Invitro Comparative Analysis of the Flexural Strength of 4 Different Commercially Available Provisional Materials Used in Fixed Partial Dentures – An Original Research

Background: Provisional Prosthesis in fixed partial dentures are subjected to Flexure under stress. Selection of appropriate material for fabrication of Provisional is of utmost importance as the Provisional prosthesis has to remain in function till definitive prosthesis is delivered. Material & Methods: Bar type specimens of four different commercially available brands for provisional restorations fabricated according to ADA specification No. 27 and immersed in artificial saliva. The specimens were fractured under 3-point loading test. Results: The flexural strength ranged between 60 to 110 Mpa. BisGMA Auto polymerizing composite resin from Dentsply Caulk shows the highest flexural strength. Conclusion: Within the limitations of this study, the flexural strengths were material specific rather than category one. The BisGMA composite based resin shows significantly higher flexural strength over other materials

Comparison of the Polymerization Shrinkage of Eclipse Resin for Prostheses with Conventional Acrylic Resins / Comparación de la Contracción de Polimerización de la Resina Eclipse para Prótesis con Resinas Acrílicas Convencionales

ABSTRACT: The objective of this study was to compare the polymerization shrinkage of Eclipse photopolymerization resin for prosthesis based on urethane dimethacrylate (UDMA) with that of three heat-cured acrylic resins based on polymethyl methacrylate (PMMA) after the polymerization process and immersion in water. A total of 40 prostheses were fabricated on a standard metallic upper edentulous model: group 1, Eclipse; group 2, Triplex hot; group 3, Veracril; and group 4, Lucitone 199. Subsequently, the polymerization contraction was tested using a microscope in which measurements were made in micrometres at 3 points located in the middle parts of the right and left sides and the middle part of the palate at three time points once the prosthesis was completed, after 30 days of immersion in water for 8 hours a day at a temperature of 37 °C, and after cutting the prosthesis at the level of the second premolar. ANOVA revealed that the contraction of the polymerization no statistically significant differences between the groups, (P> 0.05). The type of resin and its interaction with the processing method behaves similarly for all test resins. The Veracril heat-cured resin obtained the lowest contraction value in the three measurements (mm) and the highest value was obtained with the Eclipse photopolymerization resin. The Eclipse resin exhibited no lower polymerization shrinkage compared to conventional acrylic resins based on polymethyl methacrylate (PMMA), however it was not significantly affected by immersion in water.

RESUMEN: El objetivo de este estudio fue comparar la contracción de polimerización de la resina de fotopolimerización Eclipse para prótesis basadas en dimetacrilato de uretano (UDMA) con la de tres resinas acrílicas curadas con calor a base de polimetacrilato de metilo (PMMA) después del proceso de polimerización e inmersión en agua. Se fabricaron un total de 40 prótesis en un modelo edéntulo superior metálico estándar: grupo 1, Eclipse; grupo 2, triplex caliente; grupo 3, veracril; y grupo 4, Lucitone 199. Posteriormente, la contracción de la polimerización se probó utilizando un microscopio en el que se realizaron mediciones en micrometros en 3 puntos ubicados en las partes medias de los lados derecho e izquierdo y la parte media del paladar en tres puntos de tiempo una vez la prótesis se completó, después de 30 días de inmersión en agua durante 8 horas al día a una temperatura de 37 °C, y después de cortar la prótesis a nivel del segundo premolar. ANOVA reveló que la contracción de la polimerización no presenta diferencias estadísticamente significativas entre los grupos, (P> 0,05). El tipo de resina y su interacción con el método de procesamiento se comportan de manera similar para todas las resinas de prueba. La resina curada con calor Veracril obtuvo el valor de contracción más bajo en las tres mediciones (mm) y el valor más alto se obtuvo con la resina de fotopolimerización Eclipse. La resina Eclipse no mostró una contracción de polimerización menor en comparación con las resinas acrílicas convencionales basadas en polimetilmetacrilato (PMMA), sin embargo, no se vio afectada significativamente por la inmersión en agua.

