for 6, 10, and 24 h, and mRNA expression of the 13 genes was analyzed using real-time RT-PCR. The transcriptional response of 7 out of 13 genes in THP-1 monocytes was significantly correlated with DC, whereas only 2 out of 13 genes in THP-1 macrophages. After a cross-validation of a discriminant analysis of the gene expression profiles in the THP-1 monocytes, this cell model demonstrated to also have a capacity to distinguish skin sensitizers from non-sensitizers. However, the DC model was superior to the monocyte model for discrimination of (non-)sensitizing chemicals.

Composites of High-Density Polyethylene-Elastomer: Analysis by Physico-mechanical Tests and ATR-FTIR Spectrometry

The present work is concerned with the preparation and characterization of some thermoplastic vulcanizates based on high-density polyethylene (HDPE) and ethylene propylene diene terpolymer (EPDM). These blends were obtained in the presence of binary sulfur-free accelerator systems. One of the two components of these energetically active systems was tetramethylthiuram disulfide (TH) and the second was one of the following cure agents: 2-mercaptobenzothiazole (M); N-cyclohexyl benzothiazole-2-sulfenamide (CZ) or 2,2′-dithiobenzothiazole (DM). These properties were correlated with the ATR-FTIR spectra. The samples containing as cure system TH + DM in the weighed ratio 2:1 was found to exhibit better properties, especially tensile strength, modulus 300%, and tear strength.

Cure characteristics and mechanical properties of hydrogenated natural rubber/natural rubber blends

AbstractThe cure characteristics and mechanical properties of blends consisting of hydrogenated natural rubber (HNR) and natural rubber (NR) blends were investigated. The HNR/NR blends at 50/50 wt ratio were vulcanized using various cure systems: peroxide vulcanization, conventional vulcanization with peroxide, and efficient vulcanization with peroxide. The HNR/NR vulcanizates cured by the combination of peroxide and sulfur donor (tetramethylthiuram disulfide, TMTD) in the efficient vulcanization with peroxide exhibited the best mechanical properties. It was also found that the hydrogenation level of HNR did not affect the tensile strength of the vulcanizates. The tensile strength of the blends decreased with increasing HNR content because of the higher incompatibility to cause the noncoherency behavior between NR and HNR. However, the HNR/NR vulcanizate at 50/50 wt ratio showed the maximum ultimate elongation corresponding to a co‐continuous morphology as attested to by scanning electron micrographs. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

A Facile Route for the Synthesis of Poly(N-vinylcarbazole)/Manganese Sulphide Quantum Dots Nanocomposites with Enhanced Optical Properties

This communication describes a facile route for the synthesis of manganese sulphide (MnS) quantum dots (QDs) contained in poly(N-vinyl carbazole) (PNVC) nanocomposites. MnS QDs were synthesized using the single-source precursor method by thermolysing tetramethylthiuram disulfide manganese complex in hexadecylamine (HDA). Two different methods were used for the synthesis of MnS QD incorporated PNVC nanocomposites. The first method entailed the stirring of a mixture of MnS QDs and PNVC in chloroform (CHCl3) at room temperature and the second method was the refluxing of MnS QDs and PNVC solution in CHCl3 at an elevated temperature. A field emission electron microscope (FESEM) study revealed that the dispersion of MnS QDs in a PNVC matrix was improved in the case of nanocomposites prepared by the second method. The optical properties of pure PNVC were significantly altered for the case of nanocomposite prepared by the second route.

Solvent extraction followed by ultraviolet detection for investigation of tetramethylthiuram disulfide at soil-water interface

Tetramethylthiuram disulfide is a widely used pesticide and a soil treatment agent in the agricultural sector. Consequently, its detection in the environment and investigation of the distribution between the aqueous and soil phases would be of highly importance. In this study, the detection of tetramethylthiuram disulfide in CHCl3 was successfully achieved through absorbance measurements at 280 nm, which resulted in linear calibration curves. This detection method was extended for the determination of the partition coefficient (KD) of tetramethylthiuram disulfide between CHCl3 and H2O phases at ambient temperature. The partition coefficient was subsequently used to determine the apparent partition coefficient (KD) of tetramethylthiuram disulfide between sieved soil of diamater < 2.0 mm used for agricultural practices and water where by the quantification of tetramethylthiuram disulfide in water after adsorption equilibrium with soil was achieved through a solvent extraction step of tetramethylthiuram disulfide-contaminated water into CHCl3. The KD determined for an initial tetramethylthiuram disulfide concentration ranging from 3.00 ppm to 10.00 ppm showed a decreasing trend, which leveled off at high concentrations, indicating the strong irreversible adsorption behavior of tetramethylthiuram disulfide on soil at low concentrations. The proposed detection method would have the potential to determine the extent of adsorption of tetramethylthiuram disulfide in soil or its levels in water when tetramethylthiuram disulfide is introduced to soil systems for agricultural practices.

