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At least 613 records · Page 34Linked to original sources
PubMed1999

Evaluation of skin viscoelasticity and anisotropy by measurement of speed of shear wave propagation with viscoelasticity skin analyzer.

Skin viscoelasticity was evaluated by a fast, noninvasive assay based on the measurement of the speed of elastic shear wave propagation in the skin by a new portable and user-friendly viscoelasticity skin analyzer. The range of speed of elastic shear wave propagation measured by viscoelasticity skin analyzer allows the evaluation of the stiffness of a wide spectrum of artificial materials as well as the viscoelasticity of skin of laboratory animals and human subjects. The directional nature of the measurement enables to monitor the anisotropy of the materials tested. The speed of elastic shear wave propagation was shown to have a positive correlation with the stiffness of the material tested. In symmetric contralateral areas of intact skin in rabbit ears, similar viscoelasticity and anisotropy were observed. Twenty-four hours after the induction of local edema by croton oil, skin stiffness and anisotropy were significantly increased. In healthy human subjects of both sexes significant variations in skin stiffness and anisotropy were observed in three different skin areas along the forearms, but the speed of elastic shear wave propagation was similar in the symmetric contralateral areas. Age (17-65 y) seemed to have a limited effect on the viscoelasticity of the forearm skin. Hydrating creams decreased the stiffness of the forearm skin for only approximately 3 h. The stiffness and anisotropy of the skin of the breasts in female volunteers (20-86 y) increased with age, but the speed of elastic shear wave propagation was similar in symmetric contralateral areas in the same individuals. Based on these results, we propose the application of the viscoelasticity skin analyzer in experimental and clinical practice for quantitative evaluation of skin condition.

Administration, Topical↗
PubMedDate not supplied

Effectiveness of reciprocal-action instrumentation for polishing composite resin: an in vitro study.

This in vitro study investigates the use of reciprocal-action instrumentation for polishing composite resin restorative materials. Electron photomicrographs were made of surfaces of a microfilled and a hybrid composite resin restorative material polished by various reciprocal-action polishing procedures, including several types of polishing pastes used with nonabrasive plastic tips. The best polish on the microfilled composite resin restorative material tested was produced by ending with 3-mu diamond polishing paste. The best polish on the hybrid composite resin restorative material tested was produced by ending with 0.5-mu diamond polishing paste. The surfaces produced were comparable to those produced by polishing discs.

Carbon↗
PubMed2001

The reliability of the SCAN test: results from a primary school population in the UK.

The SCAN test utilizes a pre-recorded tape, with carrier phrase and target words spoken by an American English speaker, to screen for central auditory processing disorders in children. The aim of the present study was to establish whether the normative data, derived from American school children, are applicable to a UK primary school population. The SCAN test was administered to 133 British primary school children with normal hearing, stratified into one-year age bands. Mean scores from the UK sample were found to be significantly lower than US mean scores for the most of the age bands. Analysis of word errors indicates accent and word familiarity effects. This evaluation of the SCAN indicates that the test is not directly applicable to British children as currently normalized. The present study provides interim norms for the American recording for age bands six to 11 years. It is recommended that the test material is recorded by a UK English speaker, with substitution of high error-rate target words, followed by normative data collection for the new test material.

Child↗
PubMed1977

[The sensitivity of various in-vitro-test systems in biological testing of materials].

In the present paper the biological activity of methylmethacrylate Monomer and di-methylparatoluidin on stationary, cell-proliferating and bacterial cultures is examined. The equi-toxic concentrations were lower in cell culture systems than in stationary cell suspensions or bacterial cultures. Accordingly biological reaction appears to depend on the effective concentration of the toxic substance as well as on the specific sensitivity of the test system. There is no correlation between the sensitivity of cellular and of bacterial test systems.

Animals↗
PubMed2001

Modified short-term guinea pig sensitization tests for detecting contact allergens as an alternative to the conventional test.

The conventional adjuvant and patch test (APT) method of guinea pig sensitization testing was modified in 2 ways, s-APT and s-APT(2), in order to shorten the test period. These short-term test methods consist of 72-h closed application of test material with intradermal injection of emulsified Freund's complete adjuvant (E-FCA) for 1st induction, 48-h closed application of test material with (s-APT) or without (s-APT(2)) intradermal injection of E-FCA on the 7th day for 2nd induction, and open application on the 14th day for challenge. They were compared with conventional APT by using 8 allergenic chemicals (formaldehyde, nickel sulfate, cobalt sulfate, ethyl-p-aminobenzoate (benzocaine), isoeugenol, 2-mercaptobenzothiazole, 2,4-dinitrochlorobenzene (DNCB) and 1-phenylazo-2-naphthol (Sudan I)). The short-term methods gave similar results to those of conventional APT in terms of mean response, sensitization rate and sensitization potency (challenge concentration that induces a mean response equal to 1.0). Thus, our short-term methods, which are capable of evaluating skin sensitization within 17 days, are sufficiently sensitive to detect potentially hazardous contact allergens.

