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Results for “Endpoint Determination”

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At least 55 records · Page 3Linked to original sources

PubMed1993

Human basic tear fluid osmolality. II. Importance of processing strategy.

Osmolalities of 100 human inferior tear prism fluid samples collected from two subjects and 100 standard solution samples (290 mOsm/Kg) were determined from their melting-point temperatures with the Clifton Nanoliter Osmometer. Accuracy and reliability comparisons were made for endpoints obtained using a single-sample simultaneous-recalibration (SS/SR) strategy, vs a lowest-of-six periodic-recalibration (LS/PR) strategy. Tear fluid osmolality values based on the LS/PR strategy were significantly lower (hypotonic) than for the SS/SR strategy (overall mean = 302.4 and 307.8 mOsm/Kg, respectively; p < 0.0012). The mean difference (5.4 mOsm/Kg) resulted from the combined effects of machine drift and reduced reliability of endpoint determination for tear fluid in comparison to that of a homogenous standard solution. LS/PR osmolality was linearly correlated to SS/SR osmolality with a slope of 0.433 and the two endpoint strategies resulted in equivalent values at 298.4 mOsm/Kg. Eighty-four percent (84%) of individual osmolality readings were greater than 298.4 mOsm/kg, and an 'averaging-type' effect caused LS/PR osmolalities to be increasingly less than SS/SR values above this value. These outcomes from two subjects were approximated by a parallel statistical model. We suggest that physiological representation of basic human tear fluid is more accurate using the single-sample simultaneous-recalibration strategy. Basic human tear prism fluid is more hypertonic and has a greater within-subject range in normal (non-dry eye) humans than previously realized.

Humans↗

PubMed1997

Comparison of the Etest and a microbroth dilution system (Sceptor) to a reference agar dilution method for susceptibility testing of Bilophila wadsworthia.

OBJECTIVE: To compare the Etest and a microbroth dilution system (Sceptor) to a reference agar dilution method for susceptibility testing of Bilophila wadsworthia. METHODS: The susceptibility of 15 clinical isolates of Bilophila wadsworthia was determined by the National Committee for Clinical Laboratory Standards (NCCLS) agar dilution method using triphenyltetrazolium chloride for endpoint determination. The results were compared with the results obtained by the E test and a commercial microbroth dilution system (Sceptor). RESULTS: Comparison of the MICs obtained by the reference method and the Etest revealed few discrepancies, with piperacillin and metronidazole being the only exceptions. The overall agreement was 70% within one dilution step. The discrepancies did not result in major interpretative errors. The overall essential agreement using susceptibility categories was 98% for the E test and 99% for the microdilution system. CONCLUSIONS: Both methods may be considered as acceptable alternatives for testing individual isolates of B. wadsworthia.

Journal Article↗

PubMed2003

Comparison of three methods for in vitro susceptibility testing of Candida species with flucytosine.

Optimal methods for susceptibility testing of Candida spp. with flucytosine have not been determined. Breakpoints were recommended in 1984, but never validated. In this study, we compared the 1984 recommended macrodilution broth method (using an 80% endpoint) with a modification of the more recent NCCLS-recommended microdilution broth method with three endpoints-spectrophotometric 50% and 80% and a no growth endpoint determined by eye. NCCLS and British Society for Medical Mycology (BSMM) breakpoints were also compared. One hundred and fifty isolates comprised of Candida albicans, Candida tropicalis, Candida krusei, Candida glabrata, Candida parapsilosis and Candida lusitaniae were tested. Reproducibility was excellent. For C. albicans (n = 65), the correlation between tests was excellent (>75%), with few major discrepancies (<5%). For C. tropicalis (n = 27), correlation was good (59%), but there were a small number of major discrepancies (up to 11%, depending on breakpoint used). Results by the broth macrodilution method were generally higher than both microdilution methods for C. glabrata (n = 16; correlation of 18.8%), but only one major discrepancy was seen. Ten of the 11 C. parapsilosis isolates tested were susceptible by all methods, regardless of breakpoint chosen, with a correlation of 18.2%, but no major discrepancies were seen. A correlation between all methods (50%) was seen with C. lusitaniae (n = 10), with many isolates resistant or intermediate. In contrast, correlation between methods for C. krusei was poor (<5%); NCCLS microtitre modification produced results that were classified as intermediate or resistant, regardless of the breakpoint used. The methodology for susceptibility testing C. albicans is robust. Additional work to optimize susceptibility testing with flucytosine is necessary for non-albicans Candida species, especially C. krusei.