The establishment of Kunming mouse models of lung tumor / 预防医学

Objective@#To establish Kunming mouse models of lung tumor rapidly induced by urethane and butylated hydroxytoluene（BHT）.@*Methods@#Two hundred Kunming mice of SPF grade were randomly assigned to one control group and three experimental groups. The mice in the experimental groups were intraperitoneally injected with urethane at the dosage of 50,100 and 200 mg/kg（low,medium and high dose）,after one week,they were fed with fodder containing 0.75% BHT every day for two weeks;while the mice in the control group were injected with distilled water and were fed with normal fodder without BHT. At the 15th week,the lungs of all the mice were removed,tumors were counted and collected. The remaining lung tissue was cut into blocks of 1-2 mm thick,followed by paraffin section,HE staining,and was observed under light microscope.@*Results@#The incidence rates of lung tumors in Kunming mice of the low-,meidium-,high-dose group and the control group were 14.00%,24.00%,38.00% and 2.00%;the number of tumors were 1,8,22 47;the proportion of malignant tumors were 12.50%,18.18%,27.66% and 0. The incidence rate and the number of tumors in medium- and high-dose group were significantly higher than those in the control group（P<0.05）. The incidence rate,the number of tumors and the proportion of malignant tumors increased with the dosage of urethane,which indicated a dose-response relationship（P<0.05）.@*Conclusion@#The Kunming mouse models of lung tumor rapidly induced by urethane and BHT were established successfully,with significant dose-response relationship and tumorigenesis.

Immobilised Phytase Production from Aspergillus foetidus MTCC 11682 Using an Optimized Media

Aim: Immobilised fungal phytase production from the novel strain Aspergillus foetidus MTTC 11682 and optimisation of cultural conditions for a better and continuous economic yield. Study Design: The study was designed based on the classical method of changing one independent variable while fixing all other at a certain level- one factor at a time, a close ended system for the optimisation of fermentation process. Methodology: Physical and nutritional parameters were optimised for phytase production and subjected to statistical analysis. Adsorption and Entrapment techniques were employed to immobilise the production strain. Results: The optimum physical conditions for augmenting the yield up to 6 days incubation period were as follows: pH of 3.5, 30ºC temperatures and 5% inoculum size. Amongst the nutritional parameters, lactose and sodium nitrate were found to be the best carbon and nitrogen sources. K++, Mg++, Mn++ and Fe++ ions supported the phytase production. TritonX 100 and tween 80 showed an inducing effect on the secretion of phytase enzyme. Immobilised fungal phytase production resulted in an increased yield of 32.5% with poly urethane foam (PUF) as the matrix. A scale up fermentation resulted in an activity of 52.7 FTU/mL for immobilised cells as compared to 25.5 FTU/mL by its free counterpart. Conclusion: Phytase produced in an optimised media employing immobilised Aspergillus foetidus 11682 on poly urethane foam cubes exhibited better phytase activity, improved stability and long shelf life.

Animal Model of Lung Adenoma in C57BL/6J Mice Induced by Urethane / 中国药学杂志

OBJECTIVE: To compare and optimize the animal model of lung cancer on C57BL /6J mice by three different experimental methods. METHODS: Female C57BL /6J mice were divided into four groups: control group, model group , Ⅱ and III. The mice in model groupreceived 800 mg•kg-1 urethane by intraperitoneal injection twice a week, followed by 5 weeks. The mice in model group Ⅱ were injected intraperitoneally with 1 000 mg•kg-1 urethane in the same way with model group . The mice in model group III received urethane at the dose of 1 000 mg•kg-1 intraperitoneally, every 5 day continuing for 8 weeks. The control group was given equal volume of sodium chloride solutions in the same way as the model group Ⅱ. The main organs of all the groups were taken such as heart, liver, spleen, lung, kidney, brain and thymus at the 28th week, and their organs index was calculated. At the same time the lung tissues were examined to get the amount of adenomas and the diameters, and developed the lung and thymus histopathological examination. The bronchial alveolar lavage fluids were collected to classify the cells of the control and experimental groups. RESULTS: Compared with the control group, all the three experimental groups could induce lung adenomas absolutely, the number of tumors in model groupand III was 6, while tumors in model Ⅱ group was about 2. In the three experimental groups the index of lung increased and the brain, spleen and thymus decreased compared with the control group. The bronchial alveolar lavage fluids analysis showed that the number of lymphocytes and polymorphonuclear leukocytes in the model group are more than that in control group. CONCLUSION: All the three experimental groups could induce lung adenomas absolutely. Compared with model group Ⅱ, the model III and are more stable and homogeneous with the similar results of experiment.

