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At least 415 records · Page 23Linked to original sources
PubMed1996

[A 4-week oral toxicity study of prulifloxacin (NM441) in rats followed by a 4-week recovery test].

A repeated dose toxicity study of prulifloxacin, a new antibacterial agent, was conducted in Sprague-Dawley rats. Male and female rats were given the test material orally for 4 weeks at doses of 0 (control), 30, 300 and 3000 mg/kg. After discontinuation of the treatment, a 4-week recovery test was also conducted. There was one case of death in the 3000 mg/kg group. Grayish green and soft feces, unkempt fur, transient deep respiration and decreased body weight gain were observed in the 3000 mg/kg group. Decreased food consumption and increased water intake were seen in the 300 and 3000 mg/kg groups. Ophthalmoscopic examination failed to show any abnormalities related to the treatment. In urinalysis, crystalline substance in the urinary sediments, cloudy urine and decreased Na+ excretion were observed in the 300 and 3000 mg/kg groups. Increased urine volume, lowered urine specific gravity and decreased K+ and Cl- excretions were seen in the 3000 mg/kg group. Hematologic examination showed decreased Hb, Ht, MCV and MCH and increased WBC in the 3000 mg/kg group. Blood chemical examination revealed increased BUN and decreased K+ and Cl- in the 3000 mg/kg group, and decreased K+ and gamma-globulin in the 300 mg/kg group. Pathological changes caused by the treatment were as follows. Cecal weight was increased in all dose groups. Cecal distention and swelling of its absorptive cells were seen in the 300 and 3000 mg/kg groups. In kidney, tubular nephrosis with crystalline substance was observed in the 300 and 3000 mg/kg groups, and its organ weight was increased in the 3000 mg/kg group. The above-mentioned changes were reversible except for decreased gamma-globulin, increased BUN and urine volume, and lowered urine specific gravity. Ulcer and small cavities associated with proliferation of fibrous tissue in the femoral articular cartilage were observed in the 3000 mg/kg group at the end of recovery period of 4 weeks. Plasma levels and urinary concentrations of active metabolite of the test material were increased in all dose groups with dose-related manner, whereby no sex difference was observed. No effects caused by the repeated dosing were seen in the plasma concentrations. Increased cecal weight in the 30 mg/kg group was considered to be attributable to the pharmacological effect of the test material. The results show that the NOAEL of prulifloxacin is 30 mg/kg for 4-week repeated dose toxicity in rats.

Administration, Oral↗
PubMed1992

Filtration sizes of human immunodeficiency virus type 1 and surrogate viruses used to test barrier materials.

Filters with well-defined holes were used to determine the effective diameters in buffer of human immunodeficiency virus type 1, herpes simplex virus type 1, and four bacteriophages (phi X174, T7, PRD1, and phi 6), which may serve as surrogate viruses for testing barrier materials. Bacteriophages phi 6 and PRD1 most closely model human immunodeficiency virus type 1 in filtration size.

Animals↗
PubMed2001

Investigation of arsenic speciation in oyster test reference material by multidimensional HPLC-ICP-MS and electrospray tandem mass spectrometry (ES-MS-MS).

Multidimensional (size-exclusion-anion-exchange-cation-exchange) liquid chromatography with ICP-MS detection was developed to produce a map of water-soluble species in an oyster test reference material. The presence of arsenobetaine, trimethyl(2-carboxyethyl)arsonium inner salt, arsenocholine, dimethylarsonic acid, tetramethylammonium ion, As(v) and two arsenosugars was demonstrated by ES-MS-MS. A previously unreported compound was isolated and identified by ES-MS-MS as 5-dimethylarsinoyl-beta-ribofuranose. Anion-exchange chromatography was optimized to produce a chromatographically pure peak of arsenobetaine (accounting for ca. 64% of all water-soluble As present) that was used to quantify this compound.

Animals↗
PubMed1996

Evaluation of the laboratory rabbit model for screening topical mosquito repellents.

The laboratory rabbit was evaluated as a model for screening topical mosquito repellents, using data obtained in tests of deet (N,N-diethyl-3-methylbenzamide) against Aedes aegypti on humans and rabbits. Host-specific differences in the action of the test material were quantified by multiple regression analysis. The test material was less effective but more persistent in tests on rabbits, and responses of the mosquito test population were more variable.

Animals↗
PubMed1995

Influence of light intensity on shear bond strength to dentin.

