The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Miriam Rossi - One of the best experts on this subject based on the ideXlab platform.
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Taurolidine Antiadhesive Properties on Interaction with E. coli; Its Transformation in Biological Environment and Interaction with Bacteria Cell Wall
PLOS ONE, 2010Co-Authors: Francesco Caruso, James W. Darnowski, Cristian Opazo, Nina Kishore, Elin S. Agoston, Alexander Goldberg, Miriam RossiAbstract:The taurine Amino-Acid Derivative, taurolidine, bis-(1,1-dioxoperhydro-1,2,4-thiabiazinyl–4)methane, shows broad antibacterial action against gram-positive and gram-negative bacteria, mycobacteria and some clinically relevant fungi. It inhibits, in vitro, the adherence of Escherichia coli and Staphylococcus aureus to human epithelial and fibroblast cells. Taurolidine is unstable in aqueous solution and breaks down into Derivatives which are thought to be responsible for the biological activity. To understand the taurolidine antibacterial mechanism of action, we provide the experimental single crystal X-ray diffraction results together with theoretical methods to characterize the hydrolysis/decomposition reactions of taurolidine. The crystal structure features two independent molecules linked through intermolecular H-bonds with one of them somewhat positively charged. Taurolidine in a biological environment exists in equilibrium with taurultam Derivatives and this is described theoretically as a 2-step process without an energy barrier: formation of cationic taurolidine followed by a nucleophilic attack of O(hydroxyl) on the exocyclic C(methylene). A concerted mechanism describes the further hydrolysis of the taurolidine Derivative methylol-taurultam. The interaction of methylol-taurultam with the diAminopimelic NH2 group in the E. coli bacteria cell wall (peptidoglycan) has a negative ΔG value (−38.2 kcal/mol) but a high energy barrier (45.8 kcal/mol) suggesting no reactivity. On the contrary, taurolidine docking into E. coli fimbriae protein, responsible for bacteria adhesion to the bladder epithelium, shows it has higher affinity than mannose (the natural substrate), whereas methylol-taurultam and taurultam are less tightly bound. Since taurolidine is readily available because it is administered in high doses after peritonitis surgery, it may successfully compete with mannose explaining its effectiveness against bacterial infections at laparoscopic lesions.
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Taurolidine antiadhesive properties on interaction with E. coli; Its transformation in biological environment and interaction with bacteria cell wall
PLoS ONE, 2010Co-Authors: Frank Caruso, James W. Darnowski, Cristian Opazo, Nina Kishore, Elin S. Agoston, Alexander Goldberg, Miriam RossiAbstract:The taurine Amino-Acid Derivative, taurolidine, bis-(1,1-dioxoperhydro-1,2,4-thiabiazinyl-4)methane, shows broad antibacterial action against gram-positive and gram-negative bacteria, mycobacteria and some clinically relevant fungi. It inhibits, in vitro, the adherence of Escherichia coli and Staphylococcus aureus to human epithelial and fibroblast cells. Taurolidine is unstable in aqueous solution and breaks down into Derivatives which are thought to be responsible for the biological activity. To understand the taurolidine antibacterial mechanism of action, we provide the experimental single crystal X-ray diffraction results together with theoretical methods to characterize the hydrolysis/decomposition reactions of taurolidine. The crystal structure features two independent molecules linked through intermolecular H-bonds with one of them somewhat positively charged. Taurolidine in a biological environment exists in equilibrium with taurultam Derivatives and this is described theoretically as a 2-step process without an energy barrier: formation of cationic taurolidine followed by a nucleophilic attack of O(hydroxyl) on the exocyclic C(methylene). A concerted mechanism describes the further hydrolysis of the taurolidine Derivative methylol-taurultam. The interaction of methylol-taurultam with the diAminopimelic NH(2) group in the E. coli bacteria cell wall (peptidoglycan) has a negative DeltaG value (-38.2 kcal/mol) but a high energy barrier (45.8 kcal/mol) suggesting no reactivity. On the contrary, taurolidine docking into E. coli fimbriae protein, responsible for bacteria adhesion to the bladder epithelium, shows it has higher affinity than mannose (the natural substrate), whereas methylol-taurultam and taurultam are less tightly bound. Since taurolidine is readily available because it is administered in high doses after peritonitis surgery, it may successfully compete with mannose explaining its effectiveness against bacterial infections at laparoscopic lesions.
