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PubMed2001

Of flux and flooding: the advantages and problems of different isotopic methods for quantifying protein turnover in vivo : II. Methods based on the incorporation of a tracer.

The most common methods for measuring the incorporation of tracer amino acids into tissue protein are the constant tracer infusion and the flooding dose. The flooding dose is an attractive method for measuring tissue protein synthesis because of its convenience and precision. A primary assumption of the method, that the free amino acid precursor pools are equilibrated with the true precursor pool, aminoacyl-transfer RNA, has recently been validated. When short labelling periods are involved, the large dose of amino acid does not appear to alter protein synthesis. The constant tracer infusion is a satisfactory method from a theoretical point of view, but its use requires the measurement of the protein synthetic precursor pool. The best estimate of the aminoacyl-tRNA precursor pool for the constant infusion method appears to be the acid-soluble tissue pool in muscle and VLDL apolipoprotein B-100 in the liver. The experimental approach chosen for measuring tissue protein synthesis should be dictated by the question being addressed.

Amino Acids↗

PubMed2003

Identification of material constants for piezoelectric transformers by three-dimensional, finite-element method and a design-sensitivity method.

In this paper, an inversion scheme for piezoelectric constants of piezoelectric transformers is proposed. The impedance of piezoelectric transducers is calculated using a three-dimensional finite element method. The validity of this is confirmed experimentally. The effects of material coefficients on piezoelectric transformers are investigated numerically. Six material coefficient variables for piezoelectric transformers were selected, and a design sensitivity method was adopted as an inversion scheme. The validity of the proposed method was confirmed by step-up ratio calculations. The proposed method is applied to the analysis of a sample piezoelectric transformer, and its resonance characteristics are obtained by numerically combined equivalent circuit method.

Journal Article↗

PubMed1997

Grounded theory method, Part II: Options for users of the method.

Era-specific issues are presented for the consideration of the potential grounded theorist. Two of the issues are general to grounded theory method, while the other four assist in clarifying aspects relevant to the selection of a specific mode of the method. Five broad options regarding multiple possible modes of grounded theory method are suggested and detailed. The inquirer is not limited to the two major modes usually presented and discussed in the literature. Users of the method are challenged to continue contributing to the development of the method, while justifying and debating methodological modifications.

Humans↗

PubMed1993

A method of constant stimuli for examining heartbeat detection: comparison with the Brener-Kluvitse and Whitehead methods.

A method of constant stimuli (MCS) for measuring heartbeat detection was examined by comparing performance on this method with the Brener and Kluvitse (BK) method and a variant of the Whitehead (WH') method. All methods required subjects to judge the simultaneity of heartbeat sensations and tones, and each yielded measures of judgment precision and of the temporal location of heartbeat sensations relative to the electrocardiogram R-wave. Both measures were found to be significantly correlated across tasks. A greater proportion of subjects met criteria for classification as heartbeat detectors on the MCS (54%) and BK (50%) tasks than on the WH' task (33%). In the MCS and BK tasks, subjects judged tones presented 100-300 ms after the R-wave to be most simultaneous with heartbeat sensations. Intratask correlations showed that only the MCS procedure yielded stable measurements of both judgment precision and temporal location. The MCS procedure possesses commendable psychometric properties and provides a simpler means than the BK procedure of examining heartbeat detection.

Adult↗

PubMed2005

Comparison of ninhydrin method of detecting amine compounds with other methods of halitosis detection.