Evaluation of chemical-specific IgG antibodies in male workers from a urethane foam factory

BACKGROUND@#Plastic resins are complex chemicals that contain toluene diisocyanate (TDI) and/or trimellitic anhydride (TMA), which cause occupational allergies (OA), including respiratory allergies. Serum IgGs against TDI and TMA have been suggested as potential markers of the exposure status and as exploring cause of OA. Although TDI-specific IgG has been examined for suspected OA, TMA-specific IgG is not commonly evaluated in a urethane foam factory. This study therefore investigated both TDI- and TMA-specific IgGs in suspected OA patients and to evaluate the usefulness of the measurement of multiple chemical-specific IgG measurement for practical monitoring.@*METHODS@#Blood samples were collected from two male workers who developed respiratory allergies supposedly caused by occupational exposure to TDI and/or TMA for the presence of TDI- and TMA-specific IgGs. In addition, blood samples from 75 male workers from a urethane foam factory, along with 87 male control subjects, were collected in 2014 and tested for the same IgGs in 2014. The presence and levels of TDI- and TMA-specific serum IgGs were measured using dot blot assays.@*RESULTS@#We found that controls had mean concentrations of TDI- and TMA-specific IgGs of 0.98 and 2.10 μg/mL, respectively. In the two workers with respiratory allergies, the TDI-specific IgG concentrations were 15.6 and 9.51 μg/mL, and TMA-specific IgG concentrations were 4.56 and 14.4 μg/mL, which are clearly higher than those in controls. Mean concentrations of TDI- and TMA-specific IgGs in the factory workers were 1.89 and 2.41 μg/mL, respectively, and are significantly higher than those of the controls (P < 0.001 and P < 0.026 for TDI- and TMA-specific IgGs, respectively).@*CONCLUSION@#The workers suspected of OA showed an evidently high level of TDI- and TMA-specific IgG, and these levels in workers at the urethane foam factory were also significantly higher than those in controls. In conclusion, the measurement of TDI- and TMA-specific IgG among workers using plastic resins is helpful to monitor their exposure status.

Caryocar brasiliense camb protects against genomic and oxidative damage in urethane-induced lung carcinogenesis

The antioxidant effects of Caryocar brasiliense Camb, commonly known as the pequi fruit, have not been evaluated to determine their protective effects against oxidative damage in lung carcinogenesis. In the present study, we evaluated the role of pequi fruit against urethane-induced DNA damage and oxidative stress in forty 8-12 week old male BALB/C mice. An in vivo comet assay was performed to assess DNA damage in lung tissues and changes in lipid peroxidation and redox cycle antioxidants were monitored for oxidative stress. Prior supplementation with pequi oil or its extract (15 µL, 60 days) significantly reduced urethane-induced oxidative stress. A protective effect against DNA damage was associated with the modulation of lipid peroxidation and low protein and gene expression of nitric oxide synthase. These findings suggest that the intake of pequi fruit might protect against in vivo genotoxicity and oxidative stress.

Intraperitoneal co-administration of low dose urethane with xylazine and ketamine for extended duration of surgical anesthesia in rats / 한국실험동물학회지

Procedures involving complex surgical techniques in rats, such as placement of abdominal aortic graft require extended duration of surgical anesthesia, which often can be achieved by repeated administrations of xylazine-ketamine combination. However such repeated anesthetic administration, in addition to being technically challenging, may be associated with potential adverse events due to cumulative effects of anesthesia. We report here the feasibility of using urethane at low dose (~1/10 the recommended anesthetic dose) in combination with a xylazine-ketamine mix to achieve an extended duration of surgical anesthesia in rats. The anesthesia induction phase was quick and smooth with an optimal phase of surgical anesthesia achieved for up to 90 minutes, which was significantly higher compared to that achieved with use of only xylazine-ketamine combination. The rectal temperature, heart rate and respiratory rate were within the physiological range with an uneventful recovery phase. Post surgery the rats were followed up to 3 months without any evidence of tumor or any other adverse effects related to the use of the urethane anesthetic combination. We conclude that low dose urethane can be effectively used in combination with xylazine and ketamine to achieve extended duration of surgical anesthesia up to 90 minutes in rats.