Toshihiko Kasahara - One of the best experts on this subject based on the ideXlab platform.
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development of photo Amino Acid Derivative reactivity assay a novel in chemico alternative method for predicting photoallergy
Journal of Applied Toxicology, 2020Co-Authors: Yusuke Yamamoto, Sayaka Wanibuchi, Yasuhiro Katsuoka, Masaharu Fujita, Ayako Sato, Toshihiko KasaharaAbstract:: Photoallergy test of cosmetics and several types of pharmaceutical substances is often necessary for obtaining approval from authorities. However, there are no official test guidelines for photoallergy evaluation. Therefore, we tried to establish a photoallergy test by utilizing an in chemico alternative sensitization method, Amino Acid Derivative reactivity assay (ADRA). To determine the criteria for judging the photoallergy potential, photo-ADRA with or without photoirradiation was performed using 60 photoallergenic chemicals, and cysteine and lysine Derivatives were detected using high-performance liquid chromatography either by absorbance or fluorescence measurement. The accuracy of prediction was 81.4% (48 of 59) and 80.0% (48 of 60) using the absorbance and fluorescence methods, respectively. However, as chemicals can breakdown into multiple chemicals during photoirradiation, the absorbance method often cannot perform accurate detection due to co-elution, whereas the fluorescence method can do this due to lack of co-elution. Moreover, all eight chemicals that were found to be negative or false-positive for photoirritation in the 3T3 neutral red uptake phototoxicity test were confirmed as positive for photoallergy using this method. Furthermore, we prepared three types of pseudo-mixtures where we added one photoallergen along with five nonphotoallergens and performed the photo-ADRA by the ultraviolet and fluorescence methods. The result of the fluorescence method was almost the same as that obtained with the use of a single photoallergen and hence the outcome was not affected by the mixture. Thus, this study not only showed a method of evaluating the photoallergy potential of a single chemical but also a mixture, making it useful as an in chemico photoallergy alternative test.
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expanding the applicability of the Amino Acid Derivative reactivity assay determining a weight for preparation of test chemical solutions that yield a predictive capacity identical to the conventional method using molar concentration and demonstratin
Journal of Pharmacological and Toxicological Methods, 2019Co-Authors: Yusuke Yamamoto, Sayaka Wanibuchi, Yasuhiro Katsuoka, Masaru Fujita, Toshihiko KasaharaAbstract:Abstract Introduction The Amino Acid Derivative reactivity assay (ADRA) is a novel in chemico alternative to animal testing for assessment of skin sensitization potential. The conventional ADRA protocol stipulates that test chemical solutions should be prepared to a specific molar concentration, allowing only for use of test chemicals with known molecular weights. Since many potential test substances are prepared by weight concentration or contain multiple unknown chemicals, this study was conducted to verify if it is possible to accurately assess the sensitization potential of test chemical solutions prepared at a specific weight concentration. Methods (1) Test chemical solutions for 82 chemicals were prepared at four different weight concentrations. Results were evaluated for agreement with in vivo results. (2) A liquid mixture comprising ten different non-sensitizers was prepared at 1 mg/mL. Ten different sensitizers of varying sensitization potencies were added individually to this mixture. The resulting pseudobinary mixtures were tested to confirm that the sensitizers could be detected. Results (1) The accuracies for test chemical solutions prepared at 0.5 and 0.2 mg/mL were 87.8% and 86.6%, respectively, which were roughly equivalent to the accuracy of 86.6% achieved with a solution prepared at the conventional molar concentration of 1 mM. In contrast, the accuracies for solutions prepared at 0.1 and 0.05 mg/mL were 82.9% and 74.4%, respectively, both of which were lower than that obtained with the conventional method. (2) Sensitizers added to the liquid mixture at 0.5 mg/mL were all correctly detected. Discussion Preparing test chemical solutions at a weight concentration of 0.5 mg/mL decreased false negatives and increased false positives while improving prediction accuracy, which suggests that the sensitization potential of mixtures can also be assessed with this method.