OBJECTIVES: Halitosis is a result of overactivity of Gram-negative bacteria for which protein amino acids are the major source of energy. Therefore, statistical correlation between concentrations of volatile sulphur compounds (VSCs) and low-molecular-weight amines should be expected. MATERIALS AND METHODS: Eighty-four patients suffering from halitosis and 40 healthy volunteers aged 20-62 years (average 39.7) participated in the study. In all subjects low-molecular-weight amines were evaluated by the ninhydrin method. Patients with halitosis were randomized into treatment groups. Zinc tablets, tablets and mouthwash containing chlorhexidine or lyophilized lactic acid-forming bacteria were used. RESULTS: Analysis showed that the level of amines was highest in subjects with halitosis (0.39, s.d. +/- 0.06, P < 0.001) and correlated significantly with results of VSC measurement and organoleptic scores (P < 0.001). Reduction of amine levels after treatment was statistically significant (P < 0.001). Three months following treatment the amine levels began to increase (0.37, s.d. +/- 0.05). The amine levels in healthy controls were lower (0.29, s.d. +/- 0.07) and remained at a stable level. CONCLUSION: The salivary amine levels significantly correlated with VSC levels and organoleptic scores. Therefore, the ninhydrin method of detecting salivary amines may be an alternative or additional method of diagnosing halitosis. This method may also be used to evaluate treatment efficacy.

Adolescent↗

PubMed2001

A new method for true and spurious eigensolutions of arbitrary cavities using the combined Helmholtz exterior integral equation formulation method.

Integral equation methods have been widely used to solve interior eigenproblems and exterior acoustic problems (radiation and scattering). It was recently found that the real-part boundary element method (BEM) for the interior problem results in spurious eigensolutions if the singular (UT) or the hypersingular (LM) equation is used alone. The real-part BEM results in spurious solutions for interior problems in a similar way that the singular integral equation (UT method) results in fictitious solutions for the exterior problem. To solve this problem, a Combined Helmholtz Exterior integral Equation Formulation method (CHEEF) is proposed. Based on the CHEEF method, the spurious solutions can be filtered out if additional constraints from the exterior points are chosen carefully. Finally, two examples for the eigensolutions of circular and rectangular cavities are considered. The optimum numbers and proper positions for selecting the points in the exterior domain are analytically studied. Also, numerical experiments were designed to verify the analytical results. It is worth pointing out that the nodal line of radiation mode of a circle can be rotated due to symmetry, while the nodal line of the rectangular is on a fixed position.

Journal Article↗

PubMed1992

Comparison of an in vitro method and an in vivo method of Giardia excystation.

An in vitro method and an in vivo method of excystation were compared to determine the most useful method for the retrieval of Giardia duodenalis isolates. Cysts from 11 Giardia strains were used. In vitro excystation produced motile trophozoites in 16 sets, while in vivo excystation produced trophozoites in all of the 21 comparative sets of excystations. Few cultures were lost because of contamination by either method (17% of in vitro-derived trophozoites versus 23% of in vivo-derived trophozoites; P greater than 0.05). Both methods demonstrated comparable isolate retrieval rates (15% of in vitro-derived trophozoites adapting to culture compared with 29% of in vivo-derived trophozoites; P greater than 0.05), although analysis of the strains retrieved showed that two isolates were retrieved from in vitro excystation alone, compared with four from in vivo excystation. Analysis that included results of extra in vivo cultures showed that a total of nine isolates were retrieved by using this type of excystation. Despite the disadvantages of cost and labor, in vivo excystation appears to be more useful than in vitro excystation for isolate retrieval at the present time.

Animals↗

PubMed1996

Comparison of the recoveries of Escherichia coli and total coliforms from drinking water by the MI agar method and the U.S. Environmental Protection Agency-approved membrane filter method.

Drinking water regulations under the Final Coliform Rule require that total coliform-positive drinking water samples be examined for the presence of Escherichia coli or fecal coliforms. The current U.S. Environmental Protection Agency-approved membrane filter (MF) method for E. coli requires two media, an MF transfer, and a total incubation time of 28 h. A newly developed MF method, the MI agar method, containing indoxyl-beta-D-glucuronide and 4-methylumbelliferyl-beta-D-galactopyranoside for the simultaneous detection of E. coli and total coliforms, respectively, by means of their specific enzyme reactions, was compared with the approved method by the use of wastewater-spiked tap water samples. Overall, weighted analysis of variance (significance level, 0.05) showed that the new medium recoveries of total coliforms and E. coli were significantly higher than those of mEndo agar and nutrient agar plus MUG (4-methylumbelliferyl-beta-D-glucuronide), respectively, and the background counts were significantly lower than those of mEndo agar (< 5%). Generally, the tap water source, overall chlorine level, wastewater source, granular activated carbon treatment of the tap water, and method of grouping data by E. coli count for statistical analysis did not affect the performance of the new medium.