LncRNA-AK017233 expression is down-regulated in urethane-induced mouse lung tumors / 中国药理学与毒理学杂志

OBJECTIVE To explore the dyna mic change of lncRNA expression during lung carcino-genesis induced by urethane.METHODS A total of 40 BALB/c mice received weekly ip injection of urethane 1 g·kg -1 for four continuous weeks,mice were euthanized at 12th week or 24th week after the first urethane treat ment,respectively.The RNA of lung tissues were isolated and used for microarray analysis.Based on the results of the microarray we selected lncRNA-AK017233 for additional qPCR analysis in individual mouse.RESULTS The incidence of lung cancer were 85% and 100% at 12th week and 24th week after the first ad ministration of urethane,respectively.The multiplicity and dia meter of lung tu mors in 24 weeks treated group were statistically significant fro m those in 12 weeks treated group (P<0.01 ),and pathological analysis showed that tu mors were classifiable as moderately differ-entiated adenocarcino ma.Total of 26 Down-regulated lncRNAs in which lncRNA-AK017233 stand for the most down-regulated lncRNA were identified by microcarray analysis.qPCR detected that the lncRNA-AK017233 was significantly altered by 0.33 ti mes in lung tu mors of urethane treated group at 12th week, co mpared to parallel lung tissues in urethane treated group at 12th week.AK017233 expression of ure-thane treated group was significantly reduced by 0.22 ti mes at 24th week,co mpared to parallel lung tis-sues in urethane treated group at 24th week.CONCLUSION LncRNA-AK017233 was consistently down-regulated during urethane induced lung carcinogenesis.

Treatment of waste gas containing low concentration of dimethyl sulphide in a high performance biotrickling filter.

A bench-scale biotrickling filter was operated in the laboratory for the treatment of dimethyl sulphide (DMS). The biotrickling filter was packed with pre-sterilized polyurethane foam and seeded with biomass developed from garden soil enriched with DMS. The biotrickling filter was operated for the generation of process parameters. The biotrickling filter could remove an average removal efficiency of 40.95 % at an effective bed contact time of 84 sec with an average loading rate of 0.56 mg/m3/h. Evaluation of microbiological status of the biotrickling filter indicated the presence of other bacterial cultures viz. Paenibacillus polymyxa, and Bacillus megaterium, besides Bacillus sphaericus.

Caracterização de resinas para base de prótese e reembasamento: propriedades físico-químicas e mecânicas / Characterization of denture base and reline resins: physical, chemical and mechanical properties

