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PubMed1978

Skin colorimetry in Belize. I. Conversion formulae.

Comparisons between skin colorimetry reports have been hampered by the common use of two different types of portable reflectometers, which sample reflectances at different wavelengths. In an attempt to provide direct comparability between the two machines, multiple linear regression equations were derived from reflectance spectrophotometry readings on 308 Black Caribs and 175 Creoles in Belize, Central America, using both machines. Cross validation tests show the coefficients presented are applicable to independent data sets and generally applicable to other heavily pigmented populations. Comparisons with previously published conversion formulae, which were from very small samples using simple linear regression, show a definite improvement in predictive accuracy when using multiple regression equations based on a large sample.

Belize↗
PubMed1982

Skin colorimetry in Belize. II. Inter- and intra-population variation.

Skin colorimetry readings taken in Belize, Central America (formerly British Honduras) with the two most commonly used portable reflectometers reveal significant differences in mean reflectance between Garifuna (Black Caribs) and Creoles, and between Garifuna in two settlements. These differences are related to variation in African, Indian, and European admixture, as estimated from serological markers. Sex differences are not evident in univariate comparisons, but females are significantly lighter than males in multivariate analyses of variance. Polynomial age trends exist in some groups for certain variables, but account for a very small amount of the variation in skin color within these groups.

Adolescent↗
PubMed1975

Measurement of surface color and color difference of tablet colorants by tristimulus colorimetry.

The surface color of a series of color dispersions containing from one to three FD&C or D&C dyes suspended in a sucrose syrup was examined using tristimulus colorimetry. CIE (x, y) and Hunter (a, b) chromaticity data, determined directly from an integrating sphere colorimeter or from reflectance spectra and suitable calculations, were used to order materials by color on expanded chromaticity diagrams. Color difference was evaluated quantitatively from Hunter (a, b) data using the Judd color difference formula. Quality control specifications were established either by defining areas of acceptable color by applying limits to the chromaticity coordinates of color standards or by requiring the Judd color difference to be less than a specific number of National Bureau of Standards standard units. This method eliminates the subjective character of color evaluation and permits the quantitation of visual color difference. These differences can be used, in conjunction with defined color standards, to develop color specifications for tablet colorants, finished tablets, and liquid and cream pharmaceutical preparations.

Color↗
PubMed1998

Profiling expression patterns and isolating differentially expressed genes by cDNA microarray system with colorimetry detection.

A high-density cDNA microarray with colorimetry detection system to simultaneously monitor the expression of many genes on nylon membrane is described and characterized. To quantify the expression of genes and to isolate differentially expressed genes, the southern hybridization process on filter membranes was employed. The levels of gene expression were represented by color intensities generated by colorimetric reactions in place of hazardous radioisotopes or costly laser-induced fluorescence detection. The gene expression patterns on nylon membranes were digitized by devices such as an economical flatbed scanner or a digital camera. The quantitative information of gene expression was retrieved by image analysis software. Quantitative comparison of the northern dot-blotting method with the microarray system is described. Applications employing single-color detection as well as dual-color detection to isolate differentially expressed genes among thousands of genes are demonstrated.

Blotting, Northern↗
PubMed1980

Characterization of embryonic cholinesterase in chick limb bud by colorimetry and disk electrophoresis.

In the chondrogenic blastema of the chick limb bud an histochemical cholinesterase activity related to aggregation of the chondroblasts was described by Drews and Drews (1972). This cholinesterase activity was termed "embryonic cholinesterase" (Drews 1975). In the present study embryonic cholinesterase from the limb bud has been characterized by colorimetry and disk electrophoresis and compared to cholinesterase from the myotomes of the same embryos. Embryonic cholinesterase comprises both acetylcholinesterase and butyrylcholinesterase activity. The banding patterns of embryonic cholinesterase from limb bud and of cholinesterase from myotomes are identical. These findings support the hypothesis that the cholinergic system is involved in the regulation of embryonic development.

Acetylcholinesterase↗
PubMed1993

Determination of IL-2 and cytotoxicity of killer cells in MTT colorimetry.