PURPOSE: To investigate the influence of light intensity on dentin bond strength of five dentin bonding systems. MATERIAL AND METHODS: The light intensity used to polymerize specimens was controlled at the levels of 100, 200, 400, 600, 800, and 1000 W/m2 (470 +/- 40 nm). Labial surfaces of freshly extracted lower bovine incisors were ground with #600 grit SiC paper to expose dentin. After primer application, bonding agents were applied and bonded with resin composites. A shear bond strength test was performed and the data were analyzed by a one-way ANOVA followed by Newman-Keuls multiple comparison (P<0.05). RESULTS: Statistical analysis of the data indicated that light intensity affected the bond strength to dentin. The mean bond strength of all bonding systems decreased with lower light intensity. The tendency of decreasing bond strength was different among the test materials and each test material had a threshold light intensity that resulted in statistically the same bond strength obtained using a light intensity of 1000 W/m2.

Analysis of Variance↗
PubMed1997

The investigation of biocompatibility and apical microleakage of tricalcium phosphate based root canal sealers.

The biocompatibility and apical microleakage of tricalcium phosphate based Sankin Apatite (SA) Type I, II, and III root canal sealers were investigated. Teflon tubes containing freshly mixed test materials were implanted in the subcutaneous tissue of mice. The observation periods were 24 h, 7, and 30 days, after which the areas of tissue reaction to the implanted materials were histopathologically analyzed. A dye-recovery, spectrophotometric method was used to evaluate apical microleakage. Results showed that the severity of tissue reaction among the tested materials decreased with time and at the end of the observation period both SA Type II and Type III were found more biocompatible than either Type I or Grossman's cement (GC). On the other hand, a fibrous tissue capsule was seen around the implants. There was no significant difference in spectrophotometrically measured leakage among teeth obturated with the test materials.

Analysis of Variance↗
PubMed1993

[Criteria for biomechanical tests for athletic shoes].

In recent years, comparative sport shoe tests have resulted in an improvement of athletic footwear quality. Examples demonstrate the value and the limits of material tests, biomechanical investigations and subjective wear test evaluations. Biomechanical experiments have the primary goal to analyse sports shoe function with regard to shoe properties to prevent injuries. Rear foot pronation and supination measurements, in-shoe pressure distribution analyses, and the registration of ground reaction forces as well as tibial accelerations are valuable in the process of biomechanical evaluation. Material tests can be used to determine production quality between shoes and midsole material deterioration in used shoes. Wear tests with subjective evaluation are necessary for the judgement of shoe properties (e.g., shoe fit) which cannot be measured by biomechanical or material test methods.

Biomechanical Phenomena↗
PubMed2002

Clinical and SEM evaluations of three compomer systems in Class V carious lesions.

The aim of this study was to evaluate the clinical performance of three compomer systems: Compoglass F, Dyract AP and F2000 in Class V carious lesions. In addition, some restorations were placed in teeth scheduled for extractions in order to evaluate the compomer/dentin interface with the scanning electron microscope (SEM). A total of 175 Class V carious lesions having the gingival margins extending into cementum were restored with the tested materials. Each restoration was clinically evaluated immediately after placement, after 1 year and after 2 years using the USPHS criteria. After 1 year no loss of restoration was recorded. No significant difference between the materials was observed for any evaluation category. After 2 years, one Compoglass and two Dyract restorations were lost. No loss of F2000 was reported. No significant difference was reported between the tested materials and between the 2-year data and baseline ones. A well-defined hybrid layer as well as resin tags was seen at the interface between the tested materials and vital dentin.

Adult↗
PubMed1988

Tendon cell outgrowth rates and morphology associated with kevlar-49.

A rat tendon cell model was used to evaluate the in vitro biocompatibility of kevlar-49. The cell response to kevlar was compared to carbon AS-4 and nylon sutures. Three trials were run and cell growth rates were statistically similar for all the materials tested. A separate experiment was conducted in which the same fiber materials were placed in the same Petri dish. Again, the rates were similar for each material. Finally, the cells were observed with a scanning electron microscope, and the three classic cell morphologies associated with this tendon cell model were observed. Also, cellular attachment to the fiber and cellular encapsulation of the fiber were identical for the three materials tested. Kevlar-49 proved to be comparable to carbon AS4 and nylon sutures in terms of cellular response and cell outgrowth rates.

Animals↗
PubMed1991

Dye to use with virus challenge for testing barrier materials.

Can FD&C Blue no. 1 dye photoinactivate bacteriophages phi X174, T7, PRD1, and phi 6 under laboratory lighting conditions? At high levels of light, the dye (500 microM) photoinactivated only phi 6. Thus, this dye can be used at concentrations up to 500 microM with bacteriophages phi X174, T7, and PRD1 to test barrier material integrity.

Bacteriophages↗
PubMed1995

Is there a case for haemorheological screening in the haemocompatibility testing of materials?

