5 results
Search Results
2. Searching for a rat model of chronic tympanic membrane perforation: Healing delayed by mitomycin C/dexamethasone but not paper implantation or iterative myringotomy
- Author
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Jeffrey T. Wang, Magnus von Unge, Rodney J. Dilley, Lawrence J. Liew, Yi Shen, Allen Y. Wang, and Marcus D. Atlas
- Subjects
Male ,Paper ,medicine.medical_specialty ,Alkylating Agents ,Time Factors ,Tympanic Membrane ,medicine.medical_treatment ,Mitomycin ,Anti-Inflammatory Agents ,Dexamethasone ,Myringotomy ,Rats, Sprague-Dawley ,Myringoplasty ,Otology ,medicine ,Animals ,Tympanic Membrane Perforation ,Wound Healing ,business.industry ,Mitomycin C ,General Medicine ,Prostheses and Implants ,Tympanoplasty ,Surgery ,Rats ,Disease Models, Animal ,medicine.anatomical_structure ,Otorhinolaryngology ,Pediatrics, Perinatology and Child Health ,Chronic Disease ,Middle ear ,business ,medicine.drug - Abstract
Objectives Surgical intervention such as myringoplasty or tympanoplasty is an option in the current clinical management of chronic tympanic membrane perforation (TMP). Animal models of chronic TMP are needed for pre-clinical testing of new materials and to improve existing techniques. We evaluated several reported animal model techniques from the literature for the creation of chronic TMPs. The aim of this study was to evaluate production of chronic TMPs in a rat model using topical mitomycin C/dexamethasone, paper insertion into middle ear cavity (MEC) or re-myringotomy. Methods Forty male Sprague–Dawley rats underwent myringotomy of the right tympanic membrane (TM) and were randomly divided into 3 experimental groups: application of topical mitomycin C/dexamethasone, paper insertion into middle ear cavity, or re-myringotomy. Control perforations were allowed to close spontaneously. TMs were assessed regularly with otoscopy for 8 weeks. At the end of 8 weeks, animals were sacrificed for histology. Results The closure of TMPs was significantly delayed by mitomycin C/dexamethasone (mean patency, 18.9 days; P ≤ 0.01) compared with the control (mean patency, 7 days), but was not significantly delayed in the paper insertion group (mean patency, 9.4 days; P = 0.74). Repeated myringotomy of closed perforations (mean number of myringotomies, 8.9 per ear) stimulated acceleration of closure rather than delay. Histologically, the mitomycin C/dexamethasone group had almost normal TM morphology, while the paper insertion group revealed inflammatory and granulomatous responses. The re-myringotomy group had a thickened TM fibrous layer with collagen deposition. Conclusions Mitomycin C/dexamethasone delayed TMP closure in rats but the effect was not sufficiently long-lasting to be defined as a chronic TMP. Neither paper insertion into middle ear cavity nor re-myringotomy created chronic TMP in rats.
- Published
- 2015
3. Multivariate statistics of the pyrolysis products of high molecular components in pulping wastewaters to explain their toxicity
- Author
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Jaakko, Paasivirta, Jukka, Kukkola, Juha, Knuutinen, Piia, Pessala, Eija, Schultz, and Sirpa, Herve
- Subjects
Paper ,Alkylating Agents ,Principal Component Analysis ,Carbohydrates ,Industrial Waste ,Lignin ,Waste Disposal, Fluid ,Gas Chromatography-Mass Spectrometry ,Electron Transport ,Molecular Weight ,Quaternary Ammonium Compounds ,Toxicity Tests ,Linear Models ,Water Pollutants, Chemical - Abstract
At present, large-scale paper manufacture involves delignification and bleaching by elemental chlorine free (ECF), or totally chlorine free (TCF) processes. The wastewater is purified by secondary treatment (mechanical, chemical and biological) which removes most of the toxic substances from the discharge. However, we found residual toxicity in the high molecular (1000 D) matter (HMWM) of the discharge by test of the RET (reverse electronic transfer) inhibition. This fraction consists mainly of polydispersed lignin (LIG) and carbohydrate (CH) macromolecules. Structural units in these molecules are studied by pyrolysis gas chromatography/mass spectrometry (Pyr-GC/MS). In the present work, our aim was to find out those structural units which could explain the RET toxicity of LIG or CH molecules. We compared statistically RET toxicity values of the HMWM samples from treated wastewaters of pilot pulping experiments and intensity variation of the pyrolysis product gas chromatograms of these samples. This application is a novel study procedure.Pyrolysis products (Py-GC/MS results) and inhibition of RET (reverse electronic transport toxicity) as TU50 and TU20 of HMWM (High Molecular Weight Material; Mw1000 D) were compared by multivariate statistics. The samples were from laboratory pilot stages of TCF (Totally Chlorine Free) and ECF (Elemental Chlorine Free) manufacture of softwood pulp. Py-GC/MS was done without and with the addition of TMAH (Tetra Methyl Ammonium Hydroxide). The name and structure of each abundant fragment compound was identified from its retention time and mass spectrum compared to authentic reference compounds or literature. Four sets of Toxicity Units (TUs) and GC peak areas of the pyrolysis fragments were obtained. The data were normalized by division with LIG (lignin content of each sample). TU values were dependent and the fragment values independent (explanatory) variables in statistical treatments by SPSS system. Separate analyses of correlations, principal components (PCA) and stepwise multiple linear regression (SMLR) were performed from the four sample sets TCF and ECF with and without TMAH.From the CH fragments, 2-furfural in TCF, and from the LIG fragments, styrene in ECF showed the highest probabilities of originating from source structures of toxicity. Other possible compounds in concern were indicated to be CH fragment 2-methyl-2-cyclopenten-1-one in ECF and LIG fragments 2-methoxy-4-methylphenol, 4,5-dimethoxy-2-methylphenol and 2-methylphenol in TCF.
- Published
- 2005
4. Disproportionation of vitamin B12 under various mild conditions
- Author
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Shoichi Shimizu, Ryo-Hei Yamada, and Saburo Fukui
- Subjects
Electrophoresis ,Paper ,Vitamin b ,Alkylating Agents ,Alkylation ,Chemical Phenomena ,Nitrogen ,Sodium ,chemistry.chemical_element ,Disproportionation ,Sodium Chloride ,Biochemistry ,Medicinal chemistry ,Catalysis ,Chlorides ,Sodium Hydroxide ,Oxidation reduction ,Darkness ,Iodides ,Solutions ,Chemistry ,Vitamin B 12 ,chemistry ,Spectrophotometry ,Oxidation-Reduction ,Hydrogen - Published
- 1968
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5. [Emission of alkylating compounds during the burning process]
- Author
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K, Norpoth, G, Manegold, R, Brücker, and H P, Amann
- Subjects
Paper ,Alkylating Agents ,Chromatography ,Chromatography, Gas ,Polymers ,Air ,Industrial Waste ,Chromatography, Thin Layer ,Environment ,Cellulose ,Environmental Pollution ,Refuse Disposal ,Vehicle Emissions - Published
- 1972
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