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The underlying factors that explain why nucleophilic reagents rarely co-elute with test chemicals in the ADRA
Journal of Pharmacological and Toxicological Methods, 2019Co-Authors: Masaharu Fujita, Sayaka Wanibuchi, Yasuhiro Katsuoka, Yusuke Yamamoto, Toshihiko KasaharaAbstract:The Amino Acid Derivative Reactivity Assay (ADRA) is an in chemico alternative to animal testing for skin sensitization potential that uses two different nucleophilic reagents and it is known that ADRA hardly exhibts co-elution compared with the Direct Peptide Reactivity Assay (DPRA) based on the same scientific principles. In this study, we have analyzed the factors underlying why co-elution, which is sometimes an issue during DPRA testing, virtually never occurs during ADRA testing. Chloramine T and dimethyl isophthalate both exhibited co-elution during DPRA testing, but when quantified at both DPRA's 220 nm and ADRA's 281 nm, we found that when the later detection wavelength was used, these test chemicals produced extremely small peaks that did not interfere with quantification of the peptides. And although both salicylic Acid and penicillin G exhibited co-elution during DPRA testing, when tested at a concentration just 1% of that used in DPRA, the very broad peak produced at the higher concentration was reduced significantly. However, both these test chemicals exhibited very sharp peaks when the pH of the injection sample was adjusted to be Acidic. Based on these results, we were able to clarify that the reasons why nucleophlic reagents hardly co-elute with test chemicals during ADRA testing are depend on the following three major reasons: (1)differences in the detection wavelength, (2)differences in test chemical concentrations in the injection sample, (3)differences in composition of the injection solvent.
Takahiro Ogawa - One of the best experts on this subject based on the ideXlab platform.
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improvement in the osteoblastic cellular response to a commercial collagen membrane and demineralized freeze dried bone by an Amino Acid Derivative an in vitro study
Clinical Oral Implants Research, 2011Co-Authors: Masahiro Yamada, Hajime Minamikawa, Norinaga Kojima, Kaoru Sakurai, Takahiro OgawaAbstract:PURPOSE: The objectives of this in vitro study were (1) to determine whether a commercially available collagen membrane (CM) or human demineralized freeze-dried bone (DFDB) particles adversely affected viability or function in cultured osteoblasts through oxidative stress, and, if so, (2) to determine whether N-acetyl cysteine (NAC) successfully prevented loss of viability and dysfunction in osteoblasts. MATERIALS AND METHODS: Rat calvaria-derived osteoblasts were seeded onto polystyrene and commercially available CM (Cytoplast ®) or DFDB (DynaGraft ™) with or without pretreatment with NAC solution. The osteoblastic response was evaluated using a flow cytometric cell viability assay, measurement of attached viable cell number, quantification of reactive oxygen species (ROS) and alkaline phosphatase (ALP) staining. RESULTS: The percentage of viable cells on CM was <50% at 24 h after seeding. However, this increased to 70% by pretreatment with NAC. The numbers of attached osteoblasts on DFDB remained at 60% the level of that on polystyrene at 24 h after seeding, but increased to up to 90% the level of that on polystyrene with NAC pretreatment. Although collagen materials increased intracellular ROS generation 1.5-5 times that with polystyrene, this was significantly reduced by NAC pretreatment. The percentage of the ALP-positive area was consistently 7% or less on CM and DFDB at days 7 and 14, which was restored by NAC pretreatment up to 60% or more. CONCLUSIONS: Commercially available CM and DFDB impaired osteoblastic viability and function and markedly increased intracellular ROS, indicating an oxidative stress-mediated negative impact on osteoblasts. Pretreatment with NAC substantially alleviated these cytotoxic effects.