Este estudo avaliou propriedades físico-químicas e mecânicas de resinas para base de prótese, uma fotoativada (Eclipse - E) à base de UDMA e outra termicamente ativada por micro-ondas (Nature Cryl MC - NC) à base de PMMA, e um reembasador quimicamente ativado (Tokuyama Rebase Fast II - TR II) à base de PEMA. Propriedades viscoelásticas (E', tan δ e Tg), contração linear de polimerização (CLP), sorção (Sor) e solubilidade (Sol) em água e em saliva artificial, grau de conversão (GC) e coeficiente de inchamento (CI) foram avaliados para a caracterização dos polímeros. A resistência à flexão dos materiais intactos (E, NC, TR II) e reembasados (E-E, E-TRII, NC-NC- NC-TR II) também foi avaliada. As propriedades viscoelásticas foram avaliadas em corpos-de-prova retangulares (64 x 10 x 3,3 mm), submetidos (n=2) à análise térmica dinâmico-mecânica (DMTA) em dois ciclos de varredura após confecção (controle) e armazenagem em saliva. O módulo de armazenamento (E') e o amortecimento mecânico (tan δ) a 37 ºC e a temperatura de transição vítrea (Tg) foram registrados durante o 1º ciclo da DMTA. A CLP (%) foi avaliada (n=10), em projetor de perfil (Nikon 6C), em corpos-de-prova circulares (50 x 0,5 mm). A Sor e a Sol (µg/mm3) foram mensuradas (n=5) seguindo as recomendações da ISO 1567. O GC (%) foi avaliado (n=5) por espectroscopia de infravermelho por transformadas de Fourier (32 leituras; resolução 4,0 cm-1 ). O coeficiente de inchamento foi realizado (n=5) de acordo com a teoria de Flory-Rhener. Os ensaios mecânicos de flexão (0,5 mm/min) foram realizados (n=10) em corpos-de-prova (64 x 10 x 3,3 mm) intactos ou reembasados e a resistência (MPa) calculada na tensão máxima (RFM) e no limite de proporcionalidade (RFLP). Os dados foram avaliados por ANOVA, seguida por Tukey HSD (α=0,05) ou Dunnett (α=0,05). As resinas E e NC apresentaram similar E', superior a TR II. O tan δ foi ordenado como TR II > NC > E. A Tg não foi alterada após armazenagem em saliva artificial. Os maiores valores de Tg nos grupos controle e armazenados foram apresentados, respectivamente, pelos materiais E e NC. Houve deslocamento dos picos de tan δ após o segundo ciclo de DMTA. Independente do meio de imersão, a Sor (µg/mm3 ) foi ordenada em NC > E > TR II. A armazenagem em saliva reduziu a Sol (µg/mm3 ) dos materiais. A resina E exibiu os menores valores de CLP, CI e o maior GC. NC exibiu a maior CLP e CI. TR II exibiu valores intermediários de CLP, CI e o menor GC. Os maiores valores de RFM e RFLP foram produzidos por E. A RFM e RFLP dos materiais reembasados foi ordenada em E-E > NC-NC > E-TRII> NC-TR II. A armazenagem em saliva não influenciou a resistência à flexão dos materiais intactos ou reembasados. No geral, a resina para base de prótese E apresentou propriedades físico-químicas e mecânicas superiores à NC e TR II

This study evaluated the physical-chemical and mechanical properties of denture base resins, one UDMA light-activated (Eclipse-E) and one PMMA heat-polymerized (Nature Cryl MC - NC). The PEMA autopolymerizing reliner (Tokuyama Rebase Fast II - TR II) was also evaluated. Viscoelastic properties (E', tan δ e Tg), linear shrinkage polymerization (LPS), sorption (Sor) and solubility (Sol) in water and in artificial saliva, degree of conversion (DC) and coefficient of swelling (CS) were employed for polymer characterization. The flexural strength of intact (E, NC, TR II) and relined samples (E-E, E-TRII, NC-NC- NC-TR II) was also made. The viscoelastic properties were evaluated by two cycles of dynamic mechanical thermal analysis (DMTA) on each rectangular (64 x 10 x 3.3 mm) samples (n=2). The storage modulus (E') and loss tangent (tan δ) at 37 ºC and the glass transition temperature (Tg) were recorded from the 1st DMTA cycle. LPS (%) was evaluated (n=10) by a Nikon 6C optical comparator, on circular samples (50 x 0.5 mm). Sor and Sol (µg/mm3 ) were measured (n=6) according to ISO 1567. DC (%) was evaluated (n=5) by FTIR spectroscopy (32 scans; resolution 4.0 cm-1). CS was evaluated (n=5) by Flory-Rhener theory. A three-point flexural tests (0.5 mm/min) was applied (n=10) on rectangular intact and relined samples. The ultimate flexural strength (FSU) and the flexural strength at the proportional limit (FSPl) were recorded in MPa. Data were analyzed with ANOVA, followed by Tukey HSD (α=0.05) ou Dunnett (α=0.05). E and NC had similar E', higher than TR II. Tan δ was arranged as TR II > NC > E. The Tg was not affected after saliva storage. The higher Tg values were obtained for E and NC. Tan δ peaks were shifted after 2 DMTA cycles. Regardless the medium immersion, Sor (µg/mm3 was arranged as NC > E > TR II. Saliva storage reduced Sol (µg/mm3) of the materials. E showed the lowest values of LPS, CS and the highest value of DC. NC showed the highest LPS and CS.TR II showed intermediated values of LPS, CS and the lowest DC. The highest FSU and FSPl values were exhibited by E. The FSU and FSPl of relined samples were arranged as E-E > NC-NC > E-TRII > NC-TR II. Saliva storage did not affect the flexural strength of intact and relined samples. Overall, the denture base resin E showed higher physicochemical and mechanical properties than NC and TR II