Alkylphenol Disulfide Polymer Accelerators and the Vulcanization of Isobutylene Based Elastomers

Abstract Vulcanization of isobutylene/isoprene copolymer (butyl rubber) using sulfur and organic accelerators is facilitated by the presence of the carbon-carbon double bond in the copolymer isoprenyl unit. The low number of unsaturated monomer units, usually in the order of 2%, has traditionally necessitated use of ultra-fast accelerators such as tetramethyl thiuram disulfide (TMTD) or zinc dimethyldithiocarbamate (ZMDC). Use of such accelerators can result in formation of nitrosamines which may be undesirable. There are a number of alternatives to thiuram and dithiocarbamate cure systems such as use of xanthates and phosphate based accelerators. Alkylphenol disulfide based accelerators also enable attainment of favorable properties when used in butyl and halobutyl compounds. Use of alkylphenol disulfide accelerators in butyl rubber compounds can allow improvement in reversion resistance, adhesion to natural rubber tire casing compounds, and aged property retention. In bromobutyl compounds containing alkylphenol disulfide accelerators in binary (two accelerators) or tertiary (three accelerators) cure systems, adjustment in cure rate to meet specific requirements and aged property retention is possible. This, fifth in a series of studies on the vulcanization of isobutylene elastomers, explores the use of alkylphenol disulfide cure systems for vulcanization of both butyl and bromobutyl rubbers and is intended to provide a starting point for further development work.

Homolytic SS Bond Dissociation of 11 Bis(thiocarbonyl)disulfides R‐C(S)SSC(S)R and Prediction of A Novel Rubber Vulcanization Accelerator

The structures and energetics of eight substituted bis(thiocarbonyl)disulfides (RCS(2))(2), their associated radicals RCS(2)(*), and their coordination compounds with a lithium cation have been studied at the G3X(MP2) level of theory for R = H, Me, F, Cl, OMe, SMe, NMe(2), and PMe(2). The effects of substituents on the dissociation of (RCS(2))(2) to RCS(2)(*) were analyzed using isodesmic stabilization reactions. Electron-donating groups with an unshared pair of electrons have a pronounced stabilization effect on both (RCS(2))(2) and RCS(2)(*). The S-S bond dissociation enthalpy of tetramethylthiuram disulfide (TMTD, R = NMe(2)) is the lowest in the above series (155 kJ mol(-1)), attributed to the particular stability of the formed Me(2)NCS(2)(*) radical. Both (RCS(2))(2) and the fragmented radicals RCS(2)(*) form stable chelate complexes with a Li(+) cation. The S-S homolytic bond cleavage in (RCS(2))(2) is facilitated by the reaction [Li(RCS(2))(2)](+)+Li(+)-->2 [Li(RCS(2))](*+). Three other substituted bis(thiocarbonyl) disulfides with the unconventional substituents R = OSF(5), Gu(1), and Gu(2) have been explored to find suitable alternative rubber vulcanization accelerators. Bis(thiocarbonyl)disulfide with a guanidine-type substituent, (Gu(1)CS(2))(2), is predicted to be an effective accelerator in sulfur vulcanization of rubber. Compared to TMTD, (Gu(1)CS(2))(2) is calculated to have a lower bond dissociation enthalpy and smaller associated barrier for the S-S homolysis.

Complexation of the Vulcanization Accelerator Tetramethylthiuram Disulfide and Related Molecules with Zinc Compounds Including Zinc Oxide Clusters (Zn4O4)