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Amino Acid Derivative mediated detoxification and functionalization of dual cure dental restorative material for dental pulp cell mineralization
Biomaterials, 2010Co-Authors: Hajime Minamikawa, Fuminori Iwasa, Takeshi Ueno, Masahiro Yamada, Yoshiaki Deyama, Kuniaki Suzuki, Yasutaka Yawaka, Takahiro OgawaAbstract:Current dental restorative materials are only used to fill the defect of hard tissues, such as dentin and enamel, because of their cytotoxicity. Therefore, exposed dental pulp tissues in deep cavities must be first covered by a pulp capping material like calcium hydroxide to form a layer of mineralized tissue. However, this tissue mineralization is based on pathological reaction and triggers long-lasting inflammation, often causing clinical problems. This study tested the ability of N-acetyl cysteine (NAC), Amino Acid Derivative, to reduce cytotoxicity and induce mineralized tissue conductivity in resin-modified glass ionomer (RMGI), a widely used dental restorative material having dual cure mechanism. Rat dental pulp cells were cultured on untreated or NAC-supplemented RMGI. NAC supplementation substantially increased the percentage of viable cells from 46.7 to 73.3% after 24-h incubation. Cell attachment, spreading, proliferative activity, and odontoblast-related gene and protein expressions increased significantly on NAC-supplemented RMGI. The mineralization capability of cells, which was nearly suppressed on untreated RMGI, was induced on NAC-supplemented RMGI. These improved behaviors and functions of dental pulp cells on NAC-supplemented RMGI were associated with a considerable reduction in the production of intracellular reactive oxygen species and with the increased level of intracellular glutathione reserves. These results demonstrated that NAC could detoxify and functionalize RMGIs via two different mechanisms involving in situ material detoxification and antioxidant cell protection. We believe that this study provides a new approach for developing dental restorative materials that enables mineralized tissue regeneration.
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alleviation of commercial collagen sponge and membrane induced apoptosis and dysfunction in cultured osteoblasts by an Amino Acid Derivative
International Journal of Oral & Maxillofacial Implants, 2010Co-Authors: Masahiro Yamada, Fuminori Iwasa, Norio Hori, Takeshi Ueno, Katsutoshi Kubo, Takahiro OgawaAbstract:Purpose: The objectives of this in vitro study were to determine whether the commercial collagen material used in bone augmentation procedures induces oxidative stress‐mediated adverse effects on the viability and function of osteoblasts and to determine whether N-acetyl cysteine (NAC), an antioxidant Amino Acid Derivative, can alleviate these effects. Materials and Methods: Commercial collagen sponge (Collaplug) and membrane (BioGide) were treated with NAC. Rat calvaria‐derived osteoblasts were directly seeded on these materials with or without NAC pretreatment. Cytotoxic evaluation was performed by flowcytometric cell viability assay, confocal laser microscopic analysis of attached cell morphology and reactive oxygen species (ROS) localization, and alkaline phosphatase staining. Results: Cell viability was less than 40% on both collagen sponge and membrane 24 hours after seeding and increased to 50% with NAC pretreatment. Cell death was characterized by apoptosis. Colonization of attached cells was sparse on the untreated sponge and membrane on day 1, and the cells were round, small, and filled with intense and closely packed intracellular ROS. In contrast, NAC-pretreated material had dense cell colonies consisting of well-spread osteoblasts and fully developing cytoskeleton and cellular processes with little ROS generation. On day 7 of culture, NAC-pretreated collagen sponge and membrane yielded an expanded alkaline phosphatase‐positive area occupying 60% and 80% of the surface area, respectively, whereas the untreated collagen materials had limited alkaline phosphatase activity (7% or less). Conclusions: Commercial collagen sponge and membrane induced considerable cell death, impaired initial function, and generated extraordinary intracellular ROS in attached osteoblasts, whereas NAC pretreatment substantially ameliorated these effects. The potential benefits of NAC’s detoxifying capacity on bone regeneration using collagen matrix materials in an animal model should be confirmed with further study. INT J ORAL MAXILLOFAC IMPLANTS 2010;25:939‐946
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N-acetyl Cysteine Alleviates Cytotoxicity of Bone Substitute
Journal of Dental Research, 2010Co-Authors: Masahiro Yamada, Hajime Minamikawa, Fuminori Iwasa, Norio Hori, Naoko Sato, Takeshi Ueno, Takahiro OgawaAbstract:Lack of cytocompatibility in bone substitutes impairs healing in surrounding bone. Adverse biological events around biomaterials may be associated with oxidative stress. We hypothesized that a clinically used inorganic bone substitute is cytotoxic to osteoblasts due to oxidative stress and that N-acetyl cysteine (NAC), an antioxidant Amino Acid Derivative, would detoxify such material. Only 20% of rat calvaria osteoblasts were viable when cultured on commercial deproteinized bovine bone particles for 24 hr, whereas this percentage doubled on bone substitute containing NAC. Intracellular ROS levels markedly increased on and under bone substitutes, which were reduced by prior addition of NAC to materials. NAC restored suppressed alkaline phosphatase activity in the bone substitute. Proinflammatory cytokine levels from human osteoblasts on the bone substitute decreased by one-third or more with addition of NAC. NAC alleviated cytotoxicity of the bone substitute to osteoblastic viability and function, implyin...