In vitro comparison of two different materials for the repair of urethan dimethacrylate denture bases

PURPOSE: The purpose of this in vitro study was to investigate the flexural properties of a recently introduced urethane dimethacrylate denture base material (Eclipse) after being repaired with two different materials. MATERIALS AND METHODS: Two repair groups and a control group consisting of 10 specimens each were generated. The ES group was repaired with auto-polymerizing polymer. The EE group was repaired with the Eclipse. The E group was left intact as a control group. A 3-point bending test device which was set to travel at a crosshead speed of 5 mm/min was used. Specimens were loaded until fracture occurred and the mean displacement, maximum load, flexural modulus and flexural strength values and standard deviations were calculated for each group and the data were statistically analyzed. The results were assessed at a significance level of P.05) was found between the mean values of Group ES and EE. There was a statistically significant positive relation (P<.01) between the displacement and maximum load of Group ES (99.5%), Group EE (94.3%) and Group E (84.4%). CONCLUSION: The more economic and commonly used self-curing acrylic resin can be recommended as an alternative repair material for Eclipse denture bases.

Clinical Application of Polyether Ester Urethane in Endonasal Dacryocystorhinostomy

PURPOSE: To evaluate the clinical effect of intraoperative application of polyether ester urethane (Nasopore(R)) in endonasal dacryocystorhinostomy. METHODS: Endonasal dacryocystorhinostomy was performed on 77 eyes diagnosed with nasolacrimal duct obstruction between January 2010 and February 2011. Nasopore(R) was applied to the newly-formed internal lacrimal opening in the experimental group (41 eyes), and vaseline gauze was applied in the control group (36 eyes). For the evaluation of clinical effects regarding postoperative adhesion and stenosis of the internal lacrimal opening, subjective symptom improvement, lacrimal irrigation tests, and endoscopic examinations were performed at 1 week, 2 weeks, 1 month, 3 months, and 6 months, postoperatively. RESULTS: In subjective symptom improvement and lacrimal irrigation tests, differences between the 2 groups were not statistically significant. In endoscopic findings, the Nasopore(R) group showed significantly lower severity of adhesion and stenosis of the internal lacrimal opening at 1 week, 2 weeks, and 1 month after operation (p < 0.05). CONCLUSIONS: Application of the Nasopore(R) may effectively reduce initial postoperative adhesion or stenosis of the internal lacrimal opening after endonasal dacryocystorhinostomy and has usefulness as an auxiliary method.

Análise da ação da Himatanthus drasticus na progressão do câncer de pulmão induzido por uretana em camundongos / Analysis of the action of Himatanthus drasticus in progression of urethane-induced lung cancer in mice

Objective: To evaluate the effect of janaguba in inhibiting the development of lung cancer in an experimental urethane-induced model. Methods: a total of 3 mg/kg urethane was injected in 51 Balb-C mice aged 7-13 weeks of life. Janaguba was administered orally daily in two doses: 0.04 mL (Group 2, G2) and 0.06 mL (Group 3, G3), for 20 weeks. After this period, the mice were sacrificed and the number of lesions counted. Results: The mean weight of Group 2 was lower than that of Group 3, and that of Group 1 (Control, G1) (G1 = 35.533 g; G2 = 33.359 g; G3 = 37.125 g). The number of nodules did not differ between groups (mean G1 = G2 = G3 = 1; p = 0.88). Conclusion: Janaguba had an effect on the growth of mice, but had no influence on the progression of lung cancer in this model.