Antifungal Agents↗

PubMed1993

Molecular characterization of lengthy mitochondrial DNA duplications from the parasitic nematode Romanomermis culicivorax.

Complete nucleotide sequences, precise endpoints and coding potential of several 3.0-kilobase mitochondrial DNA (mtDNA) repeating units derived from two isofemale lineages of the mermithid nematode Romanomermis culicivorax have been determined. Endpoint analysis has allowed us to infer deletion and inversion events that most likely generated the present day repeat configuration. Each amplified unit contains the genes for NADH dehydrogenase subunits 3 and 6 (ND3 and ND6), an open reading frame (ORF 1) that represents a cytochrome P450-like gene, and three additional unidentified open reading frames. The primary nucleotide sequences of the R. culicivorax mt-repeat copies within individual haplotypes are highly conserved; three nearly complete copies of the repeat unit vary by 0.01% at the nucleotide level. These observations suggest that concerted evolution mechanisms may be active, resulting in sequence homogenation of these lengthy duplications.

Amino Acid Sequence↗

PubMed1976

An integrated approach to lipid profiling: enzymatic determination of cholesterol and triglycerides with a centrifugal analyzer.

We describe enzymatic methods for determination of cholesterol and triglycerides (triacylglycerols), adapted for use with a centrifugal analyzer. Triglycerides are determined by a two-point kinetic method, which utilizes a single glycerol standard for calibration and provides for a within-run reagent blank correction. The endpoint determination of cholesterol combines the unique blanking capabilities of the centrifugal analyzer to correct for sample and reagent blank interferences. Results correlate well with those obtained by procedures standardized by the Lipid Research Clinics Program for use with a continuous-flow system.

Autoanalysis↗

PubMed1990

Cancer prevention trials in China and Finland.

Intervention studies are now viewed as a useful and necessary approach to understanding the relation between nutrition and cancer. Over 20 such studies have been initiated in the past 7 years. Foreign countries may be an attractive site for such investigations, mainly because of desirable population characteristics such as unusually high rates of the cancer being studied, low dietary intake of potential chemopreventive nutrients, stability of the population, and high compliance, and also because of favorable logistical aspects including existing medical, social, or governmental structures that facilitate delivery of the intervention, ongoing cancer registries for endpoint determination, and reduced cost. The three basic elements of an intervention trial, identification and recruitment of a study population, delivery of the intervention and assessment of compliance, and ascertainment of endpoints, are the same in a foreign country as in the United States, but there are a number of special considerations, most notably communication difficulties due to language differences and distance between collaborators, which complicate foreign trials both before and during implementation. The basic elements and status of ongoing trials in China and Finland are presented.

Adult↗

PubMed1989

A spectrophotometric assay for meso-diaminopimelate decarboxylase and L-alpha-amino-epsilon-caprolactam hydrolase.

A spectrophotometric assay for the activities of mesodiaminopimelate decarboxylase and L-alpha-amino-epsilon-caprolactam hydrolase is described. With the commercially available enzyme saccharopine dehydrogenase lysine formed either by decarboxylation of meso-diaminopimelate or by hydrolysis of L-alpha-amino-epsilon-caprolactam is converted to saccharopine with the concomitant oxidation of NADH, which is monitored by the decrease in absorbance at 340 nm. For meso-diaminopimelate decarboxylase this assay can be performed either as an endpoint determination, when working with crude extracts, or as a continuous spectrophotometric assay of partially purified enzyme preparations. The activity of L-alpha-amino-epsilon-caprolactam hydrolase can only be assayed by the endpoint method because of the great differences in the pH optima of the hydrolase and the saccharopine dehydrogenase.

Azepines↗

PubMed1986

Bioluminescence for USP sterility testing of pharmaceutical suspension products.

Bioluminescence measurement significantly improved the accuracy, sensitivity, precision, and reliability of the current visual endpoint determination for the USP sterility test and eliminated the day 7 transfer/dilution step required for testing suspension products. Thirteen strains of bacteria and fungi (representing potential contaminants in sterile products), three pharmaceutical suspension products, and four media were used in the experiment. No interference from suspension products was encountered in the detection of microbial growth by the bioluminescence measurement. The poor fungal growth encountered was attributed to insufficient diffusion of oxygen into the medium and was circumvented by use of a large tube size (38 by 200 mm) or by vortexing the medium once during the 2-week incubation period. Bioluminescence measurement would facilitate automated handling of the sterility test endpoint readout operation. The optimum parameters of bioluminescence measurement for application in sterility testing were determined.