The activity of interleukin 2 (IL-2) in culture supernatants of lymphokine-activated killer (LAK) cells and tumor infiltrating lymphocytes (TIL) as well as cytotoxicity of LAK cells on cultured leukemic cells were determined by MTT colorimetry. The results showed that higher activity of IL-2 in culture supernatant of LAK and TIL cells was found; it could be used to support the culture of IL-2 dependent cell lines. The significant cytotoxicity of LAK cells on leukemic cell lines could be found in vitro, and it was consistent with the ratio of effector cells to target cells. The number of living leukemic cells is consistently related with the concentration of formazan metabolite of MTT. It suggested that the numbers of living cells and cytotoxicity of LAK cells could be estimated by determination of formazan metabolite OD value.

Colorimetry↗
PubMed1985

Sensitive assay systems for detection of hemoglobin with 2,7-diaminofluorene: histochemistry and colorimetry for erythrodifferentiation.

Sensitive and rapid assays, colorimetry and histochemistry, for hemoglobin in erythroid cells are established. The assays are based on pseudoperoxidase activity of hemoglobin using 2,7-diaminofluorene as a hydrogen donor for the peroxidase, instead of benzidine which is widely benzidine which is widely used for the detection of small amounts of hemoglobin but which is a potent carcinogen and has been banned from laboratory use. In the presence of hydrogen peroxide, hemoglobin catalyzes the formation of a blue compound (fluorene blue), which has a broad absorption band between 500 and 690 nm with a peak at 610 nm, from 2,7-diaminofluorene. The reagent is safe to use in the laboratory. The methods could be applied to the detection of hemoglobin in Friend erythroleukemia cells induced to cell differentiation along the erythroid pathway by dimethyl sulfoxide.

Animals↗
PubMed1992

Determination of 9-hydroxyellipticine by redox colorimetry.

The chemical reactions involved in the decomposition of 9-hydroxyellipticine (9-OH-E), an anticancer agent, in polar solvents is explained. The reactions, which involve the formation of 9-oxo-ellipticine and the addition of a nucleophilic acid on the C10 site of the heterocyclic system, have been used to measure 9-OH-E quantitatively by colorimetry in solution and by reflection on paper surfaces. A method for the stabilization of 9-OH-E in polar solvents is proposed.

Antineoplastic Agents↗
PubMed1994

Comparison of assay methods by second-derivative spectroscopy, colorimetry and fluorescence spectroscopy of salicylic acid in aspirin preparations with a high-performance liquid chromatographic method.

Second-derivative spectroscopy, colorimetry and fluorescence spectroscopy have been compared with a high-performance liquid chromatographic (HPLC) method for the assay of salicylic acid in preparations of aspirin. Results are presented for the linearity, sensitivity and reproducibility of these methods. The second-derivative spectroscopic and the HPLC methods were acceptable in terms of linearity, sensitivity and inter-day reproducibility and were convenient for the routine analysis of salicylic acid in aspirin preparations.

Aspirin↗
PubMed1995

20 MHz sonography, colorimetry and image analysis in the evaluation of psoriasis vulgaris.

For objective evaluation of the treatment of psoriasis vulgaris standard techniques are desirable. They should be reproducible, sensitive and non-invasive. In this study non-invasive bioengineering techniques, especially high frequency/high resolution ultrasound for measurement of the healing of psoriasis vulgaris were evaluated. Fifty patients with chronic stationary plaque type psoriasis participated in a prospective study; in each patient two psoriatic plaques were examined by means of sonography, colorimetry and image analysis during treatment until complete resolution had occurred. Skin thickness and density could be quantified by means of high frequency ultrasound. In active psoriatic lesions, an echopoor area underneath the entry echo in the ultrasound image caused by acanthosis and inflammatory infiltrate is typical. Under therapy the thickness of this echopoor area diminishes while its density increases. Intensity of the erythema especially the decrease of erythema through healing could not exactly be quantified with the colorimeter because the 'Lab'-CIE-colour representation system cannot distinguish well enough between the colours red and brown. Image analysis allowed to measure the sizes of the psoriatic plaques and to quantify their resolution under therapy. The measuring of plaque size by the aid of computer based image analysis is possible and useful.