Objetivo: Avaliar a ação da janaguba na inibição do desenvolvimento de câncer de pulmão em modelo experimental induzido por uretana. Métodos: Foram injetados 3mg/kg de uretana em 51 camundongos Balb-C , com 7 a 13 semanas de vida. Janaguba foi administrada via oral diariamente em duas doses: 0,04 mL (Grupo 2, G2) e 0,06 mL(Grupo 3,G3), por 20 semanas. Após esse período, os camundongos foram sacrificados e o número de lesões, contado. Resultados: A média de peso do Grupo 2 foi menor que a do Grupo 3, e que a do Grupo 1 (Controle, G1) (G1 = 35,533 g; G2 = 33,359 g; G3 = 37,125 g). O número de nódulos não diferiu entre os grupos (média G1 = G2 = G3 = 1; p = 0,88). Conclusão: A janaguba apresentou um efeito no crescimento dos camundongos, mas não apresentou influência na progressão do câncer de pulmão neste modelo.

The effect of bur preparation on the surface roughness and reline bond strength of urethane dimethacrylate denture base resin.

Background: The clinical success of relining depends on the ability of reline resin to bond to denture base. Surface preparations may influence reline bond strength of urethane-based dimethacrylate denture base resin. Aim: To investigate the effect of bur preparation on the surface roughness (R a ) of eclipse denture base resin and its shear bond strength (SBS) to an intra-oral self-curing reline material. The mode of reline bonding failure was also examined. Materials and Methods: Twenty-four cylindrical Eclipse™ specimens were prepared and separated into three groups of eight specimens each. Two groups were subjected to mechanical preparation using standard and fine tungsten carbide (TC) burs and the third group (control) was left unprepared. The R a of all specimens was measured using a contact stylus profilometer. Subsequently, relining was done on the prepared surface and SBS testing was carried out a day later using a universal testing machine. Results: One-way ANOVA revealed significant differences (P<0.05) in R a and SBS values for all the groups. Post-hoc Tukey's HSD test showed significant differences (P<0.05) between all the groups in the R a values. For SBS also there were significant differences (P<0.05), except between standard bur and control. Conclusions: 1) There was a statistically significant difference in the R a of Eclipse™ specimens prepared using different carbide burs (P<0.05). 2) There was a statistically significant difference in the relined SBS (P<0.05) when prepared using different burs, but the difference between the standard bur and the control group was not statistically significant.

Urban, traffic- related particles and lung tumors in urethane treated mice

OBJECTIVE: The present study was designed to evaluate the effects of urban, traffic-related, fine particulate matter (PM2.5) on mice lung tumorigenesis under controlled exposure conditions. METHODS: Four groups of female Swiss mice were treated with intraperitonial injections of urethane and saline solution. Urethane was used to start the carcinogenesis process. The animals were housed in two chambers receiving filtered and polluted air. In the polluted air chamber, pollutant levels were low. After two months of exposure, the animals were euthanized and lung tumoral nodules were counted. RESULTS: Saline-treated animals showed no nodules. Urethane-treated animals showed 2.0+2.0 and 4.0+3.0 nodules respectively, in the filtered and non-filtered chambers (p = 0.02), thus showing experimental evidence of increased carcinogenic-induced lung cancer with increasing PM2.5 exposure. CONCLUSION: Our data support the concept that low levels of PM2.5 may increase the risk of developing lung tumors.

Altered Retinoblastoma Protein Expression and Proliferative Activity in Urethane Induced Mouse Lung Tumorigenesis / Journal of the Korean Cancer Association, 대한암학회지