Agar↗

PubMed1982

Analysis of the disagreement between automated bioluminescence-based and culture methods for detecting significant bacteriuria, with proposals for standardizing evaluations of bacteriuria detection methods.

A fully automated method for detecting significant bacteriuria is described which uses firefly luciferin and luciferase to detect bacterial ATP in urine. The automated method was calibrated and evaluated, using 308 urine specimens, against two reference culture methods. We obtained a specificity of 0.79 and sensitivity of 0.75 using a quantitative pour plate reference test and a specificity of 0.79 and a sensitivity of 0.90 using a semiquantitative standard loop reference test. The majority of specimens negative by the automated test but positive by the pour plate reference test were specimens which grew several bacterial species. We suggest that such disagreement was most likely for urine containing around 10(5) colony-forming units per ml (the culture threshold of positivity) and that these specimens were ones contaminated by urethral or vaginal flora. We propose standard procedures for calibrating and evaluating rapid or automated methods for the detection of significant bacteriuria and have analyzed our results using these procedures. We recommend that identical analyses should be reported for other evaluations of bacteriuria detection methods.

Adenosine Triphosphate↗

PubMed1992

Comparison of the Histopaque-1119 method with the Plasmagel method for separation of blood leukocytes for cytomegalovirus isolation.

Histopaque-1119 (Sigma Chemical Co., St. Louis, Mo.) and Plasmagel (Cellular Products, Inc., Buffalo, N.Y.) were compared as density gradient separation reagents for the separation of polymorphonuclear leukocytes and mononuclear cells from blood from the isolation of cytomegalovirus (CMV). Of 200 peripheral blood specimens examined, CMV was recovered from 51 by both methods. The time of detection of immunofluorescent sites or a cytopathic effect associated with CMV was similar by each method. The Histopaque-1119 method was less time-consuming than the Plasmagel method since it did not require a precentrifugation step for the settling of erythrocytes. The use of Histopaque-1119 will permit an effective alternative single-step method for the separation of blood leukocytes for the isolation of CMV.

Blood Component Removal↗

PubMed1996

Comparison of rapid testing methods for enzyme production with the germ tube method for presumptive identification of Candida albicans.

The observation of germ tube production as a method for the presumptive identification of Candida albicans has been in use for many years. Methods have recently been developed for detecting the production of the enzymes L-proline aminopeptidase and beta-galactosaminidase by yeast isolates grown in culture. Both enzymes are produced by C. albicans; other yeasts may produce either L-proline aminopeptidase or beta-galactosaminidase but not both enzymes. One hundred thirty-three clinical yeast isolates, including 55 C. albicans, 27 Candida tropicalis, 22 Torulopsis (Candida) glabrata, and 29 other yeast isolates were tested by the germ tube production method and three tests for enzyme production, with the API 20C method used as a "gold standard." All three enzymatic methods evaluated provided more objective and rapid nonmicroscopic alternatives to the germ tube test and may be used to accurately distinguish C. albicans from other yeasts.

Aminopeptidases↗

PubMed1998

Comparison of broth microdilution method using Haemophilus test medium and agar dilution method for susceptibility testing of Eikenella corrodens.

Susceptibility testing of Eikenella corrodens is usually performed by a Mueller-Hinton sheep blood agar dilution (AD) method. However, this method is impractical for testing only a few strains. We compared AD with the broth microdilution method using Haemophilus test medium (HTM) in order to determine the susceptibility of 36 clinical isolates of E. corrodens to eight antimicrobial agents. MICs obtained by the HTM method yielded 95.5 and 84% agreement (within 2 and 1 log2 dilutions, respectively) with those obtained by AD. The HTM method with incubation in CO2 for 48 h was highly reproducible and constitutes an easy alternative for antimicrobial susceptibility testing of E. corrodens.

Agar↗

PubMed2001

Comparison of spectrophotometric and visual readings of NCCLS method and evaluation of a colorimetric method based on reduction of a soluble tetrazolium salt, 2,3-bis [2-methoxy-4-nitro-5-[(sulfenylamino) carbonyl]-2H-tetrazolium-hydroxide], for antifungal susceptibility testing of Aspergillus species.