Colorimetry↗
PubMed2006

Use of refractometry and colorimetry as field methods to rapidly assess antimalarial drug quality.

The proliferation of counterfeit and poor-quality drugs is a major public health problem; especially in developing countries lacking adequate resources to effectively monitor their prevalence. Simple and affordable field methods provide a practical means of rapidly monitoring drug quality in circumstances where more advanced techniques are not available. Therefore, we have evaluated refractometry, colorimetry and a technique combining both processes as simple and accurate field assays to rapidly test the quality of the commonly available antimalarial drugs; artesunate, chloroquine, quinine, and sulfadoxine. Method bias, sensitivity, specificity and accuracy relative to high-performance liquid chromatographic (HPLC) analysis of drugs collected in the Lao PDR were assessed for each technique. The HPLC method for each drug was evaluated in terms of assay variability and accuracy. The accuracy of the combined method ranged from 0.96 to 1.00 for artesunate tablets, chloroquine injectables, quinine capsules, and sulfadoxine tablets while the accuracy was 0.78 for enterically coated chloroquine tablets. These techniques provide a generally accurate, yet simple and affordable means to assess drug quality in resource-poor settings.

Antimalarials↗
PubMed1990

Rapid visual colorimetry of peritoneal lavage fluid.

STUDY HYPOTHESIS: That visual colorimetry can be used to rapidly and precisely estimate the erythrocyte count of 1:5 dilutions of simulated peritoneal lavage fluid. POPULATION: Fifty-four normal adult human subjects. METHODS: The automated or chamber RBC count is often used on fluid obtained by peritoneal lavage in patients with abdominal trauma to help determine the need for surgery. Unfortunately, this method sometimes results in excessive delay. We designed and built a simple colorimeter that facilitated rapid direct visual comparison of unknown samples with known color standards. A radiograph view box was used as a light source. Standards were prepared in 16-mm glass tubes to simulate peritoneal lavage fluid with RBC counts ranging from 0 to 140,000 in 10,000 cell/microL increments; 1:5 dilutions with water were used throughout to reduce opacity. Thimerosal was added to unknowns and standards to stabilize color; all samples were kept refrigerated at 4 C when not in use. In a double-blind in-vitro study, each subject matched 20 randomly distributed unknowns ranging from 12,000 to 131,000 erythrocytes/microL to the nearest standard. RESULTS: The mean absolute error for all 1,080 determinations was 3,560 RBC/microL (95% CI = 4,290-4,830; SD = 4,560; t = 39.6; df = 1,079; P less than .001). This method correctly predicted the RBC count to within 9,000 cells/microL 95% of the time. CONCLUSION: Visual comparison of 1:5 dilutions of simulated peritoneal lavage fluid with known color standards can be used to rapidly and precisely estimate the erythrocyte count.

Abdominal Injuries↗
PubMed1986

Simultaneous determination of serum uremic toxins, cations and anions and urea determination by post-column colorimetry using immobilized enzyme.

A column-switching method which combines ion-exchange and ion-pair reversed-phase chromatography was developed for the determination of serum uremic toxins, cations and anions. Serum urea, which was poorly separated by reversed-phase chromatography, was analyzed using an immobilized-urease column and detected by post-column colorimetry. Apart from the simultaneous analysis, anion analysis using ion-pair reversed-phase chromatography on an ODS column was also developed. The origin of the system peak observed in anion analysis with an eluent containing phthalate has been clarified.

Chromatography, Ion Exchange↗
PubMed1998

Effects of several agents on UVB- and UVA plus systemic fluoroquinolone-induced erythema of guinea pig skin evaluated by reflectance colorimetry.