Bacteria↗

PubMed2006

New process control strategy for wastewater chlorination and dechlorination using ORP/pH.

Due to its efficiency and relatively low capital demanding, many wastewater treatment plants have applied chlorination for disinfection of treated wastewater before discharging it. However, determination of optimal doses of chlorine for chlorination and sulfite for dechlorination, which removes residual chlorine, should made to guarantee complete destruction of microorganisms in treated wastewater and to protect aquatic life in a receiving stream. In this study, a new ORP/pH based approach to determine endpoints of breakpoint chlorination and of dechlorinating titration and to optimize doses of chlorine and sulfite. In this new method, significant points on the ORP and pH profiles occurring during the titrations for chlorination and dechlorination were utilized to determine chlorine demand and sulfite dosage.

Chlorine↗

PubMed1987

Detection of antibody to murine cytomegalovirus by enzyme-linked immunosorbent and indirect immunofluorescence assays.

We have compared murine cytomegalovirus (MCMV) antibody determination by enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence assay. A comparison of antibody detection with 146 serum samples at a 1:20 dilution showed 100% agreement (60 negatives and 86 positives) between the assays. There was close agreement of endpoint determinations of sera by both methods. After experimental MCMV infection, antibody to MCMV was detected by both assays as early as day 7, and high titers persisted as late as 6 months. In contrast to immunocompetent littermates, athymic nude mice did not develop antibody after infection. Mice lacking antibody detectable by ELISA were susceptible to lethal MCMV challenge. In a survey of animals from five commercial sources, MCMV antibody was not detected unless mice were experimentally infected. MCMV antibody determination by ELISA is a convenient method, comparable to the indirect immunofluorescence assay in sensitivity and specificity.

Animals↗

PubMed1999

Optimizing voriconazole susceptibility testing of Candida: effects of incubation time, endpoint rule, species of Candida, and level of fluconazole susceptibility.

Voriconazole is a new triazole antifungal agent that has potent activity against many isolates of Candida, including Candida krusei and Candida glabrata. In this work, we studied the impact of glucose supplementation, incubation time, agitation of the plates prior to reading, endpoint determination rule, visual versus spectrophotometric reading, Candida species, and fluconazole MIC on the MIC of voriconazole for Candida isolates tested by using the microdilution format assay of the National Committee for Clinical Laboratory Standards (NCCLS) M27-A antifungal susceptibility testing methodology. For both voriconazole and fluconazole, a spectrophotometric endpoint of 50% reduction in turbidity relative to the growth control correlated most closely with the NCCLS-defined visual endpoint of "prominent decrease in turbidity." Correlation was generally better after 24 h of incubation than after 48 h. Supplementation of the medium to contain 20 g of glucose/liter did not alter the MIC significantly but did enhance growth and simplify visual readings. All Candida species appeared potentially susceptible to voriconazole, including isolates of C. krusei. For some isolates for which fluconazole MICs were markedly elevated voriconazole MICs were also elevated, but the clinical significance of these observations remains to be determined.

Amphotericin B↗

PubMed2002

Determination of barbituric acid, utilizing a rapid and simple colorimetric assay.

Barbituric acid is widely used in the manufacturing of plastics, textiles, polymers, and pharmaceuticals. Three assay methods are presented, which can utilize either aqueous or solid samples. The detection of as little as 10 microg of barbituric acid can be accomplished, either as an aqueous or solid sample, when using micro reaction tubes. The red-violet endpoint is easily discerned and results upon the formation of a violuric acid derivative. A Spot Test protocol is described which allows for a positive/negative indication of barbituric acid presence. The Spot Test is sensitive to as little as 18.75 microg/ml of barbituric acid. The construction of a Standard Curve for assaying multiple samples and over longer time periods is demonstrated, and is shown to be linear from 18.75 microg/ml to 2.25 mg/ml of barbituric acid. Spectrophotometer readings are made from an absorption peak appearing at 530 nm. The molar absorptivity of the violuric acid derivative is calculated to be 31.4 per mol/l per cm. The micro reaction tube assay will quantitate as little as 10 microg of barbituric acid through interpolation with controls containing a known amount of analyte. Inorganic salts such as NaCl, NaN(3), LiBr, and CaCO(3) do not interfere with endpoint determination. Many organic compounds (also pharmaceuticals) do not inhibit the reaction.