The susceptibilities of 25 clinical isolates of various Aspergillus species (Aspergillus fumigatus, A. flavus, A. terreus, A. ustus, and A. nidulans) to itraconazole (ITC) and amphotericin B (AMB) were determined using the standard proposed by NCCLS for antifungal susceptibility testing of[filamentous fungi, a modification of this method using spectrophotometric readings, and a colorimetric method using the tetrazolium salt 2,3-bis [2-methoxy-4-nitro-5-[(sulfenylamino) carbonyl]-2H-tetrazolium-hydroxide] (XTT). Five MIC end points for ITC (MIC-0, no visible growth or 93%. Between visual and spectrophotometric readings, high levels of agreement were found for AMB (approximately 97%) and MIC-1 (approximately 92%) and MIC-2 (approximately 88%) of ITC. Poor agreement was found for MIC-0 of ITC (51% after 24 h), since the spectrophotometric readings resulted in higher MIC-0 values than the visual readings. The agreement was increased to 98% by shifting the threshold level of MIC-0 from 5 to 10% relative optical density and by establishing an optical density of greater than 0.1 for the GC as the validation criterion. No statistically significant differences were found between the NCCLS method and the XTT method, with the levels of agreement exceeding 97% for MIC-0 of AMB and 83% for MIC-0, MIC-1, and MIC-2 of ITC. The XTT method and spectrophotometric readings can increase the sensitivity and the precision, respectively, of in vitro susceptibility testing of Aspergillus species.

Amphotericin B↗

PubMed2002

E-test method for testing susceptibilities of Aspergillus spp. to the new triazoles voriconazole and posaconazole and to established antifungal agents: comparison with NCCLS broth microdilution method.

NCCLS document M38-P describes standard parameters for testing the fungistatic activities (MICs) of established agents against filamentous fungi (molds). This study evaluated the in vitro susceptibilities of 15 Aspergillus flavus isolates, 62 A. fumigatus isolates, and 10 isolates each of A. niger, A. nidulans, and A. terreus to voriconazole, posaconazole, itraconazole, and amphotericin B by the E-test and NCCLS M38-P microdilution methods. The agreement (within 3 dilutions) between methods for voriconazole was independent of the E-test incubation time (93.3 to 100% for four of five species at both incubation times). In contrast, with amphotericin B, itraconazole, and posaconazole, E-test results were more dependent on the incubation time for certain species. For A. fumigatus, posaconazole E-test MICs had better concordance with reference values after 48 h (95.2%) than after 24 h (90%), while the highest agreement for itraconazole MICs was after 24 h (90.3 versus 74.2%) of incubation. Better agreement between the methods was also obtained with 24-h E-test amphotericin B MICs for A. flavus (73.3 versus 26.7%) and A. fumigatus (96.7 versus 64.5%). E-test MICs of the four agents had the lowest percentages of agreement with reference values for A. nidulans (60 to 80%). For isolates for which high MICs were obtained for the four agents by the reference method, high MICs were also obtained by E-test at both 24 and 48 h. The utility of in vitro results of either the E-test or the NCCLS broth microdilution (M38-P) method for Aspergillus spp. needs to be established in clinical trials.

Antifungal Agents↗

PubMed1999

Two-point, timesaving method for measurement of gastric emptying with diagnostic accuracy comparable to that of the conventional method.

Solid-phase gastric emptying is linear. Therefore, the authors calculated gastric-emptying half-time, the time for half of the ingested solids or liquids to leave the stomach, with the conventional multiple-point method and the proposed two-point method (at 0 and 120 minutes) in retrospective and prospective studies of 50 patients each. The results showed excellent correlation. Results with the two-point method were comparable to those with the multiple-point method, and the two-point method substantially reduced technologist and camera times.

Adult↗

PubMed1986

Estimation of total arterial compliance: an improved method and evaluation of current methods.