Allergens↗
PubMed2006

Drug adsorption to plastic containers and retention of drugs in cultured cells under in vitro conditions.

Loss of drug content during cell culture transport experiment can lead to misinterpretations in permeability analysis. This study analyses drug adsorption to various plastic containers and drug retention in cultured cells under in vitro conditions. The loss of various drugs to polystyrene tubes and well plates was compared to polypropylene and glass tubes both in deionised water and buffer solution. In cellular uptake experiments, administered drugs were obtained from cultured cells by liquid extraction. Samples were collected at various time points and drug concentrations were measured by a new HPLC-MS/MS method. Acidic drugs (hydrochlorothiazide, naproxen, probenicid, and indomethacin) showed little if any sorption to all tested materials in either water or buffer. In the case of basic drugs, substantial loss to polystyrene tubes and well plates was observed. After 4.5 h, the relative amount remaining in aqueous test solution stored in polystyrene tubes was 64.7 +/- 6.8%, 38.4 +/- 9.1%, 31.9 +/- 6.7%, and 23.5 +/- 6.1% for metoprolol, medetomidine, propranolol, and midazolam, respectively. Interestingly, there was no significant loss of drugs dissolved in buffer to any of the tested materials indicating that buffer reduced surficial interaction. The effect of drug concentration to sorption was also tested. Results indicated that the higher the concentration in the test solution the lower the proportional drug loss, suggesting that the polystyrene contained a limited amount of binding sites. Cellular uptake studies showed considerable retention of drugs in cultured cells. The amounts of absorbed drugs in cellular structures were 0.45%, 4.88%, 13.15%, 43.80%, 23.57% and 11.22% for atenolol, metoprolol, medetomidine, propranolol, midazolam, and diazepam, respectively. Overall, these findings will benefit development and validation of further in vitro drug permeation experiments.

Adsorption↗
PubMed2001

Cognitive effects in dichotic speech testing in elderly persons.

OBJECTIVE: To study the effect of chronologic age on central auditory functions using dichotic speech tests and to study whether and how the age effect in dichotic listening is related to cognitive ability. DESIGN: Dichotic speech tests and cognitive tests were performed on 30 bilaterally hearing-impaired subjects, with a pure-tone average better than 50 dB HL. They were between 42 and 84 yr of age and were divided into an older and a younger group comprising 15 subjects each. The dichotic test material were digits, low-redundancy sentences and consonant-vowel syllables. The subjects reported stimuli heard in both ears (free report) or in one ear (directed report to left or right ear). The cognitive test battery comprised tests focusing on short-term memory, verbal information-processing speed and phonologic processing. RESULTS: A decreased overall performance in all dichotic speech tests was observed in the older group. In the syllable test the older subjects showed poorer results when focusing on the stimuli heard in the left ear, as compared with when focusing on stimuli heard in the right ear, whereas the younger group showed almost equal results for left- and right ear-focusing conditions. An age effect was also seen in reaction times recorded in the cognitive tests and in the scores of the reading span test. These cognitive parameters correlate with the results of the dichotic test when focusing to the left, but not when focusing to the right in the directed report condition. In the free report condition the overall performance showed a high correlation with cognitive test parameters. CONCLUSIONS: Effects of chronologic age in dichotic speech tests in the elderly have been verified. The degree of effect is dependent on test material, way of reporting and focusing condition. The different listening tasks in dichotic tests put different demands on cognitive ability shown by a varying degree of correlations between cognitive function and dichotic test parameters. Also, the results indicate a strong connection between age-related cognitive decline in the elderly and problems to perceive stimuli presented to the left ear.

Adult↗
PubMed1986

Normal vertebral body size and compressive strength: relations to age and to vertebral and iliac trabecular bone compressive strength.