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n acetyl cysteine restores viability and function of rat odontoblast like cells impaired by polymethylmethacrylate dental resin extract
Redox Report, 2009Co-Authors: Masahiro Yamada, Norio Hori, Norinaga Kojima, Takeo Suzuki, Takahiro OgawaAbstract:AbstractThere is concern that dental-resin materials directly loaded on a prepared tooth adversely affect dental pulp tissue by releasing the resin chemicals through dentinal tubes. This study determined whether self-curing polymethyl methacrylate (PMMA)-based dental resin extract adversely affected the viability and function of odontoblast-like cells and whether the cytotoxicity of this resin, if any, could be eliminated by N-acetyl cysteine, an antioxidant Amino Acid Derivative. Odontoblast-like cells isolated from rat maxillary incisor dental pulp tissue were exposed to a PMMA resin extract with or without N-acetyl cysteine for 1 h and then cultured in osteoblastic media. The percentage of viable cells 24 h after seeding was 20% in cells exposed to the resin extract without N-acetyl cysteine, whereas 45% of cells were viable after exposure to the N-acetyl cysteine-supplemented extract. The cells that had been exposed to the extract showed a strong tendency for apoptosis associated with the increased re...
Maria C. Viscomi - One of the best experts on this subject based on the ideXlab platform.
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A new non-natural arginine-like Amino Acid Derivative with a sulfamoyl group in the side-chain
Amino Acids, 2010Co-Authors: Rosaria Marco, Maria L. Di Gioia, Antonella Leggio, Angelo Liguori, Francesca Perri, Carlo Siciliano, Maria C. ViscomiAbstract:Sulfamoylation of the l -ornithine methyl ester side-chain generates a non-natural arginine isostere which can be coupled with N -Fmoc- l -proline to synthesize analogues which maintain the structural characteristics of the biologically important Pro-Arg dipeptide sequence. As a probe of its biological importance, the sulfamoylated Amino Acid Derivative was also incorporated as P1 residue in tripeptide structures matching the C -terminal subsequence of fibrinogen. The reported results demonstrate that the functionalization of l -ornithine side-chain with a neutral sulfamoyl group can generate an arginine bioisostere which can be used for the synthesis of prototypes of a new class of human thrombin inhibitors.
Eoin M. Scanlan - One of the best experts on this subject based on the ideXlab platform.
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Native Chemical Ligation,Thiol–Ene Click: A Methodology for the Synthesis of Functionalized Peptides
Journal of Organic Chemistry, 2013Co-Authors: Lyn Markey, Silvia Giordani, Eoin M. ScanlanAbstract:The sequential combination of native chemical ligation and thiol–ene radical chemistry (NCL-TEC) on the resulting cysteine thiol has been investigated as a methodology for rapidly accessing functionalized peptides. Three sequential cycles of native chemical ligation and subsequent thiyl radical reactions (including a free-radical-mediated desulfurization reaction) were carried out on a peptide backbone demonstrating the iterative nature of this process. The versatility of the thiyl radical reaction at cysteine was demonstrated through the introduction of a number of different side chains including an Amino Acid Derivative, a carbohydrate group, and an alkyl azide. Conditions were developed that allowed the sequential NCL-TEC process to proceed in high yield.
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native chemical ligation thiol ene click a methodology for the synthesis of functionalized peptides
Journal of Organic Chemistry, 2013Co-Authors: Lyn Markey, Silvia Giordani, Eoin M. ScanlanAbstract:The sequential combination of native chemical ligation and thiol–ene radical chemistry (NCL-TEC) on the resulting cysteine thiol has been investigated as a methodology for rapidly accessing functionalized peptides. Three sequential cycles of native chemical ligation and subsequent thiyl radical reactions (including a free-radical-mediated desulfurization reaction) were carried out on a peptide backbone demonstrating the iterative nature of this process. The versatility of the thiyl radical reaction at cysteine was demonstrated through the introduction of a number of different side chains including an Amino Acid Derivative, a carbohydrate group, and an alkyl azide. Conditions were developed that allowed the sequential NCL-TEC process to proceed in high yield.