Determination of arterial compliance in vivo has long interested physiologists. Most current methods for estimating this parameter assume that compliance is constant, i.e., that arterial pressure-volume (P-V) relations are linear, and they also assume that diastolic aortic pressure decay is an exponential function of time. Both of these assumptions, however, are questionable. This study proposes improved methods of estimating compliance based on a Windkessel model of the arterial system but which utilize the area under the pressure tracing rather than the waveform itself. Formulations accounting for both linear and three hypothetical nonlinear arterial P-V relations (exponential, logarithmic, and parabolic) are presented. Data from patients with congestive heart failure and hypertension are used for illustration. Compliances assuming linear P-V relations are reasonably close to those assuming nonlinear P-V relations only at mean aortic pressure. At end-diastolic pressure the linear assumption underestimates and at peak systolic it overestimates the compliances obtained assuming nonlinear P-V relations. The simpler linear assumption still allows a first approximation to compliance, but we show that existing methods for obtaining compliance under this assumption have severe theoretical as well as practical shortcomings. Our proposed method avoids these shortcomings primarily because deviations from an exact exponential form of the pressure wave have less influence on these compliance estimates than currently used methods.

Arteries↗

PubMed1998

Gel stretch method: a new method to measure constitutive properties of cardiac muscle cells.

Diastolic dysfunction is an important cause of congestive heart failure; however, the basic mechanisms causing diastolic congestive heart failure are not fully understood, especially the role of the cardiac muscle cell, or cardiocyte, in this process. Before the role of the cardiocyte in this pathophysiology can be defined, methods for measuring cardiocyte constitutive properties must be developed and validated. Thus this study was designed to evaluate a new method to characterize cardiocyte constitutive properties, the gel stretch method. Cardiocytes were isolated enzymatically from normal feline hearts and embedded in a 2% agarose gel containing HEPES-Krebs buffer and laminin. This gel was cast in a shape that allowed it to be placed in a stretching device. The ends of the gel were held between a movable roller and fixed plates that acted as mandibles. Distance between the right and left mandibles was increased using a stepper motor system. The force applied to the gel was measured by a force transducer. The resultant cardiocyte strain was determined by imaging the cells with a microscope, capturing the images with a CCD camera, and measuring cardiocyte and sarcomere length changes. Cardiocyte stress was characterized with a finite-element method. These measurements of cardiocyte stress and strain were used to determine cardiocyte stiffness. Two variables affecting cardiocyte stiffness were measured, the passive elastic spring and viscous damping. The passive spring was assessed by increasing the force on the gel at 1 g/min, modeling the resultant stress vs. strain relationship as an exponential [sigma = A/k(ekepsilon - 1)]. In normal cardiocytes, A = 23.0 kN/m2 and k = 16. Viscous damping was assessed by examining the loop area between the stress vs. strain relationship during 1 g/min increases and decreases in force. Normal cardiocytes had a finite loop area = 1.39 kN/m2, indicating the presence of viscous damping. Thus the gel stretch method provided accurate measurements of cardiocyte constitutive properties. These measurements have allowed the first quantitative assessment of passive elastic spring properties and viscous damping in normal mammalian cardiocytes.

Animals↗

PubMed1990

Changes in female sexual behavior of old female rats: comparison between exit method and non-exit method.

The female sexual behavior including proceptivity, receptivity and sociosexual behavior of preferential approach to males was tested in 12 young adult female rats aged from 6 to 7 months and in 59 old female rats aged from 18 to 21 months with the exit method and the traditional non-exit method. The percentage of rats displaying a high lordosis quotient (LQ) and that of rats showing solicitation were lower in old females than in young females tested either with the non-exit method or the exit method. Only with the non-exit method were the mount frequency per minute of male rats toward old females of the high-LQ group and the solicitation score of old female rats lower as compared to young females. The incidence of preferential approach of the female rats, whether young or old, toward intact young males and their time spent in the compartment of intact young males were not different, however, the frequency of old female rats to visit the arena of intact young males was lower than that of young females. In summary, the major age-related changes in female sexual behavior, the low percentage of rats displaying high LQ and of rats showing solicitation, are quite robust and environmentally independent.

Age Factors↗