Three thoracic (T5-T7) and three lumbar (L1-L3) vertebral bodies and the anterior parts of both iliac crests were removed from 44 normal individuals aged 15-87 years who had died suddenly. Small, cylindrical samples of trabecular bone (length 5 mm, diameter 7 mm) from T6, L1, and L3 and from the standard site for iliac crest biopsies were compressed in an Alwetron-250 materials testing machine. Whole vertebral bodies from T5, T7, and L2 with cut planoparallel end-plates were compressed in an Instron materials testing machine. The maximum compressive stress value sigma max of the whole vertebral bodies and of the vertical vertebral trabecular bone decreased with age with almost parallel linear regression lines. At any age the sigma max for whole vertebral bodies was about 1.6 MPa (1 MPa = 100 N/cm2) higher than for the trabecular bone. The average cross-sectional area of the vertebral bodies increased by 25-30% from the age of 20 to 80 years. The anisotropic properties of the vertebral trabecular bone (expressed as the ratio between the vertical and horizontal sigma max) increased markedly with age. A highly significant positive correlation was observed between the vertical vertebral trabecular bone sigma max (X) and the total vertebral body sigma max (y = 0.90x + 1.75, r = 0.88, P less than 0.01). The slope was not significantly different from 1, whereas the intercept was positive (P less than 0.01). The average total vertebral body sigma max (range 1.5-7.8 MPa) could be predicted from mechanical tests on horizontal iliac crest bone biopsies with standard error of estimate (SEE) of 0.92 MPa.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1977

The problem of platelet autoantibodies. II. The applicability of the 14C-serotonin release test.

To evaluate the applicability of the 14C-serotonin release test for the demonstration of platelet autoantibodies, normal test material (sera, plasmas, globulin fractions), HLA-specific complement-fixing platelet antibodies and aggregated human gamma-globulin (agammaG) were tested in comparison to sera (plasmas, globulin fractions) of 101 thrombocytopenic patients including 46 cases of idiopathic thrombocytopenic purpura. Whereas defined immunological stimuli (HLA antibodies, agammaG) were detected with satisfactory precision, platelet autoantibodies could not be demonstrated. Only sera containing HLA antibodies due to previous immunization induced reproducible 14C-serotonin release. Results with test material from thrombocytopenic patients were analyzed by 2 x 2 tables and inconsistencies were shown to be caused by methodological variations.

Autoantibodies↗
PubMed1988

Interfacial bond strengths between layers of visible light-activated composites.

The bond strengths between composite layers either cured to themselves or to other types (classes) of composites of similar or different brands were measured by using a direct tensile test (true tension). The diametral compression test for tension for each material tested was also conducted according to ADA specification No. 27. The values were used for comparison. 1. The interfacial bond strengths were generally found to be higher than the cohesive strengths of the weaker materials when cured to different types of composites or of the weak region in the specimen when composites were cured to themselves. 2. The cohesive tensile failure of the materials occurred at much lower stress levels than their corresponding diametral tensile strength (ranging from 1/4 to 1/3 of the diametral strength). 3. When two types of composites were bonded together the cohesive failure occurred consistently within the materials with lower diametral strength. Correlation was observed between the values of cohesive strength of material measured with true tension and the diametral test. 4. A urethane dimethacrylate microfilled composite bonded weakly to BIS-GMA composite, therefore, their combined use should be avoided. 5. Incremental placement produced a clinically acceptable bond strength because it exceeded or was at least comparable to the cohesive strength of the material.

Composite Resins↗
PubMed1997

IRAG working group 2. CAM-based assays. Interagency Regulatory Alternatives Group.

CAM-based assays, in which test material is applied to the chorion allantoic membrane (CAM) of embryonated chicken eggs, were assessed as alternatives to the Draize eye irritation test. Two general types of CAM-based assays are currently in use, the HET-CAM test and the CAMVA assay. Evaluations were made of five data sets produced with three different modifications of the HET-CAM test and two data sets obtained with the same CAMVA protocol. Data sets consisted of 9-133 test chemicals, usually from the sponsor's product line, and also from a validation trial. Each data set and assay protocol were analysed for quality of data, purpose and proposed use of the assay, range of responses covered, range of test materials amenable, current use in safety and risk assessment both in-house and for regulatory purposes. Since the MMAS Draize score was not available for all in vivo data sets, the sigma MMMIS, which correlates well with the MMAS, was used instead. In vitro/in vivo correlations calculated with Pearson's linear coefficient ranged from r = 0.6 to r = 0.9 for six of seven data sets. Corneal opacity and inflammation of the iris showed the best correlation to in vitro data. Prediction rates were significantly improved when partial linear regression was used, and the predictivity of three different HET-CAM protocols was almost the same. HET-CAM assays showed the best prediction with surfactants and surfactant-based formulations, whereas the CAMVA assay provided the best performance with alcohols.