Bio-interactions between a material and blood govern the compatibility of the material with the human body and, therefore, the single most important requirement for the blood interfacing implants/devices is haemocompatibility. The decisive events which control haemocompatibility occur at the molecular level and affect the various subphases of blood rheology. This effect on the already complex human blood rheology can be used to our advantage in the screening of blood-contacting materials. An attempt has been made in the present work to evaluate the haemocompatibility of materials based on changes in microrheological parameters of human blood. Samples of materials of equal surface area known to be haemocompatible (medical grade silicon, polyvinyl chloride from blood bags) and materials known to be extremely haemo-incompatible (pyrex glass, copper, cotton fabric, all commercial grade) were incubated at 37.4 degrees C in freshly drawn anticoagulated whole human blood, and changes in the haemorheological parameters (whole blood, plasma viscosity, intrinsic viscosity of red cells, platelet aggregation, albumin fibrinogen ratio) have been evaluated. The results of the study show that alterations in the haemorheological parameters are reliable indicators to the compatibility/incompatibility characteristics of well-known substances and that there is a case for haemorheological screening of biomaterials in the overall framework of haemocompatibility tests.

Absorption↗
PubMed2002

The effects of mouthrinses on microhardness and colour stability of aesthetic restorative materials.

Detrimental effects exerted on oral and dental tissues by frequent mouthrinse use are observed, but studies about their effects on aesthetic restorative materials are limited. In this study, the purpose was to examine the effects of three proprietary mouthrinses on three different aesthetic restorative materials. Mouthrinses were used as treatment groups, while distilled water served as the control. From a total of 72 specimens, each experimental group consisting of 24 samples were prepared from each restorative test material by using metal moulds. The samples were stored in 20 mL of one of the mouthrinses for 12 h, which was reported as the equivalent time to 1 year of 2-min daily mouthrinse use. Changes between baseline and after treatment measurements of surface microhardness and colour of the test materials were established by using Vickers microhardness tester and spectrophotometer. Statistical analyses were performed by analysis of variance (anova), with Bonferroni correction. The level of significance was set as 0.05 in all tests. There were no significant interactions between the test solutions and the test materials with regard to microhardness (P > 0.05), and colour changes of the materials (P > 0.05). Effects of mouthrinses on restorative materials may differ depending on many in vivo factors that could not be replicated in vitro. Therefore, routine assessment of the effects of mouthrinses on aesthetic restorative materials is recommended.

Analysis of Variance↗
PubMed1998

Effect of tubule orientation in the cavity wall on the seal of dental filling materials: an in vitro study.

Dentinal tubules are oriented perpendicularly to the root canal walls but parallel to the lateral walls of class I occlusal preparation. It was hypothesized that the contact surface area of the material may depend on the tubule orientation in the cavity wall to which the material is applied, and that the difference in contact surface may affect the seal provided by the filling material. Standard central lumens, 2.6 mm in diameter and 3 mm high, were machined in human crown or root specimens. After removal of the smear layer with a conditioner, the specimens in each experimental group, consisting of 20 crown and 20 root specimens, were filled with amalgam, Fuji II glass ionomer (with or without varnish), or gutta-percha with Ketac-Endo root canal sealer. A modified fluid transport model was used to test the leakage along the fillings. Selected specimens were then split longitudinally and observed in a scanning electron microscope. The micrographs showed that all the test materials were pressed into the dentinal tubules. The contact surface of the material was calculated to be at least 45% larger in root specimens than in crown specimens, depending on the depth of the tubular penetration of the test material. The leakage results showed that all the test materials leaked less in root specimens than in crown specimens (P = 0.0000 for amalgam, P = 0.0374 for Fuji II with varnish, P = 0.0088 for Fuji II without varnish, P = 0.002 for gutta-percha with sealer). It was concluded that the tubule orientation in the cavity wall may influence the seal provided by certain dental filling materials.

Dental Alloys↗
PubMed2004

[Biocompatibilty of silicon nitride ceramic in vitro. A comparative fluorescence-microscopic and scanning electron-microscopic study].

BACKGROUND: With regard to its favorable physical properties, silicon nitride ceramic is considered as biomaterial for human medical application. Minor controversy exists about the biocompatibility of the material. METHODS: Cytotoxicity testing, cell viability and morphology assessment was performed applying the L929-mice fibroblast cell culture model in a direct contact assay. Testing materials were silicon nitride ceramics of different surface properties and titanium alloy as a reference. Polyvinylchloride served as a negative control. The cells were stained with bisbenzimide and propidium iodine for double fluorochromasia viability testing, and evaluated by inversion-fluorescence microscopy. Scanning electron microscopy was applied to additionally investigate cell morphology. RESULTS: No cytotoxic effects were observed on the silicon nitride ceramic samples; moreover cell morphology remained the same as on titanium. Avital cells were present exclusively on PVC. The cell growth in the silicon nitride samples showed no significant differences compared to titanium. Cell counts on all polished surfaces showed significantly higher numbers. Scanning electron microscopy revealed typical fibroblast morphology with filiform extensions. CONCLUSION: The current results indicate a favorable biocompatibility of silicon nitride ceramic. Cell growth, viability and morphology are comparable to parameters of titanium. Polished surfaces appear to promote cell growth. Further in vivo studies are mandatory prior to human medical application. Owing to its favorable physiochemical properties, especially its superior resistance to mechanical stress, silicon nitride could serve as a biomaterial for osteosynthesis of bone with mucosal attachment.