Barbiturates↗

PubMed1997

The Alamar Blue assay to determine drug sensitivity of African trypanosomes (T.b. rhodesiense and T.b. gambiense) in vitro.

Alamar Blue, an indicator for metabolic cell function, was evaluated as a fluorescent and as a colorimetric dye in drug sensitivity assays for human pathogenic African trypanosomes, Trypanosoma brucei rhodesiense and T.b. gambiense. The experimental conditions were adjusted to find those where the relationship between trypanosome number and Alamar Blue signal was linear over the widest possible range. Fluorescent signals correlated to trypanosome numbers from 10(4) trypanosomes/ml (T.b. rhodesiense) and 10(5) trypanosomes/ml (T.b. gambiense) up to 2-3 x 10(6) trypanosomes/ml when trypanosomes were incubated for 2 h with 10% Alamar Blue. Trypanocidal activity of common drugs (melarsoprol, DFMO, suramin, pentamidine and diminazene aceturate) was determined employing this assay. The IC50 values obtained were comparable to those obtained with another fluorochrome, BCECF-AM. The Alamar Blue assay can be applied for drug screening, since it is simple, reproducible and economical. The assay can also be used in field sites with less equipped laboratories, because in addition to fluorometric endpoint determination, a colorimetric reading is possible.

Animals↗

PubMed1984

Clinical evaluation of the Ortho Rubella ELISA Test System.

The Ortho Rubella ELISA Test System (Ortho Diagnostics Canada Ltd., Toronto, Ontario) is an enzyme-linked immunosorbent assay (ELISA) for the determination of IgG antibodies to rubella virus. Comparison of the Ortho Rubella ELISA with a commercial hemagglutination inhibition (HAI) test revealed that the ELISA is well suited for routine use as a qualitative screening test for rubella immune status or the demonstration of seroconversions. Quantitation of rubella antibodies by the Ortho Rubella ELISA, however, requires that ELISA endpoint determination be made on serial serum dilutions.

Antibodies, Viral↗

PubMed1977

A radioimmunoassay for the measurement of 5-androstene-3beta, 17beta-diol in plasma.

A reliable radioimmunoassay for the determination of 5-androstene-3beta, 17beta-diol in plasma is described. Antisera were obtained by immunization of rabbits with 3beta, 17beta-dihydroxy-5-androsten-16-one coupled to bovine serum albumin in position 16. The antiserum was characterized by titer, affinity, and specificity. Only dehydroepiandrosterone (24.3 percent) and pregnenolone (2.7 percent) showed a small cross-reactivity. The assay method consisted of extraction with ether, thin-layer chromatography and endpoint determination. The reliability of the method was studied. The interassay variability was 7.5 percent at a concentration of 1.22 microgram/l. The limit of detection was 0.068 microgram/l. Specificity was achieved by chromatographic separation of the crossreacting steroids. Mass recovery experiments with 250 and 500 pg were performed, in which 99.0 + or - 4.6 percent of the smaller and 97.6 +/- 11.3 percent of the greater mass were recovered. In 45 healthy adult males plasma concentrations between 0.44 and 1.80 microgram/l were found. The median was 1.06 microgram/l. Stimulation of the Leydig cells with human chorionic gonadotropin (HCG) increased plasma concentrations by 93 percent (average in 12 males). Thereapeutic castration in 8 men caused an average decrease of 55.4 percent in plasma values.

Adult↗

PubMed1996

Comparison of a spectrophotometric microdilution method with RPMI-2% glucose with the National Committee for Clinical Laboratory Standards reference macrodilution method M27-P for in vitro susceptibility testing of amphotericin B, flucytosine, and fluconazole against Candida albicans.