Zinc chemicals are used as activators in the vulcanization of organic polymers with sulfur to produce elastic rubbers. In this work, the reactions of Zn(2+), ZnMe(2), Zn(OMe)(2), Zn(OOCMe)(2), and the heterocubane cluster Zn(4)O(4) with the vulcanization accelerator tetramethylthiuram disulfide (TMTD) and with the related radicals and anions Me(2)NCS(2)(*), Me(2)NCS(3)(*), Me(2)NCS(2)(-), and Me(2)NCS(3)(-) have been studied by quantum chemical methods at the MP2/6-31+G(2df,p)//B3LYP/6-31+G* level of theory. More than 35 zinc complexes have been structurally characterized and the energies of formation from their components calculated for the first time. The binding energy of TMTD as a bidendate ligand increases in the order ZnMe(2)<Zn(OOCMe)(2)<Zn(OMe)(2)<Zn(4)O(4)<Zn(2+). The last two zinc species also form very stable complexes with the radicals Me(2)NCS(2)(*) and Me(2)NCS(3)(*). Dissociation of the TMTD molecule at the S-S bond on reaction with the Zn(4)O(4) cluster is predicted to be strongly exothermic, in sharp contrast to the endothermic S-S bond dissociation of the free molecule. The same holds for tetramethylthiuram trisulfide (TMTT). Surprisingly, the resulting complexes contain Zn-S as well as S-O bonds. The Zn(4)O(4) nanocluster serves here as a model for bulk zinc oxide used as an activator in rubber vulcanization by sulfur. The further uptake of sulfur atoms by the various complexes from S(8) or TMTD with formation of species derived from the radical Me(2)NCS(3)(*) or the trithiocarbamate anion Me(2)NCS(3)(-) is endothermic for mono- and dinuclear zinc dithiocarbamate (dtc) complexes such as [Zn(dtc)(2)] and [Zn(2)(dtc)(4)], but exothermic in the case of polynuclear zinc oxide species containing bridging ligands as in [Zn(4)O(4)(mu-S(2)CNMe(2))] and [Zn(4)O(4)(mu-dtc)]. Therefore, zinc oxide as a polynuclear species is predicted to promote the formation of trisulfido complexes, which are generally assumed to serve as catalysts for the transfer of sulfur atoms during rubber vulcanization. This prediction is in accord with the empirical knowledge that ZnO is a better activator in TMTD-accelerated rubber vulcanization than zinc dithiocarbamate.

Avaliação de bis(4-metilfenilditiocarbimato)zincato(II) de tetrabutilamônio como acelerador em composições de borracha natural

Neste trabalho a substância ZNIBU [bis(4-metilfenilditiocarbimato)zincato(II) de tetrabutilamônio] foi usada em formulações de borracha natural (NR) e o seu efeito como acelerador de vulcanização foi investigado. As composições, vulcanizadas com a substância em questão, foram submetidas a testes mecânicos e os resultados comparados com os de outras composições vulcanizadas com os aceleradores comerciais CBS (N-ciclohexil-2-benzotiazol-2-sulfenamida), TMTD (dissulfeto de tetrametiltiuram) e MBTS (dissulfeto de benzotiazol). Propriedades como dureza, resiliência e densidade foram avaliadas em presença ou não da carga negro de fumo.

Role of p38 MAPK in the selective release of IL-8 induced by chemical allergen in naïve THP-1 cells

At present, the assessment of the allergenic potential of chemicals is carried out using animal models. Over the last decade, several in vitro methods mainly using primary dendritic cells have been proposed to identify the potential of chemicals to induce skin sensitization to meet current animal welfare and public opinions. The major limitations of such tests are the donor-to-donor variability, the low levels in the source, and a possible shortage of human sources. The aim of the present investigation was to establish an in vitro test to identify chemical allergens using the human promyelocytic cell line THP-1 in order to avoid some of these difficulties. We investigated whether the chemokine interleukin-8 or CXCL8 (IL-8) production could provide a methodology for the detection of both respiratory and contact allergens. THP-1 cells were exposed to contact allergens (cinnamaldehyde, dinitrochlorobenzene, nickel sulfate, penicillin G, p-phenylenediamine, tetramethylthiuram disulfide), to respiratory allergens (ammonium hexachloroplatinate, diphenylmethane diisocyanate, trimellitic anhydride) and to irritants (salicylic acid, phenol, sodium lauryl sulphate). Following 48 h of incubation, the release of IL-8 was evaluated by sandwich ELISA. IL-8 production was significantly increased after stimulation with all allergens tested, with the exception of trimellitic anhydride, whereas irritants exposure failed to induce IL-8 release. The lack of IL-8 production by trimellitic anhydride can be explained by the rapid hydrolysis of this chemical in water to trimellitic acid, which is not an allergen. In contrast to IL-8 release, CD54 and CD86 expression did not provide a sensitive method failing to correctly identify approximately 30% of the tested compounds. Although CD86 appears to be a more sensitive marker than CD54 when discriminating allergens from irritants neither of these markers provided robust methodology. We also investigated if a common activation pathway in allergen-induced IL-8 production involving p38 mitogen-activated protein kinase could be identified. By Western blot analysis we could indeed demonstrate p38 activation by all chemical allergens tested and, using the selective p38 MAPK inhibitor SB203580, a significant modulation of allergen-induced IL-8 release could be achieved in all cases. Our data suggests that production of IL-8 by naïve THP-1 cells may represent a promising in vitro model for the screening of potential chemical allergens and activation of p38 MAPK represents a common pathway triggered by allergens.