Alloys↗
PubMedDate not supplied

The inverse effects of load transfer and load sharing on axial compressive stiffness.

BACKGROUND CONTEXT: The goal of spinal instrumentation is to stabilize involved motion segments while fusion occurs. Although some degree of load sharing is necessary for fusion, the ability of the instrumentation system to transfer the load may vary. PURPOSE: The purpose of this study is to formulate a mathematical relationship between load sharing and load transfer of specific spinal instrumentation systems using a well-accepted mechanical model. STUDY DESIGN/SETTING: Forty-eight American Society for Testing Materials standard ultra high molecular weight polyethylene cylinders were used as per designation F 1717-96, standard test methods for static and fatigue for spinal implant constructs in a corpectomy model. METHODS: Twenty-four spinal assemblies consisting of anterior plates, anterior rod, and posterior rods were subjected to compression bending tests using a MTS Bionix servo-hydraulic material testing apparatus. Each implant was tested in compression bending with and without the addition of a titanium load-sharing cage. The force applied was the independent variable, and the displacement was the dependent variable. The stiffness was determined for each setup with and without the addition of an anterior load-sharing cage. RESULTS: The average axial compressive stiffness of a system increased by a factor of 8.5 with the addition of the load-sharing cage. An inverse relationship existed between the compressive stiffness of the construct and its relative increase achieved with the addition of the load-sharing cage. The compressive stiffness of the system with the addition of the load-sharing cage approached that of the anterior device itself as the system flexibility increased. The ability of instrumentation systems to load share or load transfer and their respective stiffness was determined. CONCLUSIONS: The 5-mm rod screw posterior system was compared with the 7-mm Ti posterior system with the addition of one and two devices for transverse traction (DTTs). The rods with the increased diameter had a stiffness of 1723 n/mm with one DTT and 1815 n/mm with two DTTs. The addition of an anterior cage had little effect on the stiffness of these systems. Anterior plate and screw/rod systems were analyzed and showed similar mechanical behavior to the 5-mm posterior rod/screw systems. A significant increase in stiffness was realized with the addition of an anterior cage. A means to determine the load sharing/transferring properties of a spinal instrumentation system is presented. This technique will allow the amount of load transferred from the fusion mass to the instrumentation to be predicted.

Compressive Strength↗
PubMed1983

Production and perception of rise time in the voiceless affricate/fricative distinction.

Rise times of voiceless affricates and fricatives were measured when the test material occurred in sentences, in isolated words, and in isolated nonsense syllables. As has been reported previously the rise times of affricates were significantly shorter than those of fricatives. Rise times varied with the type of test material and for all types of material were significantly longer than those reported by L.J. Gerstman [unpublished doctoral dissertation, New York University (1957)]. Differences in the way the previous measurements were made do not appear to explain the discrepancy. Because rise time varies with type of test material, no auditory sensitivity at a single rise time value can be responsible for the perceptual distinction between voiceless affricates and fricatives. This conclusion was also supported by the results of a perceptual experiment in which listeners were asked to label speech or nonspeech stimuli drawn from a continuum varying in rise time. Substantially different estimates of the category boundary were obtained when the range of rise times covered by the stimuli differed.

Computers↗
PubMedDate not supplied

Brazilian Portuguese speech material and its application in occupational audiology.

Brazilian Portuguese speech test material consisting of nine monosyllabic 25-word lists was developed and digitally recorded on one channel of a compact disk with a speech-weighted modulated broadband noise on the other channel. Speech recognition functions in quiet and in noise, with word and phoneme scores, were obtained, and normative speech recognition data were standardized by determination of the psychometric function in 21 normally-hearing volunteers in quiet, and in 30 normally-hearing subjects in noise. The homogeneity of the nine lists was investigated in phoneme recognition data with 30 normally-hearing subjects. Speech recognition functions in quiet and in noise, with word and phoneme scores, were obtained in 65 noise-exposed workers. These results were very close to normative data, when tested in quiet, but significantly worse when tested in noise. It is concluded that the speech test material can be useful for estimating the communication performance of noise-exposed workers.

Adolescent↗