The aim of this study was to clarify the mechanisms underlying the erythema of guinea pig skin induced by ultraviolet (UV) irradiation alone and in combination with a systemic fluoroquinolone (FQ). The effects of several drugs which may modify the actions of some inflammatory mediators and radicals possibly released in the inflamed site on the erythema were examined and compared in an objective and quantitative way by measuring the change in color of the irradiated skin, determined as the change in chroma (C*) with use of reflectance colorimetry. After confirming that the C* value increased in an irradiation dose-dependent manner and reached a plateau 1-2 h after irradiation of UVB alone or UVA coadministered with an FQ, Y-26611 (10 mg/kg, i.p.), guinea pigs were pretreated with indomethacin, butylated hydroxytoluene (BHT) or beta-carotene before, or treated with H1- or H2-receptor antagonist, superoxide dismutase or N omega-nitro-L- arginine methyl ester after UV irradiation, and their inhibitory effects against erythema were evaluated. It was suggested that there are some substantial differences between UVB- and UVA plus FQ-induced erythemas. Although histamine makes little contribution to both types of erythema, metabolites of arachidonic acid catalyzed by cyclooxygenase contribute more to UVB-induced erythema, whereas superoxides take more part in UVA plus FQ-induced erythema. Furthermore, nitric oxide seems to participate in both types of erythema; however, the pretreatment with BHT or beta-carotene was ineffective against both erythemas. From these results, interventions should be directed to powerfully scavenging radicals for prevention and treatment of UV plus FQ-induced phototoxicity.

4-Quinolones↗
PubMed2003

Application of tristimulus colorimetry to estimate the carotenoids content in ultrafrozen orange juices.

Tristimulus Colorimetry was applied to characterize the color of Valencia late orange juices. Color measurements were made against white background and black background. The profile of the main carotenoids related to the color of the juices was determined by HPLC. Significant correlations (p < 0.05) between b*, Cab* and h(ab) and the content of beta-cryptoxanthin, lutein + zeaxanthin and beta-carotene were found. The correlations between the color parameters L*, a*, b*, Cab* and h(ab) and the carotenoids content were also explored by partial least squares. The results obtained have shown that it is possible to obtain equations, by means of multiple regression models, which allow the determination of the individual carotenoid levels from the CIELAB color parameters, with R2 values always over 0.9. In this sense, equations have been proposed to calculate the retinol equivalents (1 RE = 1 microgram retinol = 12 micrograms beta-carotene = 24 micrograms alpha-carotene = 24 micrograms beta-cryptoxanthin) of the orange juice analyzed as a function of the color parameters calculated from measurement made against white and black backgrounds. The average RE per liter of juice obtained by HPLC was 51.07 +/- 18.89, whereas employing these equations, average RE values obtained were 51.16 +/- 1.36 and 51.21 +/- 1.70 for white background and black background, respectively.

Beverages↗
PubMed2003

Review of the CIE system of colorimetry and its use in dentistry.

UNLABELLED: When we observe the light reflected from surfaces in a scene or look directly at light emitted by light sources, we experience the sensation of color. Color is just one attribute of a complex and not fully understood set of properties that define the appearance of our surroundings. To measure or specify the color of an object, we need to take into account the nature of the light under which the object is viewed, the spectral reflectance properties of the surface, and the properties of the human color vision system. CLINICAL SIGNIFICANCE: In this article the CIE system of colorimetry is briefly reviewed and its limitations are described. The consequences of these limitations for color measurement in dentistry are discussed.

Algorithms↗
PubMed1995

Development of a sensitive chemiluminometric assay for the detection of beta-galactosidase in permeabilized coliform bacteria and comparison with fluorometry and colorimetry.

We developed a chemiluminometric assay of beta-galactosidase in coliform bacteria, using a phenylgalactose-substituted 1,2-dioxetane derivative as a substrate. Permeabilization of cells is required to ensure the efficient cellular uptake of this compound. By this method, one coliform seeded in 100 ml of sterile water can be detected after a 6- to 9-h propagation phase followed by a 45-min enzyme assay in the presence of polymyxin B. Compared with fluorometry and colorimetry, chemiluminometry afforded 4- and 1,000-fold increases in sensitivity and 1- and 6-h increases in the speed of detection, respectively.

Colorimetry↗