Oxygen consumption by Daphnia magna straus as a marker of chemical stress in the aquatic environment

Oxygen consumption by Daphnia magna Straus was investigated as a bioindicator for the presence of 11 common aquatic pollutants: Benzo[b]fluoranthene (BbF), mercury(II) chloride (HgCl(2)), 2-dimethoxyphosphinothioylthio-N-methylacetamide (dimethoate), hexachlorocyclohexane (lindane), 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron), 4-chloro-o-tolyloxyacetic acid, bis(tributyltin) oxide (TBTO), carbon tetrachloride (CCl4), tetramethylthiuram disulfide (thiram), 2,4,6-trichlorophenol, and arsenic trioxide (As(2)O(3)). The measurement of oxygen consumption by D. magna was carried out after 15 and 210 min of exposure to the toxicants under controlled laboratory conditions. The technique applied in the present study was found to be useful for the detection of significant changes in oxygen consumption for most toxicants, with the exception of BbF, dimethoate, and CCl4. Significant differences in oxygen consumption were noted, relative to the control treatments, for six of the compounds after only 15 min of exposure. For thiram and TBTO, statistically significant changes in oxygen consumption were recorded after 210 min of exposure. The present results suggest that the measurement of oxygen consumption by D. magna is a useful biomarker and could possibly be used as a biological early warning system for detecting pollutants in the aquatic environment.

Vulcanization of polybutadiene rubber with dipentamethylene thiuram tetrasulfide

AbstractThe cure of polybutadiene rubber (BR) with sulfur donor dipentamethylene thiuram tetrasulfide (DPTT) does not show reversion reaction, in contrast with similar natural rubber compounds. No polysulfure links are formed; whereas a great amount of CC crosslinks are produced. The addition of tetramethyl thiuram monosulfidic (TMTM) strongly affects the crosslinking process. Mechanical properties of the cured compounds are poor. In DPTT, curing of BR the radical species produced through homolitic cleavage of DPTT molecule seems to have sufficient energy to produce crosslinking, via allylic abstraction, and also initiate the polymerization of double bonds producing areas of high crosslinking density that induce early material failure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 106: 3481–3487, 2007

Survival of bio-inoculants on fungicides-treated seeds of wheat, pea and chickpea and subsequent effect on chickpea yield

Survival of Mesorhizobium ciceri (SP4) and Azotobacter chroococcum (CBD-15 and M4) was tested on chickpea (Cicer arietinum) seeds treated with fungicides bavistin [methyl N-(1H-benzimidazol-2yl) carbamate] and thiram (tetramethyl-thiuram disulfide), whereas survival of phosphate solubilizing bacteria (PSB), Pseudomonas striata (27) and Bacillus polymyxa (H5) was examined on two cultivars (Arkel and BV) of pea (Pisum sativum) seeds treated with thiram. Viability of Azotobacter chroococcum (W5) was also examined on wheat (Triticum aestivum) seeds treated with bavistin, captan (cis-N-trichloromethyl thio-4 cyclohexane-1, 2-dicarboximide) and thiram under laboratory conditions using standard dilution and the plate count technique. All the tested strains of diazotrophs and PSB showed decline in their viable population on prolonged contact with fungicides. However, PSB showed variation in their viable population even with the cultivar. BV cultivar of pea seeds showed better recovery of viable P. striata (10.75 to 10.61 log no. of viable cells with in 0-24 hrs) in the presence of thiram, whereas the Arkel cultivar of pea resulted in better recovery of viable B. polymyxa. Azotobacter chroococcum (W5), a potential strain for wheat, showed better survival in the presence of bavistin, compared to thiram and captan. Higher viable population of Mesorhizobium ciceri (SP4) and Azotobacter chroococcum (M4) was recovered from chickpea seeds treated with bavistin compared to thiram. However, thiram-treated seeds resulted in a greater number of extractable Azotobacter chroococcum (CBD-15). Under field conditions, adverse effect of thiram was reflected on the performance of Mesorhizobium ciceri (SP4) and A. chroococcum (M4) strains, resulting in reduced root and shoot biomass and grain yield, compared to bavistin treated and culture inoculated treatment. CBD-15 showed better performance in the presence of thiram compared to bavistin.