Allantois↗
PubMed1989

[Evaluation of cytotoxicity of VLC Dycal in tissue culture for clinical use].

The purpose of this study was to evaluate the VLC Dycal (visible light cured composite-calcium hydroxide material) to see whether it is suitable or not as a direct or indirect pulp capping agent for clinical use by means of the cell culture test. Two light cured composite resins, P-30 and Silux, and also Dycal and Ca(OH)2 were used as a control for a comparative cytotoxicity test with VLC Dycal. All test materials were put into the glass tubes (4 mm diameter X 1 mm high), then illuminated for 10, 20, 30, 40, 50 and 60 seconds through a matrix strip with direct contact with a Prisma-light source (L.D. Caulk), just before testing. Fibroblasts, 5 ml of 1 X 10(5) cells per ml in Eagle's MEM medium with 10% FCS, penicillin (100 U/ml) and streptomycin (100 micrograms/ml) were evenly seeded on a cover glass in a tissue culture dish and incubated for 24 hours at 37 degrees C in a humidified atmosphere of a 5% CO2 in air. After 24 hours, the medium was replaced with 5 ml of agar overlay medium consisting of 10% FCS, Eagle's MEM medium and 1.5% agar. Glass tubes (n = 8) filled with the test materials were placed at the center of the agar, and incubated for 24 hours in 5% CO2 in air at 37 degrees C. After 24 hours of incubation, the cover glass was removed and the cells were fixed in 10% neutral formalin and then stained by H.E. to differentiate the areas of affected and unaffected cells beneath the test specimens. The affected area was quantitatively determined using an image analysis system.(ABSTRACT TRUNCATED AT 250 WORDS)

Bisphenol A-Glycidyl Methacrylate↗
PubMed1984

Studies on migration inhibitory factors of non-lymphoid origin.

A large number of mouse fibrosarcoma and adult guinea pig fibroblast cultures were examined for their ability to produce migration inhibitory activity. In most cases culture supernatants were found to inhibit macrophage migration, in a dose-dependent manner. Toxicity of the tested material could be excluded by: a) experiments using colchicine as a stimulator of macrophage migration and, b) examination of the effect of test materials on macrophage monolayer cultures. Additionally, migration inhibitory activity was found in fibroblast, but not fibrosarcoma frozen and thawed extracts. Furthermore, incubation of cells with puromycin could only inhibit production by fibrosarcoma, thus suggesting that the fibroblast activity was due to preformed cellular constituents. Fractionation of concentrated culture supernatants by Sephadex G-200 gel filtration showed that the activity derived from fibrosarcoma cells could be eluted in a narrow molecular weight fraction (18,000-22,500), whereas the fibroblast activity was heterogenously distributed over a wide range. Migration inhibitory activity in fibroblast extracts was mainly associated with higher molecular weight material. Differences could be demonstrated between these activities and lymphocyte migration inhibitory factor, including inhibition by methyl-pentoses and the presence of macrophage aggregating activity.

Animals↗
PubMed2000

In-line moisture measurement during granulation with a four-wavelength near infrared sensor: an evaluation of particle size and binder effects.

Factors affecting in-line near infrared (NIR) moisture measurement with a four-wavelength sensor were evaluated (choice of binder used in granulation liquid and the increase in particle size). An entire NIR spectrum is not necessary for the measurement of water, and often the use of only a few NIR wavelengths around the water band enables reliable and high-speed detection of moisture. Glass ballotini and microcrystalline cellulose (MCC) were used as model test materials. The binders studied were poly[1-(2-oxo-1-pyrrolidinyl)ethylene] (PVP) and gelatin. Full off-line NIR spectra of test materials at different levels of binder solutions were measured. The major spectral features for both the binders were bands around 1700 nm (first overtones CH related stretches) and 2200 nm (combination bands). Gelatin also had an NH band around 1500 nm (first overtones of NH stretches) and combination bands at about 2050 nm. Particle size effects were observed as an increase in spectra baseline. All these factors should be considered when choosing NIR wavelengths used for detection of water with a fixed wavelength set-up. A robust calibration model enables the development of in-process control of wet granulation processes.

Calibration↗
PubMed2001

Significance of the internal locking mechanism for loop security enhancement in the arthroscopic knot.