Lung cancer develops through a multistage process involving the accumulation of diverse genetic alterations. To gain an understanding of the roles played by tumor suppressor gene proteins and proliferating cell nuclear antigen (PCNA) in chemical carcinogen-induced mouse lung tumorigenesis, we examined the expression of retinoblastoma protein (Rb), p53, and PCNA in normal lung tissues and urethane-induced mouse lung tumors. MATERIALS AND METHODS: ICR mice were given urethane by intra-peritoneal injection, and sacrificed at 5, 13, 21, 31, and 37 weeks following treatment. Sequential morphological changes and the immunohistochemical expression of Rb protein, p53, and (PCNA), during mouse lung tumorigenesis, were examined. RESULTS: During the carcinogenesis, sequential histological changes from hyperplasia of type II pneumocytes, to adenomas, and ultimately to overt adenocarcinomas were noted. Intense nuclear staining of the Rb protein was observed in normal and hyperplastic alveolar epithelial cells and adenomas. In adenocarcinomas, the Rb protein expression was significantly diminished. The p53 mutant protein was not detected in any lesion. The PCNA labeling index increased along with the advance in the histological grade. CONCLUSION: The above results indicate that mouse pulmonary adenocarcinomas develop through premalignant lesions, and down-regulation of the Rb protein expression may be implicated in the urethane-induced mouse lung tumorigenesis. In addition, the PCNA labeling index may reflect the malignant potential during the tumor progression.

Pressor Effect of Intracerebroventricular 4-Aminopyridine on the Systemic Arterial Pressure in the Rabbit

A K+-channel blocker, 4-aminopyridine(4-AP) increases neurotransmitter release from motor nerve terminals and has been shown to restore neuromuscular transmission in the myasthenic syndrome. It has been reported that the intravenous injection of 4-AP in the myasthenic patients caused many central adverse effects including anxiety and restlessness, but did not affect the blood pressure. The aim of this study was to observe the effect of intracerebroventricularly administered 4-AP on the blood pressure and to elucidate the mechanism of the action in urethane-anesthetized rabbits. Intracerebroventricular(icv) 4-AP produced pressor effects in a dose-dependent fashion, but intravenous(iv) 4-AP of the same dose did not altered the blood pressure. Tetraethylammonium, a K+-channel blocker which differs from 4-AP structurally, had little effect on the blood pressure, but 3,4-diaminopyridine, another derivative of the aminopyridine, produced pressor effect similar to 4-AP. The pressor effect of icv 4-AP was not affected by the treatment with iv phenoxybenzamine and chlorisondamine, and in bilateral adrenalectomized rabbits. These results suggest that the 4-AP pressor effect is not related to the periphral sympathetic nerve nor adrenal gland. The pretreatment with icv phentolamine and prazosin did not altered the 4-AP pressor. However, the icv 4-AP pressor effect was significantly attenuated by the treatment with icv yohimbine, and significantly potentiated by the treatment with icv clonidine. The treatment with icv diltiazem markedly inhibited the icv 4-AP pressor effect. It is concluded that 4-AP-sensitive K+-channels in rabbit brain might play a role in the regulation of blood pressure and that the 4-AP pressor effect is closely related to the central alpha2-adrenoceptors and L-type calcium channels.

Research on process of polyurethane coating for self-expandable stent in medical use / 中国介入心脏病学杂志

Objective To improve the biocompatibility of the metallic stent used for interventional treatment. Methods Inner coatings, outer coatings and micro-porous coatings were made using the solution-injection method, and salt crystallite with demanded size was added in order to develop micro-porous coatings. Results The optical concentrations of polyurethane solution and of salt crystallite (for micro-porous coatings) were obtained, and the corresponding processes were developed. Conclusion The poly-coated stent retains its elasticity, and it become very convenient to develop stents carrying drugs. Its effects on animals ard under test.

EFFECTS OF ANESTHESIA ON IR-DYN A1-13 CONTENTS IN THE BRAIN, PITUITARY AND SPINAL CORD OF RATS / 第二军医大学学报

The effects of 3 anesthetics (urethane, pentobarbital and chloraiose) on the contents of dynorphin A1-13 (ir-dyn-A1-13) in the brain, pituitary and spinal cord of male rats were studied with radioimmunoassay. Under urethane anesthesia, the contents of ir-dyn- A1-13 in the brain, pituitary and spinal cord of rats were significantly reduced. When the rats were given chloralose, the contents of ir-dyn-A1-13 were markedly reduced except in the midbrain. After the rats were anesthetized with pentobarbital, the contents of ir-dyn-A1-13 were decreased apparently except in the thalamus.