Induction of Tibial Dyschondroplasia in Turkeys by Tetramethylthiuram Disulfide (Thiram)

Tibial dyschondroplasia (TD) is a prevalent skeletal abnormality associated with rapid growth rate in many avian species; it causes enormous economic losses and is an animal welfare problem. Tibial dyschondroplasia is characterized by the presence of a nonvascularized, nonmineralized lesion that extends from the epiphyseal growth plate into the metaphysis of the proximal tibiotarsal bones. The mechanisms underlying TD development are not known, although they have been extensively studied in broilers using different induction models. However, an effective model for TD induction in turkeys has never been described. The objective of this study was to establish such a model by using tetramethylthiuram disulfide (thiram), an agent that is frequently used in broilers to induce TD. We found that dramatically longer exposures to much higher concentrations of thiram were required to induce TD in turkeys vs. broilers. In contrast to broilers, in which 50 mg/kg of thiram induces a high incidence of severe TD within 10 d, in turkeys, an exposure to 400 mg/kg of thiram for 11 wk was necessary for the development of severe TD lesions. These results show different mechanisms for TD induction in these 2 closely related species, suggesting differences in TD etiology between them.

Flow and batch systems for copper(II) potentiometric sensing

A new carbon paste electrode modified with tetramethyl thiuram disulfide is prepared to use as copper potentiometric sensor in batch and flow analysis. The influence of pH and carbon paste composition on the potentiometric response is studied. The principal parameters of the flow system are optimized and the detection limits and the selectivity coefficients of the potentiometric sensor are calculated for static and flow mode. In both cases, the sensor shows high selectivity to copper ions but in flow analysis this selectivity is higher. The obtained detection limits are 4.6 × 10 −8 M for batch measurements and 2.0 × 10 −7 M for on-line analysis. The potentiometric sensor is applied to copper(II) determination in real samples in static and flow measurements. In both analysis modes, successful results are obtained.

Induction of Tibial Dyschondroplasia by Carbamate and Thiocarbamate Pesticides

Tibial dyschondroplasia (TD) is a major poultry leg problem, the natural etiology of which is unknown. Certain dithiocarbamate pesticides such as tetramethyl thiuram disulfide (thiram) have been shown to induce the disease in chickens. Because many different carbamate and thiocarbamate chemicals are used in a number of agricultural, industrial, and household applications, the objective of this study was to determine whether all chemicals of these categories induce TD and whether there is a concentration-dependent relationship between the ingestion of these chemicals and the incidences and the severity of the disease. Week-old broiler chicks were fed diets containing thiram or other assorted carbamate and thiocarbamate pesticides mixed in feed for 24-48 hr between ages 8 and 10 days. The birds were killed on day 15 and the proximal tibial and tarsometatarsal growth plates were evaluated for the presence and severity of TD lesions. TD was distinguished by broadening of growth plates; upon histologic exam chondrocytes appeared to be shrunken and dead. When compared by including equimolar concentrations of these chemicals in the feed, the dithiocarbamates with more than two sulfide groups, such as disulfiram, ferbam, thiram, and ziram were potent inducers of TD, whereas those with two sulfides to no sulfide group appeared ineffective at inducing TD. Both thiram and ferbam also reduced the bird's body weights. Thiram increased the incidence and the severity of the disease, denoted by TD index, in a dose-dependent manner. These results suggest that inadvertent contamination of feed or litter with some of these or similar chemicals may cause leg problems in poultry.

Reclaiming of ground rubber tire by a novel reclaiming agent. I. virgin natural rubber/reclaimed GRT vulcanizates

AbstractMechanochemically devulcanized ground rubber tire (GRT) was (re)vulcanized in compositions with virgin natural rubber (NR). The NR/GRT (re)vulcanizates with GRT content from 20 to 60 wt% have been prepared and studied. Reclaiming of GRT was successfully carried out by tetra methyl thiuram disulfide (TMTD) in presence of spindle oil at around ambient temperature. The cure characteristics and mechanical properties of the virgin NR/reclaim GRT blend were studied. The optimum cure time decreases but scorch time remain unaltered with increasing reclaim rubber content in the blend. Effect of carbon black was studied in NR/RR (80/20) blend. Ageing characteristics of different NR/RR blends were evaluated. Scanning electron microscopy (SEM) studies further indicate the coherency and homogeneity in the NR/RR vulcanizate. The dynamic mechanical properties and swelling behavior of NR/RR blend vulcanizates were examined. The elastic and storage modulus of the NR/RR vulcanizates become improve with increasing reclaim rubber content. Electrical properties of NR/RR vulcanizates were also studied. POLYM. ENG. SCI., 47:1091–1100, 2007. © 2007 Society of Plastics Engineers