PURPOSE: Secure tissue fixation of an arthroscopic knot depends on the security of the initial loop and additional locking half-hitches. The purpose of this report is to evaluate the loop and knot security relative to the internal locking mechanism of arthroscopic slip knot. TYPE OF STUDY: This is an experimental study designed for knot and loop security on a material testing system. The measurements were carried out in a blinded fashion in which the tester was not aware of the type of knot being tested. METHODS: Five configurations of arthroscopic knots (overhand throw, Duncan loop, Revo knot, Tennessee slider, and SMC knot) were created around a 5-mm diameter metal bar using a No. 2 braided suture. For each knot configuration, 10 knots were tested for displacement at cyclic loading, load to clinical failure (3-mm displacement), ultimate failure load, and mode of failure on the servo-hydraulic material testing system (MTS 858 MiniBionix test system; MTS, Minneapolis, MN). A 1-way analysis of variance was used to determine the statistical difference in displacement at cyclic loading, load to clinical failure, and ultimate failure load between each knot configuration. RESULTS: In the cyclic loading test, the average displacement of all knots was clinically insignificant, with the average being less than 0.24 mm. The overhand throw had the worst characteristic in the load to failure test. The other 4 knots had an optimal load to failure. The SMC knot, which has an internal locking mechanism, had good loop and knot security in the load to clinical failure and ultimate failure load (P <.05). The SMC and the Revo knots failed by knot breakage (material failure) whereas the other knots failed by knot slippage (loop failure). CONCLUSIONS: The internal locking mechanism flips the post strand to convert the loop strand into a new post strand while rerouting the original post strand around a new post. An arthroscopic knot with an internal locking mechanism can enhance loop security.

Analysis of Variance↗
PubMed2005

Effect of one versus two distal locking bolts on the biomechanics of tibial interlocking nail: a comparative study using a new model.

OBJECTIVE: To investigate the impact of one versus two distal locking bolts on the mechanical properties of tibial interlocking intramedullary nails. METHODS: Twenty 9-mm titanium alloy locking nails were divided into two equal groups in which the nails were fixed with only one and two distal locking bolts, respectively. Each group was further divided into two sub-groups for compression and torsion tests separately using a universal material-testing machine. RESULTS: In the compression tests, the average maximum strength of double bolts was greater than that of the single bolt (P<0.05), but the number of the bolts did not significantly affect the results of the torsion tests in terms of the either the maximum torsion moment or angle (P>0.05). CONCLUSION: One distal bolt is sufficient for fixing stable fractures and double bolts are recommended for management of serious fractures. The model we used is convenient and economic for examining the biomechanics of the tibial nails, especially for comparative purposes.

Alloys↗
PubMed1998

Bioavailability and pharmacokinetics of microencapsulated 1,3-dichloropropene in rats.

The potential oral toxicity of 1,3-dichloropropene (1,3-D) has been evaluated in a number of dietary toxicity studies. The relatively high vapor pressure of 1,3-D, its short half-life in drinking water, and its reactivity with constituents of feed necessitated the use of a microencapsulated formulation (starch-sucrose shell) of 1,3-D in these studies. The bioavailability of ingested microencapsulated 1,3-D was determined by characterizing and comparing the kinetics of 1,3-D in the blood of female F344 rats coadministered microencapsulated 1,3-D and neat 13C-1,3-D (25 mg/kg each) via gavage. Blood concentrations of total or cis- and trans-isomers of 1,3-D in treated rats were determined using gas chromatography-mass spectroscopy (GC-MS) or in situ membrane extraction MS. Urine was also collected and analyzed by GC-MS for the presence of the mercapturate excretion product of 1,3-D [N-acetyl-S-(3-chloropropenyl-2)-L-cysteine; 1,3-DMA]. Blood levels of 1,3-D and 13C-1,3-D displayed similar kinetics, peaking within 10 min of dosing followed by a rapid biphasic elimination. Higher peak blood levels and greater blood curve areas (AUC) were attained for trans- than cis-1,3-D and 13C-1,3-D and greater amounts of cis- than trans-1,3-DMA and 13C-1,3-DMA were excreted in the urine consistent with the known rapid and disproportionate glutathione conjugation of the cis-isomer in the gastric mucosa. Slightly higher cis-1,3-D than cis-13C-1,3-D blood levels and AUCs were also consistently noted while the reverse was true for urinary excretion of cis-13C-1,3-DMA and cis-1,3-DMA suggesting that 1,3-D derived from microencapsulated test material may be absorbed and/or metabolized in the stomach mucosa at a slightly slower rate than that from neat material. The latter, however, would be of no consequence during the administration of 1,3-D to animals via their diets as competing test materials would not be present and 1,3-D blood kinetics were unaffected. Overall, the results of this study demonstrate the ready bioavailability of microencapsulated 1,3-D and rapid elimination of 1,3-D from the blood of rats.

Allyl Compounds↗