The National Committee for Clinical Laboratory Standards has proposed a reference broth macrodilution method for in vitro antifungal susceptibility testing of yeasts (the M27-P method). This method is cumbersome and time-consuming and includes MIC endpoint determination by visual and subjective inspection of growth inhibition after 48 h of incubation. An alternative microdilution procedure was compared with the M27-P method for determination of the amphotericin B, flucytosine, and fluconazole susceptibilities of 8 American Type Culture Collection strains (6 of them were quality control or reference strains) and 50 clinical isolates of candida albicans. This microdilution method uses as culture medium RPMI 1640 supplemented with 18 g of glucose per liter (RPMI-2% glucose). Preparation of drugs, basal medium, and inocula was done by following the recommendations of the National Committee for Clinical Laboratory Standards. The MIC endpoint was calculated objectively from the turbidimetric data read at 24 h. Increased growth of C. albicans in RPMI-2% glucose and its spectrophotometric reading allowed for the rapid (24 h) and objective calculation of MIC endpoints compared with previous microdilution methods with standard RPMI 1640. Nevertheless, good agreement was shown between the M27-P method and this microdilution test. The MICs obtained for the quality control or reference strains by the microdilution method were in the ranges published for those strains. For clinical isolates, the percentages of agreement were 100% for amphotericin B and fluconazole and 98.1% for flucytosine. These data suggest that this microdilution method may serve as a less subjective and more rapid alternative to the M27-P method for antifungal susceptibility testing of yeasts.

Amphotericin B↗

PubMed1991

Antibody responses of chimpanzees immunized with synthetic peptides corresponding to full-length V3 hypervariable loops of HIV-1 envelope glycoproteins.

Immunization of primates or humans with human immunodeficiency virus type 1 (HIV-1) glycoproteins usually elicited moderate immune responses to the principal neutralizing determinant (PND) located within the V3 hypervariable loop of gp120. Since an antibody response to the PND appears to be protective, experiments were carried out to determine the responsiveness of chimpanzees to immunization with synthetic peptides corresponding to the full-length V3 loop. Seven chimpanzees (4 preimmunized with gp160, 2 preimmunized with HIV-1 antigens unrelated to gp160, and 1 unimmunized) were vaccinated with a mixture of full-length V3 loop peptides from 21 distinct HIV-1 isolates (clones) either in unconjugated form or linked to carrier proteins from HIV-1 nef and gag P18, respectively. Six chimpanzees developed high levels of antibodies to the peptides (dilution endpoints 1: greater than 25,000), and 5 had high levels of antibodies to gp120 from HIV-1IIIB (endpoint titers 1: greater than 500,000). Chimpanzees immunized with peptide-carrier conjugates (4) had antibodies to the carrier proteins nef and gag P18, respectively (endpoint titers 1: greater than or equal to 35,000). Virus-neutralizing (VN) antibodies were detected in sera of 5 of 7 chimpanzees, but were present at titers of 1: greater than or equal to 400 only in sera of 2 chimpanzees. One of these was challenged with HIV-1 and was protected against infection, as reported elsewhere. The antibodies were primarily specific for the HIV-1 isolate used for primary immunization before boosting with peptides. The relatively low dilution endpoints of VN antibodies as compared with endpoints determined by site-specific immunoassays probably can be ascribed to imperfect mimicry of conformational epitopes by synthetic peptides. Nevertheless, sequential or simultaneous immunization with recombinant envelope glycoproteins of HIV-1 and selected synthetic peptides offers an approach for eliciting protective immunity against HIV-1.

Amino Acid Sequence↗

PubMed1994

Visual acuity measurement in exceptional children.

BACKGROUND: Numerous reports have been published describing the determination of visual acuity in infants using forced-choice preferential-looking (FPL) methods. Results confirm the effectiveness of this technique for evaluating the child who is unable to respond to conventional clinical methods of visual acuity measurement (e.g., Snellen Letter or Symbol Acuity). METHODS: Using a FPL acuity apparatus and discrimination paradigm similar to that developed and modified by Held, Gwiazda, Mohindra et al., and also used by Atkinson et al., we used grating acuity assessment with binomial method of rapid endpoint determination as well as luminance matched targets (+/- 3.4 percent) with grating regularity controlled (+/- 2.35 percent) in studies of 105 full-term infants with normally developing vision and six exceptional children. CONCLUSIONS: The results of these investigations show that monocular grating acuity thresholds measured in infants in a clinically useful way were also measurable in exceptional children when conventional visual acuity testing failed, thereby enabling the monitoring of improvements in visual acuity and performance for five of the six exceptional children studied.

Adolescent↗